Primary Human Epicardial Adipocytes Possess a Memory: Differential Release and Expression of PCSK9 Depending on Patient’s Age and Nutritional Status

Objectives: The proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates the levels of LDL receptor (LDL-R). Patients with loss-of-function mutations in the PCSK9 gene show higher levels of the LDL-R, reduced LDL, and protection against cardiovascular disease. PCSK9 inhibitors are a new class of LDL-lowering drugs. PCSK9 is mainly synthesized in the liver. Adipose tissue (AT) also expresses high PCSK9, while PCSK9 is low in cardiac tissue.

Methods: Blood and tissue samples from CABG patients (n = 136, all-comers) were investigated for PCSK9 release or expression. Human epicardial preadipocytes were isolated from these patients and in vitro differentiated to mature adipocytes within 4 weeks. Adipocytes were stimulated and examined concerning PCSK9 expression. Exogenous PCSK9 was utilized.

Results: Human epicardial AT shows a strong PCSK9 mRNA and protein expression mainly from epicardial adipocytes and preadipocytes. PCSK9 plasma levels in the coronary sinus are significantly higher than in the peripheral veins, suggesting cardiac PCSK9 release. Young normal-weight patients show lowest PCSK9 plasma levels while young and old obese patients (characterized by typical adipocytokine profiles: high leptin, low adiponectin, high inflammatory mediators, such as TNF-alpha), show highest PCSK9 plasma levels. No difference in PCSK9 expression was observed in right atrial tissue, while epicardial AT expressional patterns strongly resemble the PCSK9 plasma changes. Furthermore, mature epicardial adipocytes, in vitro differentiated for of up to 4 weeks, demonstrate a higher expression and release of PCSK9 with increasing patient’s age and BMI, suggesting a robust cellular memory. In addition, adipocytes from older patients show signs of reduced differentiation. Treatment of human epicardial adipocytes with leptin or TNF-alpha results in a strong increase in PCSK9 expression and release while adiponectin induces a reduction. Inhibition of the AMP-dependent protein kinase (AMPK) prevents the effect of adiponectin. Recombinant PCSK9 reduces AMPK-activation in response to adiponectin in these cells and impairs adiponectin-induced metabolic effects including stimulation of mitochondrial biogenesis, fatty acid uptake or oxidation and glucose uptake or oxidation.

Conclusion: Obese patients with high leptin but low adiponectin show high PCSK9 plasma levels and PCSK9 expression in epicardial adipocytes. These cells demonstrate a robust cellular memory for patient’s age and nutritional status and can mediate significant direct metabolic effects in the heart via adipocytokine and PCSK9 release.