PGC-1α-Coordinated Hypothalamic Antioxidant Defense Is Linked to SP1-LanCL1 Axis during High-Fat-Diet-Induced Obesity in Male Mice.

High-fat-diet (HFD)-induced obesity parallels hypothalamic inflammation and oxidative stress, but the correlations between them are not well-defined. Here, with mouse models targeting the antioxidant gene LanCL1 in the hypothalamus, we demonstrate that impaired hypothalamic antioxidant defense aggravates HFD-induced hypothalamic inflammation and obesity progress, and these could be improved in mice with elevated hypothalamic antioxidant defense. We also show that peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), a critical transcriptional coactivator, is implicated in regulating hypothalamic LanCL1 transcription, in collaboration with SP1 through a direct interaction, in response to HFD-induced palmitic acid (PA) accumulation. According to our results, when exposed to HFD, mice undergo a process of overwhelming hypothalamic antioxidant defense; short-time HFD exposure induces ROS production to activate PGC-1α and elevate LanCL1-mediated antioxidant defense, while long-time exposure promotes ubiquitin-mediated PGC-1α degradation and suppresses LanCL1 expression. Our findings show the critical importance of the hypothalamic PGC-1α-SP1-LanCL1 axis in regulating HFD-induced obesity, and provide new insights describing the correlations of hypothalamic inflammation and oxidative stress during this process.

Relationship between gout, hyperuricemia, and obesity-does central obesity play a significant role?-a study based on the NHANES database.

BACKGROUND: Our objective was to evaluate how various measures of obesity, such as body mass index(BMI), body roundness index(BRI), and weigh adjusted waist index(WWI), influence urate levels, prevalence of gout and to compare the disparities among these obesity indicators. METHODS: By analyzing the 2001-2018 National Health and Nutrition Examination Survey (NHANES), we assessed the relationship between BMI, WWI, and BRI indices and urate levels, hyperuricemia, and the prevalence of gout. Smoothed curve fitting was used to determine whether there was a nonlinear relationship between BMI,WWI, and BRI indices and urate levels, hyperuricemia, and the prevalence of gout, and threshold effects analysis was used to test this relationship. We also used ROC curves to determine the diagnostic efficacy of BMI, WWI, and BRI on the prevalence of hyperuricemia and gout. RESULTS: The study incorporated a total of 29,310 participants aged over 20 years, out of which 14,268 were male. Following the adjustment for the pertinent confounding factors, it was observed that higher levels of BMI, WWI, and BRI were significantly associated with a gradual and dose-dependent increase in urate levels. In the sensitivity analysis, each unit increment in BMI, WWI, and BRI levels exhibited an 8%, 72%, and 26% respective elevation in the risk of hyperuricemia, as well as a 5%, 31%, and 15% respective increase in the risk of gout. Dose-response curves provided evidence of a linear positive correlation between BMI, WWI, BRI, and urate levels, as well as the prevalence of hyperuricemia and gout. Based on the response from the ROC curve, overall, the diagnostic efficacy of BRI for hyperuricemia and gout surpasses that of BMI. CONCLUSION: The central obesity indices WWI and BRI levels are superior to BMI in detecting the prevalence of urate levels, hyperuricemia, and gout, and although a clear causal relationship has not yet been established, it is important to recognize the impact of central obesity on uric acid levels and to give it due attention.

TRIM67 Implicates in Regulating the Homeostasis and Synaptic Development of Mitral Cells in the Olfactory Bulb.

In recent years, olfactory dysfunction has attracted increasingly more attention as a hallmark symptom of neurodegenerative diseases (ND). Deeply understanding the molecular basis underlying the development of the olfactory bulb (OB) will provide important insights for ND studies and treatments. Now, with a genetic knockout mouse model, we show that TRIM67, a new member of the tripartite motif (TRIM) protein family, plays an important role in regulating the proliferation and development of mitral cells in the OB. TRIM67 is abundantly expressed in the mitral cell layer of the OB. The genetic deletion of TRIM67 in mice leads to excessive proliferation of mitral cells in the OB and defects in its synaptic development, resulting in reduced olfactory function in mice. Finally, we show that TRIM67 may achieve its effect on mitral cells by regulating the Semaphorin 7A/Plexin C1 (Sema7A/PlxnC1) signaling pathway.

Knockdown of BUB1 inhibits tumor necrosis factor-α-induced proliferation and migration of rheumatoid arthritis synovial fibroblasts by regulating PI3K/Akt pathway.

BACKGROUND: Rheumatoid arthritis (RA) is a common disease with joint cartilage destruction. BUB1 Mitotic Checkpoint Serine/Threonine Kinase (BUB1) is abnormally expressed in synovial tissues of RA patients, but its effect on RA remains unclear. In this study, we explored the role of BUB1 in RA. METHODS: An RA cell model was constructed by treating MH7A cells with tumor necrosis factor-α (TNF-α). The levels of BUB1, GAPDH, phosphorylated phosphatidylinositol 3 kinase (p-PI3K)/PI3K, and phosphorylated serine/threonine kinase (p-Akt)/Akt in MH7A cells were examined by Western blot. The MH7A cell proliferation was examined by colony formation assay. Wound healing assay and transwell assay were carried out to detect MH7A cell migration and invasion. The mRNA levels of proinflammatory cytokines were assessed by quantitative reverse transcription polymerase chain reaction. RESULTS: The results showed that knockdown BUB1 inhibited TNF-α-induced MH7A cell proliferation, migration, and invasion. Silencing BUB1 repressed the PI3K/Akt pathway in TNF-α-induced MH7A cells. We also found that the TNF-α-induced MH7A cell proliferation, migration, and invasion were repressed by si-BUB1 transfection, whereas these effects were attenuated by 740Y-P (an activator of the PI3K pathway) co-treatment. Knockdown of BUB1 reduced the expression of the proinflammatory cytokines. CONCLUSION: Knockdown BUB1 repressed TNF-α-induced MH7A cell proliferation, migration and invasion through the PI3K/Akt pathway.

Hybrid biointerface engineering nanoplatform for dual-targeted tumor hypoxia relief and enhanced photodynamic therapy.

The clinical application of photodynamic therapy (PDT) is limited by the lack of tumor selectivity of photosensitizer (PS) and the hypoxic tumor microenvironment (TME). To address these limitations of PDT, we developed a hybrid engineered biointerface nanoplatform that integrated anti-epidermal growth factor receptor (EGFR)-aptamer (EApt)-modified liposomes with tumor cell membranes (TMs) to create M/L-EApt. M/L-EApt exhibited enhanced stability and significant dual-targeting ability, enabling selectively accumulate in hypoxic tumor regions after systemic infusion. PHI@M/L-EApt, formed by M/L-EApt loaded with an oxygen carrier perfluorotributylamine (PFTBA) and IR780 (a PS), effectively promoted the therapeutic performance of PDT by reversing the hypoxic TME and increasing the accumulation of IR780 at the tumor sites, resulting in a robust anti-tumor efficacy. In vivo results showed that PHI@M/L-EApt treatment effectively suppressed the growth of triple-negative breast tumors in mice. Our findings demonstrated the synergistic effect of oxygen supply and PDT on tumor treatment using PHI@M/L-EApt. This study presented a biomimetic interface engineering strategy and dual-targeted hybrid nanoplatform for relieving hypoxic TME and potentially facilitating the clinical application of PDT.

Engineering Biomimetic Biosensor Using Dual-Targeting Multivalent Aptamer Regulated 3D DNA Walker Enables High-Performance Detection of Heterogeneous Circulating Tumor Cells.

The phenotypic heterogeneity of circulating tumor cells (CTCs) and the nonspecific adsorption of background cells impede the effective and sensitive detection of rare CTCs. Although leukocyte membrane coating approach has a good antileukocyte adhesion ability and holds great promise for addressing the challenge of capture purity, its limited specificity and sensitivity prevent its use in the detection of heterogeneous CTCs. To overcome these obstacles, a biomimetic biosensor that integrated dual-targeting multivalent aptamer/walker duplex functionalized biomimetic magnetic beads and an enzyme-powered DNA walker signal amplification strategy is designed. As compared to conventional leukocyte membrane coating, the biomimetic biosensor achieves efficient and high purity enrichment of heterogeneous CTCs with different epithelial cell adhesion molecule (EpCAM) expression while minimizing the interference of leukocytes. Meanwhile, the capture of target cells can trigger the release of walker strands to activate an enzyme-powered DNA walker, resulting in cascade signal amplification and the ultrasensitive and accurate detection of rare heterogeneous CTCs. Importantly, the captured CTCs remained viable and can be recultured in vitro with success. Overall, this work provides a new perspective for the efficient detection of heterogeneous CTCs by biomimetic membrane coating and paves the way for early cancer diagnosis.

The anthelmintic potential of Bacillus thuringiensis to counter the anthelmintic resistance against Haemonchus contortus.

Haemonchus contortus (H. contortus) has developed resistance to nearly all available anthelmintic medications. Hence, alternative strategies are required to counter anthelmintic resistance. The present study investigated the anthelmintic potential of Bacillus thuringiensis (B. thuringiensis) against H. contortus. Bacterial spp were identified by conventional methods and confirmed by PCR; In addition, PCR amplification of the bacterial 16S rRNA gene detected B. thuringiensis at 750 base pairs (bps). The amplified products were sequenced, and the sequence data were confirmed using the Basic Local Alignment Tool (BLAST), which showed a significant alignment (97.98%) with B. thuringiensis and B. cereus. B. thuringiensis were selected to isolate purified crystal proteins (toxins), The protein profile confirmed by SDS-PAGE showed three prominent bands at 70, 36, and 15 kDa. In addition, the larval development of H. contortus was examined in vitro using two different treatments. Purified crystal protein diluted in 10 mM NaCl at a concentration of 2 mg/ml significantly reduced (P < 0.001) larval development by 75.10% compared to 1 × 108 CFU/ml spore-crystal suspension reduced (43.97%). The findings of in vitro experiments indicated that purified crystal protein was more toxic to the H. contortus larva than the spore-crystal suspension and control group. Moreover, To test the antinematodal effects of B. thuringiensis toxins in vivo, we chose 12 male goats (6 months old) and reared these animals in parasite-free conditions. We performed Fecal egg count reduction tests (FECRT) on samples collected before and after treatment at various times denotes 48 h post-treatment with Purified crystal proteins was significantly decreased (842 ± 19.07) EPG compared to 24 (2560 ± 233.66) and 12 h (4020 ± 165.22). Similarly, after 48 h of treatment, the FECRT of the Spores-crystal mix was reduced (2920 ± 177.20) EPG followed by 24- and 12-h denotes (4500 ± 137.84) and (4760 ± 112.24), respectively. Results of the above experiment suggested that purified crystal proteins have more anthelmintic potential in vivo. Current findings determine that B. thuringiensis toxin against H. contortus could be used in small ruminants to counter anthelmintic resistance. This study also suggested that future research structured on these proteins' pharmacokinetics and mode of action.

Boosting the integration of cell membrane-nanomaterial hybrids via dextran-mediated dynamic dispersion system to capture bioactive compounds in natural products.

Efficient integration is a prerequisite for the application of cell membrane-nanomaterial hybrids (CN hybrids) in bioanalysis, however, the poor dispersity of nanomaterials limits the development of this technology. Although the traditional hydrophilic modification method could improve the dispersity of nanomaterials, it would hinder the coating of the cell membrane, thus making it unsuitable for the integration of CN hybrids. Herein, a method has been proposed to improve the integration efficiency of CN hybrids from a different perspective, that is, establishing a dynamic dispersion system to enhance the interfacial interaction between cell membranes and nanomaterials. Specifically, magnetic graphene oxide (MGO) nanosheets were used as the model carrier and HepG2 cells were used as the source for membrane coating. The addition of the macromolecular stabilizer dextran to the integration process enhanced the dispersity of MGO and avoided the resistance to membrane coating caused by surface modification. Intriguingly, MGO in the dynamic dispersion system showed superior membrane coating ability as compared to hydrophilic modification methods, resulting in the more efficient integration of CN hybrids and greater sensitivity in capturing bioactive compounds from natural products. The proposed design principle provides a brand-new perspective for optimizing the behavior of CN hybrids and can improve the effectiveness of CN hybrids in bioanalytical applications.

Inside-out extracellular vesicles-like biomimetic magnetic nanoparticles for efficient screening P-Glycoprotein inhibitors to overcome cancer multidrug resistance.

The discovery of P-Glycoprotein (P-gp) inhibitors to block chemotherapy drugs efflux is considered an attractive treatment strategy for overcoming cancer multidrug resistance (MDR). Cell membrane biomimetic platform has emerged as a promising candidate method for screening small molecule P-gp inhibitors from natural products. However, randomly oriented cell membrane coating does not guarantee the inward-opening conformation of P-gp, limiting the precise screening of P-gp inhibitors. Herein, inside-out orientation extracellular vesicles camouflaged magnetic nanoparticles (IOVMNPs) were prepared to discover P-gp inhibitors with low toxicity and high efficiency from natural products. The orientation of extracellular vesicles on the surface of IOVMNPs was rigorously confirmed by immunogold electron microscopy and sialic acid quantification assay. Finally, two potential P-gp inhibitors, honokiol and magnolol, were captured by obtained IOVMNPs. The effect of MDR reversal in combination with chemotherapy drugs was further verified by pharmacological activity experiments. The inside-out orientation extracellular vesicles encapsulation strategy provides an effective tool for the discovery of novel P-gp inhibitors from nature products, thus further extending the application field of orientation assembly cell membrane biomimetic magnetic nanoparticles. This inside-out extracellular vesicles coating also proposes a new concept for the assembly of cell membrane biomimetic platform.

Bioinspired nano-plate-coral platform enabled efficient detection of circulating tumor cells via the synergistic capture of multivalent aptamer and tumor cell membrane.

Circulating tumor cells (CTCs) offer rich information for early disease diagnosis and therapy evaluation. However, the limited sensitivity, binding affinity, and stability of current monovalent recognition-based CTCs detection techniques remain a challenge for extending their applications. Inspired by the highly efficient predation manner of plate corals, we firstly introduce an efficient and sensitive biomimetic CTCs recognition platform based on the conjugation of multivalent aptamer onto tumor cell membrane-coated magnetic graphene oxide to form a plate coral-like CTCs capture nanoprobe (MNPA-TCMMGO). In this method, the tumor cell membrane was employed to provide a biomimetic homologous fluidic interface for targeting homologous tumor cells. At the same time, multivalent aptamers were used as capture probes, which greatly enhanced the binding affinity and association probability between aptamer and target cells via cooperative multivalent effect. The unique features (robustness, high binding affinity and specificity, and biocompatibility) of MNPA-TCMMGO allow efficient, sensitive, and specific capture of rare tumor cells from biological samples. More importantly, the captured cells could maintain good viability, which is crucial for downstream analysis. Therefore, our developed biomimetic approach offers a new way to address the limitations of current CTCs detection methods and presents considerable potential for clinical cancer diagnostics.

Polysaccharide from Salviae miltiorrhizae Radix et Rhizoma Attenuates the Progress of Obesity-Induced Non-Alcoholic Fatty Liver Disease through Modulating Intestinal Microbiota-Related Gut-Liver Axis.

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease worldwide, thus treatments for it have attracted lots of interest. In this study, the Salviae miltiorrhizae Radix et Rhizoma (SMRR) polysaccharide was isolated by hot water extraction and ethanol precipitation, and then purified by DEAE anion exchange chromatography and gel filtration. With a high-fat-diet-induced obesity/NAFLD mouse model, we found that consumption of the SMRR polysaccharide could remarkably reverse obesity and its related progress of NAFLD, including attenuated hepatocellular steatosis, hepatic fibrosis and inflammation. In addition, we also reveal the potential mechanism behind these is that the SMRR polysaccharide could regulate the gut-liver axis by modulating the homeostasis of gut microbiota and thereby improving intestinal function.

Polyphyllin I Promotes Autophagic Cell Death and Apoptosis of Colon Cancer Cells via the ROS-Inhibited AKT/mTOR Pathway.

Colon cancer is a common malignant tumor of the digestive tract, and it is considered among the biggest killers. Scientific and reasonable treatments can effectively improve the survival rate of patients if performed in the early stages. Polyphyllin I (PPI), a pennogenyl saponin isolated from Paris polyphylla var. yunnanensis, has exhibited strong anti-cancer activities in previous studies. Here, we report that PPI exhibits a cytotoxic effect on colon cancer cells. PPI suppressed cell viability and induced autophagic cell death in SW480 cells after 12 and 24 h, with the IC50 values 4.9 ± 0.1 µmol/L and 3.5 ± 0.2 µmol/L, respectively. Furthermore, we found PPI induced time-concentration-dependent autophagy and apoptosis in SW480 cells. In addition, down-regulated AKT/mTOR activity was found in PPI-treated SW480 cells. Increased levels of ROS might link to autophagy and apoptosis because reducing the level of ROS by antioxidant N-acetylcysteine (NAC) treatment mitigated PPI-induced autophagy and apoptosis. Although we did not know the molecular mechanism of how PPI induced ROS production, this is the first study to show that PPI induces ROS production and down-regulates the AKT/mTOR pathway, which subsequently promotes the autophagic cell death and apoptosis of colon cancer cells. This present study reports PPI as a potential therapeutic agent for colon cancer and reveals its underlying mechanisms of action.

TRIM67 Deficiency Exacerbates Hypothalamic Inflammation and Fat Accumulation in Obese Mice.

Obesity has achieved the appearance of a global epidemic and is a serious cause for concern. The hypothalamus, as the central regulator of energy homeostasis, plays a critical role in regulating food intake and energy expenditure. In this study, we show that TRIM67 in the hypothalamus was responsive to body-energy homeostasis whilst a deficiency of TRIM67 exacerbated metabolic disorders in high-fat-diet-induced obese mice. We found exacerbated neuroinflammation and apoptosis in the hypothalamus of obese TRIM67 KO mice. We also found reduced BDNF in the hypothalamus, which affected the fat sympathetic nervous system innervation and contributed to lipid accumulation in adipose tissue under high-fat-diet exposure. In this study, we reveal potential implications between TRIM67 and the hypothalamic function responding to energy overuptake as well as a consideration for the therapeutic diagnosis of obesity.

Ameliorating Effects of TRIM67 against Intestinal Inflammation and Barrier Dysfunction Induced by High Fat Diet in Obese Mice.

Tripartite Motif 67 (TRIM67) is an important member of TRIM family proteins, which participates in different cellular processes including immune response, proliferation, differentiation, carcinogenesis, and apoptosis. In recent years, a high fat diet (HFD) has remained one of the main causes of different metabolic diseases and increases in intestinal permeability as well as inducing intestinal inflammation. The current study investigated the protective effects of TRIM67 in the ileum and colon of obese mice. 4-week-old wild-type (WT) C57BL/6N mice and TRIM67 knockout (KO) C57BL/6N mice were selected and randomly divided into four sub-groups, which were fed with control diet (CTR) or HFD for 14 weeks. Samples were collected at the age of 18 weeks for analysis. To construct an in vitro obesity model, over-expressed IPEC-J2 cells (porcine intestinal cells) with Myc-TRIM67 were stimulated with palmitic acid (PA), and its effects on the expression level of TRM67, inflammatory cytokines, and barrier function were evaluated. The KO mice showed pathological lesions in the ileum and colon and this effect was more obvious in KO mice fed with HFD. In addition, KO mice fed with a HFD or CTR diet had increased intestinal inflammation, intestinal permeability, and oxidative stress compared to that WT mice fed with these diets, respectively. Moreover, IPEC-J2 cells were transfected with TRIM67 plasmid to perform the same experiments after stimulation with PA, and the results were found consistent with the in vivo evaluations. Taken together, our study proved for the first time that HFD and TRIM67 KO mice have synergistic damaging effects on the intestine, while TRIM67 plays an important protective role in HFD-induced intestinal damage.

Loss of TRIM67 Attenuates the Progress of Obesity-Induced Non-Alcoholic Fatty Liver Disease.

Obesity is considered as a major cause for the development and progress of non-alcoholic fatty liver disease (NAFLD), which is one of the most prevalent chronic liver diseases worldwide. However, molecular mechanisms that implicate in obesity-driven pathophysiology of NAFLD are not well defined. Here, we report a tripartite motif (TRIM) protein family member-TRIM67-that is hardly expressed in liver but is inducible on obese conditions. Enhanced expression of TRIM67 activates hepatic inflammation to disturb lipid metabolic homeostasis and promote the progress of NAFLD induced by obesity, while the deficiency in TRIM67 is protective against these pathophysiological processes. Finally, we show that the important transcription coactivator PGC-1α implicates in the response of hepatic TRIM67 to obesity.

Animal models of male subfertility targeted on LanCL1-regulated spermatogenic redox homeostasis.

Oxidative stress in spermatozoa is a major contributor to male subfertility, which makes it an informed choice to generate animal models of male subfertility with targeted modifications of the antioxidant systems. However, the critical male germ cell-specific antioxidant mechanisms have not been well defined yet. Here we identify LanCL1 as a major male germ cell-specific antioxidant gene, reduced expression of which is related to human male infertility. Mice deficient in LanCL1 display spermatozoal oxidative damage and impaired male fertility. Histopathological studies reveal that LanCL1-mediated antioxidant response is required for mouse testicular homeostasis, from the initiation of spermatogenesis to the maintenance of viability and functionality of male germ cells. Conversely, a mouse model expressing LanCL1 transgene is protected against high-fat-diet/obesity-induced oxidative damage and subfertility. We further show that germ cell-expressed LanCL1, in response to spermatogenic reactive oxygen species, is regulated by transcription factor specific protein 1 (SP1) during spermatogenesis. This study demonstrates a critical role for the SP1-LanCL1 axis in regulating testicular homeostasis and male fertility mediated by redox balance, and provides evidence that LanCL1 genetically modified mice have attractive applications as animal models of male subfertility.

Accurate construction of cell membrane biomimetic graphene nanodecoys via purposeful surface engineering to improve screening efficiency of active components of traditional Chinese medicine.

Biomimetic nanoengineering presents great potential in biomedical research by integrating cell membrane (CM) with functional nanoparticles. However, preparation of CM biomimetic nanomaterials for custom applications that can avoid the aggregation of nanocarriers while maintaining the biological activity of CM remains a challenge. Herein, a high-performance CM biomimetic graphene nanodecoy was fabricated via purposeful surface engineering, where polyethylene glycol (PEG) was used to modifying magnetic graphene oxide (MGO) to improve its stability in physiological solution, so as to improve the screening efficiency to active components of traditional Chinese medicine (TCM). With this strategy, the constructed PEGylated MGO (PMGO) could keep stable at least 10 days, thus improving the CM coating efficiency. Meanwhile, by taking advantage of the inherent ability of HeLa cell membrane (HM) to interact with specific ligands, HM-camouflaged PMGO showed satisfied adsorption capacity (116.2 mg/g) and selectivity. Finally, three potential active components, byakangelicol, imperatorin, and isoimperatorin, were screened from Angelica dahurica, whose potential antiproliferative activity were further validated by pharmacological studies. These results demonstrated that the purposeful surface engineering is a promising strategy for the design of efficient CM biomimetic nanomaterials, which will promote the development of active components screening in TCM.

GATOR2 complex-mediated amino acid signaling regulates brain myelination.

Amino acids are essential for cell growth and metabolism. Amino acid and growth factor signaling pathways coordinately regulate the mechanistic target of rapamycin complex 1 (mTORC1) kinase in cell growth and organ development. While major components of amino acid signaling mechanisms have been identified, their biological functions in organ development are unclear. We aimed to understand the functions of the critically positioned amino acid signaling complex GAP activity towards Rags 2 (GATOR2) in brain development. GATOR2 mediates amino acid signaling to mTORC1 by directly linking the amino acid sensors for arginine and leucine to downstream signaling complexes. Now, we report a role of GATOR2 in oligodendrocyte myelination in postnatal brain development. We show that the disruption of GATOR2 complex by genetic deletion of meiosis regulator for oocyte development (Mios, encoding a component of GATOR2) selectively impairs the formation of myelinating oligodendrocytes, thus brain myelination, without apparent effects on the formation of neurons and astrocytes. The loss of Mios impairs cell cycle progression of oligodendrocyte precursor cells, leading to their reduced proliferation and differentiation. Mios deletion manifests a cell type-dependent effect on mTORC1 in the brain, with oligodendroglial mTORC1 selectively affected. However, the role of Mios/GATOR2 in oligodendrocyte formation and myelination involves mTORC1-independent function. This study suggests that GATOR2 coordinates amino acid and growth factor signaling to regulate oligodendrocyte myelination.

Rheb-regulated mitochondrial pyruvate metabolism of Schwann cells linked to axon stability.

The metabolic coupling of Schwann cells (SCs) and peripheral axons is poorly understood. Few molecules in SCs are known to regulate axon stability. Using SC-specific Rheb knockout mice, we demonstrate that Rheb-regulated mitochondrial pyruvate metabolism is critical for SC-mediated non-cell-autonomous regulation of peripheral axon stability. Rheb knockout suppresses pyruvate dehydrogenase (PDH) activity (independently of mTORC1) and shifts pyruvate metabolism toward lactate production in SCs. The increased lactate causes age-dependent peripheral axon degeneration, affecting peripheral nerve function. Lactate, as an energy substrate and a potential signaling molecule, enhanced neuronal mitochondrial metabolism and energy production of peripheral nerves. Albeit beneficial to injured peripheral axons in the short term, we show that persistently increased lactate metabolism of neurons enhances ROS production, eventually damaging mitochondria, neuroenergetics, and axon stability. This study highlights the complex roles of lactate metabolism to peripheral axons and the importance of lactate homeostasis in preserving peripheral nerves.

Rheb mediates neuronal-activity-induced mitochondrial energetics through mTORC1-independent PDH activation.

Neuronal activity increases energy consumption and requires balanced production to maintain neuronal function. How activity is coupled to energy production remains incompletely understood. Here, we report that Rheb regulates mitochondrial tricarboxylic acid cycle flux of acetyl-CoA by activating pyruvate dehydrogenase (PDH) to increase ATP production. Rheb is induced by synaptic activity and lactate and dynamically trafficked to the mitochondrial matrix through its interaction with Tom20. Mitochondria-localized Rheb protein is required for activity-induced PDH activation and ATP production. Cell-type-specific gain- and loss-of-function genetic models for Rheb reveal reciprocal changes in PDH phosphorylation/activity, acetyl-CoA, and ATP that are not evident with genetic or pharmacological manipulations of mTORC1. Mechanistically, Rheb physically associates with PDH phosphatase (PDP), enhancing its activity and association with the catalytic E1α-subunit of PDH to reduce PDH phosphorylation and increase its activity. Findings identify Rheb as a nodal point that balances neuronal activity and neuroenergetics via Rheb-PDH axis.