Regression from prediabetes to normal glucose regulation: State of the science

Prediabetes, an intermediate stage between normal glucose regulation and type 2 diabetes, is diagnosed based on documentation of impaired fasting glucose, impaired glucose tolerance, or a hemoglobin A1c level of 5.7-6.4%. Individuals with prediabetes have increased risks for the development of type 2 diabetes and multiple vascular complications. Randomized controlled trials have demonstrated the feasibility of preventing progression from prediabetes to type 2 diabetes, using lifestyle or pharmacological interventions. Lifestyle modification has a sustained effect on diabetes prevention, whereas medications lose efficacy when discontinued. Few studies have pre-specified reversal of prediabetes as the primary outcome. There is emerging evidence that reversal of prediabetes (i.e. restoration of normal glucose regulation) confers significant protection from future diabetes and complications, including premature death, during long-term follow-up. Current lifestyle intervention protocols have been more effective in preventing progression from prediabetes to type 2 diabetes than restoring normal glucose regulation; thus, interventions that prevent type 2 diabetes in people with prediabetes do not always reverse prediabetes. Given the compelling benefits of restoration of normal glucose regulation, specific protocols for reversal of prediabetes need to be developed and tested. The design of such protocols requires a deeper understanding of the pathobiology of prediabetes and early glucose dysregulation. The present review focuses on those studies that have assessed the impact of interventions on regression of the prediabetes state and restoration of normal glucose regulation. Furthermore, we discuss alterations in adiposity, glucoregulatory mechanisms, metabolomics, inflammatory markers, and other factors that predict the initial escape from normoglycemia. Such knowledge could inform the future development of novel, refined, and targeted interventions for the reversal prediabetes/early dysglycemia and restoration of normal glucose regulation. Impact statement Prediabetes increases the risks of future type 2 diabetes (T2D) and vascular complications, risks that can be prevented by restoring normal glucose regulation (NGR). Few studies have pre-specified reversal of prediabetes and restoration of NGR as primary outcome, and current approaches that prevent T2D in people with prediabetes do not always reverse the prediabetes. The present review focuses on studies that have assessed reversal of the prediabetes, and discusses known and emerging predictors of prediabetes. We argue that fuller knowledge of such predictors could inform the discovery of novel, targeted interventions for reversing prediabetes.