Chicken liver and muscle carnitine palmitoyltransferase 1: nutritional regulation of messengers

Effects of linseed oil supplementation duration on fatty acid profile and fatty acid metabolism-related genes in the muscles of Chinese crested white ducks

Meat rich in polyunsaturated fatty acids is considered beneficial to health. Supplementing the diet with linseed oil promotes the deposition of polyunsaturated fatty acids (PUFAs) in poultry, a conclusion that has been confirmed multiple times in chicken meat. However, fewer studies have focused on the effects of dietary fatty acids on duck meat. Therefore, this study aims to evaluate the effects of the feeding time of a linseed oil diet on duck meat performance and gene expression, including meat quality performance, plasma biochemical indicators, fatty acid profile, and gene expression. For this study, we selected 168 Chinese crested ducks at 28 days old and divided them into three groups, with 56 birds in each group. The linseed oil content in the different treatment groups was as follows: the control group (0% flaxseed oil), the 14d group (2% linseed oil), and the 28d group (2% linseed oil). Ducks in the two experimental groups were fed a linseed oil diet for 28 and 14 days at 28 and 42 days of age, respectively. The results showed that linseed oil had no negative effect on duck performance (slaughter rate, breast muscle weight, and leg muscle weight) or meat quality performance (pH, meat color, drip loss, and shear force) (P > 0.05). The addition of linseed oil in the diet increased plasma total cholesterol and high-density lipoprotein cholesterol levels (P < 0.05), while decreasing triglyceride content (P < 0.05). Furthermore, the supplementation of linseed oil for four weeks affected the composition of muscle fatty acids. Specifically, levels of α-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid were increased (P < 0.05), while eicosatetraenoic acid content was negatively correlated with flaxseed oil intake (P < 0.05). qRT-PCR analysis further revealed that the expression of FATP1, FABP5, and ELOVL5 genes in the breast muscle, as well as FABP3 and FADS2 genes in the thigh muscle, increased after four weeks of linseed oil supplementation (P < 0.05). However, after two weeks of feeding, CPT1A gene expression inhibited fatty acid deposition, suggesting an increase in fatty acid oxidation (P < 0.05). Overall, the four-week feeding time may be a key factor in promoting the deposition of n-3 PUFAs in duck meat. However, the limitation of this study is that it remains unknown whether longer supplementation time will continue to affect the deposition of n-3 PUFAs. Further experiments are needed to explain how prolonged feeding of linseed oil will affect the meat quality traits and fatty acid profile of duck meat.

Liver Transcriptome Response to Heat Stress in Beijing You Chickens and Guang Ming Broilers

Heat stress is one of the most prevalent issues in poultry production that reduces performance, robustness, and economic gains. Previous studies have demonstrated that native chickens are more tolerant of heat than commercial breeds. However, the underlying mechanisms of the heat tolerance observed in native chicken breeds remain unelucidated. Therefore, we performed a phenotypical, physiological, liver transcriptome comparative analysis and WGCNA in response to heat stress in one native (Beijing You, BY) and one commercial (Guang Ming, GM) chicken breed. The objective of this study was to evaluate the heat tolerance and identify the potential driver and hub genes related to heat stress in these two genetically distinct chicken breeds. In brief, 80 BY and 60 GM, 21 days old chickens were submitted to a heat stress experiment for 5 days (33 °C, 8 h/day). Each breed was divided into experimental groups of control (Ctl) and heat stress (HS). The results showed that BY chickens were less affected by heat stress and displayed reduced DEGs than GM chickens, 365 DEGs and 382 DEGs, respectively. The transcriptome analysis showed that BY chickens exhibited enriched pathways related to metabolism activity, meanwhile GM chickens’ pathways were related to inflammatory reactions. CPT1A and ANGPTL4 for BY chickens, and HSP90B1 and HSPA5 for GM chickens were identified as potential candidate genes associated with HS. The WGCNA revealed TLR7, AR, BAG3 genes as hub genes, which could play an important role in HS. The results generated in this study provide valuable resources for studying liver transcriptome in response to heat stress in native and commercial chicken lines.

Adenosine 5'-monophosphate induces hypothermia and alters gene expressions in the brain and liver of chicks

The adenosine A1 receptor is important for body temperature regulation in mammals; however, little is known about its function in avian species. In this study, we investigated the effects of the adenosine A1 receptor agonist and antagonist (adenosine 5'-monophosphate [5'-AMP] and 8 p-sulfophenyl theophylline [8-SPT], respectively) on thermoregulation in chickens. Male chicks were used in this study. After administration of 5'-AMP and 8-SPT, the rectal temperature, plasma metabolites, and gene expressions in the hypothalamus and liver were measured. The rectal temperature was reduced by peripheral administration of 5'-AMP, and the hypothermic effect of 5'-AMP was attenuated by central injection of 8-SPT in chicks. In the hypothalamus, the mRNA level of the agouti-related protein (AgRP) was increased by 5'-AMP administration, whereas it was suppressed by 8-SPT. The plasma levels of free fatty acid were elevated in 5'-AMP-treated chicks and that elevation was suppressed by the 8-SPT treatment. The gene expression of proopiomelanocortin in the hypothalamus was affected by 8-SPT. Nevertheless, the gene expressions of the thermoregulation-related genes, such as the thyrotropin-releasing hormone, were not affected by 5'-AMP and 8-SPT. Hepatic gene expressions related to lipid intake and metabolism were suppressed by 5'-AMP. However, the gene expression of the uncoupling protein was upregulated by 5'-AMP. Based on these results, birds, like mammals, will undergo adenosine A1 receptor-induced hypothermia. In conclusion, it is suggested that 5'-AMP-mediated hypothermia via the adenosine A1 receptor may affect the central melanocortin system and suppress hepatic lipid metabolism in chickens.

Effects of Thermal Conditioning on Changes in Hepatic and Muscular Tissue Associated With Reduced Heat Production and Body Temperature in Young Chickens

Effects of increased summer temperatures on poultry production are becoming more pronounced due to global warming, so it is important to consider approaches that might reduce heat stress in chickens. Thermal conditioning in chickens in the neonatal period can improve thermotolerance and reduce body temperature increases when birds are exposed to high ambient temperature later in life. The objective of this study was to investigate physiological and molecular changes associated with heat production and hence body temperature regulation under high ambient temperatures in thermally conditioned chicks. Three-day-old broiler chicks (Chunky) were thermally conditioned by exposure to a high ambient temperature (40°C) for 12 h while control chicks were kept at 30°C. Four days after the treatment, both groups were exposed to 40°C for 15 or 90 min. The increase in rectal temperature during 90 min of exposure to a high ambient temperature was less in thermally conditioned than control chicks. At 15-min of re-exposure treatment, gene expression for uncoupling protein and carnitine palmitoyletransferase 1, key molecules in thermogenesis and fatty acid oxidation, were significantly higher in pectoral muscle of control chicks but not conditioned chicks. Hepatic argininosuccinate synthase (ASS) decreased and hepatic argininosuccinate lyase (ASL) increased after reexposure to a high temperature. The concentrations of hepatic arginosuccinic acid, and ASS and ASL expression, were upregulated in conditioned chicks compared with the control chicks, indicating activity of the urea cycle could be enhanced to trap more energy to reduce heat production in conditioned chicks. These results suggest thermal conditioning can reduce the increase in heat production in muscles of chickens that occurs in high ambient temperatures to promote sensible heat loss. Conditioning may also promote energy trapping process in the liver by altering the heat production system, resulting in an alleviation of the excessive rise of body temperature.

Differential regulation of protein synthesis by skeletal muscle type in chickens

In mammalian skeletal muscles, protein synthesis rates vary according to fiber types. We herein demonstrated differences in the regulatory mechanism underlying the protein synthesis in the pectoralis major (a glycolytic twitch muscle), adductor superficialis (an oxidative twitch muscle), and adductor profound (a tonic muscle) muscles of 14-day-old chickens. Under ad libitum feeding conditions, protein synthesis is significantly higher in the adductor superficialis muscle than in the pectoralis major muscle, suggesting that protein synthesis is upregulated in oxidative muscles in chickens, similar to that in mammals. In the pectoralis major muscle, fasting significantly inhibited the Akt/S6 pathway and protein synthesis with a corresponding decrease in plasma insulin concentration. Conversely, the insulin like growth factor-1 (IGF-1) mRNA levels significantly increased. These findings suggest that the insulin/Akt/S6 pathway plays an important role in the regulation of protein synthesis in the pectoralis major muscle. Interestingly, protein synthesis in the adductor superficialis muscle appears to be regulated in an Akt-independent manner, because fasting significantly decreased S6 phosphorylation and protein synthesis without affecting Akt phosphorylation. In the adductor profound muscle, IGF-1 expression, phosphorylation of Akt and S6, and protein synthesis were decreased by fasting, suggesting that insulin and/or skeletal IGF-1 appear contribute to protein synthesis via the Akt/S6 pathway. These findings revealed the differential regulation of protein synthesis depending on skeletal muscle types in chickens.

Differential expression of genes implicated in liver lipid metabolism in broiler chickens differing in weight

1. Lipid parameters and expression of ACACA, APOA1, CPT1A, FASN, FOXO1, LIPG, PPARα and SIRT1 genes involved in lipid metabolism were investigated in two groups of high (HW) and low (LW) weight broilers from the same strain.2. Blood cholesterol and liver triglyceride levels were significantly increased in HW chickens compared to LW broilers, while other parameters, i.e. blood triglyceride, blood HDL/LDL, liver cholesterol and total liver fat showed no significant changes in either group.3. The relative expression of ACACA, APOA1 and CPT1A genes was significantly lower in the liver tissues of HW broilers than in the LW group. The mRNA levels of these three genes showed a significant negative correlation with abdominal fat deposition and live weight of broilers. However, relative expression of FASN, FOXO1, LIPG, PPARα and SIRT1 hepatic genes did not differ among broilers.4. It was concluded that, of eight hepatic genes implicated in lipid metabolism, only the expression of three (ACACA, APOA1 and CPT1A) were significant for fat and leanness within the same strain of chicken. Since reducing body fat is a major goal in the broiler industry, these data can provide fresh insight into the molecular processes underlying the regulation of fat deposition in broilers.

Antitumor effects of curcumin: A lipid perspective

Lipid metabolism plays an important role in cancer development due to the necessities of rapidly dividing cells to increase structural, energetic, and biosynthetic demands for cell proliferation. Basically, obesity, type 2 diabetes, and other related diseases, and cancer are associated with a common hyperactivated "lipogenic state." Recent evidence suggests that metabolic reprogramming and overproduction of enzymes involved in the synthesis of fatty acids are the new hallmarks of cancer, which occur in an early phase of tumorigenesis. As the first evidence to confirm dysregulated lipid metabolism in cancer cells, the overexpression of fatty acid synthase (FAS) was observed in breast cancer patients and demonstrated the role of FAS in cancer. Other enzymes of fatty acid synthesis have recently been found to be dysregulated in cancer, including ATP-dependent citrate lyase and acetyl-CoA carboxylase, which further underscores the connection of these metabolic pathways with cancer cell survival and proliferation. The degree of overexpression of lipogenic enzymes and elevated lipid utilization in tumors is closely associated with cancer progression. The question that arises is whether the progression of cancer can be suppressed, or at least decelerated, by modulating gene expression related to fatty acid metabolism. Curcumin, due to its effects on the regulation of lipogenic enzymes, might be able to suppress, or even cause regression of tumor growth. This review discusses recent evidence concerning the important role of lipogenic enzymes in the metabolism of cancer cells and whether the inhibitory effects of curcumin on lipogenic enzymes is therapeutically efficacious.

Basic mechanisms of the regulation of L-carnitine status in monogastrics and efficacy of L-carnitine as a feed additive in pigs and poultry

A great number of studies have investigated the potential of L-carnitine as feed additive to improve performance of different monogastric and ruminant livestock species, with, however, discrepant outcomes. In order to understand the reasons for these discrepant outcomes, it is important to consider the determinants of L-carnitine status and how L-carnitine status is regulated in the animal's body. While it is a long-known fact that L-carnitine is endogenously biosynthesized in certain tissues, it was only recently recognized that critical determinants of L-carnitine status, such as intestinal L-carnitine absorption, tissue L-carnitine uptake, endogenous L-carnitine synthesis and renal L-carnitine reabsorption, are regulated by specific nutrient sensing nuclear receptors. This review aims to give a more in-depth understanding of the basic mechanisms of the regulation of L-carnitine status in monogastrics taking into account the most recent evidence on nutrient sensing nuclear receptors and evaluates the efficacy of L-carnitine as feed additive in monogastric livestock by providing an up-to-date overview about studies with L-carnitine supplementation in pigs and poultry.

Multi-tissue transcriptomic study reveals the main role of liver in the chicken adaptive response to a switch in dietary energy source through the transcriptional regulation of lipogenesis

Background

Because the cost of cereals is unstable and represents a large part of production charges for meat-type chicken, there is an urge to formulate alternative diets from more cost-effective feedstuff. We have recently shown that meat-type chicken source is prone to adapt to dietary starch substitution with fat and fiber. The aim of this study was to better understand the molecular mechanisms of this adaptation to changes in dietary energy sources through the fine characterization of transcriptomic changes occurring in three major metabolic tissues – liver, adipose tissue and muscle – as well as in circulating blood cells.

Results

We revealed the fine-tuned regulation of many hepatic genes encoding key enzymes driving glycogenesis and de novo fatty acid synthesis pathways and of some genes participating in oxidation. Among the genes expressed upon consumption of a high-fat, high-fiber diet, we highlighted CPT1A, which encodes a key enzyme in the regulation of fatty acid oxidation. Conversely, the repression of lipogenic genes by the high-fat diet was clearly associated with the down-regulation of SREBF1 transcripts but was not associated with the transcript regulation of MLXIPL and NR1H3, which are both transcription factors. This result suggests a pivotal role for SREBF1 in lipogenesis regulation in response to a decrease in dietary starch and an increase in dietary PUFA. Other prospective regulators of de novo hepatic lipogenesis were suggested, such as PPARD, JUN, TADA2A and KAT2B, the last two genes belonging to the lysine acetyl transferase (KAT) complex family regulating histone and non-histone protein acetylation. Hepatic glycogenic genes were also down-regulated in chickens fed a high-fat, high-fiber diet compared to those in chickens fed a starch-based diet. No significant dietary-associated variations in gene expression profiles was observed in the other studied tissues, suggesting that the liver mainly contributed to the adaptation of birds to changes in energy source and nutrients in their diets, at least at the transcriptional level. Moreover, we showed that PUFA deposition observed in the different tissues may not rely on transcriptional changes.

Conclusion

We showed the major role of the liver, at the gene expression level, in the adaptive response of chicken to dietary starch substitution with fat and fiber.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4520-5) contains supplementary material, which is available to authorized users.

Structure and Functional Analysis of Promoters from Two Liver Isoforms of CPT I in Grass Carp Ctenopharyngodon idella

Carnitine palmitoyltransferase I (CPT I) is a key enzyme involved in the regulation of lipid metabolism and fatty acid β-oxidation. To understand the transcriptional mechanism of CPT Iα1b and CPT Iα2a genes, we cloned the 2695-bp and 2631-bp regions of CPT Iα1b and CPT Iα2a promoters of grass carp (Ctenopharyngodon idella), respectively, and explored the structure and functional characteristics of these promoters. CPT Iα1b had two transcription start sites (TSSs), while CPT Iα2a had only one TSS. DNase I foot printing showed that the CPT Iα1b promoter was AT-rich and TATA-less, and mediated basal transcription through an initiator (INR)-independent mechanism. Bioinformatics analysis indicated that specificity protein 1 (Sp1) and nuclear factor Y (NF-Y) played potential important roles in driving basal expression of CPT Iα2a gene. In HepG2 and HEK293 cells, progressive deletion analysis indicated that several regions contained cis-elements controlling the transcription of the CPT Iα1b and CPT Iα2a genes. Moreover, some transcription factors, such as thyroid hormone receptor (TR), hepatocyte nuclear factor 4 (HNF4) and peroxisome proliferator-activated receptor (PPAR) family, were all identified on the CPT Iα1b and CPT Iα2a promoters. The TRα binding sites were only identified on CPT Iα1b promoter, while TRβ binding sites were only identified on CPT Iα2a promoter, suggesting that the transcription of CPT Iα1b and CPT Iα2a was regulated by a different mechanism. Site-mutation and electrophoretic mobility-shift assay (EMSA) revealed that fenofibrate-induced PPARα activation did not bind with predicted PPARα binding sites of CPT I promoters. Additionally, PPARα was not the only member of PPAR family regulating CPT I expression, and PPARγ also regulated the CPT I expression. All of these results provided new insights into the mechanisms for transcriptional regulation of CPT I genes in fish.

Molecular characterization and nutritional regulation of carnitine palmitoyltransferase (CPT) family in grass carp (Ctenopharyngodon idellus)

The carnitine palmitoyltransferase (CPT) gene family plays an essential role in fatty acid β-oxidation in the mitochondrion. We identified six isoforms of the CPT family in grass carp and obtained their complete coding sequences (CDS). The isoforms included CPT 1α1a, CPT 1α1b, CPT 1α2a, CPT 1α2b, CPT 1β, and CPT 2, which may have resulted from fish-specific genome duplication. Sequence analysis showed that the predicted protein structure was different among the CPT gene family members in grass carp. The N-terminal domain of grass carp CPT 1α1a, CPT 1α1b, CPT 1α2a, and CPT 1α2b contained two transmembrane region domains and two acyltransferase choActase domains that exist in human and mouse proteins also; however, only one acyltransferase choActase domain was found in grass carp CPT 1β. The grass carp CPT 2 had two acyltransferase choActase domains. The grass carp CPT 1α1b, CPT 1α2a, CPT 1α2b, and CPT 1β contained 18 coding exons, while CPT 1α1a and CPT 2 consisted of 17 coding exons and 5 coding exons, respectively. The mRNA of the six CPT isoforms was expressed in a wide range of tissues, but the mRNA abundance of each CPT showed tissue-dependent expression patterns. The expression of CPT 1α1a, CPT 1α2a, and CPT 1β at 48h post-feeding was significantly increased in the liver (P<0.01, P<0.05, and P<0.01, respectively). The diverse responses of multiple isoforms in the liver during nutritional limitation suggest that they may play different roles in fatty acid β-oxidation.

Increased fatty acid β-oxidation as a possible mechanism for fat-reducing effect of betaine in broilers

Two hundred and forty 1-day-old male Arbor Acres broiler chickens were randomly assigned to five dietary treatments with six replicates of eight chickens per replicate cage for a 42-day feeding trial. Broiler chickens were fed a basal diet supplemented with 0 (control), 250, 500, 750 or 1000 mg/kg betaine, respectively. Growth performance was not affected by betaine. Incremental levels of betaine decreased the absolute and relative weight of abdominal fat (linear P < 0.05, quadratic P < 0.01), low-density lipoprotein cholesterol (LDL-C), triglyceride (TG) and total cholesterol (TC) (linear P < 0.05), and increased concentration of nonesterified fatty acid (NEFA) (linear P = 0.038, quadratic P = 0.003) in serum of broilers. Moreover, incremental levels of betaine increased linearly (P < 0.05) the proliferator-activated receptor alpha (PPARα), the carnitine palmitoyl transferase-I (CPT-I) and 3-hydroxyacyl-coenzyme A dehydrogenase (HADH) messenger RNA (mRNA) expression, but decreased linearly (P < 0.05) the fatty acid synthase (FAS) and 3-hydroxyl-3-methylglutaryl-CoA (HMGR) mRNA expression in liver of broilers. In conclusion, this study indicated that betaine supplementation did not affect growth performance of broilers, but was effective in reducing abdominal fat deposition in a dose-dependent manner, which was probably caused by combinations of a decrease in fatty acid synthesis and an increase in β-oxidation.

Methionine deficiency leads to hepatic fat accretion via impairment of fatty acid import by carnitine palmitoyltransferase I

1. To clarify the underlying mechanism of hepatic fat accretion due to methionine (Met) deficiency in broiler chickens, the present study investigated the effect of Met deficiency on the hepatic carnitine palmitoyltransferase (CPT) system, which imports fatty acids into mitochondria. 2. Fifteen-d-old male meat-type chickens were fed on either a control diet (containing 0.52 g/100 g Met) or a Met-deficient diet (containing 0.27 g Met/100 g). After a 10-d feeding period, the birds were killed by decapitation and their livers excised to determine hepatic CPT1 and CPT2 mRNA levels and for the related hepatic fatty acid-supported mitochondrial respiration to be measured. 3. Met deficiency decreased body weight gain and feed efficiency and increased hepatic lipid content compared to the control group. Whereas the hepatic CPT2 mRNA level in the Met-deficient group remained unchanged compared to that of the control group, the CPT1 mRNA level was decreased in the Met-deficient group and CPT1-dependent hepatic mitochondrial respiration was impaired. 4. Our results suggest that the hepatic lipid accretion that occurs in response to Met deficiency might be attributable to the impairment of CPT1-mediated fatty acid import into mitochondria.

Pertinent plasma indicators of the ability of chickens to synthesize and store lipids

Excessive deposition of body fat is detrimental to production efficiency. The aim of this study was to provide plasma indicators of chickens' ability to store fat. From 3 to 9 wk of age, chickens from 2 experimental lines exhibiting a 2.5-fold difference in abdominal fat content and fed experimental diets with contrasted feed energy sources were compared. The diets contained 80 vs. 20 g of lipids and 379 vs. 514 g of starch per kg of feed, respectively, but had the same ME and total protein contents. Cellulose was used to dilute energy in the high-fat diet. At 9 wk of age, the body composition was analyzed and blood samples were collected. A metabolome-wide approach based on proton nuclear magnetic resonance spectroscopy was associated with conventional measurements of plasma parameters. A metabolomics approach showed that betaine, glutamine, and histidine were the most discriminating metabolites between groups. Betaine, uric acid, triglycerides, and phospholipids were positively correlated (r > 0.3; P < 0.05) and glutamine, histidine, triiodothyronine, homocysteine, and β-hydroxybutyrate were negatively correlated (r < -0.3; P < 0.05) with relative weight of abdominal fat and/or fat situated at the top of external face of the thigh. The combination of plasma free fatty acids, total cholesterol, phospholipid, β-hydroxybutyrate, glutamine, and methionine levels accounted for 74% of the variability of the relative weight of abdominal fat. On the other hand, the combination of plasma triglyceride and homocysteine levels accounted for 37% of the variability of fat situated at the top of external face of the thigh. The variations in plasma levels of betaine, homocysteine, uric acid, glutamine, and histidine suggest the implication of methyl donors in the control of hepatic lipid synthesis and illustrate the interplay between AA, glucose, and lipid metabolisms in growing chickens.

The Origin and Diversity of Cpt1 Genes in Vertebrate Species

The Carnitine palmitoyltransferase I (Cpt1) gene family plays a crucial role in energy homeostasis since it is required for the occurrence of fatty acid β-oxidation in the mitochondria. The exact gene repertoire in different vertebrate lineages is variable. Presently, four genes are documented: Cpt1a, also known as Cpt1a1, Cpt1a2; Cpt1b and Cpt1c. The later is considered a mammalian innovation resulting from a gene duplication event in the ancestor of mammals, after the divergence of sauropsids. In contrast, Cpt1a2 has been found exclusively in teleosts. Here, we reassess the overall evolutionary relationships of Cpt1 genes using a combination of approaches, including the survey of the gene repertoire in basal gnathostome lineages. Through molecular phylogenetics and synteny studies, we find that Cpt1c is most likely a rapidly evolving orthologue of Cpt1a2. Thus, Cpt1c is present in other lineages such as cartilaginous fish, reptiles, amphibians and the coelacanth. We show that genome duplications (2R) and variable rates of sequence evolution contribute to the history of Cpt1 genes in vertebrates. Finally, we propose that loss of Cpt1b is the likely cause for the unusual energy metabolism of elasmobranch.

Molecular characterization of carnitine palmitoyltransferase IA in Megalobrama amblycephala and effects on its expression of feeding status and dietary lipid and berberine

Carnitine palmitoyltransferase I (CPT I, EC 2.3.1.21) controls the main regulatory step of fatty acid oxidation, and hence studies of its molecular characterization are useful to understand lipid metabolism in cultured fish. Here, a full-length cDNA coding CPT I was cloned from liver of blunt snout bream Megalobrama amblycephala. This cDNA obtained covered 2499bp with an open reading frame of 2181bp encoding 726 amino acids. This CPT I mRNA predominantly expressed in heart and white muscle, while little in eye and spleen. The phylogenetic tree constructed on the basis of sequence alignments among several vertebrate species suggests that this blunt snout bream CPT I sequence belongs to the CPT IA family. In order to investigate the characterization of CPT IA mRNA expression, post-prandial experiment and feeding trial were conducted. The results showed that CPT IA mRNA expression was unchanged from 2 to 12h, and then significantly increased at 24h post-feeding in liver and heart. Berberine, an alkaloid, was identified as a promising lipid-lowering drug. In order to elucidate the effect of berberine on CPT I expression, fish were fed for 8 weeks with three diets (low-fat diet (LFD, 5% fat), high-fat diet (HFD, 15% fat), and berberine-supplemented diet (BSD, 15% fat). The results showed that HFD could decrease the expression of CPT IA and PPARα, while BSD increased those expressions.

Exposure of embryos to cyclically cold incubation temperatures durably affects energy metabolism and antioxidant pathways in broiler chickens

Cyclically cold incubation temperatures have been suggested as a means to improve resistance of broiler chickens to ascites; however, the underlying mechanisms are not known. Nine hundred eggs obtained from 48 wk Ross broiler breeders were randomly assigned to 2 incubation treatments: control I eggs were incubated at 37.6°C throughout, whereas for cold I eggs the incubation temperature was reduced by 1°C for 6 h daily from 10 to 18 d of incubation. Thereafter, chickens were reared at standard temperatures or under cold exposure that was associated or not with a postnatal cold acclimation at d 5 posthatch. At hatch, hepatic catalase activity and malondialdehyde content were measured. Serum thyroid hormone and triglyceride concentrations, and muscle expression of several genes involved in the regulation of energy metabolism and oxidative stress were also measured at hatch and 5 and 25 d posthatch. Cold incubation induced modifications in antioxidant pathways with higher catalase activity, but lower expression of avian uncoupling protein 3 at hatch. However, long-term enhancement in the expression of avian uncoupling protein 3 was observed, probably caused by an increase in the expression of the transcription factor peroxisome proliferator activated receptor-γ coactivator-1α. These effects were not systematically associated with an increase in serum triiodothyronine concentrations that were observed only in chickens exposed to both cold incubation and later acclimation at 5 d with cold rearing. Our results suggest that these conditions of cyclically cold incubation resulted in the long-term in changes in antioxidant pathways and energy metabolism, which could enhance the health of chickens reared under cold conditions.

N-3 fatty acid intake altered fat content and fatty acid distribution in chicken breast muscle, but did not influence mRNA expression of lipid-related enzymes

Background

The conversions of the n-3 and n-6 fatty acid of plant origin to the C20 and C22 very long chain fatty acids (LCPUFAs) is regulated by several cellular enzymes such as elongases and desaturases.

Methods

Sixty-five male one-day old chickens (Ross 308) were randomly divided into four groups and given one of four diets; with or without linseed oil (LO), (the diets contained equal amounts of fat) and with low or high selenium (Se). Final body weight, amount of Se and fat in breast muscle, fatty acid profile, and gene expression for fatty acid desaturases (Fads1, Fads2, Fads9), HMG-CoA reductase, Acyl-CoA oxidase (Acox), carnitine palmitoyl transferase1 (Cpt1), superoxide dismutase (Sod) and glutathione peroxidase4 (Gpx4) were analyzed in all animals, and Gpx activity in whole blood was determined.

Results

mRNA expression of elongases and desaturases in chicken breast muscle was not affected by feed rich in C18:3n-3. The highly positive correlation between amount of fat in breast muscle and the product/precursor indices of monounsaturated fatty acid synthesis, and the negative correlation between muscle fat and indices of LCPUFA synthesis should be further studied.

Conclusion

mRNA expression in chicken breast muscle of elongases and desaturases was not affected by feed rich in C18:3n-3. The highly positive correlation between amount of fat in breast muscle and the product/precursor indices of monounsaturated fatty acid synthesis, and the negative correlation between muscle fat and indices of LCPUFA synthesis should be further studied.

Post-prandial regulation of hepatic glucokinase and lipogenesis requires the activation of TORC1 signalling in rainbow trout (Oncorhynchus mykiss)

To assess the potential involvement of TORC1 (target of rapamycin complex 1) signalling in the regulation of post-prandial hepatic lipid and glucose metabolism-related gene expression in trout, we employed intraperitoneal administration of rapamycin to achieve an acute inhibition of the TOR pathway. Our results reveal that rapamycin inhibits the phosphorylation of TORC1 and its downstream effectors (S6K1, S6 and 4E-BP1), without affecting Akt and the Akt substrates Forkhead-box Class O1 (FoxO1) and glycogen synthase kinase 3α/β (GSK 3α/β). These results indicate that acute administration of rapamycin in trout leads to the inhibition of TORC1 activation. No effect is observed on the expression of genes involved in gluconeogenesis, glycolysis and fatty acid oxidation, but hepatic TORC1 inhibition results in decreased sterol regulatory element binding protein 1c (SREBP1c) gene expression and suppressed fatty acid synthase (FAS) and glucokinase (GK) at gene expression and activity levels, indicating that FAS and GK activity is controlled at a transcriptional level in a TORC1-dependent manner. This study demonstrates for the first time in fish that post-prandial regulation of hepatic lipogenesis and glucokinase in rainbow trout requires the activation of TORC1 signalling.

Metabolic profiling of late-term turkey embryos by microarrays

The last stages of embryonic development are crucial for turkeys as their metabolism shifts to accommodate posthatch survival and growth. To better understand the metabolic change that occurs during the perinatal period, focused microarray methodology was used to identify changes in the expression of key genes that control metabolism of turkey embryos from 20 d of incubation (E) until hatch (E28). Gene expression patterns were evaluated in liver, pectoral muscle, and hatching muscle and were associated with measured embryonic growth and tissue glycogen concentration. Within the studied period, the expression of 60 genes significantly changed in liver, 53 in pectoral muscle, and 51 in hatching muscle. Genes related to lipid metabolism (enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase, 3-hydroxymethylglutaryl-CoA reductase, acetyl-CoA carboxylase, lipoprotein lipase, and thyroxine deiodinase) had reduced expression between E22 and E26, corresponding to the period of expected limited oxygen supply. In contrast, genes related to opposing pathways in carbohydrate metabolism, such as glycolysis and gluconeogenesis (hexokinases, glucose-6 phosphatase, phosphofructokinases, glucose 1-6 phosphatase, pyruvate kinase, and phosphoenolpyruvate carboxykinase), or glycogenesis and glycogenolysis (glycogen synthase and glycogen phosphorylase) had rather static expression patterns between E22 and E26, indicating their enzymatic activity must be under posttranscriptional control. Metabolic survey by microarray methodology brings new insights into avian embryonic development and physiology.

Expression of carnitine palmitoyl-CoA transferase-1B is influenced by a cis-acting eQTL in two chicken lines selected for high and low body weight

Carnitine palmitoyl-CoA transferase-1B is a mitochondrial enzyme in the fatty acid oxidation pathway. In a previous study, CPT1B was identified as differentially expressed in the hypothalamus of two lines of chickens established by long-term selection for high (HWS) or low (LWS) body weight. Mammals have three paralogs (CPT1a, b and c) while nonmammalian vertebrates only have two (CPT1A, B). CPT1A is expressed in liver and CPT1B in muscle. CPT1c is expressed in hypothalamus, where it regulates feeding and energy expenditure. We identified an intronic length polymorphism, fixed for different alleles in the two populations, and mapped the hitherto missing CPT1B locus in the chicken genome assembly, to the distal tip of chromosome 1p. Based on molecular phylogeny and gene synteny we suggest that chicken CPT1B is pro-orthologous of the mammalian CPT1c. Chicken CPT1B was differentially expressed in both muscle and hypothalamus but in opposite directions: higher levels in hypothalamus but lower levels in muscle in the HWS than in the LWS line. Using an advanced intercross population of the lines, we found CPT1B expression to be influenced by a cis-acting expression quantitative trait locus in muscle. The increased expression in hypothalamus and reduced expression in muscle is consistent with an increased food intake in the HWS line and at the same time reduced fatty acid oxidation in muscle yielding a net accumulation of energy intake and storage. The altered expression of CPT1B in hypothalamus and peripheral tissue is likely to be a mechanism contributing to the remarkable difference between lines.

Effects of short term fasting on the expression of genes involved in lipid metabolism in chicks

The aim of this study was to analyze the expression patterns of key genes involved in lipid metabolism in response to short term fasting in chicks (Gallus gallus). The mRNA level of the genes was analyzed after 0, 2, and 4 h of fasting in the liver and white adipose tissue. In the liver, the mRNA level of peroxisome proliferator-activated receptor α was significantly increased after 2 h of fasting. The mRNA levels of carnitine palmitoyltransferase 1a and acyl-CoA oxidase were significantly increased after 4 h of fasting. In contrast, the mRNA levels of sterol regulatory element-binding protein 1, acetyl-CoA carboxylase α, and fatty acid synthase were significantly decreased after 4 h of fasting. The mRNA levels of cholesterol metabolism-related genes such as 3-hydroxy-3-methylglutaryl-CoA reductase and cholesterol 7α-hydroxylase were significantly decreased after 4 h of fasting. In the white adipose tissue, the mRNA level of adipose triglyceride lipase was significantly increased after 4 h of fasting. In contrast, the mRNA levels of peroxisome proliferator-activated receptor γ and lipoprotein lipase were significantly decreased after 4 h of fasting. These results demonstrated that the gene expression of lipid metabolism-related genes is regulated by short term fasting in both the liver and WAT in chicks.

Chicken lines divergent for low or high abdominal fat deposition: a relevant model to study the regulation of energy metabolism

Divergent selection of chickens for low or high abdominal fat (AF) but similar BW at 63 days of age was undertaken in 1977. The selection programme was conducted over seven successive generations. The difference between lines was then maintained constant at about twice the AF in the fat line as in the lean line. The aims of the first studies on these divergent chicken lines were to describe the growth, body composition and reproductive performance in young and adult birds. The lines were then used to improve the understanding of the relationship between fatness and energy and protein metabolism in the liver, muscle and adipose tissues, as well as the regulation of such metabolism at hormonal, gene and hypothalamic levels. The effects on muscle energy metabolism in relation to meat quality parameters were also described. This paper reviews the main results obtained with these lines.

Dexamethasone facilitates lipid accumulation in chicken skeletal muscle

The effects of glucocorticoid on lipid metabolism of broiler chicken (Gallus gallus domesticus) skeletal muscle were investigated. Male Arbor Acres chickens (35 days old) were subjected to dexamethasone treatment for 3 days. We found that dexamethasone retards body growth while facilitating lipid accumulation. In M. pectoralis major (PM), dexamethasone increased the expression of glucocorticoid receptor (GR), fatty acid transport protein 1 (FATP1), heart fatty acid-binding protein (H-FABP) and long-chain acyl-CoA dehydrogenase (LCAD) mRNA and decreased the expression of liver carnitine palmitoyltransferase 1 (L-CPT1), adenosine-monophosphate-activated protein kinase (AMPK) α2 and lipoprotein lipase (LPL) mRNA. LPL activity was also decreased. In M. biceps femoris (BF), the levels of GR, FATP1 and L-CPT1 mRNA were increased. AMPKα (Thr172) phosphorylation and CTP1 activity of skeletal muscle were decreased by dexamethasone. In fed chickens, dexamethasone enhanced very low-density lipoprotein receptor (VLDLR) expression and AMPK activity in muscle, but it impaired the expression of LPL and L-CPT1 mRNA and LPL activity in PM and augmented the expression of GR, LPL, H-FABP, L-CPT1, LCAD and AMPKα2 mRNA in BF. Adipose triglyceride lipase (ATGL) protein expression was not affected by dexamethasone. In conclusion, in the fasting state, dexamethasone-induced-retarded fatty acid utilisation may be involved in the augmented intramyocellular lipid accumulation in both glycolytic (PM) and oxidative (BF) muscle tissues. In the fed state, dexamethasone promoted the transcriptional activity of genes related to lipid uptake and oxidation in muscles. Unmatched lipid uptake and utilisation are suggested to be involved in the augmented intramyocellular lipid accumulation.

Early hypothalamic FTO overexpression in response to maternal obesity--potential contribution to postweaning hyperphagia

BACKGROUND

Intrauterine and postnatal overnutrition program hyperphagia, adiposity and glucose intolerance in offspring. Single-nucleotide polymorphisms (SNPs) of the fat mass and obesity associated (FTO) gene have been linked to increased risk of obesity. FTO is highly expressed in hypothalamic regions critical for energy balance and hyperphagic phenotypes were linked with FTO SNPs. As nutrition during fetal development can influence the expression of genes involved in metabolic function, we investigated the impact of maternal obesity on FTO.

METHODS

Female Sprague Dawley rats were exposed to chow or high fat diet (HFD) for 5 weeks before mating, throughout gestation and lactation. On postnatal day 1 (PND1), some litters were adjusted to 3 pups (vs. 12 control) to induce postnatal overnutrition. At PND20, rats were weaned onto chow or HFD for 15 weeks. FTO mRNA expression in the hypothalamus and liver, as well as hepatic markers of lipid metabolism were measured.

RESULTS

At weaning, hypothalamic FTO mRNA expression was increased significantly in offspring of obese mothers and FTO was correlated with both visceral and epididymal fat mass (P<0.05); body weight approached significance (P = 0.07). Hepatic FTO and Fatty Acid Synthase mRNA expression were decreased by maternal obesity. At 18 weeks, FTO mRNA expression did not differ between groups; however body weight was significantly correlated with hypothalamic FTO. Postnatal HFD feeding significantly reduced hepatic Carnitine Palmitoyltransferase-1a but did not affect the expression of other hepatic markers investigated. FTO was not affected by chronic HFD feeding.

SIGNIFICANCE

Maternal obesity significantly impacted FTO expression in both hypothalamus and liver at weaning. Early overexpression of hypothalamic FTO correlated with increased adiposity and later food intake of siblings exposed to HFD suggesting upregulation of FTO may contribute to subsequent hyperphagia, in line with some human data. No effect of maternal obesity was observed on FTO in adulthood.

Regulation of the expression of the avian uncoupling protein 3 by isoproterenol and fatty acids in chick myoblasts: possible involvement of AMPK and PPARalpha?

The avian uncoupling protein 3 (UCP3), mainly expressed in muscle tissue, could be involved in fatty acid (FA) metabolism, limitation of reactive oxygen species production, and/or nonshivering thermogenesis. We recently demonstrated that UCP3 mRNA expression was increased by isoproterenol (Iso), a β-agonist, in chicken Pectoralis major. This upregulation was associated with changes in FA metabolism and variations in the activation of AMP-activated protein kinase (AMPK) and in the expression of the transcription factors peroxisome proliferator-activated receptor (PPAR)α, PPARβ/δ, and PPARγ coactivator-1α (PGC-1α). The aim of the present study was to elucidate the mechanisms involving AMPK and PPARα in UCP3 regulation in primary cultures of chick myoblasts. Avian UCP3 mRNA expression, associated with p38 mitogen-activated protein kinase (p38 MAPK) activation, was increased by Iso and/or FAs. The PKA pathway mediated the effects of Iso on UCP3 expression. FA stimulation also led to AMPK activation. Furthermore, the direct involvement of AMPK on UCP3 regulation was shown by using 5-aminoimidazole-4-carboxyamide ribonucleoside and Compound C. The use of the p38 MAPK inhibitor SB202190, which was associated with AMPK activation, also dramatically enhanced UCP3 mRNA expression. Finally the PPARα agonist WY-14643 strongly increased UCP3 mRNA expression. This study highlights the control of UCP3 expression by the β-adrenergic system and FA in chick myoblasts and demonstrates that its expression is directly regulated by AMPK and by PPARα. Overexpression of avian UCP3 might modulate energy utilization or limit oxidative stress when mitochondrial metabolism of FA is triggered by catecholamines.

Dexamethasone facilitates lipid accumulation and mild feed restriction improves fatty acids oxidation in skeletal muscle of broiler chicks (Gallus gallus domesticus)

Effects of dexamethasone (DEX) and mild feed restriction on the uptake and utilization of fatty acids in skeletal muscle of broiler chicks (Gallus gallus domesticus) were investigated. Male Arbor Acres chicks (7-days old, n=30) were injected with DEX or saline for 3days, and a feed restriction group was included. DEX enhanced circulating very low density lipoprotein (VLDL) level and the lipid accumulation in both adipose and skeletal muscle tissues. Compared with the control, liver-carnitine palmitoyltransferase 1 (L-CPT1) and AMP-activated protein kinase (AMPK) alpha2 mRNA level of M. biceps femoris (BF) were down-regulated significantly by DEX, while mRNA expression of lipoprotein lipase (LPL), fatty acid transport protein 1 (FATP1), heart-fatty acid binding protein (H-FABP), long-chain acyl-CoA dehydrogenase (LCAD), activities of LPL and AMPK in both skeletal muscles were not obviously affected. Feed restriction increased the mRNA expression of LPL, L-CPT1 and LCAD of M. pectoralis major (PM), and FATP1, H-FABP, L-CPT1 and LCAD of BF. In conclusion, DEX retards the growth of body mass but facilitates lipid accumulation in both adipose and skeletal muscle tissues. In contrast to the favorable effect of mild feed restriction, DEX did not alter the uptake of fatty acids in the skeletal muscle. The result suggests that DEX may promote intramyocellular lipid accumulation by suppressed fatty acid oxidation while mild feed restriction improved fatty acid oxidation in skeletal muscle, especially in red muscle. Glucocorticoids (GCs) regulated muscle fatty acid metabolism in a different way from energy deficit caused by mild feed restriction.

Gene expression and protein content in relation to intramuscular fat content in Muscovy and Pekin ducks

Independent of their nutritional condition, Pekin ducks always exhibit higher i.m. fat content than Muscovy ducks. To understand this difference between species, the expression level of genes involved in lipid metabolism was analyzed in the pectoralis major muscle of Pekin and Muscovy ducks ad libitum-fed or overfed. The lipoprotein lipase (LPL) gene expression was not different between species and not influenced by overfeeding. The protein content for LPL was higher in Pekin ducks than in Muscovy ducks when birds were ad libitum-fed, whereas in overfed ducks, we found no difference between species. Adipocyte fatty acid-binding protein (A-FABP) gene expression and protein content were higher in Pekin ducks than in Muscovy ducks for each nutritional condition (suggesting a higher intracellular transport within i.m. adipocytes of fatty acids mainly provided by liver for this species). Overfeeding did not affect the expression of genes involved in oxidation [carnitine palmitoyl transferase 1A (CPT1A), cytochrome-c oxidase 4 (COX4), succinyl-coenzyme A:3-ketoacid coenzyme A transferase (SCOT)] but increased the expression of fatty acid synthase (FAS) involved in lipogenesis. For all nutritional conditions, Pekin duck exhibited higher expression levels of CPT1A, COX4, SCOT, and FAS than Muscovy ducks. Results for mRNA SCOT suggested that the muscles of Pekin ducks use ketone bodies as an energy source. In conclusion, i.m. lipogenesis could contribute to the i.m. fat, particularly in Pekin ducks.

Transcriptome profiling of the feeding-to-fasting transition in chicken liver

BACKGROUND

Starvation triggers a complex array of adaptative metabolic responses including energy-metabolic responses, a process which must imply tissue specific alterations in gene expression and in which the liver plays a central role. The present study aimed to describe the evolution of global gene expression profiles in liver of 4-week-old male chickens during a 48 h fasting period using a chicken 20 K oligoarray.

RESULTS

A large number of genes were modulated by fasting (3532 genes with a pvalue corrected by Benjamini-Hochberg < 0.01); 2062 showed an amplitude of variation higher than +/- 40% among those, 1162 presented an human ortholog, allowing to collect functional information. Notably more genes were down-regulated than up-regulated, whatever the duration of fasting (16 h or 48 h). The number of genes differentially expressed after 48 h of fasting was 3.5-fold higher than after 16 h of fasting. Four clusters of co-expressed genes were identified by a hierarchical cluster analysis. Gene Ontology, KEGG and Ingenuity databases were then used to identify the metabolic processes associated to each cluster. After 16 h of fasting, genes involved in ketogenesis, gluconeogenesis and mitochondrial or peroxisomal fatty acid beta-oxidation, were up-regulated (cluster-1) whereas genes involved in fatty acid and cholesterol synthesis were down-regulated (cluster-2). For all genes tested, the microarray data was confirmed by quantitative RT-PCR. Most genes were altered by fasting as already reported in mammals. A notable exception was the HMG-CoA synthase 1 gene, which was up-regulated following 16 and 48 h of fasting while the other genes involved in cholesterol metabolism were down-regulated as reported in mammalian studies. We further focused on genes not represented on the microarray and candidates for the regulation of the target genes belonging to cluster-1 and -2 and involved in lipid metabolism. Data are provided concerning PPARa, SREBP1, SREBP2, NR1H3 transcription factors and two desaturases (FADS1, FADS2).

CONCLUSION

This study evidences numerous genes altered by starvation in chickens and suggests a global repression of cellular activity in response to this stressor. The central role of lipid and acetyl-CoA metabolisms and its regulation at transcriptional level are confirmed in chicken liver in response to short-term fasting. Interesting expression modulations were observed for NR1H3, FADS1 and FADS2 genes. Further studies are needed to precise their role in the complex regulatory network controlling lipid metabolism.

Hepatic metabolism of glucose and linoleic acid varies in relation to susceptibility to fatty liver inad libitum-fed Muscovy and Pekin ducks

The susceptibility to develop hepatic steatosis is known to differ between duck species, especially between Muscovy and Pekin ducks. This difference could be explained by either differential responses of species to overfeeding or genetic differences in hepatic lipid metabolism. The aim of the present study was to compare the intensities of the different hepatic pathways (oxidation, lipogenesis, esterification, secretion, etc.) of the two main nutrients (glucose and linoleic acid (LA)) reaching the liver ofad libitum-fed Muscovy (n6) and Pekin (n6) ducks using theex vivomethod of liver slices incubated for 16 h with [U-14C]glucose, [1-14C]LA and [35S]methionine added to the survival medium. In such experimental conditions, the lipogenesis pathway from glucose was 2-fold higher (P < 0·05) in the liver of the Muscovy duck than in that of the Pekin duck. Furthermore, the hepatic uptake of LA was 2-fold higher (P < 0·05) in the Muscovy duck than in the Pekin duck leading to a 2-fold higher (P < 0·05) esterification of this fatty acid in the liver of the Muscovy duck. The hepatic secretion of VLDL was higher (P < 0·01) in the Muscovy duck than in the Pekin duck but insufficient to prevent lipid accumulation in the liver of the Muscovy duck. In conclusion, these results show the influence of the species on the hepatic metabolism of ducks in relation to their susceptibility to develop fatty liver. These results should shed light on the metabolic regulations that might underlie susceptibility to hepatic steatosis in the the human liver.

Functional Annotation of Genomic Data with Metabolic Inference

Metabolomics is an appealing new approach in systems biology aimed at enabling an improved understanding of the dynamic biochemical composition of living systems. Biological systems are remarkably complex. Importantly, metabolites are the end products of cellular regulatory processes, and their concentrations reflect the ultimate response of a biological system to genetic or environmental changes. In this article, we describe the components of lipid metabolomics and then use them to investigate the metabolic basis for increased abdominal adiposity in 2 strains of divergently selected chickens. Lipid metabolomics were chosen due to the availability of well-developed analytical platforms and the pervasive physiological importance of lipids in metabolism. The analysis suggests that metabolic shifts that result in increased abdominal adiposity are not universal and vary with genetic background. Metabolomics can be used to reverse engineer selection programs through superior metabolic descriptions that can then be associated with specific gene networks and transcriptional profiles.