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Leptin, a 16-kDa circulating protein primarily derived from adipocytes, is an important factor in the regulation of appetite and energy expenditure. Using simultaneous arterio-venous blood sampling, several organs were assessed with regard to their individual roles in leptin metabolism in healthy male and female subjects constituting a range of body mass indices. Plasma leptin levels were unchanged after passage through the hepatosplanchnic and forearm circulations. In contrast, concentrations in the renal vein were consistently lower than those in the renal artery (-15%; P<0.005), indicating net extraction, whereas the brain was observed to be a net leptin releaser. Concentrations in the internal jugular vein were significantly higher than arterial levels in lean females (change, 3.0+/-1.2 ng/mL; P<0.02) and in obese males (body mass index, >28 kg/m2), but not lean (change, 2.3+/-2.3 vs. 0.1+/-0.1 ng/mL, respectively; P<0.05), indicating a probable influence of both gender and adiposity on brain leptin release. An attempt to grossly localize the site of brain release by using cerebral venous scans to distinguish between jugular venous drainage from cortical and subcortical brain areas revealed no region-specific secretion. These data raise the possibility that the brain is a nonadipose source of leptin. In addition, the higher level of brain release observed in females may contribute to the well documented gender differences in overall plasma leptin levels.

Original publication

DOI

10.1210/jcem.84.7.5854

Type

Journal article

Journal

The Journal of clinical endocrinology and metabolism

Publication Date

07/1999

Volume

84

Pages

2270 - 2274

Addresses

Baker Medical Research Institute and the Alfred Baker Medical Unit, Alfred Hospital, Melbourne, Victoria, Australia. glen@baker.edu.au

Keywords

Forearm, Liver, Kidney, Arteries, Veins, Jugular Veins, Renal Veins, Brain, Adipose Tissue, Humans, Obesity, Leptin, Proteins, Body Composition, Sex Characteristics, Splanchnic Circulation, Adult, Female, Male