Enhanced phosphorylation of Na(+)-Cl- co-transporter in experimental metabolic syndrome: role of insulin.
In the present study, we investigated the activity of the thiazide-sensitive NCC (Na(+)-Cl(-) co-transporter) in experimental metabolic syndrome and the role of insulin in NCC activation. Renal responses to the NCC inhibitor HCTZ (hydrochlorothiazide), as a measure of NCC activity in vivo, were studied in 12-week-old ZO (Zucker obese) rats, a model of the metabolic syndrome, and in ZL (Zucker lean) control animals, together with renal NCC expression and molecular markers of NCC activity, such as localization and phosphorylation. Effects of insulin were studied further in mammalian cell lines with inducible and endogenous expression of this molecule. ZO rats displayed marked hyperinsulinaemia, but no differences in plasma aldosterone, compared with ZL rats. In ZO rats, natriuretic and diuretic responses to NCC inhibition with HCTZ were enhanced compared with ZL rats, and were associated with a decrease in BP (blood pressure). ZO rats displayed enhanced Thr(53) NCC phosphorylation and predominant membrane localization of both total and phosphorylated NCC, together with a different profile in expression of SPAK (Ste20-related proline/alanine-rich kinase) isoforms, and lower expression of WNK4. In vitro, insulin induced NCC phosphorylation, which was blocked by a PI3K (phosphoinositide 3-kinase) inhibitor. Insulin-induced reduction in WNK4 expression was also observed, but delayed compared with the time course of NCC phosphorylation. In summary, we report increased NCC activity in hyperinsulinaemic rodents in conjunction with the SPAK expression profile consistent with NCC activation and reduced WNK4, as well as an ability of insulin to induce NCC stimulatory phosphorylation in vitro. Together, these findings indicate that hyperinsulinaemia is an important driving force of NCC activity in the metabolic syndrome with possible consequences for BP regulation.
Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, OR 97239, USA. komersr@ohsu.edu
Radko
R
Komers
Shaunessy
S
Rogers
Terry T
TT
Oyama
Bei
B
Xu
Chao-Ling
CL
Yang
James
J
McCormick
David H
DH
Ellison
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D006852:Hydrochlorothiazide; D006946:Hyperinsulinism / Q000097:blood / Q000378:metabolism / Q000503:physiopathology; D015151:Immunoblotting; D007328:Insulin / Q000097:blood / Q000494:pharmacology / Q000502:physiology*; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism; D024821:Metabolic Syndrome / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D009765:Obesity / Q000097:blood / Q000378:metabolism / Q000503:physiopathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D011924:Rats, Zucker; D011955:Receptors, Drug / Q000378:metabolism; D049992:Sodium Chloride Symporters / Q000378:metabolism*; D064486:Solute Carrier Family 12, Member 3; D027981:Symporters / Q000378:metabolism
D002867:Chromones; D006852:Hydrochlorothiazide; D007328:Insulin; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011955:Receptors, Drug; D049992:Sodium Chloride Symporters; D064486:Solute Carrier Family 12, Member 3; D027981:Symporters; C578876:Slc12a3 protein, rat; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C499025:Wnk4 protein, rat; C116037:PAS domain kinases