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.

中文翻译：

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缺少AGPAT2会损害褐色脂肪形成，增加IFN刺激的基因表达并改变线粒体形态。

背景

编码1-酰基甘油-3-磷酸O-酰基转移酶2的AGPAT2中的双等位基因功能缺失导致先天性广义脂肪营养不良1型，这种疾病的特征是白色脂肪组织几乎完全丧失和代谢并发症。缺乏Agpat2（Agpat2 ^-/-）的小鼠完全缺乏白色和肩inter间棕色脂肪组织（iBAT）。本研究的目的是表征AGPAT2缺乏对褐色脂肪细胞分化的影响。

方法

通过RNA微阵列，RT-qPCR，高内涵筛选（HCS），蛋白质印迹和电子显微镜比较，将从新生（P0.5）Agpat2 ^-/-和野生型小鼠iBAT获得的前脂肪细胞分化为褐色脂肪细胞。

结果

1）与野生型细胞相比，在mRNA和蛋白质水平上，分化的Agpat2 ^-/-褐色脂肪细胞的脂质负载细胞较少，Pparγ，Pparα，C /ebpα和Pgc1α的丰度较低。Prmd16水平在Agpat2 ^-/-和野生型中均相等，而Ucp1仅在野生型细胞中诱导； 2）这些差异不是由于前脂肪细胞的丰度较低所​​致； 3）分化的Agpat2 ^-/-棕色脂肪细胞富含参与I型干扰素的基因的mRNA丰度，而参与线粒体稳态的基因减少了。4）分化的Agpat2 ^-/-棕色脂肪细胞的线粒体形态发生了改变，质量降低，接触部位降低。脂质滴伴随着较低的线粒体融合蛋白2和全脂蛋白5水平。

结论

AGPAT2对于正常的棕色脂肪分化是必需的。它的缺失导致载脂细胞的比例降低，干扰素刺激基因（ISG）的表达增加，线粒体形态的改变，线粒体的质量以及接触分化的棕色脂肪细胞中脂滴的线粒体更少。