Primary pyruvate dehydrogenase complex (PDC) deficiency results from inborn errors in the genes encoding its component proteins with largely devastating outcomes. Among its genes, the X-linked PDHA1 gene is subject to a much higher rate of mutations. Despite the analysis of many PDC-deficient subjects, no specific genotype–phenotype relationship emerges from the available data. This review focuses on the observations from animal models of primary PDC deficiency. Mouse models of systemic and brain-specific PDC deficiency closely reproduced several cerebral abnormalities observed in many PDC-deficient subjects and provide new insights into the impairment of cellular proliferation, migration and differentiation. Mouse models would be useful tools to evaluate efficacy of dietary and drug treatments. The mouse model is useful for creating tissue-specific PDC deficiency to examine the importance of PDC in carbohydrate metabolism. Other animal models of PDC deficiency have provided unique insights on the impact of PDC deficiency and are useful tools for rapid screening of drugs. All animal models utilized so far carried null mutations in the PDC genes, and hence creations of missense mutations in animals, especially in the mouse, are highly desirable to evaluate the genotype–phenotype relationship in PDC deficiency.

We assessed if supplementation of an obese-inducing diet with yellow pea fibre throughout pre-pregnancy (PP), gestation, and lactation could influence maternal gut microbiome composition and improve metabolic health and liver steatosis in newly weaned rat male and female offspring. Forty female Sprague-Dawley rats were fed a low (CON) or high (HC) calorie diet for a 6-week PP period. At the end of PP, HC animals were randomly assigned to either remain on the HC diet or the HC diet with yellow pea fibre (HC + FBR) for an additional 4-weeks prior to mating and throughout gestation and lactation. At the end of lactation, caecal microbiome profile was evaluated in mothers with shotgun metagenomic sequencing, and newly weaned male and female pups were assessed for serum biochemistry and hepatic fat outcomes. Maternal obesity reduced the beta-diversity of the maternal microbiome and lowered total caecal short-chain fatty acid (SCFA) concentration. HC + FBR consumption increased caecal SCFA concentration and differentially altered the maternal caecal microbiome profile of several species that have been linked with hepatic steatosis including Bifidobacterium pseudolongum, Porphyromonas gingivalis, and several Provetella species. Newly weaned offspring from HC mothers exhibited hepatic steatosis; however, male and female pups from HC + FBR mothers demonstrated normalised liver lipid concentrations (cholesterol and triglyceride) and an increase in caecal acetate and propionate concentrations. Findings suggest that maternal obesity enhances the risk of liver steatosis in offspring and that maternal dietary fibre supplementation may have a protective influence that is partly mediated through changes in the caecal microbiome profile and activity.

Mechanisms governing the regulation of pyruvate dehydrogenase complex (PDC) are markedly modified in cancer cells compared to normal cells. PDC activity in normal cells is controlled by the reversible phosphorylation of three serine residues by dedicated kinases and phosphatases. Recent advances in metabolic reprogramming of glucose in cancer cells show that new and expanded mechanisms operate to regulate PDC. This comprehensive review presents several post-translational modifications of PDC proteins such as phosphorylation, acetylation, lactylation, methylation, and others (at least 12). Transcriptional regulation of PDC-specific kinase and phosphatase genes amplifies cancer-specific regulation of PDC. In some cancer cells, to enhance the mitochondrial oxidative metabolism to meet increased energy requirements, PDC is maintained in its active state by employing yet another novel mechanism involving AMPK-mediated phosphorylation of two different serine residues. Interestingly, impairment in PDC function as a major supplier of mitochondrial acetyl-CoA to the nuclear pool of acetyl-CoA is circumvented by the translocation of the PDC to the nucleus for histone acetylation. These cancer-specific PDC regulatory mechanisms represent an incredible advancement in our understanding of the reprogramming of cellular metabolism in cancer cells and could contribute to the development of new therapeutic strategies.

We examined the influence of dietary α-lipoic acid (LA; R enantiomer) supplementation in obese-complicated pregnancies on maternal postpartum body weight and metabolic health. Forty-eight female Sprague-Dawley rats were randomized into three dietary groups throughout pre-pregnancy, gestation, and lactation: (i) a low-calorie control diet (CON); (ii) a high calorie obesity-inducing diet (HC); or (iii) the HC diet with 0.25% LA (HC+LA). Following offspring weaning, all mothers were switched to the CON diet for a postpartum period of 140 days to assess maternal body weight and markers of metabolic health. HC-fed mothers showed excessive (p < 0.05) gestational weight gain (GWG), higher (p < 0.05) postpartum body weight, reduced (p < 0.05) glycemic control (lower glucose:insulin ratio) and higher (p = 0.06) hepatic cholesterol concentration versus CON mothers. In contrast, HC+LA mothers demonstrated lower (p < 0.05) body weight throughout the experimental period compared with HC mothers, primarily due to a marked reduction in GWG. Although LA did not protect (p > 0.05) against reduced glycemic control, it did alter several aspects of lipid metabolism including reduced serum HDL-C and a lower concentration of hepatic cholesterol which was mediated partly through a reduction in low-density lipoprotein receptor expression. We conclude that maternal obesity during pregnancy leads to a longer-term detrimental impact on weight gain and glycemic control, even after switching to a low-calorie postpartum diet. Maternal LA supplementation may be able to partially offset these effects, likely by protecting against excessive GWG during pregnancy. However, further work is required to determine the consequences of reduced serum HDL-C in LA-supplemented mothers.

We investigated the influence of maternal yellow-pea fiber supplementation in obese pregnancies on offspring metabolic health in adulthood. Sixty newly-weaned female Sprague-Dawley rats were randomized to either a low-calorie control diet (CON) or high calorie obesogenic diet (HC) for 6-weeks. Obese animals were then fed either the HC diet alone or the HC diet supplemented with yellow-pea fiber (HC + FBR) for an additional 4-weeks prior to breeding and throughout gestation and lactation. On postnatal day (PND) 21, 1 male and 1 female offspring from each dam were weaned onto the CON diet until adulthood (PND 120) for metabolic phenotyping. Adult male, but not female, HC offspring demonstrated increased body weight and feed intake vs CON offspring, however no protection was offered by maternal FBR supplementation. HC male and female adult offspring demonstrated increased serum glucose and insulin resistance (HOMA-IR) compared with CON offspring. Maternal FBR supplementation improved glycemic control in male, but not female offspring. Compared with CON offspring, male offspring from HC dams demonstrated marked dyslipidemia (higher serum cholesterol, increased number of TG-rich lipoproteins, and smaller LDL particles) which was largely normalized in offspring from HC + FBR mothers. Male offspring born to obese mothers (HC) had higher hepatic TG, which tended to be lowered ( p = 0.07) by maternal FBR supplementation. Supplementation of a maternal high calorie diet with yellow-pea fiber in prepregnancy and throughout gestation and lactation protects male offspring from metabolic dysfunction in the absence of any change in body weight status in adulthood.

The adverse influence of maternal obesity on offspring metabolic health throughout the life-course is a significant public health challenge with few effective interventions. We examined if black bean powder (BBP) supplementation to a high-calorie maternal pregnancy diet or a postnatal offspring diet could offer protection against the metabolic programming of metabolic disease risk in adult offspring. Female Sprague Dawley rats were randomly assigned to one of three diets (n = 10/group) for a 3-week pre-pregnancy period and throughout gestation and lactation: (i) a low-caloric control diet (CON); (ii) a high-caloric obesity-inducing diet (HC); or (iii) the HC diet with 20% black bean powder (HC-BBP). At weaning [postnatal day (PND) 21], one male pup from each dam was weaned onto the CON diet throughout the postnatal period until adulthood (PND120). In addition, a second male from the HC group only was weaned onto the CON diet supplemented with BBP (CON-BBP). Thus, based on the maternal diet exposure and offspring postnatal diet, four experimental adult offspring groups were compared: CON/CON, HC/CON, HC-BPP/CON, and HC/CON-BBP. On PND120, blood was collected for biochemical analysis (e.g., lipids, glycemic control endpoints, etc.), and livers were excised for lipid analysis (triglycerides [TG] and cholesterol) and the mRNA/protein expression of lipid-regulatory targets. Compared with the CON/CON group, adult offspring from the HC/CON group exhibited a higher (p < 0.05) body weight (BW) (682.88 ± 10.67 vs. 628.02 ± 16.61 g) and hepatic TG (29.55 ± 1.31 vs. 22.86 ± 1.85 mmol/g). Although maternal BBP supplementation (HC-BBP/CON) had little influence on metabolic outcomes, the consumption of BBP in the postnatal period (HC/CON-BBP) lowered hepatic TG and cholesterol compared with the other treatment groups. Reduced hepatic TG in the HC/CON-BBP was likely associated with lower postnatal BW gain (vs. HC/CON), lower mRNA and protein expression of hepatic Fasn (vs. HC/CON), and lower serum leptin concentration (vs. CON/CON and HC groups). Our results suggest that the postnatal consumption of a black-bean-powder-supplemented diet may protect male rat offspring against the programming of obesity and dyslipidemia associated with maternal obesity. Future work should investigate the bioactive fraction of BBP responsible for the observed effect.

The objective of this study was to investigate the influence of α-lipoic acid (LA; R enantiomer) supplementation on maternal and fetal metabolic health in pregnancies complicated by maternal obesity. Forty female Sprague-Dawley rats were randomized to one of four treatment groups (n=10/group) throughout pre-pregnancy (3 weeks) and gestation (20 days): (i) a low calorie control (CON); (ii) a high calorie obesity-inducing diet (HC); (iii) the HC diet with 0.25% LA (HC+LA) or; (iv) the HC diet pair-fed to match the caloric intake of the HC+LA group (HC+PF). On gestation day 20, pregnant rats were placed under anesthesia for collection of maternal/fetal blood and tissues. Compared with the HC group, LA-supplemented mothers demonstrated lower maternal pre-pregnancy and gestational weight gain (GWG), improved glycemic control (lower Homeostatic Model Assessment for Insulin Resistance), and higher cholesterol concentrations in serum [high-density lipoprotein cholesterol (HDL-C) and low-and very-low density lipoprotein cholesterol (LDL/VLDL) fractions] and liver. Male and female fetuses from LA-supplemented mothers exhibited lower body weight, improved insulin sensitivity, and evidence of altered lipid metabolism including lower serum HDL-C, lower serum triglyceride (TG), and increased hepatic TG accumulation. Although maternal LA supplementation showed some benefit for both mothers and fetuses with respect to obesity and glycemic control, concern about the potential longer-term implications of liver cholesterol (mothers) and TG accumulation (fetuses) needs further investigation.

Fig S1. Standard curves for determination of transplant hepatocyte populations; Fig S2. BNGE of electron transport chain complexes; Fig S3. Steady state levels of TCA intermediates via mass spectroscopy; Fig S4 and S5. Steady state levels of glycolytic intermediates via mass spectroscopy; Fig S6. Steady state levels of amino acids via mass spectroscopy; Table S1. Antibody information.

Increased consumption of dietary pulse protein has been shown to assist in body weight regulation and improve a range of metabolic health outcomes. We investigated if the exchange of casein for yellow pea protein (YPPN) in an obese-inducing maternal diet throughout pregnancy and lactation offered protection against obesity and dyslipidemia in offspring. Sixty female Sprague Dawley rats were fed a low-calorie control diet (CON), a high-caloric obesity-inducing diet (with casein protein (CP), HC-CP), or an isocaloric/macronutrient-matched HC diet supplemented with YPPN isolate (HC-PPN) in pre-pregnancy, gestation, and lactation. Body weight (BW) and metabolic outcomes were assessed in male and female offspring at weaning and in adulthood after consuming the CON diet in the postnatal period. Consumption of the HC-PPN diet did not protect against maternal obesity but did improve reproductive success compared with the HC-CP group (72.7% versus 43.7%) and reduced total energy, fat, and protein in maternal milk. Male, but not female, offspring from mothers fed the HC-CP diet demonstrated hyperphagia, obesity, dyslipidemia, and hepatic triglyceride (TG) accumulation as adults compared with CON offspring. Isocaloric exchange of CP for YPPN in a high-calorie obese-inducing diet did not protect against obesity but did improve several aspects of lipid metabolism in adult male offspring including serum total cholesterol, LDL/VLDL cholesterol, triglycerides (TGs), and hepatic TG concentration. Our results suggest that the exchange of CP for YPPN in a maternal obese-inducing diet selectively protects male offspring from the malprogramming of lipid metabolism in adulthood.

Storage of fuels in the fed state followed by their use in the fasted state requires metabolic flexibility. In the fed state, increased substrate supply and insulin promote the synthesis and storage of glycogen in the liver and fat in the adipose tissue. This is achieved by allosteric effectors, covalent modifications of enzymes, and gene transcription that favor glycogen and fat synthesis. In the fasted state, increased levels of glucagon promote lipolysis in the adipose tissue and glycogenolysis, gluconeogenesis, and ketogenesis in the liver. This is achieved by opposite changes in allosteric effectors, covalent modifications of enzymes, and gene transcription.

Maternal hypercholesterolemia (MHC), a pathological condition characterized by an exaggerated rise in maternal serum cholesterol during pregnancy, may influence offspring hepatic lipid metabolism and increase the risk of nonalcoholic fatty liver disease (NAFLD). As NAFLD is characterized by a sexual dimorphic response, we assessed whether early-life exposure to excessive cholesterol influences the development of NAFLD in offspring and whether this occurs in a sex-specific manner. Female apoE−/− mice were randomly assigned to a control (CON) or a high cholesterol (CH; 0.15%) diet prior to breeding. At parturition, a cross-fostering approach was used to establish three groups: (1) normal cholesterol exposure throughout gestation and lactation (CON-CON); (2) excessive cholesterol exposure throughout gestation and lactation (CH-CH); and (3) excessive cholesterol exposure in the gestation period only (CH-CON). Adult male offspring (PND 84) exposed to excessive cholesterol during gestation only (CH-CON) demonstrated hepatic triglyceride (TG) accumulation and reduced lipogenic gene expression. However, male mice with a prolonged cholesterol exposure throughout gestation and lactation (CH-CH) had a similar, but not exacerbated hepatic response. Further, with the exception of higher serum TG in adult CH-CH females, evidence for a programming effect in female offspring was largely absent in comparison with males. These results indicate a sexual dimorphic response with respect to the effect of MHC on later life hepatic steatosis and highlight the gestation period as the most influential malprogramming window for hepatic lipid dysfunction in males.

The Pyruvate Dehydrogenase Complex (PDC), a key enzyme in glucose metabolism, catalyzes an irreversible oxidative decarboxylation reaction of pyruvate to acetyl-CoA, linking the cytosolic glycolytic pathway to mitochondrial tricarboxylic acid cycle and oxidative phosphorylation. Earlier we reported a down-regulation of several key hepatic lipogenic enzymes and their upstream regulators in liver-specific PDC-deficient mouse (L-PDCKO model by deleting the Pdha1 gene). In this study we investigated gene expression profiles of key glycolytic enzymes and other proteins that respond to various metabolic stresses in liver from L-PDCKO mice. Transcripts of several, such as hexokinase 2, phosphoglycerate kinase 1, pyruvate kinase muscle-type 2, and lactate dehydrogenase B as well as those for the nonglycolysis-related proteins, CD-36, C/EBP homologous protein, and peroxisome proliferator-activated receptor γ, were up-regulated in L-PDCKO liver whereas hypoxia-induced factor-1α, pyruvate dehydrogenase kinase 1 and Sirtuin 1 transcripts were down-regulated. The protein levels of pyruvate kinase muscle-type 2 and lactate dehydrogenase B were increased whereas that of lactate dehydrogenase A was decreased in PDC-deficient mouse liver. Analysis of endoplasmic reticulum and oxidative stress indicators suggests that the L-PDCKO liver showed evidence of the former but not the latter. These findings indicate that (i) liver-specific PDC deficiency is sufficient to induce "aerobic glycolysis characteristic" in mouse liver, and (ii) the mechanism(s) responsible for these changes appears distinct from that which induces the Warburg effect in some cancer cells.

As a collection of metabolic abnormalities including inflammation, insulin resistance, hypertension, hormone imbalance, and dyslipidemia, maternal obesity has been well-documented to program disease risk in adult offspring. Although hypercholesterolemia is strongly associated with obesity, less work has examined the programming influence of maternal hypercholesterolemia (MHC) independent of maternal obesity or high-fat feeding. This study was conducted to characterize how MHC per se impacts lipid metabolism in offspring. Female ( n = 6/group) C57BL/6J mice were randomly assigned to: (1.) a standard chow diet (Control, CON) or (2.) the CON diet supplemented with exogenous cholesterol (CH) (0.15%, w/w) throughout mating and the gestation and lactation periods. At weaning (postnatal day (PND) 21) and adulthood (PND 84), male offspring were characterized for blood lipid and lipoprotein profile and hepatic lipid endpoints, namely cholesterol and triglyceride (TG) accumulation, fatty acid profile, TG production, and mRNA expression of lipid-regulatory genes. Both newly weaned and adult offspring from CH mothers demonstrated increased very low-density lipoprotein (VLDL) particle number and size and hepatic TG and n-6 polyunsaturated fatty acid accumulation. Further, adult CH offspring exhibited reduced fatty acid synthase ( Fasn ) and increased diglyceride acyltransferase ( Dgat1 ) mRNA expression. These programming effects appear to be independent of changes in hepatic TG production and postprandial lipid clearance. Study results suggest that MHC, independent of obesity or high-fat feeding, can induce early changes to serum VLDL distribution and hepatic lipid profile that persist into adulthood.

Human pyruvate dehydrogenase complex (PDC) deficiency caused by mutations of the pyruvate dehydrogenase component (PDH) of the pyruvate dehydrogenase complex (PDC) is associated with the loss of myelin in the cortex and subcortical brain regions. Similar changes occur in the heterozygous PDH+/mouse model of a partial PDC deficiency. In order to investigate the underlying mechanisms, quantitative stereological analysis of O4 expressing oligodendrocytes (OLG), double stained Ki67+/O4+ immature proliferating OLG Progenitor Cells (OPCs) and overall numbers of the proliferating cells (Ki67+) were analyzed in the brains of 35-day-old PDH+/and control PDH+/+ mice. ANOVA showed an overall depletion of all cell populations in analyzed brain regions in PDH+/mice. As a potential treatment for PDC insufficiency we tested phenylbutyrate (PB), an inhibitor of PDH kinases, to increase the residual PDC activity. In PDH+/+ mice, daily (from postnatal day 2-35) single injections of PB produced no effect, though in the PDH+/mice, PB had an overall increasing effect on O4 OLG with significant increases recorded for SVZ and SGZ. PB increased and restored depleted OPCs in PDH+/mice to the levels found in PDH+/+. In summary, loss of O4 OLG in developing PDC-deficient mice and their PB-induced recovery appear to reflect changes in their proliferating progenitors and may be beneficial for the treatment of PDC deficiency in children affected with mutations in the α subunit of PDH.

The in utero and immediate postnatal environments are recognized as critical windows of developmental plasticity where offspring are highly susceptible to changes in the maternal metabolic milieu. Maternal hypercholesterolemia (MHC) is a pathological condition characterized by an exaggerated rise in maternal serum cholesterol during pregnancy which can program metabolic dysfunction in offspring, including dysregulation of hepatic lipid metabolism. Although there is currently no established reference range MHC, a loosely defined cutoff point for total cholesterol >280 mg/dL in the third trimester has been suggested. There are several unanswered questions regarding this condition particularly with regard to how the timing of cholesterol exposure influences hepatic lipid dysfunction and the mechanisms through which these adaptations manifest in adulthood. Gestational hypercholesterolemia increased fetal hepatic lipid concentrations and altered lipid regulatory mRNA and protein content. These early changes in hepatic lipid metabolism are evident in the postweaning environment and persist into adulthood. Further, changes to hepatic epigenetic signatures including microRNA (miR) and DNA methylation are observed in utero, at weaning, and are evident in adult offspring. In conclusion, early exposure to cholesterol during critical developmental periods can predispose offspring to the early development of nonalcoholic fatty liver disease (NAFLD) which is characterized by altered regulatory function beginning in utero and persisting throughout the life cycle.

In humans, pyruvate dehydrogenase complex (PDC) deficiency impairs brain energy metabolism by reducing the availability of the functional acetyl-CoA pool. This “hypometabolic defect” results in congenital lactic acidosis and abnormalities of brain morphology and function, ranging from mild ataxia to profound psychomotor retardation. Our previous study showed reduction in total cell number and dendritic arbors in the cerebellar Purkinje cells in systemic PDC-deficient mice. Phenylbutyrate has been shown to increase PDC activity in cultured fibroblasts from PDC-deficient patients. Hence, we investigated the effects of postnatal (days 2-35) phenylbutyrate administration on the cerebellar Purkinje cell population in PDC-deficient female mice. Histological analyses of different regions of cerebellar cortex from the brain-specific PDC-deficient saline-injected mice revealed statistically significant reduction in the Purkinje cell density and increased cell size of the individual Purkinje cell soma compared to control PDC-normal, saline-injected group. Administration of phenylbutyrate to control mice did not cause significant changes in the Purkinje cell density and cell size in the studied regions. In contrast, administration of phenylbutyrate variably lessened the ill effects of PDC deficiency on Purkinje cell populations in different areas of the cerebellum. Our results lend further support for the possible use of phenylbutyrate as a potential treatment for PDC deficiency.

Supported by the National Institute for Complementary and Alternative Medicine.

The pseudo-atomic structural model of human pyruvate dehydrogenase complex (PDHc) core composed of full-length E2 and E3BP components, calculated from our cryoelectron microscopy-derived density maps at 6-Å resolution, is similar to those of prokaryotic E2 structures. The spatial organization of human PDHc components as evidenced by negative-staining electron microscopy and native mass spectrometry is not homogeneous, and entails the unanticipated formation of local clusters of E1:E2 and E3BP:E3 complexes. Such uneven, clustered organization translates into specific duties for E1-E2 clusters (oxidative decarboxylation and acetyl transfer) and E3BP-E3 clusters (regeneration of reduced lipoamide) corresponding to half-reactions of the PDHc catalytic cycle. The addition of substrate coenzyme A modulates the conformational landscape of PDHc, in particular of the lipoyl domains, extending the postulated multiple random coupling mechanism. The conformational and associated chemical landscapes of PDHc are thus not determined entirely stochastically, but are restrained and channeled through an asymmetric architecture and further modulated by substrate binding.

Glucose is the ultimate substrate for most brain activities that use carbon, including synthesis of the neurotransmitters glutamate and γ-aminobutyric acid via mitochondrial tricarboxylic acid (TCA) cycle. Brain metabolism and neuronal excitability are thus interdependent. However, the principles that govern their relationship are not always intuitive because heritable defects of brain glucose metabolism are associated with the paradoxical coexistence, in the same individual, of episodic neuronal hyperexcitation (seizures) with reduced basal cerebral electrical activity. One such prototypic disorder is pyruvate dehydrogenase (PDH) deficiency (PDHD). PDH is central to metabolism because it steers most of the glucose-derived flux into the TCA cycle. To better understand the pathophysiology of PDHD, we generated mice with brain-specific reduced PDH activity that paralleled salient human disease features, including cerebral hypotrophy, decreased amplitude electroencephalogram (EEG), and epilepsy. The mice exhibited reductions in cerebral TCA cycle flux, glutamate content, spontaneous, and electrically evoked in vivo cortical field potentials and gamma EEG oscillation amplitude. Episodic decreases in gamma oscillations preceded most epileptiform discharges, facilitating their prediction. Fast-spiking neuron excitability was decreased in brain slices, contributing to in vivo action potential burst prolongation after whisker pad stimulation. These features were partially reversed after systemic administration of acetate, which augmented cerebral TCA cycle flux, glutamate-dependent synaptic transmission, inhibition and gamma oscillations, and reduced epileptiform discharge duration. Thus, our results suggest that dysfunctional excitability in PDHD is consequent to reduced oxidative flux, which leads to decreased neuronal activation and impaired inhibition, and can be mitigated by an alternative metabolic substrate.