Hormone sensitive lipase is inhibited by?
Correct Answer: Insulin
Description: ANSWER: (A) InsulinREF: Textbook of Biochemistry for Medical S tudents by D. M. Vasudevan 6th edition page 283, Essential Biochemistry for Medicine by Dr Mitchell Fry 2010 edition page 78, Ganomg's 22nd ed p- 305"Insulin inhibits lipolysis in adipose tissue due to inhibition of hormone sensitive lipase"Hormone-sensitive lipase (HSL) also previously known as cholesteryl ester hydrolase (CEH) is an enzyme that, in humans, is encoded by the LIFE gene. HSL is an intracellular neutral lipase that is capable of hydrolyzing a variety of esters. The enzyme has a long and a short form. The long form is expressed in steroidogenic tissues such as testis, where it converts cholesteryl esters to free cholesterol for steroid hormone production. The short form is expressed in adipose tissue, among others, where it hydrolyzes stored triglycerides to free fatty acidsHSL is activated when the body needs to mobilize energy stores, and so responds positively to catecholamines, ACTH, and negatively to insulin. Previously, glucagon was thought to activate HSL, however the removal of insulins inhibitory effects ('cutting the brakes") is the source of activation.There are various types of lipases in the human body:HormoneFunction and locationBile salt dependent lipasePancreas and breast. Aids in digestion of fatPancreatic lipasePancreatic juiceLysosomal lipaseIntracellularly, in the lysosomes.Hepatic lipaseEndothelium of liver and adrenals, convert intermediate-density1, lipoprotein (IDL) to low-density lipoprotein (LDL).LipoproteinlipaseExpressed on endothelial cells in the heart, muscle, and adipose tissue. Dual functions of triglyceride hydrolase and ligand,''bridging factor for receptor-mediated lipoprotein uptake. Hydrolyzes triglycerides in lipoproteins, such as those found in chylomicrons and very low-density lipoproteins (VLDL), into two free fatty acids and one monoacylglycerol molecule. It is also involved in promoting the cellular uptake of chylomicron remnants, cholesterol-rich lipoproteins, and free fatty acids. Through catalysis, VLDL is converted to IDL and then to LDL. LPL requires Apo-CII as a cofactor.Hormone sensitive lipaseEndothelium of adipose tissue and gonads. HSL functions to hydrolyze the first fatty acid from a triacyiglycerol molecule, freeing a fatty acid and diglyceride. Enzyme is affected by hormones; hence its hormone-sensitive lipase name. It is activated by cAMP by protein kinase. Growth hormone, glucagon, glucocorticoids, thyroid hormones increase the activity, while insulin and prostaglandins decrease its activity.Gastric lipaseGastric lipase is an acidic lipase secreted by the gastric chief cells in the fun- dic mucosa in the stomach. Gastric lipase together with lingual lipase, comprise the two acidic lipases. These lipases, unlike alkaline lipases (such as pancreatic lipase), do not require bile acid or colipase for optimal enzymatic activity.
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Biochemistry
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