Brown and brown-like beige adipocytes dissipate energy for thermogenesis and have been proposed to combat obesity and metabolic disorders. Uncoupling protein 1 (UCP1) is uniquely expressed in brown and beige adipocytes, and facilitates fuel utilization and energy expenditure. Ectopic UCP1 overexpression improves obesity and insulin resistance in mice. Recently, we utilized the CRISPR/Cas9 synergistic activation mediator and specific gRNAs to boost endogenous UCP1 expression in human white adipocytes. The CRISPR/Cas9 engineered human brown fat-like (referred to as HUMBLE, hereafter) cells had acquired human brown fat features when comparing bona fide human brown adipocytes derived from the same individual. Obese mice receiving a transplantation of HUMBLE cells showed improved glucose tolerance and insulin sensitivity, as well as increased energy expenditure. This was mediated, at least in part, via activation of endogenous brown fat, which showed an increase in heat production and glucose uptake in mice receiving HUMBLE cells. Co-culture with HUMBLE cells or treatment of conditional medium from HUMBLE cells promoted glucose uptake and thermogenesis in brown adipocytes. Metabolomic analysis identified an increased ratio of arginine and asymmetrical dimethylarginine (ADMA) in the sera of mice receiving HUMBLE cell transplantation. Arginine is known to promote nitric oxide biosynthesis, which can activate thermogenic function of brown fat. Consistently, the level of nitric oxide was increased in the endogenous brown fat of mice receiving HUMBLE cells. Inhibition of nitric oxide synthase abolished the HUMBLE cells-mediated activation of brown adipocytes in vitro and in vivo.
In summary, CRISPR/Cas9-mediated activation of endogenous UCP1 expression in human white adipocytes creates brown fat-like features, and activates endogenous brown fat, potentially through arginine-related metabolites to improve the systemic glucose utilization.
C. Wang: None. M. Lundh: None. R. Kriszt: Employee; Self; QuintilesIMS. T. Huang: None. L.O. Leiria: None. F. Shamsi: None. M. Lynes: None. J. Darcy: None. B. Emanuelli: None. M. Kiebish: None. Y. Tseng: Other Relationship; Self; Chugai Pharmaceutical Co., Ltd.. Research Support; Self; MedImmune.