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BIOKIMIA KLINIKALNB2234

Dr Farah Fauzi

GANGGUANMETABOLISME LIPID

objectives

• Overview• Lipids as biochemical markers of disease Lipid Profile Test TC, HDL, LDL

• Dyslipidaemia

Blood Lipids

• The major lipids present in the plasma are: fatty acids triglycerides cholesterol lipoproteins (HDL, LDL)

Blood Lipids

• Diagnostic test for blood lipids: lipid profile test.• Recommended in the following individuals with: history of CVD and CHD history of premature CHD (occurring at age <60 years)

other major risk factors for CVD (e.g. T2DM, hypertension)

patients with clinical features of hyperlipidaemia patients whose plasma is seen to be lipaemic

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Lipid Profile Test

• Basic panel consisting of: TG total cholesterol LDL HDL

• Functions: estimate risk of developing CVD monitor responses to treatment of lipid disorders

Lipid Profile Test

• Non-diagnostic samples: e.g. Reflotron Fast results Use test strips Not comprehensive

• Diagnostic samples: e.g. Cobas Use reagents Comprehensive test Reliable

Lipid Profile Test

• 12-hr overnight fasting blood sample is required.• Factors affecting the reliability of screening: High-fat meal the night before test Physical stress (e.g. exercise, infection, surgery)

Medication (e.g. steroids, oral contraceptives)

Underlying disease (T2DM, liver disease, thyroid disease)

Alcohol intake Pregnancy

Lipid Profile Test

LIPID DESIRABLECONCENTRATION

Triglycerides < 1.7 mmol.l-1

Total Cholesterol < 5.2 mmol.l-1

LDL-C < 2.6 mmol.l-1

HDL-C > 1.5 mmol.l-1

OPTIMAL BLOOD LIPID VALUES

Values are for fasting blood samplesSource: National Cholesterol Education Program (NCEP) of the National Institutes of Health (NIH)

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TRIGLYCERIDES

TRIGLYCERIDES

• Body pool: 15 kg in non obese subjects• Plasma pool: 5 – 7 g.• Exogenous source: diet• Endogenous source: liver, adipose tissue• 95 % of body fat is triglycerides!• Triglyceride catabolism is regulated by lipase,

epinephrine and cortisol.• Mostly transported in chylomicrons and VLDL.

TRIGLYCERIDES

(ester bonds)

TRIGLYCERIDES

• Plasma triglycerides range:

TRIGLYCERIDES CONCENTRATIONOptimum < 1.7 mmol.l-1

Borderline high 1.7 – 2.3 mmol.l-1

High 2.3 - 5.6 mmol.l-1

Very high > 5.6 mmol.l-1

Source: National Cholesterol Education Program (NCEP) of the National Institutes of Health (NIH)

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TRIGLYCERIDES

• Elevated TG is an independent risk factor for CVD,more so than cholesterol/LDL levels.• Elevated TG in plasma is associated with: small, dense LDL (pattern B) small HDL particles low HDL levels

TRIGLYCERIDES

• Predisposing factors for hypertrigliceridemia: Obesity Insulin resistance, T2DM Liver, renal diseases High CHO diet Pregnancy Excess alcohol intake Defective lipoprotein lipase enzyme Medications (corticosteroids, estrogen)

TOTAL CHOLESTEROL

TOTAL CHOLESTEROL

• Found only in animals.• Important component of membranes, steroid hormones,

bile and Vitamin D.• Exogeneous source: diet• Endogenous source: liver• 70% of cholesterol is found

in cellular components.• 30% is in the plasma

(⅓ free form,⅔ esterified )

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TOTAL CHOLESTEROL

TOTALCHOLESTEROL

LDLVLDL HDL

TOTAL CHOLESTEROL

• Plasma total cholesterol range:

TOTAL CHOLESTEROL CONCENTRATIONOptimum < 5.2 mmol.l-1

Borderline high 5.2 – 6.2 mmol.l-1

High > 6.2 mmol.l-1

Source: National Cholesterol Education Program (NCEP) of the National Institutes of Health (NIH)

TOTAL CHOLESTEROL

• Elevated TC levels are associated with: Diet high in saturated fats Men > 45 yrs, women > 55 yrs Low levels of HDL (< 1.0 mml.l-1) Obesity Smoking Hypertension T2DM, CVD Family history LIPOPROTEINS

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Why are lipoproteinsimportant?• sdad

Lipoproteins

B

Tg Tg TgTg Tg Tg

TgTgTg

CE CECE CECE

B

CE CECE CECE

CE TgCE TgCE Tg

B

CE TgCE TgCE Tg

B

CECECE

A

Tg

CECECE

A

Tg

CECECE

A

Tg

Tg Tg TgTg Tg Tg

TgTgTg

B

Tg Tg Tg Tg TgTg Tg Tg Tg TgTg Tg Tg Tg TgTg Tg Tg Tg TgTg Tg Tg Tg TgTg Tg Tg Tg TgTg Tg Tg Tg Tg

Tg Tg TgTg TgCE

chylomicron VLDL LDL HDL

Lipoproteins

Fraction Diameter(nm)

Major lipids Majorapo

TG(%)

Chol(%)

Protein(%)

Chylomicrons 1000 Dietary TG B48 90 5 1

VLDL 30-80 Liver TG B100 65 13 10

LDL 20-25 CholesterolCholesteryl ester

B100 10 45 20

HDL 9-15 Cholesteryl esterPhospholipid

A1 2 18 50

Source: Frayn K.N. 2003. Metabolic Regulation: a Human Perspective

• Separation of lipoproteins through ultracentrifugation.• More buoyant lipoproteins ( ↑ fat content) will float at the

top.

Lipoproteins

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LDL

LDL

• Low density lipoproteins (↓apoproteins)

• Majority of the cholesterol in the blood is packagedas LDL.• Transport cholesterol from liver to peripheral tissues.

LDL

• Elevated levels of LDL have been stronglyassociated with an increased risk of CVD.• Hence the name – ‘bad cholesterol’…• But not all LDL are bad!• Sizes and compositions determine the

atherogenicity of an LDL particle.

LDL-C

• Plasma LDL cholesterol range:

LDL-C CONCENTRATIONOptimum < 2.6 mmol.l-1

Near optimum 2.6 – 3.3 mmol.l-1

Borderline high 3.4 – 4.1 mmol.l-1

High > 4.2 mmol.l-1Source: National Cholesterol Education Program (NCEP) of the National Institutes of Health (NIH)

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LDL subclasses

• LDL particles are separatedinto 4 major subclassesbased on density.• Density is related to TG

content.• LDL I, II: pattern A• LDL III, IV: pattern B

Rizzo et al. 2009. Atherogenic dyslipidemia and oxidative stress: a new look. Trans. Res. 153: 217- 223.

I II III IV

Small, dense LDL

• LDL pattern B: risks for CVD/CHD.• More atherogenic than larger, buoyant LDL (A).• Atherogenicity is attributed to: lower binding affinity to LDL receptor on liver penetrates arterial wall faster than larger LDL increased susceptibility to oxidation

pattern B

pattern A

oxidation

endothelial cells

atherosclerosis LDL patterns

diet high in SAT-fatT2DM

obesity

pattern A pattern B

3.3 mmol/l

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HDL

HDL

• High density lipoproteins (↑apoproteins, ↓TG)

• Transport excess cholesterol from peripheraltissues back to liver for excretion.• Process: reverse cholesterol transport.

HDL

BloodBloodPeripheralTissuesPeripheralTissues

LiverLiver

excess cholesteroltransported by HDL

bile

HDL

• Strong association between high HDL-C andprotection against CVD.• Hence the name – ‘good cholesterol’…• However, sizes and compositions determine the

functionality of an HDL particle.

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HDL-C

• Plasma HDL cholesterol levels:

HDL-C CONCENTRATIONOptimum > 1.6 mmol.l-1

Acceptable 1.0 – 1.6 mmol.l-1

Low < 1.0 mmol.l-1Source: National Cholesterol Education Program (NCEP) of the National Institutes of Health (NIH)

HDL subclasses

• HDL subclasses: HDL2 (large buoyant, more protective) HDL3 (small, less protective)

• Apolipoprotein composition: Apo A-I (cardioprotective) Apo A-II (controversial* ??) Absence of apo A-I (non-functional HDL)

*Chan et al. Apolipoprotein A-II: Evaluating its significance in dyslipidaemia,insulin resistance, and atherosclerosis. Ann. Med. 2011.

HDL-C

• High HDL levels are associated with: females exercise habit diet high in MUFA and PUFA

“Abnormal levels oflipids in the blood”

DYSLIPIDEMIA

primaryvs.

secondary

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DYSLIPIDAEMIA

• Manifested as one or more of the following: elevated total cholesterol (TC) elevated low-density lipoproteins (LDL) elevated triglycerides (TG) decreased high-density lipoproteins (HDL)

• 2 categories: Primary dyslipidaemia

(genetic disposition) Secondary dyslipidaemia

(lifestyle, disease)

1 DYSLIPIDAEMIA

• Also known as “familial” dyslipidemia.• Single or multiple gene mutations that affect: LDL receptor lipoprotein lipase enzyme ABCA-1 transporter CETP

• Result in overproduction ordefective clearance of lipids.

1 DYSLIPIDAEMIA

• Associated with very high levels of cholesterol and TGin the blood.• Classified according to the Fredrickson

classification, based on the pattern of lipoproteinthat is dominant.

Fredrickson Classification

Type Elevated particles Associated clinical disorders Serum TC Serum TG

I Chylomicrons Lipoprotein lipase deficiency,apolipoprotein C-II deficiency

↔ ↑↑

IIa LDL Familial hypercholesterolemia,polygenic hypercholesterolemia,

nephrosis, hypothyroidism,familial combined

hyperlipidemia

↑↑ ↔

IIb LDL, VLDL Familial combinedhyperlipidemia

↑↑ ↑

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Fredrickson Classification

Type Elevated particles Associated clinical disorders Serum TC Serum TG

III IDL Dysbetalipoproteinemia ↑ ↑

IV VLDL Familial hypertriglyceridemia,familial combined

hyperlipidemia,hypertriglyceridemia, diabetes

↔↑ ↑↑

V Chylomicrons,VLDL

Diabetes ↑ ↑↑

Familial Hypercholesterolaemia

• Type IIa, autosomal dominant: Heterozygous: LDL 2x Homozygous: LDL 5 – 7x

• Onset of coronary artery disease: Heterozygous: 30 – 40 yrs Homozygous: 0 – 20 yrs

• Expression of LDL receptors decreased accumulationof LDL in circulation.• Signs: xanthomas in tendons and cutaneous.

Familial Hypercholesterolaemia

• Dyslipidemia that results from existing diseases orconditions.• Result in overproduction or defective clearance of TG

and LDL, or underproduction of HDL.

2 DYSLIPIDAEMIA

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2 DYSLIPIDAEMIA

• Hypothyroidism; liver disease; nephroticsyndrome; coronary artery diseaseHypercholesterolemia

• Obesity, Type-2 DM, pregnancy, alcohol,stress, acute hepatitis, drugsHypertriglyceridemia

• Obesity, Type-2 DM, malnutrition, cigarettesmoking

Low HDL

Disturbances ininsulin functions

can result indyslipidemia….

INSULIN

Insulin

• Insulin promotes glucose uptake into cells.• Insulin also promotes lipogenesis and inhibits lipolysis in

adipose tissue.• In insulin-resistant state, cells do not respond to insulin.

Insulin Resistance

Increased lipolysis increased fatty acids (TG) incirculation fatty acid deposition in liver increasedproduction of VLDL accumulation of TG in circulation

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Atherogenic Dyslipidaemia

• Typical patterns of dyslipidaemia in T2DM and obeseindividuals:

elevatedTG

lowHDL

small,dense LDL

ATHEROGENICLIPOPROTEINPHENOTYPE

Atherogenic Dyslipidaemia

Summary

• 2° dyslipidemia is becoming more common due tounhealthy lifestyle.• TG is a prominent risk for CVD/CHD .• Insulin resistance and obesity are associated with

‘atherogenic lipoprotein phenotype’.• Measurement of HDL and LDL subclasses provide a

better picture for lipid diagnostics.

BIOKIMIA KLINIKALNB2234

Dr Farah Fauzi

GANGGUANMETABOLISME LIPID