Evidence for gender-specific associations between leptin and olfaction.
BACKGROUND
The adipocyte-derived hormone leptin regulates food intake by stimulation of the long leptin receptor isoform in the hypothalamus. The long leptin receptor is also expressed in the piriform cortex, an area involved in the relay of olfactory cues. In rodents, both olfaction and leptin influence food seeking.


OBJECTIVE
To examine whether serum leptin levels are associated with olfaction in humans.


METHODS
Two distinct samples were analyzed. The population-based sample, 60 men and 61 women, was randomly selected from a population living in Mölndal, Sweden. The obese sample, 31 men and 27 women, was from the ongoing Swedish Obese Subjects (SOS) study.


METHODS
Olfactory function was assessed with a two-part test used at Connecticut Chemosensory Clinical Research Center.


RESULTS
In the population-based sample, multiple regression analysis revealed a gender difference (interaction gender x leptin; P = .016) between the association of odor identification and logarithmically transformed (log) leptin when adjusting for smoking and log body mass index (BMI). In men the association was positive (beta = 13.2; P = .0026), whereas in women it was negative (beta = -11.4; P = .050). When further adjusting for the influence of menopause and estrogen treatment, the negative association between odor identification and leptin became stronger for women in the population-based sample (beta = -13.7; P = .027). In the obese sample, the associations were similar in direction to those observed in the population-based sample, although nonsignificant.


CONCLUSIONS
Serum leptin levels were associated with odor identification in a randomly selected population. The association was gender-specific and independent of BMI. High odor identification scores were associated with high serum leptin levels in men and low serum leptin levels in women. This provides further support for previously recognized gender differences in the leptin system and suggests alternative ways for leptin to modulate its effects.
Karlsson
A Cecilia
AC
Department of Body Composition and Metabolism, Vita Stråket 15, Sahlgrenska University Hospital, SE-413 45 Göteborg, Sweden. cecilia.karlsson@medic.gu.se
Lindroos
Anna Karin
AK
Lissner
Lauren
L
Torgerson
Jarl S
JS
Carlsson
Björn
B
Carlsson
Lena M S
LM
Sjöström
Lars
L
D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D015992:Body Mass Index; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D020738:Leptin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000503:physiopathology*; D009812:Odorants; D012044:Regression Analysis; D012737:Sex Factors; D012903:Smell; D013548:Sweden
D020738:Leptin