title: Intranasal insulin reduces body fat in men but not in women.
abstract: Insulin acts in the central nervous system to reduce food intake and body weight and is considered a major adiposity signal. After intranasal administration, insulin enters the cerebrospinal fluid compartment and alters brain functions in the absence of substantial absorption into the blood stream. Here we report the effects of 8 weeks of intranasal administration of insulin (4 x 40 IU/day) or placebo to two groups of healthy human subjects (12 men and 8 women in each group). The insulin-treated men lost 1.28 kg body wt and 1.38 kg of body fat, and their waist circumference decreased by 1.63 cm. Plasma leptin levels dropped by an average of 27%. In contrast, the insulin-treated women did not lose body fat and gained 1.04 kg body wt due to a rise in extracellular water. Our results provide a strong, first confirmation in humans that insulin acts as a negative feedback signal in the regulation of adiposity and point to a differential sensitivity to the catabolic effects of insulin based on sex.
authors.affiliation: Institute of Neuroendocrinology, University of Lübeck, Ratzeburger Allee 160, Haus 23a, 23538 Lübeck, Germany. hallschmid@kfg.mu-luebeck.de.
authors.forename: Manfred
authors.initials: M
authors.lastname: Hallschmid
authors.forename: Christian
authors.initials: C
authors.lastname: Benedict
authors.forename: Bernd
authors.initials: B
authors.lastname: Schultes
authors.forename: Horst-Lorenz
authors.initials: HL
authors.lastname: Fehm
authors.forename: Jan
authors.initials: J
authors.lastname: Born
authors.forename: Werner
authors.initials: W
authors.lastname: Kern
mesh_terms: D000273:Adipose Tissue / Q000187:drug effects / Q000502:physiology*; D000281:Administration, Intranasal; D015992:Body Mass Index; D001835:Body Weight / Q000187:drug effects; D005110:Extracellular Space / Q000187:drug effects / Q000502:physiology; D005260:Female; D006801:Humans; D007328:Insulin / Q000008:administration & dosage* / Q000134:cerebrospinal fluid / Q000494:pharmacology; D008297:Male; D010919:Placebos; D012016:Reference Values; D012727:Sex Characteristics
chemical_list: D007328:Insulin; D010919:Placebos