1633-P: Type 1 Diabetes Induced Alterations in Motor Unit Discharge Rate

Abstract

Type 1 diabetes (T1D) is a contributing factor in alterations in skeletal muscle health. It has been attributed to accelerated muscle ageing (Monaco et al., 2019), and the molecular alterations in the muscle are also associated with impaired adaptations to physical exercise (Minnock et al., 2022). However, there is no evidence about the consequences of this condition on the behaviour of individual motor units (MUs), despite them being the effectors of the contractile stimulus coming from the nervous system via modulation of their recruitment and discharge activity. This study aimed to investigate whether MUs discharge rate (DR) differs between people living with T1D compared with a control (CON) group of people living without diabetes. Eight people with T1D (4M/4F, 30.50 ± 3.66 years, HbA1c of 8.31 ± 2.40%) without comorbidities and 8 age and sex-matched CON participants undertook the study. MUs DR was evaluated from the vastus lateralis muscle during trapezoidal submaximal isometric contractions with High-Density Electromyography at 20, and 40% of the maximum voluntary contraction (MVC) and DR modulation was defined as the difference between DR at recruitment (i.e., first 3 MUs firings) and DR during the steady-state phase of the contraction. Groups were compared for maximum torque (182.06 ± 47.65 Nm T1D and 171.99 ± 101.97 Nm Non-D). MUs DR was lower for those with T1D at recruitment and during the steady-state phase, both during contractions at 20 and 40% MVC (p<0.05). MUs DR modulation was comparable between the two groups. In conclusion, reductions in MUs DR indicate initial alterations of MUs properties in people living with uncomplicated T1D when compared to CON counterparts. The reduced DR, however, was not accompanied by a reduced range of DR modulation (gain) and was not reflected in reduced force production. These findings suggest that initial alterations of MUs properties are present in people living with uncomplicated T1D and that these alterations are detectable before they become functionally manifest. Disclosure D.Minnock: Employee; Innovation Zed. G.Valli: None. R.Wu: None.