The postprandial increase in blood triglycerides has no direct effect on the brain BOLD response

A previous study showed that ingestion of a liquid meal high in polyunsaturated lipids decreased the blood-oxygenation-level-dependent (BOLD) response measured by functional magnetic resonance imaging (fMRI) during a finger-tapping motor task, and suggested that this effect was due to a direct effect of blood lipids on the cerebral vasculature. This study compared the time course and magnitude of the BOLD response in fixed anatomic locations before and 3 h after ingestion of high versus low lipid content liquid meals (235 ml Ensure Plus [Abbot Labs] with or without 50 ml added canola oil). Blood triglyceride content peaked 3 h after the high lipid meal and was elevated by 33% compared with the low lipid meal. There was no significant effect of meal composition on the time course or magnitude of the BOLD response in fixed-location clusters of voxels which were activated during either a motor (finger-tapping), a visual (flashing checkerboard), or an integrative/cognitive (number addition) block-design task paradigm. The results indicate that increased blood total triglyceride content after a meal with relatively high polyunsaturated fat does not directly alter the hemodynamic BOLD response to neural activity. However, the postprandial effect on BOLD response of other meals with varying fat types and amounts, as well as other nutrients and phytochemicals, remains to be determined.