In an early study, chronic treatment with rmIL-22 (300 ng/g, daily injection) (Generon Corporation, Shanghai, China) for 36 days ameliorated fatty liver but did not affect body weight, fasting glucose, and fasting insulin levels in HFD-fed mice [21], while a recent study reported that chronic treatment with low doses of rmIL-22 (R&D systems) (20 ng/g or 100 ng/g body weight, twice a week) ameliorated obesity and metabolic syndrome in HFD-fed mice [20]. This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.