LEP and metabolic syndrome: On the contrary, long-term high concentrations of leptin will cause metabolic dysregulation.[34] Excessive leptin can inhibit the activity of acetyl coenzyme A carboxylase, resulting in increased fatty acid oxidation in muscle.[35] Leptin pro-inflammatory function seems to result in endothelial dysfunction and insulin resistance.[36,37] Based on the above evidence, we could theorize that MetS and leptin can not only affect semen quality alone, but also can interact with each other, aggravating the impact on semen quality.