CYP2E1 and obesity due to melanocortin 4 receptor deficiency: Obesity, age, and smoking, as well as consumption of alcohol and certain drugs, have been shown to modulate CYP2E1 expression (Bebia et al. 2004; Benowitz et al. 2003; Frye and Branch 2002; Lieber 2004; Park et al. 1993; Simi and Ingelman-Sundberg 1999).