RESUMO
CONTEXT: Data on the presence/quantification of the neurotrophic adipokines retinol-binding protein-4 (RBP4), clusterin, and pigment epithelium-derived factor (PEDF) in human cerebrospinal fluid (CSF) are scarce and migration of these adipokines across of the blood-brain barrier (BBB) is uncertain. OBJECTIVE: This work aimed to quantify RBP4, PEDF, and clusterin in paired serum and CSF samples of patients undergoing neurological evaluation. METHODS: A total of 268 patients (109 male, 159 female) were included. Adipokine serum and CSF concentrations were measured by enzyme-linked immunosorbent assay in duplicate. RESULTS: RBP4 was abundant in serum (mean, 31.9â ±â 24.2 µg/mL). The serum concentrations were approximately 145 times higher than in CSF (CSF to serum RBP4 ratio, 8.2â ±â 4.3â ×â 10-3). PEDF was detectable in serum (mean, 30.2â ±â 11.7 µg/mL) and concentrations were approximately 25 times higher than in CSF (CSF to serum PEDF ratio, 42.3â ±â 15.6â ×â 10-3). Clusterin serum concentrations were abundant with mean levels of 346.0â ±â 114.6 µg/mL, which were approximately 40 times higher than CSF levels (CSF to serum clusterin ratio, 29.6â ±â 23.4â ×â 10-3). RBP4 and PEDF serum levels correlated positively with CSF levels, which were increased in overweight/obese patients and in type 2 diabetic patients. The CSF concentrations of all 3 adipokines increased with BBB dysfunction. RBP4 in CSF correlated positively with inflammatory parameters. In detail, only RBP4 showed the kinetics and associations that are mandatory for a putative mediator of the fat-brain axis. CONCLUSION: RBP4, PEDF, and clusterin are permeable to the BBB and increase with the measure of BBB dysfunction. RBP4 represents an inflammatory neurotrophic adipokine and is a promising mediator of the fat-brain axis.