National Academy of Sciences
References
61. Schweiz Med Wochenschr 1994
Aug 9;124(31-32):1373-80
[Scurvy--a mistakenly forgotten disease].
[Article in German]
Hurlimann R, Salomon F
Departement fur Innere Medizin, Universitatsspital
Zurich.
Four cases of scurvy diagnosed within a period of two
years are reported. They
comprised 2 male patients with heavy nicotine and alcohol
abuse, a 35-year-old
woman with malnutrition due to food supplements phobia, and
a 69-year-old woman
with malnutrition due to dementia and social isolation. All
four patients were
adynamic and anemic. Three patients showed typical
dermatologic signs with
hemorrhagic hyperceratosis, suffusions or cork-screw hair.
Two patients
complained of parodontol disorders. Other symptoms were
gastrointestinal
bleeding, sicca syndrome, retinal bleeding, subdural
hematoma, edema and
arthralgia. Associated disorders were folic acid and vitamin
B12 depletion in
two cases, and nephropathy and pneumonia with pneumothorax
in one case each. In
all cases the serum asorbic acid concentration was below the
scorbutic level of
11 mumol/l. Historical data, pathogenesis, incidence,
clinical presentation,
diagnosis and therapy of scurvy are discussed. We conclude
that scurvy can be
observed even in a developed country such as Switzerland at
the end of the 20th
century. The real incidence may be underestimated because
symptoms are not well
known and disappear rapidly after admission because of
sufficient vitamin C
content in normal diet. Patients at risk are socially
isolated alcoholics, old
people, psychiatric patients and diet enthusiasts. Usually
scurvy occurs in
conjunction with other deficiencies. Smoking and acute
illness enhance ascorbic
acid depletion. With a knowledge of the symptomatology of
scurvy, it is easy to
diagnose and treatment is simple and effective.
62. J Am Acad Dermatol 1994
May;30(5 Pt 2):881-3
Scurvy.
Ghorbani AJ, Eichler C
Albany Medical College, New York.
Scurvy is caused by a deficiency of ascorbic acid. We
describe a 31-year-old
Hispanic man who had perifollicular hemorrhages, follicular
hyperkeratosis,
corkscrew hairs, and gingival hemorrhage after consuming a
peculiar and
restricted diet for 1 year. A diagnosis of scurvy was made
and the patient's
disease resolved after treatment with vitamin C.
63. Free Radic Biol Med 2000
Feb 1;28(3):428-36
Vitamin C prevents the acute atherogenic effects of passive
smoking.
Valkonen MM, Kuusi T
Department of Medicine, University of Helsinki, Helsinki,
Finland.
During passive smoking the body is attacked by an excess
of free radicals
inducing oxidative stress. In nonsmoking subjects even a
short period of passive
smoking breaks down serum antioxidant defense (TRAP) and
accelerates lipid
peroxidation leading to accumulation of their low-density
lipoprotein (LDL)
cholesterol in cultured human macrophages. We now studied
whether these acute
proatherogenic effects of secondhand smoke could be
prevented by an effective
free radical scavenger, vitamin C. Blood samples were
collected from nonsmoking
subjects (n = 10) as they were consecutively exposed to
normal air or cigarette
smoke during four separate days. During the last 2 d, a
single dose of vitamin C
(3 g) was given, which doubled its plasma concentration.
Vitamin C did not
influence the plasma antioxidant defense or the resistance
of LDL to oxidation
in normal air, but prevented the smoke-induced decrease in
plasma TRAP (p
<.001), the decrease in the resistance of LDL to
oxidation (p <.05), and the
accelerated formation of serum thiobarbituric acid reactive
substances (TBARS)
(p <.05) otherwise observed 1.5 h after the beginning of
passive smoking.
Vitamin C protected nonsmoking subjects against the harmful
effects of free
radicals during exposure to secondhand smoke.
64. Clin Sci (Colch) 1997
Apr;92(4):361-5
Combination oral antioxidant supplementation reduces blood
pressure.
Galley HF, Thornton J, Howdle PD, Walker BE, Webster
NR
Clinical Oxidant Research Group, St James's University
Hospital, Leeds, UK.
1. Hypertension affects 30% of adults and low intakes of
antioxidants have been
associated with increased risk of hypertension and
cardiovascular disease. To
investigate the effect of short-term high-dose antioxidant
supplementation on
blood pressure in hypertensive and normotensive outpatients,
we undertook a
randomized, double-blind, crossover design
placebo-controlled study. 2. Forty
subjects were recruited from medical outpatient clinics, of
whom 38 completed
the study. Twenty-one were attending for treatment of
hypertension and 17 were
normotensive, attending for minor gastrointestinal
complaints. Subjects were
randomly assigned to receive either 8 weeks placebo followed
by 2 weeks washout
then 8 weeks antioxidants or vice versa. The combination of
antioxidants
consisted of 200 mg of zinc sulphate, 500 mg of ascorbic
acid, 600 mg of
alpha-tocopherol (sodium succinate salt) and 30 mg of
beta-carotene daily. 3.
Systolic blood pressure fell at the end of the antioxidant
phase compared with
the placebo phase both in subjects receiving
anti-hypertensive therapy (P <
0.01) and those who were normotensive (P = 0.067).
Circulating levels of
beta-carotene and alpha-tocopherol increased in all subjects
during
supplementation (P < 0.01) and urine nitrite increased in
hypertensive patients
(P < 0.05). 4. Short-term oral high-dose combination
antioxidant therapy reduces
blood pressure, possibly via increased availability of
nitric oxide. This study
may have implications for the innovative use of antioxidants
as an adjunct to
anti-hypertensive therapy.
65. Circulation 1999 Jun
29;99(25):3234-40
Long-term ascorbic acid administration reverses endothelial
vasomotor
dysfunction in patients with coronary artery disease.
Gokce N, Keaney JF Jr, Frei B, Holbrook M, Olesiak M,
Zachariah BJ, Leeuwenburgh
C, Heinecke JW, Vita JA
Evans Memorial Department of Medicine, Cardiology Section,
and Whitaker
Cardiovascular Institute, Boston University School of
Medicine, Boston, MA, USA.
BACKGROUND: Loss of endothelium-derived nitric oxide
(EDNO) contributes to the clinical expression of coronary
artery disease (CAD). Increased oxidative stress has been
linked to impaired endothelial vasomotor function in
atherosclerosis, and recent studies demonstrated that
short-term ascorbic acid treatment improves endothelial
function. METHODS AND RESULTS: In a randomized, double-blind,
placebo-controlled study, we examined the effects of
single-dose (2 g PO) and long-term (500 mg/d) ascorbic acid
treatment on EDNO-dependent flow-mediated dilation of the
brachial artery in patients with angiographically established
CAD. Flow-mediated dilation was examined by high-resolution
vascular ultrasound at baseline, 2 hours after the single
dose, and 30 days after long-term treatment in 46 patients
with CAD. Flow-mediated dilation improved from 6.6+/-3.5% to
10.1+/-5.2% after single-dose treatment, and the effect was
sustained after long-term treatment (9. 0+/-3.7%), whereas
flow-mediated dilation was 8.6+/-4.7% at baseline and
remained unchanged after single-dose (7.8+/-4.4%) and
long-term (7.9+/-4.5%) treatment with placebo (P=0.005 by
repeated-measures ANOVA). Plasma ascorbic acid concentrations
increased from 41.4+/-12. 9 to 115.9+/-34.2 micromol/L after
single-dose treatment and to 95. 0+/-36.1 micromol/L after
long-term treatment (P<0.001). CONCLUSIONS: In patients
with CAD, long-term ascorbic acid treatment has a sustained
beneficial effect on EDNO action. Because endothelial
dysfunction may contribute to the pathogenesis of
cardiovascular events, this study indicates that ascorbic
acid treatment may benefit patients with CAD.
66.Circulation 1999 Mar
9;99(9):1156-60
Demonstration of rapid onset vascular endothelial
dysfunction after
hyperhomocysteinemia: an effect reversible with vitamin c
therapy.
Chambers JC, McGregor A, Jean-Marie J, Obeid OA, Kooner
JS
National Heart and Lung Institute, Imperial College School
of Medicine,
Hammersmith Hospital, London, UK.
BACKGROUND: Hyperhomocysteinemia is a major and
independent risk factor for
vascular disease. The mechanisms by which homocysteine
promotes atherosclerosis are not well understood. We
hypothesized that elevated homocysteine concentrations are
associated with rapid onset endothelial dysfunction, which is
mediated through oxidant stress mechanisms and can be
inhibited by the antioxidant vitamin c. Methods and RESULTS:
We studied 17 healthy volunteers (10 male and 7 female) aged
33 (range 21 to 59) years. Brachial artery diameter responses
to hyperemic flow (endothelium dependent), and
glyceryltrinitrate (GTN, endothelium independent) were
measured with high resolution ultrasound at 0 hours
(fasting), 2 hours, and 4 hours after (1) oral methionine
(L-methionine 100 mg/kg), (2) oral methionine preceded by
vitamin c (1g/day, for 1 week), and (3) placebo, on separate
days and in random order. Plasma homocysteine increased (0
hours, 12.8+/-1.4; 2 hours, 25.4+/-2.5; and 4 hours, 31.
2+/-3.1 micromol/l, P<0.001), and flow-mediated dilatation
fell (0 hours, 4.3+/-0.7; 2 hours, 1.1+/-0.9; and 4 hours,
-0.7+/-0.8%) after oral L-methionine. There was an inverse
linear relationship between homocysteine concentration and
flow-mediated dilatation (P<0. 001). Pretreatment with
vitamin c did not affect the rise in homocysteine
concentrations after methionine (0 hours, 13.6+/-1.6; 2
hours, 28.3+/-2.9; and 4 hours, 33.8+/-3.7 micromol/l,
P=0.27), but did ameliorate the reduction in flow-mediated
dilatation (0 hours, 4. 0+/-1.0; 2 hours, 3.5+/-1.2 and 4
hours, 2.8+/-0.7%, P=0.02). GTN-induced endothelium
independent brachial artery dilatation was not affected after
methionine or methionine preceded by vitamin c. CONCLUSIONS:
We conclude that an elevation in homocysteine concentration
is associated with an acute impairment of vascular
endothelial function that can be prevented by pretreatment
with vitamin c in healthy subjects. Our results support the
hypothesis that the adverse effects of homocysteine on
vascular endothelial cells are mediated through oxidative
stress mechanisms.
67.J Cardiovasc Pharmacol 1999
Nov;34(5):690-3
Oral vitamin C reduces arterial stiffness and platelet
aggregation in humans. Wilkinson IB, Megson IL, MacCallum H,
Sogo N, Cockcroft JR, Webb DJ
Clinical Pharmacology Unit & Research Centre, University
of Edinburgh, Western General Hospital, Scotland.
Atherosclerosis is associated with stiffening of conduit
arteries and increased platelet activation, partly as a
result of reduced bioavailability of nitric oxide (NO), a
mediator that normally has a variety of protective effects on
blood vessels and platelets. Increased levels of oxygen free
radicals are a feature of atherosclerosis that contributes to
reduced NO bioavailability and might lead to increased
arterial stiffness and platelet activation. Vitamin C is a
dietary antioxidant that inactivates oxygen free radicals.
This placebo-controlled, double-blind, randomized study was
designed to establish whether acute oral administration of
vitamin C (2 g), would reduce arterial stiffness and in vitro
platelet aggregation in healthy male volunteers. Plasma
vitamin C concentrations increased from 42+/-8 to 104+/-8
microM at 6 h after oral administration, and were associated
with a significant reduction in augmentation index, a measure
of arterial stiffness (by 9.6+/-3.0%; p = 0.016), and
ADP-induced platelet aggregation (by 35+/-13%; p = 0.046).
There was no change in these parameters after placebo.
Vitamin C, therefore, appears to have beneficial effects,
even in healthy subjects. The mechanism responsible is likely
to involve protection of NO from inactivation by oxygen free
radicals, but this requires confirmation. If similar effects
are observed in patients with atherosclerosis or risk
factors, vitamin C supplementation might prove an effective
therapy in cardiovascular disease.
68. Eur Heart J 1999
Nov;20(22):1676-80
Vitamin C improves endothelial function of epicardial
coronary arteries in patients with hypercholesterolaemia or
essential hypertension--assessed by cold pressor
testing.
Jeserich M, Schindler T, Olschewski M, Unmussig M, Just H,
Solzbach U
Medizinische Klinik III, Universitat Freiburg, Freiburg,
Germany.
AIMS: There is evidence that formation of free radicals
increases in patients with hypertension or
hypercholesterolaemia, which may contribute to endothelial
dysfunction of epicardial coronary arteries due to
inactivation of the vasodilator NO. The present study was
designed to test whether the abnormal constriction of
epicardial coronary arteries due to sympathetic stimulation
by the cold pressor test in patients with essential
hypertension or hypercholesterolaemia could be reversed by
administration of the antioxidant vitamin C. METHODS and
RESULTS: In 28 patients without relevant coronary artery
stenosis the cold pressor test was performed before and after
a 3 g infusion of vitamin C. In five normal controls the cold
pressor test led to a similar increase in luminal area before
and after vitamin C (3.7+/-1.3% and 1.9+/-0.8%, ns vs before
vitamin C). In nine hypercholesterolaemic patients the cold
pressor test led to a -14.1+/-2.8% reduction in
cross-sectional area before vitamin C. This constriction was
significantly improved after vitamin C to -7.6%+/-2.0,
P=0.027 vs before vitamin C. In nine hypertensive patients,
the cold pressor test led to a -17.1+/-3.2% decrease in
cross-sectional area before vitamin C, which was improved to
-7.1+/-3.1 after vitamin C, P=0.004 vs before vitamin C. This
increase in luminal area was significant in each group in
comparison with normal controls (each P<0.05).
Administration of saline (placebo group, five patients) had
no significant effect on cold pressor test-induced
constriction (-6.9+/-3.9% before and -6. 8+/-3.7% after
saline). CONCLUSION: The antioxidant vitamin C reverses cold
pressor test-induced vasoconstriction of epicardial coronary
arteries in patients with hypertension or
hypercholesterolaemia. Our data suggest that enhanced
oxidative stress contributes to impaired endothelial function
in this patient population.
69. Proc Soc Exp Biol Med 1999
Dec;222(3):196-204
On the role of vitamin C and other antioxidants in
atherogenesis and vascular dysfunction.
Frei B
Linus Pauling Institute, Oregon State University, Corvallis,
OR 97331-6512, USA. balz.frei@orst.edu
Oxidative stress has been implicated as an important
etiologic factor in atherosclerosis and vascular dysfunction.
Antioxidants may inhibit atherogenesis and improve vascular
function by two different mechanisms. First, lipid-soluble
antioxidants present in low-density lipoprotein (LDL),
including alpha-tocopherol, and water-soluble antioxidants
present in the extracellular fluid of the arterial wall,
including ascorbic acid (vitamin C), inhibit LDL oxidation
through an LDL-specific antioxidant action. Second,
antioxidants present in the cells of the vascular wall
decrease cellular production and release of reactive oxygen
species (ROS), inhibit endothelial activation (i.e.,
expression of adhesion molecules and monocyte
chemoattractants), and improve the biologic activity of
endothelium-derived nitric oxide (EDNO) through a cell- or
tissue-specific antioxidant action. alpha-Tocopherol and a
number of thiol antioxidants have been shown to decrease
adhesion molecule expression and monocyte-endothelial
interactions. Vitamin C has been demonstrated to potentiate
EDNO activity and normalize vascular function in patients
with coronary artery disease and associated risk factors,
including hypercholesterolemia, hyperhomocysteinemia,
hypertension, diabetes, and smoking.
70. Atherosclerosis 1996 Jan
26;119(2):139-50
Effect of ascorbate supplementation on low density
lipoprotein oxidation in smokers.
Fuller CJ, Grundy SM, Norkus EP, Jialal I
Department of Clinical Nutrition, University of
Texas-Southwestern Medical Center, Dallas, USA.
The oxidative modification of low density lipoprotein
(LDL) may play a role in the pathogenesis of atherosclerosis.
Furthermore, evidence of oxidized LDL (ox-LDL) has been found
in vivo. Supplementation of some animal models with
antioxidants has been shown to retard the formation of aortic
atherosclerosis. Ascorbate (vitamin c) is a highly potent
aqueous-phase antioxidant in plasma, which has been shown in
vitro to retard LDL oxidation. Cigarette smokers have reduced
concentrations of ascorbate in their plasma, and their LDL
may be more prone to xidation. Hence, the objective of the
present study was to examine the effect of ascorbate
depletion and supplementation on the propensity of LDL to
oxidize in smokers in a 6-week study. Nineteen healthy
smokers followed a low ascorbate diet (< or = 30 mg/day)
for 2 weeks, then were randomly assigned to receive placebo
or 1000 mg ascorbate per day for 4 weeks. Blood was taken at
0 and 4 weeks of supplementation for study of LDL oxidative
susceptibility. LDL was oxidized with 5 mumol/l copper. The
ascorbate-supplemented group had significant increases in
plasma ascorbate. The placebo group showed no change in the
time course of LDL oxidation between 0 and 4 weeks. However,
the ascorbate-supplemented group has a significant reduction
in LDL oxidative susceptibility as measured by thiobarbituric
acid-reactive substances (TBARS) and the formation of
conjugated dienes. The ascorbate-supplemented group
demonstrated significantly increased lag phase and decreased
oxidation rate at 4 weeks compared to 0 weeks. No changes
were found in the placebo group. The ascorbate-supplemented
group showed no biochemical signs consistent with increased
body iron stores. Supplementation of otherwise healthy
smokers for 4 weeks with 1000 mg ascorbate per day resulted
in increased plasma ascorbate and reduced LDL oxidative
susceptibility.