Insulin sensitivity in juvenile and adult Large White pigs of low and high birthweight.

Aims/hypothesis: We have previously demonstrated poor glucose tolerance in adult pigs of naturally occurring low birthweight. The aim of this study was to examine sensitivity to insulin in juvenile (3-month-old) and adult (12-month-old) pigs of low and high birthweight.

Methods: Low (<1.47 kg) and high (>1.53 kg) birthweight piglets from 15 litters were studied at 3 (n=47) and 12 (n=17) months of age. At each age the selected pigs were tranquilised and catheters were inserted into the dorsal aorta and caudal vena cava under general anaesthesia. After recovery, insulin sensitivity was measured as the glucose decrement (mmol.l(-1).min(-1)) during the first 10 min after an intravenous insulin bolus (0.5 IU/kg). Data (means +/- SEM) were analysed by the Student's t test, ANOVA and linear regression.

Results: The body weight of low birthweight female, but not male, pigs remained smaller than that of high birthweight pigs at 3 and 12 months of age. At 3 months, thinness at birth and rapid catch-up growth in the first month of life were associated with increased insulin sensitivity in males. In females thinness at 3 months was associated with reduced sensitivity to insulin. At 12 months, early postnatal catch-up growth was associated with insulin resistance, irrespective of sex, when all data were combined.

Conclusions/interpretation: The glucose intolerance previously observed in young adult pigs of low birthweight is probably due to insulin resistance. Early catch-up growth in low birthweight pigs was the clearest predictor of adult insulin resistance.