OBJECTIVE-GPR40 is a G protein-coupled receptor regulating free fatty acid-induced insulin secretion. We generated transgenic mice overexpressing the hGPR40 gene under control of the mouse insulin II promoter and used them to examine the role of GPR40 in the regulation of insulin secretion and glucose homeostasis.RESEARCH DESIGN AND METHODS-Normal (C57BL/6J) and diabetic (KK) mice overexpressing the hGPR40 gene under control of the insulin II promoter were generated, and their glucose metabolism and islet function were analyzed.RESULTS-In comparison with nontransgenic littermates, hGPR40 transgenic mice exhibited improved oral glucose tolerance with an increase in insulin secretion. Although islet morphologic analysis showed no obvious differences between hGPR40 transgenic and nontransgenic mice, isolated islets from hGPR40 transgenic mice had enhanced insulin secretion in response to high glucose (16 mmol/l) compared with those from nontransgenic mice, and they both had similar low glucose (3 mmol/l)-stimulated insulin secretion. In addition, hGPR40 transgenic islets significantly increased insulin secretion against a naturally occurring agonist palmitate in the presence of 11 mmol/l glucose. hGPR40 transgenic mice were also found to be resistant to high-fat diet-induced glucose intolerance, and hGPR40 transgenic mice harboring KK background showed augmented insulin secretion and improved oral glucose tolerance compared with nontransgenic littermates. CONCLUSIONS-Our results suggest that GPR40 may have a role in regulating glucose-stimulated insulin secretion and plasma glucose levels in vivo and that pharmacological activation of GPR40 may provide a novel insulin secretagogue beneficial for the treatment of type 2 diabetes.

The tissue distribution of neurotrophin‐3 (NT‐3) was investigated in rats at 1 month of age using a newly established, sensitive two‐site enzyme immunoassay system for NT‐3, as well as the immunocytochemical localization of this protein. The immunoassay for NT‐3 enabled us to quantify NT‐3 at levels > 3 pg per assay. In the rat brain, NT‐3 was detectable only in the olfactory bulb (0.54 ng/g wet weight), cerebellum (0.71 ng/g), septum (0.91 ng/g), and hippocampus (6.3 ng/g). By contrast, NT‐3 was widely distributed in peripheral tissues. Appreciable levels of NT‐3 were also found in the thymus (31 ng/g), heart (38 ng/g), diaphragm (21 ng/g), liver (45 ng/g), pancreas (892 ng/g), spleen (133 ng/g), kidney (40 ng/g), and adrenal gland (46 ng/g). An antibody specific for NT‐3 bound to pyramidal cells in the CA2‐CA4 regions of the hippocampus, to A cells in the islets of Langerhans in the pancreas, to unidentified cells in the red pulp of the spleen, to liver cells, and to muscle fibers in the diaphragm from rats at 1 month of age. Molecular masses of NT‐3‐immunoreactive proteins in the hippocampus and pancreas were 14 and 12 kDa, respectively. Thus, in rats, NT‐3 was detected in restricted regions of the brain and in the visceral targets of the nodose ganglia at high concentrations. Our present results suggest that NT‐3 not only functions as a classical target‐derived neurotrophic factor but also can play other roles.

A cDNA encoding a novel human neurotrophic factor (designated nerve growth factor‐2; NGF‐2) was cloned from a human glioma cDNA library using a synthetic DNA corresponding to human nerve growth factor (NGF). The cloned cDNA encodes a polypeptide composed of 257 amino acid residues including a prepro‐sequence of 138 residues and a mature region of 119 residues. The amino acid sequence of human NGF‐2 exhibits 58% similarity with that of human NGF. Conditioned medium of COS‐7 cells transfected with an expression plasmid for human NGF‐2 cDNA supported the survival of sensory neurons isolated from dorsal root ganglia of embryonic chicks. A 1.5 kb of NGF‐2 mRNA can be detected from an early development stage in rat brain, by Northern blotting analysis.

Computer graphics indicate that a steric hindrance exists between valine-110 side chain of human lysozyme (EC 3.2.1.17) and an acetyl group of a modified substrate that contains N',O-diacetylmuramic acid. To alter the substrate specificity of human lysozyme to be effective on the modified substrate, we replaced the valune-110 residue with various amino acids by site-directed mutagenesis. One of the mutant proteins (valine residue replaced with proline: Pll0) was secreted in Saccharomyces cerevisiae as at least four components (P'10-A, P'10-B, P110-C, and P"1°-D) with different specific activities. Two components, P"10-B and P"O-D, were isolated in a pure form and structurally characterized. The results suggest that this mutation lowered the lytic activity against Micrococcus lysodeikicus by changing a local conformation of the catalytic site while keeping almost the same substrate binding sites. Our results also indicate that cis/trans isomerization of prolyl peptide bonds probably occurs in vivo and that the conformational change of protein as well as point mutations in genes might influence the molecular evolution of the protein.

OBJECTIVE-GPR40 is a G protein-coupled receptor regulating free fatty acid-induced insulin secretion. We generated transgenic mice overexpressing the hGPR40 gene under control of the mouse insulin II promoter and used them to examine the role of GPR40 in the regulation of insulin secretion and glucose homeostasis.RESEARCH DESIGN AND METHODS-Normal (C57BL/6J) and diabetic (KK) mice overexpressing the hGPR40 gene under control of the insulin II promoter were generated, and their glucose metabolism and islet function were analyzed.RESULTS-In comparison with nontransgenic littermates, hGPR40 transgenic mice exhibited improved oral glucose tolerance with an increase in insulin secretion. Although islet morphologic analysis showed no obvious differences between hGPR40 transgenic and nontransgenic mice, isolated islets from hGPR40 transgenic mice had enhanced insulin secretion in response to high glucose (16 mmol/l) compared with those from nontransgenic mice, and they both had similar low glucose (3 mmol/l)-stimulated insulin secretion. In addition, hGPR40 transgenic islets significantly increased insulin secretion against a naturally occurring agonist palmitate in the presence of 11 mmol/l glucose. hGPR40 transgenic mice were also found to be resistant to high-fat diet-induced glucose intolerance, and hGPR40 transgenic mice harboring KK background showed augmented insulin secretion and improved oral glucose tolerance compared with nontransgenic littermates.