Neuropeptide Y autoantibodies in patients with long-term type 1 and type 2 diabetes and neuropathy

Aims: The neurotransmitter Neuropeptide Y (NPY) was previously reported as a minor autoantigen in newly diagnosed type 1 diabetes (T1D) patients. The single nucleotide polymorphism at rs16139 (T1128C, L7P) in the NPY gene was associated with an increased risk for the development of type 2 diabetes (T2D). We aimed to develop a radiobinding assay for NPY-L (Leucine) and NPY-P (Proline) autoantibodies (A) to study the levels and the association with other islet autoantibodies and neuropathy. Methods: Autoantibodies against NPY-L, NPY-P, ZnT8, GAD65 and IA-2 were studied in T1D (n = 48) and T2D (n = 26) patients with duration up to 42 and 31 years. A subgroup of T1D (n = 32) patients re-examined, 5-8 years after first visit, was tested for peripheral (Z-score) and autonomic neuropathy (E/I ratio). Results: NPY-LA and NPY-PA were detected in 23% and 19% in T1D (p<0.001), and 12% and 23% in T2D patients (p<0.001) compared to 2.5% controls (n = 398). The levels of NPYA declined during follow-up in the T1D patients (p < 0.001). The neuropathy was not related to the NPYA or the other islet autoantibodies. Conclusions: Regardless of the absence of an association between NPYA and neuropathy, NPY may contribute to the pathogenesis of T1D and T2D as a minor autoantigen.