Hypothalamic Modulation of Growth Hormone Secretion in the Rhesus Monkey: Evidence from Intracerebroventricular Infusions of Glucose, Free Fatty Acid, and Ketone Bodies

Abstract

To evaluate the hypothalamus as a possible site of metabolic modulation of GH secretion, we studied the GH response to insulin hypoglycemia (IHG) and nicotinic acid (NA)-induced FFA depression in the absence and presence of third ventricular (ivt) infusions of glucose, oleic acid (Ol-Ac), or beta-hydroxybutyrate (beta OHB). Four rhesus monkeys had been prepared for chronic remote iv and ivt infusions as well as blood sampling from the adjacent room. Statistical evaluation used a two-way analysis of variance and individual comparisons with Tukey's Studentized range test. The GH response (area under the curve +/- SE) to IHG was significantly reduced by a concomitant ivt glucose infusion (control, 1.0 +/- 0.1; IHG, 12.1 +/- 3.3; IHG plus ivt glucose, 7.0 +/- 1.2 microgram/L.120 min). The GH response to FFA depression was significantly reduced by ivt Ol-Ac or beta OHB infusion (control, 6.0 +/- 1.0; NA, 51.5 +/- 4.1; Na plus Ol-Ac, 81.2 +/- 1.3; NA plus beta OHB, 38.6 +/- 3.5 microgram/L.300 min). Introcerebroventricular infusions of glucose, Ol-Ac, or beta OHB alone had no effect on plasma GH, glucose, FFA, or beta OHB concentrations. These results provide evidence for a hypothalamic site of metabolic modulation of GH secretion in the rhesus monkey. This does not exclude an additional effect directly at the pituitary gland.

Effect of hydration state on resistance exercise-induced endocrine markers of anabolism, catabolism, and metabolism

“…In the present investigation, hypohydration failed to directly influence growth hormone but clearly altered several growth hormone stimulators (the catecholamines) and inhibitors (glucose and free fatty acids) (8,44). Presumably, these opposing influences balanced each other, and no change occurred in growth hormone.…”

Metabolic changes during the transition from the fed to the acute feed-deprived state in prepuberal and mature gilts.

“…Changes in fat metabolism, serum ketone body, and IGF-I concentrations during periods of fast or nutrient deprivation could influence activity of hypothalamic neurons (Oomura et al, 1975;Abe et al, 1983;Hiney et al, 1991) and(or) pituitary responsiveness to GnRH and GRF (Quabbe et al, 1983(Quabbe et al, , 1991Barb et al, 1991bWhitley et al, 1995). Results from the present study do not allow identification of specific candidates for a role in signaling metabolic status to the neuroendocrine axis that regulates LH and GH secretion.…”

Effects of glucose, free fatty acids or arginine load on the GH‐releasing activity of ghrelin in humans

“…The potent inhibitory effect of FFA on somatotroph secretion had been explained by SS‐mediated actions and, more recently, by a direct inhibitory effect at the pituitary level (Casanueva, 1992; Ghigo et al ., 1999). In fact, intra‐cerebro‐ventricular injection of FFA inhibits GH secretion and this effect is counteracted by SS antiserum (Quabbe et al ., 1991). However, FFA also inhibit the GH response to GHRH from somatotroph cells in culture (Casanueva, 1992; Ghigo et al ., 1999) and in vivo in hypophysectomized‐transplanted rats (Alvarez et al ., 1991).…”