Chronic mild cold conditioning modulates the expression of hypothalamic neuropeptide and intermediary metabolic-related genes and improves growth performances in young chicks

Authors: NGUYGEN, PHUONG - University Of Arkansas; GREEN, ELISABETH - University Of Arkansas; ISHOLA, PETER - University Of Arkansas; Huff, Geraldine; Donoghue, Ann - Annie; DRIDI, SAMI - University Of Arkansas

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2015
Publication Date: 11/16/2015
Citation: Nguygen, P.H., Green, E., Ishola, P., Huff, G.R., Donoghue, A.M., Dridi, S. 2015. Chronic mild cold conditioning modulates the expression of hypothalamic neuropeptide and intermediary metabolic-related genes and improves growth performances in young chicks. PLoS One. 10(11):e0142319. https://doi.org/10.1371/journal.pone.0142319.
DOI: https://doi.org/10.1371/journal.pone.0142319

Interpretive Summary: Low environmental temperatures are among the most challenging stressors in poultry industries. Although landmark studies using acute severe cold exposure have been conducted, still the molecular mechanisms underlying cold-stress responses in birds are not completely defined. In the present study we assess to determine the effect of chronic mild cold conditioning (CMCC) on growth performances and on the expression of key metabolic-related genes in three metabolically important tissues: brain (main site for feed intake control), liver (main site for lipogenesis) and muscle (main site for thermogenesis). One-day old male broiler chicks were divided into two weight-matched groups and maintained in two different temperature floor pen rooms (40 birds/room). The temperature of control room was 32C, while the cold room temperature started at 26.7C and gradually reduced every day (1C/day) to reach 19.7C at the seventh day of the experiment. At day 7, growth performances were recorded (from all birds) and blood samples and tissues were collected (n=10). The rest of birds were maintained at the same standard environmental condition for two more weeks and growth performances were measured. Results: Although feed intake remained unchanged, body weight gain was significantly increased in CMCC compared to the control chicks resulting in a significant low feed conversion ratio (FCR). Circulating cholesterol and creatine kinase levels were higher in CMCC chicks compared to the control group. CMCC significantly induced the expression of 2 neuropeptides in chick brain which may explain the similar feed intake between the two groups. Interestingly, compared to the control condition, CMCC increased the mRNA abundance of two of the master energy and nutrient sensors and the expression of fatty acid synthase (FAS) gene in chick brain compared to the control. Although their roles are still unknown in avian species, adiponectin and its related receptors were upregulated in the brain of CMCC compared to control chicks. In the liver, CMCC significantly down regulated the expression of lipogenic genes and mTOR while other genes were up-regulated indicating that CMCC switches liver catabolism on and inhibits.

Technical Abstract: Background: Low environmental temperatures are among the most challenging stressors in poultry industries. Although landmark studies using acute severe cold exposure have been conducted, still the molecular mechanisms underlying cold-stress responses in birds are not completely defined. In the present study we assess to determine the effect of chronic mild cold conditioning (CMCC) on growth performances and on the expression of key metabolic-related genes in three metabolically important tissues: brain (main site for feed intake control), liver (main site for lipogenesis) and muscle (main site for thermogenesis). Methods: one-day old male broiler chicks were divided into two weight-matched groups and maintained in two different temperature floor pen rooms (40 birds/room). The temperature of control room was 32C, while the cold room temperature started at 26.7C and gradually reduced every day (1C/day) to reach 19.7C at the seventh day of the experiment. At day 7, growth performances were recorded (from all birds) and blood samples and tissues were collected (n=10). The rest of birds were maintained at the same standard environmental condition for two more weeks and growth performances were measured. Results: Although feed intake remained unchanged, body weight gain was significantly increased in CMCC compared to the control chicks resulting in a significant low feed conversion ratio (FCR). Circulating cholesterol and creatine kinase levels were higher in CMCC chicks compared to the control group (P<0.05). CMCC significantly induced the expression of both the hypothalamic orexigenic neuropeptide Y (NPY) and anorexigenic cocaine and amphetamine regulated transcript (CART) in chick brain which may explain the similar feed intake between the two groups. Interestingly, compared to the control condition, CMCC increased the mRNA abundance of AMPKa1 and mTOR (P<0.05), the master energy and nutrient sensors, respectively. It also significantly induced the 40 expression of fatty acid synthase (FAS) gene in chick brain compared to the control. Although their roles are still unknown in avian species, adiponectin (Adpn) and its related receptors (AdipoR1 and 2) were upregulated in the brain of CMCC compared to control chicks (P<0.05). In the liver, CMCC significantly down regulated the expression of lipogenic genes namely FAS, acetyl-CoA carboxylase alpha (ACCa) and malic enzyme (ME) and their related transcription factors sterol regulatory element binding protein 1/2 (SREBP-1 and 2). Hepatic mTOR mRNA levels and phosphorylated mTOR at Ser24 were down regulated (P<0.05), however phosphorylated ACCaSer79 (inactivation) was up regulated (P<0.05) in CMCC compared to control chicks, indicating that CMCC switch hepatic catabolism on and inhibits hepatic lipogenesis. In the muscle however, CMCC significantly up regulates the expression of carnitine palmitoyltransferase 1 (CPT-1) gene and the mRNA and phosphorylated protein levels of mTOR compared to the control chicks, indicating that CMCC enhanced muscle fatty acid ß-oxidation. Conclusions: In conclusion, this is the first report showing that CMCC regulates mTOR in a tissue specific manner and identify mTOR as a potential molecular signature that controls cellular fatty acid utilization (inhibition of hepatic lipogenesis and induction of muscle fatty acid Beta- oxidation) to enhance growth performance during mild cold acclimation.