What are triglycerides?

What Are Triglycerides?

Triglycerides are a type of fat (lipid) found in your blood that serve as an important source of energy for the body. They are the most common form of fat in the body and are derived from food as well as produced by the liver 1.

Structure and Function of Triglycerides

Triglycerides consist of three fatty acid chains attached to a glycerol backbone. They serve several important functions:

• Primary storage form of energy in the body
• Component of triglyceride-rich lipoproteins (TRLs), including:
  • Chylomicrons (produced in the intestines after meals)
  • Very low-density lipoproteins (VLDLs, produced by the liver)
• Source of essential fatty acids needed for various metabolic processes

Triglyceride Metabolism

Triglycerides circulate in the bloodstream through several pathways:

• Dietary triglycerides are absorbed in the intestine and packaged into chylomicrons
• The liver produces triglycerides that are packaged into VLDLs
• Lipoprotein lipase (an enzyme) breaks down triglycerides in the bloodstream, allowing tissues to use the fatty acids for energy

Clinical Significance

Classification of Triglyceride Levels

According to the American Heart Association, triglyceride levels are classified as 1, 2:

• Normal: <150 mg/dL
• Borderline high: 150-199 mg/dL
• High: 200-499 mg/dL
• Very high: ≥500 mg/dL

Health Implications

Elevated triglyceride levels have significant health implications:

1. Cardiovascular Disease Risk: Elevated triglycerides are associated with increased risk of cardiovascular disease, though the exact mechanism has been debated 1, 2. They contribute to atherosclerosis and are often part of a broader pattern of atherogenic dyslipidemia.

2. Pancreatitis Risk: Very high triglyceride levels (≥500 mg/dL) significantly increase the risk of acute pancreatitis, with levels above 1000 mg/dL posing a particularly high risk 1, 2, 3.

3. Metabolic Associations: Elevated triglycerides often occur alongside other metabolic abnormalities:

   • Obesity, particularly visceral adiposity
   • Insulin resistance
   • Type 2 diabetes
   • Low HDL cholesterol
   • Small, dense LDL particles (which are highly atherogenic)
   • Non-alcoholic fatty liver disease

Factors Affecting Triglyceride Levels

Several factors can influence triglyceride levels:

• Diet: High intake of carbohydrates (especially simple sugars), alcohol, and excess calories
• Lifestyle: Sedentary behavior, obesity
• Genetic factors: Familial hypertriglyceridemia, familial combined hyperlipidemia
• Medical conditions: Diabetes, hypothyroidism, kidney disease
• Medications: Estrogens, corticosteroids, some antipsychotics, beta-blockers, retinoids

Management of Elevated Triglycerides

Management depends on the severity of elevation:

• Lifestyle modifications (can reduce triglycerides by up to 50%) 2:

  • Weight reduction
  • Regular physical activity
  • Limiting alcohol consumption
  • Reducing intake of simple carbohydrates and sugars
  • Increasing intake of omega-3 fatty acids

• Pharmacological treatment (for severe hypertriglyceridemia) 3, 4:

  • Fibrates (gemfibrozil, fenofibrate)
  • Omega-3 fatty acids
  • Niacin

Clinical Pitfalls and Considerations

• Fasting vs. non-fasting measurements: Triglyceride levels are typically measured after fasting for 8-12 hours, as levels can increase by approximately 50% after eating 1.

• Ethnic variations: There are significant ethnic differences in triglyceride levels, with Mexican Americans having the highest prevalence of hypertriglyceridemia (34.9%), followed by non-Hispanic whites (33%) and blacks (15.6%) 1.

• Gender differences: Women may have greater cardiovascular risk from elevated triglycerides than men 2.

• Secondary causes: Always evaluate for secondary causes of hypertriglyceridemia, including medications, medical conditions, and dietary factors before initiating treatment 3, 4.