C1QTNF

C1qTNF, short for C1q and tumor necrosis factor-related proteins, designates a family of secreted vertebrate proteins. Members are characterized by a modular architecture that typically includes an N-terminal collagen-like region facilitating trimerization and a C-terminal globular C1q-like domain, resulting in secreted trimers and higher-order oligomers. In humans and other vertebrates, the C1QTNF family is represented by multiple paralogs and is often referred to in the broader literature as the CTRP family.

C1qTNF proteins are produced by a variety of tissues, including adipose tissue, liver, muscle, and immune cells, and can circulate in blood or be present in extracellular spaces. Their functional repertoire is diverse and context-dependent, encompassing roles in metabolism, glucose and lipid homeostasis, insulin sensitivity, inflammation, and innate immune responses. Some members are involved in adipose tissue remodeling, angiogenesis, and cardiovascular function. Expression levels of certain C1qTNF proteins change in metabolic disorders; circulating concentrations may correlate with adiposity, insulin resistance, or inflammatory status. However, the precise signaling pathways and receptor interactions for many members remain incompletely defined, and effects can be pro- or anti-inflammatory depending on tissue context and oligomeric state.

Research on C1qTNF contributes to understanding adipokine networks and cytokine biology, with some family members explored as potential biomarkers or therapeutic targets for metabolic and cardiovascular diseases. Further work is needed to delineate individual member functions and receptor interactions.