G. Boden et al., EFFECT OF FASTING ON SERUM LEPTIN IN NORMAL HUMAN-SUBJECTS, The Journal of clinical endocrinology and metabolism, 81(9), 1996, pp. 3419-3423
We have studied the effect of fasting on serum leptin levels in normal
volunteers. Five normal-weight (BMI < 28, 2 males/3 females) and five
obese subjects (BMI > 28, 2 males/3 females) were fasted (0 Kcal) for
52 h. Mean plasma glucose decreased from 88 +/- 3 to 63 +/- 5 mg/dl,
serum insulin from 16 +/- 1 to 10 +/- 1 mu U/ml, plasma beta-hydroxybu
tyrate increased from 0.2 +/- 0.1 to 1.8 +/- 0.4 mu mol/ml. Serum lept
in levels were higher in the obese than in the normal-weight volunteer
s (31 +/- 12 vs 11 +/- 3 ng/ml p < 0.01). In the obese, serum leptin d
ecreased from 31 +/- 10 to 12 +/- 5 ng/ml after 52 h (-72%, p < 0.001)
; in the normal-weight it decreased from 11 +/- 3 to 4 +/- 0.5 ng/ml (
-64%, p < 0.001). Serum leptin correlated positively with serum insuli
n (r = 0.51, p < 0.001) and with plasma glucose (r = 0.61, p < 0.001).
To determine effects of fasting induced decreases in plasma glucose a
nd insulin on serum leptin, four normal subjects (3 males/1 female) we
re fasted for 72 h while their plasma glucose was clamped at basal lev
els with a variable rate glucose infusion. In these volunteers, serum
leptin and insulin concentrations remained unchanged. In summary, the
rapid decrease in serum leptin levels during fasting indicated that le
ptin release was regulated by factors other than changes in body fat m
ass. The lack of leptin changes during fasting, when basal insulin and
glucose levels were maintained at basal levels, suggested that insuli
n and/or glucose may play a role in the regulation of leptin release.