3-oxoacid CoA-transferase Research Articles

Rebuttal from Manoja K. Brahma, Adam R. Wende and Kyle S. McCommis.

Drs Karwi and Lopaschuk have provided compelling evidence of the potential for ketone bodies to provide an extra source of ATP for the heart. The foundation of our opposing views most likely stems from comparing analyses of the acute effects of ketone bodies in predominantly ex vivo studies to that which occurs in vivo with more chronic ketosis. Likewise, we must all be more prudent when comparing cardiac metabolic adaptations to physiological ketosis to those observed with ‘pure’ ketosis as occurs with consumption of ketone esters or salts, or ketone infusion. In physiological states of ketosis such as fasting or consumption of a low-carbohydrate, high-fat ketogenic diet, hearts preferentially downregulate ketolytic enzymes, decreasing ketone oxidation and enhancing fatty acid oxidation (Wentz et al. 2010; McCommis et al. 2020). This downregulation of ketolytic enzymes also occurs in the hearts of diabetic mice, or in hearts overexpressing glucose transporter 4 with enhanced glucose uptake and utilization (Brahma et al. 2020). However, cardiac ketone metabolism may be directly enhanced if delivery of lipids or glucose is not concurrently elevated. Recent studies suggest that ketone ester supplementation enhanced cardiac ketone uptake in humans (Monzo et al. 2020), and ketone ester-enriched diets increased the expression of ketolytic enzymes in the rat heart (Yurista et al. 2020). These studies imply that elevated ketone extraction is associated with increased oxidation, but neither of these studies directly measured oxidation. We agree that ketone utilization appears to be more important in failing hearts. Failing hearts from humans and rodent models display enhanced expression of the ketolytic enzymes β-hydroxybutyrate dehydrogenase 1 (BDH1) and succinyl-CoA:3-oxoacid CoA transferase (SCOT) and have been shown to extract more ketones than non-failing hearts (Aubert et al. 2016; Bedi et al. 2016; Horton et al. 2019; Monzo et al. 2020; Murashige et al. 2020). Also, cardiac-specific deletion of BDH1 or SCOT in mice exacerbates cardiac dysfunction and remodelling when challenged by pressure overload (Schugar et al. 2014; Horton et al. 2019). But these knockout mouse models provide perhaps the most significant evidence that ketone body metabolism is not critical for normal hearts, as deletion of BDH1 or SCOT does not directly induce cardiac dysfunction, and these hearts can even normally adapt to physiological ketosis (Schugar et al. 2014; Horton et al. 2019). To conclude, further investigation is needed to better understand the importance of ketone body metabolism in heart failure, as well as in response to ketosis as a potential therapy for heart failure. Readers are invited to give their views on this and the accompanying CrossTalk articles in this issue by submitting a brief (250 word) comment. Comments may be submitted up to 6 weeks after publication of the article, at which point the discussion will close and the CrossTalk authors will be invited to submit a ‘Last Word’. Please email your comment, including a title and a declaration of interest, to [email protected]. Comments will be moderated and accepted comments will be published online only as ‘supporting information’ to the original debate articles once discussion has closed. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. None. All authors conceived, wrote, and edited this manuscript. All authors have read and approved the final version of this manuscript and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All persons designated as authors qualify for authorship, and all those who qualify for authorship are listed. A.R.W. is supported by NIH R01 HL133011. K.S.M. is supported by NIH R00 HL136658.

Effects of a Ketogenic Diet Containing Medium-Chain Triglycerides and Endurance Training on Metabolic Enzyme Adaptations in Rat Skeletal Muscle

Long-term intake of a ketogenic diet enhances utilization of ketone bodies, a particularly energy-efficient substrate, during exercise. However, physiological adaptation to an extremely low-carbohydrate diet has been shown to upregulate pyruvate dehydrogenase kinase 4 (PDK4, a negative regulator of glycolytic flux) content in skeletal muscle, resulting in impaired high-intensity exercise capacity. This study aimed to examine the effects of a long-term ketogenic diet containing medium-chain triglycerides (MCTs) on endurance training-induced adaptations in ketolytic and glycolytic enzymes of rat skeletal muscle. Male Sprague-Dawley rats were placed on either a standard diet (CON), a long-chain triglyceride-containing ketogenic diet (LKD), or an MCT-containing ketogenic diet (MKD). Half the rats in each group performed a 2-h swimming exercise, 5 days a week, for 8 weeks. Endurance training significantly increased 3-oxoacid CoA transferase (OXCT, a ketolytic enzyme) protein content in epitrochlearis muscle tissue, and MKD intake additively enhanced endurance training–induced increases in OXCT protein content. LKD consumption substantially increased muscle PDK4 protein level. However, such PDK4 increases were not observed in the MKD-fed rats. In conclusion, long-term intake of ketogenic diets containing MCTs may additively enhance endurance training–induced increases in ketolytic capacity in skeletal muscle without exerting inhibitory effects on carbohydrate metabolism.

Inhibition of the ketolytic acetyl CoA supply to tumors could be their “Achilles heel”

Inhibition of the ketolytic acetyl <scp>CoA</scp> supply to tumors could be their “Achilles heel”

P207 Synergetic effect of amino acid and ketone metabolism underlies empagliflozin-mediated cardioprotection in the type 2 diabetic heart

Abstract Funding Acknowledgements Boehringer Ingelheim Background Although emerging evidence has indicated that sodium glucose cotransporter 2 (SGLT2) inhibitors restore impaired cardiac energetics in type 2 diabetes mellitus (T2DM), the underlying molecular mechanisms have yet to be established. Augmented utilization of ketone is one proposed hypothesis, but depletion of succinyl-CoA triggered by the conversion of ketone back to acetyl-CoA by SCOT (succinyl-CoA:3-oxoacid CoA transferase) may hamper oxidative capacity of the tricarboxylic acid (TCA) cycle, which also requires succinyl-CoA. The recent finding that empagliflozin augments systemic amino acid metabolism in patients with T2DM led us to hypothesize that the anaplerotic effect of amino acid on the TCA cycle complements ketone oxidation. Methods and Results Myocardial infarction (MI) was induced in T2DM rats (OLETF) and control rats (LETO). Survival rate at 48 hours after MI was significantly lower in OLETF than in LETO (40% vs 84%), and empagliflozin treatment (10 mg/kg/day, 14 days) before MI improved the survival rate in OLETF to 70%. Metabolome analysis was performed using heart tissues from the non-infarct region 12 hours after MI. Using principal component analysis, data from 92 metabolites that were detected were compressed into 2 dimensions, and the first component (PC1) clearly separated empagliflozin-treated OLETF from non-treated LETO and OLETF. Analysis of factor loading of each metabolite for PC1 revealed that branched chain amino acids leucine, isoleucine and valine, the latter two of which can be oxidized to succynyl-CoA, and β-hydroxybutyrate were the top four metabolites that characterized empagliflozin treatment. Furthermore, in comparison to LETO, OLETF treated with empagliflozin showed 50% higher levels of glutamine and glutamate, both of which can replenish the TCA cycle at the level of α-ketoglutarate. In OLETF, empagliflozin significantly increased the TCA cycle intermediates citrate, cis-aconitate and malate by 74%, 119% and 59%, respectively. OLETF showed 86% higher lactate and 38% lower ATP than those in LETO, but levels of the metabolites were normalized by empagliflozin, suggesting improved glucose oxidation. Conclusions The present analyses showed that amino acid and ketone metabolism are metabolic pathways that are most affected by empagliflozin. Coordination of these "starvation-induced pathways" may underlie the favorable metabolic effect of empagliflozin in T2DM hearts.

P3476High-resolution respirometry reveals enhanced myocardial mitochondrial ketone oxidation after fasting and ventricular unloading

Abstract Background Impairment of myocardial mitochondrial function is regarded as an established pathomechanism in heart failure. Enhanced oxidation of ketone bodies may potentially exert protective effects on myocardial function. High-resolution respirometry (HRR) resembles a gold-standard methodology to determine myocardial mitochondrial metabolism and oxidative function but has not been validated for ketone substrates yet. Purpose We hypothesized that (1) quantification of ketone body oxidative capacity (OC) in myocardium utilizing ex-vivo HRR is feasible and that (2) ketone-associated OC is elevated after fasting and under conditions of chronic mechanical ventricular unloading. Methods We established new HRR (Oxygraph-2k) protocols, measuring oxygen flux generated by oxidation of the ketone substrates beta-hydroxybutyrate (HBA) and acetoacetate (ACA). Ketone protocols were then applied to twelve C57BL/6 mice' (of which six were fasted for 16h) left ventricular and right liver lobe tissue, as well as to eleven terminal heart failure patients' left ventricular tissue, harvested at heart transplantation. Heart transplant recipients were subdivided into patients with left ventricular assist device prior to transplantation (LVAD group, n=6) or no unloading prior to transplantation (HTX group, n=5). Results In non-fasted rodent hearts, HBA yielded an OC of 25±4 pmol/(s*mg tissue) above basal respiration, when applied as sole substrate (21±11 pmol/(s*mg) in liver). ACA alone did not induce oxygen flux, but ACA+succinate yielded 229% higher oxygen flux than succinate alone in state III (146±32 vs 44±12 pmol/(s*mg); p=0.0003). When titrated after succinate, ACA increased OC by 93±25 pmol/(s*mg) (p=0.0003). In 16h-fasted rodent hearts, HBA-supported OC was 27% higher (41±3 vs 52±9 pmol/(s*mg); p=0.04), while OC with ACA+succinate was unchanged (p=0.60). In rodent liver, no oxygen flux was induced by ACA, reflecting absence of 3-oxoacid CoA-transferase. However, HBA-supported OC was 118% higher in fasted liver (37±13 vs 57±13 pmol/(s*mg); p=0.03). In humans, left ventricular unloading was not associated with altered myocardial OC for fatty acids and glycolytic substrates (standard protocol, p=0.13), but HBA-supported OC was 39% higher in the LVAD group compared to the HTX group (54±12 vs 39±9 pmol/(s*mg), p=0.04). Conclusion Quantification of ketone body OC with HRR is feasible in permeabilized myocardial fibers. Applying this novel method revealed increased HBA-supported myocardial mitochondrial respiration after fasting and chronic left ventricular unloading. These data support a concept of enhanced ketone oxidation following ventricular unloading in myocardial mitochondria. Our findings facilitate new studies on myocardial ketone turnover and the interaction of mitochondrial ketone metabolism with cardiac performance. Acknowledgement/Funding CRC 1116, Research commission of the University Hospital Düsseldorf

Inhibitory Effects of Tofogliflozin on Cardiac Hypertrophy in Dahl Salt-Sensitive and Salt-Resistant Rats Fed a High-Fat Diet.

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are drugs for diabetes and might prevent heart failure. In this study, we investigated the effects of tofogliflozin, an SGLT2 inhibitor, on cardiac hypertrophy and metabolism in hypertensive rats fed a high-fat diet. Dahl salt-sensitive (DS) rats, hypertensive model rats, and Dahl salt-resistant (DR) rats, non-hypertensive model rats, were fed a high-salt and high-fat diet containing tofogliflozin (0.005%) for 9 weeks to examine the effects of this drug on cardiac hypertrophy and metabolism. Tofogliflozin tended to suppress a rise of the systolic blood pressure, relative to the control, throughout the treatment period in both DR and DS rats, and significantly suppress a rise of the systolic blood pressure, relative to the control, at the 9th week in DS rats. Tofogliflozin reduced cardiac hypertrophy (heart weight/body weight) not only in DS rats but also in DR rats. Histological analysis showed that tofogliflozin significantly decreased cardiomyocyte hypertrophy and perivascular fibrosis in both DS and DR rats. Tofogliflozin significantly decreased the expression levels of genes related to cardiac hypertrophy (encoding for natriuretic peptides A and B and interleukin-6), and to cardiac fibrosis (encoding for transforming growth factor-β1 and collagen type IV), in DS rats. Recent studies have shown that hypertrophied and failing hearts shift to oxidizing ketone bodies as a significant fuel source. We also performed metabolome analysis for ventricular myocardial tissue. Tofogliflozin reduced 3-hydroxybutyrate, a ketone body, and significantly decreased the expression levels of β-hydroxybutyrate dehydrogenase 1 and 3-oxoacid CoA-transferase, which are related to ketone oxidization. In conclusion, tofogliflozin ameliorated cardiac hypertrophy and fibrosis along with reduction of ketone usage in myocardial tissue.

Role of OXCT1 in ovine adipose and preadipocyte differentiation

3-oxoacid CoA-transferase 1 (OXCT1) is a key enzyme in ketone body metabolism that is expressed in adipose and other tissues. The present study addressed the function of OXCT1 in adipose tissue from Tan sheep. The 1563 bp ovine OXCT1 coding sequence was cloned from ovine adipose tissue. The OXCT1 protein sequence was highly homologous to OXCT1 from other species. OXCT1 was highly expressed in kidney and at lower levels in small intestine, lung, spleen, heart, stomach, liver, tail adipose, and cartilage, but not in longissimus muscle. OXCT1 was expressed at higher levels in perirenal and tail adipose tissues than in subcutaneous adipose tissue. OXCT1 expression levels increased during the in vitro differentiation of adipocytes, but decreased dramatically at day 8. OXCT1 knockdown in ovine adipocytes promoted lipid accumulation, whereas overexpression did the converse. This study demonstrates that OXCT1 may play a role in adipogenesis and provides new insight on adipose deposition in sheep.

PO-305 An 8-week, low carbohydrate, high fat, ketogenic diet enhanced exercise capacity through improved ketolysis and lipolysis in mice

PO-305 An 8-week, low carbohydrate, high fat, ketogenic diet enhanced exercise capacity through improved ketolysis and lipolysis in mice

Comprehensive analysis of metastasis-related genes reveals a gene signature predicting the survival of colon cancer patients.

ObjectiveThe mechanism underlying colon cancer metastasis remain unclear. This study aimed to elucidate the genes alteration during the metastasis of colon cancer and identify genes that crucial to the metastasis and survival of colon cancer patients.MethodsThe dataset of primary and metastasis tissue of colon cancer, and dataset of high and low metastasis capability of colon cancer cells were selected as training cohort, and the overlapped differentially expressed genes (DEGs) were screened from the training cohort. The functional enrichment analysis for the overlapped DEGs was performed. The prognostic value of overlapped DEGs were analyzed in The Cancer Genome Atlas dataset, and a gene signature was developed using genes that related to the overall survival (OS). The prognostic value of the gene signature was further confirmed in a validation cohort.ResultsA total of 184 overlapped DEGs were screened from the training cohort. Functional enrichment analysis revealed the significant gene functions and pathways of the overlapped DEGs. Four hub genes (3-oxoacid CoA-transferase 1, actinin alpha 4, interleukin 8, integrin subunit alpha 3) were identified using protein–protein network analysis. Six genes (aldehyde dehydrogenase 2, neural precursor cell expressed, developmentally down-regulated 9, filamin A, lamin B receptor, twinfilin actin binding protein 1, serine and arginine rich splicing factor 1) were closely related to the OS of colon cancer patients. A gene signature was developed using these six genes based on their risk score, and the validation cohort indicated that the prognostic value of this gene signature was high in the prediction of colon cancer patients.ConclusionsOur study demonstrates a gene profiles related to the metastasis of colon cancer, and identify a six-gene signature that acts as an independent biomarker on the prognosis of colon cancer.

Abstract 274: Regulation of Myocardial Ketone Body Oxidation Capacity by Increased Protein O-GlcNAcylation in Diabetic Heart

Diabetes increases the risk of heart failure independently of underlying coronary artery disease. Perturbations in myocardial substrate utilization have been proposed to contribute to the pathogenesis of cardiac dysfunction. However, the exact mechanisms linking impaired substrate utilization to disease progression remain elusive. Compared to the well-established roles of glucose and fatty acids metabolism in cardiac physiology and pathology, the importance of ketone body (KB) metabolism is less well understood. Several findings suggest the importance of KB in the cardiac health and disease. More recently, two independent studies have simultaneously demonstrated increased reliance on KB utilization by the failing heart in the absence of diabetes. Despite these observations, our understanding of the importance of KB metabolism in a diabetic heart is incomplete. Interestingly, our findings from the hearts of streptozotocin-induced diabetic mice confirmed elevated cardiac β-hydroxybutyrate (a major KB) levels and transcriptional suppression of Oxct1 gene expression that encodes for SCOT (succinyl-CoA:3-oxoacid CoA transferase; a rate limiting enzyme of KB oxidation), consistent with a mismatch between KB availability and utilization. To determine a specific role for glucose delivery in this regulation we used an inducible transgenic mouse model with cardiac-restricted expression of the glucose transporter 4 (GLUT4; mG4H). Interestingly, mG4H mice had reduced cardiac SCOT protein levels and oxidation of KB in isolated working heart suggesting that glucose is sufficient to regulate the ketone metabolic pathway. Hyperglycemia associated with diabetes alter protein function via post-translational O -GlcNAcylation. Interestingly, we found that myocardial SCOT expression was also reduced in a third mouse model with increased cardiac O -GlcNAc levels (overexpression of a dominant negative form of O -GlcNAcase, which normally removes O -GlcNAc; dnOGAh) suggesting that increased protein O -GlcNAcylation is directly involved. Collectively, these studies establish a novel role of glucose and its downstream regulator, O -GlcNAc, in attenuation of KB metabolism in the diabetic heart.

Male Infertility and Single-Nucleotide Polymorphisms in the Testis-Specific Succinyl CoA: 3-Oxoacid CoA Transferase (SCOT-T/OXCT2 ) gene in a Japanese Cohort

Male Infertility and Single-Nucleotide Polymorphisms in the Testis-Specific Succinyl CoA: 3-Oxoacid CoA Transferase (SCOT-T/OXCT2 ) gene in a Japanese Cohort

Low ketolytic enzyme levels in tumors predict ketogenic diet responses in cancer cell lines in vitro and in vivo

The ketogenic diet (KD) is a high-fat, very-low-carbohydrate diet that triggers a fasting state by decreasing glucose and increasing ketone bodies, such as β-hydroxybutyrate (βHB). In experimental models and clinical trials, the KD has shown anti-tumor effects, possibly by reducing energy supplies to cells, which damage the tumor microenvironment and inhibit tumor growth. Here, we determined expression levels of genes encoding the ketolytic enzymes 3-hydroxybutyrate dehydrogenase 1 (BDH1) and succinyl-CoA: 3-oxoacid CoA transferase 1 (OXCT1) in 33 human cancer cell lines. We then selected two representative lines, HeLa and PANC-1, for in vivo examination of KD sensitivity in tumors with high or low expression, respectively, of these two enzymes. In mice with HeLa xenografts, the KD increased tumor growth and mouse survival decreased, possibly because these tumors actively consumed ketone bodies as an energy source. Conversely, the KD significantly inhibited growth of PANC-1 xenograft tumors. βHB added to each cell culture significantly increased proliferation of HeLa cells, but not PANCI-1 cells. Downregulation of both BDH1 and OXCT1 rendered HeLa cells sensitive to the KD in vitro and in vivo. Tumors with low ketolytic enzyme expression may be unable to metabolize ketone bodies, thus predicting a better response to KD therapy.

AMP‐activated protein kinase in muscle is essential in ketone body utilization

BackgroundStarvation leads to a series of metabolic adaptations that enables continuous production and delivery of nutrients to critical organs, tissues and cells. Under conditions of nutrient withdrawal, ketone bodies provide an alternative source of energy for highly oxidative tissues. Although the AMP‐activated protein kinase (AMPK) is best known as a sensor of cellular energy status, its implication in ketone regulation remains unclear.ObjectiveThe aim of this study was to evaluate the effects of AMPKα2 on ketone body utilization, and to elucidate the underlying mechanisms.MethodsGlobal AMPKα2 knockout mice (AMPKα2−/−), muscle‐specific AMPKα2 knockout mice, and their age‐matched wild type (WT) littermates were subjected to either 3‐day fasting or received an intra‐peritoneal injection of β‐hydroxybutyrate salt (1.5 mg/kg body weight) to assess the β‐hydroxybutyrate consumption.ResultsFasting blood and urine ketone levels were significantly elevated in AMPKα2−/− mice when compared to their littermate WT mice. After an intra‐peritoneal bolus of β‐hydroxybutyrate, the main circulating ketone body, AMPKα2−/− mice presented a lower clearance of β‐hydroxybutyrate compared to their littermate WT mice. Further, fasting induced hyperketosis without any change in body weight or glycaemia in muscle‐specific AMPKα2 knockout mice. Consistently, these mice displayed impaired ketone utilization after β‐hydroxybutyrate injection. Furthermore, AMPKα2 deficiency in muscle significantly decreased locomotor activity, with a quicker switch from utilizing carbohydrate to fat as the predominant energy source compared to their littermate WT mice. Mechanistically, AMPKα2 deficiency in muscle presented a 50% reduced activity of succinyl‐CoA:3‐oxoacid CoA transferase compared to their littermate WT mice.ConclusionTaken together, these findings establish AMPKα2 in muscle as an essential mediator of ketolysis in fasting, through the regulation of the rate‐limiting ketolytic enzyme.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Recurrent ketoacidosis: Is it a ketone metabolism disorder?

Amac: Keton cisim olusumu (ketogenez) bozukluklari; mitokondriyel 3-hidroksi-3metil glutaril CoA sentaz (Mhs) ve 3-hidroksi-3-metil glutaril CoA liyaz (HL) enzim eksiklikleri sonucu olusur. Keton cisim yikimi (ketoliz) bozukluklari ise suksinil CoA: 3 oksoasit CoA transferaz (SCOT) ve asetoasetil CoA thiolaz-beta ketotiolaz (MAT) enzim eksiklikleri sonucu olusmaktadir. Keton metabolizma bozuklugu tanisiyla izlenen hastalarin klinik ve laboratuvar bulgulari ile degerlendirilmesi amaclandi. Yontem: Keton metabolizmasi bozuklugu tanisiyla izlenen hasta verileri retrospektif olarak incelendi. Bulgular: Dort hastada HL eksikligi, 3 hastada MAT eksikligi ve 2 hastada SCOT eksikligi tanisi mevcuttu. Hastalarin ortanca yasi 5 yil (6 ay-15,5 yil), ilk metabolik dekompanzasyon atak yasi ortalama 7,7 ay (22 gun-19 ay) idi. MAT eksikligi olan bir hasta, kardes taramasi ile asemptomatik donemde tani aldi. Iki hastada spastik tetraparezi gibi agir norolojik defisit gelisti. Dekompanzasyon ataklarinin beslenememe, kusma ve gastroenterit gibi infeksiyon sonrasi gelistigi goruldu. Sonuc: Aciklanamayan metabolik asidoz ataklari durumunda keton metabolizma bozukluklari akilda tutulmalidir. Akut dekompanzasyon degisik yaslarda ortaya cikabilir, klinik siddeti degisken olabilir. Erken tani ve uygun tedavi mortalite ve morbidite acisindan cok onemlidir.

3-Oxoacid CoA transferase 1 as a therapeutic target gene for cisplatin-resistant ovarian cancer.

Ovarian cancer (OC) is the second leading cause of mortality from gynecological malignancies and has the highest mortality rate worldwide. As it is commonly asymptomatic during the early stages of the disease, >70% of patients with OC are diagnosed at advanced stages with metastasis. Despite treatment methods, including optimal debulking surgery and chemotherapy with the platinum-based drug cisplatin, OC recurrence is often inevitable, with an overall 5-year survival rate of 45%, mostly due to the steady development of cisplatin resistance. To identify genes involved in cisplatin resistance, the present study determined the half-maximal inhibitory concentrations of eight different OC cell lines and classified them into two groups (sensitive and resistant). mRNA expression was analyzed with GeneChip Human Gene 1.0 ST Arrays, and DNA methylation profiles were evaluated with the HumanMethylation450 BeadChip. Using an integrated approach of analyzing gene expression levels and DNA methylation profiles simultaneously, 26 genes were selected that were differentially expressed and methylated between the resistant and sensitive groups. Among these 26 genes, 3-oxoacid CoA transferase 1 (OXCT1), which was demonstrated to be downregulated and hypermethylated at promoter CpGs in the cisplatin-resistant group compared with the cisplatin-sensitive group, was selected for further investigation. Treatment with a DNA methyltransferase inhibitor restored hypermethylation-mediated gene silencing of OXCT1 in the cisplatin-resistant group, but not in the cisplatin-sensitive group. Furthermore, overexpression of OXCT1 conferred sensitivity to cisplatin in OC cells. The results of the present study suggest that OXCT1 serves an important role in conferring cisplatin sensitivity, and may provide a potential therapeutic target for cisplatin chemotherapy in patients with recurrent OC.

AB076. Heterozygous carriers of succinyl-CoA:3-oxoacid CoA transferase deficiency can develop severe ketoacidosis

Succinyl-CoA:3-oxoacid CoA transferase (SCOT, gene symbol OXCT1) deficiency is an autosomal recessive disorder in ketone body utilization that results in severe recurrent ketoacidotic episodes in infancy, including neonatal periods. More than 30 patients with this disorder have been reported and to our knowledge, their heterozygous parents and siblings have had no apparent ketoacidotic episodes. Over 5 years (2008–2012), we investigated several patients that presented with severe ketoacidosis and identified a heterozygous OXCT1 mutation in four of these cases (Case1 p.R281C, Case2 p.T435N, Case3 p.W213*, Case4 c.493delG). To confirm their heterozygous state, we performed a multiplex ligation-dependent probe amplification analysis on the OXCT1 gene which excluded the presence of large deletions or insertions in another allele. A sequencing analysis of subcloned full-length SCOT cDNA showed that wild-type cDNA clones were present at reasonable rates to mutant cDNA clones. Over the following 2 years (2013–2014), we analyzed OXCT1 mutations in six more patients presenting with severe ketoacidosis (blood pH ≦7.25 and total ketone body ≧10 mmol/L) with non-specific urinary organic acid profiles. Of these, a heterozygous OXCT1 mutation was found in two cases (Case5 p.G391D, Case6 p.R281C). Moreover, transient expression analysis revealed R281C and T435N mutants to be temperature-sensitive. This characteristic may be important because most patients developed ketoacidosis during infections. Our data indicate that heterozygous carriers of OXCT1 mutations can develop severe ketoacidotic episodes in conjunction with ketogenic stresses.

Heterozygous carriers of succinyl-CoA:3-oxoacid CoA transferase deficiency can develop severe ketoacidosis

Succinyl-CoA:3-oxoacid CoA transferase (SCOT, gene symbol OXCT1) deficiency is an autosomal recessive disorder in ketone body utilization that results in severe recurrent ketoacidotic episodes in infancy, including neonatal periods. More than 30 patients with this disorder have been reported and to our knowledge, their heterozygous parents and siblings have had no apparent ketoacidotic episodes. Over 5years (2008-2012), we investigated several patients that presented with severe ketoacidosis and identified a heterozygous OXCT1 mutation in four of these cases (Case1 p.R281C, Case2 p.T435N, Case3 p.W213*, Case4 c.493delG). To confirm their heterozygous state, we performed a multiplex ligation-dependent probe amplification analysis on the OXCT1 gene which excluded the presence of large deletions or insertions in another allele. A sequencing analysis of subcloned full-length SCOT cDNA showed that wild-type cDNA clones were present at reasonable rates to mutant cDNA clones. Over the following 2years (2013-2014), we analyzed OXCT1 mutations in six more patients presenting with severe ketoacidosis (blood pH ≦7.25 and total ketone body ≧10mmol/L) with non-specific urinary organic acid profiles. Of these, a heterozygous OXCT1 mutation was found in two cases (Case5 p.G391D, Case6 p.R281C). Moreover, transient expression analysis revealed R281C and T435N mutants to be temperature-sensitive. This characteristic may be important because most patients developed ketoacidosis during infections. Our data indicate that heterozygous carriers of OXCT1 mutations can develop severe ketoacidotic episodes in conjunction with ketogenic stresses.

Brain metabolism in health, aging, andneurodegeneration.

Brain cells normally respond adaptively to bioenergetic challenges resulting from ongoing activity in neuronal circuits, and from environmental energetic stressors such as food deprivation and physical exertion. At the cellular level, such adaptive responses include the "strengthening" of existing synapses, the formation of new synapses, and the production of new neurons from stem cells. At the molecular level, bioenergetic challenges result in the activation of transcription factors that induce the expression of proteins that bolster the resistance of neurons to the kinds of metabolic, oxidative, excitotoxic, and proteotoxic stresses involved in the pathogenesis of brain disorders including stroke, and Alzheimer's and Parkinson's diseases. Emerging findings suggest that lifestyles that include intermittent bioenergetic challenges, most notably exercise and dietary energy restriction, can increase the likelihood that the brain will function optimally and in the absence of disease throughout life. Here, we provide an overview of cellular and molecular mechanisms that regulate brain energy metabolism, how such mechanisms are altered during aging and in neurodegenerative disorders, and the potential applications to brain health and disease of interventions that engage pathways involved in neuronal adaptations to metabolic stress.

Successful Management of Pregnancies in Patients with Inherited Disorders of Ketone Body Metabolism.

Patients with succinyl-CoA:3-oxoacid CoA transferase (SCOT) deficiency and 3-hydroxy-3-methylglutaryl (HMG)-CoA lyase deficiency are at increased risk of developing metabolic acidosis and hypoglycemia during pregnancy, delivery, and postpartum period. This can be fatal if not treated appropriately. Pregnancy in such patients should be managed in a specialist center by a multidisciplinary team including metabolic physician, high-risk obstetrician, and metabolic dietician. We report two pregnancies in women with SCOT deficiency and HMG-CoA lyase deficiency, which were successfully managed at this tertiary care center. The patient with SCOT deficiency had recurrent ketoacidosis due to severe nausea and vomiting requiring several hospital admissions during pregnancy, while the patient with HMG-CoA lyase deficiency remained metabolically stable. Both patients, nevertheless, had normal delivery of live-born infants and had uneventful postpartum period.

Hepatocellular carcinoma redirects to ketolysis for progression under nutrition deprivation stress

Cancer cells are known for their capacity to rewire metabolic pathways to support survival and proliferation under various stress conditions. Ketone bodies, though produced in the liver, are not consumed in normal adult liver cells. We find here that ketone catabolism or ketolysis is re-activated in hepatocellular carcinoma (HCC) cells under nutrition deprivation conditions. Mechanistically, 3-oxoacid CoA-transferase 1 (OXCT1), a rate-limiting ketolytic enzyme whose expression is suppressed in normal adult liver tissues, is re-induced by serum starvation-triggered mTORC2-AKT-SP1 signaling in HCC cells. Moreover, we observe that enhanced ketolysis in HCC is critical for repression of AMPK activation and protects HCC cells from excessive autophagy, thereby enhancing tumor growth. Importantly, analysis of clinical HCC samples reveals that increased OXCT1 expression predicts higher patient mortality. Taken together, we uncover here a novel metabolic adaptation by which nutrition-deprived HCC cells employ ketone bodies for energy supply and cancer progression.