Aerobic exercise improves microvascular dysfunction in fructose fed hamsters

• Fructose is an important component of Western daily diets.
• Fructose solution alters glucose metabolism in hamsters.
• Constant sugar ingestion elicits microvascular dysfunction.
• Aerobic exercise has positive effects on fructose microcirculatory deleterious events.
• Microvascular dysfunction elicited by continuous fructose ingestion precedes weight gain.

Fructose is a major diet component directly related to severe damages to the microcirculation and to diseases such as obesity, diabetes and hypertension to which physical activity is pointed out as an important non-pharmacological treatment since its positive effects precede anthropometric improvements. In this study we have investigated the effects of a light/moderate aerobic exercise training (AET) on microcirculatory dysfunction elicited by carbohydrate overload during a period of 5 months. Male hamsters (Mesocricetus auratus) whose drinking water was substituted (F) or not (C) by 10% fructose solution, during 20 weeks, associated or not to AET in the last 4 weeks (EC and EF subgroups) had their microcirculatory function evaluated on the cheek pouch preparation, glucose and insulin tolerance (GTT and ITT) tested. Arterial blood was collected for pO2, pCO2, HCO3−, pH, total CO2, saturated O2 and lactate determinations. Liver fragments were observed using an electron microscope. Microcirculatory responses to acetylcholine [Ach, an endothelium-dependent vasodilator; 10− 8 M — *123.3 ± 7.5% (C), 119.5 ± 1.3% (EC), *98.1 ± 3.2% (F) and 133.6 ± 17.2% (EF); 10− 6 M — *133.0 ± 4.1% (C), 135.6 ± 4.3% (EC), *103.4 ± 4.3% (F) and 134.1 ± 5.9% (EF); 10− 4 M — *167.2 ± 5.0% (C), 162.8 ± 5.4% (EC), *123.8 ± 6.3% (F) and 140.8 ± 5.0% (EF)] and to sodium nitroprusside [SNP, an endothelium-independent vasodilator; 10− 8 M — 118.8 ± 6.8% (C), 114.0 ± 5.0% (EC), 100.2 ± 2.9% (F), 104.9 ± 4.4% (EF); 10− 6 M — 140.6 ± 11.7% (C), 141.7 ± 5.5% (EC), 125.0 ± 4.7% (F), 138.3 ± 2.8% (EF); 10− 4 M — 150.4 ± 10.9% (C), 147.9 ± 6.5% (EC), 139.2 ± 7.3% (F), 155.9 ± 4.7% (EF)] and macromolecular permeability increase induced by 30 min ischemia/reperfusion (I/R) procedure [14.4 ± 3.5 (C), 30.0 ± 1.9 (EC), *112.0 ± 8.8 (F) and *22.4 ± 0.9 leaks/cm2 (EF)] have shown that endothelium-dependent vasodilatation was significantly reduced and I/R induced macromolecular permeability augmented in sedentary fructose (F) subgroup and both improved after AET. Electron microscopy analysis of the liver showed significant differences between exercised and sedentary subgroups with greater amount of glycogen in F subgroups compared to other ones. No significant changes on mean arterial pressure, heart rate or blood gase between subgroups could be detected. Our results point out that AET could normalize microcirculatory dysfunction elicited by long term substitution of drinking water by 10% fructose solution.