Abstract

Acute heat stress may trigger systemic biochemical and physiological changes in living organisms leading to rapid loss of homeostasis. Metabolic regulatory process during heat stress has been poorly understood therefore the present study was undertaken in order to have an insight of alterations in various metabolites due to acute heat stress exposure using nuclear magnetic resonance (NMR) spectroscopy. Male sprague-dawley (SD) rats were exposed to acute heat stress of 45±2°C for 3 h and urine samples were collected from control (n=6) and heat stress group (n=6) on day 0 and 1. Metabolites excreted in urine were analyzed using NMR spectroscopy in conjugation with principal component analysis (PCA). The biochemical response to acute heat stress was characterized by decreased levels of citrate, succinate, 2-oxoglutrate, phenylalanine, creatinine, hippurate and elevation in formate levels. Hence, some biological pathways such as tricarboxylic acid (TCA) cycle, catecholamine activity and gut microbiota were transiently affected due to heat stress exposure. NMR based metabonomic studies in conjugation with statistical analysis permits non-invasive and simultaneous monitoring of entire metabolic pathways. This reveals the subtle interplay of functional metabolites and pathways leading to an understanding of the systemic response to external stimuli such as heat stress. These studies form the basis for future studies to detect early biomarkers for heat stress in humans and identifying the population at risk. Furthermore, it can be used to develop methods to provide protection to the body against environmental insult, thereby reducing the adverse response to heat stress.

Key words: Heat stress, hyperthermia, nuclear magnetic resonance, spectroscopy, metabonomics, urine.

Abbreviation

NMR, Nuclear magnetic resonance; PCA, principal component analysis; SD, Sprague-Dawley; TCA, Tricarboxylic acid cycle; TSP, 3-(trimethylsilyl) propionic-2, 2, 3, 3-d4 acid sodium salt; GIT, gastrointestinal tract;SNS, sympathetic nervous system.