Decreased HMGCS1 inhibits proliferation and inflammatory response of keratinocytes and ameliorates imiquimod-induced psoriasis via the STAT3/IL-23 axis.

Psoriasis is an immuno-inflammatory disease characterized by excessive keratinocyte proliferation, requiring extensive lipids. 3-hydroxy-3-methylglutaryl-coenzyme A synthase 1 (HMGCS1) is an essential enzyme in the mevalonate pathway, involved in cholesterol synthesis and the inflammatory response. However, the role of HMGCS1 in psoriasis has remained elusive. This study aims to elucidate the mechanism by which HMGCS1 controls psoriasiform inflammation. We discovered an increased abundance of HMGCS1 in psoriatic lesions when analyzing two Gene Expression Omnibus (GEO) datasets and confirmed this in psoriatic animal models and psoriatic patients by immunohistochemistry. In a TNF-α stimulated psoriatic HaCaT cell line, HMGCS1 was found to be overexpressed. Knockdown of HMGCS1 using siRNA suppressed the migration and proliferation of HaCaT cells. Mechanistically, HMGCS1 downregulation also reduced the expression of IL-23 and the STAT3 phosphorylation level. In imiquimod-induced psoriatic mice, intradermal injection of HMGCS1 siRNA significantly decreased the expression of HMGCS1 in the epidermis, which in turn led to an improvement in the Psoriasis Area and Severity Index score, epidermal thickening, and pathological Baker score. Additionally, expression levels of inflammatory cytokines IL-23, IL1-ß, chemokine CXCL1, and innate immune mediator S100A7-9 were downregulated in the epidermis. In conclusion, HMGCS1 downregulation improved psoriasis in vitro and in vivo through the STAT3/IL-23 axis.

Downregulation of HMGCS2 mediated AECIIs lipid metabolic alteration promotes pulmonary fibrosis by activating fibroblasts.

BACKGROUND: Abnormal lipid metabolism has recently been reported as a crucial signature of idiopathic pulmonary fibrosis (IPF). However, the origin and biological function of the lipid and possible mechanisms of increased lipid content in the pathogenesis of IPF remains undetermined. METHODS: Oil-red staining and immunofluorescence analysis were used to detect lipid accumulation in mouse lung fibrosis frozen sections, Bleomycin-treated human type II alveolar epithelial cells (AECIIs) and lung fibroblast. Untargeted Lipid omics analysis was applied to investigate differential lipid species and identified LysoPC was utilized to treat human lung fibroblasts and mice. Microarray and single-cell RNA expression data sets identified lipid metabolism-related differentially expressed genes. Gain of function experiment was used to study the function of 3-hydroxy-3-methylglutaryl-Coa Synthase 2 (HMGCS2) in regulating AECIIs lipid metabolism. Mice with AECII-HMGCS2 high were established by intratracheally delivering HBAAV2/6-SFTPC- HMGCS2 adeno-associated virus. Western blot, Co-immunoprecipitation, immunofluorescence, site-directed mutation and flow cytometry were utilized to investigate the mechanisms of HMGCS2-mediated lipid metabolism in AECIIs. RESULTS: Injured AECIIs were the primary source of accumulated lipids in response to Bleomycin stimulation. LysoPCs released by injured AECIIs could activate lung fibroblasts, thus promoting the progression of pulmonary fibrosis. Mechanistically, HMGCS2 was decreased explicitly in AECIIs and ectopic expression of HMGCS2 in AECIIs using the AAV system significantly alleviated experimental mouse lung fibrosis progression via modulating lipid degradation in AECIIs through promoting CPT1A and CPT2 expression by interacting with PPARα. CONCLUSIONS: These data unveiled a novel etiological mechanism of HMGCS2-mediated AECII lipid metabolism in the genesis and development of pulmonary fibrosis and provided a novel target for clinical intervention.

Liver-Derived Ketogenesis via Overexpressing HMGCS2 Promotes the Recovery of Spinal Cord Injury.

The liver is the major ketogenic organ of the body, and ketones are reported to possess favorable neuroprotective effects. This study aims to elucidate whether ketone bodies generated from the liver play a critical role in bridging the liver and spinal cord. Mice model with a contusive spinal cord injury (SCI) surgery is established, and SCI induces significant histological changes in mice liver. mRNA-seq of liver tissue shows the temporal changes of ketone bodies-related genes, ß-hydroxybutyrate dehydrogenase (BDH1) and solute carrier family 16 (monocarboxylic acid transporters), member 6 (SLC16A6). Then, an activated ketogenesis model is created with adult C57BL/6 mice receiving the tail intravenous injection of GPAAV8-TBG-Mouse-Hmgcs2-CMV- mCherry -WPRE (HMGCS2liver ) and mice receiving equal AAV8-Null being the control group (Vectorliver ). Then, the mice undergo either a contusive SCI or sham surgery. The results show that overexpression of HMG-CoA synthase (Hmgcs2) in mice liver dramatically alleviates SCI-mediated pathological changes and promotes ketogenesis in the liver. Amazingly, liver-derived ketogenesis evidently alleviates neuron apoptosis and inflammatory microglia activation and improves the recovery of motor function of SCI mice. In conclusion, a liver-spinal cord axis can be bridged via ketone bodies, and enhancing the production of the ketone body within the liver has neuroprotective effects on traumatic SCI.

Metabolic regulation in erythroid differentiation by systemic ketogenesis in fasted mice.

Erythroid terminal differentiation and maturation depend on an enormous energy supply. During periods of fasting, ketone bodies from the liver are transported into circulation and utilized as crucial fuel for peripheral tissues. However, the effects of fasting or ketogenesis on erythroid behavior remain unknown. Here, we generated a mouse model with insufficient ketogenesis by conditionally knocking out the gene encoding the hepatocyte-specific ketogenic enzyme hydroxymethylglutary-CoA synthase 2 (Hmgcs2 KO). Intriguingly, erythroid maturation was enhanced with boosted fatty acid synthesis in the bone marrow of a hepatic Hmgcs2 KO mouse under fasting conditions, suggesting that systemic ketogenesis has a profound effect on erythropoiesis. Moreover, we observed significantly activated fatty acid synthesis and mevalonate pathways along with reduced histone acetylation in immature erythrocytes under a less systemic ketogenesis condition. Our findings revealed a new insight into erythroid differentiation, in which metabolic homeostasis and histone acetylation mediated by ketone bodies are essential factors in adaptation toward nutrient deprivation and stressed erythropoiesis.

Mitochondrial 3-hydroxymethylglutaryl-CoA synthase-2 (HMGCS2) deficiency: a rare case with bicytopenia and coagulopathy.

Mitochondrial 3-hydroxymethylglutaryl-CoA synthase-2 (HMGCS2) is the main enzyme involved in ketogenesis. It is an essential enzyme for the catalysis of ß-oxidation-derived-acetyl-CoA and acetoacetyl Co-A to produce ß-hydroxy-ß-methylglutaryl-CoA (HMG-CoA) and free coenzyme A.The deficiency of this enzyme (3-hydoxy-3-methylglutaryl-CoA synthase) is a very rare metabolic disorder with limited cases described in the literature. The manifestations of this disease include hypoketotic hypoglycaemia, metabolic acidosis, lethargy, hepatomegaly with fatty liver and encephalopathy.We report a middle childhood male who presented with hepatosplenomegaly, lymphadenopathy and bicytopenia. The case was diagnosed by the whole exome sequencing which revealed a homozygous missense variant of uncertain significance in HMGCS2 gene.

Sodium butyrate activates HMGCS2 to promote ketone body production through SIRT5-mediated desuccinylation.

Ketone bodies have beneficial metabolic activities, and the induction of plasma ketone bodies is a health promotion strategy. Dietary supplementation of sodium butyrate (SB) is an effective approach in the induction of plasma ketone bodies. However, the cellular and molecular mechanisms are unknown. In this study, SB was found to enhance the catalytic activity of 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), a rate-limiting enzyme in ketogenesis, to promote ketone body production in hepatocytes. SB administrated by gavage or intraperitoneal injection significantly induced blood ß-hydroxybutyrate (BHB) in mice. BHB production was induced in the primary hepatocytes by SB. Protein succinylation was altered by SB in the liver tissues with down-regulation in 58 proteins and up-regulation in 26 proteins in the proteomics analysis. However, the alteration was mostly observed in mitochondrial proteins with 41% down- and 65% up-regulation, respectively. Succinylation status of HMGCS2 protein was altered by a reduction at two sites (K221 and K358) without a change in the protein level. The SB effect was significantly reduced by a SIRT5 inhibitor and in Sirt5-KO mice. The data suggests that SB activated HMGCS2 through SIRT5-mediated desuccinylation for ketone body production by the liver. The effect was not associated with an elevation in NAD+/NADH ratio according to our metabolomics analysis. The data provide a novel molecular mechanism for SB activity in the induction of ketone body production.

HMGCS2-Induced Autophagic Degradation of Tau Involves Ketone Body and ANKRD24.

BACKGROUND: Accumulation of hyperphosphorylated Tau (pTau) contributes to the formation of neurofibrillary tangles in Alzheimer's disease (AD), and targeting Tau/pTau metabolism has emerged as a therapeutic approach. We have previously reported that mitochondrial 3-hydroxy-3-methylglutaryl-COA synthase 2 (HMGCS2) is involved in AD by promoting autophagic clearance of amyloid-ß protein precursor via ketone body-associated mechanism, whether HMGCS2 may also regulate Tau metabolism remains elusive. OBJECTIVE: The present study was to investigate the role of HMGCS2 in Tau/p degradation. METHODS: The protein levels of Tau and pTau including pT217 and pT181, as well as autophagic markers LAMP1 and LC3-II were assessed by western blotting. The differentially regulated genes by HMGCS2 were analyzed by RNA sequencing. Autophagosomes were assessed by transmission electron microscopy. RESULTS: HMGCS2 significantly decreased Tau/pTau levels, which was paralleled by enhanced formation of autophagic vacuoles and prevented by autophagic regulators chloroquine, bafilomycin A1, 3-methyladenine, and rapamycin. Moreover, HMGCS2-induced alterations of LAMP1/LC3-II and Tau/pTau levels were mimicked by ketone body acetoacetate or ß-hydroxybutyrate. Further RNA-sequencing identified ankyrin repeat domain 24 (ANKRD24) as a target gene of HMGCS2, and silencing of ANKRD24 reduced LAMP1/LC3-II levels, which was accompanied by the altered formation of autophagic vacuoles, and diminished the effect of HMGCS2 on Tau/pTau. CONCLUSION: HMGCS2 promoted autophagic clearance of Tau/pTau, in which ketone body and ANKRD24 played an important role.

Compartmentalized activities of HMGCS1 control cervical cancer radiosensitivity.

The underlying mechanisms by which cellular metabolism affects cervical cancer cell radiosensitivity remain poorly understood. Here, we found that loss of 3-hydroxy-3-methylglutaryl coenzyme A synthase 1 (HMGCS1), a key enzyme catalyzing the conversion of acetoacetyl-CoA to HMG-CoA in the cholesterol biosynthesis pathway, sensitizes the cervical cancer cells to radiation. We observed a compartmentalized cellular distribution of HMGCS1 in nuclei, cytosol, and mitochondria of cervical cancer cells and found that cytosolic HMGCS1 and mitochondrial HMGCS1 contribute together to the regulation of radiosensitivity. Mechanistically, we show that cytosolic HMGCS1 regulates radiosensitivity via manipulating the cholesterol metabolism, while mitochondrial HMGCS1 controls mitochondrial gene expression, thereby sustaining the mitochondrial function of cervical cancer cells. Together, our study identifies HMGCS1 as a novel regulator of radiosensitivty in cervical cancer cells, providing a molecular link between altered cholesterol metabolism, mitochondrial respiration, and radiosensitivity. Thus, targeting HMGCS1 may improve the therapeutic outcome of cervical cancer radiotherapy.

HMGCS2 Mediation of Ketone Levels Affects Sorafenib Treatment Efficacy in Liver Cancer Cells.

Primary liver cancer is the fifth leading death of cancers in men, and hepatocellular carcinoma (HCC) accounts for approximately 90% of all primary liver cancer cases. Sorafenib is a first-line drug for advanced-stage HCC patients. Sorafenib is a multi-target kinase inhibitor that blocks tumor cell proliferation and angiogenesis. Despite sorafenib treatment extending survival, some patients experience side effects, and sorafenib resistance does occur. 3-Hydroxymethyl glutaryl-CoA synthase 2 (HMGCS2) is the rate-limiting enzyme for ketogenesis, which synthesizes the ketone bodies, ß-hydroxybutyrate (ß-HB) and acetoacetate (AcAc). ß-HB is the most abundant ketone body which is present in a 4:1 ratio compared to AcAc. Recently, ketone body treatment was found to have therapeutic effects against many cancers by causing metabolic alternations and cancer cell apoptosis. Our previous publication showed that HMGCS2 downregulation-mediated ketone body reduction promoted HCC clinicopathological progression through regulating c-Myc/cyclin D1 and caspase-dependent signaling. However, whether HMGCS2-regulated ketone body production alters the sensitivity of human HCC to sorafenib treatment remains unclear. In this study, we showed that HMGCS2 downregulation enhanced the proliferative ability and attenuated the cytotoxic effects of sorafenib by activating expressions of phosphorylated (p)-extracellular signal-regulated kinase (ERK), p-P38, and p-AKT. In contrast, HMGCS2 overexpression decreased cell proliferation and enhanced the cytotoxic effects of sorafenib in HCC cells by inhibiting ERK activation. Furthermore, we showed that knockdown HMGCS2 exhibited the potential migratory ability, as well as decreasing zonula occludens protein (ZO)-1 and increasing c-Myc expression in both sorafenib-treated Huh7 and HepG2 cells. Although HMGCS2 overexpression did not alter the migratory effect, expressions of ZO-1, c-Myc, and N-cadherin decreased in sorafenib-treated HMGCS2-overexpressing HCC cells. Finally, we investigated whether ketone treatment influences sorafenib sensitivity. We showed that ß-HB pretreatment decreased cell proliferation and enhanced antiproliferative effect of sorafenib in both Huh7 and HepG2 cells. In conclusion, this study defined the impacts of HMGCS2 expression and ketone body treatment on influencing the sorafenib sensitivity of liver cancer cells.

Antidiabetic drug metformin suppresses tumorigenesis through inhibition of mevalonate pathway enzyme HMGCS1.

Metformin, an antidiabetic drug, shows some potent antitumor effects. However, the molecular mechanism of metformin in tumor suppression has not been clarified. Here, we provided evidence using in vitro and in vivo data that metformin inhibited mevalonate pathway by downregulation of 3-hydroxy-3-methylglutaryl-CoA synthase 1 (HMGCS1), a key enzyme in this pathway. Our results further demonstrated that metformin downregulated HMGCS1 expression through inhibition of transcription factor nuclear factor E2-related factor 2. In addition, we determined that HMGCS1 was highly expressed in human liver and lung cancer tissues and associated with lower survival rates. In summary, our study indicated that metformin suppresses tumorigenesis through inhibition of the nuclear factor E2-related factor 2-HMGCS1 axis, which might be a potential target in cancer prevention and treatment.

TET2 deficiency sensitizes tumor cells to statins by reducing HMGCS1 expression.

TET2 (ten-eleven-translocation) protein is a Fe(II)- and α-ketoglutarate-dependent dioxygenase that catalyzes DNA demethylation to regulate gene expression. While TET2 gene is frequently mutated in hematological cancer, its enzymatic activity is also compromised in various solid tumors. Whether TET2 deficiency creates vulnerability for cancer cells has not been studied. Here we reported that TET2 deficiency is associated with the change of lipid metabolism processes in acute myeloid leukemia (AML) patient. We demonstrate that statins, the inhibitors of ß-Hydroxy ß-methylglutaryl-CoA (HMG-CoA) reductase and commonly used cholesterol-lowering medicines, significantly sensitize TET2 deficient tumor cells to apoptosis. TET2 directly regulates the expression of HMG-CoA synthase (HMGCS1) by catalyzing demethylation on its promoter region, and conversely TET2 deficiency leads to significant down-regulation of HMGCS1 expression and the mevalonate pathway. Consistently, overexpression of HMGCS1 in TET2-deficient cells rescues statin-induced apoptosis. We further reveal that decrease of geranylgeranyl diphosphate (GGPP), an intermediate metabolite in the mevalonate pathway, is responsible for statin-induced apoptosis. GGPP shortage abolishes normal membrane localization and function of multiple small GTPases, leading to cell dysfunction. Collectively, our study reveals a vulnerability in TET2 deficient tumor and a potential therapeutic strategy using an already approved safe medicine.

An acetate-independent pathway for isopropanol production via HMG-CoA in Escherichia coli.

Isopropanol has a good potential as a new fuel substitution. In the model biosynthesis pathway of isopropanol synthesis, acetoacetyl-CoA is converted to acetoacetate by acetoacetyl-CoA transferases, which requires an acetate molecule as a substrate. Herein, a novel isopropanol synthesis pathway based on mammalian ketone metabolic pathway was developed. In this pathway, acetoacetyl-CoA is condensed with acetyl-CoA to generate 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) by HMG-CoA synthase, and then catalyzed by HMG-CoA lyase to generate acetoacetate. This process is acetate-independent. Under the same experimental system using glycerol as carbon source, the E. coli strain MG::ISOP1 containing the novel pathway produced 11.7 times more isopropanol than the strain MG::ISOP0 containing the model pathway. The pta-ackA knockout mutant strain MG∆pta-ackA::ISOP1, which reduced the conversion of acetyl-CoA to acetate, further increased the production from 76 mg/L to 360 mg/L. In another strategy, knocking out atoDA to block the acetoacetate degradation pathway in strain MG∆atoDA::ISOP1 increased the production to 680 mg/L. By knocking out both of pta-ackA and atoDA, strain MGΔpta-ackAΔatoDA::ISOP1 produced 964 mg/L of isopropanol, which was 12.7 times that of MG::ISOP1. This study indicated that the novel pathway is competent for isopropanol synthesis, and provides a new perspective for biosynthesis of isopropanol.

Hmgcs2-mediated ketogenesis modulates high-fat diet-induced hepatosteatosis.

OBJECTIVE: Aberrant ketogenesis is correlated with the degree of steatosis in non-alcoholic fatty liver disease (NAFLD) patients, and an inborn error of ketogenesis (mitochondrial HMG-CoA synthase deficiency) is commonly associated with the development of the fatty liver. Here we aimed to determine the impact of Hmgcs2-mediated ketogenesis and its modulations on the development and treatment of fatty liver disease. METHODS: Loss- and gain-of-ketogenic function models, achieved by Hmgcs2 knockout and overexpression, respectively, were utilized to investigate the role of ketogenesis in the hepatic lipid accumulation during postnatal development and in a high-fat diet-induced NAFLD mouse model. RESULTS: Ketogenic function was decreased in NAFLD mice with a reduction in Hmgcs2 expression. Mice lacking Hmgcs2 developed spontaneous fatty liver phenotype during postnatal development, which was rescued by a shift to a low-fat dietary composition via early weaning. Hmgcs2 heterozygous adult mice, which exhibited lower ketogenic activity, were more susceptible to diet-induced NAFLD development, whereas HMGCS2 overexpression in NAFLD mice improved hepatosteatosis and glucose homeostasis. CONCLUSIONS: Our study adds new knowledge to the field of ketone body metabolism and shows that Hmgcs2-mediated ketogenesis modulates hepatic lipid regulation under a fat-enriched nutritional environment. The regulation of hepatic ketogenesis may be a viable therapeutic strategy in the prevention and treatment of hepatosteatosis.

Fasting-induced HMGCS2 expression in the kidney does not contribute to circulating ketones.

Mitochondrial hydroxymethylglutaryl-CoA synthase 2 (HMGCS2) is the rate-limiting enzyme in ketogenesis. The liver expresses high levels of HMGCS2 constitutively as the main ketogenic organ. It has been suggested that the kidney could be ketogenic as HMGCS2 is expressed in the kidney during fasting and diabetic conditions. However, definitive proof of the capacity for the kidney to produce ketones is lacking. We demonstrated that during fasting, HMGCS2 expression is induced in the proximal tubule of the kidney and is peroxisome proliferator activated receptor-α dependent. Mice with kidney-specific Hmgcs2 deletion showed a minor, likely physiologically insignificant, decrease in circulating ketones during fasting. Conversely, liver-specific Hmgcs2 knockout mice exhibited a complete loss of fasting ketosis. Together, these findings indicate that renal HMGCS2 does not significantly contribute to global ketone production and that during fasting, the increase in circulating ketones is solely dependent on hepatic HMGCS2. Proximal tubule HMGCS2 serves functions other than systemic ketone provision.NEW & NOTEWORTHY The mitochondrial enzyme hydroxymethylglutaryl-CoA synthase 2 (HMGCS2) catalyzes the rate-limiting step of ketogenesis. Although the liver constitutively expresses HMGCS2 and is considered the main ketogenic organ, HMGCS2 is induced in the kidney during fasting, leading to the proposal that the kidney contributes to fasting ketosis. We showed kidney HMGCS2 does not contribute to circulating ketones during fasting and cannot compensate for hepatic ketogenic insufficiency.

Pan-cancer analysis reveals the oncogenic role of 3-hydroxy-3-methylglutaryl-CoA synthase 1.

BACKGROUND: Emerging studies reveals that 3-hydroxy-3-methylglutaryl-CoA synthase 1 (HMGCS1) plays vital oncogenic roles in a broad spectrum of human cancers, but there is no pan-cancer evidence on the relationship between HMGCS1 and various tumor types. AIM: To explore the potential role of HMGCS1 across various tumor types based on big clinical data. METHODS: We conducted a pan-cancer analysis across more than 30 tumor types, based on the most comprehensive database available, including TCGA, GSCA, clinical proteomic tumor analysis consortium, Kaplan-Meier Plotter dataset, GEPIA2, TIMER2, STRING, and GDSC dataset. RESULTS: HMGCS1 was highly expressed and negatively correlated with the prognosis in most cancer types. The infiltration levels of cancer associated fibroblast and CD8+ T-cell were closely associated with HMGCS1 expression. Amplification was the most common genetic alteration of HMGCS1 in different cancers, while the frequency of mutation was low. Besides, ACAT2 and MVD were closely correlated and bind to HMGCS1. Pathway enrichment analysis indicated that HMGCS1 was actively involved in steroid biosynthesis. Moreover, high HMGCS1 expression could reduce the sensitivity to most drugs in the GDSC dataset. CONCLUSIONS: Our study revealed the potential oncogenic role of HMGCS1 in cancers.

PXR Suppresses PPARα-Dependent HMGCS2 Gene Transcription by Inhibiting the Interaction between PPARα and PGC1α.

BACKGROUND: PXR is a xenobiotic-responsive nuclear receptor that controls the expression of drug-metabolizing enzymes. Drug-induced activation of PXR sometimes causes drug-drug interactions due to the induced metabolism of co-administered drugs. Our group recently reported a possible drug-drug interaction mechanism via an interaction between the nuclear receptors CAR and PPARα. As CAR and PXR are structurally and functionally related receptors, we investigated possible crosstalk between PXR and PPARα. METHODS: Human hepatocyte-like HepaRG cells were treated with various PXR ligands, and mRNA levels were determined by quantitative reverse transcription PCR. Reporter assays using the HMGCS2 promoter containing a PPARα-binding motif and mammalian two-hybrid assays were performed in HepG2 or COS-1 cells. RESULTS: Treatment with PXR activators reduced the mRNA levels of PPARα target genes in HepaRG cells. In reporter assays, PXR suppressed PPARα-dependent gene expression in HepG2 cells. In COS-1 cells, co-expression of PGC1α, a common coactivator of PPARα and PXR, enhanced PPARα-dependent gene transcription, which was clearly suppressed by PXR. Consistently, in mammalian two-hybrid assays, the interaction between PGC1α and PPARα was attenuated by ligand-activated PXR. CONCLUSION: The present results suggest that ligand-activated PXR suppresses PPARα-dependent gene expression by inhibiting PGC1α recruitment.

Epigenetic inactivation of hydroxymethylglutaryl CoA synthase reduces ketogenesis and facilitates tumor cell motility in clear cell renal carcinoma.

Previously, we have reported that the dysregulation of ketogenesis plays an important role in the carcinogenesis of clear cell renal cell carcinoma (ccRCC). Here, we demonstrate decreased expression of the HMGCS2 gene in ccRCC, a critical enzyme for the synthesis of the ketone body ß-hydroxybutyrate (ß-OHB). We found that the reduced transcription of the HMGCS2 gene in ccRCC cells was significantly correlated to a higher relative methylation rate in its promotor region. The higher methylation rate in the region of the transcription start site and 1st exon of the HMGCS2 gene was, in turn, correlated with a worse clinical outcome for patients. The transcription of HMGCS2 was possible to restore by treatment with 5-aza-2'-deoxycytidine and with the histone deacetylase inhibitor ß-OHB. Therefore, the low levels of the HMGCS2 enzyme in ccRCC may be the consequence of hypermethylation of the HMGCS2 promotor. The ensuing reduction in the ketone body levels further suppresses the transcription of HMGCS2 via a feedback loop. Ectopic expression of HMGCS2 attenuates the migration and invasion of ccRCC but does not affect the proliferative capacity of ccRCC cells in vitro. In addition, we showed that ectopic expression of HMGCS2 boosts the intracellular levels of ß-OHB and that exogenously applied ß-OHB suppresses the motility and invasion of ccRCC. Our study reveals crosstalk between genes that regulate metabolism and their metabolites, thus providing a better understanding of the epigenetic mechanism involved in ccRCC carcinogenesis and suggesting opportunities for metabolic therapy of tumors. Initially, we suggest that the mRNA level of HMGCS2 could serve as a potentially valuable diagnostic (AUC = 0.918, p < 0.001) and prognostic biomarker.

Why the diabetic heart is energy inefficient: a ketogenesis and ketolysis perspective.

Lack of glucose uptake compromises metabolic flexibility and reduces energy efficiency in the diabetes mellitus (DM) heart. Although increased use of fatty acid to compensate glucose substrate has been studied, less is known about ketone body metabolism in the DM heart. Ketogenic diet reduces obesity, a risk factor for T2DM. How ketogenic diet affects ketone metabolism in the DM heart remains unclear. At the metabolic level, the DM heart differs from the non-DM heart because of altered metabolic substrate and the T1DM heart differs from the T2DM heart because of insulin levels. How these changes affect ketone body metabolism in the DM heart are poorly understood. Ketogenesis produces ketone bodies by using acetyl-CoA, whereas ketolysis consumes ketone bodies to produce acetyl-CoA, showing their opposite roles in the ketone body metabolism. Cardiac-specific transgenic upregulation of ketogenesis enzyme or knockout of ketolysis enzyme causes metabolic abnormalities leading to cardiac dysfunction. Empirical evidence demonstrates upregulated transcription of ketogenesis enzymes, no change in the levels of ketone body transporters, very high levels of ketone bodies, and reduced expression and activity of ketolysis enzymes in the T1DM heart. Based on these observations, I hypothesize that increased transcription and activity of cardiac ketogenesis enzyme suppresses ketolysis enzyme in the DM heart, which decreases cardiac energy efficiency. The T1DM heart exhibits highly upregulated ketogenesis compared with the T2DM heart because of the lack of insulin, which inhibits ketogenesis enzyme.

circHMGCS1-016 reshapes immune environment by sponging miR-1236-3p to regulate CD73 and GAL-8 expression in intrahepatic cholangiocarcinoma.

BACKGROUND: Accumulating evidence indicates that circRNAs may serve as essential regulators in the progression of several human cancers, but the function and mechanism of circRNAs in intrahepatic cholangiocarcinoma (ICC) are largely unknown. METHODS: RNA-seq was used to assess differentially expressed circRNAs between 4 ICC and peritumor tissues. Quantitative RT-PCR and in situ hybridization were used to determine the circHMGCS1-016 expression in ICC tissues. The function and mechanism of circHMGCS1-016 were further identified via in vivo experiments. The clinical characteristics and prognostic significance of circHMGCS1-016 were analyzed by a retrospective study. The functions of circHMGCS1-016 were assessed via modifying circRNA expression in ICC cells. Moreover, the molecular mechanisms of circHMGCS1-016 in ICC cells were explored by circRNA precipitation, miRNA immunoprecipitation, SILAC and luciferase reporter assays. RESULTS: We identified that compared with peritumor tissues, ICC tissues expressed hsa_circ_0008621 (circHMGCS1-016) high by RNA-seq, which was further identified by qRT-PCR and in situ hybridization. Moreover, the expression of circHMGCS1-016 was revealed to be associated with survival and recurrence of ICC patients. By regulating circHMGCS1-016 expression, we found that elevated circHMGCS1-016 promoted ICC development both in vitro and in vivo. By SILAC and circRNA-pull down, we demonstrated that circHMGCS1-016 induced ICC cell invasion and reshaped the tumor immune microenvironment via the miR-1236-3p/CD73 and GAL-8 axis. In ICC tissues, we uncovered that a high level of circHMGCS1-016 was positively associated with CD73 and GAL-8 expression and negatively related to the CD8+ T cells infiltration, which was further validated by establishing a humanized mouse tumor model. Importantly, we displayed that ICC patients with high levels of circHMGCS1-016 in tumor tissues benefited less from anti-PD1 treatment compared to those with low levels of circHMGCS1-016. CONCLUSIONS: CircHMGCS1-016 is a forceful contributor in ICC development and immune tolerance via miR-1236-3p/CD73 and GAL-8 axis. CircHMGCS1-016 can be explored as a new potential biomarker and therapeutic target for PD1-resistant ICC.

TDP-43 mediates SREBF2-regulated gene expression required for oligodendrocyte myelination.

Cholesterol metabolism operates autonomously within the central nervous system (CNS), where the majority of cholesterol resides in myelin. We demonstrate that TDP-43, the pathological signature protein for amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), influences cholesterol metabolism in oligodendrocytes. TDP-43 binds directly to mRNA of SREBF2, the master transcription regulator for cholesterol metabolism, and multiple mRNAs encoding proteins responsible for cholesterol biosynthesis and uptake, including HMGCR, HMGCS1, and LDLR. TDP-43 depletion leads to reduced SREBF2 and LDLR expression, and cholesterol levels in vitro and in vivo. TDP-43-mediated changes in cholesterol levels can be restored by reintroducing SREBF2 or LDLR. Additionally, cholesterol supplementation rescues demyelination caused by TDP-43 deletion. Furthermore, oligodendrocytes harboring TDP-43 pathology from FTD patients show reduced HMGCR and HMGCS1, and coaggregation of LDLR and TDP-43. Collectively, our results indicate that TDP-43 plays a role in cholesterol homeostasis in oligodendrocytes, and cholesterol dysmetabolism may be implicated in TDP-43 proteinopathies-related diseases.