A View Beyond the Horizon

May - June 2022

A View Beyond the Horizon; The Re-Emergence of Micronized Purified Flavonoid Fractions for Venous Leg Ulcer Management

Editorial Summary

Introduction

Venous leg ulcers (VLUs) are the most severe stage of chronic venous insufficiency (CVI), defined as the CEAP class C6 (open ulcers). Patients with healed ulcers belong to CEAP class C5. According to the Clinical Practice Guidelines of the Society for Vascular Surgery and the American Venous Forum, a VLU is “a fullthickness defect of skin, most frequently in the ankle region, that fails to heal spontaneously and is sustained by chronic venous disease, based on venous duplex ultrasound testing1.”¹

How Common Are Venous Leg Ulcers?

VLUs represent 70% of all lower extremity ulcerations2 with a prevalence between 0.06% and 2%1. A study within Olmsted County, Minnesota, USA and the Rochester Epidemiology Project (REP)3³estimated the incidence (newly diagnosed venous ulcers) for the time frame 1991-2010 as 0.85/ 1000 personyear, higher than the 0.18/ 1000 person-year incidence reported in the same population for the period from 1966 to 1990. The incidence is much higher in individuals over 60 years of age: it was 8.9/ 1000 person-year in the retrospective cohort study of Olmsted County4. One third of the venous ulcers in the REP study3 had a post-thrombotic etiology. The rates of postthrombotic ulcers, according to the RIETE Registry5, with 3-year follow-up after acute deep vein thrombosis (DVT), were 2.7% at 1 year, 4.4% after 2 years and 7.1% after 3 years. A retrospective study conducted on 3,920 primary care center electronic records in Barcelona6 found the incidence and prevalence of VLUs

doubling during a 4-year period, from 0.5 and 0.8, respectively in 2010, to 1 and 2.2 cases per 1000 person-year in 2014. More than 84% of the VLUs healed and time to healing was shorter in 2014 than before 2010 (19 weeks vs. 453.9 weeks). Only 22.8% of patients were referred for vascular surgery consultation.

Pathophysiology: New Facts and Discoveries

The classic cascade of events leading to venous leg ulcers7 includes venous hypertension, chronic inflammation, edema formation and skin changes, from lipodermatosclerosis to active ulcers. The initial understanding of edema formation pathophysiology was based on foundational research by Dr. Ernest Starling regarding the properties and characteristics of the absorption of fluids from connective tissue spaces8. In his thesis, most of the interstitial fluid resulting from arterial perfusion, re-entered the vasculature via the venule, and only 10-20% of interstitial fluid was left to the domain of the lymphatic vasculature for handling. One hundred years later the Starling concept has undergone significant and clinically important revisions9,10. A new potentiator in the realm of systemic fluid homeostasis was identified and continues to undergo extensive in-vitro and in-vivo research and clinical correlations: the endothelial glycocalyx (GCX)11. The renaissance of venolymphatic research and clinical application began with the recognition of the GCX and the importance of GCX benchtop to bedside research and translation continues to grow at an accelerated pace. The relative simplicity of the endocapillary GCX appearance as ‘fine hairs’12 belies its complexity

Dr Monika Lecomte Gloviczki

This article provides an overview of Venous Leg Ulcers (VLU) including an introduction, incidence trends, new and emerging theories of pathophysiology, and a multifaceted approach to treatment. The renaissance of venolymphatic research and clinical application began with the recognition of glycocalyx benchtop to bedside research and translation continues to grow at an accelerated pace.

Dr M. Mark Melin

M Health Fairview Wound Healing Institute, University of Minnesota Physicians Minneapolis MN, United States

on the nano scale of glycoproteins, proteoglycans, glycosaminoglycans and additional interlocking components that create a dynamic interactive architecture responsible for macro- and micro vascular and biochemical signaling. Cytokines’ synthesis is involved through shear stress resulting in mechano-transduction and stimulation of the cellular cytoskeleton, provision of a permeability barrier, inflammation mitigation, and coagulation component coverage to prevent inappropriate pathological micro- and macrothrombi development. Several of the critical architectural components include heparan sulfate, hyaluron, albumin, chondroitin sulfate, dermatan sulfate, syndecans, glypicans, and sialic acids. The GCX, having a net negative charge, varies in thickness from 0.2 - 2.0 microns, dependent upon vessel size. It comprises ~25% of luminal volume along the estimated 50,000 miles of vascular and lymphatic length in the adult human; 80-90% of this length is defined as the microvasculature to the level of 5-20 microns. When the GCX is thinned or shed, loss of the GCX functional characteristics is now recognized to be an integral and critical aspect of venous hypertension and associated complications13,14, arterial disease15,16, states of inflammation17, diabetes18, and a multitude of clinical conditions including sepsis, pulmonary edema, COVID-1918A and cancer19

With respect to venous hypertension and subsequent VLU development, the shedding of the GCX results in leukocyte adhesion to the endothelium with increased cellular oxidative stress and vascular permeability leading to the interstitial edema and overload of the lymphatic capacity, widely recognized as phlebolymphedema20. Chronic interstitial edema and lymphatic failure, with persistence of GCX shedding, causes microvascular rarefaction, chronic subcritical tissue ischemia and cellular apoptosis. Hence, VLU healing is improved with resolution of venous hypertension, restoration of lymphatic function, cessation of GCX shedding, and restoration of

a viable and functional endothelial GCX. This is the basis for venolymphatic interventions: manual lymphatic drainage, complete decongestive physiotherapy, lymphatic dynamic and static compression, venous ablation, and lymphedema pumps.

Other factors, contributing to non-healing of VLUs, are associated with environment and with the role of Single Nucleotide Polymorphisms (SNPs), most frequently identified as methylene-tetrahydrofolate reductase (MTHFR) abnormalities that decrease endothelial Nitric Oxide (eNO) production. Several papers have been published regarding the incidence of MTHFR polymorphisms and its involvement in varicose veins and development of thrombophlebitis21-26. MTHFR is a small component of SNPs overall, and the narrative continues to broaden with the identification of additional multiple SNPs. A ‘Polygenic Risk Score’ will likely become more applicable to complete diagnosis of genetic risks27. The full details are beyond the scope of this paper, though research data continue to demonstrate the significance of genetic and epigenetic contributions to an inadequate response by cellular mechanisms in conditions of environmental extremes, or when the human body is required to function at extremes of cellular ability as for example in chronic diabetes, hypertension (arterial and venous), tobacco use, obesity, etc. The redundancy within the genetic is typically protective, though when SNPs reduce/ alter the genetic redundancy of cellular function, the potential for pathological symptoms become increasingly prevalent and prominent28, causing a loss of resilience and increased states of disease29

eNO is crucial to vascular and lymphatic function, neurotransmission and nonspecific host defense30,31. Reduced bioavailability of eNO has been clearly linked to endothelial dysfunction, an early precursor to atherogenesis32,33. eNO ultimately plays roles in

“With respect to venous hypertension and subsequent VLU development, the shedding of the GCX results in leukocyte adhesion to the endothelium with increased cellular oxidative stress and vascular permeability leading to the interstitial edema and overload of the lymphatic capacity, widely recognized as phlebolymphedema20.”

A

Beyond the Horizon; The Re-Emergence of Micronized Purified Flavonoid Fractions for Venous Leg Ulcer

“Precision, prescriptive, personalized healthcare delivery will be based upon understanding these connections of the patient environment, and both the physiologic and genetic response. From the macro- to the micro- to the nano-, integrative and functional health will be based upon macro- and micro-nutrient intake, bioavailability, the gut microbiome, an intact and functional endothelial GCX, and lymphatic/ glymphatic health.”

the synthesis of nucleic acids and byproduct recycling. The synthesis of eNO results from integrated pathways, with folates serving as important cofactors in the transfer and processing of 1-carbon products. Under conditions of oxidative stress or source product deficiencies (among others 5-MTHF; dietary folate, B12, B6, tetrahydrobiopterin or BH4), endothelial nitric oxide synthetase (eNOS) can become ‘uncoupled’32³which leads not only to decreased eNO production, but also to increased production of superoxides, furthering the state of oxidative stress32-36.

Production of eNO has been linked to the structure and function of the glycocalyx in conjunction with caveolae which are essential for maintenance of vascular homeostasis37. Along the entirety of the endothelial surface, caveolae contain endothelial nitric oxide synthetase (eNOS). The glycocalyx components transform the mechanical signals of luminal shear stress into biochemical signals, activating eNOS to produce eNO and decrease reactive oxygen species (ROS) that contribute to cellular oxidative stress37. Shedding of the GCX results in ‘uncoupling’ of eNOS, decreased eNO production, increased ROS production, all consequences recognized to ultimately contribute to cardiovascular diseases such as atherosclerosis and hypertension16,19. Precision, prescriptive, personalized healthcare delivery will be based upon understanding these connections of the patient environment, and both the physiologic and genetic response. From the macro- to the micro- to the nano, integrative and functional health will be based upon macro- and micro-nutrient intake, bioavailability, the gut microbiome, an intact and functional endothelial GCX, and lymphatic/ glymphatic health. Published data is now clearly supportive of the role for appropriate, individualized dosing of adjunctive micronutrients for targeted therapies38-40.

Venous Leg Ulcer and Associated Lymphatic Dysfunction Adjunctive Management With Micronized Purified Flavonoid Fraction (MPFF)

Management of VLUs and lymphedema requires comprehensive care with performance of compression, appropriate treatment of venous insufficiency, and associated lymphatic dysfunction/ lymphedema therapy with Certified Lymphedema Therapists (CLTs)4451,53. Ulcer healing requires adequate nutrition especially in view of the recent discoveries concerning the pathophysiology of chronic venous insufficiency. The Guidelines of the Society for Vascular Surgery and the American Venous Forum41⁴and the European Society for Vascular Surgery (ESVS) 2022 Clinical Practice Guidelines on the Management of Chronic Venous Disease of the Lower Limbs42 recommend nutritional assessment in any patient with VLUs with potential malnutrition. Indeed, elderly patients with VLUs might have inadequate intake of proteins, vitamins (A, E, folate, B12, B6, D,C, carotene, and others) and minerals such as zinc57-59. The healing rate can be improved by nutritional supplement60-63

From the multitude of trials with systemic medications studied for their potential benefit in improving VLU healing rates, three products have demonstrated benefit: pentoxifylline, sulodexide and micronized purified flavonoid fraction (MPFF)42.

MPFF has proven microcirculatory protective effects with pronounced inhibition of leucocytes activation and adhesion68-70. In a model of postischemic leukocyte adhesion/ migration and venular protein leakage, MPFF has shown the same strength of effectiveness as the anti-adhesive monoclonal antibodies71. The interaction of MPFF with leukocytes adhesion/ migration was demonstrated in patients with chronic venous disease72. In patients with skin changes plasma vascular endothelial growth

A View Beyond the Horizon; The Re-Emergence of Micronized Purified Flavonoid Fractions for Venous Leg Ulcer

factor (VEGF) levels were higher and decreased after treatment with MPFF73.

Hesperidin, an important component of MPFF, is one of the phenolic inhibitors of Nicotinamide Adenine Dinucleotide Phosphate (NADPH) oxidase, a key enzyme in the production of reactive oxygen species in the endothelium74. This results in increased bioavailability of eNO.

In the experimental models of venous disease with altered microvascular permeability induced by histamine, bradykinin and leukotriene B4 (LTB4), MPFF exerted a potent effect against leakage of macromolecules75. The inhibition of oxidant-induced leakage by MPFF was efficient to the same degree76.

Medical adjunctive treatment by MPFF has been recognized by international guidelines and summary reviews41,42,43.

The value of MPFF in VLUs therapy was investigated in several randomized controlled studies. MPFF (1000 mg per day) combined with standard compression increased VLUs healing rate and shortened time to healing77-80. In a meta-analysis that included 5 Randomized Controlled Trials (RCTs) with a total number of 723 patients, the estimated relative risk improvement of healing rate at 6 months was 32%81. A retrospective cost-effectiveness analysis, taking into consideration only the direct medical costs, estimated a 45% reduction of treatment costs associated with adjuvant MPFF therapy82, as compared with conventional venous ulcer care.

Conclusion

Venous leg ulcers are the ultimate consequences of chronic venous insufficiency. New discoveries in ulcer pathophysiology assign a special role to glycocalyx and eNO in venous disease development. The management of VLUs has been transformed. The diagnosis of the underlying venous disorder has been greatly improved with the development of the duplex ultrasound technique. Compression therapy options have been enhanced to improve adherence. The novel endovenous ablation and sclero therapy methods for both superficial veins and bionutrient adjunctive therapy has been used with increasing frequency for

patients with vitamins/ minerals deficiencies and oral systemic treatment with MPFF, pentoxifylline and sulodexide (Europe availability) may significantly improve ulcer healing based upon a legacy of prior data and new emerging insights and publications. Undoubtedly, we can now see beyond the horizon and a renewed era for the improved care of patients with VLU and lymphedema.

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