Adipsin
Also known as: complement factor D, CFD
Adipsin, also known as complement factor D, is a serine protease produced by adipose tissue and present in the bloodstream. It is the enzyme that initiates the alternative pathway of the complement system, and it is also studied as an adipokine, a fat-secreted signal involved in metabolic processes.
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Overview
Class of enzymes
Factor D is a protein which in humans is encoded by the CFD gene. Factor D is involved in the alternative complement pathway of the complement system where it cleaves factor B.
Mechanism of Action
As a serine protease, complement factor D cleaves factor B when factor B is bound to complement C3b, forming the C3 convertase that amplifies complement activation and supports pathogen clearance. Beyond its immune function, adipsin appears in metabolic signaling research: in diabetic mouse models it interacted with SERBP1 to lower SERPINE1 expression during blood-vessel growth after ischemia, and it limited the mitochondrial translocation of Irak2 in heart muscle.
Research History
Discovered in the 1980s, adipsin was initially identified as a protein secreted by adipose tissue, making it one of the first described adipokines. It was subsequently identified as complement factor D, a central enzyme of the alternative complement pathway. Research since then has followed both threads: its immune role in complement activation and its metabolic roles in pancreatic beta cells, blood vessels, heart muscle, and joints.
What Researchers Are Saying
Community Reports - Not Medical Advice
The following is aggregated from public forums, Reddit, and research communities. These are anecdotal reports from researchers only - not verified clinical data and not a recommendation of any kind.
Adipsin (also known as complement factor D, CFD) is studied within the metabolic health research community. Adipose-secreted serine protease studied for insulin secretion, complement activation, and metabolic dysfunction.
Last updated October 28, 2026
Research status: emerging. Adipsin appears across metabolic health research forums and academic literature. Researchers note this compound falls in the metabolic category.
Last updated October 28, 2026
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