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Perdita di funzione di PCSK9 e rischio cardiovascolare nell'ipercolesterolemia familiare

E' già stato dimostrato che anomalie genetiche che comportano una perdita di funzione di PCSK9 sono associate ad un più basso rischio cardiovascolare. E' vero anche per i portatori di ipercolesterolemia familiare. Su 582 pazienti con ipercolesterolemia familiare che per circa la metà dei casi era dovuta ad una mutazione del gene per il recettore LDL, il 3% presentava una variante, la R46L, del gene codificante per PCSK9 che determinava una perdita di funzione. I 18 portatori della mutazione avevano un valore di colesterolo LDL sensibilmente inferiore a quello degli altri pazienti con ipercolesterolemia familiare (261 vs 293 mg/dL), un minor numero ed una minore estensione di xantomi ed un minore numero di eventi cardiovascolari. La perdita di funzione di PCSK9 sembra dunque avere un effetto positivo anche in pazienti portatori di ipercolesterolemia familiare.

PCSK9 R46L, lower LDL, and cardiovascular disease risk in familial hypercholesterolemia: a cross-sectional cohort study.

Saavedra YG, Dufour R, Davignon J, Baass A

Arterioscler Thromb Vasc Biol 2014;34:2700-2705

OBJECTIVE: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a downregulator of the low density lipoprotein receptor. The aims of this cross-sectional cohort-study were to examine whether the PCSK9 R46L loss of function variant found in a cohort of familial hypercholesterolemia (FH) patients was associated with lower low density lipoprotein cholesterol, lower frequency of xanthomata, and cardiovascular risk.
APPROACH AND RESULTS: We studied FH patients attending the IRCM (Institut de Recherches Cliniques de Montréal) Lipid Clinic and whose DNA genotyping was positive for a low density lipoprotein receptor mutation. The presence of the PCSK9 loss of function R46L missense variant was determined among a cohort of 582 FH patients by genotyping. Frequency of the R46L variant was 3%. Carriers had significantly lower low density lipoprotein cholesterol (11%, P=0.002), total cholesterol (9%, P=0.007), apolipoprotein B (10%, P=0.037), and non-high density lipoprotein (12%, P<0.001) concentrations compared with noncarriers. Furthermore, R46L carriers showed a decreased average number of xanthoma per individual compared with noncarriers (0.33 and 0.76, respectively; P<0.001). Importantly, the R46L genetic variant was associated with a significant 86% lower odd of presenting a cardiovascular event (odds ratio, 0.14; 95% confidence interval, 0.032-0.63; P=0.001).
CONCLUSIONS: Even though the R46L variant was present in 3% of our FH population, carriers of this polymorphism showed attenuated effect of the low density lipoprotein receptor mutation on parameters, such as low density lipoprotein cholesterol, apolipoprotein B, total cholesterol, and non-high density lipoprotein. More importantly, this mutation is associated with a significant lower risk of cardiovascular disease compared with noncarriers. It is therefore likely that targeting PCSK9 in FH patients with novel anti-PCSK9 therapies will be useful in reducing cardiovascular risk in affected subjects.

Arterioscler Thromb Vasc Biol 2014;34:2700-2705