Insulin/insulin-like growth factor (IGF-1) signaling is important for a variety of age-related processes. However, whether or not it affects atherosclerosis is unknown.

Six groups of 6 male New Zealand white rabbits were treated for 12weeks under the following conditions: Groups YC and YIGF: Young rabbits (10weeks old) were fed regular chow w/wo IGF-1(Somazon0.1mg/kg/day, s.c.). Groups HC and HIGF: young rabbits were fed HCD (0.5% cholesterol plus regular chow) w/wo IGF-1. Groups OC and OIGF: old rabbits (120weeks old) were fed regular chow w/wo IGF-1.

Plasma lipid levels, endothelial responses and morphological findings did not differ between groups YIGF and YC. Animals in group HC had increased plasma lipid levels and atheromas. In group HIGF, IGF led to atheromas with increased plasma insulin growth factor binding protein 3 (IBP3), inducible nitric oxide synthase(iNOS) expression and nitrotyrosine staining, macrophage staining, SM1 staining and SM embryo staining compared to HC. Basal nitric oxide (NO) release evaluated by plasma NO metabolites (NOx) and cGMP levels were lowest in the HIGF group.

Overall, IGF-1 promoted atherosclerosis by affecting endothelial function and aging. These findings indicate that Insulin/IGF1 may contribute to atherogenesis in the elderly.