Stearoyl Coenzyme A Desaturase 4 (SCD4)

SCD4 is expressed exclusively in the heart. SCD4 encodes a 352-amino acid protein that shares 79% sequence identity with the SCD1, SCD2, and SCD3 isoforms. Liver X receptor alpha (LXR alpha) agonists and a high carbohydrate fat-free diet induced SCD4 expression, but unlike SCD1, SCD4 expression was not repressed by dietary polyunsaturated fatty acids. SCD4 mRNA levels were elevated 5-fold in the hearts of leptin-deficient ob/ob mice relative to wild type controls. Treatment of ob/ob mice with leptin decreased mRNA levels of SCD4, whereas levels of SCD1 and SCD2 were not affected. Furthermore, in the hearts of SCD1-deficient mice, SCD4 mRNA levels were induced 3-fold, whereas the levels of SCD2 were not altered. The current studies identify a novel heart-specific SCD isoform that demonstrates tissue-specific regulation by leptin and dietary factors.