Influence of non-vascular cells in accelerated coronary aging in diabetes

• Project/Area Number: 19F19708
• Research Category: Grant-in-Aid for JSPS Fellows
• Allocation Type: Single-year Grants
• Section: 外国
• Review Section: Basic Section 44050:Animal physiological chemistry, physiology and behavioral biology-related
• Research Institution: National Cardiovascular Center Research Institute
• Host Researcher: Pearson James 国立研究開発法人国立循環器病研究センター, 研究所, 部長 (30261390)
• Foreign Research Fellow: NGO JENNIFER 国立研究開発法人国立循環器病研究センター, その他部局等, 外国人特別研究員
• Project Period (FY): 2019-07-24 – 2021-03-31
• Project Status: Granted (Fiscal Year 2020)
• Budget Amount: ¥2,300,000 (Direct Cost: ¥2,300,000); Fiscal Year 2020: ¥1,100,000 (Direct Cost: ¥1,100,000); Fiscal Year 2019: ¥1,200,000 (Direct Cost: ¥1,200,000)
• Keywords: coronary vessels / diabetes / aging / oxidative stress / vasodilators

Outline of Research at the Start

To determine whether vascular aging in diabetes is caused by early inflammation and oxidative stress that develops in heart muscle cells and immune cells. In addition, we aim to identify whether vascular aging is then exacerbated by aging of cells lining our blood vessels due to inactivity.

Outline of Annual Research Achievements

We performed the study 1 utilising senescence accelerated mice (SAMP8) and resistant mice (SAMR1) to investigate the effect of aging in nondiabetic model. Mice were maintained on either a high fat diet (HFD, 56% fat) or normal fat diet (NFD) for 16 weeks with 1% NaCl drinking water. Some of the SAMP8 mice were concurrently treated with Nox inhibitor (apocynin 5mg/kg/d) or monoamine oxidase-A inhibitor (clorgyline 1mg/kg/d) through subcutaneous osmotic pumps. Cardiac function was assessed by echocardiography before terminal synchrotron microangiography assessment of coronary function. SAMP8 mice treated with apocynin gained less body weight than clorgyline or vehicle treated SAMP8 mice on HFD. Furthermore, aponcynin treated HFD SAMP8 mice showed lower levels of plasma catecholamines, comparable to NFD SAMR1 mice. Ongoing analyses suggest that nitric oxide bioavailability was variable among mice on HFD irrespective of drug treatment relative to NFD. Acetylcholine stimulation of coronary vessels during blockade of calcium-activated K channels and prostanoids revealed segmental and focal vasoconstriction in all HFD mouse groups. These findings suggest that senescence accelerated mice show reduced NO biovailability and endothelial-smooth muscle dysfunction following HFD exposure and that blockade of individual sources of ROS does not ameliorate this dysfunction; that is there is redundancy in the sources of oxidative stress in the heart. Western blotting for eNOS and big calcium activated K channels suggest that protein expression was most reduced in vehicle HFD SAMP8 mice.

Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

The first study was completed as planned while there was an extended period of interruption to animal experiments due to relocation of our institute at the beginning of my fellowship. Six groups of mice were prepared and evaluated for cardiac and coronary function in vivo with echocardiography and high-resolution angiography. Following these experiments we commenced image analysis, immunohistochemistry and western blotting assays to establish the mechanisms of vascular dysfunction involving the major vasodilator and constrictor pathways as well as oxidative stress. The findings to date are complex, but they are clear cut and we anticipate preparing the first publication within 2020.

Strategy for Future Research Activity

We had started preparations to perform the next part of study 1, which involved exercise treatment of HFD SAMP8 mice and preparing study 2 utilising diet-induced diabetic mice. However, COVID-19 pandemic and the suspension of our animal facility and the synchrotron facility will delay the planned experiments until the last half of 2020 FY. Nevertheless, we will next compare coronary and cardiac function in high intensity exercise treated diabetic mice with sedentary diabetic mice using the same protocols as study 1. During the continued interruption we will continue molecular analyses of samples collected to assess changes in MAO-A and Nox proteins and complete assays of oxidant-antioxidant status and quantitative assessment of coronary vascular changes in study 1.

Research Products

• [Journal Article] Ghrelin and vascular protection. (2019)
  • Author(s): Pearson JT, Shirai M, Sukumaran V, Du CK, Tsuchimochi H, Sonobe T, Waddingham MT, Katare R, Schwenke DO.
  • Journal Title: Vascular Biology Volume: 1
  • DOI: 10.1530/vb-19-0024
  • Peer Reviewed / Open Access / Int'l Joint Research