Kan Sun

Alcohol consumption and risk of metabolic syndrome: A meta-analysis of prospective studies

BACKGROUND & AIMS Epidemiological evidence suggests that alcohol consumption is related to the incidence and development of metabolic syndrome. However, data on this issue are unstable and controversial. We conducted a meta-analysis to provide a quantitative assessment of the association between alcohol intake and risk of metabolic syndrome. METHODS We searched the Pubmed and Embase databases up to May 2013 to identify prospective cohort studies related to alcohol consumption and metabolic syndrome. Summary effect estimates with 95% confidence intervals (CI) were derived using a fixed or random effects model, depending on the heterogeneity of the included studies. RESULTS Six prospective studies involving 28,862 participants with 3305 cases of metabolic syndrome were included in the meta-analysis. On the basis of the Newcastle Ottawa Scale system, 83.3% of the studies were identified as relatively high-quality. In our primary analysis, compared with nondrinker, very light drinker was associated with decreased risk of metabolic syndrome [pooled relative risk (RR) 0.86, 95% CI: 0.75-0.99, fixed-effect model] while heavy drinker was associated with increased risk of metabolic syndrome (pooled RR 1.84, 95% CI: 1.34-2.52, fixed-effect model). No indications of heterogeneity and publication bias were found in these two groups. Estimates of total effects were generally consistent in the sensitivity and stratification analyses. CONCLUSION The present meta-analysis of prospective studies suggested that heavy alcohol consumption might be associated with an increased risk of metabolic syndrome while very light alcohol consumption seemed to be associated with a reduced risk of metabolic syndrome.

AGE‐induced keratinocyte MMP‐9 expression is linked to TET2‐mediated CpG demethylation

Studies have documented that unusually high expression of matrix metalloproteinase‐9 (MMP‐9) suppresses wound healing during the late stages of diabetic foot ulcers. Recently, it has been reported that the presence of advanced glycation end products‐bovine serum albumin (AGE‐BSA) resulted in a higher expression of MMP‐9 in skin primary keratinocytes. The aim of the present study was to elucidate the molecular machinery that is responsible for the inappropriately high AGE‐BSA–induced expression of MMP‐9. It has been demonstrated that site‐specific DNA demethylation played an important role in MMP‐9 expression in AGE‐BSA–stimulated keratinocytes. Ten–eleven translocation‐2 (TET2) was up‐regulated, whereas the percentage of methylation in the MMP‐9 promoter was reduced. Furthermore, TET2 directly bound to a fragment surrounding the transcriptional start site in the MMP‐9 promoter region, contributing to the regulation of MMP‐9 expression. In addition, evidence indicated that TET2 affected the migration and proliferation in vitro of cultured skin primary keratinocytes. These findings indicated that TET2 directly interacted with the promoter region of MMP‐9 in diabetic tissues and may be a novel master regulator of wound healing.

α-ketoglutarate is associated with delayed wound healing in diabetes

A high level of matrix metalloproteinase 9 (MMP‐9) is a predictor of poor wound healing in diabetic foot ulcers. In skin keratinocytes, site‐specific DNA demethylation plays an important role in MMP‐9 expression. Ten‐eleven translocation enzyme 2 (TET2) protein, one member of TET family, could rely on α‐ketoglutarate (α‐KG) as cosubstrate to exhibit catalytic activity of DNA demethylation. Here, we aimed to explore the changes of α‐KG and its relationship with MMP‐9 and TET2 during diabetic wound healing.

AGEs trigger autophagy in diabetic skin tissues and fibroblasts

OBJECTIVE Accumulation of advanced glycation end products (AGEs) contributes to the development of diabetic ulcers. Recent evidence indicates that AGEs administration enhanced autophagy in many cell types. As a positive trigger of autophagy, the effect of AGEs on autophagy in skin tissues and fibroblasts remains unknown. METHODS Skin tissues were isolated from Spreqne-Dawley rats and immunohistochemical staining was performed to analyze the location of LC3 and FOXO1 in skin tissues. Then primary cultured foreskin fibroblast cells with treated with AGEs and the effect of AGEs on autophagy was investigated. Protein level expressions of LC3, Beclin-1 and FOXO1 in fibroblasts were analyzed by Western blotting. Autophagic flux is detected with autophagy inhibitor chloroquine and mRFP-GFP-LC3 tandem construct. RESULTS Compared with skin from normal rats, immunohistochemical staining shows a predominant LC3 localization in fibroblasts cytoplasm in diabetic rats. Elevated expression of FOXO1 also existed in diabetic rats dermis fibroblasts when compared with normal rats in immunohistochemical analysis. In human skin fibroblasts cells, AGEs administration stimulated the autophagy related LC3-II/LC3-I and Beclin-1 expressions and increased autophagy flux. In mRFP-GFP-LC3 puncta formation assays, both autolysosome and autophagosome were increased in human fibroblasts after treatment with AGEs. Fibroblasts exposed to AGEs also have increased FOXO1 expression compared with control group. CONCLUSION AGEs could induce autophagy at least in part via regulating the FOXO1 activity in diabetic skin tissues and fibroblasts.

Efficiency and Safety of β-CD-(D3)7 as siRNA Carrier for Decreasing Matrix Metalloproteinase-9 Expression and Improving Wound Healing in Diabetic Rats

Overexpression of matrix metalloproteinase-9 (MMP-9) is critical for diabetic chronic wounds involved in the refractory wound healing process. We aimed to develop a strategy through RNAi to decrease MMP-9 expression and improve diabetic wound healing. We had explored β-CD-(D3)7 as a gene carrier to take siRNA and effectively interfere with MMP-9 expression. It has been proven that β-CD-(D3)7 could be used as an effective siRNA delivery system. In this study, we want to know about the efficiency and safety of β-CD-(D3)7/MMP-9 siRNA for improving wound healing in diabetic rats. β-CD-(D3)7/MMP-9 siRNA treated animals show lower levels of MMP-9 expression, which induce faster wound-close rates. Histological evaluation indicates that β-CD-(D3)7/MMP-9 siRNA significantly increases the content of collagen around the injured tissues. The number of neutrophilic ganulocytes was significantly decreased through treatment of β-CD-(D3)7/MMP-9 siRNA. In vivo fluorescence imaging assessment shows that β-CD-(D3)7/MMP-9 siRNA could not cause organ damage and organ accumulation. The results suggest that β-CD-(D3)7/MMP-9 siRNA might be developed as a novel topical agent for the diabetic wounds treatment.

Comparison of the cellular transport mechanism of cationic, star-shaped polymers and liposomes in HaCat cells

Several biological barriers must be overcome to achieve efficient nonviral gene delivery. These barriers include target cell uptake, lysosomal degradation, and dissociation from the carrier. In this study, we compared the differences in the uptake mechanism of cationic, star-shaped polymer/MMP-9siRNA complexes (β-CD-(D3)7/MMP-9siRNA complexes: polyplexes) and commercial liposome/MMP-9siRNA complexes (Lipofectamine® 2000/MMP-9siRNA complexes: liposomes). The uptake pathway and transfection efficiency of the polyplexes and liposomes were determined by fluorescence microscopy, flow cytometry, and reverse transcriptase-polymerase chain reaction. The occurrence of intracellular processing was assessed by confocal laser scanning microscopy. Endosomal acidification inhibitors were used to explore the endosomal escape mechanisms of the polyplexes and lysosomes. We concluded that the polyplexes were internalized by non-caveolae- and non-clathrin-mediated pathways, with no lysosomal trafficking, thereby inducing successful transfection, while the majority of liposomes were internalized by clathrin-dependent endocytosis (CDE), caveolae-mediated endocytosis, and macropinocytosis, and only CDE induced successful transfection. Liposomes might escape more quickly than polyplexes, and the digestion effect of acidic organelles on liposomes was faint compared to the polyplexes, although both complexes escaped from endolysosomes via the proton sponge mechanism. This may be the key aspect that leads to the lower transfection efficiency of the β-CD-(D3)7/MMP-9siRNA complexes. The present study may offer some insights for the rational design of novel delivery systems with increased transfection efficiency but decreased toxicity.

Association between obesity measures and albuminuria: A population-based study

AIMS The effects of obesity on the micro vascular diseases have drawn much attention. The aim of the study was to investigate the relationship between obesity measures and albuminuria in Chinese population. METHODS We conducted a population-based cross-sectional study in 8600 subjects aged 40 years or older from a community in Guangzhou. Urinary albumin excretion and creatinine were measured and urinary albumin-to-creatinine ratio (ACR) was calculated as urinary albumin divided by creatinine. Low-grade albuminuria was classified as the highest quartile of ACR in participants without increased urinary albumin excretion. Increased urinary albumin excretion was defined according to the ACR ranges greater or equal than 30 mg/g. RESULTS Pearsons correlation analysis and multivariate linear regression analysis revealed that body mass index (BMI), waist circumference and body fat content were significantly correlated with ACR (all P<0.01). Prevalence of low-grade albuminuria and increased urinary albumin excretion gradually increased across the BMI, waist circumference and body fat content quartiles (all P for trend<0.0001). Compared with participants in quartile 1 of BMI, waist circumference and body fat content, participants in quartile 4 had increased prevalence of low-grade albuminuria and increased urinary albumin excretion in logistic regression analysis after adjustment for age, sex, physical activity, fasting plasma glucose, triglycerides, low-density lipoprotein cholesterol and HbA1c (all P<0.05). CONCLUSION Obesity measures are associated with urinary albumin excretion in middle-aged and elderly Chinese.

GADD45a Promotes Active DNA Demethylation of the MMP-9 Promoter via Base Excision Repair Pathway in AGEs-Treated Keratinocytes and in Diabetic Male Rat Skin

Diabetes elevates matrix metalloproteinase (MMP)-9 levels in the skin and its keratinocytes, and activated MMP-9 impairs skin wound healing. Epigenetic regulation of the DNA methylation status within the MMP-9 promoter plays an important role in the alteration of MMP-9 expression. Our aim was to investigate the role and mechanism of growth arrest and DNA damage-inducible 45a (GADD45a), a well-known DNA demethylation regulatory protein that mediates DNA methylation, in the regulation of MMP-9 expression. In this study, we showed that GADD45a was markedly upregulated in skin tissues from patients with diabetic foot ulcers, in diabetic rats, and in human keratinocyte (HaCaT) cells exposed to advanced glycation end products. We observed a substantial positive correlation between the levels of GADD45a and MMP-9 expression. Knockdown of GADD45a ameliorated the increase in MMP-9 transcription induced by a diabetic condition by inhibiting demethylation in the MMP-9 promoter and promoted diabetic HaCaT cell migration, but GADD45a knockdown did not affect HaCaT cell proliferation or apoptosis. Additionally, we demonstrated that overexpression of GADD45a activated MMP-9 expression by inducing promoter demethylation. Moreover, we found that GADD45a binds to the promoter of MMP-9 and recruits thymine-DNA glycosylase for base excision repair-mediated demethylation in diabetic HaCaT cells and diabetic rat skin. Our results reveal a mechanism in which GADD45a is required for demethylation of the MMP-9 promoter and the induction of diabetic wound healing. The inhibition of GADD45a might be a therapeutic strategy for diabetic foot ulcers.

Fatty liver index, albuminuria and the association with chronic kidney disease: a population-based study in China

Objectives The effects of lipid metabolism disorder on renal damage have drawn much attention. Using the fatty liver index (FLI) as a validated indicator of hepatic steatosis, this study aims to provide insight about the possible links between fatty liver and the development of chronic kidney disease (CKD). Setting Hospital. Participants We performed a population-based study on 9436 subjects aged 40 years or older. Primary and secondary outcome measures FLI is calculated using an algorithm based on body mass index, waist circumference, triglycerides and γ-glutamyltransferase. Increased urinary albumin excretion was defined according to the urinary albumin to creatinine ratio ranges ≥30 mg/g. CKD was defined as estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² or presence of albuminuria. Results There were 620 (6.6%) subjects categorised to have increased urinary albumin excretion and 753 (8.0%) subjects categorised to have CKD. Participants with higher FLI had increased age, blood pressure, low-density lipoprotein cholesterol, fasting plasma glucose, fasting insulin and decreased eGFR level. Prevalence of increased urinary albumin excretion and CKD tended to increase with the elevated FLI quartiles. In logistic regression analysis, compared with subjects in the lowest quartile of FLI, the adjusted ORs in the highest quartile were 2.30 (95% CI 1.36 to 3.90) for increased urinary albumin excretion and 1.93 (95% CI 1.18 to 3.15) for CKD. Conclusion Hepatic steatosis evaluated by FLI is independently associated with increased urinary albumin excretion and prevalence of CKD in middle-aged and elderly Chinese.