The bioavailability of engineered nanomaterials should be limited in marine environments, but uptake and toxicity has been noted in marine fish and invertebrates, albeit at exposure doses far exceeding predicted environmental levels. We examined the bioactivity of amine functionalized copper nanoparticles (nCu; 5-10 nm core diameter) to the euryhaline killifish, Fundulus heteroclitus, in fresh (FW) and brackish water (BW). Free copper dissolution was undetectable in either water type and nCu remained relatively well dispersed in BW, despite the high ionic strength. Exposure to an environmentally relevant concentration of nCu (10 µg L) for 48 h significantly increased the maximum rate of oxygen consumption and aerobic scope in BW killifish. This effect was associated with gill remodeling which likely increased surface area and scope for oxygen uptake. In contrast, nCu exposure had no effect on oxygen consumption in FW killifish, but gill Na/K-ATPase activity was reduced by >40%, an effect not seen in BW. Osmotic and ionic homeostasis were protected and no indications of physiological or oxidative stress were observed in either FW and BW exposure groups. The results show that functionalized nCu formulations can exhibit bioactivity in both FW and BW and that the underlying mechanisms are different between water types.
In humans, disuse is known to result in muscle atrophy and metabolic dysfunction, including reduced mitochondrial content. Previous data from this cohort found that omega-3 polyunsaturated fatty acid (n-3) supplementation attenuated declines in muscle mass, myofibrillar protein synthesis and ADP-stimulated mitochondrial respiration. Disuse has also been shown to increase apoptosis and events linked to autophagy. We investigated the effects of n-3 fatty acid supplementation on content of proteins involved in autophagy, intrinsic apoptosis, mitochondrial fission and fusion and mitochondrial area density during 14 d of immobilization and 14 d of recovery. Twenty females (18-30y) received 20mL doses of n-3 fatty acid (2.97g EPA and 2.03g DHA) or an isoenergetic sunflower oil (oleic acid content: 75%) daily during the 28-d protocol. Biopsies were taken from the vastus lateralis pre-immobilization, post-immobilization, and post-recovery. Protein and mitochondrial content were determined using Western Blot and transmission electron microscopy at 5800X magnification, respectively. Mitochondrial area density (%AD) decreased in the subsarcolemmal (SS, p=0.006) and central intramyofibrillar (IMF) (p=0.001) regions after recovery. The change in the central IMF was driven by a decrease in the n-3 group (p=0.0133). There was no change in the peripheral IMF region. P62 increased during immobilization (p<0.0001) and decreased in recovery (p<0.0001). After immobilization LC3B-I increased in the n-3 group only (p=0.0289). Procaspase-3 content was higher in the n-3 group at all timepoints, D0 (p<0.001), D14 (p<0.0001), D28 (p<0.0001). Procaspase-3 increased after immobilization in the placebo group (p=0.01), and after recovery in the n-3 group (p=0.00807). Procaspase-9 increased during immobilization (p=0.02) and remained elevated through recovery (p=0.00593), with a notable increase in the n-3 group after recovery(p=0.00923). BAX increased in recovery in the n-3 group (p=0.00137) whereas it increased during immobilisation in the placebo group (p=0.02). BCL2 decreased post-recovery (p=0.00671) and the ratio of BCL2:BAX decreased during immobilization (p<0.001) and remained low through recovery (p<0.0001) in the placebo group, whereas the BCL2:BAX ratio decreased post-recovery in the n-3 group (p=0.00712). There was no effect of immobilization or supplementation on OPA1 or FIS1. Our findings show that mitochondrial %AD did not change during immobilization, but decreased in recovery specifically in the SS and central IMF regions of the myocyte. Furthermore, we found that immobilization increased markers of apoptosis and autophagy, but not mitochondrial fusion or fission, and that supplementation attenuated these changes until after recovery. This highlights the importance of considering recovery periods after immobilization and adds to our understanding of how immobilization and n-3 supplementation influence muscle metabolic health. This study was supported with a Canadian Institutes of Health Research Award to S.M. Phillips and a Natural Sciences and Engineering Research Council of Canada Award to M.C Devries This is the full abstract presented at the American Physiology Summit 2023 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.
Muscle disuse rapidly induces insulin resistance (IR). Despite a relationship between intramyocellular lipid (IMCL) content and IR, during muscle-disuse IR develops before IMCL accumulation, suggesting that IMCL are not related to disuse-induced IR. However, recent studies show that it is not total IMCL, but IMCL size and location that are related to IR. Changes in these IMCL parameters may occur prior to increases in IMCL content, thus contributing to disuse-induced IR. Omega-3 fatty acids may mitigate the effects of disuse on IR by preventing a decline in insulin signaling proteins. Twenty women (age 22±3 y) received either 5g·d-1 omega-3 fatty acid or isoenergetic sunflower oil for 4-weeks prior to, throughout 2-weeks of single-leg immobilization, and during 2-weeks of recovery. Changes in IMCL characteristics and insulin signaling proteins were examined in vastus lateralis samples taken prior to supplementation and immobilization, and following immobilization and recovery. Omega-3 supplementation had no effect. IMCL area density decreased in the subsarcolemmal region during immobilization and recovery (-19% and -56%, respectively, p=0.009). IMCL size increased in the central intermyofibrillar region during immobilization (43%, p=0.007), returning to baseline during recovery. PLIN5 and AKT increased during immobilization (87%, p=0.002; 30%, p=0.007, respectively). PLIN 5 remained elevated and AKT increased further (15%) during recovery. IRS1, AS160 and GLUT4 decreased during immobilization (-35%, p=0.001; -44%, p=0.03; -56%, p=0.02, respectively), returning to baseline during recovery. Immobilization alters IMCL storage characteristics while negatively affecting unstimulated insulin signaling protein content in young women.
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