Linarin Ameliorates Diabetic Liver Injury by Alleviating Oxidative Stress and Inflammation through the Inhibition of AKR1B1.

AIMS: The study aims to find a new functional additive for diabetic liver injury. BACKGROUND: It is well-established that type 2 diabetes mellitus (T2DM) is a metabolic disease with multiple complications and places a significant health and economic burden on modern society. Linarin is a natural flavonoid isolated from Asteraceae and Lamiaceae, which has beneficial effects in preventing and treating metabolic diseases such as nonalcoholic steatohepatitis and diabetes. OBJECTIVE: We aimed to investigate the pharmacological effect and underlying mechanism of linarin on T2DM-associated liver injury in vivo and in vitro. METHODS: Using a high-glucose and high-palmitic acid-induced hepatocyte injury model and a type 2 diabetic rat model. Following linarin treatment, serum biochemical parameters, liver histology, and lipid profiles of rats were examined. Oxidative stress index and inflammatory response were detected in vivo and in vitro. The expression level of AKR1B1 in rat liver tissues and in vitro cells was detected by western blot and by real-time fluorescent quantitative PCR. RESULTS: The present study found that linarin could prevent oxidative stress and inflammation. In high-fat-fed diabetic rats, linarin administration (15, 30, and 60 mg/kg/day) reduced hepatic lipid accumulation, oxidative stress, and inflammation. Linarin (20 µM) significantly alleviated oxidative stress, inflammation, and apoptosis induced by high glucose combined with palmitic acid in LX-2 cells. Western blotting and overexpression experiments showed that these effects were related to AKR1B1 inhibition in vivo and in vitro. CONCLUSION: This study indicated that linarin could protect against liver injury in T2DM by alleviating oxidative stress and inflammation mediated by AKR1B1 and may be a promising additive for diabetic liver injury therapy.

Construction of a Competitive Endogenous RNA Network Related to Exosomes in Diabetic Retinopathy.

BACKGROUND: The competing endogenous RNA (ceRNA) network plays an important role in the occurrence and development of a variety of diseases. This study aimed to construct a ceRNA network related to exosomes in diabetic retinopathy (DR). METHODS: We explored the Gene Expression Omnibus (GEO) database and then analyzed the RNAs of samples to obtain differentially expressed lncRNAs (DELs), miRNAs (DEMs) and mRNAs (DEGs) alongside the progress of DR. Next, Gene Set Enrichment Analysis (GSEA) analysis of DEGs, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of up-DEGs were performed. In addition, a ceRNA network related to exosomes in DR was constructed on the base of DELs, DEMs and DEGs. Finally, the function of the ceRNA network was explored by GO and KEGG enrichment analysis. RESULTS: Through our analysis, 267 DELs (93 up and 174 down), 114 DEMs (64 up and 50 down) and 2368 DEGs (1252 up and 1116 down) were screened. The GSEA analysis results show that these genes were mainly related to cytokine-cytokine receptor interaction, hippo signaling pathway and JAK-STAT signaling pathway. The GO and KEGG results show that these up-DEGs were mainly enriched in viral gene expression, components of ribosomes, mineral absorption, Wntprotein binding, and TGF-ß signaling pathway. Besides, a ceRNA network, including 15 lncRNAs (e.g., C1orf145, FGF14-IT1, and PRNT), 3 miRNAs (miR-10a-5p, miR-1297 and miR-507) and 11 mRNAs (NCOR2, CHAC1 and LIX1L, etc.) was constructed. Those 5 lncRNAs were up-regulated, 1 miRNA was down-regulated and 5 mRNAs were up-regulated in DR, while 10 lncRNAs were downregulated, 2 miRNAs were up-regulated and 6 mRNAs were down-regulated in DR. CONCLUSION: The novel ceRNA network that we constructed will provide new insights into the underlying molecular mechanisms of exosomes in DR.

Berberine mitigates nonalcoholic hepatic steatosis by downregulating SIRT1-FoxO1-SREBP2 pathway for cholesterol synthesis.

OBJECTIVE: To investigate effects of berberine (BBR) on cholesterol synthesis in HepG2 cells with free fatty acid (FFA)-induced steatosis and to explore the underlying mechanisms. METHODS: A steatosis cell model was induced in HepG2 cell line fed with FFA (0.5 mmol/L, oleic acid:palmitic acid = 2:1), and then treated with three concentrations of BBR; cell viability was assessed with cell counting kit-8 assays. Lipid accumulation in cells was observed through oil red O staining and total cholesterol (TC) content was detected by TC assay. The effects of BBR on cholesterol synthesis mediators were assessed by Western blotting and quantitative polymerase chain reaction. In addition, both silent information regulator 1 (SIRT1) and forkhead box transcription factor O1 (FoxO1) inhibitors were employed for validation. RESULTS: FFA-induced steatosis was successfully established in HepG2 cells. Lipid accumulation and TC content in BBR groups were significantly lower (P < 0.05, P < 0.01), associated with significantly higher mRNA and protein levels of SIRT1(P < 0.05, P < 0.01), significantly lower sterol regulatory element-binding protein 2 (SREBP2) and 3-hydroxy 3-methylglutaryl-CoA reductase levels (P < 0.05, P < 0.01), as well as higher Acetyl-FoxO1 protein level (P < 0.05, P < 0.01) compared to the FFA only group. Both SIRT1 inhibitor SIRT1-IN-1 and FoxO1 inhibitor AS1842856 blocked the BBR-mediated therapeutic effects. Immunofluorescence showed that the increased SIRT1 expression increased FoxO1 deacetylation, and promoted its nuclear translocation. CONCLUSION: BBR can mitigate FFA-induced steatosis in HepG2 cells by activating SIRT1-FoxO1-SREBP2 signal pathway. BBR may emerge as a potential drug candidate for treating nonalcoholic hepatic steatosis.

Mibefradil Alleviates High-Glucose-induced Cardiac Hypertrophy by Inhibiting PI3K/Akt/mTOR-mediated Autophagy.

Cardiac hypertrophy causes heart failure and is associated with hyperglycemia in patients with diabetes mellitus. Mibefradil, which acts as a T-type calcium channel blocker, exerts beneficial effects in patients with heart failure. In this study, we explored the effects and mechanism of mibefradil on high-glucose-induced cardiac hypertrophy in H9c2 cells. H9c2 cells were incubated in a high-glucose medium and then treated with different concentrations of mibefradil in the presence or absence of the Akt inhibitor MK2206 or mTOR inhibitor rapamycin. Cell size was evaluated through immunofluorescence, and mRNA expression of cardiac hypertrophy markers (atrial natriuretic peptide, brain natriuretic peptide, and ß-myosin heavy chain) was assessed by using quantitative real-time polymerase chain reaction. Changes in the expression of p-PI3K, p-Akt, and p-mTOR were evaluated using Western blotting, and autophagosome formation was detected using transmission electron microscopy. Our results indicate that mibefradil reduced the size of H9c2 cells, decreased mRNA expression of atrial natriuretic peptide, brain natriuretic peptide, and ß-myosin heavy chain, and decreased the level of autophagic flux. However, MK2206 and rapamycin induced autophagy and reversed the effects of mibefradil on high-glucose-induced H9c2 cells. In conclusion, mibefradil ameliorated high-glucose-induced cardiac hypertrophy by activating the PI3K/Akt/mTOR pathway and inhibiting excessive autophagy. Our study shows that mibefradil can be used therapeutically to ameliorate cardiac hypertrophy in patients with diabetes mellitus.

[Effects of ursolic acid on c-Cbl-associated protein expression in 3T3-L1 adipocytes with insulin resistance].

OBJECTIVE: To observe the effects of ursolic acid (UA) on insulin resistance and cell differentiation in 3T3-L1 adipocytes and to explore the mechanisms. METHODS: 3T3-L1 adipocytes were cultured in Dulbecco's modified Eagle's medium (DMEM) supplemented with glucose (25 mmol/L) and insulin (10(-6) mol/L) to induce insulin resistance. After culture, glucose consumption of the adipocytes was detected by glucose oxidase method and glucose uptake was detected by using tritium-marked glucose. Drug concentration for following test was determined through detecting the effects of different concentrations of UA on the activity of 3T3-L1 adipocytes with insulin resistance by methyl thiazolyl tetrazolium (MTT) staining. 3T3-L1 adipocytes with insulin resistance were cultured with DMEM, rosiglitazone, and low- and high-dose UA, and then, glucose uptake and differentiation of 3T3-L1 adipocytes were detected. Finally, real-time fluorescence quantitative polymerase chain reaction and Western blot methods were used to detect the effects of UA on expressions of adipocyte lipid binding protein (aP2), c-Cbl-associated protein (CAP) and matrix metalloproteinase-1 (MMP-1) in 3T3-L1 cells with insulin resistance. RESULTS: After dealing with high glucose/hyperinsulin for 24 h, insulin resistance was induced successfully in the 3T3-L1 adipocytes. The concentrations of UA were defined to be 4 to 20 µmol/L. Compared with the model group, the glucose uptake was significantly increased in the rosiglitazone group and groups treated with low- and high-dose UA (P<0.01). The differentiation levels of 3T3-L1 adipocytes in the UA groups were lower than those in the control group and the rosiglitazone group. Effects of UA on the expressions of aP2 and MMP-1 were not obvious, but UA could up-regulate expression of CAP both in mRNA and protein levels (P<0.01). CONCLUSION: Low- and high-dose UA can improve the glycometabolism and differentiation of 3T3-L1 adipocytes with insulin resistance by up-regulating the expression of CAP.