Pseudo-nephropathy and hyper-excretion of urinary C-peptide: an overlooked adverse effect of an angiotensin receptor-neprilysin inhibitor (ARNI).

Sacubitril/valsartan, which is a combined angiotensin receptor-neprilysin inhibitor (ARNI), is used for the treatment of chronic heart failure and hypertension. Substrates of neprilysin are numerous, and the systemic effects of an ARNI remain to be determined. Increased urinary C-peptide (UCPR) and urinary albumin (UAlb) excretion has been reported with the use of an ARNI, but the mechanism is still unknown. We report an 84-year-old man with type 2 diabetes and hypertension. His UAlb and UCPR excretion and (to a lesser degree) the estimated glomerular filtration rate were increased after ARNI administration. They returned to basal levels after discontinuing ARNI administration. There was little or no change in glycemic control. Therefore, increased glomerular permeability and filtration could partially explain how neprilysin inhibition led to an elevation in UCPR excretion, in addition to other mechanisms, such as impairment of the renal ability to degrade C-peptide. Physicians must be cautious when interpreting the insulin secretion capability by UCPR and nephropathy by UAlb in ARNI-treated patients with diabetes.