Long-Term Effects of Metreleptin in Rabson-Mendenhall Syndrome on Glycemia, Growth, and Kidney Function.

CONTEXT: Rabson-Mendenhall syndrome (RMS) is caused by biallelic pathogenic variants in the insulin receptor gene (INSR) leading to insulin-resistant diabetes, microvascular complications, and growth hormone resistance with short stature. Small, uncontrolled studies suggest that 1-year treatment with recombinant leptin (metreleptin) improves glycemia in RMS. OBJECTIVE: This study aimed to determine effects of long-term metreleptin in RMS on glycemia, anthropometrics, the growth hormone axis, and kidney function. METHODS: We compared RMS patients during nonrandomized open-label treatment with metreleptin (≥ 0.15 mg/kg/day) vs no metreleptin over 90 months (5 subjects in both groups at different times, 4 only in metreleptin group, 2 only in control group). Main outcome measures were A1c; glucose; insulin; 24-hour urine glucose; standard deviation scores (SDS) for height, weight, body mass index (BMI), and insulin-like growth factor 1 (IGF-1); growth hormone; and estimated glomerular filtration rate. RESULTS: Over time, metreleptin-treated subjects maintained 1.8 percentage point lower A1c vs controls (P = 0.007), which remained significant after accounting for changes in insulin doses. Metreleptin-treated subjects had a reduction in BMI SDS, which predicted decreased A1c. Growth hormone increased after metreleptin treatment vs control, with no difference in SDS between groups for IGF-1 or height. Reduced BMI predicted higher growth hormone, while reduced A1c predicted higher IGF-1. CONCLUSION: Metreleptin alters the natural history of rising A1c in RMS, leading to lower A1c throughout long-term follow-up. Improved glycemia with metreleptin is likely attributable to appetite suppression and lower BMI SDS. Lower BMI after metreleptin may also worsen growth hormone resistance in RMS, resulting in a null effect on IGF-1 and growth despite improved glycemia.

Mecasermin in Insulin Receptor-Related Severe Insulin Resistance Syndromes: Case Report and Review of the Literature.

Mutations in the insulin receptor (INSR) gene underlie rare severe INSR-related insulin resistance syndromes (SIR), including insulin resistance type A, Rabson⁻Mendenhall syndrome and Donohue syndrome (DS), with DS representing the most severe form of insulin resistance. Treatment of these cases is challenging, with the majority of DS patients dying within the first two years of life. rhIGF-I (mecasermin) has been reported to improve metabolic control and increase lifespan in DS patients. A case report and literature review were completed. We present a case involving a male patient with DS, harbouring a homozygous mutation in the INSR gene (c.591delC). Initial rhIGF-I application via BID (twice daily) injection was unsatisfactory, but continuous subcutaneous rhIGF-I infusion via an insulin pump improved weight development and diabetes control (HbA1c decreased from 10 to 7.6%). However, our patient died at 22 months of age during the course of a respiratory infection in in Libya. Currently available data in the literature comprising more than 30 treated patients worldwide seem to support a trial of rhIGF-I in SIR. rhIGF-I represents a treatment option for challenging SIR cases, but careful consideration of the therapeutic benefits and the burden of the disease is warranted. Continuous application via pump might be advantageous compared to single injections.

First molecular diagnosis of Donohue syndrome in Africa: novel unusual insertion/deletion mutation in the INSR gene.

Donohue syndrome (DS) is a very rare autosomal recessive disease affecting less than one in a million life births. It represents the most severe form of insulin resistance due to mutations involving the insulin receptor (IR) gene "INSR". DS is characterized by pre- and postnatal growth retardation with failure-to-thrive, lipoatrophy, acanthosis nigricans, hypertrichosis, and dysmorphic features. An exhaustive INSR gene sequencing was performed after PCR amplification of coding exons and introns boundaries. Bioinformatic tools, including ESEfinder, MFOLD and Proter software were also used to predict the impact of INSR mutation on INSR on gene expression as well as on the protein structure and function. The results have shown a novel unusual c.3003_3012delinsGGAAG (p.S1001_D1004delinsRE) insertion/deletion (indel) mutation within the exon 16 in the three patients, which represent the fourth indel mutation within the INSR gene. The mutation modifies the secondary structure of DNA and RNA, as well as the composition of exonic splicing enhancers of exon 16. Moreover, despite the conservation of the secondary structure of the IR, the p.S1001_D1004delinsRE in-frame mutation is accompanied by the loss of four amino acids replaced by two residues of different nature and hydrophobicity level in the juxtamembrane domain of the receptor. The results have confirmed the role of the juxtamembrane domain of IR involved in a crucial interaction of the IR with cellular effectors essentially the IR substrate 1 (IRS-1), the SHC and the Nck proteins that ensure the signal mediated by the insulin transduction pathway in target cells. Our findings have also proven the genotype/phenotype correlation between INSR mutation and DS phenotype severity.

A novel homozygous missense mutation in the insulin receptor gene results in an atypical presentation of Rabson-Mendenhall syndrome.

Leprechaunism (Donohue syndrome) and Rabson-Mendenhall syndrome are caused by mutations in the insulin receptor gene and are associated with extreme insulin resistance. Clinically these syndromes appear to represent points on a continuum of severity of receptor dysfunction, rather than completely distinct syndromes. We investigated a Libyan infant with growth retardation, facial dysmorphism (elfin-like features), acanthosis nigricans and hirsutism. Fasting hypoglycaemia and postprandial hyperglycaemia with persistent hyperinsulinemia were found. A novel homozygous missense mutation was found in exon 2, resulting in a substitution of a glycine-132 for a serine in the INSR α-subunit (c.394G > A; p.Gly132Ser). At age ten, he developed diabetes mellitus. At age eleven, patient is still alive with mental retardation and severe growth retardation.

Ten-year improvement of insulin resistance and growth with recombinant human insulin-like growth factor 1 in a patient with insulin receptor mutations resulting in leprechaunism.

AIM: Leprechaunism, a rare genetic disease resulting from mutations in two alleles of the insulin receptor gene, is characterized by severe insulin resistance, retarded growth and, usually, premature death. The ability of treatment with recombinant human insulin-like growth factor 1 (rhIGF1) to improve metabolic and clinical parameters in the long-term is still controversial. METHODS: Mutations were looked for in the insulin receptor gene of a four-month-old female baby with leprechaunism. The patient's skin fibroblasts were analyzed for response to insulin and IGF1. At the clinical level, the very long-term effects of treatment with rhIGF1/rhIGFBP3 were evaluated by clinical and metabolic parameters. RESULTS: The patient's diagnosis was based on compound heterozygous mutations in two alleles of the insulin receptor gene, thus confirming leprechaunism. Cultured fibroblasts showed a decreased number of insulin receptors and were insulin-resistant. However, IGF1 was able to stimulate IGF1 receptor signalling, suggesting possible activation of a salvage pathway. Treatment with IGF1/IGFBP3 for 8.7 years, then IGF1 for 2 years, resulted in normalization of circulating levels of IGF1 and IGFBP3. Large daily variations in glycaemia and insulinaemia persisted, but mean glycaemia decreased. Regarding growth, the patient's BMI Z score normalized and length/height score improved. Our patient presented normal neurological development and academic achievement. The treatment was free of adverse effects. CONCLUSION: Our results provide evidence that rhIGF1 with and without rhIGFBP3 can prevent fatal outcomes, and improve growth and metabolic parameters, for more than 10 years in a patient with leprechaunism. Long-term rhIGF1 for severe insulin resistance syndrome should be considered.

Metreleptin improves blood glucose in patients with insulin receptor mutations.

CONTEXT: Rabson-Mendenhall syndrome (RMS) is caused by mutations of the insulin receptor and results in extreme insulin resistance and dysglycemia. Hyperglycemia in RMS is very difficult to treat, and patients are at risk for early morbidity and mortality from complications of diabetes. OBJECTIVE: Our objective was to study 1-year effects of recombinant human methionyl leptin (metreleptin) in 5 patients with RMS and 10-year effects in 2 of these patients. DESIGN AND SETTING: We conducted an open-label nonrandomized study at the National Institutes of Health. PATIENTS: Patients were adolescents with RMS and poorly controlled diabetes. INTERVENTION: Two patients were treated with escalating doses (0.02 up to 0.22 mg/kg/d) of metreleptin for 10 years, including 3 cycles of metreleptin withdrawal and reinitiation. In all 5 patients, 1-year effects of metreleptin (0.22 mg/kg/d) were studied. OUTCOME MEASURES: Hemoglobin A1c (HbA1c) and body mass index (BMI) z-scores were evaluated every 6 months. RESULTS: HbA1c decreased from 11.4% ± 1.1% at baseline to 9.3% ± 1.9% after 6 months and 9.7% ± 1.6% after 12 months of metreleptin (P = .007). In patients treated for 10 years, HbA1c declined with each cycle of metreleptin and rose with each withdrawal. BMI z-scores declined from -1.4 ± 1.8 at baseline, to -2.6 ± 1.6 after 12 months of metreleptin (P = .0006). Changes in BMI z-score correlated with changes in HbA1c (P < .0001). CONCLUSIONS: Metreleptin treatment for 12 months was associated with a 1.7% reduction in HbA1c; part of this improvement was likely mediated via decreased BMI. Metreleptin is a promising treatment option for RMS, but additional therapies are needed to achieve HbA1c targets.

Severe progressive obstructive cardiomyopathy and renal tubular dysfunction in Donohue syndrome with decreased insulin receptor autophosphorylation due to a novel INSR mutation.

UNLABELLED: Donohue syndrome (leprechaunism; OMIM *246200) is a rare, recessively inherited disorder of extreme insulin resistance due to mutations in the insulin receptor gene (INSR) causing either defects in insulin binding or receptor autophosphorylation and tyrosine kinase activity. We report a patient with pronounced clinical picture of leprechaunism who developed severe progressive hypertrophic obstructive cardiomyopathy (HOCM) and renal tubular dysfunction which improved on continuous subcutaneous infusion of recombinant human insulin-like growth factor-1 (rhIGF-I). INSR gene molecular analysis and insulin receptor (IR) autophosphorylation on cultured fibroblasts were performed. A novel homozygous missense mutation p.Leu795Pro was found, located in the extracellular portion of the ß subunit of the insulin receptor. The post-binding defect of the insulin receptor signaling in cultured fibroblasts demonstrated decreased insulin receptor autophosphorylation. CONCLUSION: Treatment with rhIGF-I partially reversed severe progressive HOCM and renal tubular dysfunction in a patient with Donohue syndrome associated with a novel p.Leu795Pro INSR gene mutation causing a severe decrease in IR autophosphorylation.

Functional characterization of insulin receptor gene mutations contributing to Rabson-Mendenhall syndrome - phenotypic heterogeneity of insulin receptor gene mutations.

Rabson-Mendenhall syndrome (RMS) is a rare disorder that presents as severe insulin resistance as a result of mutations present in the insulin receptor (INSR). A Chinese girl with RMS presented with profound diabetes, hyperinsulinemia, acanthosis nigricans, hirsutism, and abnormalities of teeth and nails. Direct sequencing of the patient's INSR detected heterozygote mutations at Arg83Gln (R83Q) and Ala1028Val (A1028V), with the former representing a novel mutation. Functional studies of Chinese hamster ovary (CHO) cells transfected with wild-type (WT) and mutant forms of INSR were performed to evaluate the effects of these mutations on receptor expression and activation. Receptor expression, insulin binding activity, and phosphorylation of the R83Q variant were comparable to WT. In contrast, expression of the A1028V receptor was much lower than that of WT INSR, and impairment of insulin binding and autophosphorylation were nearly commensurate with the decrease in expression detected. Reductions in the phosphorylation of IRS-1, Akt, and Erk1/2 (60%, 40%, and 50% of WT, respectively) indicate that the A1028V receptor contributes to impaired signal transduction. In conclusion, INSR mutations associated with RMS were identified. Moreover, the A1028V mutation associated with a decrease in expression of INSR potentially accounts for loss of function of the INSR.

[Insulin receptor defect as a cause of Rabson-Mendenhall syndrome and other rare genetic insulin resistance syndromes]. / Defekt receptora insuliny jako przyczyna zespolu Rabsona-Mendenhalla i innych rzadkich postaci insulinoopornosci.

Insulin plays a very important role in maintaining homeostasis of the whole organism. It regulates glucose metabolism, glycogen synthesis, lipid and protein metabolism. Insulin receptors are present in virtually all cells, which is reflected by the diversity of regulatory processes in which this hormone is involved. Any dysfunction of insulin signalling pathway as a result of insulin receptor gene mutations is linked with various forms of insulin resistance, including insulin resistance type A, Donohue or Rabson-Mendenhall syndrome, which differ in the level of severity. Molecular analysis of insulin receptor gene may lead to a better understanding of molecular mechanisms underlying various types of insulin resistance and help to develop a more efficient treatment. They may also be used as a powerful tool in prenatal diagnostics as well as in pregnancy planning.

Downregulation of Wnt-mediated ROS generation is causally implicated in leprechaunism.

Although mutations in the insulin receptor have been causally implicated with leprechaunism, the full pathophysiology of the syndrome cannot be accounted for by malfunction of this gene alone. We sought to characterize a connection between Wnt-mediated cell signaling and the production of reactive oxygen species (ROS) which revealed a novel mechanistic basis for understanding the pathogenesis of leprechaunism. To identify candidate genes involved in this process, a PCR-based subtractive hybridization was performed. Candidate genes were examined for interaction with the Wnt signaling pathway and ROS generation. We found that Dickkopf 1 (Dkk1), a Wnt inhibitor, is overexpressed in skin fibroblast cells derived from three leprechaunism patients and that the cells showed an impaired response to Wnt2 in terms of beta-catenin-Tcf activation. Knockdown of Dkk1 in the patient cell lines rescued Wnt2-mediated Tcf activation. Concerted action of Wnt2 and knockdown of Dkk1 resulted in enhanced Nox4 expression and PDGF-induced ROS generation compared to parental patient cells. Furthermore, we found that NFATc2 was activated in response to Wnt2 stimulation and directly activates Nox4 expression. These data show a crosstalk between Wnt and ROS pathways which in turn provides new mechanistic insights at the molecular level into the pathogenesis of leprechaunism.