Influence of nutritional deprivation on insulin-like growth factor I, somatotropin, and metabolic hormones in swine.
Although growth hormone (GH) is a primary stimulus for the synthesis of insulin-like growth factor I (IGF-I), other factors such as nutritional status, insulin, and thyroid hormones are important modulators of circulating IGF-I levels. Thus, the effects of feed restriction and subsequent refeeding on plasma levels of IGF-I, GH, insulin, and thyroid hormones were studied in swine. Despite an elevation in plasma GH levels after 48 h of feed restriction, circulating IGF-I levels were decreased by 53% (P less than .05). Plasma triiodothyronine (T3) and insulin were lower (P less than .05) within 24 h after the feed restriction began, whereas thyroxine (T4) did not decrease until 48 h after removal of feed. Blood glucose levels remained unchanged throughout the experiment. Refeeding after the 48-h fast was associated with a decline (P less than .05) in circulating GH levels within 2 h, concomitant with an elevation (P less than .05) in plasma insulin and T3. Refeeding fasted pigs was associated with an increase (P less than .05) in plasma IGF-I; however, levels still had not returned to prefast concentrations within 24 h after refeeding. These data indicate that the GH-IGF-I axis becomes uncoupled during nutritional restriction in swine and that inadequate nutrient supply may limit the expression of the anabolic effects of GH.
Buonomo
F C
FC
Anim. Sci. Div., Monsanto Company, St. Louis MO 63198.
Baile
C A
CA
D000818:Animals; D005508:Food Deprivation / Q000502:physiology*; D013006:Growth Hormone / Q000097:blood*; D007328:Insulin / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D013552:Swine / Q000378:metabolism*; D013963:Thyroid Hormones / Q000097:blood
D007328:Insulin; D013963:Thyroid Hormones; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone