Dietary arginine, insulin secretion, glucose tolerance and liver lipids during repletion of protein-depleted rats

Male Sprague-Dawley rats (~500 g) were fed a very low protein diet (0.5% lactalbumin) for 14 weeks. The average weight loss was 195 g. Following protein depletion the rats were randomly assigned to 5 groups and repleted for 15 days with a purified diet containing 20% protein equivalent as L-amino acids with arginine comprising 0, 0.25, 0.5, 0.75 or 1.0% of the total diet. The absence of dietary arginine during repletion significantly reduced weight gain and efficiency of feed utilization with no apparent change in feed intake. Livers of animals fed 0 and 0.25% arginine were slightly heavier and contained a greater concentration of total lipids than livers from other groups. Intravenous glucose tolerance tests performed on the animals fed 0, 0.5 and 1.0% arginine gave k coefficients for glucose disappearance which were significantly greater (P<.01) for 1.0% arginine (0.12) than for 0.5% arginine (0.56) or 0% arginine (0.45). Plasma insulin for the 1.0% arginine group peaked at 5 min following glucose injection, and declined steadily to near basal levels at 45 min. Plasma insulin for animals repleted with 0 and 0.5% arginine was elevated to a lesser degree than for 1.0% arginine by 5 min but remained above basal levels throughout the experiment and there was a concurrent decrease in the rate of glucose disappearance. The insulinogenic index (Δinsulin/Δglucose) was significantly greater (P<.01) with 1.0% and 0.5% arginine than with 0% arginine. These data suggest that glucose intolerance during arginine deficiency is related to decreased insulin release immediately following glucose administration and possible a mild insulin resistance.