Korean J Physiol Pharmacol.  2017 Jan;21(1):99-106. 10.4196/kjpp.2017.21.1.99.

High fat diet confers vascular hyper-contractility against angiotensin II through upregulation of MLCK and CPI-17

• Kim JI

• KMID: 2371073
• DOI: http://doi.org/10.4196/kjpp.2017.21.1.99

Abstract

Obesity is a critical risk factor for the hypertension. Although angiotensin II (Ang II) in obese individuals is known to be upregulated in obesity-induced hypertension, direct evidence that explains the underlying mechanism for increased vascular tone and consequent increase in blood pressure (BP) is largely unknown. The purpose of this study is to investigate the novel mechanism underlying Ang II-induced hyper-contractility and hypertension in obese rats. Eight-week old male Sprague-Dawley rats were fed with 60% fat diet or normal diet for 4 months. Body weight, plasma lipid profile, plasma Ang II level, BP, Ang II-induced vascular contraction, and expression of regulatory proteins modulating vascular contraction with/without Ang II stimulation were measured. As a result, high fat diet (HFD) accelerated age-dependent body weight gaining along with increased plasma Ang II concentration. It also increased BP and Ang II-induced aortic contraction. Basal expression of p-CPI-17 and myosin light chain (MLC) kinase was increased by HFD along with increased phosphorylation of MLC. Ang II-induced phosphorylation of CPI-17 and MLC were also higher in HFD group than control group. In conclusion HFD-induced hypertension is through at least in part by increased vascular contractility via increased expression and activation of contractile proteins and subsequent MLC phosphorylation induced by increased Ang II.

Keyword

Angiontensin II; CPI-17; Hypertension; MLCK; Obesity

MeSH Terms

Angiotensin II*
Angiotensins*
Animals
Blood Pressure
Body Weight
Contractile Proteins
Diet
Diet, High-Fat*
Humans
Hypertension
Male
Myosin Light Chains
Obesity
Phosphorylation
Phosphotransferases
Plasma
Rats
Rats, Sprague-Dawley
Risk Factors
Up-Regulation*
Angiotensin II
Angiotensins
Contractile Proteins
Myosin Light Chains
Phosphotransferases

Figure

• 

  Fig. 1 High fat diet (HFD) accelerated weight gaining.The graph summarized body weights for normal or HFD-fed group at 8 week (before differential diet) and 24 week (16 weeks of differential diet) of age. Body weight increase for 16 weeks of diet was accelerated in HFD group. Data are presented as means±SE (n=4). **p<0.01 vs. normal diet group of same age.

• 

  Fig. 2 HFD elevated blood pressure (BP).The graph summarized blood pressure before HFD at 8 week (a) and after HFD for 16 week at 24 week of age (b). Both systolic and diastolic BP was higher in HFD group than ND group. Data are presented as means±SE (n=4). *p<0.05 vs. ND group.

• 

  Fig. 3 Lipids and Angiotensin II (Ang II) in the plasma of normal or HFD-fed rats.The graph summarized total cholesterol (a), high density lipoprotein (HDL) (b), low density lipoprotein (LDL) (c), triglyceride (d), free fatty acid (e), and Ang II (f ) in the plasma of normal diet (ND) or HFD-fed rats. Plasma LDL and Ang II were higher in HFD group than ND group. Data are presented as means±SE (n=4). *p<0.05 vs. ND group. N, normal; HF, high fat.

• 

  Fig. 4 HFD increased Ang II-induced vascular smooth muscle contraction.The graph summarized KCl-induced contraction (a), Ang II-induced contraction (b), and Ang II-induced contraction normalized by KCl-induced contraction (c) of ND or HFD-fed rat aorta. Endothelium denuded aortic ring was treated with 50 mM KCl or 10 nM of Ang II. Ang II-induced aortic contraction was higher in HFD group than ND group. Data are presented as means±SE (n=4). *p<0.05 vs. Ang II-induced contraction of ND-fed rat aorta. N, normal; HF, high fat. (d, e) Representative tracings of contractile responses in normal diet group (d) or high fat diet group (e). Traces show KCl-induced contraction followed by Ang II-induced contraction.

• 

  Fig. 5 HFD increased basal expression of MLCK and phosphorylation of CPI-17.(a) Representative picture of western blot for phosphorylated MLC at Thr18 and Ser19, phosphorylated MYPT1 at Thr853, phosphorylated CPI-17 at Thr38, MLCK, and internal control GAPDH in ND or HFD-fed rat aorta with/without stimulation. (b~e) Summary of protein expression of MLCK (b), p-CPI-17 (c), p-MYPT1 (d), and p-MLC (e). (f) Representative picture of western blot for phodphorylated MLC at resting state in ND and HFD-fed rat aorta (g). Summary of phosphorylation of MLC. Basal expression of MLCK, p-CPI-17, p-MLC was increased by HFD. Ang II-induced phosphorylation of CPI-17 and MLC was also enhanced by HFD. Data are presented as means±SE (n=4). *p<0.05, **p<0.01.

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