Abstract
BackgroundEfficient and selective utilization of metabolic substrates is one of the key strategies in high-altitude animals to cope with hypoxia and hypothermia. Previous findings have shown that the energy substrate utilization of highland animals varies with evolutionary history and phylogeny. The heart is a proxy for the cardiopulmonary system, and the metabolic substrate utilization in the myocardium is also under the strong selective pressure of chronically hypoxic and hypothermic environments. However, little information is available on the physiological adjustments in relation to metabolic substrate utilization in the myocardium for coping with high-altitude environments.MethodsWe compared the metabolic enzyme activities, including hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), citrate synthase (CS), carnitine palmitoyl transferase 1 (CPT-1), lactic dehydrogenase (LDH), and creatine kinase (CK), and metabolic substrate contents including glucose (Glu), triglyceride (TG), and free fatty acid (FFA) in the myocardium of a typical human commensal species, Eurasian Tree Sparrows (Passermontanus) between the Qinghai-Tibet Plateau (the QTP, 3230 m) and low altitude population (Shijiazhuang, 80 m), and between sexes.ResultsAmong the seven metabolic enzymes and three substrates investigated, we identified no significant differences in PK, CPT-1, HK, CS, LDH, and CK activities and TG content of the myocardium between high and low altitude populations. However, the QTP sparrows had significantly lower Glu content and PFK activities but higher FFA content relative to their lowland counterparts. In addition, male sparrows had higher myocardial HK and CS activities relative to females, independent of altitude.ConclusionsOur results showed that the QTP sparrows elevated fatty acid utilization rather than glucose preference in the myocardium relative to lowland counterpart, which contributes to uncovering both the physiological adjustments for adapting to the extreme conditions of the QTP, intraspecifically.
Highlights
Efficient and selective utilization of metabolic substrates is one of the key strategies in high-altitude animals to cope with hypoxia and hypothermia
Effects of altitude and sex on metabolic enzyme activities in the myocardium The myocardial pyruvate kinase (PK), carnitine palmitoyl transferase 1 (CPT-1), creatine kinase (CK), and lactic dehydrogenase (LDH) activities of Eurasian Tree Sparrows did not vary with altitude, sex, and the interaction of altitude and sex (Table 1)
In the present study, we found that maximal enzyme activities of myocardial HK and PK in Eurasian Tree Sparrows did not vary with altitude, but the Qinghai-Tibet Plateau (QTP) population had significantly lower maximal enzyme activities of PFK and glucose content in the myocardium
Summary
Efficient and selective utilization of metabolic substrates is one of the key strategies in high-altitude animals to cope with hypoxia and hypothermia. A suppressed overall metabolic intensity and enhanced glycolysis capacity are believed to be biochemical responses to hypoxic conditions due to the lowered blood O 2-delivery capacity (Cartee et al 1991; Zinker et al 1994; Azevedo Jr et al 1995; Holden et al 1995; Roberts et al 1996a, 1996b) In contrast to their lowland counterparts, high-altitude natives have possessed a suite of traits (e.g. bigger body size, larger lung, higher blood-O2 affinity, and more capillaries in organs) to overcome the consequences of hypoxic environments (Storz and Moriyama 2008; Qu et al 2020). These findings suggest that evolutionary history, phylogeny, and habitat characteristics jointly play important roles in shaping the diversified strategies of high-altitude adaptations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
