Overexpression of miR-297b-5p in Mouse Insulin-Secreting Cells Promotes Metformin-Mediated Protection Against Stearic Acid-Induced Senescence by Targeting Igf1r.

BACKGROUND: A long-term consumption of saturated fat significantly increases the concentration of saturated fatty acids in serum, which accelerates the appearance of senescence markers in ß-cells and leads to their dysfunction. An understanding of the mechanisms underlying ß-cell senescence induced by stearic acid and the exploration of effective agents preventing it remains largely unclear. Here, we aimed to investigate the protective effect of metformin against stearic acid-treated ß-cell senescence and to assess the involvement of miR-297b-5p in this process. METHODS: To identify senescence, we measured senescence-associated ß-galactosidase activity and the expression of senescence-related genes. Gain and loss of function approaches were applied to explore the role of miR-297b-5p in stearic acid-induced ß-cell senescence. Bioinformatics analysis and a luciferase activity assay were used to predict the downstream targets of miR-297b-5p. RESULTS: Stearic acid markedly induced senescence and suppressed miR-297b-5p expression in mouse ß-TC6 cells, which were significantly alleviated by metformin. After transfection of miR-297b-5p mimics, stearic acid-evoked ß-cell senescence was remarkably prevented. Insulin-like growth factor-1 receptor was identified as a direct target of miR-297b-5p. Inhibition of the insulin-like growth factor-1 receptor prevented stearic acid-induced ß-cell senescence and dysfunction. Moreover, metformin alleviates the impairment of the miR-297b-5p inhibitor in ß-TC6 cells. Additionally, long-term consumption of a high-stearic-acid diet significantly increased senescence and reduced miR-297b-5p expression in mouse islets. CONCLUSIONS: These findings imply that metformin alleviates ß-cell senescence by stearic acid through upregulating miR-297b-5p to suppress insulin-like growth factor-1 receptor expression, thereby providing a potential target to not only prevent high fat-diet-induced ß-cell dysfunction but also for metformin therapy in type 2 diabetes.

Inhibition of miR-146a-5p and miR-8114 in Insulin-Secreting Cells Contributes to the Protection of Melatonin against Stearic Acid-Induced Cellular Senescence by Targeting Mafa.

BACKGRUOUND: Chronic exposure to elevated levels of saturated fatty acids results in pancreatic ß-cell senescence. However, targets and effective agents for preventing stearic acid-induced ß-cell senescence are still lacking. Although melatonin administration can protect ß-cells against lipotoxicity through anti-senescence processes, the precise underlying mechanisms still need to be explored. Therefore, we investigated the anti-senescence effect of melatonin on stearic acid-treated mouse ß-cells and elucidated the possible role of microRNAs in this process. METHODS: ß-Cell senescence was identified by measuring the expression of senescence-related genes and senescence-associated ß-galactosidase staining. Gain- and loss-of-function approaches were used to investigate the involvement of microRNAs in stearic acid-evoked ß-cell senescence and dysfunction. Bioinformatics analyses and luciferase reporter activity assays were applied to predict the direct targets of microRNAs. RESULTS: Long-term exposure to a high concentration of stearic acid-induced senescence and upregulated miR-146a-5p and miR- 8114 expression in both mouse islets and ß-TC6 cell lines. Melatonin effectively suppressed this process and reduced the levels of these two miRNAs. A remarkable reversibility of stearic acid-induced ß-cell senescence and dysfunction was observed after silencing miR-146a-5p and miR-8114. Moreover, V-maf musculoaponeurotic fibrosarcoma oncogene homolog A (Mafa) was verified as a direct target of miR-146a-5p and miR-8114. Melatonin also significantly ameliorated senescence and dysfunction in miR-146a-5pand miR-8114-transfected ß-cells. CONCLUSION: These data demonstrate that melatonin protects against stearic acid-induced ß-cell senescence by inhibiting miR-146a- 5p and miR-8114 and upregulating Mafa expression. This not only provides novel targets for preventing stearic acid-induced ß-cell dysfunction, but also points to melatonin as a promising drug to combat type 2 diabetes progression.

Comparative analysis of circRNA expression profile and circRNA-miRNA-mRNA regulatory network between palmitic and stearic acid-induced lipotoxicity to pancreatic ß cells.

Chronic exposure to high concentrations of circulating palmitic acid and stearic acid leads to impaired ß cell function, which accelerates the development of type 2 diabetes. However, differences in the mechanisms underlying this process between these two saturated fatty acids remain largely unknown. In this study, we screened for potential circular RNAs (circRNAs) and their associated regulatory pathways in palmitic acid- and stearic acid-induced mouse ß-TC6 cell dysfunction. CircRNA high-throughput sequencing, gene ontology enrichment and Kyoto Encyclopedia of Genes and Genomes analysis were performed and co-expression and competing endogenous RNAs (ceRNA) networks were constructed. We identified that four circRNAs that were differentially expressed specifically in ß cells exposed to palmitic acid, whereas four circRNAs were differentially expressed specifically in ß cells exposed to stearic acid. Seven circRNAs were differentially co-expressed in palmitic acid- and stearic acid-treated ß cells. In pathway exploration, we identified the core protein Solute carrier family 2 member 2 (SLc2a2), which is mainly involved in insulin resistance, maturity onset diabetes of the young and type 2 diabetes. The expressions of key circRNAs in ß-TC6 cells were validated by Real time quantitative PCR, with a consistent result in high-throughput sequencing. The findings aid our understanding of the mechanisms governing the difference between palmitic acid- and stearic acid-induced ß cell dysfunction and provide potential therapeutic targets for developing treatments against long-term high fat diet-induced ß cell injury.Abbreviations: Acvr1c: Activin A receptor, type 1C; CeRNA, Competing endogenous RNAs; circRNA, circular RNA; DEcircRNA: Differentially Expressed circular RNA; DEmiRNA: Differentially Expressed microRNA; DEmRNA: Differentially Expressed mRNA; GO: Gene Ontology; HPDHigh Palmitic acid Diet; HSD: High Stearic acid Diet; KEGG: Kyoto Encyclopedia of Genes and Genomes; miRNA: microRNA; ncRNAs: non-coding RNAs; qPCR: Real time quantitative PCRS; FAs: Saturated Fatty Acids; SLc2a2: Solute carrier family 2 member 2; T2D: Type 2 Diabetes.

[Low serum testosterone level does not predict bone metastasis of prostate cancer].

OBJECTIVE: To evaluate the role of the serum testosterone level as an independent predictor of bone metastasis of prostate cancer. METHODS: This study included 165 male patients with prostate cancer confirmed by biopsy. The patients were aged 58－78 (66.6±5.3) years and none had received androgen-deprivation therapy, chemotherapy or radiotherapy previously. We obtained the baseline clinical data from the patients, including prostate biopsy Gleason scores and the levels of serum prostate-specific antigen (PSA), total testosterone (TT), luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol (E2), alkaline phosphatase (ALP) and prolactin. According to the results of bone scanning, we divided the patients into a bone metastasis and a non-bone metastasis group and screened out the differential factors by univariate analysis and the independent predictor of bone metastasis using the multivariate non-conditional logistic regression model. RESULTS: Univariate analysis showed no statistically significant differences between the bone metastasis and non-bone metastasis groups in age (P = 0.126) or the levels of serum LH (P = 0.930), FSH (P = 0.763) and E2 (P = 0.256), but that the former had remarkably higher Gleason scores (P < 0.01), total PSA (P <0.01) and ALP (P <0.01) but a lower TT level than the latter (P = 0.013). According to the results of multivariate logistic regression analysis, serum ALP (P <0.01, OR = 1.018 ï¼»1.011－1.026ï¼½) and total PSA (P <0.01, OR = 1.029 ï¼»1.015－1.044ï¼½) could be regarded as independent predictors of bone metastasis of prostate cancer but not low serum TT (P = 0.531, OR = 0.999 ï¼»0.996－1.002ï¼½) or biopsy Gleason score (P = 0.898, OR = 0.787 ï¼»0.412－1.9559ï¼½). CONCLUSIONS: The low level of serum testosterone is closely associated with but not an independent predictor of bone metastasis of prostate cancer.