EFFECTS OF ACUTE AND CHRONIC FOOD RESTRICTION ON THE INSULIN-LIKE-GROWTH-FACTOR AXIS IN THE GUINEA-PIG

The effect of fasting (17-18 h) versus food restriction (70% for 80+/- 13 days) on the IGF-IGF binding protein (BP) axis in female guinea pig s was studied and related to body weight, weight gain and food convers ion efficiency. Circulating IGF-I was reduced in the fasted (13%) and food-restricted (50%) animals. IGF-II was only decreased (61%) in the food-restricted soup. There was no effect of Easting on IGFBP-1 to -4 while IGFBP-1, -3 and -4 were reduced by 56%, 60% and 44% respectively , and IGFBP-2 increased by 72%, in the food-restricted group. Food res triction reduced the relative sizes of fat depots, spleen, liver, thym us and heart, increased those of adrenals, kidneys, pancreas, gastroin testinal tract, M. Biceps, M. Soleus and brain while those of uterus, lungs, thyroids and M. Gastrocnemius were unchanged. IGFBP-1 and -2 we re negatively correlated to weight gain and food conversion efficiency in the ad libitum-fed group, while IGF-I, -II, IGFBP-1, -3 and -4 wer e positively correlated to body weight, weight gain and food conversio n efficiency in the food-restricted group. The results show that acute and chronic food restriction have different consequences for the IGF- IGFBP axis, Furthermore, IGF-II as well. as IGF-I are implicated in th e control of body weight, weight gain and food conversion efficiency u nder conditions of restricted nutrition. Finally, IGFBP-1 and -2 may h ave different roles during chronic undernutrition compared with unrest rained nutrition in adult life.