Engineered probiotic ameliorates hyperlipidemia and atherosclerosis by secreting <scp>PCSK9</scp> nanobodies and regulating gut microbiota

Elevated levels of low-density lipoprotein cholesterol (LDL-C) play a critical role in the onset and progression of cardiovascular disease (CVD). Inhibitors or monoclonal antibody drugs targeting pro-protein convertase subtilisin/kexin type 9 (PCSK9) are novel cholesterol-lowering medications that can effectively reduce serum LDL-C levels. However, these drugs are usually expensive and require injections, which can reduce patient compliance and increase the financial burden. In this study, we constructed an engineered probiotic strain containing a prokaryotic expression element and a high-affinity fragment of the human PCSK9 nanobody (PCSK9nb). The engineered bacterium was evaluated in vitro and in vivo for its ability to express and release PCSK9nb, as well as for its biocompatibility and stability. The therapeutic potential of the engineered probiotics was confirmed using mouse models of hyperlipidemia and atherosclerosis. We analyzed differences in mouse gut microbiota using high-throughput sequencing and compared the therapeutic efficacy of the engineered bacteria with that of atorvastatin in a mouse model of hyperlipidemia. The engineered bacteria were found to express and release PCSK9nb in vivo after oral administration, achieving the effect of lowering serum cholesterol levels, alleviating atherosclerosis, and reducing body weight. In vivo, PCSK9nb was found to increase hepatic LDL receptor (LDLR) expression levels, decrease serum LDL-C content, regulate the diversity and community structure of gut microbiota, reduce lipid accumulation in the liver, and decrease systemic inflammation. By comparing their efficacy with that of statins, the engineered probiotics demonstrated similar therapeutic effects. The research results provide a new strategy for the development of orally delivered PCSK9 antibody drugs, reducing healthcare costs and minimizing statin drug tolerance.