Conclusions
These results suggest that adiponectin decreases plasma TG levels by increasing skeletal muscle LPL and VLDLr expression and consequently VLDL-TG catabolism.
Methods
Adenoviruses were used to generate a mouse model with elevated circulating adiponectin. HepG2 and C2C12 cells were treated with recombinant human adiponectin.
Objective
Adiponectin is an adipocyte-derived hormone that plays an important role in glucose and lipid metabolism. The main aims of this study are to investigate the effects of adiponectin on VLDL triglyceride (VLDL-TG) metabolism and the underlying mechanism. Research design and
Results
Three days after Ad-mACRP30 adenovirus injection, plasma adiponectin protein levels were increased 12-fold. All three main multimeric adiponectin molecules were proportionally elevated. Fasting plasma TG levels were significantly decreased (approximately 40%) in the mice with elevated adiponectin in circulation, as were the plasma levels of large and medium VLDL subclasses. Although apolipoprotein B mRNA levels were robustly suppressed in the livers of adiponectin-overexpressing mice and in cultured HepG2 cells treated with recombinant human adiponectin, hepatic VLDL-TG secretion rates were not altered by elevated plasma adiponectin. However, Ad-mACRP30-treated mice exhibited a significant increase of postheparin plasma lipoprotein lipase (LPL) activity compared with mice that received control viral vector. Skeletal muscle LPL activity and mRNA levels of LPL and VLDL receptor (VLDLr) were also increased in Ad-mACRP30-treated mice. Recombinant human adiponectin treatment increased LPL and VLDLr mRNA levels in differentiated C1C12 myotubes. Conclusions: These results suggest that adiponectin decreases plasma TG levels by increasing skeletal muscle LPL and VLDLr expression and consequently VLDL-TG catabolism.