PA and OA induce abnormal glucose metabolism by inhibiting KLF15 in adipocytes

Ursolic Acid Modulates Estrogen Conversion to Relieve Inflammation in Metabolic Dysfunction-associated Steatotic Liver Disease via HSD17B14

Background and Aims

The incidence of metabolic dysfunction-associated steatotic liver disease (MASLD) has been escalating annually, positioning it as the leading cause of chronic liver disease worldwide. Ursolic acid has demonstrated promising therapeutic efficacy in managing MASLD, thereby justifying the need for an in-depth exploration of its pharmacological mechanisms. This study aimed to investigate elucidate the therapeutic mechanisms by which ursolic acid modulates estrogen conversion in the treatment of MASLD.

Methods

Building upon prior studies that have highlighted the potent anti-inflammatory effects of ursolic acid and its specific targeting of 17β-hydroxysteroid dehydrogenase 14 (HSD17B14), this investigation employed a western diet to induce MASLD in murine models with varying severities over different time intervals.

Results

The protein expression of HSD17B14 initially increased, followed by a subsequent decrease. This trend was accompanied by corresponding changes in 17β-estradiol (E2) and estrone (E1) levels. Intervention with ursolic acid resulted in a reduction in HSD17B14 and E1 levels during the phase of high HSD17B14 expression, while simultaneously elevating E2 levels. In steatotic hepatocytes, E1 promoted cellular inflammation, whereas E2 exhibited anti-inflammatory effects. However, the alleviated effects of E2 were antagonized by HSD17B14. As expected, ursolic acid modulated HSD17B14, thereby mitigating the inflammatory response in steatotic hepatocytes.

Conclusions

HSD17B14, a crucial enzyme regulating the balance between E1 and E2, catalyzes the conversion of estrogen E2 into E1, thereby exacerbating tissue inflammation induced by metabolic stress. Ursolic acid, by modulating HSD17B14-mediated estrogen conversion, appears to ameliorate immune-related inflammation in MASLD.

Distribution and functional significance of KLF15 in mouse cerebellum

Kruppel-like factor 15 (KLF15), a member of the KLF family, is closely involved in many biological processes. However, the mechanism by which KLF15 regulates neural development is still unclear. Considering the complexity and importance of neural network development, in this study, we investigated the potent regulatory role of KLF15 in neural network development. KLF15 was detected highly expressed in the cerebellum and enriched in Purkinje cells, with a significant increase in KLF15 expression between 15 and 20 days of neural development. Knockdown of KLF15 led to loss of Purkinje cells and impaired motility in mice. Therefore, our study aims to elucidate the relationship between KLF15 and Purkinje cells in mice, may provide a new research idea for the developmental mechanism of the mouse cerebellum.

The ubiquitination degradation of KLF15 mediated by WSB2 promotes lipogenesis and progression of hepatocellular carcinoma via inhibiting PDLIM2 expression

BACKGROUND AND AIM

Krüppel-like factors15 (KLF15) is a cancer suppressor in many cancers. However, its precise function in the development of hepatocellular carcinoma (HCC) remains unclear. Lipogenesis is necessary for the development of HCC. This research aims to investigate the role of KLF15 in the regulation of hepatic lipid production and HCC progression.

METHODS

The binding relationships among genes were confirmed by ChIP, dual luciferase assays, and Co-IP. Lipogenesis was examined by oil red O staining. Triglyceride and cholesterol levels were measured through commercial kits. The effect of treatment on HCC cell viability, proliferation, migration, and invasion were assessed using CCK-8, clone formation, or transwell assays. A subcutaneous tumorigenic model was utilized to explore the effects of PDLIM2 in HCC in vivo.

RESULTS

KLF15 were downregulated in human HCC tissues. KLF15 overexpression reduced lipid droplet production, suppressed the expression of genes associated with lipogenesis, and promoted cell proliferation, migration, and invasion. KLF15 suppressed the NF-κB pathway through transcriptional activation of PDLIM2. PDLIM2 knockdown attenuated the effect of KLF15 overexpression on HCC. WSB2 degraded KLF15 through ubiquitination to promote HCC lipogenesis and development.

CONCLUSION

The ubiquitination degradation of KLF15 was mediated by WSB2, which led to transcriptional repression of PDLIM2 and further activation of the NF-κB pathway, ultimately promoting HCC lipogenesis and development.

Glycerol Kinase Drives Hepatic de novo Lipogenesis and Triglyceride Synthesis in Nonalcoholic Fatty Liver by Activating SREBP-1c Transcription, Upregulating DGAT1/2 Expression, and Promoting Glycerol Metabolism

Glycerol kinase (GK) participates in triglyceride (TG) synthesis by catalyzing glycerol metabolism. Whether GK contributes to nonalcoholic fatty liver (NAFL) is unclear. The expression of hepatic Gk is found to be increased in diet-induced and genetic mouse models of NAFL and is positively associated with hepatic SREBP-1c expression and TG levels. Cholesterol and fatty acids stimulate GK expression in hepatocytes. In HFD-induced NAFL mice, knockdown of hepatic Gk decreases expression of SREBP-1c and its target lipogenic genes as well as DGAT1/2, increases serum glycerol levels, decreases serum TG levels, and attenuates hepatic TG accumulation. Overexpression of GK in hepatocytes in mice or in culture produces opposite results. Mechanistic studies reveal that GK stimulates SREBP-1c transcription directly by binding to its gene promoter and indirectly by binding to SREBP-1c protein, thereby increasing lipogenic gene expression and de novo lipogenesis. Studies with truncated GK and mutant GKs indicate that GK induces SREBP-1c transcription independently of its enzyme activity. GK contributes to lipid homeostasis under physiological conditions by catalyzing glycerol metabolism rather than by regulating SREBP-1c transcription. Collectively, these results demonstrate that increased hepatic GK promotes de novo lipogenesis and TG synthesis in NAFL by stimulating SREBP-1c transcription and DGAT1/2 expression and catalyzing glycerol metabolism.

Mechanism of fibroblast growth factor 1 regulating fatty liver disorder in mule ducks

Mule ducks tend to accumulate abundant fat in their livers via feeding, which leads to the formation of a fatty liver that is several times larger than a normal liver. However, the mechanism underlying fatty liver formation has not yet been elucidated. Fibroblast growth factor 1 (FGF1), a member of the FGF superfamily, is involved in cellular lipid metabolism and mitosis. This study aims to investigate the regulatory effect of FGF1 on lipid metabolism disorders induced by complex fatty acids in primary mule duck liver cells and elucidate the underlying molecular mechanism. Hepatocytes were induced by adding 1,500:750 µmol/L oleic and palmitic acid concentrations for 36 h, which were stimulated with FGF1 concentrations of 0, 10, 100, and 1000 ng/mL for 12 h. The results showed that FGF1 significantly reduced the hepatic lipid droplet deposition and triglyceride content induced by complex fatty acids; it also reduced oxidative stress; decreased reactive oxygen species fluorescence intensity and malondialdehyde content; upregulated the expression of antioxidant factors nuclear factor erythroid 2 related factor 2 (Nrf2), HO-1, and NQO-1; significantly enhanced liver cell activity; promoted cell cycle progression; inhibited cell apoptosis; upregulated cyclin-dependent kinase 1 (CDK1) and BCL-2 mRNA expression; and downregulated Bax and Caspase-3 expression. In addition, FGF1 promoted AMPK phosphorylation, activated the AMPK pathway, upregulated AMPK gene expression, and downregulated the expression of SREBP1 and ACC1 genes, thereby alleviating excessive fat accumulation in liver cells induced by complex fatty acids. In summary, FGF1 may alleviate lipid metabolism disorders induced by complex fatty acids in primary mule duck liver cells by activating the AMPK signaling pathway.

The role of free fatty acid receptor-1 in gastric contractions in Suncus murinus

Motilin is an important hormonal regulator in the migrating motor complex (MMC). Free fatty acid receptor-1 (FFAR1, also known as GPR40) has been reported to stimulate motilin release in human duodenal organoids. However, how FFAR1 regulates gastric motility in vivo is unclear. This study investigated the role of FFAR1 in the regulation of gastric contractions and its possible mechanism of action using Suncus murinus. Firstly, intragastric administration of oleic acid (C18:1, OA), a natural ligand for FFAR1, stimulated phase II-like contractions, followed by phase III-like contractions in the fasted state, and the gastric emptying rate was accelerated. The administration of GW1100, an FFAR1 antagonist, inhibited the effects of OA-induced gastric contractions. Intravenous infusion of a ghrelin receptor antagonist (DLS) or serotonin 4 (5-HT4) receptor antagonist (GR125487) inhibited phase II-like contractions and prolonged the onset of phase III-like contractions induced by OA. MA-2029, a motilin receptor antagonist, delayed the occurrence of phase III-like contractions. In vagotomized suncus, OA did not induce phase II-like contractions. In addition, OA promoted gastric emptying through a vagal pathway during the postprandial period. However, OA did not directly act on the gastric body to induce contractions in vitro. In summary, this study indicates that ghrelin, motilin, 5-HT, and the vagus nerve are involved in the role of FFAR1 regulating MMC. Our findings provide novel evidence for the involvement of nutritional factors in the regulation of gastric motility.