Carnosine Supplementation Has No Effect on Inflammatory Markers in Adults with Prediabetes and Type 2 Diabetes: A Randomised Controlled Trial

Background/Objectives: In vitro studies suggest that carnosine reduces inflammation by upregulating anti-inflammatory mediators and downregulating pro-inflammatory cytokines. However, human clinical trials examining the effects of carnosine on inflammatory biomarkers are scant. We conducted a secondary analysis of a double-blind randomised controlled trial (RCT) to examine the effects of carnosine supplementation on inflammatory markers and adipokines in participants with prediabetes or well-controlled type 2 diabetes (T2D). Methods: Out of 88 participants who were recruited, 49 adults with prediabetes or well-controlled T2D (HbA1c: 6.6 ± 0.7% [mean ± SD]) who were treated with diet and/or metformin were eligible for inclusion. Participants were randomised to receive 2 g/day of carnosine or a matching placebo for 14 weeks. We measured serum concentrations of monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-6, IL-10, C-reactive protein (CRP), tumour necrosis factor-α (TNF-α), adiponectin, leptin, adipsin, serpin, and resistin levels at baseline and after 14 weeks. The trial was registered at clinicaltrials.gov (NCT02917928). Results: Forty-one participants (M = 29/F = 12) aged 53 (42.6, 59.3) years [median (IQR)] completed the trial. After 14 weeks of supplementation, changes in pro- and anti-inflammatory cytokine and adipokine levels did not differ between the carnosine and placebo groups (p > 0.05 for all). The results remained unchanged after adjustment for confounders including age, sex, and anthropometric measures (e.g., body fat percentage and visceral adipose tissue). Conclusions: In individuals with prediabetes and well-controlled T2D, carnosine supplementation did not result in any significant changes in inflammatory markers. Larger RCTs with longer follow-up durations are needed to evaluate whether carnosine may be beneficial in individuals with poorly controlled T2D.