A Unified Theory of Human Cardiovascular Disease
Leading the Way to the Abolition of This Disease as a Cause for Human
Mortality
"An important scientific innovation rarely makes
its way by gradually winning over and converting its opponents. What does
happen is that its opponents gradually die out and that the growing
generation is familiar with the idea from the beginning." Max
Planck
This paper is dedicated to the young physicians and the medical
students of this world.
Abstract
Until now therapeutic concepts for human
cardiovascular disease (CVD) were targeting individual pathomechanisms or
specific risk factors. On the basis of genetic, metabolic, evolutionary,
and clinical evidence we present here a unified pathogenetic and
therapeutic approach. Ascorbate deficiency is the precondition and common
denominator of human CVD. Ascorbate deficiency is the result of the
inability of man to synthesize ascorbate endogenously in combination with
insufficient dietary intake. The invariable morphological consequences of
chronic ascorbate deficiency in the vascular wall are the loosening of the
connective tissue and the loss of the endothelial barrier function. Thus
human CVD is a form of pre-scurvy. The multitude of pathomechanisms that
lead to the clinical manifestation of CVD are primarily defense mechanisms
aiming at the stabilization of the vascular wall. After the loss of
endogenous ascorbate production during the evolution of man these defense
mechanisms became life-saving. They counteracted the fatal consequences of
scurvy and particularly of blood loss through the scorbutic vascular wall.
These countermeasures constitute a genetic and a metabolic level. The
genetic level is characterized by the evolutionary advantage of inherited
features that lead to a thickening of the vascular wall, including a
multitude of inherited diseases. The metabolic level is characterized by
the close connection of ascorbate with metabolic regulatory systems that
determine the risk profile for CVD in clinical cardiology today. The most
frequent mechanism is the deposition of lipoproteins, particularly
lipoprotein(a) [Lp(a)], in the vascular wall. With sustained ascorbate
deficiency, the result of insufficient ascorbate uptake, these defense
mechanisms overshoot and lead to the development of CVD. Premature CVD is
essentially unknown in all animal species that produce high amounts of
ascorbate endogenously. In humans, unable to produce endogenous ascorbate,
CVD became one of the most frequent diseases. The genetic mutation that
rendered all human beings today dependent on dietary ascorbate is the
universal underlying cause of CVD. Optimum dietary ascorbate intake will
correct this common genetic defect and prevent its deleterious
consequences. Clinical confirmation of this theory should largely abolish
CVD as a cause for mortality in this generation and future generations of
mankind.
Key words
Ascorbate, vitamin C, cardiovascular disease,
lipoprotein(a), hypercholesterolemia, hypertriglyceridemia,
hypoalphalipoproteinemia, diabetes, homocystinuria.
Introduction
We have recently presented ascorbate deficiency
as the primary cause of human CVD. We proposed that the most frequent
pathomechanism leading to the development of atherosclerotic plaques is
the deposition of Lp(a) and fibrinogen/fibrin in the ascorbate-deficient
vascular wall.1,2 In the course of this work we discovered that virtually
every pathomechanism for human CVD known today can be induced by ascorbate
deficiency. Beside the deposition of Lp(a) this includes such seemingly
unrelated processes as foam cell formation and decreased
reverse-cholesterol transfer, and also peripheral angiopathies in diabetic
or homocystinuric patients. We did not accept this observation as a
coincidence. Consequently we proposed that ascorbate deficiency is the
precondition as well as a common denominator of human CVD. This
far-reaching conclusion deserves an explanation; it is presented in this
paper. We suggest that the direct connection of ascorbate deficiency with
the development of CVD is the result of extraordinary pressure during the
evolution of man. After the loss of the endogenous ascorbate production in
our ancestors, severe blood-loss through the scorbutic vascular wall
became a life-threatening condition. The resulting evolutionary pressure
favored genetic and metabolic mechanisms predisposing to CVD.
The Loss of Endogenous Ascorbate Production in the Ancestor of
Man
With few exceptions all animals synthesize their own ascorbate
by conversion from glucose. In this way they manufacture a daily amount of
ascorbate that varies between about 1 gram and 20 grams, when compared to
the human body weight. About 40 million years ago the ancestor of man lost
the ability for endogenous ascorbate production. This was the result of a
mutation of the gene encoding for the enzyme L-gulono-g-lactone oxidase
(GLO), a key enzyme in the conversion of glucose to ascorbate. As a result
of this mutation all descendants became dependent on dietary ascorbate
intake.
The precondition for the mutation of the GLO gene was a sufficient
supply of dietary ascorbate. Our ancestors at that time lived in tropical
regions. Their diet consisted primarily of fruits and other forms of plant
nutrition that provided a daily dietary ascorbate supply in the range of
several hundred milligrams to several grams per day. When our ancestors
left this habitat to settle in other regions of the world the availability
of dietary ascorbate dropped considerably and they became prone to scurvy.
Fatal Blood Loss Through the Scorbutic Vascular Wall - An
Extraordinary Challenge to the Evolutionary Survival of Man
Scurvy
is a fatal disease. It is characterized by structural and metabolic
impairment of the human body, particularly by the destabilization of the
connective tissue. Ascorbate is essential for an optimum production and
hydroxylation of collagen and elastin, key constituents of the
extracellular matrix. Ascorbate depletion thus leads to a destabilization
of the connective tissue throughout the body. One of the first clinical
signs of scurvy is perivascular bleeding. The explanation is obvious:
Nowhere in the body does there exist a higher pressure difference than in
the circulatory system, particularly across the vascular wall. The
vascular system is the first site where the underlying destabilization of
the connective tissue induced by ascorbate deficiency is unmasked, leading
to the penetration of blood through the permeable vascular wall. The most
vulnerable sites are the proximal arteries, where the systolic blood
pressure is particularly high. The increasing permeability of the vascular
wall in scurvy leads to petechiae and ultimately hemorrhagic blood loss.
Scurvy and scorbutic blood loss decimated the ship crews in earlier
centuries within months. It is thus conceivable that during the evolution
of man periods of prolonged ascorbate deficiency led to a great death
toll. The mortality from scurvy must have been particularly high during
the thousands of years the ice ages lasted and in other extreme
conditions, when the dietary ascorbate supply approximated zero. We
therefore propose that after the loss of endogenous ascorbate production
in our ancestors, scurvy became one of the greatest threats to the
evolutionary survival of man. By hemorrhagic blood loss through the
scorbutic vascular wall our ancestors in many regions may have virtually
been brought close to extinction.
The morphologic changes in the vascular wall induced by ascorbate
deficiency are well characterized: the loosening of the connective tissue
and the loss of the endothelial barrier function. The extraordinary
pressure by fatal blood loss through the scorbutic vascular wall favored
genetic and metabolic countermeasures attenuating increased vascular
permeability.
Ascorbate Deficiency and Genetic Countermeasures
The genetic
countermeasures are characterized by an evolutionary advantage of genetic
features and include inherited disorders that are associated with
atherosclerosis and CVD. With sufficient ascorbate supply these disorders
stay latent. In ascorbate deficiency, however, they become unmasked,
leading to an increased deposition of plasma constituents in the vascular
wall and other mechanisms that thicken the vascular wall. This thickening
of the vascular wall is a defense measure compensating for the impaired
vascular wall that had become destabilized by ascorbate deficiency. With
prolonged insufficient ascorbate intake in the diet these defense
mechanisms overshoot and CVD develops.
The most frequent mechanism to counteract the increased permeability of
the ascorbate-deficient vascular wall became the deposition of
lipoproteins and lipids in the vessel wall. Another group of proteins that
generally accumulate at sites of tissue transformation and repair are
adhesive proteins such as fibronectin, fibrinogen, and particularly
apo(a). It is therefore no surprise that Lp(a), a combination of the
adhesive protein apo(a) with a low density lipoprotein (LDL) particle,
became the most frequent genetic feature counteracting ascorbate
deficiency.1 Beside lipoproteins, certain metabolic disorders, such as
diabetes and homocystinuria, are also associated with the development of
CVD. Despite differences in the underlying pathomechanism, all these
mechanisms share a common feature: they lead to a thickening of the
vascular wall and thereby can counteract the increased permeability in
ascorbate deficiency.
In addition to these genetic disorders, the evolutionary pressure from
scurvy also favored certain metabolic countermeasures.
Ascorbate Deficiency and Metabolic Countermeasures
The
metabolic countermeasures are characterized by the regulatory role of
ascorbate for metabolic systems determining the clinical risk profile for
CVD. The common aim of these metabolic regulations is to decrease the
vascular permeability in ascorbate deficiency. Low ascorbate
concentrations therefore induce vasoconstriction and hemostasis and affect
vascular wall metabolism in favor of atherosclerogenesis. Towards this end
ascorbate interacts with lipoproteins, coagulation factors,
prostaglandins, nitric oxide, and second messenger systems such as cyclic
monophosphates (for review see 1, 3-5). It should be noted that ascorbate
can affect these regulatory levels in a multiple way. In lipoprotein
metabolism low density lipoproteins (LDL), Lp(a), and very low density
lipoproteins (VLDL) are inversely correlated with ascorbate
concentrations, whereas ascorbate and HDL levels are positively
correlated. Similarly, in prostaglandin metabolism ascorbate increases
prostacyclin and prostaglandin E levels and decreases the thromboxane
level. In general, ascorbate deficiency induces vascular constriction and
hemostatis, as well as cellular and extracellular defense measures in the
vascular wall.
In the following sections we shall discuss the role of ascorbate for
frequent and well established pathomechanisms of human CVD. In general,
the inherited disorders described below are polygenic. Their separate
description, however, will allow the characterization of the role of
ascorbate on the different genetic and metabolic levels.
Apo(a) and Lp(a), the Most Effective and Most Frequent
Countermeasure
After the loss of endogenous ascorbate production,
apo(a) and Lp(a) were greatly favored by evolution. The frequency of
occurrence of elevated Lp(a) plasma levels in species that had lost the
ability to synthesize ascorbate is so great that we formulated the theory
that apo(a) functions as a surrogate for ascorbate.6 There are several
genetically determined isoforms of apo(a). They differ in the number of
kringle repeats and in their molecular size.7 An inverse relation between
the molecular size of apo(a) and the synthesis rate of Lp(a) particles has
been established. Individuals with the high molecular weight apo(a)
isoform produce fewer Lp(a) particles than those with the low apo(a)
isoform. In most population studies the genetic pattern of high apo(a)
isoform/low Lp(a) plasma level was found to be the most advantageous and
therefore most frequent pattern. In ascorbate deficiency Lp(a) is
selectively retained in the vascular wall. Apo(a) counteracts increased
permeability by compensating for collagen, by its binding to fibrin, as a
proteinthiol antioxidant, and as an inhibitor of plasmin-induced
proteolysis (1). Moreover, as an adhesive protein apo(a) is effective in
tissue- repair processes (8). Chronic ascorbate deficiency leads to a
sustained accumulation of Lp(a) in the vascular wall. This leads to the
development of atherosclerotic plaques and premature CVD, particularly in
individuals with genetically determined high plasma Lp(a) levels. Because
of its association with apo(a), Lp(a) is the most specific repair particle
among all lipoproteins. Lp(a) is predominantly deposited at predisposition
sites and it is therefore found to be significantly correlated with
coronary, cervical, and cerebral atherosclerosis but not with peripheral
vascular disease.
The mechanism by which ascorbate resupplementation prevents CVD in any
condition is by maintaining the integrity and stability of the vascular
wall. In addition, ascorbate exerts in the individual a multitude of
metabolic effects that prevent the exacerbation of a possible genetic
predisposition and the development of CVD. If the predisposition is a
genetic elevation of Lp(a) plasma levels the specific regulatory role of
ascorbate is the decrease of apo(a) synthesis in the liver and thereby the
decrease of Lp(a) plasma levels. Moreover, ascorbate decreases the
retention of Lp(a) in the vascular wall by lowering fibrinogen synthesis
and by increasing the hydroxylation of lysine residues in vascular wall
constituents, thereby reducing the affinity for Lp(a) binding.1
In about half of the CVD patients the mechanism of Lp(a) deposition
contributes significantly to the development of atherosclerotic plaques.
Other lipoprotein disorders are also frequently part of the polygenic
pattern predisposing the individual patient to CVD in the individual.
Other Lipoprotein Disorders Associated with CVD
In a large
population study Goldstein et al. discussed three frequent lipid
disorders, familial hypercholesterolemia, familial hypertriglyceridemia,
and familial combined hyperlipidemia.9 Ascorbate deficiency unmasks these
underlying genetic defects and leads to an increased plasma concentration
of lipids (e.g. cholesterol, triglycerides) and lipoproteins (e.g. LDL,
VLDL) as well as to their deposition in the impaired vascular wall. As
with Lp(a), this deposition is a defense measure counteracting the
increased permeability. It should, however, be noted that the deposition
of lipoproteins other than Lp(a) is a less specific defense mechanism and
frequently follows Lp(a) deposition. Again, these mechanisms function as a
defense only for a limited time. With sustained ascorbate deficiency the
continued deposition of lipids and lipoproteins leads to atherosclerotic
plaque development and CVD. Some mechanisms will now be described in more
detail.
Hypercholesterolemia,LDL-receptor defect
A multitude of
genetic defects lead to an increased synthesis and/or a decreased
catabolism of cholesterol or LDL. A well characterized although rare
defect is the LDL-receptor defect. Ascorbate deficiency unmasks these
inherited metabolic defects and leads to an increased plasma concentration
of cholesterol-rich lipoproteins, e.g. LDL, and their deposition in the
vascular wall. Hypercholesterolemia increases the risk for premature CVD
primarily when combined with elevated plasma levels of Lp(a) or
triglycerides.
The mechanisms by which ascorbate supplementation prevents the
exacerbation of hypercholesterolemia and related CVD include an increased
catabolism of cholesterol. In particular, ascorbate is known to stimulate
7-a- hydroxylase, a key enzyme in the conversion of cholesterol to bile
acids and to increase the expression of LDL receptors on the cell surface.
Moreover, ascorbate is known to inhibit endogenous cholesterol synthesis
as well as oxidative modification of LDL (for review see 1).
Hertriglyceridemia,Type III hyperlipidemia
A variety of
genetic disorders lead to the accumulation of triglycerides in the form of
chylomicron remnants, VLDL, and intermediate density lipoproteins (IDL) in
plasma. Ascorbate deficiency unmasks these underlying genetic defects and
the continued deposition of triglyceride-rich lipoproteins in the vascular
wall leads to CVD development. These triglyceride-rich lipoproteins are
particularly subject to oxidative modification, cellular lipoprotein
uptake, and foam cell formation. In hypertriglyceridemia nonspecific
foam-cell formation has been observed in a variety of organs.10
Ascorbate-deficient foam cell formation, although a less specific repair
mechanism than the extracellular deposition of Lp(a), may have also
conferred stability.
Ascorbate supplementation prevents the exacerbation of CVD associated
with hypertriglyceridemia, Type III hyperlipidemia, and related disorders
by stimulating lipoprotein lipases and thereby enabling a normal
catabolism of triglyceride-rich lipoproteins.11 Ascorbate prevents the
oxidative modification of these lipoproteins, their uptake by scavenger
cells and foam cell formation. Moreover, we propose here that, analogous
to the LDL receptor, ascorbate also increases the expression of the
receptors involved in the metabolic clearance of triglyceride-rich
lipoproteins, such as the chylomicron remnant receptor. The degree of
build-up of atherosclerotic plaques in patients with lipoprotein disorders
is determined by the rate of deposition of lipoproteins and by the rate of
the removal of deposited lipids from the vascular wall. It is therefore
not surprising that ascorbate is also closely connected with this reverse
pathway.
Hypoalphalipoproteinemia
Hypoalphalipoproteinemia is a
frequent lipoprotein disorder characterized by a decreased synthesis of
HDL particles. HDL is part of the `reverse-cholesterol-transport' pathway
and is critical for the transport of cholesterol and also other lipids
from the body periphery to the liver. In ascorbate deficiency this genetic
defect is unmasked, resulting in decreased HDL levels and a decreased
reverse transport of lipids from the vascular wall to the liver. This
mechanism is highly effective and the genetic disorder
hypoalphalipoproteinemia was greatly favored during evolution. With
ascorbate supplementation HDL production increases,12 leading to an
increased uptake of lipids deposited in the vascular wall and to a
decrease of the atherosclerotic lesion. A look back in evolution
underlines the importance of this mechanism. During the winter seasons,
with low ascorbate intake, our ancestors became dependent on protecting
their vascular wall by the deposition of lipoproteins and other
constituents. During spring and summer seasons the ascorbate content in
the diet increased significantly and mechanisms were favored that
decreased the vascular deposits under the protection of increased
ascorbate concentration in the vascular tissue. It is not unreasonable for
us to propose that ascorbate can reduce fatty deposits in the vascular
wall within a relatively short time. In an earlier clinical study it was
shown that 500 mg of dietary ascorbate per day can lead to a reduction of
atherosclerotic deposits within 2 to 6 months.13 This concept, of course,
also explains why heart attack and stroke occur today with a much higher
frequency in winter than during spring and summer, the seasons with
increased ascorbate intake.
Other Inherited Metabolic Disorders Associated with
CVD
Beside lipoprotein disorders many other inherited metabolic
diseases are associated with CVD. Generally these disorders lead to an
increased concentration of plasma constituents that directly or indirectly
damage the integrity of the vascular wall. Consequently these diseases
lead to peripheral angiopathies as observed in diabetes, homocystinuria,
sickle-cell anemia (the first molecular disease described,14 and many
other genetic disorders. Similar to lipoproteins the deposition of various
plasma constituents as well as proliferative thickening provided a certain
stability for the ascorbate-deficient vascular wall. We illustrate this
principle for diabetic and homocystinuric angiopathy.
Diabetic Angiopathy
The pathomechanism in this case involves
the structural similarity between glucose and ascorbate and the
competition of these two molecules for specific cell surface
receptors.15,16 Elevated glucose levels prevent many cellular systems in
the human body, including endothelial cells, from optimum ascorbate
uptake. Ascorbate deficiency unmasks the underlying genetic disease,
aggravates the imbalance between glucose and ascorbate, decreases vascular
ascorbate concentration, and thereby triggers diabetic angiopathy.
Ascorbate supplementation prevents diabetic angiopathy by optimizing
the ascorbate concentration in the vascular wall and also by lowering
insulin requirement.17
Homocystinuric angiopathy
Homocystinuria is characterized by
the accumulation of homocyst(e)ine and a variety of its metabolic
derivatives in the plasma, the tissues and the urine as the result of
decreased homocysteine catabolism.18 Elevated plasma concentrations of
homocyst(e)ine and its derivatives damage the endothelial cells throughout
the arterial and venous system. Thus homocystinuria is characterized by
peripheral vascular disease and thromboembolism. These clinical
manifestations have been estimated to occur in 30 per cent of the patients
before the age of 20 and in 60 per cent of the patients before the age of
40.19
Ascorbate supplementation prevents homocystinuric angiopathy and other
clinical complications of this disease by increasing the rate of
homocysteine catabolism.20
Thus, ascorbate deficiency unmasks a variety of individual genetic
predispositions that lead to CVD in different ways. These genetic
disorders were conserved during evolution largely because of their
association with mechanisms that lead to the thickening of the vascular
wall. Moreover, since ascorbate deficiency is the underlying cause of
these diseases, ascorbate supplementation is the universal therapy.
The Determining Principles of This Theory
The determining
principles of this comprehensive theory are schematically summarized in
Figures 1 to 3 (pages 13 to 15).
1. CVD is the direct consequence of
the inability for endogenous ascorbate production in man in combination
with low dietary ascorbate intake.
2. Ascorbate deficiency leads to
increased permeability of the vascular wall by the loss of the endothelial
barrier function and the loosening of the vascular connective
tissue.
3. After the loss of endogenous ascorbate production scurvy and
fatal blood loss through the scorbutic vascular wall rendered our
ancestors in danger of extinction. Under this evolutionary pressure over
millions of years genetic and metabolic countermeasures were favored that
counteract the increased permeability of the vascular wall.
4. The
genetic level is characterized by the fact that inherited disorders
associated with CVD became the most frequent among all genetic
predispositions. Among those predispositions lipid and lipoprotein
disorders occur particularly often.
5. The metabolic level is
characterized by the direct relation between ascorbate and virtually all
risk factors of clinical cardiology today. Ascorbate deficiency leads to
vasoconstriction and hemostasis and affects the vascular wall metabolism
in favor of atherosclerogenesis.
6. The genetic level can be further
characterized. The more effective and specific a certain genetic feature
counteracted the increasing vascular permeability in scurvy, the more
advantageous it became during evolution and, generally, the more
frequently this genetic feature occurs today.
7. The deposition of
Lp(a) is the most effective, most specific, and therefore most frequent of
these mechanisms. Lp(a) is preferentially deposited at predisposition
sites. In chronic ascorbate deficiency the accumulation of Lp(a) leads to
the localized development of atherosclerotic plaques and to myocardial
infarction and stroke.
8. Another frequent inherited lipoprotein
disorder is hypoalphalipoproteinemia. The frequency of this disorder again
reflects its usefulness during evolution. The metabolic upregulation of
HDL synthesis by ascorbate became an important mechanism to reverse and
decrease existing lipid deposits in the vascular wall.
9. The vascular
defense mechanisms associ-ated with most genetic disorders are
nonspecific. These mechanisms can aggra-vate the development of
atherosclerotic plaques at predisposition sites. Other nonspecific
mechanisms lead to peripheral forms of atherosclerosis by causing a
thickening of the vascular wall throughout the arterial system. This
peripheral form of vascular disease is characteristic for angiopathies
associated with Type III hyperlipidemia, diabetes, and many other
inherited metabolic diseases.
10. Of particular advantage during
evolution and therefore particularly frequent today are those genetic
features that protect the ascorbate-deficient vascular wall until the end
of the reproduction age. By favoring these disorders nature decided for
the lesser of two evils: the death from CVD after the reproduction age
rather than death from scurvy at a much earlier age. This also explains
the rapid increase of the CVD mortality today from the 4th decade
onwards.
11. After the loss of endogenous ascorbate production the
genetic mutation rate in our ancestors increased significantly.21 This was
an additional precondition favoring the advantage not only of apo(a) and
Lp(a) but also of many other genetic counter-measures associated with
CVD.
12. Genetic predispositions are characterized by the rate of
ascorbate depletion in a multitude of metabolic reactions specific for the
genetic disorder.22 The overall rate of ascorbate depletion in an
individual is largely determined by the polygenic pattern of disorders.
The earlier the ascorbate reserves in the body are depleted without being
resupplemented, the earlier CVD develops.
13. The genetic
predispositions with the highest probability for early clinical
manifestation require the highest amount of ascorbate supplementation in
the diet to prevent CVD development. The amount of ascorbate for patients
at high risk should be comparable to the amount of ascorbate our ancestors
synthesized in their body before they lost this ability: between 10,000
and 20,000 milligrams per day.
14. Optimum ascorbate supplementation
prevents the development of CVD indepen-dently of the individual
predisposition or pathomechanism. Ascorbate reduces existing
atherosclerotic deposits and thereby decreases the risk for myocardial
infarction and stroke. Moreover, ascorbate can prevent blindness and organ
failure in diabetic patients, thromboembolism in homocystinuric patients,
and many other manifestations of CVD.
Conclusion
In this paper we present a unified theory of human
CVD. This disease is the direct consequence of the inability of man to
synthesize ascorbate in combination with insufficient intake of ascorbate
in the modern diet. Since ascorbate deficiency is the common cause of
human CVD, ascorbate supplementation is the universal treatment for this
disease. The available epidemiological and clinical evidence is reasonably
convincing. Further clinical confirmation of this theory should lead to
the abolition of CVD as a cause of human mortality for the present
generation and future generations of mankind.
Acknowledgements
We thank Jolanta Walichiewicz for graphical
assistance, Rosemary Babcock for library services, and Dorothy Munro and
Martha Best for secretarial assistance.
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Figure 1.
Ascorbate
deficiency is the precondition and common denominator of human CVD.
Ascorbate deficiency invariably leads to an increased permeability of the
vascular wall. The evolutionary pressure from fatal blood- loss through
scorbutic vascular wall over million of years favored genetic and
metabolic countermeasures. The genetic level (A) is characterized by an
evolutionary advantage of genetic features predisposing to CVD. The
evolutionary pressure in favor of these predisposing genetic features was
so great that CVD became one of today's most common diseases. The
metabolic level (B) is characterized by the regulatory effect of ascorbate
on factors determining the clinical risk profile for CVD in cardiology
today including lipoproteins, coagulation factors, prostaglandins, and
others. Ascorbate deficiency counteracts increased vascular permeability
by inducing vasoconstriction, hemostasis, and atherogenic vascular
metabolism.
Figure 2.
Genetic countermeasures and the relation between
their efficacy and the frequency of their occurrence. The more
specifically a genetic feature counteracts the increased permeability of
the vascular wall the more it was favored during evolution and the more
frequently it occurs today. The deposition of Lp(a) in the vascular wall
is the most specific and therefore most frequent mechanism. Because of the
specificity of Lp(a) the sustained accumulation of this lipoprotein during
chronic ascorbate deficiency leads to CVD at predisposition sites.
Diabetic and homocystinuric angiopathies are typical non-specific
mechanisms. Their clinical exacerbation in chronic ascorbate deficiency
leads to peripheral vascular disease. With the exception of Lp(a), most
other lipoprotein disorders are rather nonspecific countermeasures. They
either follow the deposition of Lp(a) and aggravate CVD mainly at
predisposition sites or they lead to peripheral vascular disease, such as
in Type III hyperlipidemia. Figure 2 schematically summarizes these
principles. This scheme, of course, can not reflect the multitude of
polygenic variations in individual patients.
Figure 3.
The relation between ascorbate depletion and the
onset of clinical symptoms in the patient. As a result of most genetic
defects the rate constants for certain metabolic reactions are decreased.
Ascorbate is destroyed in the attempt to normalize these decreased rate
constants and in compensatory metabolic pathway.1,22 The overall rate of
ascorbate depletion in an individual is largely determined by the
polygenic pattern of metabolic disorders in an individual (and to some
extent also by exogenous risk factors). The earlier the body ascorbate
reserves are depleted without being resupplemented the earlier the
clinical manifestation occurs. Consequently, the higher the probability of
early clinical onset of a latent genetic predisposition, the higher is the
amount of required ascorbate intake to prevent this onset. For patients at
high risk dietary ascorbate intake is recommended in the range of 10,000
to 20,000 mg/d. This corresponds to the amount of ascorbate our ancestors
synthesized in their bodies before they lost this ability. The validity of
Figure 3 is not limited to CVD. Ascorbate deficiency, of course, also
unmasks latent disorders predisposing to cancer and to autoimmune and
other diseases.