This study reports the sarcopenia’s prevalence, according to 2010 and 2019 European consensus (EWGSOP), in community-dwelling elderly, insulin treated patients with T2DM. The prevalence found in this group of patients was much lower (6.4% by EWGSOP1 and 1.4% using EWGSOP2) than previously reported in Brazilian population with type 2 diabetes (7% using EWGSOP2, and 16.9% using EWGSOP1 criteria) (11). However, T2DM patients with sarcopenia included in that study were not stratified for insulin use, differently from our study, which we believe to be the reason for the difference in prevalence.
In the present study, 82.1% of patients taking insulin were on combination therapy with OAD and the most common OAD was metformin (75,7%). Evidence from epidemiological studies indicates that men with T2DM using insulin sensitizers, such as metformin, lost significantly less skeletal muscle mass or appendicular skeletal muscle than those treated without insulin sensitizers (16). Similarly, in a cohort of 2864 women with T2DM, patients taking metformin had less decline in usual walk speed than those not taking insulin sensitizers, without significant differences in grip strength (17). In other study, which evaluated the sarcopenia’s prevalence among patients with T2DM, it was found a prevalence of 17.12% in patients without drugs for diabetes, while the 8.1% for the group who take only metformin and 6.7% for the group of metformin combined with other drugs (18).
In our study, we found a prevalence of 1.4% sarcopenia in patients taking metformin with insulin. This very low prevalence can be explained by the possible beneficial effects of metformin on parameters of sarcopenia observed in the few clinical trials performed so far (19). The biological plausibility came from studies showing that treatment with metformin can limit the negative effects of ceramides, thus potentially preventing myoblast senescence (20), might inhibit the ageing process (21), acts on skeletal muscle by increasing insulin-stimulated glucose uptake, and finally on gastrointestinal tract promotes gut microbiome changes, intestinal glucose uptake, and secretion of gastrointestinal hormones (22).
In this study, 16.4% of the elderlies use DPP-4i plus insulin. Evidence indicates that elderly patients with T2DM treated with DPP-4i have better parameters of sarcopenia compared with those treated with other glucose lowering drugs (23). Furthermore, an improvement in mitochondrial biogenesis and exercise capacity in skeletal muscle has also been reported with DPP-4i (24). Perhaps the use of DPP-4i was not the main influencer of the low sarcopenia’s prevalence, but the use this drug parallelly with other drugs cannot be discarded for this group.
We found a prevalence of 22.1% of use the SGLT2i for this group of elderlies. The long-term effect of SGLT2i use may improve insulin sensitivity counteracting muscle catabolism and affecting skeletal muscle function and quality (25). With respect to the beneficial effects of SGLT2i on maximal handgrip strength, a possible mechanism might be the effects on chronic inflammation and adipokine profile, as well as improvement in mitochondrial function (26). In spite of the low prevalence of the use of SGLT2i in our population, we cannot discard its importance for the low sarcopenia’s prevalence in this study.
In our study, the average diabetes duration was 20 years, indicating a long disease course. Evidence available suggest the beneficial association between insulin use and parameters of sarcopenia (14), indicating that a possible prescription of exogenous insulin could improve insulin signaling in the skeletal muscle, promote protein synthesis, and protect against the loss of muscle mass among patients with diabetes, especially those with a long duration of diabetes (13). This evidence brings some attention to insulin treatment for elderly people with T2DM in prevent muscle mass loss, however more longitudinal studies can be necessary to show this possible effect.
Beyond the low sarcopenia’s prevalence found in this study, the EWGSOP2 evaluated the disease severity by the Timed Up and Go Test, which measure the functional capacity of the elderly. In our study, only 0.7% has severe sarcopenia. Despite the anabolic role of the insulin, increasing the protein synthesis, especially in supraphysiological hyperinsulinemia (27), evidence show that even preventing the muscle mass decline, including in the lower extremities (14), muscle function cannot be improved (28). More longitudinal studies evaluating muscle function, beyond the muscle mass, can be necessary to test this hypothesis.
Even with the poor glycemic control showed in this elderly group (HbA1c of the 8.4% ± 1,4), only 10% of the elderly group have grip strength below the cut point for sarcopenia (> 27kg for men and > 16kg for women). However, other studies failure in show an association between insulin therapy and muscle function (GS) (28–30). On other hand, HbA1c levels might not represents a good indicator of the glucose fluctuations, not demonstrating, for example, the hypoglycemic episodes occurrence, what is represent a sarcopenia’s risk factor (31). More studies are necessary to understand the control glycemic role in insulin treated patients in the muscle mass or function loss.
This study has some limitations. First, our study is descriptive and did not test any hypothesis. However, based on the evidence discussed, it still allows speculation on questions and hypotheses for future studies. In addition, some behaviors could have been collected using specific and validated instruments, such as the regular practice of physical exercises, where about two-thirds of the older adults stated that they did not practice, which, however, could not explain the low prevalence of sarcopenia in the analyzed population. In addition, nutritional behavior and daily protein consumption were not evaluated, which could be relevant information given the low sarcopenia’s prevalence. However, the small sample size, added to the low prevalence found, would not allow further analysis. However, one of the strengths of the present study should be highlighted, which is the specificity of the sample, which is composed of older adults with type 2 DM and using insulin.