ABSTRACT
Growth hormone secretagogues (GHSs) stimulate GH secretion and food intake. GHS receptor (GHS-R) mRNA has been identified mainly in the arcuate nucleus (Arc) and ventromedial nucleus of the hypothalamus and in the pituitary. Ghrelin, an endogenous ligand for GHS-R, has recently been purified from rat stomach. Although ghrelin is also expressed in the hypothalamus, the physiological significance of the ghrelin/GHS-R system is still unknown. We have created transgenic (Tg) rats expressing an antisense GHS-R mRNA under the control of the promoter for tyrosine hydroxylase (TH), thus selectively attenuating GHS-R protein expression in the Arc. Tg rats had lower body weight and less adipose tissue than did control rats. Daily food intake was reduced, and the stimulatory effect of GHS treatment on feeding was abolished in Tg rats. GH secretion and plasma insulin-like growth factor-I levels were reduced in female Tg rats. These results suggest that GHS-R in the Arc is involved in the regulation of GH secretion, food intake, and adiposity.
Subject(s)
Adipose Tissue/metabolism , Growth Hormone/metabolism , Peptide Hormones , Peptides/physiology , Receptors, Cell Surface/metabolism , Receptors, Cell Surface/physiology , Receptors, G-Protein-Coupled , Animals , Animals, Genetically Modified , Blotting, Western , DNA/metabolism , Dose-Response Relationship, Drug , Female , Gastric Mucosa/metabolism , Ghrelin , Hypothalamus/metabolism , Immunohistochemistry , In Situ Hybridization , Ligands , Male , Oligonucleotides, Antisense/metabolism , Oligopeptides/pharmacology , Promoter Regions, Genetic , RNA, Messenger/metabolism , Rats , Receptors, Ghrelin , Sex Factors , Time FactorsABSTRACT
A 39-year-old man with lipoprotein lipase (LPL) deficiency (height 177.7 cm, body weight 67 kg, and body mass index 21.2 kg/m2) showed severe hypertriglyceridemia (2,032 mg/dl). LPL activity and concentration were markedly low in postheparin plasma. LPL gene analysis revealed a homozygous mutation, Asp204 --> Glu in exon 5. Fasting plasma glucose (81 mg/dl) and insulin (2.7 microU/ml) levels were normal. Plasma glucose pattern during oral glucose (75 g) tolerance test was normal, however 30 minutes after glucose-loading the insulin secretion unexpectedly increased to 89.4 microU/ml. These data suggested that chylomicronemia might be related to a hyper-response of insulin secretion to glucose without obesity.
