Nicotinamide protects against diabetic kidney disease through regulation of Sirt1.

PURPOSE: To investigate the effect of nicotinamide (Nam) on diabetic kidney disease (DKD) in mice and explore its mechanism. METHODS: Thirty DBA/2 J mice were randomly assigned to three groups. After 8 weeks of hyperglycemia induced by streptozocin (STZ), Nam and saline were administrated to STZ + Nam and STZ + NS mice, respectively, for 8 weeks. Non-diabetic mice (NDM) were used as control group. Twenty In2-/- Akita mice were randomly divided into two groups. After 8 weeks of hyperglycemia, Nam and saline were administered to Akita + Nam and Akita + NS mice, respectively, for 6 weeks. Wild-type littermates were used as control group. Markers of renal injury were analyzed, and the molecular mechanisms were explored in human proximal tubular HK2 cells. RESULTS: Urinary albumin-to-creatinine ratio (UACR) and kidney injury molecule 1 (KIM-1) decreased in the STZ + Nam and Akita + Nam groups. Pathological analysis showed that Nam improved the structure of glomerular basement membrane, ameliorated glomerular sclerosis, and decreased the accumulation of extracellular matrix and collagen. Compared to the diabetic control group, renal fibrosis, inflammation, and oxidative stress were reduced in the Nam-treated mice. The expression of sirtuin 1 (Sirt1) in human proximal tubular HK2 cells was inhibited by high glucose and Nam treatment enhanced its expression. However, in HK2 cells with Sirt1 knockdown, the protective effect of Nam was abolished, indicating that the beneficial effect of Nam was partially dependent on Sirt1. CONCLUSIONS: Nam has a renoprotective effect against renal injury caused by hyperglycemia and may be a potential target for the treatment of DKD.

Nuclear translocation of metabolic enzyme PKM2 participates in high glucose-promoted HCC metastasis by strengthening immunosuppressive environment.

Although some cohort studies have indicated a close association between diabetes and HCC, the underlying mechanism about the contribution of diabetes to HCC progression remains largely unknown. In the study, we applied a novel HCC model in SD rat with diabetes and a series of high glucose-stimulated cell experiments to explore the effect of a high glucose environment on HCC metastasis and its relevant mechanism. Our results uncovered a novel regulatory mechanism by which nuclear translocation of metabolic enzyme PKM2 mediated high glucose-promoted HCC metastasis. Specifically, high glucose-increased PKM2 nuclear translocation downregulates chemerin expression through the redox protein TRX1, and then strengthens immunosuppressive environment to promote HCC metastasis. To the best of our knowledge, this is the first report to elucidate the great contribution of a high glucose environment to HCC metastasis from a new perspective of enhancing the immunosuppressive microenvironment. Simultaneously, this work also highlights a previously unidentified non-metabolic role of PKM2 and opens a novel avenue for cross research and intervention for individuals with HCC and comorbid diabetes.

ACMSD mediated de novo NAD+ biosynthetic impairment in cardiac endothelial cells as a potential therapeutic target for diabetic cardiomyopathy.

OBJECT: The highly conserved α-amino-ß-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD) is the key enzyme that regulates the de novo NAD+ synthesis from tryptophan. NAD+ metabolism in diabetic cardiomyopathy (DCM) was not elucidated yet. METHODS: Mice were assigned to non-diabetic (NDM) group, streptozocin (STZ)-induced diabetic (DM) group, and nicotinamide (NAM) treated (DM + NAM) group. ACMSD mediated NAD+ metabolism were studied both in mice and patients with diabetes. RESULTS: NAD+ level was significantly lower in the heart of DM mice than that of the NDM group. Supplementation with NAM could partially increased myocardial capillary density and ameliorated myocardial fibrosis by increasing NAD+ level through salvage pathway. Compared with NDM mice, the expression of ACMSD in myocardial endothelial cells of DM mice was significantly increased. It was further confirmed that in endothelial cells, high glucose promoted the expression of ACMSD. Inhibition of ACMSD could increase de novo NAD+ synthesis and improve endothelial cell function by increasing Sirt1 activity. Targeted mass spectrometry analysis indicated increased ACMSD enzyme activity in diabetic patients, higher ACMSD activity increased risk of heart diastolic dysfunction. CONCLUSION: In summary, increased expression of ACMSD lead to impaired de novo NAD+ synthesis in diabetic heart. Inhibition of ACMSD could potentially improve DCM.

Identification of hub genes and infiltrating immune cells in skeletal muscle in obesity.

Background: Metabolic syndrome (MetS) refers to a cluster of metabolic disorders that are mainly caused by obesity. Skeletal muscle is a central component of systemic metabolism. However, the mechanism of skeletal muscle metabolic impairment in obesity remains unclear. This study aimed to identify key early biomarkers in skeletal muscle for the prevention and treatment of MetS in obesity. Methods: The GSE85439 dataset was downloaded from the Gene Expression Omnibus database. Gene set enrichment and immune cell infiltration analyses were performed for genome-wide genes. Differentially expressed genes (DEGs) between obese and control mice were screened and subjected to functional enrichment analysis, and a protein-protein interaction network was constructed. The results of the bioinformatics analysis were confirmed by immunofluorescence and real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Results: Enrichment analysis indicated that the genes expressed in obese mice were mainly associated with acute inflammatory response. Immune cell infiltration analysis of 190 DEGs with consistent trends showed that the numbers of mast cells (MCs) and active dendritic cells were significantly higher in obese mice than in control mice. Immunofluorescence analysis confirmed that the number of MCs present in the skeletal muscle was higher in obese mice than in control mice, although no difference was observed in the active dendritic cell count. Functional enrichment analysis showed that the DEGs were mainly associated with transcriptional regulation. In the clusters of the protein-protein interaction network, four acute-phase-response genes (SAA1, SAA2, ORM1, and HP) were significantly correlated with transcription-regulating genes (SHH, IGF2, and CELA1); these seven genes were identified as hub genes. The qRT-PCR results showed that the expression levels of SAA1, SAA2, IGF2, and CELA1 were significantly higher in obese mice than in control mice; however, those of HP, ORM1, and SHH did not differ significantly between the two groups. Conclusions: The skeletal muscle of obese mice exhibits elevated MC infiltration and increased SAA1, SAA2, CELA1, and IGF2 expression. The identification of these biomarkers has increased our understanding of the potential functional mechanisms of skeletal muscle in obesity. These potential biomarkers may serve as targets for the prevention and treatment of MetS.

PS-341 alleviates chronic low-grade inflammation and improves insulin sensitivity through the inhibition of TM4 (UBAC2) degradation.

BACKGROUND: The TM4 (UBAC2) protein, which contains 4 transmembrane domains and one ubiquitin binding domain, is mainly expressed in cell and nuclear membranes. The current research aimed to explore the role of TM4 in metabolic inflammation and to examine whether the ubiquitin-proteasome inhibitor PS-341 could regulate the function of TM4. METHODS: The metabolic phenotypes of TM4 knockout (KO) mice were studied. We next explored the association between the polymorphisms of TM4 and obesity in a Chinese Han population. TM4 expression in the visceral fat of obese patients who underwent laparoscopic cholecystectomy was also analysed. Finally, the effect of PS-341 on the degradation and function of the TM4 protein was investigated in vivo and in vitro. RESULTS: TM4 KO mice developed obesity, hepatosteatosis, hypertension, and glucose intolerance under a high-fat diet. TM4 counterregulated Nur77, IKKß, and NF-kB both in vivo and in vitro. The TM4 SNP rs147851454 is significantly associated with obesity after adjusting for age and sex (OR 1.606, 95% CI 1.065-2.422 P = 0.023) in 3394 non-diabetic and 1862 type 2 diabetic adults of Han Chinese. TM4 was significantly downregulated in the visceral fat of obese patients. PS-341 induced TM4 expression through inhibition of TM4 degradation in vitro. In db/db mice, PS-341 administration led to downregulation of Nur77/IKKß/NF-κB expression in visceral fat and liver, and alleviation of hyperglycaemia, hypertension, and glucose intolerance. The hyperinsulinaemic-euglycaemic clamp demonstrated that PS-341 improved the glucose infusion rate and alleviated insulin resistance in db/db mice. CONCLUSIONS: PS-341 alleviates chronic low-grade inflammation and improves insulin sensitivity through inhibition of TM4 degradation.

Liver fibrosis is independently associated with diabetic peripheral neuropathy in type 2 diabetes mellitus.

AIMS/INTRODUCTION: Non-alcoholic fatty liver disease and type 2 diabetes mellitus are closely related, and often occur simultaneously in patients. Type 2 diabetes increases the risk of diabetic peripheral neuropathy, resulting in intolerable pain and extremity amputation that reduces the quality of life. However, the role of non-alcoholic fatty liver disease in the pathogenesis of diabetic peripheral neuropathy remains unclear. Thus, we evaluated the correlation of liver fibrosis and steatosis, which are representative histological morphologies of non-alcoholic fatty liver disease, with diabetic peripheral neuropathy in type 2 diabetes patients. MATERIALS AND METHODS: Five hundred twenty individuals with type 2 diabetes were recruited. All the patients were detected nerve conduction study for diabetic peripheral neuropathy and fibro touch for liver steatosis and fibrosis. Correlation of DPN with liver steatosis and fibrosis were analysed with binary logistic analysis. RESULTS: Among the 520 patients, the prevalence of liver steatosis, fibrosis and diabetic peripheral neuropathy was 63.0% (n = 328), 18.1% (n = 94) and 52.1% (n = 271), respectively. The prevalence of diabetic peripheral neuropathy was significantly elevated in patients with liver steatosis (55.7 vs 44.9%, P = 0.03) and fibrosis (61.5 vs 50%, P = 0.04), and it increased as liver stiffness measurement increased. Additionally, both hepatic steatosis (odds ratio 1.48, 95% confidence interval 1.04-2.11, P = 0.03) and fibrosis (odds ratio 1.60, 95% confidence interval 1.02-2.51, P = 0.04) were correlated with diabetic peripheral neuropathy. After adjusting for age, sex, weight, height, body mass index, waist hip ratio, duration of type 2 diabetes, blood glucose, homeostatic model assessment of insulin resistance, blood pressure, serum lipid, liver enzyme, urea, uric acid, creatinine and inflammatory factors, liver fibrosis remained associated with diabetic peripheral neuropathy (odds ratio 2.24, 95% confidence interval 1.11-4.53, P = 0.02). CONCLUSIONS: The prevalence of diabetic peripheral neuropathy was elevated in patients with liver steatosis and fibrosis. Liver fibrosis was also independently associated with an increased risk of diabetic peripheral neuropathy.

Interaction of TPPP3 with VDAC1 Promotes Endothelial Injury through Activation of Reactive Oxygen Species.

Endothelial injury plays a critical role in the pathogenesis of cardiovascular disorders and metabolic-associated vascular complications which are the leading cause of death worldwide. However, the mechanism underlying endothelial dysfunction is not completely understood. The study is aimed at investigating the role of tubulin polymerization-promoting protein family member 3 (TPPP3) in palmitic acid- (PA-) induced endothelial injury. The effect of TPPP3 on human umbilical vein endothelial cells (HUVECs) was determined by evaluating apoptosis, tube formation, and reactive oxygen species (ROS) production. TPPP3 silencing inhibited PA overload-induced apoptosis and production of ROS, along with the alteration of apoptosis-related key proteins such as BCL-2 and Bax. Mechanically, voltage-dependent anion channel 1 (VDAC1) was identified as a novel functional binding partner of TPPP3, and TPPP3 promoted VDAC1 protein stability and its activity. Further studies indicated that TPPP3 could promote apoptosis, ROS production, tube formation, and proapoptotic protein expression and reduce antiapoptotic protein expression through increasing VDAC1 expression under mildly elevated levels of PA. Collectively, these results demonstrated that TPPP3 could promote PA-induced oxidative damage in HUVECs via a VDAC1-dependent pathway, suggesting that TPPP3 might be considered as a potential therapeutic target in vascular disease.

Matrix Stiffness-Upregulated MicroRNA-17-5p Attenuates the Intervention Effects of Metformin on HCC Invasion and Metastasis by Targeting the PTEN/PI3K/Akt Pathway.

BACKGROUND: Metformin, a traditional first-line anti-hyperglycemic agent for diabetes, recently exhibits better antitumor effect in hepatocellular carcinoma (HCC). However, its resistance and tolerance mechanism in HCC remains largely unknown. Here, we investigated whether increased matrix stiffness attenuated the intervention effects of metformin on HCC invasion and metastasis, and explored its underlying molecular mechanism. METHODS: FN-coated gel substrates with 6, 10, and 16 kPa, which simulated the stiffness of normal, fibrotic, and cirrhotic liver tissues respectively, were established to evaluate matrix stiffness-mediated effects on HCC cells. Alterations in morphology, proliferation, motility, and invasive/metastatic-associated genes (PTEN, MMP2, MMP9) of HCC cells grown on different-stiffness substrates were comparatively analyzed before and after metformin intervention. Subsequently, the underlying molecular mechanism by which higher matrix stiffness attenuates antitumor effects of metformin in HCC was further elucidated. RESULTS: Metformin significantly inhibited proliferation, migration, and invasion of HCC cells. Compared with the controls on lower-stiffness substrate, HCC cells grown on higher-stiffness substrate exhibited an obvious resistance to intervention effects of metformin on proliferation, migration, invasion and metastasis. High stiffness stimulation significantly activated the miR-17-5p/PTEN/PI3K/Akt signaling pathway in HCC cells via integrin ß1 and in turn resulted in MMP2 and MMP9 upregulation. Meanwhile, integrin ß1 knockdown or PI3K inhibitor partially reversed the activation of the above signaling molecules. For HCC cells grown on the same-stiffness substrate, metformin remarkably upregulated PTEN expression and suppressed the activation of the PI3K/Akt/MMP pathway, but no effect on integrin ß1 expression. Importantly, the increase in fold of PTEN expression and decrease in folds of Akt phosphorylation level and MMP2 and MMP9 expressions in the treated HCC cells with metformin on 16-kPa stiffness substrate were evidently weakened compared with those in the controls on the 6-kPa stiffness substrate. CONCLUSIONS: Increased matrix stiffness significantly attenuates the inhibitory effect of metformin on HCC invasion and metastasis, and a common pathway of PTEN/PI3K/Akt/MMPs activated by mechanical stiffness signal and inactivated by metformin contributes to matrix stiffness-caused metformin resistance. To the best of our knowledge, this is the first report to clarify the mechanism of metformin intervention resistance from the perspective of tumor biophysical microenvironment.

Prevalence of positive islet autoantibody in type 2 diabetes patients: a cross-sectional study in a Chinese community.

BACKGROUND: Islet autoantibodies occur in type 2 diabetes. Our study aimed to investigate the prevalence of positive islet autoimmunity in community patients with type 2 diabetes. METHODS: A total of 495 community patients with type 2 diabetes were recruited using the method of cluster sampling in this cross-sectional study. Three islet autoantibodies including glutamic acid decarboxylase antibody (GADA), insulin autoantibody (IAA) and islet cell antibody (ICA) were measured, and clinical characteristics involved in those individuals were evaluated. RESULTS: The positive rate of islet autoantibodies was 28.5% in total, while combinations of different autoantibodies were rarely seen. Compared with GADA-negative group, positive counterparts significantly tended to have lower levels of body mass index (BMI), waist-hip ratio (WHR), and urinary microalbumin (mALB) (P < 0.05). Adjusted for confounding factors, WHR, triglycerides (TG), and mALB seemed to be negative independent predictors of GADA (OR < 1, P < 0.05). Patients with positive IAA tended to receive insulin treatment (P < 0.0001). Besides, fasting blood glucose (FBG), serum levels of high-density lipoprotein cholesterol (HDL-CH), aspartate transaminase (AST), and γ-glutamyltransferase (GGT) were more likely to be higher in IAA positive subgroup in comparison with the negative counterparts. While after AST was adjusted by unconditional logistic regression analysis, history of insulin treatment, FBG, HDL-CH, and GGT were confirmed as positive predictors of IAA. Furthermore, in patients who were IAA positive, those treated with exogenous insulin tended to have longer duration of diabetes than non-insulin treatment counterparts (P < 0.0001). With regard to ICA, however, there were no significant differences between the two subgroups, except that serum level of AST/ALT seemed to be slightly different (P = 0.064). CONCLUSION: These data suggested that type 2 diabetic community patients with positive GADA tended to be lean and were able to maintain normal lipid metabolism, while patients with positivity of IAA were frequently accompanied with insulin treatment and more closely associated with diabetic liver damage.

Islet Autoantibody Patterns in Patients With Type 2 Diabetes Aged 60 and Higher: A Cross-Sectional Study in a Chinese Hospital.

BACKGROUND: Some elderly citizens with a clinical diagnosis of type 2 diabetes had evidence of positive islet autoantibodies. We aimed to discover their islet autoantibody patterns and independent correlative factors that might lead to a better understanding of significance of islet autoimmunity in the progression of elderly diabetes. METHODS: A total of 541 inpatients of clinically diagnosed type 2 diabetes aged 60 and over were recruited. Three islet autoantibodies including insulin autoantibody (IAA), islet cell antibody (ICA), and glutamic acid decarboxylase antibody (GADA) as well as clinical and biochemical characteristics were tested and collected in Huashan Hospital. Associations between these antibodies and clinical features were analyzed by Spearman correlation and binary logistic analyses. RESULTS: In our current study, total positive rate of islet autoantibodies (IAA, ICA, and GADA) was 35.67% with 26.62% for individual IAA, 5.55% for ICA, and 5.91% for GADA, in elderly with type 2 diabetes. None of combinations of such autoantibodies were observed, with the exception of IAA + ICA (0.74%, n = 4), IAA + GADA (1.48%, n = 8), and ICA + GADA (0.18%, n = 1). Compared with GADA negative group, patients in positive group tended to have lower level of fasting and postprandial C peptide, fasting blood glucose (FBG), and body mass index (BMI). After adjusted for the BMI, FBG, and postprandial C peptide, fasting C peptide seemed to be an independent factor related to GADA positivity (OR = 0.52, p = 0.02). As for patients with positive IAA, they were more likely to have insulin treatment with longer duration of diabetes, higher level of BMI, and lower level of postprandial C peptide. After adjusted for the duration of diabetes, BMI, and postprandial C peptide, insulin treatment was a significant predictor for IAA positivity (OR = 5.20, p < 0.0001). Furthermore, hs-CRP was positively related to ICA positivity, and hs-CRP appeared to be an independent indicator for ICA (OR = 3.43, p = 0.008). CONCLUSION: In elderly with type 2 diabetes, high prevalence rate of IAA was frequently accompanied with insulin treatment, while ICA and GADA were more closely associated with the systemic inflammation and beta-cell failure, respectively.

MiR-145 improves macrophage-mediated inflammation through targeting Arf6.

PURPOSE: To explore the relationship between miR-145 and ADP ribosylation factor 6 (Arf6) in regulating macrophage-mediated inflammation. METHODS: THP-1 cells were induced by 160 nM of phorbol 12-myristate 13-acetate (PMA) for 48 h to differentiate to macrophages and then were treated with LPS (100 ng/ml) for 8 h to simulate chronic metabolic inflammation in vitro. Dual-luciferase reporter assay was performed. MiR-145 siRNA and LV-ARF6-RNAi were used to up or down regulate miR-145 and Arf6 expression in THP-1 cells, respectively. Omental adipose tissue from patients in surgical ward were collected to detect the expression of miR-145, Arf6 and production of proinflammatory cytokines. Patients were divided into three groups according to their body mass index and history of diabetes. RESULTS: Dual-luciferase reporter assays showed the direct down-regulation of Arf6 by miR-145. Forty-eight-hour-transfection of miR-145 inhibitor resulted in significant increase of Arf6, IL-1beta, TNF-alpha and IL-6 as well as phosphorylation of p65 in NF-kappaB pathway in THP-1 cells, which, inversely, were reversed by overexpressing miR-145. In addition, down-regulation of Arf6 in macrophages reduced expression and secretion of cytokines. Expression of miR-145 was found to be attenuated in the omental adipose tissue of obese patients and diabetics with greater Arf6 expression, confirming the role of miR-145 in regulating macrophage-mediated inflammation targeting Arf6. CONCLUSIONS: By means of reducing the expression of Arf6 and subsequent signal transduction via NF-kappaB, miR-145 plays a role in inhibiting the secretion of inflammatory factors and then improving the inflammatory status. MiR-145 might be one of the candidates for anti-inflammatory treatment for metabolic diseases.

Anti-interleukin-1 therapy has mild hypoglycaemic effect in type 2 diabetes.

The aim of this study was to systematically evaluate the efficacy and safety of anti-interleukin-1 therapy for type 2 diabetes. A literature search of PubMed and Embase for available trials on anti-interleukin-1 therapy in type 2 diabetes was performed. The baseline characteristics, changes in HbA1c and other metabolic parameters, and adverse events were extracted from included randomized controlled trials (RCTs) and were analysed with Review Manager. Mean differences (MDs) and 95% confidence intervals (Cis) were calculated to measure differences in metabolic parameters. Odds ratio and 95% CIs were calculated for adverse event rates. Five RCTs were included in the current meta-analysis with 357 subjects undergoing anti-interleukin-1 therapy (IL-1 receptor antagonist or anti-IL-1beta antibody) and 221 controls who received placebo. The HbA1c decrement (%) of anti-interleukin-1 group was significantly higher than that of the placebo group (MD = 0.23; 95% CI, -0.39 to -0.07; P = .005). AUC of C-peptide was improved also (MD = 14.55; 95% CI, 1.81-27.28; P = .03) after anti-interleukin-1 intervention. There was no difference in the rate of adverse events (odds ratio,1.16; 95% CI, 0.90-1.49; P = .25) between 2 groups. Anti-interleukin-1 therapy has mild hypoglycaemic effect in type 2 diabetes.