Metformin Attenuates Post-exercise Heart Rate Recovery In Prediabetic And Diabetic Individuals.

Metformin and exercise have cardioprotective benefits beyond improving glycemic control in type 2 diabetes (T2D) individuals. Nevertheless, when both T2D treatments are combined, metformin has been shown to interfere with the beneficial cardiovascular effects of exercise training, attenuating improvements in blood pressure or cardiorespiratory fitness (i.e., VO2MAX) (Moreno-Cabañas et al. 2022). T2D individuals also show an altered post-exercise sympathetic-parasympathetic balance (Sydó et al. 2016) and hypotension (Motta et al. 2010), then the blunted parasympathetic reactivation following exercise could impair heart rate recovery, increasing the risk of long-term mortality in these patients (Sydó et al. 2016) and interfering with cardiovascular exercise training adaptations. Therefore, the interactions between metformin and exercise on post-exercise cardiovascular response should be clarified in T2D individuals. Purpose: To determine the acute effects of metformin treatment on blood pressure (BP) and heart rate (HR) following high-intensity interval training (HIIT) in individuals with prediabetes and T2D. Methods: Eight T2D adults (60 ± 4 years) with overweight/obesity (32 ± 4 kg·m−2) under chronic metformin treatment (9 ± 6 years; 1281 ± 524 mg·day−1) participated in a double-blind, randomized, crossover design. Participants performed a HIIT session by taking their habitual metformin treatment (MET) or substituting their medication with a placebo (PLAC). BP and HR were monitored at rest and during the HIIT session and exercise recovery. Results: Metformin did not affect BP (i.e., systolic and diastolic BP, respectively) or HR during exercise (MET, 172 ± 11 and 78 ± 12 mmHg, and 147 ± 9 bpm; PLAC, 173 ± 9 and 81 ± 13 mmHg, and 146 ± 10 bpm; all P > 0.05). In addition, post-exercise hypotension was not attenuated by metformin (ΔMET, -16 ± 14 and -5 ± 8 mmHg; ΔPLAC, -16 ± 14 and -6 ± 12 mmHg; all P > 0.05). Nevertheless, metformin attenuated HR recovery following exercise (MET, 85 ± 9 bpm; PLAC, 79 ± 8 bpm; P = 0.018). Conclusion: Therefore, although the metformin treatment does not interfere with post-exercise hypotension after a HIIT session, it may impair post-exercise autonomic function in pre-diabetic and T2D individuals. Spanish Ministry of Science and Innovation (PID2020-116159RB-I00)