Glucose Regulation - Austin Community College

Under normal physiological conditions, the main role of insulin on the heart is the regulation of substrate utilization. Insulin regulates cardiac metabolism by modulating glucose and fatty acid transport, glycolysis, glycogen synthesis, lipid metabolism, protein synthesis, growth, contractility, and apoptosis in the cardiomyocytes (5). The actions of insulin are mediated by binding to specific cell surface receptors (insulin receptor, InsR). Each cardiomyocyte is expressed at levels of about 10,000 to 100,000 receptors of InsR. The InsR is a tetrameric enzyme comprising two extracellular a-subunits and two transmembrane P-subunits (5). The binding of insulin to the extracellular domain of InsR triggers the activation of intrinsic tyrosine kinase activity of the P-subunits of the receptor. This leads to an autotransphosphorylation of the receptor where one P-subunit phosphorylates the other on several tyrosine residues. Once activated and phosphorylated, InsR binds via its phosphotyrosine residues and phosphorylates a series of downstream elements, including the insulin receptor substrate (IRS) family and Shc (5, 50). This recruitment and activation lead to the activation of two main pathways, the phosphatidylinositol 3-kinase (PI3K) and the mitogen-activated protein kinase (MAPK) pathway respectively. PI3K is considered to be the main player of the metabolic action of insulin, whereas the MAPK pathway is principally involved in cell growth and differentiation in the heart (Fig.2) (50, 51).

GLUCONEOGENESIS: Increase of synthesis of glucose from amino acids and the glycerol portion of fat.">
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Glucose Regulation ; Anatomy of the pancreas

"The integration of glucose sensing and control of lipogenesis by LXR may explain why low-fat/high-carbohydrate diets induce hypertriglyceridemia [an elevated level of triglycerides in the blood]," Saez said. "LXR can sense surplus glucose, induce fatty acid synthesis, and prompt the liver's export of triglycerides into the bloodstream. Since LXR acts as the body's sensor of a buildup of pathogenic cholesterol, its ability to bind both glucose and oxysterols suggests that LXR may be a link between hyperglycemia and atherosclerosis."

"When you eat, glucose pours into the gut and is recognized by LXR in the liver, which then activates expression of the enzymes that turn excess glucose into triglycerides that are stored as fat," said Enrique Saez, a Scripps Research scientist who led the study. "The fact that our study demonstrates that LXR does both-it binds to glucose and it induces fatty acid synthesis-is significant and makes LXR a potential target for diabetes and obesity treatments."

glucose | Definition, Structure, & Function | …

These differences are relevant to the type of fatty acids which are found in the milk of various species, the role of glucose in fatty acid synthesis in various species, and the effect of dietary lipids on milk fat fatty acid composition in various species.

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