MEF2C loss-of-function mutation associated with familial dilated cardiomyopathy.

BACKGROUND: The MADS-box transcription factor myocyte enhancer factor 2C (MEF2C) is required for the cardiac development and postnatal adaptation and in mice-targeted disruption of the MEF2C gene results in dilated cardiomyopathy (DCM). However, in humans, the association of MEF2C variation with DCM remains to be investigated. METHODS: The coding regions and splicing boundaries of the MEF2C gene were sequenced in 172 unrelated patients with idiopathic DCM. The available close relatives of the index patient harboring an identified MEF2C mutation and 300 unrelated, ethnically matched healthy individuals used as controls were genotyped for MEF2C. The functional effect of the mutant MEF2C protein was characterized in contrast to its wild-type counterpart by using a dual-luciferase reporter assay system. RESULTS: A novel heterozygous MEF2C mutation, p.Y157X, was detected in an index patient with adult-onset DCM. Genetic screen of the mutation carrier's family members revealed that the mutation co-segregated with DCM, which was transmitted as an autosomal dominant trait with complete penetrance. The non-sense mutation was absent in 300 control individuals. Functional analyses unveiled that the mutant MEF2C protein had no transcriptional activity. Furthermore, the mutation abolished the synergistic transactivation between MEF2C and GATA4 as well as HAND1, two other transcription factors that have been associated with DCM. CONCLUSIONS: This study indicates MEF2C as a new gene responsible for human DCM, which provides novel insight into the mechanism underpinning DCM, suggesting potential implications for development of innovative prophylactic and therapeutic strategies for DCM, the most prevalent form of primary myocardial disease.

Sirt1 is involved in decreased bone formation in aged apolipoprotein E-deficient mice.

AIM: Apolipoprotein E (ApoE) plays an important role in the transport and metabolism of lipids. Recent studies show that bone mass is increased in young apoE(-/-) mice. In this study we investigated the bone phenotype and metabolism in aged apoE(-/-) mice. METHODS: Femurs and tibias were collected from 18- and 72-week-old apoE(-/-) mice and their age-matched wild-type (WT) littermates, and examined using micro-CT and histological analysis. Serum levels of total cholesterol, oxidized low-density lipoprotein (ox-LDL) and bone turnover markers were measured. Cultured bone mesenchymal stem cells (BMSCs) from tibias and femurs of 18-week-old apoE(-/-) mice were used in experiments in vitro. The expression levels of Sirt1 and Runx2 in bone tissue and BMSCs were measured using RT-PCR and Western blot analysis. RESULTS: Compared with age-matched WT littermates, young apoE(-/-) mice exhibited high bone mass with increased bone formation, accompanied by higher serum levels of bone turnover markers OCN and TRAP5b, and higher expression levels of Sirt1, Runx2, ALP and OCN in bone tissue. In contrast, aged apoE(-/-) mice showed reduced bone formation and lower bone mass relative to age-matched WT mice, accompanied by lower serum OCN levels, and markedly reduced expression levels of Sirt1, Runx2, ALP and OCN in bone tissue. After BMSCs were exposed to ox-LDL (20 µg/mL), the expression of Sirt1 and Runx2 proteins was significantly increased at 12 h, and then decreased at 72 h. Treatment with the Sirt1 inhibitor EX527 (10 µmol/L) suppressed the expression of Runx2, ALP and OCN in BMSCs. CONCLUSION: In contrast to young apoE(-/-) mice, aged apoE(-/-) mice showe lower bone mass than age-matched WT mice. Long-lasting exposure to ox-LDL decreases the expression of Sirt1 and Runx2 in BMSCs, which may explain the decreased bone formation in aged apoE(-/-) mice.

The associations between liver enzymes and the risk of metabolic syndrome in the elderly.

BACKGROUND: Studies have demonstrated that liver enzymes are associated with metabolic syndrome (MetS). However, little information is available regarding these relationships in elderly populations. Our present study aimed to explore the associations between liver enzymes and the risk of MetS in elderly populations. METHODS: This cross-sectional study included 1444 elder participants (970 men and 474 women) who attended annual physical examinations. Univariate and multivariate logistic regressions were performed to estimate the associations between liver enzymes and the risk of MetS and its components according to quartiles of the concentration of each liver enzyme. RESULTS: The prevalence of MetS and its components increased remarkably with increasing quartiles of alanine aminotransferase (ALT), gamma-glutamyltransferase (GGT) and alkaline phosphatase (ALP) but not with aspartate aminotransferase (AST) in the elderly. Compared with subjects in the bottom quartile, the adjusted odds ratio for MetS in the highest ALT, GGT and ALP quartiles were 1.78 (95% CI 1.21-2.61), 2.58 (95% CI 1.77-3.78) and 1.85 (95%CI 1.27-2.70) respectively. No statistically significant increases in the odds ratio for MetS according to increased quartiles of AST were found in either the univariate or multivariate logistic regression analyses. CONCLUSIONS: Elevated liver enzymes levels (mainly ALT, GGT and ALP but not AST) are positively associated with the prevalence of MetS in elderly populations.