ABSTRACT
Heat stress refers to a series of stress reactions such as heat balance disturbance and physiological dysfunction when the body is exposed to the thermal environment for a long time. Studies have found that heat stress can damage intestinal morphology, such as length of intestinal villi, number of goblet cells, and depth of the crypt, affecting the digestion and absorption functions. It also can increase the permeability of the intestinal barrier by damaging the tight junction of the intestinal epithelium, which in turn allows endotoxin and bacteria to enter the blood circulation from the intestinal cavity to cause a systemic inflammatory response. At the same time, heat stress can disrupt the homeostasis of intestinal microbiota, increase pathogenic bacteria, and change downstream metabolites such as short-chain fatty acids. In addition, heat stress can inhibit the occurrence of hippocampal neurons and reduce the number of neurons; decrease the density of synapses; damage important organelles of neurons; induce inflammation of the central nervous system, and then lead to cognitive dysfunction. The brain-gut axis is a two-way signal axis between the intestine and the brain. Intestinal microorganisms and the intestinal barrier can participate in central nervous system regulation, and the brain can change the intestinal homeostatic function and affect the quality of the intestinal barrier through the hypothalamic-pituitary-adrenal axis (HPA axis). The interaction plays an essential role in the body's homeostasis. Therefore, this article reviewed current understandings on the impacts of heat stress on the gut and cognitive function, aiming to provide a reference for subsequent research.
ABSTRACT
Objective To assess the series of special anti-fatigue foods including JuntiⅠ, JuntiⅡ, JuntiⅢ, and Jun-tiⅣon military physical performance capacity .Methods Fifty-four soldiers , selected from a border defense troop , were randomly designated to control group , trial group 1 and trial group 2.Subjects of two trial groups were supplied with No .1 nutritional package ( including JuntiⅠ, Ⅲand Ⅳ) and No.2 nutritional package ( including Junti Ⅱ, Ⅲand Ⅳ),re-spectively, while no additional nutritional supplements were added in control group .After 7 days’ supplementation, a hard military exercise was performed to induce fatigue and an increasing load test was used to assess physical activity .RPE scale, exhaustive time and time taken to reach the 75% maximal heart rate were recorded while serum markers , such as glucose, lactate, BUN, LDH,and CK, were detected after test .Moreover, serum lactate and fatigue recovery scale were determined on the evening of the same day and the next morning .Results Prolonged exhaustive time and time taken to reach the 75%maximal heart rate and elevated RPE scores at 6 min were detected in both two trial groups compared with the control group .Meanwhile , after the increasing load test , elevated glucose concentration and reduced lactate , BUN, LDH and CK were also observed in both trial groups .Moreover, serum lactate of both trial groups was quickly recovered on the evening of the same day compared with the control group , and the next morning , serum lactate was even much lower in trial groups than in control group .The fatigue recovery scores were higher in trial groups at both time points .Meanwhile, there was no difference of such indexes between the two trial groups .Conclusion Through the combination use , the series of special anti-fatigue foods, inclucling No.1 and No.2 nutritional packages , can significantly improve the soldiers′physi-cal performance capacity , delay the physical fatigue emergence , promote physical activity recovery and prevent military training injury.