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Biomedical subjects

A Golay

Publications and source records attributed to A Golay.

At least 109 records · Page 6Linked to original sources
PubMed1989

Blunted glucose-induced thermogenesis in 'overweight' patients: a factor contributing to relapse of obesity.

Glucose-induced thermogenesis was studied in 12 overweight patients (9F and 3M) before (mean body weight +/- s.e.m. 83 +/- 2 kg) and after weight loss (68 +/- 2 kg), and in eight of the same patients following relapse of body weight gain (84 +/- 5 kg). Expressed as a percentage of the energy content of the 100 g oral glucose load, glucose-induced thermogenesis was lower in the overweight before weight loss (6.5 +/- 0.5 per cent, P less than 0.05), after weight loss (3.9 +/- 0.6 per cent, P less than 0.01) and after weight regain (6.3 +/- 0.9 per cent, P less than 0.05) than in a group of lean control subjects, matched for sex and age (8.3 +/- 0.5 per cent). Basal energy expenditure was lower after weight reduction than before (1.16 +/- 0.04 vs 1.41 +/- 0.08 kcal/min, P less than 0.01). In the formerly overweight patients, the combined effect of a decreased basal energy expenditure and an attenuation of glucose induced thermogenesis resulted in a postprandial energy expenditure which was markedly lower than in the overweight state (P less than 0.001). Following relapse of obesity, glucose-induced thermogenesis remained attenuated compared to control subjects. These results suggest that a lowered basal energy expenditure and a reduced glucose-induced thermogenesis contribute to the positive energy balance which results in relapse of body weight gain after cessation of a hypocaloric diet.

Adult↗
PubMed1988

Oxidative and non-oxidative glucose metabolism in non-obese type 2 (non-insulin-dependent) diabetic patients.

Insulin resistance is a common feature of Type 2 (non-insulin-dependent) diabetes mellitus. This defect in insulin-mediated glucose metabolism could result from a defect in either glucose oxidation or non-oxidative glucose disposal. To examine this question, euglycaemic insulin clamp studies were performed in 16 normal weight Type 2 and 11 age-matched control subjects. In Type 2 diabetic patients the fasting plasma glucose concentration, 8.39 +/- 0.50 mmol/l, was allowed to decline (over 54 +/- 6 min) to 5.33 +/- 0.11 mmol/l before starting the insulin clamp. Total body glucose uptake was significantly decreased in Type 2 diabetic patients vs control subjects (148 +/- 15 vs 264 +/- 25 mg/min.m2, p less than 0.001). Both total glucose oxidation (59 +/- 6 vs 89 +/- 6 mg/min.m2, p less than 0.005) and non-oxidative glucose disposal (89 +/- 15 vs 179 +/- 24 mg/min.m2, p less than 0.005) were significantly reduced in the Type 2 diabetic patients. Basal glucose oxidation was also reduced in the Type 2 diabetic patients (22 +/- 3 vs 38 +/- 5 mg/min.m2, p less than 0.01). In conclusion, during the postabsorptive state and under conditions of euglycaemic hyperinsulinaemia, impairment of glucose oxidation and non-oxidative glucose disposal both contribute to the insulin resistance observed in normal weight Type 2 diabetic patients. Since lipid oxidation was normal in this group of diabetic patients, excessive non-esterified fatty acid oxidation cannot explain the defects in glucose disposal.

Blood Glucose↗
PubMed1988

Effect of insulin deficiency on low density lipoprotein metabolism in rabbits.

These studies have been carried out in rabbits with alloxan-induced diabetes in order to see if insulin deficiency affects low density lipoprotein (LDL) catabolism. The results showed that plasma LDL-cholesterol was lower in diabetic rabbits, associated with a fall in the cholesterol to protein ratio of LDL particles. In addition, 125I-LDL disappeared more slowly from plasma of diabetic rabbits, leading to a significant reduction in fractional catabolic rate and a decrease in residence time of 125I-LDL. These data demonstrated that LDL composition and catabolism are greatly altered as a consequence of insulin deficiency.

Animals↗
PubMed1988

The metabolic consequences of long-term human obesity.

Sixty-seven subjects with moderate obesity (50 +/- 3 percent above ideal body weight) were given an oral glucose tolerance test with the simultaneous measurement of rates of glucose and lipid oxidation by continuous indirect calorimetry. When the subjects were stratified into nine 5-year classes of duration of obesity, the prevalence of impaired glucose tolerance (IGT) and overt diabetes both increased with increasing duration of obesity. Both basal and post-OGTT lipid oxidation rates were, however, similar in all classes. To assess the independent influence of IGT, diabetes, age, and duration of obesity on glucose metabolism, the data were subjected to analysis of variance using a factorial design with metric covariates. Age by itself was found to be associated (P less than 0.05) with a decline in total post-OGTT glucose oxidation. Both IGT and diabetes, on the other hand, were associated with increased plasma insulin and free fatty acid (FFA) levels, both in the fasting state and following glucose ingestion (P = 0.05-P less than 0.002). Only diabetes, however, was associated with a drastic reduction in nonoxidative glucose disposal, which marked the appearance of, and strongly correlated with (r = -0.81, P less than 0.001), fasting hyperglycemia. Duration of obesity had significant metabolic consequences in its own right: a fall in the insulin response to glucose (P = 0.05) and in the rate of total glucose oxidation (P = 0.03), and a rise in post-OGTT glucose levels (P = 0.04). We conclude that: (a) increased lipid oxidation is common in obesity, but is not sufficient to explain the deterioration of glucose tolerance in long-term obesity; (b) very-long-term obesity may be associated with partial exhaustion of the beta cell, and the resultant insulinopenia may cause depressed glucose oxidation and impaired glucose tolerance, and (c) a defect in nonoxidative glucose disposal is a characteristic feature of frank diabetes at any stage of obesity.

Adult↗
PubMed1987

Insulin suppression of plasma-free fatty acid concentration in normal individuals and patients with type 2 (non-insulin-dependent) diabetes.

In order to define the effect of Type 2 (non-insulin-dependent) diabetes mellitus on the ability of insulin to regulate plasma-free fatty acid (FFA) concentrations, we determined the plasma FFA response to the intravenous infusion of various amounts of insulin. Plasma FFA concentrations were higher in patients with Type 2 diabetes (two way analysis of variance, p less than 0.001) over a plasma insulin concentration which ranged from approximately 5 to 55 mU/l of insulin. Although plasma FFA concentrations were higher in patients with Type 2 diabetes at any given insulin concentration, the relative ability of insulin to suppress plasma FFA concentration to half the initial value was comparable in normal individuals and patients with Type 2 diabetes, occurring at a plasma insulin concentration of approximately 20 mU/l. These data demonstrate that plasma FFA levels are regulated over a narrow range of plasma insulin concentrations in humans, and that plasma concentrations are higher than normal in patients with Type 2 diabetes throughout this range.

Aged↗
PubMed1987

Relationships between plasma-free fatty acid concentration, endogenous glucose production, and fasting hyperglycemia in normal and non-insulin-dependent diabetic individuals.

Measurements of fasting and postprandial plasma glucose, insulin, and free fatty acid (FFA) concentrations were made in 32 individuals--16 with normal glucose tolerance and 16 with non-insulin dependent diabetes mellitus (NIDDM)--further subdivided into two equal groups on the basis of body weight. In addition, endogenous glucose production was estimated in 32 subjects. Both fasting plasma glucose (251 +/- 14 v 86 +/- 1 mg/dL) and FFA (672 +/- 35 v 434 +/- 45 microEq/L) concentrations were significantly higher in patients with NIDDM (P less than .001), and the differences between normal and diabetic existed in both weight groups. Rates of endogenous glucose production were also significantly elevated (P less than .001) in diabetic (120 +/- 6 mg/m2 X min) as compared to normal subjects (73 +/- 6 mg/m2 X min), and these differences were also independent of degree of obesity. However, there were no significant differences between normal subjects and patients with NIDDM in either fasting or postprandial insulin concentrations. The similarity in insulin values for normal and diabetic subjects was true of both obesity groups, although insulin concentrations were somewhat higher in normal obese individuals as compared to their normal nonobese counterparts. Significant relationships were seen between values for fasting plasma glucose and endogenous glucose production (r = .89), fasting plasma glucose and fasting FFA (r = .64), and FFA levels and endogenous glucose production (r = .58) when all nonobese subjects were considered together. Essentially identical relationships, both qualitatively and quantitatively, were seen within the obese group.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗
PubMed1987

Documentation of hyperglucagonemia throughout the day in nonobese and obese patients with noninsulin-dependent diabetes mellitus.

Plasma glucose, insulin, FFA, glucagon, and GH concentrations were measured over an 8-h period in normal subjects and patients with noninsulin-dependent diabetes mellitus (NIDDM). Meals were consumed at 0800 h (20% of daily calories) and noon (40% of daily calories), and measurements were made hourly from 0800-1600 h. Day-long plasma glucose, insulin, and FFA concentrations were higher than normal (by two-way analysis of variance) in patients with NIDDM, whether obese or nonobese. In addition, day-long plasma glucagon concentrations were also higher than normal (by two-way analysis of variance) in both nonobese and obese patients with NIDDM. Furthermore, direct relationships were found between the total plasma glucagon response from 0800-1600 h and total plasma glucose (r = 0.57; P less than 0.001) and FFA (r = 0.30; P less than 0.06) responses. In contrast, plasma GH levels were not increased in patients with NIDDM. These data demonstrate that ambient plasma concentrations of both glucose and FFA are higher in patients with NIDDM, despite the fact that coexisting plasma insulin levels are equal to or higher than normal. The higher day-long plasma glucagon levels in patients with NIDDM may contribute to their higher plasma glucose and FFA concentrations.

Activity Cycles↗
PubMed1987

Resistance to insulin suppression of plasma free fatty acid concentrations and insulin stimulation of glucose uptake in noninsulin-dependent diabetes mellitus.

The ability of insulin to stimulate tissue glucose uptake and lower plasma FFA concentrations was quantified in 12 individuals with normal glucose tolerance and 12 patients with noninsulin-dependent diabetes mellitus (NIDDM), further subdivided into obese and nonobese subjects. Measurements were made during 5-h glucose clamp studies, carried out at plasma insulin concentrations of about 10 microU/ml (0-150 min) and about 60 microU/ml (150-300 min). Differences between the patient groups were compared by two-way analysis of variance. The ability of insulin to either suppress plasma FFA concentrations or stimulate glucose uptake was significantly reduced (P less than 0.001) in patients with NIDDM, and this was true of both the obese and nonobese groups. The defect in the ability of insulin to suppress plasma FFA concentrations in patients with NIDDM was more apparent at the lower insulin concentration, whereas resistance to insulin-stimulated glucose uptake in NIDDM was more dramatic at the high insulin concentration. Finally, a significant correlation (r = -0.67; P less than 0.001) between insulin-stimulated glucose uptake and plasma FFA concentration was found in the entire group. These data emphasize the fact that patients with NIDDM are resistant to multiple actions of insulin, and that the magnitudes of the defect in insulin suppression of plasma FFA levels and stimulation of tissue glucose uptake are roughly comparable.

Aged↗
PubMed1987

High density lipoprotein (HDL) metabolism in noninsulin-dependent diabetes mellitus: measurement of HDL turnover using tritiated HDL.

High density lipoprotein (HDL) kinetics were studied by injecting [3H]apoprotein A-I (apoA-I)/HDL into 12 subjects with normal glucose tolerance and 12 patients with noninsulin-dependent diabetes mellitus (NIDDM). The results indicate that the mean fractional catabolic rate (FCR) of apoA-I/HDL was significantly faster [0.63 +/- 0.07 (+/- SEM) vs. 0.39 +/- 0.02 1/day; P less than 0.001] and the apoA-I/HDL synthetic rate greater (29.4 +/- 2.9 vs. 22.9 +/- 1.3 mg/kg X day; P less than 0.02) in patients with NIDDM than in normal subjects. Furthermore, there were statistically significant inverse relationships between apoA-I/HDL FCR and plasma levels of both HDL cholesterol (r = -0.71; P less than 0.001) and apoA-I (r = -0.63; P less than 0.001). In addition, the increase in apoA-I/HDL FCR was directly related to fasting plasma glucose (r = 0.78; P less than 0.001) and insulin (r = 0.76; P less than 0.001) concentrations. These data support the view that the decrease in plasma HDL cholesterol and apoA-I levels commonly found in patients with noninsulin-dependent diabetes is due to an increase in the catabolic rate of apoA-I/HDL secondary to the defects in carbohydrate metabolism present in these patients.

Aged↗
PubMed1987

Role of lipid oxidation in pathogenesis of insulin resistance of obesity and type II diabetes.

Increased lipid oxidation is generally observed in subjects with obesity and diabetes and has been suggested to be responsible for the insulin resistance associated with these conditions. We measured, by continuous indirect calorimetry, lipid and glucose oxidation and nonoxidative glucose disposal in 82 obese subjects during a 100-g oral glucose tolerance test (OGTT) and in 26 during a euglycemic insulin (40 mU.min-1.m-2) clamp. The obese subjects were subdivided into those with normal glucose tolerance (group A), those with impaired glucose tolerance (group B), and those with overt diabetes (group C). Forty-five healthy nonobese subjects were subdivided into a young and an older control group, which were age-matched to the nondiabetic obese (groups A and B) and diabetic obese (group C) subjects, respectively. In the postabsorptive state, as well as in response to insulin stimulation (both OGTT and insulin clamp), lipid oxidation was significantly increased in all three obese groups in comparison with either young or older controls. Basal glucose oxidation was significantly decreased in obese nondiabetic and obese glucose--intolerant subjects (groups A and B) compared with age-matched controls. During the OGTT and during the insulin clamp, insulin-stimulated glucose oxidation was decreased in all three obese groups. In contrast, nonoxidative glucose disposal was markedly inhibited in nondiabetic and diabetic obese patients during the euglycemic insulin clamp but not during the OGTT. After glucose ingestion, nonoxidative glucose uptake was normal in nondiabetic obese and glucose-intolerant obese subjects and decreased in diabetic obese subjects. Statistical analysis revealed that lipid and glucose oxidation were strongly and inversely related in the basal state, during euglycemic insulin clamp, and during OGTT. The negative correlation between lipid oxidation and nonoxidative glucose uptake, although significant, was much weaker. Fasting and post-OGTT hyperglycemia were the strongest (negative) correlates of nonoxidative glucose disposal in both single and multiple regression models. We conclude that 1) reduced glucose oxidation and reduced nonoxidative glucose disposal partake of the insulin resistance of nondiabetic obese and diabetic obese individuals; 2) hyperglycemia provides a compensatory mechanism for the defect in nonoxidative glucose disposal in nondiabetic obese subjects; however, this compensation is characteristically lost when overt diabetes ensues; and 3) increased lipid oxidation may contribute, in part, to the defects in glucose oxidation and nonoxidative glucose uptake in obesity.

Adult↗
PubMed1987

Role of insulin in regulation of high density lipoprotein metabolism.

The effect of alloxan-induced insulin deficiency on high density lipoprotein (HDL) metabolism was studied in rabbits. Rabbits with alloxan-induced diabetes had significantly higher (P less than 0.001, mean +/- SEM) plasma concentrations of glucose (541 +/- 13 vs. 130 +/- 2 mg/dl), triglyceride (2851 +/- 332 vs. 101 +/- 10 mg/dl), and total plasma cholesterol (228 +/- 55 vs. 42 +/- 4 mg/dl) than did normal control rabbits. However, diabetic rabbits had lower plasma HDL-cholesterol (7.2 +/- 1 vs. 51.3 +/- 1.3 mg/dl, P less than 0.001) and HDL apoA-I (38.3 +/- 6.0 vs. 87.2 +/- 4.3 mg/dl, P less than 0.001) concentrations. HDL kinetics were compared in diabetic and normal rabbits, using either 125I-labeled HDL or HDL labeled with 125I-labeled apoA-I, and it was demonstrated that HDL fractional catabolic rate (FCR) was slower and residence time was longer in the diabetic rabbits when either tracer was used. The slow FCR and the low apoA-I pool size led to reduced apoA-I/HDL synthetic rate in diabetic rabbits (0.97 +/- 0.11 vs. 0.34 +/- 0.07 mg per kg per hr). Thus, the reduced plasma HDL-cholesterol concentrations seen in rabbits with alloxan-induced insulin deficiency was associated with a lower total apoA-I/HDL synthetic rate. Since insulin treatment restored to normal all of the changes in plasma lipoprotein concentration and kinetics seen in diabetic rabbits, it is unlikely that the phenomena observed were secondary to a nonspecific toxic effect of alloxan. These data strongly support the view that insulin plays an important role in regulation of HDL metabolism.

Animals↗
PubMed1987

Relationship between autonomic neuropathy and thermogenesis in non diabetic and diabetic obese patients.

Autonomic neuropathy is a well known complication of diabetes. Diabetes is often superimposed on obesity. A reduction in the variability of the heart rate in the resting state has been demonstrated in 16 obese diabetic subjects as well as in 34 obese non-diabetic subjects. The coefficient of variation (CV) of the heart rate during 30 minutes of resting was significantly decreased in both obese groups (3.9 +/- 0.2% for the diabetics; 5.2 +/- 0.2%, p less than 0.01 for the non diabetics) as compared to their own controls (4.5 +/- 0.6% and 6.5 +/- 0.4%, respectively). Age also contributes to decreased heart rate variability. Furthermore, this defect of autonomic function has been correlated with the blunted glucose-induced thermogenesis (GIT) seen in both obese groups (r = 0.52, p. less than 0.001): the increase in energy expenditure over basal values following a 100 g oral glucose load was only 4.8 +/- 0.8% for the diabetic obese group (p less than 0.001), and 8.5 +/- 0.7% for the non-diabetic obese group (p less than 0.001) as opposed to their own controls (12.4 +/- 1.3% and 13.3 +/- 0.6% respectively). Measurement of the variability of heart rate in obese individuals may be of predictive value in assessing blunted glucose-induced thermogenesis in non diabetic and diabetic obese patients.

Adult↗
PubMed1986

The effect of selective beta adrenergic blockade on glucose-induced thermogenesis in man.

We have previously shown that the increase in energy expenditure following glucose/insulin infusion is, in large part, mediated by the sympathetic nervous system and that this sympathetic component can be blocked by the nonselective beta-1, beta-2 antagonist propranolol. To examine which beta adrenergic receptor mediates this thermogenic response, we performed euglycemic insulin clamp studies in eight healthy control subjects with and without metoprolol at a dose known to block only the beta-1 adrenergic receptor. Basal glucose oxidation and energy expenditure were similar in the control and metoprolol groups. During the last hour of the insulin clamp study, glucose oxidation (3.06 +/- 0.25 v 2.92 +/- 0.21 mg/kg X min), total body glucose uptake (8.17 +/- 0.70 v 7.13 +/- 0.49 mg/kg X min), and nonoxidative glucose uptake (5.11 +/- 0.60 v 4.21 +/- 0.44 mg/kg X min) were not different in the control compared to the metoprolol group. However, the increment in energy expenditure was inhibited by 64% during metoprolol infusion (0.04 +/- 0.01 v 0.11 +/- 0.02 kcal/min, P less than 0.01). Glucose/insulin-induced thermogenesis was similarly reduced by metoprolol (2.56 +/- 0.81 v 5.04 +/- 0.74%, P less than 0.01). These results are quantitatively quite similar to those observed with propranolol. We conclude that the beta adrenergic nervous system and, specifically, the beta-1 receptor mediates the thermogenic response to glucose/insulin infusion.

Adult↗
PubMed1986

Effect of differences in glucose tolerance on insulin's ability to regulate carbohydrate and free fatty acid metabolism in obese individuals.

The effect of variations in glucose tolerance on insulin's ability to regulate glucose uptake and plasma glucose and FFA concentrations was assessed in 22 obese individuals [8 with normal glucose tolerance, 7 with impaired glucose tolerance (IGT), and 7 with noninsulin-dependent diabetes mellitus (NIDDM)]. Patients with IGT had ambient insulin levels that were higher than normal, associated with elevated postprandial glucose levels and a marked reduction in insulin-stimulated glucose uptake. On the other hand, plasma FFA levels were relatively normal in IGT, possibly because of the hyperinsulinemia. Patients with NIDDM were also hyperinsulinemic, with insulin levels throughout the day that were approximately twice normal. Hyperinsulinemia in patients with NIDDM was associated with a significant decline in insulin-stimulated glucose uptake as well as with significant increases in both ambient plasma glucose and FFA concentrations. Thus, and in contrast to patients with IGT, plasma FFA metabolism in NIDDM was grossly abnormal, despite the concomitant hyperinsulinemia. These data indicate that insulin resistance in obese individuals varies as a function of degree of glucose tolerance, and insulin resistance in patients with NIDDM involves defects in the regulation of both plasma glucose and FFA metabolism.

Adult↗
PubMed1986

Effect of obesity on ambient plasma glucose, free fatty acid, insulin, growth hormone, and glucagon concentrations.

Fasting and postprandial plasma concentrations of glucose, FFA, insulin, glucagon, and GH concentrations were determined in 10 nonobese and 10 obese subjects with normal glucose tolerance. Measurements were made at 0800 h (after a 14-h fast) and at hourly intervals from then until 1600 h. During this time period all individuals ate breakfast at 0800 h (20% of total daily calories) and lunch (40% of total daily calories). Although plasma glucose concentrations were similar throughout the 8-h period in the 2 groups, plasma insulin concentrations were significantly (P less than 0.001) higher in the obese individuals. However, despite the presence of hyperinsulinemia, the obese group also had higher (P less than 0.001) plasma FFA concentration throughout the day. On the other hand, both the absolute and the relative declines in plasma FFA concentration after meals were similar in the 2 groups. Since plasma glucagon and GH concentrations were similar in the 2 groups, altered production of these lipolytic hormones was not responsible for the elevated plasma FFA levels in the obese individuals. These data document the presence in obese individuals of a disassociation in their ability to maintain normal plasma glucose as opposed to plasma FFA homeostasis, and indicate that the increase in plasma FFA concentrations in obesity occurs in the presence of hyperinsulinemia and is not related to abnormalities of either glucagon or GH secretion.

Adult↗