Regulation of diabetic serum growth factors for human vascular cells by the metabolic control of diabetes mellitus.

Serum factors from non-ketotic poorly controlled non-insulin-dependent diabetic patients stimulated growth and protein synthesis of human arterial smooth muscle cells and fibroblasts by 15-42%, compared to serum factors from well controlled diabetics. In contrast, the growth stimulating effect of pooled sera from well controlled diabetics did not differ from the effect of normal sera. Single sera from the same diabetics before and after improvement of the metabolic control stimulated cell growth to a similar degree as the respective pooled sera from different diabetic populations. As far as increased growth stimulation of vascular cells is related to increased angiopathic risk in diabetics, this metabolic regulation of growth factors supports the demand for a continuous optimal control of diabetic metabolism.

Increased growth of human fibroblasts and arterial smooth muscle cells from diabetic patients related to diabetic serum factors and cell origin.

Fibroblasts from 3 diabetic patients (DF) grew faster, resulting in higher cell counts in the stationary phase than fibroblasts from 3 age-matched healthy volunteers (NF). This difference was apparent when DF or NF were cultured in either diabetic (DS) or normal serum (NS). Diabetic serum increased growth of both DF and NF compared with normal serum. Total protein content per plate paralleled the increase of cell number per plate in relation to cell origin and serum type. DS increased growth and total protein per plate in the arterial smooth muscle cell line from a non-diabetic patient in a way similar to in DF and NF. It is concluded that increased growth of DF in vivo could result in an increased turnover of vascular cells with a shortened replicative lifespan, leading to an accumulation of basal lamina. This effect would be even further accentuated by exposure of DF to DS. Taken together with the increased protein synthesis the accelerated development of diabetic angiopathy could be the final consequence.

Increased growth stimulation of fibroblasts from diabetics by diabetic serum factors of low molecular weight.

Serum factors from non-ketotic poorly controlled diabetic patients when compared to serum factors from normal subjects, stimulate growth and protein synthesis of cultured fibroblasts from diabetic patients by 25-50%. This increased growth stimulating effect of diabetic serum is mainly related to low molecular weight components (mol. wt. < 12,000 daltons), but not to insulin or glucose. These low molecular weight components of diabetic serum are effective only in combination with serum factors of a molecular weight > 12,000 daltons which are essential for initiation and continuous stimulation of cellular growth. As the growth stimulation by diabetic serum factors with a molecular weight < 12,000 daltons does not differ from comparable normal serum factors, the relevance of these serum factors (e.g. growth hormone, lipoproteins) for the increased growth stimulation of mesenchymal cells in diabetes mellitus seems to be only of limited importance. In as much as these in vitro results represent the in vivo situation, chronic exposure of vascular cells from diabetics to these serum factors could be related to the increased angiopathic risk in diabetes mellitus.

Increased growth stimulation of human vascular cells by serum from patients with primary hyper-LDL-cholesterolemia.

Premature atherosclerosis in hypercholesterolemic patients may be due, in part, to increased growth of vascular cells. Therefore, the growth stimulating effect of serum and serum fractions from patients with primary hyper-LDL-cholesterolemia (LDL-cholesterol: 7.5 +/- 1.7 mmol/l) and from healthy subjects on human arterial smooth muscle cells and fibroblasts has been investigated over 5-7 days in culture. Human hypercholesterolemic sera increased the growth of both cell types up to a mean of 133% compared with normal sera (100%) (P less than 0.001). Removal of the dialyzable serum fraction (m.w. less than 3,500 daltons) reduced the growth effect of the hypercholesterolemic sera by 32% (P less than 0.001) and of the normal sera by 11% (P less than 0.01). Readdition of the hypercholesterolemic serum dialysate to its dialyzed serum restored completely the original growth effect. There was no significant difference in growth stimulation between the dialyzed hypercholesterolemic and normal sera excluding a major additional growth effect by LDL-cholesterol. The low molecular weight growth factor(s) of hypercholesterolemic serum (m.w. less than 3,500 daltons) showed a linear dependence of growth stimulation over a 20-fold concentration range. Increased amounts of this factor(s) might easily penetrate the arterial wall, thus contributing to atherogenesis.

Modified low density lipoprotein from diabetic patients causes cholesterol accumulation in human intimal aortic cells.

Fifty-five serum samples from 99 Type 1 and 71 serum samples from 81 Type 2 diabetic patients (56% and 88%, respectively) brought about a 1.5-3.5-fold increase in total cholesterol content of cultured human intimal aortic cells. This atherogenic effect did not correlate with patient's age, diabetes duration or plasma lipid levels, and was mainly due to low density lipoprotein (LDL). Cholesterol accumulation in cells incubated with LDL highly correlated with that in cells exposed to corresponding patient's serum (r = 0.872 and r = 0.811, P < 0.0001, in Type 1 and Type 2 diabetic patients, respectively). In LDL from diabetic patients the sialic acid content was decreased by an average of 30% (P < 0.05), as compared with healthy subjects, and the fructosyl lysine content was increased by an average of 25% (P < 0.05). Atherogenic effect of patients' LDL significantly correlated with their fructosyl lysine content (P < 0.0001) and negatively correlated with sialic acid content (P < 0.0001). Two LDL fractions were further separated from the total LDL preparation by affinity chromatography on Ricinus communis agglutinin-agarose. The bound (desialylated) LDL fraction was characterized by an increased fructosyl lysine content and the altered neutral lipid and phospholipid composition, while non-bound (sialylated) LDL fraction did not differ from normal LDL. Desialylated, but not sialylated, LDL fraction induced massive cholesterol accumulation in cultured cells. In conclusion, the cholesterol accumulating effect of diabetic patients' blood sera is mainly related to atherogenic low density lipoprotein fraction, which is modified in various ways--by increased non-enzymatic glycosylation, desialylation and alterations in lipid composition. This multiple-modified LDL may contribute to the premature atherosclerosis development in diabetes mellitus.

Vascular growth factors and the development of macrovascular disease in diabetes mellitus.

There are two different classes of humoral growth factors for arterial smooth muscle and endothelial cells that age of potential relevance for the development of macrovascular disease inn diabetes mellitus: hormones (growth hormone, insulin like growth factor I and II, insulin) and locally released growth factors of platelet origin. The following hormones have to be considered: Increased growth hormone plasma levels might contribute to macrovascular disease, but its actual relevance remains to be determined. Insulin like growth factor I and II are present in vivo and stimulate growth of vascular cells in vitro but their relevance for macrovascular disease in diabetes is unproven. To insulin, see Dr. Stout's paper. Human platelets contain at least six growth peptides or proteins that all stimulate in vitro growth of arterial wall cells: platelet derived growth factor, epidermal growth factor, platelet derived endothelial cell mitogen, endothelial growth factor, diabetic serum growth factor (DSGF), transforming growth factor-beta. As their plasma concentrations have not been shown to be increased in diabetes increased local availability at sites of stimulated platelet aggregation has been postulated. Therefore, their relevance for macrovascular disease i diabetics is based mainly on circumstantial evidence. The concentration of DSGF of platelet origin depends on the metabolic control: it increases in vivo in poorly controlled diabetics and is normalized after 2-3 weeks of good metabolic control in the same diabetic patient. The growth potency of DSGF from poorly controlled diabetics is greater than that of physiological amounts of insulin or growth hormone.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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. less than 12,000) reduced the growth effect of the diabetic sera by 37% (2p less than 0.005) and of the non-diabetic sera by only 8% (2p less than 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 mol. wt. below 3,500. Ten times the concentration of the low molecular weight growth factor (mol. wt. less than 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 less than 0.01). The growth stimulating potency of this serum fraction (mol. wt. less than 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 degrees C for 30 min, or (b) with two different proteases: Serva pronase E (Streptomyceus griseus) or Calbiochem protease (Subtilisin calsberg).(ABSTRACT TRUNCATED AT 250 WORDS)

Vascular growth factors and the development of macrovascular disease in diabetes mellitus.

The pathogenesis of macrovascular disease in diabetes mellitus is still incompletely understood. Within the various pathomechanisms abnormal growth of vascular cells is well established as an intrinsic part of the angiopathic process. In this regard, there are different groups of vascular growth factors that are of potential relevance for the development of macrovascular disease in diabetes : hormones, locally released growth factors of platelet and of arterial wall cell origin. The following hormones whose blood levels could increase under various conditions in diabetes have to be considered : growth hormone, insulin-like growth factor I and II and insulin. Human platelets contain at least eight growth peptides or proteins that all stimulate in vitro growth of arterial wall cells : platelet-derived-, epidermal-, fibroblast-, diabetic serum-, endothelial- and transforming growth factor, vascular endothelial cell proliferation factor and platelet-derived endothelial cell mitogen. In serum and plasma from type II diabetics only the diabetic serum growth factor has been shown to be increased. Platelets from type I and II diabetic patients contain increased growth stimulating activity. This increased growth activity returned to normal levels in both types of diabetes after strict metabolic control. Arterial endothelial and smooth muscle cells, fibroblasts and monocyte/macrophages of different species release at least in culture a variety of growth factors that could participate in an autocrine or paracrine manner in the growth regulation of the arterial wall. Diabetes may affect the release of these factors, but direct evidence to which degree this would contribute to the development of macrovascular disease is lacking.(ABSTRACT TRUNCATED AT 250 WORDS)