Serum leptin in relation to resting energy expenditure and fuel metabolism in obese subjects.
OBJECTIVE
Leptin is the product of ob gene shown to regulate body fat in mice. It is produced by human adipose tissue as well, but its physiological functions in man are not known. We explored if there is a relationship in obese humans with serum leptin and energy and fuel metabolism.


METHODS
Cross-sectional study including 45 obese (10 men, 35 women; age and body mass index: 42 +/- 7 y and 35.1 +/- 3.6 kg/m2, respectively).


METHODS
Food intake by a four-day-food record, blood samples for serum leptin concentrations and resting energy expenditure by indirect calorimetry.


RESULTS
Leptin concentrations showed an inverse association (adjusted for fat mass, age and sex) with resting energy expenditure, respiratory quotient and carbohydrate oxidation rate (r = -0.324, P < 0.05; r = -0.420, P < 0.01; r = 0.478, P = < 0.01, respectively), and interestingly, also with dietary fat intake (unadjusted r = -0.30, P < 0.05). Especially, leptin concentrations were elevated in those with low resting energy expenditure and respiratory quotient (below the median).


CONCLUSIONS
Serum leptin concentrations in obese subjects showed an inverse association with resting energy expenditure, respiratory quotient and carbohydrate oxidation rate. The physiological significance of these associations is unclear at the moment but could indicate that obese subjects show resistance to the actions of leptin also outside the brain in terms of regulating metabolic rate and fuel metabolism.
Niskanen
L
L
Department of Clinical Nutrition, University of Kuopio, Finland.
Haffner
S
S
Karhunen
L J
LJ
Turpeinen
A K
AK
Miettinen
H
H
Uusitupa
M I
MI
D000328:Adult; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004041:Dietary Fats; D002149:Energy Intake; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D020738:Leptin; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood* / Q000378:metabolism* / Q000503:physiopathology; D010101:Oxygen Consumption / Q000502:physiology*; D011506:Proteins / Q000032:analysis*; D012727:Sex Characteristics
D004041:Dietary Fats; D020738:Leptin; D011506:Proteins