Sterol O-Acyltransferase 2-Driven Cholesterol Esterification Opposes Liver X Receptor-Stimulated Fecal Neutral Sterol Loss

ACAT1/SOAT1 maintains adipogenic ability in preadipocytes by regulating cholesterol homeostasis

Maintaining cholesterol homeostasis is critical for preserving adipocyte function during the progression of obesity. Despite this, the regulatory role of cholesterol esterification in governing adipocyte expandability has been understudied. Acyl-coenzyme A (CoA):cholesterol acyltransferase / Sterol O-acyltransferase 1 (ACAT1/SOAT1) is the dominant enzyme to synthesize cholesteryl ester in most tissues. Our previous study demonstrated that knockdown of either ACAT1 or ACAT2 impaired adipogenesis. However, the underlying mechanism of how ACAT1 mediates adipogenesis remains unclear. Here, we reported that ACAT1 is the dominant isoform in white adipose tissue of both humans and mice and knocking out ACAT1 reduced fat mass in mice. Furthermore, ACAT1-deficiency inhibited the early stage of adipogenesis via attenuating PPARγ pathway. Mechanistically, ACAT1 deficiency inhibited SREBP2-mediated cholesterol uptake and thus reduced intracellular and plasma membrane cholesterol level during adipogenesis. While replenishing cholesterol could rescue adipogenic master gene - Pparγ's transcription in ACAT1 deficient cells during adipogenesis. Finally, overexpression of catalytically functional ACAT1, not the catalytic-dead ACAT1, rescued cholesterol level and efficiently rescued the transcription of PPARγ, as well as the adipogenesis in ACAT1-deficient preadipocytes. In summary, our study revealed the indispensable role of ACAT1 in adipogenesis via regulating intracellular cholesterol homeostasis.

Inhibition of miR-486 and miR-92a decreases liver and plasma cholesterol levels by modulating lipid-related genes in hyperlipidemic hamsters

In the present study we aimed to evaluate the potential of in vivo inhibition of miR-486 and miR-92a to reverse hyperlipidemia, then to identify and validate their lipid metabolism-related target genes. Male Golden-Syrian hamsters fed a hyperlipidemic (HL) diet (standard chow plus 3% cholesterol and 15% butter, 10 weeks) were injected subcutaneously with lock-nucleic acid inhibitors for either miR-486 or miR-92a. Lipids and miRNAs levels in liver and plasma, and hepatic expression of miRNAs target genes were assessed in all HL hamsters. MiR-486 and miR-92a target genes were identified by miRWalk analysis and validated by 3'UTR cloning in pmirGLO vectors. HL hamsters had increased liver (2.8-fold) and plasma (twofold) miR-486 levels, and increased miR-92a (2.8-fold and 1.8-fold, respectively) compared to normolipidemic hamsters. After 2 weeks treatment, liver and plasma cholesterol levels decreased (23 and 17.5% for anti-miR-486, 16 and 22% for miR-92a inhibition). Hepatic triglycerides and non-esterified fatty acids content decreased also significantly. Bioinformatics analysis and 3'UTR cloning in pmirGLO vector showed that sterol O-acyltransferase-2 (SOAT2) and sterol-regulatory element binding transcription factor-1 (SREBF1) are targeted by miR-486, while ATP-binding cassette G4 (ABCG4) and Niemann-Pick C1 (NPC1) by miR-92a. In HL livers and in cultured HepG2 cells, miR-486 inhibition restored the levels of SOAT2 and SREBF1 expression, while anti-miR-92a restored ABCG4, NPC1 and SOAT2 expression compared to scrambled-treated HL hamsters or cultured cells. In vivo inhibition of miR-486 and miR-92a could be a useful and valuable new approach to correct lipid metabolism dysregulation.