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1.
JOHANNSSON, GUDMUNDUR, CECILIA KARLSSON, LARS LÖNN, PER MÅRIN, PER BJÖRNTORP, LARS SJÖSTRÖM, BJÖRN CARLSSON, LENA M.S. CARLSSON, BENGT-ÅKE BENGTSSON. Serum leptin concentration and insulin sensitivity in men with abdominal obesity. Obes Res. 1998;6:416–421. Objective : We have examined the association between generalized adiposity, abdominal adiposity, insulin sensitivity, and serum levels of leptin in a cross-sectional study of abdominally obese men. Research Methods and Procedures : Thirty men, 48 to 66 years of age with a body mass index (BMI) of between 25 kg/m2 and 35 kg/m2 and a waist hip ratio of <0.95, were included in the study. Serum leptin concentration was measured using radioimmunoassay. Total body fat percentage was determined from total body potassium, abdominal adiposity was measured by computed tomography, and the glucose disposal rate (GDR) was measured during an euglycemic, hyperinsulinemic glucose clamp. Results : Significant correlations were found between serum leptin concentration and BMI, percentage body fat, abdominal subcutaneous adipose tissue, serum insulin, GDR, and 24-hour urinary-free Cortisol. In a multiple regression analysis, it was shown that abdominal subcutaneous adipose tissue, GDR, and BMI explained 72% of the variability of serum leptin concentration. GDR demonstrated an independent inverse correlation with serum leptin concentration. Discussion : In abdominally obese men with insulin resistance, it was demonstrated that most of the individual variability in serum leptin concentration was explained by the amount of subcutaneous abdominal adipose tissue, insulin sensitivity, and BMI.  相似文献   

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Objective: Previous studies have reported racial differences in the amount of visceral adipose tissue (VAT), a risk factor for metabolic diseases. These results are equivocal and have not controlled for hormonal influences on VAT mass. This study was designed to measure the extent to which race is associated with VAT, controlling for total adipose tissue (TAT) mass and testosterone. Research Methods and Procedures: Using a cross‐sectional study design, we measured TAT mass using DXA, VAT and subcutaneous adipose tissue mass using magnetic resonance imaging, and sex hormones using radioimmunoassay in 224 African‐American and white men and women. Results: White men had increased VAT mass, even when controlling for TAT and age, compared with African‐American men. White women also had a higher VAT mass compared with African‐American women, but only when controlling for TAT and age. When multiple linear regression was used to evaluate the racial differences in VAT mass in a subset of subjects (n = 80), controlling for sex hormones, it was found that white men, but not women, had increased VAT mass compared with their African‐American counterparts. Discussion: Based on the results of this study, we conclude that, when controlling for TAT, sex hormone levels, and age, white men, but not women, have more VAT mass than African‐American men and women. Additional studies are needed to explore possible environmental and genetic influences on fat distribution relative to race and sex.  相似文献   

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Objective : This study was designed to determine if serum leptin concentrations (adjusted for fat mass) after weight loss on a low-calorie diet predict subsequent weight gain. Research Methods and Procedures : Body composition and serum leptin concentrations were determined on 14 moderately obese, postmenopausal, nondiabetic women with a familial predisposition to obesity. Assessments were obtained under tightly controlled metabolic ward conditions of macronutrient intake and weight maintenance both before (obese state) and after a mean weight loss of 12.0 kg to normal body weight (postobese state). Four years later, without intervention, body weight and body composition were reassessed. Results : Weight loss resulted in significant decreases in fat mass (29.7 ± 5.4 vs. 20.3 ± 4.7; kg), body mass index (27.7 ± 1.6 vs. 23.0 ± 1.5; kg/m2), percent body fat (40.7 ± 4.3 vs. 33.1 ± 5.0), and serum leptin concentrations (31.8 ± 16.0 vs. 11.5 ± 5.4; ng/mL). Serum leptin concentrations were positively correlated (p<<0.05) with fat mass in both the obese and postobese states (r = 0.67 and r = 0.56, respectively). However, residual serum leptin concentrations (adjusted for fat mass) in the obese and postobese states were not related to changes in body weight (p<= 0.61 and 0.52), fat mass (p = 0.72 and 0.42), body mass index (p = 0.59 and 0.33), or percent body fat (p = 0.84 and 0.46) over the follow-up period. Discussion : These finding do not support the hypothesis that relatively low concentrations of leptin predict weight regain after weight loss. However, because the number of subjects in this study was limited, further studies are warranted.  相似文献   

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Emilia Sanabria 《Ethnos》2013,78(4):377-401
Sex hormones in Brazil are mobilised as modes of regulatory control and to discipline subjectivites. Their packaging effectively differentiates between two forms of citizenship. The first, available to those with private health, is founded on notions of personal autonomy, individual choice and self-enhancement, while the second frames decisions in terms of the individual's moral responsibility to the wider collectivity. Here, technical and biomedical interventions on middle-class bodies have personalising tendencies, while those effected on the bodies of the urban poor can be read as modes of inclusion through standardisation. Personalisation, in the Brazilian sense, concerns the attribution of privileges which place a person above the undifferentiated mass of individuals. The paper critically engages with approaches to bio-citizenships developed in contexts where biological inclusion is predicated on patient activism and shows how, in Brazil, complying with medical regimes is an integral part of constituting oneself as a citizen  相似文献   

7.
葡萄糖与胰岛素对3T3-F442A脂肪细胞中Leptin表达的调节   总被引:1,自引:0,他引:1  
为了解葡萄糖与胰岛素对3T3F442A脂肪细胞中Leptin表达的调节,应用RTPCR方法以betaactin为内对照对不同葡萄糖和/或胰岛素浓度培养条件下3T3F442A脂肪细胞中LeptinmRNA表达水平进行相对定量分析。结果表明葡萄糖与胰岛素对3T3F442A脂肪细胞中Leptin表达有促进作用,过高浓度的葡萄糖抑制Leptin的表达及胰岛素对Leptin表达的促进。葡萄糖和胰岛素对Leptin表达的促进作用无协同效应,且这种促进作用表现出饱和性特点。葡萄糖浓度的变化对脂肪细胞中Leptin的表达与调控具有十分重要的影响。  相似文献   

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Objective: Anatomically distinct adipose tissue regions differ in their predominant modality of growth (i.e., cellular hypertrophy vs. hyperplasia). We examined site‐specific patterns of expression of two genes whose products, leptin and insulin‐like growth factor‐I (IGF‐I), could be involved in mediating differential growth and metabolism of white adipose tissue. We also related these patterns of expression to measures of adipose depot cellularity. Research Methods and Procedures: Male Wistar rats were fed ad libitum and studied from ages 7 weeks to ~12 months. Terminal measures of body weights; weights, composition, and cellularity of four white adipose depots; circulating leptin and IGF‐I; and adipose depot‐specific expression levels of leptin and IGF‐I were measured in subsets of rats at 7, 12, 22, 42, and 46 weeks of age. Results: Both leptin and IGF‐I mRNAs are quantitatively expressed in a depot‐specific manner, in the following order: retroperitoneal ? epididymal > mesenteric > subcutaneous inguinal. Furthermore, there is a marked correlation between the expressions of these hormones in the various regions of adipose tissue of rats during the first year of life. The mechanisms that underlie the parallel expressions of leptin and IGF‐I appear to be related to fat‐cell volume. Discussion: Because both leptin and IGF‐I have been implicated in the regulation of energy homeostasis and are both expressed in adipose tissue, the depot‐specific linkage between the two genes suggests interaction at the autocrine level. This interaction may have an important role in determining functional properties particular to individual adipose depots.  相似文献   

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Objective: The contribution of visceral adipose tissue (VAT) to insulin resistance is well‐established; however, the role of subcutaneous abdominal adipose tissue (SAT) in insulin resistance remains controversial. Sex may determine which of these two components of abdominal obesity is more strongly related to insulin resistance and its consequences. The aim of this study was to determine whether both VAT and SAT contribute to insulin resistance in African Americans and to examine the effects of sex on this relationship. Research Methods and Procedures: This was a cross‐sectional study of 78 nondiabetic African‐American volunteers (44 men, 35 women; age 33.8 ± 7.3 years; BMI 30.9 ± 7.4 kg/m2). VAT and SAT volumes were measured using serial computerized tomography slices from the dome of the diaphragm to the iliac crest. The insulin sensitivity index (SI) was determined from the minimal model using data obtained from the frequently sampled intravenous glucose tolerance test. Results: In men, both VAT and SAT were negatively correlated with SI (r for both correlations = ?0.57; p < 0.01). In women, the correlation coefficient between VAT and SI was ?0.50 (p < 0.01) and between SAT and SI was ?0.67 (p < 0.01). In women, the correlation coefficient for SI with SAT was significantly greater than the correlation coefficient with VAT (p = 0.02). Discussion: Both SAT and VAT are strongly correlated with insulin resistance in African Americans. For African‐American women, SAT may have a greater effect than VAT on insulin resistance.  相似文献   

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Objective: To determine the effects of fat gain, time, and race on the accumulation of visceral adipose tissue (VAT) in a group of normal‐weight premenopausal women. Research Methods and Procedures: Sixty‐five women participated in the study (32 African American and 33 white). The mean age of subjects was 34 ± 6 years (range, 22 to 47 years). Eligible subjects were women who had body mass indices <25 kg/m2 at baseline and who had completed evaluations at baseline and at follow‐up year 1, without intervention. A subset of subjects was reevaluated annually for up to 4 years. Body composition was assessed by DXA, and VAT was determined from a single computed tomography scan. A linear mixed model was used to examine changes in VAT over time, with total body fat as a covariate Results: Total fat mass was not significantly different between races at baseline and increased significantly in both groups over time (p < 0.001). Time‐related increases in total body fat were greater in African‐American women (p < 0.01). VAT was significantly higher in white women at baseline (p < 0.01) and increased significantly over time in both races (p < 0.01), but remained higher in white women (p < 0.001). Increases in VAT, relative to total body fat, were greater than the increases in total body fat over time, independent of age and race (p < 0.001). Discussion: Gaining total body‐fat mass results in a higher increase in VAT, relative to total body fat, regardless of race and age, although African‐American women maintain a lower VAT levels across time.  相似文献   

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Objective: To evaluate the effect of plasma leptin, nonsterified fatty acids (NEFAs), and tumor necrosis factor‐receptor 1 (TNFR1) on plasma insulin and insulin‐resistance status in children. Research Methods and Procedures: One thousand thirty‐two children (521 boys and 511 girls) were included in this study. We measured plasma insulin and leptin levels by radioimmunoassay, plasma NEFA levels by enzymatic acyl‐coenzyme A synthase—acyl‐coenzyme A oxidase spectrophotometric methods, and TNFR1 levels by enzyme‐linked immunosorbent assay. We calculated insulin resistance index (IRI) using homeostasis model assessment and calculated insulin‐resistance syndrome summary score (IRS) by adding the quartile ranks from the distribution of systolic blood pressure (BP), serum triglyceride, high‐density lipoprotein‐cholesterol (inverse), and insulin levels. Results: Overweight children had higher BP, plasma leptin, and insulin levels and higher IRI and IRS than normal‐weight children. Plasma leptin and TNFR1 were positively correlated with insulin levels, IRI, and IRS. The correlation coefficients of leptin and TNFR1 in IRI were 0.53 and 0.12, respectively, for boys and 0.25 and 0.18, respectively, for girls. In multivariate regression analyses, TNFR1 was positively associated with insulin level and IRI in girls; NEFA was positively associated only with IRS. Plasma leptin levels were significantly positively associated with insulin levels, IRI, and IRS, even after adjusting for BMI and other potential confounders. Discussion: Overweight children had higher BP, plasma insulin, and leptin levels and adverse insulin‐resistance status than normal‐weight children. Plasma leptin levels, rather than NEFA and TNFR1, may play a significant role in the development of hyperinsulinemia and insulin resistance in children.  相似文献   

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Objective : Leptin, an adipocyte-secreted hormone, has been shown to signal the status of energy stores to the brain, regulate energy homeostasis, and mediate the neuroendocrine response to food deprivation. Obesity is associated with increased leptin levels, and several hormones, including insulin and glucocorticoids, have been associated with leptin levels and expression in rodents. Although obesity has been strongly associated with increased leptin in humans, a significant percentage of leptin's variability remains unexplained. The role of endogenous hormones, demographic factors, or certain life-style factors in explaining the residual variability of leptin levels has not yet been clarified. We performed this cross-sectional study to document the relative importance of obesity, lifestyle factor, and endogenous hormones in determining serum leptin levels. Research Methods and Procedures : We measured serum concentrations of insulin, Cortisol, testosterone, growth hormone, and dehydroepiandrosterone sulfate; ascertained anthropometric, demographic, and lifestyle characteristics; and studied these variables in relationship to serum leptin concentrations in a sample of young healthy men. Results : Obesity and alcohol intake were independently and positively associated with circulating leptin concentrations. Additionally, cigarette smoking was negatively and independently associated with leptin concentrations. Finally, serum insulin concentration was an independent hormonal determinant of circulating leptin concentrations, whereas serum testosterone was negatively associated with leptin only by bivariate analysis. Discussion : We conclude that, in addition to obesity, cigarette smoking, alcohol intake, and serum insulin levels are associated with leptin levels in a population of healthy young men.  相似文献   

14.
Objective: To reassess the relationship between body fat and fasting leptin concentrations comparing plasma vs. serum assessments of leptin; ratios vs. regression adjustment for body composition; fat and lean mass vs. percent body fat; and gender‐, ethnic‐, and age‐related variations. Research Methods and Procedures: Subjects included 766 adults from the nondiabetic cohort of the San Luis Valley Diabetes Study examined at follow up (1997 to 1998). Body composition was determined by dual energy X‐ray absorptiometry. Leptin concentrations were determined after an overnight fast. Results: Fasting serum and plasma assessments of leptin were correlated with percent body fat to the same degree. Women had significantly higher serum leptin concentrations than men when leptin concentrations were divided by body mass index, fat mass in kilograms or percent body fat. The methodological problem inherent in interpreting these ratio measures is pictorially demonstrated. In regression analysis, fat mass alone did not explain the gender difference. However, lean body mass was inversely related to leptin concentrations (p < 0.0001) and explained 71% of the gender difference at a given fat mass. Percent body fat explained all of the gender difference in leptin concentrations in both Hispanics and non‐Hispanic whites. Similar to findings about gender differences, ethnic‐ and age‐related variations in the leptin‐body fat association were minimized when percent body fat was employed as the body fat measure. Discussion: Regression analysis and percent body fat measured with dual energy X‐ray absorptiometry are recommended when assessing the relationship between leptin and body fat. Gender differences in leptin concentrations were accounted for by percent body fat in free living (no diet control), Hispanic and non‐Hispanic white adults.  相似文献   

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The activity of choline acetyltransferase (ChAT) was investigated in the human placenta before and after long-term incubation (24 h) to test the effects of sex hormones, nicotine and forskolin. ChAT activity differed considerably between the amnion (0.03 mol/mg protein/h) and the villus (0.56). After long-term incubation, ChAT activity persisted in the latter but declined in the amnion. Neither sex hormones (-estradiol, testosterone, progesterone; 10 or 100 nM each) nor follicle stimulating hormone and luteinizing hormone (FSH/LH; 8.4 U/ml each) modified ChAT activity. Also nicotine (1 nM–100 M) did not affect ChAT activity. Forskolin, an activitor of adenylyl cyclase, reduced ChAT activity in the villus but not in amnion. The present model offers the possibility to investigate ChAT regulation in intact tissue under long-term incubation. The risks of maternal smoking during pregnancy cannot be attributed to an effect of nicotine on placental ChAT activity. Differences in the regulation of ChAT appear to exist between neuronal and nonneuronal cells.  相似文献   

16.
Objective: To study the impact of a weight‐loss program on sex hormones and sexual function among 38 middle‐aged obese men (BMI ≥35 kg/m2). Research Methods and Procedures: A randomized controlled clinical trial was conducted. The treatment group (n = 19) participated in a 4‐month weight‐loss program including 10 weeks on a very‐low‐energy diet (VLED) and 17 behavior modification visits. There was no intervention in the control group (n = 19). Both groups were followed for 8 months, i.e., 22 weeks after the active weight loss in the treatment group. The outcome measures (weight, sex hormones, sexual function, leptin, and metabolic variables) were obtained at baseline and at three time‐points during follow‐up. Results: The mean weight loss in the treatment group was 21 kg at the end of the 10‐week VLED. At the end of follow‐up, the maintained weight loss was 17 kg of baseline weight. The control group was weight stable throughout the study. In the treatment group, increases in sex hormone‐binding globulin, testosterone, and high‐density lipoprotein‐cholesterol, as well as decreases in insulin and leptin, were maintained until the end of follow‐up, although with VLED, the level of several hormones and metabolic variables improved transiently during the rapid weight loss. There were no significant changes in the questionnaire scores on sexual function in either group. Discussion: We conclude that obese men lose weight and increase their serum testosterone level on a weight‐loss program with VLED and behavior modification. However, they do not change their sexual function scores.  相似文献   

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目的:探讨女性性激素水平与骨代谢指标的关系。方法:202例女性按年龄分为40、40~49、50~59、60~69、≥70岁组,用化学发光法测定血清卵泡刺激素(FSH)、黄体生成素(LH)、雌二醇(E2)、睾酮(TES)和骨钙素(OC)、I型胶原羟基端肽β特殊序列(β-CTX)、I型前胶原氨基端前肽(PINP)。比较各组间性激素水平与骨代谢指标的差异,并进一步分析其相关性。结果:血清FSH和LH随年龄增长而升高,50岁以后达高峰;E2随年龄增长而降低,50岁以后各年龄组显著低于49岁以下年龄组(P0.05);血清OC、β-CTX、PINP随年龄增长而升高,50岁以后各年龄组显著高于49岁以下年龄组(P0.05)。校正年龄后,血清FSH、LH与OC、β-CTX呈显著正相关,E2与β-CTX呈显著负相关(均P0.01)。将FSH、LH、E2水平由低到高分成四等分组,随着FSH、LH的递增,OC、β-CTX逐渐递增;随着E2水平的递增,β-CTX逐渐递减(趋势P均0.05)。多元线性回归分析显示,FSH与β-CTX独立正相关(β=0.218,P=0.033),LH与OC独立正相关(β=0.322,P=0.004),而E2与OC、β-CTX、PINP均未见独立相关性。结论:女性骨代谢与循环中性激素水平变化有关,其主要影响因素可能是FSH、LH水平的增加,雌激素水平的下降可能起次要作用。  相似文献   

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Objective: It is under debate whether free fatty acids (FFAs) play an independent role in the regulation of adipose cell functions. In this study, we evaluated whether leptin secretion induced by FFA is due directly to an increased FFA availability or whether it is mediated by insulin levels. Research Methods and Procedures: To test this hypothesis, we compared the effects of six different experimental designs, with different FFA and insulin levels, on plasma leptin: euglycemic clamp, euglycemic clamp + FFA infusion, FFA infusion alone, FFA + somatostatin infusion, somatostatin infusion alone, and saline infusion. Results: Our results showed that euglycemic clamp, FFA infusion, or both in combination induced a similar increment of circulating leptin (3.31 ± 0.30, 3.40 ± 0.90, and 3.35 ± 0.80 ng/mL, respectively). Moreover, the inhibition of FFA‐induced insulin increase by means of somatostatin infusion completely abolished the rise of leptin in response to FFA (1.05 ± 0.30 vs. 3.40 ± 0.90 ng/mL, p < 0.001). Discussion: In conclusion, our data showed that the effects of high FFA levels on plasma leptin were mediated by the rise of insulin concentration. These data confirm a major role for insulin in the regulation of leptin secretion from rat adipose tissue and support the hypothesis that leptin secretion is coupled to net triglyceride synthesis in adipose tissue.  相似文献   

19.
Objective: Leptin concentrations increase with obesity and tend to decrease with weight loss. However, there is large variation in the response of serum leptin levels to decreases in body weight. This study examines which endocrine and body composition factors are related to changes in leptin concentrations following weight loss in obese, postmenopausal women. Research Methods and Procedures: Body composition (DXA), visceral obesity (computed tomography), leptin, cortisol, insulin, and sex hormone‐binding globulin (SHBG) concentrations were measured in 54 obese (body mass index [BMI] = 32.0 ± 4.5 kg/m2; mean ± SD), women (60 ± 6 years) before and after a 6‐month hypocaloric diet (250 to 350 kcal/day deficit). Results: Body weight decreased by 5.8 ± 3.4 kg (7.1%) and leptin levels decreased by 6.6 ± 11.9 ng/mL (14.5%) after the 6‐month treatment. Insulin levels decreased 10% (p < 0.05), but mean SHBG and cortisol levels did not change significantly. Relative changes in leptin with weight loss correlated positively with relative changes in body weight (r = 0.50, p < 0.0001), fat mass (r = 0.38, p < 0.01), subcutaneous fat area (r = 0.52, p < 0.0001), and with baseline values of SHBG (r = 0.38, p < 0.01) and baseline intra‐abdominal fat area (r = ?0.27, p < 0.06). Stepwise multiple regression analysis showed that baseline SHBG levels (r2 = 0.24, p < 0.01), relative changes in body weight (cumulative r2 = 0.40, p < 0.05), and baseline intra‐abdominal fat area (cumulative r2 = 0.48, p < 0.05) were the only independent predictors of the relative change in leptin, accounting for 48% of the variance. Discussion: These results suggest that obese, postmenopausal women with a lower initial SHBG and more visceral obesity have a greater decrease in leptin with weight loss, independent of the amount of weight lost.  相似文献   

20.
Objective: To determine the relationships between visceral and general adiposity, cardiovascular fitness, and markers of the insulin resistance syndrome in obese black and white teenagers. Research Methods and Procedures: Cross‐sectional survey of 81 obese 13‐ to 16‐year‐old youths. Visceral adipose tissue was measured with magnetic resonance imaging, and percentage body fat was measured with dual‐energy X‐ray absorptiometry. Cardiovascular fitness was assessed with a submaximal treadmill test. Fasting blood samples were analyzed for lipids/lipoproteins and insulin. Resting blood pressure was obtained using an automated cuff. Results: Visceral adipose tissue was significantly correlated with unfavorable levels of: triacylglycerol (r = 0.27, p < 0.05), total cholesterol (r = 0.27, p < 0.05), high‐density lipoprotein cholesterol (r = ?0.26, p < 0.05), the ratio of total cholesterol/high‐density lipoprotein cholesterol (r = 0.42, p < 0.01), low‐density lipoprotein cholesterol (r = 0.27, p < 0.05), apolipoprotein B (r = 0.38, p < 0.01), and systolic blood pressure (r = 0.30, p < 0.01). Multiple regression analyses revealed that visceral adipose tissue was more powerful than percentage body fat for explaining variance in lipoproteins (e.g., for the ratio of total cholesterol/high‐density lipoprotein cholesterol, r2 = 0.13, p < 0.01, and for systolic blood pressure, r2 = 0.07, p < 0.05). Ethnicity was the most powerful of the demographic predictors for blood lipids (r2 = 0.15 for triacylglycerol with lower levels in blacks; r2 = 0.10 for high‐density lipoprotein cholesterol with higher levels in blacks; r2 = 0.06 for the ratio of total cholesterol/high‐density lipoprotein cholesterol with lower levels in blacks). Cardiovascular fitness was not retained as a significant predictor of markers of the insulin resistance syndrome. Discussion: Some of the deleterious relationships between visceral adiposity and markers for the insulin resistance syndrome seen in adults were already present in these obese young people.  相似文献   

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