Connie Waihong Woo

Background and Purpose: Radiation therapy‐induced gastrointestinal distress is partly associated with the elimination of gut microbiota. The effectiveness of 5‐HT receptor antagonists to treat radiation therapy‐induced emesis implies a pathophysiological role of 5‐HT. Peripheral 5‐HT is derived from intestinal epithelium. We have investigated the role of gut microbiota in regulating intestinal 5‐HT availability.Experimental Approach: A radiation therapy murine model accompanied by faecal microbiota transplantation from donors fed different diets was investigated, and mouse ileal organoids were used for mechanistic studies. The clinical relevance was validated by a small‐scale human study.Key Results: Short‐term high‐fat diet (HFD) induced gut bacteria to produce butyrate. Irradiated mice receiving HFD‐induced microbiome had the lowest ileal levels of 5‐HT, compared with other recipients. Treatment with butyrate increased 5‐HT uptake in mouse ileal organoids, assayed by the real‐time tracking of a fluorescent substrate for monoamine transporters. Silencing the 5‐HT transporter (SERT) in the organoids abolished butyrate‐stimulated 5‐HT uptake. The competitive tests using different types of selective 5‐HT reuptake inhibitors suggested that butyrate acted as a positive allosteric modulator of SERT. In human gut microbiota, butyrate production was associated with the interconversion between acetate and butyrate. Faecal contents of both acetate and butyrate were negatively associated with serum 5‐HT, but only butyrate was positively correlated with body mass index in humans.Conclusion and Implications: Short‐term HFD may be beneficial for alleviating gastrointestinal reactions by increasing butyrate to suppress local 5‐HT levels and providing energy to cancer patients given radiation therapy.

The proteome analysis reveals that stress granules are the predominant form of cytosolic messenger ribonucleoproteins of brown adipose tissue (BAT) at the early phase of cold exposure in mice for both sexes. The transcriptome of stress granules of BAT unveils a sex difference of molecular response in early phase of cold exposure in mice, and such difference prepares for a prompt response to cold stress in male mice while for long-term adaptation in female mice.

The gut microbiota can be beneficial and harmful to cardiovascular health depending on the mechanisms. The interaction between gut microbiota-derived flagellin and toll-like receptor 5 in hepatocytes, resulting in apolipoprotein A1 (ApoA1) production, brings forth a cardiovascular benefit to the host. Here, the association between flagellated microbiota and high-density lipoprotein-cholesterol (HDL-C) in humans was explored. Through sex-based gut microbiota analysis of two population-based cohorts, the 500 Functional Genomics Project (500FG) and Chinese cohorts, we found positive correlations between the capacity to produce flagellins in the gut microbiota and HDL-C in females of the 500FG and males of Chinese cohorts. Eubacterium rectale, Lachnospira pectinoschiza, Roseburia intestinalis and Roseburia inulinivorans were crucial species for such correlations. Diverse types of flagellins and TLR5, but not NAIP/NLRC4, flagellin-engaging receptors, were detectable by proteomic analysis of the human liver. However, not all flagellated bacteria yield the same degree of such benefit because of differences in the penetration of flagellins where other factors such as geographics and diets may play important roles.

Background: Increasing evidence has shown associations between gut microbiota and cardiovascular risks. However, whether sex influences the cardiovascular outcome of gut microbiota remains elusive. Methods: The gut microbiota metagenomic data from two previous population-based cohorts and the proteomics data from human liver samples were analyzed. Results: Through a sex-based analysis of 500 Functional Genomics Project (500FG) cohort, we found that the capacity of producing flagellin in Eubacterium rectale, Roseburia Intestinalis and Roseburia inulinivorans partially explained the levels of high-density lipoprotein-cholesterol (HDL-C) and apolipoprotein A1 in female participants. By comparing the bacterial species showing positive correlations with HDL-C and the flagellin species found in human liver samples, we found that E. rectale and R. inulinivorans appeared to be the major prevalent flagellated species in gut microbiota contributed to the host’s HDL-C level. The analysis of the Chinese-based cohort in which the male participants had relatively higher abundance of these two bacteria, the abovementioned positive correlation was also observed. Conclusions: The flagellin-producing function of E. rectale and R. inulinivorans in the gut microbiota partially explained the HDL-C level in the host, and there is a sex-specific difference in the sensitivity of this beneficial interaction. Our findings suggest a potential interaction between commensal bacteria and the host that yields a cardiovascular benefit. Clinical Perspective: What is new?: The flagellin-producing capacity of certain species in gut microbiota is positively associated with the HDL-C and ApoA1 levels in human. By comparing the flagellated bacteria in the gut and flagellin species in the liver, Eubacterium rectale and Roseburia inulinivorans are shown to be the most prevalent species contributing to such cardiovascular benefits. The sensitivity of such beneficial interaction with the gut flagellated bacteria is different between male and female. What are the clinical implications? (maximum 100 words, formatted as 2-3 bullets): Beside the role in metabolic inflammation, gut microbiota can be beneficial against cardiovascular risk by modulating HDL-C level through certain flagellated species. The interaction between flagellated bacteria in the gut and the host provide a different insight in exploring potential therapeutic targets to increase HDL-C level.

Background: Exercise is an effective nonpharmacological strategy to alleviate diabetic cardiomyopathy (DCM) through poorly defined mechanisms. FGF21 (fibroblast growth factor 21), a peptide hormone with pleiotropic benefits on cardiometabolic homeostasis, has been identified as an exercise responsive factor. This study aims to investigate whether FGF21 signaling mediates the benefits of exercise on DCM, and if so, to elucidate the underlying mechanisms. Methods: The global or hepatocyte-specific FGF21 knockout mice, cardiomyocyte-selective β-klotho (the obligatory co-receptor for FGF21) knockout mice, and their wild-type littermates were subjected to high-fat diet feeding and injection of streptozotocin to induce DCM, followed by a 6-week exercise intervention and assessment of cardiac functions. Cardiac mitochondrial structure and function were assessed by electron microscopy, enzymatic assays, and measurements of fatty acid oxidation and ATP production. Human induced pluripotent stem cell–derived cardiomyocytes were used to investigate the receptor and postreceptor signaling pathways conferring the protective effects of FGF21 against toxic lipids-induced mitochondrial dysfunction. Results: Treadmill exercise markedly induced cardiac expression of β-klotho and significantly attenuated diabetes-induced cardiac dysfunction in wild-type mice, accompanied by reduced mitochondrial damage and increased activities of mitochondrial enzymes in hearts. However, such cardioprotective benefits of exercise were largely abrogated in mice with global or hepatocyte-selective ablation of FGF21, or cardiomyocyte-specific deletion of β-klotho. Mechanistically, exercise enhanced the cardiac actions of FGF21 to induce the expression of the mitochondrial deacetylase SIRT3 by AMPK-evoked phosphorylation of FOXO3, thereby reversing diabetes-induced hyperacetylation and functional impairments of a cluster of mitochondrial enzymes. FGF21 prevented toxic lipids-induced mitochondrial dysfunction and oxidative stress by induction of the AMPK/FOXO3/SIRT3 signaling axis in human induced pluripotent stem cell–derived cardiomyocytes. Adeno-associated virus-mediated restoration of cardiac SIRT3 expression was sufficient to restore the responsiveness of diabetic FGF21 knockout mice to exercise in amelioration of mitochondrial dysfunction and DCM. Conclusions: The FGF21-SIRT3 axis mediates the protective effects of exercise against DCM by preserving mitochondrial integrity and represents a potential therapeutic target for DCM. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT03240978.

Toll plays an important role in innate immunity and embryonic development in lower-ranked animals, but in mammals, the homolog toll-like receptors (TLR) are reported to facilitate postnatal development of immunity only. Here, we discovered a role of TLR5 in placental development. Tlr5 was highly transcribed during the placenta-forming and functional phases. TLR5 deletion led to a smaller placental labyrinthine zone and lower embryo weight, and the smaller size of embryo was overcorrected, resulting in a higher postnatal body weight. Examination of TLR5-deficient conceptus revealed a decrease in nuclear cAMP-response element-binding protein (CREB), mechanistic target of rapamycin (mTOR) and insulin growth factor-1 receptor (IGF1R) abundances in the placenta-forming phase. Non-flagellin-based TLR5 ligands were detected in serum of female mice and the overexpression of TLR5 alone was sufficient to induce CREB nuclear translocation and mTOR transcriptional activation in trophoblasts. Taken together, we uncovered the participation of TLR5 in the early placental formation in mice, unveiling a role of TLR in embryonic development in higher-ranked animals.

Rationale: Dysbiosis of gut microbiota plays an important role in cardiovascular diseases but the molecular mechanisms are complex. An association between gut microbiome and the variance in HDL-C (high-density lipoprotein-cholesterol) level was suggested in a human study. Besides, dietary fat was shown to increase both HDL-C and LDL-C (low-density lipoprotein-cholesterol) levels. We speculate that certain types of gut bacteria responding to dietary fat may help to regulate HDL-C level and potentially affect atherosclerotic development. Objective: We aimed to investigate whether and how high-fat diet (HFD)-associated gut microbiota regulated HDL-C level. Methods and Results: We found that HFD increased gut flagellated bacteria population in mice. The increase in HDL-C level was adopted by mice receiving fecal microbiome transplantation from HFD-fed mouse donors. HFD led to increased hepatic but not circulating flagellin, and deletion of TLR5 (Toll-like receptor 5), a receptor sensing flagellin, suppressed HFD-stimulated HDL-C and ApoA1 (apolipoprotein A1) levels. Overexpression of TLR5 in the liver of TLR5-knockout mice was able to partially restore the production of ApoA1 and HDL-C levels. Mechanistically, TLR5 activation by flagellin in primary hepatocytes stimulated ApoA1 production through the transcriptional activation responding to the binding of NF-κB (nuclear factor-κB) on Apoa1 promoter region. Furthermore, oral supplementation of flagellin was able to stimulate hepatic ApoA1 production and HDL-C level and decrease atherosclerotic lesion size in apolipoprotein E-deficient ( Apoe ^−/− ) mice without triggering hepatic and systemic inflammation. The stimulation of ApoA1 production was also seen in human ApoA1-transgenic mice treated with oral flagellin. Conclusions: Our finding suggests that commensal flagellated bacteria in gut can facilitate ApoA1 and HDL-C productions in liver through activation of TLR5 in hepatocytes. Hepatic TLR5 may be a potential drug target to increase ApoA1.

Folate is an essential micronutrient for biological function. The liver, a primary organ for folate metabolism and storage, plays an important role in folate homeostasis. Proton-coupled folate transporter (PCFT) and reduced folate carrier (RFC) are the major folate transporters responsible for folate uptake at basolateral membrane of hepatocytes. Low serum folate levels are frequently associated with obesity. We investigated the mechanism that regulated folate status in a mouse model with diet-induced obesity. Mice (C57BL/6J) were fed a high-fat diet (60% kcal fat) for 8 weeks. Mice displayed increased hepatic lipid accumulation and decreased folate levels in the liver and serum compared to mice fed a normal chow diet (10% kcal fat). High-fat diet-fed mice had low expression of PCFT and RFC and decreased nuclear respiratory factor-1 (NRF-1)/DNA-binding activity. Treatment with NRF-1 siRNA or palmitic acid reduced folate transporter expression in hepatocytes. Inhibition of NRF-1 mediated folate transporter expression significantly reduced intracellular folate levels. These results suggest that chronic consumption of high-fat diets impairs folate transporter expression via NRF-1-dependent mechanism, leading to reduced hepatic folate storage. Understanding the regulation of folate homeostasis in obesity may have an important implication in current guideline of folate intake.

Nonalcoholic fatty liver disease (NAFLD) includes a spectrum of diseases that ranges in severity from hepatic steatosis to steatohepatitis, the latter of which is a major predisposing factor for liver cirrhosis and cancer. Toll-like receptor (TLR) signaling, which is critical for innate immunity, is generally believed to aggravate disease progression by inducing inflammation. Unexpectedly, we found that deficiency in TIR domain–containing adaptor-inducing interferon-β (TRIF), a cytosolic adaptor that transduces some TLR signals, worsened hepatic steatosis induced by a high-fat diet (HFD) and that such exacerbation was independent of myeloid cells. The aggravated steatosis in Trif^−/− mice was due to the increased hepatocyte transcription of the gene encoding stearoyl–coenzyme A (CoA) desaturase 1 (SCD1), the rate-limiting enzyme for lipogenesis. Activation of the TRIF pathway by polyinosinic:polycytidylic acid [poly(I:C)] suppressed the increase in SCD1 abundance induced by palmitic acid or an HFD and subsequently prevented lipid accumulation in hepatocytes. Interferon regulatory factor 3 (IRF3), a transcriptional regulator downstream of TRIF, acted as a transcriptional suppressor by directly binding to the Scd1 promoter. These results suggest an unconventional metabolic function for TLR/TRIF signaling that should be taken into consideration when seeking to pharmacologically inhibit this pathway.