Photobiomodulation Therapy on the Treatment of Insulin Resistance: A Narrative Review

Background: Insulin resistance (IR) is the main risk factor for the development of type 2 diabetes mellitus (DM2). Noninvasive and nonpharmacological therapies, such as exercise and diet are effective in treating IR and DM2; however, adherence to them generally is low and diminishes positive effects in the long term. Photobiomodulation therapy (PBMT) is another noninvasive and nonpharmacological therapy, which produces positive effects on mitochondrial metabolism, oxidative stress, and inflammation generally linked to IR and DM2 and may improve or attenuate the severity of these diseases. Objective: In this narrative review, we focus on the available literature related to the effects of PBMT on IR. Results: In fact, recent in vitro and in vivo studies have demonstrated improvements in IR in skeletal muscle, adipose tissue, and hepatic cells mediated by PBMT. Further, there is evidence that PBMT can potentiate exercise-induced improvement in IR through ameliorating mitochondrial dysfunction, reducing inflammation, and modulating oxidative stress. Moreover, reduced adiposity and altered gut microbiota also appear to mediate PBMT effects on IR. Conclusions: Although these results are exciting, randomized clinical trials are urgently needed to confirm the clinical relevance of PBMT in the treatment of IR. Investigation about the effects of PBMT combined with different volumes of physical exercises may also contribute significantly for those patients having difficulty to adhere to the recommended minimal exercise volume. Finally, studies on PBMT parameters (e.g., dosimetry, wavelengths, single-point vs. full-body irradiation) are also necessary for the appropriate prescription of PBMT for the treatment of IR.