Hormonal and nutritional regulation of muscle carnitine palmitoyltransferase I gene expression in vivo

Aging and short-term calorie restriction differently affect the cardiac and skeletal muscle expression of genes regulating energy substrate utilization in male rats

Aging affects the energy metabolism differently in the cardiac and skeletal muscles. The study aim was to assess the effects of short-term calorie restriction (SCR) and refeeding on the expression of genes involved in the control of cardiac and skeletal muscle energy metabolism in old vs. young male rats. Young (4 mo) and old (24 mo) rats were subjected to 60% SCR for 30 days, and refed ad libitum for 2 or 4 days. In the cardiac (CM) and skeletal muscles (SM) we compared the gene expression (qPCR) of carnitine palmitoyltransferase-I (Cpt-I), peroxisome proliferator-activated receptor beta/delta (Ppar-β/δ), glucose transporter 4 (Glut4), peroxisome proliferator-activated receptor-γ coactivator-1α (Pgc-1α), and sirtuin 3 (Sirt3). In CM, aging increased Cpt-I expression but did not affect the other genes. In SM, Cpt-I, Glut4, Pgc-1α, and Sirt3 mRNA levels were lower in old than young rats. In CM of only young rats SCR increased Cpt-I expression which remained elevated after refeeding. Upon SCR, the expression of Ppar-β/δ, Glut4, Pgc-1α, and Sirt3 in CM increased in young but not old rats, and refeeding re-established control levels. In SM of young rats SCR increased Ppar-β/δ and Pgc-1α, and decreased Sirt3 expression, whereas refeeding generally decreased these mRNA levels. In SM of old rats SCR decreased only Pgc-1α expression. The adaptive response to SCR and subsequent refeeding is muscle tissue-specific and differs in young and old male rats. SCR appears to increase the efficiency of glucose and fatty acid utilization in the cardiac muscle of young, but not old male rats.

Bilobalide Enhances AMPK Activity to Improve Liver Injury and Metabolic Disorders in STZ-Induced Diabetes in Immature Rats via Regulating HMGB1/TLR4/NF-κB Signaling Pathway

This study was aimed at examining the effect and underlying mechanisms of bilobalide (BB) on hepatic injury in streptozotocin- (STZ-) induced diabetes mellitus (DM) in immature rats. Immature rats (one day old) were randomly divided into five groups: group I, control nondiabetic rats; group II, STZ-induced, untreated diabetic rats; groups III/IV/V, STZ-induced and BB-treated diabetic rats, which were intraperitoneally injected with BB (2.5 mg/kg, 5 mg/kg, or 10 mg/kg) after 3 days followed by STZ treatment. We observed that BB improved the histopathological changes and maintained normal glucose metabolism, blood lipid, and liver function indicators, such as fasting blood glucose, obesity index, HbA1c, HOMA-IR, fast serum insulin, adiponectin, total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), aspartate transaminase (AST), and alanine transaminase (ALT) in STZ-induced DM in immature rats by a biochemical analyzer or ELISA. Meanwhile, Western blot analysis showed that in STZ-induced DM immature rats, BB decreased the expression of apoptosis-related proteins Bax, cleaved caspase-3, and cleaved caspase-9 while enhancing the Bcl-2 expression; BB downregulated the expression of ACC related to fat anabolism, while upregulating the expression of CPT-1 related to fat catabolism. Strikingly, treatment with BB significantly increased the expression of AMPKα1 as well as inhibited HMGB1, TLR4, and p-P65 expression in hepatic tissues of immature DM rats. AMPK inhibitor (compound C, CC) cotreated with BB undermined the protective effect of BB on the liver injury. The results of the present study suggested BB may have a significant role in alleviating liver damage in the STZ-induced immature DM rats.

Mutation yellow in agouti loci prevents age-related increase of skeletal muscle genes regulating free fatty acids oxidation

The lethal yellow mutation in agouti loci (Ay mutation) reduces the activity of melanocortin (MC) receptors and causes hyperphagia, obesity and type two diabetes mellitus in aging mice (Ay mice). It is unknown if changes in distinct elements of the metabolic system such as white adipose tissue (WAT) and brown adipose tissue (BAT), and skeletal muscle will manifest before the development of obesity. The aim of this work was to measure the relative gene expression of key proteins that regulate carbohydrate-lipid metabolism in WAT, BAT and skeletal muscle in Ay mice before the development of obesity. C57Bl/6J mice bearing a dominant autosomal mutation Ay (Ay /a mice) and mice of the standard genotype (a/a mice, control) have been studied in three age groups: 10, 15 and 30 weeks. The relative mRNA level of genes was measured by real-time PCR in skeletal muscles (uncoupling protein 3 (Ucp3) and carnitine palmitoyl transferase 1b (Cpt1b) (free fatty acids oxidation), solute carrier family 2 (facilitated glucose transporter), member 4 (Slc2a4) (glucose uptake)), in WAT lipoprotein lipase (Lpl) (triglyceride deposition), hormone-sensitive lipase (Lipe) (lipid mobilization), and Slc2a4 (glucose uptake)), and in BAT: uncoupling protein 1 (Ucp1) (energy expenditure). The expression of Cpt1b was reduced in young Ay mice (10 weeks), there was no transient peak of transcription of Cpt1b, Ucp3 in skeletal muscle tissue and Lipe, Slc2a4 in WAT in early adult Ay mice (15 weeks), which was noted in а/а mice. Reduction of the transcriptional activity of the studied genes in skeletal muscle and white adipose tissue can initiate the development of melanocortin obesity in Ay mice.

Carnitine palmitoyltransferase 1B 531K allele carriers sustain a higher respiratory quotient after aerobic exercise, but β3-adrenoceptor 64R allele does not affect lipolysis: a human model

Carnitine palmitoyltransferase IB (CPT1B) and adrenoceptor beta-3 (ADRB3) are critical regulators of fat metabolism. CPT1B transports free acyl groups into mitochondria for oxidation, and ADRB3 triggers lipolysis in adipocytes, and their respective polymorphisms E531K and W64R have been identified as indicators of obesity in population studies. It is therefore important to understand the effects of these mutations on ADRB3 and CPT1B function in adipose and skeletal muscle tissue, respectively. This study aimed to analyze the rate of lipolysis of plasma indicators (glycerol, free fatty acids, and beta hydroxybutyrate) and fat oxidation (through the non-protein respiratory quotient). These parameters were measured in 37 participants during 30 min of aerobic exercise at approximately 62% of maximal oxygen uptake, followed by 30 min of recovery. During recovery, mean respiratory quotient values were higher in K allele carriers than in non-carriers, indicating low post-exercise fatty acid oxidation rates. No significant differences in lipolysis or lipid oxidation were observed between R and W allele carriers of ADRB3 at any time during the aerobic load. The substitution of glutamic acid at position 531 by lysine in the CPT1B protein decreases the mitochondrial beta-oxidation pathway, which increases the non-protein respiratory quotient value during recovery from exercise. This may contribute to weight gain or reduced weight-loss following exercise.

Obesity: considerations about etiology, metabolism, and the use of experimental models

Studies have been conducted in order to identify the main factors that contribute to the development of obesity. The role of genetics has also been extensively studied. However, the substantial augmentation of obesity prevalence in the last 20 years cannot be justified only by genetic alterations that, theoretically, would have occurred in such a short time. Thus, the difference in obesity prevalence in various population groups is also related to environmental factors, especially diet and the reduction of physical activity. These aspects, interacting or not with genetic factors, could explain the excess of body fat in large proportions worldwide. This article will focus on positive energy balance, high-fat diet, alteration in appetite control hormones, insulin resistance, amino acids metabolism, and the limitation of the experimental models to address this complex issue.

Increased carnitine palmitoyl transferase 1 expression and decreased sterol regulatory element-binding protein 1c expression are associated with reduced intramuscular triglyceride accumulation after insulin therapy in high-fat-diet and streptozotocin-induced diabetic rats

We previously reported that early insulin treatment reduced intramuscular triglyceride content in type 2 diabetes mellitus Sprague-Dawley rats; the underlying mechanisms are, however, not completely understood. Here we investigated the regulation of insulin on molecular expressions involved in lipid metabolism pathways in skeletal muscle of high-fat-diet and streptozotocin-induced diabetic Sprague-Dawley rats. Neutral protamine Hagedorn insulin and gliclazide were initiated at the third day after streptozotocin injection and lasted for 3 weeks. Compared with normal rats, untreated diabetic rats had a 30% and 61% increase in lipoprotein lipase protein expression and activity, which were decreased by insulin and gliclazide (P < .05). Fatty acid translocase protein was down-regulated by 45% in untreated diabetic rats, which was up-regulated by 31% and 26% with insulin and gliclazide, respectively (P < .05). Insulin failed to affect fatty acid transport protein 1 and fatty acid binding protein expressions. Carnitine palmitoyl transferase 1 had a 47% decrease in untreated diabetic rats, which was normalized by insulin (P < .05). Moreover, compared with normal rats, untreated diabetic rats had higher expressions of sterol regulatory element-binding protein 1c, tumor necrosis factor alpha, and Tyr(705) phosphorylation of signal transducer and activator of transcription 3 levels, which all were down-regulated after insulin treatment. These results suggested that early insulin reduced intramuscular triglyceride levels in diabetic rats potentially through amelioration of lipid dysfunction and inhibition of lipid synthesis.