Effects of intragastric fructose and dextrose on mesenteric microvascular inflammation and postprandial hyperemia in the rat

Objectives: Fructose superfused on the mesenteric venules of rats induces microvascular inflammation via oxidative stress. It is unknown whether intragastric fructose exerts a similar effect and whether fructose impairs postprandial hyperemia (PPH). The goals were to determine whether intragastric fructose administration promotes leukocyte adherence and whether fructose, owing to its oxidative properties, may also impair nitric oxide–dependent PPH in the mesenteric microcirculation of rats. Methods: Leukocyte adherence to mesenteric venules, arteriolar velocity, and diameter were measured in Sprague‐Dawley rats before and 30 minutes after intragastric (1 mL 0.5 M, ~0.3 g/kg) dextrose (n = 5), fructose (n = 6), and fructose after intravenous injection of the antioxidant α‐lipoic acid (ALA, n = 6). Results: Only fructose increased leukocyte adherence: control 2.3 ± 0.3 per 100 µm; fructose 9.7 ± 1.4 per 100 µm (P < .001). This effect was independent of changes in venular shear rate: control 269 ± 48 s^?1; fructose 181 ± 27 s^?1 (P > .05, r ² = 0.083 for shear rate vs leukocyte adherence). Dextrose had no effect on leukocyte adherence: control 1.52 ± 0.13 per 100 µm; dextrose 2.0 ± 0.7 per 100 µm (P > .05). ALA prevented fructose‐induced leukocyte adherence: control 1.9 ± 0.2 per 100 µm; fructose + ALA 1.8 ± 0.3 per 100 µm (P > .05). Neither fructose nor dextrose induced PPH: arteriolar velocity: control 3.3 ± 0.49 cm/s, fructose 3.06 ± 0.34 cm/s (P > .05); control 3.3 ± 1.0 cm/s, dextrose 3.15 ± 1.1 cm/s (P > .05); arteriolar diameter: control 19.9 ± 1.10 µm, fructose 19.7 ± 1.0 µm (P > .05); control 21.5 ± 2.6, dextrose 20.0 ± 2.7 µm (P > .05). Conclusions: Intragastric fructose induced leukocyte adherence via oxidative stress. Neither dextrose nor fructose induced PPH, likely because of the inhibitory effect of anesthesia on splanchnic vasomotor tone.