Whey Protein Supplementation Post Resistance Exercise in Elderly Men Induces Changes in Muscle miRNA's Compared to Resistance Exercise Alone

Abstract

Progressive muscle loss with aging results in decreased physical function, frailty, and impaired metabolic health. Deficits in anabolic signaling contribute to an impaired ability for aged skeletal muscle to adapt in response to exercise and protein feeding. One potential contributing mechanism could be exerted by dysregulation of microRNAs (miRNAs). Therefore, the aim of this study was to determine if graded protein doses consumed after resistance exercise altered muscle miRNA expression in elderly men. Twenty-three senior men (67.9 ± 0.9 years) performed a bout of resistance exercise and were randomized to consume either a placebo, 20 or 40 g of whey protein (n = 8, n = 7, and n = 8, respectively). Vastus lateralis biopsies were collected before, 2 and 4 h after exercise. Expression of 19 miRNAs, previously identified to influence muscle phenotype, were measured via RT-PCR. Of these, miR-16-5p was altered with exercise in all groups (p = 0.032). Expression of miR-15a and-499a increased only in the placebo group 4 h after exercise and miR-451a expression increased following exercise only in the 40 g whey supplementation group. Changes in p-P70S6K^Thr389 and p-Akt^Ser473 following exercise were correlated with alterations in miR-208a and-499a and-206 expression, irrespective of protein dose, suggesting a possible role for miRNA in the regulation of acute phosphorylation events during early hours of exercise recovery.

Keywords: P70S6 K; mTOR pathway; microRNA; older adults; protein dose; resistance training; skeletal muscle.

Figure 1

miRNA expression. Fold changes of (A) miR-1, (B) miR-15a, (C) miR-99a, (D) miR-148b, (E) miR-149, (F) miR-451a, (G) miR-499a, and (H) miR-16 in placebo, 20 g and 40 g whey groups at 2 hr and 4 hr following exercise. ^*Difference between respective pre exercise expression P < 0.05. #Difference compared to placebo group at respective post-exercise time point, P < 0.05. Data are expressed as median ±1–99% confidence intervals as a fold change to respective pre-exercise expression. The boxes depict interquartile ranges. Dotted line reflects pre-exercise expression levels.

Figure 2

Phosphoprotein expression. Fold changes of (A) p-P70S6k^Thr389 and (B) p-Akt^Ser473in placebo, 20 g and 40 g whey groups at 2 h and 4 h following exercise. (C) Shows representative western blot images. *Difference between respective pre-exercise expression, P < 0.05. #Difference compared to placebo group at respective post-exercise time point, P < 0.05. Data are expressed as median ±1–99% confidence intervals as a fold change to respective pre-exercise expression. The boxes depict interquartile ranges. Dotted line reflects pre-exercise expression levels. Data for p-P70S6k^Thr389 was originally published for a larger cohort (15).

Figure 3

miRNAs correlated with post-exercise P70S6K^Thr389 phosphorylation. (A) miR-208a and (B) miR-499a. miRNAs are plotted as a fold change from pre-exercise on the y-axis with fold change of p-P70S6K^Thr389/ERK1/2 on the x-axis. The solid line represents the line of best fit as determined by linear regression with 95% confidence intervals.

Figure 4

miRNAs significantly correlated with post-exercise Akt^Ser473 phosphorylation. (A) miR-206 and (B) miR-208a. miRNAs are plotted as a fold change from pre-exercise on the y-axis with fold change of p-Akt^Ser473/total Akt on the x-axis. The solid line represents the line of best fit as determined by linear regression with 95% confidence intervals.

Figure 5

Correlation between resting miR-133a and thigh muscle CSA. miRNA expression is plotted as 2^−ΔCT on the y-axis with thigh CSA (cm²) one the x-axis. The solid line represents the line of best fit as determined by linear regression with 95% confidence intervals.