Lactate effects on muscle regeneration in vivo and in vitro models: a systematic review

Introduction: Lactate is a substance that, over the years, has been responsible for numerous effects, mainly linked to muscle fatigue, being recently highlighted in systemic processes and muscle regeneration, which still has many points to be clarified, one of them being the participation of lactate in this process. Objective: Verify the effect of lactate on muscle recovery in in vivo and in vitro models. Methods: The search was conducted in five databases (16 June 2022) (PROPERO nº CRD42020209324), using the search words in English and Portuguese: ‘lactate’, ‘lactic acid’, ‘muscle regeneration’, ‘MyoD protein’, and ‘myogenin’. We included experimental and in vitro studies that investigated the use of lactate in relation to muscle (all species and both sexes – males and females). The methodological quality was assessed by a specific questionnaire for in vitro and in vivo studies. Results: Eight articles were selected, of which three studies were found exclusively in vitro, one exclusively in animal models, and four studies with in-vitro models and animal models. Three studies scored overall methodological quality above 90%, another three between 80-90% and two between 70-75%. Both types of studies showed results that may point to the mechanism by which lactate acts in the proliferation and differentiation of myoblasts, either by the action of myogenic regulatory factors (MRFs) or by the actions in the metabolism of these cells. Conclusion: The lactate presence in myoblasts strongly suggests a correlation with the expression of regulatory molecules during muscle regeneration. Future studies must investigate this correlation to advance our understanding of the regulatory mechanisms involved in this process