Cluster 4, annotated as previously reported lipid-associated macrophages (LAM) for its high expression of TREM2, LGALS3 and LIPA, was the fewest subpopulation and mostly detected in VAT, possibly because LAM mainly relates to the obesity phenotype and functions as a homeostatic mechanism against adipocyte hypertrophy38. The gene discussed is LIPA; the disease is obesity due to melanocortin 4 receptor deficiency.