Nature Medicine
2, 589 - 593 (1996)
doi:10.1038/nm0596-589
Cerebrospinal fluid leptin levels: Relationship to plasma levels and to adiposity in humansMichael W. Schwartz1, 3, 4, Elaine Peskind1, 2, 3, Murray Raskind1, 2, 3, Edward J. Boyko1, 3
& Daniel Porte Jr.1, 3
1Department of Medicine, Education and Clinical Center,University of Washington School of Medicine, Seattle, Washington 98105, USA
2Departments of Psychiatry and Behavioral Sciences and Geriatric Research, Education and Clinical Center,University of Washington School of Medicine, Seattle, Washington 98105, USA
3Veterans Affairs Puget Sound Health Care System, 1660 South Columbian Way, Seattle, Washington 98108, USA
4Correspondence should be addressed to M.W.S. The adipocyte hormone, leptin (OB protein), is proposed to be an "adiposity signal" that acts in the brain to lower food intake and adiposity1−5. As plasma leptin levels are elevated in most overweight individuals, obesity may be associated with leptin resistance6,7. To investigate the mechanisms underlying brain leptin uptake and to determine whether reduced uptake may contribute to leptin resistance, we measured immunoreactive leptin levels in plasma and cerebrospinal fluid (CSF) of 53 human subjects. Leptin concentrations in CSF were strongly correlated to the plasma level in a nonlinear manner (r = 0.92; P = 0.0001). Like levels in plasma, CSF leptin levels were correlated to body mass index (r = 0.43; P = 0.001), demonstrating that plasma leptin enters human cerebrospinal fluid in proportion to body adiposity. However, the efficiency of this uptake (measured as the CSF:plasma leptin ratio) was lower among those in the highest as compared with the lowest plasma leptin quintile (5.4−fold difference). We hypothesize that a saturable mechanism mediates CSF leptin transport, and that reduced efficiency of brain leptin delivery among obese individuals with high plasma leptin levels results in apparent leptin resistance.
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