Effects of metformin on clinical, hormonal and relevant gene expression parameters in patients with acne: an observational study

Abstract Background Acne vulgaris is associated with insulin resistance and elevated insulin-like growth factor-1 (IGF-1). Metformin is commonly used for treatment of acne in patients with polycystic ovarian syndrome (PCOS). However, the benefits of metformin in patients with acne in general are not well established. Aim To study the effectiveness of metformin treatment in patients with acne but who do not have PCOS and to understand the mechanisms of action of metformin in acne not related to PCOS. Method In this observational study, 30 patients with clinically confirmed acne vulgaris were treated with metformin (1000 mg daily) for 3 months without any other topical or systemic active intervention for their acne. The effect of metformin at the clinical, hormonal and genetic level was assessed. Results Metformin monotherapy significantly (P < 0.001) decreased the global acne grading score for acne followed by a marginal increase in insulin; with a significant (P = 0.03) increase in insulin-like growth factor-1 (IGF-1). A significant (P < 0.001) decrease in free androgen index resulting from a significant (P < 0.001) increase in sex hormone-binding globulin (SHBG) with decrease in testosterone was observed. Homeostasis model assessment insulin resistance (HOMA-IR) was not significantly changed. Forkhead box protein O1 (FOXO1) expression was significantly (P = 0.006) downregulated with metformin treatment at the mRNA level without any significant changes at protein level. Expression of lipogenic genes, namely HMGCR, SQLE and ACSL5 (P = 0.001, P = 0.03, P = 0.03, respectively) were also downregulated. Conclusion Metformin monotherapy led to significant clinical improvement in acne, possibly by reducing testosterone, inhibiting FOXO1 and reducing lipid synthesis by decreasing the expression of lipogenic genes.