Biomedical subjects

I Zavaroni

Publications and source records attributed to I Zavaroni.

At least 55 records · Page 3Linked to original sources

PubMed1984

Inhibition of carbohydrate-induced hypertriglyceridemia by metformin.

The ability of metformin to prevent carbohydrate-induced hypertriglyceridemia was studied in fructose fed rats. The results indicated that plasma triglycerides were approximately 50% reduced in the drug treated rats and the reduction was associated with lowered very low density lipoprotein-triglyceride secretion rates and plasma insulin levels. Since the drug does not affect the fructose intestinal absorption, it did not prevent normal rate of weight gain. These results provide further evidence for the existence of a causal relationship between plasma TG concentration and plasma insulin concentration; metformin is able to modify both these variables likely affecting primarily the ambient insulin level.

Animals↗

PubMed1984

Evidence for unimpaired pancreatic secretion and hepatic removal of insulin in healthy offspring of type 2 (noninsulin-dependent) diabetic couples.

The aim of the present study was to investigate the secretion and the hepatic removal of insulin in a group of 14 unaffected offspring of 14 type 2 (noninsulin-dependent) diabetic couples compared to 14 healthy subjects without family history of diabetes mellitus. The two groups, each consisting of 5 obese and 9 nonobese subjects, were carefully matched for sex, age, and body weight. We examined glucose, insulin, and C-peptide levels, as well as C-peptide to insulin ratios and relations during the oral glucose tolerance test. Glucose concentrations and incremental areas were similar in the two groups, as well as insulin and C-peptide levels and areas. C-peptide to insulin molar ratios, both in fasting state and after glucose load, as well as relations between C-peptide and insulin incremental areas were not different. Our results suggest that the healthy offspring of type 2 diabetic couples have a normal response of beta-cell to oral glucose as well as a normal removal of insulin by the liver.

Administration, Oral↗

PubMed1984

Lack of effect of intravenous metformin on plasma concentrations of glucose, insulin, C-peptide, glucagon and growth hormone in non-diabetic subjects.

A study was carried out to evaluate the acute effect of an intravenous injection of metformin on the fasting plasma concentrations of glucose, insulin, C-peptide, glucagon and growth hormone in 15 non-diabetic subjects. Metformin (1 g) was administered as a bolus in a peripheral vein and blood was sampled 2, 5, 10, 15 and 30 minutes after the drug injection. No significant change in fasting concentration of glucose nor in C-peptide, insulin, glucagon and growth hormone fasting levels was noticed. It is concluded that metformin does not possess an acute direct hypoglycaemic effect in non-diabetic subjects and does not acutely affect the basal activity of endocrine pancreas and pituitary gland in releasing insulin, glucagon and growth hormone.

Adult↗

PubMed1984

Peripheral hyperinsulinemia of simple obesity: pancreatic hypersecretion or impaired insulin metabolism?

Insulin and C-peptide levels in peripheral blood in the fasting state and after an oral glucose load were measured in 65 nondiabetic, obese subjects and 65 age- and sex-matched nondiabetic normal weight subjects. Fasting insulin and C-peptide levels were significantly higher in obese than in nonobese subjects, whereas 1 and 2 h after the oral glucose load only insulin concentrations were significantly higher in the obese subjects. C-peptide to insulin molar ratios, as well as the relation between the incremental areas of the two peptides, were used as relative measures of hepatic insulin extraction. In the fasting state the ratios between C-peptide and insulin were similar in obese and nonobese subjects, whereas after glucose they were significantly lower in the obese individuals. Similarly, the relations between C-peptide and insulin incremental areas were significantly lower in obese than in nonobese subjects. The comparison of the corresponding plasma levels and areas of C-peptide and insulin after glucose showed that for the same C-peptide value, the insulin value was higher in the obese group. Last, in obese subjects the parameter used as an estimate of hepatic removal of insulin after oral glucose inversely correlated with the fasting insulin concentration and the insulin incremental area after glucose. These results suggest that in obesity peripheral hyperinsulinemia depends on pancreatic hypersecretion of insulin in the fasting state and impaired hepatic insulin metabolism after oral glucose loading.

Adult↗

PubMed1984

Secretion and hepatic removal of insulin in the healthy offspring of type 2 (non-insulin-dependent) diabetic subjects.

The aim of the present study was to investigate the secretion and hepatic removal of insulin in the healthy offspring of type 2 (non-insulin-dependent) diabetic subjects. For this purpose, we examined the insulin and C-peptide responses to a 75 g oral glucose tolerance test in a group of 55 healthy subjects each having one parent with type 2 diabetes mellitus, and in a group of 55 individuals without a family history of diabetes. All the 110 subjects in the study were ambulatory volunteers, in good general health, and with normal glucose tolerance. The two groups were carefully matched for sex, age, and body weight. Glucose and insulin concentrations as well as incremental areas were similar in the two groups. C-peptide levels and incremental areas were almost identical. C-peptide to insulin molar ratios both in fasting state and after glucose load, as well as relations between C-peptide and insulin incremental areas did not differ in the two groups. In conclusion, the healthy offspring of only one non-insulin-dependent diabetic parent show a normal beta-cell response to glucose, and normal removal of insulin by the liver.

Adult↗

PubMed1983

Decreased hepatic insulin extraction in subjects with mild glucose intolerance.

The fact that hyperinsulinemia occurs in simple obesity and mild glucose intolerance has been well established. Altered hepatic insulin extraction may influence the levels of circulating hormone. The simultaneous measurement of insulin and C-peptide concentrations in peripheral blood enables an in vivo estimation of hepatic insulin removal. To evaluate hepatic insulin extraction, insulin and C-peptide responses to oral glucose were studied in 176 obese and nonobese subjects with normal, impaired, or diabetic glucose tolerance. Insulin levels as well as insulin incremental areas in glucose intolerant subjects were significantly higher than in weight-matched controls. The levels of C-peptide as well as C-peptide incremental areas were only slightly enhanced in subjects with impaired glucose tolerance, whereas they were reduced in subjects with diabetic tolerance. The molar ratios of C-peptide to insulin, both in the fasting state and after ingestion of glucose, as well as the relationship between the incremental areas of the two peptides were used as measures of hepatic insulin extraction. They were significantly reduced in glucose intolerant subjects and, to a lesser extent, in nondiabetic obese subjects. These results indicate that peripheral hyperinsulinemia in subjects with simple obesity or impaired glucose tolerance is a result of both pancreatic hypersecretion and diminished hepatic insulin extraction. In subjects with a more severe degree of glucose intolerance, decreased hepatic insulin removal is the primary cause of hyperinsulinemia.

Adolescent↗

PubMed1982

Mechanism of insulin resistance in fructose-fed rats.

Previous results from our laboratory demonstrated that chronic administration of fructose to normal rats led to both hyperinsulinemia and in vivo insulin resistance. To localize the major tissue site of insulin resistance in fructose-fed animals, we compared glucose uptake by perfused hindlimb skeletal muscle and liver from rats fed either a 60% fructose diet or laboratory chow. Glucose uptake by perfused muscle from chow and fructose-fed rats was comparable at perfusate insulin levels of 0 microunit/ml (15.2 versus 15.5 microliters/min/g muscle), 100 microunits/ml (18.3 versus 19.8), and greater than 500 microunits/ml (35.5 versus 33.4). In contrast, glucose outflow from livers of fructose-fed rats was significantly greater (p less than .02) than chow-fed animals perfused in the absence of added insulin (52.1 versus 36.5 mumol/g). Furthermore, the ability of insulin to suppress glucose outflow was less in livers from fructose-fed rats at perfusate insulin level of 165 microunits/ml (13.2 versus 41.4% as well as at insulin concentration greater than 900 microunits/ml, (32.5% versus 62.2%). These findings suggest that the insulin resistance resulting from chronic fructose feeding is due to the diminished ability of insulin to suppress hepatic glucose output, and not to a decrease in insulin-stimulated glucose uptake by muscle.

Animals↗

PubMed1982

Studies of the mechanism of fructose-induced hypertriglyceridemia in the rat.

Carbohydrate-induced hypertriglyceridemia is easily produced in the rat, and fructose has been shown to be particularly potent in this regard. In this study we have compared the effects of feeding rats diets high (66% of total calories) in fructose or glucose on various aspects of carbohydrate and lipid metabolism. The results confirmed previous observations that fructose (456 +/- 276 mg/dl) was more potent (p less than 0.001) in raising plasma TG concentration than was glucose (242 +/- 13 mg/dl), and indicated that the difference in magnitude of hypertriglyceridemia produced by the two carbohydrates was closely related to the ability of the test diets to increase VLDL-TG secretion (r = 0.85, p less than 0.001). Both glucose and fructose feeding led to comparable degrees of hyperinsulinemia, and plasma TG concentrations increased before hyperinsulinemia evolved in fructose-fed rats. Therefore, it was concluded that fructose can act directly on the liver to increase VLDL-TG secretion, and that fructose-induced hypertriglyceridemia can occur in the absence of hyperinsulinemia. On the other hand, the rise in plasma TG concentration produced by fructose was reduced dramatically in exercise-trained rats, and this was associated with a decrease in plasma insulin concentration. Based upon these observations, we suggest that fructose feeding produces hypertriglyceridemia by directly stimulating hepatic VLDL-TG secretion, as well as by producing insulin resistance and hyperinsulinemia, and that it is the combined effect of these two separate actions which accounts for the magnitude of fructose-induced hypertriglyceridemia.

Animals↗

PubMed1982

The effect of pyridoxine-alpha-ketoglutarate (PAK) on exercise-induced increase of blood lactate in patients with type I diabetes.

Administration of pyridoxine-alpha-ketoglutarate (PAK) to a group of insulin-independent non-ketotic diabetics decreased (p less than 0.01) the plasma concentration of lactate response to isometric exercise. The mechanism of action of PAK could be interpreted as a consequence of changes induced by the drug on the Krebs' cycle with a subsequent reduction of lactate production.

Adolescent↗

PubMed1981

Inhibition of carbohydrate-induced hypertriglyceridemia by a disaccharidase inhibitor.

The ability of an inhibitor of intestinal alpha-glucosiadase activity to prevent sucrose-induced hypertriglyceridemia was studied in nonobese rats. The results indicated that plasma triglyceride levels were approximately twice as high in untreated rats, and the reduction in plasma triglyceride levels of drug-treated rats was associated with lowered very low density lipoprotein-triglyceride secretion rates and plasma insulin levels. Since these changes could be produced with an amount of glucosidase inhibitor which did not prevent normal rate of weight gain, the possibility arises that this approach may be useful in the treatment of various hypertriglyceridemic states in man. Finally, the observation that the fall in plasma TG concentration was associated with a fall in plasma insulin concentration provides further evidence for the existence of a causal relationship between the two variables.

Acarbose↗

PubMed1981

Ability of exercise to inhibit carbohydrate-induced hypertriglyceridemia in rats.

The ability of spontaneous running to prevent carbohydrate-induced hypertriglyceridemia was studied in young, nonobese rats. Exercise-trained and sedentary rats were fed a diet consisting of (as percent total calories) 12% fat, 22% protein, and 66% carbohydrate. The source of the carbohydrate was varied, and experiments were carried out with sucrose and glucose as the sole dietary carbohydrate. Plasma triglyceride (TG) levels rose in response to both forms of dietary carbohydrate in both sedentary and exercise-trained rats, but the magnitude of the elevation was greatly attenuated in the exercise-trained group. Plasma insulin concentrations were also significantly lower in exercise-trained rats. Measurements of hepatic very low density lipoprotein (VLDL)-TG secretion rate and adipose tissue lipoprotein lipase (LPL) activity were made in an effort to determine how exercise-training prevented the development of carbohydrate-induced hypertriglyceridemia. The results of these studies indicated that perfused livers of exercise-trained rats secreted significantly less VLDL-TG, whereas adipose tissue LPL activity of the two groups was similar. On the basis of these results, it is postulated that the ability of exercise-training to inhibit carbohydrate-induced hypertriglyceridemia is due to an increase in insulin sensitivity resulting from chronic exercise. As a result, the postprandial insulin responses to high carbohydrate diets would be relatively reduced in exercise-trained rats, leading to decreased hepatic VLD-TG secretion, and lower plasma triglyceride concentrations.

Adipose Tissue↗

PubMed1980

Effect of fructose feeding on insulin secretion and insulin action in the rat.

Insulin secretion and insulin action were studied in rats fed either a diet containing (as percent of calories) 66% fructose, 22% protein, and 12% fat, or standard rat chow (60% vegetable starch, 29% protein, 11% fat) for 7 days. Plasma glucose concentration following either an oral glucose or fructose load (180 mg/100 g body weight) were slightly higher in the fructose-fed rats, and this was associated with a much greater elevation of plasma insulin concentrations. The ability of insulin to stimulate disposal of glucose load was determined during the continuous infusion of epinephrine, propranolol, glucose, and insulin. Under these condtions the steady state plasma insulin levels were the same in the two groups of rats, whereas the steady state plasma glucose levels were almost twice as high in the fructose fed rats. Thus, fructose feeding for 7 days resulted in an increase in the insulin response to an oral carbohydrate challenge, as well as to a loss of normal insulin sensitivity.

Animals↗

PubMed1978

[Genetic markers in insulin-dependent juvenile diabetes].

A significant association has been established between insulin-dependent diabetes and HL-A. This was appraised in a selected series of 16 patients and 64 of their first-degree relatives by HL-A typing. The relatives also underwent a glucose tolerance test. The results showed a high incidence of B8 in the patients (31%, VS 15% in controls: p less than 0.01). A previously observed prevalence of Bw 15, however, was not noted. In addition, an increased incidence of Bw 35 was detected (38%, VS 23% in the controls: p less than 0.02). In the case of the relatives, no significant differences in HL-A frequency were apparent, nor could a relationship between HL-A phenotype and altered glucose tolerance be established. The true aetiopathogenetic significance of this association is discussed in the light of recent views concerning HL-A and diseases.

Chromosome Mapping↗

PubMed1977

HLA antigens and insulin dependent diabetes mellitus. A family study.

Sixteen insulin dependent diabetic patients (age at onset less than 35 years) and their families were tissue typed for HLA antigens. Glucose tolerance of relatives was also tested. Among diabetic patients two HLA antigens were found with increased frequency: B8 (31 percent, control 15 percent) and Bw35 (38 percent, control 23 percent). Among normal relatives B8 and Bw35 had the same frequency as the control group. Bw15 frequency was not increased in either group. In relatives, no correlation between HLA antigens (B8 or Bw35) and abnormal glucose tolerance, obesity and over-weight at birth was found. Present data confirm previous reports of high B8 frequency in early onset diabetic patients, but fail to demonstrate a raised frequency of abnormal glucose tolerance among relatives bearing B8 (or, in our cases, Bw35). B8 may be considered a genetic indicator for susceptibility to juvenile diabetes. On the basis of present results in families, however non genetic factors clearly also play a determinant role. Furthermore, that diabetogenesis arises from a link between Ir-genes and HLA-B8 antigen should only be considered a suggestive hypothesis.

Adult↗

PubMed1976