Dysregulation of dimethylargininedimethylaminohydrolase/asymmetric dimethylarginine pathway in rat type II diabetic nephropathy.

An impaired generation of nitric oxide has been associated with diabetic renal disease. In order to elucidate the underlying molecular mechanisms into how nitric oxide synthesis is impaired in diabetic renal disease, we examined changes in activities and expressions of some renal enzymes involved in nitric oxide production during the development of diabetic nephropathy in type II diabetic Otsuka Long-Evans Tokushima Fatty rats. Ten-week old Otsuka Long-Evans Tokushima Fatty (n = 40) and control Long-Evans Tokushima Otsuka rats (n = 20) were given drinking water containing 20% sucrose to accelerate the development of diabetic nephropathy. Otsuka Long-Evans Tokushima Fatty rats developed diabetic nephropathy in an age-dependent manner. Renal nitric oxide synthase activities in Otsuka Long-Evans Tokushima Fatty rats gradually declined with the progression of diabetic mellitus and were significantly lower than those of age-matched Long-Evans Tokushima Otsuka rats after 22 weeks of age. The lower activities of renal nitric oxide synthase in Otsuka Long-Evans Tokushima Fatty rats were correlated with relatively higher levels of renal free asymmetric dimethylarginine, an endogenous nitric oxide synthase inhibitor, and were also correlated with decreased activities of dimethylargininedimethylaminohydrolase which metabolizes asymmetric dimethylarginine to citrulline. These results imply that dimethylargininedimethylaminohydrolase dysregulation may play an important role in the development of diabetic nephropathy by increasing asymmetric dimethylarginine levels, which leads to inhibition of renal nitric oxide synthesis.

Insulin secretory capacity and insulin sensitivity in impaired fasting glucose in Japanese.

UNLABELLED: Aims/Introduction: Impaired fasting glucose (IFG) increases the risk of developing diabetes mellitus (DM). This study was carried out to characterize Japanese patients who have fasting glucose levels (FPG) between 100 and 109 mg/dL (IFG100-109). MATERIALS AND METHODS: A total of 1383 Japanese participants were examined by oral glucose tolerance test. We compared insulin secretory capacity (insulinogenic index) and insulin sensitivity (ISI composite) of IFG100-109/normal glucose tolerance (NGT; 100 ≤ FPG < 110 mg/dL and 2-h postchallenge glucose level (2-hPG) < 140 mg/dL) with NGT (100 mg/dL < FPG and 2-hPG < 140 mg/dL) and IFG110-125/NGT (110 ≤ FPG < 126 mg/dL and 2-hPG < 140 mg/dL). In addition, IFG100-109 patients were analyzed in three subgroups according to glucose intolerance by 2-hPG. RESULTS: Of the three categories of IFG100-109, IFG100-109/DM had the lowest insulinogenic index despite an ISI composite showing only a small decline from IFG100-109/NGT through IFG100-109/IGT (100 ≤ FPG < 110 mg/dL and 140 ≤ 2-hPG < 200 mg/dL) to IFG100-109/DM (100 ≤ FPG < 110 mg/dL and 200 mg/dL < 2-hPG). By multiple regression analysis, the insulinogenic index showed a significant relationship with 2-h PG levels. Both insulinogenic index and ISI composite were decreased significantly from NGT through IFG100-109/NGT to IFG110-125/NGT. CONCLUSIONS: Although impaired early-phase insulin secretion plays the more important role in the elevation of postchallenge glucose in IFG100-109 patients, both impaired early-phase insulin secretion and decreased insulin sensitivity are involved in the deterioration of FPG in Japanese. In addition, insulin secretory defect and decreased insulin sensitivity already have begun in patients with IFG100-109. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2012.00201.x, 2012).

Smoking, white blood cell counts, and TNF system activity in Japanese male subjects with normal glucose tolerance.

BACKGROUND: Cigarette smokers have increased white blood cell (WBC) counts and the activation of tumor necrosis factor (TNF). The effect of smoking on WBC counts and TNF system activity, however, has not been separately investigated yet. SUBJECTS AND METHODS: One hundred and forty-two Japanese male subjects with normal glucose tolerance were recruited. They were stratified into two groups based on the questionnaire for smoking: one with current smokers (n = 48) and the other with current non-smokers (n = 94). Whereas no significant differences were observed in age, BMI, high molecular weight (HMW) adiponectin, and TNF-α between the two groups, current smokers had significantly higher soluble TNF receptor 1 (sTNF-R1) (1203 ± 30 vs. 1116 ± 21 pg/ml, p = 0.010) and increased WBC counts (7165 ± 242 vs. 5590 ± 163/µl, p < 0.001) and lower HDL cholesterol (55 ± 2 vs. 60 ± 1 mg/dl, p = 0.031) as compared to current non-smokers. Next, we classified 48 current smokers into two subpopulations: one with heavy smoking (Brinkman index ≥ 600) and the other with light smoking (Brinkman index < 600). RESULTS: Whereas no significant difference was observed in age, BMI, HMW adiponectin, WBC counts and TNF-α, sTNF-R1 and sTNF-R2 were significantly higher in heavy smoking group (1307 ± 44 vs. 1099 ± 30 pg/ml, p < 0.001; 2166 ± 86 vs. 827 ± 62 pg/ml, p = 0.005) than in light smoking group, whose sTNF-R1 and sTNF-R2 were similar to non-smokers (sTNF-R1: 1116 ± 15 pg/ml, p = 0.718, sTNF-R2; 1901 ± 32 pg/ml, p = 0.437). In contrast, WBC counts were significantly increased in heavy (7500 ± 324/µl, p < 0.001) or light (6829 ± 352/µl, p = 0.001) smoking group as compared to non-smokers (5590 ± 178/µl). There was no significant difference in WBC counts between heavy and light smoking group (p = 0.158). CONCLUSION: We can hypothesize that light smoking is associated with an increase in WBC counts, while heavy smoking is responsible for TNF activation in Japanese male subjects with normal glucose tolerance.

Inhibition of L-arginine metabolizing enzymes by L-arginine-derived advanced glycation end products.

N(omega)-Carboxymethyl-arginine (CMA), N(omega)-carboxyethyl-arginine (CEA) and N(delta)-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1) have been identified as L-arginine-derived advanced glycation end products (AGEs) formed by non-enzymatic reactions between reducing sugars such as glucose and amino groups in proteins. These AGEs are structurally analogous to endogenous inhibitors of nitric oxide synthases (NOS) including N(G)-monomethyl-L-arginine (L-NMMA) and asymmetric N(G),N(G)-dimethyl-L-arginine (ADMA). Increased plasma levels of these NOS inhibitors, and thus impaired generation of NO in vivo has been associated with the pathogenesis of vascular complications such as kidney failure and atherosclerosis. For these reasons we examined whether L-arginine-derived AGEs inhibit the activities of three L-arginine metabolizing enzymes including three isoforms of NOS (endothelium, neuronal and inducible NOS), dimethylarginine dimethylaminohydrolase (DDAH) that catalyzes the hydrolytic degradation of L-NMMA and ADMA to L-citrulline, and arginase that modulates intracellular L-arginine bioavailability. We found that AGEs inhibited the in vitro activities of endothelium type NOS weakly (IC(50) values of CMA, CEA and MG-H1 were 830, 3870 and 1280 microM, respectively) and were also potential endogenous inhibitors for arginase (IC(50) values of CMA and CML were 1470 and 1060 microM), but were poor inhibitors for DDAH. These results suggest that the tested L-arginine- and L-lysine-derived AGEs appear not to impair NO biosynthesis directly.

Crystallization and preliminary diffraction studies of prostaglandin E2-specific monoclonal antibody Fab fragment in the ligand complex.

Prostaglandin E(2) is a major lipid mediator that regulates diverse biological processes. To elucidate how prostaglandin E(2) is recognized specifically by its antibody, the Fab fragment of a monoclonal anti-prostaglandin E(2) antibody was prepared and its complex with prostaglandin E(2) was crystallized. The stable Fab-prostaglandin E(2) complex was prepared by gel-filtration chromatography. Crystals were obtained by the microbatch method at 277 K using polyethylene glycol 4000 as a precipitant. A diffraction data set was collected to 2.2 A resolution. The crystals belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 70.3, b = 81.8, c = 82.2 A. The asymmetric unit was suggested to contain one molecule of the Fab-prostaglandin E(2) complex, with a corresponding crystal volume per protein weight of 2.75 A(3) Da(-1).