Leucine-enriched whey protein supplementation,resistance-based exercise, and cardiometabolic healthin older adults: a randomized controlled trial

Abstract

Background Increasing protein intake (above the Recommended Dietary Amount) alone or with resistance-based exercise is suggested to improve cardiometabolic health; however, randomized controlled trials (RCTs) are needed to confirm this. Methods The Liverpool Hope University-Sarcopenia Aging Trial (LHU-SAT) was a 16 week RCT (ClinicalTrials.gov Identifier: NCT02912130) of 100 community-dwelling older adults [mean age: 68.73 ± 5.80 years, body mass index: 27.06 ± 5.18 kg/m2 (52% women)] who were randomized to four independent groups [Control (C), Exercise (E), Exercise + Protein (EP), Protein (P)]. E and EP completed supervised and progressive resistance-based exercise (resistance exercise: two times per week, functional circuit exercise: once per week), while EP and P were supplemented with a leucine-enriched whey protein drink (three times per day) based on individual body weight (0.50 g/kg/meal, 1.50 g/kg/day). Outcome measures including arterial stiffness (pulse wave velocity), fasting plasma/serum biomarkers [glucose/glycated haemoglobin, total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein, insulin, resistin, leptin, adiponectin, C-reactive protein, tumour necrosis factor-alpha, interleukin-6, cystatin-C, & ferritin], insulin resistance (HOMA-IR), and kidney function (eGFR) were measured before and after intervention. Results Total protein intake (habitual diet plus supplementation) increased to 1.55 ± 0.69 g/kg/day in EP and to 1.93 ± 0.72 g/kg/day in P, and remained significantly lower (P < 0.001) in unsupplemented groups (E: 1.08 ± 0.33 g/kg/day, C: 1.00 ± 0.26 g/kg/day). At 16 weeks, there was a group-by-time interaction whereby absolute changes in LDL-cholesterol were lower in EP [mean difference: �0.79 mmol/L, 95% confidence interval (CI): �1.29, �0.28, P = 0.002] and P (mean difference: �0.76 mmol/L, 95% CI: �1.26, �0.26, P = 0.003) vs. C. Serum insulin also showed group-by-time interactions at 16 weeks whereby fold changes were lower in EP (mean difference: �0.40, 95% CI: �0.65, �0.16, P = 0.001) and P (mean difference: �0.32, 95% CI: �0.56, �0.08, P = 0.009) vs. C, and fold changes in HOMA-IR improved in EP (mean difference: �0.37, 95% CI: �0.64, �0.10, P = 0.007) and P (mean difference: �0.27, 95% CI: �0.53, �0.00, P = 0.048) vs. C. Serum resistin declined in P only (group-by-time interaction at 16 weeks: P = 0.009). No other interactions were observed in outcome measures (P > 0.05), and kidney function (eGFR) remained unaltered. Conclusions Sixteen weeks of leucine-enriched whey protein supplementation alone and combined with resistance-based exercise improved cardiometabolic health markers in older adults. Keywords Aging; Insulin resistance; Inflammation; Lipoprotein