Vascular improvements in individuals with type 2 diabetes following a 1 year randomised controlled exercise intervention, irrespective of changes in cardiorespiratory fitness

Aims/hypothesis: Vascular changes in individuals with type 2 diabetes mellitus majorly contribute to the development of cardiovascular disease. Increased cardiorespiratory fitness (CRF) has been associated with improvements in vascular health. Although CRF tends to improve with exercise training, there remains a portion of participants with little or no improvement. Given the importance of vascular function in individuals with type 2 diabetes, we assessed whether individuals who failed to improve CRF following a 1 year exercise intervention also failed to improve arterial stiffness and structural indices. Methods: Individuals with type 2 diabetes with no major micro- and macrovascular complications and aged between 30 and 75 years old (n = 63) participated in a three-arm, 1 year, randomised controlled exercise intervention in Lisbon, Portugal. The study involved a non-exercise control group, a moderate continuous training combined with resistance training (RT) group and a high-intensity interval training with RT group. Allocation of participants into the intervention and control groups was done using a computer-generated list of random numbers. An improvement in CRF was defined as a change in V̇ O _{2 peak} ≥5%. Vascular stiffness and structural indices were measured using ultrasound imaging and applanation tonometry. Generalised estimating equations were used to compare changes in vascular measures across individuals in the control group (n = 22) and those in the exercise groups who either had improved CRF (CRF responders; n = 14) or whose CRF did not improve (CRF non-responders; n = 27) following 1 year of exercise training. Results: Compared with the control group, exercisers, with and without improvements in CRF, had decreased carotid intima–media thickness (IMT) (CRF responders: β = −2.84 [95% CI −5.63, −0.04]; CRF non-responders: β = −5.89 [95% CI −9.38, −2.40]) and lower-limb pulse wave velocity (PWV) (CRF responders: β = −0.14 [95% CI −0.25, −0.03]; CRF non-responders: β = −0.14 [95% CI −0.25, −0.03]), the latter being an indicator of peripheral arterial stiffness. Only CRF responders had decreased PWV of the upper limb compared with control participants (β = −0.12 [95% CI −0.23, −0.01]). As for central stiffness, CRF non-responders had increased aortic PWV compared with CRF responders (β = 0.19 [95% CI 0.07, 0.31]), whereas only the CRF non-responders had altered carotid distensibility coefficient compared with the control group (β = 0.00 [95% CI 3.01 × 10⁻⁵, 0.00]). No interaction effects between the CRF responders and non-responders vs control group were found for the remaining stiffness or haemodynamic indices (p>0.05). Conclusions/interpretation: Regardless of improvements in CRF, individuals with type 2 diabetes had significant improvements in carotid IMT and lower-limb arterial stiffness following a 1 year exercise intervention. Thus, a lack of improvement in CRF following exercise in people with type 2 diabetes does not necessarily entail a lack of improvement in vascular health. Trial registration: ClinicalTrials.gov NCT03144505 Funding: This work was supported by fellowships from the Portuguese Foundation for Science and Technology. This work is also financed by a national grant through the Fundação para a Ciência e Tecnologia (FCT), within the unit I&D 472.