Influence of nutritional deprivation on insulin-like growth factor I, somatotropin, and metabolic hormones in swine.

Abstract

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.

Increased Expression of Fibroblast Growth Factor 21 (FGF21) during Chronic Undernutrition Causes Growth Hormone Insensitivity in Chondrocytes by Inducing Leptin Receptor Overlapping Transcript (LEPROT) and Leptin Receptor Overlapping Transcript-like 1 (LEPROTL1) Expression

“…In many experimental models food restriction is associated with reduced skeletal growth, with such association primarily resulting from impaired growth hormone action (7)(8)(9)(10)(11)(12)(13)(14)(15)(16). In a previous study we demonstrated that mice undergoing 4 weeks of food restriction exhibited increased expression of Fgf21 (both in the liver and in the growth plate), growth hormone (GH) 3 insensitivity, and a concomitant reduction of their body linear growth and growth plate chondrogenesis (17).…”

Influence of feed restriction in primiparous lactating sows on body condition and metabolic parameters

“…IGF-I levels were lower in L than in H sows during lactation despite slightly higher GH levels, which suggests an uncoupling of IGF-I secretion from GH secretion under nutrient deficit, as observed in restricted growing pigs [11] and in lactating cows [44]. In well-fed multiparous sows, Schams et al [45] suggested that the uncoupling between IGF-I and GH secretions was absent.…”

Insulin-Like Growth Factor-I as a Possible Hormonal Mediator of Nutritional Regulation of Reproduction in Cattle

“…During periods of nutritional deficit GH concentrations are elevated in several species including the pig [15], sheep [88] and cow [11], reflecting the effects of factors such as hypoglycemia and stress on pituitary secretion of GH. Gluckman and Breier [35] observed an increase in GH pulse amplitude in steers fed at 1% dry matter (DM) in comparison with steers fed at 3% DM of live weight of a high concentrate diet.…”