Glucose tolerance, plasma insulin, and plasma glucagon in relation to obesity in chickens
Relationships among glucose tolerance, plasma insulin, and plasma glucagon were examined in chicks developed through selection for high (HW) and low (LW) body weight, and in F, crosses (HL) between HW males and LW females. At 21, 42, 63, and 84 days of age, chicks from each population were intubated with glucose (2 g/kg body weight) following a 24-hr fast. Blood was collected at 20-minute intervals up to 100 minutes postadministration.
At all ages, the LW chicks were better able to metabolize glucose than their HW counterparts, while the HLs exhibited intermediate responses. Impaired glucose tolerance in the HWs and HLs was not associated with insulin insufficiency; the HWs and HLs, in comparison to the LWs, were hyperinsulinemic at 42 and 63 days of age and plasma insulin levels did not differ among populations at 21 or 84 days of age. Plasma glucagon responses to glucose administration were inconsistent, but plasma glucagon levels were consistently higher in the HWs and HLs than in the LWs. It was concluded that excessive fat deposition in chickens selected for rapid growth is associated with hyperinsulinemia and insulin resistance.