
International Textbook of Diabetes Mellitus, 4th Ed., Excerpt #82: Insulin Actions In Vivo: Glucose Metabolism Part 9 of 9
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International Textbook of Diabetes Mellitus, 4th Ed., Excerpt #82: Insulin Actions In Vivo: Glucose Metabolism Part 9 of 9
At any point in time, the glycemic response to exogenous glucose is the balance between the rate at which glucose appears in the systemic circulation (from oral as well as endogenous sources) and the rate at which glucose is disposed of. Oral glucose appearance in the peripheral circulation depends on: (a) the rate at which the gastric contents are passed on to the small intestine; (b) the rate of intestinal glucose absorption; (c) the extent of gut glucose utilization; (d) the degree of hepatic glucose trapping; and (e) the dynamics of glucose transfer through gut, liver, and posthepatic circulation on to the right heart. The contribution of endogenous glucose to the glycemic response to feeding depends on the extent and rate of change of hepatic glucose production. Finally, glucose disposal depends on changes in the pattern of hormonal stimuli and substrate availability.
Being a summation phenomenon, the response to oral glucose explores the whole of glucose tolerance, not the individual contribution of the various components. The rate-limiting step in the transfer of ingested glucose from the stomach to the liver is the rate of gastric emptying. This depends on the volume, temperature, and osmolarity of the glucose solution in the case in which glucose alone is ingested. Glucose absorption
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