The "ligandless" palladium acetate-catalyzed Suzuki cross-coupling reaction of ArX with aryl- and vinylboronic acids in water without organic cosolvent in the presence of tetrabutylammonium bromide is reported. Aryl bromides give high yields and considerably accelerate the coupling. A wide variety of functional groups can be tolerated. Aryl iodides, however, give incomplete conversion and aryl triflate coupling shows no improvement over reported conditions.
Abstract-Insulin resistance is associated with increased risk of atherosclerosis. Insulin receptor substrate-1 (IRS-1) plays a key role in tissue insulin sensitivity. A common mutation (G972R) of the IRS-1 gene has been shown to impair IRS-1 function, and it has been associated with reduced insulin sensitivity and lipid abnormalities. This led us to investigate the role of the G972R mutation in predisposing individuals to coronary artery disease (CAD). The DNA of 318 subjects with angiographically documented coronary atherosclerosis (Ͼ50% stenosis) and 208 population control subjects was analyzed for the presence of the G972R mutation. This mutation was detected by nested polymerase chain reaction and BstNI restriction enzyme digestion. The frequency of the G972R mutation was significantly higher among patients with CAD than controls (18.9% versus 6.8%, respectively; PϽ0.001). After controlling for other coronary risk factors, the relative risk of CAD associated with the G972R mutation was 2. 001).The IRS-1 gene variant was associated with a higher frequency of diabetes mellitus (14.9% among carriers versus 6.5% among noncarriers; PϽ0.01) and with a 60% increase of plasma total triglycerides (PϽ0.001). Also, plasma concentrations of total cholesterol and the ratio of total cholesterol to HDL cholesterol were significantly (PϽ0.001) higher among carriers than noncarriers, although to lesser a extent. These effects were independent of CAD status. The G972R mutation in the IRS-1 gene was found to be a significant independent predictor of CAD. Moreover, this mutation greatly increased the risk of CAD in obese subjects and in patients with the cluster of abnormalities of insulin resistance syndrome. Besides the increased frequency of diabetes, carriers showed a more atherogenic lipid profile, suggesting a potential role of the IRS-1 gene in the pathogenesis of lipid abnormalities associated with CAD. (Arterioscler Thromb
The hormone resistin has been suggested to link obesity to type 2 diabetes by modulating steps in the insulinsignaling pathway and inducing insulin resistance. Thus, the resistin gene represents a potential candidate for the etiology of insulin resistance and type 2 diabetes. In this study, we analyzed the coding sequence of the three exons of the resistin gene, together with its 5 regulatory region and 3 untranslated region (UTR), by singlestrand conformation polymorphism (SSCP) in 58 type 2 diabetic subjects, 59 obese subjects, and 60 normal subjects. Only one sequence variant was detected in the resistin gene. Sequencing of this variant revealed the presence of a single nucleotide substitution (SNP) in the 3-UTR of exon 3 (G1326C). Because 3-UTR SNPs have been shown to affect gene expression, we examined the frequency of this SNP in 591 subjects (198 obese subjects, 207 diabetic subjects, and 186 control subjects) by PCR amplification and BseRI digestion. No significant association was found between the G1326C variant and diabetes and obesity. Comparison of clinical and metabolic parameters between G1326C carriers and noncarriers again showed no significant difference. In conclusion, our data suggest that genetic defects of the resistin gene are unlikely to play a role in the etiology of these common disorders in our population. Diabetes 51:860 -862, 2002
Animal insulinoma cell lines are widely used to study physiological and pathophysiological mechanisms involved in glucose metabolism and to establish in vitro models for studies on -cells. In contrast, human insulinoma cell lines are rarely used because of difficulties in obtaining and culturing them for long periods.The aim of our study was to investigate, under different experimental conditions, the capacity of the human insulinoma cell line CM to retain -cell function, particularly the expression of constitutive -cell genes (insulin, the glucose transporters GLUT1 and GLUT2, glucokinase), intracellular and secreted insulin, -cell granules, and cAMP content.Results showed that CM cells from an early-passage express specific -cell genes in response to glucose stimulation, in particular the insulin and GLUT genes. Such capacity is lost at later passages when cells are cultured at standard glucose concentrations. However, if cultured at lower glucose concentration (0·8 mM) for a longer time, CM cells re-acquire the capacity to respond to glucose stimulation, as shown by the increased expression of -cell genes (insulin, GLUT2, glucokinase). Nonetheless, insulin secretion could not be restored under such experimental conditions despite the presence of intracellular insulin, although cAMP response to a potent activator of adenylate cyclase, forskolin, was present indicating a viable system.In conclusion, these data show that the human insulinoma cell line CM, at both early-passage and late-passage, posseses a functional glucose-signalling pathway and insulin mRNA expression similar to normal -cells, representing, therefore, a good model for studies concerning the signalling and expression of -cells. Furthermore, we have previously shown that it is also a good model for immunological studies. In this respect it is important to note that the CM cell line is one of the very few existing human -cell lines in long-term culture.
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