Curcumin and insulin resistance-Molecular targets and clinical evidences.

Curcumin ((1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione), the main component of the Indian spice turmeric, has been used in traditional medicine to improve diabetes and its comorbidities. Since the last two decades, scientific research has shown that in addition to its antioxidant properties, curcumin could also work as protein homeostasis regulator and it is able to modulate other intracellular pathways. Curcumin supplementation has been proposed to improve insulin resistance (IR) through the activation of the insulin receptor and its downstream pathways in several experimental models, pointing out that its clinical use may be a good and innocuous strategy to improve IR-related diseases. IR is associated with many diseases and syndromes like carbohydrate intolerance, diabetes, metabolic syndrome, and cardiovascular disease. Therefore, it is imperative to identify safe therapeutic interventions aimed to reduce side effects that could lead the patient to leave the treatment. To date, many clinical trials have been carried out using turmeric and curcumin to improve metabolic syndrome, carbohydrate intolerance, diabetes, and obesity in individuals with IR. Results so far are inconclusive because dose, time of treatment, and type of curcumin can change the study outcome significantly. However, there is some clinical evidence suggesting a beneficial effect of curcumin on IR. In this review, we discuss the factors that could influence curcumin effects in clinical trials aimed to improve IR and related diseases, and the conclusions that can be drawn from results obtained so far.