Impact of Hypoxia and Temperature Manipulation on Spontaneous Physical Activity and Proteins Related to Energy Metabolism

• Grant number: 25/05646-3
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate (Direct)
• Start date: August 28, 2025
• End date: December 27, 2025
• Field of knowledge: Biological Sciences - Physiology
• Principal Investigator: Claudio Alexandre Gobatto
• Grantee: Juan Bordon Orsi
• Supervisor: Bruno Tesini Roseguini
• Host Institution: Faculdade de Ciências Aplicadas (FCA). Universidade Estadual de Campinas (UNICAMP). Limeira , SP, Brazil
• Institution abroad: Purdue University, United States
• Associated to the scholarship: 24/04688-1 - EFFECTS OF THE "LIVE HIGH - TRAIN LOW" TRAINING MODEL ON HEMATIMETRIC, BIOMOLECULAR AND BIOCHEMICAL RESPONSES ASSOCIATED WITH ENERGY BALANCE, BP.DD

Abstract

The utilization of oxygen by cells and their responses to hypoxia are widely studied due to their impact on physiology and metabolism. Individuals native to high altitudes, known as highlanders, have adaptations such as higher hemoglobin concentration and lung capacity. These factors have prompted research into the physiological mechanisms of hypoxia, leading to the development of normobaric tents that simulate the environment. However, these systems only control the fraction of oxygen available, without faithfully reproducing environmental variations, such as temperature, which have a strong influence on energy metabolism. Biomolecular proteins such as HIF-1¿ (Hypoxia-inducible factor 1 alpha) and PGC-1¿ (Peroxisome proliferator-activated receptor-gamma coactivator-1 alpha) regulate anaerobic and aerobic metabolism and are influenced by both hypoxia and temperature. HIF-1¿ is activated in conditions of low oxygen availability, stimulating physiological processes linked to glucose metabolism. At high temperatures, its stabilization depends on HSP90 (Heat Shock Protein 90), while at low temperatures, its activation favours the use of lipids to sustain muscle activity and heat production. PGC-1¿, on the other hand, besides being associated with aerobic metabolism, shows increased expression in hypoxia and at low temperatures, participating in thermogenesis. At high temperatures, it regulates the expression of HSPs, promoting cellular protection against hyperthermia. In addition, food intake and Spontaneous Physical Activity (SPA) play a central role in energy metabolism. SPA, which includes posture, restlessness and walking, is reduced in hypoxia and is often associated with lower food intake. However, evidence suggests that this reduction is also related to a decrease in peripheral body temperature. In this context, hypothalamic orexins (A and B) are fundamental, as they stimulate SPA. These proteins interact with the HCRT-R1 and HCRT-R2 receptors, whose activation influences food intake, thermogenesis and energy metabolism. Studies indicate that orexinergic neurons are highly sensitized in hypoxia, and inhibition of HCRT-R1 reduces both food intake and SPA. Orexins also regulate brown adipose tissue, food intake, energy expenditure and body temperature, as well as influencing glucose uptake by skeletal muscle. Therefore, this project will investigate the effects of cold and heat in C57BL/6J mice exposed to hypoxia for two weeks, analyzing SPA, body composition, food and water intake, as well as the protein content of PGC-1¿ and HIF-1¿ in the hypothalamus and in the soleus (oxidative) and gastrocnemius (glycolytic) muscles, and the HCRT-R1 and HCRT-R2 receptors in the hypothalamus. Sixty mice will be divided into normoxia (N) or hypoxia (H). Within each condition, the animals will be subdivided into 3 groups: control (C), hyperthermic (E) and hypothermic (O). The animals in group H will be subjected to an inspired oxygen fraction of 14.5% (~3000m altitude) with SPA monitored for 22 hours a day. The E groups will be exposed to heat (37.5°C) and the O groups to cold (4°C), both exposures lasting 4 hours, 5 days a week, for 2 weeks. At the end of the experiment, the mice will be euthanized to collect the tissues of interest for later analysis. We hypothesize that hypoxia and heat therapy will reduce SPA by increasing the expression of HCRT-R1 in the hypothalamus. In the case of cold therapy, SPA will increase by stimulating HCRT-R1 and HCRT-R2, reducing fat mass, especially in hypoxia. In addition, we expect exposure to heat and cold to increase PGC-1¿ in the hypothalamus and soleus muscle, with less effect in the gastrocnemius. HIF-1¿ expression may be elevated by heat therapy and potentiated in hypoxia, especially in the glycolytic muscle.