|Rodriguez-morato, Jose - Jean Mayer Human Nutrition Research Center On Aging At Tufts University|
|Gallucio, Jean - Jean Mayer Human Nutrition Research Center On Aging At Tufts University|
|Dolnikowski, Gregory - Jean Mayer Human Nutrition Research Center On Aging At Tufts University|
|Lichtenstein, Alice - Jean Mayer Human Nutrition Research Center On Aging At Tufts University|
|Matthan, Nirupa - Jean Mayer Human Nutrition Research Center On Aging At Tufts University|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/18/2018
Publication Date: 6/11/2018
Citation: Rodriguez-Morato, J., Gallucio, J., Dolnikowski, G.G., Lichtenstein, A.H., Matthan, N. 2018. Comparison of the postprandial metabolic fate of 13C-labeled stearic and oleic acids in postmenopausal women [abstract]. American Society of Nutrition. Abstract #OR17-04.
Technical Abstract: Objective: Not all dietary saturated fatty acids behave similarly. Saturated fatty acids (FA) 12:0, 14:0, and 16:0 have hypercholesterolemic effects whereas stearic acid (18:0) appears to have a neutral effect, similar to oleic acid (18:1). The mechanism is frequently attributed to the in vivo conversion of 18:0 to 18:1. This study was designed to compare the metabolic fate of 13C18:0 and 13C18:1 in the fed state after habituation to diets enriched in the corresponding fatty acid. Methods: Hypercholesterolemic postmenopausal women (N=6, >/=50 years; BMI, 25.6 +/-3.0 kg/m^2, LDL-C >/=110 mg/dL) consumed both 18:0 and 18:1 enriched diets for 5 weeks each, according to a randomized-controlled cross-over design. Diets provided 55%E carbohydrate, 15%E protein, and 30%E fat, with half the fat contributed by 18:0 or 18:1, respectively. On day 1 of week 5, following a 12 hour fast, participants receive their usual diet divided into 13 hourly meals beginning at 8 AM. A purified tracer (1.0 mg/kg BW) of 13C18:0 or 13C18:1 was incorporated into the 1:00 PM meal. Serial blood and breath samples were collected throughout day 1 and fasting blood and breath samples on the mornings of days 2 and 3. Plasma FA profile was assessed by GC, isotope enrichment by Q-TOF, and FA oxidation rate (expired 13CO2) by IRMS. Results: Plasma enrichment curves followed a similar pattern but the area under the curve (AUC) of 13C18:0 was higher than 13C18:1 (9,310 vs 5,318 ngh/mL; p<0.05). Interestingly, 13C18:0 was first converted to 13C16:0, desaturated to 13C16:1, then elongated to 13C18:1, the latter being the major metabolite (9%). No FA metabolites of 13C18:1 were detected. A higher proportion of 18:0 and its metabolites (29%) were incorporated into the plasma triglyceride fraction than 18:1 (8%). Breath 13CO2 kinetic curves indicated that 13C18:0 had a 34% lower cumulative oxidation rate than 13C18:1. Conclusion: Results indicate that the neutrality of 18:0 on plasma cholesterol concentrations is not attributable to a single factor. The higher plasma 13C18:0 AUC reflects lower oxidation rates, multi-stage conversion to 18:1, and preferential incorporation along with its metabolites into plasma triglycerides. These data provide new insights on the differential metabolism of 18:0 and 18:1.