Anti-Insulin receptor antibodies improve hyperglycaemia in a mouse model of human insulin receptoropathy
Loss-of-function mutations in both alleles of the human insulin receptor gene (INSR) cause extreme insulin resistance (IR) and usually death in childhood, with few therapeutic options. Bivalent anti-receptor antibodies can elicit insulin-like signaling by mutant INSR in cultured cells, but whether this translates into meaningful metabolic benefits in vivo, where dynamics of insulin signaling and receptor recycling are more complex, is unknown. To address this we adopted a strategy to model human insulin receptoropathy in mice, using Cre recombinase delivered by adeno-associated virus to knock out endogenous hepatic Insr acutely in floxed Insr mice (L- IRKO+GFP), before adenovirus-mediated add-back of wild-type (WT) or mutant human INSR. Two murine anti-INSR monoclonal antibodies, previously shown to be surrogate agonists for mutant INSR, were then tested by intraperitoneal injections. As expected, L-IRKO+GFP mice showed glucose intolerance and severe hyperinsulinemia, and this was fully corrected by add-back of WT but neither D734A nor S350L mutant INSR. Antibody injection improved glucose tolerance in D734A INSR-expressing mice and reduced hyperinsulinemia in both S350L and D734A INSR-expressing animals, and did not cause hypoglycemia in WT INSR-expressing mice. Antibody treatment also downregulated both wild-type and mutant INSR protein, attenuating its beneficial metabolic effects. Anti-INSR antibodies thus improve IR in an acute model of insulin receptoropathy, but these findings imply a narrow therapeutic window determined by competing effects of antibodies to stimulate receptors and induce their downregulation. One Sentence SummaryBivalent anti-insulin receptor antibodies improve glycaemic control, but downregulate receptor expression, in a novel mouse model of lethal human insulin receptoropathy.