Abstract
The Tibetan chickens (Gallus gallus; TBCs) are an indigenous breed found in the Qinghai-Tibet Plateau that are well-adapted to a hypoxic environment. As of now, energy metabolism of the TBCs embryonic brain has been little examined. This study investigated changes in energy metabolism in TBCs during hypoxia, and compared energy metabolism in TBCs and Dwarf Laying Chickens (DLCs), a lowland chicken breed, to explore underlying mechanisms of hypoxia adaptation. We found TBCs exhibited decreased oxygen consumption rates (OCR) and ATP levels as well as an increased extracellular acidification rate (ECAR) during hypoxia. Nevertheless, OCR/ECAR ratios indicated aerobic metabolism still dominated under hypoxia. Most important, our results revealed significant differences in TBCs brain cellular metabolism compared to DLCs under hypoxia. Compared to DLCs, TBCs had higher OCR and TCA cycle activities during hypoxia. Also, TBCs had more mitochondrial content, increased mitochondrial aspect ratio and MFN1, MFN2, and OPA1 proteins which have previously been reported to control mitochondrial fusion were expressed at higher levels in TBCs compared to DLCs, suggesting that TBCs may regulate energy metabolism by increasing the level of mitochondrial fusion. In summary, TBCs can reduce aerobic metabolism and increase glycolysis to enable adaptation to hypoxia. Regulation of mitochondrial fusion via MFN1, MFN2, and OPA1 potentially enhances the ability of TBCs to survive on the Qinghai-Tibet Plateau.
Highlights
The Tibetan chickens (Gallus gallus; TBCs) are widely distributed at altitudes of 2,200–4,100 m in the Qinghai-Tibet Plateau
Study has found TBCs have a higher embryo survival rate than lowland chickens (54.1–24.7%) under hypoxia (Wu et al, 2012). Our result proved it that the survival rate in TBCs and Dwarf Laying Chickens (DLCs) was 87.14% and 89.74% under normoxia, yet 49.44 and 27.66% under hypoxia
Genomic analysis reveals that the calcium signaling pathway, which indirectly regulates energy metabolism related to the mitochondrion, is an important target for selection in hypoxic high-altitude adaptation in TBCs (Wang et al, 2015)
Summary
The Tibetan chickens (Gallus gallus; TBCs) are widely distributed at altitudes of 2,200–4,100 m in the Qinghai-Tibet Plateau. This unique breed has been present in the region for at least 1,000 years. Hypoxia imposes severe constraints on aerobic metabolism Cells in this state are unable to acquire enough energy to maintain basic life activities and suffer a variety of serious problems (Grocott et al, 2007; Storz et al, 2007). As the highest nerve center and most oxygen-sensitive organ, it is important to understand changes in brain energy metabolism under hypoxic incubation conditions, especially in the study of high-altitude hypoxia adaptation. The energy metabolism of TBCs embryonic brain under hypoxia still remains ununderstood
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