The plasma metabolome is associated with preservation of physiological function following lifelong aerobic exercise in mice

Abstract

Declines in physiological function with aging are strongly linked to age-related diseases. Lifelong voluntary aerobic exercise (LVAE) preserves physiological function with aging, possibly by increasing cellular quality control processes, but the circulating molecular transducers mediating these processes are incompletely understood. The plasma metabolome may predict biological aging and is impacted by a single bout of aerobic exercise. Here, we conducted an ancillary analysis using plasma samples, and physiological function data, from previously reported studies of LVAE in male C57BL/6N mice randomized to LVAE (wheel running) or sedentary (SED) (n = 8-9/group) to determine if LVAE alters the plasma metabolome and whether these changes correlated with preservation of physiological function with LVAE. Physical function (grip strength, coordination, and endurance) was assessed at 3 and 18 months of age; vascular endothelial function and the plasma metabolome were assessed at 19 months. Physical function was preserved (%decline; mean ± SEM) with LVAE vs SED (all p < 0.05)-grip strength, 0.4 ± 1.7% vs 12 ± 4.0%; coordination, 10 ± 4% vs 73 ± 10%; endurance, 1 ± 15% vs 61 ± 5%. Vascular endothelial function with LVAE (88.2 ± 2.0%) was higher than SED (79.1 ± 2.5%; p = 0.03) and similar to the young controls (91.4 ± 2.9%). Fifteen metabolites were different with LVAE compared to SED (FDR < 0.05) and correlated with the preservation of physiological function. Plasma spermidine, a polyamine that increases cellular quality control (e.g., autophagy), correlated with all assessed physiological indices. Autophagy (LC3A/B abundance) was higher in LVAE skeletal muscle compared to SED (p < 0.01) and inversely correlated with plasma spermidine (r = - 0.5297; p = 0.054). These findings provide novel insight into the circulating molecular transducers by which LVAE may preserve physiological function with aging.

Keywords: Aging; Autophagy; Endothelial function; Metabolomics; Physical function; Skeletal muscle; Spermidine.

Fig. 1

A Principal component analysis performed on raw metabolomics data in sedentary (SED) and lifelong voluntary aerobic exercise (LVAE) groups. B Volcano plot illustrating the impact of LVAE on plasma metabolites. Significance was considered to meet both parameters of a false discovery rate (FDR)-adjusted p-value (Benjamani–Hochberg) < 0.05 and Log₂ Fold change (L2FC) ± 1 (relative to SED). Thirteen metabolites were found higher (red) and two lower (blue) with LVAE. C Heat map of individual changes for each of the 15 significantly altered plasma metabolites observed with LVAE normalized to SED (red = higher in LVAE; blue = lower in LVAE). LVAE group changes normalized to SED for each metabolite are shown in the L2FC column. FDR-adjusted p-values are reported in the last column. Gray boxes with X’s indicate identified and removed outliers. D KEGG enrichment analysis performed with Metaboanalyst using the 15 significant metabolites shown in “C”. Circle size represents the number of metabolite hits; the color of circles represents FDR-adjusted p-value; fold enrichment ratio is the number of metabolite hits within a pathway relative to expected metabolite hits by random chance. All pathways met an FDR-adjusted p-value < 0.2

Fig. 2

Assessment of physical function (A grip strength; C coordination; E endurance) in male mice at 3 months and then at 18 months of age following sedentary (SED, black) or lifelong voluntary aerobic exercise (LVAE, gold). P < 0.05 compared with (‡) 3 months within groups and (†) between groups at 18 months. Two-way repeated measures ANOVA. Percent (%) change in physical function (B grip strength; D coordination; F endurance) at 18 months of age compared to 3 months of age in SED and LVAE. Unpaired t-test. G Vascular endothelial function assessed as percent (%) peak endothelium-dependent dilation (EDD) following SED or LVAE at 19 months of age (Old SED, Old LVAE) or in a Young SED reference group at 6 months of age. The Young SED reference group was previously published in the parent study [16] and repurposed here to perform this specific analysis. One-way ANOVA, Tukey’s post-hoc. *p < 0.05; **p < 0.01; ****p < 0.0001. All data mean ± SEM

Fig. 3

Significant Pearson or Spearman correlations between abundance of significant plasma metabolites and (1) percentage change in indices of physical function (grip strength, coordination, endurance) or (2) vascular endothelial function [percent (%) peak endothelium-dependent dilation (EDD)]. Numbers and color gradients correspond with r values. *p < 0.05; **p < 0.01; ***p < 0.001

Fig. 4

Spearman correlations between plasma spermidine and percentage change in indices of physical function (A grip strength; B coordination; C endurance) and D vascular endothelial function [percent (%) peak endothelium-dependent dilation (EDD)]. Sedentary (black, SED); lifelong voluntary aerobic exercise (gold, LVAE). AU arbitrary units

Fig. 5

A Assessment of LC3A/B (marker of autophagy) protein normalized to total protein in quadriceps skeletal muscle after sedentary (SED) and lifelong voluntary aerobic exercise (LVAE) conditions in 19-month-old male mice (N = 7/condition). Representative LC3A/B protein content and total protein for each SED and LVAE are provided. Student’s t-test; **p < 0.01. AU arbitrary units. B Spearman correlation between LC3A/B abundance in quadriceps skeletal muscle and circulating spermidine in 19-month-old male mice following SED (black) and LVAE (gold) (N = 7/condition)