Conjugated linoleic acid (CLA) reduces intestinal fatty acid uptake and chylomicron formation in HFD-fed mice associated with the inhibition of DHHC7-mediated CD36 palmitoylation and the downstream ERK pathway.

The anti-obesity effect of conjugated linoleic acid (CLA) has been well elucidated, but whether CLA affects fat deposition by regulating intestinal dietary fat absorption remains largely unknown. Thus, this study aimed to investigate the effects of CLA on intestinal fatty acid uptake and chylomicron formation and explore the possible underlying mechanisms. We found that CLA supplementation reduced the intestinal fat absorption in HFD (high fat diet)-fed mice accompanied by the decreased serum TG level, increased fecal lipids and decreased intestinal expression of ApoB48 and MTTP. Correspondingly, c9, t11-CLA, but not t10, c12-CLA induced the reduction of fatty acid uptake and TG content in PA (palmitic acid)-treated MODE-K cells. In the mechanism of fatty acid uptake, c9, t11-CLA inhibited the binding of CD36 with palmitoyltransferase DHHC7, thus leading to the decreases of CD36 palmitoylation level and localization on the cell membrane of the PA-treated MODE-K cells. In the mechanism of chylomicron formation, c9, t11-CLA inhibited the formation of the CD36/FYN/LYN complex and the activation of the ERK pathway in the PA-treated MODE-K cells. In in vivo verification, CLA supplementation reduced the DHHC7-mediated total and cell membrane CD36 palmitoylation and suppressed the formation of the CD36/FYN/LYN complex and the activation of the ERK pathway in the jejunum of HFD-fed mice. Altogether, these data showed that CLA reduced intestinal fatty acid uptake and chylomicron formation in HFD-fed mice associated with the inhibition of DHHC7-mediated CD36 palmitoylation and the downstream ERK pathway.

Knockdown of the VEGFB/VEGFR1 signaling suppresses pubertal mammary gland development of mice via the inhibition of PI3K/Akt pathway.

Vascular endothelial growth factor B (VEGFB) has been well demonstrated to play a crucial role in regulating vascular function by binding to the VEGF receptors (VEGFRs). However, the specific role of VEGFB and VEGFRs in pubertal mammary gland development remains unclear. In this study, we observed that blocking the VEGF receptors with Axitinib suppressed the pubertal mammary gland development. Meanwhile, the proliferation of mammary epithelial cells (HC11) was repressed by blocking the VEGF receptors with Axitinib. Additionally, knockdown of VEGFR1 rather than VEGFR2 and NRP1 elicited the inhibition of HC11 proliferation, suggesting the essential role of VEGFR1 during this process. Furthermore, Axitinib or VEGFR1 knockdown led to the inhibition of the PI3K/Akt pathway. However, the inhibition of HC11 proliferation induced by Axitinib and or VEGFR1 knockdown was eliminated by the Akt activator SC79, indicating the involvement of the PI3K/Akt pathway. Finally, the knockdown of VEGFB and VEGFR1 suppressed the pubertal development of mice mammary gland with the inhibition of the PI3K/Akt pathway. In summary, the results showed that knockdown of the VEGFB/VEGFR1 signaling suppresses pubertal mammary gland development of mice via the inhibition of the PI3K/Akt pathway, which provides a new target for the regulation of pubertal mammary gland development.

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.

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.

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.

Supplementation of microencapsulated probiotics modulates gut health and intestinal microbiota.

The beneficial effect of probiotics on host health is impaired due to the substantial loss of survivability during gastric transit caused by small intestinal enzymes and bile acids. Encapsulation helps to preserve the probiotics species from severe environmental factors. Lactobacillus paracasei, highly sensitive probiotic species to gastric acid, was encapsulated with polyacrylate resin. C57BL/6 male mice were equally divided into three groups; control group was fed with basal diet without any additives, the un-encapsulated group was fed with 0.1% of a mixture of encapsulating material and L. paracasei, and encapsulated group was fed with 0.1% encapsulated L. paracasei (microcapsule) for 4 weeks. The result showed elevated fecal moisture percentage in the encapsulated group, but not in the un-encapsulated group. Further study showed that the ratio of villus height to crypt depth in the small intestine was significantly higher compared to un-encapsulated and the control group. Microencapsulated probiotics also remarkably increased intestinal mucin and secretory immunoglobulin A (sIgA) concentration, intestinal MUC-2, and tight junction protein mRNA expression levels improving the intestinal barrier function of mice. In addition, microcapsules also reduced proinflammatory factor mRNA expression, while considerably increasing anti-inflammatory factor mRNA expression. Microbiota metabolites, fecal LPS (Lipopolysaccharide) were downregulated, and acetate and lactate were upraised compared to control. Furthermore, glutathione peroxidase (GSH-Px) and TAOC levels were increased and Malondialdehyde (MDA) was decreased improving antioxidant capacity. Microflora and bioinformatic predictive analysis of feces showed that encapsulated probiotics remarkably increased Lactobacillus proportions. Mice's intestinal health can thus be improved by using microencapsulated probiotics.

Proline hydroxylase 2 (PHD2) promotes brown adipose thermogenesis by enhancing the hydroxylation of UCP1.

OBJECTIVE: Brown adipose tissue (BAT) plays a crucial role in regulating non-shivering thermogenesis under cold exposure. Proline hydroxylases (PHDs) were found to be involved in adipocyte differentiation and lipid deposition. However, the effects of PHDs on regulatory mechanisms of BAT thermogenesis are not fully understood. METHODS: We detected the expression of PHDs in different adipose tissues by using immunoblotting and real-time PCR. Further, immunoblotting, real-time PCR, and immunostaining were performed to determine the correlation between proline hydroxylase 2 (PHD2) and UCP1 expression. Inhibitor of PHDs and PHD2-sgRNA viruses were used to construct the PHD2-deficiency model in vivo and in vitro to investigate the impacts of PHD2 on BAT thermogenesis. Afterward, the interaction between UCP1 and PHD2 and the hydroxylation modification level of UCP1 were verified by Co-IP assays and immunoblotting. Finally, the effect of specific proline hydroxylation on the expression/activity of UCP1 was further confirmed by site-directed mutation of UCP1 and mass spectrometry analysis. RESULTS: PHD2, but not PHD1 and PHD3, was highly enriched in BAT, colocalized, and positively correlated with UCP1. Inhibition or knockdown of PHD2 significantly suppressed BAT thermogenesis under cold exposure and aggravated obesity of mice fed HFD. Mechanistically, mitochondrial PHD2 bound to UCP1 and regulated the hydroxylation level of UCP1, which was enhanced by thermogenic activation and attenuated by PHD2 knockdown. Furthermore, PHD2-dependent hydroxylation of UCP1 promoted the expression and stability of UCP1 protein. Mutation of the specific prolines (Pro-33, 133, and 232) in UCP1 significantly mitigated the PHD2-elevated UCP1 hydroxylation level and reversed the PHD2-increased UCP1 stability. CONCLUSIONS: This study suggested an important role for PHD2 in BAT thermogenesis regulation by enhancing the hydroxylation of UCP1.

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.

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.

Mannan Oligosaccharides Promoted Skeletal Muscle Hypertrophy through the Gut Microbiome and Microbial Metabolites in Mice.

Mannan oligosaccharides (MOSs) have been implicated in the animal growth rate, health indices, and lipid oxidative stability. MOSs have been indicated to maintain intestinal health and anti-inflammatory effects via modulation of gut microbiota. Furthermore, the role of MOSs in modulating skeletal muscle function is largely unknown. Here, this study aimed to investigate the effects of MOS supplementation on muscle function and muscle mass in mice. Additionally, the possible underlying mechanisms, including the contributions of gut microbiota and microbial metabolites, were explored. In our study, 3-week-old C57BL/6J male mice (body weight of approximately 10.7 ± 1.1 g) were given pure water or pure water with 1% MOS. To study the effect of MOSs on gut-microbiota-derived metabolites, serum metabolic profiles were analyzed through untargeted metabolomic profiling. Moreover, we detected the downstream signals of differential metabolites, and decanoic acid (DA) was selected as our target spot. Then, DA was used to treat C2C12 cells, and we found that DA promotes C2C12 cell differentiation via the GPR84 and PI3K/AKT signaling pathways. In conclusion, these results showed that MOS supplementation improves muscle function and muscle mass. Additionally, gut microbiome and microbial metabolites were regulated by MOSs, and DA may be one of the most important links between the gut microbiome and skeletal muscle function regulation.

Transcriptional and post-transcriptional control of autophagy and adipogenesis by YBX1.

Obesity is strongly associated with metabolic diseases, which have become a global health problem. Exploring the underlying mechanism of adipogenesis is crucial for the treatment of excess white fat. Oncogene YBX1 is a multifunctional DNA- and RNA-binding protein that regulates brown adipogenesis. However, the role of YBX1 in white adipogenesis and adipose tissue expansion remains unknown. Here, we showed that YBX1 deficiency inhibited murine and porcine adipocyte differentiation. YBX1 positively regulated adipogenesis through promoting ULK1- and ULK2-mediated autophagy. Mechanistically, we identified YBX1 serves as a 5-methylcytosine (m5C)-binding protein directly targeting m5C-containing Ulk1 mRNA by using RNA immunoprecipitation. RNA decay assay further proved that YBX1 upregulated ULK1 expression though stabilizing its mRNA. Meanwhile, YBX1 promoted Ulk2 transcription and expression as a transcription factor, thereby enhancing autophagy and adipogenesis. Importantly, YBX1 overexpression in white fat enhanced ULK1/ULK2-mediated autophagy and promoted adipose tissue expansion in mice. Collectively, these findings unveil the post-transcriptional and transcriptional mechanism and functional importance of YBX1 in autophagy and adipogenesis regulation, providing an attractive molecular target for therapies of obesity and metabolic diseases.

Diet containing stearic acid increased food intake in mice by reducing serum leptin compared with oleic acid.

In today's society, obesity is becoming increasingly serious, and controlling food intake and maintaining weight balance have become increasingly important. Here, we found that a stearic acid diet can increase food intake without causing obesity in mice compared with an oleic acid diet. Stearic acid increases food intake in mice by reducing serum leptin and increasing NPY neuronal excitability through the JAK2/STAT3 pathway. The impaired anorexic effect of leptin is probably due to repressive cholesterol-oxysterol-LXR-α/SREBP-1c-mediated leptin expression in mouse iWAT. At the same time, we found that stearic acid was not only poorly absorbed by itself in the small intestine but also reduced the entire absorption system of the small intestine. In conclusion, we have proven that a stearic acid diet can increase food intake in mice and avoid obesity, but whether a stearic acid diet could cause adverse reactions in the body remains to be studied.

TLR4 in Tph2 neurons modulates anxiety-related behaviors in a sex-dependent manner.

TLR4 belongs to the TLR receptor family and can induce a proinflammatory response to invading pathogens. Recent studies have identified that TLR4 is associated with major anxiety disorder. Tph2 is a rate-limiting enzyme for 5-HT biosynthesis that is expressed at high levels in the DRN, which includes the main 5-HT projection to the hippocampus and prefrontal cortex and regulates anxiety disorder. Here, we show that TLR4 expressed in Tph2 neurons in the DRN can modulate anxiety-like behaviors in a sex-dependent manner. Deletion of TLR4 in Tph2 neurons decreases anxiety-like behaviors in male but not in female mice. Meanwhile, a similar phenotype was found by selectively ablating TLR4 in the DRN of adult male but not female mice using AAV-Cre-GFP virus. Inhibition of TLR4 in DRN by infusion of LPS-RS via intra-Aq is sufficient to reverse anxiety-like behavior induced by chronic immobilization stress (CIS). The underlying mechanisms seem to involve alterations in the activity of Tph2 neurons and key components of 5-HT transmission, including synthesis, reuptake, and transmission. Our results suggest that TLR4 in Tph2 neurons is a key modulator in anxiety-like behaviors and the 5-HT system in the brain between different sexes.

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.

Tauroursodeoxycholic acid (TUDCA) improves intestinal barrier function associated with TGR5-MLCK pathway and the alteration of serum metabolites and gut bacteria in weaned piglets.

BACKGROUND: Tauroursodeoxycholic acid (TUDCA), a hydrophilic bile acid, is the main medicinal component of bear bile and is commonly used to treat a variety of hepatobiliary diseases. Meanwhile, TUDCA has been shown to modulate the intestinal barrier function and alleviate DSS-induced colitis in mice. However, the effect of TUDCA on the intestinal barrier of weaned piglets remains largely unclear. METHODS: The weaned piglets and porcine IPEC-J2 intestinal epithelial cells were used to investigate the effects of TUDCA on intestinal barrier function in weaned piglets and explore the possible underlying mechanisms. In vivo, 72 healthy weaned piglets were randomly allocated into 2 groups according to their gender and body weight, and piglets were fed the basal diet with 0 (control, CON) and 200 mg/kg TUDCA for 30 d, respectively. Three female and three male piglets reflecting the average bodyweight were slaughtered in each group and samples were collected. In vitro, IPEC-J2 cells were subjected to 100 µmol/L TUDCA to explore the possible underlying mechanisms. RESULTS: Our results demonstrated that dietary TUDCA supplementation significantly reduced the diarrhea incidence of weaned piglets, possibly attributing to the TUDCA-enhanced intestinal barrier function and immunity. In addition, TUDCA supplementation altered serum metabolites and the relative abundance of certain gut bacteria, which might contribute to the improved intestinal barrier function. Furthermore, the in-vitro results showed that TUDCA improved the E. coli-induced epithelial barrier impairment of IPEC-J2 cells and increased Takeda G-coupled protein receptor 5 (TGR5) protein expression. However, knockdown of TGR5 and inhibition of myosin light chain kinase (MLCK) pathway abolished the TUDCA-improved epithelial barrier impairment in E. coli-treated IPEC-J2 cells, indicating the involvement of TGR5-MLCK in this process. CONCLUSIONS: These findings showed that TUDCA improved intestinal barrier function associated with TGR5-MLCK pathway and the alteration of serum metabolites and gut bacteria in weaned piglets, suggesting the potential application of TUDCA in improving gut health in piglet production.

Effect of novel Lactobacillus paracaesi microcapsule on growth performance, gut health and microbiome community of broiler chickens.

The beneficial action of probiotics is questioned time and again due to the loss of their survivability under gastrointestinal conditions, particularly gastric acid. In this experiment, a probiotic species was encapsulated to improve its delivery to the distal parts, and its effects on production performance, gut health, and microbial profile in broilers were investigated. A total of 240 Arbor acres (AA) broilers were randomly allotted into 3 treatments with 8 replicate pens per treatment and 10 broilers in each pen for 42 d. Dietary treatments were 1) basal feed without any additives (CON), 2) CON+15 ppm Virginiamycin (ANT), and 3) CON+500 ppm encapsulated Lactobacillus paracaesi (ELP). The result showed that the addition of ELP to the feed did not affect growth performance and carcass characteristics significantly. However, ELP increased the ratio of villus height to crypt depth (P < 0.05) and mRNA expression of ZO-1 (P < 0.05) relative to the CON or ANT group. Similarly, qPCR showed that dietary supplementation of ELP raised gene expression of the anti-inflammatory cytokine and tended to decrease proinflammatory cytokines resulting improve in immunity. Moreover, chicks fed with ELP had lower malondialdehyde (MDA) (P < 0.05) than CON and lower reactive oxygen species (ROS) (P < 0.05) level than ANT in serum. In contrast, the total antioxidant capacity (TAOC) level was tended to increase. The ammonia level of ileum and cecum chyme was decreased (P < 0.05) in the ELP group than CON while the level of propionic acid of cecal content was increased (P < 0.05). 16S rRNA sequencing revealed the dietary treatment modulated the diversity and composition of cecal microflora. At the phylum level, Bacteroidetes was enriched, and Proteobacteria was depleted in the ELP group. At the genus level, ELP increased Bacteroides (P < 0.05) compared to control. The results indicate that oral delivery of probiotics via microcapsule could impart beneficial effects on birds and be used as an alternative to antibiotics.

α-Ketoglutaric acid ameliorates hyperglycemia in diabetes by inhibiting hepatic gluconeogenesis via serpina1e signaling.

Previously, we found that α-ketoglutaric acid (AKG) stimulates muscle hypertrophy and fat loss through 2-oxoglutarate receptor 1 (OXGR1). Here, we demonstrated the beneficial effects of AKG on glucose homeostasis in a diet-induced obesity (DIO) mouse model, which are independent of OXGR1. We also showed that AKG effectively decreased blood glucose and hepatic gluconeogenesis in DIO mice. By using transcriptomic and liver-specific serpina1e deletion mouse model, we further demonstrated that liver serpina1e is required for the inhibitory effects of AKG on hepatic gluconeogenesis. Mechanistically, we supported that extracellular AKG binds with a purinergic receptor, P2RX4, to initiate the solute carrier family 25 member 11 (SLC25A11)-dependent nucleus translocation of intracellular AKG and subsequently induces demethylation of lysine 27 on histone 3 (H3K27) in the seprina1e promoter region to decrease hepatic gluconeogenesis. Collectively, these findings reveal an unexpected mechanism for control of hepatic gluconeogenesis using circulating AKG as a signal molecule.

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.

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.

trans 10, cis 12, but Not cis 9, trans 11 Conjugated Linoleic Acid Isomer Enhances Exercise Endurance by Increasing Oxidative Skeletal Muscle Fiber Type via Toll-like Receptor 4 Signaling in Mice.

Conjugated linoleic acid (CLA) has been implicated in regulating muscle fiber. However, which isomer elicits this effect and the underlying mechanisms remain unclear. Here, male C57BL6/J mice and C2C12 cells were treated with two CLA isomers, and the exercise endurance, skeletal muscle fiber type, and involvement of Toll-like receptor 4 (TLR4) signaling were assessed. The results demonstrated that dietary t10, c12, but not c9, t11-CLA isomer enhanced exercise endurance of mice (from 115.88 ± 11.21 to 130.00 ± 15.84 min, P < 0.05) and promoted the formation of oxidative muscle fiber type of gastrocnemius muscle (from 0.15 ± 0.04 to 0.24 ± 0.05, P < 0.05). Consistently, t10, c12-CLA isomer increased the mRNA expression of oxidative muscle fiber type in C2C12 myotubes (from 1.00 ± 0.08 to 2.65 ± 1.77, P < 0.05). In addition, t10, c12-CLA isomer increased TLR4 signaling expression in skeletal muscle and C2C12 myotubes. More importantly, knockdown of TLR4 eliminated the t10, c12-CLA isomer-induced enhancement of exercise endurance in mice and elevation of oxidative muscle fiber type in C2C12 myotubes and gastrocnemius muscle. Together, these findings showed that t10, c12, but not c9, t11-CLA isomer enhances exercise endurance by increasing oxidative skeletal muscle fiber type via TLR4 signaling.