Absence of AGPAT2 impairs brown adipogenesis, increases IFN stimulated gene expression and alters mitochondrial morphology.

BACKGROUND

Biallelic loss of function variants in AGPAT2, encoding 1-acylglycerol-3-phosphate O-acyltransferase 2, cause congenital generalized lipodystrophy type 1, a disease characterized by near total loss of white adipose tissue and metabolic complications. Agpat2 deficient (Agpat2-/-) mice completely lacks both white and interscapular brown adipose tissue (iBAT). The objective of the present study was to characterize the effects of AGPAT2 deficiency in brown adipocyte differentiation.

METHODS

Preadipocytes obtained from newborn (P0.5) Agpat2-/- and wild type mice iBAT were differentiated into brown adipocytes, compared by RNA microarray, RT-qPCR, High-Content Screening (HCS), western blotting and electron microscopy.

RESULTS

1) Differentiated Agpat2-/- brown adipocytes have fewer lipid-laden cells and lower abundance of Pparγ, Pparα, C/ebpα and Pgc1α, both at the mRNA and protein levels, compared those to wild type cells. Prmd16 levels were equivalent in both, Agpat2-/- and wild type, while Ucp1 was only induced in wild type cells, 2) These differences were not due to lower abundance of preadipocytes, 3) Differentiated Agpat2-/- brown adipocytes are enriched in the mRNA abundance of genes participating in interferon (IFN) type I response, whereas genes involved in mitochondrial homeostasis were decreased, 4) Mitochondria in differentiated Agpat2-/- brown adipocytes had altered morphology and lower mass and contacting sites with lipid droplets concomitant with lower levels of Mitofusin 2 and Perlipin 5.

CONCLUSION

AGPAT2 is necessary for normal brown adipose differentiation. Its absence results in a lower proportion of lipid-laden cells, increased expression of interferon-stimulated genes (ISGs) and alterations in mitochondrial morphology, mass and fewer mitochondria to lipid droplets contacting sites in differentiated brown adipocytes.