Glycerol phosphate shuttle enzyme GPD2 regulates macrophage inflammatory responses.

Macrophages are activated during microbial infection to coordinate inflammatory responses and host defense. Here we find that in macrophages activated by bacterial lipopolysaccharide (LPS), mitochondrial glycerol 3-phosphate dehydrogenase (GPD2) regulates glucose oxidation to drive inflammatory responses. GPD2, a component of the glycerol phosphate shuttle, boosts glucose oxidation to fuel the production of acetyl coenzyme A, acetylation of histones and induction of genes encoding inflammatory mediators. While acute exposure to LPS drives macrophage activation, prolonged exposure to LPS triggers tolerance to LPS, where macrophages induce immunosuppression to limit the detrimental effects of sustained inflammation. The shift in the inflammatory response is modulated by GPD2, which coordinates a shutdown of oxidative metabolism; this limits the availability of acetyl coenzyme A for histone acetylation at genes encoding inflammatory mediators and thus contributes to the suppression of inflammatory responses. Therefore, GPD2 and the glycerol phosphate shuttle integrate the extent of microbial stimulation with glucose oxidation to balance the beneficial and detrimental effects of the inflammatory response.

Uncoupled glycerol-3-phosphate shuttle in kidney cancer reveals that cytosolic GPD is essential to support lipid synthesis.

The glycerol-3-phosphate shuttle (G3PS) is a major NADH shuttle that regenerates reducing equivalents in the cytosol and produces energy in the mitochondria. Here, we demonstrate that G3PS is uncoupled in kidney cancer cells where the cytosolic reaction is ∼4.5 times faster than the mitochondrial reaction. The high flux through cytosolic glycerol-3-phosphate dehydrogenase (GPD) is required to maintain redox balance and support lipid synthesis. Interestingly, inhibition of G3PS by knocking down mitochondrial GPD (GPD2) has no effect on mitochondrial respiration. Instead, loss of GPD2 upregulates cytosolic GPD on a transcriptional level and promotes cancer cell proliferation by increasing glycerol-3-phosphate supply. The proliferative advantage of GPD2 knockdown tumor can be abolished by pharmacologic inhibition of lipid synthesis. Taken together, our results suggest that G3PS is not required to run as an intact NADH shuttle but is instead truncated to support complex lipid synthesis in kidney cancer.

A ferroptosis defense mechanism mediated by glycerol-3-phosphate dehydrogenase 2 in mitochondria.

Mechanisms of defense against ferroptosis (an iron-dependent form of cell death induced by lipid peroxidation) in cellular organelles remain poorly understood, hindering our ability to target ferroptosis in disease treatment. In this study, metabolomic analyses revealed that treatment of cancer cells with glutathione peroxidase 4 (GPX4) inhibitors results in intracellular glycerol-3-phosphate (G3P) depletion. We further showed that supplementation of cancer cells with G3P attenuates ferroptosis induced by GPX4 inhibitors in a G3P dehydrogenase 2 (GPD2)-dependent manner; GPD2 deletion sensitizes cancer cells to GPX4 inhibition-induced mitochondrial lipid peroxidation and ferroptosis, and combined deletion of GPX4 and GPD2 synergistically suppresses tumor growth by inducing ferroptosis in vivo. Mechanistically, inner mitochondrial membrane-localized GPD2 couples G3P oxidation with ubiquinone reduction to ubiquinol, which acts as a radical-trapping antioxidant to suppress ferroptosis in mitochondria. Taken together, these results reveal that GPD2 participates in ferroptosis defense in mitochondria by generating ubiquinol.

Dual-function AzuCR RNA modulates carbon metabolism.

SignificanceWhile most small, regulatory RNAs are thought to be "noncoding," a few have been found to also encode a small protein. Here we describe a 164-nucleotide RNA that encodes a 28-amino acid, amphipathic protein, which interacts with aerobic glycerol-3-phosphate dehydrogenase and increases dehydrogenase activity but also base pairs with two mRNAs to reduce expression. The coding and base-pairing sequences overlap, and the two regulatory functions compete.

Mitochondrial Glycerol-3-Phosphate Dehydrogenase Restricts HBV Replication via the TRIM28-Mediated Degradation of HBx.

Hepatitis B virus (HBV) infection affects hepatic metabolism. Serum metabolomics studies have suggested that HBV possibly hijacks the glycerol-3-phosphate (G3P) shuttle. In this study, the two glycerol-3-phosphate dehydrogenases (GPD1 and GPD2) in the G3P shuttle were analyzed for determining their role in HBV replication and the findings revealed that GPD2 and not GPD1 inhibited HBV replication. The knockdown of GPD2 expression upregulated HBV replication, while GPD2 overexpression reduced HBV replication. Moreover, the overexpression of GPD2 significantly reduced HBV replication in hydrodynamic injection-based mouse models. Mechanistically, this inhibitory effect is related to the GPD2-mediated degradation of HBx protein by recruiting the E3 ubiquitin ligase TRIM28 and not to the alterations in G3P metabolism. In conclusion, this study revealed GPD2, a key enzyme in the G3P shuttle, as a host restriction factor in HBV replication. IMPORTANCE The glycerol-3-phosphate (G3P) shuttle is important for the delivery of cytosolic reducing equivalents into mitochondria for oxidative phosphorylation. The study analyzed two key components of the G3P shuttle and identified GPD2 as a restriction factor in HBV replication. The findings revealed a novel mechanism of GPD2-mediated inhibition of HBV replication via the recruitment of TRIM28 for degrading HBx, and the HBx-GPD2 interaction could be another potential therapeutic target for anti-HBV drug development.

The glycerol-3-phosphate dehydrogenases GpsA and GlpD constitute the oxidoreductive metabolic linchpin for Lyme disease spirochete host infectivity and persistence in the tick.

We have identified GpsA, a predicted glycerol-3-phosphate dehydrogenase, as a virulence factor in the Lyme disease spirochete Borrelia (Borreliella) burgdorferi: GpsA is essential for murine infection and crucial for persistence of the spirochete in the tick. B. burgdorferi has a limited biosynthetic and metabolic capacity; the linchpin connecting central carbohydrate and lipid metabolism is at the interconversion of glycerol-3-phosphate and dihydroxyacetone phosphate, catalyzed by GpsA and another glycerol-3-phosphate dehydrogenase, GlpD. Using a broad metabolomics approach, we found that GpsA serves as a dominant regulator of NADH and glycerol-3-phosphate levels in vitro, metabolic intermediates that reflect the cellular redox potential and serve as a precursor for lipid and lipoprotein biosynthesis, respectively. Additionally, GpsA was required for survival under nutrient stress, regulated overall reductase activity and controlled B. burgdorferi morphology in vitro. Furthermore, during in vitro nutrient stress, both glycerol and N-acetylglucosamine were bactericidal to B. burgdorferi in a GlpD-dependent manner. This study is also the first to identify a suppressor mutation in B. burgdorferi: a glpD deletion restored the wild-type phenotype to the pleiotropic gpsA mutant, including murine infectivity by needle inoculation at high doses, survival under nutrient stress, morphological changes and the metabolic imbalance of NADH and glycerol-3-phosphate. These results illustrate how basic metabolic functions that are dispensable for in vitro growth can be essential for in vivo infectivity of B. burgdorferi and may serve as attractive therapeutic targets.

GPD1L inhibits renal cell carcinoma progression by regulating PINK1/Parkin-mediated mitophagy.

Few approaches have been conducted in the treatment of renal cell carcinoma (RCC) after nephrectomy, resulting in a high mortality rate in urological tumours. Mitophagy is a mechanism of mitochondrial quality control that enables selective degradation of damaged and unnecessary mitochondria. Previous studies have found that glycerol-3-phosphate dehydrogenase 1-like (GPD1L) is associated with the progression of tumours such as lung cancer, colorectal cancer and oropharyngeal cancer, but the potential mechanism in RCC is still unclear. In this study, microarrays from tumour databases were analysed. The expression of GPD1L was confirmed by RT-qPCR and western blotting. The effect and mechanism of GPD1L were explored using cell counting kit 8, wound healing, invasion, flow cytometry and mitophagy-related experiments. The role of GPD1L was further confirmed in vivo. The results showed that GPD1L expression was downregulated and positively correlated with prognosis in RCC. Functional experiments revealed that GPD1L prevented proliferation, migration and invasion while promoting apoptosis and mitochondrial injury in vitro. The mechanistic results indicated that GPD1L interacted with PINK1, promoting PINK1/Parkin-mediated mitophagy. However, inhibition of PINK1 reversed GPD1L-mediated mitochondrial injury and mitophagy. Moreover, GPD1L prevented tumour growth and promoted mitophagy by activating the PINK1/Parkin pathway in vivo. Our study shows that GPD1L has a positive correlation with the prognosis of RCC. The potential mechanism involves interacting with PINK1 and regulating the PINK1/Parkin pathway. In conclusion, these results reveal that GPD1L can act as a biomarker and target for RCC diagnosis and therapy.

MicroRNA-210 Controls Mitochondrial Metabolism and Protects Heart Function in Myocardial Infarction.

BACKGROUND: Ischemic heart disease remains a leading cause of death worldwide. In this study, we test the hypothesis that microRNA-210 protects the heart from myocardial ischemia-reperfusion (IR) injury by controlling mitochondrial bioenergetics and reactive oxygen species (ROS) flux. METHODS: Myocardial infarction in an acute setting of IR was examined through comparing loss- versus gain-of-function experiments in microRNA-210-deficient and wild-type mice. Cardiac function was evaluated by echocardiography. Myocardial mitochondria bioenergetics was examined using a Seahorse XF24 Analyzer. RESULTS: MicroRNA-210 deficiency significantly exaggerated cardiac dysfunction up to 6 weeks after myocardial IR in male, but not female, mice. Intravenous injection of microRNA-210 mimic blocked the effect and recovered the increased myocardial IR injury and cardiac dysfunction. Analysis of mitochondrial metabolism revealed that microRNA-210 inhibited mitochondrial oxygen consumption, increased glycolytic activity, and reduced mitochondrial ROS flux in the heart during IR injury. Inhibition of mitochondrial ROS with MitoQ consistently reversed the effect of microRNA-210 deficiency. Mechanistically, we showed that mitochondrial glycerol-3-phosphate dehydrogenase is a novel target of microRNA-210 in the heart, and loss-of-function and gain-of-function experiments revealed that glycerol-3-phosphate dehydrogenase played a key role in the microRNA-210-mediated effect on mitochondrial metabolism and ROS flux in the setting of heart IR injury. Knockdown of glycerol-3-phosphate dehydrogenase negated microRNA-210 deficiency-induced increases in mitochondrial ROS production and myocardial infarction and improved left ventricular fractional shortening and ejection fraction after the IR treatment. CONCLUSIONS: MicroRNA-210 targeting glycerol-3-phosphate dehydrogenase controls mitochondrial bioenergetics and ROS flux and improves cardiac function in a murine model of myocardial infarction in the setting of IR injury. The findings suggest new insights into the mechanisms and therapeutic targets for treatment of ischemic heart disease.

[Effect of calcium-independent phospholipase A2 on the expression of glycerol 3-phosphate dehydrogenase in human non-alcoholic fatty liver disease cells].

Objective: To explore the effect of calcium-independent phospholipase A2 (iPLA2) on the expression of mitochondrial glycerol 3-phosphate dehydrogenase (mGPDH) in human non-alcoholic fatty liver disease cells. Methods: Oleic acid was used to construct a non-alcoholic fatty liver disease cell model by inducing lipid deposition in THLE-2 cells in vitro. Simultaneously, intracellular triglyceride content, iPLA2 expression levels, and mGPDH levels were determined at various induction times (0, 24, 48, and 72 h) using a triglyceride assay kit, quantitative RT-PCR, and western blotting. The model cells were treated with bromelenol lactone, an iPLA2 inhibitor, and N-acetylcysteine, a ROS inhibitor, respectively. Following continuous culture for 24 and 48 hours, the cells were harvested, and the mRNA and protein expression levels of mGPDH were measured. Statistical analysis was performed using the t-test, one-way analysis of variance, and linear correlation. Results: The intracellular triglyceride content gradually increased (P < 0.01), the mGPDH mRNA and protein expression decreased (P < 0.01), and the iPLA2 mRNA and protein expression increased (P < 0.01) in THLE-2 cells with the prolonging time effect of oleic acid therapy. In addition, the mGPDH mRNA expression level was negatively correlated with the iPLA2 mRNA level (r = -0.878, P = 0.002). The expression levels of mGPDH mRNA and protein in the iPLA2 inhibitor group and ROS inhibitor group were increased compared with the model control group (P < 0.01). The expression of mGPDH mRNA was increased at 24 h compared with 48 h in the iPLA2 inhibitor group (P < 0.01). The expression of mGPDH mRNA was gradually increased in the ROS inhibitor group with the prolongation of inhibitor action time (P < 0.01). Compared with the two inhibitor groups, the increase in mGPDH mRNA was significantly higher in the ROS inhibitor group than that in the iPLA2 inhibitor group, and the difference was statistically significant (P < 0.01). Conclusion: iPLA2 can inhibit the expression of mGPDH in non-alcoholic fatty liver cells to a certain extent.

Mitochondrial GCN5L1 regulates cytosolic redox state and hepatic gluconeogenesis via glycerol phosphate shuttle GPD2.

Hepatic gluconeogenesis is crucial for maintaining blood glucose during starvation, and a major contributor for hyperglycemia. Cellular redox state is related to mitochondrial biology and regulates conversion of specific metabolites to glucose. General control of amino acid synthesis 5 (GCN5) like-1 (GCN5L1) is a mitochondria-enriched protein which modulates glucose and amino acid metabolism. Here we show a new regulatory mode of GCN5L1 on gluconeogenesis using lactate and glycerol. We observed GCN5L1 deletion dramatically inhibited glucose production derived from glycerol and lactate, due to increased cytosolic redox state. The underlying mechanism is that GCN5L1 directly binds to the key component of mitochondrial shuttle glycerol phosphate dehydrogenase 2 (GPD2) and modulates its activity. These results have significant implications for understanding the physiological role and regulatory mechanism of mitochondrial shuttle in diabetes development and provide a novel therapeutic potential for diabetes.

Lactate dehydrogenase and glycerol-3-phosphate dehydrogenase cooperatively regulate growth and carbohydrate metabolism during Drosophila melanogaster larval development.

The dramatic growth that occurs during Drosophila larval development requires rapid conversion of nutrients into biomass. Many larval tissues respond to these biosynthetic demands by increasing carbohydrate metabolism and lactate dehydrogenase (LDH) activity. The resulting metabolic program is ideally suited for synthesis of macromolecules and mimics the manner by which cancer cells rely on aerobic glycolysis. To explore the potential role of Drosophila LDH in promoting biosynthesis, we examined how Ldh mutations influence larval development. Our studies unexpectedly found that Ldh mutants grow at a normal rate, indicating that LDH is dispensable for larval biomass production. However, subsequent metabolomic analyses suggested that Ldh mutants compensate for the inability to produce lactate by generating excess glycerol-3-phosphate (G3P), the production of which also influences larval redox balance. Consistent with this possibility, larvae lacking both LDH and G3P dehydrogenase (GPDH1) exhibit growth defects, synthetic lethality and decreased glycolytic flux. Considering that human cells also generate G3P upon inhibition of lactate dehydrogenase A (LDHA), our findings hint at a conserved mechanism in which the coordinate regulation of lactate and G3P synthesis imparts metabolic robustness to growing animal tissues.

Atrial myocyte-derived exosomal microRNA contributes to atrial fibrosis in atrial fibrillation.

BACKGROUND: Atrial fibrosis plays a critical role in the development of atrial fibrillation (AF). Exosomes are a promising cell-free therapeutic approach for the treatment of AF. The purposes of this study were to explore the mechanisms by which exosomes derived from atrial myocytes regulate atrial remodeling and to determine whether their manipulation facilitates the therapeutic modulation of potential fibrotic abnormalities during AF. METHODS: We isolated exosomes from atrial myocytes and patient serum, and microRNA (miRNA) sequencing was used to analyze exosomal miRNAs in exosomes derived from atrial myocytes and patient serum. mRNA sequencing and bioinformatics analyses corroborated the key genes that were direct targets of miR-210-3p. RESULTS: The miRNA sequencing analysis identified that miR-210-3p expression was significantly increased in exosomes from tachypacing atrial myocytes and serum from patients with AF. In vitro, the miR-210-3p inhibitor reversed tachypacing-induced proliferation and collagen synthesis in atrial fibroblasts. Accordingly, miR-210-3p knock out (KO) reduced the incidence of AF and ameliorated atrial fibrosis induced by Ang II. The mRNA sequencing analysis and dual-luciferase reporter assay showed that glycerol-3-phosphate dehydrogenase 1-like (GPD1L) is a potential target gene of miR-210-3p. The functional analysis suggested that GPD1L regulated atrial fibrosis via the PI3K/AKT signaling pathway. In addition, silencing GPD1L in atrial fibroblasts induced cell proliferation, and these effects were reversed by a PI3K inhibitor (LY294002). CONCLUSIONS: Atrial myocyte-derived exosomal miR-210-3p promoted cell proliferation and collagen synthesis by inhibiting GPD1L in atrial fibroblasts. Preventing pathological crosstalk between atrial myocytes and fibroblasts may be a novel target to ameliorate atrial fibrosis in patients with AF.

Depletion of cardiolipin induces major changes in energy metabolism in Trypanosoma brucei bloodstream forms.

The mitochondrial inner membrane glycerophospholipid cardiolipin (CL) associates with mitochondrial proteins to regulate their activities and facilitate protein complex and supercomplex formation. Loss of CL leads to destabilized respiratory complexes and mitochondrial dysfunction. The role of CL in an organism lacking a conventional electron transport chain (ETC) has not been elucidated. Trypanosoma brucei bloodstream forms use an unconventional ETC composed of glycerol-3-phosphate dehydrogenase and alternative oxidase (AOX), while the mitochondrial membrane potential (ΔΨm) is generated by the hydrolytic action of the Fo F1 -ATP synthase (aka Fo F1 -ATPase). We now report that the inducible depletion of cardiolipin synthase (TbCls) is essential for survival of T brucei bloodstream forms. Loss of CL caused a rapid drop in ATP levels and a decline in the ΔΨm. Unbiased proteomic analyses revealed a reduction in the levels of many mitochondrial proteins, most notably of Fo F1 -ATPase subunits and AOX, resulting in a strong decline of glycerol-3-phosphate-stimulated oxygen consumption. The changes in cellular respiration preceded the observed decrease in Fo F1 -ATPase stability, suggesting that the AOX-mediated ETC is the first pathway responding to the decline in CL. Select proteins and pathways involved in glucose and amino acid metabolism were upregulated to counteract the CL depletion-induced drop in cellular ATP.

LPL/AQP7/GPD2 promotes glycerol metabolism under hypoxia and prevents cardiac dysfunction during ischemia.

In the heart, fatty acid is a major energy substrate to fuel contraction under aerobic conditions. Ischemia downregulates fatty acid metabolism to adapt to the limited oxygen supply, making glucose the preferred substrate. However, the mechanism underlying the myocardial metabolic shift during ischemia remains unknown. Here, we show that lipoprotein lipase (LPL) expression in cardiomyocytes, a principal enzyme that converts triglycerides to free fatty acids and glycerol, increases during myocardial infarction (MI). Cardiomyocyte-specific LPL deficiency enhanced cardiac dysfunction and apoptosis following MI. Deficiency of aquaporin 7 (AQP7), a glycerol channel in cardiomyocytes, increased the myocardial infarct size and apoptosis in response to ischemia. Ischemic conditions activated glycerol-3-phosphate dehydrogenase 2 (GPD2), which converts glycerol-3-phosphate into dihydroxyacetone phosphate to facilitate adenosine triphosphate (ATP) synthesis from glycerol. Conversely, GPD2 deficiency exacerbated cardiac dysfunction after acute MI. Moreover, cardiomyocyte-specific LPL deficiency suppressed the effectiveness of peroxisome proliferator-activated receptor alpha (PPARα) agonist treatment for MI-induced cardiac dysfunction. These results suggest that LPL/AQP7/GPD2-mediated glycerol metabolism plays an important role in preventing myocardial ischemia-related damage.

Metformin lowers glucose 6-phosphate in hepatocytes by activation of glycolysis downstream of glucose phosphorylation.

The chronic effects of metformin on liver gluconeogenesis involve repression of the G6pc gene, which is regulated by the carbohydrate-response element-binding protein through raised cellular intermediates of glucose metabolism. In this study we determined the candidate mechanisms by which metformin lowers glucose 6-phosphate (G6P) in mouse and rat hepatocytes challenged with high glucose or gluconeogenic precursors. Cell metformin loads in the therapeutic range lowered cell G6P but not ATP and decreased G6pc mRNA at high glucose. The G6P lowering by metformin was mimicked by a complex 1 inhibitor (rotenone) and an uncoupler (dinitrophenol) and by overexpression of mGPDH, which lowers glycerol 3-phosphate and G6P and also mimics the G6pc repression by metformin. In contrast, direct allosteric activators of AMPK (A-769662, 991, and C-13) had opposite effects from metformin on glycolysis, gluconeogenesis, and cell G6P. The G6P lowering by metformin, which also occurs in hepatocytes from AMPK knockout mice, is best explained by allosteric regulation of phosphofructokinase-1 and/or fructose bisphosphatase-1, as supported by increased metabolism of [3-3H]glucose relative to [2-3H]glucose; by an increase in the lactate m2/m1 isotopolog ratio from [1,2-13C2]glucose; by lowering of glycerol 3-phosphate an allosteric inhibitor of phosphofructokinase-1; and by marked G6P elevation by selective inhibition of phosphofructokinase-1; but not by a more reduced cytoplasmic NADH/NAD redox state. We conclude that therapeutically relevant doses of metformin lower G6P in hepatocytes challenged with high glucose by stimulation of glycolysis by an AMP-activated protein kinase-independent mechanism through changes in allosteric effectors of phosphofructokinase-1 and fructose bisphosphatase-1, including AMP, Pi, and glycerol 3-phosphate.

The unusual di-domain structure of Dunaliella salina glycerol-3-phosphate dehydrogenase enables direct conversion of dihydroxyacetone phosphate to glycerol.

Dunaliella has been extensively studied due to its intriguing adaptation to high salinity. Its di-domain glycerol-3-phosphate dehydrogenase (GPDH) isoform is likely to underlie the rapid production of the osmoprotectant glycerol. Here, we report the structure of the chimeric Dunaliella salina GPDH (DsGPDH) protein featuring a phosphoserine phosphatase-like domain fused to the canonical glycerol-3-phosphate (G3P) dehydrogenase domain. Biochemical assays confirm that DsGPDH can convert dihydroxyacetone phosphate (DHAP) directly to glycerol, whereas a separate phosphatase protein is required for this conversion process in most organisms. The structure of DsGPDH in complex with its substrate DHAP and co-factor nicotinamide adenine dinucleotide (NAD) allows the identification of the residues that form the active sites. Furthermore, the structure reveals an intriguing homotetramer form that likely contributes to the rapid biosynthesis of glycerol.

GlcA-mediated glycerol-3-phosphate synthesis contributes to the oxidation resistance of Aspergillus fumigatus via decreasing the cellular ROS.

Fungi activate corresponding metabolic pathways in response to different carbon sources to adapt to different environments. Previous studies have shown that the glycerol kinase GlcA that phosphorylates glycerol to the intermediate glycerol-3-phosphate (G3P) is required for the growth of Aspergillus fumigatus when glycerol is used as the sole carbon source. The present study identified there were two putative glycerol kinases, GlcA and GlcB, in A. fumigatus but glycerol activated only glcA promoter but not glcB promoter, although both glcA and glcB could encode glycerol kinase. Under normal culture conditions, the absence of glcA caused no detectable colony phenotypes on glucose and other tested carbon sources except glycerol, indicating dissimilation of glucose and these tested carbon sources bypassed requirement of glcA. Notably, the oxidative stress agent H2O2 on the background of glucose medium clearly induced GlcA expression and promoted G3P synthesis. Deletion and overexpression of glcA elicited sensitivity and resistance to oxidative stress agent H2O2, respectively, accompanied by decrease and increase of G3P production. In addition, the sensitivity to oxidative stress in the glcA mutant was probably associated with dysfunction of mitochondria with a decreased mitochondrial membrane potential and an abnormal accumulation of the cellular reactive oxygen species (ROS). Furthermore, overexpressing the glycerol-3-phosphate dehydrogenase GfdA thatcatalyzes the reduction of dihydroxyacetone phosphate (DHAP) to G3P rescued phenotypes of the glcA null mutant to H2O2. Therefore, the present study suggests that GlcA-involved G3P synthesis participates in oxidative stress tolerance of A. fumigatus via regulating the cellular ROS level.

Contribution of GPD2/mGPDH to an alternative respiratory chain of the mitochondrial energy metabolism and the stemness in CD133-positive HuH-7 cells.

HuH-7 cells, derived from human hepatocarcinoma, are known to contain the CD133-positive cancer stem cell populations. HuH-7 cells showed higher ATP synthesis activity through the respiratory chain compared to another human hepatocarcinoma cell line HepG2 and showed an especially higher glycerol-3-phosphate (G3P)-driven ATP synthesis (G3P-ATPase) activity. We found that the CD133-positive HuH-7 cells expressed high levels of GPD2 (glycerol-3-phosphate dehydrogenase or mGPDH) and showed high G3P-ATPase activity. Next, to elucidate the relationship between CD133 and GPD2, we inhibited downstream factors of CD133 and found that a p38 inhibitor decreased the expression of GPD2 and decreased the G3P-ATPase activity. Furthermore, GPD2-knockdown (GPD2-KD) cells exhibited strong reduction of the G3P-ATPase activity and reduction of lactic acid secretion. Finally, we validated the effect of GPD2-KD on tumorigenicity. GPD2-KD cells were found to show decreased anchorage-independent cell proliferation, suggesting the linkage of G3P-ATPase activity to the tumorigenicity of the CD133-positive HuH-7 cells. Inhibition of G3P-ATPase disrupts the homeostasis of energy metabolism and blocks cancer development and progression. Our results suggest inhibitors, targeting GPD2 may be potential new anticancer agents.

Pomolic acid in persimmon peel suppresses the increase in glycerol-3 phosphate dehydrogenase activity in 3T3-L1 adipocytes.

Persimmon peels, though usually discarded, are useful sources of nutraceuticals. In this study, persimmon peel-derived pomolic acid was found to suppress the increase in the activity of glycerol-3 phosphate dehydrogenase, a neutral fat synthesis-related enzyme, in 3T3-L1 adipocytes, whereas oleanolic and ursolic acids did not exert this effect. Therefore, persimmon peel may be an effective functional food material.

Effects of Baccharin Isolated from Brazilian Green Propolis on Adipocyte Differentiation and Hyperglycemia in ob/ob Diabetic Mice.

Propolis is a honeybee product with various biological activities, including antidiabetic effects. We previously reported that artepillin C, a prenylated cinnamic acid derivative isolated from Brazilian green propolis, acts as a peroxisome proliferator-activated receptor γ (PPARγ) ligand and promotes adipocyte differentiation. In this study, we examined the effect of baccharin, another major component of Brazilian green propolis, on adipocyte differentiation. The treatment of mouse 3T3-L1 preadipocytes with baccharin resulted in increased lipid accumulation, cellular triglyceride levels, glycerol-3-phosphate dehydrogenase activity, and glucose uptake. The mRNA expression levels of PPARγ and its target genes were also increased by baccharin treatment. Furthermore, baccharin enhanced PPARγ-dependent luciferase activity, suggesting that baccharin promotes adipocyte differentiation via PPARγ activation. In diabetic ob/ob mice, intraperitoneal administration of 50 mg/kg baccharin significantly improved blood glucose levels. Our results suggest that baccharin has a hypoglycemic effect on glucose metabolic disorders, such as type 2 diabetes mellitus.