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Lecture- Diabetes

Lecture- Diabetes - Lecture Diabetes 03:03 PM Lecture...

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04/26/2007 03:03 PM Lecture: Diabetes Page 1 of 27 http://www.zoology.ubc.ca/~auld/bio456/lectures/lecture_diabetes.html Lecture: Diabetes Diabetes mellitus: Type 1 and Type 2 Diabetes mellitus is defined as elevated blood glucose levels. A reduction in insulin secretion and/or resistance to insulin is a common cause of Diabetes mellitus. A classic test for diabetes is the administration of a large oral liquid glucose load (75 g) combined with measurements of the subsequent changes in blood glucose concentration. This "glucose tolerance" is a measure of the ability of the body to deal with a large glucose dose. Common symptoms of diabetes mellitus: Polyuria. Polyuria is increased diuresis (urine production). One of the classic signs of diabetes is frequent urination. The maximal rate that glucose can be reabsorbed in the kidney from the glomerular filtrate is ~ 2.0 mmol min/l. This is reached when plasma glucose concentrations are between 1015 mmol/l. Once above this level the glucose remains in the filtrate and causes enhanced secretion of water into the filtrate (diuresis) with loss of sodium and potassium. Polydipsia. Polydipsia is increased and abnormally large intake of fluids by mouth. This is due to dehydration due to excessive urination. As urination increases hormones that control blood volume and osmolality also stimulate thirst. Another classic symptom of diabetes is excessive thrist. Hunger and weight loss. Insulin has anabolic effects on muscle and fat. Loss of insulin signaling causes muscle and fat breakdown. Calories are also lost in the urine. Blurred vision. High circulating glucose concentrations cause osmotic swelling of the lens of the eye. Fatigue. The mechanism for such fatigue is seen in all types of diabetes when circulating concentrations of glucose are high. The mechanism is not well understood. Ketosis. Produces a fruity odor in the breath and urine of a person. Ketones form in the blood when a fat is broken due to insufficient insulin. Free fatty acids are broken down into fatty acids, which are then chemically changed into ketones in the liver. Ketones (acetoacetic acid, beta hydroxybutyric acid ) are often found in the blood and urine of persons with uncontrolled diabetes. Type 1 Diabetes Type 1 DM is an autoimmue disease where the T-lymphocytes infiltrate and destroy the islets of Langerhans (the islets of the Pancreas). The trigger for this distruction has yet to be clearly identified, whether viral, environmental. Genetics does play a part as 40% of monozygotic twins who have an affected sibling will also be affected.
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04/26/2007 03:03 PM Lecture: Diabetes Page 2 of 27 http://www.zoology.ubc.ca/~auld/bio456/lectures/lecture_diabetes.html Figure 1 Possible mechanisms for virus-induced diabetes. Viruses can induce diabetes either by infection of beta cells or systemic infection. Viruses can kill beta cells by the replication within the cell, by altering the beta cell-expression of potential autoantigens or other immunogenic molecules or by the induction of a general immune response that is misdirected against beta cells. From Diabetes/Metabolism Research and Reviews 2002, 19:8-31
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