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Elevated Lp(a) and PCSK9 levels associated with higher CAC in FH patients

Alonso R et al., Atherosclerosis 2016

PCSK9 and lipoprotein (a) levels are two predictors of coronary artery calcification in asymptomatic patients with familial hypercholesterolemia

 
Alonso R, Mata P, Muniz O, et al.
Atherosclerosis 2016; published online ahead of print
 

Background

Familial hypercholesterolaemia (FH) is a genetic disorder associated with the development of CAD early in life. In over 90% of patients, FH is due to a mutation in one allele of the LDL receptor gene that leads to elevated LDL-C levels [1]. Other factors that affect the age at which FH patients may develop premature atherogenesis include high Lp(a) levels and PCSK9 levels [2,3].
In this study, the effects of elevated PCSK9 and Lp(a) levels on coronary artery calcification (CAC) were evaluated in 161 asymptomatic molecularly defined FH patients on stable chronic lipid-lowering therapy, who were recruited from the Spanish Familial Hypercholesterolemia Followup Study (SAFEHEART). CAC was assessed in the epicardial coronary arteries on CT scans, with calculation of a CAC score according to Agatston’s method. CAC was detected in 98 patients (61%), of whom 55 had a mild score (0.1-100), 25 had elevated CS (101-400) and 18 patients had severe CS (>400). In 63 patients no CAC was detected.
 

Main results

In patients with a positive calcium score (CS) compared with patients without CAC: In an analysis of PCSK9 and Lp(a) levels separately in patients with mild vs. high (>100) CS: Age was the strongest predictor of an elevated score (standardised coefficient, β = 0.478; P < 0.0001), followed by male sex (β = 0.227; P < 0.005).
After correction for potential confounders, only PCSK9 (β = 0.179; P = 0.02), Lp(a) (β = 0.158; P = 0.03), and apo(a) (β = 0.156; P = 0.04) remained significantly predictive of positive CAC scores.
 

Conclusion

Elevated Lp(a) and PCSK9 levels were both associated with higher CAC in asymptomatic FH patients on stable chronic lipid-lowering therapy, after adjusting for other CV risk factors. It should be noted that circulating PCSK9 levels do not necessarily reflect PCSK9 function, since statin treatment increase PCSK9 levels. Higher statin doses may to some extent explain why patients with CAC have higher PCSK9 levels than those without CAC. However, other studies have shown associations between PCSK9 and the volume of necrotic core tissue in coronary atheroma lesions and with total carotid plaque area, independently of LDL-c levels and statin use. Because monoclonal antibodies targeting PCSK9 reduce LDL-c as well as Lp(a), these agents may be beneficial in these patients.
 
Find this article online at Atherosclerosis
 

References

1. Hobbs HH, Brown MS, Goldstein JL. Molecular genetics of the LDL receptor gene in familial hypercholesterolemia, Hum. Mutat. 1 (1992) 445e466.
2. Alonso R, Andres E, Mata N, et al. Lipoprotein(a) levels in Familial Hipercholesterolaemia: an important predictor for cardiovascular disease independent of the type of LDL-receptor mutation, J. Am. Coll. Cardiol. 63 (2014) 1982e1989.
3. Lambert G, Petrides F, Chatelais M, et al. Elevated plasma PCSK9 level is equally detrimental for patients with nonfamilial hypercholesterolemia and heterozygous familial hypercholesterolemia, irrespective of low-density lipoprotein receptor defects, J. Am. Coll. Cardiol. 63 (2014)2365e2373.