Haploinsufficiency of theNF1gene is associated with protection against diabetes

Abstract

BackgroundThe hereditary predisposition to diabetes is only partially explained by genes identified so far. Neurofibromatosis type 1 (NF1) is a rare monogenic dominant syndrome caused by aberrations of the NF1 gene. Here, we used a cohort of 1410 patients with NF1 to study the association of the NF1 gene with type 1 (T1D) and type 2 diabetes (T2D).MethodsA total of 1410 patients were confirmed to fulfil the National Institutes of Health diagnostic criteria for NF1 by individually reviewing their medical records. The patients with NF1 were compared with 14 017 controls matched for age, sex and area of residence as well as 1881 non-NF1 siblings of the patients with NF1. Register-based information on purchases of antidiabetic medication and hospital encounters related to diabetes were retrieved. The Cox proportional hazards model was used to calculate the relative risk for diabetes in NF1.ResultsPatients with NF1 showed a lower rate of T2D when compared with a 10-fold control cohort (HR 0.27, 95% CI 0.17 to 0.43) or with their siblings without NF1 (HR 0.28, 95% CI 0.16 to 0.47). The estimates remained practically unchanged after adjusting the analyses for history of obesity and dyslipidaemias. The rate of T1D in NF1 was decreased although statistically non-significantly (HR 0.58, 95% CI 0.27 to 1.25).ConclusionHaploinsufficiency of the NF1 gene may protect against T2D and probably T1D. Since NF1 negatively regulates the Ras signalling pathway, the results suggest that the Ras pathway may be involved in the pathogenesis of diabetes.

Metabolic Features of Neurofibromatosis Type 1-Associated Tumors

“…This could be caused by a general imbalance in the levels of several hormones, including lower levels of leptin and visfatin and higher adiponectin in NF1 patients with respect to control subjects. It remains to be explained the mechanistic connection between heterozygous loss of neurofibromin and these metabolic changes, confirmed in a large cohort of patients [11]. Moreover, NF1 individuals show reduced cerebral glucose metabolism, specifically in the thalamus [12].…”

Rationale for haploinsufficiency correction therapy in neurofibromatosis type 1

“…NF1 therapies blocking RAS signaling pathways, such as the MEKi Selumetinib, have shown partial shrinkage of NF1 plexiform tumors [176] . However, as neurofibromin's regulatory role is not limited to one signaling pathway, any therapy targeting a specific downstream effector will likely result in only partial NF1-phenotype resolution, as opposed to therapies that restore neurofibromin levels and thus correct all dysregulated pathways.…”