Project description:Triacylglyceride (TAG) synthesis in the small intestine determines the absorption of dietary fat, but the mechanisms underlying are largely unknown. Here, we report that the RNA-binding protein HuR (ELAVL1) promotes TAG synthesis in the small intestine. HuR associates with the 3’UTR of Dgat2 mRNA and the introns 1 of Mgat2 pre-mRNA. Association of HuR with Dgat2 3’UTR stabilizes Dgat2 mRNA, while association of HuR with intron 1 of Mgat2 pre-mRNA promotes the processing of Mgat2 pre-mRNA. Intestinal epithelium-specific HuR knockout reduces the expression of DGAT2 and MGAT2, thereby reducing the dietary fat absorption through TAG synthesis and mitigating high-fat diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) and obesity. Our findings highlight a critical role of HuR in promoting dietary fat absorption.
Project description:Triacylglyceride (TAG) synthesis in the small intestine determines the absorption of dietary fat, but the mechanisms underlying are largely unknown. Here, we report that the RNA-binding protein HuR (ELAVL1) promotes TAG synthesis in the small intestine. HuR associates with the 3’UTR of Dgat2 mRNA and the introns 1 of Mgat2 pre-mRNA. Association of HuR with Dgat2 3’UTR stabilizes Dgat2 mRNA, while association of HuR with intron 1 of Mgat2 pre-mRNA promotes the processing of Mgat2 pre-mRNA. Intestinal epithelium-specific HuR knockout reduces the expression of DGAT2 and MGAT2, thereby reducing the dietary fat absorption through TAG synthesis and mitigating high-fat diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) and obesity. Our findings highlight a critical role of HuR in promoting dietary fat absorption.
Project description:Monocyte-derived liver macrophages are critical in the pathogenesis of metabolic dysfunction-associated steatohepatitis (MASH) and liver fibrosis, but their recruitment mechanisms remain unclear. Serotonin (5-hydroxytryptamine, 5HT) is a conserved monoamine synthesized by tryptophan hydroxylase (Tph) 1 in peripheral tissues and Tph2 in the brain. We show that in mice housed at thermoneutrality and fed a high-fat, high-fructose diet, inhibition of peripheral serotonin (pe5HT) through genetic deletion of Tph1 prevents MASH independently of reductions in body weight. Liver flow cytometry and single-nuclei sequencing showed reduced pro-inflammatory Ly6Chigh monocytes, monocyte-derived Kupffer cells (moKCs), and lipid-associated macrophages (LAMs) in Tph1 KO mice. Tph1 deletion also decreased circulating monocytes, specifically Ly6Chigh monocytes. A single 5HT injection increased Ly6Chigh monocytes, while Tph1 KO mice had reduced monocytes without affecting bone marrow monocytes. Mechanistically, serotonin inhibition increases liver AMPK activity, and this is important for reducing CCL2 and monocyte recruitment. These findings link two ancient energy sensors, 5HT and AMPK, with obesity-associated liver fibrosis.
Project description:Specific gut microbiota is critically involved in metabolic diseases, including obesity. Through analysis of gut microbiota in diabetic patients and animal models, it was found that Romboutsia ilealis is closely associated with obesity. Here, our findings show that oral administration of Romboutsia ilealis significantly alleviates diet-induced obesity and metabolic dysfunction. Interestingly, this effect occurs not through modulation of food intake or energy expenditure, but by regulating lipid absorption and metabolism in the gut. Additionally, metabolomics analysis identified 2-oxindole-3-acetic acid (OAA) as the key metabolite involved in the regulation of obesity by Romboutsia ilealis. Its regulatory effect on intestinal lipid absorption was further validated both in vitro and in vivo. Mechanistically, using biotin-labeled OAA combined with proteomic analysis, we found that OAA directly interacts with the deubiquitin enzyme PSMD3, increasing the ubiquitination level of m6A binding protein YTHDF2 and reducing its protein stability, thereby enhancing intestinal lipid absorption. Furtherly, through m6A-seq, we discovered that YTHDF2 negatively regulates the expression of RXRB by recognizing the m6A sites on its mRNA, which in turn downregulates the expression of lipid absorption and transport proteins CD36 and FABP2, ultimately inhibiting intestinal lipid absorption. In summary, our findings reveal that Romboutsia ilealis and OAA regulate obesity-associated lipid accumulation through PSMD3-mediated deubiquitination of YTHDF2, suggesting that they represent novel prebiotics and probiotics with potential as therapeutic agents against obesity.
Project description:In this study, we investigated the effects of organic vegetable juice supplementation on modulating the microbial community, and how its consumption ameliorates blood lipid profiles in diet-induced obese mice. Here, we analyzed the effect of organic vegetable juice on the microbial community and fatty acid synthesis via animal experiments using diet-induced obese mice and continuous colon simulation system. Organic vegetable juice supplement influenced intestinal bacterial composition from phylum to genus level, including decreased Proteobacteria in the ascending colon in the phylum. At the family level, Akkermansia which are associated with obesity, were significantly augmented in the transverse colon and descending colon compared to the control juice group. In addition, treatment with organic vegetable juice affected predicted lipid metabolism function genes related to lipid synthesis. Organic vegetable juice consumption did not have a significant effect on weight loss but helped reduce epididymis fat tissue and adipocytes. Additionally, blood lipid profiles, such as triglyceride, high-density lipoprotein, and glucose, were improved in the organic vegetable juice-fed group. Expression levels of genes related to lipid synthesis, including SREBP-1, PPARγ, C/EBPα, and Fas, were significantly decreased. Analysis of antioxidant markers, including 8-OHdG and MDA, in the vegetable juice group, indicated that blood lipid profiles were improved by the antioxidant effect. These results suggest that organic vegetable juice supplementation may modulate gut microbial community and reduce the potential role of hyperlipidemia in diet-obese mice.
Project description:High-fat diets (HFD) exacerbate excessive lipid absorption by compelling the small intestine (SI) to take in redundant calories, yet host-encoded mechanisms are not fully explored. Previous research demonstrated that intestinal group 3 innate lymphoid cell (ILC3)–interleukin-22 (IL-22)–phosphorylated signal transducer and activator of transcription 3 (pSTAT3) axis fluctuates with feeding rhythms and engages in nutrient absorption. We found that prolonged HFD feeding enhances this axis in the proximal SI, leading to adaptively increased lipid absorption. Notably, we identified Eph receptor B4 (EphB4), an intestinal epithelial regulator that interacts with ILC3s microbiota-independently, thereby boosting pre-meal IL-22 secretion and subsequent lipid absorption, elucidating its crucial role in the interplay between diet, immune axis, and metabolism. In HFD-induced obesed mice, deleting EphB4 in intestinal epithelial cells (IECs) reduced proximal intestinal lipid absorption, improved obesity and metabolic disorders.
Project description:The intestinal microbiota is a key regulator of mammalian lipid absorption, metabolism, and storage. Here we show that the microbiota reprograms intestinal lipid metabolism in mice by repressing the expression of long non-coding RNA (lncRNA) Snhg9 in small intestinal epithelial cells. Snhg9 suppressed the activity of the transcription factor peroxisome proliferator–activated receptor γ (PPARγ) – a central regulator of lipid metabolism – by dissociating the PPARγ inhibitor Sirtuin 1 from cell cycle and apoptosis protein 2 (CCAR2). Forced expression of Snhg9 in the intestinal epithelium of conventional mice lowered dietary lipid absorption, reduced body fat, and protected against diet-induced obesity. The microbiota repressed Snhg9 expression through an immune cell signaling relay encompassing myeloid cells and innate lymphoid cells. Our findings thus identify an unanticipated role for a lncRNA in microbial control of host metabolism.
Project description:Fatty Acid Esters of Hydroxy Fatty Acids (FAHFAs), endogenous lipids with anti-inflammatory and metabolic benefits, face challenges in clinical translation due to instability and high synthesis costs. This study introduces a scalable synthetic platform to engineer novel FAHFA derivatives with enhanced stability through bioisosteric modifications (e.g., amide, triazole bonds). Screening identified 12-TAASA and 12-HDTZSA as lead compounds, demonstrating potent inhibition of lipid uptake in hepatic cells without compromising glucose absorption. In a diet-induced obesity mouse model, oral administration of these derivatives reduced weight gain, improved glucose tolerance, and attenuated ectopic lipid deposition, rivaling the efficacy of semaglutide. Mechanistically, 12-TAASA and 12-HDTZSA remodeled the gut microbiome by enriching SCFA producing taxa. 12-TAASA also suppressed intestinal lipid absorption via transcriptomic regulation of key genes. These findings position synthetic FAHFAs as dual-action therapeutics, targeting both host lipid metabolism and gut microbiota dysbiosis, offering a promising strategy for obesity and metabolic disorders.
Project description:Intake and absorption of cholesterol (the latter determined by double labeled cholesterol methodology) were nearly unchanged in mice fed the saturated fat diet, but the fecal excretion of neutral sterols (i.e. cholesterol and its microbial conversion products) was increased compared with control diet(+80%; p<0.01). The saturated fat diet did neither significantly affect biliary cholesterol secretion nor intestinal cholesterol absorption (49% vs. 65% in controls, double labeled water methodology, p>0.1). Thus, the increased fecal neutral sterol excretion was primarily due to increased net transintestinal cholesterol excretion (+89% versus control; p<0.05). Since a major fraction of TICE cholesterol absorption is normally reabsorbed (J Lipid Res 2019 Sep;60(9):1562-1572), the increased fecal cholesterol excretion could be due to more transintestinal excretion of cholesterol into the intestinal lumen and/or to its decreased reabsorption. The saturated fat diet increased jejunal expression of genes involved in cholesterol synthesis (Srebf2 and target genes), but did not affect whole body de novo cholesterol synthesis. Conclusion This proof-of-principle study shows that increasing the saturation of the dietary fat can stimulate fecal cholesterol excretion. Individual components of saturated fat diets are to be explored to address the responsible molecular mechanisms
Project description:Purpose: Obesity and dyslipidemia are associated with increased risk of renal disease.Testosterone deficiency aggravated high-fat diet-induced obesity and hypercholeterolemia. However,whether testosterone deficiency or testosterone deficiency-induced dyslipidemia aggravate the progression of renal disease is not clear. To gain insight into the role of testosterone in modulating renal lipid metabolism, we profiled renal gene expression by RNA-Seq in HFC-fed intact male pigs (IM), castrated male pigs (CM), and castrated male pigs with testosterone replacement (CMT). Methods: Sexually mature male miniature pigs were either surgical castrated or sham-operated, and castrated with testosterone replacement. We administrated to pigs a high-fat and high-cholesterol (HFC) diet for twelve weeks. RNA-Seq was employed to profile renal gene expression in pigs with different testosterone levels. Conclusions: This study demonstrated that testosterone deficiency aggravated renal lipid accumulation in pigs fed an HFC diet and that these effects could be reversed by testosterone replacement therapy. Impaired metabolic processes, bile acid secretion,estrogen signaling pathway and enhanced triglyceride synthesis may contribute to the increased renal lipid accumulation induced by testosterone deficiency and an HFC diet.