Metformin Decreases Insulin Resistance in Type 1 Diabetes Through Regulating p53 and RAP2A in vitro and in vivo

Metformin improves high‑fat diet‑induced insulin resistance in mice by downregulating the expression of long noncoding RNA NONMMUT031874.2

Metformin (MET) is the first-line therapeutic option for patients with type 2 diabetes that has garnered substantial attention over recent years. However, an insufficient number of studies have been performed to assess its effects on insulin resistance and the expression profile of long noncoding RNAs (lncRNAs). The present study divided mice into three groups: Control group, high-fat diet (HFD) group and HFD + MET group. A high-throughput sequencing analysis was conducted to detect lncRNA and mRNA expression levels, and differentially expressed lncRNAs were selected. Subsequently, the differentially expressed lncRNAs were validated both in vivo and in vitro (mouse liver AML12 cells treated with Palmitic acid) models of insulin resistance. After validating randomly selected lncRNAs via reverse transcription-quantitative PCR a novel lncRNA, NONMMUT031874.2, was identified, which was upregulated in the HFD group and reversed with MET treatment. To investigate the downstream mechanism of NONMMUT031874.2, lncRNA-microRNA (miR/miRNA)-mRNA co-expression network was constructed and NONCODE, miRBase and TargetScan databases were used, which indicated that NONMMUT031874.2 may regulate suppressor of cytokine signaling 3 by miR-7054-5p. For the in vitro part of the present study, AML12 cells were transfected with small interfering RNA to knock down NONMMUT031874.2 expression before being treated with palmitic acid (PA) and MET. The results showed that the expression of NONMMUT031874.2 was significantly increased whereas miR-7054-5p expression was significantly decreased by PA treatment. By contrast, after knocking down NONMMUT031874.2 expression or treatment with MET, the aforementioned in vitro observations were reversed. In addition, it was also found that NONMMUT031874.2 knockdown and treatment with MET exerted similar effects in alleviating insulin resistance and whilst decreasing glucose concentration in AML12 cells. These results suggest that MET treatment can ameliorate insulin resistance by downregulating NONMMUT031874.2 expression.

High expression of CD52 in adipocytes: a potential therapeutic target for obesity with type 2 diabetes

The aim of the present study was to evaluate the involvement of CD52 in adipocytes as well as to explore its effect on type 2 diabetes mellitus (T2DM), and to improve our understanding of the potential molecular events of obesity with type 2 diabetes. Global changes in the CD52 expression patterns were detected in adipocytes and preadipocytes derived from obese and lean individuals. In particular, CD52 was identified as significantly differentially upregulated and was analyzed, both in vitro and in vivo, using various approaches. In vitro experiments, CD52 was a significantly up-regulated mRNA in mature adipocytes and preadipocytes. In addition, CD52 gradually increased with the differentiation of preadipocytes. In vivo experiments, the expression of CD52 in high-fat diet (HFD) -fed mice tended to be higher than that in regular diet (RD) -fed mice. Further analysis showed that CD52 expression was positively correlated with Smad3 and TGF-β in mice, and the downregulation of CD52 was accompanied by increased glucose tolerance and insulin sensitivity. Moreover, a comparison of CD4+CD52^high T cells and CD4+CD52^low T cells showed that many T2DM-related genes were aberrantly expressed. Overall, CD52 may functioned as an important potential target for obesity with T2DM via TGF-β/Smad3 axis.

Metformin improves depressive-like symptoms in mice via inhibition of peripheral and central NF-κB-NLRP3 inflammation activation

Emerging evidence indicates that NLRP3 inflammasome-induced inflammation plays a crucial role in the pathogenesis of depression. Thus, inhibition of NLRP3 inflammasome activation may offer a therapeutic benefit in the treatment of depression. Metformin has been shown to have potential anti-inflammatory activity, but the underlying mechanisms remain obscure. We used a chronic mild stress model of depression and cultured primary macrophage to investigate the effects of metformin on depression and its underlying mechanisms. We demonstrated that metformin alleviated depressive-like behaviors in the chronic mild stress-induced anhedonia model of depression. We further found that metformin significantly suppressed NLRP3 inflammasome activation, subsequent caspase-1 cleavage, and interleukin-1β secretion in both peripheral macrophages and central hippocampus. Our findings reveal that metformin confers an antidepressant effect partly through inhibition of peripheral and central NLRP3 inflammasome activation. In light of metformin favorable properties, it should be evaluated in the treatment of depression and related neurologic disorders characterized by NLRP3 inflammasome activation.