Greater hyperthermia in men with type 2 diabetes does not lead to higher serum levels of cellular stress biomarkers following exercise-heat stress.

Type 2 diabetes (T2D) is associated with worsening age-related impairments in heat loss, causing higher core temperature during exercise. We evaluated whether these thermoregulatory impairments occur with altered serum protein responses to heat stress by measuring cytoprotection, inflammation, and tissue damage biomarkers in middle-aged-to-older men (50-74 years) with (n = 16) and without (n = 14) T2D following exercise in 40°C. There were no changes in irisin, klotho, HSP70, sCD14, TNF-α, and IL-6, whereas NGAL (+539 pg/mL, p = 0.002) and iFABP (+250 pg/mL, p < 0.001) increased similarly across groups. These similar response patterns occurred despite elevated core temperature in individuals with T2D, suggesting greater heat vulnerability.

Changes in gastrointestinal cell integrity after marathon running and exercise-associated collapse.

PURPOSE: Endurance exercise and hyperthermia are associated with compromised intestinal permeability and endotoxaemia. The presence of intestinal fatty acid-binding protein (I-FABP) in the systemic circulation suggests intestinal wall damage, but this marker has not previously been used to investigate intestinal integrity after marathon running. METHODS: Twenty-four runners were recruited as controls prior to completing a standard marathon and had sequential I-FABP measurements before and on completion of the marathon, then at four and 24 h later. Eight runners incapacitated with exercise-associated collapse (EAC) with hyperthermia had I-FABP measured at the time of collapse and 1 hour later. RESULTS: I-FABP was increased immediately on completing the marathon (T0; 2593 ± 1373 ng·l-1) compared with baseline (1129 ± 493 ng·l-1; p < 0.01) in the controls, but there was no significant difference between baseline and the levels at four hours (1419 ± 1124 ng·l-1; p = 0.7), or at 24 h (1086 ± 302 ng·l-1; p = 0.5). At T0, EAC cases had a significantly higher I-FABP concentration (15,389 ± 8547 ng.l-1) compared with controls at T0 (p < 0.01), and remained higher at 1 hour after collapse (13,951 ± 10,476 ng.l-1) than the pre-race control baseline (p < 0.05). CONCLUSION: I-FABP is a recently described biomarker whose presence in the circulation is associated with intestinal wall damage. I-FABP levels increase after marathon running and increase further if the endurance exercise is associated with EAC and hyperthermia. After EAC, I-FABP remains high in the circulation for an extended period, suggesting ongoing intestinal wall stress.