mRNA Levels Of Carnitine Palmitoyltransferase-1 Research Articles

Therapeutic Effect of Gypenosides on Nonalcoholic Steatohepatitis via Regulating Hepatic Lipogenesis and Fatty Acid Oxidation.

Nonalcoholic steatohepatitis (NASH) is the most frequent cause of liver dysfunction and a common global problem. Gypenosides can decrease pathological modifications of high-fat diet-induced rat atherosclerosis; however, its effect and mechanism on NASH remain unclear. In this study, rats were randomly divided into normal control and model groups. Model rats were fed with a high-fat diet and treated with gypenosides, rosiglitazone, or water for 6 weeks. We found that liver tissues showed significant hepatic steatosis and vacuolar degeneration with significantly higher triglyceride (TG), free fatty acid (FFA) and malonyl CoA, serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT) activities in model group versus normal control group (p<0.01). Liver tissue mRNA and protein levels of sterol regulatory element binding protein-1c (SREBP-1c), carbohydrate response element binding protein (ChREBP), acetyl-CoA carboxylase (ACCase), and stearoyl CoA desaturase enzyme 1 (SCD1) were significantly increased, while the carnitine palmitoyl transferase-1 (CPT-1) level was significantly decreased in the model group versus the normal control group (p<0.01). Pathological changes of hepatic steatosis; body weight and liver wet weight; liver tissue TG, FFA and malonyl CoA concentrations; serum ALT, AST and GGT activities; liver tissue mRNA and protein levels of SREBP-1c, ChREBP, ACCase, and SCD-1 were significantly decreased; protein and mRNA levels of CPT-1 were significantly increased in the gypenosides group versus model group (p<0.01). In conclusion, gypenosides has therapeutic effect on NASH through regulating key transcriptional factors and lipogenic enzymes involved in fatty acid oxidation during hepatic lipogenesis.

Cannabinoid receptor type 1 mediates high-fat diet-induced insulin resistance by increasing forkhead box O1 activity in a mouse model of obesity.

Hepatic glucose production is promoted by forkhead box O1 (FoxO1) under conditions of insulin resistance. The overactivity of cannabinoid receptor type 1 (CB1R) partly causes increased liver fat deposits and metabolic dysfunction in obese rodents by decreasing mitochondrial function. The aim of the present study was to investigate the role of FoxO1 in CB1R-mediated insulin resistance through the dysregulation of mitochondrial function in the livers of mice with high-fat diet (HFD)-induced obesity. For this purpose, male C57BL/6 mice were randomly assigned to groups and either fed a standard diet (STD), a HFD, or a HFD with 1-week treatment of the CB1R inverse agonist, AM251, at 1 or 5 mg/kg. For in vitro experiments, AML12 hepatocytes were incubated with FoxO1 siRNA prior to challenge with arachidonyl-2'-chloroethylamide (ACEA) or a high concentration of free fatty acids (HFFA). Plasma parameters were analyzed using colorimetric methods. Liver histopathology and hepatic status markers were examined. The HFD-fed mice exhibited an increase in CB1R levels in the liver. Moreover, in response to increased hepatic oxidative stress, the HFD-fed mice also displayed hepatic mitochondrial dysfunction, as indicated by the decreased mRNA levels of carnitine palmitoyltransferase-1 (CPT-1), mitochondrial transcription factor A (TFAM), nuclear respiratory factor-1 (NRF-1) and citrate synthase. On the contrary, these effects in the HFD-fed mice were reversed by treatment with 5 mg/kg AM251. The administration of AM251 suppressed the induction of FoxO1, phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6-phosphatase (G6Pase) expression in the livers of the mice fed a HFD by enhancing the phosphorylation of insulin signaling cascades thus, further lowering the high level of the homeostatic model assessment of insulin resistance (HOMA‑IR) index. In our in vitro experiments, transfection with FoxO1 siRNA prevented the HFFA- and ACEA-induced decrease in the gene expression of mitochondrial biogenesis-related factors, and abrogated the HFFA- and ACEA-induced increase in PEPCK and G6Pase expression. Taken together, our findings suggest that the anti-insulin resistance effect of AM251, which leads to an improvement of mitochondrial function in hepatic steatosis, is mediated through FoxO1.

Effects of feed deprivation on the AMPK signaling pathway in skeletal muscle of broiler chickens.

The 5'-adenosine monophosphate-activated protein kinase (AMPK) plays a key role in rapid metabolic adaptations to maintain energy homeostasis in poultry. It remains unclear if AMPK is involved in muscular energy metabolism in broiler chickens. Hence, in the present study, seven-day-old male broilers were equally divided into three groups: fed ad libitum (control); feed-deprived for 24h (S24); feed-deprived for 24h and then refed for 24h (S24R24). Compared to the control group, the plasma levels of glucose, insulin, T3 and triglycerides in the S24 group were significantly lower (P<0.05), whereas the uric acid levels were significantly higher (P<0.01). Except for glucose, refeeding for 24h reversed the fasting-induced alterations in plasma metabolite. Fasting decreased the liver kinase B1 (LKB1), AMPK alpha 2 subunit (AMPKα2), and fatty acid synthase (FAS) mRNA levels (P<0.05) in M. pectoralis major (PM). Feed deprivation did not affect the phosphorylated AKT, mammalian target of rapamycin (mTOR) and ribosomal protein S6 kinase (p70S6K) in PM (P>0.05), but upregulated carnitine palmitoyltransferase 1 (CPT1) gene expression and increased phosphorylated LKB1 (0.05<P<0.1) and AMPKα (P<0.05) levels. AMPKα2, FAS, and CPT1 mRNA levels and the protein levels of phosphorylated AMPK and LKB1 of the PM muscle returned to control group levels after 24h refeeding. In M. biceps femoris (BF), the AMPKα2 and FAS mRNA levels were decreased by fasting compared to control (P<0.05), whereas CPT1 mRNA and phosphorylated LKB1 and AMPK protein levels were increased. Refeeding for 24h reversed the changes in AMPKα2 and CPT1 gene expression and phosphorylated AMPKα2 subunit. Fasting did not affect the AKT, mTOR and p70S6K in both PM and BF muscles (P>0.05). However, refeeding after 24h of fasting increased the phosphorylated mTOR level in BF muscle which was in parallel with increased plasma insulin concentration. It was likely that increased phospho-mTOR level in the BF muscle was due to the higher sensitivity of BF to insulin. Together, the results suggested that the AMPK signaling pathway might be involved in the energy metabolism alterations in the skeletal muscles of broiler chickens and was also dependent upon the muscle fiber type. Furthermore, the regulatory effects of AMPK on energy metabolism in muscles of broiler chickens might be mediated by the AMPK/FAS pathway.

Effects of resveratrol on lipid metabolism in muscle and adipose tissues: A reevaluation in a pig model

The body fat-lowering effect and mechanisms of action of resveratrol (0, 300, 600 mg resveratrol/kg diet) was evaluated in a pig model. Resveratrol improved serum lipid profiles, and decreased visceral adipose tissue weight and serum leptin level. In adipose tissue, peroxisome proliferator activated receptor γ (PPARγ) and fatty acid synthase (FAS) mRNA levels, and FAS and lipoprotein lipase (LPL) activities were decreased by resveratrol, while hormone sensitive lipase (HSL), adipose triglyceride lipase (ATGL) and carnitine palmitoyl transferase-1(CPT-1) mRNA levels, and HSL and CPT-1 activities were increased. In muscle tissue, PPARγ, FAS, acetyl-CoA carboxylase (ACC) and LPL mRNA levels and FAS and ACC activities were decreased by resveratrol, while HSL mRNA levels and CPT-1 activity were increased. Moreover, compared with the control group, LPL activity was decreased, and CPT-1 mRNA levels and HSL activity were increased in the 600 mg resveratrol/kg diet group. This study provides the very first evidence in a pig model that resveratrol could improve serum lipid profiles and decrease body fat deposition, which might be mediated by a reduction in fatty acid uptake and de novo lipogenesis, as well as an increase in fat mobilization and fatty acid oxidation in muscle and adipose tissues.

Supplementation dietary zinc levels on growth performance, carcass traits, and intramuscular fat deposition in weaned piglets.

This study was conducted to estimate dietary zinc (Zn) levels on growth performance, carcass traits, and intramuscular fat (IMF) deposition in weaned piglets. Sixty piglets were randomly divided into five groups, as follows: control (basal diet), Zn250, Zn380, Zn570, and Zn760 with supplementation of 250, 380, 570, and 760 mg Zn/kg of the basal diet, respectively. The final weight, average daily gain (ADG), gain/feed (G/F), lean meat percentage, fat meat percentage, lean eye area, backfat thickness, and IMF content were dose-dependently increased in all groups of Zn treatment. The serum total triglycerides (TG) and free fatty acid (FFA) were significantly higher in all Zn treatments than in the control. The enzyme activities of lipoprotein lipase (LPL), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC) were markedly higher, while enzyme activities of hormone-sensitive lipase (HSL) and carnitine palmitoyltransferase-1 (CPT-1) were significantly lower in all Zn treatments than in the control. The messenger RNA (mRNA) levels of sterol regulatory element-binding protein 1 (SREBP-1), stearoyl-CoA desaturase (SCD), FAS, ACC, peroxisome proliferator-activated receptor γ (PPARγ), LPL, and adipocyte fatty acid-binding protein (A-FABP) were significantly higher, while the mRNA levels of CPT-1 and HSL were significantly lower in all Zn treatments compared with the control. These results indicated that high levels of Zn increased IMF accumulation by up-regulating intramuscular lipogenic and fatty acid transport gene expression and enzyme activities while down-regulating lipolytic gene expression and enzyme activities.

Moderate calorie restriction during gestation programs offspring for lower BAT thermogenic capacity driven by thyroid and sympathetic signaling

Maternal calorie restriction during pregnancy programs offspring for later overweight and metabolic disturbances. Brown adipose tissue (BAT) is responsible for non-shivering thermogenesis and has recently emerged as a very likely target for human obesity therapy. Here we aimed to assess whether the detrimental effects of undernutrition during gestation could be related to impaired thermogenic capacity in BAT and to investigate the potential mechanisms involved. Offspring of control and 20% calorie-restricted rats (days 1-12 of pregnancy) (CR) were studied at the age of 25 days. Protein levels of uncoupling protein 1 (UCP1) and tyrosine hydroxylase (TyrOH); mRNA levels of lipoprotein lipase (LPL), carnitine palmitoyltransferase 1 (CPT1) and deiodinase iodothyronine type II (DIO2) in BAT; and blood parameters including thyroid hormones, were determined. The response to 24-h cold exposure was also studied by measuring body temperature changes over time, and final BAT UCP1 levels. Compared with controls, CR animals displayed in BAT lower UCP1 and TyrOH protein levels and lower LPL and CPT1 mRNA levels; they also showed lower triiodothyronine (T3) plasma levels. CR males, but not females, revealed lower DIO2 mRNA levels than controls. When exposed to cold, CR rats experienced a transient decline in body temperature, but the values were reestablished after 24 h, despite having lower UCP1 levels than controls. These results suggest that BAT thermogenic capacity is diminished in CR animals, involving impaired BAT sympathetic innervation and thyroid hormone signaling. These alterations make animals more sensitive to cold and may contribute to long-term outcomes of gestational calorie restriction in promoting obesity and related metabolic alterations.

A high‐fat diet reduces ceramide synthesis by decreasing adiponectin levels and decreases lipid content by modulating HMG‐CoA reductase and CPT‐1 mRNA expression in the skin

Molecules involved in skin function are greatly affected by nutritional conditions. However, the mechanism linking high-fat (HF) diets with these alterations is not well understood. This study aimed to investigate the molecular changes in skin function that result from HF diets. Sprague-Dawley rats were fed HF diets for 28 days. The skin levels of ceramide, lipids and mRNAs involved in lipid metabolism were evaluated using TLC, oil red O staining and quantitative PCR, respectively. The serum adiponectin concentration was determined by ELISA. HF diets led to reduced ceramide levels and lowered skin lipid content. They also decreased mRNA levels of serine palmitoyltransferase (SPT) and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase in the skin and those of peroxisome proliferator-activated receptor-α -PPAR-α), which upregulates SPT and HMG-CoA reductase expression. The HF diets reduced the serum concentration of adiponectin, which acts upstream of PPAR-α. Finally, these diets led to increased mRNA levels of carnitine palmitoyltransferase-1, the rate-limiting enzyme that acts in β-oxidation. Our study suggests that HF diets reduce ceramide and lipid synthesis in the skin by reducing levels of SPT and HMG-CoA reductase through lowered adiponectin and PPAR-α activity. Additionally, they decrease lipid content by enhancing β-oxidation.

Abstract P4-03-02: Establishing a Relationship between Breast Cancer, Prolactin and Altered Fat Metabolism

Abstract Despite decades of research, breast cancer remains one of the most common cancers world-wide. Mammary carcinoma has been associated with a high-fat diet, and its rate in overweight post-menopausal women is up to 50% higher than in normal-weight women. The current study examined breast cancer as a metabolic disease in the context of altered fat catabolism, with a focus on examining the effects of prolactin (PRL) on the adenosine 5'-monophosphate-activated protein kinase (AMPK) energy sensing pathway that culminates with carnitine palmitoyl transferase 1 (CPT1), an enzyme that shuttles long-chain fatty acids into the mitochondrial matrix for beta oxidation. When a cell has high energy demands or is stressed, AMPK activation leads to either increased glucose uptake or the phosphorylation of acetyl-CoA carboxylase (ACC), resulting in a reduction in malonyl-CoA levels that lift an allosteric inhibition on CPT1, in turn leading to an increase in CPT1 enzyme activity. Conversely, increased malonyl-CoA levels, together with increased fatty acid synthase activity, favor lipogenesis. PRL has been shown to affect fat metabolism in adipocytes by altering malonyl-CoA levels, and we therefore examined whether CPT1 expression was altered in breast cancer cells in response to treatment with recombinant human PRL. The metabolic effects of this hormone, which is normally produced in breast tissue and has been epidemiologically linked with breast cancer, were investigated in a normal human breast epithelial cell line (184B5) and in breast cancer cells. PRL up-regulated CPT1 expression at both the mRNA and protein levels in cancer cells, but not in 184B5 cells. Of note, compared to MCF-7 or MDA-MB-231 cells, T47D cells expressed the highest levels of CPT1. The 85 kDa PRL receptor isoform was also highly expressed in this cell line compared to 184B5 or MCF-7 cells. Furthermore, PRL dose-dependently increased CPT1 enzyme activity in T47D cells, also inducing the phosphorylation of both the AMPKα catalytic subunit at threonine 172 and ACC. In T47D cells treated with AMPKα siRNA, transient knock-down of the catalytic AMPK subunit correlated with a similar knock-down in CPT1 mRNA levels. CPT1 levels in the knock-down cells could not be restored by treatment with PRL, suggesting that the PRL-mediated effect requires activation of the AMPK pathway. We also demonstrated that treatment with PRL leads to the phosphorylation of TAK1 and LKB1, two kinases that are known to activate AMPKα. It is known that PRL contributes to breast cancer by inducing cell proliferation, survival, motility, and angiogenesis. Our work proposes a novel role for this hormone in mammary carcinogenesis through its effect on fat metabolism via the induction of the AMPK pathway. Elucidating how breast cancer cells differentially produce and utilize energy compared to normal breast epithelial cells may lead to the development of new therapies for the treatment or improved management of this complex disease. (Research supported by Canadian Institutes of Health Research.) Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-03-02.

Effects of Changes of Diet from High‐fat to Low‐fat on Hepatic mRNA Levels of ACS, CPT‐1, and ACC

AimsThe purpose of this study was to investigate the effects of dietary changes from high‐fat diet (HFD, 45% of total calories from fat) to low‐fat diet (LFD, 10% of total calories from fat) on hepatic mRNA levels of acyl coenzyme A synthetase(ACS), carnitine palmitoyltransferase‐1(CPT‐1), and acetyl coenzyme A carboxylase(ACC) as well as on serum and hepatic lipids in mice.MethodsFive weeks‐old male C57BL/6 mice were fed high‐fat diet for 9 weeks then switched to a low‐fat diet or continued the high‐fat diet for 3 weeks. Body weight, serum and hepatic lipid levels were measured. Expressions of ACS, CPT‐1, and ACC mRNA were also analyzed.ResultsThe results showed that after the high‐fat diets were switched to low fat diets, body weight, epididymal and retroperitoneal fats were significantly reduced (p&lt;0.05). The levels of serum and hepatic total cholesterol were not different between the two groups however, serum TG levels of high‐fat diet followed by low‐fat diet group were significantly lower than those of high‐fat diet group (p&lt;0.05). Hepatic mRNA levels of CPT‐1 and ACC were higher significantly in the group of high‐fat diet followed by low‐fat diet (p&lt;0.05) however mRNA levels of ACS were not different between the two groups.ConclusionsChanges in the composition of dietary fat from high to low decreased significantly body fats and the serum TGs. Furthermore, changes of dietary fat composition affected differently the hepatic mRNA levels of ACS, CPT‐1 and ACC.