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Interpretive Summary: Rapamycin administration during an acute heat stress challenge in growing pigs

By: Dr. Emily Taylor

Heat stress causes the animal industry over $2.5 billion in economic losses each year. As a result, much research has been conducted to mitigate the adverse effects of heat stress during the summer months. Some of the more identifiable adverse effects include decreased growth rates, altered characteristics, poor reproduction, and reduced milk yield; however, heat stress also markedly alters metabolism, endocrinology, and immunophysiology. The exact mechanisms of these changes are not fully understood, though there is some evidence suggesting an alteration in the intestinal barrier integrity. 

In recent years, autophagy has been shown to play a crucial role in preserving the intestinal barrier function; however, the multiple studies published have contradictory evidence to support autophagy as a plausible mechanism to alleviate the detrimental effects of heat stress. The authors hypothesized that Rapamycin, a well-known macrolide compound, will stimulate autophagy. Therefore, the objective of the current study was to evaluate the therapeutic effects of Rapamycin on markers of metabolism and inflammation in growing pigs exposed to an acute heat stress challenge. 

During a 24-h acute heat stress challenge, pigs experienced an increase in body temperature leading to a dramatic decrease in feed intake, as well as a marked loss of BW. Authors suggest further investigation into this BW loss, as the severity observed suggests other mechanisms, independent of feed intake, may have further influenced this response. Additionally, heat-stressed pigs had altered metabolic responses, including increased circulating insulin on a feed intake basis, decreased glucagon, and altered NEFA patterns. In contrast to their hypothesis, Rapamycin administration had little effect on measurements. Further research investigating the molecular level and assessing the efficacy of Rapamycin stimulating autophagy during heat stress is needed.

This article is available on the Journal of Animal Science website.