Background

The growing interest in how exercise and carbohydrate (CHO) restriction may modify molecular responses that promote endurance adaptations has led to many interesting controversies.

Objective

We conducted a systematic review and a meta-analysis regarding the effect of low-carbohydrate availability (LOW) pre-, during, or post-exercise, on the mRNA content of commonly measured genes involved in mitochondrial biogenesis (PGC-1α, TFAM mRNA) and metabolism (PDK4, UCP3 and GLUT4 mRNA), and on muscle glycogen levels, compared with a high-CHO (CON) condition.

Methods

MEDLINE, Scopus, and Web of Science databases were searched following the PRISMA 2020 guidelines (with an end date of November 2023). In total, 19 randomized-controlled studies were considered for inclusion. We evaluated the methodological quality of all studies using the Cochrane Risk of Bias tool for randomized clinical studies. A meta-analysis was performed using a random effects model to calculate the standardized mean difference (SMD), estimated by Hedges’ g, and 95% confidence intervals (CIs).

Results

The LOW condition was associated with an increased mRNA content of several genes during the early recovery period post-exercise, such as PDK4 (SMD 1.61; 95% CI 0.80–2.42), GLUT4 (SMD 1.38; 95% CI 0.46–2.30), and UCP3 (SMD 2.05; 95% CI 0.40–3.69). However, overall, there was no significant effect on the mRNA content of PGC-1α or TFAM. Finally, CHO restriction and exercise significantly reduced muscle glycogen levels (SMD 3.69; 95% CI 2.82–5.09). A meta-analysis of subgroups from studies with a difference in muscle glycogen concentration of > 200 mmol kg dw⁻¹ between the LOW and CON conditions showed an increase in exercise-induced PGC-1α mRNA (SMD 2.08; 95% CI 0.64–3.52; p = 0.005; I² = 75%) and a greater effect in PDK4 and GLUT4 mRNA.

Conclusion

The meta-analysis results show that CHO restriction was associated with an increase in the exercise-induced mRNA content of PDK4, UCP3, and GLUT4, but not the exercise-induced mRNA content of PGC-1ɑ and TFAM. However, when there were substantial differences in glycogen depletion between CON and LOW CHO conditions (> 200 mmol kg dw⁻¹), there was a greater effect of CHO restriction on the exercise-induced mRNA content of metabolic genes, and an increase in exercise-induced PGC-1α mRNA.

中文翻译：

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对低碳水化合物可用性的运动对肌糖原和细胞信号传导的反应：系统评价和荟萃分析

 背景

人们对运动和碳水化合物 （CHO） 限制如何改变促进耐力适应的分子反应的兴趣日益浓厚，这导致了许多有趣的争议。

 目的

与高 CHO （CON） 条件相比，我们进行了关于运动前、运动中或运动后低碳水化合物可用性 （LOW） 对参与线粒体生物发生（PGC-1α、TFAM mRNA）和代谢（PDK4、UCP3 和 GLUT4 mRNA）的常用测量基因的 mRNA 含量以及肌糖原水平的影响进行了系统评价和荟萃分析.

 方法

按照 PRISMA 2020 指南（结束日期为 2023 年 11 月）检索了 MEDLINE、Scopus 和 Web of Science 数据库，总共考虑了纳入 19 项随机对照研究。我们使用Cochrane偏倚风险工具评估了所有研究的方法学质量，以进行随机临床研究。使用随机效应模型进行荟萃分析，以计算由 Hedges' g 估计的标准化平均差 （SMD） 和 95% 置信区间 （CIs）。

 结果

LOW 条件与运动后早期恢复期几个基因的 mRNA 含量增加有关，例如 PDK4 （SMD 1.61;95% CI 0.80-2.42）、GLUT4 （SMD 1.38;95% CI 0.46-2.30） 和 UCP3 （SMD 2.05;95% CI 0.40-3.69）。然而，总体而言，对 PGC-1α 或 TFAM 的 mRNA 含量没有显着影响。最后，CHO 限制和运动显著降低了肌糖原水平 （SMD 3.69;95% CI 2.82–5.09）。对 LOW 和 CON 条件下肌糖原浓度差异为 > 200 mmol kg ^dw-1 的研究亚组的荟萃分析显示，运动诱导的 PGC-1α mRNA 增加（SMD 2.08;95% CI 0.64-3.52;p = 0.005;I² = 75%），并且对 PDK4 和 GLUT4 mRNA 的影响更大。

 结论

荟萃分析结果显示，CHO 限制与运动诱导的 PDK4 、 UCP3 和 GLUT4 mRNA 含量的增加有关，但与运动诱导的 PGC-1ɑ 和 TFAM mRNA 含量无关。然而，当 CON 和 LOW CHO 条件之间的糖原消耗存在显着差异 （> 200 mmol kg ^dw-1） 时，CHO 限制对运动诱导的代谢基因 mRNA 含量的影响更大，运动诱导的 PGC-1α mRNA 增加。