Vitamin D3 improves impaired glucose tolerance and insulin secretion in the vitamin D-deficient rat in vivo

Endocrinology. 1986 Jul;119(1):84-90. doi: 10.1210/endo-119-1-84.


It has previously been shown in this laboratory that vitamin D3 is essential for normal insulin secretion from the perfused rat pancreas. In this present study, the influence of vitamin D status on insulin secretion in vivo was investigated. Intravenous glucose tolerance tests were performed on conscious vitamin D-deficient rats (-D), vitamin D-replete rats fed ad libitum (+D AL), and vitamin D-replete rats pair fed to the D-deficient animals (+D PF). Vitamin D deficiency, easily recognizable by low daily dietary intake and depressed plasma calcium levels, was found to impair plasma glucose clearance as characterized by an elevated KG value (representing a function of the area beneath the tolerance curve). KG values for the +D AL, +D PF, and -D groups were 504 +/- 15, 480 +/- 46, and 641 +/- 28, respectively. The increase in KG corresponded to a significant reduction in glucose-mediated insulin secretion as compared to the +D animals. This difference appeared not to be related to the increase caloric intake associated with vitamin D repletion, since +D rats which had been pair fed to the -D animals also exhibited restored plasma insulin levels in response to glucose. Plasma phosphorus concentrations were comparable in all three groups, and thus this parameter is also unlikely to be a contributory factor in the observed phenomenon. Additional experiments were conducted to evaluate the involvement of hypocalcemia in the observed impaired glucose tolerance. Normalization of plasma calcium levels (from 4.8 mg/100 ml to 9.6/100 ml) of the -D rats, by dietary calcium and phosphorus manipulation, failed to improve glucose clearance (KG for -D normocalcemic rats = 639 +/- 61) or insulin secretion. These results support the concept that vitamin D plays a physiological role in insulin secretion, acting, at least in part, independently of nutritional factors and the prevailing plasma calcium and phosphorus concentrations.

MeSH terms

  • Animals
  • Blood Glucose / analysis
  • Calcium / blood
  • Cholecalciferol / pharmacology*
  • Cholecalciferol / therapeutic use
  • Energy Intake
  • Glucose Tolerance Test
  • Hyperglycemia / etiology
  • Hyperparathyroidism, Secondary / etiology
  • Insulin / metabolism*
  • Insulin Secretion
  • Islets of Langerhans / drug effects*
  • Islets of Langerhans / physiopathology
  • Male
  • Phosphates / blood
  • Rats
  • Vitamin D / physiology*
  • Vitamin D Deficiency / complications
  • Vitamin D Deficiency / drug therapy
  • Vitamin D Deficiency / metabolism*


  • Blood Glucose
  • Insulin
  • Phosphates
  • Vitamin D
  • Cholecalciferol
  • Calcium