Two weeks of single-leg immobilization alters intramyocellular lipid storage characteristics in healthy, young women.

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 content, 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 yr) received either 5 g·day-1 omega-3 fatty acid or isoenergetic sunflower oil for 4 wk prior to, throughout 2 wk of single-leg immobilization, and during 2 wk of recovery. Changes in IMCL characteristics and insulin signaling proteins were examined in vastus lateralis samples taken before 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.NEW & NOTEWORTHY We report that the subcellular storage location of IMCL is altered by limb immobilization, highlighting the need to evaluate IMCL storage location when assessing the effects of disuse on IMCL content. We also found that AKT content increased during immobilization in our female population, contrary to studies in males finding that AKT decreases during disuse, highlighting that men and women may respond differently to disuse and the necessity to include women in all research.

Environmentally relevant concentrations of amine-functionalized copper nanoparticles exhibit different mechanisms of bioactivity in Fundulus Heteroclitus in fresh and brackish water.

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-1) 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.