Influence of oral insulin supplementation on carbohydrate, lipid and protein metabolism in weaned Balb/c mice.

Background: [corrected] Insulin is substantially present in human milk. Suckling animal models have demonstrated local trophic effects of insulin on the gut mucosa, but the effects of oral insulin in the post-weaning period are controversial.
Objective: To examine local and systemic effects of oral insulin supplementation in the post-weaning period.
Materials and Methods: Balb/c mice received oral insulin supplementation in their drinking water (1 U/ml) from beyond weaning during 40 days (S group). Plasma glucose, lipid levels, amylase and insulin were measured. The liver and intestine were weighed and thiobarbituric acid-reactive substance (TBARS) levels were examined in liver tissue. These data were compared to a control group (C group).
Results: Fasting glucose levels (mean +/- SD) were lower in the S than in the C group (116. 5 +/- 10.7 vs 143.9 +/- 25.4 mg/dl; p < 0.001), as were prandial glucose levels (123.1 +/- 12.2 vs 145.1 +/- 18.0 mg/dl; p = 0.03). Plasma insulin levels were higher in the S than in the C group (1,110.28 +/- 721.59 vs 308.17 +/- 100.50 pmol/; p = 0.03). Total triglyceride levels (130.4 +/- 32.4 vs 193.6 +/- 48.4 mg/dl; p < 0.02) and total cholesterol levels (83.6 +/- 5.7 vs 93.3 +/- 7.9 mg/dl; p < 0.05) were lower in the S group compared with the C group. Liver weight was significantly higher in the S group compared with C (0.75 +/- 0.1 vs 0. 7 +/- 0.1 g, p = 0.05).
Conclusions: In the post-weaning period, oral insulin supplementation had a significant effect on plasma glucose levels and lipid profile, as well as on liver weight and protein content in Balb/c mice. The application of these findings in humans should be studied.