30. Lipids and lipoproteins in the blood plasma

Parameter	Sample	Reference range
Cholesterol	Serum	4,0 – 5,6 mM
LDL	Serum	0,0 – 3,4 mM
HDL	Serum	0,9 – 1,7 mM

Analysis of lipids
- Enzymatic assay
  - Cholesterol
  - HDL, LDL
  - FFA
  - Triglycerides
- Immunoassay
  - ApoA1
  - ApoB
  - Lp(a)
- Lipoprotein electrophoresis
- Ultracentrifugation – sorted after density
Cholesterol
- Component of cell membrane
- Precursor of steroid hormones and bile acids
Triglycerides
- Energy store
- Risk factor for CVD, acute pancreatitis
HDL
- Contains mostly protein and phospholipid
- Transports cholesterol back to liver from peripheral tissues
- Negative risk factor for CVD
LDL
- Contains mostly cholesterol
- Transports cholesterol from liver to peripheral tissues
- Risk factor for CVD
- Small, dense LDL
  - Greater atherogenic potential than other LDL subtypes
  - Less affinity to LDL receptor
  - Higher endothelial permeability
VLDL
- Contains mostly triglycerides
- Transports triglycerides from liver to peripheral tissues
Lipoprotein(a)
- LDL-like particle
- Contains mostly cholesterol
- Increased level -> increased risk for CVD, atherosclerosis
- Independent predictor of CVD
- Recommended to be tested in people with moderate or high risk for CVD
Chylomicron
- Contains mostly triglycerides
- Transports dietary triglycerides to peripheral tissues and liver
Nonfasting lipid panel
- Measures HDL and total cholesterol
- Screening every 5 years from around 40 y old, from 20y if high risk
Fasting lipid panel
- Measures HDL, total cholesterol, triglycerides, LDL
- LDL can be calculated: LDL = TC – HDL – (TG/5)
Hereditary dyslipidaemias
- Familial hypercholesterolaemia
  - Mutated LDL receptor
  - High risk for AS and xanthoma
- Familial combined hyperlipidaemia
  - Decreased LDL receptor
- Familial hypertriglyceridaemia
  - Can cause pancreatitis
Metabolic syndrome
- Definition: 3 or more of the following:
  - Insulin resistance
  - Hypertension
  - Hypertriglyceridaemia
  - Low HDL
  - Abdominal obesity