Inhibition of de novo ceramide synthesis by Sirtuin-1 improves beta-cell function and glucose metabolism in type 2 diabetes.

BACKGROUND: Obesity and type 2 diabetes (T2D) are major risk factors for cardiovascular diseases (CVD). Dysregulated pro-apoptotic ceramide synthesis reduces ß-cell insulin secretion, thereby promoting hyperglycemic states which may manifest as T2D. Pro-apoptotic ceramides modulate insulin sensitivity and glucose tolerance while being linked to poor cardiovascular outcomes. Sirtuin-1 (SIRT1) is a NAD + - dependent deacetylase that protects against pancreatic ß-cell dysfunction; however, systemic levels are decreased in obese T2D mice and may promote pro-apoptotic ceramide synthesis and hyperglycemia. Herein, we aimed to assess the effects of restoring circulating SIRT1 levels to prevent metabolic imbalance in obese and diabetic mice. METHODS AND RESULTS: Circulating SIRT1 levels were reduced in obese diabetic mice (db/db) as compared to age-matched non-diabetic db/+ controls. Restoration of SIRT1 plasma levels with recombinant murine SIRT1 for 4-weeks prevented body weight gain, improved glucose tolerance, insulin sensitivity and vascular function in mice models of obesity and T2D. Untargeted lipidomics revealed that SIRT1 restored insulin-secretory function of ß-cells by reducing synthesis and accumulation of pro-apoptotic ceramides. Molecular mechanisms involved direct binding to and deacetylation of Toll-like receptor 4 (TLR4) by SIRT1 in ß-cells thereby decreasing the rate limiting enzymes of sphingolipid synthesis SPTLC1/2 via AKT/NF-κB. Among T2D patients, those with high baseline plasma levels of SIRT1 prior to metabolic surgery displayed restored ß-cell function (HOMA2- ß) and were more likely to have T2D remission during follow-up. CONCLUSION: Acetylation of TLR4 promotes ß-cell dysfunction via ceramide synthesis in T2D, which is blunted by systemic SIRT1 replenishment. Hence, restoration of systemic SIRT1 may provide a novel therapeutic strategy to counteract toxic ceramide synthesis and mitigate cardiovascular complications of T2D.

Long non-coding RNAs H19 and NKILA are associated with the risk of death and lacunar stroke in the elderly population.

INTRODUCTION: Differential expression of long non-coding RNAs (lncRNAs) is a hallmark of cardiovascular aging, cerebrovascular diseases, and neurodegenerative disorders. This research article investigates the association between a panel of lncRNAs and the risk of death and ischemic stroke in a cohort of non-institutionalized elderly subjects. METHOD: A total of 361 healthy individuals aged 75 years old, prospectively recruited in the Vienna Transdanube Aging (VITA) cohort, were included. Expression of lncRNAs at baseline was assessed using quantitative polymerase chain reaction PCR with pre-amplification reaction, using 18S for normalization. The primary endpoint was all-cause mortality; the secondary endpoint was the incidence of new ischemic brain lesions. Death was assessed over a 14-year follow-up, and ischemic brain lesions were evaluated by magnetic resonance imaging (MRI) over a 90-month follow-up. Ischemic brain lesions were divided into large brain infarcts (Ø≥ 1.5 cm) or lacunes (Ø< 1.5 cm) RESULTS: The primary endpoint occurred in 53.5 % of the study population. The incidence of the secondary endpoint was 16 %, with a 3.3 % being large brain infarcts, and a 12.7 % lacunes. After adjustment for potential confounders, the lncRNA H19 predicted the incidence of the primary endpoint (HR 1.194, 95 % C.I. 1.012-1.409, p = 0.036), whereas the lncRNA NKILA was associated with lacunar stroke (HR 0.571, 95 % C.I. 0.375-0.868, p = 0.006). CONCLUSION: In a prospective cohort of non-institutionalized elderly subjects, high levels of lncRNA H19 are associated with a higher risk of death, while low levels of lncRNA NKILA predict an increased risk of lacunar stroke.

Circulating GDF11 exacerbates myocardial injury in mice and associates with increased infarct size in humans.

AIMS: The heart rejuvenating effects of circulating growth differentiation factor 11 (GDF11), a transforming growth factor-ß superfamily member that shares 90% homology with myostatin (MSTN), remains controversial. Here, we aimed to probe the role of GDF11 in acute myocardial infarction (MI), a frequent cause of heart failure and premature death during ageing. METHODS AND RESULTS: In contrast to endogenous Mstn, myocardial Gdf11 declined during the course of ageing and was particularly reduced following ischaemia/reperfusion (I/R) injury, suggesting a therapeutic potential of GDF11 signalling in MI. Unexpectedly, boosting systemic Gdf11 by recombinant GDF11 delivery (0.1 mg/kg body weight over 30 days) prior to myocardial I/R augmented myocardial infarct size in C57BL/6 mice irrespective of their age, predominantly by accelerating pro-apoptotic signalling. While intrinsic cardioprotective signalling pathways remained unaffected by high circulating GDF11, targeted transcriptomics and immunomapping studies focusing on GDF11-associated downstream targets revealed attenuated Nkx2-5 expression confined to CD105-expressing cells, with pro-apoptotic activity, as assessed by caspase-3 levels, being particularly pronounced in adjacent cells, suggesting an indirect effect. By harnessing a highly specific and validated liquid chromatography-tandem mass spectrometry-based assay, we show that in prospectively recruited patients with MI circulating GDF11 but not MSTN levels incline with age. Moreover, GDF11 levels were particularly elevated in those at high risk for adverse outcomes following the acute event, with circulating GDF11 emerging as an independent predictor of myocardial infarct size, as estimated by standardized peak creatine kinase-MB levels. CONCLUSION: Our data challenge the initially reported heart rejuvenating effects of circulating GDF11 and suggest that high levels of systemic GDF11 exacerbate myocardial injury in mice and humans alike. Persistently high GDF11 levels during ageing may contribute to the age-dependent loss of cardioprotective mechanisms and thus poor outcomes of elderly patients following acute MI.

Chronic SIRT1 supplementation in diabetic mice improves endothelial function by suppressing oxidative stress.

AIMS: Enhancing SIRT1 activity exerts beneficial cardiovascular effects. In diabetes, plasma SIRT1 levels are reduced. We aimed to investigate the therapeutic potential of chronic recombinant murine SIRT1 (rmSIRT1) supplementation to alleviate endothelial and vascular dysfunction in diabetic mice (db/db). METHODS AND RESULTS: Left internal mammary arteries obtained from patients undergoing coronary artery bypass grafting with or without a diagnosis of diabetes were assayed for SIRT1 protein levels. Twelve-week-old male db/db mice and db/+ controls were treated with vehicle or rmSIRT1 intraperitoneally for 4 weeks, after which carotid artery pulse wave velocity (PWV) and energy expenditure/activity were assessed by ultrasound and metabolic cages, respectively. Aorta, carotid, and mesenteric arteries were isolated to determine endothelial and vascular function using the myograph system.Arteries obtained from diabetic patients had significantly lower levels of SIRT1 relative to non-diabetics. In line, aortic SIRT1 levels were reduced in db/db mice compared to db/+ mice, while rmSIRT1 supplementation restored SIRT1 levels. Mice receiving rmSIRT1 supplementation displayed increased physical activity and improved vascular compliance as reflected by reduced PWV and attenuated collagen deposition. Aorta of rmSIRT1-treated mice exhibited increased endothelial nitric oxide (eNOS) activity, while endothelium-dependent contractions of their carotid arteries were significantly decreased, with mesenteric resistance arteries showing preserved hyperpolarization. Ex vivo incubation with reactive oxygen species (ROS) scavenger Tiron and NADPH oxidase inhibitor apocynin revealed that rmSIRT1 leads to preserved vascular function by suppressing NADPH oxidase (NOX)-related ROS synthesis. Chronic rmSIRT1 treatment resulted in reduced expression of both NOX1 and NOX4, in line with a reduction in aortic protein carbonylation and plasma nitrotyrosine levels. CONCLUSIONS: In diabetic conditions, arterial SIRT1 levels are significantly reduced. Chronic rmSIRT1 supplementation improves endothelial function and vascular compliance by enhancing eNOS activity and suppressing NOX-related oxidative stress. Thus, SIRT1 supplementation may represent novel therapeutic strategy to prevent diabetic vascular disease.

Genotype Associations with the Different Phenotypes of Atopic Dermatitis in Children.

This study deals with detecting the associations of atopic dermatitis' (AD) phenotypes in children: alone or combined with seasonal allergic rhino-conjunctivitis (SARC) and/or perennial allergic rhinitis (PAR), and/or with bronchial asthma (BA) with single nucleotide polymorphisms (SNP) of filaggrin (FLG), thymic stromal lymphopoietin (TSLP) and orsomucoid-like-1 protein 3 (ORMDL3) genes. Male and female pediatric patients aged from 3 to 18 years old were recruited into the main (AD in different combinations with SARC, PAR, BA) and control groups (disorders of digestives system, neither clinical nor laboratory signs of atopy). Patients were genotyped for SNP of rs_7927894 FLG, rs_11466749 TSLP, rs_7216389 ORMDL3 variants. Statistically significant associations of the increased risk were detected of AD combined with SARC and/or PAR and AD combined with BA (possibly, SARC and/or PAR) with C/T rs_7927894 FLG and T/T rs_7216389 ORMDL3 genotypes. Genotype C/C rs_7927894 FLG significantly decreases the risk of AD combined with SARC and/or PAR by 2.56 fold. Several genotypes' associations had a trend to significance: C/C rs_7216389 ORMDL3 decreases and C/T rs_7216389 ORMDL3 increases the risk for developing AD alone phenotype; A/G rs_11466749 TSLP decreases the risk of AD combined with BA (possibly, SARC and/or PAR) phenotype development.

Altered biogenesis of microRNA-1 is associated with cardiac dysfunction in aging of spontaneously hypertensive rats.

Currently we face the issues of aging-associated pathologies, particularly those leading to heart failure. With that in mind, in current research we focus on aging and hypertension combination as a widely spread threating problem. In a row with functional and morphological characterization of these aging- and hypertension-associated cardiac changes, we evaluate biogenesis of microRNA-1 being one of major microRNAs in the heart. The aim of this study was to check the hypothesis if dysregulation of microRNA-1 biogenesis is associated with heart failure in aged and especially aged hypertensive rats. The experiments were carried out on male SHR and Wistar rats of age 6 months (young) and 18 months (old). The evaluation of hemodynamic parameters was performed in heart left ventricles of narcotized rats using the ultra-small 2F catheter. The development of fibrosis was determined using light and electron microscopy. Levels of mature and immature forms of microRNA-1 and mRNA encoding the proteins involved in its biogenesis were determined using reverse transcription and quantitative PCR. Aging of both Wistar and SHRs is accompanied with altered hemodynamic parameters compared with correspondent younger mates. SHRs, especially old ones, demonstrated significant heart fibrosis. In aged animals, the level of primary microRNA-1 in Wistar rats were 7 times higher (p < 0.05) and in SHR 17 times higher (p < 0.05) in comparison with young rats of the same strain. We also observed 22 times higher level of immature microRNA-1 in the heart of Wistar and 5.9 times higher level for aged hypertensive rats (p < 0.05) compared to young rats. At the same time, the level of mature microRNA-1 occurred 2.5 and 3.2 times lower in respective groups (p < 0.05). In the current study, we observe the significant dysregulation of microRNA-1 processing in the heart associated with aging and arterial hypertension.