Hepatic lipogenesis in broiler chickens with different fat deposition during embryonic development

Effects and Mechanisms Investigation of Heat Stress on Egg Yolk Quality in Huaixiang Chickens

The purpose of this study was to examine the effects of high temperature on internal egg yolk quality parameters and their possible mechanisms in Huaixiang chickens. This study consisted of two treatments, and each treatment had six replicates with six birds per cage. A total of seventy-two 26-week-old female Huaixiang chickens were randomly divided into a normal-temperature group (NT) and a high-temperature group (HT) for 6 weeks. And these hens were exposed to 25 ± 2 °C and 32 ± 2 °C, respectively. Their relative humidity was maintained at 55-65%. The results showed that the HT group significantly reduced yolk weight, yolk color, and egg weight compared to the NT group (p < 0.05). Heat stress caused vacuolar degeneration of the liver and reduced the absolute liver weight (p < 0.05). Both yolk triglyceride (TG) and liver TG in the HT group were significantly higher than in the NT group (p < 0.05). However, the liver total cholesterol (TC) level in the HT group was remarkably lower than that in the NT group (p < 0.05). Additionally, heat stress remarkably enhanced SREBP-1c, ACACA, and FASN lipid metabolism-related gene mRNA expression levels in Huaixiang chicken liver after 6 weeks of heat exposure (p < 0.05). Furthermore, the HT group had remarkably reduced total amino acid, Cys, and Tyr levels in the yolk when compared with the NT group in our experiment (p < 0.05). In conclusion, heat stress causes egg yolk quality reduction and abnormal lipid metabolism in Huaixiang chickens. These findings provided novel insights into the role of high temperature on egg yolk parameters and the underlying mechanisms in Chinese indigenous laying hens.

Chicken CDS2 isoforms presented distinct spatio-temporal expression pattern and regulated by insulin in a breed-specific manner

The cytidine diphosphate diacylglycerol synthases (CDSs) gene encodes the cytidine diphosphate-diacylglycerol (CDP-DAG) synthase enzyme that catalyzes the formation of CDP-diacylglycerol from phosphatidic acid. At present, there are no reports of CDS2 in birds. Here, we identified chicken CDS2 transcripts by combining conventional RT-PCR amplification, 5′ rapid amplification of cDNA ends (RACE), and 3′ RACE, explored the spatio-temporal expression profiles of total CDS2 and the longest transcript variant CDS2-4, and investigated the effect of exogenous insulin on the mRNA level of total CDS2 via quantitative RT-PCR. Four transcripts of chicken CDS2 (CDS2-1, -2, -3, and -4) were identified, which were alternatively spliced at the 3′-untranslated region (UTR). Both total CDS2 and CDS2-4 were prominently expressed in adipose tissue, and exhibited low expression in liver and pectoralis of 49-day-old chickens. Regarding the spatio-temporal expression patterns of CDS2 in chicken, total CDS2 exhibited a similar temporal expression tendency with a high level in the later period of incubation (embryonic day 19 [E19] or 1-day-old) in the brain, liver, and pectoralis. While CDS2-4 presented a distinct temporal expression pattern in these tissues, CDS2-4 levels peaked at 21 d in the brain and pectoralis, while liver CDS2-4 mRNA levels were highest at the early stage of hatching (E10). Total CDS2 (P < 0.001) and CDS2-4 (P = 0.0090) mRNA levels in the liver were differentially regulated throughout the development of the chicken. Total CDS2 levels in the liver of Silky chickens were higher than that of the broiler in the basal state and after insulin stimulation. Exogenous insulin significantly down-regulated the level of total CDS2 at 240 min in the pectoralis of Silky chickens (P < 0.01). In conclusion, chicken CDS2 isoforms with variation at the 3′-UTR were identified, which was prominently expressed in adipose tissue. Total CDS2 and CDS2-4 presented distinct spatio-temporal expression patterns, that is they were differentially regulated with age in brain, liver, and pectoralis. Insulin could regulate chicken CDS2 levels in a breed- and tissue-specific manner.

Effects of maternal dietary energy restriction on laying performance, embryonic development, and lipid Metabolism in broilers

Objective

The objective of this study was to investigate the effects of different degrees of maternal dietary energy restriction on lipid deposition in embryonic tissues during the medium laying period (37 to 39 weeks) in Arbor Acres (AA) broiler breeders.

Methods

A single factor design was adopted, and 400 AA broiler breeders (20 weeks of age) with a similar weight were randomly allocated into four groups. The birds in the control group were fed a corn-soybean meal based diet, and those in trial groups were fed diets with 80%, 70%, and 50% energy levels of the basal diet. Incubated eggs from the medium laying period were collected. Samples of developing embryos at various stages were prepared for composition analysis.

Results

The embryo weight in the 80% energy group was higher than those of the other groups on embryonic day (E) 13, but at 21 E, they were significantly decreased with decreasing energy intake of the broiler breeders (p<0.05). Additionally, the levels of crude fat in tissues in the restriction groups were significantly decreased (p<0.05). The long axis and area of adipocytes in breast muscle, thigh muscle and the liver were significantly decreased (p<0.05) at 21 E in the 80%, 70%, and 50% energy groups.

Conclusion

The effects of the 80% maternal dietary energy restriction energy affects egg production performance, egg quality, and nutrient deposition in egg weights, which then directly impacts on the developmental process of embryos, especially on fat utilization and deposition.

Hepatic transcriptome analysis reveals altered lipid metabolism and consequent health indices in chicken supplemented with dietary Bifidobacterium bifidum and mannan-oligosaccharides

This study investigated the role of dietary prebiotic mannan-oligosaccharides (MOS), and probiotic Bifidobacterium bifidum (BFD) in lipid metabolism, deposition, and consequent health indices in broiler chicken. The supplementation of 0.2% MOS along with either 10⁶ or 10⁷ CFU BFD/g feed resulted in downregulation of Acetyl-CoA carboxylase, fatty acid synthase, sterolregulatory element binding protein-1, and apolipoprotein B100; and up-regulation of peroxisome proliferator activated receptor-α AMP-activated protein kinase α-1, and stearoyl CoA (∆9) desaturase-1 hepatic expression in broiler chicken. The birds supplemented with 0.2% MOS along with either 10⁶ or 10⁷ CFU BFD/g feed depicted lower body fat percentage, palmitic acid, stearic acid, and saturated fatty acid contents, whereas, higher palmitoleic acid, oleic acid, and MUFA contents were observed. The ∆9-desaturase indices of chicken meat have shown higher values; and elongase index (only thigh) and thioesterase index have shown lower values in birds supplemented with 0.2% MOS along with either 10⁶ or 10⁷ CFU BFD/g feed. The meat health indices such as Polyunsaturated fatty acids (PUFA)/Saturated fatty acids (SFA) ratio, Mono-saturated fatty acids (MUFA)/SFA ratio, unsaturated fatty acids (UFA)/SFA ratio, hypocholesterolemic/hypercholesterolemic fatty acid ratio, saturation index, atherogenic index, thrombogenic index, and hypercholesterolemic fatty acid content were positively improved in birds supplemented with 0.2% MOS along with either 10⁶ or 10⁷ CFU BFD/g feed. Similarly, the birds supplemented with 0.2% MOS along with either 10⁶ or 10⁷ CFU BFD/g feed have shown lower serum triglyceride and total cholesterol levels along with higher high density levels and improved serum health indices cardiac risk ratio, atherogenic coefficient, and, atherogenic index of plasma.

Dietary Lactobacillus acidophilus and Mannan-Oligosaccharides Alter the Lipid Metabolism and Health Indices in Broiler Chickens

The effects of dietary Lactobacillus acidophilus (LBA) and mannan-oligosaccharide (MOS) supplementation on lipid metabolism and consequent lipid profile and health indices in broiler chicken were investigated in this study. Supplementation of 0.2% MOS along with either 10⁶ or 10⁷ LBA/g feed in broiler chicken downregulated hepatic expression of genes involved in lipogenesis, and upregulated expression of lipolytic genes. It caused decline of lipogenesis and increase of lipid oxidation which resulted in lower carcass fat content. None of the genes studied influenced fatty acid profile of chicken meat except the expression of stearoyl CoA (Δ9) desaturase-1 (SCD-1) whose upregulation increased monounsaturated fatty acid (MUFA) content at the cost of saturated fatty acid (SFA) content. The lipid metabolism indices of chicken meat such as ∆9 desaturase index (DI) increased in birds supplemented with 0.2% MOS along with either 10⁶ or 10⁷ CFU LBA/g feed, whereas no effect was observed on ∆5 + ∆6 DI. The supplementation of 0.2% MOS along with either 10⁶ or 10⁷ CFU LBA/g feed in birds improved the health indices of chicken meat due to upregulation of SCD-1 expression. The supplementation of 0.2% MOS along with either 10⁶ or 10⁷ CFU LBA/g feed in broiler chicken produced hypocholesterolemic and hypolipidemic effects with improved serum cardio-protective indices.

Effects of taurine on growth performance, antioxidant capacity, and lipid metabolism in broiler chickens

To investigate the effects of dietary taurine supplementation on growth performance, antioxidant status, and lipid metabolism in broilers, 384 male broilers (Arbor Acres, 1 D of age) were randomly allocated into 4 groups with 8 replicates of 8 birds. Dietary treatments were supplemented with taurine at the level of 0.00, 2.50, 5.00, and 7.50 g/kg of the diet (denoted as CON, TAU1, TAU2, TAU3, respectively). The BW gain from 1 to 21 D and from 22 to 42 D were all increased linearly (linear, P < 0.001) by taurine supplementation. Throughout the trial period, the highest BW gain and favorable gain-to-feed ratio were observed in the TAU2 group. Taurine supplementation increased the antioxidant enzyme activities and decreased (linear, P < 0.001) the content of malondialdehyde in both serum and the liver of broilers and alleviated oxidative damage through enhancing (P < 0.05) the hepatic genes expression of nuclear factor erythroid-2-related factor 2 (NRF2), glutathione peroxidase (GPX), and heme oxygenase-1 (HO-1). Correspondingly, in serum, the activities of hepatic lipase and total lipase were decreased linearly and quadratically (linear and quadratic, P < 0.001) with the increasing inclusion of taurine in the diet. Meanwhile, in serum, the content of triglycerides was significantly decreased (P < 0.05), and except for TAU3, the total cholesterol content was also significantly decreased (P < 0.05) by taurine supplementation. In addition, the hepatic content of triglycerides was significantly decreased (P < 0.05) in the TAU1 and TAU2 groups. Compared with the CON group, the hepatic genes expression of adenosine monophosphate-activated protein kinase alpha (AMPKα), silent 1, (SIRT1) and carnitine palmitoyltransferase 1 (CPT-1) were all increased (P < 0.05), and sterol regulatory element-binding protein-1 (SREBP-1) expression was decreased (P < 0.05) in the TAU2 group. These results indicated that taurine supplementation improved the growth performance, antioxidant capacity, and lipid metabolism of broilers.

Fatty Acid Composition and Regulatory Gene Expression in Late-Term Embryos of ACRB and COBB Broilers

Cobb broilers (COBB) have been heavily selected for their production performance in the past several decades, while the Athens Canadian Random Bred (ACRB) chickens, a meat-type breed, have been kept as a non-selected control strain. The purpose of this study was to compare these two lines of chickens at late embryonic development and identify the molecular markers and fatty acid profiles underlining their differences in growth performance due to selection. Fertilized eggs of the ACRB (n = 6) and COBB (n = 6) were used at 14 and 18 embryonic days. Genes involved in lipogenesis and myogenesis were measured using quantitative real-time reverse transcroption-polymerase chain reaction (RT-PCR), and fatty acid (FA) compositions of egg yolk, muscle, and liver were measured using gas chromatography. COBB had higher egg weight, embryo weight, and breast and fat ratio. The gene expression in the liver showed an interaction between age and breed on FASN expression, with the highest level in COBB at E18. ACRB had higher ApoB and MTTP expression, but lower SREBP-1 expression compared to COBB. No difference was found in myogenesis gene expression in the muscle between two breeds. For the FA composition, muscle was largely affected by both breed and age. Yolk and liver were affected mainly by breed and age, respectively. Constant interaction effects in docosahexaenoic acid (DHA), indicating the highest level in all the tested tissues of ACRB at E14 and the constant main effects with higher myristic, palmitic, and gondoic, but lower linolenic acid in the liver and yolk of COBB compared to the levels in those of ACRB. Finally, fat accumulation in the liver had no obvious difference between the breeds but was higher when embryo was older. In conclusion, broiler breed affects egg, embryo, and tissue weight, as well as FA composition in initial egg yolk and throughout the embryonic development. The highest docosahexaenoic percentage was observed in ACRB, indicating that genetic selection may result in fatty acid profile changes such as lower DHA content in chicken tissues and eggs.

Folic acid perfusion administration reduced abdominal fat deposition in starter Arbor Acres broilers

With intensive selection for meat production in broilers, excessive fat accumulation is also accompanied and causes economic concerns. Folic acid was reported to be involved in lipid metabolism. The present study was conducted to investigate the role of folic acid in reducing abdominal fat deposition. A total of 105 one-day-old healthy Arbor Acres broilers were randomly distributed into 3 treatments, including the control (Con), saline-perfusion group (NS), and folic acid perfusion group (FA). The growth performance, biochemical characteristics in serum, and lipid metabolism in the liver and abdominal fat tissues were evaluated. Results have shown that folic acid significantly reduced abdominal fat percentage (P < 0.05) and had no effects on BW, ADFI, ADG, and FCR (P > 0.05). Serum triglycerides (TG), total cholesterol (TC), and alanine aminotransferase (ALT) levels were lower in FA group but albumin concentration was higher (P < 0.05). Hepatic ACC, SCD, ELOVL6, PI3K, LDLR, HMGCR, and ABCA1 mRNA abundance were all down-regulated in FA group (P < 0.05) when compared with the Con and NS groups, while CPT1 and PPARα were not affected. In addition, MTTP mRNA abundance was higher in the liver of birds subjected to folic acid (P < 0.05). There was no difference about TG deposition in the liver among all groups based on hematoxylin−eosin (HE) and Oil Red O staining. On the other hand, ELOVL6, PPARγ, IGF1, and TGFβ2 expression were notably decreased in the abdominal fat in FA group (P < 0.05). In conclusion, our data demonstrated that folic acid has reduced abdominal fat percentage by decreasing hepatic lipogenesis and suppressing adipocytes proliferation and differentiation. And the inhibiting effect of adipocytes might be mediated by IGF1 and TGFβ2 down-regulation.

The effects of chronic lead exposure on the liver of female Japanese quail (Coturnix japonica): Histopathological damages, oxidative stress and AMP-activated protein kinase based lipid metabolism disorder

Lead (Pb) is one of the most toxic metals to human and wildlife. It also had multiple negative influences on birds with physical, neurological and hematological clinical signs. However, the impacts of lead on bird liver lipid metabolism are still unclear. In this study, female Japanese quails were used to examine the effects of chronic lead exposure on liver histology, oxidative stress and AMPK (AMP-activated protein kinase) based lipid metabolism. Quails were randomly divided into 5 groups and each group was respectively fed with 0, 50, 250, 500 and 1000 ppm lead solution for 49 days. The result showed that exposure to 250, 500 and 1000 ppm Pb induced severe histopathological damages characterized by liver lipid vacuoles and accumulation, hepatic cytoplasmic hyalinization and vacuolization, hepatocytes necrosis, hepatic sinusoid congestion, and it also caused ultrastructural alterations featured by swelling and vacuolar mitochondria, the depolymerization of polyribosome, and lipid droplets accumulation. Moreover, significant decrease of activities of GPx (glutathione peroxidase), SOD (superoxide dismutase), CAT (catalase) and level of T-AOC (total antioxidant capacity) while significant increase of MDA (malondialdehyde) content were found in livers of all Pb groups. In addition, the expressions of genes related to fatty synthesis were significantly upregulated in livers of all Pb groups while the expressions of genes related to fatty β-oxidation were significantly downregulated in livers of 250 ppm Pb group. The present study indicated lead exposure does cause bird health damages through inducing liver microstructural and ultrastructural injury, oxidative damages and lipid metabolism disorder.

Developmental changes in hepatic lipid metabolism of chicks during the embryonic periods and the first week of posthatch

The liver is the main site of de novo lipogenesis in poultry, and hepatic lipid metabolism disorder will lead to excessive abdominal fat deposition or fatty liver disease, finally causing huge economic loss. The present study was conducted to investigate developmental changes in hepatic lipid metabolism of chicks from embryonic periods to the first week after hatching. Liver samples were collected from embryonic day 11 (E11) to the age of day 7 posthatch (D7) for lipid metabolism analysis. Hematoxylin–eosin and Oil Red O staining analysis showed that hepatic lipids increased gradually during embryonic period and declined posthatch; The sum of hepatic triglycerides and cholesterol reached the peak at E19 and D1 by ELISA analysis (P < 0.05). Acetyl-CoA carboxylase, fatty acid synthase, and acyl-CoA desaturase 1 mRNA expression in the liver were higher from E17 to D1 with the peak at E19 when compared with those at E13 and E15 (P < 0.05). Hepatic elongase of very long-chain fatty acids 6 and microsomal triglyceride transfer protein mRNA abundance were lower during embryonic periods but reached relative higher level after hatching (P < 0.05). On the contrary, hepatic carbohydrate response element binding protein (ChREBP), carnitine palmitoyltransferase 1, and peroxisome proliferators–activated receptor α expression were higher during embryonic periods but decreased posthatch (P < 0.05). The mRNA abundance of sterol-regulatory element binding protein 1c was the lowest at E13 and E15, then increased gradually from E17 to D1, while decreased from D3 to D7 little by little (P < 0.05). In summary, hepatic lipogenesis genes have different expression patterns during the embryonic periods and the first week of posthatch, which might be activated by ChREBP during embryonic periods; fatty acid oxidation was enhanced around the hatched day but declined posthatch. These findings will broaden the understanding of physiological characteristics and dynamic pattern about hepatic lipid metabolism in chicks.

Increased fat synthesis and limited apolipoprotein B cause lipid accumulation in the liver of broiler chickens exposed to chronic heat stress

Chronic heat stress can enhance fat synthesis in broilers, and excessive triglyceride (TG) synthesized by the liver needs to be transported to extrahepatic tissues by very low density lipoprotein (VLDL) otherwise will accumulate in the liver, which may even result in hepatic steatosis. To investigate the molecular mechanisms by which chronic heat stress enhances fat synthesis and results in lipid accumulation in the liver of chickens, 144 broilers (Arbor Acres, 28-day-old) were randomly allocated to the normal control (NC, 22°C), heat stress (HS, consistent 32°C), or pair-fed (PF, 22°C) groups for a 14-D trial. The 7 D of heat exposure significantly increased the respiratory rate, relative weight of abdominal fat, the levels of glucose, TG, corticosterone, insulin, and VLDL in plasma, as well as the levels of TG, total cholesterol, acyl-CoA carboxylase (ACC), and fatty acid synthase (FAS) in the liver, and mRNA expression levels of carbohydrate response element-binding protein (ChREBP), ACC, FAS, and microsomal triglyceride transfer protein (MTTP) in comparison with the other 2 groups. After 14 D of heat exposure, the relative weights of abdominal fat and liver and levels of TG and FAS in the liver were significantly higher in the HS group than in the other 2 groups, and there were no significant differences in the respiratory rate, plasma corticosterone concentration, apolipoprotein B (ApoB) level in the liver, and mRNA expression levels of key genes of fat synthesis among the 3 groups. In conclusion, chronic heat exposure activated LXRα pathway and enhanced fat synthesis in the liver after 7 D of heat exposure. After 14 D of heat exposure, heat-stressed broilers exhibited an adaptation to the high temperature in parameters of stress and fat synthesis gene expression levels. Moreover, chronic heat stress resulted in lipid accumulation in the liver of broilers, which is probably because the limited ApoB was not enough to transport the excessive TG synthesized by the liver in chronic heat-stressed broilers.

Dietary taurine supplementation decreases fat synthesis by suppressing the liver X receptor α pathway and alleviates lipid accumulation in the liver of chronic heat-stressed broilers

BACKGROUND

Chronic heat stress can enhance fat synthesis and result in lipid accumulation in the liver of broilers. To investigate the effects and molecular mechanisms of dietary taurine supplementation on fat synthesis and lipid accumulation in the liver of chronic heat-stressed broilers, 144 28 day-old chickens (Arbor Acres) were randomly distributed to normal control (NC, 22 °C, basal diet), heat stress (HS, consistent 32 °C, basal diet), or heat stress plus taurine (HS + T, consistent 32 °C, basal diet +5.00 g kg^-1 taurine) groups for a 14-day feeding trial.

RESULTS

Compared with those of the HS group, dietary taurine supplementation significantly decreased the level of very-low-density lipoprotein and the activity of aspartate aminotransferase in plasma and the relative weight of liver in the HS + T group. In addition, dietary taurine supplementation also significantly decreased the levels of triglyceride, acyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), and suppressed the mRNA expression levels of liver X receptor α (LXRα), sterol response element-binding protein 1c, ACC and FAS in the liver of chronic heat-stressed broilers. Meanwhile, dietary taurine supplementation effectively alleviated lipid accumulation in the liver of broilers exposed to chronic heat stress.

CONCLUSION

Chronic heat stress significantly increased fat synthesis and resulted in excess lipid deposition in the liver of broilers. Dietary taurine supplementation can effectively decrease fat synthesis by suppressing the LXRα pathway and alleviate lipid accumulation in the liver of chronic heat-stressed broilers. © 2019 Society of Chemical Industry.

Dietary supplementation with olive mill wastewaters induces modifications on chicken jejunum epithelial cell transcriptome and modulates jejunum morphology

BACKGROUND

The Mediterranean diet is considered one of the healthier food habits and olive oil is one of its key components. Olive oil polyphenols are known to induce beneficial effects in several pathological conditions, such as inflammatory bowel disease, and to contrast the proliferation of cancer cells or hypercholesterolemia. Polyphenols are also present in waste products derived from the olive industry: olive mill wastewaters (OMWW) are rich in polyphenols and there is an increasing interest in using OMWW in animal nutrition. OMWW are attributed with positive effects in promoting chicken performance and the quality of food-derived products. However, a tissue-specific transcriptome target analysis of chickens fed with OMWW has never been attempted.

RESULTS

We explored the effect of dietary OMWW on the intestinal function in broilers. A morphological analysis of the jejunum revealed that OMWW reduced crypt depth, whereas no significant modifications were observed for villus height and the villus height/crypt depth ratio. An RNA Sequencing analysis was performed on isolated, intestinal, epithelial cells and 280 differentially expressed genes were found using a count-based approach. An enrichment analysis revealed that the majority of up regulated genes in the OMWW group were over-represented by the regulation of viral genome replication-related GO-Terms, whereas down regulated genes were mainly involved in cholesterol and lipid metabolism.

CONCLUSIONS

Our study showed how an industrial waste product can be recycled as a feed additive with a positive relapse. OMWW dietary supplementation can be a nutritional strategy to improve chicken performance and health, prevent intestinal damage, enhance innate immunity and regulate cholesterol metabolism and fat deposition.

Oregano dietary supplementation modifies the liver transcriptome profile in broilers: RNASeq analysis

Intensive farming of broilers involves stressful conditions that reduce animal welfare and performance. New dietary strategies to improve performance and meat quality include the administration of plant extracts. Oregano (Origanum vulgare L.) is known for its antimicrobial, anti-fungal, insecticidal and antioxidant properties. However, studies on diet supplementation with oregano are mainly focused on the evaluation of animal performance, while partial information is available on transcriptomics and nutrigenomics and, in particular, Next Generation Sequencing (NGS) is not widely applied. In this study we tested the effect of an oregano aqueous extract supplemented diet on gene expression in broiler chickens. Whole liver transcriptome of 10 birds fed with a supplemented diet versus 10 controls was analyzed using the RNA-Seq technique. One hundred and twenty-nine genes were differentially expressed with an absolute log fold change >1. The analysis reveals a massive down-regulation of genes involved in fatty acid metabolism and insulin signaling pathways in broilers fed with the oregano aqueous extract supplementation. Down-regulated genes could be associated to chicken lean line, suggesting the potential beneficial effect of oregano supplementation in reducing both abdominal and visceral fat deposition. Down-regulation of insulin signaling pathway related genes suggest that dietary oregano supplementation might be an option in obesity and diabetes conditions.

Identification and characterization of genes that control fat deposition in chickens

BACKGROUND

Fat deposits in chickens contribute significantly to meat quality attributes such as juiciness, flavor, taste and other organoleptic properties. The quantity of fat deposited increases faster and earlier in the fast-growing chickens than in slow-growing chickens. In this study, Affymetrix Genechip® Chicken Genome Arrays 32773 transcripts were used to compare gene expression profiles in liver and hypothalamus tissues of fast-growing and slow-growing chicken at 8 wk of age. Real-time RT-PCR was used to validate the differential expression of genes selected from the microarray analysis. The mRNA expression of the genes was further examined in fat tissues. The association of single nucleotide polymorphisms of four lipid-related genes with fat traits was examined in a F2 resource population.

RESULTS

Four hundred genes in the liver tissues and 220 genes hypothalamus tissues, respectively, were identified to be differentially expressed in fast-growing chickens and slow-growing chickens. Expression levels of genes for lipid metabolism (SULT1B1, ACSBG2, PNPLA3, LPL, AOAH) carbohydrate metabolism (MGAT4B, XYLB, GBE1, PGM1, HKDC1)cholesttrol biosynthesis (FDPS, LSS, HMGCR, NSDHL, DHCR24, IDI1, ME1) HSD17B7 and other reaction or processes (CYP1A4, CYP1A1, AKR1B1, CYP4V2, DDO) were higher in the fast-growing White Recessive Rock chickens than in the slow-growing Xinghua chickens. On the other hand, expression levels of genes associated with multicellular organism development, immune response, DNA integration, melanin biosynthetic process, muscle organ development and oxidation-reduction (FRZB, DMD, FUT8, CYP2C45, DHRSX, and CYP2C18) and with glycol-metabolism (GCNT2, ELOVL 6, and FASN), were higher in the XH chickens than in the fast-growing chickens. RT-PCR validated high expression levels of nine out of 12 genes in fat tissues. The G1257069A and T1247123C of the ACSBG2 gene were significantly associated with abdominal fat weight. The G4928024A of the FASN gene were significantly associated with fat bandwidth, and abdominal fat percentage. The C4930169T of the FASN gene was associated with abdominal fat weight while the A59539099G of the ELOVL 6 was significantly associated with subcutaneous fat. The A8378815G of the DDT was associated with fat band width.

CONCLUSION

The differences in fat deposition were reflected with differential gene expressions in fast and slow growing chickens.

De novo lipogenesis in the liver and adipose tissues of ducks during early growth stages after hatching

In vivo de novo lipogenesis (DNL) in the liver and adipose tissues of ducks during early developmental stages after hatching has not previously been investigated. In this study, female Peking ducks (Anas platyrhynchos) at weeks 1 to 8 post-hatching were selected for experimentation. We measured the mRNA levels of 6 DNL-related genes in the duck liver, subcutaneous adipose tissue and abdominal adipose tissue by real-time PCR during the 8 weeks. Correlations of the plasma triacylglycerol (TG) and very low density lipoprotein (VLDL) concentrations with fat deposition at these sites were also detected during growth. Our results showed that fat content was highest in the subcutaneous adipose tissue and lowest in the liver during the growth period we studied. Additionally, plasma VLDL and TG were significantly associated with lipid content in adipose tissue (P<0.05), but not in the liver. Lastly, in the growing birds, the expression levels of lipogenic genes (with the exceptions SREBP-1c and SCD1) were much higher in the liver than in the adipose tissues, and the maximal expression levels of these genes occurred at week 4 or 5 at these sites. These findings indicated that the main site of DNL is always the liver in post-hatching ducks, and adipose tissues are of little importance for DNL. Taken together, our results suggested that the plasma lipoproteins contribute greatly to fat deposition in adipose tissues originating from hepatic lipogenesis.

Developmental changes of protein profiles in the embryonic Sanhuang chicken liver

Understanding embryonic liver development bears the potential to provide important insights into treatments and preventative strategies for paediatric liver disease. Using Sanhuang (SH) chicken as a model system, we sought to identify the proteomic changes associated with embryonic liver development using differential display of proteins with two-dimensional (2-D) polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry analysis. Embryonic livers from 200 SH chicken embryos were isolated on days 9, 14 and 19 during incubation and also immediately after hatching. Six hundred and two protein spots were displayed on 2-D gels stained with colloidal Coomassie brilliant blue, of which, 25 protein spots were found to have changes up to threefold in abundance during development. We identified these spots using MALDI-TOF mass spectrometry and found 23 of 25 proteins to be associated with carbohydrate metabolism, cell division, lipid metabolism and signal transduction. Our results provide insight into the biochemical events taking place during the development of SH chicken embryonic liver and highlight the value of proteomics in characterizing complex biochemical processes. Furthermore, the proteome maps may facilitate future studies addressing the effects of genetic and environmental factors and related studies on the development and quality of chicken embryonic liver.

Effects of In Ovo Administration of DHEA on Lipid Metabolism and Hepatic Lipogenetic Genes Expression in Broiler Chickens During Embryonic Development

In order to study the mechanism of DHEA (Dehydroepiandrosterone) in reducing fat in broiler chickens during embryonic development, fertilized eggs were administrated with DHEA before incubation and its effect on lipid metabolism and expression of hepatic lipogenetic genes was investigated. The mRNA levels of acetyl CoA carboxylase (ACC), fatty acid synthase (FAS), malic enzyme (ME), apolipoprotein B100 (apoB100) and sterol regulator element binding protein-1c (SREBP-1c) were determined using real time quantitative PCR. Samples of livers were collected from the chickens on days 9, 14, and 19 of embryonic development as well as at hatching. Blood samples were extracted on days 14, 19 of incubation and at hatching. The results showed that DHEA decreased the concentration of triacyglycerol in the blood and the content in liver, and the mRNA levels of ACC, FAS, ME, SREBP-1c and apoB. This suggested that DHEA decreased the expression of hepatic lipogenetic genes and suppressed triglycerols transport, by which it reduced the deposition of fat in adipose tissue in broiler chickens during embryonic development and hatching.