Plasma glucose, insulin and lipids during growth of genetically lean and obese swine

Female pigs were selected at birth from litters of genetically lean and obese and contemporary commercial-type pigs to quantify the biweekly changes in fasting concentrations of plasma glucose, immunoreactive insulin, triglyceride and cholesterol during the growing period (birth to 22 weeks of age). Pigs were weaned at 4 weeks of age to a standard corn-soybean meal type dry diet fed ad libitum. Four pigs from each genetic group were used at weeks 4 and 16 of age for a standard oral glucose tolerance test. Plasma concentrations of glucose, insulin, triglyceride and cholesterol were generally similar in all breed from birth to 22 weeks of age. Overall means (N = 306) were: glucose 93.2 mg/dl; triglyceride 37.5 mg/dL, cholesterol 101.8 mg/dL and insulin 10.8 micron Units/ml. There were significant breed differences in a given plasma variable at individual sampling periods, but most were not sustained at earlier or later ages. The genetically lean pigs had lower insulin and triglyceride levels, especially at older ages. Glucose clearance from the plasma at 4 and 16 weeks of age was similar in the three breed groups. It is concluded that these genetically obese pigs selected for fatness over many generations do not manifest their propensity to obesity through modifications in circulating glucose, insulin, triglyceride or cholesterol. Net differences in body fat accretion between these genetically lean and obese populations apparently reside in adipocyte metabolism and are not complicated by an inability to maintain homeostasis of plasma glucose or lipids as is the case with many animal models for obesity. This population of obese and lean swine selected for many generations from a common parental population appears to be a useful model for studies of the metabolic bases of obesity.