Insulin Stimulates Intestinal Calcium Absorption in Man and the Rat
Ingestion of carbohydrates leads to abnormally-high plasma-insulin levels in idiopathic hypercalciuric (IHC) Ca-urolithiasis patients (1, 2). In view of the calciuretic effect of insulin (3), hyper-insulinemia has served as one explanation for “idiopathic” hypercalciuria (2). However, the mediators of increased intestinal Ca absorption (CaA) which most of these patients exhibit are largely unknown. Besides enhancing calciuria, insulin affects the metabolism of Ca in many respects. It promotes bone growth in the rat (4), and insulin administration normalizes the low duodenal CaA of streptozotocin-diabetic rats (5). In insulinopenic diabetes, low bone mass is common (6), and so-called diabetic bone disease may ensue. Starting with the hypothesis that postprandial hyper-insulinemia and hyperabsorption of Ca in IHC might be interrelated, we studied the effects of postprandial-like plasma insulin levels on the duodenal CaA of the rat and small intestinal CaA of healthy man.
KeywordsInsulin Infusion Glucose Infusion Intestinal Calcium Absorption Glucose Infusion Rate Duodenal Loop
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