Age-related differences in skeletal muscle lipid profiles of Weddell seals: clues to developmental changes

Abstract

SUMMARYOur objective was to elucidate age-related changes in lipids associated with skeletal muscle of Weddell seals and to suggest possible physiological implications. Muscle biopsies were collected from pups, juveniles and adults in McMurdo Sound, Antarctica and analyzed for intramuscular lipid (IML) and triacylglyceride (IMTG) amounts, fatty acid groups, as well as individual fatty acid profiles. The results from this study suggest a switch from primarily saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) in the skeletal muscle of young pups to increases in polyunsaturated fatty acids (PUFAs) as the percentage of blubber increases, resulting in possible thermoregulatory benefits. As Weddell pups continue to develop into juveniles, fatty acids associated with the skeletal muscle changes such that MUFA levels are relatively higher, which may be in response to energy depletion associated with their restricted diving ability and rapid growth. As juveniles transform into adults, a reduction in n-3 PUFA levels in the muscle as the percentage of blubber increases may be indicative of a trigger to prepare for deep diving or could be a mechanism for oxygen conservation during long-duration dives. We speculate that the observed change in lipids associated with the skeletal muscle of Weddell seals is related to ontogenetic differences in thermoregulation and locomotion.

High fatty acid oxidation capacity and phosphorylation control despite elevated leak and reduced respiratory capacity in northern elephant seal muscle mitochondria

“…However, the highly variable relative differences in respiratory flux between seals and humans highlights the importance of considering substrate utilization and multiple respiratory states when evaluating adaptive changes in muscle aerobic capacity. Previous studies indicate that diving mammals rely almost exclusively on lipid metabolism for muscle ATP production (Davis, 1983;Davis et al, 1991;Davis et al, 1993;Kanatous et al, 2008;Trumble et al, 2010;Trumble and Kanatous, 2012;Houser et al, 2013;Crocker et al, 2014). Consequently, it was not surprising that compared with humans, adult NES mitochondria exhibited a greater capacity to oxidize lipid versus carbohydrate substrates (Fig.…”

“…During deep foraging dives, NES engage in brief bouts of stroking 'exercise' to acquire prey, separated by longer periods of 'gliding' that reduce energy costs and facilitate longer and deeper dives (Davis et al, 2001;Aoki et al, 2011). Both activities are supported almost entirely by aerobic metabolism of fatty acids, made possible by high cellular levels of lipid and oxygen (Snyder, 1983;Ponganis et al, 1993;Guyton et al, 1995;Noren et al, 2001;Kanatous et al, 2002;Williams et al, 2004;Trumble et al, 2010). As noted above, such conditions might favor enhanced mitochondrial ROS release, leading to cellular oxidative stress unless balanced by adaptive increases in uncoupling and/or antioxidant defenses.…”

“…In addition, incomplete coupling of mitochondrial electron transfer to phosphorylation of ADP results in oxygen consumption in the absence of ATP production, reflecting a dissipation of mitochondrial membrane potential independent of proton flux through the ATP synthase. In endotherms, this respiratory 'leak' is thought to contribute significantly to metabolic heat production at the expense of phosphorylation efficiency (van den Berg et al, 2011). However, the extent to which modulation of these processes contributes to phenotypic adjustments of mammalian muscle at the organismal and evolutionary levels remains largely speculative because of a paucity of studies evaluating mitochondrial physiology in species uniquely adapted to extreme bioenergetic stress and environmental conditions.…”

In the face of hypoxia: myoglobin increases in response to hypoxic conditions and lipid supplementation in cultured Weddell seal skeletal muscle cells

“…10751788-00. Animal handling and biopsy techniques were performed according to previously published protocols (Kanatous et al, 2008;Trumble et al, 2010). Primary Weddell seal skeletal muscle cells were isolated from the primary swimming muscle (M. longissimus dorsi) of an adult male (8years old, mass 430kg) using a muscle biopsy taken on 25 October 2006 near McMurdo Sound, Antarctica.…”

Adiposity and fat metabolism during combined fasting and lactation in elephant seals

“…increases in respiratory pigments (Somo et al, 2015)], and the development of cardiovascular control and skeletal muscle features (Castellini et al, 1994) needed for their initial foraging trip at sea as well as potential thermoregulatory considerations (Noren et al, 2003(Noren et al, , 2008Kanatous et al, 2008). The provision of specific milk fatty acids to pups may affect neural development (Larque et al, 2002) as well as potentially altering muscle development (Trumble et al, 2010;Wheatley et al, 2008b). Thus, not only energy content but also specific fatty acids are important for pup development.…”