New oral fat tolerance tests feature tailoring of the polyunsaturated/saturated fatty acid ratio to elicit a specific postprandial response Mark J. Dekker, Amanda J. Wright, Vera C. Mazurak, Terry E. Graham, Alejandro G. Marangoni, and Lindsay E. Robinson Abstract: The impact of dietary fat on postprandial metabolic biomarkers for obesity-related chronic diseases, such as type-2 diabetes and cardiovascular disease, has received significant recent attention. However, there is no standard method to evaluate the postprandial response to dietary fat alone. Our goals were to develop a novel oral fat tolerance test (OFTT) consisting solely of emulsified lipids tailored for specific fatty acid compositions and to evaluate the functionality of spe- cific ratios of polyunsaturated/saturated fatty acid (P/S) loading on postprandial triacylglyceride (TAG) concentrations. Two OFTTs of emulsified lipids were prepared with specific P/S ratios of 0.2 and 2.0. Physical characteristics of the fat blends, including TAG composition, melting point, and emulsion droplet size were quantified. Healthy, older (age > 45 y) men (n = 8) underwent an 8 h postprandial study wherein they received the OFTT treatment (either the P/S ratio of 0.2 or 2.0), with a total lipid load of 1 g/kg subject body mass. All subjects received both treatments separated by at least 1 week. Both the P/S 0.2 and 2.0 OFTT significantly elevated (p < 0.05) blood TAG and free fatty acid concentrations for 8 h without increasing blood glucose or serum insulin concentrations. The predominant fatty acids contained in the P/S 0.2 (palmitic acid, 16:0) and 2.0 (linoleic acid, 18:2(n–6)) OFTT blends were significantly elevated in the blood (p < 0.05) during their respective postprandial periods. We concluded that blood TAGs are elevated in a specific pattern through the administration of novel OFTTs with specific P/S blends without eliciting an insulin or glucose response. Key words: oral fat tolerance test, postprandial, triacylglycerides, metabolic biomarkers, polyunsaturated/saturated fatty acid ratio, insulin, glucose, free fatty acids. Re ´sume ´: Plusieurs e ´tudes s’inte ´ressent a ` l’impact des graisses alimentaires sur les marqueurs me ´taboliques postprandiaux en pre ´sence de maladies associe ´es a ` l’obe ´site ´ (diabe `te de type 2, maladies cardiovasculaires). Cependant, il n’y a pas de me ´thode standardise ´e pour e ´valuer la re ´ponse postprandiale de l’organisme a ` la consommation de graisses alimentaires seules. Le but de l’e ´tude est de de ´velopper un nouveau test per os de tole ´rance aux graisses alimentaires (OFTT) consistant uniquement d’une e ´mulsion de lipides conc ¸ue pour un ratio d’acides gras spe ´cifiques et d’e ´valuer l’impact fonctionnel d’un me ´lange d’acides gras polyinsature ´s et sature ´s (P/S) sur les concentrations postprandiales de triacylglyce ´rides (TAG). Nous pre ´parons 2 e ´mulsions de lipides pre ´sentant un ratio donne ´ d’acides gras; 0,2 et 2,0 et nous de ´crivons les caracte ´risti- ques physiques des me ´langes de graisses par leur contenu de TAG, leur point d’e ´bullition et la dimension des gouttelettes de l’e ´mulsion. Huit hommes de plus de 45 ans en bonne sante ´ participent aux se ´ances d’une dure ´e de 8 h au cours des- quelles ils consomment un des 2 me ´langes de graisses au ratio donne ´ (0,2 ou 2,0) a ` raison de 1 g/kg de masse corporelle. Tous les sujets consomment l’autre me ´lange une semaine plus tard tout au plus. Les 2 me ´langes causent une augmentation significative des concentrations sanguines de TAG et d’acides gras libres (p < 0,05) qui persiste durant 8 h sans qu’on ob- serve une augmentation du glucose sanguin ou de l’insuline se ´rique. Les acides gras surtout pre ´sents dans les me ´langes dont le ratio est de 0,2 (acide palmitique, 16:0) et de 2,0 (acide linole ´ique, 18:2(n-6)) se retrouvent en concentration signi- ficativement plus grande (p < 0,05) dans le sang au cours des pe ´riodes postprandiales correspondantes. Les concentrations sanguines de TAG augmentent selon des modalite ´s spe ´cifiques apre `s la consommation de me ´langes de graisses alimentai- res au ratio donne ´ sans qu’il y ait une re ´ponse insulinique ou glucose ´e. Mots-cle ´s : test per os de tole ´rance aux graisses alimentaires, postprandial, triacylglyce ´rides, biomarqueurs me ´taboliques, ratio d’acides gras polyinsature ´s/sature ´s, insuline, glucose, acides gras libres. [Traduit par la Re ´daction] Received 4 December 2006. Accepted 19 March 2007. Published on the NRC Research Press Web site at apnm.nrc.ca on 2 November 2007. M.J. Dekker, T.E. Graham, and L.E. Robinson. 1 Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada. A.J. Wright. Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada; Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada. V.C. Mazurak. Alberta Institute for Human Nutrition, University of Alberta, Edmonton, AB T6B 2P5, Canada. A.G. Marangoni. Department of Food Science, University of Guelph, Guelph, ON N1G 2W1, Canada. 1 Corresponding author (e-mail: lrobinso@uoguelph.ca). 1073 Appl. Physiol. Nutr. Metab. 32: 1073–1081 (2007) doi:10.1139/H07-101 # 2007 NRC Canada