CTRP

CTRP stands for C1q/TNF-related protein, a family of secreted proteins that function as adipokines in mammals. Members of the CTRP family are structurally related to adiponectin, featuring a C-terminal globular C1q-like domain and a collagen-like stalk. They typically assemble into multimers and are encoded by distinct genes, with the mammalian genome described as containing multiple CTRP members designated CTRP1 through CTRP15 and beyond.

Expression and distribution are widespread, with adipose tissue being a major source, but many CTRPs are also produced by liver, skeletal muscle, heart, and immune cells. Circulating CTRP levels respond to nutritional status, physical activity, and metabolic state, and altered levels have been linked to metabolic disorders. Some CTRPs increase in obesity or insulin resistance, while others decline, reflecting diverse roles in metabolism.

Functions attributed to CTRPs include regulation of energy homeostasis, glucose and lipid metabolism, and inflammatory responses. They can act in autocrine, paracrine, or endocrine fashion and influence signaling pathways such as AMPK and PPAR-α. Several CTRPs can interact with adiponectin receptors or other cell-surface receptors to mediate metabolic effects, contributing to improvements or impairments in insulin sensitivity and lipid handling depending on the member and context.

Clinical relevance is an area of active research. Altered CTRP expression or circulating levels have been observed in type 2 diabetes, obesity, metabolic syndrome, and cardiovascular disease. Because of their roles in metabolism and accessibility in blood, CTRPs are studied as potential biomarkers and therapeutic targets, though the specific functions of individual members vary and are still being clarified.