Sera from Type 2 (non-insulin-dependent) diabetic and healthy subjects contain different amounts of a very low molecular weight growth peptide for vascular cells

Abstract

Summary. Diabetic angiopathy may be due, in part, to increased growth in vascular cells. We have investigated serum growth factors in Type 2 (non-insulin-dependent) diabetic and healthy subjects and their effect on cultured human arterial smooth muscle cells and fibroblasts. Removal of the dialyzable serum fraction (mol. wt. < 12,000) reduced the growth effect of the diabetic sera by 37% (2p < 0.005) and of the nondiabetic sera by only 8% (2p < 0.01). In contrast, there was no difference in growth stimulation between the dialyzed diabetic or non-diabetic sera. Complete recovery of the dialyzable serum growth fraction was also obtained at a tool. wt. below 3,500. Ten times the concentration of the low molecular weight growth factor (tool. wt. <3,500) from diabetic sera stimulated growth of fibroblasts or arterial smooth muscle cells by a mean of 243% or 174% and from non-diabetic sera by a mean of 146% or 137%, respectively (2p<0.01). The growth stimulating potency of this serum fraction (mol. wt. < 3,500) contained in 10% diabetic sera, was two to ten times higher than that of human growth hormone or insulin, added in amounts equivalent to 10% or physiological serum concentrations. This diabetic serum growth factor was further characterized by: (1) linear dependence of growth stimulation over a concentration range of twenty times and by (2) reduction of the growth stimulating activity to control levels by pretreatment: (a) at 95~ for 30rain, or (b) with two different proteases: Serva pronase E (Streptomyceus griseus) or Calbiochem protease (Subtilisin calsberg). Increased amounts of the very low molecular weight serum growth peptide in Type 2 diabetes might easily penetrate the arterial wall, thus contributing to the genesis of angiopathy.Keywords: Type 2 diabetes, very low molecular weight serum growth peptide, human arterial smooth muscle cells, fibroblasts, cell culture, diabetic angiopathy.Increased vascular cell growth contributes, in part, to diabetic angiopathy. This increased growth may be under the influence of growth factors, present in sera of both diabetic and non-diabetic subjects. In Type 2 diabetic subjects, dialyzable serum growth factors (mol. wt. < 12,000) stimulate increased growth and protein synthesis in human arterial smooth muscle cells and fibroblasts [1]. The increased growth-stimulating effect of these diabetic serum factors depends on metabolic control as it tends to occur in poorly controlled but not in well controlled Type 2 diabetes [2].As the nature of these growth factors (tool. wt. < 12,000) is unknown, we have studied their effect on human mesenchymal cells in vitro in relation to (1) their specificity for diabetes, (2) their relative potency compared with growth hormone, insulin, glucagon and cortisol, and (3) their physicochemical properties, including temperature and pH stability, molecular weight and peptide nature. Table 1 shows the clinical data for the poorly controlled Type2 diabetic patients (n = 140) treated with sulphonylurea or diet alone and for the healthy subjects...

Growth-Promoting Effects of Diabetes and Insulin on Arteries: An In Vivo Study of Rat Aorta

“…An as yet unidentified growth peptide of very low molecular weight appears to be responsible. 4 Umeda et al, 22 however, reported that plasma from patients with insulin-dependent diabetes was less capable of stimulating DNA synthesis in cultured smooth muscle cells from rat aorta than was plasma from control subjects. We found that the cellular growth kinetics of injured aortic intima-media did not differ in healthy and in streptozocindiabetic rats.…”