Glycolysis glucagon

Figure 25-7. Metabolism of adipose tissue. Hormone-sensitive lipase is activated by ACTH, TSH, glucagon, epinephrine, norepinephrine, and vasopressin and inhibited by insulin, prostaglandin E, and nicotinic acid. Details of the formation of glycerol 3-phosphate from intermediates of glycolysis are shown in Figure 24-2. (PPP, pentose phosphate pathway TG, triacylglycerol FFA, free fatty acids VLDL, very low density lipoprotein.)...

The answer is a. (Hardman, p 1510.) Although the mechanism of action of metformin and other biguanicies is unclear, biguanides virtually never cause hypoglycemia They operate independently of pancreatic p cells but are not useful in insulin-dependent diabetes mellitus (IDDM). Some possible mechanisms of action are direct stimulation of glycolysis in peripheral tissues, increased sensitivity to insulin, and reduction of glucagon levels. 

Glucagon stimulation of liver cells in particular leads to phosphorylation of regulatory enzymes whereas insulin has the opposite effect. So, after a meal, we would expect glycolysis and glycogen synthesis to operate very efficiently so the control enzymes will be dephosphorylated. 

Effect of insulin and glucagon on the synthesis of key enzymes of glycolysis in liver. 

Figure 17-20 The interlocking pathways of glycolysis, gluconeogenesis, and fatty acid oxidation and synthesis with indications of some aspects of control in hepatic tissues. (— ) Reactions of glycolysis, fatty acid degradation, and oxidation by the citric acid cycle. ) Biosynthetic pathways. Some effects of insulin via indirect action on enzymes , 0, or on transcription 0/ 0. Effects of glucagon , .

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