TYPE 2 DIABETES MELLITUS CASE: Wilma Williams, a 48-year-old woman presented to the emergency room with exhaustion, vomiting, and lower abdominal cramps. She had been on a starvation diet and had lost 11 pounds over the last 12 days. She started noticing the symptoms about 3 days ago. The last two nights she has had night sweats and chills. She has been obese since the age of 22. There is no known history of diabetes or hypertension. She has had three births that were normal. Her son is 20 and her two girls are 18 and 16. Height, 5 ft 6 in; Weight, 190 lbs; Blood pressure, 130/88 mm Hg; Pulse, 98 beats/min; Respiration rate, 16/min; Temperature, 101 Fo: Acetone breath but good oral hygiene: Slight costovertebral angle tenderness. Normal: Neck, Heart, Lungs, Extremities, CNS, Pelvic and Rectal examinations. You order the following tests: LABORATORY RESULTS FROM SERUM (S) ARTERY (A) and URINE (U) - WILMA'S VALUES REFERENCE RANGE - WILMA'S VALUES REFERENCE RANGE pH (A) 7.4 7.38 - 7.44 Creatinine (S) 0.8 mg/ dL 0.7 - 1.5 mg/ dL pO2(A) 96 mm Hg 75 - 100 mm Hg GLUCOSE (S) 400 mg/ dL 70 - 105 mg/ dL pCO2(A) 35 mm Hg 35 - 45 mm Hg Glucose (U) ++++ Negative Hemoglobin 13 g/ dL 12 - 16 g/ dL  Ketones (U)  ++++ Negative  Blood Urea Nitrogen 23 mg/ dL 5 - 25 mg/ dL  Albumin  ++ Negative  Her chest X-ray and ECG were normal.

EXPLANATION OF OBJECTIVES I Answering these objectives should result in an overview of glucose tolerance, insulin resistance, and insulin production in normal people and people with type 2 diabetes. [The instructor should bring a copy of Figure 58-2, p822 from deGroot for this objective.] IA. Is type 2 diabetes a disease because the B-cells of the pancreas do not release enough insulin, either absolute or relative to the level of blood sugar, or because liver, adipose, muscle and other cells are resistant to insulin, or both? Answer: Both! Type 2 diabetics may have very high blood insulin levels early in the progress of their disease, before or at the time of diagnosis, and they may have insulin in the normal range for the first 10 to 15 years after diagnosis, but their level of insulin is never high enough for the level of blood glucose present. That is, they always have either a relative or absolute imparment of glucose release. Type 2 diabetics all have insulin resistance. References: http://www.mdconsult.com; Wilson: Williams Textbook of Endocrinology, 9th ed., W.B. Saunders Company; 1998 www.mdconsult.com; Goldman: Cecil Textbook of Medicine, 21st ed. 2000; DeGroot, Leslie; Jameson, Larry; Endocrinology; W.B. Saunders Company; 2001; pg 821-822 Porte, Daniel M.D., Sherwin, Robert M.D., Ellenberg and Rifin's Diabetes Mellitus; 5th ed. Appleton & Lange; 1997; pg 736 IB. What is meant by the terms glucose tolerance and glucose intolerance ? Using words or a graph, explain the levels of blood glucose you would anticipate to find in Wilma's blood (a typical person with type 2 diabetes) at the point in time when the diagnosis could have been made, fifteen years after the diagnosis was made, and fifteen years before the diagnosis was made. (NOTE! You must assume that the patient was not being treated for the disease at the time the measurments were made.) Was Wilma glucose tolerant at each of these times? Answer. Glucose tolerance is the ability to metabolize glucose in a normal fasion. It is usually measured using fasting (12 hour) glucose. Post-meal glucose is sometimes used. Fifteen years before reaching 126 mg per dL, all blood glucose measurements would be normal so Wilma was tolerant. At the time of diagnosis, the bood glucose would be126 mg/dL (New ADA Standard) so Wilma would be intolerant. For the rest of the Wilma's life, her blood glucose levels would rise and she would be glucose intolerant. References: Kahn, C. Ronald, Weir, Gordon; Joslin's Diabetes Mellitus; Williams and Wilkins, PA 1994; pg 194-197 Porte, Daniel M.D., Sherwin, Robert M.D., Ellenberg and Rifin's Diabetes Mellitus; 5th ed. Appleton & Lange; 1997; pg 736 www.mdconsult.com; Goldman: Cecil Textbook of Medicine, 21st ed. 2000; IC. What is meant by the term insulin resistance? Using words or a graph, compare the levels of Wilma's insulin resistance 10 years before becomming diabetic, when blood glucose levels reached 126 mg/dL, and 15 years later. Answer. Insulin resistance is a state in which a given concentration of insulin produces a subnormal biological response. Most commonly, it refers to diminished effectiveness of insulin in lowering blood sugar levels, but it is just as important in all other types of metabolism. It is arbitrarily defined as requiring 200 units or more of insulin per day to prevent hyperglycemia or ketosis. The molecular explanation(s) for insulin resistance in type 2 diabetes remains unknown but it almost surely involves some of the pathways of metabolism. It is not known whether typical type 2 diabetics have normal insulin resistance early in life. It is known that one can measure insulin resistance 10 to 15 years prior to the time their blood sugar reaches 126 mg/dL. Insulin resistance increases steadily until fasting blood sugar is about 126 mg/dL and then remains steady for the rest of the patient's life. References: 1. Harrison's Online, Chapter 334; keyword: INSULIN RESISTANCE. 2. Williams Textbook of Endocrinology, 3rd Edition, p. 133. 3. DeGroot: Endocrinology, 3rd Edition, pp. 1441-1453. ID. Define impaired glucose tolerance. Before being diagnosed as having type 2 diabetes, did Wilma go through a period where she had .impared glucose tolerance? Was Wilma insulin resistant during this time? Compare Wilma's insulin output when she had impaired glucose tolerance with the insulin output of normal people in response to a glucose load. Answer. Persons having a fasting blood glucose between 110 and 126 mg/dL have impaired glucose tolerance according to the ADA. Yes, Wilma had impaired glucose tolerance as do all persons who develope type 2 diabetes. Yes, Wilma had insulin resistance. In response to insulin resistance or increased blood glucose, Wilma responds by releasing much more than a normal person, but not enough insulin to bring her blood sugar levels to normal. The impaired person never makes enough insulin in relation to the level of blood glucose. References: 1. Behrman: Nelson Textbook of Pediatrics, 16th Edition, pp. 1787-8. 2. Rosen: Emergency Medicine: Concepts and Clinical Practice, 4th Edition, p. 2458; MDConsult keywords: GLUCOSE TOLERANCE, IMPAIRED IE. How will Wilma's insulin production in response to a glucose load change from around the time of being diagnosed as a type 2 diabetic throughout the rest of her life. Answer. The reason Wilma became diabetic was because her B-cells could no longer increase their output enough to keep pace with the increased insulin resistance and decreases for the rest of her life. References: 1. Robbins Pathologic Basis of Disease, 6th Edition, p. 917; MDConsult keywords: TYPE 2 DIABETES, PATHOGENESIS. 2. DeGroot's Endocrinology, 3rd Edition, p. 1437. IF. Sulfonylureas such as Glipizide are used to treat type 2 diabetics. If you gave this drug to Wilma, what cell type(s) would be targated by the drug and what would be the beneficial result? What is the mechanism of action of the drug? Answer: Sulfonyureas enhance insulin secretion by B-cells. They bind to specific receptors on the B-cells which results in the inhibition of the potassium channels. These are the same channels that are sensitive blood glucose via ATP. Inhibition of these channels results in depolarization of the membrane, activation of calcium channels, and fusion of insulin granules with the cell membrane. Fasting blood glucose can be lowered by about 60 mg/dL. Eventually, Wilma will need to be switched to insulin because her cell will stop responding. References: 1. Wilson: Williams Textbook of Endocrinology, 9th Edition, pp. 1036-7; MDConsult keyword: SULFONYLUREA. 2. Katzung's Basic Clinical Pharmacology, 8th Edition, pp. 723-727. IG. The biguanide Metformin is given to type 2 diabetics like Wilma. State the principal target tissues of the drug and the affect that the drug has on the tissues. If you can find a mechanism of action for the drug, so much the better. Answer: Metformin enhances insulin sensitivity, primarily in the liver but also in muscles and adipose tissue, i.e., it decreases insulin resistance of the tissues. It can lower bood glucose in the fasting state by approximately 60 mg/dL. It also lowers blood triglycerides, LDL-cholesterol, and free fatty acids. [???Since it acts primarily on liver, Metformin would be most useful during fasting since overproduction of glucose is the cause of hyperglycemis at this time.???] References: 1. Katzung's Basic Clinical Pharmacology, 8th Edition, pp. 727-8. 2. Goroll: Primary Care Medicine, 4th Edition, p. 635 only; MDConsult keyword: BIGUANIDE IH. Thiazolidinediones like Pioglitazoneare and Rosiglitazone are given to type 2 diabetics like Wilma. For either Pioglitazoneare or Rosiglitazone, state the principal target tissues of the drug and the affect that the drugs has on the tissues. If you can find a mechanism of action for the drug, so much the better. Answer: Pioglitazone and Rosiglitazone primarily enhanse insulin sensitivity (i.e., make less insulin resistant) of muscle and adipose tissue and also have some affect upon liver. They bind to a family of nuclear receptors called "peroxisome proliferator-activated receptor (PPAR-gamma and PPAR-alpha)." Binding enhanses the expression of multiple genes encoding proteins which modulate glucose and to some degree, lipid metabolism. Both drugs lower blood sugar and also have an affect upon blood lipids. [???Since thses drugs act principaly on muscle and adipose tissue, they would have a major effect during the post prandial time when the entrance of glucose into muscle is the principal cause of hyperglycemia.???] References: 1. Katzung's Basic Clinical Pharmacology, 8th Edition, pp. 728-9. 2. Goroll: Primary Care Medicine, 4th Edition, p. 635-636; MDConsult keyword: THIAZOLIDINEDIONE

EXPLANATION OF OBJECTIVE II This objective is to understand the synthesis of insulin and glucagon and how their release is controlled. IIA. Draw or find a cartoon demonstrating the pathway for the biosynthesis of insulin in a B-cell. Include mRNA, ribosomes, endoplasmic reticulum, preproinsulin, signal peptide, signal peptidase, golgi, mature insulin granule, prohormone converting enzymes, insulin, zinc, and C peptide in your explaination. References: 1. DeGroot's Endocrinology, 3rd Edition, p. 1303 IIB. Glucose is the most effective insulin secretagogue. Explain the sequence of events whereby increases in blood glucose cause increases in insulin release from B-cells of the pancreas. Include the synthesis of ATP, the affect of ATP on potassium channels, the affect of potassium ions upon calcium channels, and the affect of intracellular calcium upon fusion of the insulin granule with the membrane. Answer. Increased glucose causes increases in glucose-6-P formation, glycolysis, TCA cycle activity and ATP formation by oxidative phosphorylation. Increased ATP inhibits ATP sensitive postsssium channels, depolariization of the cell membrane, and activation of a voltage sensitive calcium channel. The resultant increase in intracellular calcium activates the secretory machinery which eventually causes fusion of the insulin granules with the cell membrane. References: 1. DeGroot's Endocrinology, 3rd Edition, p. 1309. IIC. As a group, how would the gastrointestinal peptide hormones cholecystokinin, glucose-dependent insulinotropic peptide, and glucagon-like peptide-1 effect the release of insulin? When would they be most active? How about dietary amino acids like leucine, arginine and lysine, i.e., how would they affect the release of insulin and when would this be important. How about epinephrine and alpha-adrenergic antagonists? Answer Insulin secretory response is greater following oral as opposed to intravenous glucose administration. [This is called the incretin effect.] The gastrointestinal peptide hormones cholecystokinin, glucose-dependent insulinotropic peptide, and glucagon-like peptide-1 are released from the gut postprandially following exposure to glucose. They travel in the blood to the B-cells where they act through second messengers to increase the sensitivity of the cells to glucose. [They are NOT themselves secretagogues and their effects are evident only in the presence of hyperglycemia. Leucine, arginine and lysine from a protein meal will cause an increase in insulin release from B-cells. [The release is independent from that caused by glucose.] The mechanism is not known. This would be most important after a high protein meal. Epinephrine inhibits insulin release in response to glucose and other agents and, thus, causes a decrease in blood insulin levels. Alpha-adrenergic antagonist abolish the inhibitory effect of epinephrine. [This implicates alpha-receptors]. This would be important during times of stress, including during hypoglycemia. References: 1. Hasegawa H - Metabolism - 1996 Feb; 45(2): 196-202: Oral glucose ingestion stimulates cholecystokinin release in normal subjects and patients with non-insulin-dependent diabetes mellitus; 2. Zhou J - Diabetes - 1999 Dec; 48(12): 2358-66 Glucagon-like peptide 1 and exendin-4 convert pancreatic AR42J cells into glucagon- and insulin-producing cells. MDConsult keywords: CHOLECYSTOKININ, INSULIN RELEASE. 3. Strandgaard C - Pancreas - 1998 Jul; 17(1): 65-71 Differential insulin secretory responses to cationic and branched-chain amino acids. MDConsult keywords: INSULIN RELEASE, LEUCINE, LYSINE, ARGININE. 4. Pourmotabbed G - Obstet Gynecol Clin North Am - 2001 Jun; 28(2); 383-400 HYPOGLYCEMIA; MDConsult keywords: EPINEPHRINE, INSULIN RELEASE IID. What is the half-life of insulin in solution administered intravenously? How does this compare to the half-life of most other protein hormones? How does the half-life for protein hormones in general compare to the half-lives for steroid hormones and thyroxine? Answer. Around three minutes but as long as 8 minutes have been reported. Half-lives for protein hormones are usually measured in minutes. The half-life for steroid hormones is measured in hours or days and for thyroxine the half-life is measured in weeks. References: 1. Guyton & Hall's Textbook of Medical Physiology, 10th Edition, p. 885. 2. Cecil's Textbook of Medicine, 21st Edition, p. 1185; MDConsult keywords: HALF-LIFE, PEPTIDE HORMONE IIE. Which tissues are responsible for removing (clearing) circulating insulin ? What happens to the insulin molecule? Answer. Most insulin, about 60 to 80%, is inactivated by the liver. Another 10 to 30% by the kidney. Some studies have shown that between 40% and 60% of the insulin reaching the liver is removed by the liver (The 60% removal was for fasting conditions). The kidney extracts about 30 to 40% of the insulin passing through it. Many other cell types have the ability to bind, internalize, and degrade insulin but they account for a very low percentage of total degradation. Insulin binds to receptors on the hepatocytes and much of it is internalized. The polypeptide chain is hydrolyzed to amino acids. References: 1. Guyton & Hall's Textbook of Medical Physiology, 10th Edition, p. 885. 2. Cecil's Textbook of Medicine, 21st Edition, p. 1265; MDConsult keywords: INSULIN, METABOLISM. IIF. What is the effect of the the following upon upon the release of glucagon: Insulin? Dietary proteins containing arginine, glutamine and alanine? Epinephrine and norepinephrine as a result of stress or exercise? Increased gastrointestinal hormones like cholecystokinnin and gastric inhibitory peptide? Hypoglycemia? Answer: 1. Insulin has a major inhibitory effect upon the release of glucagon. 2. Argenine, glutamine, alanine, and protein in general increases the release of glucagon. 3. Epinephrine and norepinephrine both increase the relaeas of glucagon.[Autonomic stimulation of the pancreas will also cause glucagon to be released.] 4. Gastrointestinal hormones increase the rate of glucagon release. 5. Hypoglycemia will increase glucagon release in normal people. [Both alpha and beta-adrenergic receptors stimulate the release of glucagon.via protein kinase A enhancement of calcium ion influx through L-type calcium channels. The increased intracellular calcium initiates the process of granule exocytosis.] References: 1. Goldman: Cecil Textbook of Medicine, 21st Edition, pp. 1265-1266; MDConsult keywords: GLUCAGON, INSULIN. 2. DeGroot's Endocriology, 3rd Edition, p. 1342. 3. Williams' Textbook of Endocrinology, 9th Edition, pp. 696-7; MDConsult keywords: GLUCAGON, EPINEPHRINE. 4. DeGroot's Endocrinology, 3rd Edition, p. 1343. 5. Williams' Textbook of Endocrinology, 9th Edition, pp. 950-2.

EXPLANATION OF OBJECTIVE III: Compare and contrast the blood levels and tissue utilization of glucose, amino acids, fatty acids, and ketone bodies during starvation, illness, and type 2 diabetes. Also, what are the relative blood levels of insulin, glucagon, catecholamines, and cortisol during these states? IIIA. What is the effect of a crash diet on the concentration of blood glucose in a normal person? Draw a graph showing the change in blood glucose for 4 weeks following a high carbohydrate meal! Could a crash diet explain Wilma's increase in blood glucose? Would the rate of glucose utilization change with time during a crash diet in a normal person? Answer. The concentration of glucose would drop to about 68 mg/dlL (3.8 mM) at three days. This is at or just below the lower limit for normal blood glucose depending upon which definition for "normal blood glucose" you are using. Blood glucose then drops very slowly so that at 5 weeks it is about 64 mg/dL (3.6 mM). Blood glucose is not high during starvation so starvation would not explain Wilma's hyperglycemia. Even though blood glucose remains rather steady in a starving person, the use of blood glucose decreases. If it didn't, we would use our protein stores in approximately 2 weeks. References: 1) www.teaching-boimed.ac.uk/student_projects/2000/mnby7012/secretion_diagram.htm 2) Stryer, BIOCHEMISTRY, 4th ed, pp.776 3) Search on MDconsult....Wilson: William's Endocrinology 4) Degroot, Endocrinology, pp738 IIIB. What happens to the concentrations of insulin, glucagon, cortisol, epinephrine and norepinephrine during a 4 week fast following a high carbohydrate meal? Would you expect the blood levels of glucagon, epinephrine, and cortisol to be of much help in differentiating between starvation and type 2 diabetes with illness? Answer. Insulin concentration would first increase and then decrease dramatically too near the fasting state by approximately 4 to 6 hours. Next, there would be a slow decrease in insulin over the next 4 weeks. Glucagon, it's release being inhibited by insulin, would have it's blood concentration decreased dramatically following a high carbohydrate meal. Next, as the insulin concentration dropped, glucagon's concentration would rise too near the fasting value. Next, there would be a slow rise in the concentration over the next 4 weeks. The concentration of epinephrine, norepinephrine and cortisol would not be effected by the carbohydrate meal but would rise slowly and steadily over the next 4 weeks. Starvation, illness and diabetes all result in an increase in stress hormones (glucagon, cortisol, epinephrine, etc.) so I would not expect differences. We did not ask about insulin! Early in the disease, Wilma might have high to normal insulin so there might be a study out there somewhere showing a difference but I would guess this measurment would not be helpful. References: 1) www.teaching-boimed.ac.uk/student_projects/2000/mnby7012/secretion_diagram.htm 2) William's Textbook of Endocrinology, pp701 used MDCONSULT search "starvation" 3) Porterfield, Endocrine Physiology, 1997, pp95-96 IIIC. What is the effect of a crash diet on the concentration of free fatty acids in a normal person? Add this data to the graph for blood glucose with time. What happens to the rate of utilization of free fatty acids for fuel over this 4 week period? Answer. According to the student's text, the blood concentration of free fatty acids doubles during the first 3 to seven days and remains fairly constant after that. However, after a high carbohydrate meal , the free fatty acid concentration is about 0.14 mM and this fises to 1.2 mM in three days and 1.4 mM in five weeks. [The continued rise in ketone bodies after about the third day is due to decreased utilization in a normal person.] The rate of free fatty acid utilization increases dramatically over the first two days, and perhaps, causes the decrease use of glucose. After the initial rise in fatty acid utilization, there is a decrease over the 4 week period because of a slow down in metabolism in general. It spares the use of glucose in muscle and many other tissues. Also, by being converted to ketone bodies, it eventually supplies about 50% of the energy to the brain. References: DeGroot, Leslie; Jameson, Larry; Endocrinology; W.B. Saunders Company; 2001; pg 643 Http://www.mdconsult.com; Feldman: Sleisenger & Fordtran's Gastrointestinal and Liver Disease; 6th ed; 1998 IIID. Use your graph to show the change in ketone bodies for 4 weeks following a high carbohydrate meal! What happens to ketone body utilization by muscle and brain during this time? Could Wilma's fast explain her ketonuria? Answer: Ketone bodies increase dramatically during the first 7 to 10 days. As the concentration of ketone bodies rises dramatically, they supply a much greater percentage of energy to muscles. However, after about 2 weeks muscle starts to favor the use of fatty acids over ketones and thus spares the ketones for brain. After about 48 hours, the brain induces enzymes needed for catabolism of ketones. After that, the use of ketones steadily increases until they supply approximately 50% of the brains energy. Yes! Starvation could explain Wilma's ketonurea. Also, diabetes and stress could explain Wilma's high ketone bodies. [All three states have high glucagon to insulin ration and low malonyl CoA.] References: http://www.mdconsult.com; Goldman: Cecil Textbook of Medicine, 21st Ed; W.B. Saunders Company; 2000; pg 1150 DeGroot, Leslie; Jameson, Larry; Endocrinology; W.B. Saunders Company; 2001; pg 643; pg 752-753; pg 908

EXPLANATION OF OBJECTIVE IV: For each of the following questions, compare Wilma with a normal patient. Assume that both are at rest, that stress is minimized, and that they have just finished a high carbohydrate meal.  IVA. The postprandial production of insulin by the pancreas in absolute terms (high, normal, low) and in relation to the blood levels of glucose. Would you guess that glucagon would be higher than normal in relation to the levels of blood glucose? Answer. In absolute terms, insulin levels might initially be above normal if the diagnosis of type 2 diabetes is made very early in the progress of the disease but will usually be normal by the time of diagnosis. After many years, insulin levels will fall below normal. Remember that during impaired glucose tolerance, blood glucose was kept normal by hypersecreton of insulin. The transition from impaired glucose tolerance to frank type 2 diabetes occurs because of a decrease in B-cell function, i.e., a droop in insulin output. In relation to the concentration of glucose in the blood, the beta-cells of type 2 patients are less responsive to the combination of neural stimulation, gut hormones, and blood glucose. The result is that the timing of the insulin response is delayed in the diabetic and the amount of insulin response to any given blood glucose level is lower in the type 2 patient. Since the major control of glucagon release is insulin concentration, a decrease in insulin with respect to blood glucose usually results in an inappropriately high glucagon concentration with respect to blood glucose. References: DeGroot, Leslie; Jameson, Larry; Endocrinology; W.B. Saunders Company; 2001; pg 730-732; pg 778-779 http://www.mdconsult.com; Wilson: Williams Textbook of Endocrinology; 9th ed; W.B. Saunders Company; 1998; pg 989 http://www.mdconsult.com; Goldman: Cecil Textbook of Medicine, 21st Ed.; W.B. Saunders Company; 2000; pg 1268 IVB. The contribution of the insulin to glucagon ratio to the uptake or production of glucose by the liver due to glycogen synthesis or degradation (This is in addition to the direct control of glucose over these processes). Include second messenger systems, key pathways, and control enzymes. Answer. At any given time following ingestion of the meal, the insulin to glucagon ratio would be lower in the type 2 patient. Thus, the switch from glycogenolysis to glycogen synthesis would be slower to occur. Also, the switch from glycogen synthesis to glycogenolysis should happen earlier as one enters the fasting state. Two known mechanisms could explain this. The first mechanism would be the effect of insulin and glucagon on the cyclic-AMP cascade which results in the activation of protein kinase A. Protein kinase A in turn activates glycogen phosphorylase kinase and glycogen phosphorylase and, at the same time, inactivates glycogen synthetase. The cascade also inhibits phosphoprotein phosphatase. In addition, the insulin cascade directly activates glycogen kinase-3 which inturn phosphorylates and activates glycogen synthase. References: DeGroot, Leslie; Jameson, Larry; Endocrinology; W.B. Saunders Company; 2001; pg 731-732; Pg 909-910 http://www.mdconsult.com; Wilson: Williams Textbook of Endocrinology, 9th ed.; W.B. Saunders Company; 1998; pg 1003 IVC. The contribution of the insulin to glucagon ratio to the uptake or production of glucose by the liver due to glycolysis or gluconeogenesis. Include second messenger systems, key pathways, and control enzymes. Answer. At any given time following ingestion of the meal, the insulin to glucagon ratio would be lower in the type 2 patient. Thus, the switch from gluconeogenesis to glycolysis would be slower to occur. Also, the switch from glycolysis to gluconeogenesis should happen earlier as one enters the fasting state. This would result in the liver contributing to the high blood glucose instead of using blood glucose as it should. The mechanism would be the effect of insulin and glucagon on the cyclic-AMP cascade. A more active cAMP cascade decreases phosphokinase-2 and increase fructose-2,6-bisphosphatase. This, in turn, would decrease the concentration of fructose-2,6-bisphosphate which would remove the activation of phosphokinase-1 and the inhibition of fructose-1,6-bisphosphatase. These are the control enzymes for glycolysis and gluconeogenesis respectively. References: DeGroot, Leslie; Jameson, Larry; Endocrinology; W.B. Saunders Company; 2001; pg 909-910, Figure 65-2 http://www.mdconsult.com; Wilson: Williams Textbook of Endocrinology, 9th ed.; W.B. Saunders Company; 1998; pg 1003 IVD. The post prandial action of insulin on the uptake of glucose by skeletal muscle. Include a biochemical mechanisms if possible. Answer. The insulin rises slower than normal and never reaches the level that would be reached in a normal person for a given level of blood glucose. In addition, the muscle cells are insulin resistant. The relative deficiency in insulin and the resistance of skeletal muscle result a slower rate of uptake, i.e., less utilization of glucose by muscle. [This is the major cause of hyperglycemia following a meal.] Type 2 diabetics have receptor defects (less receptors) and post receptor defects that make the utilization of glucose occur to a lesser degree. It is known that there are less Glut-4 transporters in the muscle membrane of type-2 diabetics so this acounts for at least some of the problem. The defect might be in any of the kinases and phosphatases that affect the insulin second messenger cascade. References: Cotran: Robbins Pathologic Basis of Disease, 6th ed.; W.B. Saunders Company; 1999; pg 918 http://www.mdconsult.com; Goldman: Cecil Textbook of Medicine, 21st Ed., W.B. Saunders Company; pg 1268 http://www.mdconsult.com; Wilson: Williams Textbook of Endocrinology, 9th ed., W.B. Saunders Company; pg 1008-1009 IVE. The uptake of free fatty acids from VLDLs in adipose tissue. The uptake of glucose in adipose tissue. The mobilization of free fatty acids from adipose tissue. Name the key enzymes or transport systems activated or inhibited by insulin. Explain the mechanisms if they are known. Answer: Because of insulin resistance, insulin will be less effective in activating lipoprotein lipase in a person with type 2 diabetes. Thus, type 2 diabetics will be less effective in converting VLDLs into LDLs and will take in less free fatty acids. Because of insulin resistance, type two diabetics are less effectuve in removing glucose and producing glycerol-3-phosphate for triacylglycerol synthesis. The ratio of insulin to glucagon, epinephrine, ACTH, and other hormones is the major determinant of hormone sensitive lipase activity. Because of insulin resistance, hormone sensitive lipase is more active than it should be and more free fatty acids will be mobilized than normal. References: http://www.mdconsult.com; Wilson: Williams Textbook of Endocrinology, 9th ed., W.B. Saunders Company; pg 1008-1009 http://www.mdconsult.com; Goldman: Cecil Textbook of Medicine, 21st ed.; W.B. Saunders Company; pg 1091 DeGroot, Leslie; Jameson, Larry; Endocrinology; W.B. Saunders Company; 2001; pg 910 Ganong, William F.; Review of Medical Physiology; Lange Medical Books; McGraw-Hill; 1997; pg 292-293; pg 326-329 IVF. The postprandial action of insulin and glucagon on the uptake of glucose by the brain. Answer. The brain uses the same amount of glucose no matter what the ratio of blood insulin to blood glucagon. Neither hormone has an effect on the rate of blood glucose uptake by the brain. References: http://www.mdconsult.com; Goldman: Cecil Textbook of Medicine, 21st ed.; W.B. Saunders Company; pg 2097 DeGroot, Leslie; Jameson, Larry; Endocrinology; W.B. Saunders Company; 2001; pg 742 Ganong, William F.; Review of Medical Physiology; Lange Medical Books; McGraw-Hill; 1997; pg 320-322

EXPLANATION OF OBJECTIVE V:  For each of the following questions, compare a non-insulin-dependent diabetic with a normal patient. Assume that both are at rest, that stress is minimized, and that they have just finished an overnight fast. VA. The fasting production of insulin and glucagon by the pancreas. Answer. The beta-cells of the type 2 patients are less responsive to the combination of neural stimulation and blood glucose. The result is that the production of insulin in response to any given blood glucose level is lower in the type 2 patient. Since the major inhibitor of glucagon release is insulin concentration, a decrease in insulin with respect to blood glucose usually results in an inappropriately high glucagon concentration with respect to blood glucose. References: 1) Harrison's online, search "fasting" chapter 335: Hypoglycemia 2) http://home.mdconsult.com/das/book/body/31403568/882/189.htm 3) Stryer, Biochemistry, 4th ed, pp740 VB. The contribution of the insulin to glucagon ratio to the production of glucose by the liver due to glycogen degradation. Include second messenger systems, key pathways, and control enzymes. Answer. The insulin to glucagon ratio would be lower in the type 2 patient. Thus, glycogenolysis would be occurring at an increased rate. So, the contribution of glycogenolysis would be greater in the diabetic. One mechanism would be the effect of insulin and glucagon on the cyclic-AMP cascade which results in the activation of glycogen phosphorylase by glycogen phosphorylase kinase and the inactivation of glycogen synthetase by protein kinase A. References: 1) Stryer, Biochemistry, 4th ed, pp574, 779-780 2) Harrison's online, chapter 335-Hypoglycemia, Table 335-1 VC. The contribution of the insulin to glucagon ratio to the production of glucose by the liver due to gluconeogenesis. Include second messenger systems, key pathways, and control enzymes. Answer. The insulin to glucagon ratio would be lower in the type 2 patient. Thus, gluconeogenesis would be faster. This would result in the liver causing the high blood glucose. One mechanism would be the effect of insulin and glucagon on the cyclic-AMP cascade. A more active cAMP cascade decreases the concentration of fructose-2,6-bisphosphate. Decreased fructose-2,6-bisphosphate would inactivate phosphofructokinase and activate fructose-1,6-bisphosphatase. These are the control enzymes for glycolysis and gluconeogenesis respectively. Pyruvate kinase would also be inactivated. Gluconeogenesis would also be increased because more gluconeogenic substrate was available. References: 1) Harrison's online, search "fasting" chapter 335: Hypoglycemia 2) Stryer, Biochemistry, 4th ed, pp574 3) Meissenburge, Principles of Medical biochemistry pp.338 VD. The rate of production of lactate, alanine, and glycerol and their possible contribution to gluconeogenesis. Answer: Alanine, lactate, and glycerol production rates are increased in fasting type two diabetics with fasting hyperglycemia. The blood levels of lactate and glycerol increase. The blood levels of alanine do not rise but more alanine is extracted from the blood to correspond to the increased alanine production. References: 1) Harrison's online, search "fasting" chapter 335: Hypoglycemia, table 335-1 2) Stryer, Biochemistry, 4th ed, pp577 VE. The uptake of glucose by muscle. Include a biochemical mechanisms. Answer: We can say that there is not enough insulin to cause glucose to enter muscle tissue at a normal rate. All type 2 diabetics have receptor defects (less receptors) and post receptor defects that make the utilization of glucose occur to a lesser degree. The mechanism of the post receptor defect is unknown. So, we can say that the slow uptake of glucose is probably due to lower insulin than necessary and receptor defects in the muscle tissue. [Some evidence indicates that the rate limiting step for glucose uptake in type 2 diabetics is glucose transport.] References: 1) Robbin's, Pathologic Basis of Disease, 6th ed, pp915-920 2) MDconsult.com search, "Cecil Textbook of Medicine", pp1267 VF. The blood concentrations of free fatty acids. Suggest a mechanism including the key words cyclic-amp cascade, hormone sensitive lipase activity and insulin. Answer: Type 2 diabetics have a higher blood concentration of free fatty acids than normal people. The activity of hormone sensitive lipase in adipose cells is under the control of the cyclic-AMP cascade. Thus, glucagon, epinephrine, and other counter regulatory hormones increase its activity of the cascade and, thus, activate hormone sensitive lipase. Insulin normaly inhibits the cascade and, thus, the higher the insulin, the less hormone sensitive lipase activity. In a patient with type 2 diabetes, insulin resistance and the real or relative insulin deficiency result in less inhibition of the cascade and, thus, more hormone sensitive lipase activity, more free fatty acid release, and a higher blood concentration of free fatty acids. References: 1) Harrison's online, Chapter 335- Hypoglycemia, Chart #1 2) Stryer, Biochemistry, 4th ed, pp780 VG. The affect of the change in blood free faty acids upon VLDL synthesis in the liver. Answer: A portion of the free fatty acids ariving at the liver are converted back to triacylglycerols and exported in VLDLs. Thus, the more free fatty acids the more VLDLs. VH. The action of insulin and glucagon on the uptake of glucose by the brain. Answer: The brain uses the same amount of glucose no matter what the ratio of insulin to glucagon. Neither hormone has an effect on the rate of blood glucose uptake by the brain. The brain uses a constant amount of glucose unless the fast is prolonged .

EXPLANATION OF OBJECTIVE VI: VIA. After an overnight fast in a resting person, what is the proportion of blood glucose used by the brain and what proportion is used by all other tissues? Answer. The brain is using 50 to 60% of the blood glucose. All other tissues use approximately 40 to 50 % of the total blood glucose. [One study reported brain 46%, muscle 29%, liver 13%, gut 7%, kidney 2%, and heart 2%.] VIB. Which of the following tissues might significantly increase their use of glucose as a result of increased insulin reacting with their insulin receptors?: Brain, RBCs, Fat Cells, Muscle Cells. Answer. Increases in glucose uptake and utilization as a result of increased binding of insulin to insulin receptors would not occur in brain and RBCs. The rate of glucose uptake into fat and muscle cells is increased by insulin binding.  VIC. Explain the effect on blood glucose of injecting insulin into a normoglycemic patient after an overnight fast? What changes would you expect in the rate of blood glucose utilization and the rate of glucose production? Why? Answer. Glucose uptake into muscle and other tissue would be greatly increased. The effect on the pancreas would be to lower the concentration of glucagon. The change in the insulin to glucagon ratio would dramatically decrease gluconeogenesis and glycogenolysis in the liver. Hopoglycemia would result.

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