Characterization and heritability of obesity and associated risk factors in vervet monkeys

Objective: The objective was to determine the prevalence and heritability of obesity and risk factors associated with metabolic syndrome (MS) in a pedigreed colony of vervet monkeys. Design: A cross-sectional study of plasma lipid and lipoprotein concentrations, glycemic indices, and morphometric measures with heritability calculated from pedigree analysis. A selected population of females was additionally assessed for insulin sensitivity and glucose tolerance. Subjects: All mature male (n = 98), pregnant (n = 40) and non-pregnant female (n = 157) vervet monkeys were included in the study. Seven non-pregnant females were selected on the basis of high or average glycated hemoglobin (GHb) for further characterization of carbohydrate metabolism. Measurements: Morphometric measurements included body weight, length, waist circumference, and calculated BMI. Plasma lipids [total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C)] and glycemic measures (fasting blood glucose, insulin, and GHb) were measured. A homeostasis model assessment index was further reported. Glucose tolerance testing and hyperinsulinemic-euglycemic clamps were performed on 7 selected females. Conclusion: Vervet monkeys demonstrate obesity, insulin resistance, and associated changes in plasma lipids even while consuming a low-fat (chow) diet. Furthermore, these parameters are heritable. Females are at particular risk for central obesity and an unfavorable lipid profile (higher TG, TC, and no estrogen-related increase in HDL-C). Selection of females by elevated GHb indicated impaired glucose tolerance and was associated with central obesity. This colony provides a unique opportunity to study the development of obesity-related disorders, including both genetic and environmental influences, across all life stages.