Hypoglycaemia revealing heterozygous insulin receptor mutations

Case report: Glycaemic management and pregnancy outcomes in a woman with an insulin receptor mutation, p.Met1180Lys

BACKGROUND

Heterozygous insulin receptor mutations (INSR) are associated with insulin resistance, hyperglycaemia and hyperinsulinaemic hypoglycaemia in addition to hyperandrogenism and oligomenorrhoea in women. Numerous autosomal dominant heterozygous mutations involving the INSR β-subunit tyrosine kinase domain resulting in type A insulin resistance have been previously described. We describe the phenotype, obstetric management and neonatal outcomes in a woman with type A insulin resistance caused by a mutation in the β-subunit of the INSR.

CASE PRESENTATION

We describe a woman with a p.Met1180Lys mutation who presents with hirsutism, oligomenorrhoea and diabetes at age 20. She has autoimmune thyroid disease, Coeliac disease and positive GAD antibodies. She is overweight with no features of acanthosis nigricans and is treated with metformin. She had 11 pregnancies treated with insulin monotherapy (n = 2) or combined metformin and insulin therapy (n = 9). The maximum insulin dose requirement was 134 units/day or 1.68 units/kg/day late in the second pregnancy. Mean birthweight was on the 37th centile in INSR positive offspring (n = 3) and the 94th centile in INSR negative offspring (n = 1).

CONCLUSION

The p.Met1180Lys mutation results in a phenotype of diabetes, hirsutism and oligomenorrhoea. This woman had co-existent autoimmune disease. Her insulin dose requirements during pregnancy were similar to doses observed in women with type 2 diabetes. Metformin may be used to improve insulin sensitivity in women with this mutation. Offspring inheriting the mutation tended to be smaller for gestational age.

Heterozygous Insulin Receptor (INSR) Mutation Associated with Neonatal Hyperinsulinemic Hypoglycaemia and Familial Diabetes Mellitus: Case Series

Mutations in the insulin receptor (INSR) gene are associated with insulin resistance and hyperglycaemia. Various autosomal dominant heterozygous INSR mutations leading to hyperinsulinemic hypoglycaemia (HH) have been described in adults and children (more than 3 years of age) but not in the neonatal period. Family 1: A small for gestational age (SGA) child born to a mother with gestational diabetes presented with persistent hypoglycaemia, was diagnosed with HH and responded well to diazoxide treatment. Diazoxide was gradually weaned and discontinued by 8 months of age. Later, the younger sibling had a similar course of illness. On genetic analysis a heterozygous INSR missense variant p.(Met1180Lys) was found in the siblings, mother and grandfather but not in the father. Family 2: A twin preterm and SGA baby presented with persistent hypoglycaemia, which was confirmed as HH. He responded to diazoxide, which was subsequently discontinued by 10 weeks of life. Genetic analysis revealed a novel heterozygous INSR missense variant p.(Arg1119Gln) in the affected twin and the mother. Family 3: An SGA child presented with diazoxide responsive HH. Diazoxide was gradually weaned and discontinued by 9 weeks of age. Genetic analysis revealed a novel heterozygous INSR p.(Arg1191Gln) variant in the proband and her father. We report, for the first time, an association of INSR mutation with neonatal HH responsive to diazoxide therapy that resolved subsequently. Our case series emphasizes the need for genetic analysis and long-term follow up of these patients.

Arg1201Gln mutation of insulin receptor impairs tyrosine kinase activity and causes insulin resistance: a case report

Type A insulin resistance syndrome (TAIRS) is a rare subtype of congenital insulin resistance (IR), which is characterized by specific clinical manifestations without clear diagnostic criteria and is easily misdiagnosed or overlooked. Herein we present a case of TAIRS with acanthosis nigricans (AN), severe IR, polycystic ovaries, hyperandrogenism and its consequence such as menstrual disturbances, acne and hirsutism. A heterozygous mutation, p.Arg1201Gln, in the insulin receptor (INSR) was detected. This mutation in the tyrosine kinase domain has been described before and shown to impair tyrosine kinase activity and is responsible for IR.

Rare causes of hypoglycemia in adults

Hypoglycemia is defined by a low blood glucose level associated to clinical symptoms. Hypoglycemia may be related to treatment of diabetes, but also to drugs, alcohol, critical illness, cortisol insufficiency including hypopituitarism, insulinoma, bariatric or gastric surgery, pancreas transplantation or glucagon deficiency, or may be surreptitious. Some hypoglycemic episodes remain unexplained, and genetic, paraneoplastic and immune causes should be considered. Genetic causes may be related to endogenous hyperinsulinism and to inborn errors of metabolism (IEM). Endogenous hyperinsulinism is related to monogenic congenital hyperinsulinism, and especially to mutations of the glucokinase-activating gene or of insulin receptors, both characterised by postprandial hypoglycemia with major hyperinsulinism. In adulthood, IEM-related hypoglycemia can persist in a previously diagnosed childhood disease or may be a presenting sign. It is suggested by systemic involvement (rhabdomyolysis after fasting or exercising, heart disease, hepatomegaly), sometimes associated to a family history of hypoglycemia. The timing of hypoglycemic episodes with respect to the last meal also helps to orientate diagnosis. Fasting hypoglycemia may be related to type 0, I or III glycogen synthesis disorder, fatty acid oxidation or gluconeogenesis disorder. Postprandial hypoglycemia may be related to inherited fructose intolerance. Exercise-induced hyperinsulinism is mainly related to activating mutation of the SLC16A1 gene. Besides exceptional ectopic insulin secretion, paraneoplastic causes involve NICTH (Non-Islet-Cell Tumour Hypoglycemia), caused by Big-IGF2 secretion by a large tumour, with low blood levels of insulin, C-peptide and IGF1. Autoimmune causes involve antibodies against insulin (HIRATA syndrome), especially in case of Graves' disease, or against the insulin receptor. Medical history, timing, and insulin level orientate the diagnosis.

Attenuation of Insulin Action by an Allosteric Insulin Receptor Antibody in Healthy Volunteers

BACKGROUND

XOMA 358 (X358) is a fully human monoclonal antibody to the insulin receptor that acts as a negative allosteric modulator of insulin signaling. It is being developed as a novel treatment of hyperinsulinemic hypoglycemia. This report describes pharmacokinetic (PK) and pharmacodynamic (PD) data from a first-in-human clinical trial.

METHODS

A double-blind, placebo-controlled, single-ascending-dose study was performed with 29 healthy adult males randomized to intravenous infusion of placebo or X358 at 0.1-, 0.3-, 1-, 3-, 6-, or 9-mg/kg dose levels. The primary objective was to assess safety and tolerability, and secondary objectives included PK and PD analyses. A short insulin tolerance test (ITT) was implemented in the 3- to 9-mg/kg dose cohorts at baseline and postinfusion.

RESULTS

There were no deaths, serious adverse events (AEs), or subject discontinuations due to AEs. There were no clinically meaningful safety findings. X358 exhibited dose-proportional PK with a half-life of 21 days. Dose-dependent elevations of circulating insulin levels, likely related to reduced insulin clearance via monoclonal antibody action at receptors, represented a sensitive biomarker of X358 exposure. X358-dependent increases in postprandial glucose levels and fasting homeostatic model assessment of insulin resistance values were observed and persisted for at least 1 week at the higher dose levels. In all the ITT cohorts, the slope for glucose lowering was substantially attenuated after X358 infusion of a similar magnitude, but with increasing duration with rising dose level.

CONCLUSION

Single X358 infusions were well tolerated and resulted in a dose-dependent reduction in insulin sensitivity. Clinical development of X358 in hyperinsulinemic, hypoglycemic conditions is proceeding.