miR-548ag promotes DPP4 expression in hepatocytes through activation of TLR(7/8)/NF-κB pathway.

OBJECTIVE: In our previous study, we identified a notable increase in miR-548ag content after obesity, which contributes to the progression of Type 2 diabetes Mellitus(T2DM) through the up-regulation of Dipeptidyl Peptidase-4(DPP4) expression within the liver. However, the precise molecular mechanisms underlying the upregulation of DPP4 by miR-548ag remain elusive. Mature miRNAs rich in GU sequences can activate the TLR(7/8)/NF-κB signalling pathway, which transcriptionally activates DPP4 expression. Notably, the proportion of GU sequences in hsa-miR-548ag was found to be 47.6%. The study proposes a hypothesis suggesting that miR-548ag could potentially increase DPP4 expression in hepatocytes by activating the TLR(7/8)/NF-κB signalling pathway. METHODS: Male C57BL/6J mice were fed normal chow diet (NCD, n = 16) or high-fat diet (HFD, n = 16) for 12 weeks. For a duration of 6 weeks, NCD mice received intraperitoneal injections of a miR-548ag mimic, while HFD mice and db/db mice (n = 16) were administered intraperitoneal injections of a miR-548ag inhibitor. qRT-PCR and Western Blot were used to detect the expression level of miR-548ag, DPP4 and the activation of TLR(7/8)/NF-κB signalling pathway. HepG2 and L02 cells were transfected with miR-548ag mimic, miR-548ag inhibitor, TLR7/8 interfering fragment, and overexpression of miR-548ag while inhibiting TLR7/8, respectively. RESULTS: (1) We observed elevated levels of miR-548ag in the serum, adipose tissue, and liver of obese mice, accompanied by an upregulation of TLR7/8, pivotal protein in the NF-κB pathway, and DPP4 expression in the liver. (2) miR-548ag promotes DPP4 expression in hepatocytes via the TLR(7/8)/NF-κB signalling pathway, resulting in a reduction in the glucose consumption capacity of hepatocytes. (3) The administration of a miR-548ag inhibitor enhanced glucose tolerance and insulin sensitivity in db/db mice. CONCLUSIONS: MiR-548ag promotes the expression of DPP4 in hepatocytes by activating the TLR(7/8)/NF-κB signalling pathway. MiR-548ag may be a potential target for the treatment of T2DM.

Association of saturated fatty acids with cancer risk: a systematic review and meta-analysis.

OBJECTIVE: Extensive research has explored the link between saturated fatty acids (SFAs) and cardiovascular diseases, alongside other biological dysfunctions. Yet, their association with cancer risk remains a topic of debate among scholars. The present study aimed to elucidate this association through a robust meta-analysis. METHODS: PubMed, Embase, Cochrane Library, and Web of Science databases were searched systematically to identify relevant studies published until December 2023. The Newcastle-Ottawa Scale was used as the primary metric for evaluating the quality of the included studies. Further, fixed- or random-effects models were adopted to determine the ORs and the associated confidence intervals using the Stata15.1 software. The subsequent subgroup analysis revealed the source of detection and the cancer types, accompanied by sensitivity analyses and publication bias evaluations. RESULTS: The meta-analysis incorporated 55 studies, comprising 38 case-control studies and 17 cohort studies. It revealed a significant positive correlation between elevated levels of total SFAs and the cancer risk (OR of 1.294; 95% CI: 1.182-1.416; P-value less than 0.001). Moreover, elevated levels of C14:0, C16:0, and C18:0 were implicated in the augmentation of the risk of cancer. However, no statistically significant correlation of the risk of cancer was observed with the elevated levels of C4:0, C6:0, C8:0, C10:0, C12:0, C15:0, C17:0, C20:0, C22:0, and C24:0. Subgroup analysis showed a significant relationship between excessive dietary SFA intake, elevated blood SFA levels, and heightened cancer risk. Increased total SFA levels correlated with higher risks of breast, prostate, and colorectal cancers, but not with lung, pancreatic, ovarian, or stomach cancers. CONCLUSION: High total SFA levels were correlated with an increased cancer risk, particularly affecting breast, prostate, and colorectal cancers. Higher levels of specific SFA subtypes (C14:0, C16:0, and C18:0) are also linked to an increased cancer risk. The findings of the present study would assist in providing dietary recommendations for cancer prevention, thereby contributing to the development of potential strategies for clinical trials in which diet-related interventions would be used in combination with immunotherapy to alter the levels of SFAs in patients and thereby improve the outcomes in cancer patients. Nonetheless, further high-quality studies are warranted to confirm these associations.

KLF7 promotes adipocyte inflammation and glucose metabolism disorder by activating the PKCζ/NF-κB pathway.

In the obesity context, inflammatory cytokines secreted by adipocytes lead to insulin resistance and are key to metabolic syndrome development. In our previous study, we found that the transcription factor KLF7 promoted the expression of p-p65 and IL-6 in adipocytes. However, the specific molecular mechanism remained unclear. In the present study, we found that the expression of KLF7, PKCζ, p-IκB, p-p65, and IL-6 in epididymal white adipose tissue (Epi WAT) in mice fed a high-fat diet (HFD) was significantly increased. In contrast, the expression of PKCζ, p-IκB, p-p65, and IL-6 was significantly decreased in Epi WAT of KLF7 fat conditional knockout mice. In 3T3-L1 adipocytes, KLF7 promoted the expression of IL-6 via the PKCζ/NF-κB pathway. In addition, we performed luciferase reporter and chromatin immunoprecipitation assays, which confirmed that KLF7 upregulated the expression of PKCζ transcripts in HEK-293T cells. Collectively, our results show that KLF7 promotes the expression of IL-6 by upregulating PKCζ expression and activating the NF-κB signaling pathway in adipocytes.

Stress-inducible IL-6 is regulated by KLF7 in brown adipocytes.

Stress-inducible interleukin 6 (IL-6) is generated in brown adipocytes via beta-3 adrenergic receptor (ADRB3) signaling, which is necessary in stress hyperglycemia, the kind of metabolic adaptation enabling "fight or flight" response by means of liver gluconeogenesis. Nevertheless, the mechanism of ADRB3 signaling mediates IL-6 in brown adipocytes remains unclear. As a result, it is critical to understand how brown adipocytes produce IL-6 via ADRB3 signaling. We found that the ADRB3 agonist and cold stimulation promoted the expression of KLF7 and IL-6 in brown adipocytes of mice. In parallel to these results in vivo, treatment with ADRB3 agonist promoted the expression of KLF7 and the release of IL-6 in primary brown adipocytes of mice. Notably, we discovered that KLF7 positively controls the expression of IL-6 and downregulated KLF7 largely blunted ADRB3 agonist induced IL-6 expressions in brown adipocytes. Our findings suggest that KLF7 is required for the generation of IL-6 when ADRB3 signaling is activated in brown adipocytes.

Hepatic Glucose Metabolism Disorder Induced by Adipose Tissue-Derived miR-548ag via DPP4 Upregulation.

The present study aimed to explore the molecular mechanism underlying the regulation of glucose metabolism by miR-548ag. For the first time, we found that miR-548ag expression was elevated in the abdominal adipose tissue and serum of subjects with obesity and type 2 diabetes mellitus (T2DM). The conditional knockout of adipose tissue Dicer notably reduced the expression and content of miR-548ag in mouse adipose tissue, serum, and liver tissue. The combined use of RNAseq, an miRNA target gene prediction software, and the dual luciferase reporter assay confirmed that miR-548ag exerts a targeted regulatory effect on DNMT3B and DPP4. miR-548ag and DPP4 expression was increased in the adipose tissue, serum, and liver tissue of diet-induced obese mice, while DNMT3B expression was decreased. It was subsequently confirmed both in vitro and in vivo that adipose tissue-derived miR-548ag impaired glucose tolerance and insulin sensitivity by inhibiting DNMT3B and upregulating DPP4. Moreover, miR-548ag inhibitors significantly improved the adverse metabolic phenotype in both obese mice and db/db mice. These results revealed that the expression of the adipose tissue-derived miR-548ag increased in obese subjects, and that this could upregulate the expression of DPP4 by targeting DNMT3B, ultimately leading to glucose metabolism disorder. Therefore, miR-548ag could be utilized as a potential target in the treatment of T2DM.