# DNA2 acts as a brake on β cell insulin hypersecretion and diet-induced metabolic dysfunction

## TL;DR

DNA2 limits insulin overproduction in pancreatic cells and prevents metabolic issues when diet is poor.

## Contribution

DNA2 is identified as a brake on β cell hyperactivity and metabolic dysfunction under dietary stress.

## Key findings

- DNA2 deficiency leads to increased insulin secretion and metabolic dysfunction under high-fat diet.
- DNA2 regulates mitochondrial activity and ATP production in β cells.
- Both nuclease and helicase activities of DNA2 are required for metabolic regulation.

## Abstract

DNA replication helicase/nuclease 2 (DNA2) is an evolutionarily conserved nuclease-helicase with known role in maintaining nuclear genome stability. However, its potential involvement in metabolic regulation and disease remains unclear. This study investigates the role of DNA2 in pancreatic β cell physiology and diabetes pathogenesis.

β cell-specific DNA2 knockout mice (DNA2INS2−/−) were generated and fed either a chow diet (CD) or high-fat diet (HFD). Metabolic phenotyping, insulin secretion assays, transcriptomic profiling, mitochondrial function analysis, and ultrastructural imaging were performed. INS-1 cells were used to assess the functions of DNA2 in vitro through knockdown, overexpression and site-directed mutagenesis.

DNA2INS2−/− mice exhibited normal metabolic profiles under CD, but developed severe hyperglycemia, hyperinsulinemia, insulin resistance, and ectopic lipid deposition upon HFD feeding. This phenotype was accompanied by increased β cell proliferation and glucose-stimulated insulin secretion. RNA sequencing revealed the dysregulation of mitochondrial regulatory genes in DNA2-deficient islets. Functional assays confirmed that DNA2 deletion enhanced mitochondrial ATP production and oxidative phosphorylation, whereas its overexpression suppressed mitochondrial activity. Domain-specific mutagenesis demonstrated that both nuclease and helicase activities are essential for DNA2-mediated metabolic regulation.

Our findings identify DNA2 as a negative regulator of mitochondrial bioenergetics and insulin secretion in β cells. By limiting mitochondrial activity, DNA2 serves as a rheostat that prevents β cell overactivation during metabolic stress, thereby preserving systemic glucose homeostasis.