The biological role and clinical significance of leptin in pediatrics

The review is devoted to the study of the effects of leptin, as one of the most important hormones that regulate the body's vital processes. His participation in the regulation of carbohydrate metabolism and insulin levels in the blood was revealed; maintaining vascular tone; the formation of eating behavior (including newborns); sexual development, as well as a role in the occurrence of a predisposition or the development of a number of diseases. Enzyme and receptor systems by which leptin exerts its effects are presented. The results of leptin replacement therapy are considered and the goals of further study of the effects of this adipokine are outlined. Key words: leptin, leptin resistance, obesity, hunger, leptin receptor, bronchial asthma, children, leptin in pediatrics, endocrinology

LEPTIN AND ADIPONECTIN PLASMA CONCENTRATION IN OBESE AND OVERWEIGHT PATIENTS

In obese patients, Leptin plasma concentration is high. This problem is called “leptin resistance”.In reverse, adiponectin concentration is low in overweight and obese patients with insulin resistance, dyslipidemia. Objectives: 1. To determine the plasma leptin and adiponectin concentration in overweight and obese patients. 2. To evaluate the correlation between plasma leptin concentration with plasma adiponectin, glucose concentration, BMI, and blood pressure in overweight and obese patients. Methods: The study was carried out on 137 people (67 normal individuals and 70 overweight and obese patients). Concentrations of leptin and adiponectin were determined by ELISA (Enzyme Linked Immuno Sorbent Assay). Results and conclusions: concentrations of leptin in control group was 6.75 ± 5.17 ng/ml, overweight group was 8.95 ± 4.98 ng/ml, and obese group was 11.59 ± 5.76 ng/ml. Concentrations of adiponectin in control group were 9.67 ± 5.06 µg/ml, overweight group was 7.81 ± 4.83 µg/ml, and obese group was 5.87 ± 4.1 µg/ml. Concentrations of leptin in overweight and obese patients was higher than control group. Concentrations of adiponectin in overweight and obese patients was lower than control group. There were positive correlation between leptin concentration and BMI, blood pressure, fasting glucose concentration. And there was inverse correlation between leptin concentration and adiponectin concentration. Key words: Leptin, adiponectin, obese, overweight.

Failure of short-term feed restriction to affect luteinizing hormone and leptin secretion or subcutaneous adipose tissue expression of leptin in the prepuberal gilt

Previously we reported that 24-h fast increased serum non-esterified fatty acids (NEFA) concentrations, and decreased leptin pulse frequency, but not mean serum leptin concentrations in the OVX prepuberal gilt. The present study was conducted to determine if short-term feed restriction in the prepuberal gilt would reduce BF gene transcript expression, pulsatile LH secretion and serum leptin concentrations. OVX prepuberal gilts 79 ± 4 kg BW were control fed 3 kg (CF; n = 6) or feed restricted (RST; 33% of CF diet; n = 6) for 8 d to determine the effects of RST on leptin and LH secretion, metabolism, leptin, Ob-rb and transcription factor expression in BF. Blood samples were collected on day 8 and BF on day 9. RST gilts lost BW (-2.5 vs. +8.2 kg; SE = 0.6 kg; P < 0.001) and BF (-3 vs. +2 mm; SE = 1mm; P < 0.02) compared with CF gilts. Postprandial serum T4 concentrations increased (P < 0.04) in CF, but not in RST pigs. Postprandial serum insulin and BHBA concentrations were similar between treatments. A treatment × time interaction was detected for plasma glucose (P < 0.02) and NEFA (P < 0.04) concentrations. Feed restriction failed to affect leptin or LH secretion except for LH pulse amplitude was greater (P < 0.01) in RST gilts. RST failed to affect BF leptin, Ob-rb, AFABP, C/EBPα, or PPARγ2 expression. In conclusion, the ability of the prepuberal gilt to maintain energy level in the normal range suggests the prepuberal animal is resistant to moderate reduction in nutrition. Thus, leptin may not play a primary role in the regulation of LH secretion in the prepuberal gilt, but may serve as a metabolic signal reflecting the amount of stored energy, which may be necessary for activation of the reproductive axis during puberal development in the gilt. Key words: Leptin, luteinizing hormone, nutrition, adipocyte, pig

Cellular, molecular and physiological aspects of leptin: Potential application in animal production

This review encompasses the biochemistry and physiology of the newly discovered adipose hormone, leptin. Leptin appears to fulfill the role of the long sought after "lipostat", which functions to regulate energy intake in relation to body stores in the form of fat. Leptin is a 16 000 Dalton polypeptide which interacts with specific receptors in the hypothalamus to regulate food intake and body fat stores. Leptin receptors exist in several forms, which can be divided into those with small cytoplasmic domains and one with a single long cytoplasmic tail. The latter is thought to mediate most of leptin's effects, acting through the JAK-STAT signal transduction pathway. Several reports have shown direct effects of leptin on tissues with the short form of the leptin receptor. Specific effects of leptin on appetite, energy metabolism and reproduction are reviewed. Leptin may prove to be most useful to animal producers as a stimulant of the reproductive system or as a molecular marker to genetically select livestock for improved reproductive capacities or carcass characteristics, while leptin antagonists may improve metabolic rate and body composition. Key words: Leptin, obese protein, leptin receptor, review, livestock production

Leptin, the Creation of Obesity Gene and its task in Pregnancy

Leptin is a protein encoded by the ‘ob' gene. Leptin is primarily produced by adipocytes and its primary physiologic function is to suppress body fat. Obese individuals have high serum leptin levels and obesity is a leptin resistant state. There are evidences that leptin levels are higher in pregnant women compared to non pregnant women. Leptin levels increase as pregnancy advances and at term, approximate those found in obese adults. There is speculation that leptin is synthesized in placenta in addition to adipose tissue mass. Leptin may have a permissive, indirect role in regulation of fetal growth. Key Words: Leptin, Adipose tissue, Placenta, Fetus, Growth  doi: 10.3329/jbsp.v3i0.1803  J Bangladesh Soc Physiol.2008 Dec;(3):79-84.

Leptin and Other Factors as Determinants of Insulin Secretion and Sensitivity in Bangladeshi Type 2 Diabetic Subjects

Background: The relative contribution of insulin secretion and sensitivity in the development of Type 2 diabetes mellitus (T2DM) vary from population to population due to the heterogeneous nature of the disease. The study was undertaken to evaluate insulin secretory capacity and sensitivity in a Bangladeshi Type 2 diabetic population and to explore the association of some of the anthropometric and biochemical factors known to modulate B-cell function and insulin action. Methods: Ninety one T2DM subjects and 32 age-matched controls were studied for their fasting plasma glucose (FPG), lipids, HbA1c (by HPLC), leptin and C-peptide (ELISA). Insulin secretion (HOMA B) and insulin sensitivity (HOMA S) were calculated by homeostasis model assessment (HOMA). Results: Both insulin secretion and sensitivity were significantly reduced in diabetic as compared to control (HOMA B%, geometric mean±SD, 35.65±1.75 vs. 96.29±1.50, p < 0.001; HOMA S%, 68.66±1.71 vs. 104.951.63, p < 0.001). However, B-cell dysfunction was predominant than insulin resistance in predicting T2DM as the discriminate function coefficient for HOMA B (1.098) was greater than that for HOMA S (0.821). In T2DM, HOMA B had positive correlation with BMI (r=0.368, p < 0.001) and HOMA S was inversely correlated to BMI (r=-0.261, p < 0.01), WHR (r=-0.258, p < 0.01) and plasma TG (r=-0.233, p < 0.001). On multiple regression analysis HOMA B and HOMA S were found to be inversely associated to FPG (p < 0.001) and leptin (p < 0.05) in T2DM. Conclusions: Both insulin secretory dysfunction and insulin resistance are present in Bangladeshi T2DM subjects, but B-cell failure seems to be the predominant abnormality. BMI, plasma glucose, insulin and leptin are the major determinants of insulin secretory capacity and generalized as well as central obesity, plasma glucose, triglycerides, insulin and leptin are among the major determinants of insulin sensitivity in this population. Key Words: Leptin, Insulin, Diabetes  doi: 10.3329/jbsp.v3i0.1786 J Bangladesh Soc Physiol. 2008 Dec;(3):1-7.