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      Distribution of growth hormone-responsive cells in the brain of rats and mice

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      Brain Research

      Elsevier BV

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          Most cited references 76

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          Effects of growth hormone on glucose, lipid, and protein metabolism in human subjects.

          In evolutionary terms, GH and intracellular STAT 5 signaling is a very old regulatory system. Whereas insulin dominates periprandially, GH may be viewed as the primary anabolic hormone during stress and fasting. GH exerts anabolic effects directly and through stimulation of IGF-I, insulin, and free fatty acids (FFA). When subjects are well nourished, the GH-induced stimulation of IGF-I and insulin is important for anabolic storage and growth of lean body mass (LBM), adipose tissue, and glycogen reserves. During fasting and other catabolic states, GH predominantly stimulates the release and oxidation of FFA, which leads to decreased glucose and protein oxidation and preservation of LBM and glycogen stores. The most prominent metabolic effect of GH is a marked increase in lipolysis and FFA levels. In the basal state, the effects of GH on protein metabolism are modest and include increased protein synthesis and decreased breakdown at the whole body level and in muscle together with decreased amino acid degradation/oxidation and decreased hepatic urea formation. During fasting and stress, the effects of GH on protein metabolism become more pronounced; lack of GH during fasting increases protein loss and urea production rates by approximately 50%, with a similar increase in muscle protein breakdown. GH is a counterregulatory hormone that antagonizes the hepatic and peripheral effects of insulin on glucose metabolism via mechanisms involving the concomitant increase in FFA flux and uptake. This ability of GH to induce insulin resistance is significant for the defense against hypoglycemia, for the development of "stress" diabetes during fasting and inflammatory illness, and perhaps for the "Dawn" phenomenon (the increase in insulin requirements in the early morning hours). Adult patients with GH deficiency are insulin resistant-probably related to increased adiposity, reduced LBM, and impaired physical performance-which temporarily worsens when GH treatment is initiated. Conversely, despite increased LBM and decreased fat mass, patients with acromegaly are consistently insulin resistant and become more sensitive after appropriate treatment.
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            The effects of treatment with recombinant human growth hormone on body composition and metabolism in adults with growth hormone deficiency.

            In a double-blind, placebo-controlled trial, we studied the effects of six months of growth hormone replacement in 24 adults with growth hormone deficiency. Most of the patients had acquired growth hormone deficiency during adulthood as a consequence of treatment for pituitary tumors, and all were receiving appropriate thyroid, adrenal, and gonadal hormone replacement. The daily dose of recombinant human growth hormone (rhGH) was 0.07 U per kilogram of body weight, given subcutaneously at bedtime. The mean (+/- SE) plasma concentration of insulin-like growth factor I increased from 0.41 +/- 0.05 to 1.53 +/- 0.16 U per liter during rhGH treatment. Treatment with rhGH had no effect on body weight. The mean lean body mass, however, increased by 5.5 +/- 1.1 kg (P less than 0.0001), and the fat mass decreased by 5.7 +/- 0.9 kg (P less than 0.0001) in the group treated with growth hormone; neither changed significantly in the placebo group. The basal metabolic rate, measured at base line and after one and six months of rhGH administration, increased significantly; the respective values were 32.4 +/- 1.4, 37.2 +/- 2.2, and 34.4 +/- 1.6 kcal per kilogram of lean body mass per day (P less than 0.001 for both comparisons). Fasting plasma cholesterol levels were lower (P less than 0.05) in the rhGH-treated group than in the placebo group, whereas plasma triglyceride values were similar in the two groups throughout the study. We conclude that growth hormone has a role in the regulation of body composition in adults, probably through its anabolic and lipolytic actions.
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              Ghrelin O-acyltransferase (GOAT) is essential for growth hormone-mediated survival of calorie-restricted mice.

              Ghrelin O-acyltransferase (GOAT) attaches octanoate to proghrelin, which is processed to ghrelin, an octanoylated peptide hormone that stimulates release of growth hormone (GH) from pituitary cells. Elimination of the gene encoding ghrelin or its receptor produces only mild phenotypes in mice. Thus, the essential function of ghrelin is obscure. Here, we eliminate the Goat gene in mice, thereby eliminating all octanoylated ghrelin from blood. On normal or high fat diets, Goat(-/-) mice grew and maintained the same weights as wild-type (WT) littermates. When subjected to 60% calorie restriction, WT and Goat(-/-) mice both lost 30% of body weight and 75% of body fat within 4 days. In both lines, fasting blood glucose initially declined equally. After 4 days, glucose stabilized in WT mice at 58-76 mg/dL. In Goat(-/-) mice, glucose continued to decline, reaching 12-36 mg/dL on day 7. At this point, WT mice showed normal physical activity, whereas Goat(-/-) mice were moribund. GH rose progressively in calorie-restricted WT mice and less in Goat(-/-) mice. Infusion of either ghrelin or GH normalized blood glucose in Goat(-/-) mice and prevented death. Thus, an essential function of ghrelin in mice is elevation of GH levels during severe calorie restriction, thereby preserving blood glucose and preventing death.
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                Author and article information

                Contributors
                Journal
                Brain Research
                Brain Research
                Elsevier BV
                00068993
                January 2021
                January 2021
                : 1751
                : 147189
                Article
                10.1016/j.brainres.2020.147189
                © 2021

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