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Biomedical subjects

G Tamburrano

Publications and source records attributed to G Tamburrano.

At least 73 records · Page 4Linked to original sources
PubMed1992

Idiopathic reactive hypoglycemia: a role for glucagon?

We previously reported that patients with idiopathic reactive hypoglycemia (plasma glucose concentration lower than 2.5 mmol/L 2-4 h after the ingestion of 75 g of glucose) display reduced or absent counterregulatory response of the glucagon secretion and increased insulin sensitivity. In order to examine the effect of glucagon on the increased insulin sensitivity in these patients, 12 subjects with idiopathic reactive hypoglycemia underwent a two-step hyperinsulinemic (1 mU/kg.min) euglycemic glucose clamp and were compared with 12 normal control subjects matched for age, weight and sex. During the first step of the glucose clamp (only insulin + glucose infusion) the patients with Idiopathic Reactive Hypoglycemia required higher glucose infusion rates to maintain euglycemia than normal subjects (9.09 +/- 0.29 mg/kg. min vs 7.61 mg/kg.min). When basal glucagon secretion was replaced (+ somatostatin and glucagon, second step of the clamp) the glucose infusion rates required to maintain euglycemia in patients with Idiopathic Reactive Hypoglycemia significantly decreased (to 7.17 +/- 0.40 mg/kg.min) and resulted similar to normal subjects (7.64 +/- 0.41 mg/kg.min). Thus, in patients affected by Idiopathic Reactive Hypoglycemia, glucagon secretion may play an important role in the pathogenesis of the increased insulin sensitivity and hypoglycemia.

Adult↗
PubMed1992

Changes in central and peripheral nervous system function during hypoglycemia in man: an electro-physiological quantification.

We measured somatosensory evoked potentials (SEP) in normal subjects during acute (group A) and moderately prolonged (group B) hypoglycemia. We considered the following parameters: peripheral conduction velocity (wrist-Erb CV), conduction time (CT) between brachial plexus and the cervical cord (Erb-N13) and central CT from the cervical cord/lower brainstem lemniscal pathway to the cortex (N13-N20). In group A, the electrophysiological parameters did not change significantly throughout the study. In group B, mean N13-N20 CT increased from a basal values of 5.82 +/- 0.11 to 6.22 +/- 0.11 msec at 105 min (p less than 0.02) and 6.33 +/- 0.11 msec at 120 min (p less than 0.05). This study indicates that neither acute nor moderately prolonged hypoglycemia influence the peripheral nerve function in normal subjects and provides evidence that hypoglycemia as low as 2.4 mmol/L, lasting more than 60 min, can significantly increase the conduction time of central somatosensory pathways.

Adult↗
PubMed1992

[Familial acromegaly. Apropos of a case. Review of the literature].

Two brothers and a sister with acromegaly--one of them with acromegalogigantism--are described. They all presented pituitary adenomas, and the diagnosis was made between the ages of 17 and 29. There was no feature of multiple endocrine neoplasia. The familial investigation consisted of detailed interrogation, basal hormonal evaluation and HLA determination (haplotypes A and B) in 14 members, including the patients themselves. Despite basal plasma GH levels ranging from 8.00 to 10.00 ng/ml in 3 other family members, the normality of both GH response to induced-hyperglycemia and CT-imaging of the pituitary gland excluded the diagnosis of acromegaly in these subjects. No correlation with the HLA haplotypes was observed. Differential diagnosis with familial multiple endocrine neoplasia (MEN type 1) is discussed. Previous reports of familial acromegaly are reviewed and analysed. It appears that familial acromegaly may be considered as a specific entity for two main reasons: 1) owing to the low incidence of acromegaly in the general population, familial cases are unlikely to be fortuitous. 2) most of the reported cases share some common clinical features, such as a male predominance, a high incidence of acromegalogigantism, and the presence of a pituitary macroadenoma. However, the primitive disorder and the genetic transmission of the disease are still unknown.

Acromegaly↗
PubMed1990

Resistance to insulin suppression of plasma free fatty acids in liver cirrhosis.

Insulin action on carbohydrate metabolism is known to be reduced in liver cirrhosis. However, little is known about the effect of insulin on free fatty acid (FFA) metabolism in these patients. To investigate this aspect we performed a two-step insulin euglycemic clamp in 11 cirrhotic patients and 6 controls. Insulin was infused at 0.25 mU/Kg min from 0 to 100 min and at 1 mU/Kg from 100 to 200 min. The FFA lowering capacity of insulin was studied during the first step; the glucose metabolizing capacity (M) was evaluated during the second step. In the cirrhotic patients, the M value was lower than in controls (3.91 +/- 0.48 vs 7.75 +/- 1.09 mg/kg/min, respectively). During the low insulin infusion, FFA and glycerol plasma levels were decreased in both groups. However, the ability of insulin to suppress plasma FFA and glycerol was lower in cirrhotics than in controls. In fact, at 100 min, FFA were 50% of basal values in cirrhotics and 20% in controls (p less than 0.01), while glycerol plasma levels decreased to 70% of basal values in patients and to 56% in controls. The slope of the linear regression obtained between Ln-FFA concentrations vs time was significantly less in cirrhotic patients than in controls (p less than 0.001). In addition, a positive correlation was found between the M value (r = 0.70; p less than 0.01) and the slope of the Ln-FFA in each patient. These findings suggest that in cirrhotic patients the effects of insulin on both FFA and glucose metabolism are reduced.

Blood Glucose↗
PubMed1990

Growth hormone does not inhibit its own secretion during prolonged hypoglycemia in man.

In man, continuous infusion of GH-releasing hormone (GHRH) does not sustain GH secretion, unlike prolonged hypoglycemia. To further evaluate this difference in the stimulation of GH release we measured GH concentrations for 3 h during prolonged insulin-induced hypoglycemia and GHRH-(1-29)NH2 (100 micrograms/h) infusion in normal individuals. We also assessed the GH response to combined and separate administration of insulin and GHRH. Plasma GH levels increased during prolonged hypoglycemia and remained elevated for the third hour (22-24 micrograms/L). GH concentrations increased during GHRH infusion, peaked at 60 min (23.5 micrograms/L), and rapidly declined. Thus, our findings confirmed that prolonged hypoglycemia, unlike GHRH infusion, sustained elevated GH levels and that these high levels did not appear to influence GH secretion from the pituitary. Changes in FFA did not account for the sustained GH secretion. FFA levels initially declined during insulin infusion, but after 3 h of hypoglycemia they returned to near-basal values (basal, 0.1 +/- 0.02 g/L; 180 min, 0.09 +/- 0.02). The maximal GH concentration attained during the combined insulin and GHRH test was significantly higher than that with the insulin tolerance test or GHRH test (insulin plus GHRH, 71.9 +/- 13.5; insulin tolerance test, 34.2 +/- 2.9; P less than 0.025; GHRH test, 27.9 +/- 3.2; P less than 0.02), indicating an additive effect on GH secretion. These data suggest that insulin-induced hypoglycemia stimulates GH secretion through a mechanism partly independent of GHRH. The release from somatostatin inhibition and stimulation through other neuropeptides (e.g. galanin) is suggested as possible causes of hypoglycemia-induced GH secretion.

Adult↗
PubMed1989

Intravenous dexamethasone and subsequent ACTH test in comparison with dexamethasone oral test in the diagnosis of Cushing's syndrome: a report of 20 cases.

Dexamethasone inhibits ACTH secretion in the pituitary corticotropic cells of normal subjects; this ability is variously affected in Cushing's syndrome. The iv infusion of dexamethasone is not time consuming, nor it is influenced by the variability of intestinal absorption or hepatic metabolism, as occurs with oral administration. Iv dexamethasone (1.5 mg/h) over 7 h and an ACTH bolus at the 6th h were administered to 17 patients with Cushing's disease, 3 patients with Cushing's syndrome (2 with adrenal adenoma, 1 with ectopic ACTH secretion) and 13 normal subjects. After 4 days the 20 patients were also given the standard oral low-dose and high-dose dexamethasone test. Two h after starting the drug infusion, cortisol concentrations were inhibited by more than 50% in each control subject. In contrast, in all but one patient they remained higher than 50% over the baseline. At the 6th heach control subject and 15 of the 17 patients with Cushing's disease showed an inhibition of plasma cortisol concentration which was greater than 50%. Inhibition was less than 50% in 2 patients with Cushing's disease and in the 3 patients with non-pituitary dependent Cushing's syndrome. The sensitivity and specificity of this test are comparable with those of the dexamethasone oral test. Although statistically significant, results obtained from ACTH bolus were not sufficiently discriminating. If studies conducted on a larger population confirm these preliminary data, the rapidity and reliability of the dexamethasone infusion test could make it an important new tool in diagnosing Cushing's syndrome.

Administration, Oral↗
PubMed1989

Increased insulin sensitivity in patients with idiopathic reactive hypoglycemia.

We performed a euglycemic hyperinsulinemic glucose clamp in 20 patients selected from a large number of subjects referred to our clinic with symptoms suggesting reactive hypoglycemia. Diagnosis was made on the basis of blood glucose measurements during symptoms in their daily life and confirmed by a 5-h oral glucose tolerance test. The patients were divided into the following groups: 8 patients with idiopathic reactive hypoglycemia (IRH), i.e. biochemical hypoglycemia associated with symptoms and plasma insulin concentrations in the normal range; 6 patients with nonhypoglycemia (NH), i.e. patients experiencing the symptoms evoking hypoglycemia at essentially normal plasma glucose levels; and 6 patients with alimentary hypoglycemia secondary to previous gastric surgery (GS). Eight normal volunteers formed the control group (N). Hypoglycemia in this study was considered to be present when plasma glucose concentrations were below 2.5 mmol/L. The peak cortisol levels after glycemic nadir were higher (2P less than 0.05) in IRH compared to GS and N. In the same group, a partially deficient glucagon response to hypoglycemia was noted. During the euglycemic clamp, the glucose uptake appeared to be significantly greater in the IRH group than in NH, GS, and N groups (8.13 +/- 0.49 vs. 7.02 +/- 0.35, 6.48 +/- 0.22, and 6.66 +/- 0.42 mg/kg.min, respectively; 2P less than 0.05). Therefore, our data suggest that increased insulin sensitivity represents a feature of idiopathic reactive hypoglycemia.

Adult↗
PubMed1988

Electroencephalography and visually evoked potentials during moderate hypoglycemia.

The effects of hypoglycemia per se on the electroencephalogram (EEG) and visually evoked potentials (VEPs) were studied in eight normal young adults. The EEG and VEPs were recorded before and during hypoglycemic clamp studies, carried out at plasma insulin and glucose concentrations of about 287 pmol/L and 2.38 mmol/L, respectively. From the mean power EEG spectra obtained during each testing condition, several parameters in each frequency band considered were compared statistically. During the eyes closed recording, the mean frequency of the alpha-band (8-13 Hz) decreased from 10.1 +/- 0.2 (+/- SE) Hz in both the right and left frontal leads during euglycemia to 8.8 +/- 0.2 and 8.8 +/- 0.1 Hz (left and right frontal leads, respectively; P less than 0.05) during hypoglycemia. In the same leads, the peak frequency decreased from 10.6 +/- 0.4 and 10.3 +/- 0.4 Hz to 9.6 +/- 0.4 and 9.5 +/- 0.3 Hz, respectively (P less than 0.05). A similar pattern of variation was found during the eyes open recording. In contrast, mean VEP latencies did not vary significantly; they were 118 +/- 3 ms (smallest image size; square wave signals subtending 30 min of arc) and 116 +/- 3 ms (largest image size; square wave signals subtending 60 min of arc) during euglycemia to 121 +/- 3 and 119 +/- 3 ms, respectively, during hypoglycemia. This study demonstrates that the earliest hypoglycemia-induced EEG alterations occur in the frontal regions and can be quantified in terms of decreased mean and peak frequencies of the alpha-band. VEP latency is less sensitive. If confirmed in diabetic patients, these data may provide a theoretical basis for developing a portable device to detect early hypoglycemia in those patients who lack warning symptoms.

Adult↗
PubMed1987

Dose-response effect of somatostatin-14 on human basal pancreatic hormones.

The effect of increased doses of Somatostatin-14 (3, 10, 30, 100, 300 micrograms/h) on basal release of insulin, pancreatic glucagon and pancreatic polypeptide (PP) was investigated on eight normal volunteers. Levels of Somatostatin-like immunoreactivity (SLI) was determined in order to correlate the increased SLI levels with the degree of islet hormone inhibition (r = 0.9947, p less than 0.01). By increasing the basal levels of SLI by one-third, a significant inhibition (p less than 0.01) of insulin, glucagon, and PP was noted (78.5, 78.6, 75.2%, respectively, on basal levels). The maximal effect was obtained with 300 micrograms/h for insulin, with 30 micrograms/h for glucagon and 100 micrograms/h for PP. In evaluating the relative inhibitory potency of somatostatin, expressed as ED50, the theoretic potency of somatostatin on each peptide had similar values, ranging from 30 to 10 micrograms/h. The present data show that a minimal peripheric increase in SLI is able to regulate basal islet pancreatic hormones.

Adult↗
PubMed1985

Temporal correlation of some endocrine circadian rhythms in elderly subjects.

The aim of this chronobiological study was to investigate temporal correlations in the circadian patterns of 6 hormones, namely somatotrophic hormone (STH), prolactin (PRL), cortisol (F), aldosterone (ALD), insulin (IRI) and C-peptide (CP), assayed in systemic blood serum drawn at 07:00, 10:00, 13:00, 16:00, 19:00 and 22:00 h from an antecubital vein in 19 young subjects (aged 20-29 yr, comprising 10 males and 9 females; and 20 elderly subjects (aged 70-81 yr, comprising 10 males and 10 females). All subjects were sampled on a normal dietary sodium intake (120-140 mEq/24h) while following a social routine of diurnal activity (07:00-23:00) and nocturnal rest (23:00-07:00). Time-qualified data were analyzed by lead-lag correlation and by cosinor analysis. According to the lead-lag correlation findings, it would appear that the correlation which exists between several time-qualified series in young subjects is no longer present in elderly subjects. The circadian rhythms which were found to have lost their temporal correlations with advancing age were those between STH and IRI, STH and ALD, PRL and IRI, PRL and CP, and ALD and CP. It should be noted that the correlation between hormonal rhythms breaks down mainly on account of a peculiar age-related change in the magnitude of the circadian fluctuation. This chronological decline in amplitude led to the conclusion that the senescence of endocrine rhythmic functions is a biological phenomenon characterized by altered circadian variability.

Adult↗
PubMed1985

Nutritional effects of total gastrectomy. A prospective randomized study of Roux-en-Y vs Longmire-Mouchet reconstruction.

A prospective randomized study was carried out to evaluate the nutritional and clinical results of two reconstructive procedures after total gastrectomy for gastric cancer: Longmire-Mouchet (LM) operation with loop interposition and maintained duodenal transit and Roux-en-Y (RY) reconstruction with duodenal exclusion. 22 patients, 11 with LM reconstruction and 11 with RY reconstruction were studied pre-and postoperatively. The average follow-up was of 30 +/- 8 months. The clinical results were shown to be substantially similar to the two groups. No patients complained of heartburn or dysphagia. At esophagoscopy no signs of esophagitis were detected in both groups. The two time course curves of body weight variation did not show statistically significant differences even though in RY patients the body weight has reverted more rapidly to basal values.

Aged↗
PubMed1984

Total and individual free fatty acid concentrations in liver cirrhosis.

The finding of high plasma free fatty acid (FFA) levels in cirrhotic patients has been attributed either to decreased hepatic clearance or to enhanced fat mobilization. To better clarify these hypotheses, total and individual FFA and glycerol levels were determined in 21 cirrhotic patients with different degrees of hepatocellular damage (evaluated by liver function tests), portal hypertension (evaluated by endoscopy and clinical signs), and nutritional status (evaluated by anthropometric and biohumoral parameters) and in 10 age- and sex-matched healthy subjects. Glucose tolerance and insulin and glucagon levels were determined in all individuals. Well-nourished and malnourished patients were identified within the cirrhotic group. Plasma FFA and glycerol concentrations were well correlated (r = 0.47, P less than 0.05), levels being significantly higher in cirrhotic individuals than in controls (746.6 +/- 46.29 SE v 359.22 +/- 40.82 mumol/L, P less than 0.001 for plasma FFA; 150.1 +/- 3.12 v 82.5 +/- 9.2 mumol/L, P less than 0.01 for glycerol). Plasma FFA and glycerol showed no correlation with the liver function test results or portal hypertension parameters. Interestingly, plasma levels of FFA and glycerol were influenced by the nutritional status, significantly higher FFA levels being observed in the well-nourished than in the malnourished patients (842.5 +/- 47.5 v 563.4 +/- 78 mumol/L, P less than 0.005). Furthermore, a positive correlation was found between plasma glycerol level and percentage of triceps skinfold (r = 0.45, P less than 0.05). No correlation was found between plasma levels of FFA or glycerol and glucose tolerance, insulin and glucagon.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Glucose-induced GIP levels in patients with insulinoma.

Gastric inhibitory polypeptide (GIP) levels during an oral glucose tolerance test (OGTT) have been determined in eight patients suffering from a single benign beta-cell adenoma. GIP hypersecretion and an absent correlation between the insulin: glucose ratio and plasma GIP concentration have been observed. Our data show that the insulinotropic effect of GIP is almost abolished in insulinoma patients. This finding may help explain blood glucose levels and the inappropriate plasma insulin response to oral glucose often observed in these patients.

Adenoma, Islet Cell↗
PubMed1983

Diazoxide infusion test in patients with single benign insulinoma.

The diazoxide infusion test (600 mg i.v. over a 1-hour period) was performed in 12 patients bearing single benign islet B-cell adenoma and in 6 normal subjects. Blood glucose, plasma insulin and glucagon concentrations were measured every 15 min during the infusion and thereafter up to 150 min. In insulinoma patients, blood glucose levels failed to increase significantly while in the control group a significant rise starting from 30 min persisted throughout the test (p less than 0.05 or less). Plasma insulin mean levels decreased significantly in normal subjects from 30 to 60 min (p less than 0.05), while they were significantly suppressed in hypoglycemic patients from 15 to 120 min (p less than 0.02). Diazoxide administration induced in the normal group a significant decrease in glucagon levels (p less than 0.02 from 30 to 150 min) whereas no such suppression occurred in patients. In our experience, insulin response to diazoxide infusion in patients with insulinoma may provide additional information for diagnosis.

Adenoma, Islet Cell↗
PubMed1983

Effect of bombesin on plasma insulin, pancreatic glucagon, and gut glucagon in man.

The effect of bombesin on insulin, pancreatic glucagon, and gut glucagon was investigated in eight healthy volunteers and two pancreatectomized patients. Bombesin, infused iv at the constant rate of 5 ng kg-1 min-1, produced a sharp and statistically significant rise in the plasma insulin concentration. The peak was reached at 5 min (26 +/- 2.17 microU/ml; P less than 0.005 vs. basal values), followed by a prolonged and statistically significant (P less than 0.05) decrease in blood glucose. Pancreatic glucagon rapidly rose to a maximal value of 80.5 +/- 7.6 pmol/liter (P less than 0.005 vs. basal values). In contrast with the prompt increase in insulin and glucagon plasma levels, the peak in gut glucagon concentration (55.8 +/- 4.6 pmol/liter; P less than 0.005 vs. basal values) was reached 30 min after bombesin infusion was discontinued. In the two pancreatectomized patients, bombesin induced an increase in gut glucagon concentrations only. The results presented indicate that bombesin acts directly on the A and B cells of the pancreas, influencing glucose homeostasis; however, more complex mechanisms seem to be involved in gut glucagon secretion.

Adult↗