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Acute blood glucose and vascular endothelial responses to passive heating in individuals with type 2 diabetes
Author(s) -
Behzadi Parya,
Gravel Hugo,
Ravanelli Nicholas,
Gag Daniel
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.02305
Subject(s) - medicine , brachial artery , diabetes mellitus , type 2 diabetes , type 2 diabetes mellitus , endothelial dysfunction , endocrinology , blood pressure , population , insulin , heart rate , cardiology , environmental health
Insulin resistance and hyperglycemia predispose individuals with type 2 diabetes mellitus (T2DM) to endothelial dysfunction and a greater risk of cardiovascular diseases. Numerous animal studies suggest that heat exposure improves glucose control and human studies suggest that it improves markers of vascular health. However, the physiological responses to heat exposure remain understudied in individuals with T2DM, particularly within a therapeutic context. Objective To characterize blood glucose and vascular endothelial responses to heat exposure in T2DM and determine if heating acutely improves glucose control and endothelial function in this population. Methods On separate randomized days, six adults (2 males/4 females, 60 ± 12 years) with T2DM (≥1 year, HbA1c: 7.0 ± 0.5%, fasting glucose: 7.79 ± 1.13 mmol/L) were immersed in control (34°C, 90 minutes) or hot (40–41°C, core temperature ≥38.5°C for 60 minutes) water. Participants were fasted (12 hours) and withheld anti‐diabetic medication (≥24 hours). Blood glucose and insulin as well as brachial artery shear rates were measured at baseline, during immersion and 45–60 minutes after immersion. Brachial artery flow‐mediated dilation (FMD) was measured at baseline and 45 minutes after immersion. Blood glucose control was evaluated during an oral glucose tolerance test (OGTT, 75 g) 60 minutes after immersion. Core (T core , rectal) and mean skin (T skin ) temperatures, heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressures were measured throughout the protocol. Results Compared to control, hot water immersion increased T core (+1.44°C [1.05, 1.83], P<0.01), T skin (+2.36°C [1.21, 3.51], P<0.01), HR (+35 bpm [26, 43], P<0.01), and decreased DBP (−7 mmHg [−2, −13], P<0.01) and SBP (−9 mmHg [−1, −16], P=0.03). Hot water immersion increased antegrade (+71 s −1 [35, 107], P<0.01) and decreased retrograde (−15 s −1 [0.9, 3], P=0.06) shear rates. Nonetheless, FMD was unchanged during both control (−0.74% [−4.33, 2.86], P=0.81) and hot (−1.93% [−5.53, 1.66], P=0.30) water immersion. Blood glucose decreased progressively throughout the control protocol (−1.3 mmol/L [−0.8, −1.9], P<0.01), whereas hot water immersion attenuated this decrease (+0.1 mmol/L [−0.5, +0.6], P=0.93). Hot water immersion did not alter glucose (P=0.17) and insulin (P=0.99) area under the curve during the OGTT. Conclusion These preliminary results suggest that the physiological responses associated with heat exposure do not translate into acute improvements in blood glucose control or brachial artery endothelial function in individuals with T2DM. Support or Funding Information Cardiometabolic Health, Diabetes and Obesity Research Network and Diabetes Quebec.