Mutational analysis of the coding region of the uncoupling protein 2 gene in obese NIDDM patients: Impact of a common amino acid polymorphism on juvenile and maturity onset forms of obesity and insulin resistance

Summary Recently, a gene encoding a novel human uncoupling protein, designated UCP2, was discovered. The murine UCP2 was mapped to a region on mouse chromosome 7 which in several models has been shown to be linked to obesity and hyperinsulinaemia. Single strand conformation polymorphism (SSCP) analysis and direct sequencing of the coding region of the UCP2 gene in 35 obese Caucasian NIDDM patients of Danish ancestry revealed one nucleotide substitution, replacing an alanine with a valine at codon 55. The amino acid polymorphism was present in 24 of the 35 (69 %) examined subjects. The allelic frequency of the A/V55 variant was 48.3 % (95 % CI: 42.5–54.1 %) among 144 subjects with juvenile onset obesity, 45.6 % (40.5–50.7 %) among 182 subjects randomly selected at the draft board examination, and 45.5 % (37.1–53.9 %) among lean control subjects selected from the same study cohort. Within these cohorts there were no differences in BMI values at different ages among wild-type carriers and A/V55 carriers. In a population-based sample of 369 young healthy Caucasians the variant showed no association with alterations in BMI, waist-to-hip ratio, fat mass or weight gain during childhood or adolescence. The A/V55 polymorphism was not related to alterations in fasting values of serum insulin and C-peptide or to an impaired insulin sensitivity index. We conclude that genetic variability in the human UCP2 gene is not a common factor contributing to NIDDM in obese Danish Caucasian subjects and the common A/V55 amino acid polymorphism of the gene is not implicated in the pathogenesis of juvenile or maturity onset obesity or insulin resistance in Caucasians. [Diabetologia (1997) 40: 1227–1230] Received: 20 June 1997     

Interactions between physical activity and variants of the genes encoding uncoupling proteins -2 and -3 in relation to body weight changes during a 10-y follow-up

OBJECTIVE: To examine interactions between physical activity and possibly functional variants of the genes encoding uncoupling proteins -2 and -3 in relation to body weight change. We hypothesize that physical inactivity acts synergistically with a 45 bp insertion variant in the 3'untranslated region (3'UTR) of the UCP2-gene and with a t-allele of codon -55 in the promoter of the UCP3-gene in relation to subsequent weight change. DESIGN: Population-based longitudinal study of cohorts of juvenile obese and nonobese men, who were identified at the mandatory draft board examination in Copenhagen and adjacent regions at a median age of 19 y in 1943-77 and later examined at general health surveys in 1981-83 and 1991-93. The juvenile obese cohort included 568 men who at the draft board had a BMI > or =31 kg/m2 and the cohort of controls included 717 randomly selected draftees. MEASUREMENTS: Height and weight were measured, and information about physical activity was collected from a self-administered questionnaire. The genotyping of the polymorphisms was performed using RFLP techniques. The main outcome measure was change in BMI during the 10-y follow-up period. Additional outcome measures were obesity, waist circumference and body fat mass index measured at follow-up. RESULTS: Physical activity, the 3'UTR insertion polymorphism and the -55 c/t polymorphism were not consistently associated with changes in BMI, and there were no evidence for interactions between the UCP-variants and physical activity in relation to changes in BMI. No evidence for interaction between the UCP-variants and physical activity was found in relation to the additional obesity measures. CONCLUSION: This study does not support that interactions between physical activity and variants in the UCP2- or UCP3-gene are major determinants of subsequent weight changes in Danish Caucasian men.     

A genetic variation in the 5 ′ flanking region of the UCP3 gene is associated with body mass index in humans in interaction with physical activity

Aims/hypothesis. In obese French Caucasian subjects we previously described a silent UCP3 Tyr99Tyr mutation, associated with body mass index. We hypothesised that an unknown polymorphism in the vicinity of the gene could contribute to obesity.¶Methods. Morbidly obese subjects were screened for mutations in 1 kb upstream from the UCP3 gene. Association studies were done between a variant and obesity in 401 morbidly obese and 231 control subjects.¶Results. We detected three rare genetic variants and one polymorphism: a + 5 G→A in exon 1, a –155 C→T, a –439 A insertion and a –55 C→T located 6 bp from the putative TATA box. This variant was in linkage disequilibrium with the Tyr99Tyr polymorphism. Frequencies of the variant allele at the –55 locus were similar in the obese and control groups (0.23 vs 0.21). The –55 polymorphism was associated with BMI in the obese group (p = 0.0031): BMI was higher in TT than in CC or CT patients. Likewise control subjects with a TT genotype had a higher BMI (p = 0.03). In the obese group, homozygocity for this variant is a risk factor for high BMI (odds ratio: 1:75, p = 0.02). Obese patients were divided into tertiles according to physical activity. In the group with a wild C/C genotype, BMI was negatively associated with physical activity (p = 0.015).¶Conclusion/interpretation. The C→T polymorphism in the 5 ′ sequences of the UCP3 gene might contribute to the corpulence in obese and normal weight subjects and alter the benefit of physical activity. The UCP3 gene can be considered as a gene modifying corpulence. [Diabetologia (2000) 43: 245–249]     

Variants of uncoupling protein-2 gene and obesity: interaction with peroxisome proliferator-activated receptorgamma2

OBJECTIVE: To analyse the association of the UCP2 gene, alone or in combination with the PPARgamma2 gene, with obesity. DESIGN: Cross-sectional, case-control study. STUDY POPULATION: From a working population of 4500 Italian Caucasian employees of the Italian telephone company participating in a firm-sponsored health screening programme, we selected all those with obesity [n = 122; body mass index (BMI) > or = 30 kg/m2]. For each case, three nonobese age- and sex-matched individuals were selected as controls from the same population (n = 374). Included in the study were also 76 severely obese (BMI > or = 40 kg/m2) patients consecutively admitted to the obesity clinic of the department. Diabetic individuals were excluded. MEASUREMENTS: The -866G/A UCP2 and the Pro12Ala PPARgamma2 polymorphisms were determined on genomic DNA of the studied individuals. Several metabolic and anthropometric measures were also obtained, like plasma glucose, insulin, triglycerides, total cholesterol, high-density lipoprotein (HDL) cholesterol and BMI. RESULTS: BMI, plasma glucose, insulin, triglycerides, total and HDL cholesterol were not significantly different in carriers and noncarriers of the -866G/A variant. No significant association was observed between the -866G/A UCP2 gene polymorphism and moderate or severe obesity. This was also observed when the UCP2 polymorphism was analysed in combination with the PPARgamma2 polymorphisms. CONCLUSIONS: The -866G/A variants of the UCP2 gene are not associated with either obesity or other features of the metabolic syndrome in the studied groups of the Italian population. This negative finding is not modified after a combined analysis of the UCP2 polymorphism and the Pro12Ala polymorphism of PPARgamma2.     

A prevalent polymorphism in the promoter of the UCP3 gene and its relationship to body mass index and long term body weight change in the Danish population

Variability of the uncoupling protein 3 (UCP3) promoter has been associated with increased body mass index (BMI) and altered lipid profiles. Here we tested the hypothesis that variation of the UCP3 promoter is associated with either juvenile or maturity-onset obesity or body weight change over a 26-yr follow-up among Danish subjects. Mutation screening of approximately 1 kb 5' upstream of the UCP3 gene revealed one previously described -55 C-->T variant. The frequency of the polymorphism was evaluated by restriction fragment length polymorphism analysis in four groups of subjects: 1) a group of 744 obese Danish men who at the draft board examinations had a body mass index (BMI) of at least 31 kg/m(2), 2) a randomly selected control group consisting of 857 draftees, 3) 258 middle-aged subjects, and 4) 409 60-yr-old subjects. The frequency of the T allele was 26.0% (95% confidence interval, 23.8-28.2%) among the obese draftees and 26.9% (24.8-29.0%) in the control group (P = 0.6). The variant was not associated with BMI at a young age or with weight gain after a 26-yr follow-up. The frequency of the T allele was 29.5% (25.6-33.4%) in the middle-aged group and 25.8% (22.8-28.8%) among the 60-yr-old subjects. The polymorphism was not associated with increased BMI or percent body fat in these 2 groups. It is concluded that this variant does not play a major role in the development of common obesity among Danish subjects.     

An untranslated insertion variant in the uncoupling protein 2 gene is not related to body mass index and changes in body weight during a 26-year follow-up in Danish Caucasian men

Aims: Associations between a 45 bp 3 ′untranslated insertion polymorphism in the uncoupling protein 2 (UCP2) gene and both body mass index (BMI) and sleeping metabolic rate have previously been reported. We investigated the impact of this polymorphism on BMI and long-term body weight changes.¶Methods. The allelic frequency of the UCP2 insertion variant was determined in a cohort of 744 obese Danish Caucasian men who had a BMI of at least 31 kg/m² at the draft-board examinations and a randomly selected control cohort consisting of 872 draftees. Follow-up measurements of BMI were done on average 26 years after the draft-board examinations.¶Results. The prevalence of the insertion allele was 30.4 % (95 % confidence interval: 28.0–32.8 %) among the obese and 29.6 % (27.4–31.8 %) in the control group (p = 0.6). In a lean group selected as the 354 subjects with a BMI less than 25 kg/m² at 46 years of age from the control group, the frequency of insertion allele was 29.0 % (27.2–30.8 %) (p = 0.5 compared with the obese cohort). The BMI at the ages of 20 and 46 years did not differ between genotypes either in the obese or the control group. Similarly, the changes in BMI/year between examinations at 20 and 46 years of age did not differ between genotypes in either group.¶Conclusion/interpretation. In a large group of Danish Caucasian men we found no association between a 3 ′untranslated insertion polymorphism in the UCP2 gene and obesity. Neither did we identify a relation between this variant and BMI changes during adult age. [Diabetologia (1999) 42: 1413–1416]     

UCP2 A55V variant is associated with obesity and related phenotypes in an aboriginal community in Taiwan

OBJECTIVE: Human uncoupling proteins 2 and 3 (UCP2 and UCP3) are two mitochondrial proteins that are involved in the control of metabolism of fatty acid and possibly protect against oxidative damage. The aim of this study was to analyze genetic associations of four polymorphisms of the UCP2 and UCP3 genes with insulin, leptin concentration and obesity in Taiwan aborigines. RESEARCH METHODS: Four polymorphisms were compared in 324 obese (body mass index (BMI) > or =30 kg/m(2)) and overweight (30>BMI > or =25 kg/m(2)) subjects, and 114 normal weight subjects (BMI <25 kg/m(2)) in an aboriginal community of southern Taiwan. Anthropometric characteristics and fasting levels of insulin, leptin, triglycerides and cholesterol were measured. RESULTS: Before and after adjusting for age distribution, only the Val55 allele in exon 4 of the UCP2 gene increased the risk of overweight and obesity (adjusted odds ratio (OR)=2.02, P=0.004) in comparison with Ala55. UCP2 V55V is also associated with higher fasting insulin levels than A55V (P=0.01) and A55A (P=0.04) in the obese/overweight group. Using the COCAPHASE program of the UNPHASED software, haplotype analysis of three single nucleotide polymorphisms (A55V-G866A-C-55T) revealed that A-G-C (73% in obese subjects and 77% in controls) was the most common haplotype and that the haplotype V-A-T (13% in obese subjects and 5% in controls) was significantly increased in obese and overweight subjects (BMI > or =25 kg/m(2)) (OR=2.62, P<0.001). DISCUSSIONS: UCP2 A55V variant might predispose to obesity and Val55 allele to confer population-attributable risk for 9.5% of obese disorders and increase insulin concentrations. The V-A-T haplotype within UCP2-UCP3 gene cluster is also significantly associated with obesity in Paiwan aborigines.     

Association of UCP3 gene -55C>T polymorphism and obesity in a Spanish population

BACKGROUND/AIMS: The uncoupling protein 3 (UCP3) gene has been suggested as a possible determinant affecting obesity risk given its function in the regulation of energy metabolism. However, available genetic association studies have been inconsistent, which could be attributable to not considering individual lifestyle patterns, such as physical activity, a factor that affects UCP3 expression. The objective of this study was to assess the association between the UCP3 -55C>T polymorphism and the risk of obesity. METHODS: Case-control study conducted in a sample of Spanish adults. 157 obese subjects (BMI > or = 30) and 150 controls (BMI < 25) participated in the study. UCP3 -55C>T polymorphism was identified by the polymerase chain reaction-restriction fragment length polymorphism methodology. RESULTS: The odds ratio (OR) for obesity (95% confidence interval [CI]) according to the presence of UCP 3 gene -55C>T polymorphism (heterozygotes and homozygotes merged together), adjusting for age, sex, and recreational physical activity, was 0.61 (0.37-1.00), p = 0.05. Interestingly, this association was only manifest among those with higher recreational physical activity (OR: 0.46, 95% CI 0.21-0.99, p = 0.05) and not among those with lower physical activity (OR: 0.84, 95% CI 0.41-1.70, p = 0.84). CONCLUSION: UCP3 -55C>T polymorphism carriers have apparently a lower risk of obesity when taking into consideration recreational energy expenditure. Interestingly, this inverse beneficial association may only occur in people with a high level of physical activity.     

Sex-specific effect of the Val1483Ile polymorphism in the fatty acid synthase gene (FAS) on body mass index and lipid profile in Caucasian children

OBJECTIVE: A Val1483Ile polymorphism in the human fatty acid sythase gene (FAS) has recently been shown to be associated with lower percentage of body fat and substrate oxidation rates in Pima Indians, but its role in other populations has not been described. Here, we investigate the effect of this variant on obesity in Caucasian children and adolescents. SUBJECTS AND METHODS: In total, 738 Caucasian children and adolescents aged 6-17 years of the Leipzig Schoolchildren cohort, which constitutes an unselected representative German population and 205 obese children (body mass index (BMI) 2.71+/-0.04 SDS) were genotyped for genotype-phenotype associations. RESULTS: The frequency of the Ile-allele was lower in German Caucasians compared with Pima Indians (0.03 compared to 0.10). Using generalized linear regression models, there was no effect of the polymorphism on BMI in the whole normal population. However, we identified a significant interaction effect between sex and genotype (P=0.004). Subsequent sex stratified analyses revealed a lower BMI SDS in boys with Ile/Val genotype compared to Val/Val (-0.36+/-0.29 vs 0.09+/-0.05, P<0.05), while an opposite effect was observed in girls (0.48+/-0.19 vs 0.09+/-0.05, P<0.05). In genotype-phenotype associations in obese children, the polymorphism did not affect parameters of insulin, glucose, or lipid metabolism in the whole population. Again, however, obese boys with Ile/Val genotype had significantly higher high-density lipoprotein (HDL) cholesterol levels (1.46+/-0.07 vs 1.23+/-0.03 mmol/l, P<0.05). CONCLUSION: In conclusion, our findings suggest a sex-specific protective effect of the Val1483Ile polymorphism in FAS for obesity in Caucasian boys. In addition, the polymorphism may be associated with a beneficial lipid profile in obese boys.     

Genetic variation in the corticotrophin-releasing factor receptors: identification of single-nucleotide polymorphisms and association studies with obesity in UK Caucasians

OBJECTIVE: To investigate whether genetic variation at the loci encoding the corticotropin-releasing factor receptors-1 and -2 (CRF-R1 and CRF-R2) contributes to human obesity. DESIGN: The coding region of the CRF-R1 and CRF-R2 genes was screened in 51 severely obese children (body mass index (BMI)>4 kg/m(2) standard deviations above the age-related mean) using denaturing high-performance liquid chromatography and direct nucleotide sequencing. Common polymorphisms that were identified were typed from a UK Caucasian population-based cohort by a PCR-based forced restriction digestion. A repeated measures analysis was used to determine associations between the C861T and G1047A genotypes and anthropometric and biochemical indices relevant to obesity. RESULTS: In subjects with extreme early-onset obesity, four missense mutations were found, each in a single individual: CRF-R1 (Val161Met) and CRF-R2 (Glu220Asp, Val240Ile and Val411Met). However, none of these missense mutations clearly cosegregated with obesity in family studies. Two common single-nucleotide polymorphisms, C861T (Cys287Cys) in CRF-R1 and G1047A (Ser349Ser) in CRF-R2, were also detected. G1047A did not associate with any obesity-related phenotype. In contrast, carriers of the CRF-R1 polymorphism, C861T, had a significantly higher body mass index (BMI). CONCLUSION: Mutations in the coding sequence of the CRF-R1 and CRF-R2 genes are unlikely to be a common monogenic cause of early-onset obesity. In an adult UK Caucasian population, the CRF-R1 C861T polymorphism is associated with increased BMI.     

Lack of association between UCP2 gene polymorphisms and obesity phenotype in Italian Caucasians

The importance of the genetic component on adipose tissue accumulation has been clearly demonstrated. Among the candidate genes investigated, there are those that regulate thermogenesis and, thus, can affect energy expenditure. The uncoupling proteins (UCPs) are a family of proteins that uncouple respiration leading to generation of heat and increased energy expenditure. Contradictory data indicate that allelic variants in their coding genes might be associated with obesity. In this study we evaluated the role of two allelic variants of the UCP2 gene in obesity and the association with its sub-phenotypic characteristics. To this aim, 360 morbidly obese patients [age: 45 +/- 15 yr, body mass index (BMI): 46 +/- 7 kg/m2] and 103 normal weight subjects (BMI < 24 kg/m2) were genotyped for the 45 bais-pair (bp) insertion/deletion (I/D) in the 3'-untraslated region of exon 8 of the UCP2 gene while the presence of an Ala/Val substitution at codon 55 (Ala55Val) of the same gene was studied in 104 obese and 50 lean subjects. Patients also underwent a study protocol including measurements of BMI, waist-to-hip ratio (WHR), resting energy expenditure (REE), energy intake, fat mass (FM) and free fat mass (FFM), total cholesterol (TCH), high density lipoprotein (HDL) cholesterol, triacylglyceroles (TG), leptin levels, basal glucose, immunoreactive insulin (IRI), glycated haemoglobin (HbA1c), insulin sensitivity and thyroid hormones. No significant association between the two polymorphisms studied and the clinical, metabolic and anthropometric parameters characteristic of the obese phenotype was found. These results, in accordance with similar findings previously obtained in other ethnic groups, suggest that these two UCP2 allelic variants may not have a direct role in the pathogenesis and development of obesity.     

The common -55 C/T polymorphism in the promoter region of the uncoupling protein 3 gene reduces prevalence of obesity and elevates serum high-density lipoprotein cholesterol levels in the general Japanese population

Uncoupling protein 3 (UCP3) is considered to be associated with obesity, given its function in the regulation of energy and lipid metabolism. An increased body mass index (BMI) and a decreased level of high-density lipoprotein cholesterol (HDL-C) are risk factors for cardiovascular disease. The purpose of this study was to investigate whether the UCP3 promoter -55 C/T single nucleotide polymorphism (UCP3 -55 C/T SNP) was associated with obesity according to the criteria for Japanese (BMI > or = 25 kg/m2), BMI, and serum HDL-C levels in the general Japanese population. The subjects, numbering 282 and aged 65 +/- 13 years (mean +/- SD), were recruited through an annual health checkup of residents of Mima city, Tokushima, in Japan. Body mass index, blood pressure, biochemical indexes including lipid, and lipoprotein profiles were measured. The UCP3 -55 C/T SNP was determined with a fluorescence-based allele-specific DNA primer assay system. The frequency of the -55 T allele was 30.0%. Subjects with the T/T genotype had significantly higher HDL-C levels than those with the C/C genotype or the C/T genotype. Furthermore, subjects with the T/T genotype had a significantly lower BMI than those with the C/C genotype. A multivariate analysis revealed that the -55 T allele was a significant independent variable contributing to the variance in HDL-C levels and BMI. The T/T genotype was associated with a lower prevalence of obesity than the C/C and C/T genotypes, with an odds ratio of 0.358 (95% confidence interval, 0.132-0.972; P = .037). In conclusion, the UCP3 -55 C/T SNP was associated with elevated HDL-C levels and a reduced BMI, independent of modifiable factors such as lifestyle. Furthermore, this polymorphism, when expressed in its homozygous form, reduced the prevalence of obesity in Japanese.     

Association between senescence-related uncoupling protein 2 gene polymorphisms and abdominal obesity in Japanese subjects: The Tanno and Sobetsu study

Background:   Uncoupling protein 2 ( UCP2 ) plays an important role in regulating body weight, energy expenditure and insulin secretion. UCP2 is upregulated in white fat in response to fat feeding, and negatively controls insulin secretion. UCP2 also has a function that protects cells from apoptosis and oxidative stress, which shows UCP2 might be a senescence-related gene. Previously, UCP2 -866G/A polymorphism in the promoter region has been reported to alter adipose tissue mRNA expression and is associated with obesity in Caucasians.
Methods:   In this study, we investigated the association between this polymorphism and obesity, insulin secretion and hypertension in the general Japanese population.
Results:   The allele frequency of UCP2 -866G/A polymorphism was significantly higher in Japanese subjects compared to Caucasians. It revealed that subjects only in the obese group with the AA type of UCP2 -866G/A polymorphism had significantly higher levels of body mass index (BMI) and waist circumference. Multiple logistic regression analysis showed that this polymorphism was independently associated with waist circumference. This positive association remained in the analysis of the subgroup younger than 65 years, but not in the older group. This polymorphism did not affect levels of insulin and homeostasis model assessment ratio (HOMA-R).
Conclusions:   These results suggest that the AA type of UCP2 -866G/A polymorphism is related to abdominal obesity, which indicates the possible role of this polymorphism in causing metabolic syndromes.     

Studies of the synergistic effect of the Trp/Arg64 polymorphism of the beta3-adrenergic receptor gene and the -3826 A-->G variant of the uncoupling protein-1 gene on features of obesity and insulin resistance in a population-based sample of 379 young Danish subjects

This study examined whether the simultaneous presence of the previously identified Trp/Arg64 polymorphism of the beta3-adrenergic receptor (BAR) gene and the -3826 A-->G nucleotide variant of the uncoupling protein-1 (UCP1) gene are associated with obesity, insulin resistance, or alterations in size at birth in a Danish study population comprising 379 unrelated young Caucasian subjects. All study participants underwent an iv glucose tolerance test with addition of tolbutamide after 20 min. In addition, a number of biochemical and anthropometric measures were performed on each subject. The subjects were genotyped for the 2 polymorphisms by applying PCR-restriction fragment length polymorphism. The subjects were divided into 4 groups according to their BAR and UCP1 genotype: wild-type carriers (n = 184), only Trp/Arg64 carriers (n = 29), only A-->G UCP1 carriers (n = 146), and carriers of both genetic variants (n = 20). There were no differences across the genotype groups with respect to body mass index, fat mass, waist to hip ratio, birth weight or length, ponderal index, or weight gain during childhood or adolescence, nor was the combined genotype related to alterations in fasting serum levels of lipids, insulin, or C peptide or the insulin sensitivity index. In conclusion, the present study failed to demonstrate an additive or synergistic effect of the Trp/Arg64 variant of the BAR gene and the -3826 A-->G variant of the UCP1 gene on the development of obesity and insulin resistance among randomly recruited Danish Caucasian subjects.     

Organisation of the coding exons and mutational screening of the uncoupling protein 3 gene in subjects with juvenile-onset obesity

Summary Uncoupling proteins (UCPs) are mitochondrial transporters that uncouple the cellular respiration releasing stored energy as heat. Recently a third member of the UCP family was identified. Human UCP3 is different from UCP1 and UCP2 by its high and preferential expression in skeletal muscle and consequently the UCP3 gene is an attractive candidate gene for obesity. In this study we have determined the intron/exon organization of the coding region of the UCP3 gene and performed single strand conformation polymorphism (SSCP) analysis and direct sequencing of variants of the gene in 60 Caucasian subjects with juvenile-onset obesity. We detected 4 nucleotide substitutions in the intron regions and 2 silent amino acid variants. During the identification of the intron/exon structure of the gene in a normal healthy male subject with a BMI of 23.5 kg/m², a nucleotide substitution replacing a glycine with a serine was identified at codon 84. This variant was neither found among 156 subjects with juvenile-onset obesity nor among 205 control subjects. In a population based sample of 380 young healthy subjects the Gly/Ser84 variant was found in one female subject with a BMI of 25.5 kg/m² and a fat mass of 23.7 kg. We conclude it is unlikely that variants in the coding region of the UCP3 gene contribute to the pathogenesis of juvenile-onset obesity among Danish Caucasians. [Diabetologia (1998) 41: 241–244] Received: 8 October 1997 and in revised form: 30 October 1997     

Systematic screening for mutations in the human necdin gene (NDN): identification of two naturally occurring polymorphisms and association analysis in body weight regulation.

BACKGROUND: NDN, which codes for the human necdin protein, is a candidate gene for Prader-Willi syndrome (PWS). One feature of this neurogenetic disorder is hyperphagia resulting in extreme obesity observed later in development. OBJECTIVE AND DESIGN: In this study we have used single-strand conformation polymorphism (SSCP) analysis to identify sequence variants at the human necdin gene. Furthermore we tested whether these variants were associated with obesity in extremely obese German children and adolescents. RESULTS: Two gene variants could be identified: a g.1352T-->C polymorphism in the putative promotor region and a silent g.2311C-->T polymorphism in the coding region. Genotype and allele frequency distribution of both of the polymorphisms were not significantly different between lower and higher body mass index (BMI) subjects. CONCLUSIONS: Hence, it is unlikely that these polymorphisms play a major role in the emergence of juvenile onset human obesity.     

Comparison of ultrasonographic and anthropometric methods to assess body fat in childhood obesity

BACKGROUND: Pattern of fat distribution rather than obesity is of importance for cardiovascular morbidity and mortality. The accurate measurement of total and regional fat mass requires sophisticated and often expensive methods that have limited applicability in the clinical setting. OBJECTIVE: The aim of this study is to evaluate body fat distributions by ultrasound (US) as a gold standard method for measuring visceral, preperitoneal and subcutaneous fat layers and comparing with anthropometric results, and then to find the most reliable anthropometric measurement in childhood obesity. MATERIALS AND METHODS: Study group of 51 obese children (21 F, 30 M) (mean age+/-s.d.: 11.5+/-2.6 years) and control group of 33 non-obese children (17 F, 16 M) (mean age+/-s.d.: 12.2+/-2.7 years) were recruited for this study. Anthropometric measurements as body mass index (BMI), waist circumference (WC), waist/hip ratio (WHR), triceps and subscapular skinfold thicknesses were taken from all the participants. Abdominal preperitoneal (P), subcutaneous (S) fat at their maximum (max) and minimum (min) thickness sites, visceral (V), triceps (TrUS) and subscapular (SsUS) fat thicknesses were also measured ultrasonographically. RESULTS: In the obese group, BMI was significantly correlated with US measurements of fat thicknesses, except Pmin and SsUS, whereas in the control group, BMI was significantly correlated with all US fat measurements. The relation of US measurements with skinfold thickness and WC was more significant in the control than in the obese group. No relation between WHR and US fat thickness measurements was found in both groups. Multiple regression analysis, using V as the dependent variable and anthropometric parameters, gender and the group as the independent variables, revealed BMI was the best single predictor of V (R(2): 0.53). CONCLUSION: This study suggests that the validity of the anthropometric skinfold thickness in the obese children is low. Despite the limitations reported in the literature, in our study, BMI provides the best estimate of body fat. WHR in children and adolescents is not a good index to show intra-abdominal fat deposition.     

The A19G polymorphism in the 5' untranslated region of the human obese gene does not affect leptin levels in severely obese patients

Recently, the presence of different polymorphisms in the regulatory region of the ob gene has been associated with variations in leptin levels. However, the results of these studies are still contradictory. The aim of the present investigation was to evaluate the presence of the A19G polymorphism in an Italian population of obese patients and to verify its association with leptin levels and anthropometric, metabolic, and clinical parameters. Two hundred five obese patients [body mass index (BMI) > 36 kg/m2; 135 women and 70 men; mean age, 46.9+/-14.23 yr] were screened for presence of the polymorphism; 61 normal-weight controls (mean BMI, 21.05 kg/m2; 53 women, 8 men) were also screened to compare polymorphism frequency. For obese patients, BMI, waist-to-hip ratio, resting energy expenditure, body composition, fasting leptin, total cholesterol, high-density lipoproteins, triglycerides, and caloric intake were determined. Genotype frequencies in obese and control subjects were compared using the contingency table chi-square test; in obese subjects an ANOVA was performed to evaluate association between the polymorphism and several clinical parameters. No significant differences in genotype distribution between control and obese subjects were found. No significant correlations were found between this polymorphism and serum leptin levels and the other parameters considered. These findings confirm the results obtained in both a Finnish and a French population; taken together, these observations might rule out a significant role for the A19->G polymorphism in the regulation of leptin levels and other clinical, anthropometric, and metabolic parameters.     

Importance of plasma leptin in predicting future weight gain in obese children: a two-and-a-half-year longitudinal study

OBJECTIVE: To determine whether relatively low leptin levels predict changes in adiposity in prepubertal and pubertal obese children. RESEARCH METHODS AND PROCEDURES: In a biracial cohort of 68 obese children (33 male and 35 female; 46 Caucasians and 22 African-Americans, age range 7-18 y), we measured at baseline fasting insulin and leptin levels, height and weight and calculated body mass index (kg/m(2)) and expressed body mass index as (BMI) Z-score. After a 2.5-y follow-up, anthropometric measurements were repeated and changes in weight gain were calculated as changes in BMI Z-score. RESULTS: At baseline obese preadolescent boys and girls had similar age and BMI Z-score, fasting insulin and leptin levels. After an average follow-up of 2.5 y, mean weight change calculated by changes in BMI Z-score from baseline was similar in both groups. In obese adolescent boys and girls at baseline, no significant gender differences were observed for BMI Z-score and insulin levels. In contrast, plasma leptin levels were significantly higher in obese girls compared with obese adolescent boys. At follow-up, there was no significant difference in change in BMI Z-score between obese boys and girls. Multiple linear regression analysis revealed that high basal leptin levels were positively associated with greater changes in BMI Z-score only in girls (r(2)=0.18, P<0.02), after adjusting for basal BMI Z-score, Tanner stage, years of follow-up and basal insulin. High basal leptin levels in girls explained 18% of the weight gain. CONCLUSION: High leptin levels are associated with excessive future weight gain only in girls.