Effects of Ingestion of Long-chain and Medium-chain Triglycerides on Glucose Tolerance in Man

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Abstract
A mild hyperketonemia was induced in 7 normal subjects by oral administration of a medium-chain triglyceride (MCT) composed of C8 and C10 fatty acids. One hour following MCT administration and during the period of hyperketonemia, an intravenous glucose tolerance test was performed on each subject. On other occasions, similar glucose tolerance tests were performed on the same subjects one hour following the ingestion of either water or corn oil. K values for the slopes of the disappearance curves following glucose administration were derived, and mean K values and their standard errors following water, corn oil, and MCT, respectively, were 1.80 [plus or minus] 0.38; 2.64 [plus or minus] 0.41; and 2.99 [plus or minus] 0.89. Thus MCT-induced hyperketonemia did not inhibit the rate of disappearance of the intravenously given glucose. The apparent enhancement of glucose tolerance after ingestion of the MCT and corn oil meals is not readily explained. It is possible that the presence of these fats in the gastrointestinal tract promoted the secretion of certain beta-cytotropic enteric hormones. In addition, the mild hyperketonemia induced by the MCT may, of itself, have accelerated the rate of glucose disappearance by stimulating insulin production. Finally, the medium-chain fatty acids derived from MCT may have enhanced glucose tolerance by virtue of an inhibitory effect on hepatic-glucose output.