Effects Of Stress On Skeletal Muscle Mitochondrial Biogenesis And Function In Broilers

Mitochondrial function is associated with feed efficiency, and plays an important role in muscle development. In this study we set glucocorticoid treatment and heat exposure as a model to study the impact of stress on broiler skeletal muscle mitochondrial biogenesis and oxidative phosphorylation, to lay the foundation for elucidating the pathways regulating energy metabolism of stress.First study examines the impact of glucocorticoid on broiler skeletal muscle mitochondria biogenesis and function, it comprising three tests.Test 1: 10-15-day-old broilers was used for the study, provided stress group(intramuscular DEX, 2 mg/kg BW/d), the control group(intramuscular same dose of saline)and food intake matched group(treatment same with the control group, food intake same with the stress group), collecting blood, breast and thigh muscle as samples. The results showed that DEX treatment reduced broiler weight gain and feed conversion efficiency, reduce breast and thigh muscles, inhibition of mitochondrial respiratory chain complexes I(P < 0.05), II(P< 0.05) in breast muscles and mitochondrial respiratory chain complex II(P < 0.05) activity in thigh muscles, increased breast and thigh muscle mitochondria PGC-1α(peroxisome proliferator-activated receptor activator auxiliary 1α),(nuclear respiratory factor 1) NRF1 gene expression(P < 0.05), reduce the protrin expression of PGC-1α(P < 0.05).Test 2: myoblasts was used for the study, provided stress group(DEX, 25 μM) and the control group were treated 10, 20 and 30 h. DEX treatment after 10 h, it can significantly inhibit the chicken embryo myoblasts mitochondrial respiratory chain complex I activity(P <0.05), inhibiting PGC-1α’s downstream gene NRF1 and Tfam mRNA expression, but promote the expression of PGC-1α(P < 0.05); 20 and 30 h treatment can significantly improve the PGC-1α and NRF1 mRNA expression(P < 0.05), reduce the protrin expression of PGC-1α(P < 0.05).Test 3: chicken embryo myoblasts source for the study, the control group, stress group(DEX, 25 μM), resveratrol group(RES, 10 μM) and combined treatment group(25 μM DEX+10 μM RES), processing 10 h explore stress mitigation RES in myoblasts of DEX. RES and DEX treatment alone can significantly increase PGC-1α and NRF1 mRNA expression(P <0.05), no additive effect when combined treatment of RES and DEX.The second study examines the impact of heat stress on broiler skeletal muscle mitochondria biogenesis and function, 40-47-day-old broilers was used for the study, set heat stress group(32 ± 0.5 oC, 8:00-16:00), the control group(25 ± 0.5 oC) and feed intakematched group(treated with the control group, feed intake with stress group), collecting blood,breast and thigh muscle as samples.The results showed that 1 and 4 days of heat stress on broiler performance, mitochondrial function and gene expression have a little efffect. But when the heat exposure for 7 days significantly inhibited broiler feed intake(P < 0.05),significantly inhibits breast muscle mitochondrial respiratory chain complex I activity(P <0.05), significantly increased PGC-1α, mRNA expression NRF1 and Tfam of(P < 0.05).These results suggest that, glucocorticoids reduce broiler skeletal muscle PGC-1α protein expression, restrain activity of mitochondrial respiratory chain complex I, II, cause mitochondrial oxidative damage. It has a tissue specific reaction between the breast and thigh muscles. Effect of heat stress on broiler skeletal muscle mitochondrial biogenesis and oxidative phosphorylation has a time-dependent manner. In this process, the expression of PGC-1α increased first, then changing the downstream signal molecules. Above all, Stress damage broiler skeletal muscle mitochondria generation and function, gene and protein expression of PGC-1α/NRF1/Tfam was involoved in it.