Hydrogen peroxide stimulates tyrosine phosphorylation of the insulin receptor and its tyrosine kinase activity in intact cells.

H-35 rat hepatoma cells were labelled with [32P]orthophosphate and their insulin receptors isolated on wheat germ agglutinin (WGA)-agarose and anti-(insulin receptor) serum. The incubation of these cells with 10 mM-H2O2 for 10 min increased the phosphorylation of both the serine and tyrosine residues of the beta subunit of the insulin receptor. Next, insulin receptors were purified on WGA-agarose from control and H2O2-treated H-35 cells and the purified fractions incubated with [gamma-32P]ATP and Mn2+. Phosphorylation of the beta subunit of insulin receptors obtained from H2O2-treated cells was 150% of that of control cells. The kinase activity of the WGA-purified receptor preparation obtained from H2O2-treated cells, as measured by phosphorylation of src-related synthetic peptide, was increased about 4-fold over control cells. These data suggest that in intact cell systems, H2O2 may increase the insulin receptor kinase activity by inducing phosphorylation of the beta subunit of insulin receptor.     

Enhanced insulin-induced mitogenesis and mitogen-activated protein kinase activities in mutant insulin receptors with substitution of two COOH-terminal tyrosine autophosphorylation sites by phenylalanine.

We have studied the function of a mutant human insulin receptor in which two COOH-terminal autophosphorylation sites (Tyr-1316 and -1322) were replaced by phenylalanine (F/Y COOH-terminal 2 tyrosines (CT2)). In addition, we have also constructed a mutant receptor in which Lys-1018 in the ATP-binding site was changed to arginine (R/K 1018). Both the wild type insulin receptor (HIR) and the mutant receptors were expressed in Chinese hamster ovary (CHO) cells by stable transfection. Autophosphorylation of solubilized and partially purified F/Y CT2 was decreased by approximately 30% compared with the HIR. Tyrosine kinase activities of F/Y CT2 and HIR toward exogenous substrates were almost equal. When CHO cells transfected with F/Y CT2 (CHO-F/Y CT2) were stimulated with insulin, autophosphorylation of the beta-subunit of the insulin receptor and the phosphorylation of an endogenous substrate (pp185) in the intact cell were normal compared with cells expressing HIR (CHO-HIR). CHO-F/Y CT2 exhibited the same insulin sensitivity as CHO-HIR with respect to 2-deoxyglucose uptake. However, the dose-response curve of insulin-stimulated thymidine incorporation in CHO-F/Y CT2 was shifted to the left (approximately 5-7-fold) compared with that in CHO-HIR. There was no significant difference in insulin-like growth factor 1-stimulated thymidine incorporation between CHO-F/Y CT2 and CHO-HIR. Furthermore, the dose-response curve of insulin-stimulated kinase activity toward myelin basic protein in CHO-F/Y CT2 was also shifted to the left (approximately 5-fold) compared with that in CHO-HIR. Kinase assays in myelin basic protein-containing gels revealed that both species of MAP kinases (M(r) 44,000, 42,000) were more sensitive to activation by insulin in CHO-F/Y CT2 than in CHO-HIR. This observation was confirmed in immune complex kinase assays toward microtubule-associated protein 2 (MAP2) using specific antibodies against mitogen-activated protein (MAP) kinase. R/K 1018 mutant insulin receptors showed an absence of insulin-stimulated kinase activity and CHO cells transfected with R/K 1018 (CHO-R/K 1018) failed to enhance 2-deoxyglucose uptake or thymidine incorporation in response to insulin. In addition, R/K 1018 kinase-defective insulin receptors were unable to mediate insulin-stimulated MAP kinase activation. These data suggest that: 1) tyrosine kinase activity of the insulin receptor is required for activation of insulin-stimulated MAP kinases and 2) phosphorylation of COOH-terminal tyrosine residues may play an inhibitory role in mitogenic signaling through regulation of MAP kinases.     

Are the Rates of Hypertension and Diabetes Higher in People from Lower Socioeconomic Status in Bangladesh? Results from a Nationally Representative Survey

ObjectiveA well-established belief regarding inequalities in health around the world is that hypertension and diabetes are higher in groups of lower socioeconomic status. We examined whether rates of hypertension, diabetes, and the coexistence of hypertension and diabetes are higher in people from a lower socioeconomic status than in those from a higher socioeconomic status in Bangladesh.MethodsWe investigated a nationally representative dataset from the 2011 Bangladesh Demographic and Health Survey with objective measures for hypertension and diabetes. A wealth index was constructed from data on household assets using principal components analysis. Chi-square tests and logistic regressions were performed to test the associations between wealth level, hypertension and diabetes.FindingsPeople from the highest wealth quintile were significantly more likely to have hypertension (Adjusted odds ratios [AOR] = 1.65, 95% confidence interval [CI] = 1.22-2.25), diabetes (AOR = 1.81, 95% CI = 1.21-2.71), and the coexistence of hypertension and diabetes (AOR = 2.17, 95% CI = 1.05-4.49) than people from the lowest wealth quintile. The odds of having hypertension, diabetes, and their coexistence were higher for older people, women, people who engaged in less physical labor, and people who were overweight and obese.ConclusionWealthier people, particularly people from the fourth and highest wealth quintiles, should be careful to avoid unhealthy lifestyles to prevent hypertension and diabetes. Health policy makers and planners are urged to target wealthier strata in terms of hypertension and diabetes initiatives while paying special attention to older people, women, people who engage in less physical labor, and individuals who are overweight.     

Effect of dietary fish oil replacement with palm oil on growth performance,hematology and liver anti‐oxidative enzymes of juvenile Japanese flounder Paralichthys olivaceus (Temminck & Schlegel, 1846)

A 60‐day feeding trial was conducted to evaluate the effects of dietary palm oil supplements on growth performances, hematology, liver anti‐oxidative enzymes and air exposure resistance of Japanese flounder, Paralichthys olivaceus (initial weights 2.56 ± 0.01 g). Five diets were tested wherein the dietary fish oil was replaced by palm oil at: 0% (Control), 20% (20%), 40% (40%), 50% (50%) and 60% (60%). After the feeding trial, the 20% dietary palm oil was shown to provide similar growth rates and feed efficiency with no negative effects compared to the control group (P > 0.05). Significantly lower growth rates and feed utilization were found in fish fed higher than 40% palm oil in the diet (P < 0.05). Except for total serum protein, the blood parameters, liver anti‐oxidative enzymes, stress resistance and proximate compositions of Japanese flounder were not altered, even with dietary palm oil up to 60% of the lipid source (P > 0.05). According to the present results, palm oil is a valuable lipid source substitute in Japanese flounder diets; around 20–40% fish oil can be replaced with palm oil with no negative effects.     

Protein requirement of the prawn Marsupenaeus japonicus estimated by a factorial method

The protein requirement to give maximum body protein retention in the prawn Marsupenaeus japonicus was assessed by determining both daily protein needed for maintenance (M) and daily body protein increment (G) when the juvenile prawn was maintained on a diet containing high quality protein. The body protein increment was obtained by determining carcass nitrogen increment when the prawn was fed on casein-based diets. The protein required for maintenance was estimated by regressing weight gains of the prawn on the diets containing graded levels of casein. True daily increase or retention of body protein in the prawn corresponded to the sum of G and M, and it was 3.2 g protein per kg body weight per day. The dietary protein requirement of juvenile M. japonicus for maximum body protein retention was suggested to be about 10 g per kg body weight per day providing that the prawn was fed the casein-based diet containing 50% crude protein (net protein utilization = 32) at the feeding level of 2%.     

Optimization of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepine-5-ylidene)acetamide derivatives as arginine vasopressin V2 receptor agonists and discussion of their binding modes

A series of (4,4-difluoro-1,2,3,4-tetrahydro-5H-1-benzazepine-5-ylidene)acetamide derivatives were optimized to achieve potent agonistic activity, both in vitro and in vivo, for the arginine vasopressin V₂ receptor, resulting in the eventual discovery of compound 1g. Molecular modeling of compound 1g with V₂ receptor was also examined to evaluate the binding mode of this series of compounds.     

Phosphorylation state and biological function of a mutant human insulin receptor Val996

Chinese hamster ovary (CHO) cell transfectants that expressed human insulin receptors whose glycine 996 was substituted by valine were studied. Receptor processing and insulin binding were unaffected by this mutation; however, this mutant insulin receptor had little or no tyrosine kinase activity. Nevertheless, the Val996 mutant exhibited seryl and threonyl phosphorylation in both the basal and insulin-stimulated state in intact cells. This is in contrast to the Lys----Ala1018 tyrosine kinase deficient mutant (Russell, D. S., Gherzi, R., Johnson, E. L., Chou, C-K., and Rosen, O. M. (1987) J. Biol. Chem. 262, 11833-11840). Cells expressing the normal human receptor were 10-fold more sensitive to insulin than the untransfected CHO cells with respect to phosphorylation of a cellular substrate (pp 185) on tyrosyl residues, glucose incorporation into glycogen, thymidine incorporation into DNA, and phosphorylation of ribosomal protein S6. Cells expressing the mutant receptor exhibited the same insulin sensitivity as the untransfected CHO cells. Insulin was rapidly internalized in cells expressing the normal human receptor and the number of receptors expressed on the cell surface was decreased in response to exposure to insulin. However, little insulin was internalized in cells expressing the mutant receptor, and the number of receptors on the cell surface was not significantly diminished in response to exposure to insulin. It is concluded that despite the occurrence of seryl and threonyl phosphorylations, post-receptor effects of insulin described above are not mediated by the tyrosine kinase-deficient receptor, Val996.     

The Role of Gcr1p in the Transcriptional Activation of Glycolytic Genes in Yeast Saccharomyces Cerevisiae

To study the interdependence of Gcr1p and Rap1p, we prepared a series of synthetic regulatory sequences that contained various numbers and combinations of CT-boxes (Gcr1p-binding sites) and RPG-boxes (Rap1p-binding sites). The ability of the synthetic oligonucleotides to function as regulatory sequences was tested using an ENO1-lacZ reporter gene. As observed previously, synthetic oligonucleotides containing both CT- and RPG-boxes conferred strong UAS activity. Likewise, a lone CT-box did not show any UAS activity. By contrast, oligonucleotides containing tandem CT-boxes but no RPG-box conferred strong promoter activity. This UAS activity was not dependent on position or orientation of the oligonucleotides in the 5'' noncoding region. However, it was dependent on both GCR1 and GCR2. These results suggest that the ability of Gcr1p to bind Gcr1p-binding sites in vivo is not absolutely dependent on Rap1p. Eleven independent mutants of GCR1 were isolated that conferred weak UAS activity to a single CT-box. Five mutants had single mutations in Gcr1p''s DNA-binding domain and displayed slightly higher affinity for the CT-box. These results support the hypothesis that Gcr1p and Gcr2p play the central role in glycolytic gene expression and that the function of Rap1p is to facilitate the binding of Gcr1p to its target.