title: High-salt diet enhances insulin signaling and induces insulin resistance in Dahl salt-sensitive rats.
abstract: A high-salt diet, which is known to contribute to the pathogenesis of hypertension, is also reportedly associated with insulin resistance. We investigated the effects of a high-salt diet on insulin sensitivity and insulin signaling in salt-sensitive (Dahl-S) and salt resistant (Dahl-R) strains of the Dahl rat. Evaluation of hyperinsulinemic-euglycemic clamp studies and glucose uptake into the isolated soleus muscle revealed that salt loading (8% NaCl) for 4 weeks induced hypertension and significant insulin resistance in Dahl-S rats, whereas no significant effects were observed in Dahl-R rats. Despite the presence of insulin resistance, insulin-induced tyrosine phosphorylation of the insulin receptor and insulin receptor substrates, activation of phosphatidylinositol 3-kinase, and phosphorylation of Akt were all enhanced in Dahl-S rats fed a high-salt diet. The mechanism underlying this form of insulin resistance thus differs from that previously associated with obesity and dexamethasone and is likely due to the impairment of one or more metabolic steps situated downstream of phosphatidylinositol 3-kinase and Akt activation. Interestingly, supplementation of potassium (8% KCl) ameliorated the changes in insulin sensitivity in Dahl-S rats fed a high-salt diet; this was associated with a slight but significant decrease in blood pressure. Evidence presented suggest that there is an interdependent relationship between insulin sensitivity and salt sensitivity of blood pressure in Dahl-S rats, and it is suggested that supplementing the diet with potassium may exert a protective effect against both hypertension and insulin resistance in salt-sensitive individuals.
authors.affiliation: Department of Internal Medicine, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
authors.forename: Takehide
authors.initials: T
authors.lastname: Ogihara
authors.forename: Tomoichiro
authors.initials: T
authors.lastname: Asano
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Ando
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Sakoda
authors.forename: Motonobu
authors.initials: M
authors.lastname: Anai
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Shojima
authors.forename: Hiraku
authors.initials: H
authors.lastname: Ono
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Onishi
authors.forename: Midori
authors.initials: M
authors.lastname: Fujishiro
authors.forename: Miho
authors.initials: M
authors.lastname: Abe
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Fukushima
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Kikuchi
authors.forename: Toshiro
authors.initials: T
authors.lastname: Fujita
mesh_terms: D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D003847:Deoxyglucose / Q000493:pharmacokinetics; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017419:Potassium, Dietary / Q000008:administration & dosage; D051381:Rats; D020303:Rats, Inbred Dahl; D015398:Signal Transduction / Q000502:physiology*; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*; D013045:Species Specificity; D014443:Tyrosine / Q000378:metabolism
chemical_list: C526292:IRS1 protein, human; C526297:IRS2 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; C526296:Irs1 protein, rat; C526299:Irs2 protein, rat; D010750:Phosphoproteins; D017419:Potassium, Dietary; D017673:Sodium Chloride, Dietary; D014443:Tyrosine; D003847:Deoxyglucose; D019869:Phosphatidylinositol 3-Kinases