Fasting Metabolic Profiles are Cell-Autonomous in Elephant Seal Primary Muscle Cells

Abstract

Northern elephant seals ( Mirounga angustirostris) undergo prolonged terrestrial fasts during energetically intensive life stages including breeding, molting, and postnatal development. Fasting-tolerant vertebrates generally extend the second phase of fasting, during which body mass declines but homeostasis is preserved through reliance on lipid fuel sources and sparing of body protein stores. In elephant seals, the postnatal fast coincides with development of the extensive body oxygen stores required to support extended breath-hold diving, as well as an increased capacity for apnea-related metabolic suppression. Studies in grizzly bears, another large-bodied fasting-tolerant mammal, have identified both serum-derived and intrinsic cellular regulation of the adipocyte metabolic phenotype. However, it is unknown whether these mechanisms extend across species, tissue, or fasting type (active vs inactive). Thus, we derived proliferative primary skeletal muscle cells (myoblasts) from weaned elephant seal pups; biopsies that yielded cells were collected at both early (~1 week) and late (~8 weeks) points in the postnatal fast. We found that total ATP production rate was greater in myoblasts collected from animals late in the fast (27% increase over early, p=0.08). Throughout the fast, myoblasts relied predominantly on glycolytic rather than oxidative ATP production (p<0.001), and this reliance increased as the fast progressed (p<0.014). Together, these data suggest that metabolic reliance is at least partially cell-autonomous in elephant seal myoblasts. KNA is supported by an NSF Graduate Research Fellowship (DGE 1752814 & 2146752) and a UC Berkeley Fellowship. JPV-M is supported by a NIH/NIGMS grant (R35GM146951). Research was funded by UC Berkeley startup funds and the Winkler Family Foundation. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.