Microbiota derived D-malate inhibits skeletal muscle growth and angiogenesis during aging via acetylation of Cyclin A.

Metabolites derived from the intestinal microbiota play an important role in maintaining skeletal muscle growth, function, and metabolism. Here, we found that D-malate (DMA) is produced by mouse intestinal microorganisms and its levels increase during aging. Moreover, we observed that dietary supplementation of 2% DMA inhibits metabolism in mice, resulting in reduced muscle mass, strength, and the number of blood vessels, as well as the skeletal muscle fiber type I/IIb ratio. In vitro assays demonstrate that DMA decreases the proliferation of vascular endothelial cells and suppresses the formation of blood vessels. In vivo, we further demonstrated that boosting angiogenesis by muscular VEGFB injection rescues the inhibitory effects of D-malate on muscle mass and fiber area. By transcriptomics analysis, we identified that the mechanism underlying the effects of DMA depends on the elevated intracellular acetyl-CoA content and increased Cyclin A acetylation rather than redox balance. This study reveals a novel mechanism by which gut microbes impair muscle angiogenesis and may provide a therapeutic target for skeletal muscle dysfunction in cancer or aging.

SVision: a deep learning approach to resolve complex structural variants.

Complex structural variants (CSVs) encompass multiple breakpoints and are often missed or misinterpreted. We developed SVision, a deep-learning-based multi-object-recognition framework, to automatically detect and haracterize CSVs from long-read sequencing data. SVision outperforms current callers at identifying the internal structure of complex events and has revealed 80 high-quality CSVs with 25 distinct structures from an individual genome. SVision directly detects CSVs without matching known structures, allowing sensitive detection of both common and previously uncharacterized complex rearrangements.

Comparison and benchmark of structural variants detected from long read and long-read assembly.

Structural variant (SV) detection is essential for genomic studies, and long-read sequencing technologies have advanced our capacity to detect SVs directly from read or de novo assembly, also known as read-based and assembly-based strategy. However, to date, no independent studies have compared and benchmarked the two strategies. Here, on the basis of SVs detected by 20 read-based and eight assembly-based detection pipelines from six datasets of HG002 genome, we investigated the factors that influence the two strategies and assessed their performance with well-curated SVs. We found that up to 80% of the SVs could be detected by both strategies among different long-read datasets, whereas variant type, size, and breakpoint detected by read-based strategy were greatly affected by aligners. For the high-confident insertions and deletions at non-tandem repeat regions, a remarkable subset of them (82% in assembly-based calls and 93% in read-based calls), accounting for around 4000 SVs, could be captured by both reads and assemblies. However, discordance between two strategies was largely caused by complex SVs and inversions, which resulted from inconsistent alignment of reads and assemblies at these loci. Finally, benchmarking with SVs at medically relevant genes, the recall of read-based strategy reached 77% on 5X coverage data, whereas assembly-based strategy required 20X coverage data to achieve similar performance. Therefore, integrating SVs from read and assembly is suggested for general-purpose detection because of inconsistently detected complex SVs and inversions, whereas assembly-based strategy is optional for applications with limited resources.

Exercise-induced α-ketoglutaric acid stimulates muscle hypertrophy and fat loss through OXGR1-dependent adrenal activation.

Beneficial effects of resistance exercise on metabolic health and particularly muscle hypertrophy and fat loss are well established, but the underlying chemical and physiological mechanisms are not fully understood. Here, we identified a myometabolite-mediated metabolic pathway that is essential for the beneficial metabolic effects of resistance exercise in mice. We showed that substantial accumulation of the tricarboxylic acid cycle intermediate α-ketoglutaric acid (AKG) is a metabolic signature of resistance exercise performance. Interestingly, human plasma AKG level is also negatively correlated with BMI. Pharmacological elevation of circulating AKG induces muscle hypertrophy, brown adipose tissue (BAT) thermogenesis, and white adipose tissue (WAT) lipolysis in vivo. We further found that AKG stimulates the adrenal release of adrenaline through 2-oxoglutarate receptor 1 (OXGR1) expressed in adrenal glands. Finally, by using both loss-of-function and gain-of-function mouse models, we showed that OXGR1 is essential for AKG-mediated exercise-induced beneficial metabolic effects. These findings reveal an unappreciated mechanism for the salutary effects of resistance exercise, using AKG as a systemically derived molecule for adrenal stimulation of muscle hypertrophy and fat loss.

Conjugated linoleic acid (CLA) reduces HFD-induced obesity by enhancing BAT thermogenesis and iWAT browning via the CD36-AMPK pathway.

The antiobesity effect of conjugated linoleic acid (CLA) has been reported. However, the underlying mechanisms have not been fully clarified. Thus, this study aimed to investigate the effects of CLA on thermogenesis of interscapular brown adipose tissue (iBAT) and browning of inguinal subcutaneous white adipose tissue (iWAT) and explore the possible signaling pathway. The in vivo results showed that CLA enhanced the O2 consumption and heat production in HFD (high-fat diet)-fed female mice by roughly 38%. Meanwhile, CLA increased the average iBAT temperature by 2°C at the room temperature and cold exposure, respectively. Correspondingly, CLA caused 1.6- and 2.4-fold increases in the expression of UCP1 (uncoupling protein 1) of BAT and iWAT, respectively, suggesting the activated iBAT thermogenesis and iWAT browning in HFD-fed female mice. Meanwhile, CLA could promote the formation of brown and beige adipocytes in differentiated stromal vascular cells (SVCs) isolated from iBAT and iWAT (the expressions of UCP1 were promoted by about twofold changes). In possible mechanisms, CLA stimulated the expression of CD36 and the activation of the AMPK pathway in mice iBAT and iWAT as well as the differentiated SVCs. However, inhibition of CD36 and AMPK (adenosine 5'-monophosphate-activated protein kinase) abolished the promotive effects of CLA on brown and beige adipocytes formation. Hence, we showed that CLA reduced HFD-induced obesity through enhancing iBAT thermogenesis and iWAT browning via the  CD36-AMPK pathway.

Associations between Urinary Concentrations of Polycyclic Aromatic Hydrocarbons and Overactive Bladder in US Adults: Data from the National Health and Nutrition Examination Survey 2005-2016.

INTRODUCTION: Polycyclic aromatic hydrocarbons (PAHs) are a group of chemicals that can induce oxidative stress and related cytotoxicity. Whether urinary concentrations of PAHs have effects on overactive bladder (OAB) in the general population is still unclear. This study investigated the associations between urinary PAHs and OAB. METHODS: 7,146 adults aged over 20 who participated in the US National Health and Nutrition Examination Survey 2005-2016 were studied. The impact of the six PAHs on OAB was evaluated by multivariate logistic regression, and percent changes related to different quartiles of those six PAH levels were calculated. Confounders including age, logarithmic urinary creatinine, gender, race, body mass index, educational level, marriage, poverty income ratio, diabetes, hypertension, and metabolic syndrome were controlled. RESULTS: There is a significant positive correlation between urinary concentrations of the six PAHs we include in the study and the occurrence of OAB. Furthermore, individuals with higher PAH levels also reported a more severe OAB symptom score (OABSS). CONCLUSIONS: Our findings revealed that adult men in the USA with higher urinary PAHs had a higher risk of OAB incidence. These findings suggest the importance of strong environmental regulation of PAHs to protect population health. However, the underlying mechanisms still need further exploration.

TLR4 in POMC neurons regulates thermogenesis in a sex-dependent manner.

The rising prevalence of obesity has become a worldwide health concern. Obesity usually occurs when there is an imbalance between energy intake and energy expenditure. However, energy expenditure consists of several components, including metabolism, physical activity, and thermogenesis. Toll-like receptor 4 (TLR4) is a transmembrane pattern recognition receptor, and it is abundantly expressed in the brain. Here, we showed that pro-opiomelanocortin (POMC)-specific deficiency of TLR4 directly modulates brown adipose tissue thermogenesis and lipid homeostasis in a sex-dependent manner. Deleting TLR4 in POMC neurons is sufficient to increase energy expenditure and thermogenesis resulting in reduced body weight in male mice. POMC neuron is a subpopulation of tyrosine hydroxylase neurons and projects into brown adipose tissue, which regulates the activity of sympathetic nervous system and contributes to thermogenesis in POMC-TLR4-KO male mice. By contrast, deleting TLR4 in POMC neurons decreases energy expenditure and increases body weight in female mice, which affects lipolysis of white adipose tissue (WAT). Mechanistically, TLR4 KO decreases the expression of the adipose triglyceride lipase and lipolytic enzyme hormone-sensitive lipase in WAT in female mice. Furthermore, the function of immune-related signaling pathway in WAT is inhibited because of obesity, which exacerbates the development of obesity reversely. Together, these results demonstrate that TLR4 in POMC neurons regulates thermogenesis and lipid balance in a sex-dependent manner.

RNA-binding protein YBX1 promotes brown adipogenesis and thermogenesis via PINK1/PRKN-mediated mitophagy.

Promoting the thermogenic function of brown adipose tissue (BAT) is a promising strategy to combat obesity and metabolic disorders. While much is known about the transcriptional regulation of BAT activation, however, the underlying mechanism of post-transcriptional control by RNA binding proteins remains largely unknown. Here, we found that RNA binding protein Y-box binding protein 1 (YBX1) expression was abundant in BAT and induced by cold exposure and a ß-adrenergic agonist in mice. Loss-of-function experiments showed that YBX1 deficiency inhibited mouse primary brown adipocyte differentiation and thermogenic function. Further study showed that YBX1 positively regulates thermogenesis through enhancing mitophagy. Mechanistically, RNA immunoprecipitation identified that YBX1 directly targeted the transcripts of PTEN-induced kinase 1 (Pink1) and parkin RBR E3 ubiquitin-protein ligase (Prkn), two key regulators of mitophagy. RNA decay assay proved that loss of YBX1 decreased mRNA stability of Pink1 and Prkn, leading to reduced protein expression, thereby alleviating mitophagy and inhibiting thermogenic program. Importantly, in vivo experiments demonstrated that YBX1 overexpression in BAT promoted thermogenesis and mitophagy in mice. Collectively, our results reveal novel insight into the molecular mechanism of YBX1 in post-transcriptional regulation of PINK1/PRKN-mediated mitophagy and highlight the critical role of YBX1 in brown adipogenesis and thermogenesis.

A chromosome conformation capture ordered sequence of the barley genome.

Cereal grasses of the Triticeae tribe have been the major food source in temperate regions since the dawn of agriculture. Their large genomes are characterized by a high content of repetitive elements and large pericentromeric regions that are virtually devoid of meiotic recombination. Here we present a high-quality reference genome assembly for barley (Hordeum vulgare L.). We use chromosome conformation capture mapping to derive the linear order of sequences across the pericentromeric space and to investigate the spatial organization of chromatin in the nucleus at megabase resolution. The composition of genes and repetitive elements differs between distal and proximal regions. Gene family analyses reveal lineage-specific duplications of genes involved in the transport of nutrients to developing seeds and the mobilization of carbohydrates in grains. We demonstrate the importance of the barley reference sequence for breeding by inspecting the genomic partitioning of sequence variation in modern elite germplasm, highlighting regions vulnerable to genetic erosion.

Lithocholic acid promotes skeletal muscle regeneration through the TGR5 receptor.

Lithocholic acid (LCA) is a classical secondary bile acid formed by the metabolism of gut microbiota. The TGR5 receptor (also known as G protein-coupled receptor 1, GPBAR1) is an important bile acid membrane receptor that mediates a variety of metabolic processes in vivo. In recent years, most studies have focused on the role of bile acid receptors in the intestine and liver. However, there are few reports on its effect on skeletal muscle regeneration, and the specific mechanism remains unclear. Therefore, it is necessary to investigate the mechanism of the TGR5 receptor in the regulation of skeletal muscle regeneration. The results demonstrate that muscle injection with LCA significantly reduces the necrosis rate of injured muscle and improves muscle injury. Moreover, treatment of C2C12 cells with LCA significantly increases AKT/mTOR/FoxO3 phosphorylation through the TGR5 receptor, enhances MyoG transcription and reduces FBXO32 transcription. These findings indicate that LCA can activate the TGR5/AKT signaling pathway, inhibit protein degradation and promote protein synthesis to enhance the myogenic process and promote skeletal muscle regeneration.

Skeletal Muscle-Derived Exosomal miR-146a-5p Inhibits Adipogenesis by Mediating Muscle-Fat Axis and Targeting GDF5-PPARγ Signaling.

Skeletal muscle-fat interaction is essential for maintaining organismal energy homeostasis and managing obesity by secreting cytokines and exosomes, but the role of the latter as a new mediator in inter-tissue communication remains unclear. Recently, we discovered that miR-146a-5p was mainly enriched in skeletal muscle-derived exosomes (SKM-Exos), 50-fold higher than in fat exosomes. Here, we investigated the role of skeletal muscle-derived exosomes regulating lipid metabolism in adipose tissue by delivering miR-146a-5p. The results showed that skeletal muscle cell-derived exosomes significantly inhibited the differentiation of preadipocytes and their adipogenesis. When the skeletal muscle-derived exosomes co-treated adipocytes with miR-146a-5p inhibitor, this inhibition was reversed. Additionally, skeletal muscle-specific knockout miR-146a-5p (mKO) mice significantly increased body weight gain and decreased oxidative metabolism. On the other hand, the internalization of this miRNA into the mKO mice by injecting skeletal muscle-derived exosomes from the Flox mice (Flox-Exos) resulted in significant phenotypic reversion, including down-regulation of genes and proteins involved in adipogenesis. Mechanistically, miR-146a-5p has also been demonstrated to function as a negative regulator of peroxisome proliferator-activated receptor γ (PPARγ) signaling by directly targeting growth and differentiation factor 5 (GDF5) gene to mediate adipogenesis and fatty acid absorption. Taken together, these data provide new insights into the role of miR-146a-5p as a novel myokine involved in the regulation of adipogenesis and obesity via mediating the skeletal muscle-fat signaling axis, which may serve as a target for the development of therapies against metabolic diseases, such as obesity.

Browning of Mammary Fat Suppresses Pubertal Mammary Gland Development of Mice via Elevation of Serum Phosphatidylcholine and Inhibition of PI3K/Akt Pathway.

Mammary fat plays a profound role in the postnatal development of mammary glands. However, the specific types (white, brown, or beige) of adipocytes in mammary fat and their potential regulatory effects on modulating mammary gland development remain poorly understood. This study aimed to investigate the role of the browning of mammary fat on pubertal mammary gland development and explore the underlying mechanisms. Thus, the mammary gland development and the serum lipid profile were evaluated in mice treated with CL316243, a ß3-adrenoceptor agonist, to induce mammary fat browning. In addition, the proliferation of HC11 cells co-cultured with brown adipocytes or treated with the altered serum lipid metabolite was determined. Our results showed that the browning of mammary fat by injection of CL316243 suppressed the pubertal development of mice mammary glands, accompanied by the significant elevation of serum dioleoylphosphocholine (DOPC). In addition, the proliferation of HC11 was repressed when co-cultured with brown adipocytes or treated with DOPC. Furthermore, DOPC suppressed the activation of the PI3K/Akt pathway, while the DOPC-inhibited HC11 proliferation was reversed by SC79, an Akt activator, suggesting the involvement of the PI3K/Akt pathway in the DOPC-inhibited proliferation of HC11. Together, the browning of mammary fat suppressed the development of the pubertal mammary gland, which was associated with the elevated serum DOPC and the inhibition of the PI3K/Akt pathway.

Corticotropin-releasing factor receptor type 2 in the midbrain critically contributes to the hedonic feeding behavior of mice under heat stress.

Heat stress is an important factor that affects food intake. Previous studies have proven that heat stress can regulate feeding behavior through a homeostasis pathway and decrease appetite in animals and humans. However, the relationship between heat stress and midbrain reward regulation has not been reported. Corticotropin-releasing factor receptor type 2 (CRFR2) is the receptor of corticotropin-releasing factor (CRF), which is the key hypothalamic pituitary adrenal axis (HPA axis) regulating the stress response. In our study, the effects of heat stress on hedonic feeding behavior were investigated. The results showed that heat stress can affect hedonic feeding behavior and decrease high-fat diet (HFD) intake. Furthermore, the mRNA expression of tyrosine hydroxylase in the VTA decreased under heat stress compared with that at 25 °C. Meanwhile, intraventricular injection of a CRFR2 antagonist reversed the decrease in HFD intake and conditional place preference (CPP) caused by heat stress. In conclusion, CRFR2 in the midbrain plays an important role in the decrease in hedonic feeding behavior caused by heat stress.

SPTBN1 abrogates renal clear cell carcinoma progression via glycolysis reprogramming in a GPT2-dependent manner.

BACKGROUND: Renal clear cell carcinoma (ccRCC) is the most prevalent tumors worldwide. Discovering effective biomarkers is essential to monitor the prognosis and provide alternative clinical options. SPTBN1 is implicated in various cancerous processes. However, its role in ccRCC remains unelucidated. This study intends to explore the biological function and mechanism of SPTBN1 in ccRCC. METHODS: Single-cell and bulk RNA-seq, tissue microarray, real-time quantitative PCR, and western blotting were applied to verify the expression and predictive value of SPTBN1 in ccRCC. Gain or loss of functional ccRCC cell line models were constructed, and in vitro and in vivo assays were performed to elucidate its tumorigenic phenotypes. Actinomycin D experiment, RNA immunoprecipitation (RIP), specific inhibitors, and rescue experiments were carried out to define the molecular mechanisms. RESULTS: SPTBN1 was down-regulated in ccRCC and knockdown of SPTBN1 displayed a remarkably oncogenic role both in vitro and in vivo; while overexpressing SPTBN1 reversed this effect. SPTBN1 mediated ccRCC progression via the pathway of glutamate pyruvate transaminase 2 (GPT2)-dependent glycolysis. The expression of GPT2 was significantly negatively correlated with that of SPTBN1. As an RNA binding protein SPTBN1, regulated the mRNA stability of GPT2. CONCLUSION: Our research demonstrated that SPTBN1 is significantly down-regulated in ccRCC. SPTBN1 knockdown promotes ccRCC progression via activating GPT2-dependent glycolysis. SPTBN1 may serve as a therapeutic target for the treatment of ccRCC.

PHD3 mediates denervation skeletal muscle atrophy through Nf-κB signal pathway.

Skeletal muscle is the largest organ of the body, the development of skeletal muscle is very important for the health of the animal body. Prolyl hydroxylases (PHDs) are the classical regulator of the hypoxia inducible factor (HIF) signal pathway, many researchers found that PHDs are involved in the muscle fiber type transformation, muscle regeneration, and myocyte differentiation. However, whether PHDs can impact the protein turnover of skeletal muscle is poorly understood. In this study, we constructed denervated muscle atrophy mouse model and found PHD3 was highly expressed in the atrophic muscles and there was a significant correlation between the expression level of PHD3 and skeletal muscle weight which was distinct from PHD1 and PHD2. Then, the similar results were getting from the different weight muscles of normal mice. To further verify the relationship between PHD3 and skeletal muscle protein turnover, we established a PHD3 interference model by injecting PHD3 sgRNA virus into tibialis anterior muscle (TA) muscle of MCK-Cre-cas9 mice and transfecting PHD3 shRNA lentivirus into primary satellite cells. It was found that the Knock-out of PHD3 in vivo led to a significant increase in muscle weight and muscle fiber area (P < .05). Besides, the activity of protein synthesis signal pathway increased significantly, while the protein degradation pathway was inhibited evidently (P < .05). In vitro, the results of 5-ethynyl-2'-deoxyuridine (EdU) and tetramethylrhodamine ethyl ester (TMRE) fluorescence detection showed that PHD3 interference could lead to a decrease in cell proliferation and an increase of cell apoptosis. After the differentiation of satellite cells, the production of puromycin in the interference group was higher than that in the control group, and the content of 3-methylhistidine in the interference group was lower than that in the control group (P < .05) which is consistent with the change of protein turnover signal pathway in the cell. Mechanistically, there is an interaction between PHD3, NF-κB, and IKBα which was detected by immunoprecipitation. With the interfering of PHD3, the expression of the inflammatory signal pathway also significantly decreased (P < .05). These results suggest that PHD3 may affect protein turnover in muscle tissue by mediating inflammatory signal pathway. Finally, we knocked out PHD3 in denervated muscle atrophy mice and LPS-induced myotubes atrophy model. Then, we found that the decrease of PHD3 protein level could alleviate the muscle weight and muscle fiber reduction induced by denervation in mice. Meanwhile, the protein level of the inflammatory signal pathway and the content of 3-methylhistidine in denervated atrophic muscle were also significantly reduced (P < .05). In vitro, PHD3 knock-out could alleviate the decrease of myotube diameter induced by LPS, and the expression of protein synthesis pathway was also significantly increased (P < .05). On the contrary, the expression level of protein degradation and inflammatory signal pathway was significantly decreased (P < .05). Through these series of studies, we found that the increased expression of PHD3 in denervated muscle might be an important regulator in inducing muscle atrophy, and this process is likely to be mediated by the inflammatory NF-κB signal pathway.

Influence of fermented feed additive on gut morphology, immune status, and microbiota in broilers.

BACKGROUND: This study examined the effects of a solid-state fermented feed additive (FFA) on the small intestine histology/morphology, immunity and microbiota of broilers. Two hundred eighty-eight day-old Arbor Acre chicks, were randomly assigned to one of four groups (each group has 6 replicates, with each replicate containing 12 chickens). The negative control (NC; basal diet), the positive control (PC; basal diet +antibiotic 15 ppm), the fermented feed additive low dose (FFL; basal diet + 0.3 kg/t FFA), and the fermented feed additive high dose (FFH; 3 kg/t FFA) with Lactobacillus casei (L.casei). RESULTS: The study found that the FFH and FFL groups gained more weight (1-21d) and the FFL and PC diets had better feed conversion ratio (P < 0.05) than the NC from 0-42d. The FFH group had higher villus height (P < 0.05) in the duodenum than the PC and villus height to crypt depth ratio VH/CD compared to PC and FFL groups. The FFL chickens had greater (P < 0.05) jejunal and ileal villus height than PC and NC groups respectively. The FFL group had a higher ileal VH/CD ratio (P < 0.05). Jejunum VH/CD was higher in FFL and FFH (P < 0.05) than PC (P < 0.05). FFH had a smaller thymus than NC (P < 0.05). FFA diets also increased IL-10 expression (P < 0.05). While IL-1 and TLR4 mRNA expression decreased (P < 0.05) compared to NC. The microbiota analysis showed that the microorganisms that have pathogenic properties such as phylum Delsulfobacterota and class Desulfovibriona and Negativicutes was also significantly reduced in the group treated with FFH and PC while microorganisms having beneficial properties like Lactobacillaceae family, Lactobacillus aviarus genus and Lactobacillus spp were also tended to increase in the FFH and FFL fermented feed groups compared to the PC and NC groups. CONCLUSION: These findings suggested that the FFA diet may modulate cecal microbiota by reducing pathogenic microorganisms such as phylum Delsulfobacterota and class Desulfovibriona and Negativicutes improve beneficial microorganisms like Lactobacillaceae family, Lactobacillus aviarus genus and Lactobacillus spp. While FFA diet also affect immunity, and gene expression related to immunity.

Knockdown of VEGFB/VEGFR1 Signaling Promotes White Adipose Tissue Browning and Skeletal Muscle Development.

It has been demonstrated that vascular endothelial growth factor B (VEGFB) and vascular endothelial growth factor receptor 1 (VEGFR1) play a vital role in regulating vascular biological function. However, the role of VEGFB and VEGFR1 in regulating fat deposition and skeletal muscle growth remains unclear. Therefore, this study was conducted to investigate the effects of VEGFB and VEGFR1 on fat deposition and skeletal muscle growth in mice. Our results showed that knockdown of VEGFB decreased body weight and iWAT index, stimulated the browning of mice iWAT with increased expression of UCP1, decreased the diameters of adipocytes, and elevated energy expenditure. In contrast, knockdown of VEGFB increased gastrocnemius (GAS) muscle index with increased proliferation of GAS muscle by expression of PCNA and Cyclin D1. Meanwhile, knockdown of endothelial VEGFR1 induced the browning of iWAT with increased expression of UCP1 and decreased diameters of adipocytes. By contrast, knockdown of endothelial VEGFR1 inhibited GAS muscle differentiation with decreased expression of MyoD. In conclusion, these results suggested that the loss of VEGFB/VEGFR1 signaling is associated with enhanced browning of inguinal white adipose tissue and skeletal muscle development. These results provided new insights into the regulation of skeletal muscle growth and regeneration, as well as fat deposition, suggesting the potential application of VEGFB/VEGFR1 as an intervention for the restriction of muscle diseases and obesity and related metabolic disorders.

Hyodeoxycholic acid (HDCA) suppresses intestinal epithelial cell proliferation through FXR-PI3K/AKT pathway, accompanied by alteration of bile acids metabolism profiles induced by gut bacteria.

Bile acids (BAs) have been implicated in regulation of intestinal epithelial signaling and function. This study aimed to investigate the effects of hyodeoxycholic acid (HDCA) on intestinal epithelial cell proliferation and explore the underlying mechanisms. IPEC-J2 cells and weaned piglets were treated with HDCA and the contributions of cellular signaling pathways, BAs metabolism profiles and gut bacteria were assessed. In vitro, HDCA suppressed IPEC-J2 proliferation via the BAs receptor FXR but not TGR5. In addition, HDCA inhibited the PI3K/AKT pathway, while knockdown of FXR or constitutive activation of AKT eliminated the inhibitory effects of HDCA, suggesting that FXR-dependent inhibition of PI3K/AKT pathway was involved in HDCA-suppressed IPEC-J2 proliferation. In vivo, dietary HDCA inhibited intestinal expression of proliferative markers and PI3K/AKT pathway in weaned piglets. Meanwhile, HDCA altered the BAs metabolism profiles, with decrease in primary BA and increase in total and secondary BAs in feces, and reduction of conjugated BAs in serum. Furthermore, HDCA increased abundance of the gut bacteria associated with BAs metabolism, and thereby induced BAs profiles alternation, which might indirectly contribute to HDCA-suppressed cell proliferation. Together, HDCA suppressed intestinal epithelial cell proliferation through FXR-PI3K/AKT signaling pathway, accompanied by alteration of BAs metabolism profiles induced by gut bacteria.

Food reward depends on TLR4 activation in dopaminergic neurons.

The rising prevalence of obesity and being overweight is a worldwide health concern. Food reward dysregulation is the basic factor for the development of obesity. Dopamine (DA) neurons in the ventral tegmental area (VTA) play a vital role in food reward. Toll-like receptor 4 (TLR4) is a transmembrane pattern recognition receptor that can be activated by saturated fatty acids. Here, we show that the deletion of TLR4 specifically in DA neurons increases body weight, increases food intake, and decreases food reward. Conditional deletion of TLR4 also decreased the activity of DA neurons while suppressing the expression of tyrosine hydroxylase (TH) in the VTA, which regulates the concentration of DA in the nucleus accumbens (NAc) to affect food reward. Meanwhile, AAV-Cre-GFP mediated VTA-specific TLR4-deficient mice recapitulates food reward of DAT-TLR4-KO mice. Food reward could be rescued by re-expressing TLR4 in VTA DA neurons. Moreover, effects of intra-VTA infusion of lauric acid (a saturated fatty acid with 12 carbon) on food reward were abolished in mice lacking TLR4 in DA neurons. Our study demonstrates the critical role of TLR4 signaling in regulating the activity of VTA DA neurons and the normal function of the mesolimbic DA system that may contribute to food reward.

Succinate induces skeletal muscle fiber remodeling via SUNCR1 signaling.

The conversion of skeletal muscle fiber from fast twitch to slow-twitch is important for sustained and tonic contractile events, maintenance of energy homeostasis, and the alleviation of fatigue. Skeletal muscle remodeling is effectively induced by endurance or aerobic exercise, which also generates several tricarboxylic acid (TCA) cycle intermediates, including succinate. However, whether succinate regulates muscle fiber-type transitions remains unclear. Here, we found that dietary succinate supplementation increased endurance exercise ability, myosin heavy chain I expression, aerobic enzyme activity, oxygen consumption, and mitochondrial biogenesis in mouse skeletal muscle. By contrast, succinate decreased lactate dehydrogenase activity, lactate production, and myosin heavy chain IIb expression. Further, by using pharmacological or genetic loss-of-function models generated by phospholipase Cß antagonists, SUNCR1 global knockout, or SUNCR1 gastrocnemius-specific knockdown, we found that the effects of succinate on skeletal muscle fiber-type remodeling are mediated by SUNCR1 and its downstream calcium/NFAT signaling pathway. In summary, our results demonstrate succinate induces transition of skeletal muscle fiber via SUNCR1 signaling pathway. These findings suggest the potential beneficial use of succinate-based compounds in both athletic and sedentary populations.