Lipoprotein secretion and triglyceride stores in the heart

The genes for apolipoprotein B and microsomal triglyceride transfer protein are expressed in mouse and human heart tissue. Why the heart would express these "lipoprotein assembly" genes has been unclear. Here we demonstrate t hat the beating mouse heart actually secretes spherical lipoproteins. Moreo ver, increased cardiac production of lipoproteins (e.g., in mice that expre ss a human apolipoprotein B transgene) was associated with increased trigly ceride secretion from the heart and decreased stores of triglycerides withi n the heart. Increased cardiac production of lipoproteins also reduced the pathological accumulation of triglycerides that occurs in the hearts of mic e lacking long-chain acyl coenzyme A dehydrogenase. In contrast, blocking h eart lipoprotein secretion (e.g., in heart-specific microsomal triglyceride transfer protein knockout mice) increased cardiac triglyceride stores. Thu s, heart lipoprotein secretion helps regulate cardiac triglyceride stores a nd may protect the heart from the detrimental effects of surplus lipids.