This study presents the results of the research on transcapillary filtration of
plasma proteins in patients with
non-insulin dependent diabetes mellitus (
NIDDM). The aims of the study were as follows: (a) Examination of transcapillary filtration of
plasma proteins in patients with
NIDDM; (b) Search for correlations between metabolic status of diabetes, severity of
diabetic microangiopathy and penetration of individual
protein fractions into the
blister fluid; (c) Examination of the influence of nonenzymatic glycation on
albumin fragmentation and its transcapillary filtration. It was also decided to check whether changes in the
blister fluid would appear earlier than fundal
fluorescein angiography or microalbuminuria, two markers of
diabetic microangiopathy. The study enrolled 34 patients with type II
diabetes mellitus, aged 35-78 years, with a mean disease duration of 12.5 years (SD = 7.8). The control group included 10 non-diabetic volunteers aged 31-76 years. The mean age in both groups did not differ significantly. The
cantharidin blister method was used to study the permeability of capillary vessels. The following laboratory tests were done: concentrations of serum
urea,
creatinine,
glucose,
fructosamine,
glycated hemoglobin,
cholesterol, and
triglycerides. Electrophoretic separation of
proteins in plasma and
blister fluid was performed and the concentration of
fructosamine in fluid was measured. Routine urinalysis was supplemented with microalbuminuria. The eye fundus was inspected and fundal
fluorescein angiography was done. The influence of nonenzymatic glycation on
protein fragmentation and its possible impact on the permeability of capillary vessels was determined with in vitro glycation of
human serum albumin. In patients without
diabetic retinopathy the Cb:Cs ratio for
beta-globulin turned out to be significantly lower than in patients with proliferative retinopathy. Patients with normoalbuminuria had the Cb:Cs ratio for alpha 2-globulin significantly lower than patients with urinary
albumin concentrations > or = 165 mg/L. When the group was divided with regard to serum
fructosamine concentrations, the subgroup with
fructosamine concentrations lower than 3 mmol/L revealed a significantly higher Cb:Cs ratio for
fructosamine than the subgroup with
fructosamine > or = 3 mmol/L. Concentrations of total
protein,
albumin,
beta-globulin and
gamma-globulin in
blister fluid correlated positively with glycemia in the control group.
Blister fluid concentration of
beta-globulin correlated positively with HbAIC concentration. In the study group, total
protein content in
blister fluid correlated negatively with duration of diabetes and level of
glycosuria. Concentrations of
blister fluid alpha 1-globulin and
gamma-globulin correlated negatively with
glycosuria. Concentrations of
blister fluid
beta-globulin correlated negatively with duration of diabetes. Electrophoretic separation of in vitro SDS glycosylated human serum revealed no additional fraction in the incubated samples. Electrophoretic separation of in vitro glycosylated
albumin disclosed co-migration of
albumin monomers incubated for varying times with
glucose.
CONCLUSIONS: 1. Glycation of human serum and
albumin does not cause fragmentation of the
proteins, but decreases transcapillary filtration of
albumin due to change of molecular electric charge. 2. Patients with non-
insulin dependent diabetes and microangiopathic complications reveal increased transcapillary transport of alpha 2- and
beta-globulin in skin. 3. Increased permeability of skin capillary vessels for alpha 2- and
beta-globulin in
diabetic microangiopathy reflects an advanced stage of the disease and may facilitate progression.