Diabetes mellitus type 2 is the most common type of diabetes

Diabetes mellitus type 2 is the most common type of diabetes. The disease is characterized by high levels of glucose in the blood (hyperglycemia) that exceed the renal threshold. Common symptoms for someone that might have type 2 diabetes include increased urination (polyuria) and increased thirst (polydipsia) Because of this, individuals with diabetes are at risk for dehydration. a. Explain how hyperglycemia causes polyuria and polydipsia. b. Provide a mechanism for how the body might compensate for the altered blood osmolarity due to hyperglycemia. c. Provide a mechanism for how the body would compensate for the altered blood volume and blood pressure due to hyperglycemia (While this mechanism provided in \'b\' might also be used to compensate for altered blood volume and blood pressure, provide an alternative mechanism). d. What effect might hyperglycemia have on aldosterone secretion? Explain.

Solution

Diabetes mellitus is a condition where there are elevated levels of blood glucose. There are two types of diabetes mellitus i.e. type 1 and type 2.

Type-1: This is a type of diabetes where a body does not produce enough insulin to metabolize glucose, this results in elevated blood glucose levels, weight loss, frequent urination, hunger, thirst, tiredness, less healing power and blurred vision.

Type-2: It is due to the disorder in the metabolism characterized by elevated blood sugar levels, insulin resistance with symptoms of increased thirst (Polydipsia), urination (Polyuria), weight loss, tired, hunger (Polyphagia) etc. It mostly occurs in obese patients.

a)The excess levels of blood glucose in the urine filtrate act as an osmotic diuretic in kidneys due to its hypertonic nature, resulting in inhibition of water reabsorption by kidneys and therefore causes loss of more water with urine due to osmosis (Polyuria). Due to this excessive water loss and electrolytes, the person blood volume decreases, resulting in dehydration. The dehydration stimulates the hypothalamic thirst centers of a brain which give the feeling of being thirsty known as polydipsia.

b) Regulating water content is crucial to regulate blood volume and blood pressure. The kidneys are the major detectors to identify fluctuations in the blood pressure and inorder to regulate them, they either excrete more water or retain water for decreasing or increasing blood volume and blood pressure. Kidneys release angiotensin which functions in many cascades to regulate the blood pressure and blood volume i.e. vasoconstriction and sodium reabsorption via aldosterone in response to low blood pressure, the release of ADH and reduction of hydrostatic pressure in the peritubular capillaries regulate blood volume etc.

C) The loss of blood osmolarity due to dehydration in hyperglycemic conditions is being maintained alternatively by a short peptide hormone known as antidiuretic hormone (ADH) or 8-arginine-vasopressin (AVP) released by the posterior pituitary gland into the blood stream. This hormone lead reduction in the rate of urine flow due to reabsorption of water from the filtrate in the distal tubules and collecting ducts of nephrons. Due to back diffusion of water without solutes then reduces urine flow. Furthermore, ADH leads NaCl reabsorption in ascending loop of Henle. Conclusively, the major functions of ADH is to cause increased urine osmolality, tubular conservation of water, decreased serum osmolality.

D) The angiotensin stimulates the release of aldosterone that is involved in the reabsorption of sodium through the renal tubules causing blood volume and blood pressure to be regulated in diabetic or hyperglycemic patients.