Blunted DOCA/high salt induced albuminuria and renal tubulointerstitial damage in gene-targeted mice lacking SGK1

Mineralocorticoids stimulate renal tubular Na+ reabsorption, enhance salt appetite, increase blood pressure, and favor the development of renal fibrosis. The effects of mineralocorticoids on renal tubular Na+ reabsorption and salt appetite involve the serum- and glucocorticoid-inducible kinase 1 (SGK1). The kinase is highly expressed in fibrosing tissue. The present experiments thus explored the involvement of SGK1 in renal fibrosis. To this end, SGK1-knockout mice (sgk1(-/-)) and their wild-type littermates (sgk1(+/+)) were implanted with desoxycorticosterone acetate (DOCA)-release pellets and offered 1% saline as drinking water for 12 weeks. The treatment led to significant increases in fluid and Na+ intake and urinary output of fluid and Na+ in sgk1(+/+) mice, effects blunted in sgk1(-/-) mice. Blood pressure increased within the first 7 weeks to a similar extent in both genotypes, but within the next 5 weeks, it increased further only in sgk1(+/+) mice. Creatinine clearance did not change significantly but albuminuria increased dramatically in sgk1(+/+) mice, an effect significantly blunted in sgk1(-/-) mice. Histology after 12 weeks treatment revealed marked glomerular sclerosis and tubulointerstitial damage with interstitial fibrosis and inflammation in kidneys from sgk1(+/+) mice, but not from sgk1(-/-) mice. In conclusion, a lack of SGK1 protects against DOCA/high-salt-induced albuminuria and renal fibrosis.