Lipoprotein Biomarkers: Apolipoprotein B (Apo B)

Optimal Takeaways

Apolipoprotein B, the protein component of LDL and VLDL, can initiate atherosclerosis and contribute to pathogenic plaque buildup and rupture. Oxidation of Apo B makes it even more atherogenic. Elevated levels are associated with genetic hyperlipoproteinemia, hypothyroidism, obesity, and diabetic complications. Lower levels may be associated with chronic conditions such as hyperthyroidism, chronic anemia, inflamed joints, malnutrition, Reye syndrome, and Tangier disease.

Standard Range: 52.00 - 80.00 mg/dL (0.52 - 0.80 g/L)

The ODX Range: 52.00 - 80.00 mg/dL (0.52 - 0.80 g/L)

Low Apo B is associated with hyperthyroidism, inflammatory joint disease, chronic pulmonary disease, weight reduction, malnutrition, chronic anemia, Reye syndrome, Tangier disease, and the use of niacin, cholestyramine, thyroxine, estrogen, neomycin, and statin drugs (Pagana 2021).

High Apo B is seen with atherosclerosis, coronary artery disease, hyperlipoproteinemia (IIa, IIb, IV, V), CAD, diabetes, hypothyroidism, nephrotic syndrome, renal failure, hemodialysis, biliary obstruction, pregnancy, anorexia nervosa, alcohol abuse, and use of androgens, progestins, diuretics, and beta blockers (Pagana 2021). Elevated Apo B can also be associated with diabetic retinopathy (Ankit 2017) and obesity (Bissonnette 2018).

Overview

Apolipoprotein B (Apo B) is the main protein component of LDL and chylomicrons, accounting for 40% of the protein in VLDL. Cholesterol is made more soluble by Apo B, thus making it easier to deposit into the artery wall (Pagana 2021).

The Apo B particle initiates atherosclerosis when trapped in the arterial wall. Here it contributes to plaque buildup and even transformational high-risk changes such as plaque rupture and endothelial erosion. Smaller cholesterol-depleted Apo B will likely become trapped and become increasingly atherogenic when oxidized. Lipoproteins that contain Apo B include chylomicrons and chylomicron remnants, which contain Apo B48 and VLDL, IDL, LDL, and Lp(a), which contain Apo B100. Each lipoprotein carrier contains one molecule of Apo B (Sniderman 2019).

An elevated Apo B predicts the severity of CAD. In a cross-sectional study of 90 subjects with acute coronary syndrome, the highest Apo B, with a mean of 115.5 mg/dL, was associated with the highest Gensini score (GS). This score reflects the severity of atherosclerosis and is significantly elevated in myocardial infarction. The lowest Apo B, with a mean of 65.77 mg/dL, was associated with the lowest GS (Yaseen 2021).

In one study of 115 individuals with stable CAD undergoing a PCI procedure, patients with Apo B levels above 90 mg/dL had more unstable plaque than those with a level of 90 mg/dL or below. The mean value in the low Apo B group was 75.8 mg/dL (Ohwada 2019).

Measuring Apo B is more important than measuring LDL-C when evaluating statin-treated patients. Follow-up of 13,015 statin patients found that elevated Apo B and non-LDL-C corresponded with an increased risk of all-cause mortality, while mortality increased when LDL-C decreased. The lowest risk of all-cause mortality was associated with an Apo B level of 73 mg/dL and followed a J-shaped curve with increasing mortality below and above this level. (Johannesen 2021).

The severity of diabetic retinopathy (DR) is significantly associated with increasing Apo B levels. One cross-sectional study of diabetic patients found that an Apo B of 74.98 mg/dL was associated with mild DR, 96.45 mg/dL was associated with moderate DR, and a level of 101 mg/dL was associated with severe DR (Ankit 2017).

The Apo B molecule is also associated with obesity and can promote dysfunction of white adipose tissue resulting in hyperinsulinemia, insulin resistance, and postprandial hypertriglyceridemia (Bissonnette 2018).

References

Ankit, B S et al. “Stronger relationship of serum apolipoprotein A-1 and B with diabetic retinopathy than traditional lipids.” Indian journal of endocrinology and metabolism vol. 21,1 (2017): 102-105. doi:10.4103/2230-8210.196030

Bissonnette, Simon et al. “High plasma apolipoprotein B identifies obese subjects who best ameliorate white adipose tissue dysfunction and glucose-induced hyperinsulinemia after a hypocaloric diet.” The American journal of clinical nutrition vol. 108,1 (2018): 62-76. doi:10.1093/ajcn/nqy070

Johannesen, Camilla Ditlev Lindhardt et al. “Apolipoprotein B and Non-HDL Cholesterol Better Reflect Residual Risk Than LDL Cholesterol in Statin-Treated Patients.” Journal of the American College of Cardiology vol. 77,11 (2021): 1439-1450. doi:10.1016/j.jacc.2021.01.027

Ohwada, Takayuki et al. “Apolipoprotein B correlates with intra-plaque necrotic core volume in stable coronary artery disease.” PloS one vol. 14,2 e0212539. 19 Feb. 2019, doi:10.1371/journal.pone.0212539

Pagana, Kathleen Deska, et al. Mosby's Diagnostic and Laboratory Test Reference. 15th ed., Mosby, 2021.

Sniderman, Allan D et al. “Apolipoprotein B Particles and Cardiovascular Disease: A Narrative Review.” JAMA cardiology vol. 4,12 (2019): 1287-1295. doi:10.1001/jamacardio.2019.3780

Yaseen, Rehab Ibrahim et al. “The relation between ApoB/ApoA-1 ratio and the severity of coronary artery disease in patients with acute coronary syndrome.” The Egyptian heart journal : (EHJ) : official bulletin of the Egyptian Society of Cardiology vol. 73,1 24. 16 Mar. 2021, doi:10.1186/s43044-021-00150-z