Serum metabolic alterations after two weeks of step-reduction and following four weeks of exercise rehabilitation in older adults: a secondary analysis of the ENDURE randomised controlled trial

Objectives This study examined the effects of step-reduction and subsequent step-recovery and exercise rehabilitation on systemic metabolism in older adults. Methods Participants were 66 eligible participants from the ENDURE randomised controlled trial allocated to an intervention group (n=32; 25 % male) or control group (n=34; 21 % male). The intervention group was instructed to limit their daily steps to a maximum of 2000 for two weeks (Period I), followed by a four-week exercise rehabilitation program (Period II) involving twice-weekly sessions of whole-body resistance and bicycle ergometer-based endurance training. Fasting blood samples were collected at baseline, after Period I, and after Period II. Systemic metabolism was assessed using high-throughput proton nuclear magnetic resonance spectroscopy. Data were normalised using Box-Cox transformation and analysed with linear mixed-effects models including random intercepts. Results Period I and Period II had largely opposing effects on systemic metabolism. For instance, compared to the control group, Period one led to increases in VLDL-phospholipids (0.54 SD, P = 0.005), VLDL-cholesterols (0.41 SD, P = 0.012) and VLDL-triglycerides (0.79 SD, P = 0.002), and decreases in HDL-phospholipids (−0.31 SD, P = 0.037) and HDL-cholesterols (−0.47 SD, P = 0.011), alongside an increase in HDL-triglycerides (0.64 SD, P = 0.011). These changes reversed during Period II. Glycoprotein acetylation biomarker GlycA levels were unaffected by either intervention. Conclusions These findings suggest that short-term inactivity does not markedly influence the inflammatory state but adversely affects lipoprotein metabolism and glycolytic pathways; however, these changes are reversible through the resumption of physical activity.