Blocking VLDL secretion causes hepatic steatosis but does not affect peripheral lipid stores or insulin sensitivity in mice

Kaori Minehira, Stephen G. Young, Claudio J. Villanueva, Laxman Yetukuri, Matej Oresic, Marc K. Hellerstein, Robert V. Farese . Jr, Jay D. Horton, Frederic Preitner, Bernard Thorens, and Luc Tappy

Department of Physiology, Center for Integrative Genomics, Lausanne 1015

Corresponding Author: kaori.minehira{at}unil.ch

The liver secretes triglyceride-rich very low density lipoproteins (VLDL), and the triglycerides in these particles are taken up by peripheral tissues, mainly by heart, skeletal muscle, and adipose tissue. Blocking hepatic VLDL secretion interferes with the delivery of liver-derived triglycerides to peripheral tissues and results in an accumulation of triglycerides in the liver. However, it is unclear how interfering with hepatic triglyceride secretion affects adiposity, muscle triglyceride stores, and insulin sensitivity. To explore these issues, we examined mice that cannot secrete VLDL [due to the absence of microsomal triglyceride transfer protein (Mttp) in the liver]. These mice exhibit markedly reduced levels of apo-B100 in the plasma along with reduced levels of triglycerides in the plasma. Despite the low plasma triglyceride levels, triglyceride levels in skeletal muscle were unaffected. Adiposity and adipose tissue triglyceride synthesis rates were also normal, and body weight curves were unaffected. Even though the blockade of VLDL secretion caused hepatic steatosis, the mice exhibited normal glucose tolerance and were sensitive to insulin at the whole-body level, as judged by hyperinsulinemic euglycemic clamp studies. Normal hepatic glucose production and insulin signaling were also maintained in the fatty liver induced by Mttp deletion despite increased levels of ceramides and diacylglycerols. Thus, blocking VLDL secretion causes hepatic steatosis without insulin resistance, and there is little effect on muscle triglyceride stores or adiposity.

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