Phosphatidylethanolamine is an important inner-leaflet
phospholipid, and
CTP:
phosphoethanolamine cytidylyltransferase-Pcyt2 acts as the main regulator of the de novo
phosphatidylethanolamine synthesis from
ethanolamine and
diacylglycerol. Complete deletion of the mouse Pcyt2 gene is embryonic lethal, and the single-allele deficiency leads to development of the
metabolic syndrome phenotype, including
liver steatosis,
hypertriglyceridemia,
obesity, and
insulin resistance. This study aimed to specifically elucidate the mechanisms of
hypertriglyceridemia in Pcyt2 heterozygous mice (Pcyt2(+/-)). Evidence here shows that unlike 8 week-old mice, 32 week- and 42 week-old Pcyt2(+/-) mice experience increased VLDL secretion and liver
microsomal triglyceride transfer protein activity. Older Pcyt2(+/-) mice also demonstrate increased levels of postprandial plasma TAGs, increased stimulation of genes responsible for intestinal
lipid absorption, transport and
chylomicron secretion, and dramatically elevated plasma Angptl4,
apoB-100, and
apoB-48 content. In addition, plasma HL and LPL activities and TAG clearance following a
lipid challenge were significantly reduced in Pcyt2(+/-) mice relative to control littermates. Collectively, these results establish that the
hypertriglyceridemia that accompanies Pcyt2 deficiency is the result of multiple metabolic adaptations, including elevated hepatic and intestinal
lipoprotein secretion and stimulated expression and/or activity of genes involved in
lipid absorption and transport and
lipoprotein assembly, together with reduced plasma TAG clearance and utilization with peripheral tissues.