leptin and Diabetes-Insipidus

Leptin is known to regulate food intake and energy expenditure. Moreover, recent studies in rodents have shown that leptin in high doses decreases urine osmolality and increases water intake, together with renal sodium and water excretion. Since it is not clear whether leptin is involved in either the pathogenesis or in resulting metabolic abnormalities in diabetes insipidus, we measured leptin levels in 16 male patients with idiopathic central diabetes insipidus (DI) in comparison to a group of age- and BMI-matched male control subjects (no.=30). We found that plasma leptin concentration did not differ between patients with DI (4.45+/-3.24 microg/l) and healthy control group (3.69+/-2.81 microg/l; t test, p=0.41). Urine osmolality, plasma osmolality and urine volume of the patients with DI was not correlated to leptin. However, leptin was positively associated with body mass index (r=0.67; p=0.005). We conclude that leptin plasma concentrations are unchanged in diabetes insipidus. Furthermore, the lack of correlation between plasma leptin and urine osmolality, plasma osmolality or urine volume suggests that ADH deficiency does not have any impact on the plasma leptin levels.

Topics: Adult; Body Mass Index; Diabetes Insipidus; Humans; Leptin; Male; Osmolar Concentration; Proteins; Reference Values

Galanin, ghrelin, and leptin are three peptides involved in feeding regulation and more particularly in fat intake. The Brattleboro (di/di) rat is a genetic model of diabetes insipidus characterized by a preference for fat when it is in a food choice situation. Here, we measured hypothalamic galanin concentrations, plasma ghrelin and leptin and dietary preferences of adult di/di Brattleboro rats, di/+ and Long-Evans controls. The Brattleboro rats weighed significantly less than the di/+ rats (-18%; P<0.001). The fat-to-carbohydrate intake ratio was significantly greater in Brattleboro rats than in di/+ (P<0.02) when the rats could choose between a high-fat diet and a high-carbohydrate diet. Galanin concentrations were significantly lower in di/di rats than in di/+ rats in the paraventricular nucleus (-56%; P<0.001), but not in the arcuate nucleus. Plasma leptin was significantly lower in the di/di rats than in the di/+ rats (3.49+/-0.20 vs. 6.94+/-0.49 ng/ml; P<0.001). Plasma ghrelin concentrations were significantly lower in Long-Evans rats than in the di/di rats (-21%; P< 0.01). Given that galanin mRNA is overexpressed in the paraventricular nucleus of Brattleboro rats, these data are consistent with increased release of the peptide. In the Brattleboro rat, this overactive galanin system and the variations of ghrelin and leptin maintain an orexigenic drive favoring a preferential intake of fat which provides the animal with enough energy for its metabolism.

Topics: Animals; Diabetes Insipidus; Energy Intake; Galanin; Ghrelin; Hypothalamus; Leptin; Male; Rats; Rats, Brattleboro; Rats, Long-Evans