[Cardiovascular prevention: could the polypill reduce the risk of clinical inertia and poor compliance?]

The concept of "polypill" for cardiovascular prevention was introduced in 2003 in a landmark paper of the British Medical Journal. A model based on results provided by evidence-based medicine suggested that a "polypill", that contains a statin, three blood pressure lowering drugs (each at half standard dose), aspirin and folic acid, would result in an 80% reduction in the incidence of coronary and cerebrovascular events, while being associated with a good tolerance profile and offering a favourable cost-effectiveness ratio. The present paper aims at presenting the new advances dealing with this new paradigm in cardiovascular prevention. We will present the progresses of the "polypill" concept since 2003, the results of a first controlled clinical trial, the pharmaceutical feasibility for routine clinical use and the potential pharmaco-economical impacts of such a strategy. The "polypill" may offer a solution to avoid physician's clinical inertia and reduce patients's lack of compliance, two drawbacks in the field of cardiovascular prevention.

[Insulin glargine and cancer: a storm in a glass of water?]

Insulin glargine is widely used as basal insulin in the treatment of type 1 and type 2 diabetes mellitus. However, this insulin analogue has been recently suspected to be associated with an increased risk of cancer, especially breast cancer, in patients with type 2 diabetes. The present article aims at briefly presenting the state of the art based upon currently available data. We will first summarize the observations reported in recent publications, then we will present a critical analysis of these in fact non-conclusive findings, and finally we will conclude with some practical recommendations.

Cardiovascular risk factors in a sample of a rural Belgian population: the Bellux MONICA Study

A sample of 1949 subjects of the population of the Belgian province of Luxembourg was screened for levels of cardiovascular risk factors. Cigarette smoking was more prevalent among males (51%) than among females (17%). The relationship between smoking and socio-economic status was inverse in males (M) and direct in females (F). Blood pressure (BP) measurements showed definite high BP in 10% of this sample, and 60% of those with definite high BP were not taking any hypertensive drugs. The average total cholesterol value was 6.49 mmol/L in M and 6.45 mmol/L in F. F had lower values than M at a younger age, but higher values than M at an older age. The high-density lipoprotein cholesterol was higher in F (1.57 mmol/L) than in M (1.27 mmol/L). Diabetes was present in 4.2% of this sample. In nearly half of these participants, the disease had been discovered during the screening. Obesity was especially frequently among F in all three age groups. In conclusion, the main cardiovascular risk factors were found to be at a fairly high level in this population sample.

[United Kingdom Prospective Diabetes Study (UKPDS): 10 years later]

A 10-year post-trial monitoring of patients with newly diagnosed type 2 diabetes randomised in the "United Kingdom Prospective Diabetes Study" (UKPDS) demonstrated a continued reduction in microvascular risk (-24%, p = 0.001) and emergent risk reductions for myocardial infarction (-15%, p = 0.01) and death from any cause (-13%, p = 0.007), despite an early loss of glycaemic differences ("legacy effect"). A continued benefit after metformin therapy was evident during the ten-year post-trial follow-up among overweight patients (-33%, p = 0.005 for myocardial infarction and -27%, p = 0.002 for death from any cause). In contrast, the benefits of previously improved blood pressure control were not sustained when between-groups differences in blood pressure were lost during follow-up, except for a reduced risk for peripheral vascular disease. These observations are strong arguments in favour of an early optimisation of blood glucose control and of a sustained control of blood pressure in patients with type 2 diabetes.

[How to explore...the metabolic syndrome by its new IDF definition]

The International Diabetes Federation recently proposed a so-called consensus definition of metabolic syndrome. According to this new definition, a subject has the metabolic syndrome if he/she has abdominal obesity (considered as a prerequisite and assessed, in the European population, by a waist circumference > 80 cm in women and > 94 cm in men) and, in addition, at least two other risk factors among 1) elevated fasting triglycerides > or = 150 mg/dl; 2) low HDL cholesterol HDL < 50 mg/dl in women and < 40 mg/dl in men; 3) increased arterial blood pressure > or = 130/ 85 mm Hg; and 4) elevated fasting plasma glucose concentration > or = 100 mg/dl. We will discuss the advantages and limitations of this new definition as well as the consequences of its use on the prevalence of the metabolic syndrome in the Belgian population.

Risk of developing retinopathy in Diabetes Control and Complications Trial type 1 diabetic patients with good or poor metabolic control

OBJECTIVE

The study goal was to assess and predict the risk of developing retinopathy in type 1 diabetic patients with extreme metabolic control.

RESEARCH DESIGN AND METHODS

Based on material from the Diabetes Control and Complications Trial (DCCT) study (n = 1,441 patients), patients without retinopathy at baseline (DCCT primary cohort) were considered under good or poor metabolic control if the mean HbA(1c) level (until the last visit) fell in the lower or upper 20% of the overall HbA(1c) distribution, respectively. Retinopathy was recorded as either absent or present. Logistic regression was used to predict retinopathy from covariates used in the DCCT retinopathy study.

RESULTS

Among the 153 DCCT patients with "good metabolic control" (mean HbA(1c) < or = 6.87%), three-step change retinopathy developed in 15 (9.8%), and 138 (90%) remained free of retinopathy. Conversely, among the 166 patients with "poor metabolic control" (mean HbA(1c) > or = 9.49%), the complication did not develop in 71 (43%) and did develop in 95 (57%). Whereas occurrence of diabetic retinopathy was primarily due to metabolic control (P < 0.0001) and duration of participation in the study (P < 0.0001), two other covariates were found to be significant prognostic factors of the complication: HbA(1c) at baseline (OR 1.37, P < 0.001) and BMI (OR 1.11, P < 0.05).

CONCLUSIONS

This study confirms that retinopathy develops in approximately 10% of patients with type 1 diabetes under good metabolic control, whereas > 40% of patients with type 1 diabetes remain free of retinopathy despite poor metabolic control. After adjusting for metabolic control and duration of participation in the study, it was found that previous glycemic exposure (HbA(1c)) and BMI may provide a possible explanation to such paradoxical clinical situations.

Thymic expression of insulin-related genes in an animal model of autoimmune type 1 diabetes

BACKGROUND

Insulin and multiple other autoantigens have been implicated in the pathogenesis of autoimmune type 1 diabetes, but the origin of immunological self-reactivity specifically oriented against insulin-secreting islet beta-cells remains obscure. The primary objective of the present study was to investigate the hypothesis that a defect in thymic central T-cell self-tolerance of the insulin hormone family could contribute to the pathophysiology of type 1 diabetes. This hypothesis was investigated in a classic animal model of type 1 diabetes, the Bio-Breeding (BB) rat.

METHODS

The expression of the mammalian insulin-related genes (Ins, Igf1 and Igf2) was analysed in the thymus of inbred Wistar Furth rats (WF), diabetes-resistant BB (BBDR) and diabetes-prone BB (BBDP) rats.

RESULTS

RT-PCR analyses of total RNA from WF, BBDP and BBDR thymi revealed that Igf1 and Ins mRNAs are present in 15/15 thymi from 2-day-old, 5-day-old and 5-week-old WF, BBDR and BBDP rats. In contrast, a complete absence of Igf2 mRNA was observed in more than 80% of BBDP thymi. The absence of detectable Igf2 transcripts in the thymus of BBDP rats is tissue-specific, since Igf2 mRNAs were detected in all BBDP brains and livers examined. Using a specific immunoradiometric assay, the concentration of thymic IGF-2 protein was significantly lower in BBDP than in BBDR rats (p<0.01).

CONCLUSIONS

The present study suggests an association between the emergence of autoimmune diabetes and a defect in Igf2 expression in the thymus of BBDP rats. This tissue-specific defect in gene expression could contribute both to the lymphopenia of these rats (by impaired T-cell development) and the absence of central T-cell self-tolerance of the insulin hormone family (by defective negative selection of self-reactive T-cells).

Non-alcoholic steatohepatitis: association with obesity and insulin resistance, and influence of weight loss

Non-alcoholic steatohepatitis (NASH) is a disease of emerging identity and importance, and is now considered as one of the commonest liver diseases in western countries. It is frequently associated with severe obesity, especially abdominal adiposity, and is intimately related to various clinical and biological markers of the insulin resistance syndrome. Especially, both the prevalence and the severity of liver steatosis are related to male sex, body mass index, waist circumference, hyperinsulinaemia, hypertriglyceridaemia and impaired glucose tolerance or type 2 diabetes. A substantial weight loss following gastroplasty is accompanied by a marked reduction in the prevalence and the severity of the various biological abnormalities of the metabolic syndrome and, concomitantly, by an important regression of liver steatosis in most obese patients. However, in some patients, this rapid and drastic weight loss may result in a mild increase in inflammatory lesions (hepatitis), despite the regression of steatosis, which might result from the rapid mobilization of fatty acids or cytokines from adipose tissue, especially visceral fat. The intimate relationship between NASH and obesity leads to the concept that NASH may be considered as another disease of affluence, as is the insulin resistance syndrome and perhaps being part of it.

Long-term effects of oral estradiol and dydrogesterone on carbohydrate metabolism in postmenopausal women

OBJECTIVE

To determine in postmenopausal women the long-term effects on carbohydrate metabolism of the administration of oral micronized 17 beta-estradiol (2 mg/day continuously) and cyclical dydrogesterone (10 mg/day for 14 days per 28-day cycle).

METHODS

A 2-year open-label prospective, non-comparative study was carried out of 13 healthy postmenopausal women receiving cyclical estradiol and dydrogesterone and serving as their own controls. Concentrations of blood glucose, plasma insulin, C-peptide, glucagon and free fatty acids (FFAs) were determined before treatment (base-line) and at 6, 12 and 24 months of hormone replacement therapy under fasting conditions and during a standard 75-g, 3-h, oral glucose tolerance test (OGTT).

RESULTS

Fasting blood glucose levels were unchanged throughout the study, and the mean areas under the curves (AUCs) for glucose response increased slightly but non-significantly versus baseline; fasting plasma insulin levels tended a decrease, and AUCs for insulin responses to the glucose load fell by 23% from baseline (not significant); fasting C-peptide levels and AUCs were unchanged; plasma glucagon fasting levels and responses were in the normal range and stable throughout the study; and plasma FFA fasting levels decreased significantly, as well as FFA AUCs during OGTTs, at the 12th and 24th months of the study.

CONCLUSIONS

During a 2-year treatment with oral estradiol and cyclical dydrogesterone, a direct progesterone derivative, tolerance to glucose was unchanged, fasting plasma insulin and insulin response to repeated glucose loads were decreased, and C-peptide levels remained unchanged, indicating a potential improvement in insulin sensitivity and clearance, as in younger women; additionally, a slightly enhanced antilipolytic activity of insulin was observed.

Insulin sensitivity, clearance and release in kininogen-deficient rats

Insulin sensitivity of kininogen-deficient rats was compared with that of normal rats using euglycaemic hyperinsulinaemic glucose clamping. Anaesthetized animals were infused with 2-50 mU kg-1 min-1 of insulin and the glucose infusion rates needed to maintain euglycaemia were determined. Maximum glucose uptake, insulin sensitivity index and insulin clearance were reduced in kininogen-deficient rats. Captopril increased the amount of glucose needed to maintain euglycaemia during infusion of 2 and 10 mU kg-1 min-1 of insulin in normal rats, but had no effect in kininogen-deficient rats. Anaesthetized rats of both strains were given an intraperitoneal injection of glucose and the evolution of blood glucose was followed for 120 min. The peak increase was higher in kininogen-deficient rats. Similar larger increases in blood glucose were observed after glucose injection in normal rats previously treated with HOE 140, a bradykinin B2 receptor antagonist. After glucose injection, plasma insulin increased in both groups of rats but reached lower levels in kininogen-deficient animals. These results suggest that bradykinin is involved not only in the clearance of glucose and insulin by the tissues during insulin infusion but also that bradykinin can affect the release of insulin after a glucose load.

Effects of gastroplasty on body weight and related biological abnormalities in morbid obesity

Obesity is a prevalent metabolic disorder associated with high morbidity and mortality rates. Medical treatment rarely succeeds, and bariatric surgery has been proposed as an alternative therapy. The purpose of this non-controlled retrospective study was to evaluate time-course changes in body weight in severely obese patients who underwent vertical ring gastroplasty or adjustable silicone gastric banding, and to assess the prevalence and potential reversibility of several of the biological abnormalities associated with morbid obesity. From an initial cohort comprising 658 patients, regular body weight measurements and biological data were obtained in 505 patients [419 females, 86 males; age 36 +/- 11 years; body mass index 42.7 +/- 6.9 kg/m2; (mean +/- SD)] with a mean follow-up of 26 +/- 14 months. Mean weight loss was 32 +/- 16 kg. Most weight reduction occurred within the first 6 months, followed by near-stabilisation or even slight weight regain. Most biological parameters were obtained before surgery and after at least 6 months of follow-up. The high prevalence and severity of metabolic disturbances associated with the insulin resistance syndrome (hyperglycaemia, hyperinsulinaemia, decreased HDL cholesterol, hypertriglyceridaemia, elevated fibrinogen levels and hyperuricaemia) before gastroplasty were significantly decreased after weight loss. No major biological deficiencies were observed following gastroplasty, except low iron serum levels. It is concluded that marked weight loss associated with gastroplasty involved a remarkable reduction in the prevalence and severity of several biological abnormalities classically considered as cardiovascular risk factors.

[How I evaluate...diabetic nephropathy. First part: micro- and macroalbuminuria]

Diabetic nephropathy (DN) appears in about 30% of patients with type 1 diabetes (D1) and 15 to 60% of patients with type 2 diabetes (D2). It is preceded by microalbuminuria. Microalbuminuria is defined as an albumin excretion rate between 30 and 300 mg/24 h (on a 24-hour urine collection) or between 20 and 200 micrograms/min (on an overnight collection) in at least two out of three consecutive collections made within a 6-month period. Alternative screening techniques use either dipstick (Micral-Test II) or the albumin to creatinine ratio on an early morning urine sample (30-300 mg/g creatinine). Once persistent microalbuminuria is confirmed, 80% of type 1 diabetic patients and 20 to 50% of type 2 diabetic patients will progress to DN. In D2, microalbuminuria also represents a powerful predictor of early mortality from cardiovascular disease. Macroalbuminuria (AER > 300 mg/24 h, corresponding to a total protein excretion > 500 mg/24 h) will eventually lead to a end-stage renal insufficiency within 10 to 20 years. In D2, numerous patients will die from cardiovascular disease before reaching end-stage renal failure. Angiotensin-converting enzyme inhibitors can slow down the evolution toward DN when prescribed when microalbuminuria appears. Screening for microalbuminuria should therefore be a part of the annual clinical assessment in every diabetic patient.

[Bronchial reactivity in diabetic patients]

The data of the literature concerning bronchial reactivity in diabetic patients are controversial. Therefore, we studied the influence of the presence of a diabetic cardiac autonomic neuropathy (CAN) on the ventilatory parameters measured during a methacholine-induced bronchoconstriction test. Ten insulin-dependent diabetic patients without CAN, ten insulin-dependent diabetic patients with CAN and ten healthy volunteers, all non-smokers and free of respiratory symptoms, have undergone a functional respiratory check-up before the methacholine test. The presence of CAN was classically studied by the decrease in heart rate changes during three standardized tests (deep breathing at 6 cycles/min, Valsalva manoeuver, orthostatism) which all mainly explore the parasympathetic function. The bronchial response to methacholine was similar in the healthy subjects and in the diabetic patients without CAN. However, the fall in forced expiratory volume in 1 second induced by the highest dose of methacholine was significantly less marked in the diabetic subjects with CAN than in the two other groups. These results suggest that the diabetic autonomic neuropathy also involves the vagal innervation of the respiratory tract.

The involvement of the opioid system in human obesity: a study in normal weight relatives of obese people

The involvement of the opioid system in human obesity has been demonstrated, but whether the abnormalities in the endorphinergic system play a primary role in overfeeding and weight gain or represent a simple biochemical feature is still unclear. The objectives of this study were to investigate the effects of both physiological and pharmacological plasma beta-endorphin levels on some metabolic and hormonal parameters in a normal weight, but prone to obesity, young population consisting of first degree relatives of obese subjects and in body mass index-, sex, and age- matched control subjects without a family history of obesity. Each subject underwent a 1-h infusion of synthetic human beta-endorphin at a constant rate of 4.5 ng/kg.min (low rate), then after a 1-week interval, at a rate of 500 micrograms/h (high rate). Under basal conditions, there was no significant difference in plasma glucose and pancreatic hormones (insulin, C peptide, and glucagon) between the two groups, except for plasma beta-endorphin levels, which were significantly (P < 0.01) higher in relatives of obese individuals. The low rate of beta-endorphin infusion induced physiological elevations of plasma opioid levels in both groups; no significant change in plasma glucose and pancreatic products in control subjects; and a significant (at least P < 0.05) rise in plasma insulin, C peptide, and glucagon concentrations in relatives of the obese. The high rate of beta-endorphin infusion produced pharmacological elevations of opioid plasma levels in both groups; significant (at least P < 0.05) increments in plasma glucose and glucagon levels and no appreciable modification of plasma insulin and C peptide levels in the control group; and a significant (at least P < 0.05) positive response of plasma glucose, insulin, C peptide, and glucagon levels in relatives of obese subjects. These findings suggest that 1) opioid peptides at least in part play a primary, rather than secondary, role in some metabolic events of obesity; and 2) both physiological and pharmacological plasma levels of beta-endorphin are able to provoke marked islet hormone release in the early phase of human obesity.

[Non-insulin-dependent diabetes: from physiopathology to treatment]

Non-insulin-dependent (or type 2) diabetes mellitus is a common, underdiagnosed and growing disease in our society. It is responsible for increased morbidity and mortality and represents an important public health problem. This polygenic disease is often expressed late in life and its evolution is accelerated by environmental factors leading to obesity. It combines defects in both insulin secretion and insulin action, and such defects are present in various proportions according to the type of patient and the stage of the disease. Diet and physical activity recommendations are the basis of the treatment. Current pharmacological approaches aim at improving insulin secretion and/or insulin cellular action. After secondary failure to oral drugs, insulin therapy should be initiated, the patient becoming "insulin-requiring". A synergy should be searched in the combination of various therapeutic modalities in order to improve the glycaemic control.

Retinopathy, but not neuropathy, is influenced by the level of residual endogenous insulin secretion in type 2 diabetes

The files of 132 patients with Type 2 diabetes were retrospectively studied to characterize the influence of metabolic control and residual insulin secretion on neuropathy and retinopathy, the two most frequent degenerative diabetic complications. Patients were classified according to their metabolic control (mean HbA1C either < or > or = 8%; reference values: 3-6%) and residual endogenous insulin secretion (fasting plasma C-peptide levels either < or > or = 0.600 nmol/l). Neuropathy was more frequent in patients with poor metabolic control (32/64 = 50%) than in those adequately controlled (17/68 = 25%; p < 0.005). In both subgroups, the level of endogenous insulin secretion did not influence the prevalence of neuropathy. Retinopathy was less effected than neuropathy by the degree of metabolic control (37.5% in the subgroup with HbA1C > or = 8% v.s. 25% in the subgroup with HbA1C < 8%; p < 0.10), but was influenced by residual insulin secretion. Indeed, in patients with inadequate metabolic control, the prevalence of retinopathy was significantly increased in those with higher endogenous insulin secretion (51.4 versus 20.6%, p < 0.02) and thus probably higher insulin resistance. Furthermore, higher systolic arterial blood pressure was observed in the subgroups with a higher prevalence of retinopathy. Such conclusions were confirmed using multivariate analysis. Thus, in Type 2 diabetes, neuropathy is essentially affected by the degree of metabolic control, whereas retinopathy is also influenced by the level of residual endogenous insulin secretion and the presence of systolic hypertension.

Cryptocrine signaling in the thymus network and T cell education to neuroendocrine self-antigens

Both during phylogeny and ontogeny the thymus appears as a nodal point between the two major systems of cell-to-cell signaling, the neuroendocrine and immune systems. This review presents the experimental observations which support a dual role in T cell selection played by the thymic repertoire of neuroendocrine polypeptide precursors. Through the mode of cryptocrine intercellular signaling thymic neuroendocrine-related precursors synthesized in thymic epithelial cells have been shown to influence the early steps in T cell differentiation. In addition, thymic neuroendocrine-related polypeptides are a source of self-antigens which are presented by the major histocompatibility system of the thymic epithelium. Preliminary data also suggest that the intrathymic T cell education to neuroendocrine self-antigens is not strictly superimposible to the antigen presentation by dedicated presenting cells. Insulin-like growth factor-II (IGF-II) was identified as one dominant member of the insulin family expressed by thymic epithelial and nurse cells. The intrathymic presentation of IGF-II or IGF-II derived self-antigens is under current investigation. If further confirmed, the central tolerogenic properties of IGF-II could be considered in the elaboration of a strategy for an efficient and safe prevention of insulin-dependent diabetes.

Modified glucagon test allowing simultaneous estimation of insulin secretion and insulin sensitivity: application to obesity, insulin-dependent diabetes mellitus, and noninsulin-dependent diabetes mellitus

The aim of this study was to describe an adaptation of the glucagon test allowing the simultaneous characterization of insulin secretion and sensitivity. A glucagon test (1 mg/m2) was performed in healthy subjects (n = 11), obese patients (n = 5), insulin-dependent diabetics (n = 9), nonobese noninsulin-dependent diabetics (n = 7), and overweight noninsulin-dependent diabetics (n = 8). Previously, they had been connected to the Biostator, modified for continuous blood collection. Endogenous insulin secretion induced by glucagon was derived from integrated C-peptide concentrations. An index of insulin sensitivity was obtained by dividing the rate of decrease in blood glucose by the total amount of insulin entering the circulation (secreted+infused by the Biostator). The indices of insulin sensitivity obtained in the above groups of subjects were, respectively, 0.064 +/- 0.006, 0.030 +/- 0.006, 0.037 +/- 0.007, 0.021 +/- 0.006, and 0.016 +/- 0.002 mmol/L.U.min (P < 0.001). The estimated insulin secretion values in the 20 min following glucagon injection were, respectively, 0.38 +/- 0.05, 0.65 +/- 0.08, 0.05 +/- 0.01, 0.26 +/- 0.15, and 0.30 +/- 0.07 U (P < 0.001). The insulin sensitivity index obtained from this test correlated with the glucose MCR obtained from a euglycemic glucose clamp (r = 0.816; P < 0.001; n = 12). C-Peptide levels after glucagon administration were also significantly correlated with the estimated endogenous insulin secretion (r = 0.808; P < 0.001; n = 30). This adaptation of the classical glucagon test is an efficient and simple method to simultaneously evaluate insulin secretion and insulin sensitivity.

Reduction of the acute bioavailability of metformin by the alpha-glucosidase inhibitor acarbose in normal man

In a double-blind cross-over study, we investigated a possible influence of the alpha-glucosidase inhibitor acarbose on the bioavailability of the biguanide compound metformin. Each of the six healthy young male volunteers was randomly allocated during two consecutive 7 day periods to either acarbose (days 1-3: 3 x 50 mg day-1; days 4-7: 3 x 100 mg day-1) or placebo. At day 7 and 14 of the study, the overnight-fasted subjects ingested 1000 mg metformin with the first bite of a standardized breakfast (500 kcal; 60 g carbohydrates) and together with either placebo or 100 mg acarbose. Acarbose significantly (P < 0.05) reduced the meal-induced increase in blood glucose and plasma insulin levels. Acarbose induced a significant (P < 0.05) reduction in early (90, 120, 180 min) serum levels, peak concentrations (Cmax: 1.22 +/- 0.14 vs. 1.87 +/- 0.60 mg l-1) and area under the curve of metformin (AUC 0-540 min: 423 +/- 55 vs. 652 +/- 55 mg min l-1), but did not diminish its 24 h urinary excretion. In conclusion, acarbose significantly reduces the acute bioavailability of metformin in normal subjects.

The use of acarbose in the prevention and treatment of hypoglycaemia

This paper reviews the use of acarbose in the prevention and treatment of hypoglycaemia. In diet- or sulfonylurea-treated patients, acarbose may reduce the incidence of late postprandial hypoglycaemia. In insulin-treated patients, acarbose treatment usually requires reduction of the insulin dose; one study has shown that 100 mg acarbose at night significantly reduces the incidence of mid-evening and nocturnal hypoglycaemia. Several studies have suggested acarbose to be a useful adjunct to the management of reactive hypoglycaemia in the non-diabetic patients. Long-term prospective studies are still needed to document this last indication of acarbose or other alpha-glycosidase inhibitors.

Measurement of insulin sensitivity by the minimal model method using a simplified intravenous glucose tolerance test: validity and reproducibility

This study aimed at testing whether 12 rather than 26 plasma glucose and insulin determinations can be used to calculate the indices of insulin sensitivity and of glucose effectiveness using Bergman's minimal model during a simple intravenous glucose tolerance test performed without tolbutamide injection. Two intravenous glucose tolerance tests (separated by 1 week) were performed in 7 lean normal subjects and a single test was performed in 9 severely obese non-diabetic subjects. Intra-subject reproducibility of insulin sensitivity was not significantly different when 26 or 12 time-points were analyzed (CV = 16.8 +/- 3.4 versus 18.9 +/- 3.8% respectively). Compared with the insulin sensitivity of the lean subjects, that of obese subjects was significantly (P < 0.001) and similarly reduced when using 12 (2.14 +/- 0.34 versus 7.97 +/- 1.29 10(-4)min-1/mU.1-1) rather than 26 determinations (2.13 +/- 0.42 versus 6.95 +/- 1.12 10(-4) min-1/mU.1-1) respectively. Glucose effectiveness was less reproducible than insulin sensitivity and was slightly diminished by the reduction of blood samples (relative error: -9.7 +/- 4.4%; P < 0.05). Finally, glucose effectiveness tended to be slightly lower in the morbidly obese subjects than in the lean controls with both modes of calculation. In conclusion, in non-diabetic subjects, the insulin sensitivity index can be accurately measured during a simple intravenous glucose tolerance test, without tolbutamide injection and with only 12 blood samples. The possibility of performing a simplified test should contribute to increase the use of the minimal model method for estimating insulin sensitivity in clinical practice.

Changes in glucose turnover parameters and improvement of glucose oxidation after 4-week magnesium administration in elderly noninsulin-dependent (type II) diabetic patients

The aim of the present study was to investigate the effects of magnesium supplementation on glucose uptake and substrate oxidation in noninsulin-dependent (type II) diabetic patients. Nine elderly non-obese noninsulin-dependent (type II) diabetic patients, treated by diet only, participated in the study, which was designed as randomized, double blind, and cross-over. Each patient was followed up for a prestudy period of 3 weeks before inviting him/her to receive placebo or magnesium supplementation (15.8 mmol/day) for 4 weeks. At the end of each treatment period, a euglycemic hyperinsulinemic glucose clamp with simultaneous D-[3-3H]glucose infusion and indirect calorimetry was performed. Magnesium supplementation resulted in significantly increased plasma and erythrocyte magnesium levels, whereas body weight and fasting plasma glucose did not change. In the last 60 min of the glucose clamp, insulin-mediated glucose disappearance, total body glucose disposal (24.5 +/- 0.4 vs. 28.2 +/- 0.7 mumol/kg.min; P < 0.005), and glucose oxidation (13.0 +/- 0.4 vs. 16.3 +/- 0.8 mumol/kg.min; P < 0.01) were increased after chronic magnesium supplementation. Endogenous glucose production, nonoxidative glucose disposal, lipid and protein oxidation, and insulin MCR were not affected. In conclusion, a 4-week magnesium supplementation improves insulin sensitivity and glucose oxidation in the course of a euglycemic-hyperinsulinemic glucose clamp in noninsulin-dependent diabetic patients. Long term studies are needed to determine whether magnesium supplementation is useful in the management of type II diabetes.

Metabolic clearance rate of insulin in type 2 diabetic patients treated with combined insulin and sulfonylurea therapy

The metabolic clearance rate of insulin (MCRI) in 10 non-obese type 2 diabetic patients treated with either insulin alone or combined insulin plus sulfonylurea therapy is investigated. A classical 2-hour euglycaemic hyperinsulinaemic glucose clamp using the artificial pancreas was performed in a randomized order after two 6-week periods of treatment: either with subcutaneous injections of insulin alone or with insulin plus oral administration of the sulfonylurea compound glipizide at the dose of 3 x 10 mg/day. The MCRI was calculated knowing the constant insulin infusion rate (0.1 U.kg-1.h-1) and measuring basal and steady-state plasma free insulin and C-peptide levels. When the test was performed at the end of the period of treatment with insulin plus glipizide and 30 min after the ingestion of the last dose of 10 mg glipizide, plasma C-peptide levels were significantly increased and steady-state free insulin levels tended to be slightly higher whereas the metabolic clearance rate of glucose was not affected. The MCRI was significantly reduced by glipizide from 23.3 +/- 2.9 to 18.9 +/- 2.0 ml.kg-1.min-1 p < 0.05. These results demonstrate that the sulfonylurea glipizide decreases the MCRI. This effect may play a role in the hypoglycemic action of sulfonylureas.

Detection of early sympathetic cardiovascular neuropathy by squatting test in NIDDM

OBJECTIVE

To determine the role of the squatting test in the detection of early sympathetic neuropathy in patients with non-insulin-dependent diabetes mellitus (NIDDM).

RESEARCH DESIGN AND METHODS

Three groups of nonsmoking, nonobese subjects were studied: 10 healthy subjects, 10 NIDDM patients without autonomic neuropathy (AN), and 10 NIDDM patients with AN defined by the presence of a pathological deep-breathing value. All subjects were given three postural tests: lying-to-standing, sitting-to-standing, and squatting test. Heart rate (HR) and finger arterial pressure were recorded with a noninvasive technique.

RESULTS

Blood pressure (BP) fall (expressed as decremental area) was not significantly different among the groups at standing up after sitting or lying. By contrast, a significantly greater BP drop occurred in NIDDM patients with AN (1,123 +/- 245 mm2) compared with NIDDM patients without AN (460 +/- 232 mm2) or normal subjects (429 +/- 138 mm2, P < 0.001). The HR increase after all the orthostatic maneuvers was smaller in diabetic patients with AN (P < 0.01) compared with that recorded in other groups. Significant correlations were observed between BP fall after squatting and either the expiration:inspiration ratio at deep breathing (r = -0.77, P < 0.001) or the duration of diabetes (r = 0.76, P < 0.001).

CONCLUSIONS

The intrinsic orthostatic load of the squatting test, which is greater than conventional postural maneuvers, makes the squatting test an easy and useful test to detect early orthostatic dysregulation in NIDDM.

Pharmacological treatment of the obese diabetic patient

Obesity is a well-known risk factor for non-insulin-dependent (or Type 2) diabetes mellitus. Consequently, reduction of weight excess comes to the front line in the prevention and management of NIDDM. It is only when diet and physical exercise fail that drug treatment should be considered. Pharmacological treatment of obesity should favour drugs which not only promote weight loss, by reducing caloric intake and/or increasing thermogenesis and energy expenditure, but also, and especially, improve insulin sensitivity. Serotoninergic anorectic compounds (dexfenfluramine, fluoxetine) appear to possess, to some extent, all these properties. Metformin significantly reduces insulin resistance and improves glycaemic control without inducing weight gain, and even favouring some weight loss. This biguanide is now considered as the first line drug for the obese diabetic patient. Alpha-glucosidase inhibitors may help to reduce post-prandial glucose excursions but do not promote weight loss per se. Sulfonylureas can be prescribed to an obese patient when hyperglycaemia persists despite diet and the above-mentioned oral agents, but their use should be associated with reinforcement of dietary advices in order to prevent further weight increase; it is also the case for insulin therapy. Finally, drugs specifically stimulating thermogenesis and energy expenditure, new agents sensitizing tissues to the action of insulin and various compounds interfering with lipid metabolism are currently under extensive investigation with promising preliminary results in the obese diabetic patient. In conclusion, obesity remains a major problem in the management of Type 2 diabetes mellitus and this justifies the search for new, safe and effective, pharmacological approaches.

Evidence that insulin-like growth factor 2 (IGF2) is the dominant thymic peptide of the insulin superfamily

The central T-cell tolerance of neuroendocrine functions has been proposed to be primarily induced by the thymic repertoire of neuroendocrine self antigens. The present study aimed at characterizing the human thymic insulin-related autoantigen able to represent the pancreatic B-cell function in face of the developing T-cells. Immunofluorescence studies were performed on human and rat thymic sections, as well as on the rat IT-45R1 thymic epithelial cell line using several antibodies to epitopes of the insulin peptide superfamily. These studies identify beyond any doubt that insulin-like growth factor 2 (IGF2) is the dominant thymic peptide of the insulin family. The sequence of an insulin-derived autoantigen is proposed. This autoantigen is a nonamer and has a hydrophobic residue leucine (L) at position 9. In the human species, this autoantigen would primarily be tolerogenic for the pancreatic B-cell endocrine function during fetal development.

Impaired immune responses in diabetes mellitus: analysis of the factors and mechanisms involved. Relevance to the increased susceptibility of diabetic patients to specific infections

The reasons why diabetic patients present with an increased susceptibility to frequent and protracted infections remain unclear. The virtual absence of epidemiological studies of the independent risk factors involved contrasts with the multitude of in vitro models focused on the metabolism and function of immune cells from diabetic patients. This review analyzes some of these models and their clinical relevance. The different levels of diabetes pathogenesis: genetic (Type 1), autoimmune (Type 1) and metabolic (Type 1 and Type 2) are responsible for immune abnormalities demonstrated in in vitro models. The participation of genetic and autoimmune factors has been mainly characterized on T lymphocyte function. The B8 DR3 haplotype is associated with several minor immunologic abnormalities in vitro. However, the high frequency of this haplotype in healthy individuals argues against its involvement in significant defects of antimicrobial immunity. Genetic deficiency of C4, present in 25% of Type 1 diabetic patients could, on the other hand, be responsible for opsonization defects against encapsulated pathogens. Several immunological abnormalities related to the autoimmune process preceding the onset of Type 1 diabetes mellitus, such as the depletion of memory CD4+ cells and the defective natural killer activity could transiently impair host defences against viral diseases. Several in vitro functional defects of the immune system have been correlated with the metabolic control of diabetic patients. This suggests the involvement of insulinopenia in some of the abnormalities observed. Insulinopenia-induced enzymatic defects have often been proposed to inhibit energy-requiring functions of phagocytes and lymphocytes. However, the relevance of this mechanism could be confined to patients with extremely severe metabolic abnormalities. The importance of systemic consequences of insulinopenia such as hyperglycaemia and ketosis has also been addressed. Usually, the defects induced in vitro by these factors are slight and require supraphysiologic concentrations of glucose or ketone bodies. Recent studies have shown abnormalities of signal transduction mechanisms in which insulinopenia itself and other factors such as circulating immune complexes could be involved. Despite numerous controversies, many in vitro studies of the immune cells of diabetic patients have demonstrated significant defects which bear quantitative similarities with abnormalities described in other immunodeficiency syndromes. Furthermore, several mechanisms have been proposed to link the different defects observed with the specific infections encountered in diabetic patients.

Physiological elevations of plasma beta-endorphin alter glucose metabolism in obese, but not normal-weight, subjects

The present study was undertaken to evaluate the metabolic and hormonal responses to physiologic elevations of plasma beta-endorphin concentrations in both normal-weight and obese healthy subjects. The infusion of synthetic human beta-endorphin (4.5 ng/kg/min) produced the following: (1) in normal-weight subjects, no significant change of plasma glucose and pancreatic hormones (insulin, C-peptide, and glucagon), a significant plasma free fatty acids (FFA) increase, and a suppression of glycerol plasma levels; (2) in obese subjects, significant increases of glucose, insulin, C-peptide, and glucagon, a progressive decline of circulating FFA, and no change in glycerol plasma levels. In obese subjects, the intravenous administration of naloxone, given as a bolus (5 mg injected in 5 minutes) before the start of beta-endorphin infusion, reduced the plasma glucose response to the opioid by approximately half, annulled the pancreatic hormonal responses, and also reduced the FFA, but not glycerol, response. In normal-weight subjects, naloxone pretreatment did not induce any change of the flat glucose and hormonal responses to beta-endorphin, but reversed its effects on circulating FFA and glycerol. These data suggest that physiological elevations of plasma beta-endorphin concentrations produce metabolic and hormonal effects in obese subjects significantly different from those occurring in normal-weight subjects; these effects are partially naloxone-sensitive, suggesting the mediation of endogenous opioid receptors.

Assessment of insulin resistance in vivo: application to the study of type 2 diabetes

Besides insulin secretion, insulin sensitivity plays a key role in the feedback glucose-insulin closed loop. It can be altered in numerous physiological, pathological and pharmacological conditions. It can be estimated in vivo using methods that open the feedback loop (insulin suppression test, glucose clamp) or that analyze the closed loop by employing mathematical models of glucose kinetics. The most popular method is the euglycemic hyperinsulinemic glucose clamp. This test should be ideally coupled with a priming-constant infusion of a glucose tracer together with indirect calorimetry. This combination allows to study the glucose kinetics (Ra and Rd, and thus endogenous-mainly hepatic-glucose production) and its metabolism (oxidation or storage as glycogen), respectively. One alternative approach is the frequently sampled intravenous glucose tolerance test where the dynamic changes in plasma insulin and glucose levels are analyzed using the so-called 'minimal model' method. Noninsulin-dependent or type 2 diabetes is characterized by a significant defect in both insulin secretion and action. The insulin resistance is located at the liver site (increased glucose production) and at the peripheral tissues (decreased oxidation and, even more, defective storage of glucose in the muscles). This insulin resistance, which predominates at the postreceptor level, seems to be genetically determined but is worsened by weight excess and by hyperglycemia itself. This contributes to a vicious circle which aggravates progressively the severity of the disease.

Anti-oxidants show an anti-hypertensive effect in diabetic and hypertensive subjects

1. In this study an acute anti-hypertensive effect of three anti-oxidant agents (vitamin C, thiopronine and glutathione) in hypertensive subjects and in both hypertensive and non-hypertensive diabetic patients is reported. 2. The anti-oxidants had no effect on blood pressure in healthy normal subjects at a dose of 6 mmol, but thiopronine and glutathione produced a significant hypotensive effect at a dose of 12 mmol. 3. These data suggest that anti-oxidants might have a dilatatory effect and that an imbalance of the nitric oxide-free radical interaction might facilitate the development of hypertension in humans.

A role for beta-endorphin in the pathogenesis of human obesity?

The discovery of several endogenous substances with morphine-like activity (endorphins and enkephalins) which possess potent behavioral effects, interfering with food and water intake, has led to suggest their implications in the pathogenesis of human obesity. This suggestion is mainly based on: 1) the ability of opiate antagonists naloxone and naltrexone to reduce food intake in some particular situations associated with obesity: 2) the existence of raised plasma levels of beta-endorphin in obese children and adults not corrected by weight loss; and 3) the increased responsiveness to the metabolic and hormonal effects of opiate agonism and antagonism found in obese but not in normal weight subjects. Although the problem still awaits a definite answer, it seems not hazardous to hypothesize a role for beta-endorphin in some pathogenetic events associated with human obesity.

[Lack of benefit from the intermittent administration of insulin in treatment using subcutaneous perfusion pump in type 1 diabetes]

Our study is based on two constatations: 1) Hyperinsulinaemia, a possible atherogenic factor, is frequent under continuous subcutaneous insulin infusion. 2) Pulsatile intravenous insulin delivery improve the insulin's hypoglycaemic activity. To test if equivalent metabolic control can be obtained with a reduced intermittent subcutaneous infused insulin dose, we compared nocturnal metabolic control of 8 c-peptide negative type 1 diabetic patients under three experimental conditions: Continuous usual dose test (1.0 +/- 0.1 u/h); Intermittent half dose test (1.0 +/- 0.1 u/h, 30 min/h); Continuous half dose test (0.5 +/- 0.05 u/h) Five parameters were monitored: blood glucose, plasma free insulin and beta-hydroxy-butyrate, free fatty acid and glycerol plasma level. No significant differences were found between intermittent and continuous half-dose tests. We conclude that, in our experimental conditions, intermittent subcutaneous insulin infusion does not reduce the metabolic degradation induced by insulin dose reduction.

Persistence of altered metabolic responses to beta-endorphin after normalization of body weight in human obesity

The responses of plasma glucose, insulin, C-peptide and glucagon to an infusion of human beta-endorphin (0.5 mg/h) were studied in 10 formerly obese subjects who had lost 35 kg by dieting (body mass index less than 25) and compared with those of 10 normal-weight control (body mass index less than 25) and 10 obese (body mass index greater than 30) subjects. The fasting plasma concentrations of beta-endorphin were significantly higher in both the obese and the post-obese group than in the control group. In both obese and post-obese subjects, the infusion of beta-endorphin caused significant increases in peripheral plasma glucose, insulin, C-peptide and glucagon concentrations. In the control group, matched for age, sex and weight with the formerly obese group, there was no appreciable change in plasma insulin and C-peptide concentrations during the infusion of beta-endorphin, but the rise in plasma glucose was more sustained. Thus, 1. the increased plasma beta-endorphin concentrations found in human obesity are not corrected by normalization of body weight; and 2. formerly obese, normal-weight subjects behave as obese subjects in their metabolic and hormonal responses to beta-endorphin infusion. The alteration of the opioid system in human obesity may play some role in the predisposition to weight gain.

Vitamin E reduction of protein glycosylation in diabetes. New prospect for prevention of diabetic complications?

OBJECTIVE

This study evaluated the possibility of inhibiting protein glycosylation in vivo with vitamin E.

RESEARCH DESIGN AND METHODS

Two groups of 10 insulin-requiring diabetic patients, matched for duration of disease and metabolic control, received daily vitamin E supplementation of 1200 and 600 mg, respectively, for 2 mo. A third group of 10 diabetic patients, matched for duration of disease and metabolic control, served as the control group and received placebo. Fasting plasma glucose, mean daily plasma glucose, fasting labile HbA1, and glycosylated proteins were measured in the basal state and after 1 and 2 mo of treatment. In addition, hyperglycemic clamp studies were performed in basal state and after 1 mo of vitamin E administration in all patients.

RESULTS

Glycemic indices did not show any significant changes during the study, whereas fasting labile HbA, and glycosylated proteins decreased significantly after 1 and 2 mo in patients on vitamin E administration. Stable HbA1 decreased after 2 mo. Mean glycemic incremental area in the hyperglycemic clamp procedure was similar before and after treatment, whereas a significant reduction in mean labile HbA1 incremental area was found after vitamin E supplementation. A significant difference was also found in both fasting and incremental labile HbA1 levels, stable HbA1, and glycosylated proteins between the two groups of diabetic patients on the two doses of vitamin E; the diabetic patients who received the higher dose of vitamin E showed the greater reduction. No significant changes in these parameters were observed in diabetic patients on placebo administration.

CONCLUSIONS

These results demonstrate that vitamin E administration may reduce protein glycosylation in diabetic subjects independently of changes in plasma glucose, an effect that may be due to the inhibition of labile glycosylation, the first step of the Maillard reaction. Long-term studies will help establish the usefulness of vitamin E administration for the prevention of diabetic complications.

Effects of ethinyl estradiol combined with desogestrel and cyproterone acetate on glucose tolerance and insulin response to an oral glucose load: a one-year randomized, prospective, comparative trial

To investigate the effects of two slightly estrogen-dominant, monophasic, low-dose oral contraceptives on carbohydrate metabolism, 40 healthy young women were randomly allocated to receive either 30 micrograms of ethinyl estradiol + 150 micrograms of desogestrel, a 19-nortestosterone-derived progestin (Marvelon; n = 21) or 35 micrograms of ethinyl estradiol + 2 mg of cyproterone acetate, a 17-acetoxyprogesterone derivative (Diane-35; n = (19) for a prospective observation period of 1 year. At baseline, 6, and 12 months, blood glucose, plasma insulin, and plasma C-peptide levels were measured during an oral glucose tolerance test. Although the changes were absent (Marvelon) or minimal (Diane-35) at 6 months, both groups had a slight increase in blood glucose levels at 12 months; overall glucose tolerance remaining, however, within the normal range. Plasma insulin levels remained unchanged in the Diane-35-group, which suggested increased insulin resistance, but were significantly decreased in the Marvelon group despite significant rises in plasma C-peptide levels. Comparison of plasma C-peptide and insulin changes suggests enhanced pancreatic insulin secretion and increased hepatic insulin metabolism with both Marvelon and Diane-35.

Clinical aspects of the relationship between oral contraceptives, abnormalities in carbohydrate metabolism, and the development of cardiovascular disease

Although large epidemiologic studies indicated no difference in the frequency of diabetes mellitus in nonusers and everusers of high-dose combination oral contraceptives, other studies had shown an increased risk of impaired glucose tolerance in current users, which is estimated to be roughly twice as frequent as that in nonusers. Women at risk of developing impaired glucose tolerance while receiving high-dose oral contraceptives either had previous gestational diabetes mellitus or were older, obese, or had a positive family history of diabetes mellitus. The tendency to decreased glucose tolerance seems essentially related to the dosage and chemical structure of the progestogen used in oral contraceptives, namely, estrane and particularly gonane progestins. However, increased frequency of impaired glucose tolerance and potentially diabetes mellitus are obviously not linked to the use of the more potent gonane progestins. The use of low-dose oral contraceptives, particularly with reduced progestogen content (such as in the triphasic formulations and last-generation monophasic preparations), is accompanied by a low risk of impaired glucose tolerance, even in previous gestational diabetes mellitus. The mechanism of decreased glucose tolerance in oral contraceptive users is unknown but seems related partially to increased peripheral resistance that is potentially caused by a postreceptor defect in insulin action. Changes in insulin production or metabolic clearance rate are not excluded by recent, sophisticated investigations of carbohydrate metabolism in oral contraceptive users. Impaired glucose tolerance and diabetes mellitus, chronic hyperglycemia, and hyperinsulinemia are believed to increase atherogenic risk either by their direct action or their effects on lipid metabolism. Newer epidemiologic studies now indicate that the incidence of cardiovascular disease in low-dose, low-risk, current oral contraceptive users has been substantially decreased. The use of low-dose oral contraceptives with reduced dosages of better adapted progestogens seems effective in decreasing alterations in carbohydrate metabolism and may thereby contribute to decrease further atherogenic risk in oral contraceptive users.

[Diabetes in the Belgian province of Luxembourg: frequency, importance of the oral glucose tolerance test and a modestly increased fasting blood glucose]

A sample of 1949 subjects aged 35-64 years has been studied in the Belgian Province of Luxembourg according with the MONICA project (MONItoring of Trends and Determinants in CArdiovascular Diseases) elaborated by the World Health Organization. Among the data collected, were a fasting glycaemia and a glycaemia at the second hour of a 75 grams oral glucose load. Analysis of these two parameters has allowed to divide the individuals of the study into: 4.1% of diabetic subjects which half of them being unknown, 5.2% of subjects presenting an impaired glucose tolerance, 3.4% of subjects with an early reactive hypoglycaemia and 87.3% of normoglycaemic subjects. The measurement of the fasting glycaemia alone has allowed to display 15 glucidic abnormalities (that is to say 0.8%) whereas the complementary realization of the oral glucose tolerance test has disclosed about 10% of additional abnormalities. The fact to consider a borderline fasting glycaemia (included between 110 and 140 mg/dl on venous plasma) result in a greater probability to find an abnormal blood glucose value at the second hour of the oral glucose tolerance test.

Effects of pulsatile delivery of insulin and glucagon in humans

The purpose of the present study was to investigate the respective effects of continuous intravenous delivery of both insulin and glucagon compared with those of pulsatile insulin (and continuous glucagon), pulsatile glucagon (and continuous insulin) and both hormones administered in a pulsatile manner (but out of phase) on various parameters of glucose turnover. The study was performed on six healthy male volunteers submitted to a 325-min glucose-controlled glucose intravenous infusion using the Biostator. The endogenous secretion of pancreatic hormones was inhibited by somatostatin (2 micrograms/min). Four combinations of continuous and pulsatile infusions of insulin and glucagon were performed on different days and in random order. The amounts of hormone infused were identical in all instances and were 0.2 mU.kg-1.min-1 (continuous insulin), 67 ng/min (continuous glucagon), 1.3 mU.kg-1.min-1 and 435 ng/min with a switching on-off length of 2-11 min (for intermittent insulin and glucagon delivery, respectively). In the case of pulsatile administration of both hormones, the pulses of insulin and glucagon were given out of phase with a 6-min interval. Blood glucose levels and glucose infusion rate were monitored continuously by the Biostator, and classic methodology using a D-[3-3H]glucose infusion allowed to study glucose turnover. When compared with pulsatile insulin and continuous glucagon, pulsatile glucagon and continuous insulin were characterized by a significantly higher endogenous (hepatic) glucose production. When both insulin and glucagon were delivered in a pulsatile manner, the effect of pulsatile glucagon was predominant, maintaining a high endogenous glucose production. Under no circumstance was an effect on glucose utilization or clearance detected. This study demonstrates that pulsatile delivery of insulin or glucagon in humans has greater effects in modulating endogenous glucose production than continuous infusion. Furthermore, when both insulin and glucagon are delivered intermittently and out of phase, the stimulatory effect of glucagon on endogenous glucose production prevails over the inhibitory effect of insulin.

Effect of osmolality on availability of glucose ingested during prolonged exercise in humans

The aim of this study was to investigate whether the osmolality of a glucose solution, ingested at the beginning of a prolonged exercise bout, affects exogenous glucose disposal. We investigated the hormonal and metabolic response to a 50-g glucose load dissolved in either 200 (protocol A), 400 (protocol B), or 600 (protocol C) ml of water and given orally 15 min after adaptation to exercise in five healthy male volunteers. Naturally labeled [13C]glucose was used to follow the conversion of the ingested glucose to expired-air CO2. Total carbohydrate oxidation (indirect calorimetry) was similar in the three protocols (A, 237 +/- 20; B, 258 +/- 17; C, 276 +/- 20 g/4 h), as was lipid oxidation (A, 128 +/- 4; B, 132 +/- 15; C, 124 +/- 12 g/4 h). Exogenous glucose oxidation rates were similar under the three experimental conditions, and the total amount of exogenous glucose utilized was slightly, but not significantly, increased with the more diluted solution (A, 42.6 +/- 4.4; B, 43.4 +/- 4.1; C, 48.7 +/- 7.2 g/4 h). The blood glucose response was similar in the three protocols. Thus, within the range investigated, the osmolality of the glucose solution ingested had no significant influence either on its oxidation (which was 86-98% of the load ingested) or on the utilization of endogenous carbohydrate, lipid, or protein stores.

[Role of insulin and counter-regulatory hormones in the metabolic changes caused by insulin deprivation in diabetic patients]

In eight insulin dependent diabetic patients treated by continuous subcutaneous insulin infusion (1.1 +/- 0.2 U/h), the levels (measured hourly from 23 h to 05 h) of blood glucose, non esterified fatty acids (NEFA), glycerol and 3-OH-butyrate (3-OH-B) have been correlated to the circulating levels of free insulin (FIRI), glucagon, growth hormone or cortisol, in two experimental conditions: A. Insulin being infused as usual (physiological FIRI levels) and B. Progressively declining FIRI levels (insulin infusion arrested at 23 h). In condition A, blood glucose levels correlated significantly to both insulin and glucagon; NEFA, glycerol and 3OH-B correlated only to insulin. In condition B, blood glucose was significantly correlated to insulin but not to glucagon while NEFA, glycerol and 3-OH-B were significantly correlated to both hormones but not to growth hormone or cortisol. Therefore, on the metabolic deterioration that follows insulin withdrawal, growth hormone and cortisol seem to play a minor role, the main role being played by the decrease in circulating insulin levels and to a lesser extent by the increase in glucagon levels.