Enrichment Of Triglyceride-Rich Lipoproteins With Apolipoprotein C-I Is Positively Associated With Their Delayed Plasma Clearance Independently Of Other Transferable Apolipoproteins In Postmenopausal Overweight And Obese Women

Background: The role of plasma apolipoprotein (apo) C-I in cardiometabolic risk in humans is unclear. However, in vitro studies showed a dual role for apoC-I, both protective and harmful, depending on the carrier lipoprotein.Objective: We tested the hypothesis that triglyceride (TG)-rich lipoprotein (TRL) apoC-I, not total or HDL apoC-I, is associated with delayed postprandial plasma clearance of TRLs, independently of apoC-II, apoC-III, and apoE.Methods: This cross-sectional study examines the plasma clearance of a C-13-triolein-labeled high-fat meal (68% fat energy) in 20 postmenopausal overweight and obese women [body mass index (in kg/m(2)) >= 27; aged 45-74 y] as the increment change in area under the 6-h postprandial curves (iAUC(6h)) of TRL parameters. Lipoproteins were fractionated by fast-protein LC. Transferable apolipoproteins were measured by ELISA. TRL enrichment with apolipoproteins was calculated by dividing their TRL concentrations by TRL apoB. The effects of human apoC-I and apoC-III on the hydrolysis and storage of H-3-triolein-labeled TRLs were tested in 3T3-L1 adipocytes.Results: TRL apoC-I was positively associated with plasma apo B-48 and total and non-HDL TGs, cholesterol, and apoB (r = 0.52-0.97) and negatively with HDL cholesterol (r = -0.52) and LDL diameter (r = -0.91) (P < 0.05). Total and HDL apoC-I were correlated only with total (r = 0.62) and HDL (r = 0.75) cholesterol. Women with high fasting TRL enrichment with apoC-I (99-365 mu mol apoC-I/mu mol apoB), but not apoC-II, apoC-III, or apoE, had higher iAUC(6h) for TGs (+ 195%), C-13-TGs (+ 319%), and apo B-48 (+ 186%) than those with low enrichment (14-97 mu mol apoC-I/mu mol apoB). The 4-h postprandial increase in TRL apoC-I was associated with a 4-h increase in TRL TGs and iAUC(6h) for TGs, C-13-TGs, and apo B-48 (r = 0.74-0.86, P < 0.001), independently of 4-h changes in TRL apoB, apoC-II, apoC-III, or apoE. ApoC-I and apoC-III inhibited H-3-TRL clearance by adipocytes by > 75% (P < 0.001).Conclusions: TRL enrichment with apoC-I is positively associated with postprandial hypertriglyceridemia and remnant accumulation in postmenopausal overweight and obese women, independently of apoC-II, apoC-III, or apoE, which may be due to inhibiting TRL clearance by adipocytes. Reducing TRL apoC-I may ameliorate delayed postprandial plasma clearance of TRLs and associated risks in humans.