Defective stimulation of proliferation and collagen biosynthesis of human bone cells by serum from diabetic patients

We studied the influence of fasting serum from nine insulin-dependent diabetic children and adolescents under insufficient metabolic control on normal human bone cells in vitro compared with serum from eight sex- and age-matched controls. Cell number 24 h after plating was significantly less under diabetic serum, indicating impaired cell attachment, spreading and initiation of cell proliferation. Cell number after five days was reduced by 1% diabetic serum, while higher serum concentrations had diverging effects on osteoblast proliferation. Collagen synthesis of human osteoblasts was significantly reduced by 8% diabetic serum compared to 8% control serum, while synthesis of non-collagenous proteins was not affected. Duration of diabetes (several weeks up to 12 years) had no influence on these parameters. The serum from one patient, which was studied a second time under excellent metabolic control three months later, however, had lost its inhibitory influence on collagen synthesis of osteoblasts. The pattern of the interstitial collagen types I, III and V was not altered by diabetic serum. These results indicate that defective regulation of proliferation and collagen synthesis of osteoblasts by components present in human diabetic serum may be an important factor in the development of diabetic osteopenia. The negative influence might be explained in part by reduced levels of IGF-I and elevated levels of IGF binding protein-1 in the diabetic sera.