Supraphysiological hyperinsulinemia increases plasma leptin concentrations after 4 h in normal subjects

Area of Science:

• Endocrinology
• Metabolism
• Obesity Research

Background:

• Rodent studies show insulin and food intake affect leptin levels.
• Human data on insulin's regulation of plasma leptin is lacking.

Purpose of the Study:

• To investigate whether insulin regulates plasma leptin concentrations in humans.
• To determine the time course and magnitude of insulin's effect on leptin.

Main Methods:

• A 6-hour euglycemic hyperinsulinemic clamp was performed on 27 healthy subjects.
• Sequential insulin infusions (1, 2, and 5 mU.kg-1.min-1) were administered.
• Plasma leptin concentrations were measured basally and during insulin infusions.

Main Results:

• Plasma leptin increased significantly with increasing insulin levels (up to 50% increase).
• Leptin levels rose during insulin infusion but decreased during saline infusion in a control group.
• Women had higher baseline and insulin-stimulated leptin, explained by greater body fat.

Conclusions:

• Insulin regulates plasma leptin concentrations in humans, requiring prolonged high insulin levels.
• This effect is unlikely to regulate short-term postprandial satiety.
• Insulin may play a role in long-term or diurnal leptin regulation.