Dietary monounsaturated fat activates metabolic pathways for triglyceride-rich lipoproteins that involve apolipoproteins E and C-III.
BACKGROUND
Dietary monounsaturated fat (MUFA) and complex carbohydrates have different effects on triglyceride-rich lipoprotein (TRL) metabolism.


OBJECTIVE
We hypothesized that apolipoprotein (apo) E and apo C-III might be involved in these dietary effects because of their crucial role in TRL metabolism.


METHODS
Twelve adults consumed, for 3 wk each, 2 isocaloric diets: first a carbohydrate-rich diet (48% complex carbohydrate, 8% MUFAs) and then a MUFA-rich diet (31% complex carbohydrate, 24% MUFAs) 12 mo later. The dietary composition of other macronutrients in the 2 diets was similar. Body weight was kept constant. Postprandial apo B kinetic studies using stable-isotope tracers were performed after each dietary intervention. Multiple VLDL, intermediate-density lipoprotein (IDL), and LDL fractions were prepared on the basis of apo E and apo C-III contents.


RESULTS
The MUFA diet increased by approximately 4-6-fold, the secretion of VLDLs and IDLs containing both apo E and apo C-III (E+CIII+) (P < 0.05). These are TRLs that mostly cleared from the circulation and are minor precursors of LDL. The MUFA diet also decreased by 60% (P < 0.05) the secretion of the TRLs without apo E or apo C-III (major precursors of LDL in plasma) and decreased their flux to LDLs. Total LDL flux did not change because the MUFA diet increased the flux to LDL from E-CIII+ TRLs, a process that requires the removal of apo C-III. In addition, the MUFA diet significantly increased the TRL fractional catabolic rate by 50% and doubled the percentage of TRLs that were cleared rather than being converted to LDLs.


CONCLUSIONS
MUFA intake activates synthetic and rapid catabolic pathways for TRL metabolism that involve apo E and apo C-III and suppresses the metabolism of more slowly metabolized VLDLs and IDLs, which do not contain these apolipoproteins.
Zheng
Chunyu
C
Department of Nutrition, Harvard School of Public Health, Boston, MA, USA.
Khoo
Christina
C
Furtado
Jeremy
J
Ikewaki
Katsunori
K
Sacks
Frank M
FM
D053305:Apolipoprotein C-III / Q000097:blood / Q000378:metabolism*; D001057:Apolipoproteins E / Q000097:blood / Q000378:metabolism*; D008078:Cholesterol, LDL / Q000097:blood / Q000378:metabolism; D015243:Cholesterol, VLDL / Q000097:blood / Q000378:metabolism; D018592:Cross-Over Studies; D004032:Diet; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005229:Fatty Acids, Monounsaturated / Q000008:administration & dosage* / Q000378:metabolism; D005260:Female; D006801:Humans; D007700:Kinetics; D008055:Lipids / Q000097:blood; D008074:Lipoproteins / Q000097:blood* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D014280:Triglycerides / Q000097:blood / Q000378:metabolism*
D053305:Apolipoprotein C-III; D001057:Apolipoproteins E; D008078:Cholesterol, LDL; D015243:Cholesterol, VLDL; D004040:Dietary Carbohydrates; D005229:Fatty Acids, Monounsaturated; D008055:Lipids; D008074:Lipoproteins; D014280:Triglycerides