Endothelial Dysfunction - Assessment Part 2

Endothelial Dysfunction & Blood Biomarkers

Dicken Weatherby, N.D. and Beth Ellen DiLuglio, MS, RDN, LDN

A number of findings on a blood test can point toward an increasing likelihood of atherosclerosis, inflammation, and endothelial dysfunction:

  • Elevated Homocysteine
    • Blood levels of homocysteine are associated with endothelial dysfunction:[1]
    • Homocysteine reduces BH4, a cofactor for NO synthesis
    • Conversion of methionine to homocysteine promotes elevated asymmetric dimethylarginine (ADMA) which in turn inhibits endothelial NOS (eNOS)
    • Atherosclerosis increases progressively with a homocysteine level above 11 umol/L.[2]
  • Elevated Blood Glucose
    • Post-prandial glucose levels above 122 mg/dL (6.8 mmol/L) may impair flow-mediated arterial dilation.[3]
  • Elevated Fibrinogen
    • Fibrinogen synthesis is stimulated by inflammatory IL-6, promotes coagulation, and increases risk of endothelial dysfunction, CAD, and stroke.[4]
  • Elevated C-Reactive Protein (CRP, hs-CRP)
    • Elevation of inflammatory markers such as high sensitivity C-reactive protein may serve as an indirect measure of endothelial function.[5]
    • Hs-CRP was found to be higher when vitamin D was lower in obese non-diabetics free of cardiovascular abnormalities.[6]
  • Insufficient Testosterone
    • Low testosterone (free and total) significantly correlated with reduced flow-mediated vasodilation and was found to be an independent risk factor for endothelial dysfunction in men[7]
  • Elevated Iron
    • High iron levels cause oxidative damage to the endothelial lining and can impair the action of nitric oxide
    • Iron chelation with deferoxamine reduced serum iron significantly from 85±26 to 39±24 μg/dL and improved resting forearm blood flow in both CAD patients and controls. Chelation did not affect ferritin levels which were higher in CAD patients (127±108 ng/mL) than in controls (76±68 ng/mL). Researchers suggest that it may be circulating unbound iron that contributes to lipid peroxidation, NO impairment, and endothelial dysfunction.[8]
  • Elevated Ferritin
    • Ferritin levels increase in inflammation. However, elevated ferritin may also be an independent risk factor for arterial stiffness and an indicator of the presence of atherosclerosis in those with glucose intolerance.[9]
  • Neutrophil:Lymphocyte Ratio (NLR)
    • Low risk in those with neutrophil–lymphocyte ratio <1.5,
    • Intermediate risk in patients between 1.5 and 3,
    • High risk in those with neutrophil- to-lymphocyte ratio >3.
    • NLR is a marker of systemic inflammation and is associated with increased circulating pro-inflammatory cytokines.
    • NLR can help stratify risk of endothelial dysfunction in asymptomatic patients[10]
  • Oxidized LDL (OxLDL)
    • Elevated oxidized low density lipoprotein (OxLDL) contributes to foam cell formation, atherosclerosis, and endothelial dysfunction.[11]
    • Risk of atherosclerosis was significantly higher in subjects with levels of oxidized LDL of 44.3 U/L and above. The study concluded that serum oxLDL independently predicted the progression of subclinical atherosclerosis regardless of cholesterol or number and size of LDL particle.[12]
    • Administration of a low dose of oxLDL (8 ug/mL), below that seen in clinical CAD, activated immune mast cells and macrophages and increased monocyte-endothelium adhesion to a greater extent than directly exposing endothelial cell to a higher dose of 80 ug/mL.[13]
  • Elevated Asymmetric Dimethylarginine (ADMA)
    • Another potential contributor to endothelial dysfunction is elevated asymmetric dimethylarginine (ADMA)[14]
    • ADMA inhibits synthesis of eNOS and can even cause uncoupling of eNOS which further exacerbates oxidative stress[15]
    • Optimal levels of ADMA are below 100 ng/mL[16]
  • Elevated Myeloperoxidase (MPO)
    • Reduces nitric oxide bioavailability
    • Increases macrophage uptake of oxidized lipids
    • It may promote atherosclerosis and has been identified in atherosclerotic plaque
    • Levels may help predict outcomes in acute coronary syndromes and in those presenting with chest pain suspected to be due to endothelial dysfunction
    • MPO is a pro-oxidant enzyme released by neutrophils and monocytes[17]
  • Elevated Malondialdehyde (MDA)[18]
    • Malondialdehyde is an oxidative stress marker. It is an oxygenated aldehyde produced by the action of free radicals on polyunsaturated fatty acids and cell membrane lipoproteins
    • MDA is elevated by up to 2.48 fold in hyperlipidemia, increasing as level of oxidative stress increased
  • Suboptimal Omega-3 Index
    • Provide antioxidant and anti-inflammatory protection
    • Reduce blood pressure
    • Improve vasodilation as measured by FMD
    • Measures percent of long-chain omega-3 fatty acids in red blood cell membranes
    • Omega-3 fatty acids have vasoprotective effects[19]
    • Optimal goal for omega-3 Index is greater than 8%[20]
  • Elevated Gamma-Glutamyl Transferase (GGT)
    • GGT can be an important biomarker for atherosclerosis and vascular injury as it is strongly associated with C-reactive protein, oxidized LDL, IL-6, and sICAM-1.[21]
    • Elevated GGT also appears to correlate with cardiovascular and       metabolic disorders including congestive heart failure, vascular events, type 2 diabetes, hypertension.[22]
    • GGT may be an independent risk factor for cardiovascular disease and events. In healthy males free of heart disease, those with the highest GGT (35 units/L or greater) had a 2.34 greater risk of acute coronary event than those with a GGT of less than 13 units/L.[23]  
  • Low Adiponectin
    • Adiponectin is an anti-inflammatory cytokine released by adipose tissue.
    • Factors that increase serum levels of adiponectin include aging, calorie restriction, and estrogen deficiency, and factors that decrease it include oxidative stress, cigarette smoke, obesity and type 2 diabetes.[24]
    • Low levels of adiponectin were found to be associated with endothelial dysfunction in diabetics and non-diabetics. In non-diabetics, low adiponectin was the only predictor of endothelial dysfunction compared to HOMA-IR, BMI, triglycerides, and insulin. Serum adiponectin has been found to be inversely correlated with carotid intima-thickness in both healthy and diabetic individuals.[25]

Advanced biomarkers in endothelial dysfunction[26] [27]

  • Elevated cellular adhesion molecules (released from damaged endothelial cells)
  • Vascular cell adhesion molecule-1 – VCAM-1, endothelial leukocyte adhesion molecule-1 E-selectin, intercellular adhesion molecule-1-ICAM-1
  • Elevated von Willebrand factor indicative of endothelial damage
  • Elevated Endothelin-1 peptide
  • Soluble NOX2-derived peptide (sNOX2-dp) and 8-iso-prostaglandin F2α (8-isoPGF2α) reflect oxidative stress.
  • Endothelial progenitor cells (EPCs) and microvesicles (MVs) are biomarkers for inflammation and endothelial dysfunction.
    • Elevated endothelial progenitor cells from bone marrow assist in endothelial repair

References

[1] Bendall, Jennifer K et al. “Tetrahydrobiopterin in cardiovascular health and disease.” Antioxidants & redox signaling vol. 20,18 (2014): 3040-77. 

[2] University of Michigan. Pathology Handbook. Accessed October 25, 2020 

[3] Whisner, Corrie M et al. “Effects of Low-Fat and High-Fat Meals, with and without Dietary Fiber, on Postprandial Endothelial Function, Triglyceridemia, and Glycemia in Adolescents.” Nutrients vol. 11,11 2626. 2 Nov. 2019.

[4] Ellins, Elizabeth A et al. “Increased fibrinogen responses to psychophysiological stress predict future endothelial dysfunction implications for cardiovascular disease?.” Brain, behavior, and immunity vol. 60 (2017): 233-239. 

[5] Anderson, Todd J. “Nitric oxide, atherosclerosis and the clinical relevance of endothelial dysfunction.” Heart failure reviews vol. 8,1 (2003): 71-86.

[6] Ilinčić, Branislava et al. “Vitamin D status and circulating biomarkers of endothelial dysfunction and inflammation in non-diabetic obese individuals: a pilot study.” Archives of medical science : AMS vol. 13,1 (2017): 53-60. 

[7] Akishita, Masahiro et al. “Low testosterone level is an independent determinant of endothelial dysfunction in men.” Hypertension research : official journal of the Japanese Society of Hypertension vol. 30,11 (2007): 1029-34. 

[8] Duffy, S J et al. “Iron chelation improves endothelial function in patients with coronary artery disease.” Circulation vol. 103,23 (2001): 2799-804. 

[9] Sciacqua, Angela, et al. "Effect modification by ferritin on the relationship between inflammation and arterial stiffness in hypertensive patients with different glucose tolerance." (2020). [R]

[10] Martínez-Urbistondo, Diego et al. “The neutrophil-to-lymphocyte ratio as a marker of systemic endothelial dysfunction in asymptomatic subjects.” “El índice neutrófilo/linfocito como marcador de disfunción sistémica endotelial en sujetos asintomáticos.” Nefrologia : publicacion oficial de la Sociedad Espanola Nefrologia vol. 36,4 (2016): 397-403. doi:10.1016/j.nefro.2015.10.018 [R]

[11] Chen C, Khismatullin DB. Oxidized low-density lipoprotein contributes to atherogenesis via co-activation of macrophages and mast cells. PLoS One. 2015 Mar 26;10(3):e0123088. doi: 10.1371/journal.pone.0123088. PMID: 25811595; PMCID: PMC4374860. [R]

[12] Gao, Shen et al. “Circulating Oxidized Low-Density Lipoprotein Levels Independently Predict 10-Year Progression of Subclinical Carotid Atherosclerosis: A Community-Based Cohort Study.” Journal of atherosclerosis and thrombosis vol. 25,10 (2018): 1032-1043. doi:10.5551/jat.43299 [R]

[13] Chen C, Khismatullin DB. Oxidized low-density lipoprotein contributes to atherogenesis via co-activation of macrophages and mast cells. PLoS One. 2015 Mar 26;10(3):e0123088. doi: 10.1371/journal.pone.0123088. PMID: 25811595; PMCID: PMC4374860. [R]

[14] Widmer, R Jay, and Amir Lerman. “Endothelial dysfunction and cardiovascular disease.” Global cardiology science & practice vol. 2014,3 291-308. 16 Oct. 2014, doi:10.5339/gcsp.2014.43 [R] This is an open access article distributed under the terms of the Creative Commons Attribution license CC BY 4.0, which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited.

[15] Bendall, Jennifer K et al. “Tetrahydrobiopterin in cardiovascular health and disease.” Antioxidants & redox signaling vol. 20,18 (2014): 3040-77. doi:10.1089/ars.2013.5566 [R]

[16] Quest Diagnostics. [R] [R]

[17] Upadhyay, Ravi Kant. “Emerging risk biomarkers in cardiovascular diseases and disorders.” Journal of lipids vol. 2015 (2015): 971453. doi:10.1155/2015/971453 [R] This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

[18] Yang, Rui-Li et al. “Increasing Oxidative Stress with Progressive Hyperlipidemia in Human: Relation between Malondialdehyde and Atherogenic Index.” Journal of clinical biochemistry and nutrition vol. 43,3 (2008): 154-8. doi:10.3164/jcbn.2008044 [R]

[19] Zehr, Kayla R, and Mary K Walker. “Omega-3 polyunsaturated fatty acids improve endothelial function in humans at risk for atherosclerosis: A review.” Prostaglandins & other lipid mediators vol. 134 (2018): 131-140. doi:10.1016/j.prostaglandins.2017.07.005 [R]

[20] Harris, William S. “The omega-3 index as a risk factor for coronary heart disease.” The American journal of clinical nutrition vol. 87,6 (2008): 1997S-2002S. doi:10.1093/ajcn/87.6.1997S [R]

[21] Bradley, Ryan D et al. “Associations between γ-glutamyltransferase (GGT) and biomarkers of atherosclerosis: the Multi-ethnic Study of Atherosclerosis (MESA).” Atherosclerosis vol. 233,2 (2014): 387-393. doi:10.1016/j.atherosclerosis.2014.01.010 [R]

[22] Bradley, Ryan et al. “Associations between total serum GGT activity and metabolic risk: MESA.” Biomarkers in medicine vol. 7,5 (2013): 709-21. doi:10.2217/bmm.13.71 [R]

[23] Meisinger, C et al. “Serum gamma-glutamyltransferase is a predictor of incident coronary events in apparently healthy men from the general population.” Atherosclerosis vol. 189,2 (2006): 297-302. doi:10.1016/j.atherosclerosis.2006.01.010 [R]

[24] Mancuso, Peter. “The role of adipokines in chronic inflammation.” ImmunoTargets and therapy vol. 5 47-56. 23 May. 2016, doi:10.2147/ITT.S73223 [R]

[25] Hui, Xiaoyan et al. “Adiponectin and cardiovascular health: an update.” British journal of pharmacology vol. 165,3 (2012): 574-90. doi:10.1111/j.1476-5381.2011.01395.x [R]

[26] Roberto Carnevale, Vittoria Cammisotto, Francesca Pagano and Cristina Nocella (November 5th 2018). Effects of Smoking on Oxidative Stress and Vascular Function, Smoking Prevention and Cessation, Mirjana Rajer, IntechOpen, DOI: 10.5772/intechopen.78319. Available from: [R] This chapter is distributed under the terms of the Creative Commons Attribution 3.0 License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

[27] Jezovnik, Mateja K. "How to assess endothelial function for detection of pre-clinical atherosclerosis." E-journal Cardiology Practice 10.22 (2011): 10. [R]

[28] Roberto Carnevale, Vittoria Cammisotto, Francesca Pagano and Cristina Nocella (November 5th 2018). Effects of Smoking on Oxidative Stress and Vascular Function, Smoking Prevention and Cessation, Mirjana Rajer, IntechOpen, DOI: 10.5772/intechopen.78319. Available from: [R] This chapter is distributed under the terms of the Creative Commons Attribution 3.0 License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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