Epidemiological studies demonstrated the importance of postprandial hyperglycemia on the progression of atherosclerosis. However, whether treatment of postprandial hyperglycemia by insulin or insulin secretagogues has a beneficial effect on atherosclerosis has not been elucidated. To elucidate the effects of reduction of postprandial rise of blood glucose by insulin and nateglinide on monocyte adhesion to endothelial cells, we used non-obese type 2 diabetic Goto-Kakizaki (GK) rats fed twice daily, as a model of repetitive postprandial hyperglycemia. We investigated the effects of insulin injection and nateglinide administration just before each meal for 12 weeks on monocyte adhesion to endothelial cells. By setting the doses of insulin and nateglinide, both treatment significantly reduced postprandial hyperglycemia without significant reduction of HbA(1)c. Nateglinide also reduced serum insulin level just after I h meal. Both nateglinide and insulin therapy reduced the number of monocytes adherent to the aortic endothelial layer. Nateglinide, but not insulin, reduced intimal thickness of the thoracic aorta. While increased serum insulin level might be regarded as a factor responsible for the progression of atherosclerosis, our data showed that treatment with pre-meal insulin or nateglinide, which reduces postprandial hyperglycemia, reduced monocyte adhesion to endothelial cells. (c) 2006 Elsevier Inc. All rights reserved.