Chickens from lines selected for high and low body weight show differences in fatty acid oxidation efficiency and metabolic flexibility in skeletal muscle and white adipose tissue

Abstract

OBJECTIVE: The Virginia lines of chickens have resulted from more than 55 generations of artificial selection for low (LWS) or high (HWS) juvenile body weight. We hypothesized that the relative hyperphagia and greater body weight in juvenile HWS chickens are associated with altered fatty acid oxidation efficiency and metabolic flexibility in tissues associated with energy sensing and storage, and relative cellular hypertrophy in white adipose tissue. METHODS: Hypothalamus, liver, pectoralis major, gastrocnemius, abdominal fat, clavicular fat and subcutaneous fat were collected from the juvenile (56-65 days old) LWS and HWS chickens for metabolic, gene expression and histological assays. RESULTS: The HWS chickens had reduced fatty acid oxidation efficiency in abdominal fat (Po0.0001) and reduced rates of oxidation in abdominal fat and gastrocnemius (Po0.0001) as compared with the LWS. There was reduced citrate synthase activity in white adipose tissue (Po0.0001) and greater metabolic inflexibility in skeletal muscle (P = 0.006) of the HWS compared with the LWS. Greater pyruvate dehydrogenase kinase 4 (PDK4) and forkhead box O1A (FoxO1) mRNA were found in skeletal muscle and white adipose tissue of 56-day-old HWS than LWS. Expression of peroxisome proliferator-activated receptor γ (PPARγ) in all adipose tissue depots was greater (Po0.05) in LWS than in HWS chickens. The HWS chickens had larger (Po0.0001) and fewer (Po0.0001) adipocytes per unit area than the LWS. CONCLUSION: Compared with the LWS, the HWS chickens have impaired metabolic flexibility and fatty acid oxidation efficiency due to greater pyruvate dehydrogenase activity to accommodate the influx of acetyl-CoA from fatty acid oxidation in skeletal muscle and adipose tissue. These metabolic adaptations can be linked to differences in gene expression regulation, adipocyte cellularity and body composition between the lines, which may provide valuable insight into metabolic disorders in other species.