Beta-Cell Insulin Secretory Response to Glucose in Odd-Carbon Number Fatty Acid-enriched Rats: Preservation During Starvation

The adipose tissue of fifty male Sprague-Dawley rats was enriched with 26.3 per cent odd-carbon number fatty acids (OCE) by feeding a complete diet containing a 7:3 mixture of triundecanoin and corn oil for six weeks. An equal number of control animals (C) was fed a similar diet except that the fat was exclusively corn oil. After six weeks, the animals were given intravenous glucose (500 mg.) either in the fed state cr after forty-eight- or ninety-six-hour fasts. Fasting plasma glucose and immunoreactive insulin levels were higher in OCE than in C during starvation. K values of glucose disappearance after an intravenous glucose load were similar in OCE and C in the fed state; with starvation, K values were less impaired in OCE than in C. The areas under the insulin response curve on days 2 and 4 of starvation were reduced to 24 per cent and 19 per cent of the fed value in C and 73 per cent and 47 per cent in OCE. Insulin-to-glucose ratio diminished significantly with starvation in C, whereas no significant change occurred in dCE. Total pancreatic insulin was not different in fed or two- and four-day starved OCE and C animals. Thus, fasting in C appears to impair the insulin secretory response of beta cells to glucose, whereas OCE maintain significantly greater responsiveness. The sustained beta-cell sensitivity to glucose of the starved OCE animal probably is related to preservation in the beta cells of a glucose receptor or an intracellular enzymatic system.