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Lipoprotein:- Part 5 – Triglycerides (TG)

January 8, 2023Chemical pathologyLab Tests

Table of Contents

  • Triglycerides (TG)
      • Sample for Triglycerides (TG)
      • Precautions for Triglycerides (TG)
      • Indications for Triglycerides (TG)
      • Definition of Triglyceride (TG)
      • Pathophysiology of Triglycerides (TG)                                                                                                                                   
      • Source of Triglyceride:
      • Triglyceride structure:
      • Triglyceride catabolism:
      • Storage of the Triglycerides (TG):
      • Normal Triglycerides (TG)
      • Critical values of triglycerides are:
      • Increased Triglycerides values are seen in the following:
      • Decreased Triglycerides level is seen in:
      • Management of Hypertriglyceridemia:
      • Critical value:
      • Questions and answers:

Triglycerides (TG)

Sample for Triglycerides (TG)

  1. This is done ideally on the fasting serum of the patient. Venous blood is taken.
  2. Fasting for 12 to 14 hours is required.
  3. Plasma with EDTA can be used.
  4. The sample is stable at 4 °C for 7 days and at -20 °C for 3 months.
  5. If plasma is used, then multiply the result by 1.03.

Precautions for Triglycerides (TG)

  1. Patients must have at least fasting for 12 hours.
  2. If  TG in males> 160  mg/dL and females> 135 mg/dL, then two more samples should be done in the next 6 to 8 weeks.
  3. Intake of the fatty meal may increase the TG.
  4. Alcohol intake increases TG.
  5. In pregnancy, the TG level is raised.
  6. Take H/O drubs like oral contraceptives and estrogen to increase the TG level.
  7. Take H/O ascorbic acid, clofibrate, and colestipol to decrease the TG level.

Indications for Triglycerides (TG)

  1. This is done to evaluate the causes of atherosclerosis (Coronary artery disease).
  2. This is done to evaluate the turbid serum (milky).
  3. Triglyceride is part of the lipid profile.
  4. Triglyceride is advised in a patient with a suspected fat metabolism disorder.

Definition of Triglyceride (TG)

  • Triglyceride (TG) is primarily found in chylomicrons and VLDL.
  • Triglyceride (TG)  provides a good estimate of VLDL.
  • Triglycerides are good risk factors for coronary heart disease is controversial.

Pathophysiology of Triglycerides (TG)                                                                                                                                   

Source of Triglyceride:

  1. Plants contain polyunsaturated fatty acids.
    1. Corn.
    2. Sunflower.
    3. Safflower.
  2. The animal source contains mostly saturated fatty acids and solids at room temperature.
  3. Glucose must be present in the cells for the formation of TG.
  4. One of the sources gives the following ratio of triglycerides in various fats.
Triglycerides (TG) composition

Triglycerides (TG) composition

Triglyceride structure:

  1. TG consists of three fatty acids + one molecule of glycerol by ester bond, so-called Triglycerides.
  2.  Glycerol and fatty acids are building blocks for TG.
    1. Three fatty acids  + one molecule of glycerol (ester bond)  =  Triglyceride
  3. TG is present in the blood and transported by the VLDL and LDL.
Triglyceride esterification

Triglyceride esterification

  1. There is Triglyceride formation by the glycolytic pathway in glucose catabolism.
  2. This triglyceride formation may be absent in the case of:
    1. Fasting.
    2. Starvation.
    3. Uncontrolled diabetes mellitus.
Triglyceride and glucose pathway

Triglyceride and glucose pathway

Triglyceride catabolism:

  1. TG, when catabolized, forms a small fraction of free fatty acid, which appears in plasma bound to albumin.
  2. These nonesterified fatty acids, after oxidation, enter the Acetyl CoA cycle.
  3. The end result is water, CO2, and ATP, the energy source.
Triglyceride catabolism and energy source

Triglyceride catabolism and energy source

Triglycerides and role of VLDL

Triglycerides and role of VLDL

Storage of the Triglycerides (TG):

  1. Triglycerides (TG) are the fat in the bloodstream.
  2. Triglycerides (TG) account for more than 90 % of the food intake and are 95% of the fat stored.
  3. Triglycerides (TG) are insoluble in water; this is the main glycerol ester.
  4. TG is stored in adipose tissue as :
    1. Glycerol.
    2. Fatty acids.
    3. Monoglyceride.
  5. The liver is the factory to convert all the above into triglycerides.
Triglyceride and role of liver

Triglyceride and the role of liver

  1. Triglycerides (TG) are Transported and present in :
    1. 80% are in VLDL.
    2. 15% are in LDL.
Triglycerides transportation

Triglycerides transportation

  1. TG is the source of energy.
  2. When TG is high then starts depositing in fatty tissue.
  3. The Fredrickson-levy classification method for hyperlipidemia:  Keep the plasma at 4 °C refrigerate for 16 hours, and then made an observation of the creamy layer at the top of turbidity.
    1. This can be completed by doing a lipid profile.

Normal Triglycerides (TG)

Source 1

Age  Male mg/dL  Female mg/dL
 Cord blood 13 to 95 11 to 76
 0 to 9 year 30 to 100 35 to 110
 10 to 14 year 32 to 125 37 to 131
 15 to 19 year 37 to 148 39 to 124
 20 to 24 year 44 to 201 36 to 131
 25 to 29 year  46 to 249 37 to 144
30 to 34 year 50 to 266 39 to 150
35 to 39 year 54 to 321 40 to 176
40 to 44 year 55 to 320 45 to 191
45 to 49 year 58 to 327 46 to 214
50 to 54 year 58 to 320 52 to 233
55 to 59 year 58  to 286 55 to 262
60 to 64 year 58 to 291 56 to 239
>65 year 55 to 260 60 to 240
  • To convert into SI unit x 0.0113 = mmol/L
  • Recommended cutoff point for evaluating triglyceridemia status:
    • Normal = <250 mg/dL
    • Borderline high = 250 to 500 mg/dL
    • Hypertriglyceridemic = >500 mg/dL
    • High risk for pancreatitis = >1000 mg/dL

Source 2

  • Male Adult  = 40 to 160 mg /dL.
  • Female Adult  = 35 to 135 mg /dL.
Children Male  mg/dL Female mg/dL
0 to 5 years 30 to 86 32 to 99
6 to 11 years 33 to 108 35 to 114
12 to 15 years 36 to 138 41 to 138
16 to 19 years 40 to 163 40 to 128 mg

Critical values of triglycerides are:

  • Desirable = < 150 mg /dL.
  • Borderline high = 150 to 199 mg /dL.
  • High = 200 to 499 mg /dL.
  • Very high = > 500 mg /dL.
  • Critical value  >400 mg/dL

Triglycerides (TG) concentration, according to the National cholesterol education program:

(Adult treatment panel (NECP-ATP II).

Risk factor Serum Triglyceride mg/dL
Normal <200
Borderline 200 to 400
High 400 to 1000
Very high >1000

Increased Triglycerides values are seen in the following:

  1. Hyperlipidemia.
  2. Hyperlipoproteinemia.
  3. Nephrotic syndrome.
  4. Liver diseases.
  5. Alcoholism (alcoholic cirrhosis).
  6. Diabetes Mellitus, uncontrolled.
  7. Glycogen storage disease (Von Gierke disease).
  8. Familial hypertriglyceridemia.
  9. Hypothyroidism.
  10. Gout.
  11. Anorexia nervosa.
  12. Down’s syndrome.
  13. Myocardial infarction.

Decreased Triglycerides level is seen in:

  1. Malnutrition.
  2. Hyperthyroidism.
  3. Congenital α-β- lipoproteinemia.
  4. Malabsorption.

Management of Hypertriglyceridemia:

  1. If Triglycerides (TG) are < 200 mg/dL, then the person needs diet control, and he should be advised to repeat triglyceride once a year.
  2. If Triglycerides (TG) are 200 to 500 mg/dL, then evaluate the patient with risk factors like:
    1. Diabetes mellitus
    2. Alcoholism
    3. Hypothyroidism
    4. Hypertension
    5. Hyperuricemia
    6. Medication like beta-blockers, Estrogen, corticosteroids, and oral contraceptives.
    7. Diseases like kidney and pancreatitis.
      1. No above risk factors in a person need only diet control
      2. Positive above risk factors and family history in a person needs diet and medication

Critical value:

  • If a person’s triglyceride is >500 mg/dL, then these patients need diet control and medication.

Table showing the summary of characteristics of the lipoproteins:

Characteristics Chylomicron HDL LDL VLDL
Size (diameter nm) >70.0 4 to 10 19.6 to 22.7 25 to 70
Electrophoretic mobility Origin α – region β – region Pre – β region
Molecular weight 0.4 to 30 x 109 3.6 x 109 2.75 x 109 5 to 10 x 109
Synthesized in Intestine Intestine and liver Intravascular Liver and intestine
Composition by weight in %
                     Cholesterol esterified 5 38 49 11 to 14
                    Cholesterol unesterified 2 10 13 5 to 8
                    Triglycerides 84 9 11 44 to 60
                    Phospholipids 7 22 27 20 to 23
                    Proteins 2 21 23 4 to 11

Questions and answers:

Question 1: What is the critical value of the triglycerides?
Show answer
Critical value of the triglycerides is >500 mg/dL.
Question 2: What is the role of VLDL in case of triglycerides?
Show answer
VLDL carries triglycerides 80% of its portion.

Possible References Used
Go Back to Chemical pathology

Comments

Fatemeh panah Reply
June 17, 2022

Thank you so much

Dr. Riaz Reply
June 17, 2022

Thanks.

Add Comment Cancel


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