Aortic collagen alterations in human diabetes mellitus. Changes in basement membrane collagen content and in the susceptibility of total collagen to cyanogen bromide solubilisation

Structural alterations in arterial extracellular matrix components have been suggested to play a role in the development of arterial disease among patients with diabetes mellitus. This study examines the quantity and quality of collagenous components in aortas from diabetic patients. In order to obtain data about the arterial tissue concentration of type IV and V collagen in diabetic and non-diabetic patients, aortas from 21 patients with diabetes (9 with Type 1 (insulin-dependent) diabetes and 12 with Type 2 (non-insulin-dependent) diabetes), were collected at autopsy together with aortas from groups of sex- and age-matched patients. Intima and media samples from normal and fibrous plaque areas from the individual vessels were evaluated. Pulverized, dried and defatted tissue samples were subjected to chemical solubilization with cyanogen bromide and subsequent immuno-chemical quantitation of the dissolved type IV and V collagen in an ELISA. It was found that the concentration of type IV collagen was increased in the tunica media both in plaque and non-plaque areas in the samples from the diabetic patient groups as compared to the non-diabetic groups. No consistent differences in type IV collagen concentrations were found between diabetic and non-diabetic patients in tunica intima. The type V collagen concentrations and the total collagen content were not altered in the diabetic samples. The fraction of the total collagen that was solubilized during cyanogen bromide treatment was determined, and it was found that this fraction was decreased in most tissue areas in the diabetic patient groups.(ABSTRACT TRUNCATED AT 250 WORDS)

[Basal and reactive renin and aldosterone secretion in arterial hypertension of insulin dependent diabetics]

The aim of the study was to assess the significance of the renin-angiotensin-aldosterone system (R-A-A) in the pathogenesis of arterial hypertension in patients with diabetes type I (IDDM). Testing was accomplished in the hospital conditions in a group of 131 patients with long-term IDDM, who beside of diabetes mellitus and its chronic complications did not show any symptoms of additional diseases. The patients were divided in 5 groups (A-E) depending on the type of coexisting late diabetic complications. The control group was consisted of 20 healthy persons matched for sex and age. In each case the following tests were performed: measurement of blood pressure in succumbent position, daily profile of glycemia and glucosuria, Hb A1 level, ophthalmoscopy, functional assessment of kidney and autonomic system status. Tenin activity in plasma (ARO) and plasma aldosterone (ALD) were determined in basal (after 6 h of succumbent position) and after i.v. administration of 40 mg of furosemide and 3 h of standing position (reactive values). In all groups under study the significant decrease of average, basal and reactive ARO was found in comparison with the control group. This abnormality was the most distinct in subjects with diabetic nephropathy. The autonomic neuropathy was abolishing this tendency. The mean concentration ob basal ALD was in all diabetic subgroups similar as in the controls. The mean reactive ALD was however significantly decreased. In diabetes complicated by retinopathy the negative correlation between ARO and systolic, diastolic and mean blood pressure existed. In diabetes complicated by nephropathy the dependence between blood pressure and ARO and ALD was not found.(ABSTRACT TRUNCATED AT 250 WORDS)

Microvascular clearance of macromolecules in skeletal muscle of spontaneously diabetic rats

Microvascular clearance of FITC-Dextran 150 (fluorescein isothiocyanate dextran, MW 150,000) was studied in cremaster muscles of control (BB/W-R) and diabetic (BB/W-DM) rats following daily injections of a full (FD) or a 1/2 (reduced; RD) dose of insulin. The cremaster muscle was placed in an intravital chamber and superfused with bicarbonate buffer (pH 7.4, equilibrated with 95% N2-5% CO2). A 1-hour period of stabilization was followed by the i.v. injection of FITC-dextran 150 and an equilibration period of 45 min. Suffusate samples were collected for 1 h for control measurements. Following this period, bradykinin was applied topically at a concentration of 10(-7) M. Samples were collected for a final hour for the assessment of clearance. The mean +/- SEM FITC-dextran 150 clearance values (microliter/60 min/g) for BB/W-R, BB/W-DM FD, and BB/W-DM RD were 11.5 +/- 1.8, 14.8 +/- 3.4, and 90.5 +/- 12.0, respectively. The corresponding values after topical application of 10(-7) M bradykinin were 23.7 +/- 5.9, 24.2 +/- 4.4, and 98.7 +/- 25.0. Our results indicate that bradykinin evokes a twofold increase in FITC-dextran 150 clearance in the BB/W-R (control) animals and in the BB/W-DM rats receiving full-dose insulin. In contrast, bradykinin does not further enhance the eightfold increase in FITC-Dextran 150 clearance observed in the reduced-insulin dose-treated BB/W-DM group. Thus, our data show that insulin, administered at a full dose, protects the functional integrity of microvascular perm-selectivity in diabetes mellitus.

Tympanometry in patients with insulin-dependent diabetes mellitus

Tympanograms were studied in 53 patients with insulin-dependent diabetes mellitus (IDDM) and 42 randomly selected non-diabetic control subjects, aged between 20 and 40 years, using the Madsen Model ZO 73 Impedance Bridge. Subjects with abnormal tympanic membrane, conductive hearing loss and known reason for hearing impairment (e.g. noise damage) were excluded from the study. The mean tympanogram amplitudes in diabetic patients were significantly lower in both ears than those of control subjects. The duration of diabetes and microvascular complications (nephropathy and retinopathy) were associated with decreased amplitudes. These findings indicate that decreased tympanogram amplitudes in patients with IDDM are probably caused by diabetes of long duration and the microvascular complications associated with it.

Association of elastin glycation and calcium deposit in diabetic rat aorta

The relationship between glycation of the aortic elastin and calcium deposits in the aorta was studied in streptozocin (STZ)-induced diabetic rats. 5-Hydroxymethylfurfural (5-HMF) which was released from aortic elastin by acid, was assayed after STZ treatment as an index of early stage glycation. The amount of released 5-HMF increased at 5 weeks and paradoxically decreased at 10 weeks after STZ treatment, though it remained higher than that of control rats. This paradoxical pattern was reproduced by the in vitro incubation of elastin with glucose and it is presumably due to further advancement of glycation reactions in diabetic rats. The level of 5-HMF did not change significantly in control rats at corresponding time points of 9, 11 and 16 weeks of age. Fluorescence of porcine pancreatic elastase I-digested elastin which served as an index of advanced glycation, increased by 1.6 times at 3 weeks and reached a maximum of 1.9-fold higher than that of control rats at 10 weeks. The calcium content of the aorta at 10 weeks in diabetic rats was significantly increased by 1.4-fold compared with control rats. This study showed that the increased elastin glycation in the aorta even at the early stage of diabetes is associated with calcium deposit in the aorta. These results are consistent with the interpretation that elastin glycation in the aorta is the potential accelerating factor for diabetic macroangiopathy.

Effects of high levels of fatty acids on functional recovery of ischemic hearts from diabetic rats

In this study we determined the effects of high levels of fatty acids on recovery of heart function when present either during or after ischemia. Isolated working hearts from 6-wk streptozotocin diabetic and control rats perfused with 11 mM glucose were subjected to 25 min of global ischemia followed by 30 min of aerobic reperfusion. Four groups were studied: 1) 1.2 mM palmitate present before, during, and after ischemia; 2) 1.2 mM palmitate present before and during ischemia, followed by reperfusion in the absence of palmitate; 3) no palmitate before and during ischemia, followed by 1.2 mM palmitate during reperfusion; and 4) no palmitate before and during ischemia or during reperfusion. In control hearts, palmitate during reperfusion depressed recovery of function regardless of whether palmitate was present or absent during ischemia. In contrast, palmitate present during reperfusion did not depress recovery of mechanical function in the diabetic rat hearts. However, the presence of palmitate during ischemia itself in diabetic rat hearts was detrimental to recovery of mechanical function. The presence of palmitate during ischemia resulted in an accelerated rate of ATP loss and a decreased rate of lactate accumulation during ischemia, although this effect was similar in control and diabetic rat hearts. Our results demonstrate that high concentrations of fatty acids depress functional recovery of control rat hearts during the reperfusion period but depress recovery of function in diabetic rat hearts when present during ischemia itself.

Increases in plasma lysosomal enzymes in type 1 (insulin-dependent) diabetes mellitus: relationship to diabetic complications and glycaemic control

Lysosomal enzymes degrade membrane glycoconjugates, and increased circulating enzyme activity may be an important mechanism in the pathogenesis of diabetic microangiopathy. We have assayed a profile of seven lysosomal enzyme activities (nmol.h-1.ml-1) in platelet-free plasma from 54 Type 1 (insulin-dependent) diabetic subjects (median age 31 years) and 42 matched normal control subjects. A significant increase in median (interquartile range) enzyme activity was measured in diabetic compared to control subjects for beta-D-glucuronidase, 121 (97.7-171) vs 88.8 (62.8-113), p less than 0.001; beta-D-Nacetylglucosaminidase, 693 (568-799) vs 568 (462-686), p less than 0.001; alpha-D-mannosidase, 23.8 (16.7-28.9) vs 14.5 (10.1-20.0), p less than 0.001; and beta-D-galactosidase, 6.94 (6.11-9.99) vs 6.66 (4.78-8.33), p less than 0.04. In contrast, alpha-L-fucosidase, alpha-D-galactosidase and beta-D-mannosidase activities were similar in diabetic and control subjects. None of the enzyme activities differed significantly (p less than 0.05) between 24 diabetic patients with clinical complications and 30 complication-free diabetic patients with similar glycaemic control which does not support the hypothesis that enzyme increases in diabetes arise simply by leakage from damaged tissues. In the diabetic subjects HbA1, median (interquartile range) 9.10 (7.40-10.60), was significantly related to beta-D-glucuronidase (rs = 0.56, p less than 0.001) and beta-D-Nacetylglucosaminidase (rs = 0.55, p less than 0.001). We have therefore demonstrated in diabetic subjects an increase in certain lysosomal glycosidases, that correlates with glycaemic control.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical localization of type IV collagen and laminin in the gingival capillary basement membrane of the diabetic rat

Distribution of type IV collagen and laminin in the gingival capillary basement membrane from streptozotocin-induced diabetic rats was investigated using immunoelectron microscopy. Both type IV collagen and laminin were found throughout the basement membrane. Quantitative analysis revealed that the immunoreactive area for laminin did not change with age, and the width of laminin deposition remained constant, even when diabetes was induced in the animals. However, the immunoreactive area for type IV collagen thickened with age. Further, the width of type IV collagen in the basement membrane increased markedly 36 weeks after diabetes was induced. It was concluded that the thickening of the gingival capillary basement membrane in experimentally induced diabetic rats was due an increase of type IV collagen deposition.

Nonenzymatic glycosylation of macromolecules. Prospects of pharmacologic modulation

Diabetes increases the risk of developing atherosclerotic arterial disease significantly. Although elevated glycohemoglobin was shown to be an independent risk factor in older women in the Framingham Heart Study, the relationship between hyperglycemia and macrovascular disease is complicated by the many other factors that influence atherogenesis in nondiabetic people. Studies in vitro suggest that chronic hyperglycemia may accelerate the atherogenic process through excessive glycation of various components of the arterial wall. These data are reviewed critically, and the biochemistry and pharmacological potential of the glycation-inhibitor aminoguanidine is discussed.

Aminoguanidine, a novel inhibitor of nitric oxide formation, prevents diabetic vascular dysfunction

Increased blood flow and vascular leakage of proteins preferentially affect tissues that are sites of diabetic complications in humans and animals. These vascular changes in diabetic rats are largely prevented by aminoguanidine. Glucose-induced vascular changes in nondiabetic rats are also prevented by aminoguanidine and by NG-monomethyl-L-arginine (NMMA), an established inhibitor of nitric oxide (NO.) formation from L-arginine. Aminoguanidine and NMMA are equipotent inhibitors of interleukin-1 beta-induced 1) nitrite formation (an oxidation product of NO.) and cGMP accumulation by the rat beta-cell insulinoma cell line RINm5F, and 2) inhibition of glucose-stimulated insulin secretion and formation of iron-nitrosyl complexes by islets of Langerhans. In contrast, NMMA is approximately 40 times more potent than aminoquanidine in elevating blood pressure in nondiabetic rats. These results demonstrate that aminoguanidine inhibits NO. production and suggest a role for NO. in the pathogenesis of diabetic vascular complications.

[Microvascular complications in diabetes mellitus. Pathogenetic aspects]

Chronic microvascular complications are important causes of mortality and morbidity in people with diabetes mellitus. After 10 years of disease, nearly 70% of diabetics are affected by retinopathy and about 40% by nephropathy. Genetic factors have a great influence on the development of diabetic microvascular complications, as pointed out by their association with HLA system and Na/Li countertransport, but epidemiological and experimental studies show that the greater role is played by the metabolic milieu. Protein glycation, sorbitol pathway and lipid abnormalities can be responsible for early and fast development of the microvascular complications of diabetes mellitus.

Glycosylation of proteins and microangiopathy

Diabetic complications may result from chronic glycosylation of protein within cells and in the extracellular matrix. Prevention of glycosylation with aminoguanidine has forestalled complications in experimental diabetes.

Tissue-specific regulation of basic fibroblast growth factor mRNA levels by diabetes

Because basic fibroblast growth factor (bFGF) is recognized as an angiogenic factor and diabetes is characterized by multiple vascular complications, including diabetic microangiopathy, we examined the regulation of tissue bFGF mRNA levels by diabetes. Diabetes was induced in male Sprague-Dawley rats by injection of 125 mg/kg body wt i.v. streptozocin (STZ), with intensive insulin therapy initiated in half of the diabetic rats. Rats were killed 96 h postinjection of STZ. Tissue bFGF and insulinlike growth factor I (IGF-I) mRNA levels were measured simultaneously with a solution hybridization-RNase protection assay. bFGF mRNA levels increased from 1.7- to 2.7-fold in eye, heart, lung, and brain from diabetic compared with buffer-injected control rats. In skeletal muscle, bFGF mRNA levels decreased to 23% of control levels, whereas bFGF mRNA levels were unchanged in kidneys from diabetic versus control rats. Changes in tissue bFGF mRNA levels were partially reversed by insulin treatment in all tissues. In contrast, IGF-I mRNA levels were significantly decreased from 15 to 50% of control levels in all tissues studied except those in brain, which decreased to only 85% of control levels. These data demonstrate that bFGF mRNA levels are altered by diabetes in a tissue-specific fashion and are consistent with the hypothesis that increased production of bFGF may contribute to the development of diabetic microangiopathy in some tissues.

Effects of aldose reductase inhibitors on prostacyclin (PGI2) synthesis by aortic rings from rats with streptozotocin-induced diabetes

The effects of aldose reductase inhibitors (ARIs) on the synthesis of prostacyclin (PGI2) by aortic rings from diabetic rats were examined. The ARIs studied were ONO-2235 and isoliquiritigenin, a new compound extracted from glycyrrhizae radix. The content of sorbitol in the sciatic nerve of diabetic rats induced by streptozotocin was significantly increased as compared with that of controls. This increase was significantly inhibited by the administration of an ARI. On the other hand, there was a marked decrease in the synthesis of PGI2 by the diabetic rats compared with the control rats. The decrease in PGI2 synthesis was significantly reversed by the administration of an ARI. Furthermore, the synthesis of PGI2 by the aortic rings was inversely correlated with the content of sorbitol in sciatic nerves. Those observations suggest that an ARI may have a beneficial effect on the vascular synthesis of PGI2 in diabetes mellitus.

[Association of atherosclerosis and nephropathy in diabetes mellitus. Role of lipid anomalies]

Atherosclerosis is the main cause of mortality in diabetic patients, and the incidence of coronary heart disease is increased in the presence of microalbuminuria. The mechanisms of this association are not known and could involve genetic factors (predisposition to hypertension), renal disease and dyslipidemia. An increase in plasma triglyceride and apoprotein B levels, a decrease in plasma HDL cholesterol, qualitative abnormalities of VLDL and HDL are related to cardiovascular risk in diabetic patients. All these factors are worsened by nephropathy. Lipoproteins abnormalities could be involved in the progression of renal injury. In microalbuminuric patients, it seems important to reduce glomerular hyperfiltration and to normalize glycemia and blood pressure in order to prevent impairment of renal injury and dyslipidemia induced by nephropathy. Early treatment of lipoprotein abnormalities could decrease the incidence of cardiovascular complications.

Induction and possible role of fibrinolysis in diabetes mellitus

This article reviews the evidence supporting a relationship between an enhanced tissue injury, increased fibrin formation, defective fibrinolysis, and the evolution of the complications of late diabetic disease. Particular attention is drawn to the role of a defective endothelial cell mediated fibrinolysis with respect to increased fibrin formation and a delayed tissue repair in diabetic patients. Reviewed are studies that indicate that it is possible in patients with diabetes by means of sulfonylurea compounds to increase endothelial cell-produced t-PA without affecting PAI-1. It is advocated that potent compounds should be searched for, with the capability to modify the hemostatic process of the diabetic endothelial cell in order to express more fibrinolytic activity independent of the patient's metabolic state in an attempt to delay the complications of late diabetes.

[Diabetic angiopathies 1990]

In the submitted review the author summarizes recent knowledge on the biochemistry and pathophysiology of diabetic micro- and macroangiopathy. Hyperglycaemia and hyperinsulinaemia are the main cause of a complicated complex of changes which take place at different levels of the organism. Their consequence is an irreversible affection of the vascular wall with a subsequent effect on the organism as a whole.

[Improving home auto-control in diabetic children: reducing atherogenic risk]

Insulin-dependent Diabetes (IDDM) is a major endocrine abnormality in children and the greatest morbi-mortality problems for diabetic patients are those related to cardiovascular complications (macro-microangiopaties), where kept hyperlipidemia and hyperglucemia play a fundamental patogenic role. The programs for optimization of home autocontrol have reduced frequent metabolic derangements. The aim of this study was to analyze the metabolic control state and its relationships with plasma lipids and atherogenic ratios in diabetic patients that were submitted to a program for optimization of home autocontrol of this illness.

MATERIAL AND METHODS

Blood samples were taken fom 49 IDDM, aged 10.53 +/- 0.51 (+/- SEM) years old, with a mean evolution period of 4.34 +/- 0.38 years, at the begining of the program (Stage I) and 6 months later (Stage II). Biochemical Analysis: Total Cholesterol (TC), cholesterol joined to high density lipoprotein (HDLc), Triglycerides (TG) and Phospholipids (Ph) were measured by microspectrphotometric methods. Cholesterol joined to very low and low density lipoproteins (VLDLc and LDLc, respectively) were calculated by Friedwald's formula. Apoproteins A and B (Apo A and Apo B) were measured using Mancini's method, Glycemia levels (Gly) by peroxidase's method, Glycosilated Serum Protein (GSP) by colormetric's method and Glycosilated haemoglobine (HbA1c) by chromatographic separation using cationic interchange microcolumns.

RESULTS

65% of the patients showed a significant decrease in plasma levels of Gly, GSP and HbA1c percentage between Stages I and II (Favourable Metabolic Control).(ABSTRACT TRUNCATED AT 250 WORDS)

Oxygen affinity of hemoglobin and peripheral nerve degeneration in experimental diabetes

Peripheral neuropathy remains a major complication of diabetes. Numerous etiological theories of metabolic and/or vascular disturbances have been suggested including decreased endoneurial oxygen tension with presumed tissue hypoxia. Increases in the affinity of hemoglobin for oxygen (Hb-O2 affinity) may also produce tissue hypoxia and such Hb-O2 affinity changes have been implicated in the pathogenesis of diabetic microangiopathy. In order to test whether affinity hypoxia might contribute to the development of diabetic peripheral neuropathy, we have utilized a rat model of high and normal Hb-O2 affinity produced by backcrossing animals with increased and decreased levels of 2,3-diphosphoglycerate (DPG). Diabetes was induced in ten high and ten low DPG animals with a tail vein injection of 55 mg/kg streptozotocin (STZ). Five animals in each group were treated with 2.4 U protamine zinc insulin (PZI)/day while the remaining animals were untreated. All rats were killed after 30 days, sections of tibial and sural nerve were rapidly removed and processed for teased fiber analysis. A minimum of 125 axons were assessed per nerve for E degeneration (myelin ovoids) using the classification developed by Dyck et al. Untreated animals, regardless of DPG levels, demonstrated 0% neuropathy. In contrast, all insulin-treated animals showed degeneration (0.4-17%) that inversely correlated with the DPG level (r = -0.59, P less than 0.04). The results of this study suggest that the level of RBC DPG (and presumably the Hb-O2 affinity) with its attendant effect on tissue oxygen release may play a role in the development of peripheral neuropathy in STZ-induced diabetic rats treated with insulin.

Immunoglobulin deposits in diabetic microangiopathy. Observations in autopsy materials

Non-enzymatic glycosylation of vascular wall collagen is considered to be most important in the pathogenesis of diabetic microangiopathy, and glycosylated collagens are reported to bind immunoglobulins in vivo. We investigated the occurrence of IgG or IgM deposits in the microvasculature of certain organs of diabetics using routine autopsy materials. Glomerular capillary basement membrane/endothelium was often positive for IgM in diabetics. Endothelial cells of glomerular capillaries were positive for HLA-DR in 6 of 16 diabetics and in 2 of 11 controls. This was associated with IgM or IgG deposits in 5 cases. In the esophagus and/or tongue of diabetics, IgG was frequently deposited in the microvasculature. In total, IgG deposits were found in 13 of 16 diabetics, either in the esophagus or the tongue, but in only 3 of 16 controls. The difference was significant at p less than 0.005. These observations suggest that deposition of immunoglobulins is a component of diabetic microangiopathy. Differences in expression of HLA-DR in glomeruli between diabetics and non-diabetics remain to be explored.

Diabetic microangiopathy in KK mice. VI. Effect of glycemic control on renal glycoprotein metabolism and established glomerulosclerosis

Twenty-three nonobese KK mice with abnormal tolerance to glucose, hyperinsulinemia with insulin resistance and human diabetic-like nephropathy were treated with either saline (12 mice) or glipizide, an oral hypoglycemic compound, 1 mg/kg, (11 mice) from 120 to 360 days of age. These mice develop significant increases in mesangial volume and matrix by 40 days of age. Oral glucose tolerance (OGTT), glucosyltransferase and N-acetyl-beta-glucosaminidase (enzymes involved in synthesis and degradation of kidney glycoproteins, respectively) in the kidney and serum, 24-hr proteinuria, and light microscopy studies of the kidney were performed. Glipizide-treated mice improved their OGTT. There was no difference in body weight; however, a 16% decrease (P less than 0.05) in kidney weight was observed in glipizide-treated mice. Both enzymes were significantly increased in the kidneys of mice treated with glipizide. No difference in serum enzymes was found between the two groups of mice. About 58% of the saline-treated mice had moderate glomerulosclerosis. By contrast, only 27% of glipizide-treated mice had moderate glomerulosclerosis. Also, a significant decrease in proteinuria was found in glipizide-treated mice. These data suggest that glipizide improves glucose metabolism, decreases kidney size, prevents kidney glycoprotein and mesangial matrix accumulation, and reduces proteinuria in type II diabetic KK mice. This indicates that good glycemic control prevents further progression of established diabetic nephropathy in animals.

Long-term bone loss in insulin-dependent diabetic patients with microvascular complications

Insulin-dependent diabetic patients have an approximately 10% decreased bone mineral content (BMC) when they are studied a few years after clinical onset of diabetes. After that time, patients without diabetic microvascular complications have no, or only very little, further bone loss. The aim of the present study was to investigate if any substantial long-term bone loss occurs in diabetic patients with microvascular complications. We studied 19 insulin-dependent diabetic patients with neither physiologic nor pathologic conditions known to interfere with bone metabolism, other than diabetes. BMC was determined twice, with an interval of 11 years. At initial examination, no patient had diabetic microangiopathy, but at final examination 7 patients had developed diabetic microvascular complications while 12 patients had not. As compared with gender- and age-matched controls, both subgroups had significantly decreased BMC at the initial examination. During the study period, the patients with complications showed further bone loss, whereas the subgroup without complications had unchanged decreased BMC. At final examination, BMC was significantly lower in patients with microvascular complications than in patients without them. The biochemistry of bone metabolism showed a significantly increased fasting urinary excretion of calcium and hydroxyproline in patients with complications, but not in the group without complications, and there was a negative correlation between plasma BGP (osteocalcin) and hemoglobin A1C for all patients. These findings indicate that, in addition to a decreased BMC (before or shortly after clinical onset of diabetes), patients who develop microvascular complications also develop ongoing bone loss. This loss may be caused by an increased bone resorption, but decreased bone formation during periods of poor diabetic control may be involved as well.

Effects of felodipine on urinary albumin excretion and metabolic control in hypertensive non-insulin-dependent diabetics

The effect of a blood pressure reduction by 10 mg extended release felodipine once daily on urinary albumin excretion (UAE) as well as the possible diabetogenic effect of felodipine was studied. A 2 X 12 week placebo-controlled double-blind crossover study was performed in 12 hypertensive non-insulin-dependent diabetic (NIDDM) patients without nephropathy on concomitant treatment with beta-blocker and/or a diuretic agent. Metabolic control as estimated by fasting plasma glucose, hemoglobin A1c and fasting plasma C-peptide was unaltered after felodipine. Blood pressure was significantly reduced by felodipine: systolic 166 +/- 26 mm Hg (placebo) v 153 +/- 26 mm Hg (felodipine) (P less than .05) and diastolic 95 +/- 7 mm Hg v 90 +/- 8 mm Hg (P less than .05). Heart rate was unchanged. There was no correlation between blood pressure and UAE, but the relative change in UAE expressed as UAE placebo/UAE felodipine was significantly correlated to the fall in systolic blood pressure (r = 0.64, P = .03) and mean blood pressure (r = 0.66, P = .02). Since microalbuminuria predicts proteinuria and reduced survival, early antihypertensive treatment may be beneficial in NIDDM as it is in IDDM. Long-term consequences on kidney function and mortality remains, however, to be elucidated.

Alterations of the respiratory burst of polymorphonuclear leukocytes from diabetic children. A chemiluminescence study

The respiratory burst of polymorphonuclear leukocytes was investigated in 24 children with insulin dependent diabetes mellitus and 24 healthy controls. This oxygen dependent, membrane associated process generates a number of toxic oxygen metabolites which are implicated in the pathogenesis of endothelial damage. The activity of polymorphonuclear leukocytes was studied in terms of luminol amplified chemiluminescence. It was found that the resting luminol amplified chemiluminescence activity of isolated polymorphonuclear leukocytes from diabetic children was significantly higher than that of controls (342,000 +/- 174,000 cpm vs. 165,000 +/- 82,000 cpm, p less than 0.01). The addition of respiratory burst inhibitors caused a significant reduction of basal chemiluminescence (greater than 80%). When the ratio of phorbol myristate acetate stimulated activity to basal activity was calculated and used as an activation index, it was found to be significantly reduced in diabetics relative to controls (4.29 +/- 2.46 vs. 8.34 +/- 3.21, p less than 0.01). These observations suggest that increased release of toxic oxygen metabolites from polymorphonuclear leukocytes in diabetic subjects may play a role in the development of diabetic angiopathies.

Changes in steady-state levels of mRNAs coding for type IV collagen, laminin and fibronectin following capillary basement membrane thickening in human adult onset diabetes

The development of capillary basement membrane thickening has been linked to microvascular changes known to occur in tissues of patients with type II diabetes. Previous evidence has suggested that capillary basement membrane thickening is due to increased basement membrane synthesis. In this study, skin samples from 8 diabetic patients with confirmed capillary basement membrane thickening and 7 non-diabetic controls were used to assess steady state levels of mRNAs coding for several basement components including pro alpha 1(IV) collagen, laminin and fibronectin. Total RNA was extracted from abdominal skin samples and levels of mRNAs coding for the basement membrane components laminin, fibronectin and pro alpha 1(IV) collagen, a fibrillar collagenous protein, pro alpha 1(I) collagen and an intracellular polypeptide, gamma-actin, were determined by dot blot hybridization analysis. While there were no changes of steady state levels of pro alpha 1(I) collagen mRNA and laminin mRNA, a significant reduction was noted in the quantitative recovery of mRNA levels for pro alpha 1(IV) collagen, gamma-actin and fibronectin in total RNA isolated from the skin of diabetic patients. This reduction in levels of mRNAs coding for basement membrane components contrasts with pathological confirmation of an accumulation of endothelial capillary basement membrane in skin from diabetic patients and suggests that basement membrane thickening arises more as a consequence of reduced basement membrane degradation than elevated synthesis of basement membrane components.

The effect of sulfonylurea therapy on defective calcium movement associated with diabetic cardiomyopathy

Adult rats exposed to 70 mg/kg streptozocin developed characteristic symptoms of overt diabetes, such as muscle wasting and severely elevated blood glucose levels. Chronic treatment of these rats with the sulfonylurea glyburide for a period of 5 weeks did not affect either the weight of the animal or the degree of hyperglycemia. The drug also failed to influence myocardial glucose metabolism. Nevertheless, the decline in myocardial function associated with the diabetic cardiomyopathy was less in the glyburide-treated rats. At higher preload, myocardial work was significantly reduced in the untreated diabetic but was only moderately depressed in the glyburide-treated heart relative to the nondiabetic heart. The improvement in mechanical function was associated with partial recovery of sarcolemmal calcium pump activity. The drug did not alter the initial rate of Na+-Ca2+ exchange, but decreased the capacity of the transport system. The results indicate that glyburide benefits the diabetic heart by a mechanism independent of carbohydrate metabolism.

[The crevicular fluid in diabetics before and after initial periodontal treatment]

In this study gingival crevicular fluid was used as a parameter to estimate the efficacy of initial treatment in diabetic patients. The patients with diabetes had significantly more gingival inflammation before initial treatment than after. A Periotron with Periopaper was used to measure gingival crevicular fluid.

[Prevalence and management of arterial hypertension in diabetic patients treated with insulin]

In small series of selected hypertensive diabetic patients the short-term benefit of antihypertensive treatments is well documented. The purpose of this study was to analyse the management of arterial hypertension in a cohort of 612 insulin-treated diabetic out-patients routinely and consecutively examined in a diabetologic clinic between January 1, 1985 and April 1, 1986. The prevalence of arterial hypertension (i.e. patients with blood pressure values greater than or equal to 160 and/or 95 mmHg or on antihypertensive treatment) was 38 per cent (232 patients). One hundred and eighty-two patients (29.7 per cent) received an antihypertensive treatment (one drug 78 per cent, two drugs 17 per cent, three drugs 5 per cent). In decreasing order of frequency these drugs were: beta-blockers, diuretics, central acting agents, angiotensin-converting enzyme inhibitors and calcium antagonists. In treated hypertensive diabetic patients the mean +/- SD systolic blood pressure (157.1 +/- 19.1 mmHg) and diastolic pressure (85.3 +/- 9.3 mmHg) remained higher than in patients without antihypertensive treatment (133.4 +/- 17.2 and 77.8 +/- 8.3 mmHg respectively). One hundred and forty-two diabetic patients still had blood pressure values greater than or equal to 160 and/or 95 mmHg during visits; 92 were on antihypertensive treatment, 50 were untreated. In hypertensive diabetic patients the mean total glycosylated haemoglobin (HbA1) level was higher than in normotensive diabetic patients (9 +/- 1.6 versus 8.6 +/- 1.8; P less than 0.05). Hypertensive insulin-treated diabetics are the most seriously ill patients, they are under inadequate care. Wrong choice of antihypertensive drugs, incorrect goals of blood pressure reduction, lack of information and education to improve compliance were the main reasons for the poor results of this study.

Influence of prostaglandin E1 on muscular tissue-PO2 in patients with diabetic gangrene

Intraarterial infusions of short acting vasoactive drugs have been established in the treatment of peripheral occlusive disease. We studied the effect of prostaglandin E1 on the tissue pO2 of the tibialis ant. muscle. Using a fast responding polarographic pO2-probe of the hypodermic needle type, tip diameter 300 microns, we made tissue pO2 investigations in 9 patients with diabetic gangrene. pO2-measurements were done before, during and after administration of 0.2 microgram PGE1/min i.a.. PGE1 led to a slight decrease of the mean muscular pO2 during application followed by a reincrease after the end of infusion. It is known that intraarterial PGE1 infusion leads to an increase of transcutaneous pO2 of the forefoot. Our results show, that there is no increase of tissue pO2 of the tibialis ant. muscle. The reason might be a changed distribution of blood flow in favour of an increased oxygenation of the skin due to PGE1 administration.

Modification of anionic sites in myocardial capillary basal laminae of diabetic rats

Capillary basal laminar thickening is a distinctive feature of diabetic microangiopathy; however, the mechanism responsible for this abnormality remains to be clarified. Recent reports have described a reduction in the distribution of anionic sites in diabetic glomerular basement membranes, with the suggestion that this reduction may generate a compensatory synthesis of basal laminar constituents, causing laminar thickening. In order to provide additional information, the character and distribution of the basal laminar anionic profile were examined in the myocardium of diabetic rats. Diabetes mellitus was induced in 14 rats by injection with streptozotocin, ip; 6 rats served as controls. Myocardial tissue was subjected to Charonis' procedure for the demonstration of anionic sites with the cationic electron-dense dye, ruthenium red, following the sacrifice of the animals at intervals up to 11 months after the induction of the diabetes. The tissues were then processed routinely for electron microscopic examination. A total of 20 electron micrographs, at magnifications of 13,000x and 33,000x, were obtained from each rat for the quantitation of anionic sites. A length measuring 6 micron along each basal lamina was utilized for determining the number of anionic loci. Results of this study show that (1) the number and size of anionic sites in myocardial basal laminae is reduced in diabetic rats, (2) this decrease becomes more pronounced with prolongation of the diabetes, (3) it is detectable prior to the demonstration of basal laminar thickening by electron microscopy, and (4) enzyme digestion treatments indicated that heparan sulfate proteoglycan is the essential stainable component of the anionic sites. These findings provide evidence that the laminar anionic profile is altered in the diabetic myocardium and support the view that this abnormality constitutes a significant initial event in the pathogenesis of basal laminar thickening.

Diabetes and hypertension in the elderly

Hypertension combined with diabetes in the elderly is characterized by many important metabolic and cardiovascular changes, among which insulin resistance, hyperinsulinaemia and increased total peripheral resistance appear to be the most relevant. Non-insulin dependent diabetes mellitus is also characterized by insulin resistance and hyperinsulinaemia. Moreover, hyperinsulinaemia itself has been shown to increase total peripheral resistance. Hyperinsulinaemia thus seems to play a key role in the pathophysiology of hypertension in elderly diabetic subjects. Therefore elderly hypertensive diabetic patients should be treated with thiazide diuretics in low doses, calcium channel blockers and alpha-adrenergic blockers.

Captopril does not alter metabolic control in elderly hypertensive diabetics during secondary failure

In elderly patients diabetes and hypertension play an important and synergistic role in the development of cardiovascular complications. For this reason therapy must reduce blood pressure without compromising blood glucose control. We investigated the question of whether captopril, an angiotensin converting enzyme inhibitor, can be used without interference to glucose metabolism in diabetics with secondary failure. Ten elderly hypertensive diabetics (diastolic blood pressure greater than 95 mmHg), maintained in good metabolic control using oral hypoglycaemic agents and insulin, were studied before and after 30 days of captopril at 100 mg/day. We measured the following parameters: blood pressure, heart rate, fructosamine and a daily profile for blood glucose and c-peptide. There was a statistically significant reduction in systolic and diastolic blood pressure. No difference was observed in the levels of blood glucose and fructosamine. Insulin secretion as determined by c-peptide levels was not modified, in contrast with findings reported for the use of beta-blockers, diuretics or nifedipine. It seems that captopril is useful and without side effects, even in secondary-failure diabetic patients characterized by unstable metabolic control.

Hypertension and diabetes

Diabetes mellitus and hypertension are both common diseases, especially with an increasingly aged population. Hypertension accelerates the development of diabetic retinopathy, nephropathy, and peripheral vascular disease in the diabetic patient. Diabetes represents a type of premature aging and hypertension in the diabetic patient is characterized by many of the same pathophysiologic properties seen in the elderly hypertensive patient.

Lipids, clotting factors, and diabetes: endogenous risk factors for cardiovascular disease

Theories of intimal injury leading to plaque formation include platelet adhesion and production of growth factors, hypercholesterolemia, smooth muscle cell proliferation, macrophage activity, defective utilization of low-density lipoproteins via deficient receptors, and deficiency in cellular lysosomal enzymes. High levels of low-density lipoproteins and intermediate-density lipoproteins, as well as their apoproteins, are strong risk factors for cardiovascular disease. The lowering of the cholesterol level has been shown to produce significant regression of atherosclerotic lesions. Data also suggest an interaction between lipids and platelets, although the role of coagulation disorders as an independent risk factor for atherosclerosis is difficult to assess. Although much of the data are controversial, there is evidence that platelet survival time is a strong predictor of severe vessel damage. In addition, some studies have reported decreased activity of antithrombin III with coronary artery disease, and there appears to be a direct correlation between fibrinogen and cholesterol levels. Finally, diabetes mellitus (both types I and II) is a significant independent risk factor for atherosclerosis. The risk is not related to the severity or duration of diabetes, and it appears to be greater in women than in men.

Plasma factors influencing prostacyclin-like activity in patients with diabetic microangiopathy

Plasma factors influencing PGI2-like activity in 19 patients with diabetes mellitus /Dm/ and 17 controls were studied through a comparison with the signs of retinal and glomerular angiopathy. The plasma PGI2 supporting activity /PSA/ was lower in 15 Dm cases than in the controls. Inhibitory activity against PGI2 production was detected in 6 patients. In the cases of more serious retinopathy associated with glomerulopathy, a significantly lower level of PSA was observed than in patients with mild retinopathy without glomerular diseases. The plasma concentrations of total and LDL-cholesterol were significantly higher, while the level of HDL-cholesterol was lower than in the controls. There was a positive correlation between PSA and HDL-cholesterol values and a negative correlation between PSA and LDL-cholesterol levels, which relates to an inhibitory effect of LDL and a protective role of HDL in PGI2 synthesis.