Background Dietary sulfur amino acid (SAA) restriction is an established animal model for increasing lifespan and improving metabolic health. Data from human studies are limited. In the study outlined in this protocol, we will evaluate if dietary SAA restriction can reduce body weight and improve resting energy expenditure (REE) and parameters related to metabolic health. Method/design Men and women (calculated sample size = 60), aged 18–45 years, with body mass index of 27–35 kg/m2 will be included in a double-blind 8-week dietary intervention study. The participants will be randomized in a 1:1 manner to a diet with either low or high SAA. Both groups will receive an equal base diet consisting of low-SAA plant-based whole foods and an amino acid supplement free of SAA. Contrasting SAA contents will be achieved using capsules with or without methionine and cysteine (SAAhigh, total diet SAA ~ 50–60 mg/kg body weight/day; SAAlow, total diet SAA ~ 15–25 mg/kg body weight/day). The primary outcome is body weight change. Data and material collection will also include body composition (dual X-ray absorptiometry), resting energy expenditure (whole-room indirect calorimetry) and samples of blood, urine, feces and adipose tissue at baseline, at 4 weeks and at study completion. Measures will be taken to promote and monitor diet adherence. Data will be analyzed using linear mixed model regression to account for the repeated measures design and within-subject correlation. Discussion The strength of this study is the randomized double-blind design. A limitation is the restrictive nature of the diet which may lead to poor compliance. If this study reveals a beneficial effect of the SAAlow diet on body composition and metabolic health, it opens up for new strategies for prevention and treatment of overweight, obesity and its associated disorders. Trial registration ClinicalTrials.gov: NCT04701346, Registration date: January 8th, 2021

No abstract

AimTo investigate whether mesna—sodium‐2‐mercaptoethane sulfonate) can reduce diet‐induced fat gain in mice, and to assess the safety of single ascending mesna doses in humans to find the dose associated with lowering of plasma tCys by at least 30%.MethodsC3H/HeH mice were shifted to a high‐fat diet ± mesna in drinking water; body composition was measured at weeks 0, 2 and 4. In an open, phase I, single ascending dose study, oral mesna (400, 800, 1200, 1600 mg) was administered to 17 men with overweight or obesity. Mesna and tCys concentrations were measured repeatedly for a duration of 48 hours postdosing in plasma, as well as in 24‐hour urine.ResultsCompared with controls, mesna‐treated mice had lower tCys and lower estimated mean fat mass gain from baseline (week 2: 4.54 ± 0.40 vs. 6.52 ± 0.36 g; week 4: 6.95 ± 0.35 vs. 8.19 ± 0.34 g; Poverall = .002), but similar lean mass gain. In men with overweight, mesna doses of 400‐1600 mg showed dose linearity and were well tolerated. Mesna doses of 800 mg or higher decreased plasma tCys by 30% or more at nadir (4h post‐dosing). With increasing mesna dose, tCys AUC0‐12h decreased (Ptrend < .001), and urine tCys excretion increased (Ptrend = .004).ConclusionsMesna reduces diet‐induced fat gain in mice. In men with overweight, single oral doses of mesna (800‐1600 mg) were well tolerated and lowered plasma tCys efficiently. The effect of sustained tCys‐lowering by repeated mesna administration on weight loss in humans deserves investigation.