Clustering effects on postprandial insulin secretion and sensitivity in response to meals with different fatty acid compositions

Dietary fatty acids play a role in glucose homeostasis. The aim of this study was to assess the individual relationship between dietary saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids with postprandial b-cell function and insulin sensitivity in subjects with normal and high fasting triglycerides. We assessed postprandial b-cell function (by the insulinogenic index and the ratio of the insulin to glucose areas under the time concentration curve) and insulin sensitivity (by the oral glucose and the minimal model insulin sensitivity indices) over four nonconsecutive, randomly assigned, high fat meals containing a panel of SFA (palmitic and stearic acids), MUFA (palmitoleic and oleic acids) and PUFA (linoleic and alpha linolenic acids) in 14 subjects with normal and in 14 subjects with high fasting triglycerides. The proportions of each fatty acid in the meals and the values for surrogate measures of postprandial b cell function and insulin sensitivity were subjected to a Pearson correlation and hierarchical cluster analysis, which revealed two classes of dietary fatty acids for regulating postprandial glucose homeostasis. We successfully discriminated the adverse effects of SFA palmitic acid from the beneficial effects of MUFA oleic acid on postprandial b cell function and insulin sensitivity both in subjects with normal and high fasting triglycerides. In conclusion, dietary MUFA oleic acid, in contrast to SFA palmitic acid, favours the tuning towards better postprandial glycaemic control in subjects with normal and high fasting triglycerides. (Authors abstract)
 
Information regarding the individual contribution of each dietary SFA and MUFA to postprandial glucose homeostasis in humans is yet unknown. In this study, different dietary fats with a gradual change in the MUFA to SFA ratio were tested in subjects with high fasting triglycerides and reanalysed the previously collected data to investigate whether the content of palmitic acid or stearic acid among the major dietary SFAs in the meals, or the content of oleic acid or palmitoleic acid among the major dietary MUFAs in the meals, displays a linear relationship with surrogate measures of insulin secretion and action in the postprandial period in subjects with normal and high fasting triglycerides. The analysis included linoleic acid and alpha linolenic acid. The results show evidence of specific associations of dietary MUFA oleic acid, in contrast to dietary SFA palmitic acid, with postprandial beta cell function and insulin sensitivity. The study also indicates that dietary SFA stearic, MUFA palmitoleic and PUFA linoleic or alpha linolenic acids remain neutral regarding the antagonism of dietary MUFA oleic and SFA palmitic acids on postprandial glycaemic control. The results provide evidence demonstrating the individual contribution of major dietary SFA, MUFA and PUFA to postprandial beta cell function and insulin sensitivity, both in subjects with normal and high fasting triglycerides. This study shows that postprandial glycaemic control may be at risk from dietary SFA palmitic acid but not SFA stearic acid and may be protected by dietary MUFA oleic acid but not MUFA palmitoleic acid. ALA remained neutral in its effects. (Editors comments)