Insulin and C-peptide plasma levels in patients with severe chronic pancreatitis and fasting normoglycemia.

The aim of the present study was to evaluate insulin secretion by the pancreatic B cell in a group of patients with severe chronic pancreatitis and without overt diabetes. For this purpose we have measured plasma insulin and C-peptide peripheral levels in the fasting state and after a 100-g oral glucose load in 10 patients with severe chronic pancreatitis and fasting normoglycemia, and in 10 sex-, age-, and weight-matched healthy controls. As compared to normal subjects, patients with chronic pancreatitis showed: (1) significantly higher plasma glucose levels after oral glucose load (area under the plasma glucose curve 1708 +/- 142 vs 1208 +/- 47 mmol/liter X 240 min, P less than 0.

Relationship between blood pressure and plasma insulin in non-obese and obese non-diabetic subjects.

In this study, we have measured plasma insulin at fasting and following an oral glucose load and blood pressure after glucose load in 367 (247 non-obese, 120 obese) normotensive and untreated mildly hypertensive subjects. Overall, there was no independent association between fasting plasma insulin levels and blood pressure values. After controlling for age and body weight, a significant relationship between postglucose plasma insulin levels and diastolic blood pressure was found.

Influence of the menstrual cycle on glucose tolerance and insulin secretion.

To evaluate the impact of the menstrual cycle on glucose tolerance and insulin secretion, in the present study we have measured the plasma concentrations of glucose, insulin, and C-peptide during a 2-hour oral glucose tolerance test in 110 healthy, nonobese, regularly menstruating women. Fifty-five women were in the follicular phase, and 55 were in the luteal phase of the cycle. The two groups were well matched for age and body weight.

Relationships between insulin secretion, insulin metabolism and insulin resistance in mild glucose intolerance.

The aim of this study was to evaluate whether the correlation between insulin resistance and peripheral hyperinsulinaemia existing in mild glucose intolerance corresponds to a relationship between insulin resistance and insulin overproduction by the pancreas. In addition, the possibility that insulin resistance is related to insulin metabolism was examined. Twenty five subjects with fasting normoglycaemia and an abnormal glucose response to the oral glucose tolerance test (OGTT) were studied.

Fractional hepatic extraction of insulin in man: is it constant?

The present study was designed to compare insulin extraction by the liver following oral glucose administrations of different size, in order to evaluate insulin removal by the liver in relation to the insulin exposure, and to the amount of ingested glucose. Insulin secretion by the pancreas was estimated by the measurement of peripheral C-peptide levels, and insulin extraction by the liver by the analysis of peripheral C-peptide to insulin ratios and relations. Ten healthy subjects (5 males and 5 females), aged 16 to 66 yr, with normal bw, and without family history of diabetes mellitus were investigated by means of the administration, on alternate days, of 50 and 150 g oral glucose loads.

TSH and PRL responses to domperidone and TRH in men with insulin-dependent diabetes mellitus of different duration.

The effect of domperidone, a specific blocker of dopamine receptors, on serum TSH and PRL levels was evaluated in 16 euthyroid men affected by insulin-dependent diabetes mellitus (IDDM) of different duration and in 7 age-matched normal controls. Diabetics were divided into 2 groups of 8 men according to the duration of their disease (group I: 1-9 years; group II: 11-18 years). Both groups had normal basal levels of TSH and PRL.

Effect of domperidone on the release of insulin after intravenous glucose load in man.

To determine whether the blockade of the dopaminergic system is capable of modifying glucose-induced insulin release in man, the responses of insulin to an iv glucose load were measured at various domperidone infusion rates. The infusion of 5 micrograms/kg/min of domperidone increased significantly plasma insulin levels during the acute phase of glucose-induced insulin release and lowered plasma glucose values at 50 and 60 min; the k of glucose disappearance improved significantly. At lower domperidone infusion rates the acute increment of insulin after glucose load was indistinguishable from the response observed at 5 micrograms/kg/min until 0.

Further evidence that insulin metabolism is a major determinant of peripheral insulin response to oral glucose in subjects with mild glucose intolerance.

In mild glucose intolerance plasma concentration of C-peptide seems to give an estimate of pancreatic B cell secretion more reliable than plasma insulin itself. In the present study we measured the plasma levels of insulin and C-peptide after oral glucose load in 100 mildly glucose intolerant subjects, focusing our attention on high and low insulin responders. According to an insulin incremental area after oral glucose higher or lower than the mean +/- SD of the mean, 16 subjects were classified as "high insulin responders", and 17 as "low insulin responders".

Glucose tolerance after portacaval shunt in liver cirrhosis.

The liver plays a key role in glucose homeostasis and insulin metabolism. Altered glucose and insulin levels in peripheral blood are common findings in chronic liver disease. The aim of the present study was to investigate the effect of surgical portosystemic shunt on plasma glucose and insulin responses to glucose administration in a group of cirrhotic patients.

Nicotinic-cholinergic involvement in arginine-vasopressin response to insulin-induced hypoglycemia in normal men.

In order to establish whether arginine-vasopressin (AVP) release in response to insulin-induced hypoglycemia is mediated by a muscarinic and/or nicotinic cholinergic pathway, 12 normal men had an insulin tolerance test (ITT) in basal conditions and after treatment with the muscarinic receptor blocker pirenzepine (40 mg IV (intravenously) ten minutes before ITT in six subjects) or the nicotinic receptor antagonist trimethaphan (0.3 mg/min X 30 min IV before ITT in six subjects). The drugs did not modify arterial blood pressure nor produce side effects capable of altering AVP secretion.

Insulin and C-peptide responses to 75 g oral glucose load in the healthy man.

Plasma insulin and C-peptide levels in the fasting state and after a 2-h 75 g oral glucose tolerance test (OGTT) in a large number of healthy subjects are reported. 247 volunteers (134 males, 113 females), aged 13-69 years, who had a negative history of diabetes, no history of significant disease, normal physical examination, normal body weight, normal glucose tolerance, normal blood tests, and who were taking no drugs were studied. Results, mean +/- SEM (range): fasting glucose concentration = 4.

Pathogenetic mechanisms of the endogenous hypertriglyceridemia in a nonobese rat model.

Male Sprague-Dawley IVA-SIV rats were compared to male Sprague-Dawley Charles River rats of the same age, body weight, and daily food intake. The IVA-SIV rats demonstrated hypertriglyceridemia (182 +/- 9.4 v 131 +/- 9.

Diminished pituitary responsiveness to growth hormone-releasing factor in aging male rats.

The pattern of GH secretion undergoes substantial changes in the aging rat, resulting in decreased daily secretion of GH. In this study, the pituitary responsiveness to GH-releasing factor (GRF) was examined in young (2- to 5-month old) and aging (14- to 18-month old) male rats. In vivo studies were performed under sodium pentobarbital anesthesia.

Effect of age and environmental factors on glucose tolerance and insulin secretion in a worker population.

The effect of age on glucose tolerance, as differentiated from the effects of obesity, work and leisure physical activity, family history of diabetes, and the use of drugs known to adversely affect glucose tolerance and/or insulin secretion, has been analyzed in 732 factory workers aged 22 to 73 years. Glucose tolerance, as evaluated by the plasma glucose response to 75 g of oral glucose deteriorated with age, associated with an increase in plasma insulin levels. However, the age-related decrease in glucose tolerance also correlated significantly with degree of obesity, leisure-time physical activity, and the use of potential diabetogenic drugs.

Muscarinic cholinergic modulation of insulin response to an intravenous glucose tolerance test in normal man.

The effect of pirenzepine, a specific muscarinic cholinergic receptor antagonist, on insulin and glucagon responses to an intravenous injection of glucose was investigated in eight normal adult subjects. These volunteers received two iv glucose tolerance tests (0.33 g/kg) before and after the oral administration of 125 mg of pirenzepine (three doses of 25 mg during the day before the experiment and a fourth dose of 50 mg 2 h before glucose injection).

Insulin metabolism is a major factor responsible for high or low peripheral insulin levels in response to oral glucose loading in the healthy man.

In the present study we evaluated C-peptide peripheral levels after an oral glucose load in 30 healthy subjects (18 females, 12 males, aged from 15 to 55) with high or low insulin response to glucose challenge in order to clarify whether or not their beta-cell secretion rate keeps pace with peripheral insulin levels. Moreover, by the study of the relations between C-peptide and insulin in peripheral blood, we had an insight into the extent of insulin metabolism. On the basis of an insulin incremental area higher or lower than the mean +/- 1 SD after a 100-gram oral glucose load, 6 subjects were classified as 'high insulin responders' and 6 other subjects as 'low insulin responders'.

Evidence for an independent relationship between plasma insulin and concentration of high density lipoprotein cholesterol and triglyceride.

Increased plasma insulin and triglycerides and decreased high density lipoprotein concentrations are primary risk factors in the development of coronary artery disease. The aim of the present study was to verify whether there was an independent relationship between plasma insulin levels and both HDL cholesterol and triglyceride in a worker population of 607 subjects, 389 men and 218 women, aged 23-73 years. An oral glucose tolerance test (75 g) was performed.

Activation of PRL secretion by combined treatment with cyproterone acetate and ethinylestradiol.

Two groups of patients affected by idiopathic androgenization have been treated with ethinylestradiol (EE) associated with two different (high and low) dosages of cyproterone acetate (CA); the aim of this study was to evaluate the possible endocrine side effects at the pituitary level. After three and six months of treatment gonadotropins secretion appeared significantly inhibited with higher evidence for LH than for FSH and especially in the patients on high dose of CA. Nevertheless the most impressive finding was represented by the increase in PRL responses to TRH documented when higher doses of CA were employed without significant change in TSH secretion.