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NUTR 3210 Lecture Notes - Lecture 3: Atwater System, Nutrition, Energy Economics

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maroonleopard339
10 Jun 2016
School
University of Guelph
Department
Nutrition
Course
NUTR 3210
Professor
Justine Tishinsky

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Document Summary

De ning energy metabolism: energy metabolism: de ned as the sum of all chemical reactions in obtaining and utilizing food energy. Requires the quanti cation of energy in and out of living systems. To quantify energy in (intake) we need to understand caloric values of the different macronutrients found in our diet, and the obligatory losses that occur as we move these substrates into metabolism. To quantify energy out (expenditure), we need to understand the physiology of heat production, and how it can be measured directly or estimated by measuring oxygen consumption and carbon dioxide release: main ideas of energy metabolism are: Energy is the capacity to do metabolic or physical work. At the cellular level, the predominant energy source is atp. Cellular atp pools are supported by dietary macronutrient intake. E. g. dietary proteins are sources of amino acids, which are used by organisms to make their own proteins and enzymes.

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Related Questions

The people of Malaysia belong to three communities: the local people called Malays, immigrants from South India called Tamils, and immigrants from China. During the early 20th century, the Malays lived mainly in coastal villages, the Tamils worked on rubber estates, and the Chinese worked in tin mines. In general, the people were very poor and they consumed a limited variety of foods.[1] Rice was the staple diet of all three communities and therefore the key source of caloric and nutrient content. Malays typically grew their own rice and dehulled it before consuming it; dehulling partially removes the aleurone layer of the rice seed. Following their South Indian food habits, the Tamils ate parboiled rice, and the Chinese ate polished white rice imported from Thailand. It was found that among the three Malaysian communities, the Chinese community was much more prone to suffer from some degree of sub-optimal thiamin intake. Out of every 1,000 Chinese inhabitants, about 120 had mild thiamin deficiency, about 80 had severe thiamin deficiency, and about 16 people had died of it. Suboptimal intake of thiamin was rare in Malays and was not reported at all in Tamils.[1] Thiamin, also called Vitamin B1, is required for all tissues, and its deficiency causes the disease Beriberi. Less severe deficiency results in non-specific symptoms such as weight loss, malaise, irritability, and confusion. Although the origin of the word Beri-beri is disputed, it is believed to be a Philippine word meaning “I can’t, I can’t” and was probably coined to refer to the lack of neuromotor coordination in people afflicted with this disease.[2] Thiamin is water-soluble and is stable in the acidic medium. It is unstable to heat, oxygen, and UV light in neutral and alkaline medium. The active form of thiamin is thiamin pyrophosphate (TPP). This active form is a cofactor for pyruvate dehydrogenase and transketolase enzymes that are involved in the metabolism of carbohydrates. These enzymes play an important role in the biosynthesis of a number of cell constituents such as neurotransmitters, pentoses, and reduced equivalents, used in oxidant stress. The human body cannot store thiamin and therefore requires a continuous supply of the vitamin. The thiamin in an individual on a thiamin-free diet typically depletes in fewer than two weeks. Thiamin absorption is affected by compounds, called thiamin antagonists or anti-thiamin factors, that alter the structure of thiamin. These compounds include alcohols, polyphenols, flavonoids, and thiaminase, a heat labile enzyme found in certain foods.[2] In affluent countries, where the diet is rich in thiamin, the most common cause of thiamin deficiency is excessive alcohol consumption. Alcohol intake affects thiamin status in two ways. First, alcoholics get a significant percentage of their daily energy intake from alcoholic beverages, which are nutrient deficient. In other words, alcoholics replace their consumption of nutrient dense foods that are part of their normal diet with the consumption of nutrient deficient alcohol. Second, alcohol inhibits the intestinal ATPase involved in the absorption of thiamin.[4] Sub-clinical thiamin insufficiency associated with excessive alcohol consumption produces an encephalopathy called Wernicke-Korsafoff syndrome. Patients with this syndrome have a higher than normal incidence of abnormal transketolase, which has a very low binding affinity to TPP. This problem can be overcome by putting patients on high-dose thiamin therapy. Some patients, however, might have a form of abnormal transketolase that does not bind at all with TPP. Such people do not respond to high-dose thiamin therapy.[4] Thiamin deficiency is observed in individuals who have low thiamin intake and a diet rich in polished rice, especially if their diet also consists of anti-thiamin factors such as tea, coffee, raw fermented fish, and betel nuts. The minimum amount of thiamin needed by the body can increase because of increased physiological or metabolic demands arising from pregnancy and lactation, heavy physical exertion, illnesses like cancer, liver diseases, hyperthyroidism, and surgery. Since TPP is required for carbohydrate metabolism, the recommended dietary allowances for thiamin are based on the assumption that its intake is related to total energy intake. The recommended dietary allowance in the United States is 0.5 mg/1000 Kcal.

Questions
1. Thiamin deficiency was observed only in the Chinese community even though all three
communities had the same staple (rice) diet. Explain.
2. On packages of enriched rice sold in supermarkets, the rice preparation directions state that the
rice should not be washed before cooking. Explain.
3. Severe metabolic acidosis caused by high levels of lactate is often associated with thiamin
deficiency. Explain.
4. Provide two plausible explanations for what might cause above normal levels of pyruvate in blood
and urine. How can one determine which of the two explanations is correct?
5. Why does thiamin utilization increase among cancer patients?
6. A negative correlation exists between the need for thiamin and the amount of fat in the diet.
Explain.

OOC #3 Due: Monday, March 19, 2018, 5pm CASE: The Runners’ Experiment, Integration of Metabolism Case Study Overview This case is designed to help students understand the importance of glucogenic substrates in human metabolism and the interconnections between carbohydrate, fat, and protein metabolism in humans. Because the focus of this case is the integration of metabolic pathways, we recommend that students be exposed to the topics through Chapter 23 (Chapters 19 and 20 are not necessarily required); referring to Sections 27.4 and 27.5 of the textbook (Stryer 8E) before beginning this case may also be useful for this out-of-class assignment. You may work individually or in groups to complete this case study, but you must submit your own work in Canvas (“Enter your ooc #3 answers here”). You are encouraged to refer to your textbook throughout the case, and internet access is permitted, although it is not necessary for the completion of the case. You will need to iteratively acquire, analyze, and integrate data as you progress through the case and answer assessment questions found throughout the case. You are encouraged to carefully consider investigation options; guessing is discouraged. Your score on this assignment will reflect correct answers. Learning Objectives This case is intended for remediating or extending student capabilities in these difficult topics: 1) The real-world applications of the study of human metabolism. Students will: • Use real biochemical tests to evaluate and ‘solve’ a metabolic disorder case. • Consider the importance of factors like personal and family history, diet, medications taken, and symptoms in solving a biochemical case. 2) Critical and interrelated pathways in human central metabolism. Students will: • Review carbohydrate, lipid, and amino acid metabolic pathways. • Review fatty acid metabolism and recognize the distinctions between the oxidation of even- and odd-chain fatty acids. 3) Connections between carbohydrate, fat, and protein metabolism in humans. Students should be able to: • Outline and explain the importance of glucogenic substrates in human metabolism. o Understand why the inability to convert acetyl-CoA to glucogenic substrates in humans leads to protein wasting. o Explain the importance of ketone body formation and ammonia transport/disposal in human metabolism. • Explain the important differences between the metabolic intermediates produced by the oxidation of even- vs. odd-chain fatty acids. 4) Practice critical thinking skills involving data. Students will: • Evaluate data provided by metabolite and enzyme tests. • Integrate multiple pieces of biochemical data. “The Runners’ Experiment”, Integration of Metabolism Case Study Introduction Race day had come. ‘Finally’ thought Michael. He was a marathon veteran, but this race was different. He felt terrible: “Probably a cold” he had told his girlfriend, but nothing was going to stop him today. Today was the day he would finally prove his brother Dave wrong and he had 26.2 miles to do it. The two young men shook hands shortly before the race started. Dave was thin, like Michael, but not ‘gaunt’. Michael’s girlfriend Jan, had actually used that word to describe Michael a few days prior. His cheeks had receded recently. “Seriously, you should stop this... you look terrible!” Jan said. ‘It’s just pre-race training... and of course, the experiment’ he thought. “I’ll be fine!” he assured her with a wink before leaving their apartment. “Today is the day we settle this!” he now called to Dave as they took off down the race route. But Dave only smiled and accelerated to leave Michael behind. As Dave disappeared into the crowd, Michael called out: “It’s not about speed! It’s about endurance dummy!”, but Dave was too far ahead to hear. 1 For weeks they had been talking about their plan, the experiment, and how much money they were going to make. Michael smiled to himself and then put his head down to focus on the run. Dave was long gone but Michael was certain that he would see him again soon enough... that is, until he started to feel dizzy... Juan had worked at several marathon-medical tents before. It was always the same: people try to run the race without training properly, and they end up at the tents. Most are dehydrated and exhausted, others just ‘hit the wall’, when their bodies run out of glycogen and some even have heart attacks, mainly due to poor training. This particular day wasn’t very hot, but it didn’t take much to overwhelm people during a marathon. Working the races was a nice excuse for an ER doctor to get out in the sun for a few hours on the weekend and a chance to help some people... for Juan that was as addicting as running. Two hours in and Juan was bored. The chatter on the radio was the same as always: dehydrated runners at both tents, and one elderly person from the crowd had to be treated for heat exhaustion, just from standing too long... so far it was a slow day. Suddenly the radio chatter picked up. The ambulance from the medical tent at the 10-mile mark was headed in to his direction with a young man who was unresponsive. The incoming call was interrupted by a second voice: the ambulance from the medical tent at the 20-mile mark ALSO had an unresponsive man. ‘What are the odds?’ Juan thought. The two ambulances arrived simultaneously. Runner ID tags identified both subjects immediately: Michael and Dave Gard, two brothers! Dave was unconscious, but otherwise looked OK. When Juan saw Michael however, he was startled into action; he would not have guessed that the two men were brothers! You are a biochemistry student who is shadowing an ER doctor who has just admitted two young males. One man, Dave, regained consciousness prior to arrival, while the other, Michael, regained consciousness only after arriving at the hospital and is still delirious. Neither man was particularly dehydrated, having drunk water during the race. Both have been stabilized, but blood and urine samples from before they were treated are available for you to test. It is up to you to discover what might be the problem with the two brothers. Consider that there are two primary questions to answer in this case study: • What caused both brothers to lose consciousness during the race? Here are some potential biochemical hypotheses for you to consider: Ketoacidosis Lactic acidosis Ammonia toxicity Mercury poisoning Acute hyperglycemia due to type II diabetes Hypoglycemia Phenylketonuria Maple-syrup urine disease • What is the biochemical explanation for the differences in the conditions of the two brothers? You may now conduct additional investigations to explore the details of this case and to test hypotheses so that you can eventually answer both of these questions. Note: for this case, you are encouraged to explore ALL possible investigations to gather as much information as possible to explain the brothers’ conditions before finishing the case by continuing to the final assessments. You will be scored on this exercise based on your answers to assessment questions found throughout the case so you are STRONGLY encouraged to use your textbook to complete this exercise; you may also use the internet as necessary. RECOMMENDED INITIAL INVESTIGATIONS: Evaluate the overall physical appearance of the two brothers including insect bites or other injuries Results: The men are identical in height. Dave has a lean, athletic build, but is not unusually thin for a long- distance runner. Michael, on the other hand, appears to be severely emaciated. You note sunken eyes and 2 cheek bones and protruding ribs, indicating a lack of not only body fat but also muscle tone. No injuries or other abnormalities are apparent. Investigate past medical history including current medications Results: Neither man smokes, drinks, or uses illegal drugs. They are not on any medications. Dave reports that Michael had not been feeling well prior to the race, but had thought that he was “just coming down with a cold or something”. Given that the men were both avid marathoners, no one apart from Michael’s girlfriend Jan had been concerned about Michael’s recent and rapid weight-loss. Investigate the relationship between the two brothers in greater detail Dave explains that the two of them are not just brothers, they are best friends and despite their grossly different appearances at the moment, they are identical twins! He says: “Before we started our experiment just a few weeks ago, most people couldn’t tell us apart!” Dave mentioned something about an experiment; you could ask him more about this. The following is now a new investigation option: Ask Dave about “The Experiment” Results: Dave tells you that the two brothers had been planning to develop a new dietary supplement company, Gard Nutraceuticals, selling purified fish oil, which they believe is a health panacea. They disagreed on the best fish oil to bring to market however, so the men had been conducting an experiment to settle this disagreement. Both had been taking fish-oil pills along with a multi-vitamin for the past three weeks while they tapered back their training runs dramatically. When you press Dave about what else he and Michael were eating, shockingly he says “nothing”. They had been eating enough fish oil to consume 3000 Calories per day, which is normal for marathon training (approximately 330 grams of fish oil per day). Each brother had been touting a different product: Michael was taking wild-caught salmon oil, while Dave was eating oil from a flathead (striped) mullet. The bet was to determine whether fish oil was an adequate caloric- replacement supplement for athletes, and whose product was better. To make the decision unambiguous, the pair was going to use the marathon to decide the winner since the boys had nearly identical marathon times in previous races. The details of this fish-oil experiment may merit further investigation. In particular, some fish contain high levels of mercury, which could be toxic if consumed in large quantities. You now have the following two new investigation options available to you: Test hair for common toxins (heavy metals and narcotics) and ask Dave about mercury contamination in the supplements Investigate the composition of the dietary supplements the subjects were eating SECONDARY INVESTIGATIONS: DETERMINE BLOOD SERUM CONCENTRATIONS OF: Common immunoglobins (IgG, IgA, IgM) and ammonium (NH4+) levels Results for Dave: All values for immunoglobin concentrations are at the low end of the normal ranges, which is normal for someone finishing a marathon. (normal ranges: [IgG] = 560–1800 mg/dL; [IgM] = 45–250 mg/dL; [IgA] = 100–400 mg/dL); [NH4+] = 20 mmol/L (normal range: 12- 48 mmol/L) Results for Michael: Severely low levels of IgG, IgM, and IgA. [NH4+] = 67 mmol/L (normal range: 12–48mmol/L)

1. Which of the following might cause the concentration of ammonium ions found in the blood to increase? (Select ALL that apply!) A. An increase in the rate of fatty acid catabolism by β-oxidation B. An increase in the rate of protein and amino acid catabolism C. An increase in the rate of glucose oxidation through the pentose phosphate pathway D. An increase in the rate of glucose oxidation through glycolysis and the citric acid cycle E. A defect in the urea cycle F. Galactosemia G. Lactose intolerance

Free fatty acids (FFAs) and triacylglycerides (TAGs) Results for Dave: 500 mg/dL FFAs (normal range: 190–420 mg/dL); 190 mg/dL TAGs (normal range: 40–150 mg/dL) Results for Michael: 660 mg/dL FFAs (normal range: 190–420 mg/dL); 230 mg/dL TAGs (normal range: 40–150 mg/dL) Glucose and Glycosylated Hemoglobin (HbA1c as a marker) Results for Dave: [Glc] = 39 mg/dL (normal range: 70–110 mg/dL) Note: This value indicates severe hypoglycemia; HbA1c = 4.4% (normal range: 4–6.5%) Results for Michael: [Glc] = 31 mg/dL (normal range: 70–110 mg/dL) Note: This value indicates severe hypoglycemia; HbA1c = 3.2% (normal range: 4–6.5%)

2. When a typical person runs a marathon, they do not become severely hypoglycemic to the extent that either Michael or Dave did. Some people consume carbohydrates during the race in the form of foods, gels, or sports drinks that have added sugar. However, even when dietary carbohydrates are not consumed during the race, how does the body of a healthy individual maintain adequate levels of blood glucose during sustained aerobic exercise such as running a marathon? (Select ALL that apply!) Hint: You may wish to review pages 657-661, 698-699, & 814-819 of Stryer 8E before attempting this question! In addition, remember to consider the sources of glucose, not ATP. A. Even numbered fatty acids are catabolized and the carbon is used for gluconeogenesis in the liver. B. Muscles run gluconeogenesis and export glucose into blood. C. Ketone bodies are produced by adipose cells and converted into glucose by the liver. D. Muscles convert lactate back into glucose and export this glucose back out into the blood. E. The exclusively ketogenic amino acids (leucine and lysine) are deaminated and the carbon skeletons used to synthesize glucose. F. Glucogenic amino acids are deaminated and the carbon skeletons used to synthesize glucose. G. Most blood glucose will come from the breakdown of muscle glycogen (glycogenolysis) and the export of this glucose from muscles to the blood. H. Most blood glucose will come from the breakdown of brain glycogen (glycogenolysis) and the export of this glucose from brain to the blood. I. Most blood glucose will come from the breakdown of liver glycogen (glycogenolysis) and the export of this glucose from the liver to the blood.

H3O+ ions: blood pH Results for Dave: pH = 7.31 (normal range: 7.35–7.45) Results for Michael: pH = 7.2 (normal range: 7.35–7.45) The physician you are shadowing tells you that a value of 7.31 indicates acidosis but this value will not normally cause a loss of consciousness. A pH value of 7.2 indicates severe acidosis and could result in neurological problems. 4 Ketone bodies (acetoacetate and acetone) Results for Dave: low but detectable levels (normal range: undetectable) Results for Michael: dangerously high levels of both found.

3. What macromolecules can be catabolized such that the resulting carbon can be used to create ketone bodies? A. Fatty acids B. Amino acids C. Glucose D. Glycogen E. All of the above can be used to produce acetyl-CoA, so they can all be used to make ketone bodies.

4. When are ketone bodies produced in an otherwise healthy human being? A. When fatty acid levels in the blood are low B. When glutamine levels in the blood are low C. When glucose levels in the blood are low D. When lactate levels in the blood are low E.

When blood pH is low Lactate and pyruvate Results for Dave: [lactate] = 2.0 meq/L (normal range: 0.5–2.2 meq/L); [pyruvate] = 0.05 meq/L (normal range: 0–0.11 meq/L) Results for Michael: [lactate] = 0.7 meq/L (normal range: 0.5–2.2 meq/L); [pyruvate] = 0.02 meq/L (normal range: 0–0.11 meq/L) DETERMINE URINE CONCENTRATIONS OF: branched-chain a-keto acids Results for both Dave and Michael: undetectable levels (normal range: undetectable)

5. What would an increased amount of branched-chain a-keto acids in the urine indicate? (Select ALL that apply!) A. A defect in fatty acid catabolism B. A defect in fatty acid transport C. A defect in a citric acid cycle enzyme D. A defect in carbohydrate metabolism E. A defect in amino acid catabolism F. Phenylketonuria G. Lactose intolerance H. Maple-syrup urine disease phenyl-pyruvate (a phenylketone)

Results: Both Dave and Michael: undetectable levels (normal range: undetectable)

6. What would an increased amount of phenyl-pyruvate in the urine indicate? (Select ALL that apply!) A. A defect in fatty acid catabolism B. A defect in fatty acid transport C. A defect in a citric acid cycle enzyme D. A defect in carbohydrate metabolism E. A defect in amino acid catabolism F. Phenylketonuria G. Lactose intolerance H. Maple-syrup urine disease

SPECIFIC ENZYME TESTS: Lactate dehydrogenase (LDH) Results for both Dave and Michael: [LDH] = 150 U/L (normal range: 110–210 U/L) Liver Asp amino-transaminases (AST) and Ala amino-transferase (ALT) Results for Dave: Both enzymes are within normal range (normal range: 7–55 U/L) Results for Michael: Both enzyme expression levels are elevated. Pyruvate dehydrogenase (PDH) Results for both Dave and Michael: PDH complex activity= 2.5 nmol/(min•mg) (normal range: 2– 2.5 nmol/(min•mg) Test cells for Electron Transport Chain enzyme activities Results for both Dave and Michael: ETC enzyme activities were normal. SPECIAL INVESTIGATIONS Test hair for common toxins (heavy metals and narcotics) and ask Dave about mercury contamination in the supplements Results: Dave immediately points out that they worked with a chemist to extensively purify the fish oils to remove any mercury contamination. An independent laboratory verified that there are only trace levels of mercury left in their formulations, and Dave brings up the documentation on his smart-phone, showing that the analysis is good. Mercury toxicity will be negligible regardless of how much oil is consumed. Also, no heavy metals or narcotics were detected in hair samples from either brother. Investigate the composition of the dietary supplements the subjects were eating. Results: Complete hydrolysis followed by esterification of the TAGs in the two fish oil samples allowed fatty acid composition to be analyzed by gas chromatography. The table shows the compositions of oil consumed by Dave (from the striped mullet Mugil cephalus) and Michael (from Atlantic salmon Salmo salar) Dave Michael 16:0 fatty acid 11% 16% 16:1∆7 fatty acid 5% 6% 18:1∆9 fatty acid 15% 20% 20, 22, or 24 carbon omega-3 or omega-6 fatty acids 36% 45% 15, 17, 19, and 21 carbon fatty acids 25% 4% 12 or 14 carbon fatty acids 6% 7% Unidentified 2% 2% 6

7. What is the most significant difference between these two fish oil samples in terms of their fatty acid compositions? Note: it may be helpful to briefly review fatty acid structure and nomenclature from Section 12.1, pages 342-344, Table 12.1 of Stryer 8E before answering this question. A. The oil that Dave is consuming is much higher in saturated fatty acids than Michael’s oil. B. The oil that Dave is consuming is much higher in oleic acid than Michael’s oil. C. The oil that Dave is consuming is much higher in palmitic acid than Michael’s oil. D. The oil that Michael is consuming is much higher in omega-3 fatty acids than in omega-6 fatty acids. E. The oil that Dave is consuming is much higher in odd-numbered fatty acids than Michael’s oil. F. The oil that Michael is consuming is much higher in unsaturated fatty acids than Dave’s oil.

8. What is different about the metabolism of odd- vs. even-numbered fatty acids? (Select ALL that apply!) A. Odd-numbered fatty acids are not broken down by β-oxidation. B. Odd-numbered fatty acids are primarily broken down by ω-oxidation. C. Odd-numbered fatty acids cannot be broken down by humans. D. Odd-numbered fatty acids require additional enzymatic steps to fully degrade. E. Odd-numbered fatty acids do not require carnitine in order to be transported into the mitochondria. F. Odd-numbered fatty acid metabolism produces a four-carbon succinyl group attached to CoA.

9. What is an important consequence of producing succinyl-CoA at the end of odd-numbered fatty acid metabolism rather than the normal product by β-oxidation of even-numbered fatty acids? A. Acetyl-CoA is a citric acid cycle intermediate but succinyl-CoA is not. B. Acetyl-CoA is glucogenic but succinyl-CoA is strictly ketogenic. C. Succinyl-CoA is glucogenic, but acetyl-CoA is strictly ketogenic. D. None of the above are true.

10. Review again which brother is taking which oil and which oil contains a large percentage of odd- numbered fatty acids. What is a critical physiological consequence of this difference? A. Michael can make ketones from the oil in his diet but Dave cannot. B. Dave can make ketones from the oil in his diet but Michael cannot. C. Michael can make ATP using the oil in his diet but Dave cannot. D. Dave can make ATP using the oil in his diet but Michael cannot. E. Dave can make far more glucose from the oil in his diet than Michael can. F. Michael can make glucose from the oil in his diet but Dave cannot. You have uncovered a critically important aspect of this case. As you continue your investigation, consider what biochemical consequences might occur when someone is not consuming glucose and cannot convert the food that they are eating into glucose. ENDING THE CASE AND THE ASSESSMENT QUESTIONS: The student should be able to fully explain the reason(s) for Dave and Michael’s incidents in biochemical and physiological terms, including reasons for the significant differences between the two brothers’ conditions and to fully justify and completely explain their reasoning based on the evidence gathered. Criteria to complete the case are the selection of ALL possible investigation options and completion of the associated assessment questions. If all of the criteria are not met: you may be missing vital information to sufficiently explain this incident. Assessment Questions for “The Runners’ Experiment”

11. The citric acid cycle begins with the condensation of acetyl-CoA with oxaloacetate. Possible sources for carbon that may be converted into acetyl-CoA in active muscle include: (Select ALL that apply!) A. Pyruvate B. β-oxidation of fatty acids C. Amino acid catabolism D. Conversion of ketone bodies from the blood back to acetyl-CoA E. Stored glycogen in the muscle

12. Though not included in the case, both men had elevated levels of the enzymes carnitine acyltransferase I and II. Why might the men have elevated levels of these enzymes? A. These enzyme levels rise after eating a carbohydrate-rich meal to aid in carbohydrate metabolism (glycolysis). B. Carnitine levels rise after eating and these enzymes are expressed to catabolize the extra carnitine. C. Both men are producing abnormally high levels of these enzymes as a side effect of utilizing amino acids for energy. D. These enzymes are elevated because both men are getting their energy primarily from β- oxidation and these enzymes are needed for fatty acids to be transported into the mitochondria. E. Likely both men have high levels of these enzymes because they are identical twins and share a genetic polymorphism.

13. Why is glucose a necessary fuel in the human body and what organs or cell types rely most heavily on glucose? A. Most human tissues cannot use glucose as an energy source. B. Glucose is necessary for the continued function of the Na+/K+ pump, and the brain is the only organ that uses glucose as an energy source. C. During exercise, the brain stops using glucose so that it can be used by the muscles. D. Glucose is necessary because it is used by almost all tissues for energy and biosynthesis, and the brain relies almost entirely on glucose as an energy source. E. Glucose is necessary because it is the only source of energy that can fully be oxidized to produce ATP, and the liver relies heavily on glucose as its sole energy source.

14. During their three-week, pre-marathon self-experiment, both Dave’s and Michael’s livers had to produce some glucose. Which of the following molecules could be used by the liver to create the glucose that is needed to supply the brain and other tissues in a healthy person on a normal diet? (Select ALL that apply) A. Pyruvate B. Lactate C. Glycerol D. Any citric acid cycle intermediate (this excludes acetyl-CoA!) E. Even-chain fatty acids F. Alanine G. Acetyl-CoA 8

15. Which of the following statements about even-chain fatty acids is/are FALSE? (Select ALL that apply) A. The product of the oxidation of even-numbered fatty acid chains is multiple acetyl groups bound to CoA molecules. B. Humans have all the appropriate enzymes necessary to use even-chain fatty acids as glucogenic precursors through their conversion to acetyl-CoA. C. A difference between even-chain and odd-chain fatty acids is that only odd-chain fatty acids produce propionyl groups bound to CoA. D. The products of the oxidation of an odd-numbered fatty acid chain are multiple 3-carbon propionyl groups bound to CoA. E. The products of the oxidation of an odd-numbered fatty acid chain are acetyl groups and a final propionyl group attached to CoA.

16. What is happening to Dave and Michael in regard to their metabolisms? (Select ALL that apply) A. Because the human body cannot create glucose from even-chain fatty acid oxidation, both runners are starving their bodies of glucose due to their restrictive diets. B. Most of their energy is coming from fatty acid oxidation, so ketone bodies are being produced to free up CoA for continued β-oxidation. C. The brothers have compromised immune systems because of a genetic disorder that affects their metabolism. D. Their diet high in fatty acids resulted in a large build-up of glycogen in their livers and muscles. E. Excessive fatty acid oxidation resulted in protein wasting, which led to acidification of the blood.

17. What are the functions of Asp aminotransferase (AST) and Ala aminotransferase (ALT)? And why are they elevated in Michael? A. These enzymes function in glucose catabolism, catalyzing the transfer of an amino group; levels of these enzymes would be elevated due to the excessive protein wasting occurring in Michael’s body to meet his need to produce glucose in the absence of other dietary gluconeogenic substrates. B. These enzymes function in fatty acid catabolism, catalyzing the transfer of a hydroxyl group; levels of these enzymes would be elevated due to excessive glycogenolysis occurring in Michael’s body to meet his need to produce glucose in the absence of other dietary gluconeogenic substrates. C. These enzymes function in protein catabolism, catalyzing the transfer of an amino group; levels of these enzymes would be elevated due to the excessive protein wasting occurring in Michael’s body to meet his need to produce glucose in the absence of other dietary gluconeogenic substrates. D. These enzymes function in protein catabolism, catalyzing the transfer of an amino group; levels of these enzymes would be elevated due to the excessive ketone body production that is occurring in Michael’s body to meet his need for energy sources in the absence of other dietary gluconeogenic substrates. E. These enzymes function in ketone body catabolism, catalyzing the transfer of an amino group; levels of these enzymes would be elevated due to the excessive ketone body production that is occurring in Michael’s body to meet his need for energy sources in the absence of other dietary gluconeogenic substrates.

18. Why are Michael’s blood ammonia levels elevated and why are high levels of ammonia dangerous? A. Ammonia levels in the blood are high due to the rapid degradation of proteins; high levels of ammonia lead to dangerous levels of ketone bodies in muscle. B. Ammonia levels in the blood are high because of burning calories from vigorous exercise; high levels of ammonia lead to dangerous levels of ketone bodies in muscle. C. Michael’s blood ammonia is high due to the rate of ketone body production in his body; high levels of ammonia are dangerous because ammonia passes easily through the blood-brain barrier and is highly toxic to the brain. D. Ammonia levels are high because it is a byproduct of β-oxidation of fatty acids; high levels of ammonia lead to dangerous levels of ketone bodies. E. Michael’s blood ammonia is high due to the rate of protein wasting (catabolism of non-essential proteins to provide glucogenic carbon skeletons) in his body; high levels of ammonia are dangerous because ammonia passes easily through the blood-brain barrier and is highly toxic to the brain.

19. What is/are the source(s) of the excessively high levels of ketone bodies in Michael but not Dave? (Select ALL that apply) A. Ketone bodies are being formed from catabolism of carbohydrates for energy metabolism. B. Ketone bodies are being formed as a byproduct of excessive glycogenolysis. C. Ketone bodies are being formed from ketogenic amino acids released from protein catabolism. D. Ketone bodies are being formed from the products of β-oxidation of fatty acids from both stored triglycerides and the ingested fish oil. E. Ketone bodies are being produced in Michael’s brain to provide energy for the liver. F. Michael is producing large amounts of ketone bodies because he is severely hypoglycemic and has likely been hypoglycemic for most of the past few weeks.

20. Why are the two twins experiencing such different symptoms? (Select ALL that apply) A. Michael probably has a genetic inborn error in metabolism that Dave does not. B. One brother is in much better shape for the run than the other because of training. C. Michael’s case is more severe because he relies on glycolysis (by way of lactic acid fermentation) for energy. D. Michael’s supplement has almost no odd-numbered fatty acids, so his body is undergoing more protein wasting, and producing dangerous levels of ketones. E. Dave’s case is milder because the supplement he is taking contains a significant amount of odd- numbered fatty acids, some of which may be used to produce glucose. F. The twins exhibit minor variations in metabolic adaptation to dietary changes based on their genetics.

21. Which of the following would likely be true if the brothers were NOT identical twins? A. Carnitine levels would be higher in Dave than in Michael. B. Their bodies would have used different sources of energy to respond to a long term run. C. They would not have overexerted their bodies because they would be less competitive if they were not identical twins. D. The brothers would have had the same amount of ketone production. E. It would be more difficult to determine the impact of diet in this case because there would have been a greater chance that their differing symptoms were due to genetic variation in metabolism.

22. What is causing Michael’s neurological issues and what is the cause of this problem? (Select ALL that apply) A. Michael is exhibiting the first signs of diabetes, trigged by the vigorous run. B. Michael has depleted his main stores of glucose and is therefore experiencing neurological effects from hypoglycemia. C. Michael has severe hypoglycemia and ketoacidosis because of metabolic failures, both which are known to affect mental status. D. As a result of excessive protein and amino acid degradation, Michael is also experiencing mild ammonia toxicity, which is likely exacerbating his neurological issues. E. Michael is experiencing side effects of extreme dehydration.

Summarize the following reading (Nutrient (zinc and vitamin E)-gene interactions related to inflammatory and antioxidant response in aging and inflammation) and it should be at least one paragraph (100-200 words) and include the following information:

* Main point of the reading

* Describe how the health deviations you read about alter normal physiology.

* Provide your key take away from the reading. This could be something that made you pause, changed your thinking, supported your thinking, or made you question something.

INTRODUCTION Aging is an inevitable biological process that is accompanied by gradual and spontaneous biochemical and physiological changes including increased susceptibility to diseases, adverse environmental conditions, and loss of mobility and agility. Alterations in neuroendocrine-immune interactions as well as in antioxidant capacity also play a fundamental role in aging. The inability of an organism to remodel these changes may lead to the appearance of some degenerative age-related diseases. As a result, the remodeling theory of aging has been proposed (1). Various nutritional factors are directly linked to these phenomena, as, for instance, in restoring the neuroendocrine-immune network, metabolic harmony, and the capacity to respond to oxidative stress (2). Approximately 40 micro nutrients (vitamins, essential minerals, and other compounds required in small amounts for normal metabolism) have been reported as essential components in the diet (3). The dietary intake of essential macro nutrients and micronutrients is usually inadequate in the elderly (4). Several causes contribute to this gap. First of all, the poor socio-economic conditions in which a large part of the older population live may lead to a consumption of inexpensive foods deficient in micronutrients, such as carbohydrates (5). The gap is worsened by the loss of appetite, lack of teeth, intestinal malabsorption, and decreased requirements for energy that lead finally to frailty, disability, and mortality (6). Some authors have reported that the deficiency of macro nutrients and micronutrients in aging is strictly related to global impairments of immune functions, metabolic harmony, and antioxidant defense by external noxae with subsequent appearance of age-related diseases (7). Indeed, many micronutrients contribute directly or indirectly to the biological activity of some antioxidant enzymes (e.g., SOD, GPx, and catalase) (8), to the efficiency of the immune system (9), and to the maintenance of metabolic function especially in preventing mitochondrial decay (4). In this last context, feeding studies in older rats have shown that mitochondrial metabolites and antioxidants protect neuronal cells from neurotoxin- and oxidant-induced toxicity and oxidative damage, delay the normal senescence of human diploid fibroblasts, and inhibit the oxidant-induced acceleration of senescence (10). With advancing age, increased oxidative damage to proteins and lipid membranes, particularly in mitochondria, causes a deformation of the structure of enzymes, with a consequent decrease in enzyme activity as well as substrate binding affinity for their substrates. An increased level of the substrate by micro nutrients restores the speed of the reaction as well as mitochondrial function, thus delaying mitochondrial decay and aging (10, 11). In contrast, recent longitudinal studies of dietary daily intake in human nonagenarians and centenarians (successful aging) have shown that an adequate consumption of micronutrients and macronutrients, as well as a satisfactory content of some trace elements within the cells, leads to good performance in several immune functions, metabolic compensation, and preservation of antioxidant activity (12, 13). In this context, polyunsaturated fatty acids, highly sensitive to reactive oxygen species, decrease in liver mitochondria from human centenarians, a feature acquired during evolution as a protective mechanism to favor longevity (14). Therefore, nutritional factors may play a pivotal role for healthy aging and longevity. However, the effects of the nutritional factors are strongly influenced by genetic factors, in particular by the genes involved in inflammatory/immune responses. Proinflammatory cytokines such as IL-1, IL-6, and TNF-α; the antiinflammatory cytokine IL-10; the HSP70 chaperones; and the regulators of trace element homeostasis, metallothioneins (MTs), seem particularly relevant, taking into account that the same genes are involved in the susceptibility to major geriatric disease/disorders such as diabetes, osteoporosis, osteoarthritis, dementia, cardiovascular diseases, and infections (15, 16). Indeed this reemphasizes that up to 25% of the variation in human life span is heritable (17); the rest is due to environmental and lifestyle factors, which impact the aging process, contributing as such to a large interindividual variability. Therefore, one current challenge is to understand how the interaction between genetic factors and nutrients may influence aging and longevity, in view of the high impact on gene expression, protein production, and epigenetic mechanisms implicated in regulating the life span (18). Some dietary patterns with likely different impacts on longterm disease occurrence and survival have been identified. In this context, strong evidence for a beneficial effect of higher conformity with the Mediterranean dietary pattern on causes of death, including those of cardiovascular diseases and cancer, has been reported (19). Anyway, it is also commonly accepted that the complex interactions of multiple polymorphisms play a key role in how individuals may respond to dietary interventions (20). For each nutrient, there is a window of intake between the recommended dietary allowance (RDA), which is defined as the dietary intake sufficient to meet the requirements of 97% of healthy individuals in a particular stage of life and sex group, and the tolerable upper limit (UL), which is the highest nutrient intake that can be achieved without incurring a risk of adverse health effects for most individuals in the general population (21). Although worldwide research on genetic variations that require a different RDA or UL is still in progress, several genes and alleles have been suggested to affect nutrient utilization, including genes involved in the metabolism of folate and vitamin B12 (22), vitamin E (23), lipids (24), iron (25), and zinc (26). In this last case, it is important to note that the RDA (11 mg/day for men, and 8 mg/day for women) and UL (40 mg/day for adults) for zinc are very close (Food and Nutrition Board and Institute of Medicine, 2001). Without excluding the beneficial effects of all of these nutrients for healthy aging and longevity (27), but taking into account the pivotal role played by zinc and vitamin E in fighting oxidative stress in aging and in some age-related diseases, such as atherosclerosis (23), we herein report the studies carried out on the interrelationships between zinc and some genes related to the inflammatory/immune response (such as MT and IL-6), as well as the interactions between vitamin E and the gene expressions related to inflammation. Clinical trials of zinc and vitamin E are also reported for their possible beneficial effects on longevity or in preventing the initiation and progression of cardiovascular diseases.

ZINC-MT GENE INTERACTION MTs MTs are essential to intracellular zinc homeostasis by sequestration and release of the metal when it occurs and thereby controlling available free zinc ions (28). The cysteine sulfur ligands in the cluster structure of MT can be reduced (zinc sequestration) or oxidized (zinc release), thus with concomitant changes in the relative amount of bound and free zinc (29). MTs are genetically polymorphous protein families with subfamilies, subgroups, and various isoforms. Humans possess genes for 4 subfamilies (encoded by at least 10 functional MT genes), all located on chromosome 16: the brainspecific MT3, the squamous epithelium–specific MT4, and the ubiquitous MT1 and MT2 (30). One of the first functions of MT1 and MT2 is to regulate zinc homeostasis and to limit oxidative damage within the cells (28). Following an injurious stimulus, such as a transient inflammation, the subsequent oxidative stress induces the release of zinc from MT via nitric oxide (NO), to promote the activity and expression of antioxidant enzymes, including MT itself, thus reducing the oxidative damage and the consequences of the injurious stimulus (31). However, the increased expression of proinflammatory cytokines occurring in aging, leads to increased expression of MTs, which in turn sequester considerable amounts of zinc, making it less available for an efficient immune response (32). If, on the one hand, the reduced zinc ion availability in old age might indicate an excessive sequestration of zinc ions by MTs, on the other, consideration of recent findings on oxidative modification of MTs leading to their loss of function suggests also a mechanism whereby these proteins can also lose their ability to buffer the intracellular free zinc concentration (33). In this case, MTs would be unable either to bind or to consequently release zinc in response to stressors. However, it is still unclear if dysfunctional MTs can be considered a typical alteration associated with specific disease/disorders, such as hyperhomocysteinemia and type 2 diabetes, or if they are a common feature of aging. Anyway, as a consequence of the altered zinc metabolism, a large number of genes that act as zinc sensors and transcriptional activators and/or repressors are also altered in aging (34). This may have a deep impact on the regulation of zincdependent transcription factors, because they not only regulate “zinc sensitive” genes but also control their own transcription through positive autoregulatory mechanisms (35). Taking into account that healthy centenarians display a low MT expression and satisfactory zinc ion availability despite increases in proinflammatory cytokines (IL-6, TNF-α) (36), it may be suggested that this feature reflects the existence of compensatory phenomena able to counteract the effects of inflammation in these exceptional individuals. Moreover, these data suggest that a preservation of zinc homeostasis is an important feature of healthy centenarians. Therefore, the role played by the zinc-gene interaction is pivotal to successful aging and, at the same time, to escape from some age-related diseases. Since, the persistence of inflammatory stimuli over time represents the biological background favoring susceptibility to age-related diseases/ disabilities, the absence of specific “robust” gene variants and/or the presence of specific “frail” gene variants might predict, on the one hand, longevity, and on the other, the predisposition to the appearance of the more common age-related diseases, such as infections and cardiovascular diseases. In this context, it has to be considered that the genes selected, because they confer a reproductive advantage early in life, may have dangerous effects in the postreproductive period. In fact, negative selection against these harmful effects fails due to the decline of natural selection with age. This fact means that one gene that is “favorable” in young/adult age may be “disadvantageous” in aging (the antagonistic pleiotropy theory of ageing (37)). Following this perspective, the beneficial effect of inflammation, via an optimal MFT-1-MT-zinc-gene interaction, in young and adult age may become detrimental in old age (32). The recent discovery of novel polymorphisms of MT2A and MT1A supports this assumption. Indeed, older subjects carrying the AA genotype for the MT2A polymorphism display low zinc ion bioavailability, chronic inflammation by high IL-6 and altered lipid assessments, with subsequent elevated risk for atherosclerosis and type 2 diabetes (38). By contrast, a polymorphism corresponding to an A/T (asparagine/ threonine) transition at the +647 nt position in the MT1A-coding region is the most often involved in female longevity (39). Such allelic variants may be very useful tools to screen older subjects at risk for zinc deficiency on a genetic basis, taking into account that the actual methodological procedures to test “zinc status” are often misleading and that laboratory investigations to assay zinc ion bioavailability are scarcely reproducible and poorly applicable to clinical practice (40). In this context, a novel reproducible system for testing intracellular zinc ion bioavailability has been developed using a zinc fluorescent probe (Zynpir-1) associated with MT values, with both tests representing valid methods to detect the intracellular zinc status (41).

ZINC–INTERLEUKIN-6 GENE INTERACTION Interleukin-6 (IL-6) is a pleiotropic cytokine capable of regulating proliferation, differentiation, and activity of a variety of cell types, and it plays a pivotal role in immune response. In particular, the most important function of IL-6 is most likely as a mediator of acute phase inflammatory responses. These include the balance of the proinflammatory/antiinflammatory pathways, lymphocyte activation, and hepatocellular stimulation of acute phase protein synthesis (42). Studies of the effects of aging on inflammatory response show IL-6 to be an important “cytokine for gerontologists”. Recent evidence has shown that abnormally increased concentrations of IL-6 are reliable markers for functional disability and predictors of disability and mortality among the elderly (43). Moreover, IL-6 dysregulation is involved in age-related inflammatory diseases, such as cancer, lymphoma, cardiovascular diseases, osteoporosis, Alzheimer’s disease, diabetes and atherosclerosis (44). The human IL-6 gene is located on chromosome band 7p21 and consists of 5 exons and 4 introns (45). Genetic studies have identified 4 polymorphisms in the Lattanzio et al 121 promoter region of the IL-6 gene (-597G/A, -572G/C, - 373A/T, -174G/C) that have a significant effect on IL-6 expression in an in vitro system (46). A variable number of tandem repeat (VNTR) polymorphisms were found in the 3’ flanking region of the IL-6 gene (C allele) (47). In humans, a polymorphism in the IL-6 promoter (A/C polymorphism at position -174) altered IL-6 gene transcription rates in vitro (48) and IL-6 levels in vivo (49). In this last paper, people carrying CC or GC genotypes are defined as C+, while those carrying GG genotypes are indicated as C-. It has been suggested that IL-6 -174G/C locus variability is capable of modulating, on the one hand, individual susceptibility to common causes of morbidity and mortality among elderly, while, on the other hand, it may play a crucial role in longevity (50). Therefore, the genetic variations of this locus of IL-6 gene are fundamental in the elderly population to better understand the intrinsic causes of the longevity. The association of these genetic variations to the possible, different immune responses is an attractive focus in elucidating the molecular mechanisms involved in immunosenescence. The genetic variations of the IL-6 -174G/C locus have been extensively studied by different groups with, however, contradictory data. Bonafè et al (51) studied IL-6 promoter genetic variability at the -174C/G locus and its effect on IL-6 levels in 700 Italians aged 60 to 110 years, including 323 centenarians. Individuals who are genetically predisposed to produce high levels of IL-6 during aging – i.e., C- men (GG genotype) – at the IL-6 -174C/G locus are disadvantaged for longevity. On the other hand, the capability of C+ individuals (CC and CG genotypes) to produce low levels of IL-6 throughout their life span appears to be beneficial for longevity, at least in men. Women have, conversely, high IL-6 serum levels later in life with respect to men, independently of -174C/G locus polymorphism (51). The inhibitory tone of estrogens on IL-6 gene expression could explain the sex-based difference (52), assuming that its long-term effects last until the extreme limits of the human life span. The major production of IL-6 in C- subjects for their whole life, including centenarians, has also been confirmed by other in vivo longitudinal studies (53). A more recent study in older and nonagenarian subjects has confirmed that IL-6 production is higher in C- carriers and that these subjects are prone to contract one of the more common age-related inflammatory pathologies such as atherosclerosis (54). Interestingly, in this last study, C- older and nonagenarian subjects also display impaired innate immune response (NK cell cytotoxicity) coupled with increased MT, zinc deficiency, and low zinc ion availability, in comparison with C+ carriers (54). A functional effect of the IL-6 -174G/C locus on MT expression and zinc-regulated genes has also been confirmed recently by targeted studies with in vitro and in vivo zinc supplementation (55, 56). These findings clearly suggest that the genetic variations of the IL-6 -174G/C locus play a key role in longevity also at a functional level, and confirm the existence of a higher number of C+ centenarians than C– ones as previously found by Bonafè et al (51). In this context, an intriguing point is the low expression of the signal-transducing component (gp130) of the IL-6 receptor in centenarians, in comparison with the elderly, despite high circulating levels of IL-6 (57), which in turn may be inactive in centenarians (36). Therefore, inflammatory status is not so detrimental in very old age, as, in contrast, occurs in normal aging. However, the discrepancies among all of the genetic studies on the variations of the IL-6 -174G/C locus in relation to longevity in the elderly means that the subject is still unclear. Ethnic, lifestyle, and cultural differences among these populations could also play a role, as well as other undefined factors. Large-scale studies at the European level in many different ethnic populations are needed to clarify this important topic. For this reason, ZINCAGE project (www.zincage.org) has been developed, and the clarification of this point has been one of is tasks. The determination of the genetic variations of the IL-6 - 174G/C locus associated with a dietary assessment or with a comprehensive evaluation of zinc status has been reported as an useful strategy to identify older subjects who can benefit from zinc supplementation without health risks (see next paragraph).

ZINC SUPPLEMENTATION IN THE ELDERLY ON THE BASIS OF GENETIC BACKGROUND One possible cause of the discrepancies existing in the literature on the effect of zinc supplementation upon immune response and antioxidant performance in the elderly (see review in (58)) may be the choice of older subjects who effectively need zinc supplementation in strict relationship with dietary habits and inflammatory status. This fact is supported by the discovery that older subjects carrying GG genotypes (i.e., C- carriers) in the IL-6 -174G/C locus display increased IL-6 production, low intracellular zinc ion availability, and impaired innate immune responses coupled with enhanced MT (56). By contrast, older subjects carrying the GC and CC genotypes (C+ carriers) in the same IL-6 -174 locus display satisfactory intracellular zinc as well as innate immune responses. But, the more intriguing finding is that males carriers of the C+ allele are more likely to reach centenarian age than C- carriers. Therefore, older C- subjects are more likely to benefit from zinc supplementation than older C+ carriers. The distribution of the IL-6 -174 genotype is very different among the various European countries, with large differences between northern and southern European countries (58). Zinc supplementation in older C- subjects restores NK cell cytotoxicity to values present in older C+ carriers and considerably improves both zinc status, assessed by the percentage increment of granulocyte Zn (56), and stress response, assessed by the percentage increment of clusterin (CLU) expression and MT protein (58). When the genetic variations for the IL-6 polymorphism are also associated with the genetic variations of MT1A in position +647, the plasma zinc deficiency and the altered immune response are more evident (58), suggesting that the genetic variations of IL-6 and MT1A would be very useful tools for the choice of older people who effectively need zinc supplementation. These results open the hypothesis that the daily requirement for zinc might be different in elderly with a different genetic background. Such a role played by genetic background on the beneficial effects of zinc supplementation is also evident in the better control of proinflammatory cytokine and chemokine production (59), as well as in reducing the expression of genes related to inflammatory status, such as IL-1 and its receptor (55). A very intriguing point is also the beneficial effect of zinc supplementation in the cognitive performance of older individuals selected on the basis of IL-6 polymorphism (60). In any case, from a microarray analysis in vitro, zinc at a dose of 50 mM down-regulates the gene expression of proinflammatory cytokines (Fig. 1), strengthening its antiinflammatory role (56, 58).

Fig. 1 - In vitro zinc treatment (50 µM) down-regulates proinflammatory cytokine expression (custom array) when refereed to the value 1 (baseline control) in human peripheral blood mononuclear cells from young adult donors. The red square represents the proinflammatory cytokines (IL-6, IL-1, and TNF pathways). Data redrawn from the Zincage Project (www.zincage.org) (61).