Mean Leptin Concentration Research Articles

Socio-Cultural Influences on Obesity and Inflammation among 2-Year Old Puerto-Rican Children at Risk for Asthma Development

ISEE-0322 Background and Objective: Recent studies have shown obesity tends to pre-date childhood asthma. While the pathways are not understood, inflammatory biomarkers are thought to play a role. The objectives are to assess serum levels of leptin and high-sensitivity C-reactive protein (hs-CRP) in early childhood and investigate their associations with body mass index (BMI), respiratory symptoms, and allergy. Methods: In a birth cohort of 181 Puerto-Rican babies born in New York City with a maternal history of inhalant allergy and/or allergic asthma, home/demographic characteristics and respiratory symptom questionnaires were administered every 6 months from birth through age 2 years. Children’s weight and height were measured and blood was collected at age 2. Serum was analyzed for leptin, hs-CRP, and allergen-specific sensitization. Obesity was defined as >95th percentile of BMI. Results: At age 2-years, median BMI percentile was 85%. Geometric mean leptin and hs-CRP concentrations were 2.66 (GSD = 1.7) and 0.30 (GSD = 7.5) ng/ml, respectively. Leptin was associated with obesity (OR = 2.4; 1.4–2.9). More girls had leptin levels above the median than did boys (60% vs 37%, P = 0.0061). At age 2 years, children in daycare were more likely to be obese (43% vs 26%, P = 0.03). While maternal birthplace was not significantly associated with the children’s leptin levels, Puerto Rican-born mothers were less likely to have children with hs-CRP above the mean (OR = 0.14, 0.02–1.10; P < 0.06) compared with women born on the U.S mainland. Leptin and hs-CRP levels were not significantly associated with sensitization to any of the measured inhalant allergens. Neither leptin nor hs-CRP levels were associated with asthma morbidity markers at age 2. Conclusion: Leptin was positively associated with female gender, BMI and obesity. Children in daycare were more likely to have higher leptin levels. Maternal birthplace (Puerto Rico) was inversely associated with hs-CRP in children, but not significantly associated with leptin. Funding acknowledgment for project: NIEHS R01 ES10922.

Serum Pattern of Circulating Adipokines throughout the Physiological Menstrual Cycle

This study investigated the serum levels of resistin, adiponectin and leptin during the physiological menstrual cycle. Sixteen women (age: 19-30 years; body mass index: 19.46-24.9) with regular menstrual cycles participated. Fasting blood samples were collected on alternate days throughout a full menstrual cycle. Mean resistin concentrations were slightly higher during the luteal phase (5.30+/-0.23 ng/ml) compared to the follicular (4.68+/-0.07 ng/ml) and midcycle (4.86+/-0.09 ng/ml) phases (p=0.032). Mean leptin concentrations during the follicular phase (18.14+/-0.28 ng/ml) were significantly lower compared to the midcycle (21.79+/-0.29 ng/ml, p=0.006) and luteal phases (23.75+/-0.64 ng/ml, p<0.001). The variation of adiponectin concentrations throughout the menstrual cycle was not significant. According to the results, circulating resistin, likewise leptin concentrations vary significantly during the physiological menstrual cycle presenting with higher values during the luteal phase. This pattern, although its physiological importance is not clear, suggests that resistin, likewise to leptin, may have a role in the regulation of cyclic female reproductive functions. The stable adiponectin concentrations throughout the menstrual cycle indicate that this adipokine probably does not play a considerable role in female reproductive functions.

A meta-analysis of leptin reference ranges in the healthy paediatric prepubertal population

The initial discovery of leptin (1994) has given rise to a substantial number of published studies. This study aimed at identifying the published data on the reference ranges of total, free and bound leptin concentration in the healthy prepubertal population. A search was conducted on original English language studies published from 1994 to 2005 in the following databases: PubMed (n = 58), EMBASE (n = 4), Biological Abstracts (n = 2) and Science Finder Scholar (n = 66). A cited reference search was completed in Science Citation Index on studies with a leptin range. A meta-analysis was completed on included studies containing a dataset and a sample size for a leptin concentration range and/or mean+/-standard deviation for a healthy prepubertal population. Preanalytical and analytical variations were examined. Preanalytical variables included aspects such as fasting state and gender, while analytical variation comprised the type of leptin assay methodology. Twelve studies met the inclusion criteria. One study examined free leptin; 11 studies examined total concentration. No studies reported leptin reference ranges established by Clinical and Laboratory Standards Institute (CLSI) criteria, although four studies reported specific study leptin ranges. The methodology of enzyme-linked immunosorbent assay demonstrated a wider leptin range than radio immunoassay (0.56-36.35 vs. 1.01-12.21 ng/mL). Males had a significantly lower mean leptin concentration than females (P = 0.0006); obese children had a higher concentration than non-obese (P = 0.0001). No studies have established CLSI-based leptin reference ranges in prepubertal healthy children and there is a wide variation in the published leptin concentrations. These differences suggest that caution should be used in the interpretation and comparison between studies.

Hyperleptinemia in Mares: Prevalence in Lactating Mares and Effect on Rebreeding Success

Previous research from our laboratory showed that approximately one third of obese, nonfoaling mares displayed a condition of hyperleptinemia coupled with hyperinsulinemia that resembled type 2 diabetes in humans. The current study was performed to evaluate the prevalence of the hyperleptinemic syndrome in lactating mares and its possible impact on their rebreeding success. Additionally, we investigated possible relationships between leptin levels in lactating versus nonlactating mares. In experiment 1, jugular blood samples were collected from 198 lactating mares on two occasions approximately 2 weeks apart. The mares resided on eight farms in Louisiana; breeds included Thoroughbred (n = 86), Quarter Horse (n = 71), Warmblood (n = 24), and draft-type (n = 17). Body condition scores (BCS) were measured at the time of blood sampling; plasma samples were assessed for leptin and progesterone concentrations. Reproductive and medical histories, as well as feeding regimens, were compiled on each mare. Based on our previous reports and examination of the current data, a mare was considered hyperleptinemic if her plasma samples contained greater than10 ng/mL leptin; normal was considered 6.0 ng/mL or less; mares with levels above 6.0 and 10 ng/mL or greater were classified as intermediate. Overall mean leptin concentration was 4.7 ng/mL, and average BCS was 5.5. After analysis, 24 mares were classified as hyperleptinemic (12%), 138 were classified as normal (70%), and 36 were classified as intermediate (18%). Leptin concentrations were affected by BCS ( P = .08), with higher concentrations in mares with higher body condition; however, there were hyperleptinemic mares with BCS of 4 to 5.5. Feeding regimen affected leptin concentrations ( P < .01), with mares on pasture full-time having the highest concentrations. There was no effect of breed, mare age, number of years the mare had been bred, number of live foals, progesterone concentrations, or last foaling date on leptin concentrations. Rebreeding success averaged 81% overall and was not affected by leptin classification. In experiment 2, nonfoaling mares kept on pasture had mean leptin concentrations of 7.0 ng/mL; 8 of 31 mares (26%) displayed hyperleptinemia. Mean leptin concentration was correlated with BCS ( R 2 = 0.65; P < .02) but was not affected by age of the mare. It was concluded that the hyperleptinemic condition occurs in lactating broodmares, even at BCS as low as 4. The overall incidence appears to be lower in broodmares than in nonfoaling mares, likely because of their lower BCS in general and the energy demands of lactation. Hyperleptinemia did not affect rebreeding success at the end of the breeding season.

Breast cancer screening in Korea

Leptin plays an important role in the regulation of body fat homeostasis, and potential associations of leptin receptor gene (LEPR) polymorphisms with obesity have been suggested. Obesity is considered to relate to breast cancer. We assessed the role of leptin in relation to breast cancer. We measured the serum leptin concentrations of 45 Korean pre-treatment patients with breast cancer and 45 age-matched controls. By direct sequencing, we investigated four leptin receptor gene (LEPR) polymorphisms at codons 109, 223, 656, and 1019. There was no significant difference between the mean leptin concentrations of the patient and control groups in both pre- and post-menopausal women. The frequencies of the wild-type for LEPR codons 109, 223, and 1019 were very low. No increased risk estimate was found for the four LEPR polymorphisms. Our results indicate that it is difficult to explain breast cancer on the basis of serum leptin concentrations or polymorphisms in the LEPR gene.

Leptin secretory burst mass correlates with body mass index and insulin in normal women but not in women with polycystic ovary syndrome

Leptin secretion exhibits a pulsatile, circadian pattern and may play a role in reproduction. No previous studies have compared leptin secretory burst characteristics in normal eumenorrheic women and women with polycystic ovary syndrome (PCOS) who are appropriately matched for body mass index (BMI). To determine if leptin secretory burst characteristics and/or the relationships of BMI, insulin, or testosterone to these characteristics differ between PCOS and normal women, we studied 9 normal eumenorrheic women and 9 women with PCOS. Each woman underwent blood sampling every 10 minutes for 24 hours to measure leptin and insulin under controlled conditions. Leptin secretory bursts were identified and characterized using multiparameter deconvolution procedures (Deconv), and the 24-hour periodicity of leptin was characterized with cosinor analysis. Relationships between BMI, area under the curve (AUC) insulin, and testosterone and leptin secretory burst characteristics in PCOS and normal women were sought using linear regression. There were no significant differences in mean serum leptin concentrations or in secretory burst characteristics between PCOS and normal women. Although the 24-hour serum leptin concentration correlated with BMI in both normal and PCOS women, leptin secretory burst mass correlated with BMI only in normal women. Similarly, the 24-hour serum leptin concentration correlated with serum insulin AUC in both normal and PCOS women; but insulin AUC correlated with leptin burst mass only in normal women. Although there was a strong trend toward a correlation between both mean 24-hour serum leptin concentration and leptin secretory burst mass with the serum testosterone concentration in normal women, such trends were not seen in PCOS women. Both normal and PCOS women exhibited a diurnal rhythm of leptin secretion with the peak occurring at night. However, neither the peak amplitude nor the timing of the peak amplitude differed between normal and PCOS women. The presence of strong relationships between BMI and insulin with both mean serum leptin and leptin secretory burst mass in normal women as opposed to PCOS women suggests that the mechanisms subserving leptin secretion differ in these 2 groups.

Changes in the Hypothalamic-Pituitary-Adrenal Axis and Leptin Levels during Antidepressant Treatment

Background: In depressed patients, overstimulation of the hypothalamo-pituitary-adrenocortical (HPA) system, probably caused by glucocorticoid receptor resistance, is the most consistent neurobiological finding. Glucocorticoids themselves are reported to increase leptin synthesis and secretion in humans. Methods: We examined alterations in plasma levels of leptin as well as changes in the HPA system function using the combined dexamethasone/corticotropin-releasing hormone (dex/CRH) test on admission and at discharge in 74 depressed inpatients. Results: Mean leptin concentration did not change significantly between admission and discharge. However, changes in ACTH response and partial cortisol response to the combined dex/CRH test between admission and discharge were significantly correlated with leptin levels at discharge. Conclusions: Leptin levels at discharge rise as the HPA axis normalizes. These findings may be explained by an improvement in glucocorticoid receptor sensitivity among depressed patients during antidepressant therapy and a consecutively increased influence of glucocorticoids on leptin levels via the glucocorticoid receptor.

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 &lt; 0.001) and BF (-3 vs. +2 mm; SE = 1mm; P &lt; 0.02) compared with CF gilts. Postprandial serum T4 concentrations increased (P &lt; 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 &lt; 0.02) and NEFA (P &lt; 0.04) concentrations. Feed restriction failed to affect leptin or LH secretion except for LH pulse amplitude was greater (P &lt; 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

Gingival crevicular fluid and serum leptin: their relationship to periodontal health and disease

Leptin is a pleiotrophic hormone produced by adipose tissue and it plays an important role in protection of the host from inflammation and infection. The purpose of this study is to determine the presence of leptin in gingival crevicular fluid (GCF) and serum samples and to find out their association, if any. Forty two subjects were selected based on their body mass index and were divided into three groups of 14 each; healthy (Group I), chronic gingivitis (Group II) and chronic periodontitis (Group III). GCF samples (by microcapillary pipettes) and serum samples (by venipuncture) were collected to estimate the levels of leptin using enzyme linked immunosorbent assay kit. The highest mean leptin concentration in GCF was obtained for Group I (2658 pg/ml) and the least for Group III (1312 pg/ml). In contrast, the lowest serum leptin concentration was obtained for the Group I (8783 pg/ml), and the highest for Group III (12082 pg/ml). This suggests a negative correlation of GCF leptin concentration and a positive correlation of serum leptin concentration as the clinical attachment level progresses (p<0.05). These results suggest that greater the periodontal destruction, lesser is the GCF leptin concentration and greater the serum leptin concentration.

Intra-follicular leptin concentration as a predictive factor for in vitro oocyte fertilization in assisted reproductive techniques

Granulosa-cells are able to produce and store leptin, suggesting that this hormone is locally involved in the regulation of follicular growth. In this study, the role of follicular fluid (FF) leptin concentration in predicting oocyte fertilization and embryo quality was evaluated in 35 normogonadotrophic women undergoing controlled ovarian stimulation (COS) for assisted reproductive techniques. Leptin concentration was measured in 47 consecutively collected FF in which a mature oocyte had been found during the ovum pick-up. Embryos deriving from fertilized oocytes were submitted to quality scoring systems. Mean leptin concentration was significantly higher in FF whose oocytes showed 2 pronuclei (no. 25) when compared with those with no evidence of fertilization (no. 22) at the 16-18 h check (26.0+/-6.1 vs 15.3+/-10.6 ng/ml, respectively, p<0.01). Follicular mean diameters were similar in the two groups (21.4+/-3.4 and 21.0+/-5.1 mm, respectively). Logistic regression analysis identified FF leptin levels as the best predictive parameter for oocyte fertilization (p<0.001). When receiving operating characteristics curve was employed, a FF leptin concentration of 20.25 ng/ml was the most reliable cut-off in predicting fertilization of oocytes. FF with leptin concentrations higher than this value (no. 27) had an oocyte fertilization rate of 85.7%. In contrast, FF levels < or =20.25 ng/ml (no. 20) were associated with a rate of 16.7% (p<0.05). No correlation emerged between FF leptin and the score attributed to 15 valuable embryos at the zygote stage (r=-0.01) and at 48 h after insemination (r=0.1). FF leptin levels are a better predictor of oocyte fertilization success rates than follicular diameter. These results underline the relevance of FF variables in developing methods for oocyte selection.

Meal size and feeding frequency influence serum leptin concentration in yearling horses

Energy is an essential nutrient for all horses, and it is especially important in performance horses, pregnant and lactating mares, and young growing horses. A negative energy balance in horses such as these may result in unsatisfactory performance, decreased fertility, or slow growth. Therefore, ensuring adequate energy intake is an important aspect of the nutritional management of the equine. This study was undertaken to investigate the effects of feeding large, carbohydrate-rich, concentrate meals on the satiety-inducing hormone, leptin. Three groups of yearling horses were rotated through 3 feeding schedules in a replicated 3x3 Latin square design. Horses were fed 2, 3, or 4 times per day (2x, 3x, and 4xfeeding schedules, respectively), each for a period of 11 d, with the total amount of daily feed held constant. Horses were weighed and BCS was determined on the first day of each period. Blood samples were collected before the morning meal on d 1, 4, and 7 of each period. Additionally, blood was sampled for the last 24 h of the 2xand 4xdietary periods. Neither weight nor BCS changed during the study (P = 0.99 and P = 0.28, respectively). Both mean and peak plasma glucose were greatest in 2xhorses (P < 0.05), as were mean areas under the curve. Serum leptin concentration increased in 2xhorses (P < 0.05), but not in horses fed 3 or 4 times daily. Leptin was elevated in horses with greater BCS (P < 0.05) and increased steadily throughout the study (P < 0.05). Data from the 24-h collection indicated that 2xhorses had fluctuations in leptin production throughout the day (P < 0.05), whereas horses fed 4 times daily did not. Overall, this study indicates that feeding horses 2 large concentrate meals daily can increase mean serum leptin concentrations and may cause fluctuations in leptin production over a 24-h period. This departure from baseline leptin concentration has the potential to affect appetite, along with numerous other physiological processes.

Serum Adiponectin and Leptin Concentrations in HIV-Infected Children with Fat Redistribution Syndrome

Human immunodeficiency virus (HIV)-related lipodystrophy is characterized by adipose tissue redistribution, dyslipidemia, and insulin resistance. We hypothesized that fat redistribution and metabolic abnormalities in HIV-infected children are related to alterations in endocrine function of adipose tissue. A multicenter study was conducted in 130 HIV-infected children. Lipodystrophy definition was based on the central to peripheral skinfold ratio. Fasting adiponectin, leptin, insulin concentrations, glycemia, and lipid profile were measured in all children. Fat redistribution syndrome was apparent in 32 children: 14 with atrophic (LPDA) and 18 with hypertrophic lipodystrophy (LPDH). Mean serum adiponectin levels were significantly decreased in LPDA and LPDH groups compared with the group with no lipodystrophy (LPD-). Fasting insulin concentration was significantly higher in LPDA and LPDH groups versus LPD-. Mean serum leptin concentration was significantly increased only in LPDH compared with LPDA and LPD- groups. Triglyceride levels were significantly increased and high-density lipoprotein (HDL)-cholesterol concentration decreased in the LPDA versus LPD- group. Controlling for puberty stage, gender, percentage of total fat mass, serum lipids, HIV treatment, and disease severity, adiponectin was significantly and inversely associated with central obesity and insulin/glucose ratio. Fat redistribution had no significant effect on leptin concentration, which was directly related to the percentage of body fat, female gender, and insulin/glucose ratio. In conclusion, HIV-infected children with symptoms of fat redistribution have decreased levels of adiponectin, associated with insulin resistance and dyslipidemia.

Effect of alterations in the quantity and composition of the pre-mating diet on embryo survival and foetal growth in the pig

This trial examined the effects of feeding six diets, which varied in either amount or composition, during the oestrous cycle prior to insemination on embryo survival and foetal development on day 27 ± 2 of pregnancy in gilts. Ten or 11 gilts per group received either a maintenance (M) diet, 1.8 × M, 2.6 × M or nutritionally balanced diets in which the content of fibre, protein or starch was increased. Of the six diets tested, only the high fibre diet significantly increased embryo survival when compared to its 1.8 × M isoenergetic control (88.20 ± 1.96% versus 81.25 ± 2.67%; P < 0.05). More litters from gilts fed the 1.8 × M and the starch diets had foetuses defined as intra-uterine growth retarded (IUGR; 50% and 62.5 of litters, respectively), compared to the other four groups in which 0–12.5% of litters contained IUGR foetuses ( P < 0.05). There was no effect of dietary treatment on foetal or placental size or on the within-litter variability in foetal and placental size. Plasma concentrations of oestradiol and progesterone on days 4–8 of the oestrous cycle and on day 27 ± 2 of pregnancy were unaffected by treatment. Feed intake was positively related to mean plasma IGF-1 concentrations on days 4–8 of the cycle ( P < 0.01) and to mean leptin concentrations on days 4 and 5 ( P < 0.001). Leptin concentrations were unaffected by alterations in the composition of the diet, whereas IGF-1 concentrations were higher in gilts fed the starch diet compared to the M control (159 ± 9.52 versus 127 ± 7.65 ng/ml; P < 0.05). These data demonstrate that alteration to the composition of the feed consumed during the cycle before insemination can affect both embryo survival and the distribution of foetal size within the litter. The underlying mechanism(s) remain to be determined, but probably involve dietary-induced changes in concentrations of reproductive hormones and/or intermediary metabolites that in turn affect ovarian follicular and oocyte development.

Circulating leptin and body composition in chronic obstructive pulmonary disease

Nutritional depletion and weight loss are two features of chronic obstructive pulmonary disease (COPD), and the association between low body mass index (BMI) and poor prognosis in patients with COPD is a common clinical observation. Mechanisms of weight loss are still unclear in COPD. Excessive energy expenditure partly due to increased work of breathing was shown, but other mechanisms have been searched for. Leptin is a hormone secreted by adipocytes that plays an important role in energy homeostasis and regulates body weight through control of appetite and energy expenditure. The aim of this study was to evaluate the association of circulating leptin levels and measures of body composition in COPD patients. Thirty male COPD outpatients (mean age 66.3 +/- 8.4) and 20 controls (mean age 65.9 +/- 10.8) were included in the study. After standard spirometry and body composition measurements, serum leptin concentration was measured by ELISA assay. COPD patients were grouped according to BMI. Mean BMI was 19.01 +/- 2.26 kg/m2 in group 1 (COPD patients with low BMI), 26.85 +/- 4.51 in group 2 COPD (COPD patients with normal/high BMI) and 27.64 +/- 2.75 kg/m2 in healthy controls (group 3). Mean serum leptin concentration was 1.41 +/- 1.86 ng/ml in group 1, 2.60 +/- 1.38 ng/ml in group 2 and 2.82 +/- 1.46 ng/ml in group 3 (p = 0.002). Leptin correlated to not only BMI but also body weight, waist circumference, triceps and biceps skinfold thickness and body fat percent (p < 0.05 for all). Results of this study suggest that the cause of weight loss is not increased circulating leptin in COPD. Instead, leptin remains regulated in COPD and further decreased in patients with low BMI, probably as a compensatory mechanism to preserve body fat content, which should be evaluated in further studies.

Relationships among serum leptin, leptin receptor gene polymorphisms, and breast cancer in Korea

Leptin plays an important role in the regulation of body fat homeostasis, and potential associations of leptin receptor gene ( LEPR) polymorphisms with obesity have been suggested. Obesity is considered to relate to breast cancer. We assessed the role of leptin in relation to breast cancer. We measured the serum leptin concentrations of 45 Korean pre-treatment patients with breast cancer and 45 age-matched controls. By direct sequencing, we investigated four leptin receptor gene ( LEPR) polymorphisms at codons 109, 223, 656, and 1019. There was no significant difference between the mean leptin concentrations of the patient and control groups in both pre- and post-menopausal women. The frequencies of the wild-type for LEPR codons 109, 223, and 1019 were very low. No increased risk estimate was found for the four LEPR polymorphisms. Our results indicate that it is difficult to explain breast cancer on the basis of serum leptin concentrations or polymorphisms in the LEPR gene.

Effects of short-term feed deprivation and melatonin implants on circadian patterns of leptin in the horse1

Leptin is a protein hormone produced by adipose tissue that influences hypothalamic mechanisms regulating appetite and energy balance. In species tested thus far, including horses, concentrations of leptin increase as animal fat mass increases. The variables and mechanisms that influence the secretion of leptin are not well known, nor is it known in equine species how the secretion of leptin is influenced by acute alterations in energy balance, circadian patterns, and/or reproductive competence. Our objectives were to determine in horses: 1) whether plasma concentrations of leptin are secreted in a circadian and/or a pulsatile pattern; 2) whether a 48-h period of feed restriction would alter plasma concentrations of leptin, growth hormone, or insulin; and 3) whether ovariectomy and/or a melatonin implant would affect leptin. In Exp. 1, mares exposed to ambient photoperiod of visible light (11 h, 33 min to 11 h, 38 min), received treatments consisting of a 48-h feed restriction (RES) or 48 h of alfalfa hay fed ad libitum (FED). Mares were maintained in a dry lot before sampling and were tethered to a rail during sampling. Analyses revealed that leptin was not secreted in a pulsatile manner, and that mean leptin concentrations were greater (P < 0.001) in FED vs. RES mares (17.20 +/- 0.41 vs. 7.29 +/- 0.41 ng/mL). Plasma growth hormone was pulsatile, and mean concentrations were greater in RES than FED mares (2.15 +/- 0.31 vs. 1.08 +/- 0.31 ng/mL; P = 0.05). Circadian patterns of leptin secretion were observed, but only in FED mares (15.39 +/- 0.58 ng/mL for morning vs. 19.00 +/- 0.58 ng/mL for evening; P < 0.001). In Exp. 2, mares that were ovariectomized or intact received either a s.c. melatonin implant or a sham implant. Thereafter, blood was sampled at weekly intervals at 1000 and 1700. Concentrations of leptin in samples collected at 1700 were greater (P < 0.001) than in those collected at 1000 (28.24 +/- 1.7 vs. 22.07 +/- 1.7 ng/mL). Neither ovariectomy nor chronic treatment with melatonin affected plasma concentrations of leptin or the circadian pattern of secretion. These data provide evidence that plasma leptin concentrations in the equine are sensitive to acute changes in nutritional status and vary in a circadian pattern that is sensitive to fasting but not to melatonin treatment or ovariectomy.

Association between serum leptin concentration and white blood cell count in middle-aged Japanese men and women

Leptin's hematopoietic or proinflammatory role has been experimentally reported. We investigated whether serum leptin concentrations are associated with white blood cell (WBC) counts in humans. Serum leptin concentrations of Japanese civil servants aged 40 to 59 years (1082 men and 200 women) were analyzed in relation to their WBC count. Serum leptin concentrations and WBC counts were measured by radioimmunoassay and automated particle counter respectively, using samples obtained at the time of the participants' annual health checkups. The geometric mean (+/-geometric standard deviation) leptin concentrations were 3.25 +/- 1.82 ng/mL and 6.25 +/- 3.99 ng/mL, and the geometric mean WBC counts, 5770 +/- 1269/mm(3) and 5107 +/- 1228/mm(3), in men and women respectively. The WBC count adjusted for age, body mass index (BMI), physical activity, and drinking and smoking habits increased together with the increase in leptin concentration. Multiple linear regression against WBC count by the leptin concentration and those covariates revealed a significant and independent association with serum leptin concentration especially in women (standardized beta = 0.31, p < 0.001), and also in men (standardized beta = 0.17, p < 0.001). BMI was not significantly associated with WBC counts in the multivariate model adjusting for leptin levels in both sexes. Our results are in line with leptin's hematopoietic or proinflammatory functions. The increased WBC counts often observed in obese people would be mediated by the increased leptin concentration.

Proinflammatory Cytokines and Leptin Are Increased in Serum of Prepubertal Obese Children

It has not yet been shown in prepubertal children how cytokines, leptin, and body mass, as well as parameters of obesity are interrelated. The aim of this study was to explore the relation between circulating levels of some cytokines with leptin and body mass index. A case control study was carried out in obese children of both sexes. An obese group was carried out with 63 school prepubertal children and a control group comprised the same number of nonobese children paired by age and by sex. Mean serum leptin concentration was significantly higher in the obese children at 19.9 ± 7.4 ng/mL, than the control group (7.9 ± 5.1 ng/mL). Serum IL-1β, IL-6, and TNF-α levels were also significantly higher in the obese group than controls (33.0 ± 8.9, 45.2 ± 11.8, and 9.2 ± 2.3 pg/mL, versus 3.6 ± 1.0, 13.1 ± 3.9, and 3.9 ± 1.0 pg/mL, resp). In controversy, serum IL-2 level was diminished in the obese group as 0.4 ± 0.1 versus 0.9 ± 0.1 U/L. Obesity may be a low-grade systemic inflammatory disease. Obese prepubertal children have elevated serum levels of IL-1β, IL-6, and TNF-α which are known as markers of inflammation.

Serum leptin concentrations and body adipose measures in older black and white adults

Among US adults, serum leptin concentrations are higher in women than in men and are higher in blacks than in whites independent of anthropometric measures of body fatness. Using radiographic measures of body fat, we determined the best correlates of leptin and whether adiposity can explain sex and race differences in leptin concentrations in older adults. This was a cross-sectional analysis of fasting serum leptin concentrations and body fat measured by dual-energy X-ray absorptiometry (DXA), abdominal computed tomography, and standard anthropometry in 3026 well-functioning 70-79-y-old participants (42% black, 51% women) of the Health, Aging, and Body Composition Study. Geometric mean (+/-SE) leptin concentrations (ng/mL) were higher in the women than in the men (16.5 +/- 0.3 and 5.7 +/- 0.1, respectively) and in the black women than in the white women (20.2 +/- 0.6 and 13.9 +/- 0.4, respectively), but did not differ significantly between the white and black men (5.8 +/- 0.2 and 5.5 +/- 0.2, respectively). Percentage fat estimated from DXA showed the highest correlation with leptin (R(2) = 0.56 for both sexes). Addition of abdominal visceral fat minimally increased the correlation. In the multivariate analysis, the association with sex was eliminated after adjustment for percentage fat and visceral fat in both whites (P = 0.051) and blacks (P = 0.34). Among women, higher leptin concentrations in blacks remained after adjustment for percentage fat and visceral fat (mean race difference = 4.95 ng/mL; P < 0.001). Among men, an association with black race emerged after adjustment for these factors (mean race difference = 1.42 ng/mL; P < 0.001). Among older adults, higher serum leptin concentrations in women are explained by a greater percentage of body fat. Higher leptin concentrations in blacks are not explained by percentage of body fat.

Serum leptin concentrations in children with mild protein‐energy malnutrition and catch‐up growth

The aim of the present study was to clarify the relationship between changing nutritional anthropometric data and serum leptin concentrations during the catch-up growth process in children. Thirty children with mild protein-energy malnutrition (PEM) were followed for 6 months and their anthropometric measurements and serum leptin concentrations were recorded during follow up. Twenty-two (73.3%) of the 30 children showed catch-up growth. All parameters and serum leptin concentrations increased during the period of catch-up growth. In the remaining eight children, weight for height, percentage standard body mass index, percentage standard body height and mean serum leptin concentrations did not show any significant increase at the 6 month follow-up. Mean serum leptin concentration was higher in children with catch-up growth than in the controls. During recovery from malnutrition, leptin concentrations increase in relation to fat mass if the fat mass reaches a critical point, and leptin might trigger catch-up growth with its regulator effects on growth. Although weight gain was noted in both groups, an increase in leptin concentration was observed only in children who showed catch-up growth. More interestingly, the mean leptin concentration was much higher in children with PEM who had catch-up growth compared to the control group and in children who failed to have catch-up growth. In children with catch-up growth, the higher serum leptin concentrations compared to healthy children and to children without catch-up growth despite significant weight gain suggests that leptin affects nutritional status in catch-up growth as a dynamic process, rather than merely being an index of body fat content.