Associations between Plasma Branched Chain Amino Acids and Health Biomarkers in Response to Resistance Exercise Training Across Age

Abstract

Leucine, isoleucine and valine (i.e., the branched chain amino acids, BCAA) play a key role in the support and regulation of tissue protein regulation and also as energy substrates. However, positive relationships exist between elevated levels of BCAA and insulin resistance (IR). Thus, we sought to investigate the links between fasting plasma BCAA following a progressive resistance exercise training (RET) programme, an intervention known to improve metabolic health. Fasting plasma BCAA were quantified in adults (young: 18-28 y, n = 8; middle-aged: 45-55 y, n = 9; older: 65-75 y, n = 15; BMI: 23-28 kg/m², both males and females (~50:50), in a cross-sectional, intervention study. Participants underwent 20-weeks whole-body RET. Measurements of body composition, muscle strength (1-RM) and metabolic health biomarkers (e.g., HOMA-IR) were made pre- and post-RET. BCAA concentrations were determined by gas-chromatography mass spectrometry (GC-MS). No associations were observed across age with BCAA; however, RET elicited (p < 0.05) increases in plasma BCAA (all age-groups), while HOMA-IR scores reduced (p < 0.05) following RET. After RET, positive correlations in lean body mass (p = 0.007) and strength gains (p = 0.001) with fasting BCAA levels were observed. Elevated BCAA are not a robust marker of ageing nor IR in those with a healthy BMI; rather, despite decreasing IR, RET was associated with increased BCAA.

Keywords: ageing; branched chain amino acids; health; resistance exercise.

Figure 1

The relationship between circulating BCAA concentrations and age at baseline (A) and after (B) 20-weeks of supervised, whole-body RET (n = 8–15/ group) and in distinct age groups at baseline (C) and after RET (D).

Figure 2

Circulating plasma leucine (A), isoleucine (B) and valine (C) at baseline and after 20-weeks of RET (n = 32). Bars represent mean and SEM. Quantification achieved via GC-MS with reference to a calibration curve. Statistical analysis via paired t-tests. * p < 0.05; *** p < 0.001 vs. baseline.

Figure 3

Insulin resistance (via homeostatic model assessment of insulin resistance; HOMA-IR) at baseline and after 20-weeks, whole-body resistance exercise training RET (A) and the relationship between IR and circulating BCAA concentrations at baseline (B) and after (C) RET. * p < 0.05 vs. baseline.

Figure 4

Principle component analysis (PCA) plot visually displaying overlap of clinical variables of health; no distinctive clustering of metabolites predicative of circulating branched chain amino acid (BCAA) concentrations are present at baseline (red), nor emerge following RET (green) (A). Heatmap of correlations that are predictive of circulating BCAA concentrations at baseline (B) and after RET (C). The strength of relationships are based on a scale of −1 (red), representing a negative relationship and 1 (blue) a positive relationship. The strength of the relationships are depicted by the size of the circle.

Figure 5

The relationship between circulating branched chain amino acid (BCAA) concentrations and muscle strength (A,B) and mass (C,D) at baseline and after 20-weeks, whole-body RET.

Figure 6

The relationship between circulating BCAA levels and low-density lipoprotein (LDL) before (A) and after 20-weeks of RET (B).