Family histories of Type II diabetes and hypertension predict intima-media thickness in patients with Type I diabetes.

AIMS/HYPOTHESIS: Hyperglycaemia predicts microvascular complications but data on macrovascular disease are limited. We searched for predictors of carotid artery intima-media thickness in young adults with Type I (insulin-dependent) diabetes mellitus. METHODS: A total of 71 children (F/M = 34/37) were followed after their diagnosis until they reached 32 +/- 1 years of age, when duration of diabetes averaged 22 +/- 1 years. Cardiovascular risk markers [lipids, blood pressure, smoking, urinary albumin excretion rate, lifetime glycaemic exposure (A(1c) months), exercise habits, alcohol consumption, family history] were evaluated at age 21 +/- 1 for the baseline examination and at age 32 +/- 1 years for the follow-up examination years. During follow-up, intima-media thickness of common and internal carotid arteries and the carotid bulb were quantitated using a high-resolution B-mode ultrasound. RESULTS: In univariate analysis, age, BMI, blood pressure, lifetime glycaemic exposure, a positive family history of Type II (non-insulin-dependent) diabetes mellitus, hypertension and cardiovascular disease were predictors of carotid intima-media thickness. In multivariate analysis, a positive family history of Type II diabetes predicted maximal ( p< 0.05) and common ( p< 0.005) carotid artery intima-media thickness, family history of hypertension predicted increases in maximal ( p< 0.04), and far wall ( p< 0.006) carotid artery intima-media thickness, and lifetime glycaemic exposure was an independent predictor of increased carotid bulb thickness ( p< 0.03). CONCLUSION/INTERPRETATION: Positive family histories of Type II diabetes and hypertension are independent predictors of carotid intima-media thickness in patients with Type I diabetes, and could therefore predispose these patients to atherosclerosis

Time-dependent inhibition of glioblastoma cell proliferation by dexamethasone.

Because of the outstanding importance of the glucocorticoid Dexamethasone (DEX) as supportive therapy in the management of brain tumours, the direct effect of DEX on tumour cell proliferation is of particular interest. Previous in vitro studies led to contradictory results. To characterise more precisely the influence of DEX, we investigated the glioblastoma multiforme (GM) cell lines A172, T98G and 86HG39. Cells were treated with DEX concentrations ranging from 5 x 10(-9) to 5 x 10(-5) M from 24 to 240h under different treatment conditions. Influence of DEX on glioma cell viability was assessed daily for 5 days by MTT-assay: (I) with continuous DEX incubation (acute treatment), (II) in a recultivation period without DEX after 5 days of DEX pre-incubation (pre-treatment), (III) with continuous DEX incubation after 5 days of DEX pre-incubation (combination treatment). DEX acute treatment led to strongly decreased proliferation of A172 cells, whereas T98G and 86HG39 cells remained uninfluenced. In opposite, a time-delayed inhibition of cell proliferation was observed in all three cell lines after DEX pre-treatment. Combination treatment induced a significant increase of the inhibitory effect in A172 and T98G cells. These data show a variable, partial time-dependent inhibitory effect of DEX on the proliferation of GM cells and may open new treatment strategies for malignant brain tumours.

Predictors of abnormal cardiovascular autonomic function measured by frequence domain analysis of heart rate variability and conventional tests in patients with type 1 diabetes.

OBJECTIVE: Frequency domain analysis of heart rate variability (HRV) is used to assess cardiovascular autonomic function. There are no prospective data on the sensitivity of its various components to glycemia or other diabetes-related risk factors compared with conventional tests and with other complications of diabetes. RESEARCH DESIGN AND METHODS: In 1985, possible risk factors of future complications were determined in 115 children with type 1 diabetes. In 1996, the presence of complications (HRV analysis, conventional tests of autonomic function, urinary albumin excretion rate [UAER], and retinopathy) were assessed in 83 of these patients (age 32 +/- 1 years, duration of diabetes 22 +/- 1 years). RESULTS: Poor glycemic control (measured as lifetime glycemic exposure or HbA1c in 1985) was the most important independent predictor of decreases in all measures of absolute power of HRV (total power [TP] and very low frequency, low frequency [LF], and high frequency [HF] power) and square root of the mean square of R-R interval differences but not of changes of normalized measures or ratios (normalized HF and LF LF/HF). Other significant independent predictors of autonomic dysfunction were late age of onset of diabetes, female sex, and high BMI. To examine the sensitivity of the various tests to glycemia, the patients were divided into tertiles based on lifetime glycemic exposure (A1c months). Glycemic exposure in the tertiles averaged 194 +/- 25 A1c months (20 years of HbA1c 0.8% above normal), 556 +/- 19 A1c months(20 years of HbA1c 2.3% above normal), and 963 +/- 30 A1c months (20 years of HbA1c 4% above normal). Tests of complications that were significantly abnormal in patients already in the lowest tertile and were correlated with glycemia were TP and severity of retinopathy. Of conventional tests, only the ratio of length of R-R intervals during expiration to inspiration (E/I ratio) was significantly related to glycemic exposure, but it required high glycemic exposure (20 years of HbA1c 4% above normal) to be abnormal. UAER was significantly increased only in the highest tertile of glycemic exposure. CONCLUSIONS: TP and retinopathy score were much more sensitive to antecedent glycemia than conventional tests of autonomic function or UAER and were significantly abnormal in patients exposed to approximately 20 years' duration of an HbA1c 0.8% above normal.

Insulin-induced decrease in large artery stiffness is impaired in uncomplicated type 1 diabetes mellitus.

Normal insulin action in vivo involves a decrease in stiffness of large arteries (a decrease in aortic pressure augmentation). We determined whether the ability of insulin to decrease arterial stiffness is altered in uncomplicated type 1 diabetes. Nine type 1 diabetic men (age 28+/-2 years, body mass index 24+/-1 kg/m(2)) and 9 matched normal men were studied under normoglycemic hyperinsulinemic (sequential 2-hour insulin infusions of 1 [step 1] and 2 [step 2] mU x kg(-1) x min(-1)) conditions. Central aortic pressure waveforms were synthesized from those recorded in periphery with applanation tonometry on the radial artery and a validated reverse transfer function to construct the central aortic pressure wave every 30 minutes. This allowed the determination of aortic augmentation (the pressure difference between the first and the second systolic peaks) and the augmentation index (augmentation divided by pulse pressure), as the measure of stiffness of large arteries. Whole-body glucose uptake was 44% (step 1) and 37% (step 2) lower (P<0.001) in the diabetic patients than in the normal subjects. At baseline, before the insulin infusion, augmentation averaged 0+/-1 and 2+/-1 mm Hg (NS) and the augmentation index was -1.5+/-4.5% and 4.0+/-3.7% (NS) in the normal and diabetic subjects, respectively. After 1 hour of hyperinsulinemia, the augmentation index had decreased significantly (P<0.01) to -9.5+/-4.8% in the normal subjects but remained at 4.4+/-4.2% in the diabetic patients. A significant decrease was not observed in the diabetic patients until 150 minutes (-1.2+/-4.1%, P<0.05 versus baseline). Whole-body glucose uptake was significantly inversely correlated with the change in the augmentation index during step 1 (r=-0.61, P<0.01). Insulin resistance in type 1 diabetes involves a defect in the ability of insulin to decrease central aortic pressure. This defect could predispose these patients to premature stiffening of large arteries.

Insulin therapy improves endothelial function in type 2 diabetes.

A total of 75 in vivo endothelial function tests (intrabrachial artery infusions of endothelium-dependent [acetylcholine] and -independent [sodium nitroprusside] vasoactive agents) were performed in 18 type 2 diabetic patients (aged 58+/-2 years, body mass index 28.5+/-0.6 kg/m(2), and fasting plasma glucose 229+/-11 mg/dL) and 27 matched normal subjects. These tests were performed before and 6 months after combination therapy with insulin and metformin and before and 6 months after metformin therapy only. Before insulin therapy, blood flow responses to acetylcholine (15 microg/min) were significantly blunted in type 2 diabetic patients (7.5+/-0.7 mL x dL(-1) x min(-1)) compared with normal subjects (11.6+/-0.9 mL x dL(-1) x min(-1), P<0.01). During insulin therapy, the acetylcholine response increased by 44% to 10.8+/-1.6 mL x dL(-1) x min(-1) (P<0.05). Insulin therapy also significantly increased the blood flow responses to both low and high doses of sodium nitroprusside. We conclude that insulin therapy improves endothelium-dependent and -independent vasodilatation. These data support the idea that insulin therapy has beneficial rather than harmful effects on vascular function.

Impaired endothelium-dependent vasodilation in type 2 diabetes. Relation to LDL size, oxidized LDL, and antioxidants.

OBJECTIVE: To search for determinants of endothelial dysfunction in type 2 diabetes. RESEARCH DESIGN AND METHODS: We performed a comprehensive analysis of cardiovascular risk markers and measured blood flow responses to endothelium-dependent (acetylcholine [ACh] and NG-monomethyl-L-arginine) and -independent (sodium nitroprusside [SNP]) vasoactive agents in 30 nonsmoking men with type 2 diabetes (age 51 +/- 1 years, BMI 27.8 +/- 0.4 kg/m2, HbA1c 7.4 +/- 0.3%) and 12 matched normal control men. RESULTS: ACh-induced vasodilation was 37% lower in type 2 diabetic (6.1 +/- 0.5) than in normal subjects (9.7 +/- 1.5 ml.dl-1.min-1, P < 0.01), while flows during SNP were similar (9.1 +/- 0.6 vs. 9.9 +/- 1.3 ml.dl-1.min-1, NS). The ratio of endothelium-dependent vs. -independent flow (ACh:SNP ratio) was 31% lower in type 2 diabetic (0.70 +/- 0.05) than in normal subjects (1.10 +/- 0.18, P < 0.01). Total (2.2 +/- 0.4 vs. 1.3 +/- 0.2 mmol/l, P < 0.05), VLDL, and intermediate-density lipoprotein triglycerides were significantly higher, and the mean LDL particle diameter was significantly smaller in type 2 diabetic than in normal subjects. The lag times for LDL oxidation by Cu2+ in vitro were similar in patients with type 2 diabetes (183 +/- 7) and in normal subjects (183 +/- 9 min, NS). Measured and calculated (sum of concentration of individual antioxidants in serum) total peroxyl radical-trapping capacities (TRAPs) were comparable between the groups. In the patients with type 2 diabetes, LDL size was significantly correlated with endothelium-dependent vasodilation (r = 0.43, P < 0.05), serum triglycerides (r = -0.75, P < 0.001), and the lag time for LDL oxidation in vitro (r = 0.38, P < 0.05). HbA1c was inversely correlated with the lag time for LDL oxidation in vitro (r = -0.41, P < 0.05) and TRAP. CONCLUSIONS: In summary, patients with type 2 diabetes exhibited impaired endothelium-dependent vasodilation in vivo, elevated serum triglycerides, decreased LDL size, and normal antioxidant capacity. Of these parameters, LDL size was significantly correlated with endothelial function.

Serum total renin, an independent marker of the activity and severity of retinopathy in patients with IDDM.

BACKGROUND/AIMS: Recent studies have demonstrated marked renin and prorenin concentration gradients between ocular tissues and blood, and local expression of the renin-angiotensin system (RAS) in the eye. The authors determined whether serum total renin, which mostly consists of prorenin, is a marker of the activity and severity of diabetic retinopathy independent of other microvascular complications. METHODS: Total renin concentrations (TRC) were measured with a time resolved immunofluorometric assay in 38 patients with IDDM (age 34 (SD 7) years, duration of disease 22 (7) years, serum creatinine 95 (15) mumol/l, urinary albumin excretion rate (UAER) 207 (829) micrograms/min, HbA1c 8.5% (1.2%)), and in 13 matched normal subjects. All subjects were carefully characterised with respect to the presence and severity of retinopathy (RP score), nephropathy, and neuropathy using seven different tests of autonomic neuropathy. RESULTS: Serum TRC was on average twofold higher in IDDM (396 (SE 211) ng/l) than in normal subjects (201 (88) ng/l, p < 0.001). It was nearly twofold higher in patients with preproliferative or active proliferative retinopathy requiring careful follow up or therapy (TRC 596 (268) ng/l, n = 11) compared with those with quiescent proliferative retinopathy after laser treatment (TRC 338 (183) ng/l, p < 0.01, n = 5); moderately severe non-proliferative retinopathy (337 (106) ng/l, p < 0.01, n = 13), no retinopathy, or only minimal non-proliferative retinopathy (270 (43) ng/l, p < 0.001, n = 9). In multiple linear regression analysis, RP score (p < 0.01), but not the UAER or any index of autonomic neuropathy, was an independent determinant of serum TRC, and explained 32% of its variation (R = 0.57, p < 0.005). CONCLUSIONS: Serum TRC in patients with diabetic retinopathy is increased independent of renal function and autonomic neuropathy especially in those with severe active changes requiring careful follow up or treatment. These findings support the idea that diabetic retinopathy is the most important determinant of serum TRC in patients with IDDM, and that TRC is produced when retinopathy is active.

Mechanisms of altered hemodynamic and metabolic responses to insulin in patients with insulin-dependent diabetes mellitus and autonomic dysfunction.

Patients with autonomic neuropathy are more susceptible to insulin-induced hypotension than normal subjects, but the mechanisms are unclear. We quantitated the hemodynamic and metabolic effects of two doses of i.v. insulin (1 and 5 mU/kg.min, 120 min each) and several aspects of autonomic function in 28 patients with insulin-dependent diabetes mellitus (IDDM) and in 7 matched normal subjects under standardized normoglycemic conditions. The autonomic function tests included those predominantly assessing the integrity of vagal heart rate control (the expiration inspiration ratio during deep breathing and high frequency power of heart rate variability) and tests measuring sympathetic nervous function (reflex vasoconstriction to cold and blood pressure responses to standing and handgrip). During hyperinsulinemia, heart rate increased less (2 +/- 1 vs. 6 +/- 2 beats/min; P < 0.04) and diastolic blood pressure fell more (-3.1 +/- 1.2 vs. 0.9 +/- 2.1; P = NS) in the patients with IDDM than in the normal subjects. Forearm vascular resistance decreased significantly in the patients with IDDM [by -7.1 +/- 1.4 mm Hg/(mL/dL.min); P < 0.001 for high vs. low dose insulin], but not in the normal subjects (-0.1 +/- 2.5 mm Hg/(mL/dL.min; P = NS). Reflex vasoconstriction to cold was inversely correlated with the decreases in diastolic (r = -0.51; P < 0.005) and systolic (r = -0.59; P < 0.001) blood pressure and forearm vascular resistance (r = -0.53; P < 0.005), but not with the change in heart rate. The expiration inspiration ratio was, however, directly correlated with the insulin-induced change in heart rate (r = 0.63; P < 0.001), but not with diastolic or systolic blood pressure or forearm vascular resistance. Whole body (48 +/- 2 vs. 67 +/- 5 mumol/kg.min; P < 0.005) and forearm (44 +/- 4 vs. 67 +/- 8 mumol/kg.min; P < 0.05) glucose uptake were significantly lower in the IDDM patients than in the normal subjects. The latter could be attributed to a defect in the forearm glucose arterio-venous difference (1.5 +/- 0.1 vs. 2.2 +/- 0.2 mmol/L, respectively; P < 0.01), but not in blood flow. We conclude that both impaired vagal heart rate control and sympathetic nervous dysfunction exaggerate the hemodynamic effects of insulin in patients with IDDM and could contribute to insulin-induced hypotension.

Hyperreactivity to nitrovasodilators in forearm vasculature is related to autonomic dysfunction in insulin-dependent diabetes mellitus.

BACKGROUND: The link between diabetes and vascular disease is poorly understood. Data regarding endothelial function in vivo in patients with insulin-dependent diabetes mellitus (IDDM) have been inconsistent with in vitro studies demonstrating hyperglycemia-induced impairments in endothelium-dependent vasodilation. METHODS AND RESULTS: We determined whether alterations in neural control of the vascular tone might contribute to blood flow responses to intrabrachial infusions of acetylcholine (ACh), sodium nitroprusside (SNP), and L-N-monomethyl-arginine (L-NMMA) in 22 men with IDDM (12 with normoalbuminuria. HbA1c = 8.6 +/- 0.3%; 10 with macroalbuminuria, HbA1c = 8.6 +/- 0.3%) and 11 matched normal men. Autonomic function was assessed from reflex vasoconstriction to cold, the blood pressure response to standing and hand grip, and heart rate variation, including spectral analysis, during controlled breathing, and the Valsalva maneuver. IDDM with macroalbuminuria exhibited hyperresponsiveness to both ACh and SNP compared with the patients with normoalbuminuria or normal subjects. Reflex sympathetic vasoconstriction to cold was severely impaired in the IDDM patients with macroalbuminuria (-19 +/- 6%) compared with normoalbuminuric patients (-39 +/- 5%, P < .05) and normal subjects (-54 +/- 7%, P < .001). The macroalbuminuric patients also had evidence of autonomic dysfunction during controlled and deep breathing tests and during the Valsalva maneuver. Within the group of IDDM patients, neither the urinary albumin excretion rate nor other parameters such as HbA1c or serum cholesterol correlated with forearm blood flow during the vasoactive drug infusions. There were, however, significant inverse correlations between several measures of both sympathetic and parasympathetic autonomic functions and vascular hyperresponsiveness to SNP and ACh. For example, the Valsalva ratio was inversely correlated with the increase in blood flow in response to infusion of 3 (r = -.74, P < .001) and 10 (r = -.73, P < .001) micrograms/min SNP and 7.5 (r = -.73, P < .001) and 15 (r = -.75, P < .001) micrograms/min ACh. CONCLUSIONS: These data are consistent with idea that altered neurotransmission is an important determinant of vascular reactivity of diabetic blood vessels to nitrovasodilators in vivo.

Anti-endothelial cell antibodies in insulin-dependent diabetes mellitus.

The prevalence of IgG class antibodies to endothelial cells (AECA) was studied in 136 young patients with insulin-dependent diabetes mellitus by an enzyme immunoassay using human umbilical cord vein endothelial cells. The patients were divided into four groups according to the time between diagnosis and study and their results were compared with those in control children and blood donors. AECA became progressively more frequent with the duration of diabetes, being 4% in diabetics tested within 2 weeks of diagnosis and reaching 34% after an average disease duration of 11.2 years. They were not more common in patients with neuropathy, retinopathy or nephropathy than in patients without these complications, but were associated with co-existing thyroid disease and IgA deficiency. The results suggest that in insulin-dependent diabetes mellitus AECA are associated with co-existing autoimmune disorders but not with diabetic microvascular disease.

Thyroid peroxidase antibodies in children with autoimmune thyroiditis.

AIMS: To compare the prevalence of thyroid peroxidase antibodies in 25 children with autoimmune thyroid disorders and in 41 children and young adults with type 1 diabetes, and to test the prevalence of thyrotropin receptor antibodies. METHODS: Two commercially available radioimmunoassays for antibodies to thyroid peroxidase, a commercially available agglutination test of particles coated with thyroid microsomal antigens, and a radioimmunoassay for thyrotropin receptor antibodies were used. Patients and controls were studied. RESULTS: One of the radioimmunoassays detected thyroid peroxidase antibodies not only in all children with autoimmune thyroid disorders and children and young adults with type 1 diabetes and thyroid microsomal antibodies, but also in 20% of healthy control children without microsomal antibodies. With this thyroid peroxidase assay and with microsomal agglutination, 94% of the children with autoimmune thyroiditis, 71% of those with Graves' disease, and over 90% of those with type 1 diabetes and thyroid dysfunction tested positive. In the other radioimmunoassay for thyroid peroxidase antibodies thyroid peroxidase antibody titres in half or more of the children with microsomal antibodies failed to reach the level of positivity given by the producers. Eighty five percent of children with Graves' disease and 71% of those with autoimmune thyroiditis had thyrotropin receptor antibodies but so did 35% of children studied for other endocrinological disorders such as delayed growth or puberty. CONCLUSIONS: Testing patients with well characterised disorders of thyroid function and with other endocrine disorders is important in evaluating the efficacy of new diagnostic tests for thyroid autoantibodies.

Frequencies of HLA-DR3, -DR4, -B8 and -Bw62 in diabetic children diagnosed between 1960 and 1990.

An analysis of the HLA-types of 351 children in whom a diagnosis of insulin dependent diabetes mellitus (IDDM) had been made between 1960 and 1990 revealed that although the frequencies of HLA-DR3, -DR4, -DR3/4, -B8 and -Bw62 were increased there was, depending on the year of diagnosis, a marked fluctuation in the frequencies of these HLA-antigens and in the frequency with which -B8 was associated with -DR3 and -Bw62 with -DR4 suggesting heterogeneity/variation in agents initiating/triggering IDDM.

Autoantibodies and autoimmune diseases in young diabetics.

Another autoimmune disease was found to accompany insulin dependent diabetes mellitus (IDDM) in 14% of the young diabetics (n = 14) studied. Thyroid autoimmune disease was the most common of the accompanying autoimmune diseases, and was detected in 11% (n = 15) of the patients. Two thirds of the IDDM patients with autoimmune thyroiditis were hypothyroid, one was hyperthyroid, and 20% lacked detectable thyroid antibodies when thyroid disease was diagnosed. Coeliac disease was found in 2% of the patients, and one had Addison's disease. Autoantibodies were found in one third of the patients. Thyroid microsomal antibodies were detected in 22% of the patients, IgA anti-gliadin in 11%, gastric parietal cell antibodies in 3% and rheumatoid factor in 7%. Autoimmune disease and the relevant autoantibodies coexisted in 11% of the patients. Autoimmune disorders and autoantibodies were not associated to any particular HLA type. The distribution of the HLA-types in the patients was unusual in that the frequency of HLA-DR3 was not increased. The value of autoantibody tests in the diagnosis of functional disorders of the thyroid and of coeliac disease are discussed.