Stimulation Of Pyruvate Dehydrogenase Research Articles

The antianginal ranolazine fails to improve glycaemia in obese liver-specific pyruvate dehydrogenase deficient male mice.

Recent studies have demonstrated that stimulating pyruvate dehydrogenase (PDH, gene Pdha1), the rate-limiting enzyme of glucose oxidation, can reverse obesity-induced non-alcoholic fatty liver disease (NAFLD), which can be achieved via treatment with the antianginal ranolazine. Accordingly, our aim was to determine whether ranolazine's ability to mitigate obesity-induced NAFLD and hyperglycaemia requires increases in hepatic PDH activity. We generated liver-specific PDH-deficient (Pdha1Liver-/- ) mice, which were provided a high-fat diet for 12 weeks to induce obesity. Pdha1Liver-/- mice and their albumin-Cre (AlbCre ) littermates were randomized to treatment with either vehicle control or ranolazine (50 mg/kg) once daily via oral gavage during the final 5weeks, following which we assessed glucose and pyruvate tolerance. Pdha1Liver-/- mice exhibited no overt phenotypic differences (e.g. adiposity, glucose tolerance) when compared to their AlbCre littermates. Of interest, ranolazine treatment improved glucose tolerance and mildly reduced hepatic triacylglycerol content in obese AlbCre mice but not in obese Pdha1Liver-/- mice. The latter was independent of changes in hepatic mRNA expression of genes involved in regulating lipogenesis. Liver-specific PDH deficiency is insufficient to promote an NAFLD phenotype. Nonetheless, hepatic PDH activity partially contributes to how the antianginal ranolazine improves glucose tolerance and alleviates hepatic steatosis in obesity.

The Production of Oxalate by Aspergillus niger under Different Lead Concentrations

In this study, using a typical acid-producing fungi, Aspergillus niger (A. niger, CGMCC 23272), we investigated the capacity of organic acid production under different lead (Pb) concentrations. A. niger has a high Pb tolerance, which can maintain the growth of hypha at 1500 mg/L Pb concentration. Oxalic acid is the primary organic acid produced by A. niger. A. niger was shown to maintain the ability to produce oxalic acid under different Pb concentrations, which ranged from 522.8 to 1130.5 mg/L. The formed lead oxalate also confirmed the production of oxalic acid by A. niger. Meanwhile, the formation of lead oxalate minerals dominated the resistance of Pb toxicity by A. niger. More than 95% of Pb cations were removed by A. niger under different Pb concentrations. The high Pb toxicity (1500 mg/L) could stimulate pyruvate dehydrogenase enzyme activities, which increased from 0.05 to 0.13 nmol/min/g after three days of incubation. The low Pb toxicity (500 and 1000 mg/L) could improve the production of oxalic acid by A. niger. This indicates that the metabolism of organic acid by A. niger can be improved by a high Pb concentration via the tricarboxylic acid cycle.

233-LB: Ranolazine Fails to Improve Glycemia in Obese Liver-Specific Pyruvate Dehydrogenase–Deficient Mice

Background: Nonalcoholic fatty liver disease (NAFLD) increases risk for obesity-related insulin resistance and type 2 diabetes. Recent studies have demonstrated that stimulating pyruvate dehydrogenase (PDH) , the rate-limiting enzyme in glucose oxidation, can reverse obesity-induced NAFLD. Moreover, our lab has observed that treatment with the antianginal drug, ranolazine, augments hepatic PDH activity, leading to a reversal of obesity-induced glucose intolerance and NAFLD in mice. Our aim herein was to determine whether ranolazine's ability to mitigate obesity-induced NAFLD and hyperglycemia requires increases in hepatic PDH activity. Methods: We generated liver-specific PDH deficient (PDHLiver-/-) mice by crossing floxed Pdha1 mice with albumin-Cre (Alb-Cre) mice. PDHLiver-/- and Alb-Cre mice were placed on a high-fat diet for 12-weeks to induce obesity, whereas their lean controls were fed a low-fat diet. Mice were randomized to treatment with either vehicle control or ranolazine (50 mg/kg) once daily via oral gavage for 5-weeks, following which we assessed glucose homeostasis and hepatic steatosis. Results: Lean PDHLiver-/- mice exhibited no overt phenotypic differences (e.g. adiposity, glucose tolerance) from their Alb-Cre littermates, though a mild but nonsignificant worsening of pyruvate tolerance was observed. Similar findings were observed in obese PDHLiver-/- mice compared to their Alb-Cre littermates. Of interest, ranolazine treatment produced mild improvements in glucose tolerance in obese Alb-Cre mice, but not in obese PDHLiver-/- mice. However, this improvement in ranolazine treated Alb-Cre mice appears to be independent of decreases in hepatic triacylglycerol content. Conclusions: Although hepatic PDH activity appears to contribute to the glucose-lowering actions of ranolazine, this appears to be dissociated from its actions on hepatic steatosis, and impaired hepatic PDH activity per se is not sufficient to produce an NAFLD phenotype. Disclosure C. T. Saed: None. S. Tabatabaei dakhili: None. A. A. Greenwell: None. J. S. F. Chan: None. K. Yang: None. K. Gopal: None. F. Eaton: None. J. R. Ussher: None.

Balancing energy demand and production by mitochondrial trafficking of RHEB.

In this issue of Developmental Cell,Yang etal. (2021) discover that, RHEB traffics to mitochondria to promote energy production by stimulating pyruvate dehydrogenase to convert pyruvate to acetyl-CoA.

Abstract 5990: The potential role of artificial lactate influx in remodeling cancer-specific metabolism of colorectal cancer

Abstract Cancer cells have a specific metabolic pathway that produces a large quantity of lactate from glucose by abnormal aerobic glycolysis, it can provide a secondary path that meets the metabolic needs for persistent survival. Accordingly, regulating cancer-specific metabolism has important implications for the discovery of novel therapeutics. In this study, the possibility of an impact on colorectal cancer was investigated that focused on the remodeling of cancer-specific aerobic glycolysis by the artificial influx of lactate. Intracellular lactate levels were assessed in the colorectal cancer cells following lactate calcium salt treatment. Expression of lactate dehydrogenase and pyruvate dehydrogenase were confirmed to investigate the effect of the increased lactate influx. The nicotinamide adenine dinucleotide ratio and concentration of α-ketoglutarate were measured to confirm the tricarboxylic acid coupling. The tube formation and wound healing assay were performed as well as the expression of hypoxia-inducible factor-1α and vascular endothelial growth factor receptor to confirm the loss of malignancy. Xenograft animal models were established to evaluate the antitumor efficacy by monitoring changes in the tumor volume. We demonstrated that an artificial influx of lactate was increased in colon cancer cells under a hypoxic condition thereby reversible activation of lactate dehydrogenase reacting to lactate. Then, the conversion to pyruvate was promoted, and as a result of increased stimulation of pyruvate dehydrogenase, the tricarboxylic acid was coupled, showing an oxidative metabolism similar to normal cells. The malignancy of cancer cells was lost by undergoing remodeling of such cancer-specific, and a significant decrease in tumor growth was confirmed as a result of the anticancer effect of artificial lactate influx. These findings suggest the unique mechanisms in which the artificial influx of lactate would have anticancer effects by regulating cancer-specific aerobic glycolysis. Citation Format: Keun-Yeong Jeong. The potential role of artificial lactate influx in remodeling cancer-specific metabolism of colorectal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5990.

Stimulating pyruvate dehydrogenase complex reduces itaconate levels and enhances TCA cycle anabolic bioenergetics in acutely inflamed monocytes.

The pyruvate dehydrogenase complex (PDC)/pyruvate dehydrogenase kinase (PDK) axis directs the universal survival principles of immune resistance and tolerance in monocytes by controlling anabolic and catabolic energetics. Immune resistance shifts to immune tolerance during inflammatory shock syndromes when inactivation of PDC by increased PDK activity disrupts the tricarboxylic acid (TCA) cycle support of anabolic pathways. The transition from immune resistance to tolerance also diverts the TCA cycle from citrate-derived cis-aconitate to itaconate, a recently discovered catabolic mediator that separates the TCA cycle at isocitrate and succinate dehydrogenase (SDH). Itaconate inhibits succinate dehydrogenase and its anabolic role in mitochondrial ATP generation. We previously reported that inhibiting PDK in septic mice with dichloroacetate (DCA) increased TCA cycle activity, reversed septic shock, restored innate and adaptive immune and organ function, and increased survival. Here, using unbiased metabolomics in a monocyte culture model of severe acute inflammation that simulates sepsis reprogramming, we show that DCA-induced activation of PDC restored anabolic energetics in inflammatory monocytes while increasing TCA cycle intermediates, decreasing itaconate, and increasing amino acid anaplerotic catabolism of branched-chain amino acids (BCAAs). Our study provides new mechanistic insight that the DCA-stimulated PDC homeostat reconfigures the TCA cycle and promotes anabolic energetics in monocytes by reducing levels of the catabolic mediator itaconate. It further supports the theory that PDC is an energy sensing and signaling homeostat that restores metabolic and energy fitness during acute inflammation.

161 Dichloroacetate influences the mitochondrial activity of bovine oocytes impairing meiotic progression

Pyruvate is a key energy substrate for the oocyte during maturation and acquisition of developmental competence. Mitochondrial activity is also essential for oocyte competence. Dichloroacetate (DCA) is an inhibitor of pyruvate dehydrogenase kinase that indirectly stimulates pyruvate dehydrogenase (PDH), increasing pyruvate oxidation. PDH converts pyruvate into acetyl coenzyme A (acetyl-CoA) and thereby modulates the entry of glucose-derived carbons into the tricarboxylic acid (TCA) cycle, the main ATP production pathway within the oocyte. It was reported that DCA addition to embryo culture media improves embryo development in aged mice, by enhancing mitochondrial membrane potential (MMP) and decreasing oxidative stress (McPherson et al. 2014 Fertil. Steril. 101, 1458-1466). We hypothesised that increased pyruvate metabolism through the oxidative pathway, by stimulating PDH activity with DCA, could influence in vitro oocyte maturation. The aim of this work was to evaluate the effect of different concentrations of DCA during in vitro maturation (IVM) of bovine oocytes on maturation rate and mitochondrial activity, by assessing MMP and levels of flavin adenine dinucleotide (FADH2), nicotinamide adenine dinucleotide hydride (NADH), and reactive oxygen species (ROS). Abattoir-derived bovine cumulus-oocytes complexes (COC; n=360, over 4 replicates) were in vitro-matured with 0 (Control; n=120), 0.5mM (n=120) and 5mM (n=120) of DCA. After maturation, all matured COC were denuded by mechanical pipetting and meiotic progression was assessed by Hoechst 33342 staining and MMP by MitoTracker Red CMXRos test (Thermo Fisher Scientific, Waltham, MA, USA). Moreover, FADH2 and NADH levels were evaluated by autofluorescence (Dumollard et al. Development 134, 455-465) and ROS levels by CellRox® Green test (Thermo Fisher Scientific). Data were analysed by ANOVA, and the Tukey post hoc test was used to evaluate the difference among groups. The α-level was set at 0.05. Treatment with both concentrations of DCA decreased maturation rate (86.1, 67.8, and 67.6% in 0, 0.5, and 5mM groups, respectively; P<0.05). The MMP increased in oocytes matured with the highest concentration of DCA (3.42±0.28, 4.44±0.51, and 6.32±0.89 pixel/mm2, with 0, 0.5, and 5mM DCA, respectively; P<0.05). In line with this, higher levels of FADH2 (3.16±0.15, 3.96±0.24, and 3.83±0.20 pixel/mm2, with 0, 0.5, and 5mM DCA, respectively; P<0.05) and NADH (3.86±0.14, 4.80±0.16, and 4.95±0.17 pixel/mm2, with 0, 0.5, and 5mM DCA, respectively; P<0.05) were found in both DCA-treated groups compared with the control. Unexpectedly, ROS levels increased in the presence of DCA (0.9±0.07, 1.30±0.12, and 1.54±0.16 pixel/mm2, with 0, 0.5, and 5mM DCA, respectively; P<0.05) compared with the control. These results suggest that DCA was effective in stimulating mitochondrial activity of bovine oocytes, but also resulting in increased oxidative stress that likely accounts for the decreased maturation rate. Therefore, alternative strategies should be identified for the manipulation of the oocyte metabolic profile to improve oocyte developmental competence.

Dichloroacetate is an antimetabolite that antagonizes acetate and deprives cancer cells from its benefits: A novel evidence-based medical hypothesis

Dichloroacetate (DCA) is a promising safe anticancer drug that cured a patient with chemoresistant non-Hodgkin's lymphoma and treated lactic acidosis effectively. The well-known mechanism of DCA action is through stimulating Krebs cycle (stimulating pyruvate dehydrogenase via inhibiting pyruvate dehydrogenase kinase). This prevents lactate formation (Warburg effect) depriving cancer cells of lactate-based benefits e.g. angiogenesis, chemoresistance and radioresistance. Here, we introduce novel evidence-based hypotheses to explain DCA-induced anticancer effects. On pharmacological and biochemical bases, we hypothesize that DCA is a structural antagonist of acetate competing with it for target enzymes and biological reactions. We hypothesize that DCA exerts its anticancer effects via depriving cancer of acetate benefits. We hypothesize also that acetate is an antidote of DCA capable of treating DCA toxicity. Many reports support our hypotheses. Acetate is vital for cancer cells (tumors depend on acetate) and DCA is structurally similar to acetate. DCA exerts opposite effects to acetate. Acetate caused a decrease in serum potassium, phosphorus and glucose, and an increase in serum lactate, citrate, free fatty acids and ketone bodies (serum acetoacetate and beta-hydroxybutyrate levels). Acetate decreased the proportion of active (dephosphorylated) pyruvate dehydrogenase in perfused rat heart. DCA produced quite opposite effects. Intravenous infusion of acetate produced metabolic alkalemia while DCA caused minimal effects on acid-base status. Acetate is important for cancer cells metabolism and survival as elevated acetate can drive resistance to targeted cancer treatments. Acetate is required for epidermal growth factor receptor vIII mutation in lethal brain tumors. Experimentally, DCA inhibited acetate oxidation in hearts of normal rats and reversed inhibitory effects of acetate on the oxidation of glucose. During presence of DCA with no glucose in heart perfusions with [1-14C]acetate, DCA decreased the specific radioactivity of acetyl CoA and its product citrate. This proves our hypotheses that DCA is an antimetabolite that antagonizes acetate for vital reactions in cancer cells. Acetate may be used as an antidote to combat DCA toxicity.

Abstract 13015: Inhibition of Mitochondrial Calcium Uptake in the Heart Does Not Compromise Cardiac Energetics or Function Due to a Preferential Increase in Fatty Acid Oxidation During Increased Cardiac Work

The mitochondrial calcium (Ca 2+ ) uniporter (MCU) is primarily responsible for relaying cytosolic Ca 2+ transients to the mitochondria. Increasing cardiac workload by positive inotropes results in increased mitochondrial Ca 2+ , increasing glucose oxidation in comparison to fatty acid oxidation. This has been attributed to Ca 2+ stimulation of pyruvate dehydrogenase, the rate-limiting enzyme in glucose oxidation. We examined what effect increasing workload has on cardiac energetics and cardiac function if mitochondrial Ca 2+ levels are decreased in hearts from inducible cardio-specific deleted MCU (MCU -/- ) mice. Hearts from MCU -/- and MCU fl/fl control mice were isolated and perfused as working hearts with 5 mM glucose, 0.8 mM palmitate, 3% albumin, ± insulin (100 μU/ml) and isoproterenol (10 nM). Surprisingly, MCU -/- hearts showed increased cardiac work (p<0.05 vs. MCU fl/fl ). MCU -/- hearts were also not energy-starved, displaying basal rates of glucose and fatty acid oxidation comparable to controls, and even higher glucose oxidation in response to insulin (3027±213 vs. 2268±166 nmol . g dry wt -1. min -1 in MCU fl/fl , p <0.05). In response to isoproterenol treatment, MCU -/- hearts showed a similar increase in glucose oxidation, compared to controls. However, palmitate oxidation increased to a larger extent in MCU -/- hearts compared to controls (793±60 vs. 558±55 nmol . g dry wt -1. min -1 , p <0.05, respectively), resulting in a greater reliance on fatty acid oxidation for ATP production (40.1±1.9 % vs. 32.7±2.1% in MCU fl/fl , p <0.05). This high fatty acid oxidation supported the higher energy demand at increased workload and provided a higher energy reserve as evident by higher acetyl-CoA/ CoA ratios (0.36±0.03 vs. 0.26±0.02 in MCU fl/fl , p<0.05). The rise in fatty acid oxidation correlated with lower levels of malonyl CoA, an endogenous fatty acid oxidation inhibitor, (4.50±0.29 vs. 8.66±0.98 nmol . g dry wt -1 in MCU fl/fl , p< 0.05), and to an increase in acetylation of the fatty acid oxidation enzyme 3-hydroxyacyl CoA dehydrogenase (which stimulates activity). These results suggest that low mitochondrial Ca 2+ does not compromise cardiac energetics due to a compensatory stimulation of fatty acid oxidation.

Hyperpolarized 13C NMR observation of lactate kinetics in skeletal muscle.

The production of glycolytic end products, such as lactate, usually evokes a cellular shift from aerobic to anaerobic ATP generation and O2 insufficiency. In the classical view, muscle lactate must be exported to the liver for clearance. However, lactate also forms under well-oxygenated conditions, and this has led investigators to postulate lactate shuttling from non-oxidative to oxidative muscle fiber, where it can serve as a precursor. Indeed, the intracellular lactate shuttle and the glycogen shunt hypotheses expand the vision to include a dynamic mobilization and utilization of lactate during a muscle contraction cycle. Testing the tenability of these provocative ideas during a rapid contraction cycle has posed a technical challenge. The present study reports the use of hyperpolarized [1-(13)C]lactate and [2-(13)C]pyruvate in dynamic nuclear polarization (DNP) NMR experiments to measure the rapid pyruvate and lactate kinetics in rat muscle. With a 3s temporal resolution, (13)C DNP NMR detects both [1-(13)C]lactate and [2-(13)C]pyruvate kinetics in muscle. Infusion of dichloroacetate stimulates pyruvate dehydrogenase activity and shifts the kinetics toward oxidative metabolism. Bicarbonate formation from [1-(13)C]lactate increases sharply and acetyl-l-carnitine, acetoacetate and glutamate levels also rise. Such a quick mobilization of pyruvate and lactate toward oxidative metabolism supports the postulated role of lactate in the glycogen shunt and the intracellular lactate shuttle models. The study thus introduces an innovative DNP approach to measure metabolite transients, which will help delineate the cellular and physiological role of lactate and glycolytic end products.

Abstract 5058: Glucose OxidationStimulation Affords Dramatic Protection Against in vivo Myocardial Ischemia Reperfusion Injury

During reperfusion of the ischemic myocardium, fatty acid oxidation rates quickly recover, while glucose oxidation rates remain low, which decreases cardiac efficiency during reperfusion. Malonyl CoA decarboxylase (MCD) degrades malonyl CoA and increases fatty acid oxidation by relieving malonyl CoA-dependent inhibition of carnitine palmitoyl transferase-1. Studies have shown that MCD inhibition improves reperfusion recovery of ischemic hearts ex vivo by reducing fatty acid oxidation rates and increasing glucose oxidation rates. The objective of this study was to determine whether MCD inhibition would translate into a reduction in infarct size. Wild Type (WT, n = 7) or MCD deficient (MCD−/−, n = 7) mice had their left anterior descending coronary artery ligated for 30 min followed by 24 hr reperfusion. MCD−/− mice demonstrated a dramatic reduction in infarct size compared to WT mice (10.8±3.8 vs. 39.5±4.7 % of area at risk, P < 0.05) despite similar areas at risk (53 vs. 52 % of left ventricle). Furthermore, malonyl CoA levels were higher in the area at risk of hearts from MCD−/− mice (3.9±0.7 vs. 1.9±0.5 nmol/g wet weight, P < 0.05). Because the protection against ex vivo ischemia/reperfusion injury in MCD−/− mice was associated with increased myocardial glucose oxidation rates, secondary to an inhibition of fatty acid oxidation, we next determined whether direct stimulation of pyruvate dehydrogenase (PDH) and subsequent glucose oxidation would also afford protection against myocardial infarction. Infusion of the PDH activator, dichloroacetate (100 mg/kg intraperitoneal injection, followed by hourly injections of 50 mg/kg for the 24 hr duration of reperfusion), demonstrated significant protection against myocardial infarction (36.4±2.4 vs. 50.3±3.2 % of area at risk, P < 0.05). We demonstrate that MCD inhibition is beneficial against ischemia/reperfusion injury, possibly due to its effects on glucose oxidation stimulation, validating the optimization of myocardial metabolism as a novel therapy for ischemic heart disease.

Regulation of metabolic activity of peritoneal fibroblasts by dichloroacetate provides a potential target for interventions to reduce postoperative adhesions

OBJECTIVE: Adhesion fibroblasts manifested lower apoptosis as compared to normal peritoneal fibroblasts. Since adhesions provide oxygen and nutrients to postsurgical ischemic tissue, we sought to examine the role of aerobic metabolism in regulating apoptosis. Utilizing a compound, dichloroacetic acid (DCA), which stimulates pyruvate dehydrogenase, causing pyruvate to be converted in the Kreb's cycle rather than into lactate, thereby converting anaerobic to aerobic metabolism.DESIGN: Primary cultures of fibroblasts from normal peritoneal and adhesion tissues from the same patients (n=5).MATERIALS AND METHODS: Adhesion and normal peritoneal fibroblasts were treated with DCA (0, 100 mg/ml) for 2 hours, under normal (20% O2) and hypoxic (2%, O2) conditions. Apoptosis of fibroblasts was assessed by: 1) the TUNEL assay that measures nuclear DNA fragmentation by incorporating fluorescein-12-dUTP at the 3′-OH ends, and 2) the caspase 3 assay kit (Sigma) that measures caspase 3 activity.RESULTS: DCA treatment, under normoxic conditions, resulted in significant increases in caspase 3 activity from 1.62 to 7.34 and from 1.11 to 8.03 micromoles of pNA/min/mL in normal peritoneal and adhesion fibroblasts, respectively (p<0.05). In addition, DCA treatment, under hypoxic conditions, resulted in significant increases in caspase 3 activity from 1.62 to 5.67 and from 1.11 to 6.17 micromoles of pNA/min/mL in normal peritoneal and adhesion fibroblasts, respectively (p<0.05). These results were supported by the observed increase in nuclear DNA fragmentation that occurred in the DCA treated fibroblasts under normal and hypoxic conditions.CONCLUSIONS: These findings confirm that fibroblasts from adhesions are characterized by lower apoptosis, which is further accentuated by hypoxia. Stimulation of oxidative metabolism by DCA is associated with induction of apoptosis. These support the suggestion that regulation of metabolic activity of peritoneal cells may provide a target for interventions designed to reduce postoperative adhesions. OBJECTIVE: Adhesion fibroblasts manifested lower apoptosis as compared to normal peritoneal fibroblasts. Since adhesions provide oxygen and nutrients to postsurgical ischemic tissue, we sought to examine the role of aerobic metabolism in regulating apoptosis. Utilizing a compound, dichloroacetic acid (DCA), which stimulates pyruvate dehydrogenase, causing pyruvate to be converted in the Kreb's cycle rather than into lactate, thereby converting anaerobic to aerobic metabolism. DESIGN: Primary cultures of fibroblasts from normal peritoneal and adhesion tissues from the same patients (n=5). MATERIALS AND METHODS: Adhesion and normal peritoneal fibroblasts were treated with DCA (0, 100 mg/ml) for 2 hours, under normal (20% O2) and hypoxic (2%, O2) conditions. Apoptosis of fibroblasts was assessed by: 1) the TUNEL assay that measures nuclear DNA fragmentation by incorporating fluorescein-12-dUTP at the 3′-OH ends, and 2) the caspase 3 assay kit (Sigma) that measures caspase 3 activity. RESULTS: DCA treatment, under normoxic conditions, resulted in significant increases in caspase 3 activity from 1.62 to 7.34 and from 1.11 to 8.03 micromoles of pNA/min/mL in normal peritoneal and adhesion fibroblasts, respectively (p<0.05). In addition, DCA treatment, under hypoxic conditions, resulted in significant increases in caspase 3 activity from 1.62 to 5.67 and from 1.11 to 6.17 micromoles of pNA/min/mL in normal peritoneal and adhesion fibroblasts, respectively (p<0.05). These results were supported by the observed increase in nuclear DNA fragmentation that occurred in the DCA treated fibroblasts under normal and hypoxic conditions. CONCLUSIONS: These findings confirm that fibroblasts from adhesions are characterized by lower apoptosis, which is further accentuated by hypoxia. Stimulation of oxidative metabolism by DCA is associated with induction of apoptosis. These support the suggestion that regulation of metabolic activity of peritoneal cells may provide a target for interventions designed to reduce postoperative adhesions.

Fructose-1,6-Bisphosphate Enhances Hypothermic Preservation of Cardiac Myocytes

Previous studies from our project found that fructose-1,6-bisphosphate (FBP) enhanced the functional recovery of animal hearts after hypothermic preservation, and that rat cardiac myocytes take up FBP at 3 degrees C. In this study we tested the effects of FBP, as well as other compounds related to glycolysis and pyruvate oxidation, on the hypothermic preservation of myocytes. Isolated myocytes were incubated in ischemic suspensions at 3 degrees C, and aliquots examined over 72 hours for retention of rod-shaped morphology. In some experiments adenine nucleotide levels were measured by high-performance liquid chromatography (HPLC). FBP at 1 to 10 mmol/liter markedly reduced the death rate (65% reduction at 5 mmol/liter). Glucose at 2 to 10 mmol/liter was less beneficial (20% reduction). Insulin increased the death rate by about 25% when present alone, and it did not enhance the beneficial effects of FBP or glucose. Dichloroacetate (DCA), which stimulates pyruvate dehydrogenase, had little effect at 0.5 to 10 mmol/liter. Glucose and DCA did not increase the beneficial effects of FBP. After 6 to 24 hours of hypothermia, FBP- and glucose-treated cells had 25% to 50% higher ATP levels and 10% to 20% higher ATP:ADP ratios than untreated cells. Effects of FBP on preservation of morphology were much greater than effects on ATP levels. The results suggest that the effects of FBP and glucose were through glycolytic ATP production rather than through sugar oxidation via pyruvate dehydrogenase. The divergence in effects on preservation and effects on ATP suggests a role for a sub-cellular compartment of ATP in preservation.

Dichloroacetate inhibition of angiogenesis caused by hypoxia treatment of normal peritoneal and adhesion fibroblasts in human umbilical vein endothelial cells

Postoperative adhesion development and fibrosis represent a major complication of surgical procedures. They are a major cause of infertility, abdominopelvic pain, and small bowel obstruction. Adhesions provide a means of supplying oxygen and nutrients to postsurgical ischemic tissue. Hypoxia as a result of peritoneal injury has been reported to induce angiogenesis in variety of fibroblasts. Dichloroacetate is known to stimulate pyruvate dehydrogenase, causing pyruvate to be converted into the Kreb's cycle rather than into lactate, thereby converting anaerobic to aerobic metabolism.

Improvement of glucose homeostasis in obese diabetic db/db mice given Plasmodium yoelii glycosylphosphatidylinositols

We have previously reported that infection with Plasmodium yoelii, Plasmodium chabaudi, or injection of extracts from malaria-parasitized red blood cells induces hypoglycemia in normal mice and normalizes the hyperglycemia in streptozotocin (STZ)-diabetic mice. P yoelii glycosylphosphatidylinositols (GPIs) were extracted in chloroform:methanol:water (CMW) (10:10:3), purified by high-performance thin layer chromatography (HPTLC) and tested for their insulin-mimetic activities. The effects of P yoelii GPIs on blood glucose were investigated in insulin-resistant C57BL/ks- db/db diabetic mice. A single intravenous injection of GPIs (9 and 30 nmol/mouse) induced a significant dose-related decrease in blood glucose ( P < .001), but insignificantly increased plasma insulin concentrations. A single oral dose of 2.7 μmol GPIs per db/db mouse significantly lowered blood glucose ( P < .01). P yoelii GPIs in vitro (0.062 to 1 μmol/L) significantly stimulated lipogenesis in rat adipocytes in a dose-dependent manner both in the presence and absence of 10 −8 mol/L insulin ( P < .01). P yoelii GPIs stimulated pyruvate dehydrogenase phosphatase (PDH-Pase) and inhibited both cyclic adenosine monophosphate (cAMP)-dependent protein kinase A and glucose-6-phosphatase (G6Pase). P yoelii GPIs had no effect on the activity of the gluconeogenic enzymes fructose-1,6-bisphosphatase (FBPase) and phosphoenolpyruvate carboxykinase (PEPCK). This is the first report of the hypoglycemic effect of P yoelii GPIs in murine models of type 2 diabetes. In conclusion, P yoelii GPIs demonstrated acute antidiabetic effects in db/db mice and in vitro. We suggest that P yoelii GPIs, when fully characterized, may provide structural information for the synthesis of new drugs for the management of diabetes.

Insulin stimulation of pyruvate dehydrogenase in adipocytes involves two distinct signalling pathways.

In isolated rat adipocytes, the insulin stimulation of pyruvate dehydrogenase can be partially inhibited by inhibitors of PI3K (phosphoinositide 3-kinase) and MEK1/2 (mitogen-activated protein kinase/extracellular signal-regulated kinase kinase). In combination, U0126 and wortmannin completely block the insulin stimulation of pyruvate dehydrogenase. It is concluded that the effect of insulin on pyruvate dehydrogenase in rat adipocytes involves two distinct signalling pathways: one is sensitive to wortmannin and the other to U0126. The synthetic phosphoinositolglycan PIG41 can activate pyruvate dehydrogenase but the activation is only approx. 30% of the maximal effect of insulin. This modest activation can be completely blocked by wortmannin alone, suggesting that PIG41 acts through only one of the pathways leading to the activation of pyruvate dehydrogenase.

Metabolic regulation of collagen I in fibroblasts isolated from normal peritoneum and adhesions by dichloroacetic acid

Objective: We have previously demonstrated that collagen I, a major component of postoperative adhesions, is differentially regulated in fibroblasts isolated from normal human peritoneum and adhesions. Collagen I messenger RNA (mRNA) levels are significantly lower in fibroblasts from normal peritoneum compared with levels from adhesion fibroblasts. This variation is further accentuated by hypoxia. Because adhesions provide a means of supplying oxygen and nutrients to postsurgical ischemic tissue, we sought to examine the role of aerobic metabolism in the differential expression of collagen I. To examine this issue, we used a compound, dichloroacetic acid (DCA), that stimulates pyruvate dehydrogenase, causing pyruvate to be metabolized in the Kreb's cycle rather than converted into lactate, thereby switching anaerobic to aerobic metabolism. Specifically, we have exposed human fibroblast cultures from normal peritoneum and adhesions to DCA (0, 50, and 100 μg/mL) for 24 hours under normal and hypoxic (2% oxygen) conditions. Study Design: Multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) of collagen I and β-actin was performed by using mRNA extracted from all treatment points. Analysis of PCR-amplified products was performed by fractionation over a 2% agarose gel, followed by ethidium bromide staining of DNA bands. A scanning densimeter was used to determine the ratio of intensity of each band relative to β-actin. Densimetric analysis of gel bands was performed by using the National Institutes of Health image analysis program. Results: Although DCA stimulated peritoneal fibroblast collagen I mRNA expression under normoxic conditions, its expression was reduced during hypoxia. In adhesion fibroblasts, DCA treatment consistently lowered collagen I mRNA expression; this effect was manifested to a greater extent under hypoxic conditions. Conclusion: In summary, these findings confirm that fibroblasts from adhesions are characterized by excessive collagen I production, which is further accentuated by hypoxia. These observations are extended to show the stimulation of oxidative metabolism by DCA increases collagen I production; in contrast DCA inhibits collagen I production by normoxic adhesion fibroblasts as well as under hypoxic conditions in both types of fibroblasts. Thus, regulation of metabolic activity of peritoneal cells may provide a target for future interventions for reduction of postoperative adhesions. (Am J Obstet Gynecol 2002;187:1456-61.)

Dichloroacetate accelerates the fall in intracellular PO2 at onset of contractions in Xenopus single muscle fibers.

mM DCA, whereas the second group [control (Con); n = 10] was incubated for 30 min in Ringer solution only. After incubation, fibers were electrically stimulated to elicit tetanic contractions (0.5 Hz) for 2 min during which PiO2 was monitored. PiO2 before contractions began was 32.0 +/- 1.8 and 29.0 +/- 1.8 Torr for DCA and Con, respectively, and fell to 6.0 +/- 1.3 and 8.8 +/- 2.4 Torr (no significant difference), respectively, after steady state was reached. The kinetics of the fall, determined by both the time delay (from the start of contractions to the initial decrease in PiO2) and the tau (63% of the change to a steady state in PiO2), were calculated. In DCA cells, the tau was significantly (P < 0.05) faster than Con (22.1 +/- 3.6 vs. 39.7 +/- 5.8 s). In contrast, the time delay was not significantly (P > 0.45) different between the two groups (11.4 +/- 1.7 vs. 12.6 +/- 2.3 s, respectively). The amount of fatigue, reflected by a decrease in force production from initial, was not significantly different between groups. These data suggest that by stimulating pyruvate dehydrogenase with DCA in isolated single skeletal muscle cells, the faster fall in PiO2 is indicative of oxidative metabolism being more rapidly activated. This is the first evidence that oxygen uptake at the onset of contractions may be altered by DCA during moderate- to high-intensity contractile activity.

Effects of hypothermia on myocardial substrate selection

Background. Hypothermia lowers the metabolic rate and increases ischemic tolerance but the effects of temperature on myocardial substrate selection are not well defined. Methods. Isolated rat hearts were perfused with physiologic concentrations of 13C labeled lactate, pyruvate, acetoacetate, mixed long-chain fatty acids, and glucose. Hearts were cooled over 5 to 10 minutes to one of four target temperatures (37°, 32°, 27°, or 17°C), then perfused for an additional 30 minutes, freeze-clamped, and extracted. 13C NMR spectra were obtained and substrate oxidation patterns were determined by isotopomer analysis. Results. Although hearts in all groups were supplied with identical substrates, the percentage of acetyl-CoA oxidized within the citric acid cycle that arose from fatty acids decreased significantly from 53.8% ± 0.8% in the 37°C group to 33.1% ± 3.3% in the 17°C group. Lactate or pyruvate utilization increased from 3.3% ± 0.5% to 25.7% ± 3.6%, respectively ( p < 0.05 by one-way ANOVA). Conclusions. These data suggest that moderate hypothermia suppresses fatty acid oxidation and deep hypothermia significantly increases utilization of lactate and pyruvate. These effects may result from relative inhibition of catabolism of complex molecules such as fatty acids, or stimulation of pyruvate dehydrogenase. These effects on substrate metabolism may play a role in myocardial protection afforded by hypothermia.

Dichloroacetate (DCA) significantly increase the expression of inducible nitric oxide synthase (iNOS) in human fibroblasts of adhesion tissues but not in normal peritoneium

Objective: Since adhesions provide a means of supplying oxygen and nutrients to postsurgical ischemic tissue, we sought to examine the role of aerobic metabolism in the differential expression of iNOS, the enzymes that produce nitric oxide (NO), which is a critical mediator of various biological functions. NO have been reported to increase apoptosis in various cells. Dichloroacetate is known to stimulate pyruvate dehydrogenase, causing pyruvate to be converted into the Krebs cycle rather than into lactate, thereby converting anaerobic to aerobic metabolism. To evaluate the mRNA levels of inducible nitric oxide (NO) synthase (iNOS) in fibroblasts isolated from normal peritoneal tissues and adhesions after treatment with DCA under normal and hypoxic conditions.