homocysteine: an overlooked biomarker in clinical medicine

Homocysteine – The “H factor”

Dr. Furquan Alam MD (Biochemistry)

Assistant Professor

Glocal Medical College, SSH & RC, Saharanpur

An Overlooked Biomarker in

Clinical Medicine

Why it is

important to

discuss?

07 March 2017 Dr. Furquan Alam 2

• High levels of homocysteine, or a high "H

Score," predicts the risk of more than 100

diseases and medical conditions including

CVD, CVA, Diabetes, Renal Disease etc.

• Elevated Plasma Homocysteine is an

important, Strong, Graded and

Modifiable Risk Factor.

• ↑ Hcy at baseline also Predicts higher long

term Mortality. 07 March 2017

Dr. Furquan Alam 4

Factors affecting blood Homocysteine Level


What is

homocysteine?


Introduction

• Homocysteine (Hcy), a sulphur containing amino acid

with a molecular weight of 135.2 Dalton.

• Derived from Methionine

• First isolated from a urinary bladder stone in 1933 by

Vincent du Vigneaud.

• Later Vincent du Vigneaud received the Nobel Prize in

chemistry in 1955.


9

Homocysteine

Three forms in plasma/serum

Sulfuration

07 March 2017 Dr. Furquan Alam

• Varying forms

• 1% free

• 70-80% bound to albumin via a disulfide link

• 20-30% either as a homocysteine dimer or a

cysteine-homocysteine-mixed disulfide.

* The type(s) of species responsible for the CVD

pathology have yet to be determined.


Homocysteine

• Normal levels :

• In serum: 13-18 µmol/L

• In plasma: 10- 15 µmol/L

• In pediatric patients: 3.7-10.3 µmol/L

• Desirable Serum Level: <10 µmol/lit, preferably between 7-8 µmol/lit.

Hyperhomocysteinemia:

Mild

• 15 – 30 µmol/lit

Moderate

• 30 -100 µmol/lit

Severe

• >100 µmol/lit


Hyperhomocysteinemia


Methionine

Homocysteine

Cystathionine

Cysteine

Cystathionine synthase

Cystathioninase

Vitamin B6

Vitamin B6

Methyl transferase

Homocysteine metabolism

S-Adenosyl

methionine

S-Adenosyl

homocysteine

Acceptor

Methylated

acceptor

【Remethylation】

【Trans-sulfuration】

B12

Methyl B12

Methyl THF

THF


Increase Homocysteine concentration

Methionine

Homocysteine

Cystathionine

Cysteine

Cystathionine synthase

Cystathioninase

Vitamin B6

Vitamin B6

Methyl transferase

【Nutritional deficiencies,

Life style , Drugs ,

Some diseases 】

【Genetic deficiency】


Etiology of Hyperhomocysteinemia

• Genetic mutations

• Nutritional deficiencies

• Disease states

• Drugs


Genetic Mutations

5-methyleneterahydrofolate reductase (MTHFR)

polymorphism due to a point mutation on chromosome 1.

Prevalence MTHFR

15% in European, Middle Eastern and Japanese

1.4% or less in African Americans.

Mild to moderate condition

Higher risk of neural tube defects and pregnancy loss

Mother with the MTHFR mutation who have normal

homocysteine levels are not at increased risk for clots.


Nutritional deficiencies

• Folate deficiency

• Vitamin B12 (Cobalamine) deficiency

• Vitamin B6 (Pyridoxine) deficiency


Disease states

• Cystathione β-synthase deficiency • Homocysteinuria

• Methionine synthase deficiency

* Both are rare autosomal recessive disorders that are correlated with Hyperhomocysteinemia and vascular thrombosis.

• Chronic renal failure regardless of etiology, duration, or type of dialysis

• Severe psoriasis • Possibly through increased cell turnover

• Pernicious anemia • Cobalamine deficiency


Drugs That Raise Homocysteine Levels

• A number of prescription drugs and natural compounds

can elevate blood levels of homocysteine by interfering

with folate absorption or metabolism of homocysteine.

Caffeine Niacin

Cholestyramine Nitrous oxide

Colestipol Pemetrexed

Fenofibrate Phenytoin

Levodopa Pyrimethamine

Metformin Sulfasalazine

Methotrexate Carbamazepine


Drugs

• Cholestyramine (reduces cholesterol in blood) • Impairs folate absorption

• Methotrexate (treatment of psoriasis) • Depletes folate metabolites

• Anti-epileptics (carbamazepine, phenytoin) • Lower folate concentrations

Tobacco and caffeinated coffee


Who should have their Homocysteine level tested?


Sample Collection & Patient Preparation

Sample type: Blood (Serum/Plasma)

It can be measured at any time of day but preferably

overnight fasting and morning Sample. No special

preparations.

Once blood is drawn, Serum should separated within

1 hour.

serum or plasma is first treated with a reducing agent

that converts all Hcy species into the reduced form which

is measured either directly or after derivatization.

Homocysteine levels increase ~10% for every hour the serum/plasma is not separated from the RBCs at room temperature.


How is the Homocysteine level measured ?

Currently, there are three main tHcy test methods

available to the clinical laboratories. They include:

• Chromatographic method (HPLC) :

• developed in the early 1980s, and is mainly used in

research laboratories.

• Immunoassay method:

• developed in the mid 1990s, and has been

automated for special immunoassay instruments.

• Enzyme cycling method:

• Latest, developed in last few years, Used on any

Automated clinical chemistry analyzer, and is quickly

becoming the preferred method for clinical

laboratories. 07 March 2017 Dr. Furquan Alam 24

Advantages and Disadvantages of these

tHcy test methods:


http://www.who.int/mediacentre/factsheets/fs310/en/ 07 March 2017 Dr. Furquan Alam 26

Hyperhomocysteinemia and CVD

Cardiovascular Disease is the world’s

number one killing disease.

constituting about 30% of annual

worldwide deaths.

Up to 80% of all heart attacks occur in

people with normal cholesterol

In 25% of adults, the first sign of heart

disease is sudden death from a heart

attack.

Copyright 2010 - Drjoeesposito.com

July, 2006 Vol. 3 No. 4 Homocysteine - Revisited


The right idea but the wrong era

Dr Kilmer McCully, a researcher who graduated

from Harvard Medical School in the mid-1960s and

came up with the hypothesis that moderate

elevations of homocysteine could lead to heart

attacks and strokes.

It was the time that the cholesterol-heart-attack

theory was gaining tremendous momentum and Mc

Cully’s hypothesis clearly challenged its future.

He found himself moved down to the basement,

funding for his research dried up and he was

eventually asked to leave Harvard.


Prevalence of hyperhomocysteinemia is not insignificant:

• General population: 5 - 10%

• Elderly population: 30 - 40%

• Pts with vascular disease: 20 - 40%.

Epidemiology

Annu Rev Med 1998;49:31-62. HCY and cardiovascular disease. Refsum H, Ueland PM, et.al. Jacques PF, Bostom AG, Wilson PW, et.al. Determinants of plasma total HCY concentration in the Framingham Offspring cohort. Am J Clin Nutr. 2001;73:613-621


Why is Homocysteine harmful?

Experiments on arteries of both animals

and humans with an elevated level of

homocysteine showed that homocysteine

level in blood is an independent risk

factor for atherosclerotic vascular disease

affecting the coronary (arteries supplying

the heart), cerebral (arteries supplying the

brain) and peripheral arteries (supplying

the rest of the body).

Copyright 2010 - Jeremy E. Kaslow, M.D. - all rights reserved


Homocysteine and disease

Bipolar Disorder

PCOS


Risk Factors for CVD Non-modifiable

Advancing age

Heredity or family

history

Gender

Ethnicity or race

Major modifiable

High blood pressure.

Abnormal blood lipids

Tobacco use.

Physical inactivity

Obesity

Diabetes mellitus

Unhealthy diets

Novel Risk Factors

Excess homocysteine in

blood

Inflammation e.g. CRP

Abnormal blood coagulation:

e.g. Fibrinogen

Lp ( a)


What Homocysteine Does to Arteries

Homocysteine Lysyl residues of collagen

Interferes collagen crosslinking & bind to fibrillin

endothelial dysfunction.

Homocysteine thiolactone (free radical)

Thiolates LDL particles

Aggregate

Endocytosed by macrophages

↑ed tendency for atherogenesis

07 March 2017

Dr. Furquan Alam

33

What Homocysteine Does to Arteries

It changes coagulation factor levels so as to encourage

blood clot formation

It causes the smooth muscle cells that support the

arterial wall to multiply-part of the atherogenic process.

Homocysteine activation of Hageman factor

↑platelet adhesiveness life threatening intravascular

thrombosis.

The net result is a threefold increase in heart attack risk

（Loscalzo et al., 1998;Maxwal., 2000 ）


07 March 2017 35

If cholesterol and a high-fat diet are

the key culprits in heart disease,

why haven't we seen more of a

reduction in our number-one

disease killer over these past

several decades?


Homocysteine vs. Cholesterol

Researchers conclude that homocysteine

is up to 40 times more predictive than

cholesterol in assessing cardiovascular

disease risk.

Many studies concluded that the risk of

arteriosclerotic vascular disease does in

fact increase with the homocysteine level,

regardless of whether cholesterol is

normal or elevated.

heart44; 11-01-2004


Abnormally raised insulin seen in most diabetics stops the body from lowering and maintaining a healthier homocysteine level.

One third of the diabetic patients had elevated blood Homocysteine

Type 2 diabetic patients with elevated homocysteine levels are nearly 200% more likely to die from a heart attack within 5 years than those with normal Homocysteine levels

Homocysteine & Diabetes

Vasc Health Risk Manag. 2010; 6: 327–332.


• tHcy levels are highly elevated in renal failure

patients.

• Impaired renal excretion and/or tubular

metabolism of Hcy, and extra renal factors, like

secondary vitamin deficiencies (e.g., in

connection with hemodialysis), genetic causes

and altered Hcy metabolism are among the

reasons.

Homocysteine & Renal Disease/Failure


Homocysteine & Osteoporosis

An increased homocysteine level appears to be a

strong and independent risk factor for

osteoporotic fractures in older men and women

high serum homocysteine concentration may

weaken bone by interfering with collagen cross-

linking, thereby increasing the risk of

osteoporotic fracture

N Engl J Med. 2004;350:2033-2041


Homocysteine & Pregnancy

Homocysteine conc. decreased in pregnancy due to

• Hemodilution

• Raised GFR

• Hormonal changes of pregnancy

• Increased fetal uptake


Homocysteine & Pregnancy Complication


Hyperhomocysteinemia, Pregnancy Complications and the Timing of Investigation Re´gine P. Steegers-Theunissen,et al. VOL. 104, NO. 2, AUGUST 2004 The American College of Obstetricians and Gynecologists as accessed on 29th April 2012

NTDs

Other congenital defects

spontaneous

miscarriage recurrent abortion

IUGR

Pre-eclampsia

placental abruption

Pre-term labour

Intrauterine fetal death

Hyperhomocysteinemia


Homocysteine & Pregnancy Complication

Values in Early Pregnancy are more reliable.

Folic acid supplements decrease homocysteine

levels during pregnancy and substantially

reduce the risk of central nervous system

malformations

2004 issue of "Clinical Chemistry


5,883 women in Norway were followed through

14,492 pregnancies with their outcomes and

complications recorded against their

homocysteine levels.

The Hordaland Homocysteine Study. JAMA 1995;274:1526–33


Higher homocysteine level and % Rise in

Risk of Complications

0

20

40

60

80

100

120

Pre -eclampsia Premature

Birth Very LowBirth Weight

32 38

101

07 March 2017 48

Homocysteine & PCOS

• In PCOS early atherosclerosis is not exclusively

dependent on hyperinsulinemia and elevated

lipid profile – PCOS patients are exposed to

significantly higher homocysteine levels which

might increase the cardiovascular disease risk.

Loverro G, Lorusso F, Mei L, Depalo R, Cormio G, Selvaggi L. The plasma homocysteine

levels are increased in polycystic ovary syndrome. Gynecologic and obstetric

investigation. 2002 Jun 6;53(3):157-62.


Homocysteine and Alzheimer's Disease

People with the highest levels of blood homocysteine had

almost double the risk of Alzheimer's and other dementia as

compared to people with lower blood homocysteine.

Increase of 5 micromoles of homocysteine per liter of blood

increased the risk of Alzheimer's Disease by 40%.

The mechanism linking Hcy and Alzheimer’s disease is

poorly understood, it is possible that Hcy is toxic to brain

cells, possibly by excessive stimulation, resulting in

neuronal damage due to CNS ischemia.

New England Journal of Medicine", 2002;346(7):466-468.

: 07 March 2017 Dr. Furquan Alam 50

Homocysteine and Alzheimer's Disease


CANCER – CUT YOUR RISK BY A THIRD

Cancer is triggered by damage to DNA – and having

a high homocysteine level means your DNA is more

vulnerable to damage

homocysteine levels have been found to be a very

good indicator of whether cancer therapies are

working. The homocysteine level rises when tumours

grow, and falls when they shrink.

Cancer Council Victoria 2011 07 March 2017 Dr. Furquan Alam 52

REDUCE YOUR RISK OF DEATH FROM ALL

CAUSES

One of the best ways to extend your lifespan is by

reducing your homocysteine level. With every five-

point decrease in your H score, you will gain:

A 49% reduced risk of death from all causes.

A 50% reduced risk of death from cardiovascular

disease .

A 26% reduced risk of death from cancer .

A 104% reduced risk of death from causes other

than cancer or heart disease 2005 Orthomolecular conference


Homocysteine New studies

Raised Homocysteine levels are seen in sufferers

of chronic fatigue syndrome [CFS]

Homocysteine accelerates the aging process by

shortening telomeres.

RA patients are 20-30% more likely to have

higher Homocysteine levels than the normal

population

In traditionally-treated dialysis patients, 91% of

HD and 67% of PD patients have elevated Hcy

levels

Nutridisk 2011


Should Hyperhomocysteinemia Be Treated?

Arguments favoring treatment

Approximately 80 clinical and epidemiological studies

suggest that elevated homocysteine is a risk factor for

coronary heart , cerebro vascular, and peripheral

vascular diseases

Risk factor treatment of cardiovascular disease is an

accepted clinical practice

Treatment is inexpensive and unobtrusive under

medical supervision

Coronary Heart Disease ,Homocysteine,heart disease and stroke 2008 07 March 2017 Dr. Furquan Alam 56

Should Hyperhomocysteinemia Be Treated?

Arguments against treatment

Many prospective studies shows that

Lowering homocysteine with folic acid

supplementation is safe, but does not reduce

the risk of vascular events

The American Heart Association has not yet

called hyperhomocysteinemia (high

homocysteine level in the blood) a major risk

factor for cardiovascular disease.

Coronary Heart Disease ,Homocysteine,heart disease and stroke 2008 07 March 2017 Dr. Furquan Alam 57

Reduction in Homocysteine Levels

• Supplementation of B vitamins

• Folate, B6, and B12

• Restriction of methionine containing

substances

• Sesame seeds, brazil nuts, fish, meats

• Exercise


Homocysteine and Nutrition:

The Vitamin Connection

Screening for HCY may indirectly assess a

patient’s vitamin B6, B12 and folate status, thus

offering a useful window into the patient’s

nutrition profile.

Total homocysteine measurements are now

recommended to screen for vitamin deficiency in

both the general and high risk populations.

Homocysteine may, in fact, be a more sensitive

marker of Vitamin B12 , B6 or folate deficiency

and… may precede deficiency of circulating

vitamins.

Screening for vitamin B12 and folate deficiency in older persons. Am J

Clin Nutr 2003; 77: 1241-7. 07 March 2017 Dr. Furquan Alam 59

Vitamins and Food sources

Folic acid - Green leafy vegetables (e.g.

spinach, broccoli), legumes (e.g. lentils,

chick peas, lima beans), orange

Vitamin B6 - Meat, poultry, fish, green

leafy vegetables, legumes, seeds,

potatoes, cantaloupe, milk, egg yolks,

cereals, grains, wheat, wheat germ.

Vitamin B12 - Beef, poultry, fish

(particularly crab, oyster, salmon and

herring), liver, kidney, soy, fruit juice, dairy

products, egg yolks, fortified cereals, breads 07 March 2017 Dr. Furquan Alam 61

Folic acid fortification of enriched grain

products in the late 1990’s appears to

have resulted in a decline in stroke and

ischemic heart disease deaths.

There has been evidence of three-fold

acceleration in the decline of stroke

related mortality that has been

temporarily related to folic acid

fortification.

American Journal of Clinical Nutrition, Vol. 86, No. 5, 1563S-1568S, November 2007


RDA for Vitamins B6, B12 and Folate

Vitamin B6 2 mg

Vitamin B12 6 mcg

Folate 400 mcg


Treatment of hyperhomocysteinemia

Recheck every 6

months 64

Take Home Message

The lower the Hcy level, the lower the risk of

developing coronary artery disease and

suffering fatal heart attacks and strokes .

Your Homocysteine level is excellent single

indicator of whether you are going to live a long

and healthy life, or die young. A high

Homocysteine level is a greater risk factor for

many health problems

Without any doubt, the demand for plasma

homocysteine testing will increase soon,

perhaps explosively.


Take Home Message

Hcy test is Costly but definitely not costlier than you

Life.

Tobacco, caffeine and excessive intake of

Methionine rich diet (Meat, Fish etc.) should be

avoided.


Prevention is always better than cure


homocysteine: an overlooked biomarker in clinical medicine

Health & Medicine