Fasting Hypoglycemia and Preserved Renal Function in Endothelial NO Synthase Knockout Mice

Nitric oxide (NO) is an important signaling molecule that regulates numerous physiological processes. Impairment of nitric oxide production and inactivation of genes encoding various NOS isoforms most commonly affect such target organs as the kidneys and liver. The aim of the present study was to investigate kidney and liver morphology, renal ion-regulating function, and glycemia in adult mice with nos3 gene knockout (NOS3 KO). A line of homozygous NOS3 KO mice was generated on a C57Bl/6 background using CRISPR-Cas9 genome editing technology. In NOS3 KO and wild-type mice aged 3–7 months, glycemia levels and/or urinary sodium excretion were assessed under conditions of free access to food, after a 17-hour fast, and following a salt loading test. At the age of 9 months, the animals were euthanized; kidneys and liver were fixed in neutral formalin, followed by standard histological processing and staining. Under conditions of free access to food, fasting, and in the salt loading test, sodium excretion and the sodium/creatinine ratio did not differ between NOS3 KO and wild-type mice. NOS3 KO mice maintained the corticomedullary structure of the kidneys, and no pathological changes were detected. Male NOS3 KO mice exhibited reduced liver glycogen stores and a pronounced decrease in blood glucose levels under fasting conditions. Pharmacological correction of nitric oxide levels by administration of an NO donor (isosorbide dinitrate) led to an increase in blood glucose levels in male NOS3 KO mice. Thus, the study demonstrates that mice with an endothelial NO synthase gene knockout maintain normal kidney structure and function. Male NOS3 KO mice showed a tendency to develop fasting hypoglycemia and a reduced glycogen content in hepatocytes, indicating the involvement of NOS3 in the regulation of carbohydrate metabolism.