Dietary monounsaturated fat activates metabolic pathways for triglyceride-rich lipoproteins that involve apolipoproteins E and C-III.
Study Goal
The researchers aimed to determine how monounsaturated fat (MUFA) affects triglyceride-rich lipoprotein (TRL) metabolism, specifically the roles of apolipoproteins E and C-III.
Results Summary
The MUFA-rich diet increased secretion and rapid clearance of TRLs containing apo E and apo C-III while reducing secretion of TRLs without these apolipoproteins, which are major precursors of LDL. It also enhanced TRL fractional catabolic rate and shifted metabolism toward clearance rather than LDL conversion.
Population
Twelve adults
Effective Dosage
24% MUFAs in the MUFA-rich diet (vs. 8% in the carbohydrate-rich diet)
Duration
3 weeks per diet
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
MUFA diet | increase | secretion of VLDLs and IDLs containing both apo E and apo C-III (E+CIII+) | Twelve adults | approximately 4-6-fold | increased by approximately 4-6-fold | #1 |
MUFA diet | decrease | secretion of the TRLs without apo E or apo C-III | Twelve adults | 60% | decreased by 60% | #2 |
MUFA diet | decrease | flux to LDLs from TRLs without apo E or apo C-III | Twelve adults | - | decreased | #3 |
MUFA diet | no change | Total LDL flux | Twelve adults | - | did not change | #4 |
MUFA diet | increase | flux to LDL from E-CIII+ TRLs | Twelve adults | - | increased | #5 |
MUFA diet | increase | TRL fractional catabolic rate | Twelve adults | 50% | significantly increased by 50% | #6 |
MUFA diet | increase | percentage of TRLs that were cleared rather than being converted to LDLs | Twelve adults | doubled | doubled | #7 |
MUFA intake | increase | synthetic and rapid catabolic pathways for TRL metabolism that involve apo E and apo C-III | Twelve adults | - | activates | #8 |
MUFA intake | decrease | metabolism of more slowly metabolized VLDLs and IDLs, which do not contain these apolipoproteins | Twelve adults | - | suppresses | #9 |
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. DESIGN: 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. CONCLUSION: 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.