Medium-chain acyl-CoA Dehydrogenase mRNA Research Articles

A gene therapy targeting medium-chain acyl-CoA dehydrogenase (MCAD) did not protect against diabetes-induced cardiac pathology.

Diabetic cardiomyopathy describes heart disease in patients with diabetes who have no other cardiac conditions but have a higher risk of developing heart failure. Specific therapies to treat the diabetic heart are limited. A key mechanism involved in the progression of diabetic cardiomyopathy is dysregulation of cardiac energy metabolism. The aim of this study was to determine if increasing the expression of medium-chain acyl-coenzyme A dehydrogenase (MCAD; encoded by Acadm), a key regulator of fatty acid oxidation, could improve the function of the diabetic heart. Male mice were administered streptozotocin to induce diabetes, which led to diastolic dysfunction 8 weeks post-injection. Mice then received cardiac-selective adeno-associated viral vectors encoding MCAD (rAAV6:MCAD) or control AAV and were followed for 8 weeks. In the non-diabetic heart, rAAV6:MCAD increased MCAD expression (mRNA and protein) and increased Acadl and Acadvl, but an increase in MCAD enzyme activity was not detectable. rAAV6:MCAD delivery in the diabetic heart increased MCAD mRNA expression but did not significantly increase protein, activity, or improve diabetes-induced cardiac pathology or molecular metabolic and lipid markers. The uptake of AAV viral vectors was reduced in the diabetic versus non-diabetic heart, which may have implications for the translation of AAV therapies into the clinic. KEY MESSAGES: The effects of increasing MCAD in the diabetic heart are unknown. Delivery of rAAV6:MCAD increased MCAD mRNA and protein, but not enzyme activity, in the non-diabetic heart. Independent of MCAD enzyme activity, rAAV6:MCAD increased Acadl and Acadvl in the non-diabetic heart. Increasing MCAD cardiac gene expression alone was not sufficient to protect against diabetes-induced cardiac pathology. AAV transduction efficiency was reduced in the diabetic heart, which has clinical implications.

Decreased Fatty Acid Oxidation Gene Expression in Pre-Eclampsia According to the Onset and Presence of Intrauterine Growth Restriction.

Mitochondrial fatty acid oxidation (FAO) is lower in placentas with pre-eclampsia. The aim of our study was to compare the placental mRNA expression of FAO enzymes in healthy pregnancies vs. different subgroups of pre-eclampsia according to the severity, time of onset, and the presence of intrauterine growth restriction (IUGR). By using real-time qPCR, we measured the mRNA levels of long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD), medium-chain acyl-CoA dehydrogenase (MCAD), and carnitine palmitoyltransferases 1A and 2 (CPT1A, CPT2) on the maternal side (anchoring villi in the basal decidua) and on the fetal side (chorionic plate) of the placenta (n = 56). When compared to the controls, LCHAD, MCAD, and CPT2 mRNA had decreased in all pre-eclampsia subgroups globally and on the fetal side. On the maternal side, LCHAD mRNA was also lower in all pre-eclampsia subgroups; however, MCAD and CPT2 mRNA were only reduced in severe and early-onset disease, as well as CPT2 in IUGR (p < 0.05). There were no differences in CPT1A mRNA expression. We conclude that the FAO enzymes mRNA in the placenta was lower in pre-eclampsia, with higher reductions observed in severe, early-onset, and IUGR cases and more striking reductions on the fetal side.

Messenger RNA rescues medium-chain acyl-CoA dehydrogenase deficiency in fibroblasts from patients and a murine model.

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common inherited disorder of mitochondrial fatty acid β-oxidation (FAO) in humans. Patients exhibit clinical episodes often associated with fasting. Symptoms include hypoketotic hypoglycemia and Reye-like episodes. With limited treatment options, we explored the use of human MCAD (hMCAD) mRNA in fibroblasts from patients with MCAD deficiency to provide functional MCAD protein and reverse the metabolic block. Transfection of hMCAD mRNA into MCAD- deficient patient cells resulted in an increased MCAD protein that localized to mitochondria, concomitant with increased enzyme activity in cell extracts. The therapeutic hMCAD mRNA-lipid nanoparticle (LNP) formulation was also tested in vivo in Acadm-/- mice. Administration of multiple intravenous doses of the hMCAD mRNA-LNP complex (LNP-MCAD) into Acadm-/- mice produced a significant level of MCAD protein with increased enzyme activity in liver, heart and skeletal muscle homogenates. Treated Acadm-/- mice were more resistant to cold stress and had decreased plasma levels of medium-chain acylcarnitines compared to untreated animals. Furthermore, hepatic steatosis in the liver from treated Acadm-/- mice was reduced compared to untreated ones. Results from this study support the potential therapeutic value of hMCAD mRNA-LNP complex treatment for MCAD deficiency.

Genistein, daidzein, and resveratrols stimulate PGC‐1β‐mediated gene expression

PGC‐1β is a transcriptional co‐activator of nuclear receptors such as the estrogen receptor‐related receptor (ERR). Transgenic overexpression of PGC‐1β in mice increases energy expenditure and suppresses high‐fat diet‐induced obesity. In this study, we screened various food‐derived and natural compounds using a reporter assay system to measure the transcriptional activity of PGC‐1β. Soy‐derived isoflavones, genistein and daidzein, and several resveratrols activated PGC‐1β. Genistein, daidzein, and trans‐oxyresveratrol activated ERR‐responsive element‐mediated reporter activity in the presence of PGC‐1β. Stable overexpression of PGC‐1β in C2C12 myoblasts increased the expression of medium‐chain acyl‐CoA dehydrogenase (MCAD), an important enzyme in fatty acid β‐oxidation. Genistein and daidzein increased MCAD mRNA levels and mitochondrial content in PGC‐1β‐expressing C2C12 cells. These compounds activated ERR/PGC‐1β complex‐mediated gene expression, and our findings may be a practical foundation for developing functional foods targeting obesity.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Genistein, daidzein, and resveratrols stimulate PGC-1β-mediated gene expression

PGC-1β is a transcriptional co-activator of nuclear receptors such as the estrogen receptor-related receptor (ERR). Transgenic overexpression of PGC-1β in mice increases energy expenditure and suppresses high-fat diet-induced obesity. In this study, we screened various food-derived and natural compounds using a reporter assay system to measure the transcriptional activity of PGC-1β. Soy-derived isoflavones, genistein and daidzein, and several resveratrols activated PGC-1β. Genistein, daidzein, and trans-oxyresveratrol activated ERR-responsive element-mediated reporter activity in the presence of PGC-1β. Stable overexpression of PGC-1β in C2C12 myoblasts increased the expression of medium-chain acyl-CoA dehydrogenase (MCAD), an important enzyme in fatty acid β-oxidation. Genistein and daidzein increased MCAD mRNA levels and mitochondrial content in PGC-1β-expressing C2C12 cells. These compounds activated ERR/PGC-1β complex-mediated gene expression, and our findings may be a practical foundation for developing functional foods targeting obesity.

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

Cannabidiol Protects against Doxorubicin-Induced Cardiomyopathy by Modulating Mitochondrial Function and Biogenesis.

Doxorubicin (DOX) is a widely used, potent chemotherapeutic agent; however, its clinical application is limited because of its dose-dependent cardiotoxicity. DOX's cardiotoxicity involves increased oxidative/nitrative stress, impaired mitochondrial function in cardiomyocytes/endothelial cells and cell death. Cannabidiol (CBD) is a nonpsychotropic constituent of marijuana, which is well tolerated in humans, with antioxidant, antiinflammatory and recently discovered antitumor properties. We aimed to explore the effects of CBD in a well-established mouse model of DOX-induced cardiomyopathy. DOX-induced cardiomyopathy was characterized by increased myocardial injury (elevated serum creatine kinase and lactate dehydrogenase levels), myocardial oxidative and nitrative stress (decreased total glutathione content and glutathione peroxidase 1 activity, increased lipid peroxidation, 3-nitrotyrosine formation and expression of inducible nitric oxide synthase mRNA), myocardial cell death (apoptotic and poly[ADP]-ribose polymerase 1 [PARP]-dependent) and cardiac dysfunction (decline in ejection fraction and left ventricular fractional shortening). DOX also impaired myocardial mitochondrial biogenesis (decreased mitochondrial copy number, mRNA expression of peroxisome proliferator-activated receptor γ coactivator 1-alpha, peroxisome proliferator-activated receptor alpha, estrogen-related receptor alpha), reduced mitochondrial function (attenuated complex I and II activities) and decreased myocardial expression of uncoupling protein 2 and 3 and medium-chain acyl-CoA dehydrogenase mRNA. Treatment with CBD markedly improved DOX-induced cardiac dysfunction, oxidative/nitrative stress and cell death. CBD also enhanced the DOX-induced impaired cardiac mitochondrial function and biogenesis. These data suggest that CBD may represent a novel cardioprotective strategy against DOX-induced cardiotoxicity, and the above-described effects on mitochondrial function and biogenesis may contribute to its beneficial properties described in numerous other models of tissue injury.

Effects of Roux-en-Y gastric bypass and ileal transposition surgeries on glucose and lipid metabolism in skeletal muscle and liver

BackgroundRoux-en Y gastric bypass (RYGB) and ileal transposition (IT) surgeries produce weight loss and improve diabetic control; however, the mechanisms of glycemic improvements are largely unknown. Because skeletal muscle and liver play a key role in glucose homeostasis, we compared the effects of RYGB and IT surgeries on key molecules of glucose and lipid metabolism in muscle and liver. MethodsSprague-Dawley rats were subjected to RYGB, IT, or sham surgeries; sham-animals were ad-lib fed or pair-fed to RYGB rats (n = 7-9/group). At 8 weeks postoperatively, blood samples were collected for glucagon-like peptide-1 (GLP-1) and insulin analyses by ELISA. Leg muscle and liver tissues were analyzed for mRNA (RT-qPCR) and/or protein abundance (immuno blotting) of important molecules of glucose and lipid metabolism [glucose transporter-4 (GLUT-4), hexokinase, phosphofructokinase (PFK), adenosine monophosphate activated protein kinase-α (AMPKα), cytochrome C oxidase-IV (COX-IV), citrate synthase, carnitine palmitoyl transferase-1 (CPT-1), medium-chain acyl-CoA dehydrogenase (MCAD), peroxisome proliferator-activated receptor gamma co-activator 1 α (PGC-1 α), PGC-1-related coactivator (PRC), uncoupling protein-3 (UCP-3)]. ResultsPlasma GLP-1 concentrations were increased comparably with RYGB and IT. RYGB and IT increased muscle GLUT-4 protein content, muscle hexokinase mRNA, and liver PFK mRNA. IT increased muscle AMPKα and COX-IV protein content and liver citrate synthase activity. IT increased muscle CPT-1, MCAD and PRC mRNA, whereas RYGB increased UCP-3 mRNA in muscle and liver, and PGC-1 α mRNA in liver. ConclusionThe data suggest that RYGB and IT surgeries lead to enhanced GLP-1 secretion and produce similar stimulatory effects on important molecules of glucose metabolism but differential effects on key molecules of lipid oxidation in muscle and liver.

Genetic downregulation of receptor‐interacting protein 140 uncovers the central role of Akt signalling in the regulation of fatty acid oxidation in skeletal muscle cells

The role of the nuclear co-repressor receptor-interacting protein 140 (RIP140) in metabolic regulation, gene and protein expression and insulin signalling in skeletal muscle cells remains to be delineated. To study this question, L6 myotubes were treated with or without an RNA interference oligonucleotide sequence to downregulate RIP140 expression and incubated with or without insulin (1 μM). Downregulation of RIP140 increased (P < 0.05) basal palmitate uptake (by 20%) and decreased (P < 0.05) basal palmitate oxidation (by 38%). In control small interfering RNA-treated cells, insulin increased (P < 0.05) glucose (by 31%) and palmitate uptake (by 20%) and decreased (P < 0.05) palmitate oxidation (by 35%). However, in RIP140 small interfering RNA-treated cells, insulin did not affect (P > 0.05) palmitate uptake and increased (P < 0.05) palmitate oxidation (by 79%). In insulin-mediated conditions, downregulation of RIP140 decreased (P < 0.05) Akt(Ser473) and atypical protein kinase C-ζ(Thr403/410) phosphorylation. As expected, downregulation of RIP140 was accompanied by an increase (P < 0.05) in cytochrome c oxidase subunit 4 isoform 1 and peroxisome proliferator-activated receptor receptor γ coactivator-1α mRNA content. Downregulation of RIP140 increased (P < 0.05) fatty acid transport protein 1 mRNA content and carnitine palmitoyltransferase 1b protein content and decreased (P < 0.05) medium chain acyl-CoA dehydrogenase mRNA content in basal conditions. In insulin-mediated conditions, downregulation of RIP140 increased (P < 0.05) carnitine palmitoyltransferase 1b, fatty acid transport protein 1 and fibroblast growth factor 21 mRNA content and decreased (P < 0.05) medium chain acyl-CoA dehydrogenase mRNA content and plasma membrane fatty acid translocase/cluster of differentiation 36 protein content. Our data show that, in skeletal muscle cells, RIP140 expression significantly impacts palmitate uptake and oxidation and that alterations in gene expression and Akt-atypical protein kinaseC-ζ signalling can partly explain these changes.

Association of the peroxisome proliferator-activated receptor α gene L162V polymorphism with stage C heart failure

To analyze whether genetic variants of PPARA are associated with the development of stage C heart failure. We analyzed the distribution of the rs1800206, rs4253778 and rs135551 polymorphisms in genomic DNA extracted from peripheral blood cells of 534 patients in different heart failure stages and 63 healthy individuals. The mRNA expression of the peroxisome proliferator-activated receptor (PPAR)α target genes long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) and medium-chain acyl-CoA dehydrogenase (MCAD) was measured in myocardial biopsies of a subgroup of stage B and C patients. Functional studies were performed in HL-1 cardiomyocytes. The V162 allele of the rs1800206 polymorphism was more frequent in stage C patients than in stage A and B patients and healthy individuals. Patients with the V162 allele exhibited decreased myocardial LCHAD and MCAD mRNA expression as compared to L162 homozygote patients. In addition, stage C patients exhibited lower myocardial LCHAD and MCAD mRNA expression than stage B patients. Cardiomyocytes transfected with the V162 allele presented decreased PPARα transcriptional activity, LCHAD mRNA expression and ATP production compared to cardiomyocytes transfected with the L162 variant. These findings suggest that the V162 allele of the human PPARA gene can be a new risk factor in the development of stage C heart failure, likely via depressed cardiac PPARα activity.

A potential link between peroxisome proliferator-activated receptor signalling and the pathogenesis of arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by major fibro-fatty replacement of the right ventricle (RV). We hypothesized that changes in peroxisome proliferator-activated receptor (PPAR) signalling contributed to myocardium fatty accumulation and contractile dysfunction in ARVC. Real-time quantitative reverse transcriptase-polymerase chain reaction and western blotting were used to assess cardiac expression of PPARalpha and gamma and two of their downstream target genes--medium-chain acyl-CoA dehydrogenase (MCAD) and phosphoenolpyruvate carboxykinase (PEPCK)--in both RV and left ventricle (LV) from five controls and five ARVC patients. In vitro motility assays were used to analyse functional properties of myosin. In the RV, sliding velocity was nearly two-fold lower in ARVC than in controls, whereas a 10% reduction in velocity values was noted between ARVC and non-failing myocardium in the LV. In controls, PPARalpha and MCAD mRNA and protein levels were higher in the RV compared with the LV. In ARVC, the expression of PPARalpha and MCAD mRNA and/or proteins was decreased in both RV and LV. RV from ARVC was also characterized by a dramatic activation of the PPARgamma pathway, as attested by the increase in PPARgamma mRNA and protein (500 and 270%, respectively, each P < 0.001) and by the induction of PEPCK gene. In contrast, the LV of ARVC heart exhibited no changes in the expression of the PPARgamma regulatory pathway compared with control. ARVC is associated with major disturbances in the PPARalpha and PPARgamma signalling pathway in the RV that may contribute to intracellular lipid overload and severe myosin dysfunction.

Skeletal Muscle Characteristics of Rats with Obesity, Diabetes, Hypertension, and Hyperlipidemia

Data on the skeletal muscle characteristics of patients and animals with lifestyle-related diseases are limited. We investigated mRNA expression levels and fiber profiles in the skeletal muscles of rats with obesity, diabetes, hypertension, and/or hyperlipidemia. The mRNA expression levels of peroxisome proliferator-activated receptors (PPARalpha and PPARdelta/beta), PPARgamma coactivator-1alpha (PGC-1alpha), stearoyl-CoA desaturase-1 (SCD-1), carnitine palmi-toyl-transferase I (CPT I), medium-chain acyl-CoA dehydrogenase (MCAD), and mitochondrial transcriptional factor A (TFAM) in the soleus muscles were compared among 15-week-old control (WR), type 2 diabetic (GK), hypertensive (SHR), and hyperlipidemic (CP) rats. The fiber profiles in the soleus muscles of these rats were also determined. GK rats showed lower PPARdelta/beta, PGC-1alpha, and MCAD expression levels than WR rats. SHR rats showed higher PPARalpha and MCAD and lower PPARdelta/beta expression levels than WR rats. CP rats showed lower PPARdelta/beta and higher SCD-1 expression levels than WR rats. The muscles of WR, SHR, and CP rats had low-oxidative type I and high-oxidative type IIA and type IIC fibers, whereas the muscle of GK rats had only low-oxidative type I fibers. The skeletal muscles of rats with lifestyle-related diseases have unique mRNA expres-sion patterns and fiber profiles depending on the type of disease. For example, the lower PGC-1alpha and MCAD mRNA expression levels in the soleus muscles of type 2 diabetic rats are associated with the presence of only low-oxidative type I fibers in the muscle.

Effects of dietary genistein on hepatic lipid metabolism and mitochondrial function in mice fed high-fat diets

Objective Genistein has been suggested to prevent insulin resistance and its related diseases. We investigated the effects of dietary genistein at different levels on hepatic lipid levels and mitochondrial functions in mice fed high-fat diets. Methods C57BL/6J mice were randomly divided into four groups and fed a high-fat diet containing genistein at levels of 0%, 0.1%, 0.2%, and 0.4% (HF, HF + 0.1G, HF + 0.2G, and HF + 0.4G) for 12 wk. We measured lipid levels in the blood and liver. We also observed messenger RNA (mRNA) expression of genes encoding proteins related to lipid and energy metabolism and antioxidant defense system and mitochondrial enzyme activities in the liver. Results The induction of fatty liver by HF was substantially decreased in the HF + 0.2G and HF + 0.4G groups. Peroxisome proliferator-activated receptorγ coactivator mRNA was increased by HF + 0.4G. Although genistein did not affect peroxisomal acyl-CoA oxidase mRNA expression, it increased medium-chain acyl-CoA dehydrogenase mRNA expression in a dose-dependent manner and HF + 0.2G increased uncoupling protein-2 mRNA expression two-fold relative to HF mice. Genistein decreased malondialdehyde levels and increased glutathione levels in liver homogenates, regardless of dose. The HF + 0.1G diet increased mitochondrial glutathione peroxidase activity and mitochondrial succinate dehydrogenase activity. Conclusions Although genistein at higher levels decreased hepatic fat accumulation possibly by increasing fatty acid oxidation and uncoupling protein, low-dose genistein increased mitochondrial enzyme activities in mice with fatty liver and obesity induced by high-fat diets.

Homozygosity for a severe novel medium-chain acyl-CoA dehydrogenase (MCAD) mutation IVS3-1G > C that leads to introduction of a premature termination codon by complete missplicing of the MCAD mRNA and is associated with phenotypic diversity ranging from sudden neonatal death to asymptomatic status

Virtually all patients with medium-chain acyl-CoA dehydrogenase deficiency (MCADD) are homozygous or compound heterozygous for the 985A > G mutation, which limits the study of a possible genotype/phenotype correlation. A newborn Palestinian infant died suddenly on the second day of life. A previous sibling had also died in similar circumstances aged 3 weeks. Urine organic acid and bloodspot acylcarnitine analysis were consistent with MCADD. He was homozygous for a novel MCAD splice mutation, IVS3-1G > C. This mutation leads to deletion of 7 bp and introduction of a premature termination codon as a result of complete missplicing of MCAD mRNA. This misspliced MCAD mRNA encodes a non-functional protein and is furthermore reduced in amounts due to nonsense-mediated decay, resulting in total lack of functional MCAD enzyme. This is the first molecular identification of MCADD in an Arab patient and the first reported splice mutation in the MCAD gene that has been functionally characterized. The association of homozygosity for a null mutation with lethal neonatal presentation in the index patient and presumably the previous infant suggested a genotype/phenotype correlation. However, a 6-year-old completely asymptomatic sibling also had the characteristic MCADD biochemical phenotype and was homozygous for the same IVS3-1G > C mutation. As a first candidate to modify the disease presentation, by modulating the overlapping enzyme activity, we tested the entire family for the prevalent SCAD gene 625G > A susceptibility variant. Interestingly, all family members were 625G > A homozygous. Additional genetic and/or environmental factors must play a major role in determining the phenotypic diversity of MCADD.

Beneficial effects of tea catechins on diet-induced obesity: stimulation of lipid catabolism in the liver.

Obesity has increased at an alarming rate in recent years and is now a worldwide health problem. We investigated the effects of long-term feeding with tea catechins, which are naturally occurring polyphenolic compounds widely consumed in Asian countries, on the development of obesity in C57BL/6J mice. We measured body weight, adipose tissue mass and liver fat content in mice fed diets containing either low-fat (5% triglyceride (TG)), high-fat (30% TG), or high-fat supplemented with 0.1-0.5% (w/w) tea catechins for 11 months. The beta-oxidation activities and related mRNA levels were measured after 1 month of feeding. Supplementation with tea catechins resulted in a significant reduction of high-fat diet-induced body weight gain, visceral and liver fat accumulation, and the development of hyperinsulinemia and hyperleptinemia. Feeding with tea catechins for 1 month significantly increased acyl-CoA oxidase and medium chain acyl-CoA dehydrogenase mRNA expression as well as beta-oxidation activity in the liver. The stimulation of hepatic lipid metabolism might be a factor responsible for the anti-obesity effects of tea catechins. The present results suggest that long-term consumption of tea catechins is beneficial for the suppression of diet-induced obesity, and it may reduce the risk of associated diseases including diabetes and coronary heart disease.

Effects of fatty acids on mitochondrial beta-oxidation enzyme gene expression in renal cell lines.

Regulatory effects of fatty acids on gene expression of medium-chain acyl-CoA dehydrogenase (MCAD), a mitochondrial beta-oxidation enzyme, were investigated in rabbit kidney cell lines derived from proximal tubule (RC.SV1), thick ascending limb of Henle's loop (RC.SV2), or collecting duct (RC.SV3). Exposure to long-chain fatty acids led to significant increases (2-fold) in MCAD mRNA abundance in RC.SV1 and RC.SV2 cells; kinetics and dose-response studies established that maximal MCAD gene stimulation was reached 4 h after addition of 50 microM oleate (C18:1) in the culture medium. These effects of fatty acids were totally abolished in the presence of 1 microg/ml actinomycin D, a transcription inhibitor. Staining of cellular lipids revealed that fatty acid-induced gene stimulation could occur in the absence of cellular fatty acid accumulation. Altogether, these data indicate that small changes in cellular fatty acid flux can have direct short-term effects on fatty acid oxidation enzyme gene expression in renal cells, and this might take part in the regulation of cellular fatty acid homeostasis in response to changes in tubular fluid composition.

食餌性茶カテキンはマウスの脂質代謝酵素の遺伝子発現を伴う肥満の進行を低減する（原標題は英語）

Obesity is a metabolic disorder due to less energy expenditure than its uptake and is a strong risk factor for non-insulin-dependent diabetes mellitus (NIDDM), hypertension and atherosclerosis. The present study examines the effects of long-term feeding of tea catechins on body weight, fat accumulation, and mRNA of genes involved in β-oxidation in obesity-prone C57BL/6J mice. Four months high fat diet (30% TG+13% sucrose) administration significantly increased body weight, epididymal fat accumulation and circulating leptin compared to the control diet mice (5% TG). High fat feeding-induced body weight gain and epididymal fat weight were reduced by 81% and 63%, respectively, in mice fed the catechin diet (30% TG+13% sucrose+0.5% tea catechins). Circulating leptin was reduced by 68%. Compared with the high fat diet group, catechin-feeding up-regulated medium-chain acyl-CoA dehydrogenase mRNA expression in the liver, suggesting tea catechins to possibly stimulate lipid metabolism in the liver. Long-term feeding of tea catechins is thus shown beneficial for suppressing high fat diet-induced body fat accumulation. The stimulation of lipid metabolism in the liver may possibly be a factor for the anti-obesity effects of tea catechins in mice.

The energy substrate switch during development of heart failure: gene regulatory mechanisms (Review).

During cardiac hypertrophy and in the failing heart, the chief myocardial energy substrate switches from fatty acids to glucose. In this review, we describe recent progress in the elucidation of the molecular regulatory events involved in the dramatic downregulation of the expression of fatty acid utilization enzymes during development of cardiac hypertrophy and failure. Much of this work has focused on the gene encoding medium-chain acyl-CoA dehydrogenase (MCAD), which catalyzes a pivotal step in the mitochondrial fatty acid -oxidation (FAO) cycle. In vivo ventricular pressure overload studies performed in mice transgenic for human MCAD promoter fragments linked to reporter genes have shown that transcription is markedly downregulated within seven days of pressure overload. The temporal pattern of this alteration in MCAD gene expression has also been characterized in a rat model of progressive pressure overload-induced left ventricular hypertrophy (LVH) and heart failure (HF) [SHHF/Mcc-facp (SHHF) rat]. MCAD mRNA levels are downregulated (>70%) during both the LVH and HF stages in the SHHF rats compared with controls. In contrast, the activity and immunodetectable levels of MCAD enzyme were not significantly reduced until the HF stage, indicating additional compensatory control at the translational or post-translational levels in the hypertrophied but non-failing ventricle. FAO enzyme expression was also shown to be downregulated in human subjects with dilated cardiomyopathy compared to age-matched controls. Taken together, these results have identified a gene regulatory program that is involved in the alterations in myocardial energy substrate utilization in the failing heart. The temporal correlation of diminished enzyme expression with onset of heart failure suggests that this alteration in lipid metabolism may play a role in the pathogenesis of pressure-overload induced heart failure. This gene regulatory pathway should be a useful target for experimental studies aimed at the molecular pathogenesis of the transition from stable cardiac hypertrophy to overt heart failure.

Tissue-specific regulation of medium-chain acyl-CoA dehydrogenase gene by thyroid hormones in the developing rat

During development, gene expression of medium-chain acyl-CoA dehydrogenase (MCAD), a nuclear-encoded mitochondrial enzyme that catalyses the first step of medium-chain fatty acid beta-oxidation, is highly regulated in tissues in accordance with fatty acid utilization, but the factors involved in this regulation are largely unknown. To investigate a possible role of thyroid hormones, rat pups were made hypothyroid by the administration of propylthiouracyl to the mother from day 12 of gestation, and their kidneys, heart and liver were removed on postnatal day 16 to determine MCAD mRNA abundance, protein level and enzyme activity. Similar experiments were run in 3,3',5-tri-iodothyronine (T3)-replaced hypothyroid (1 microg of T3/100 g body weight from postnatal day 5 to 15) and euthyroid pups. Hypothyroidism led to an increase in MCAD mRNA abundance in kidney and a decrease in abundance in heart, but had no effect in liver. The protein levels and enzyme activity were lowered in hypothyroid heart and kidney, suggesting that hypothyroidism affects post-transcriptional steps of gene expression in the kidney. All the effects of hypothyroidism were completely reversed in both heart and kidney by T3 replacement. Injection of a single T3 dose into 16-day-old euthyroid rats also led to tissue-specific changes in mRNA abundance. Nuclear run-on assays performed from hypothyroid and hypothyroid plus T3 rats showed that T3 stimulates MCAD gene transcription in heart and represses it in the kidney. These results indicate that the postnatal rise in circulating T3 is essential to the developmental regulation of the MCAD gene in vivo.

Activation of a novel metabolic gene regulatory pathway by chronic stimulation of skeletal muscle.

To determine whether expression of a nuclear gene encoding a mitochondrial fatty acid oxidation enzyme is regulated in parallel with skeletal muscle fibre-type-specific energy substrate preference, expression of the gene encoding medium-chain acyl-CoA dehydrogenase (MCAD) was delineated in canine latissimus dorsi muscle subjected to chronic motor nerve stimulation. In predominantly fast-twitch canine latissimus dorsi muscle, MCAD mRNA levels were regulated by chronic stimulation in a biphasic pattern. During the 1st wk of stimulation, steady-state MCAD mRNA levels decreased to 50% of unstimulated levels. MCAD mRNA levels began to increase during the 3rd wk of stimulation to reach a level 3.0-fold higher than levels in unstimulated contralateral control muscle by day 70. Immunodetectable MCAD mRNA levels throughout the stimulation period. The temporal pattern and magnitude of MCAD mRNA accumulation in response to muscle stimulation was distinct from that of mRNAs encoding other enzymes known to be regulated by this stimulus, including glyceraldehyde phosphate dehydrogenase, citrate synthase, and sarcoplasmic reticulum Ca-ATPase, but paralleled the protein levels of the peroxisome proliferator-activated receptor (PPAR), an orphan member of the nuclear hormone receptor superfamily known to regulate genes encoding fatty acid oxidation enzymes in liver. The skeletal muscle expression pattern of PPAR was also similar to that of MCAD in unstimulated rat skeletal muscles with distinct fiber-type compositions. These results demonstrate that a nuclear gene encoding a mitochondrial beta-oxidation enzyme is dynamically regulated in a pattern that parallels skeletal muscle fiber-type-specific energy substrate utilization and implicate an orphan nuclear receptor transcription factor as a candidate transducer of this response.