Miopatia diabética: padrões morfofuncionais e efeitos musculares da fotobiomodulação em portadores de Diabetes Mellitus tipo 2

Abstract

In type 2 diabetes mellitus (T2DM), chronic muscular disorders increase the risk of ulcers and amputations, yet they are frequently diagnosed at advanced stages. The use of different algorithms, tests, and cutoff points complicates the evaluation of primary sarcopenia (typically in older adults) and are not established for “diabetic sarcopenia,” hindering the classification of these patients in relation to their muscular condition. Physical exercise is the first-line treatment for muscular disorders; however, individuals with T2DM may require adjunctive interventions in specific contexts. Low-Level Photobiomodulation Therapy (LL-PBMT) is a therapeutic option for muscular treatment, but its role in the musculature of individuals with T2DM remains unclear. Objectives: To identify potential morphometric (muscle thickness) and functional patterns in individuals with T2DM based on statistical similarity, and to investigate the effects of LL-PBMT on functional parameters in individuals with T2DM. Results: Cluster analysis grouped 10 morphofunctional items into four domains: muscle thickness (ultrasound), maximal strength/muscle mass, functionality (sit-and stand test, 30-second sit-to-stand test, and timed chair rise test), and submaximal aerobic capacity (6-minute walk test), revealing distinct patterns compared to non diabetic older adults. The muscular impairments already present in T2DM (functional deficits) were not detected by the applied sarcopenia guideline, as there was no reduction in muscle quantity or absolute muscle strength. In the randomized controlled trial (RCT), no statistically significant differences were observed in function (sit-and stand test and timed chair rise), dynamic balance (Timed Up and Go), or submaximal aerobic capacity (6-minute walk test) after six applications of LL-PBMT (red laser vs. infrared laser vs. placebo) on the gastrocnemius muscles in individuals with T2DM. Although the increase in sit-and-stand test performance in the irradiated groups was considered clinically relevant, it did not reach statistical significance or exhibit a meaningful effect size. Conclusions: Individuals with T2DM exhibited functional impairments (mainly in sit-and-stand performance) despite the absence of muscle atrophy or weakness, differing from their non-diabetic counterparts. They also presented with reduced relative strength (particularly when normalized by BMI), suggesting impaired muscular efficiency. Metrics specifically developed for individuals with T2DM using mixed qualitative–quantitative statistical methods may help prevent the apparent underdiagnosis of muscular disorders in this population. No significant functional effects were observed following isolated laser application on the muscles of adults or older adults with T2DM (neuropathic, long-standing disease, and suboptimal glycemic control). Adjustments in dosimetry and inclusion criteria should be explored in future studies.