No abstract

Mitochondria play a central role in aerobic performance. Studies aimed at elucidating how evolved variation in mitochondrial physiology contributes to adaptive variation in aerobic performance can therefore provide a unique and powerful lens to understanding the evolution of complex physiological traits. Here, we review our ongoing work on the importance of changes in mitochondrial quantity and quality to adaptive variation in aerobic performance in high-altitude deer mice. Whole-organism aerobic capacity in hypoxia (VO2max) increases in response to hypoxia acclimation in this species, but high-altitude populations have evolved consistently greater VO2max than populations from low altitude. The evolved increase in VO2max in highlanders is associated with an evolved increase in the respiratory capacity of the gastrocnemius muscle. This appears to result from highlanders having more mitochondria in this tissue, attributed to a higher proportional abundance of oxidative fiber-types and a greater mitochondrial volume density within oxidative fibers. The latter is primarily caused by an over-abundance of subsarcolemmal mitochondria in high-altitude mice, which is likely advantageous for mitochondrial O2 supply because more mitochondria are situated adjacent to the cell membrane and close to capillaries. Evolved changes in gastrocnemius phenotype appear to be underpinned by population differences in the expression of genes involved in energy metabolism, muscle development, and vascular development. Hypoxia acclimation has relatively little effect on respiratory capacity of the gastrocnemius, but it increases respiratory capacity of the diaphragm. However, the mechanisms responsible for this increase differ between populations: lowlanders appear to adjust mitochondrial quantity and quality (i.e., increases in citrate synthase [CS] activity, and mitochondrial respiration relative to CS activity) and they exhibit higher rates of mitochondrial release of reactive oxygen species, whereas highlanders only increase mitochondrial quantity in response to hypoxia acclimation. In contrast to the variation in skeletal muscles, the respiratory capacity of cardiac muscle does not appear to be affected by hypoxia acclimation and varies little between populations. Therefore, evolved changes in mitochondrial quantity and quality make important tissue-specific contributions to adaptive variation in aerobic performance in high-altitude deer mice.

Background: As diet-related diseases have increased over the past decades, large food companies have come under scrutiny for contributing to this public health crisis. In response, the food industry has implemented Corporate Social Responsibility (CSR) initiatives related to nutrition and physical activity to emphasize their concern for consumers. This study sought to describe the nature and targeted demographic of physical activity and nutrition-related CSR initiatives of large food companies in Canada and to compare companies who participate in the Canadian Children's Food and Beverage Advertising Initiative (CAI), a self-regulatory initiative aimed at reducing unhealthy food advertising to children, with non-participating companies. Methods: A cross-sectional study was conducted in 2016. Thirty-nine large food companies, including 18 participating in the CAI, were included in the study. The webpages, Facebook pages and corporate reports of these companies were surveyed to identify CSR initiatives related to nutrition and physical activity. Initiatives were then classified by type (as either philanthropic, education-oriented, research-oriented or other) and by targeted demographic (i.e. targeted at children under 18 years or the general population). Differences between CAI and non-CAI companies were tested using chi-square and Mann-Whitney U tests. Results: Overall, 63 CSR initiatives were identified; 39 were nutrition-related while 24 were physical activity-related. Most (70%) initiatives were considered philanthropic activities, followed by education-oriented (20%), researchoriented (8%) and other (2%). Almost half (47%; n = 29) of initiatives targeted children. Examples of child-targeted initiatives included support of school milk programs (n = 2), the sponsorship of children's sports programs (n = 2) and the development of educational resources for teachers (n = 1). There were no statistically significant differences in the number of CSR initiatives per company (CAI: Mdn = 1, IQR = 3; non-CAI: Mdn = 0, IQR = 2; p = .183) or the proportion of child-targeted initiatives (CAI: 42%; non-CAI: 54%; p = .343) between CAI and non-CAI companies.

Background Prognosis and disposition among older emergency department (ED) patients with suspected infection remains challenging. Frailty is increasingly recognized as a predictor of poor prognosis among critically ill patients; however, its association with clinical outcomes among older ED patients with suspected infection is unknown. Methods We conducted a multicenter prospective cohort study at two tertiary care EDs. We included older ED patients (≥75 years) with suspected infection. Frailty at baseline (before index illness) was explicitly measured for all patients by the treating physicians using the Clinical Frailty Scale (CFS). We defined frailty as a CFS 5–8. The primary outcome was 30-day mortality. We used multivariable logistic regression to adjust for known confounders. We also compared the prognostic accuracy of frailty with the Systemic Inflammatory Response Syndrome (SIRS) and Quick Sequential Organ Failure Assessment (qSOFA) criteria. Results We enrolled 203 patients, of whom 117 (57.6%) were frail. Frail patients were more likely to develop septic shock (adjusted odds ratio [aOR], 1.83; 95% confidence interval [CI], 1.08–2.51) and more likely to die within 30 days of ED presentation (aOR 2.05; 95% CI, 1.02–5.24). Sensitivity for mortality was highest among the CFS (73.1%; 95% CI, 52.2–88.4), compared with SIRS ≥ 2 (65.4%; 95% CI, 44.3–82.8) or qSOFA ≥ 2 (38.4; 95% CI, 20.2–59.4). Conclusions Frailty is a highly prevalent prognostic factor that can be used to risk-stratify older ED patients with suspected infection. ED clinicians should consider screening for frailty to optimize disposition in this population.

No abstract