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Biomedical subjects

A J Scheen

Publications and source records attributed to A J Scheen.

At least 307 records · Page 17Linked to original sources
PubMed1996

Insulin action in man.

Insulin action is crucial for the regulation of glucose metabolism. Insulin plays a key role in suppressing endogenous glucose production by the liver, both in fasting and postprandial states. Insulin is also necessary for the maintenance of normal rates of glucose oxidation and storage in insulin-sensitive tissues and for the prevention of excessive gluconeogenic substrate production. Various methods have been developed to assess insulin action in vivo, essentially at liver and muscle sites. Such methods evaluate the effect of exogenous or endogenous insulin, using respectively the open-loop approach (interruption of the feedback loop by inhibiting endogenous insulin secretion) or the closed-loop approach (mathematical modelling of the insulin-glucose feedback loop). Knowledge of the successive steps of cellular insulin action has markedly improved during the last ten years. Preceptor, receptor and postreceptor levels need to be considered since they may be affected in insulin-resistant states. This general progress in the understanding of insulin action in man improves our approach to the complex pathophysiology of non-insulin-dependent diabetes mellitus and opens up new prospects for treatment of the insulin-resistant syndrome which is associated with several atherosclerotic risk factors.

Computer Simulation↗
PubMed1996

[Medical assessment prior to gastroplasty: indications and contraindications].

Because of the common failure of the various medical procedures used for the treatment of morbid obesity, surgeons have searched alternatives among which gastroplasty appears to offer now the best efficacy/safety ratio. Such approach has become more and more popular in our country, but success is almost highly variable from patient to patient. A careful medical assessment is necessary before performing gastroplasty. It mainly aims at choosing the appropriate indications (failure of previous well-applied medical therapy, exclusion of any hormonal cause of obesity, presence of complications due to weight excess, ...) and at excluding cardiovascular (unstable coronaropathy, carotid stenosis, ...), digestive (recurrent oesophagitis, ...) or psychiatric contra-indications. Such medical assessment before gastroplasty should allow to increase the success rate and to reduce the incidence of complications after the surgical procedure.

Adolescent↗
PubMed1996

Assessment of residual insulin secretion in diabetic patients using the intravenous glucagon stimulatory test: methodological aspects and clinical applications.

Defective insulin secretion plays a crucial role in insulin-dependent (Type 1) and non-insulin-dependent (Type 2) diabetes mellitus as well as in many secondary forms of the disease. Glucagon is a potent stimulus for the islet beta-cell, and intravenous bolus injection of 1 mg glucagon has been widely used to assess endogenous insulin secretion for clinical or research purposes. Plasma C-peptide levels (less commonly insulin) are usually measured immediately before and 6 min after glucagon injection. The C-peptide response to glucagon is well-correlated with the beta-cell response to mixed meals or other stimuli commonly used to characterize endogenous insulin secretion (oral or intravenous glucose, standard meals, arginine, etc.) and has the advantage of shorter duration and simple standardization. The glucagon test shows good intra-subject reproducibility, although in diabetic patients it may be influenced by variable prevailing blood glucose levels. Several applications of the glucagon test have been developed. In Type 1 diabetes, the glucagon test has been used to discriminate between patients with and without residual insulin secretion. This can be especially important during the first few months, or even years, following initiation of insulin therapy when attempts to stop the immunological destruction of the beta-cell are made. Assessment of endogenous insulin secretion is also important after pancreas or islet transplantation. In patients with Type 2 diabetes mellitus, in which residual endogenous insulin secretion is common, characterization of the disease may help in the choice of therapy for the individual patient (insulin, sulphonylureas or combined therapy). Thus, the glucagon test is a simple, reliable and useful tool for clinical evaluation of diabetes mellitus.

Arginine↗
PubMed1996

Exhaustion of blood glucose response and enhancement of insulin response after repeated glucagon injections in type-2 diabetes: potentiation by progressive hyperglycemia.

AIMS: To investigate the hyperglycemic and insulinemic response to repeated glucagon injections in Type-2 (non-insulin-dependent) diabetic patients. METHODS: In overnight fasted Type-2 diabetic patients, three i.v. glucagon (1 mg) injections were given as a bolus at two-hour intervals. In the hour preceding each glucagon injection, 6 patients received saline and they were tested at near-baseline blood glucose levels, while 8 patients received a glucose-controlled glucose infusion and they were tested at increasing blood glucose levels (7.5 +/- 0.2, 12.9 +/- 0.5 and 18.7 +/- 0.7 mmol/l). Blood samples were collected at 0, 3, 5, 10, 15, 30 and 60 min after each glucagon injection. RESULTS: In the patients tested at near-baseline blood glucose levels, the blood glucose rise induced by glucagon was smaller after repeated injections. By contrast, the B-cell response to glucagon was well preserved. In the patients tested at increasing blood glucose levels, the blood glucose response to glucagon was abolished after repeated injections. By contrast, the B-cell response was significantly potentiated. The respective areas under the curve of plasma insulin levels in response to glucagon were 563 +/- 72, 1047 +/- 154 and 1844 +/- 305 m U x 30 min/l (p < 0.001). CONCLUSION: In Type-2 (non-insulin-dependent) diabetic patients, repeated glucagon injections, even when administered in a short (4 h) period of time, do not exhaust the B-cell. Endogenous insulin secretion is even potentiated at increasing blood glucose levels. By contrast, the hyperglycemic response to glucagon is significantly abolished, particularly at high blood glucose levels.

Aged↗
PubMed1996

[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.

Combined Modality Therapy↗