Aging / Biological Sciences / Insulin Resistance / Cell and Tissue Transplantation / Glucose / Insulin / Animals / Male / Leptin / Lipid metabolism / Body Mass Index / Rats / Analysis of Variance / Time Factors / Age Factors / Glucose Tolerance Test / Insulin / Animals / Male / Leptin / Lipid metabolism / Body Mass Index / Rats / Analysis of Variance / Time Factors / Age Factors / Glucose Tolerance Test