Effects of age and strain on the expression of leptin receptor, neuropeptide Y and pro-opiomelanocortin in the hypothalamus of young chickens

Hypothalamic regulation of energy homoeostasis when consuming diets of different energy concentrations: comparison between Tibetan and Small-tailed Han sheep

Seasonal energy intake of Tibetan sheep on the harsh Qinghai-Tibetan Plateau (QTP) fluctuates greatly and is often well below maintenance requirements. The aim of this study was to gain insight into how the hypothalamus regulates energy homoeostasis in Tibetan sheep. We compared Tibetan and Small-tailed Han sheep (n 24 of each breed), which were each allocated randomly into four groups and offered one of four diets that differed in digestible energy densities: 8·21, 9·33, 10·45 and 11·57 MJ/kg DM. Sheep were weighed every 2 weeks, and it was assumed that the change in body weight (BW) reflected the change in energy balance. The arcuate nucleus of the hypothalamus in Tibetan sheep had greater protein expressions of neuropeptide Y (NPY) and agouti-related peptide (AgRP) when in negative energy balance, but lesser protein expressions of proopiomelanocortin (POMC) and cocaine and amphetamine-regulated transcript (CART) when in positive energy balance than Small-tailed Han sheep. As a result, Tibetan sheep had a lesser BW loss when in negative energy balance and stored more energy and gained more BW when in positive energy balance than Small-tailed Han sheep with the same dietary intake. Moreover, in the hypothalamic adenosine monophosphate-activated protein kinase (AMPK) regulation pathway, Tibetan sheep had greater adenosine monophosphate-activated protein kinase-α 2 protein expression than Small-tailed Han sheep, which supported the premise of a better ability to regulate energy homoeostasis and better growth performance. These differences in the hypothalamic NPY/AgRP, POMC/CART and AMPK pathways between breeds conferred an advantage to the Tibetan over Small-tailed Han sheep to cope with low energy intake on the harsh QTP.

Association of LEPR polymorphisms with egg production and growth performance in female Japanese quails

This study aimed to screen intron 8 of the leptin receptor (LEPR) gene for polymorphisms in female Japanese quails. Two adjacent novel SNPs (A277G and A304G) were detected using PCR-SSCP and sequencing. These SNPs produced three haplotypes (AA/AA, AG/AG, and GG/GG) that were significantly (p ≤ 0.05) associated with growth and egg production traits. GG/GG haplotype-quails had significantly (p ≤ 0.05) lower egg production, feed intake, growth performance, lipid profile, serum levels of sex hormones (estradiol, progesterone, FSH, LH), and ovarian expressions of survivin, FSHR, and IGF1 than other quails. However, GG/GG quails had significantly (p ≤ 0.05) higher serum levels of LEP and mRNA levels of LEPR, LEP, and caspase 3 in the hypothalamus and ovaries. These higher levels of LEP/LEPR could not only reduce feed intake and body weight gain but also could induce apoptosis of ovarian cells (as indicated by lower survivin and IGF1 and higher caspase3 expression) which could inhibit the development of the follicles and the release of sex hormones with a subsequent decrease in egg production in GG/GG quails. Therefore, with these results, we suggest selecting Japanese quails with AA/AA and AG/AG haplotypes to improve the reproduction and growth performance of this flock.

Dietary overload lithium decreases the adipogenesis in abdominal adipose tissue of broiler chickens

To investigate the toxic effects of dietary overload lithium on the adipogenesis in adipose tissue of chicken and the role of hypothalamic neuropeptide Y (NPY) in this process, one-day-old male chicks were fed with the basal diet added with 0 (control) or 100mg lithium/kg diet from lithium chloride (overload lithium) for 35days. Abdominal adipose tissue and hypothalamus were collected at day 6, 14, and 35. As a percentage of body weight, abdominal fat decreased (p<0.001) at day 6, 14, and 35, and feed intake and body weight gain decreased during day 7-14, and day 15-35 in overload lithium treated broilers as compared to control. Adipocyte diameter and DNA content in abdominal adipose tissue were significantly lower in overload-lithium treatment than control at day 35, although no significant differences were observed at day 6 and 14. Dietary overload lithium decreased (p<0.01) transcriptional expression of preadipocyte proliferation makers ki-67 (KI67), microtubule-associated protein homolog (TPX2), and topoisomerase 2-alpha (TOP2A), and preadipocyte differentiation transcriptional factors peroxisome proliferator-activated receptor-γ (PPARγ), and CCAAT/enhancer binding protein (C/EBP) α mRNA abundance in abdominal adipose tissue. In hypothalamus, dietary overload lithium influenced (p<0.001) NPY, and NPY receptor (NPYR) 6 mRNA abundance at day 6 and 14, but not at day 35. In conclusion, dietary overload lithium decreased the adipogenesis in abdominal adipose tissue of chicken, which was accompanied by depressing transcriptional expression of adipogenesis-associated factors. Hypothalamic NPY had a potential role in the adipogenesis in abdominal adipose tissue of broilers with a short-term overload lithium treatment.

Effect of intravenously injected zinc on tissue zinc and metallothionein gene expression of broilers

1. The effect of intravenously injected zinc (Zn) on tissue Zn concentrations and pancreas metallothionein (MT) gene expression in broilers was investigated to detect differences in the tissue utilisation of Zn from different Zn sources. 2. A total of 432 male chickens were randomly allotted on d 22 post-hatch to one of nine treatments in a completely randomised design. Chickens were injected with either a 0.9% (w/v) NaCl solution (control) or a saline solution supplemented with Zn sulphate or one of three organic Zn chelates with weak (Zn-AA W), moderate (Zn-Pro M) or strong (Zn-Pro S) chelation strengths at two injected Zn dosages calculated according to two Zn absorbability levels (6 and 12%). 3. Bone and pancreas Zn concentrations, pancreas MT mRNA levels and MT concentrations increased on d 6 and 12 after Zn injections as the injected Zn dosages increased. Chickens injected with the Zn-Pro S had lower bone Zn concentration than those injected with the Zn-Pro M or Zn-AA W on d 6 after injections. However, no differences among Zn sources were observed in bone Zn concentration on d 12 after injections, pancreas Zn concentrations, pancreas MT mRNA levels and MT concentrations on both d 6 and d 12 after injections. 4. It was concluded that the injected Zn-Pro S was the least favourable for bone Zn utilisation of broilers. The pancreas Zn concentration and pancreas MT gene expressions might not be sensitive enough to detect differences in the tissue utilisation of injected Zn in broilers between organic and inorganic Zn sources or among organic Zn sources.

Polymorphisms of the pro-opiomelanocortin and agouti-related protein genes and their association with chicken production traits

Pro-opiomelanocortin (POMC) and agouti-related protein (AGRP) are hypothalamic neuropeptides that play a central role in the regulation of food intake and energy expenditure and for this reason the variations in the POMC and AGRP genes in chicken were examined by screening the DNA pools. Two silent cSNPs mutations in POMC gene and one silent cSNP mutation in AGRP gene were identified. PCR-restriction fragment length polymorphism (RFLP) was used to test the cSNPs c. C495T in the POMC and c. C9T in the AGRP gene in the F2 resource population of Gushi chicken crossed with Anak broiler. The association analysis on the polymorphisms of POMC, AGRP gene and production traits showed that the c. C495T mutation in the POMC gene was significantly linked to the pelvis breadth at 4 weeks of age (P = 0.035), body weight at 2 weeks of age (P = 0.013) and was highly significantly linked to the chest depth at 12 weeks of age (P = 0.006). The c. T9T genotype in the AGRP gene was associated with a low breast muscle water loss rate (P = 0.025), increased chest width at 12 weeks of age (P = 0.005) and body weight at 2 weeks of age (P = 0.036), a high slaughter rate (P = 0.049) and semi-evisceration weight (P = 0.019). These findings may have important implications for the molecular aspects of chicken breeding.