Pediatric Nutrition in Practice

Hypercholesterolemia 235

3

Lipoproteins

Lipids are transported in the plasma by lipopro-
teins ( table 1 ), which carry apoproteins that medi-
ate their receptor binding and tissue uptake. Tri-
glyceride-rich chylomicrons are formed in intesti-
nal epithelial cells from absorbed dietary fats, are
secreted into the lymph and consecutively trans-
ported into the blood stream. Chylomicron tri-
glycerides are hydrolyzed by lipoprotein lipase
linked to the capillary endothelium. Lipolysis
products are taken up and utilized by tissues. Li-
poprotein lipase also hydrolyzes triglycerides in
VLDL synthesized in the gut and liver. This lipol-

ysis results in the formation of intermediate-den-

sity lipoproteins and further of LDL in the circula-

tion. LDL are rich in cholesterol and apoprotein

B100, bind to apoprotein receptors in hepatocytes

and peripheral cells and transport cholesterol to

tissues. High plasma concentrations of LDL lead

to increased deposition of cholesterol in the vas-

cular intima, atherosclerotic vascular damage and

premature coronary artery disease. LDL choles-

terol can be measured directly by using ultracen-

trifugation but in clinical practice is usually deter-

mined from after an overnight fast using the Frie-

dewald formula: LDL cholesterol (mg/dl) = total

cholesterol (mg/dl) – HDL cholesterol (mg/dl) –

Ta b l e 1. Characteristics of plasma lipoproteins

Chylomicrons VLDL LDL HDL

Major lipids Triglycerides Triglycerides Cholesterol Cholesterol, phospholipids
Major apoproteins A, B48, C B100, C, E B100 A, E
Formation Gut Gut, liver VLDL catabolism Gut, liver
Major function Transport of
exogenous
triglycerides

Transport of endogenous

triglycerides from the liver

to extrahepatic tissues

Cholesterol transport

to extrahepatic tissues

Cholesterol transport from

extrahepatic tissues to the

liver

Ta b l e 2. Assessment of plasma lipid, lipoprotein and apoprotein concentrations (mg/dl) in children and adolescents

Lipid Low Acceptable Borderline
(∼75th centile)

Increased

(∼95th centile)

Total cholesterol – <170 170 – 199 ≥200
LDL cholesterol – <110 110 – 129 ≥130
Non-HDL cholesterola – <123 120 – 144 ≥145
Triglycerides
0 b – 9 years – <75 75 – 99 ≥100
10 – 19 years – <90 90 – 129 ≥130
HDL cholesterol <35 >45 35 – 45 –
Apolipoprotein A-1 <115 >120 115 – 120 –
Apolipoprotein B – <90 90 – 109 ≥110
Lipoprotein(a) <30 >30

Modified from refs. 3, 8 and 9. Cholesterol in mg/dl × 0.0259 = mmol/l; triglycerides in mg/dl × 0.01 = mmol/l.
a Non-HDL cholesterol = total cholesterol – HDL cholesterol.
b Triglyceride concentrations above these reference values are frequently observed in infancy when dietary fat in-
takes are high and fasted blood samples cannot be obtained.

Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 234–238
DOI: 10.1159/000375191