Molecular mechanisms underlying the development of endothermy in birds (Gallus gallus): a new role of PGC-1α?

Abstract

In endotherms, plasticity of internal heat production in response to environmental variability is an important component of thermoregulation. During embryogenesis endotherms cannot regulate their body temperature metabolically and are therefore similar to ectotherms. The transition from ectothermy to endothermy occurs by the development of metabolic capacity during embryogenesis. Here we test the hypothesis that the development of metabolism during embryogenesis in birds is under transcriptional control and that metabolic capacity is upregulated in colder environments. The peroxisome proliferator-activated receptor-γ (PPARγ) coactivator-1α (PGC-1α) is the major metabolic regulator in mammals. PGC-1α and its target PPARγ were significantly elevated during development in pectoral muscle and liver of chickens ( Gallus gallus) compared with adults. However, the timing of upregulation of PGC-1α and PPARγ was not in synchrony. In cool incubation temperatures (35°C) both PGC-1α and PPARγ gene expression was increased in liver but not in skeletal muscle, compared with a 38°C incubation treatment. Cytochrome c oxidase and citrate synthase enzyme activities and ATP synthase gene expression increased during embryonic development in liver and muscle, and there was a significant effect of incubation temperature on these parameters. Our findings suggest that PGC-1α might be important for establishing endothermic metabolic capacity during embryogenesis in birds.

Endothermy in birds: underlying molecular mechanisms

“…In chickens, mRNA levels of the catalytic α 1 subunit correlate with the activity of the enzyme, so that during the transition from ecothermy to endothermy Na + /K + -ATPase activity is transcriptionally controlled by the catalytic α 1 subunit but not by the glycosylated β 1 subunit. PGC1α, the major metabolic regulator in mammals, and its target PPARγ are significantly elevated in pectoral muscle and liver during embryonic development of chickens compared with adults (Walter and Seebacher, 2007). Here we show that muscle PGC-1α gene expression, and thereby mitochondrial function and capacity, is regulated by thyroid hormone in birds.…”

“…Furthermore, thyroid hormones can modulate aerobic metabolic capacity by regulating Endothermy in birds mitochondrial biogenesis (Nelson et al, 1995) and PGC1α gene expression (Irrcher et al, 2008). The transcriptional coactivator PGC1α is a prominent metabolic regulator in mammals (Finck and Kelly, 2006;Puigserver and Spiegelman, 2003) and it has recently been shown to play a role in metabolic regulation in birds (Walter and Seebacher, 2007).…”

Early nutrition and phenotypic development: ‘catch-up’ growth leads to elevated metabolic rate in adulthood

“…In addition, dietary amino acids can be used as energy precursors as well as for structural somatic (muscle) or reproductive (vitellogenin) proteins; the relative balance of these alternate pathways of intermediary protein metabolism has recently been shown to underlie intraspecific variation in life-history trade-offs (Zera & Zhao 2006) and therefore may be subjected to early life modulation. The molecular basis behind the upregulation in metabolism during the development of endothermy is beginning to be unravelled ( Walter & Seebacher 2007). An examination of how amino acid metabolism is programmed in these birds may reveal much about the mechanisms linking growth and metabolic rate.…”

Differences in locomotor performance between individuals: importance of parvalbumin, calcium handling and metabolism

“…A 1mg sample of total RNA was treated with DNAse I (Sigma) and reverse-transcribed using RNAse H-MMLV reverse transcriptase (Bioscript, Bioline, London, UK) and random hexamer primers (Bioline). Quantitative RT-PCR was performed on an Applied Biosystems 7500 qRT-PCR machine (Applied Biosystems, Scoresby, VIC, Australia) according to published protocols (Walter and Seebacher, 2007).…”