Effect of copper on carbohydrate metabolism in rats.

Rats fed a copper-poor diet were found to have a reduced plasma insulin response to an oral glucose load in comparison with rats fed a copper-supplemented diet. In addition, the increment in plasma glucose above the fasting level at 60 min and at 120 min was significantly higher in rats maintained on the copper-poor diets. In vitro glucose incorporation into diaphragm glycogen and into epididymal fat-pad lipids was stimulated greater than twofold by the addition of 100 micrograms/ml CuCl2 to the incubation medium. In tissues of streptozotocin-diabetic rats, the stimulatory effect of copper on glucose incorporation in vitro was also noted, but was significantly smaller. These results indicate that glucose utilization by peripheral tissues and insulin release may be added to the many vital functions for which copper is essential.