Effects of metformin on experimentally induced acne on rabbit ear

Evidence for the effectiveness of metformin in the treatment of acne is limited. To assess its efficacy, comedones were experimentally induced in young New Zealand rabbit ear using Isopropyl Myristate (IM) followed by metformin treatment (30 mg/kg bodyweight) for 60 days with continued IM application. In another group, to check whether metformin pre-treatment affects subsequent comedone development by IM, metformin was given for 14 days and then withdrawn (14 days) followed by comedone development with IM and metformin treatment. At different time points, dermatoscopic images of rabbit ear were taken for clinical assessment. Blood and biopsy samples were taken for hormonal assessment, histological examination and gene expression. Histologically confirmed acne model was developed in rabbit ear. Follicular size increased significantly (p = 0.0004 in both groups) upon IM application. Metformin significantly decreased comedones size as observed in dermatoscopic (p = 0.0003 in group I, p = 0.0190 in group II) and histological examination (p = 0.0313 in group I and II). However, size of comedones developed after metformin pretreatment was significantly (p < 0.0001) smaller. The lipid content of sebaceous glands decreased with metformin without any significant changes in the assessed hormones and genetic expression. Overall, metformin was found to be clinically effective in experimentally induced acne and can be used in humans.