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Active pyruvate dehydrogenase and impaired gluconeogenesis in orthotopic hepatomas of rats.

ABSTRACT: BACKGROUND:Therapies targeting altered activity of pyruvate dehydrogenase (PDH) and pyruvate carboxylase (PC) have been proposed for hepatomas. However, the activities of these pathways in hepatomas in vivo have not been distinguished. Here we examined pyruvate entry into the tricarboxylic acid (TCA) cycle through PDH versus PC in vivo using hepatoma-bearing rats. METHODS:Hepatoma-bearing rats were generated by intrahepatic injection of H4IIE cells. Metabolism of ¹³C-labeled glycerol, a physiological substrate for both gluconeogenesis and energy production, was measured with ¹³C NMR analysis. The concentration of key metabolites and the expression of relevant enzymes were measured in hepatoma, surrounding liver, and normal liver. RESULTS:In orthotopic hepatomas, pyruvate entry into the TCA cycle occurred exclusively through PDH and the excess PDH activity compared to normal liver was attributed to downregulated pyruvate dehydrogenase kinase (PDK) 2/4. However, pyruvate carboxylation via PC and gluconeogenesis were minimal, which was linked to downregulated forkhead box O1 (FoxO1) by Akt activity. In contrast to many studies of cancer metabolism, lactate production in hepatomas was not increased which corresponded to reduced expression of lactate dehydrogenase. The production of serine and glycine in hepatomas was enhanced, but glycine decarboxylase was downregulated. CONCLUSIONS:The combination of [U-¹³C₃]glycerol and NMR analysis enabled investigation of multiple biochemical processes in hepatomas and surrounding liver. We demonstrated active PDH and other related metabolic alterations in orthotopic hepatomas that differed substantially not only from the host organ but also from many earlier studies with cancer cells.

SUBMITTER: Lee MH

PROVIDER: S-EPMC6892165 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Active pyruvate dehydrogenase and impaired gluconeogenesis in orthotopic hepatomas of rats.

Lee Min Hee MH DeBerardinis Ralph J RJ Wen Xiaodong X Corbin Ian R IR Sherry A Dean AD Malloy Craig R CR Jin Eunsook S ES

Metabolism: clinical and experimental 20191028

<h4>Background</h4>Therapies targeting altered activity of pyruvate dehydrogenase (PDH) and pyruvate carboxylase (PC) have been proposed for hepatomas. However, the activities of these pathways in hepatomas in vivo have not been distinguished. Here we examined pyruvate entry into the tricarboxylic acid (TCA) cycle through PDH versus PC in vivo using hepatoma-bearing rats.<h4>Methods</h4>Hepatoma-bearing rats were generated by intrahepatic injection of H4IIE cells. Metabolism of <sup>13</sup>C-la ...[more]

PMID: 31672442

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Project description:IntroductionThere is no denying the clinical benefits of exogenous pyruvate in the treatment of pathological metabolic acidosis. However, whether it can prevent exercise physiological metabolic acidosis, delay the occurrence of exercise fatigue, and improve the beneficial effects of exercise and its internal mechanism remain unclear.MethodsWe randomly divided 24 male SD rats into 3 groups: one group was a control without exercise (CC, n = 8), and the other two groups were supplemented with 616 mg/kg/day pyruvate (EP, n = 8) or distilled water of equal volume (EC, n = 8). These groups completed acute high-intensity interval exercise (HIIE) after 7 days of supplementation. The acid metabolism variables were measured immediately after exercise including blood pH (pHe), base excess (BE), HCO3 -, blood lactic acid and skeletal muscle pH (pHi). The redox state was determined by measuring the oxidized coenzyme I/reduced coenzyme I (nicotinamide adenine dinucleotide [NAD+]/reduced NAD+ [NADH]) ratio and lactate/pyruvate (L/P) ratio. In addition, the activities of lactate dehydrogenase A (LDHA), hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK) were determined by ELISA.ResultsPyruvate supplementation significantly reversed the decrease of pHe, BE, HCO3 - and pHi values after HIIE (p < 0.001), while significantly increased the activities of LDHA (p = 0.048), HK (p = 0.006), and PFK (p = 0.047). Compared with the CC, the NAD+/NADH (p = 0.008) ratio and the activities of LDHA (p = 0.002), HK (p < 0.001), PFK (p < 0.001), and PK (p = 0.006) were significantly improved in EP group.DiscussionThis study provides compelling evidence that oral pyruvate attenuates HIIE-induced intracellular and extracellular acidification, possibly due to increased activity of LDHA, which promotes the absorption of H+ in the LDH reaction. The beneficial effects of improving the redox state and glycolysis rate were also shown. Our results suggest that pyruvate can be used as an oral nutritional supplement to buffer HIIE induced metabolic acidosis.

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Active pyruvate dehydrogenase and impaired gluconeogenesis in orthotopic hepatomas of rats.

Publications

Active pyruvate dehydrogenase and impaired gluconeogenesis in orthotopic hepatomas of rats.

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