High-fat diet amplifies renal renin angiotensin system expression, blood pressure elevation, and renal dysfunction caused by Ceacam1 null deletion

Abstract

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAMl), a substrate of the insulin receptor tyrosine kinase, regulates insulin action by promoting insulin clearance. Global null mutation of Ceacam1 gene (Cc1(-/-)) results in features of the metabolic syndrome, including insulin resistance, hyperinsulinemia, visceral adiposity, elevated blood pressure, and albuminuria. It also causes activation of the renal renin-angiotensin system (RAS). In the current study, we tested the hypothesis that high-fat diet enhances the expression of RAS components. Three-month-old wild-type (Cc1(+/+)) and Cc1(-/-) mice were fed either a regular or a high-fat diet for 8 wk. At baseline under regular feeding conditions, Cc1(-/-) mice exhibited higher blood pressure, urine albumin-to-creatinine ratio (UACR), and renal expression of angiotensinogen, renin/prorenin, angiotensin-converting enzyme, (pro)renin receptor, angiotensin subtype AT1 receptor, angiotensin II, and elevated PI3K phosphorylation, as detected by p85α (Tyr(508)) immunostaining, inflammatory response, and the expression of collagen I and collagen III. In Cc1(+/+) mice, high-fat diet increased blood pressure, UACR, the expression of angiotensin-converting enzyme and angiotensin II, PI3K phosphorylation, inflammatory response, and the expression of collagen I and collagen III. In Cc1(-/-) mice, high-fat intake further amplified these parameters. Immunohistochemical staining showed increased p-PI3K p85α (Tyr(508)) expression in renal glomeruli, proximal, distal, and collecting tubules of Cc1(-/-) mice fed a high-fat diet. Together, this demonstrates that high-fat diet amplifies the permissive effect of Ceacam1 deletion on renal expression of all RAS components, PI3K phosphorylation, inflammation, and fibrosis.

Keywords: carcinoembryonic antigen-related cell adhesion molecule 1; high-fat diet; kidney; phosphatidylinositol 3′-kinase; renin-angiotensin system.

Fig. 1.

Effect of high-fat (HF) diet on blood pressure and urine albumin-to-creatinine ratio in carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) wild-type (Cc1^+/+) and CEACAM1 KO mice (Cc1^−/−) mice. A: blood pressure. B: urine albumin/creatinine ratio. WTRD, wild-type (WT) mice fed regular diet (RD); WTHF, WT mice fed HF diet; KORD, knockout-type (KO) mice fed regular diet (RD); KOHF, KO-type mice fed HF diet. Values are means ± SE; n = 6 mice/group.

Fig. 2.

Effect of HF diet on mRNA and protein levels of angiotensinogen (AGT) and renin (REN) in the kidney of Cc1^+/+ and Cc1^−/− mice. A: real-time PCR analysis of AGT mRNA expression in whole kidney lysates. B: Western blot analysis of AGT protein expression in whole kidney lysates. C: real-time PCR analysis of renin mRNA expression in whole kidney lysates. D: Western blot analysis of renin protein in whole kidney lysates. Values are means ± SE; n = 6 mice/group.

Fig. 3.

Effect of HF diet on (pro)renin receptor (PRR) mRNA and protein levels in the kidneys of Cc1^+/+ and Cc1^−/− mice. A: real-time PCR analysis of PRR mRNA expression in whole kidney lysates. B: reconstructed Western blot analysis as representative of PRR protein expression in whole kidney lysates; 1 band was chosen randomly from each treatment group. Values are means ± SE; n = 6 mice/group.

Fig. 4.

Effect of HF diet on angiotensin-converting enzyme (ACE) mRNA and protein levels in the kidneys of Cc1^+/+ and Cc1^−/− mice. A: real-time PCR analysis of ACE mRNA expression in kidney lysates. B: Western blot analysis of ACE protein expression in whole kidney lysates. Values are means ± SE; n = 6 mice/group.

Fig. 5.

Effect of HF diet on renal interstitial fluid (RIF) angiotensin (Ang) levels in Cc1^+/+ and Cc1^−/− mice. A: RIF Ang II. Values are means ± SE; n = 6 mice/group.

Fig. 6.

Effect of HF diet on angiotensin subtype 1 receptor (AT1R) mRNA and protein levels in the kidneys of Cc1^+/+ and Cc1^−/− mice. A: real-time PCR analysis of AT1R mRNA expression in whole kidney lysates. B: Western blot analysis of AT1R protein expression in whole kidney lysates. Values are means ± SE; n = 6 mice/group.

Fig. 7.

Immunostaining of phosphorylated (phospho) phospatidylinositol 3′-kinase (PI3K) p85α in the kidneys of Cc1^+/+ and Cc1^−/− mice. Immunostaining of phospho-PI3K p85α (Tyr⁵⁰⁸) in the kidneys of Cc1^+/+ and Cc1^−/− mice fed RD or HF diet; n = 6 mice/group. PT, proximal tubule; DT, distal tubule; CD, collecting ducts.

Fig. 8.

Immunostaining of collagen I and collagen III in the kidneys of male Cc1^+/+ and Cc1^−/− mice. A: immunostaining of collagen I in the kidneys of Cc1^+/+ and Cc1^−/− mice fed RD or HF diet. B: typical immunostaining of collagen III in the kidneys of Cc1^+/+ and Cc1^−/− mice fed RD or HF diet; n = 6 mice/group.