Altered control of growth hormone secretion in patients with cirrhosis of the liver

Ten male patients with cirrhosis of the liver (three with portacaval anastomosis [PCA]) and eight sex- and age-matched controls underwent an arginine infusion test followed by an intravenous glucose tolerance test. Plasma glucose and growth hormone (GH) levels were measured during a period of three hours. In the normal subjects, the peak GH response to arginine occurred 60 minutes after the start of the infusion and was followed by a progressive decline in GH concentration; dextrose injection resulted in a further rapid fall in GH concentration. In cirrhotic patients, both fasting and postarginine GH concentrations were significantly higher than in controls; in addition, the dextrose injection, after causing a transitory drop in plasma GH levels, resulted in a marked increase in plasma GH concentration. In the patients with PCA, the plasma GH increase after arginine and after dextrous was more marked. In these cirrhotic patients, the plasma GH levels correlated directly with the magnitude of the portal hypertension and inversely with the serum albumin concentration, suggesting that the abnormality of GH secretion was a reflection of the derangement in liver function.

Metabolic effects of glucagon in endogenous hypertriglyceridemia

The metabolic effects of glucagon, administered i.v. in doses of 1 microgram/kg, were evaluated in two groups of patients with endogenous hypertriglyceridemia (Types IV and V according to Fredrickson) with normal and reduced glucose tolerance and in a control group. Glucagon had a lipolytic effect, evaluated as the plasma increase of free fatty acids (FFA) during the first 20 min in normal subjects, but not in the two hyperlipemic groups. A negative correlation was observed between fasting IRI level and FFA mobilization. The ketogenic and hypotriglyceridemic effects of glucagon were demonstrated in normal and hyperlipemic groups. It would seem, therefore, that at the pharmacological doses injected, there is no resistance to the hypotriglyceridemic effect of glucagon in endogenous hypertriglyceridemia.

Glucagon and insulin secretion in potential diabetes

Insulin and glucagon have been studied in 20 subjects (both of the subjects' parents were diabetic or in case of only one diabetic parent, the other showed a first degree familiarity of diabetes): 10 showed normal glucose tolerance ('true prediabetics') and 10 impaired glucose tolerance ('genetic chemical diabetes'). Mean insulin response to oral (100 g) and i.v. glucose load (200 mg/kg followed by 20 mg/kg/min for 60 min) and to arginine infusion (25 g in 30 min) was normal in the prediabetics and delayed and higher in the subjects with chemical diabetes as compared to the control group. Glucagon response to arginine was higher, but not significantly, in prediabetics and in subjects with chemical diabetes. In both of these groups glucagon suppression by glucose was not observed. The insulin/glucagon molar ratio was significantly reduced after glucose infusion in these two groups. No correlation was found between insulin and glucagon secretion after arginine or glucose. A possible alteration in the mechanism controlling glucagon secretion even in the earliest phases of diabetes is suggested.

Insulin and glucagon secretion in diabetic and non-diabetic patients with circulating islet cell antibodies

Thirty-nine patients (14 non-diabetics, 8 chemical diabetics, and 17 overt diabetics) with circulating islet cell antibodies (ICA) were studied. Insulin and glucagon secretion after oral (100 g) and intravenous glucose loading (200 mg/kg bolus injection followed by an infusion of 20 mg/min over 60 min) and arginine infusion (25 g over 30 minutes) were evaluated in these patients and in non diabetic and diabetic ICA-negative controls. In the non-diabetic groups with or without ICA, insulin and glucagon responses to glucose were similar. Moreover, in ICA positive patients the response of these hormones to arginine infusion was reduced. Similar alterations in insulin and glucagon secretion were observed in the CIA positive and negative patients with chemical or overt diabetes. In particular, fasting hyperglucagonaemia and glucagon hyperresponse to arginine are associated with a lack of insulin secretion in the patients with overt diabetes. Hormonal differences between diabetics with and without ICA could not be detected.

[Clinical and metabolic aspects of juvenile myocardial infarct]

A clinical and metabolic study of 61 patients with myoocardial infarct before the age of 40 yr showed a high frequency of familial involvement, particularly in subjects with type IIA and IIB hyperbetalipoproteinaemia. Excess weight and arterial hypertension were rare, while premonitory angina was absent in 59%. Four subjects were diabetic. Oral glucose tolerance was normal in 14 and of diabetic type in 26 of 40 patients examined; the insulin response pointed to insulin-resistance. Dyslipidaemia was noted in 45%, including type IIA and IIB hyperbetalipoproteinaemia in 27%. Distribution of the frequency of infarct in function of cholesterolaemia classes gave a bimodal curve indicative of distinct normo- and hypercholesterolaemic groups within the series. Reduced glucose tolerance was more frequent in patients with low blood cholesterol. This suggests that reduced tolerance and high blood cholesterol are independent risk factors in coronary disease. No relation between the clinical and metabolic data could be ascertained.

Effects of clofibrate treatment on arginine-induced insulin secretion in endogenous hypertriglyceridemia

Arginine-induced insulin secretion was evaluated in 13 patients with endogenous hypertriglyceridemia (Fredrickson's Type IV) before and after a two-month period of Clofibrate therapy. Clofibrate reduced triglyceride, cholesterol and FFA levels by 68, 28 and 15% respectively and provoked a significant reduction in arginine-induced insulin secretion without modifying glucose response. Arginine-induced insulin secretion was also studied in 11 normal subjects during saline and intralipid infusions. Glucose and insulin basal values, and glucose and insulin response to arginine infusion were not influenced by Intralipid infusion in these controls. These results confirm that clofibrate reduces insulin secretion thereby contributing to decreased serum triglyceride levels.

Chronobiological pattern of growth hormone secretion in normal subjects and in retinopathic diabetics. Lack of suppression by a plurichronocorticoid drug

Nyctohemeral variations in plasma concentrations of HGH, glucose, and FFA were studied in 22 normal subjects and 48 diabetic patients affected with retinopathy. In the normal subjects, (fourteen males and eight females, mean age 40+/-3 years; body weight less than 110% of I.B.W.) the determinations were made on blood samples drawn every hour. Seven of these normal subjects were examined before and after 10 days of administration of a new plurichronocorticoid drug (administered at 08(00) and 15(00), with a total amount of 14 mg of prednisolone and 15 mg of cortisone). In patients with diabetic retinopathy (32 male and sixteen female patients, mean age 46+/-2 years, body weight less than 110% of I.B.W.) the determinations were made on blood samples drawn every 3 hrs. All the diabetic patients were insulin treated and were under good or discrete metabolic control, and presented advanced retinopathy. Both in the normal subjects and in retinopathic diabetics, the mean HGH curve showed a characteristic elevation during the early nighttime hours (between 21(00) and 02(00). Despite higher values in plasma glucose and FFA, in diabetics the nocturnal elevation of HGH was only slightly lower than in the normals. The comparison between daytime and nighttime determinations, both in the normal subjects and in the diabetics, reveals statistically significant differences. These results suggest that in subjects with diabetic retinopathy, in the phase of good or discrete metabolic control, spontaneous HGH secretion is not increased, and that nocturnal elevation of HGH is not substantially influenced by higher plasma levels of glucose and FFA. Ten days of plurichronocorticoid treatment with a new drug which exhausts its activity before the evening, did not modify the circadian rhythm of HGH.

Hypolipidemic effects of metformin in hyperprebetalipoproteinemia

Metformin's hypolipidemic effects (2.55 g/day for 3 months) have been studied in 19 subjects with Fredrickson's Type IV hyperprebetalipoproteinemia. The majority of patients were above ideal body weight (relative body weight = 118 +/- 2.7 %). Eleven of the subjects presented chemical diabetes, 5 fasting hyperglycemia, and 3 normal glucose tolerance. After treatment with metformin, body weight showed a slight, but significant reduction (--2.4 +/- 0.3 kg). Glucose tolerence was not substantially altered while basal glucose was significantly reduced in the 5 subjects with fasting hyperglycemia. Basal plasma insulin was significantly reduced in all the patients following metformin treatment. Insulin response to OGTT was slightly reduced in the subjects with fasting hyperglycemia. Independent of the patients' glucose tolerance, metformin treatment induced a marked decrease in plasma triglycerides (-- 40 %) and a reduction in plasma cholesterol (-- 12 %). No correlation was found between triglyceride and cholesterol reduction and body weight, glucose, and plasma insulin variations. Like phenformin, metformin acts not only on glucose metabolism and insulin secretion but on lipid metabolism as well.

Suppression and stimulation mechanisms controlling glucagon secretion in a case of islet-cell tumor producing glucagon, insulin, and gastrin

The mechanisms controlling secretion of glucagon and other pancreatic hormones were studied in a patient affected with multihormone-secreting islet-cell tumor. Fasting glucagon levels (3,000 pg./ml.) rose to 10 ng./ml. following arginine stimulation. While oral glucose load and intravenous glucose infusion did not suppress glucagon secretion, insulin administration induced a prompt depression in glucagon levels. Glucagon, insulin, and gastrin levels were suppressed by somatostatin while calcium infusion caused a paradoxical increase. It is suggested that only some of the stimulation-inhibition mechanisms were conserved in this case of glucagon-secreting pancreatic tumor.

Hormonal counterregulation in ethanol-induced hypoglycemia-Glucagon and cortisol secretion in pigs

Plasma glucagon and cortisol levels were determined in pigs during ethanol-induced hypoglycemia. This hypoglycemia is due to an inhibition of gluconeogenesis which could be related to an abnormal secretion of gluconeogenetic hormones. In six pigs the infusion of ethanol for seven hours (6 mg/kg/min) induced a significant decrease of plasma glucose which was associated with a significant increase of plasma glucagon in the portal vein, femoral artery and hepatic vein. Corresponding with the period of maximal hypoglycemia, plasma cortisol in the femoral artery was also significantly increased. On the other hand, plasma insulin levels were consistently reduced during hypoglycemia. In a second group of six pigs ethanol was infused along with a glucose infusion (3 mg/kg/min) in order to obtain a relatively constant glucose concentration. In this group ethanol did not produce any significant modification of plasma glucagon and cortisol. Therefore, glucagon and cortisol hypersecretion is related to hypoglycemia induced by ethanol. Both the increase in plasma glucagon and cortisol and the decrease in plasma insulin could represent a protective mechanism against alcohol-hypoglycemia.

Growth hormone response to insulin and to arginine in patients with familial hypercholesterolaemia

Human growth hormone (HGH) response to i.v. insulin (0.1 U/kg body weight) and arginine infusion (25 g of L-arginine for 30 min) was studied in 9 patients (5 males and 4 females) with primary familial hypercholesterolaemia and belonging to 4 families. Mean age was 28 +/- 2 years (range 18-36) and body weight was less than 105% of ideal body weight. Glucose tolerance and insulin response to oral glucose were normal in all patients. HGH release after insulin and after arginine was slightly increased as compared to 21 normal controls, but the differences were not significant. Insulin and glucagon response to arginine in these patients was within the normal range. Plasma glucose and free fatty acids were normal after both insulin and arginine. Moreover, no significant correlation was found between fasting cholesterol and HGH peaks after insulin and after arginine, nor between cholesterol and insulin and glucagon responses. Despite marked hyperlipidaemia, HGH-deficient patients examined by other authors never present signs of atherosclerotic disease. Our data suggest that HGH, in the presence of elevated cholesterol levels, might play an important role in the development of atherosclerotic lesions.

The influence of plasma triglycerides on human growth hormone response to arginine and insulin: a study in hyperlipemics and normal subjects

Human growth hormone (HGH) response to arginine (25 gm IV in 30 min) and to insulin (0.1 U/kg B.W.) was studied in 12 male patients (mean age 36 +/- 2 years), with normal glucose tolerance and normal body weight, affected with Fredrickson's Type IV primary hyperlipemia. The patients were examined both when plasma triglycerides (TG) were elevated and following clofibrate (2 gm/die for 30-60 days) induced TG reduction. No variations in glucose or FFA behaviour or in body weight were observed after clofibrate. HGH response to arginine was absent, while that to insulin was only inhibited, when plasma TG were elevated. A significant increase in HGH peaks after arginine (from 1.99 +/- 0.59 to 9.34 +/- 1.58 ng/ml) and a slight increment in HGH peaks after insulin (from 23.09 +/- 7.19 to 31.46 +/- 7.95 ng/ml) were observed following reduction in plasma TG. Arginine test was carried out in 7 normal subjects during saline infusion and at the 3rd hour of lipid infusion (Intralipid 20%). HGH response to arginine was absent in all of the subjects during lipid infusion. The HGH response to insulin test, carried out in 9 other normal subjects during saline infusion and at the 3rd hour of lipid infusion (Lipiphysan 15%) was significantly inhibited during lipid infusion. Since lipid infusion provoked an increment, not only in plasma TG but also in FFA, the inhibition of HGH release could be correlated with the elevated plasma levels of both TG and FFA. The results obtained in both spontaneous and experimental hyperlipemia not only confirm the role played by FFA in the regulation of HGH secretion, but also support the hypothesis that elevated TG levels could inhibit HGH response to some stimuli.

Human growth hormone and cortisol response to insulin stimulation in aging

The influence of age on plasma growth hormone (HGH) and cortisol response to i.v. insulin (0.1 U/kg of body weight) was evaluated in 32 healthy subjects whose ages ranged between 20 and 84 years. A significant reduction in HGH response to insulin was observed with aging. In the young (20-34 years), middel-aged (35-49 years), and elderly (53-84 years) groups, average HGH peaks were 46.51 +/- 7.37, 29.95 +/- 5.35, and 14.31 +/- 2.39 ng/ml while average HGH areas were 2.911 +/- 0.484, 1.654 +/- 0.316, and 0.699 +/- 0.149 mug-min, respectively. Since insulin's hypoglycemic effect became less rapid with aging, this could, in part, explain the progressive decline in the HGH response to insulin. This phenomen may also be attributed to histological changes occurring in the pituitary with aging. Moreover, cortisol response was similar to all three age groups. These findings suggest that, while HGH response to insulin is correlated with age, adrenal response does not show any important modifications with aging.

Glucagon secretion in primary endogenous hypertriglyceridemia before and after clofibrate treatment

Arginine-induced insulin and glucagon secretion preceding and following clofibrate treatment was studied in 13 patients with endogenous hypertriglyceridemia. A positive correlation was demonstrated between fasting insulin and triglyceride levels and between the fasting insulin/glucagon molar ratio and triglyceride levels. In patients with endogenous hypertriglyceridemia, anginine infusion induced a significantly increased glucagon response with respect to that found in controls. No correlation was found to exist between glucagon and free fatty acids (FFA) or between glucagon and triglyceride levels. The same lack of correlation was found in normal subjects rendered hypertriglyceridemic by means of Intralipid infusion, which did not modify the fasting glucagon-like immunoreactivity (GLI) or the GLI response to arginine. Clofibrate treatment induces a triglyceride reduction (incrementTG) which is correlated with the reduction in the insulin/glucagon molar ration (incrementI/G). After clofibrate treatment there is also a significant reduction in fasting GLI levels and in the insulin response to arginine, and an increase in the glucagon response. Clofibrate could exercise its hypolipidemic effect by modifying the relationship between insulin and glucagon levels.