Age-related modifications of circadian rhythm of serum leptin in healthy men

BACKGROUND: Leptin, the product of the ob gene, is secreted by the adipocyte and is involved in the regulation of body weight, energy homeostasis and a wide spectrum of biological activities. OBJECTIVE: We studied how variations in circadian serum leptin levels change as people age. METHODS: Serum leptin levels were studied on a circadian basis in 26 men, 6 overweight (BMI >27.8) and 20 with normal weight. The normal-weight men were divided into four age groups: (A) in their 30s, (B) in their 40s, (C) in their 50s, and (D) in their 60s. Serum samples were drawn at 2-hour intervals from 8:00 to 22:00 and hourly from 22:00 to 8:00 for a total of 24 h. RESULTS: A significant circadian variation of leptin levels was found whatever the age with a peak at night and a trough around noon. The circadian leptin levels were higher in the older normal-weight groups (50s and 60s) and in the groups with a BMI >27.8. CONCLUSION: Our study demonstrates that changes in the characteristics of the circadian rhythm of serum leptin in healthy men are associated with both advancing age and increased BMI.