Serum Triglyceride Test 20 Serum Triglyceride Test Fifth Stage Student By Dr. Sakar Karem Abdulla M.Sc. Clinical Biochemistry

Triglyceride TG are the major fat in the human diet and comprise 85-90% of body lipids. TG are serve as energy reserve for the body and store in adipose tissue as lipid droplets. TG in human plasma can be exogenous (derived from food) or can be endogenous (synthesized in the body). TG contain a glycerol backbone to which three fatty acid are esterified.

Triglyceride structure

Digestion of Triglyceride Action of bile salts: which emulsified dietary fat and increase surface area for attacked by pancreatic digestive enzyme. Action of pancreatic lipase: major enzyme that digest dietary TG to free fatty acid and 2-monoacylglycerol. Secretion of bile salt and pancreatic enzyme are stimulated by cholecystokinin.

Absorption and transport of dietary TG The FA and 2-monoacylglycerol produced by digestion are packaged into micelles which is tiny microdroplet emulsified by BS and absorb to epithelial cell of the intestine. Within intestinal epithelial cell FA and 2- monoacylglycerol are condensed to form TG. Intestinal cell package TG with Cholesterol, protein, phospholipid and fat soluble vitamin in chylomicron.

Digestion and absorption of triglyceride

Fate of dietary TG in chylomicron

Synthesis of TG TGs are produced in liver and adipose tissue. In liver glycerol-3-phosphate is produced from glycerol by glycerol kinase or from DHAP derived from glycolysis. In adipose tissue glycerol-3-phosphate is produced only from DHAP derived from glycolysis.

Synthesis of TG

Fate of VLDL-Triglyceride

Storage of TG in adipose tissue

Release of FA from adipose tissue TGs

Hypertriglyceridemia Hypertriglyceridemia: means high plasma concentration of triglyceride that include two types: Primary Hypertriglyceridemia Secondary Hypertriglyceridemia

Primary Hypertriglyceridaemia Chylomicron syndrome Familial lipoprotein lipase deficiency Apolipoprotein C2 deficiency Familial dysbeta-lipoproteinaemia Familial hypertriglyceridaemia Familial combined hyperlipidaemia

Secondary Hypertriglyceridaemia Alcohol Obesity Diabetes mellitus Chronic kidney disease Hypothyroidism Certain drugs e.g. estrogen, B-blocker

Reagents composition R1 Buffer: magnesium chloride, chloro-4- Phenol, preservative R2 Enzyms: lipase, peroxidase, glycerol 3 phosphate oxydase, glycerol kinase, 4 – Amino-antipyrine, ATP R3 Standard: Triglyceride 200mg/dl Reagent preparation: add the content of vial R2 into vial R1, mix gently until complete dissolution.

Principle of S.TG test Triglycerides→ glycerol + free fatty acids(by Lipase) glycerol+ ATP→ glycerol 3 phosphate + ADP (by glycerokinase) glycerol 3 phosphate + O2 → dihydroxyacetone- phosphate+H2O2(by glycerol 3 phosphate oxydase) H2O2+4-chlorophenol+PAP → quinoneimine + H2O (by peroxidase) The absorbance of coloured complex proportional to the concentration of cholesterol in the sample

S.Triglyceride test Patient should be fast overnight for 12hr, only allowed water to drink. Patient should be on usual diet for two weeks preceding the test.

Test Procedure

calculation S.Triglyceride=Abs.Assay/Abs.standard  x conc.standard (200mg/dl) Normal value TG 35-160 mg/dl