Clinical endocrinology of human leptin

Abstract

Since the discovery of leptin, a boom of scienti®c knowledge became available about the OB-protein gene and its role and signi®cance in weight regulation. Both from animal and human research data, serum leptin can probably be considered as one of the best biological markers to re¯ect total body fat, and this ®nding is true over a wide range of body mass indexes (BMIs) and in different pathologies: in normal weight, anorexic and obese subjects; in non insulindependent diabetes mellitus (NIDDM) patients, PCO women, Prader-Willi children and subjects with hypogonadism and growth hormone de®ciency.Gender differences clearly exist, probably related to sex hormone differences, and from fat distribution studies it could be shown that subcutaneous fat is much more related to serum leptin concentrations than visceral fat: also leptin messenger-RNA (m-RNA) expression is signi®cantly higher in subcutaneous fat from human obese subjects.Leptin is not only correlated to a series of endocrine parameters such as insulin, insulin-like growth factor, (IGF) and SHBG, it seems involved as a mediator in some endocrine mechanisms (onset of puberty, insulin secretion, etc) as well.Weight loss will reduce human leptin concentrations, whereas the administration of human recombinant leptin seems to show only limited effects.Keywords: leptin; body fat distribution; endocrinology; hormones IntroductionObesity is becoming a major health problem in western countries, with an annual growing incidence and its association with increased morbidity and mortality. Furthermore, obesity is a very complex problem in its development, being a multifactorial disease, as well as in its treatment. Knowledge of the mechanisms by which obesity develops can help in prevention and better treatment. The discovery of leptin 1 and the subsequent wealth of research on the subject, has already led to more insight into these mechanisms. 2 Evidence from the research until now points out that leptin is likely to be a crucial hormone in the regulation of body weight, in humans as well as in animal models. 2 It is clear that leptin plays an important role in the regulation of body weight, more speci®cally of body fat stores. Almost all studies hitherto found a strong relationship between leptin and weight, expressed as body mass index (BMI) or percent body fat. 2 ± 4 But for a certain BMI, a large variability in leptin levels is found. 2,3,5 Also manifest differences in leptin concentration between men and women have been found by different authors. 6,7 Given the close interrelationships between body weight, body fat distribution and many hormonal functions, in energy balance regulation, leptin may play an important and triggering role as a hormonal determinant of energy balance in addition to the well-known role played by insulin, catecholamines, glucagon 8 and thyroid hormones. 9 As it is a fact that leptin and its receptor are two important components of a homeostatic system regulating body fat, it is likely that the process of leptin's signalling by the hypothalam...

Effect of Diet and Exercise on Body Composition, Energy Intake and Leptin Levels in Overweight Women and Men

“…In primary human cell lines, serum testosterone has been shown to reduce leptin secretion and mRNA by 62% [39]. Hence, it is possible that the reduction in serum leptin levels observed in males in E, which was not observed in females in E, was due to the effect of testosterone suppressing the expression of mRNA in the fat cells or directly suppressing leptin secretion [39].…”

“…It is possible, however, that other parameters may have affected the change in serum leptin levels of females in D, including: metabolic hormones (e.g., insulin, cortisol, epinephrine, and neuropeptides) [35], cytokines, leptin-binding proteins, and/or leptin clearance [39]. Metabolic hormones influence food intake, energy expenditure, and body weight.…”

“…Exercise may have had an impact on the levels of the male hormone testosterone, which has been proposed to be one of the major regulatory factors of serum leptin levels in men [39]. Serum testosterone levels may regulate the expression of mRNA in fat cells [39].…”

Leptin levels in the differential diagnosis between benign and malignant ascites

“…In humans, circulating leptin levels exhibit a particularly strong positive correlation with the body fat mass (BFM), body mass index (BMI) and sex. Serum leptin concentration is higher in obese than in lean subjects and in females than in males [6] . On the other hand, leptin serum levels can be altered in various diseases [7] .…”

Establishment of reference ranges for Serum Leptin and C-Peptide using enzymelinked immmunosorbent assay method: a preliminary report

“…Several researches have recommended the inclusion of serum Leptin (Abdelgadir et al, 2002;Sweeney, 2002;Van Gaal et al, 1999) and serum C-peptide (Jones and Hattersley, 2013) in the routine tests for management of diabetic and related patients. This prompted the need to establish reference ranges for these analytes.…”