title: Plasma leptin concentrations during extended fasting and graded glucose infusions: relationships with changes in glucose, insulin, and FFA.
abstract: Despite numerous studies, the in vivo regulation of plasma leptin levels in response to nutritional factors continues to remain unclear. We investigated temporal and dose-response relationships of plasma leptin in response to physiological changes in insulin/glucose. After an overnight fast of 10 h, lean, healthy subjects were investigated for an additional 16 h of either extended fasting or one of three levels of glycemia/insulinemia induced by stepwise increasing iv glucose infusions. During extended fasting, plasma leptin values declined steadily and significantly. Plasma leptin levels remained constant at glucose concentrations between 5.8-6.5 mmol/liter, which maintained normoinsulinemia at 41.5-45.4 pmol/liter and FFA at 106-123 mg/liter, but leptin concentrations were increased at higher rates of glucose infusion (with plasma glucose rising to 8.7 mmol/liter). Concentrations of serum leptin were inversely related to FFA levels during extended fasting and at all levels of glycemia. Our data indicate that in lean healthy subjects, physiological changes in glycemia and insulinemia significantly alter plasma FFA and leptin concentrations. The increases in leptin concentrations demonstrate dose-dependent relationships that appear to relate to changes in FFA levels as well as to changes in glycemia/insulinemia.
authors.affiliation: Division of Endocrinology, Metabolism, and Clinical Nutrition, Department of Medicine, Medical College of Wisconsin, 9200 West Wisconsin Avenue, Milwaukee, WI 53226, USA. gsonnen@mcw.edu
authors.forename: G E
authors.initials: GE
authors.lastname: Sonnenberg
authors.forename: G R
authors.initials: GR
authors.lastname: Krakower
authors.forename: R G
authors.initials: RG
authors.lastname: Hoffmann
authors.forename: D L
authors.initials: DL
authors.lastname: Maas
authors.forename: M M
authors.initials: MM
authors.lastname: Hennes
authors.forename: A H
authors.initials: AH
authors.lastname: Kissebah
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D005215:Fasting; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000097:blood*; D020738:Leptin / Q000097:blood*; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D020738:Leptin; D005947:Glucose