Acute mild cold exposure with shivering reduces 24 h glucose levels in individuals with type 2 diabetes but not prediabetes.
AIMS/HYPOTHESIS: Repeated cold exposure with shivering has been proposed as a potential strategy to enhance glucose metabolism by increasing energy expenditure and substrate utilisation. However, acute effects/benefits of cold-induced shivering on glucose homeostasis in metabolically compromised individuals are unknown. Here, we aimed to determine whether cold exposure at two different intensities improves 24 h glucose homeostasis in individuals with prediabetes and type 2 diabetes. METHODS: In a randomised crossover trial conducted in the South Limburg/Maastricht region of the Netherlands, men and postmenopausal women with prediabetes (n=12) and stable type 2 diabetes (n=12), aged 40-75 years, body mass index ≥27 and ≤35 kg/m2, non-smoking and sedentary, underwent two whole-body cold exposure sessions using a water-perfused suit. Session order was randomised using an online randomisation tool (randomizer.org); participants were masked to the cold exposure intensity received, but investigators were not. Sessions were designed to elicit ~1.5-fold (mild, 15°C) and ~2.5-fold (moderate, 4°C) increases in resting metabolic rate (RMR). Continuous glucose monitoring assessed interstitial glucose concentrations over 24 h periods before and after each intervention, with controlled diet and activity. Shivering was confirmed via indirect calorimetry and electromyography. RESULTS: In both study groups and periods, RMR increased significantly vs baseline (p<0.001 for all). In prediabetes, the increase in the final 1 h of cold was 1.53 × RMR in mild and 1.94 × RMR in moderate cold. In type 2 diabetes, the increase was 1.57 × RMR and 2.09 × RMR in the final 1 h of mild and moderate cold, respectively. In prediabetes, neither mild nor moderate cold exposure altered mean 24 h glucose levels. In contrast, after mild cold exposure the type 2 diabetes group exhibited a significant reduction in mean 24 h glucose levels (-0.6 ± 0.5 mmol/l, p=0.003) and fasting glucose (-0.6 ± 0.8 mmol/l, p=0.019), as well as an increase in time in normal range (+8.8 ± 10.3%, p=0.013) and reduced time in hyperglycaemia (-10.9 ± 12.9%, p=0.014). Moderate cold did not significantly affect any of the glucose outcomes in type 2 diabetes. Baseline fasting glucose, age and ALT levels were predictors of the glucose-lowering response, suggesting greater benefits in individuals who have higher baseline glucose levels, are younger and/or have more optimal liver health, i.e. lower ALT. CONCLUSIONS/INTERPRETATION: Acute mild cold exposure with shivering reduced 24 h glucose levels in individuals with type 2 diabetes. No changes were observed in prediabetes. The observed effects appear to depend on baseline metabolic status rather than acute substrate utilisation during cold exposure. These findings support the potential of cold exposure as an adjunct non-pharmacological therapy for type 2 diabetes, although further mechanistic studies and validation in larger cohorts are warranted. TRIAL REGISTRATION: ClinicalTrials.gov NCT05576025 FUNDING: Dutch Organisation for Knowledge and Innovation in Health, Healthcare and Well-being (ZonMw): 09120012010062.