Hepatitis b virus in human life style

Dr. Hazem GhneimDisorders of Carbohydrate Metabolism

* Carbohydrate is the major component of human diet and is an important source of energy. However, the capacity of the body to store carbohydrate is limited and is confined to the liver (10% of its weight) and to muscles (0.5% of its weight). This storage amount can only fulfill the energy requirement of half a day.* All tissues can utilize glucose however under fasting conditions only a few tissues depend entirely upon glucose as the only source of energy. These are:The brainTo a lesser (**): RBC, platelets, leukocyte and kidney medullaDr. Hazem GhneimMaintenance of blood glucose level:-Normal blood glucose level = (70-110 mg/dl). There are 2 major mechanisms for the maintenance of this (**) under fasting conditions:-Biochemical mechanismsHormonal mechanismsDr. Hazem Ghneima- Biochemical mechanisms:Blood glucose level is maintained during fasting by:-When blood glucose level begin to drop, glycogen is converted to glucose by GLYCOGENOLYSIS, a catabolic pathway require a specific set of enzymes.When blood glucose level rise, cells start breaking down glucose by glycolysis at a faster rate. Excess glucose is then polymerized into glycogen by GLYCOGENESIS and anabolic pathway.Liver synthesizes glucose from certain non-carbohydrate precursor such as lactate, pyruvate and certain amino acids primarily alanine. This is done via a pathway known as GLUCONEOGENESIS. Liver gluconeogenesis predominates during fasting thus providing glucose to tissues that are completely dependent on glucose for energy production.Dr. Hazem GhneimUnder prolonged fasting, the body starts mobilizing muscle proteins (proteolysis) into amino acids. The amino acids can be converted into glucose by gluconeogenesis or are degraded for energy production.In cases of starvation and during diseases conditions such as diabetes, the body stars mobilizing fat stores in adipose tissues into fatty acids (lipolysis). The fat is used as an alternative source of energy. Degradation if fat lead to acetyl-CoA which is further catabolised via TCA cycle. Some of the acetyl-CoA molecules condense together and lead to the formation of acetoacetyl-CoA and -hydroxybutyrate in liver mitochondria. Collectively these products are known as ketone bodies which leave the liver and go into blood causing KETOSIS. The ketone bodies are then filtered at the kidney nephrons and appear in the urine (KETONURIA). Part of the ketone bodies are utilized to make cholesterol.

Dr. Hazem Ghneim

Dr. Hazem Ghneim

Dr. Hazem GhneimHormonal Regulation of PlasmaInsulin: A hormone synthesized and produced by the pancreatic -cells, is the only hormones that LOWER the concentration of plasma glucose.A group of other hormones act to increase plasma glucose levels. These include:-Growth hormone: synthesized and secreted by (Anterior pituitary)Adrenaline : = = = = (Adrenal medulla)Cortisol : = = = = (Adrenal cortex)Thyroxin : = = = = (Thyroid tissue)Glucagon : = = = = (Pancreatic cells)

Dr. Hazem GhneimInsulin exerts a plasma glucose lowering (**) by several mechanisms:By increasing the rate of entry of glucose from plasma into muscle and adipose tissue cells.By promoting liver glycogenesis thus converting glucose to glycogen.By promoting glycolysis which accelerates glucose utilization.By promoting lipid synthesis from glucose in adipose tissue.By promoting amino acid synthesis from glucose intermediates.Thus a relative excess of insulin produces a lowering of plasma glucose, whereas a relative deficiency of insulin products an elevated plasma glucose.

Dr. Hazem GhneimThe rate of insulin secretion from -cells into the blood is governed by the blood glucose level itself. When plasma glucose rises, the -cells are stimulate to secret more insulin. Insulin secretion return to the resting baseline state when plasma glucose levels return to normal. Conversely, a plasma glucose concentration below normal shuts off the secretion of insulin.

Dr. Hazem GhneimIncrease of Plasma Glucose level:A group of hormones known as insulin antagonists act to raise plasma glucose level:- Growth hormone: Growth hormone raises plasma glucose level by several mechanisms:By inhibiting entry of glucose into muscles.By inhibiting glycolysis.By inhibiting the formation of triglyceride from glucose

Adrenaline (Epinephrine): this raises plasma glucose level by causing rapid breakdown of liver glycogen into glucose. The stimulus is physical and emotional stress (neurogenic).Glucagon: This raises plasma glucose by promoting the conversion of glycogen into glucose in the liver and by accelerating the absorbance of glucose from intestines during meals.

Dr. Hazem GhneimThe EndDr. Hazem Ghneim