Changes in Hippocampus and Amygdala Volume with Hypoxic Stress Related to Cardiorespiratory Fitness under a High-Altitude Environment.

Zhi-Xin Wang,Jian-Guo Wu,Hao Li,Dong-Mei Chen,De-Long Zhang,Hai-Lin Ma,Tong-Ao Zeng,Peng Dang,Rui Su

doi:10.3390/brainsci12030359

Zhi-Xin Wang, Jian-Guo Wu + Show 7 more

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https://doi.org/10.3390/brainsci12030359

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Journal: Brain sciences	Publication Date: Mar 8, 2022
Citations: 2	License type: CC BY 4.0

Affiliation: Tibet University, South China Normal University

Abstract

The morphology of the hippocampus and amygdala can be significantly affected by a long-term hypoxia-induced inflammatory response. Cardiorespiratory fitness (CRF) has a significant effect on the neuroplasticity of the hippocampus and amygdala by countering inflammation. However, the role of CRF is still largely unclear at high altitudes. Here, we investigated brain limbic volumes in participants who had experienced long-term hypoxia exposure in Tibet (3680 m), utilizing high-resolution structural images to allow the segmentation of the hippocampus and amygdala into their constituent substructures. We recruited a total of 48 participants (48 males; aged = 20.92 ± 1.03 years) to undergo a structural 3T MRI, and the levels of maximal oxygen uptake (VO2max) were measured using a cardiorespiratory function test. Inflammatory biomarkers were also collected. The participants were divided into two groups according to the levels of median VO2max, and the analysis showed that the morphological indexes of subfields of the hippocampus and amygdala of the lower CRF group were decreased when compared with the higher CRF group. Furthermore, the multiple linear regression analysis showed that there was a higher association with inflammatory factors in the lower CRF group than that in the higher CRF group. This study suggested a significant association of CRF with hippocampus and amygdala volume, which may be related to hypoxic stress in high-altitude environments. A better CRF reduced physiological stress and a decrease in the inflammatory response was observed, which may be related to the increased oxygen transport capacity of the body.

Highlights

Under a high-altitude environment, the decrease in atmospheric pressure and the consequent drop in the partial pressure of oxygen (PO2) can result in hypobaric hypoxia
We found that the gray matter volume in the hippocampal subfields and amygdala subfields were increased in the high-Cardiorespiratory fitness (CRF) group when high-altitude participants were divided into two groups according to median VO2max
Our results showed that the hippocampus and amygdala in the low-CRF group were more susceptible to inflammation at high altitudes, resulting in smaller amygdala and hippocampal volumes

Summary

Introduction

Under a high-altitude environment, the decrease in atmospheric pressure and the consequent drop in the partial pressure of oxygen (PO2) can result in hypobaric hypoxia. Hypoxic stress has serious effects on brain structures, such as the hippocampus and amygdala [2–4]. At the level of the organism, a hypoxic challenge is perceived as a non-specific stress, and hypoxia could upregulate the setpoint of the HPA axis and augment adrenal steroidogenic production, resulting in neuroinflammation and neuronal cell death [8]. Changes in the amygdala and hippocampus under high-altitude hypoxia stress may be due to the influence of inflammation [10,11]. Similar studies have found that after hypoxia stress, the inflammatory response of the hippocampus and amygdala increase, leading to the death of neurons [14,15]. Studies of hypoxia stress in the brain caused by human disease have found that inflammation can trigger neuron damage in the hippocampus and amygdala [14]. Inflammation caused by altitude hypoxia stress seriously affects the hippocampus and amygdala

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