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Biomedical subjects

A J Scheen

Publications and source records attributed to A J Scheen.

At least 433 records · Page 24Linked to original sources
PubMed1986

Insulin oscillations per se do not affect glucose turnover parameters in normal man.

To compare the metabolic effects of pulsatile vs. continuous iv insulin infusion, normal men had two glucose-controlled iv glucose infusions using the Biostator for 260 min, during which endogenous pancreatic hormone secretion was inhibited by a somatostatin infusion and glucagon was replaced by continuous glucagon infusion. The two tests were performed at 1-week intervals, during which human insulin was infused either continuously at a constant rate of 0.2 mU kg-1 min-1 or in a pulsatile manner at a rate of 1.3 mU kg-1 min-1 with a switching on/off length of 2/11 min. Blood glucose levels and glucose infusion rates (GIR) were continuously monitored, and glucose turnover was estimated using a [3H]glucose infusion. In both tests, plasma C-peptide dropped markedly, whereas plasma glucagon levels were about twice basal values. Plasma insulin averaged 7 mU liter-1 during continuous infusion and oscillated between 1.5 and 35 mU liter-1 during pulsatile delivery. During the first 30-60 min of both tests, the glucose appearance rate and endogenous glucose production (EGP) increased, resulting in moderate hyperglycemia, which completely suppressed GIR. During the last 65 min, EGP declined, while the glucose disappearance rate and the glucose MCR increased, so that GIR increased progressively to maintain the blood glucose clamped at about 5 mmol liter-1. During this period, no significant differences were found between the two modes of insulin administration for any of the parameters studied. Thus, continuous and pulsatile insulin iv infusion, resulting in physiological peripheral plasma insulin levels, altered the glucose turnover parameters equally, in particular inhibiting EGP, which was stimulated by glucagon during the first part of the study, and stimulating peripheral glucose uptake at the end of the study period.

Adult↗
PubMed1984

Glipizide increases plasma insulin but not C-peptide level after a standardized breakfast in type 2 diabetic patients.

Peripheral blood glucose, plasma insulin and C-peptide levels were investigated after giving a standardized breakfast (500 kcal, 60 g carbohydrates) to 10 nonobese Type 2 diabetic patients previously treated by diet alone. Each patient received at random, at 1 week intervals, either 5 mg glipizide (meal + glipizide) or a placebo (meal alone) 30 min before breakfast. Basal values of blood glucose, plasma insulin and C-peptide were similar on both occasions. After meal + glipizide, the blood glucose increase was sharply limited whereas the rise in plasma insulin was steeper and reached twice as high a level. In contrast, the rise in plasma C-peptide was similar in both conditions. Consequently, the areas under the curves (0-300 min) showed a marked reduction in blood glucose after meal + glipizide (2289 +/- 149 versus 3101 +/- 169 mmol X min/1; 2p less than 0.001), associated with a significant increase in plasma insulin (14219 +/- 3261 versus 7591 +/- 1173 microU X min/ml; 2p less than 0.025) but no significant change in plasma C-peptide (342 +/- 45 versus 326 +/- 34 pmol X min/ml; N.S.). The insulin/C-peptide molar ratio was thus significantly increased after meal + glipizide (0.41 +/- 0.06 versus 0.23 +/- 0.04 at the 60th min; 2p less than 0.02). The dissociation between the responses of insulin and C-peptide suggests that a single dose of 5 mg glipizide in Type 2 diabetic subjects may enhance availability of peripheral insulin by extrapancreatic mechanism(s). This phenomenon may result in a higher circulating level of the hormone and therefore represent a further mode of action of sulphonylureas.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗
PubMed1983

Blood collection while using a continuous glucose analyzer without insertion of an additional venous catheter.

A new method for continuous blood collection using the Biostator is described. Blood is withdrawn through the double lumen catheter by a tube installed in the optional channel of the infusion pump. The amount of blood withdrawn from the patient is slightly greater than that necessary for continuous glucose analysis; the excess blood can be collected into assay tubes. Blood collection is continuous and produces a sample of diluted heparinized blood. The volume of blood collected depends on the size of the tube used, i.e. for a tube with a lumen diameter of 0.020 inches, the mean (+/- SD) volume collected was 1.21 +/- 0.07 ml/10 min (n = 13). The mean time interval between sampling and arrival at the glucose sensor by the double lumen catheter was 119 versus 108 s with the conventional method. The proposed modification does not affect blood glucose measurements (correlation coefficient compared with the reference method r = 0.9572; n = 13). To compensate for blood dilution, a dilution-factor depending on tubing diameter has to be calculated in each experiment.

Blood Glucose↗
PubMed1983

Effect of protein-supplemented fasting on the fuel-hormone response to prolonged exercise in obese subjects.

This study aimed at investigating the influence of protein-supplemented fasting (PSF) on the tolerance and the fuel-hormone response to endurance exercise in the severely obese subject. For this purpose, eight obese men (27 +/- 2 yr, 182 +/- 7 per cent of ideal body weight) exercised on a horizontal treadmill (4 km/h) during 3 h before and after 13 d of PSF (Alburone, 70 g protein/day). Because of the 8.9 +/- 0.7 kg weight loss and the corresponding lower energy cost, exercise oxygen consumption decreased from 1.6 +/- 0.1 (before PSF) to 1.4 +/- 0.1 l/min (after PSF). In contrast, mean exercise heart rate was identical (119 +/- 5/min) in both conditions, resulting in a lower oxygen pulse after PSF. The mean respiratory quotient measured during exercise was lower after PSF (0.72 +/- 0.01 vs 0.75 +/- 0.01 2 P less than 0.05), thus demonstrating a higher fat utilization. This was supported by a higher exercise-induced plasma free fatty acid (FFA) mobilization after PSF (delta plasma FFA: + 675 +/- 101 vs + 376 +/- 121 mumol/l, 2 P less than 0.05). This metabolic adaptation mainly results from two mechanisms: a significantly lower plasma IRI at rest and during exercise after PSF (5.7 +/- 0.8 vs 11.4 +/- 1.4 microunits/ml, 2 P less than 0.001); and a lower basal blood glucose (4.2 +/- 0.2 vs 4.6 +/- 0.1 mmol/l) and an earlier decrease of glucose (30th vs 90th min) during exercise after PSF, suggesting a relative depletion of the carbohydrates stores. The lipolytic hormones (glucagon, epinephrine, norepinephrine, cortisol, growth hormone) did not significantly increase during exercise after PSF when compared to exercise before PSF; thus, their role in the enhanced FFA mobilization appears less important. Only two of our eight subjects were unable to achieve the third hour of exercise after PSF; however, no major clinical events or electrocardiographical disturbances were observed in any of the eight subjects. In conclusion, moderate exercise can be tolerated at least for 2 h during PSF when appropriate fluid, mineral and vitamin therapy is given. Under these conditions it induces a preferential utilization of fat-derived substrates and selectively augments fat mobilization which favors weight loss. For these reasons, moderate exercise can be recommended under strict medical supervision as part of all weight reduction therapy.

Adolescent↗
PubMed1983

Metabolic adaptation to prolonged exercise in severely obese subjects.

In investigating the metabolic adaptation to prolonged exercise in markedly obese subjects, we compared blood glucose, plasma lactate, free fatty acids, insulin and glucagon concentrations during 3 h of treadmill exercise in nine severely obese male patients (OB) (weight excess 84 +/- 7 per cent of their ideal body weight) and in nine healthy controls (C). Speed and slope of treadmill were selected to give a similar oxygen consumption in both groups (OB: 1.61 +/- 0.08 1/min; C: 1.72 +/- 0.07 1/min). Under these conditions, heart rate was similar in both groups, whereas ventilation was significantly lower in overweight subjects. In obese patients, plasma free fatty acid (FFA) levels were higher in the basal state (OB: 740 +/- 43 mumol/l; C: 602 +/- 40 mumol/l, 2 P less than 0.05) but showed a lower increase during the exercise period (OB: + 576 +/- 135 mumol/l; C: + 1071 +/- 100 mumol/l, 2 P less than 0.02). This impaired FFA mobilization was related to significantly higher insulin (IRI) levels throughout the exercise period as shown by the regression line of exercise-induced FFA increase (y, mumol/l) vs mean plasma IRI during exercise (x, microU/ml): y = 1238 - 60 x, r = -0.709, 2 P less than 0.001. Lack of glucagon increase could also contribute to the lower rise of FFA in obese subjects. A correspondingly increased contribution of carbohydrates to the energy supply is suggested by a significant decline in blood glucose and higher lactate plasma concentrations during the second half of the exercise period in overweight patients. These abnormalities could represent a metabolic limitation for performing prolonged exercise in markedly obese patients.

Blood Glucose↗
PubMed1982

Hormonal and metabolic adaptation to protein-supplemented fasting in obese subjects.

Thirty hospitalized, severely obese patients (40 +/- 2 yr, 82 +/- 4 percent weight excess) were submitted to a 13-d protein-supplemented fast (PSF) with 70 g milk proteins/d (1.26 MJ or 300 kcal). The mean weight loss during PSF was 5.4 +/- 0.3 kg corresponding to 422 +/- 39 g/d. Comparison of the urinary nitrogen excretion with daily protein intake revealed that the nitrogen balance was equilibrated during PSF. Blood glucose decreased moderately but significantly during the whole PSF period whereas plasma insulin was only reduced during the first 9 d and tended to rise thereafter. Plasma FFA increased rapidly and remained elevated until the end of the study (+ 60 per cent); serum total cholesterol and plasma triglycerides showed a 26 and a 35 per cent decrease respectively. Basal plasma glucagon was slightly increased. Due to the low sodium intake (42 mmol/d) urinary sodium excretion dropped rapidly. Simultaneously both systolic (-13 mmHg) and diastolic (-7 mmHg) arterial blood pressure decreased significantly. The biological tolerance was good: metabolic acidosis was prevented with sodium bicarbonate, excessive rise in serum uric acid was corrected with allopurinol and a marked decrease in serum potassium was avoided with an appropriate dose of spironolactone. Twenty-six patients could be weighed 6 to 15 months after PSF: 12 showed a further weight reduction (6.6 +/- 1.6 kg) and seven a discrete weight gain (1.0 +/- 0.4 kg). Thus, PSF was well accepted and was profitable in 19 out of our 30 patients. It should be restricted to cases of severe and refractory obesity and performed under careful medical supervision.

Adult↗
PubMedDate not supplied

Antiobesity pharmacotherapy in the management of type 2 diabetes.

Obesity is a well-known risk factor for the development of Type 2 diabetes mellitus. The management of the obese diabetic patient remains a challenge for the clinician but, in any case, weight reduction should be considered as a key objective. In this respect, several antiobesity drugs have demonstrated potential. However, while fenfluramine and dexfenfluramine have been shown to promote weight loss and to directly improve insulin sensitivity, being two mechanisms contributing to better blood glucose control in obese Type 2 diabetic patients, they were recently withdrawn due to safety problems. Sibutramine, a new selective norepinephrine and serotonin reuptake inhibitor, promotes weight loss by decreasing food intake, an effect which leads to a mild improvement (significant in patients losing > or =5% of initial body weight) of blood glucose control in obese diabetic patients. Similarly, orlistat, a selective gastrointestinal lipase inhibitor which increases faecal fat losses, enhances diet-induced weight reduction and improves both blood glucose control and vascular risk profile, especially dyslipidaemia, in obese Type 2 diabetic patients. Further studies are required to better identify good responders to pharmacotherapy and specify the role of antiobesity agents in the overall long-term management of obese subjects with Type 2 diabetes. Other novel pharmacological approaches deserve further consideration, for instance beta-3 agonists aiming to increase energy expenditure, drugs interfering with tumor necrosis factor-alpha (TNF-alpha) or free fatty acid release by the adipose tissue or agents that slow gastric emptying. However, until now, results regarding efficacy and/or safety have been disappointing or preliminary in humans.

Appetite Depressants↗
PubMedDate not supplied

From obesity to diabetes: why, when and who?

Obesity is considered as the most important risk factor for type 2 diabetes. We will briefly discuss why does obesity predispose to diabetes, when does diabetes occur in obese subjects and who among obese individuals is particularly prone to develop diabetes. Obesity, especially intraabdominal adiposity, is associated with increased FFA plasma concentrations which exert a major negative effect on insulin sensitivity at both muscular and hepatic sites. Various metabolic, haemodynamic and hormonal theories have been proposed to explain insulin resistance in obese subjects. A specific role of TNF-alpha has been recently suggested. However, besides insulin resistance, defective insulin secretion is a prerequisie for the development of overt type 2 diabetes. Both lipotoxicity and glucotoxicity may initiate and perpetuate a vicious circle responsible for the metabolic deterioration. Diabetes occurs as a late phenomenon in obesity and is preceded by years of impaired glucose tolerance. The progression to diabetes is heralded by an inability of the B cell to maintain its previously high rate of insulin secretion in response to glucose in face of insulin resistance. This propensity to develop type 2 diabetes may be genetically determined and/or triggered by environmental factors. The evolution from obesity to diabetes represents a continuum that progresses through different phases in which defects in both insulin action and insulin secretion play a critical interaction and must be looked at in concert.

Adipose Tissue↗
PubMedDate not supplied

Nonalcoholic steatohepatitis and insulin resistance: interface between gastroenterologists and endocrinologists.

Nonalcoholic steatohepatitis (NASH), along with other forms of nonalcoholic fatty liver disease, is an increasingly common clinico-pathological syndrome. It is frequently associated with obesity, especially visceral fat, and type 2 diabetes, and is intimately related to markers of the insulin resistance syndrome. Both the prevalence and the severity of liver steatosis are related to body mass index, waist circumference, hyperinsulinaemia, hypertriglyceridemia and impaired glucose tolerance. The pathophysiology of NASH involves two steps: 1) insulin resistance, which causes steatosis; 2) and oxidative stress, which produces lipid peroxidation and activates inflammatory cytokines. The identification of subjects who may progress from fatty liver to NASH, and from NASH to fibrosis/cirrhosis is an important clinical challenge as well as the finding of appropriate therapy that could prevent such deleterious process. Substantial weight loss is accompanied by a marked attenuation of insulin resistance and related metabolic syndrome and, concomitantly, by an important regression of liver steatosis in most patients, although mild inflammation may be detected in some subjects. Thus, NASH may be considered as another disease of affluence, as is the insulin resistance syndrome and perhaps being part of it.

Comorbidity↗
PubMedDate not supplied

Pathophysiology of type 2 diabetes.

Type 2 diabetes mellitus is a heterogeneous syndrome characterized by abnormalities in carbohydrate and fat metabolism. The causes of type 2 diabetes are multi-factorial and include both genetic and environmental elements that affect beta-cell function and tissue (muscle, liver, adipose tissue, pancreas) insulin sensitivity. Although there is considerable debate as to the relative contributions of beta-cell dysfunction and reduced insulin sensitivity to the pathogenesis of diabetes, it is generally agreed that both these factors play important roles. However, the mechanisms controlling the interplay of these two impairments are unclear. A number of factors have been suggested as possibly linking insulin resistance and beta-cell dysfunction in the pathogenesis of type 2 diabetes. A majority of individuals suffering from type 2 diabetes are obese, with central visceral adiposity. Therefore, the adipose tissue should play a crucial role in the pathogenesis of type 2 diabetes. Although the predominant paradigm used to explain this link is the portal/visceral hypothesis giving a key role in elevated non-esterified fatty acid concentrations, two new emerging paradigms are the ectopic fat storage syndrome (deposition of triglycerides in muscle, liver and pancreatic cells) and the adipose tissue as endocrine organ hypothesis (secretion of various adipocytokins, i.e. leptin, TNF-alpha, resistin, adiponectin, implicated in insulin resistance and possibly beta-cell dysfunction). These two paradigms constitute the framework for the study of the interplay between insulin resistance and beta-cell dysfunction in type 2 diabetes as well as between our obesogenic environment and diabetes risk in the next decade.

Adipocytes↗
PubMedDate not supplied

Prevention of metabolic alterations by insulin supplements administered either before or after 2-h nocturnal interruption of CSII.

To evaluate the efficacy of a bolus insulin injection to prevent the metabolic alterations induced by a 2-h nocturnal interruption of a continuous subcutaneous insulin infusion (CSII), nine type I (insulin-dependent) C-peptide-negative diabetic patients were studied from 2200 to 0800 h during two randomized tests. An insulin bolus (2.1 +/- 0.2 U) was administered via the pump either at 2300 h, just before CSII interruption, or at 0100 h, after reactivating the pump at its usual basal rate (1.05 +/- 0.11 U/h). The insulin bolus at 2300 h induced a significant rise in plasma free-insulin levels at 2400 h (+6.9 +/- 1.8 mU/L, P less than .01), resulting in an early and marked fall in blood glucose concentrations between 2300 and 0100 h (-2.7 +/- 0.5 mM, P less than .001), with hypoglycemic values in five patients. The insulin bolus at 0100 h counteracted the fall in plasma free-insulin levels observed between 2300 and 0100 h and significantly increased plasma insulin at 0200 h (+3.2 +/- 0.8 mU/L, P less than .01). Blood glucose concentrations that remained stable during the 2-h arrest of the pump fell significantly between 0100 and 0400 h (-2.1 +/- 0.5 mM, P less than .005). This fall rate was significantly lower than that measured within the 3 h after the insulin bolus given before CSII interruption but significantly higher than that observed in a reference control group of patients whose pump was functioning normally throughout the night.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

U-100 insulin gives some protection against metabolic deterioration due to CSII interruption.

We investigated the influence of insulin concentration within the insulin pump on the metabolic and plasma free-insulin changes induced by a 6-h nocturnal interruption of continuous subcutaneous insulin infusion (CSII) in five C-peptide-negative insulin-dependent diabetic patients with low circulating levels of anti-insulin antibodies. We compared the changes in blood glucose, plasma free fatty acids, 3-hydroxybutyrate, and free insulin during the interruption from 2300 to 0500 h of the Nordisk Infuser loaded with either U-100 or U-20 regular insulin. The decrease in plasma free-insulin levels was slower, resulting in a significantly delayed and smaller increase in blood glucose levels (2.4 +/- 1.6 vs. 7.6 +/- 2.9 mM, P less than .025) when the pump contained U-100 instead of U-20 insulin. Although the increases in levels of plasma free fatty acids were similar in both tests, the rise in plasma 3-hydroxybutyrate levels tended to be reduced with U-100 insulin (414 +/- 139 vs. 639 +/- 67 microM, P less than .10). Thus, our observations indicate that U-100 insulin gives some protection against the metabolic deterioration due to the interruption of CSII so that diabetic patients may be able to remain without the pump for longer periods with concentrated rather than diluted insulin.

3-Hydroxybutyric Acid↗