TY - JOUR

T1 - Insulin downregulates C3 gene expression in human HepG2 cells through activation of PPARγ

AU - Shavva, Vladimir S.

AU - Bogomolova, Alexandra M.

AU - Efremov, Alexander M.

AU - Trofimov, Alexander N.

AU - Nikitin, Artemy A.

AU - Babina, Anna V.

AU - Nekrasova, Ekaterina V.

AU - Dizhe, Ella B.

AU - Oleinikova, Galina N.

AU - Missyul, Boris V.

AU - Orlov, Sergey V.

PY - 2018/4/1

Y1 - 2018/4/1

N2 - C3 is an acute phase protein, and thus its plasma concentration increases quickly and drastically during the onset of inflammation. Insulin plays a complex role in inflammation. Elevated level of plasma C3 was shown to correlate with heightened fasting insulin levels and insulin resistance and appears to be a risk factor for the cardiovascular disease and atherosclerosis. The main source of plasma C3 is liver. Nothing is known about effects of insulin on C3 gene expression and protein secretion by hepatocytes. In light of these data we asked if insulin is capable of regulating C3 production in hepatocytes. Here we show that insulin downregulates C3 gene expression in human hepatoma cells HepG2 through activation of PI3K, mTORC1, p38 and MEK1/2 signaling pathways. Transcription factors PPARα, PPARγ, HNF4α and NF-κB are important contributors to this process. Insulin activates PPARγ through PI3K/Akt/mTORC1 pathway, which results in PPARγ binding to DR4 and DR0 cis-acting elements within the C3 promoter and subsequent displacement of HNF4α and PPARα from these sites. As a result PPARα/NF-κB complex, which exists on C3 promoter, is broken down and C3 gene expression is downregulated. The data obtained can potentially be used to explain the molecular mechanism underlying the correlation between heightened level of plasma C3 and insulin resistance in humans.

AB - C3 is an acute phase protein, and thus its plasma concentration increases quickly and drastically during the onset of inflammation. Insulin plays a complex role in inflammation. Elevated level of plasma C3 was shown to correlate with heightened fasting insulin levels and insulin resistance and appears to be a risk factor for the cardiovascular disease and atherosclerosis. The main source of plasma C3 is liver. Nothing is known about effects of insulin on C3 gene expression and protein secretion by hepatocytes. In light of these data we asked if insulin is capable of regulating C3 production in hepatocytes. Here we show that insulin downregulates C3 gene expression in human hepatoma cells HepG2 through activation of PI3K, mTORC1, p38 and MEK1/2 signaling pathways. Transcription factors PPARα, PPARγ, HNF4α and NF-κB are important contributors to this process. Insulin activates PPARγ through PI3K/Akt/mTORC1 pathway, which results in PPARγ binding to DR4 and DR0 cis-acting elements within the C3 promoter and subsequent displacement of HNF4α and PPARα from these sites. As a result PPARα/NF-κB complex, which exists on C3 promoter, is broken down and C3 gene expression is downregulated. The data obtained can potentially be used to explain the molecular mechanism underlying the correlation between heightened level of plasma C3 and insulin resistance in humans.

KW - C3

KW - HepG2

KW - HNF4α

KW - Insulin

KW - PPARα

KW - PPARγ

UR - http://www.scopus.com/inward/record.url?scp=85043508015&partnerID=8YFLogxK

U2 - 10.1016/j.ejcb.2018.03.001

DO - 10.1016/j.ejcb.2018.03.001

M3 - Article

C2 - 29550264

AN - SCOPUS:85043508015

VL - 97

SP - 204

EP - 215

JO - European Journal of Cell Biology

JF - European Journal of Cell Biology

SN - 0171-9335

IS - 3

ER -