How reliable is assessment of true vocal cord-arytenoid unit mobility in patients affected by laryngeal cancer? a multi-institutional study on 366 patients from the ARYFIX collaborative group.

PURPOSE: In clinical practice the assessment of the "vocal cord-arytenoid unit" (VCAU) mobility is crucial in the staging, prognosis, and choice of treatment of laryngeal squamous cell carcinoma (LSCC). The aim of the present study was to measure repeatability and reliability of clinical assessment of VCAU mobility and radiologic analysis of posterior laryngeal extension. METHODS: In this multi-institutional retrospective study, patients with LSCC-induced impairment of VCAU mobility who received curative treatment were included; pre-treatment endoscopy and contrast-enhanced imaging were collected and evaluated by raters. According to their evaluations, concordance, number of assigned categories, and inter- and intra-rater agreement were calculated. RESULTS: Twenty-two otorhinolaryngologists evaluated 366 videolaryngoscopies (total evaluations: 2170) and 6 radiologists evaluated 237 imaging studies (total evaluations: 477). The concordance of clinical rating was excellent in only 22.7% of cases. Overall, inter- and intra-rater agreement was weak. Supraglottic cancers and transoral endoscopy were associated with the lowest inter-observer reliability values. Radiologic inter-rater agreement was low and did not vary with imaging technique. Intra-rater reliability of radiologic evaluation was optimal. CONCLUSIONS: The current methods to assess VCAU mobility and posterior extension of LSCC are flawed by weak inter-observer agreement and reliability. Radiologic evaluation was characterized by very high intra-rater agreement, but weak inter-observer reliability. The relevance of VCAU mobility assessment in laryngeal oncology should be re-weighted. Patients affected by LSCC requiring imaging should be referred to dedicated radiologists with experience in head and neck oncology.

Metformin improves endothelial function in type 1 diabetic subjects: a pilot, placebo-controlled randomized study.

AIMS: Several studies have investigated the effects of metformin treatment in patients with type 1 diabetes mellitus (T1DM). No study has hitherto examined its effects on endothelial function in these patients. In this study we sought to evaluate the effect of metformin on endothelial function in type 1 diabetic patients. METHODS: Forty-two uncomplicated T1DM patients were randomized in a placebo-controlled, double-blind, 6-month trial to treatment with either metformin or placebo. Glycometabolic and clinical parameters as well as flow-mediated dilation (FMD) and nitrate-mediated dilation (NMD) of the right brachial artery were measured at baseline and at the end of the study. Glycaemic variability (GV, calculated from continuous glucose monitoring data) and a biomarker of oxidative stress [urinary 8-iso-prostaglandin F2α (PGF2α)] were also assessed. RESULTS: Baseline data were similar in the two groups. Compared with placebo, metformin significantly reduced body weight [-2.27 kg (95% confidence interval: -3.99; -0.54); p = 0.012] whilst improved FMD [1.32% (0.30; 2.43); p = 0.013] and increased PGF2α [149 pg/mg creatinine (50; 248); p = 0.004]. Notably, the improvement of FMD did not correlate with the decrease of body weight (r(2) < 1%). NMD, haemoglobin A1c, GV, daily insulin dose and other parameters did not significantly change after the treatment comparing the two groups. CONCLUSIONS: Our pilot trial showed that, in uncomplicated type 1 diabetic subjects, metformin improved FMD and increased PGF2α, a marker of oxidative stress, irrespective of its effects on glycaemic control and body weight. Randomized, blinded clinical trials are needed to evaluate the benefits and risks of metformin added to insulin in type 1 diabetes.

Fields of application of continuous subcutaneous insulin infusion in the treatment of diabetes and implications in the use of rapid-acting insulin analogues.

In western countries, diabetes mellitus, because of macrovascular and microvascular complications related to it, is still an important cause of death. Patients with type 1 diabetes mellitus (T1DM) have a six-time higher risk of mortality than healthy patients. Since the Diabetes Control and Complications Trial (DCCT) established how an intensive therapy is necessary to prevent diabetes mellitus complications, many studies have been conducted to understand which method is able to reach an optimal metabolic control. In the past 30 years continuous subcutaneous insulin infusion established/introduced as a validate alternative to multiple daily injections. Several trials demonstrated that, when compared to MDI, CSII brings to a better metabolic control, in terms of a reduction of glycated hemoglobin and blood glucose variability, hypoglycemic episodes and improvement in quality of life. Because of their pharmacokinetic and pharmacodynamic characteristics, rapid-action insulin analogues are imposed as best insulin to be used in CSII. The rapid onset and the fast reached peak make them better mimic the way how pancreas secretes insulin. CSII by pump is not free from issues. Catheter occlusions, blockages, clogs can arrest insulin administration. The consequent higher levels of glycemic values, can easily bring to the onset of ketoacidosis, with an high risk for patients' life. Aspart is a rapid analogue obtained by aminoacidic substitution. It is as effective as lispro and glulisine in gaining a good metabolic control and even better in reducing glucose variability. Some studies tried to compare rapid analogues in terms of stability. Obtained data are controversial. An in vivo study evidenced higher stability or glulisine, while studies in vitro highlighted a higher safety of aspart. Nowadays it is not possible to assess which analogues is safer. When the infusion set is changed every 48 hours equivalent rates of occlusions have been observed.

Effect of carbohydrate counting and medical nutritional therapy on glycaemic control in Type 1 diabetic subjects: a pilot study.

AIMS: The effect of a balanced, carbohydrate-counting diet on glycaemic control in Type 1 diabetic subjects is unclear. Our aim was to determine its effect in a small, pilot trial. METHODS: We randomized 256 Type 1 diabetic subjects to a Nutritional Education Programme (group A) or not (group B). Weight, body mass index, glycated haemoglobin (HbA1c), lipid profile, urate, creatinine, microalbuminuria and daily insulin requirements were measured at baseline and at the end of the study (9 months). During the study, the number of hypoglycaemic events (blood glucose<3.9 mmol/l) was also measured. RESULTS: Compared with group B, group A showed: (i) a reduction in HbA1c (group A: 7.8+/-1.3-7.4+/-0.9%; group B: 7.5+/-0.8-7.5+/-1.1%; P<0.01); (ii) less hypoglycaemic events (4% vs. 7%; P<0.05); (iii) a reduction in dose of rapid insulin analogues (23.5+/-10.9 vs. 27.7+/-17.1 IU/24 h; P=0.03). No other between-group changes were observed. CONCLUSIONS: This study shows the importance of medical nutritional therapy on glycaemic control in Type 1 diabetic subjects.

Diabetes and severity of COVID-19: What is the link?

In Diabetes Mellitus the loss of capacity to regulate immunity, the reduction of pulmonary functions and the pro-thrombotic state determine the severity of COVID-19.

Slight association between type 1 diabetes and "ff" VDR FokI genotype in patients from the Italian Lazio Region. Lack of association with diabetes complications.

BACKGROUND: Vitamin D receptor (VDR) mediates the effects of vitamin D. Our paper evaluates the FokI and BsmI VDR genotypes in 246 Caucasian (Italian from Lazio Region) T1DM patients compared with 246 Caucasian healthy controls, sharing age and gender and regional provenience with the patients. In addition, T1DM patients without complications were compared with those carrying three complications. METHODS: Genotyping has been obtained by RFLP-PCR technique. RESULTS: A slight significant association of T1DM with FokI homozygous "f" genotype was observed. No association was observed with the presence of multiple complications by a multivariate analysis. CONCLUSION: T1DM patients showed slightly increased prevalence of "ff" VDR genotype.

Defective plasma antioxidant defenses and enhanced susceptibility to lipid peroxidation in uncomplicated IDDM.

Oxidative stress is postulated to be increased in patients with IDDM. Accumulating evidence suggests that oxidative cell injury caused by free radicals contributes to the development of IDDM complications. On the other side, a decreased efficiency of antioxidant defenses (both enzymatic and nonenzymatic) seems to correlate with the severity of pathological tissue changes in IDDM. Thus, we determined plasma antioxidant defenses, measuring the total radical-trapping antioxidant capacity (TRAP) and the two markers of oxidative stress, lipid hydroperoxides (ROOHs) and conjugated dienes, in 72 patients with well-controlled IDDM and without evident complications, compared with 45 nondiabetic subjects. Compared with control subjects, IDDM patients showed significantly reduced plasma TRAP (669 +/- 131 vs. 955 +/- 104 micromol/l, P < 0.001) and significantly increased levels of ROOHs (7.13 +/- 2.11 vs. 2.10 +/- 0.71 micromol/l, P < 0.001) and conjugated dienes (0.0368 +/- 0.0027 vs. 0.0328 +/- 0.0023 arbitrary units [AU], P < 0.01), especially in the trans-trans conformation (0.0340 +/- 0.0028 vs. 0.0259 +/- 0.0022 AU, P < 0.001), with a concurrent reduction of conjugated dienes in the cis-trans conformation (0.0028 +/- 0.0011 vs. 0.0069 +/- 0.0012 AU, P < 0.001). The oxidative parameters studied did not appear to be correlated with metabolic control (HbA1c levels) and lipid profile (cholesterol or triglyceride levels). The reduced TRAP and the increased ROOH and conjugated diene plasma levels, together with the decreased ratio of cis-trans/trans-trans conjugated dienes, which reflects an altered redox status of plasma, indicate that in IDDM patients, oxidative stress is enhanced and antioxidant defenses are defective, regardless of diabetes duration, metabolic control, or presence of complications.

Abnormal agonist-stimulated cardiac parasympathetic acetylcholine release in streptozocin-induced diabetes.

We examined the effect of three distinct depolarizing conditions on [3H]ACh release from cardiac postganglionic parasympathetic neurons in age-matched controls and insulin-treated STZ-induced diabetic rats to determine whether alterations in neurotransmitter release were present in the diabetic group. The effect of TTX, which exerts a use- and voltage-dependent block of sodium channels, was examined on the release of ACh stimulated by SRIF14 (preferentially acts at the cell body). We also studied the effect of STZ-induced diabetes on [3H]ACh release by the relatively site-specific depolarizing agent VT (preferentially acts at the axon) and high potassium (non-site-specific). Basal, SRIF14-(10(-7) M), VT-(10(-4) M), and K+ (100 mM)-stimulated [3H]ACh release was similar in control and STZ-induced diabetic animals. However, in STZ-induced diabetic but not control rats, SRIF14-induced [3H]ACh release was resistant to TTX (2 x 10(-7) M). In addition, the response to submaximal K+ (25 mM) stimulation was greater in STZ-induced diabetic compared with control animals. Treatment with insulin corrected these abnormalities. These data indicate that in the acute STZ-induced diabetic rat, SRIF14-, VT-, and high K(+)-evoked release of ACH is not impaired, which suggests that the mechanisms associated with ACh storage and release in postganglionic cardiac parasympathetic neurons are not affected in this model.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of angiotensin-converting enzyme (ACE) gene polymorphism on progression of renal disease and the influence of ACE inhibition in IDDM patients: findings from the EUCLID Randomized Controlled Trial. EURODIAB Controlled Trial of Lisinopril in IDDM.

We examined whether the ACE gene insertion/deletion (I/D) polymorphism modulates renal disease progression in IDDM and how ACE inhibitors influence this relationship. The EURODIAB Controlled Trial of Lisinopril in IDDM is a multicenter randomized placebo-controlled trial in 530 nonhypertensive, mainly normoalbuminuric IDDM patients aged 20-59 years. Albumin excretion rate (AER) was measured every 6 months for 2 years. Genotype distribution was 15% II, 58% ID, and 27% DD. Between genotypes, there were no differences in baseline characteristics or in changes in blood pressure and glycemic control throughout the trial. There was a significant interaction between the II and DD genotype groups and treatment on change in AER (P = 0.05). Patients with the II genotype showed the fastest rate of AER progression on placebo but had an enhanced response to lisinopril. AER at 2 years (adjusted for baseline AER) was 51.3% lower on lisinopril than placebo in the II genotype patients (95% CI, 15.7 to 71.8; P = 0.01), 14.8% in the ID group (-7.8 to 32.7; P = 0.2), and 7.7% in the DD group (-36.6 to 37.6; P = 0.7). Absolute differences in AER between placebo and lisinopril at 2 years were 8.1, 1.7, and 0.8 microg/min in the II, ID, and DD groups, respectively. The significant beneficial effect of lisinopril on AER in the II group persisted when adjusted for center, blood pressure, and glycemic control, and also for diastolic blood pressure at 1 month into the study. Progression from normoalbuminuria to microalbuminuria (lisinopril versus placebo) was 0.27 (0.03-2.26; P = 0.2) in the II group, and 1.30 (0.33-5.17; P = 0.7) in the DD group (P = 0.6 for interaction). Knowledge of ACE genotype may be of value in determining the likely impact of ACE inhibitor treatment.

Association of serum creatinine and age with headache caused by nitrates. Gruppo Italiano di Farmacovigilanza nell'Anziano.

To assess whether serum creatinine and age are associated with headache induced by nitrates, 2742 hospitalized patients taking nitrates were studied during their hospital stay. Those patients with admission serum creatinine levels from 97 to 133 mumol/L and > 133 mumol/L were compared with patients with creatinine levels < 97 mumol/L. Gender, body mass index, comorbidity, cognitive status, new intake of nitrates, number of daily administrations, and daily dosage, as well as intake of angiotensin converting enzyme inhibitors, calcium antagonists, diuretics and nonsteroidal anti-inflammatory drugs were examined as possible confounders. Fifty-six patients had headaches that had a causal link with intake of nitrates. Compared with the lowest creatinine group, after adjustment for potential confounding variables, the odds ratios and 95% confidence interval (95% CI) for headache caused by nitrates associated with increasing serum creatinine levels were 0.6 (95% CI, 0.3 to 1.1) and 0.2 (95% CI, 0.0 to 1.2), respectively (p for trend = 0.013). Increasing age was inversely associated with headache (odds ratio for 10-year increase, 0.6 [95% CI, 0.5 to 0.7]). Serum creatinine and age were independently and inversely associated with headache caused by nitrates.

Metabolic implications of coenzyme Q10 in red blood cells and plasma lipoproteins.

Plasma coenzyme Q10 (CoQ10) is currently assayed in our laboratory for its well-known diagnostic meaning; in fact plasma CoQ10 levels are inversely related to metabolic demand. Definite levels of CoQ10 are also found in white and red blood cell components, as well as in platelets. Plasma and erythrocyte CoQ10 has a well assessed antioxidant role, which was demonstrated through a series of experiments. Erythrocytes previously enriched with exogenous CoQ10 were found more resistant to a hemolysis induced by a free radical initiator. Several enzymatic activities of erythrocyte ghosts were also protected by different side chain CoQ homologues, both when reduced and, although at a lesser extent, in the oxidized state. CoQ was not effective in preventing metal-catalyzed oxidation of erythrocyte membrane enzymes, and this effect is likely to be due to lack of interaction of CoQ with the metal target. Moreover CoQ was able to protect isolated enzymes and erythrocyte membrane bound enzymes from the inactivating effect of free radicals generated by water sonolysis or radiolysis. As far as plasma lipoproteins are concerned it is well known that LDL isolated from healthy volunteers supplemented with CoQ10 are more resistant to peroxidation induced by an azoinitiator. We started to systematically investigate CoQ10 and vitamin E levels in isolated human LDL and HDL. Both CoQ10 and vitamin E concentrations, referred to protein, were found higher in LDL than in HDL. Susceptibility to exogenously applied peroxidation did not correlate with the endogeneous content of the two antioxidants, possibly on the basis of different lipid content of these lipoproteins.

Age and severe adverse drug reactions caused by nifedipine and verapamil. Gruppo Italiano di Farmacovigilanza nell' Anziano (GIFA).

The association of age with risk for severe adverse drug reactions (SADRs) was studied in 2371 and 862 hospitalized patients taking nifedipine and verapamil, respectively. Nifedipine caused hypotension (n = 22), tachycardia (n = 3), and acute renal failure (n = 1) (total SADR rate, 1.1%, 26/2371). Verapamil caused hypotension (n = 3), bradycardia (n = 9), and atrioventricular blocks (n = 2) (total SADR rate, 1.6%, 14/862). The mean age of patients with and without SADRs was for nifedipine 77.1 +/- 1.7 and 71.8 +/- 0.8 years, respectively (p < 0.05), and for verapamil 73.4 +/- 2.9 and 73.1 +/- 0.4 years, respectively. Sex, length of stay, comorbidity, polypharmacy, intake of slow-release preparations, daily dosage, and new intake of calcium antagonists were examined as potential confounders of the age-SADR association. After adjusting for potential confounders, age was significantly and independently associated with SADRs caused by nifedipine, but not with SADRs caused by verapamil (OR = 1.69, 95% CI = 1.05-2.72 and OR = 1.06, 95% CI = 0.63-1.68 for 10-year increase, respectively). Although nifedipine and verapamil did not have significantly different rates of SADRs, an age-related gradient was found only for nifedipine.

Postural variations of pulmonary diffusing capacity in insulin-dependent diabetes mellitus.

STUDY OBJECTIVE: To assess whether posture-related changes of diffusing capacity could be considered as an early sensitive marker of pulmonary abnormalities in patients with insulin-dependent diabetes mellitus (IDDM) and whether the postural variations of pulmonary capillary blood volume (Vc) could reflect the lung capillary damage that characterizes the diabetic microangiopathy. DESIGN: Carbon monoxide diffusing capacity (DCO) was measured by the single-breath method. Four DCO measurements, two in sitting and two in supine position, were performed in each subject using gas mixtures containing different oxygen concentrations. Membrane and capillary volume components of the diffusion capacity were calculated and both were expressed as absolute value and corrected by alveolar volume (VA). PATIENTS: Twenty IDDM patients and 20 normal subjects matched for age and sex were studied. MEASUREMENTS AND RESULTS: The IDDM patients showed normal pulmonary volumes and flows. No significant differences between the two groups were found for DCO, coefficient of diffusion, Vc, and pulmonary capillary blood volume corrected by alveolar volume in sitting position. All these indexes significantly increased in normal subjects but not in diabetics, by changing the posture of the subject from sitting to supine position. In a multivariate analysis, the presence of diabetes mellitus and the age of the subjects were the only significant predictors of Vc postural changes. CONCLUSIONS: This postural test, adjusted for age, could be included in a screening diagnostic procedure for an early assessment of pulmonary abnormalities in diabetic patients. The lack of Vc postural increase in diabetics could reflect the presence of a microangiopathy involving the pulmonary small vessels.

Disability and severe gastrointestinal hemorrhage. A prospective study of community-dwelling older persons.

OBJECTIVE: To describe the occurrence of severe gastrointestinal bleeding in community-dwelling older persons and to examine whether disability is a risk factor for this life-threatening condition independent of other known predictors. DESIGN: Prospective cohort survey. SETTING: Three communities of the Established Populations for Epidemiologic Studies of the Elderly (EPESE). PARTICIPANTS: 8205 persons age > or = 68 years. MEASUREMENTS: The hospital discharge diagnoses provided by the Medicare Provider Analysis and Review files and the death certificates were prospectively surveyed for 3 years. Those with at least 1 discharge diagnosis of gastrointestinal bleeding and who received a blood transfusion or died were identified as cases of severe gastrointestinal hemorrhage. Physical disability, cognitive function, smoking and alcohol intake habits, body mass index, blood pressure, chronic conditions, number of hospital admissions in past year and medications taken were assessed at baseline. RESULTS: The occurrence rate of severe gastrointestinal bleeding was 10.8 per 1000 person-years (241 events/22,277 person-years). In proportional hazards regression models, compared with no disability, > or = 1 disabilities in the Rosow-Breslau scale (RR = 2.1, 95% CI = 1.5-2.9), and > or = 1 ADLs limitations (RR = 3.1, 95% CI = 2.1-4.6) independently predicted gastrointestinal hemorrhage after adjusting for age, gender, body mass index, comorbidity, number of hospital admissions, blood pressure, intake of coumarin, corticosteroids, aspirin and other nonsteroidal anti-inflammatory drugs. CONCLUSIONS: In this prospective analysis, disability is an independent predictor of gastrointestinal hemorrhage. Further studies are needed to explain the mechanisms by which disability may cause gastrointestinal hemorrhage. Because physical disability is potentially modifiable, strategies to lower the risk of gastrointestinal bleeding should be evaluated.

Factors associated with cognitive impairment among older Italian inpatients. Gruppo Italiano di Farmacovigilanza nell'Anziano (G.I.F.A.).

OBJECTIVE: To examine the association of cognitive impairment with educational, demographic, and nutritional variables in older hospitalized people. DESIGN: Survey of older patients admitted consecutively to a hospital during two 2-month periods in 1993. SETTING: Patients admitted for general medical care at 35 hospitals participating in the GIFA study throughout Italy. PARTICIPANTS: A total of 3628 patients aged 65 or older were studied. MEASUREMENTS: The Hodkinson Abbreviated Mental Test (HAMT) was used as a screening method to assess the patients' basic cognitive function. Multiple logistic regression was used to examine the association between cognitive impairment and demographic, educational or nutritional variables. RESULTS: Twenty-nine percent of older inpatients were classified as having cognitive impairment, with similar distribution of HAMT score found in both genders. Educational attainment has a highly significant inverse relationship with cognitive impairment (highest education: OR 0.32; 95% CI 0.20-0.52). Moreover, cognitive impairment decreased with increasing body mass index (3rd tertile: OR 0.69; 95% CI: 0.51-0.93), cholesterol serum level (highest values: OR 0.59; 95% CI 0.37-0.93), circulating lymphocytes (highest values: OR 0.55; 95% CI 0.45-0.69), and serum albumin (highest values: OR 0.60; 95% CI 0.47-0.76), with a gradient of influence for each variable. CONCLUSIONS: Educational attainment affects cognitive function in older inpatients. The strong association between cognitive impairment and nutritional variables suggests that every effort to improve nutritional status is needed in approaching cognitive impairment in older patients.

Evidence of plasma CoQ10-lowering effect by HMG-CoA reductase inhibitors: a double-blind, placebo-controlled study.

Inhibitors of HMG-CoA reductase are new safe and effective cholesterol-lowering agents. Elevation of alanine-amino transferase (ALT) and aspartate-amino transferase (AST) has been described in a few cases and a myopathy with elevation of creatinine kinase (CK) has been reported rarely. The inhibition of HMG-CoA reductase affects also the biosynthesis of ubiquinone (CoQ10). We studied two groups of five healthy volunteers treated with 20 mg/day of pravastatin (Squibb, Italy) or simvastatin (MSD) for a month. Then we treated 30 hypercholesterolemic patients in a double-blind controlled study with pravastatin, simvastatin (20 mg/day), or placebo for 3 months. At the beginning, and 3 months thereafter we measured plasma total cholesterol, CoQ10, ALT, AST, CK, and other parameters (urea, creatinine, uric acid, total bilirubin, gamma GT, total protein). Significant changes in the healthy volunteer group were detected for total cholesterol and CoQ10 levels, which underwent about a 40% reduction after the treatment. The same extent of reduction, compared with placebo was measured in hypercholesterolemic patients treated with pravastatin or simvastatin. Our data show that the treatment with HMG-CoA reductase inhibitors lowers both total cholesterol and CoQ10 plasma levels in normal volunteers and in hypercholesterolemic patients. CoQ10 is essential for the production of energy and also has antioxidative properties. A diminution of CoQ10 availability may be the cause of membrane alteration with consequent cellular damage.

Somatostatin response to a mixed meal in normals and in type I diabetics.

Somatostatin has been proposed as a regulatory peptide of nutrient entry and fuel homeostasis because of its ability to inhibit the release of substances involved in food digestion and metabolism. The aim of the study was to evaluate the somatostatin response to a test meal in type I diabetics at the clinical onset of the disease and after two months of intensive insulin therapy. Normal subjects and diabetics in good metabolic control showed a characteristic biphasic somatostatin rise after a test meal; this response was lacking in diabetics at the onset of the disease. The response of somatostatin to a mixed meal in normals confirms its involvement in nutrient digestion and metabolism. The lacking somatostatin response in newly diagnosed type I diabetics might be related to deficient GIP response to the test meal or to other factors such as the insulinopenia or metabolic derangement characteristic of the clinical onset of the disease.

NA+/K+ ATPase impairment and experimental glycation: the role of glucose autoxidation.

Non enzymatic glycation could be involved in the early impairment of Na+/K+ ATPase that occurs in sciatic nerve of diabetic rats. In fact, decrease of Na+/K+ ATPase activity is one of the first alterations showed in experimental diabetic neuropathy. In this respect, it is known that in the presence of transition metals under physiological conditions, glucose can autoxidize yielding hydrogen peroxide (H2O2) and free radical intermediates, which, in turn, inhibit the cation pump. Our experiments were designed to determine if glucose autoxidation has any relevance in the early steps of Na+/K+ ATPase experimental glycation. Compared experiments with and without the sodium borohydride (NaBH4) reduction step demonstrated that incubation of brain Na+/K+ ATPase with glucose 6-phosphate (G 6-P) and trace metals induced a significant decrease in enzyme activity dramatically enhanced by addition of copper (Cu2+). A concomitant production of H2O2 was noticed. The presence of diethylenetriaminepentaacetic acid (DTPA), a strong metal chelator, completely prevented Na+/K+ ATPase impairment and hydrogen-peroxide formation. No gross structural and conformational alterations of the enzyme can be demonstrated by intrinsic and extrinsic fluorescence measurements. Our results suggest that during the exposure of brain NA+/K+ ATPase to glucose 6-phosphate in vitro (experimental glycation), the decrease in activity can be correlated, at lease in the early phases, to metal-catalyzed production of oxidative species, such as H2O2, through the glucose autoxidation process, and not to glucose attachment to the enzyme. Since plasma hydroperoxides and copper appear to be elevated in diabetic patients with complications, our data suggest a critical role for oxidative reactions in the pathophysiology of the chronic complications of diabetes like neuropathy.

Lower limb arterio-venous shunts, autonomic neuropathy and diabetic foot.

We have quantitatively assessed the percentage of lower limb arterio-venous (a-v) shunting using a radioisotopic technique and correlated it with autonomic neuropathy evaluated by cardiovascular tests. We have studied three groups of diabetic patients: Group A, 12 non-neuropathic subjects without foot lesions; Group B, 12 neuropathic subjects without foot lesions; Group C, 12 neuropathic subjects with recurrent foot ulcers. Shunting was higher in Group C (10.4 +/- 2.7%) than in Group B (6.8 +/- 2.3%, P less than 0.01) and Group A (3.8 +/- 1.2%, P less than 0.001). Shunts in Group B were higher than in Group A (P less than 0.05). All the tests exploring autonomic function were more impaired in Groups B and C than in Group A, with no difference between Groups B and C. A direct correlation was found between a-v shunting and the following cardiovascular tests: postural hypotension (PH) (r = 0.41, P less than 0.02), sustained handgrip (SH) (r = 0.56, P less than 0.001), deep breathing (DB) (r = 0.40, P less than 0.005) and lying to standing (LS) (r = 0.44, P less than 0.01). A positive correlation was also found between a-v shunts and duration of the disease (r = 0.62, P less than 0.001). Arterio-venous shunting was found to be directly related to autonomic neuropathy even if the higher shunting found in the patients with foot ulcers was not related to a higher degree of autonomic involvement; in addition, this group of patients was characterized by having a more advanced sensory and motor neuropathy. In conclusion, autonomic neuropathy, through its influence on a-v shunts, may play a role in the pathogenesis of diabetic foot, but peripheral neuropathy probably plays a key role in conditioning the development of the overt clinical manifestations of diabetic foot.