Biochemistry

according to the type of feedback, with an excess of glucose-6-phosphate, glycogen synthesis is activated and its break down is inhibited, and the lack of glucose in the blood triggers the hydrolysis of glucose-6-phosphate to free glucose. Symptoms of carbohydrate metabolism are hyperglycemia, glycosuria, hypoglycemia. Hyperglycemia can be of insular or extrainsular origin. Insular hyperglycemia develops when insulin production decreases as a result of damage to the islets of Langerhans of the pancreas. Hyperglycemia, not associated with the production of insulin, can be caused by physiological and other reasons. As is well known, nutritional hyperglycemia occurs during excessive consumption of hight carbohydrates foods (for example, fruits, sweets). Neurogenic hyperglycemias (central) are associated with various emotional factors (joy, anxiety, fear) that stimulate the production of adrenaline, which causes an increased breakdown of glycogen to glucose and its entry into the blood. The causes of extrainsular hyperglycemia can be diseases of the endocrine glands (pituitary tumors, adrenal glands, thyrotoxicosis), causing hypersecretion of the corresponding hormones. Hyperglycemia leads to poisoning with phosphorus, carbon monoxide, trauma, brain tumors, etc. A decrease in the level of glucose metabolism and, as a result, an increase of its content in the blood, can be caused by impaired functions of the enzyme systems during inflammatory processes in the body. In the urine of a healthy person, there is practically no glucose, since it is reabsorbed in the renal tubules. If the blood glucose level exceeds the “ renal threshold ” (6.68 mmol/g), then the kidneys stop resorbing this monosaccharide, part of the glucose enters the urine, and glucosuria develops. The decrease in the blood glucose(below 2,40 mmol/g) - hypoglycemia is manifested by symptoms: weakness, sweating, deterioration of the central nervous system, loss of consciousness. It may develop with an overdose of insulin in diabetic patients. Hypoglycemia occurs with increased insulin production, low thyroid hormone production, and adrenal gland diseases (Addison's disease). The flow of glucose into the blood is reduced due to a violation of its absorption in the intestine with diseases of the small intestine (enterocolitis) and biliary tract. Hypoglycemia also occurs in liver diseases (fatty infiltration, etc.) and a number of infectious diseases. Among other disorders of carbohydrate metabolism, certain hereditary diseases should be distinguished, leading to changes in the synthesis of a number of enzymes. So, hereditary diseases, which are based on disorder of the enzymes that catalyze the processes of glycogen breakdown, are called glycogenosis. It is connected to the phosphorylase deficiency in the liver or in the skeletal muscles, the absence of glucose-6-phosphatase in the liver, etc. 215