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[en] GLUT4 is unique among specialized glucose transporters in being exclusively expressed in muscle and adipocytes. In the absence of insulin the distribution of GLUT4 is preferentially intracellular and insulin stimulation results in the movement of GLUT4 containing vesicles to the plasma membrane. This process is responsible for the insulin stimulation of glucose uptake in muscle and fat. While signalling pathways triggering the translocation of GLUT4 are well understood, the mechanisms regulating the intracellular retention of GLUT4 are less well understood. Here we report a role for β-catenin in this process. In 3T3-L1 adipocytes in which β-catenin is depleted, the levels of GLUT4 at and near the plasma membrane rise in unstimulated cells while the subsequent increase in GLUT4 at the plasma membrane upon insulin stimulation is reduced. Small molecule approaches to acutely activate or inhibit β-catenin give results that support the results obtained with siRNA and these changes are accompanied by matching changes in glucose transport into these cells. Together these results indicate that β-catenin is a previously unrecognized regulator of the mechanisms that control the insulin sensitive pool of GLUT4 transporters inside these adipocyte cells.
[en] Highlights: • Telmisartan treatment alleviates insulin resistance in adipocytes stimulated with TNFα. • Telmisartan treatment reduces phosphorylation of PPARγ in adipocytes stimulated with TNFα. • Telmisartan treatment regulates the expressions of PPARγ downstream genes. • Telmisartan treatment promotes the secretion of adiponectin in adipocytes. Telmisartan is an angiotensin II receptor blocker (ARB) and a partial agonist of peroxisome proliferator activated receptor γ (PPARγ). It has been shown to significantly enhance insulin sensitivity in clinical studies and in vitro experiments. However, the effect of telmisartan on PPARγ in adipocytes remains unknown.
[en] The adaptation of human somatotropin and insulin assays to the automated Centria radioimmunoassay system [Clin. Chem. 21, 1305 (1975)] is reported. For the somatotropin assay, reaction conditions include a borate/bovine serum albumin buffer (pH 8.4) and a 20-h incubation at 40C. Assay results for clinical samples compared favorably (correlation coefficient = 0.930) with values obtained from a reference laboratory. The means determined for 92 patients' samples were 4.3 μg/liter (reference laboratory) and 5.1 μg/liter (Centria). Intra- and inter-run precision ranged from 3.2 to 15.9%. For the insulin assay, a phosphate/bovine serum albumin buffer (pH 7.4) is used, with a 20-h incubation at 40C. Previously analyzed insulin samples from a reference laboratory were determined by the Centria analyzer with excellent correlation (r = 0.965). Means for patients' samples were 43.0 milli (USP) units of insulin per liter (reference laboratory) and 47.5 milliunits of insulin per liter (Centria). In both assays an anionicexchange gel is used in the separation step. The criterion of parallelism, an indication of the validity of a radioimmunoassay, was satisfied in both assays. The Centria radioimmunoassay system offers the advantage of automating all the critical steps of these radioimmunoassays
[en] Schistosomes are parasitic platyhelminths that threaten over 600 million people globally. In recent years, RNA interference (RNAi) has been widely used as a molecular tool in research into the genomic function of parasites. We aim to develop effective protocols for application of RNAi technology in the intra-mammalian life stages of Schistosoma japonicum. In this work, the expression of the parasite gene encoding cathepsin B1 (SjCB1) was targeted by exposing the worms to 10 μg of long dsRNA dissolved in 0.1 ml of 0.7% NaCl injected into the tail vein of infected mice. This method was effective and specific for eliciting SjCB1 gene suppression in both male and female adult worms in vivo (>79.4% in male and >91.5% in female knockdown relative to control). In 60 cercaria infected mice, RNAi suppression of gene expression was best achieved by using 10 μg of target dsRNA for at least 4 days. The recommended procedure for interference producing long-term suppression was an injection of dsRNA on the first day of infection with booster injections administered every 4 days for up to 26 days. Long-term suppression of three published functional genes (peroxiredoxin-1, mago nashi, insulin receptor) in S. japonicum provided more information about the role of the expression of these genes in producing particular phenotypes. The protocols described here may be more convenient, economical and applicable, than currently available technology and have contributed to the observation of more phenotypes during worm development from schistosomula to adult. These approaches may promote and facilitate further studies into functional schistosome genomics.
[en] A methodological approach that permits, in a radioimmunoassay, the evaluation of rat insulin by using bovine insulin as reference is presented. As in general the technics for radioimmunoassay of different substances follow the same principles (competitive inhibition), we believe that the methodology presented here could be used for evaluation of other hormones when the adequated referential, of know biological activity, is not available. (Author)
[pt]Apresenta-se metodologia que torna possivel, em um radioimunoensaio, o uso de insulina bovina como referencial para avaliacao de insulina de rato. Como os radioimunoensaios utilizados para dosagem de diferentes substancias o mesmo principio (inibicao competitiva), acredita-se que a metodogologia apresentada possa ser utilizada tambem para avaliacao de outros hormonios, quando nao se dispuser do referencial adequado, de atividade biologica conhecida. (Autor)
[en] Highlights: • Acute and chronic exercises have a stimulatory effect on plasma IGF-I and Klotho. • Plasma IGF-I has an association with exercise-induced cardiac hypertrophy especially LVEDDI and LVMI. • Klotho acts as a negative regulator for exercise-induced cardiac hypertrophy most probably through modulating IGF-I effect. Owing to the role of insulin-like growth factor 1 (IGF-I) in cardiac hypertrophy and the ability of Klotho in inhibiting the IGF-I action, we investigated effects of exercise on plasma Klotho and IGF-I and their association with cardiac hypertrophy. In this study, 10 non-athlete and 10 athlete women underwent a Bruce test (acute exercise) and 12-weeks water aerobics training (chronic exercise). Electrocardiographic parameters, plasma IGF-I and Klotho levels were measured in different time courses. The exercise training could significantly increase left ventricular end-diastolic diameter index (LVEDDI) in the non-athletes. Plasma levels of IGF-I significantly increased following acute and chronic exercises. The Klotho levels at the baseline were higher in athletes than non-athletes and its levels significantly increased immediately after acute exercise in both groups. The Klotho levels significantly decreased in non-athletes 24 h after chronic exercise, but its level was still higher than the baseline in the athletes. We found positive and negative correlations between cardiac hypertrophy indexes (LVEDDI and left ventricular mass index) with respectively IGF-I and Klotho. In conclusion, we found a stimulatory effect of acute and chronic exercises on plasma IGF-I and Klotho and association of IGF-I with exercise-induced cardiac hypertrophy. Moreover, Klotho could act as a negative regulator for exercise-induced cardiac hypertrophy.
[en] A soluble-phase proinsulin assay has been developed which does not require solid-phase antibody-binding. A human proinsulin standard curve is prepared in insulin-free and proinsulin-free plasma for comparison with unknown plasma samples. Proinsulin and insulin are bound with excess anti-insulin antiserum, and free C-peptide is removed by charcoal adsorption. The supernatant is then assayed using a routine C-peptide radioimmunoassay which utilises anti-C-peptide antiserum. The sensitivity of the assay (2 standard deviations above zero) is 9 pmol/L using 200 μL plasma sample. The assay is free from insulin cross-reactivity up to 100 mU/L and C-peptide up to 2000 pmol/L. Between-assay CV is 13% at 100 pmol/L. The assay has been used in subjects with hypoglycaemia of various aetiologies and has shown that a raised plasma proinsulin in the presence of hypoglycaemia can occur in sulphonylurea-induced and reactive hypoglycaemia as well as in insulinomas. After hyperglycaemic clamps at 7.5, 10 and 15 mmol/L glucose, type II diabetics both on and off sulphonylurea, were found to have lower proinsulin concentrations compared with normal subjects, commensurate with the diabetics' lower insulin responses. (author)
[en] (1) 125I labelling of insulin and the standardization of the labelled insulin for RIA use are well established. (2) A protocol of routine kit preparation is established. (3) Maximum two 100 tube kits can-be prepared from one batch. (4) The kits show steep dose-response curve. The expire date is usually 40 days after preparation.