Li Leng

Comparison of adipose tissue cellularity in chicken lines divergently selected for fatness

After 13 generations of divergent selection for abdominal fatness, 2 chicken lines (a fat line and a lean line) have been established. To clarify the cellular mechanism underlying the differences in fatness between the fat and lean lines, cellularity characteristics of the abdominal adipose tissues were analyzed during the first 7 wk of age by electron microscopy, proliferating cell nuclear antigen staining, and DNA content measurement. The abdominal fat percentage at 7 wk of age in the fat chicken line was 3.8 times that of the lean line, and was accompanied by a 1.3-fold increase in adipocyte diameter and a 2.4-fold increase in adipocyte number. The total cell number of the abdominal fat pad in the fat chicken line was 1.9 times that of the lean line at 7 wk of age. However, no significant difference was observed in the proliferation rate of stroma vascular fraction cells between the 2 chicken lines. These findings suggest that the divergently selected fat and lean chickens have different adipose tissue ontogeny.

A genome-wide scan of selective sweeps in two broiler chicken lines divergently selected for abdominal fat content

BackgroundGenomic regions controlling abdominal fatness (AF) were studied in the Northeast Agricultural University broiler line divergently selected for AF. In this study, the chicken 60KSNP chip and extended haplotype homozygosity (EHH) test were used to detect genome-wide signatures of AF.ResultsA total of 5357 and 5593 core regions were detected in the lean and fat lines, and 51 and 57 reached a significant level (P<0.01), respectively. A number of genes in the significant core regions, including RB1, BBS7, MAOA, MAOB, EHBP1, LRP2BP, LRP1B, MYO7A, MYO9A and PRPSAP1, were detected. These genes may be important for AF deposition in chickens.ConclusionsWe provide a genome-wide map of selection signatures in the chicken genome, and make a contribution to the better understanding the mechanisms of selection for AF content in chickens. The selection for low AF in commercial breeding using this information will accelerate the breeding progress.

Selection signature analysis implicates the PC1/PCSK1 region for chicken abdominal fat content

We conducted a selection signature analysis using the chicken 60k SNP chip in two chicken lines that had been divergently selected for abdominal fat content (AFC) for 11 generations. The selection signature analysis used multiple signals of selection, including long-range allele frequency differences between the lean and fat lines, long-range heterozygosity changes, linkage disequilibrium, haplotype frequencies, and extended haplotype homozygosity. Multiple signals of selection identified ten signatures on chromosomes 1, 2, 4, 5, 11, 15, 20, 26 and Z. The 0.73 Mb PC1/PCSK1 region of the Z chromosome at 55.43-56.16 Mb was the most heavily selected region. This region had 26 SNP markers and seven genes, Mar-03, SLC12A2, FBN2, ERAP1, CAST, PC1/PCSK1 and ELL2, where PC1/PCSK1 are the chicken/human names for the same gene. The lean and fat lines had two main haplotypes with completely opposite SNP alleles for the 26 SNP markers and were virtually line-specific, and had a recombinant haplotype with nearly equal frequency (0.193 and 0.196) in both lines. Other haplotypes in this region had negligible frequencies. Nine other regions with selection signatures were PAH-IGF1, TRPC4, GJD4-CCNY, NDST4, NOVA1, GALNT9, the ESRP2-GALR1 region with five genes, the SYCP2-CADH4 with six genes, and the TULP1-KIF21B with 14 genes. Genome-wide association analysis showed that nearly all regions with evidence of selection signature had SNP effects with genome-wide significance (P<10–6) on abdominal fat weight and percentage. The results of this study provide specific gene targets for the control of chicken AFC and a potential model of AFC in human obesity.

Adipocyte fatty acid-binding protein: An important gene related to lipid metabolism in chicken adipocytes

Fatty acid-binding proteins (FABPs) may facilitate the diffusion of fatty acids within the cytoplasm. Adipocyte FABP (A-FABP) null mice exhibit altered rates of lipolysis, and reprogrammed expression of genes related to lipid metabolism. In the current study, chicken adipocytes with short hairpin RNA-mediated knockdown and cDNA overexpression of A-FABP were used to investigate the role of chicken A-FABP in lipid metabolism of adipocytes. The results showed that there was no significant change of lipid metabolism in the A-FABP interference adipocytes. However, in the A-FABP overexpression adipocytes, the lipolysis was increased significantly at 36 h (p<0.05), and lipid accumulation was increased significantly at 48, 60 and 72 h (p<0.05). The expression of PPAR γ and perilipin genes were upregulated, while the expression of E-FABP gene was downregulated after transfection with pcDNA3.1/A-FABP (p<0.05). The present study suggested that A-FABP gene might affect the lipid metabolism through the PPAR γ pathway, and the function between A-FABP and E-FABP gene was compensatory in the chickens.

Tissue expression characterization of chicken adipocyte fatty acid-binding protein and its expression difference between fat and lean birds in abdominal fat tissue.

Fatty acid-binding proteins are considered to be the carriers for the transportation of intracellular fatty acids and play an important role in the development of fatness traits. Adipocyte fatty acid-binding protein (A-FABP) is one of the family members. The current study was designed to analyze the tissue expression characterization of chicken A-FABP and its expression difference between the fat and lean males in abdominal fat tissue to reveal the possible relationship between the expression of A-FABP and abdominal fat tissue development and growth in chicken. First, fusion protein glutathione S-transferase/A-FABP was induced and purified, and then the antiserum containing specific polyclonal antibodies was obtained by immunizing healthy female rabbits using the purified fusion protein. Second, tissue expression characterization of A-FABP was investigated by Western blot. Finally, A-FABP expression difference in abdominal fat tissue between the fat and lean males was investigated by real-time reverse transcription-PCR and Western blot methods. The results showed that A-FABP expressed specifically in abdominal fat tissue and the mRNA expression level of A-FABP in fat males was lower than that of lean males at 2, 3, 4, 6, 7, 9, and 10 wk of age (P<0.05), and the protein expression level of fat males was lower than that of lean males at 6 and 10 wk of age (P<0.05). These results suggested that chicken A-FABP might affect abdominal fat deposition through changing its expression level, and the possible mechanism may be that a high expression level of A-FABP induced the high lipolytic rate and led to the decreased abdominal fat mass accordingly.

Comparison of serum biochemical parameters between two broiler chicken lines divergently selected for abdominal fat content

In humans, obesity is associated with increased or decreased levels of serum biochemical indicators. However, the relationship is not as well understood in chickens. Due to long-term intense selection for fast growth rate, modern broilers have the problem of excessive fat deposition, exhibiting biochemical or metabolic changes. In the current study, the Northeast Agricultural University broiler lines divergently selected for abdominal fat content (NEAUHLF) were used to identify differences in serum biochemical parameters between the 2 lines. A total of 18 serum biochemical indicators were investigated in the 16th, 17th, and 18th generation populations of NEAUHLF, and the genetic parameters of these serum biochemical indicators were estimated. After analyzing the data from these 3 generations together, the results showed that the levels of 16 of the tested serum biochemical parameters were significantly different between the lean and fat birds. In the fat birds, serum concentrations of high-density lipoprotein cholesterol (HDL-C), HDL-C:low-density lipoprotein cholesterol (LDL-C), total bile acid, total protein, albumin, globulin, aspartate transaminase (AST):alanine transaminase (ALT), γ-glutamyl transpeptidase (GGT), uric acid, and creatinine were very significantly higher (P < 0.01), whereas LDL-C, albumin:globulin, glucose, AST, ALT, and free fatty acids concentrations in serum were very significantly lower than those in the lean birds (P < 0.01). Of these 16 serum biochemical parameters, 5 (LDL-C, HDL-C:LDL-C, total bile acid, albumin, and albumin:globulin) had high heritabilities (0.58 ≤ h2 ≤ 0.89), 6 (HDL-C, total protein, globulin, AST:ALT, GGT, and creatinine) had moderate heritabilities (0.29 ≤ h2 ≤ 0.48), and the remaining 5 had low heritabilities (h2 < 0.20). Serum HDL-C, HDL-C:LDL-C, and glucose had higher positive genetic correlation coefficients (rg) with abdominal fat traits (0.30 ≤ rg ≤ 0.80), whereas serum globulin, AST, and uric acid showed higher negative genetic correlations with abdominal fat traits (–0.62 ≤ rg ≤ –0.30). The remaining 10 serum biochemical parameters had lower genetic correlations with abdominal fat traits (–0.30 < rg < 0.30). In conclusion, we identified serum HDL-C and HDL-C:LDL-C levels as potential biomarkers for selection of lean birds. These findings will also be useful in future studies for investigating obesity and lipid metabolism in humans as well as in other animal species.

A single nucleotide polymorphism of chicken acetyl-CoA carboxylase A gene associated with fatness traits.

Acetyl-CoA carboxylase α (ACCα) is a major rate-limiting enzyme in the biogenesis of long-chain fatty acids. It can catalyze the carboxylation of acetyl-CoA to form malonyl-CoA that plays a key role in the regulation of fatty acid metabolism. The objective of the present study was to investigate the associations of ACCα gene polymorphisms with chicken growth and body composition traits. The Northeast Agricultural University broiler lines divergently selected for abdominal fat content and the Northeast Agricultural University F2 Resource Population were used in the current study. Body weight and body composition traits were measured in the aforementioned two populations. A synonymous mutation was detected in the exon 19 region of ACCα gene, then polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was developed to genotype all the individuals derived from the aforementioned populations. Association analysis revealed that the polymorphism was associated with abdominal fat weight and percentage of abdominal fat in the two populations. The results suggested that ACCα gene could be a candidate locus or linked to a major gene that affects abdominal fat content in the chicken.

Polymorphism of Heart Fatty Acid-Binding Protein Gene Associatied with Fatness Traits in the Chicken

Fatty acid-binding proteins (FABP) belong to a superfamily of lipid binding proteins that exhibit a high affinity for long chain fatty acids and appear to function in metabolism and intracellular transportation of lipids. The current study was designed to investigate the effects of heart (H)-FABP gene on chicken growth and body composition traits. The Northeast Agricultural University divergent broiler lines for abdominal fat and a broiler X silkie F2 population were used in this study. Body weight and body composition traits were measured in the populations. Primers were designed according to the chicken H-FABP gene sequence. Polymorphisms between parental lines were detected by DNA sequencing. PCR-RFLP and PCR-fragment length polymorphism methods were developed to genotype the populations. The results showed that the H-FABP gene polymorphisms in the two populations were associated with abdominal fat percentage. It implied that H-FABP gene can be a candidate locus or linked to a major gene(s) that affects abdominal fat content in the chicken.

Differential fecal microbiota are retained in broiler chicken lines divergently selected for fatness traits

Our study combined 16S rRNA-pyrosequencing and whole genome sequencing to analyze the fecal metagenomes of the divergently selected lean (LL) and fat (FL) line chickens. Significant structural differences existed in both the phylogenic and functional metagenomes between the two chicken lines. At phylum level, the FL group had significantly less Bacteroidetes. At genus level, fourteen genera of different relative abundance were identified, with some known short-chain fatty acid producers (including Subdoligranulum, Butyricicoccus, Eubacterium, Bacteroides, Blautia) and a potentially pathogenic genus (Enterococcus). Redundancy analysis identified 190 key responsive operational taxonomic units (OTUs) that accounted for the structural differences between the phylogenic metagenome of the two groups. Four Cluster of Orthologous Group (COG) categories (Amino acid transport and metabolism, E; Nucleotide transport and metabolism, F; Coenzyme transport and metabolism, H; and Lipid transport and metabolism, I) were overrepresented in LL samples. Fifteen differential metabolic pathways (Biosynthesis of amino acids, Pyruvate metabolism, Nitrotoluene degradation, Lipopolysaccharide biosynthesis, Peptidoglycan biosynthesis, Pantothenate and CoA biosynthesis, Glycosaminoglycan degradation, Thiamine metabolism, Phosphotransferase system, Two-component system, Bacterial secretion system, Flagellar assembly, Bacterial chemotaxis, Ribosome, Sulfur relay system) were identified. Our data highlighted interesting variations between the gut metagenomes of these two chicken lines.

Divergent selection-induced obesity alters the composition and functional pathways of chicken gut microbiota

BackgroundThe gastrointestinal tract is populated by a complex and vast microbial network, with a composition that reflects the relationships of the symbiosis, co-metabolism, and co-evolution of these microorganisms with their host. The mechanism that underlies such interactions between the genetics of the host and gut microbiota remains elusive.ResultsTo understand how genetic variation of the host shapes the gut microbiota and interacts with it to affect the metabolic phenotype of the host, we compared the abundance of microbial taxa and their functional performance between two lines of chickens (fat and lean) that had undergone long-term divergent selection for abdominal fat pad weight, which resulted in a 4.5-fold increase in the fat line compared to the lean line. Our analysis revealed that the proportions of Fusobacteria and Proteobacteria differed significantly between the two lines (8 vs. 18% and 33 vs. 24%, respectively) at the phylum level. Eight bacterial genera and 11 species were also substantially influenced by the host genotype. Differences between the two lines in the frequency of host alleles at loci that influence accumulation of abdominal fat were associated with differences in the abundance and composition of the gut microbiota. Moreover, microbial genome functional analysis showed that the gut microbiota was involved in pathways that are associated with fat metabolism such as lipid and glycan biosynthesis, as well as amino acid and energy metabolism. Interestingly, citrate cycle and peroxisome proliferator activated receptor (PPAR) signaling pathways that play important roles in lipid storage and metabolism were more prevalent in the fat line than in the lean line.ConclusionsOur study demonstrates that long-term divergent selection not only alters the composition of the gut microbiota, but also influences its functional performance by enriching its relative abundance in microbial taxa. These results support the hypothesis that the host and gut microbiota interact at the genetic level and that these interactions result in their co-evolution.