Biology: Triglycerides and Lipid Profile

Triglycerides

• Triglycerides are the main lipids present in human plasma, making up about 95% of adipose tissue lipids.
• They are synthesized in the intestinal mucosa by the esterification of glycerol and free fatty acids.

When is Triglyceride Testing Requested?

• Lipid profile, including triglycerides, is commonly tested when you reach the age of 40.
• It is also requested if you have risk factors for cardiovascular disease, such as:
  • Family history of high cholesterol or heart disease in close relatives.
  • Being overweight or obese.
  • Diabetes mellitus.
  • High blood pressure (hypertension).
  • Smoking cigarettes.

Test Preparation

• Previously, fasting for 12 hours was recommended, as triglycerides increase after a meal for several hours.
• However, studies now show that readings after a meal are just as useful as fasting levels.

Assay Principle

• Triglycerides are determined by enzymatic hydrolysis with lipase enzyme.
• The absorbance of rosy-colored Quinoneimine, which is proportionate to TG concentration, is measured spectrophotometrically at λ=500 nm.

Procedure

• Assay conditions: wavelength 500 nm, cuvette 1 cm light path, temperature 37ºC or 15-25ºC.
• The patient should be fasting for 10 to 14 hours before sampling.
• The best specimen is unhemolysed serum, which should be analyzed on the day of collection.
• Specimens are stable for 7 days when stored at 4C, several months at –20C, and for years at –70C.

Calculations and Expected Values

• TG concentration (mg/dL) is calculated using the concentration of the standard.
• Conversion factor: mg/dl x 0.0114 = mmol/l.
• Expected values: males 40 – 160 mg/dL, females 35 – 135 mg/dL.
• Suspicious >150 mg/dl, elevated >200 mg/dl.

Interpretation of Results

• Elevated levels of triglycerides are associated with a high risk of severe atherosclerosis.
• High triglyceride levels can be inherited or secondary to disorders, including diabetes mellitus, nephrosis, biliary obstruction, and metabolic disorders associated with endocrine disturbances.
• High triglycerides can lead to pancreatitis.

Causes of High Triglycerides

• Factors that can cause high triglycerides include a high fat or high sugar diet, high intake of alcohol, obesity, and diabetes.
• Genetic factors can also increase triglyceride levels.
• Lifestyle changes can be effective in reducing triglyceride levels.

Additional Information

• If you are diabetic and your blood glucose concentrations are out of control, triglyceride concentrations will be very high.
• Triglyceride levels in the blood may change dramatically after a meal.