April - June 2005, Volume 1, Issue 2

Poiana C, Stefanescu AM, Caragheorgheopol A, Badiu C, Galoiu S, Coculescu M

Blood brain barrier by-pass produced by pituitary adenomas for pituitary peptides does not involve leptin

Acta Endo (Buc) 2005, 1 (2): 157-166
doi: 10.4183/aeb.2005.157

Introduction: The impaired transport of leptin into the brain through a decreased permeability of the blood-brain barrier (BBB) for leptin in obesity represents one of the important mechanisms involved in leptin resistance which is characteristic in human obesity. Some pituitary tumors can increase the blood-cerebrospinal fluid barrier (BCB) permeability for peptides. BCB is a part of BBB.\r\nObjectives: The aim of our study was to search if the by-pass of BCB for pituitary hormones produced by adenomas does influence the transport of leptin into the central nervous system in obese patients.\r\nMaterials and methods: We investigated 20 males with pituitary adenomas: group A (11 patients) had cerebrospinal fluid (CSF) to serum ratio more than one for prolactin (PRL) and in some patients for growth hormone (GH) and follicle stimulating hormone (FSH), suggesting an increased permeability of BCB and a control group C (9 patients), which had CSF/serum ratio less than one for GH, PRL or FSH, suggesting an intact BCB. Both A and C groups contain subgroups of patients with obesity (body mass index, BMI>30 kg/m2) and normal body weight (BMI<25 kg/m2). In these patients we measured the CSF to serum leptin ratio in order to clinically evaluate the leptin transport into the brain. Rapid fluoroimmunoassay method with europium was used. Leptin was assayed by ELISA method.\r\nResults: The patients of group A with pituitary adenomas show a higher level of pituitary peptides, PRL and in some cases GH, FSH in CSF as compared to serum (ratio CSF/serum over 1), both in obese and non-obese. By contrast, in the same patients, there is\r\na low level of CSF leptin as compared to serum leptin (ratio CSF/serum less than 1). In the subgroup of obese patients from group A we found even less ratio of CSF to serum leptin, than in non-obese. There is a well known higher leptin concentration in the plasma of obese patients with pituitary adenomas as compared to non-obese ones (26.4?3.8ng/ml vs 12.4?3.4ng/ml, p<0.05). In the control group C, both pituitary peptides (PRL, or GH, FSH) and leptin showed a ratio CSF/serum less than 1, in all patients.\r\nConclusions: These data show a decrease in hemato-encephalic barrier permeability for leptin in obese patients through a specific mechanism, not influenced by other peptides passing through injuries of BBB produced by pituitary adenomas. It is tempting to suggest that there is a specific by-pass of BCB for pituitary peptides, in some pituitary adenomas.

Keywords: leptin, blood brain barrier, cerebrospinal fluid, obesity, pituitary adenomas

Correspondence: Mihail Coculescu, Endocrinology Department, ?Carol Davila? University of Medicine and Pharmacy, 34-36 Bd. Aviatorilor, 011863, Bucharest, Romania, Tel/Fax; + 4021 3198718, e-mail; m.coculescu@uni-davila.ro

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