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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.

In response to contraction during exercise, skeletal muscle growth and metabolism are dynamically regulated by nerve action, blood flow, and metabolic feedback. α-Ketoglutarate (AKG), a bioactive intermediate in the tricarboxylic acid cycle released during exercise, has been shown to promote skeletal muscle hypertrophy. However, the underlying mechanism of AKG in regulating skeletal muscle development and metabolism is still less known. 2-Oxoglutarate receptor 1 (OXGR1), the endogenous AKG receptor, is found to be distributed in the vascular smooth muscle (VSM) of skeletal muscles. OXGR1 knockout results in skeletal muscle atrophy, accompanied by decreased expression of myosin heavy chain I (MyHC I), capillary density, and endurance exercise capacity. Furthermore, the study found that dietary AKG supplementation increased mice endurance exercise distance, MyHC I/MyHC IIb ratio, arteriole, and capillary densities in skeletal muscle. Meanwhile, acute AKG administration gradually increased the blood flow in the lower limbs. Further, by using OXGR1 global knockout and OXGR1 VSM-specific (MYH11-Cre × OXGR1-FloxP) knockdown models, we found that OXGR1 in VSM is essential for AKG-induced improvement of skeletal muscle performances. According to the in vitro study, AKG expanded the cell area in VSM with a decreased intracellular pH by OXGR1. Our results demonstrated a novel role of AKG/OXGR1 in VSM of skeletal muscle to regulate blood flow and then enhance slow muscle fiber conversion and capillarization. These findings provide a theoretical basis for the AKG/OXGR1 signaling pathway to maintain human muscle function and improve meat production and livestock and poultry meat quality.

Background A stable intestinal microenvironment determines the balance of intestinal flora and body health, which is influenced by intestinal motility. 2-Oxoglutarate receptor 1 (OXGR1) is a G-protein-coupled receptor whose endogenous ligand is the resistance exercise metabolic intermediate α-ketoglutarate (AKG). Here, we aimed to determine the function of OXGR1 in intestinal motility, which modulate intestinal microenvironment. Results Through intestinal co-location, we found OXGR1 was highly expressed in intestinal smooth muscle. The model of OXGR1 lose-of-function mice showed enhanced intestinal barrier and motility, as well as improved intestinal flora. We further found that in gastrointestinal smooth muscle cells (GSMCs), AKG downregulates Car2 expression and modulates cellular acid-base balance by OXGR1, ultimately leading to the relaxation and reduction of motility of intestinal smooth muscle. Conclusions OXGR1 deletion improves intestinal microenvironment by enhanced intestinal motility; and these results provide a new target for intestinal motility regulation, OXGR1 may be developed for the treatment of some diseases such as microbiota disorders and enteritis.

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.

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 new mediator in the inter-tissue communication still remains unclear. Recently, we discovered that miR-146a-5p was mainly enriched in skeletal muscle-derived exosomes (SKM-Exos), more 50-fold higher than fat exosomes. Here, we investigated the role of skeletal muscle-derived exosome regulating lipid metabolism in adipose tissue by delivering miR-146a-5p. The results showed that exosomes from skeletal myoblast significantly inhibited the differentiation of preadipocytes and its 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) significantly increased body weight gain and decreased oxidative metabolism in mice. Whereas the internalization of this miRNA into the mKO mice by injecting skeletal muscle-derived exosomes from the Flox mice (Flox-Exos) resulted in the significant phenotypic reversion, including down-regulation of genes and proteins involved in fat synthesis. 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 fat synthesis 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 lipogenesis and obesity via mediating the skeletal muscle-fat signaling axis, and may serve as a target for the development of therapies against various metabolic diseases, including obesity, lipodystrophy and insulin resistance.

Obesity is primarily a consequence of consuming calories beyond energetic requirements, but underpinning drivers have not been fully defined. 5-Hydroxytryptamine (5-HT) neurons in the dorsal Raphe nucleus (5-HTDRN) regulate different types of feeding behavior, such as eating to cope with hunger or for pleasure. Here, we observed that activation of 5-HTDRN to hypothalamic arcuate nucleus (5-HTDRN → ARH) projections inhibits food intake driven by hunger via actions at ARH 5-HT2C and 5-HT1B receptors, whereas activation of 5-HTDRN to ventral tegmental area (5-HTDRN → VTA) projections inhibits non-hunger-driven feeding via actions at 5-HT2C receptors. Further, hunger-driven feeding gradually activates ARH-projecting 5-HTDRN neurons via inhibiting their responsiveness to inhibitory GABAergic inputs; non-hunger-driven feeding activates VTA-projecting 5-HTDRN neurons through reducing a potassium outward current. Thus, our results support a model whereby parallel circuits modulate feeding behavior either in response to hunger or to hunger-independent cues.

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.

The current obesity epidemic faces a lack of mechanistic insights. It is known that the acute activity changes of a growing number of brain neurons rapidly alter feeding behaviour; however, how these changes translate to obesity development and the fundamental mechanism underlying brain neurons in controlling body weight remain elusive. Here, we show that chronic activation of hypothalamic arcuate GABAergic (GABA+), agouti-related protein (AgRP) neurons or arcuate non-AgRP GABA+ neurons leads to obesity, which is similar to the obese phenotype observed in ob/ob mice. Conversely, chronic inhibition of arcuate GABA+, but not AgRP, neurons reduces ageing-related weight gain and corrects ob/ob obesity. These results demonstrate that the modulation of Arc GABA+ neuron activity is a fundamental mechanism of body-weight regulation, and that arcuate GABA+ neurons are the major mediator of leptin action, with a profound and redundant role in obesity development. Zhu and colleagues show that chronic activation of arcuate nucleus GABA+ neurons, agouti-related protein (AgRP) neurons alone or non-AgRP GABA+ neurons promotes severe obesity, but only inhibition of all GABA+ neurons can reverse the obese phenotype of hyperphagic mice, thus suggesting a redundant role for arcuate GABA+ neurons in obesity.

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.

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 β-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.

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.

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

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.

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.

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 (P0.05) and mRNA expression of ZO-1 (P0.05) 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) (P0.05) than CON and lower reactive oxygen species (ROS) (P0.05) 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 (P0.05) in the ELP group than CON while the level of propionic acid of cecal content was increased (P0.05). 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 (P0.05) 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.

Plastic waste poses an ecological challenge1. While current plastic waste management largely relies on unsustainable, energy-intensive, or even hazardous physicochemical and mechanical processes, enzymatic degradation offers a green and sustainable route for plastic waste recycling2. Poly(ethylene terephthalate) (PET) has been extensively used in packaging and for the manufacture of fabrics and single-used containers, accounting for 12% of global solid waste3. The practical application of PET hydrolases has been hampered by their lack of robustness and the requirement for high processing temperatures. Here, we use a structure-based, deep learning algorithm to engineer an extremely robust and highly active PET hydrolase. Our best resulting mutant (FAST-PETase: Functional, Active, Stable, and Tolerant PETase) exhibits superior PET-hydrolytic activity relative to both wild-type and engineered alternatives, (including a leaf-branch compost cutinase and its mutant4) and possesses enhanced thermostability and pH tolerance. We demonstrate that whole, untreated, post-consumer PET from 51 different plastic products can all be completely degraded by FAST-PETase within one week, and in as little as 24 hours at 50 °C. Finally, we demonstrate two paths for closed-loop PET recycling and valorization. First, we re-synthesize virgin PET from the monomers recovered after enzymatic depolymerization. Second, we enable in situ microbially-enabled valorization using a Pseudomonas strain together with FAST-PETase to degrade PET and utilize the evolved monomers as a carbon source for growth and polyhydroxyalkanoate production. Collectively, our results demonstrate the substantial improvements enabled by deep learning and a viable route for enzymatic plastic recycling at the industrial scale.

Background: The beneficial impact of probiotics on host health is impaired due to the significant loss of survivability during gastric transit, small intestinal enzymes, and bile acids. Encapsulation helps to preserve the probiotics species from severe environmental factors. This study investigated the effects of oral delivery of probiotics via microcapsule on different parameters of gut health. Methods: Lactobacillus paracasei, highly sensitive probiotic species to gastric acid, was encapsulated with novel encapsulating material, polyacrylate resin, to get a microcapsule. C57BL/6 male mice were equally divided into three groups; supplementing basal feed, a mixture of encapsulating material and Lactobacillus paracasei, and encapsulated Lactobacillus paracasei (microcapsule) for four weeks. Fecal moisture percentage was measured regularly, which was elevated in the encapsulated group, but not in the mixed group. Based on this data, mice from control and encapsulated groups were sacrificed to study the different parameters of gut health. Results: Compared to control, encapsulated probiotics increased villi height, the ratio of villi height to crypt depth, and decreased crypt depth. Simultaneously, the tight junction proteins were upregulated on encapsulated group showing enhancement of intestinal barrier functions. The level of SigA and mucin increased along with gene expression of MUC-2 but, albumin level was decreased. In addition, we found a rise in the relative gene expression of anti-inflammatory factor (IL-10) and decreased pro-inflammatory factors (IL-1β, IL-6, IL-8, and TNF-α). Meanwhile, microbiota metabolites, fecal LPS and TMAO were downregulated while SCFA and lactate were upraised compared to control. Furthermore, GSH-Px and TAOC level were increased and MDA was decreased. Microbiota analysis revealed the proportion of firmicutes was higher at the phylum level on an encapsulated group, while Lactobacillus was elevated at the genus level. We also found a remarkable increase in the population of Lactobacillus murinus at the species level. In summary, the oral delivery of probiotics via microcapsule effectively improves the animals' gut health by improving morphology, barrier function, anti-inflammatory action, antioxidant ability and modulating gut microbiota.

Hypoxanthine (Hx), an intermediate metabolite of the purine metabolism pathway which is dramatically increased in blood and skeletal muscle during muscle contraction and metabolism, is characterized as a marker of exercise exhaustion. However, the physiological effects of Hx on skeletal muscle remain unknown. Herein, we demonstrate that chronic treatment with Hx through dietary supplementation resulted in skeletal muscle fatigue and impaired the exercise performance of mice without affecting their growth and skeletal muscle development. Hx increased the uncoupling protein 2 (UCP2) expression in the skeletal muscle, which led to decreased energy substrate storage and enhanced glycolysis. These effects could also be verified in acute treatment with Hx through intraperitoneal injection. In addition, muscular specifically knockout of UCP2 through intra-muscle tissue injection of adenovirus-associated virus reversed the effects of Hx. In conclusion, we identified a novel role of Hx in the skeletal muscular fatigue mediated by UCP2-dependent mitochondrial uncoupling. This finding may shed light on the pathological mechanism of clinical muscle dysfunctions due to abnormal metabolism, such as muscle fatigue and weakness.

While resistance exercise effectively improves overall health in diabetic patients, the underlying biological mechanism by which resistance exercise improves metabolic function and glucose homeostasis remain mostly unknown. Previously, we identified a myometabolite-mediated metabolic pathway that is essential for the beneficial effects of resistance exercise on metabolic function. We found that resistance exercise-induced α-ketoglutaric acid (AKG) stimulates muscle hypertrophy and fat loss through 2-oxoglutarate receptor 1 (OXGR1)-dependent adrenal activation. Here, we provided evidence for the beneficial effects of AKG on glucose homeostasis in a diet-induced obesity (DIO) mouse model, which are independent of OXGR1. We showed that circulating AKG levels are negatively correlated with the fraction of blood glycated hemoglobin (HbA1c) in both humans and mice and significantly decreased in DIO mice. Consistently, pharmacological elevation of AKG effectively decreased body weight, blood glucose, and hepatic gluconeogenesis without changing insulin sensitivity and glucose tolerance in DIO mice. Notably, OXGR1KO blocked the inhibitory effects of AKG on body weight but failed to affect AKG’s suppression on blood glucose and hepatic gluconeogenesis, indicating distinct mechanisms for AKG’s regulation on energy balance and glucose homeostasis. In supporting this view, we showed that serpina1e, a member of protease inhibitor serpins superfamily, mediates the direct inhibitory effects of AKG on gluconeogenesis in both in vitro hepatocytes and liver slice. By using a liver-specific serpina1e deletion mouse model, we further demonstrated that liver serpina1e is required for the inhibitory effects of AKG on hepatic gluconeogenesis and hyperglycemia in DIO mice. Finally, we provided in vitro evidence to support a model in which AKG decreases hepatic gluconeogenesis by targeting trimethylation of lysine 27 on histone 3 (H3K27me3) in seprina1e promoter region. Our studies established an important role of AKG in glucose homeostasis, and identified the AKG-serpina1e pathway as potential therapeutic targets to attenuate hyperglycemia.

Skeletal muscle weight loss is accompanied by small fiber size and low protein content. Alpha-ketoglutarate (AKG) participates in protein and nitrogen metabolism. The effect of AKG on skeletal muscle hypertrophy has not yet been tested, and its underlying mechanism is yet to be determined. In this study, we demonstrated that AKG (2%) increased the gastrocnemius muscle weight and fiber diameter in mice. Our in vitro study also confirmed that AKG dose increased protein synthesis in C2C12 myotubes, which could be effectively blocked by the antagonists of Akt and mTOR. The effects of AKG on skeletal muscle protein synthesis were independent of glutamate, its metabolite. We tested the expression of GPR91 and GPR99. The result demonstrated that C2C12 cells expressed GPR91, which could be upregulated by AKG. GPR91 knockdown abolished the effect of AKG on protein synthesis but failed to inhibit protein degradation. These findings demonstrated that AKG promoted skeletal muscle hypertrophy via Akt/mTOR signaling pathway. In addition, GPR91 might be partially attributed to AKG-induced skeletal muscle protein synthesis.

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 Cβ 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.

It has been demonstrated that vascular endothelial growth factor B (VEGFB) plays a vital role in regulating vascular biological function. However, the role of VEGFB in regulating skeletal muscle cell proliferation and differentiation remains unclear. Thus, this study aimed to investigate the effects of VEGFB on C2C12 myoblast proliferation and differentiation and to explore the underlying mechanism. For proliferation, VEGFB significantly promoted the proliferation of C2C12 myoblasts with the upregulating expression of cyclin D1 and PCNA. Meanwhile, VEGFB enhanced vascular endothelial growth factor receptor 1 (VEGFR1) expression and activated the PI3K/Akt signaling pathway in a VEGFR1-dependent manner. In addition, the knockdown of VEGFR1 and inhibition of PI3K/Akt totally abolished the promotion of C2C12 proliferation induced by VEGFB, suggesting that VEGFB promoted C2C12 myoblast proliferation through the VEGFR1-PI3K/Akt signaling pathway. Regarding differentiation, VEGFB significantly stimulated the differentiation of C2C12 myoblasts via VEGFR, with elevated expressions of MyoG and MyHC. Furthermore, the knockdown of VEGFR1 rather than NRP1 eliminated the VEGFB-stimulated C2C12 differentiation. Moreover, VEGFB activated the PI3K/Akt/mTOR signaling pathway in a VEGFR1-dependent manner. However, the inhibition of PI3K/Akt/mTOR blocked the promotion of C2C12 myoblasts differentiation induced by VEGFB, indicating the involvement of the PI3K/Akt pathway. To conclude, these findings showed that VEGFB promoted C2C12 myoblast proliferation and differentiation via the VEGFR1-PI3K/Akt signaling pathway, providing new insights into the regulation of skeletal muscle development.

Skeletal muscle atrophy due to excessive protein degradation is the main cause for muscle dysfunction, fatigue, and weakening of athletic ability. Endurance exercise is effective to attenuate muscle atrophy, but the underlying mechanism has not been fully investigated. α-Ketoglutarate (AKG) is a key intermediate of tricarboxylic acid cycle, which is generated during endurance exercise. Here, we demonstrated that AKG effectively attenuated corticosterone-induced protein degradation and rescued the muscle atrophy and dysfunction in a Duchenne muscular dystrophy mouse model. Interestingly, AKG also inhibited the expression of proline hydroxylase 3 (PHD3), one of the important oxidoreductases expressed under hypoxic conditions. Subsequently, we identified the β2 adrenergic receptor (ADRB2) as a downstream target for PHD3. We found AKG inhibited PHD3/ADRB2 interaction and therefore increased the stability of ADRB2. In addition, combining pharmacologic and genetic approaches, we showed that AKG rescues skeletal muscle atrophy and protein degradation through a PHD3/ADRB2 mediated mechanism. Taken together, these data reveal a mechanism for inhibitory effects of AKG on muscle atrophy and protein degradation. These findings not only provide a molecular basis for the potential use of exercise-generated metabolite AKG in muscle atrophy treatment, but also identify PHD3 as a potential target for the development of therapies for muscle wasting.—Cai, X., Yuan, Y., Liao, Z., Xing, K., Zhu, C., Xu, Y., Yu, L., Wang, L., Wang, S., Zhu, X., Gao, P., Zhang, Y., Jiang, Q., Xu, P., Shu, G. α-Ketoglutarate prevents skeletal muscle protein degradation and muscle atrophy through PHD3/ADRB2 pathway.

Laminarin, a type of β-glucan isolated from brown seaweeds, exhibits verity of physiological activities, which include immunology modulation and antitumor function. To investigate the effect of laminarin on energy homeostasis, mice were orally administrated with laminarin to test food intake, fat deposition, and glucose homeostasis. Chronically, laminarin treatment significantly decreases high-fat-diet-induced body weight gain and fat deposition and reduces blood glucose level and glucose tolerance. Acutely, laminarin enhances serum glucagon-like peptide-1 (GLP-1) content and the mRNA expression level of proglucagon and prohormone convertase 1 in ileum. Subsequently, laminarin suppresses the food intake of mice, the hypothalamic AgRP neuron activity, and AgRP expression but activates pancreatic function. Furthermore, laminarin-induced appetite reduction was totally blocked by Exendin (9-39), a specific competitive inhibitor of GLP-1 receptor. Then, STC-1 cells were adopted to address the underlying mechanism, by which laminarin promoted GLP-1 secretion in vitro. Results showed that laminarin dose-dependently promoted GLP-1 secretion and c-Fos protein expression in STC-1 cells, which were independent of Dectin-1 and CD18. Interestingly, BAPTA-AM, a calcium-chelating agent, potently attenuated laminarin-induced [Ca2+]i elevation, c-Fos expression, and GLP-1 secretion. In summary, our data support that laminarin counteracts diet-induced obesity and stimulates GLP-1 secretion via [Ca2+]i; this finding provides an experimental basis for laminarin application to treat obesity and maintain glucose homeostasis.

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., The Krebs cycle intermediate α‐ketoglutaric acid acts as a systemic myometabolite promoting energy expenditure and lipolysis in mice.

The current obesity epidemic mainly results from high-fat high-caloric diet (HFD) feeding and may also be contributed by chronic stress; however, the neural basis underlying stress-related diet-induced obesity remains unknown. Corticotropin-releasing hormone (CRH) neurons in the paraventricular hypothalamus (PVH), a known body weight-regulating region, represent one key group of stress-responsive neurons. Here, we found that HFD feeding blunted PVH CRH neuron response to nutritional challenges as well as stress stimuli and dexamethesone, which normally produce rapid activation and inhibition on these neurons, respectively. We generated mouse models with the activity of these neurons clamped at high or low levels, both of which showed HFD-mimicking, blunted PVH CRH neuron responsiveness. Strikingly, both models developed rapid HFD-induced obesity, associated with HFD-mimicking, reduced diurnal rhythmicity in feeding and energy expenditure. Thus, blunted responsiveness of PVH CRH neurons, but not their absolute activity levels, underlies HFD-induced obesity and may also contribute to stress-induced obesity.

N-Acyl amino acids (NAAAs) are conjugate products of fatty acids and amino acids, which are available in animal-derived food. We compared the effects of N-arachidonoylglycine (NAGly), N-arachidonoylserine (NASer), and N-oleoylglycine (OLGly) on in vivo food intake and in vitro [Ca2+]i of Agouti-related protein (AgRP) neurons to identify the role of these compounds in energy homeostasis. Hypothalamic neuropeptide expression and anxiety behavior in response to OLGly were also tested. To further identify the underlying mechanism of OLGly on food intake, we first detected the expression level of potential OLGly receptors. The cannabinoid receptor type 1 (CB1R) antagonist was cotreated with OLGly to analyze the activation of AgRP neuron, including [Ca2+]i, expression levels of PKA, CREB, and c-Fos, and neuropeptide secretion. Results demonstrated that only OLGly (intrapertioneal injection of 6 mg/kg) can induce hyperphagia without changing the expression of hypothalamic neuropeptides and anxiety-like behavior....

It is well known that endurance training is effective to attenuate skeletal muscle atrophy. Succinate is a typical TCA metabolite, of which exercise could dramatically increase the content. The present study aimed to investigate the effect of succinate on protein synthesis in skeletal muscle, and try to delineate the underlying mechanism. The in vitro study revealed that succinate dose-dependently increased protein synthesis in C2C12 myotube along with the enhancement of phosphorylation levels of AKT Serine/Threonine Kinase 1(Akt), mammalian target of rapamycin, S6, eukaryotic translation initiation factor 4E, 4E binding protein 1 and forkhead box O (FoxO) 3a. Furthermore, it was demonstrated that 20 mM succinate markedly increased [Ca2+]i. Then, the phospho-extracellular regulated kinase (Erk), -Akt level and the crosstalk between Erk and Akt were elevated in response to succinate. Notably, the Erk antagonist (U0126) or mTOR inhibitor (rapamycin) abolished the effect of succinate on protein synthesis. The in vivo study verified that succinate dose-dependently increased the protein synthesis, in addition to phosphorylation levels of Erk, Akt and FoxO3a in gastrocnemius muscle. In summary, these findings demonstrated that succinate promoted skeletal muscle protein deposition via Erk/Akt signaling pathway.

Adipocyte dysfunction is associated with many metabolic diseases such as obesity, insulin resistance and diabetes. Previous studies found that phloretin promotes 3T3-L1 cells differentiation, but the underlying mechanisms for phloretin's effects on adipogenesis remain unclear. In this study, we demonstrated that phloretin enhanced the lipid accumulation in porcine primary adipocytes in a time-dependent manner. Furthermore, phloretin increased the utilization of glucose and nonesterified fatty acid, while it decreased the lactate output. Microarray analysis revealed that genes associated with peroxisome proliferator-activated receptor-γ (PPARγ), mitogen-activated protein kinase and insulin signaling pathways were altered in response to phloretin. We further confirmed that phloretin enhanced expression of PPARγ, CAAT enhancer binding protein-α (C/EBPα) and adipose-related genes, such as fatty acids translocase and fatty acid synthase. In addition, phloretin activated the Akt (Thr308) and extracellular signal-regulated kinase, and therefore, inactivated Akt targets protein. Wortmannin effectively blocked the effect of phloretin on Akt activity and the protein levels of PPARγ, C/EBPα and fatty acid binding protein-4 (FABP4/aP2). Oral administration of 5 or 10 mg/kg phloretin to C57BL BKS-DB mice significantly decreased the serum glucose level and improved glucose tolerance. In conclusion, phloretin promotes the adipogenesis of porcine primary preadipocytes through Akt-associated signaling pathway. These findings suggested that phloretin might be able to increase insulin sensitivity and alleviate the metabolic diseases.

Two experiments were conducted to determine the effects of different dietary lysine levels on the apparent nutrient digestibility, the serum amino acid (AA) concentration, and the biochemical parameters of the precaval and portal vein blood in growing pigs. In Experiment 1, 15 noncannulated pigs received diets with different lysine densities (0.65%, 0.95%, and 1.25% lysine) for 13 d. A total collection digestion test was performed, and blood samples were collected from the precaval vein at the end of the experiment. In Experiment 2, four cannulated pigs were fed the same diets of Experiment 1. The experiment used a self-control experimental design and was divided into three periods. On d 5 of each period, at 0.5 h before feeding and hourly up to 8 h after feeding, single blood samples were collected from catheters placed in the portal vein. In Experiment 1, some serum AAs (including lysine), serum urinary nitrogen (SUN), and total protein (TP) concentrations were significantly affected by the dietary lysine levels (p

Skeletal muscle weight loss is accompanied by small fiber size and low protein content. Alpha-ketoglutarate (AKG) participates in protein and nitrogen metabolism. The effect of AKG on skeletal muscle hypertrophy has not yet been tested, and its underlying mechanism is yet to be determined. In this study, we demonstrated that AKG (2%) increased the gastrocnemius muscle weight and fiber diameter in mice. Our in vitro study also confirmed that AKG dose increased protein synthesis in C2C12 myotubes, which could be effectively blocked by the antagonists of Akt and mTOR. The effects of AKG on skeletal muscle protein synthesis were independent of glutamate, its metabolite. We tested the expression of GPR91 and GPR99. The result demonstrated that C2C12 cells expressed GPR91, which could be upregulated by AKG. GPR91 knockdown abolished the effect of AKG on protein synthesis but failed to inhibit protein degradation. These findings demonstrated that AKG promoted skeletal muscle hypertrophy via Akt/mTOR signaling pathway. In addition, GPR91 might be partially attributed to AKG-induced skeletal muscle protein synthesis.

Skeletal muscle weight loss is accompanied by small fiber size and low protein content. Alpha-ketoglutarate (AKG) participates in protein and nitrogen metabolism. The effect of AKG on skeletal muscle hypertrophy has not yet been tested, and its underlying mechanism is yet to be determined. In this study, we demonstrated that AKG (2%) increased the gastrocnemius muscle weight and fiber diameter in mice. Our in vitro study also confirmed that AKG dose increased protein synthesis in C2C12 myotubes, which could be effectively blocked by the antagonists of Akt and mTOR. The effects of AKG on skeletal muscle protein synthesis were independent of glutamate, its metabolite. We tested the expression of GPR91 and GPR99. The result demonstrated that C2C12 cells expressed GPR91, which could be upregulated by AKG. GPR91 knockdown abolished the effect of AKG on protein synthesis but failed to inhibit protein degradation. These findings demonstrated that AKG promoted skeletal muscle hypertrophy via Akt/mTOR signaling pathway. In addition, GPR91 might be partially attributed to AKG-induced skeletal muscle protein synthesis.

The regulation of food intake is a promising way to combat obesity. It has been implicated that various fatty acids exert different effects on food intake and body weight. However, the underlying mechanism remains poorly understood. The aim of the present study was to investigate the effects of linoleic acid (LA) and stearic acid (SA) on agouti-related protein (AgRP) expression and secretion in immortalized mouse hypothalamic N38 cells and to explore the likely underlying mechanisms. Our results demonstrated that LA inhibited, while SA stimulated AgRP expression and secretion of N38 cells in a dose-dependent manner. In addition, LA suppressed the protein expression of toll-like receptor 4 (TLR4), phosphorylation levels of JNK and IKKα/β, suggesting the inhibition of TLR4-dependent inflammation pathway. However, the above mentioned inhibitory effects of LA were eliminated by TLR4 agonist lipopolysaccharide (LPS). In contrast, SA promoted TLR4 protein expression and activated TLR4-dependent inflammation pathway, with elevated ratio of p-JNK/JNK. While TLR4 siRNA reversed the stimulatory effects of SA on AgRP expression and TLR4-dependent inflammation. Moreover, we found that TLR4 was also involved in LA-enhanced and SA-impaired leptin/insulin signal pathways in N38 cells. In conclusion, our findings indicated that LA elicited inhibitory while SA exerted stimulatory effects on AgRP expression and secretion via TLR4-dependent inflammation and leptin/insulin pathways in N38 cells. These data provided a better understanding of the mechanism underlying fatty acids-regulated food intake and suggested the potential role of long-chain unsaturated fatty acids such as LA in reducing food intake and treating obesity.