Humans, mice, and most other mammals are constantly exposed to fluctuations in the temperature of their environment. These fluctuations cause striking metabolic effects in the body.
For example, exposure to cold promotes the burning of calories to generate heat, thereby reducing how much fat accumulates in the body. On the other hand, warmer temperatures strengthen the bones and protect against a bone disease known as osteoporosis.
Previous studies observed that temperature had significant effects on the functioning of specific organs. To understand the overall biological mechanism at stake, scientists from the University of Geneva (UNIGE) analyzed changes in gene expression simultaneously in various organs in mice.
They examined the expression of genes in eleven organs (all adipose (fat) tissues, muscle, liver, brain, hypothalamus, ileum, spinal cord, spleen, and bone marrow). The mice subjects were classified into three groups. Scientists exposed the groups to a temperature of 10°C, 22°C, or 34°C.
They found that all organs in the body strongly respond to temperature changes, each showing its specific modulation.
Mirko Trajkovski, Professor in the Department of Cell Physiology and Metabolism and the Diabetes Centre in the UNIGE Faculty of Medicine, who directed this research, said, “The data show that the whole body profoundly reacts to temperature changes. However, there is no uniformed response: each organ changes its gene expression in its way, somewhat different from the rest of the tissues.”
Further analyses were performed to determine whether this phenomenon was due to the unique expression of genes specific to each organ. This time, scientists focused on genes that are expressed in all organs. And even when considering only this restricted set of genes, the differences in activation were still striking.
Mirko Trajkovski said, “Knowing that exposure to alternating temperatures causes major effects on metabolic diseases such as obesity and osteoporosis, or even on auto-immune diseases, indicates the use of temperature shifts as a potential therapeutic lifestyle intervention. However, we first need to decipher the temperature-induced effects in an integrative manner throughout the body, not only at a single organ level. Our work allows precisely that – investigating and understanding the mechanisms at work in various organs simultaneously.”
To stimulate research and potential therapeutic applications, scientists created a free-to-use and easily accessible web-based application that allows searching for the expression of thousands of genes in response to exposure to cold or warmth in various organs.
- Noushin Hadadi, Martina Spiljar et al. Comparative multi-tissue profiling reveals extensive tissue-specificity in transcriptome reprogramming during thermal adaptation. DOI: 10.7554/eLife.78556