Magnetic Resonance Spectroscopy provides measures of brain chemistry that are sensitive to cardiorespiratory fitness and body composition. The concentration of N-acetyl aspartic acid (NAA) is of interest because it is a marker of neuronal integrity. The ratio of NAA to creatine, a standard reference metabolite, has been shown to correlate with measures of both cardiorespiratory fitness and body composition. However, previous studies have explored these effects in isolation, making it impossible to know which of these highly correlated measures drive the correlations with NAA/Cr. As a result, the mechanisms underlying their association remain to be established. We therefore conducted a comprehensive study to investigate the relative contributions of cardiorespiratory fitness and percent body fat in predicting NAA/Cr. We demonstrate that NAA/Cr in white matter is correlated with percent body fat, and that this relationship largely subsumes the correlation of NAA/Cr with cardiorespiratory fitness. These results underscore the association of body composition with axonal integrity and suggests that this relationship drives the association of NAA/Cr with physical fitness in young adults.

中文翻译：

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体重和心肺健康与大脑新陈代谢的改变有关。

磁共振波谱提供对心肺健康和身体成分敏感的大脑化学指标。N-乙酰天冬氨酸 (NAA) 的浓度令人感兴趣，因为它是神经元完整性的标志。NAA 与肌酸（一种标准参考代谢物）的比率已被证明与心肺健康和身体成分的测量相关。然而，之前的研究孤立地探讨了这些影响，因此无法知道这些高度相关的措施中哪些与 NAA/Cr 相关。因此，它们关联的潜在机制仍有待建立。因此，我们进行了一项综合研究，以调查心肺适能和体脂百分比在预测 NAA/Cr 方面的相对贡献。我们证明白质中的 NAA/Cr 与体脂肪百分比相关，并且这种关系在很大程度上包含了 NAA/Cr 与心肺健康的相关性。这些结果强调了身体成分与轴突完整性的关联，并表明这种关系推动了 NAA/Cr 与年轻人身体健康的关联。