Lack of association between plasma PCSK9 and LDL-apoB100 catabolism in patients with uncontrolled type 2 diabetes

Pro-protein convertase subtilisin/kexin type 9 (PCSK9) is a post-transcriptional inhibitor of LDL-receptor. In non-diabetic men, plasma PCSK9 levels were found to be inversely correlated with low-density lipoprotein (LDL) apolipoprotein B100 (apoB) fractional catabolic rate (FCR). Here, we aimed to determine the effect of type 2 diabetes on the association between plasma PCSK9 and FCR of LDL.

A kinetic study of LDL-apoB100, using stable isotopes, was performed in 38 individuals (20 men, 18 women) including 23 non-diabetic normolipidemic subjects and 15 patients with type 2 diabetes.

In the non-diabetic group, plasma PCSK9 was positively correlated with LDL-C (r=0.64, p=0.001), apoB (r=0.67, p<0.001), and inversely correlated with LDL-apoB FCR (r=-0.61, p=0.002). In contrast, in type 2 diabetic patients, plasma PCSK9 was not associated with LDL-C, apoB and LDL-apoB FCR. However, the lack of association between PCSK9 and LDL-apoB FCR seemed to be limited to the patients with "uncontrolled" diabetes (HbA1c>7%) since a borderline significant negative correlation between PCSK9 and LDL FCR (r=-0.70, p=0.08) was retrieved in patients with HbA1c≤7%. In multivariate analysis, LDL-apoB FCR was independently associated with PCSK9 (p=0.001) and fasting glycaemia (log) (p=0.030) in the non-diabetic population and with PCSK9 (p=0.040) and HbA1c (p=0.029) in diabetic patients.

Our data indicate that both PCSK9 and glycaemia are independent factors influencing LDL catabolism. Plasma PCSK9 influences significantly the catabolism of LDL-apoB100 in individuals without diabetes, but not in patients with uncontrolled type 2 diabetes. Thus, the influence of diabetes on LDL-apoB FCR catabolism may overwhelm the influence of PCSK9.