Tissue Specific Energy Metabolism

Energy Metabolism During Fasting

The brain depends almost exclusively on glucose for energy. Since it cannot store compounds for oxidation, it has to receive a constant supply of glucose. To make this possible, a minimum blood glucose level has to be maintained at all times A . The brain uses about 120 g of glucose per day during phases of prolonged fasting or starvation it can use ketone bodies instead, but only to a limited extent. Muscle tissue, on the contrary, possesses large glycogen stores. When broken down, it is...

Metabolism Distribution and Regulation

Triglyceride Metabolism

Once absorbed, carbohydrates are carried to the liver A . There, fructose and galactose are converted into glucose. Some of the absorbed glucose reaches the peripheral bloodstream, where it is recognized by pancreatic receptors. This triggers increased insulin secretion by the p-cells and reduces glucagon secretion. These hormonal changes provide a signal which affects the entire metabolism absorption of glucose into the liver, muscle cells, and fatty tissues is increased, and its conversion...

Metabolism Glucose Storage

Metabolism Glucose Muscles

The glucose stored in the liver as glyco-gen can be considered a reservoir for buffering blood glucose levels A . Since glucose is the essential energy source of the CNS, blood glucose levels are regulated within a tight margin through the interplay of glucagon and insulin. Muscle glycogen is not directly integrated into the blood glucose regulation system. Since muscles lack glucose-6-phosphatase, their cells are unable to convert glucose-6-phosphate formed during glycogen breakdown into...

Fatty Acids Metabolism

Palmitate Metabolism

Triglyceride triacylglycerol hydrolysis in adipocytes is subject to complex hormonal regulation A . Besides by glu-cagon, growth hormones, and others, hormone-sensitive lipase is activated, in particular, by catecholamines released during times of heightened energy need. Hormone-sensitive lipase is activated via a p-receptor and subsequent formation of the second messenger cAMP in the adenylate cyclase system. Hormone-sensitive lipase releases free fatty acids FFA from tri- and di-glycerides...

Fructose and Galactose

Fructose Galactose Metabolism

Fructose, which has no influence on the release of insulin, is metabolized in the liver A . Which metabolic pathway is used depends on the presence or absence of other monosaccharides. In case of simultaneous supply of glucose and fructose, fructose is transformed into intermediate products of the glycolytic pathway. Since only one phosphorylated product results from the splitting of fructose-1-phosphate, the remaining glyceraldehyde has to be processed via a different pathway first. Like...