Detection of adiponectin in cerebrospinal fluid in humans.
Adiponectin circulates in the body in high concentrations, and 100-fold lower amounts were described in the cerebrospinal fluid (CSF) of mice, whereas in humans, contradictory results have been published. To clarify whether adiponectin is present in human CSF and is derived from the circulation, it was determined in human CSF and plasma of 52 nonselected patients. Adiponectin was detected by immunoblot in CSF and was quantified in CSF and serum by ELISA. CSF adiponectin was positively correlated to systemic levels, and the CSF/serum adiponectin ratio was correlated to the CSF/serum albumin ratio. Furthermore, disturbed function of the blood-brain barrier (BBB) was associated with an elevated CSF/serum adiponectin ratio. Adiponectin mRNA was not found in the brain, indicating that adiponectin crosses the BBB and/or the blood-cerebrospinal fluid barrier (BCB). Rat adiponectin with a COOH-terminal tag was injected into the tail vein of rats and was detected 3 h later in CSF. However, CSF adiponectin in humans and rats was approximately 0.1% of the serum concentration and therefore was below the 0.5% expected in the CSF because of the residual leakage of an undisturbed BBB/BCB. Taken together, data from the present study show that adiponectin in human CSF is far below the level expected by the baseline BBB/BCB permeability, indicating that adiponectin enters the brain much less efficiently than albumin, thus supporting recent data that exclude adiponectin transport to the CSF. Additional studies are needed to reveal whether these low levels of adiponectin in CSF have a physiological function.
Neumeier
Markus
M
Dept. of Internal Medicine I, Regensburg Univ. Hospital, D-93042 Regensburg, Germany.
Weigert
Johanna
J
Buettner
Roland
R
Wanninger
Josef
J
Schäffler
Andreas
A
Müller
André Michael
AM
Killian
Stephan
S
Sauerbruch
Sophie
S
Schlachetzki
Felix
F
Steinbrecher
Andreas
A
Aslanidis
Charalampos
C
Schölmerich
Jürgen
J
Buechler
Christa
C
D052242:Adiponectin / Q000097:blood / Q000134:cerebrospinal fluid; D000368:Aged; D000818:Animals; D002478:Cells, Cultured; D004058:Diffusion; D042783:Endothelial Cells / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D051381:Rats
C499918:ADIPOQ protein, human; D052242:Adiponectin