Physiology and Food: How Does Diet Influence Tolerance to Oxidative Stress and Heat?

Diet may hold the key to animals’ ability to tolerate increasingly prevalent stressors, such as heat and oxidative stress (OS). Certain macronutrients—particularly, dietary proteins—are critical for producing antioxidative enzymes and heat shock proteins, which help mitigate physiological stress. In addition, exposure to one stressor can improve (or impair) an animal’s tolerance to a different stressor, meaning that OS may provide cross-protection (or cross-susceptibility) to heat stress. Thus, fitness-related traits and the stress response may be determined by diet and stress history. In this study, we examined how three isocaloric diets (balanced carbohydrate and protein vs. high-carbohydrate vs. high-protein) influenced tolerance to paraquat (PQ)-induced oxidative stress and heat stress, as well as the effect of PQ on heat tolerance. In the first week of adulthood, we injected long-winged female variable field crickets (Gryllus lineaticeps) three times with control (saline) or PQ solutions. We then measured (1) consumption of calories, carbohydrates, and protein, (2) investment into self-maintenance (amount of somatic mass gained), (3) reproductive investment (amount of ovary mass gained), (4) flight capacity (functional status of flight muscle), and (5) heat tolerance (duration to knock-down at 45°C). We hypothesized that individuals fed a high-protein diet would be less affected by OS and have higher heat tolerance. We further hypothesized that PQ-exposed individuals would exhibit greater heat tolerance due to their chronic upregulation of antioxidant defenses. This investigation clarifies the fundamental role of nutrition in mediating organisms’ physiological resilience to their changing environments.