Phosphatidylinositol 3-Kinase/Akt Signaling Pathway Activates the WNK-OSR1/SPAK-NCC Phosphorylation Cascade in Hyperinsulinemic db/db Mice

• Published in: Hypertension (Dallas, Tex. 1979) Vol. 60; no. 4; pp. 981 - 990
• Main Authors: Nishida, Hidenori, Sohara, Eisei, Nomura, Naohiro, Chiga, Motoko, Alessi, Dario R, Rai, Tatemitsu, Sasaki, Sei, Uchida, Shinichi
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD American Heart Association, Inc 01-10-2012; Lippincott Williams & Wilkins
• Subjects: Animals; Arterial hypertension. Arterial hypotension; Biological and medical sciences; Blood and lymphatic vessels; Blood Pressure - physiology; Cardiology. Vascular system; Clinical manifestations. Epidemiology. Investigative techniques. Etiology; Hyperinsulinism - metabolism; Kidney - drug effects; Kidney - metabolism; Kidney - physiopathology; Medical sciences; Mice; Minor Histocompatibility Antigens; Phosphatidylinositol 3-Kinases - metabolism; Phosphorylation - drug effects; Phosphorylation - physiology; Protein Serine-Threonine Kinases - metabolism; Proto-Oncogene Proteins c-akt - metabolism; Receptors, Drug - metabolism; Signal Transduction - drug effects; Signal Transduction - physiology; Sodium Chloride Symporter Inhibitors - pharmacology; Solute Carrier Family 12, Member 3; Symporters - metabolism; WNK Lysine-Deficient Protein Kinase 1; Hypertension; Obesity; Phosphorylation; sodium-dependent hypertension; Rodentia; Nutrition disorder; Cardiovascular disease; Akt; Insulin; Vertebrata; Mammalia; Sodium; Mouse; PI3K; WNK; Animal; NaCl cotransporter; Nutritional status
• ISSN: 0194-911X; 1524-4563
• DOI: 10.1161/HYPERTENSIONAHA.112.201509

Metabolic syndrome patients have insulin resistance, which causes hyperinsulinemia, which in turn causes aberrant increased renal sodium reabsorption. The precise mechanisms underlying this greater salt sensitivity of hyperinsulinemic patients remain unclear. Abnormal activation of the recently identified with-no-lysine kinase (WNK)-oxidative stress-responsive kinase 1 (OSR1)/STE20/SPS1-related proline/alanine-rich kinase (SPAK)-NaCl cotransporter (NCC) phosphorylation cascade results in the salt-sensitive hypertension of pseudohypoaldosteronism type II. Here, we report a study of renal WNK-OSR1/SPAK-NCC cascade activation in the db/db mouse model of hyperinsulinemic metabolic syndrome. Thiazide sensitivity was increased, suggesting greater activity of NCC in db/db mice. In fact, increased phosphorylation of OSR1/SPAK and NCC was observed. In both Spak and Osr1 knock-in db/db mice, which carry mutations that disrupt the signal from WNK kinases, increased phosphorylation of NCC and elevated blood pressure were completely corrected, indicating that phosphorylation of SPAK and OSR1 by WNK kinases is required for the increased activation and phosphorylation of NCC in this model. Renal phosphorylated Akt was increased in db/db mice, suggesting that increased NCC phosphorylation is regulated by the phosphatidylinositol 3-kinase/Akt signaling cascade in the kidney in response to hyperinsulinemia. A phosphatidylinositol 3-kinase inhibitor (NVP-BEZ235) corrected the increased OSR1/SPAK-NCC phosphorylation. Another more specific phosphatidylinositol 3-kinase inhibitor (GDC-0941) and an Akt inhibitor (MK-2206) also inhibited increased NCC phosphorylation. These results indicate that the phosphatidylinositol 3-kinase/Akt signaling pathway activates the WNK-OSR1/SPAK-NCC phosphorylation cascade in db/db mice. This mechanism may play a role in the pathogenesis of salt-sensitive hypertension in human hyperinsulinemic conditions, such as the metabolic syndrome.