|Year : 2018 | Volume
| Issue : 2 | Page : 56-61
Response of internal mammary artery wall to L-carnitine in patients undergoing coronary artery bypass
Najah R Hadi1, Fadhil Al-Amran2, Mahamed Al-Turfy3, Saad Rasool Shaker3, Nasser Ghaly Yousif4, Hayder A Al-Aubaidy5
1 Department of Pharmacology and Therapeutics, Faculty of Medicine, University of Kufa, Kufa, Iraq
2 Department of Cardiothoracic Surgical, Kufa University, Najaf; Department of Cardiothoracic Surgery, Faculty of Medicine, University of Kufa, Kufa, Iraq
3 Department of Cardiothoracic Surgery, Faculty of Medicine, University of Kufa, Kufa, Iraq
4 Department of Medicine, Faculty of Medicine, University of Al Muthanna, Samawah, Iraq
5 Department of Pharmacology, School of Medicine, University of Tasmania, Hobart, Tas 7001, Australia
|Date of Web Publication||26-Sep-2018|
Najah R Hadi
Department of Pharmacology and Therapeutics, Faculty of Medicine, University of Kufa, Al-Najaf
Source of Support: None, Conflict of Interest: None
BACKGROUND: This study attempts to highlight the vasodilatation effects of L-carnitine on the left internal mammary artery (LIMA) in patients undergoing coronary artery bypass graft (CABG) surgery.
PATIENTS AND METHODS: A total of 45 male patients (age 55–60 years), and body weight (70–75 kg) were included in this study. Participants were planned to undertake elective CABG surgery, and they were randomly allocated into two study groups as follows: Control group included 15 patients received placebo capsule (lactose capsules), twice daily for 3 successive days before CABG surgery. L-carnitine-treated group included the remaining 30 participants received L-carnitine capsules, 500 mg twice daily for 3 days before CABG surgery.
RESULTS: The two groups were comparable according to their age and comorbidities. There was significant increase in the plasma levels of endothelial nitric oxide synthase (eNOS) and matrix Gla-protein (MGP) among the L-carnitine group as compared with the control group (P < 0.001, P = 0.011, respectively). At the same time, tissue eNOS levels and tissue MGP levels were significantly higher (P = 0.078, P < 0.001, respectively) in the L-carnitine group as compared with the control group. Plasma levels of angiotensin II (ANGII) and endothelin-1 (ET-1) levels were significantly lower (P < 0.001) in the L-carnitine group. Tissue levels of ANGII and ET-1 were significantly lower (P = 0.039, P < 0.001, respectively).
CONCLUSIONS: We can conclude that L-carnitine has potent vasodilatation effects on LIMA during CABG surgery as evidenced by the increase in plasma and tissue levels of eNOS and MGP, associated with a decrease in plasma and tissue levels of ANGII and ET-1.
Keywords: Coronary artery bypass graft, L-carnitine, left internal mammary artery, papaverine, vasodilator
|How to cite this article:|
Hadi NR, Al-Amran F, Al-Turfy M, Shaker SR, Yousif NG, Al-Aubaidy HA. Response of internal mammary artery wall to L-carnitine in patients undergoing coronary artery bypass. Vasc Invest Ther 2018;1:56-61
|How to cite this URL:|
Hadi NR, Al-Amran F, Al-Turfy M, Shaker SR, Yousif NG, Al-Aubaidy HA. Response of internal mammary artery wall to L-carnitine in patients undergoing coronary artery bypass. Vasc Invest Ther [serial online] 2018 [cited 2019 Feb 17];1:56-61. Available from: http://www.vitonline.org/text.asp?2018/1/2/56/242260
| Introduction|| |
Left internal mammary artery (LIMA) had many properties making it as a first choice in coronary artery bypass graft (CABG) surgery such as its freedom from atherosclerosis when harvested and long-term patency in high rate when grafted. However, the main cause of graft failure as described by the previous studies is called the “string phenomenon.” Other causes include harvesting and mobilization of peripheral blood vessels, vascular spasm, as well as inflammation as a part of a postpericardiotomy syndrome, or a steal phenomenon. The LIMA, when compared with saphenous vein-grafts in CABG, has been shown a greater long-term patency., Arterial grafts spasm tendency is the major problem during surgical dissection and preoperative period, and these act as the main cause for perioperative morbidity and mortality.,
Maintaining a vascular tone is one of the vascular endothelium functions. Vasoconstrictor and vasodilator substances derived from endothelium and play a role in maintaining a balance between vasoconstriction and vasodilatation and this is known as a vascular tone. Endothelium-derived contracting factors produced from the endothelial cell and played a role in mediating smooth muscle contraction by increasing intracellular calcium concentration. Endothelium-dependent relaxation has a major function in vascular relaxation. These are endothelium-derived nitric oxide (NO),, prostacyclin, and endothelium-derived hyperpolarizing factor. L-carnitine is a vitamin-like nutrient synthesized from N-trimethyllysine in the liver and the kidneys; lysine and methionine are the substrates for carnitine synthesis. L-carnitine may increase NO involve in endothelium-dependent relaxation and may reduce reactive oxygen species. This study aims to evaluate the vasodilation effects of L-carnitine on the LIMA in patients undergoing CABG surgery.
| Patients and Methods|| |
A total of 45 male patients (aged 55–60 years) and body weight (70–75 kg) were included in this study between October 2014 and December 2015. Participants were recruited from Al-Sadr Hospital Cardiothoracic Center, Al-Najaf, Iraq. All participants in this study were planned to undertake elective CABG surgery. This study was approved by the Human Ethics Committee, College of Medicine, University of Kufa, Iraq. All participants were received information sheets, and they signed informed consent for their participation in this study.
This is a randomized, single-blind, placebo-controlled study. Participants were divided into two study groups:
- Group 1: (15 patients) (placebo-control group): Patients received placebo capsule (lactose) twice a day for 3 successive days before CABG surgery. On the CABG day surgery, papaverine was injected at room temperature through the endothoracic fascia parallel to the mammary artery and intraluminal with blunt needle
- Group 2: (30 patients) (L-carnitine-treated group): Patients received L-carnitine 500 mg capsule (BioActive T, U.K) twice a day for 3 successive days before CABG surgery. On the CABG day, papaverine was injected at room temperature through the endothoracic fascia parallel to the mammary artery and intraluminal with blunt needle. The two study groups were comparable according to the age and comorbidities.
The LIMA was surgically removed. On one end of the artery which was prepared for bypass grafting, papaverine (10 mg) (1 mg/ml 0.9 saline) was injected at room temperature through the endothoracic fascia parallel to the mammary artery and intraluminal with blunt needle. Off-pump CABG is used for all patients.
Two and a half milliliters of arterial blood samples were collected immediately preoperative and 4 h postoperative using a disposable syringe. Samples were placed in anticoagulant test tubes (disodium ethylenediaminetetraacetic acid, 22 mg/ml) and mixed thoroughly. Samples were mixed completely and then centrifuged at 300 rpm for 15 min; supernatants were used for determination of plasma endothelin-1 (ET-1), angiotensin II (ANG II), endothelial NO synthase (eNSO), as well as matrix Gla-protein (MGP).
Preparation of left internal mammary artery tissue sample
On the day of the CABG surgery, the surgeon mobilizes the LIMA (as preparation step in CABG surgery). A 2-cm length of the LIMA was placed in a saline solution and kept in the deep freezer for homogenization with high-intensity liquid processor in 1:10 (W/V) phosphate-buffered saline which contains 1% triton X-100 and protease inhibitor cocktail (6). At 14,000 rpm, the homogenate was centrifuged for 20 min at 4°C. The supernatant was collected for determination ET-1, ANG II, eNSO, and MGP. Hematoxylin and eosin stain was used for tissue staining, and the light microscope was used for visualization and study of the microscopic architecture of the arterial tissue. By using light microscope pointer and both sides scales, we calculated the artery lumen diameter (in millimeters), and the artery wall thickness and the relative lumen artery diameter were calculated  as follows:
Measurement of biomarkers
All biomarkers measured in this study (ET-1; ANG II; eNOS; and MGP) were measured using enzyme-linked immunosorbent assay kits (Elabscience Biotechnology, USA), in both plasma and tissues.
Statistical analyses were done using SPSS statistical package for the social sciences version 20 (IBM in 2009, Chicago, USA). Chi-squared test was performed to test for categorical data and paired t-test and independent sample t-test for numerical data and Pearson correlation coefficient. P ≤ 0.05 was considered as statistically significant.
| Results|| |
[Table 1] shows the demographic values of the IMA characteristics between the two study groups:
|Table 1: The demographic characteristics of the two study groups in terms of wall thickness (mm), lumen diameter (mm), and the relative diameter (mm)|
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- Effect of L-carnitine on human plasma eNOS – Plasma levels of eNOS were significantly higher in the L-carnitine-treated group as compared with the placebo-control group. Preoperatively, plasma eNOS levels were significantly higher in the L-carnitine-treated group (7694.93 ± 249.55, pg/ml) than the placebo-control group (6572.06 ± 196.28, pg/ml) P = 0.005 [Figure 1]
Postoperatively, plasma eNOS levels were significantly higher in the L-carnitine-treated group (7881.76 ± 147.96, pg/ml) as compared with the placebo-control group (6683.16 ± 132.23, pg/ml), P < 0.001 [Figure 1]
- Effect of L-carnitine on human tissue eNOS – Tissue levels of eNOS were significantly higher in the L-carnitine-treated group (2205.7 ± 241.27, pg/mg) as compared with the placebo-control group (916.64 ± 115.17, pg/mg), P = 0.078
- Effect of L-carnitine on human plasma ANGII – Preoperatively, plasma levels of the ANGII were significantly lower in L-carnitine-treated group (455.72 ± 4.99, pg/ml) as compared with the placebo-control group (557.34 ± 83.74, pg/ml), P = 0.001 [Figure 2]
Similarly, the plasma levels of ANGII were also significantly lower in the L-carnitine-treated group (340.13 ± 3.93, pg/ml) as compared with the placebo-control group (504.80 ± 267.54, pg/ml) after the CABG surgery, P < 0.001 [Figure 2]
- Effect of L-carnitine on human ANGII tissue level – Tissue ANGII levels were significantly lower in the L-carnitine-treated group during the CABG operation, (448.18 ± 20.97), as compared with the placebo-control group (578.08 ± 13.44), P = 0.039
- Effect of L-carnitine on human ET-1 plasma level – Before the CABG, the plasma levels of ET-1 were significantly lower in the L-carnitine-treated group (29.12 ± 4.02) as compared with the placebo-control group (45.30 ± 0.43), P < 0.001. Postoperatively, the plasma ET-1 levels were also significantly lower in the L-carnitine-treated group (24.91 ± 10.46) as compared with the placebo-control group (44.81 ± 0.32), P < 0.001 [Figure 3]
- Effect of L-carnitine on human ET-1 tissue level – Tissue ET-1 levels were significantly lower in the L-carnitine-treated group (21.69 ± 3.36) as compared with the placebo-control group (24.55 ± 1.6), P < 0.001
- Effect of L-carnitine on human MGP plasma level – Preoperatively, plasma MGP levels were significantly higher in L-carnitine-treated group (413.35 ± 20.11) than placebo-control group (300.34 ± 18.82) P = 0.001. Postoperatively, plasma MGP levels were significantly higher in L-carnitine-treated group (463.3 ± 31.81) than placebo-control group (339.9 ± 16.32), P = 0.011 [Figure 4]
- Effect of L-carnitine on human MGP tissue level – Tissue MGP levels were significantly higher in the L-carnitine-treated group (378.78 ± 139.16) than placebo-control group (248.45 ± 78.91), P < 0.001.
|Figure 1: The mean plasma levels of endothelial nitric oxide synthase (pg/ml), before and after coronary artery bypass graft surgery for the two study groups, P is significant ≤ 0.05. *Significant P ≤ 0.05 between the two groups before the coronary artery bypass graft surgery. #Significant P ≤ 0.05 between the two groups after the coronary artery bypass graft surgery|
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|Figure 2: The mean plasma levels of angiotensin II (pg/ml), before and after coronary artery bypass graft surgery for the two study groups, P is significant ≤ 0.05. *Significant P ≤ 0.05 between the two groups before the coronary artery bypass graft surgery. #Significant P ≤ 0.05 between the two groups after the coronary artery bypass graft surgery|
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|Figure 3: The mean plasma levels of endothelin-1 (pg/ml), before and after coronary artery bypass graft surgery for the two study groups, P is significant ≤ 0.05. *Significant P ≤ 0.05 between the two groups before the coronary artery bypass graft surgery. #Significant P ≤ 0.05 between the two groups after the coronary artery bypass graft surgery|
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|Figure 4: The mean plasma levels of matrix Gla-protein (pg/ml), before and after coronary artery bypass graft surgery for the two study groups, P is significant ≤ 0.05. *Significant P ≤ 0.05 between the two groups before the coronary artery bypass graft surgery. #Significant P ≤ 0.05 between the two groups after the coronary artery bypass graft surgery|
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| Discussion|| |
To the best of our knowledge, this is the first study of its type to examine the effects of L-carnitine on the selected biomarkers of this study. There are many reasons behind graft failure in patients after having CABG surgery. These mainly include spasm during harvesting and mobilization injury, postpericardiotomy syndrome, and inflammation. The endothelium of the blood vessels responds to hemodynamic forces and blood-borne signals by releasing of various paracrine and autocrine substances. The releasing of these bioactive factors control vascular homeostasis; therefore, endothelial cells dysfunction will disrupt this balance and may cause vasoconstriction, leukocyte adherence, platelet activation, mitogenesis, pro-oxidation, thrombosis, coagulation impairment, as well as vascular inflammation and atherosclerosis. Furthermore, intracoronary papaverine causes a significant increase in coronary arterial diameter. This has clinical implications for assessing coronary flow reserve with devices that detect flow velocity.
Our study found a significant rise in the levels of eNOS in the L-carnitine-treated group as compared with the placebo-control group. NO synthase is responsible for the NO synthesis from L-arginine. Increase in eNSO levels improves endothelial function and decreases the formation of unwanted oxidants such as superoxide and hydrogen peroxide., NO plays a major role in maintaining vascular tone and reactivity which act as a key for endothelium-derived relaxing factor. The action of potent endothelium-derived contracting factors such as ANG II and ET-1 was negated by action of NO (20). Previous studies described the vasodilatation action of the L-carnitine through restoring endothelial dysfunction, reducing reactive oxygen species, and increasing NO participation in endothelium-dependent relaxation.
ET-1, on the other side, acts as a potent endothelium-derived contracting factor; hence, it counteracts NO action (a potent endothelium-derived relaxing factor), both of them had significant role in maintaining vascular tone. During cardiac surgery such as in CABG operation, ET-1 has a strong association with coronary and/or graft vasospasm. Our study proved that L-carnitine could significantly reduce ET-1 levels, inhibiting a potent endothelium-derived contracting factor.
Similarly, ANGII acts as a contractile agonist by inducing signals in vascular smooth muscle cells and cardiomyocytes which related to contraction through mobilizing intracellular calcium (Ca +2) ions and activation of protein kinase C., Our data showed that L-carnitine decreased the ANGII levels, providing a good indication for improving the endothelial function and reversing the contractile effects of ANGII on blood vessel.,
Circulating MGP serves as a biomarker of vascular calcification. MGP had a major role in suppressing inflammation and increasing cell survival. There is a strong positive correlation between coronary artery calcium deposition and coronary atherosclerosis.,,, In our study, L-carnitine showed to be significantly increasing MGP levels; hence, it can reduce coronary artery calcification, suppresses atherosclerosis development, and vascular inflammation and endothelial dysfunction.,,,
| Conclusions|| |
We can conclude that L-carnitine plays a central role in producing vasodilatation of the LIMA during CABG surgery as it evidenced by the increase in plasma and tissue levels of the eNOS and MGP, associated with decrease plasma and tissue levels of ANGII and ET-1.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]