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Loss of NPC1 function in a patient with a co-inherited novel insulin receptor mutation does not grossly modify the severity of the associated insulin resistance

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      Abstract

      In Npc1 null mice, a model for Niemann Pick Disease Type C1, it has been reported that hepatocyte insulin receptor function is significantly impaired, consistent with growing evidence that membrane fluidity and microdomain structure have an important role in insulin signal transduction. However, whether insulin receptor function is also compromised in human Niemann Pick disease Type C1 is unclear. We now report a girl who developed progressive dementia, ataxia and opthalmoplegia from 9 years old, followed by severe acanthosis nigricans, hirsutism and acne at 11 years old. She was diagnosed with Niemann Pick Disease type C1 (OMIM#257220) based on positive filipin staining and reduced cholesterol-esterifying activity in dermal fibroblasts, and homozygosity for the p.Ile1061Thr NPC1 mutation. Further analysis revealed her also to be heterozygous for a novel trinucleotide deletion (c.3659 + 1_3659 + 3delGTG) at the end of exon 20 of INSR, encoding the insulin receptor, leading to deletion of Trp1193 in the intracellular tyrosine kinase domain. INSR mRNA and protein levels were normal in dermal fibroblasts, consistent with a primary signal transduction defect in the mutant receptor. Although the proband was significantly more insulin resistant than her father, who carried the INSR mutation but was only heterozygous for the NPC1 variant, their respective degrees of IR were very similar to those previously reported in a father–daughter pair with the closely related p.Trp1193Leu INSR mutation. This suggests that loss of NPC1 function, with attendant changes in membrane cholesterol composition, does not significantly modify the IR phenotype, even in the context of severely impaired INSR function.

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      Global and societal implications of the diabetes epidemic.

      Changes in human behaviour and lifestyle over the last century have resulted in a dramatic increase in the incidence of diabetes worldwide. The epidemic is chiefly of type 2 diabetes and also the associated conditions known as 'diabesity' and 'metabolic syndrome'. In conjunction with genetic susceptibility, particularly in certain ethnic groups, type 2 diabetes is brought on by environmental and behavioural factors such as a sedentary lifestyle, overly rich nutrition and obesity. The prevention of diabetes and control of its micro- and macrovascular complications will require an integrated, international approach if we are to see significant reduction in the huge premature morbidity and mortality it causes.
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        Elevated plasma adiponectin in humans with genetically defective insulin receptors.

        Adiponectin has been suggested to play a role in the etiopathogenesis of at least some forms of insulin resistance, in part based on a strong correlation between plasma levels of adiponectin and measures of insulin sensitivity. The objective of the study was to establish whether this relationship is maintained at extreme levels of insulin resistance. This was a cross-sectional study in a university teaching hospital of subjects recruited from the United Kingdom and the United States. Participants included 75 subjects with a range of syndromes of severe insulin resistance and 872 nondiabetic controls. Fasting plasma insulin, adiponectin, and leptin were measured. Unexpectedly, subjects with mutations in the insulin receptor, despite having the most severe degree of insulin resistance, had elevated plasma adiponectin [median 24.4 mg/liter; range 6.6-36.6 (normal adult range for body mass index 20 kg/m(2) = 3-19 mg/liter)], whereas all other subjects had low adiponectin levels (median 2.0 mg/liter; range 0.12-11.2). Plasma leptin in all but one subject with an insulin receptoropathy was low or undetectable [median 0.5 ng/ml; range 0-16: normal adult range for body mass index of < 25 kg/m(2) = 2.4-24.4 (female) and 0.4-8.3 ng/ml (male)]. We conclude that the relationship between plasma adiponectin and insulin sensitivity is complex and dependent on the precise etiology of defective insulin action and that the combination of high plasma adiponectin with low leptin may have clinical utility in patients with severe insulin resistance as a marker of the presence of a genetic defect in the insulin receptor.
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          Clinical course of genetic diseases of the insulin receptor (type A and Rabson-Mendenhall syndromes): a 30-year prospective.

          The interaction of insulin with its cell surface receptor is the first step in insulin action and the first identified target of insulin resistance. The insulin resistance in several syndromic forms of extreme insulin resistance has been shown to be caused by mutations in the receptor gene. We studied 8 female patients with the type A form of extreme insulin resistance and 3 patients (2 male and 1 female) with the Rabson-Mendenhall syndrome and followed the natural history of these patients for up to 30 years. The 11 patients ranged in age from 7 to 32 years at presentation. All 11 patients had extreme insulin resistance, acanthosis nigricans, and hyperandrogenism in the female patients, and all but 1 were of normal body weight. This phenotype strongly predicts mutations in the insulin receptor: of the 8 patients studied, 7 were found to have mutations. Similar results from the literature are found in other patients with type A and Rabson-Mendenhall syndromes and leprechaunism. The hyperandrogenic state resulting from hyperinsulinemia and insulin resistance in these patients was extreme: 6 of 8 patients had ovarian surgery to correct the polycystic ovarian syndrome and elevation of serum testosterone. By contrast, a larger group of insulin-resistant patients who were obese with hyperandrogenism, insulin resistance, and acanthosis nigricans (HAIR-AN syndrome) did not have a high probability of mutations in the insulin receptor. The morbidity and mortality of these patients were high: 3 of 11 died, 9 of 11 were diabetic and 1 had impaired glucose tolerance, and 7 of 9 patients had 1 or more severe complication of diabetes. Our literature review revealed that the mortality of leprechaunism is so high that the term leprechaunism should be restricted to infants or young children under 2 years of age. Analogous to patients with the common forms of type 2 diabetes, these patients had a heterogeneous course. In 2 patients who were able to maintain extremely high endogenous insulin production, the fasting blood glucose remained normal even though post-glucose-challenge levels were elevated. Most patients, however, required large doses of exogenous insulin to ameliorate the severe hyperglycemia. Preliminary results of a recent study suggest that recombinant leptin administration may benefit these patients with severe insulin resistance.
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            Author and article information

            Affiliations
            [ ]Department of Endocrinology, Birmingham Children’s Hospital, Steelhouse Lane, Birmingham, B4 6NH United Kingdom
            [ ]Metabolic Research Laboratories, Institute of Metabolic Science, Addenbrooke’s Hospital, University of Cambridge, Cambridge, CB2 0QQ UK
            [ ]The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA United Kingdom
            [ ]Clinical Inherited Metabolic Disorders, Birmingham Children’s Hospital, Steelhouse Lane, Birmingham, B4 6NH United Kingdom
            Author notes

            Communicated by: Ed Wraith

            Contributors
            +44-122-3769035 , +44-122-3330598 , rks16@cam.ac.uk
            Journal
            J Inherit Metab Dis
            J. Inherit. Metab. Dis
            Journal of Inherited Metabolic Disease
            Springer Netherlands (Dordrecht )
            0141-8955
            1573-2665
            3 June 2010
            3 June 2010
            2010
            : 33
            : 227-232
            20521171 3757264 9107 10.1007/s10545-010-9107-5
            © The Author(s) 2010
            Categories
            Case Report
            Custom metadata
            © SSIEM and Springer Science+Business Media Dordrecht 2010

            Internal medicine

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