Possible role of avian uncoupling protein in down‐regulating mitochondrial superoxide production in skeletal muscle of fasted chickens

Abstract

Little is known about the precise physiological roles of uncoupling protein 1 (UCP1) homologs (UCP2, UCP3, avian UCP) whose levels are up-regulated during fasting. UCPs in skeletal muscle are thought to play a role in the regulation of lipids as fuel substrates, and/or in controlling the production of reactive oxygen species (ROS). The aim of this investigation, using skeletal muscle from fasted chickens, was to examine alterations in the expression of genes encoding for avian UCP and key enzymes relevant to lipid flux across the mitochondrial b-oxidation pathway. We also clarified whether an increase in avUCP content could be associated with altered ROS production by mitochondria. Transcription levels of avUCP and CPT-I genes were increased 7.7-and 9.5-fold after a 24 h fast and slightly diminished but remained about 5.0-and 7.7-fold higher than baseline levels, respectively, after 48 h of fasting. In contrast, members of the b-oxidation pathway, LCAD and 3HADH, were gradually up-regulated from 12 to 48 h of fasting. This suggests that processes involved in the transfer and oxidation of fatty acids are up-regulated differently during the initial stage of fasting. Analysis of ROS production by lucigenin-derived chemiluminescence showed that the FFA-sensitive portion of carboxyatractyloside-upregulated ROS production was greater in skeletal muscle mitochondria from 24 h-fasted chickens compared with control, which leads us to postulate that ROS production is potentially down-regulated by UCP. The possible involvement of a backlog of fatty acid for oxidation, observed in chickens after a 24 h fast, in a transmembrane gradient of free non-oxidized fatty acids is also discussed.

Sequential changes in superoxide production, anion carriers and substrate oxidation in skeletal muscle mitochondria of heat‐stressed chickens

“…To study progressive alterations in the expression of skeletal muscle target genes, that is, avUCP, avANT and fatty acid oxidation-related genes (CPT-I: carnitine-palmitoyl-transferase-I; CPT-II carnitine-palmitoyl-transferase-II, 3HADH: 3-hydroxyacyl CoA dehydrogenase; and LCAD: long-chain acyl CoA dehydrogenase), real-time RT-PCR analysis was performed using the iCycler Real Time Detection System (Bio-Rad Laboratories, Hercules, CA). Five micrograms of total RNA, prepared using Trizol-Reagent (Invitrogen, San Diego, CA), was reverse transcribed using a mixture of oligo(dT) [12][13][14][15][16][17][18] and random primers, and M-MLV reverse transcriptase (Invitrogen, San Diego, CA). One microliter of each reverse transcription reaction product then served as a template in a 50 lL PCR reaction containing 2 mM MgCl 2 , 0.5 lM of each primer and 0.5· SYBR Green master mix (Bio Whittaker Molecular Applications, Rockland, ME).…”

Increased thermoregulation in cold-exposed transgenic mice overexpressing lipoprotein lipase in skeletal muscle: an avian phenotype?

“…Although these data indicate that skeletal muscle hmUCP and avUCP may play a role in the thermogenic response to cold temperatures, some questions remain regarding whether it functions as a true uncoupler of oxidative phosphorylation or in the prevention of oxygen free radicals that would be expected to accumulate during a period of high energy flux. In transfected yeast mitochondria (42) and skeletal muscle mitochondria of chickens (43), avUCP prevented reactive oxygen species generation, similar to the role now ascribed to UCP3 both in rodent skeletal muscle (44) and in muscle cells in vitro (45). Regardless of the exact function of UCPs in skeletal muscle, their induction appears to be an important part of the adaptation when skeletal muscle contributes significantly to the thermogenic response.…”

Expressão do mRNA de genes mitocondriais e desempenho produtivo de codornas alimentadas com glicerol

“…A maior expressão da UCP na dieta com 8% de glicerol, em comparação àquela com 12%, pode ter ocorrido em razão da maior quantidade de ácidos graxos de cadeia longa (Abe et al, 2006) proveniente do óleo de soja, que esteve presente em concentrações mais altas nesta dieta, o que corrobora os resultados de Gasparino et al (2012).…”