The Effect of Diet on Improved Endurance in Male C57BL/6 Mice

Abstract

The consumption of fruits and vegetables appears to help with maintaining an adequate level of exercise and improves endurance. However, the mechanisms that are involved in this process are not well understood. In the current study, the impact of diets enriched in fruits and vegetables (GrandFusion^®) on exercise endurance was examined in a mouse model. GrandFusion (GF) diets increased mitochondrial DNA and enzyme activity, while they also stimulated mitochondrial mRNA synthesis in vivo. GF diets increased both the mRNA expression of factors involved in mitochondrial biogenesis, peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), mitochondrial transcription factor A (Tfam), estrogen-related receptor alpha (ERRα), nuclear respiratory factor 1 (NRF-1), cytochrome c oxidase IV (COXIV) and ATP synthase (ATPsyn). Mice treated with GF diets showed an increase in running endurance, rotarod perseverance and grip strength when compared to controls who were on a regular diet. In addition, GF diets increased the protein expression of phosphorylated AMP-activated protein kinase (AMPK), sirtuin 1 (SIRT1), PGC-1α and peroxisome proliferator-activated receptor delta (PPAR-δ), which was greater than exercise-related changes. Finally, GF reduced the expression of phosphorylated ribosomal protein S6 kinase 1 (p-S6K1) and decreased autophagy. These results demonstrate that GF diets enhance exercise endurance, which is mediated via mitochondrial biogenesis and function.

Keywords: autophagy; diet; endurance; mitochondrial biogenesis.

Figure 1

Effects of GF diets on food intake and body weight. (A) Food intake changes in 10 weeks. (B) Body weight changes in mice on various diets over 10 weeks. Mice were fed a normal diet or diets that were supplemented with 2% GF. Each point represents mean ± SD (n = 10 per group).

Figure 2

Effects of GF diets on exercise endurance and skeletal muscle mass in C57BL/6 mice. (A) Running distance and (B) time of normal mice and mice that were fed a normal diet enriched with GF supplements. (C) Time to fall in a rotarod test (D) grip strength and (E) the ratio of skeletal muscle mass (soleus and gastrocnemius muscle)/body weight in normal and GF supplemented mice. Data are expressed as the mean ± SD (n = 10 per group), * p < 0.01 compared to control group.

Figure 3

Effect of GF diets on muscle mitochondrial biogenesis in C57BL/6 mice. (A) The amount of mitochondrial DNA (mtDNA) in mice that were fed a control diet or a diet enriched in GF as determined by the mtDNA/genomic DNA ratio. (B) The activity of mitochondrial enzymes COX, β-HAD and CS were evaluated as a percent of control. (C) The relative mRNA levels of PGC-1α, Tfam, ERRα, NRF-1, COXIV and ATPsyn in controls and GF fed mice. The results are expressed as the mean ± SD (n = 10 per group), * p < 0.01 compared to the control group.

Figure 4

The effect of GF diets on the exercise signaling pathways and autophagy. (A) The protein expression of exercise-associated markers, such as p-AMPK, AMPK, SIRT1, PGC-1α and PPARδ, was evaluated by Western blot analysis. (B) The protein expression levels in (A) were plotted for statistical analysis. (C) Mice that were fed control or GF diets were evaluated for p-S6K1 and S6K1 activity. (D) Evaluation of data from (C). The results are expressed as mean ± SD (n = 10 per group), * p < 0.01 compared to the control group.

Figure 5

The effect of GF diets on the exercise signaling pathways and autophagy. The expression of GF/exercise-associated adiponectin levels were evaluated by ELISA. Mice that were fed control or GF diets were evaluated for adiponectin levels. The results are expressed as mean ± SD (n = 10 per group), * p < 0.01 compared to the control group.