Glycine increases fat‐free mass in malnourished haemodialysis patients: a randomized double‐blind crossover trial

Abstract

Background Protein energy wasting is associated with negative outcome in patients under chronic haemodialysis (HD). Branched‐chain amino acids (BCAAs) may increase the muscle mass. This post hoc analysis of a controlled double‐blind randomized crossover study assessed the impact of BCAAs on nutritional status, physical function, and quality of life. Methods We included 36 chronic HD patient features of protein energy wasting as plasma albumin <38 g/L, and dietary intakes <30 kcal/kg/day and <1 g protein/kg/day. Patients received either oral BCAA (2 × 7 g/day) or glycine (2 × 7 g/day) for 4 months (Period 1), followed by a washout period of 1 month, and then received the opposite supplement (Period 2). The outcomes were lean body mass measured by dual‐energy X‐ray absorptiometry, fat‐free mass index measured by bioelectrical impedance, resting energy expenditure, dietary intake and appetite rating, physical activity and function, quality of life, and blood parameters. Analyses were performed by multiple mixed linear regressions including type of supplementation, months, period, sex, and age as fixed effects and subjects as random intercepts. Results Twenty‐seven patients (61.2 ± 13.7 years, 41% women) were compliant to the supplementations (consumption >80% of packs) and completed the study. BCAA did not affect lean body mass index and body weight, but significantly decreased fat‐free mass index, as compared with glycine (coeff −0.27, 95% confidence interval −0.43 to −0.10, P = 0.002, respectively). BCAA and glycine intake had no effect on the other clinical parameters, blood chemistry tests, or plasma amino acids. Conclusions Branched‐chain amino acid did not improve lean body mass as compared with glycine. Unexpectedly, glycine improved fat‐free mass index in HD patients, as compared with BCAA. Whether long‐term supplementation with glycine improves the clinical outcome remains to be demonstrated.

Alterations in glycine metabolism in obesity and chronic metabolic diseases – an update on new advances

“…The few results obtained in rodent models are detailed in the following paragraph. However, unexpectedly, glycine supplementation in chronic haemodialysis patients was found to improve fat-free mass index, compared to BCAA [13 ▪ ]. Although it is outside the scope of the present review, it is worth mentioning this work, but it remains to be demonstrated that long-term glycine supplementation improves clinical outcomes in chronic haemodialysis patients or may benefit other patients.…”

The effect of glycine administration on the characteristics of physiological systems in human adults: A systematic review

“…No significant effect on upper and lower body strength was reported in resistance-trained adults with a single oral glycine bolus of 0.3 g/kg body weight 1 h prior to assessment [ 61 ]. Patients undergoing chronic haemodialysis with protein energy wasting (PEW) showed positive effects, including improvements in handgrip strength and fat-free mass index following oral glycine administration of 7 g X 2/day over 4 months [ 45 ] (Table 1 , Fig. 2 , Supplementary Table A ).…”

“…In diseased populations, positive effects included mitigation of symptoms in patients with overactive bladder administered with 3 g X 2/day of oral glycine over 4 weeks; and decreased daily proteinuria in early preeclampsia patients administered with placebo 1% glycine solution for up to 7 days [ 35 ]. Although increased levels of pre-dialysis urea and normalised protein catabolic rate (nPCR) were reported in chronic haemodialysis patients with PEW following oral glycine administration of 7 g X 2/day over 4 months, these results were attributed to the patients’ compliance to glycine treatment [ 45 ] (Table 1 , Fig. 2 , Supplementary Table A ).…”

Sarcopenia and sarcopenic obesity in chronic kidney disease: update on prevalence, outcomes, risk factors and nutrition treatment

“…Creatine and glycine supplements were also investigated in two separate pilot randomized controlled trials. The results of both were promising, though larger trials are needed before routine adoption of these supplements in recommended [65,66].…”