ABSTRACT Intramuscular fat (IMF) content is a crucial parameter for estimating meat quality. Growing evidence indicates that gene regulation plays an important role in IMF deposition. This study aimed to determine the function of Mfsd2a in chicken intramuscular preadipocytes. In the present study, high Mfsd2a mRNA levels were observed in the liver and adipose tissues of broilers. Subsequently, we synthesized small interfering RNAs to silence the expression of Mfsd2a in chicken intramuscular preadipocytes. The following results suggested that CDK2, PCNA, CCND1, CCND2 and MKI67 were inhibited, with CCK-8 and EdU assays revealing that cell proliferation was inhibited. Scratch test showed that cell migration ratios were declined. We also found that Mfsd2a silencing decreased the mRNA levels of PPARγ, RXRG and their target genes. The similar results were found in some key genes that contribute to lipid synthesis, including C/EBPα, C/EBPβ, FABP4, FASN, ACACA and ACSL1. Finally, Oil red O staining showed that IMF accumulation was blocked after Mfsd2a silencing. In conclusion, our results implied that Mfsd2a promotes the proliferation and migration of chicken intramuscular preadipocytes, as well as the differentiation and adipogenesis through PPARγ signaling pathway, which may provide a potential target to improve chicken meat quality.

ABSTRACT In this study, immunohistochemistry and real-time fluorescent-based quantitative PCR were used to evaluate the expression of heat shock protein (HSP) 60, HSP70, and HSP90 in the small intestine of Wenchang chicks. Compared with the control group (CK), the positive expression of HSP60 and HSP60 mRNA in the heat stress group (HS) were initially higher and subsequently lower in the duodenum (p<0.01). In the HS jejunum, the levels of HSP60 were higher (p<0.01) and the HSP60 mRNA was lower (p<0.05). Whereas the levels of HSP60 in the HS ileum were higher (p<0.05) and then lower (p<0.01), and the HSP60 mRNA was higher (p<0.01). The levels of HSP70 were higher (p<0.01) and the HSP70 mRNA was lower in the duodenum (p<0.05), while the expression of both HSP70 and HSP70 mRNA was higher in the jejunum (p<0.01) and the ileum (p<0.05) of the HS. In the HS duodenum the levels of HSP90 were lower and then higher (p<0.01), and the HSP90 mRNA was higher (p<0.01). The expression of both HSP90 and HSP90 mRNA was higher in the HS jejunum (p<0.05). The levels of HSP90 were lower while the HSP90 mRNA was higher in the HS ileum (p<0.01). These results indicate that heat stress disturbed the expression of HSP60, HSP70, and HSP90 in the small intestine of chicks.

ABSTRACT The hypothalamic-pituitary-gonadal (HPG) axis is a key neuroen-docrine regulation system involved in the growth and reproduction of poultry. High-temperature conditions lead to the physiological dysfunction of target organs of the HPG axis of poultry, ultimately affecting the animals’ growth and development. In this study, we evaluated the effect of heat stress (HS) on the development of cells secreting major reproductive hormones of the HPG axis (i.e., hypothalamus, pituitary gland, ovary, and testis) of Wenchang chicks. Seventy-two one-day-old healthy Wenchang chicks were randomly divided into control (CK) and HS groups. The HS group was placed in a 40 ± 0.5°C artificial climate chamber for heat-stress treatment from 13:00 to 15:00 daily for six consecutive weeks. As development progressed, compared with the CK group, the gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) levels in the hypothalamus and testosterone (T) levers in the testes of male chicks in the HS group were significantly decreased at three weeks of age (p<0.05). However, GnRH levels in the hypothalamus and estradiol (E2) levels in the ovaries of female chicks in the HS group were variable and significantly lower than those of the CK group at four and five weeks of age (p<0.05). In addition, the LH and FSH levels in the pituitary gland were significantly lower than those in the CK group at two and four weeks of age and at four and six weeks of age, respectively (p<0.05). In brief, HS caused dysfunction of the corresponding target organs of the HPG axis in Wenchang chicks, and this affected the normal growth and development of the cells’ HPG axis.

ABSTRACT This study conducted an in-depth investigation on the development of GABAergic neurons and their receptors in HPG axis-related target organs of Wenchang chicks under heat stress. One-day-old healthy Wenchang chicks were randomly divided into control (CK) and heat stress (HS) groups. Chicks in the HS group were placed in a 40±0.5°C climatic chamber for HS treatment from 13:00 to 15:00 daily. By immunohistochemistry and Western blotting, GABA and GABAA receptor (GABAAR) expression in the hypothalamus of the HS group was significantly higher (p<0.05), but GABAB receptor (GABABR) expression was significantly lower than that of the CK group (p<0.05). Expression of GABA and its two receptors in the pituitary tissues of the HS group was significantly lower than in the CK group (p<0.05). Expression of GABA and GABABR in ovaries in the HS group was significantly higher, but expression of GABAAR in the testes of the HS group was lower than that of the CK group (p<0.05). In the male chicks, expression of GABA and its two receptors in the hypothalamus, pituitary, and testicular tissues of the HS group was significantly higher than that of the CK group (p<0.05). Western blotting showed that the GABAAR and GABABR expression of the HS group was significantly higher than that of the CK group at 3 and 5 weeks of age. Thus, HS caused GABAergic nervous system disorder in the HPG axis of Wenchang chicks and seriously hindered the normal development of GABAergic neurons in chicks, leading to the disorder of the expression of GABA and its receptors in tissues.