SIK1 localizes with nephrin in glomerular podocytes and its polymorphism predicts kidney injury.

Mutant α-adducin and endogenous ouabain levels exert a causal role in hypertension by affecting renal Na-K ATPase. In addition, mutant ß-adducin is involved in glomerular damage through nephrin down-regulation. Recently, the salt-inducible kinase 1 (SIK1) has been shown to exert a permissive role on mutant α-adducin effects on renal Na-K ATPase activity involved in blood pressure (BP) regulation and a SIK1 rs3746951 polymorphism has been associated with changes in vascular Na-K ATPase activity and BP. Here, we addressed the role of SIK1 on nephrin and glomerular functional modifications induced by mutant ß-adducin and ouabain, by using congenic substrains of the Milan rats expressing either mutant α- or ß-adducin, alone or in combination, ouabain hypertensive rats (OHR) and hypertensive patients. SIK1 co-localized and co-immunoprecipitated with nephrin from glomerular podocytes and associated with caveolar nephrin signaling. In cultured podocytes, nephrin-gene silencing decreased SIK1 expression. In mutant ß-adducin congenic rats and in OHR, the podocyte damage was associated with decreased nephrin and SIK1 expression. Conversely, when the effects of ß-adducin on podocytes were blocked by the presence of mutant α-adducin, nephrin and SIK1 expressions were restored. Ouabain effects were also reproduced in cultured podocytes. In hypertensive patients, nephrinuria, but not albuminuria, was higher in carriers of mutant SIK1 rs3746951 than in wild-type, implying a more direct effect of SIK1 on glomerular damage. These results demonstrate that, through nephrin, SIK1 is involved in the glomerular effects of mutant adducin and ouabain and a direct effect of SIK1 is also likely to occur in humans.

Risk for cardiovascular events in an Italian population of patients with type 2 diabetes.

BACKGROUND AND AIM: This study aims to analyse the risk of cardiovascular events in a local cohort of patients with type 2 diabetes, and to evaluate the prognostic accuracy of four algorithms used to estimate cardiovascular risk: the Framingham study, United Kingdom Prospective Diabetes Study (UKPDS), Riskard study and Progetto Cuore. METHOD AND RESULTS: We analysed clinical charts of the Diabetes Clinics of Modena for the period 1991-95. Patients in the age range of 35-65 with type 2 diabetes and no previous cardiovascular disease were eligible. The incidence of new cardiovascular disease was compared with estimated rates deriving from the different functions. A stratification was obtained in subgroups at different cardiovascular risk, allowing comparison between the algorithms. A total of 1532 patients were eligible; women presented a worse cardiovascular risk profile. An absolute 10-year rate of cardiovascular events of 14.9% was observed. Comparing patients with events with event-free subjects, we found significant differences in systolic blood pressure, age at visit, smoking, high-density lipoprotein (HDL)-cholesterol, duration of diabetes, glycosylated haemoglobin (HbA1c) and co-morbidities. Comparing the estimated risk rate according to the different functions, Italian algorithms were more consistent with observed data; however, Progetto Cuore and Riskard show underestimation of events when applied to females. CONCLUSIONS: Estimation of cardiovascular risk is dependent on the algorithm adopted and on the baseline risk of the reference cohort. Functions designed for a specific population, including risk variables peculiar for diabetes, should be adopted to increase the performance of such functions which is clearly unsatisfactory at present.

The benzamide MS-275 is a potent, long-lasting brain region-selective inhibitor of histone deacetylases.

The association of the histone deacetylase (HDAC) inhibitor valproate (VPA) with atypical antipsychotics has become a frequent treatment strategy for schizophrenia and bipolar disorder. Because the VPA doses administered are elevated, one cannot assume that the benefits of the VPA plus antipsychotic treatment are exclusively related to the covalent modifications of nucleosomal histone tails. We compared the actions of N-(2-aminophenyl)-4-[N-(pyridin-3-yl-methoxycarbonyl)aminomethyl]benzamide derivative (MS-275), which is a potent HDAC inhibitor in vitro, with the actions of VPA for their ability to (i) increase the acetylated status of brain nucleosomal histone tail domains and (ii) to regulate brain histone-RELN and histone-GAD(67) promoter interactions. MS-275 increases the content of acetylhistone 3 (Ac-H3) in the frontal cortex. Whereas this response peaks after a s.c. injection of 15 micromol/kg, the increase in Ac-H3 content in the hippocampus becomes significant only after an injection of 60 micromol/kg, suggesting that MS-275 is 30- to 100-fold more potent than VPA in increasing Ac-H3 in these brain regions. In contrast to VPA, MS-275, in doses up to 120 micromol/kg, fails to increase Ac-H3 content in the striatum. Chromatin immunoprecipitation shows that MS-275 increases Ac-H3-RELN and Ac-H3-GAD(67) promoter interaction in the frontal cortex. These results suggest that MS-275 is a potent brain region-selective HDAC inhibitor. It is likely that, in addition to MS-275, other benzamide derivatives, such as sulpiride, are brain-region selective inhibitors of HDACs. Hence, some benzamide derivatives may express a greater efficacy than VPA as an adjunctive to antipsychotics in the treatment of epigenetically induced psychiatric disorders.

Reelin and glutamic acid decarboxylase67 promoter remodeling in an epigenetic methionine-induced mouse model of schizophrenia.

Reduction of prefrontal cortex glutamic acid decarboxylase (GAD67) and reelin (mRNAs and proteins) expression is the most consistent finding reported by several studies of postmortem schizophrenia (SZ) brains. Converging evidence suggests that the reduced GAD67 and reelin expression in cortical GABAergic interneurons of SZ brains is the consequence of an epigenetic hypermethylation of RELN and GAD67 promoters very likely mediated by the overexpression of DNA methyltransferase 1 in cortical GABAergic interneurons. Studies of the molecular mechanisms (DNA methylation plus related chromatin remodeling factors) that cause the down-regulation of reelin and GAD67 in SZ brains have important implications not only to understand the disease pathogenesis but also to improve present pharmacological interventions to treat SZ. The mouse treated with l-methionine models some of the molecular neuropathologies detected in SZ, including the hypermethylation of RELN promoter CpG islands and the down-regulation of reelin and GAD67 expression. We now report that in these mice, RELN and GAD67 promoters express an increased recruitment of methyl-CpG binding domain proteins. In these mice the histone deacetylase inhibitor valproate, which increases acetylated histone content in cortical GABAergic interneurons, also prevents MET-induced RELN promoter hypermethylation and reduces the methyl-CpG binding domain protein binding to RELN and GAD67 promoters. These findings suggest that DNA hypermethylation and the associated chromatin remodeling may be critically important in mediating the epigenetic down-regulation of reelin and GAD67 expression detected in cortical GABAergic interneurons of SZ patients.