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See detailThe Intrathymic Expression of Insulin-Related Genes: Implications for Pathophysiology and Prevention of Type 1 Diabetes
Geenen, Vincent ULg; Lefebvre, P. J.

in Diabetes/Metabolism Reviews (1998), 14(1), 95-103

Recent experimental work has challenged and shattered the old concept of a sequestration of pancreatic islet antigens from developing T-cells within the thymic environment. There is now compelling ... [more ▼]

Recent experimental work has challenged and shattered the old concept of a sequestration of pancreatic islet antigens from developing T-cells within the thymic environment. There is now compelling evidence that the central immunological tolerance of the whole insulin family may be induced during the process of T-cell ontogeny in the thymus. Transcripts of insulin-like growth factor II (IGF-II), IGF-I and insulin genes have been characterized in human, rat and mouse thymuses. At the peptide level, IGF-II was shown to be the dominant polypeptide of the insulin family in the thymus from different species. Data are presented which support a dual role of thymic IGF-II both in T-cell development as well as in T-cell negative selection. Using animal models of autoimmune diabetes, current research is investigating the hypothesis that a defect of thymic T-cell education to the insulin family is implicated in the pathophysiology of human Type 1 diabetes. An efficient and secure prevention of Type 1 diabetes could be designed on the basis of the strong natural tolerogenic properties of the thymus. [less ▲]

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See detailHow to Measure Insulin Action in Vivo
Scheen, A. J.; Paquot, Nicolas ULg; Castillo, M. J. et al

in Diabetes/Metabolism Reviews (1994), 10(2), 151-88

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See detailInsulin sensitivity in anorexia nervosa: a mirror image of obesity?
Scheen, André ULg; Castillo, M.; Lefebvre, Pierre ULg

in Diabetes/Metabolism Reviews (1988), 4(7), 681-90

Although, in many respects and from a metabolic point of view, obesity and AN are clearly two opposite pathological conditions, the available data concerning insulin sensitivity in these two syndromes are ... [more ▼]

Although, in many respects and from a metabolic point of view, obesity and AN are clearly two opposite pathological conditions, the available data concerning insulin sensitivity in these two syndromes are not so obviously opposite. Indeed, whereas everybody is convinced that obesity is characterized by an increased insulin resistance, the papers reporting insulin sensitivity parameters in AN contain some apparently contradictory results. The observations of simultaneously low fasting blood glucose and plasma-insulin levels in anorectic patients could suggest increased insulin sensitivity in AN. However, if this is the case, it would be present despite other metabolic and hormonal changes (increased plasma concentrations of free fatty acids, cortisol, and growth hormone) which are known factors of insulin resistance. During an oral glucose-tolerance test, an impaired glucose-tolerance occurring despite sustained insulin response to glucose is usually found in anorectic patients before treatment; these abnormalities are, at least partially, reversed after successful refeeding. From these results, such conclusive, if indirect, evidence exists for relative insulin insensitivity in untreated AN. Similar results were initially reported with the intravenous glucose-tolerance test. Typically, the coefficient of glucose assimilation K was reduced in anorectic patients before treatment and increased after realimentation. This seemed to occur despite a relative increase in insulin response to glucose, which again may be related to insulin resistance in these undernourished subjects. However, more recent data demonstrated that the early insulin response is significantly lower in anorectic patients than in controls and that more than half of these patients have normal glucose-tolerance despite decreased peripheral plasma insulin levels. These latter observations, on the contrary, suggest an increased insulin sensitivity, at least in some patients with AN. Only the recently developed minimal model method allows us to discriminate between changes in insulin secretion and action after intravenous glucose injection and thus to infer accurately the sensitivity of the tissues to insulin. Unfortunately, this technique has not been applied to anorectic patients, until now, to solve the controversy. The simplest way to assess the action in vivo of insulin is to perform an intravenous insulin-tolerance test. However, the initial findings with this test, which showed exaggerated fall in plasma-glucose values and delayed return to basal levels after intravenous injection of insulin in AN, do not necessarily mean increased insulin sensitivity in these self-starved patients.(ABSTRACT TRUNCATED AT 400 WORDS) [less ▲]

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