CCL5 and obesity due to melanocortin 4 receptor deficiency: In addition, depleting Treg cells in lean mice induces the gene expression of inflammatory mediators (such as TNF-α, IL-6, and CCL5) and impairs the metabolic signal pathway in VAT, whereas expanding Treg cells in HFD-fed obese mice improves metabolic parameters, possibly through the regulation of adipose tissue inflammation, suggesting that Treg cells play crucial roles in the maintenance of immune and metabolic homeostasis of adipose tissue and may have beneficial effects on systemic metabolic abnormalities associated with obesity (31, 41).