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The biochemical mechanisms by which hyperglycemia causes microvascular disease and neuropathy are poorly understood. Experimental studies have established that oxidative stress is present in diabetic rodents with neuropathy, and that antioxidant therapy is protective. Oxidative stress is also present in human diabetes, but its clinical importance is uncertain. We examined several biochemical measures of oxidative stress in 37 patients with recent-onset (less than 2 years) type 1 diabetes annually in a 3-year longitudinal study. We also performed a comprehensive annual evaluation of somatosensory and autonomic nerve function. A total of 41 control subjects were studied. Malondialdehyde excretion, a measure of lipid peroxidation, was 1.5l ± .1 μmol/g creatinine in the control subjects, but 2.43 ± . 3 in the diabetic patients in year one, 2.39 ± .2 in year two and 1.92 ± .15 in year three, which was different from controls across all years; p

The purpose of this study was to analyze biochemical measures of oxidative stress and assess their relationship to insulin requirements early in type 1 diabetes. Thirty-seven patients enrolled in a 3-yr longitudinal study of the effects of oxidative stress on the early natural history of this disorder. We measured plasma nitrite and nitrate (collectively NOx), nitrotyrosine, and 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)). Plasma NOx was 34.0 +/- 4.9 micro mol/liter in the control subjects and 52.4 +/- 5.1, 50.0 +/- 5.1, and 49.0 +/- 5.2 micro mol/liter in the diabetic patients at the first, second, and third evaluations, respectively (P < 0.01). Nitrotyrosine was 13.3 +/- 2.0 micro mol/liter in controls and 26.8 +/- 4.4, 26.1 +/- 4.3, and 32.7 +/- 4.3 micro mol/liter in the diabetic patients (P < 0.01). 8-Iso-PGF(2alpha) was higher in the poorly controlled than in the well controlled patients. NOx correlated with insulin dose at the first (P < 0.05), second (P < 0.025), and third (P < 0.05) evaluations. 8-Iso-PGF(2alpha) correlated with insulin dose at the first (P < 0.01) and third (P < 0.0025) evaluations. Systemic measures of oxidative stress correlate with insulin requirements in early type 1 diabetes. These results suggest that oxidative stress is taking place in the pancreas and damaging the beta-cell.

The present study was performed to determine whether nitric oxide overproduction is associated with deterioration in peripheral nerve function in type 1 diabetes. We measured peripheral nerve function and biochemical indicators of nitrosative stress annually for 3 years in 37 patients with type 1 diabetes. Plasma nitrite and nitrate (collectively NOx) were 34.0 ± 4.9 μmol/l in the control subjects and 52.4 ± 5.1, 50.0 ± 5.1, and 49.0 ± 5.2 in the diabetic patients at the first, second, and third evaluations, respectively (P < 0.01). Nitrotyrosine (NTY) was 13.3 ± 2.0 μmol/l in the control subjects and 26.8 ± 4.4, 26.1 ± 4.3, and 32.7 ± 4.3 in the diabetic patients (P < 0.01). Uric acid was suppressed by 20% in the diabetic patients (P < 0.001). Composite motor nerve conduction velocity for the median, ulnar, and peroneal nerves was decreased in patients with high versus low NTY (mean Z score −0.522 ± 0.25 versus 0.273 ± 0.22; P < 0.025). Patients with high NOx had decreased sweating, and those with suppressed uric acid had decreased autonomic function. In conclusion, nitrosative stress in early diabetes is associated with suppressed uric acid and deterioration in peripheral nerve function.

Patients with diabetic neuropathy typically have decreased sweating in the feet but excessive sweating in the upper body. Previous studies of sudomotor function in diabetes have included patients with long-standing disease. The present study was designed to test for the early presence of sudomotor dysfunction and to characterize its relation to glycemic control and other aspects of peripheral nerve function. A total of 37 patients (10 males, 27 females) enrolled in a longitudinal study, in which autonomic function was evaluated annually for 3 years. Patients enrolled 2-22 months after the diagnosis of type 1 diabetes. Forty-one age- and sex-matched healthy control subjects were also studied. Sweat production in response to acetylcholine stimulation was dramatically increased in the forearm at the time of the first evaluation (1.67 ± 0.24 μl/cm2 in the diabetic patients vs. 1.04 ± 0.14 μl/cm2 in the control subjects, P < 0.05). Likewise, the ratio of sweating in the forearm to sweating below the waist was higher in the diabetic patients (0.553 ±0.07 μl/cm2) than in the control subjects (0.385 ± 0.04μl/cm2, P < 0.05). Forearm sweat was negatively associated with the renin-to-prorenin ratio and vanillylmandelic acid (VMA)excretion (P < 0.025), tests of sympathetic nerve function. The ratio of sweating in the forearm to sweating in the foot was likewise increased in diabetic patients with poor glycemic control. We interpret this redistribution of sudomotor responses to be indicative of sympathetic nerve injury and conclude 1) that the sympathetic nervous system is especially vulnerable to the adverse effects of chronic hyperglycemia and 2) that sympathetic dysfunction can be detected very early in type 1 diabetes.

It is well documented that diabetic patients with chronic complications have decreased renin secretion and elevations in the renin precursor prorenin. It is uncertain, however, whether the abnormal processing of prorenin is reflective of microvascular disease, hypertension, or autonomic neuropathy. Dechaux et al. (Transplant Proc. 18:1598–1599, 1986) observed abnormalities in prorenin processing in uncomplicated diabetes and suggested that it was the result of subclinical autonomic neuropathy. To test this hypothesis, we measured renin, prorenin, and autonomic function in early type 1 diabetes at a time when there is little or no microvascular disease or hypervolemia. Thirty-seven patients (10 males, 27 females) enrolled 2–22 months after diagnosis in a longitudinal study in which renin, prorenin, and autonomic function were measured annually for 3 years. Forty-one age-matched control subjects were also studied. PRA in the diabetic patients at the time of the second and third evaluations was 1.71 ± 0.24 ng angiotensin I/mL·h and 1.67± 0.24 ng angiotensin I/mL·h, respectively, significantly lower (P < 0.05) than that of the control subjects in whom PRA was 2.96 ± 0.38 ng angiotensin I/mL·h. Prorenin was not different in the diabetic patients in comparison with controls. The renin to prorenin ratio in the diabetic patients at the time of the first, second, and third evaluations was 0.260 ± 0.03, 0.235± 0.05, and 0.227 ± 0.05, respectively, significantly lower (P < 0.01) than in control subjects in whom the renin to prorenin ratio was 0.475 ± 0.08. Despite this, at the time of the first and second evaluations, there was no evidence of autonomic dysfunction and no correlation between any test of autonomic function and the renin to prorenin ratio. At the time of the third evaluation, however, the intermediate frequency (0.04–0.15 Hz) power spectra while patients were supine (an index of sympathetic modulation of heart rate variability) showed a highly significant (P < .001) correlation with the renin to prorenin ratio. High frequency (0.15–0.40 Hz) spectra from supine patients at the third evaluation also correlated with the renin to prorenin ratio (P < 0.01). We conclude abnormal processing of prorenin develops in diabetic patients prior to microvascular disease, even before the first evidence of autonomic dysfunction. Although the latter may play a contributory role, additional as yet unidentified mechanisms seem to interrupt the processing of prorenin in early diabetes.

The purpose of this study was to compare two treatments for orthostatic hypotension, midodrine (an alpha adrenergic agonist), and octreotide (an SRIH analogue) to each other and to combination therapy. Sixteen patients participated. Our hypothesis was that the 2 drugs together would be more effective than either drug alone. The effect of the drugs on the hemodynamic response to food ingestion was evaluated while patients were sitting. Midodrine (5 mg orally, 30 min before breakfast) increased mean blood pressure slightly (5-10 mm Hg, over 30 min) before the patients started eating, but it only partially reversed the hypotensive effect of food ingestion. The nadir in postprandial blood pressure after midodrine was 69 +/- 4 mm Hg, not different from placebo (63 +/- 5). Nevertheless, midodrine accentuated the response to sc octreotide (0.5 microgram/kg). Fifteen minutes after octreotide administration to midodrine-pretreated patients, the average mean blood pressure was 115 +/- 9 mm Hg, higher (P = .0095) than after octreotide given alone (102 +/- 7). Drug effects on orthostatic hypotension were assessed by measuring standing time (minutes before symptoms of hypotension or definite hypotension). In the absence of treatment, standing time was 3.5 +/- 7 min; 1 h after 10 mg midodrine, 8.4 +/- 2.7 min (P = .11); after 1.0 microgram/kg octreotide, 13.2 +/- 3.9 min (P = .0034 vs. no treatment); and after both drugs, 21.2 +/- 5.5 min (P = .0002 vs. no treatment, P = .036 vs. octreotide only). The combination of midodrine and octreotide is more potent than either drug alone.

OBJECTIVE To analyze the effect of antibodies to glutamic acid decarboxylase (GAD65Ab) and islet cells (ICA512Ab) on glycemic control early in IDDM. RESEARCH DESIGN AND METHODS GAD65Ab and ICA512Ab were measured twice in 35 patients (10 male, 25 female; age 10–40 years) initially within 2 years of diagnosis and again 1 year later. The glycosylated hemoglobin was measured one to four times each year, and the average glycosylated hemoglobin for the preceding year was calculated each time the antibodies were measured. RESULTS The mean HbA1 at the time of the initial evaluation was 8.04 ± 0.30 (reference range 4.7–7.3% for nondiabetic patients), the average GAD65Ab index was 0.735 ± 0.306, and the mean ICA512Ab index was 1.94 ± 0.65. The GAD65Ab index correlated with HbA1 (r = 0.41, P < 0.025), whereas the ICA512Ab index did not (r = 0.13). One year later, the mean GAD65Ab index was 0.94 ± 0.34, the mean ICA512Ab index was 1.04 ± 0.40, and the mean HbA1 was 9.03 ± 0.30. The GAD65Ab index correlated with HbA1 (r = 0.61 P < 0.001), whereas the ICA512Ab index did not (r = −0.06). Stratification of patients into tertiles according to the average GAD65 index revealed, at the follow-up evaluation, that the better glycemic control in the lowest GAD65Ab tertile was accomplished with significantly less insulin (0.43 ± 0.08 U/kg for the lowest tertile vs. 0.71 ± 0.09 and 0.64 ± 0.09 for the middle and highest tertiles, respectively; P < 0.05). CONCLUSIONS In summary, patients with IDDM and low GAD65Ab have better glycemic control even though they require less insulin. The ICA512Ab index, however, fails to correlate with glycemia.

Oxidative stress damages DNA in experimental diabetes, and in vitro studies have suggested that it is linked to lipid peroxidation. The objective of the study was to determine whether lipid peroxidation, as assessed with malondialdehyde excretion in recent-onset type 1 diabetes mellitus, is associated with oxidative damage to DNA, as assessed from 8-hydroxydeoxyguanosine excretion. A 3-year longitudinal study of recent-onset type 1 diabetes mellitus was performed. Age- and sex-matched control subjects were studied once. Patients were studied as inpatients at West Virginia University Hospitals. Thirty-seven patients with recent-onset (2-22 months) type 1 diabetes mellitus (male, 10; female, 27) were enrolled in a longitudinal study of oxidative stress. The mean age of the patients was 20 years. None of the patients had hyperlipidemia or were treated with lipid-lowering drugs. Only 1 patient had hypertension and was being treated with beta-adrenergic blocking therapy. Thirty-six patients completed the study; one withdrew after the second evaluation. Lipid peroxidation was assessed by measuring malondialdehyde excretion. Oxidative damage to DNA was assessed from 8-hydroxydeoxyguanosine excretion. Malondialdehyde excretion was increased in the diabetic patients at the first evaluation (2.43 +/- 0.31 micromol/g creatinine), second evaluation (2.34 +/- 0.24), and third evaluation (1.93 +/- 0.15) compared with control subjects (1.51 +/- 0.11) (P.005). 8-Hydroxydeoxyguanosine excretion, however, was not increased in the diabetic patients. There was no correlation between malondialdehyde and 8-hydroxydeoxyguanosine excretion. We confirmed the presence of oxidative stress in early diabetes as assessed from malondialdehyde excretion. We were unable, however, to confirm oxidative damage to DNA in this cohort of patients; and there was no evidence of a correlation between lipid peroxidation and DNA damage.

We have previously documented that octreotide therapy suppresses sweating and palpitations in patients with the postural tachycardia syndrome. We now report that octreotide also suppresses these and related symptoms in patients with postmenopausal hot flushes.

The purpose of this study was to determine whether autonomic neuropathy and the postural tachycardia syndrome can be treated with octreotide LAR (Long Acting Release). This was an open-label pilot project. Protocol 1 Patients with autonomic neuropathy (n = 4) were given increasing doses of octreotide LAR once a month for three months. Blood pressure was measured in the sitting posture every two weeks. Pretreatment mean blood pressure averaged 83.8 +/- 7.1 mm Hg. After four, six and eight weeks of therapy the blood pressures averaged 96.3 +/- 6.4, 98.2 +/- 6.1 (p < .025), and 104.1 +/- 3.1 (p < .025) respectively. Therapy led to a dramatic improvement in symptoms in one patient but another had an unacceptable elevation in supine blood pressure. Protocol 2 Patients with POTS or orthostatic intolerance were given 10, 20, or 30 mg of octreotide LAR over three months. Seven patients entered and five completed the study. After two months treatment, standing time increased from 36.0 +/- 9.2 to 59.2 +/- .8 minutes (p < .01). Heart rate in the standing position was suppressed from 106 +/- .83 to 93.2 +/- .8 beats per minute (p < .05). Orthostatic dizziness and chronic fatigue improved. We conclude that octreotide LAR can be used to treat autonomic neuropathy but there is a risk of an excessive pressor response. Octreotide LAR improved standing time and suppressed tachycardia in patients with orthostatic intolerance.

Antibodies to the smaller isoform of glutamic acid decarboxylase (GAD65Ab) have been linked to the presence of neuropathy in Type 1 diabetes in several small studies. We attempted to confirm this association by measuring GAD65Ab, GAD65Ab epitopes and IA-2Ab in 511 patients who participated in the Diabetes Control and Complications Trial (DCCT). We also tested for correlations between these autoantibodies and C-peptide and glycemic control. We only included patients for whom serum was available from the first 4 years of their illness. The presence or absence of neuropathy was determined by electrophysiological studies, autonomic testing and clinical evaluation at baseline and 5 years into the trial or at close out. Samples from controls (patients without neuropathy at 5 years) were selected for patients who had similar C-peptide responses to a standardized meal at baseline. The GAD65Ab index correlated with HgbA(1c) only in the adult participants and only at baseline. The adults initially in poor control (upper tertile for glycemia) had higher GAD65Ab and lower C-peptides. The GAD65Ab index was not significantly different in patients with confirmed clinical neuropathy at 5 years versus controls matched for C-peptide (.248+/-.03 versus .278+/-.03). Epitope analysis, based on the blocking of conformational epitopes by recombinant Fab, revealed that the binding to multiple epitopes was decreased in the patients with neuropathy.

Peroxynitrite is a toxic compound formed during the inactivation of nitric oxide (NO) by the superoxide anion. The physiologic significance of this pathway of NO metabolism has never been documented in vivo. Because peroxynitrite provides a pathway for the inactivation of NO we postulated that peroxynitrite's correlation with physiologic parameters would be the opposite of those associated with NO, which is a vasodilator and suppresses sudomotor function. We assessed the significance of peroxynitrite by comparing its associations with blood pressure (BP) and sudomotor responses with those of NO.Thirty-seven patients with type 1 diabetes enrolled in a longitudinal study of oxidative stress. Nitric oxide was assessed from nitrite and nitrate (collectively NOx) and peroxynitrite was assessed from the nitrotyrosine (nTy) content of protein.nTy was 13.3 +/- 2.0 micromol/L in the control subjects and 26.8 +/- 4.4 micromol/L, 26.1 +/- 4.3 micromol/L, and 32.7 +/- 4.3 micromol/L in the diabetic patients (P.01) at the time of the first, second, and third evaluations, respectively. Patients with increased nitrotyrosine/tyrosine (nTy/Ty) had higher mean BP than those with low nTy/Ty (81.1 +/- l.9 mm Hg v 75.5 +/- 1.7 at the third evaluation, P.025). The ratio of nTy/NOx correlated with BP at the first (P.05), second (P.05), and third (P.01) evaluations. Patients with high nTy/Ty had increased sudomotor responses (5.85 +/- 0.75 microL of total sweat) at the third evaluation compared to those with low nTy/Ty (3.32 +/- 0.43 microL, P.005) and normal controls (3.90 +/- 0.41 microL, P.05). The associations of nTy with BP and sudomotor responses were the opposite of those with NOx.The conversion of NO oxide to peroxynitrite is physiologically significant in humans.

Autoimmune mechanisms have been implicated in the pathophysiology of diabetic neuropathy. We studied the association between glutamic acid decarboxylase (GAD65) and islet cell (IA-2) autoantibodies as well as autoantibodies to the autonomic nervous system and peripheral nerve function in recent onset type 1 diabetes. Thirty-seven patients (27 females and 10 males) enrolled 2–22 months after diagnosis. Humoral factors, glycemic control, and peripheral nerve function were measured annually for 3 yr. Patients with high GAD65Ab had worse glycemic control and higher insulin requirements. Patients with high GAD65Ab had slower motor nerve conduction velocities in the median, ulnar, and peroneal nerves (P < 0.025 for each nerve). The mean motor nerve conduction velocity Z scores at the time of the third evaluation was 0.341 ± 0.25 for the low GAD65Ab patients and −0.600 ± 0.25 for the high GAD65Ab patients (P < 0.01). Similar differences between the low and high GAD65Ab groups were observed for F wave latencies, thermal threshold detection, and cardiovascular autonomic function. The composite peripheral nerve function Z scores in the low GAD65Ab patients were 0.62 ± 11, 0.71 ± 0.19, and 0.21 ± 0.14 at the first, second, and third evaluations, significantly different from those in the high GAD65Ab patients in whom they were −0.35 ± 0.15, −0.46 ± 0.18, and −0.42 ± 0.16 (P < 0.001). In summary, GAD65Ab in patients with recent onset type 1 diabetes are associated with worse glycemic control and slightly worse peripheral nerve function. Although the latter remained within normal limits and none of the patients had clinical neuropathy, the GAD65Ab-related differences in composite peripheral nerve function were highly significant (P < 0.001) and could not be attributed to GAD65Ab-related differences in glycemic control.

PURPOSE To determine whether increasing red blood cell volume with erythropoietin reverses the hemodynamic response to standing in patients with orthostatic tachycardia. PATIENTS AND METHODS Eight patients (2 men, 6 women) with orthostatic tachycardia were administered erythropoietin (50 U/kg body weight 3 times a week for 6 to 12 weeks) in order to reverse their red blood cell volume deficit. Six of the patients also received fludrocortisone (0.1 mg/d). Plasma and red blood cell volumes as well as the hemodynamic response to orthostatic stress were measured before and after erythropoietin therapy. RESULTS Erythropoietin therapy increased the mean +/- hematocrit from 37.6 +/- 1.0 to 46.4 +/- 1.4 (+/- standard error) (P < 0.01) and increased the red blood cell volume from 17.7 +/- 1.1 to 24.6 +/- 2.0 mL/kg (P < 0.01). Treatment increased supine mean blood pressure (from 87 +/- 4 to 93 +/- 5 mm Hg, P < 0.025) and standing mean blood pressure (from 87 +/- 4 to 94 +/- 5 mm Hg, P < 0.025). Erythropoietin therapy, however, failed to reverse orthostatic tachycardia. Following treatment, the mean heart rate after 5 minutes standing was 129 +/- 7 bpm, not significantly different from the pretreatment standing heart rate (134 +/- 5 bpm). CONCLUSIONS Although patients with the orthostatic tachycardia syndrome have a deficit in red blood cell volume, this is not the cause of their abnormal hemodynamic response to standing. Erythropoietin therapy fails to reverse orthostatic tachycardia.