Differences in Fecal Microbiota in Different European Study Populations in Relation to Age, Gender, and Country: a Cross-Sectional Study

A cross-sectional study on intestinal microbiota composition was performed on 230 healthy subjects at four European locations in France, Germany, Italy, and Sweden. The study participants were assigned to two age groups: 20 to 50 years (mean age, 35 years; n = 85) and >60 years (mean age, 75 years; n = 145). A set of 14 group- and species-specific 16S rRNA-targeted oligonucleotide probes was applied to the analysis of fecal samples by fluorescence in situ hybridization coupled with flow cytometry. Marked country-age interactions were observed for the German and Italian study groups. These interactions were inverse for the predominant bacterial groups Eubacterium rectale-Clostridium coccoides and Bacteroides-Prevotella. Differences between European populations were observed for the Bifidobacterium group only. Proportions of bifidobacteria were two- to threefold higher in the Italian study population than in any other study group, and this effect was independent of age. Higher proportions of enterobacteria were found in all elderly volunteers independent of the location. Gender effects were observed for the Bacteroides-Prevotella group, with higher levels in males than in females. In summary, age-related differences in the microbiota makeup were detected but differed between the study populations from the four countries, each showing a characteristic colonization pattern.     

The impact of perinatal probiotic intervention on gut microbiota: double-blind placebo-controlled trials in Finland and Germany

Specific probiotic combinations during early feeding, via the mother or incorporated in early formula-feeding, mold the intestinal microbiota composition in infants. The objective was to analyze the impact of probiotic administration to mother or infant on gut microbiota composition in 6-month-old Finnish and German infants. In Finland probiotics were given to mothers (n = 79) for 2 months prior to and 2 months after delivery. In Germany probiotics were started in infants (n = 81) at weaning, at the latest at 1 month of age, and continued for 4 months. A breast-fed group of 6-month-old infants (22 from Finland, 8 from Germany) were compared. Gut microbiota were analyzed by FCM-FISH and qPCR methods. In breast-fed infants a trend toward higher counts of bifidobacteria was detected in Finland (p = 0.097) as against Germany, where a more diverse microbiota was reflected in higher Akkermansia (p = 0.003), Clostridium histolyticum (p = 0.035) and Bacteroides-Prevotella (p = 0.027) levels and a higher percentage of Akkermansia (p = 0.004). Finnish LPR + BL999 intervention group (Lactobacillus rhamnosus LPR and Bifidobacterium longum BL999) had higher percentages of fecal Lactobacillus-Enterococcus (9.0% vs. 6.1% placebo, p = 0.003) and lower bifidobacteria levels (10.03 log cells/g vs. 10.68 log cells/g placebo, p = 0.018). Probiotic treatment had different impacts on gut microbiota composition in Finnish and German infants due to differences in mode of feeding and the early commensal microbiota. Probiotic treatment had different impacts on gut microbiota composition in Finnish and German infants due to differences in mode of feeding and the basic commensal microbiota.     

A comparison of dental enamel defects in Christian and Meroitic populations from Geili,central Sudan

El Geili, located in the region of the Middle Nile, was occupied successively by Neolithic, Meroitic, and Christian populations at betweenn 3,500 BC and 1,500 AD. The scant archaeological evidence suggests that the Meroitic and Christian populations at Geili were patoral nomads. Dental enamel hypoplasias, indicators of general stress (malnutrition/disease), were studied in order to characterize and compare the health of these groups. A total of 130 individuals comprise the skeletal populations examined, from which a variety of appropriate sub-samples were analysed for defect presence, type, and age of occurence. Permanent incisors and canines represent the period of enamel development between birth and 6.5 years of age. Sample consisting of sets of incisors and canines (n=29) showed a negligibile difference of 77,8% vs. 81.8% in the Meroitic and Christian groups, respectively. Frequency differences by hypoplasia type reveal no obvious consistencies. Chronological analyses show chronic stress between 1 and 6 years of age. The research was supported by the Italian Ministery of Education (M.P.I. quota 40%) and the Italian Council of Research C.N.R. grant n. 89.00902.15).     

Regional adiposity, body composition and central body fat distribution of 10-16 years old Bengalee boys of Nimta, North 24 Parganas, West Bengal, India

A cross-sectional study of 502 Bengalee boys aged 10-16 years of Nimta, North 24 Parganas, West Bengal, India, was undertaken to study regional adiposity, body composition and central body fat distribution. The subjects were classified into seven age groups: 10-10.9 years (n = 74), 11-11.9 (n = 53), 12-12.9 (n = 87), 13-13.9 (n = 116), 14-14.9 (n = 58), 15-15.9 (n = 57), 16-16.9 (n = 57). In general, there was a significant linear increasing trend from 10 to 16 years for all the anthropometric variables. There was a net increase of 30.5 cm and 22.8 kg in mean height and weight, respectively, between 10 and 16 years of age. Mean BMI increased by 3.7 kg/m2 during the same period. Among circumferences, the largest increase was in hip followed by chest while the smallest increase was in mid upper arm, between 10 and 16 years of age. Subscapular skinfold showed the largest increase followed by abdomen and suprailiac skinfolds, while the increase was least in forearm skinfold. Significant linear increasing trend was observed for all the body composition measures. The largest increase in percent of body fat (PBF) was observed between ages 10 and 11 years while mean fat mass (FM), fat free mass (FFM) and fat mass index (FMI) increased the most between 14 to 15 years. However, an overall decreasing trend was observed, in mean waist-to-hip ratio (WHR) from 10 to 16 years. Boys aged 10 years had the highest mean WHR while those aged 15 years had the lowest mean WHR. There was an increase in mean WHR among 16 years old boys.     

Genetic and morphological variation in a Mediterranean glacial refugium: evidence from Italian pygmy shrews,Sorex minutus (Mammalia: Soricomorpha)

At the Last Glacial Maximum (LGM), the southern European peninsulas were important refugia for temperate species. Current genetic subdivision of species within these peninsulas may reflect past population subdivision at the LGM, as in ‘refugia within refugia’, and/or at other time periods. In the present study, we assess whether pygmy shrew populations from different regions within Italy are genetically and morphologically distinct. One maternally and two paternally inherited molecular markers (cytochrome b and Y‐chromosome introns, respectively) were analysed using several phylogenetic methods. A geometric morphometric analysis was performed on mandibles to evaluate size and shape variability between populations. Mandible shape was also explored with a functional approach that considered the mandible as a first‐order lever affecting bite force. We found genetically and morphologically distinct European, Italian, and southern Italian groups. Mandible size increased with decreasing latitude and southern Italian pygmy shrews exhibited mandibles with the strongest bite force. It is not clear whether or not the southern Italian and Italian groups of pygmy shrews occupied different refugia within the Italian peninsula at the LGM. It is likely, however, that geographic isolation earlier than the LGM on islands at the site of present‐day Calabria was important in generating the distinctive southern Italian group of pygmy shrews, and also the genetic groups in other small vertebrates that we review here. Calabria is an important hotspot for genetic diversity, and is worthy of conservation attention. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 774–787.     

Demographic Histories,Isolation and Social Factors as Determinants of the Genetic Structure of Alpine Linguistic Groups

Great European mountain ranges have acted as barriers to gene flow for resident populations since prehistory and have offered a place for the settlement of small, and sometimes culturally diverse, communities. Therefore, the human groups that have settled in these areas are worth exploring as an important potential source of diversity in the genetic structure of European populations. In this study, we present new high resolution data concerning Y chromosomal variation in three distinct Alpine ethno-linguistic groups, Italian, Ladin and German. Combining unpublished and literature data on Y chromosome and mitochondrial variation, we were able to detect different genetic patterns. In fact, within and among population diversity values observed vary across linguistic groups, with German and Italian speakers at the two extremes, and seem to reflect their different demographic histories. Using simulations we inferred that the joint effect of continued genetic isolation and reduced founding group size may explain the apportionment of genetic diversity observed in all groups. Extending the analysis to other continental populations, we observed that the genetic differentiation of Ladins and German speakers from Europeans is comparable or even greater to that observed for well known outliers like Sardinian and Basques. Finally, we found that in south Tyroleans, the social practice of Geschlossener Hof, a hereditary norm which might have favored male dispersal, coincides with a significant intra-group diversity for mtDNA but not for Y chromosome, a genetic pattern which is opposite to those expected among patrilocal populations. Together with previous evidence regarding the possible effects of “local ethnicity” on the genetic structure of German speakers that have settled in the eastern Italian Alps, this finding suggests that taking socio-cultural factors into account together with geographical variables and linguistic diversity may help unveil some yet to be understood aspects of the genetic structure of European populations.     

Genetic discontinuity, breeding-system change and population history of Arabis alpina in the Italian Peninsula and adjacent Alps

Arabis alpina is a widespread plant of European arctic and alpine environments and belongs to the same family as Arabidopsis thaliana. It grows in all major mountain ranges within the Italian glacial refugia and populations were sampled over a 1300 km transect from Sicily to the Alps. Diversity was studied in nuclear and chloroplast genome markers, combining phylogeographical and population genetic approaches. Alpine populations had significantly lower levels of nuclear genetic variation compared to those in the Italian Peninsula, and this is associated with a pronounced change in within-population inbreeding. Alpine populations were significantly inbred (F(IS) = 0.553), possibly reflecting a change to the self-incompatibility system during leading edge colonization. The Italian Peninsula populations were approaching Hardy-Weinberg equilibrium (outbreeding, F(IS) = 0.076) and genetic variation was highly structured, consistent with independent local 'refugia within refugia' and the fragmentation of an established population by Quaternary climate oscillations. There is very little evidence of genetic exchange between the Alps and the Italian Peninsula main distribution ranges. The Alps functioned as a glacial sink for A. alpina, while the Italian Peninsula remains a distinct and separate long-term refugium. Comparative analysis indicated that inbreeding populations probably recolonized the Alps twice: (i) during a recent postglacial colonization of the western Alps from a Maritime Alps refugium; and (ii) separately into the central Alps from a source outside the sampling range. The pronounced geographical structure and inbreeding discontinuities are significant for the future development of A. alpina as a model species.     

The variation in age at menarche: an indicator of historic developmental tempo

Ample literature describes the history of the association between the advances in the health and wealth of people, and mortality rates, life expectancy and adult height. Twenty-nine German studies with n > 200 subjects published since 1848 on menarcheal age, were reanalyzed, and 101 studies from various other European and non-European countries. On average, mean age at menarche declined since the mid-19th century. Historic urban samples tended to decline earlier than rural groups, upper class women earlier than working class women. In Germany, minimum values for the age at menarche were seen already between the two World Wars (Leipzig 12.6 years in 1934, Halle 13.3 years in 1939). Values for mean age and SD for age at menarche were strongly associated. With improving historic circumstances, the two parameters declined in parallel. The standard deviation for menarcheal age dropped from over 2.5 years in mid-19" century France to little more or even less than 1 year in most modern countries. In the German studies the correlation between menarcheal age and SD was almost complete with r = 0.96 (y = 0.35x - 3.53). Similar associations between mean age at menarche and SD for age were found in other European countries. The obvious and immediate effects of historic events on menarcheal age, and particularly on the age distribution, indicate that menarche is a sensitive indicator of public health and wealth, and may be an appropriate estimator for the socio-economic background of historic populations.     

Postnatal development of the rabbit caecal microbiota composition and activity

This study describes the development of the rabbit caecum microbiota and its metabolic activities from the neonatal (day 2) until the subadult period (day 70). The caecal microbiota was analysed using 16S rRNA gene approaches coupled with capillary electrophoresis single-stranded conformation polymorphism (CE-SSCP) and qPCR. At day 2, rabbits harboured population levels up to 8.4, 7.2 and 7.4 log(10) copy number g(-1) full caecum of the total bacteria, Bacteroides-Prevotella and Firmicutes groups, respectively. These populations reached their maximum levels from day 14 for Firmicutes groups (10.8 log(10) copy number g(-1) caecal content) and day 21 (11.4 and 10.7 log(10) copy number g(-1) caecal content of the total bacteria and the Bacteroides-Prevotella group, respectively). The archaeal population could be detected only from day 7 onwards (5.5 log(10) copy number g(-1) full caecum) and reached its maximum level at day 35 (7.4 log(10) copy number g(-1) caecal content). Similarity analysis, diversity calculation and quantitative evaluation of the stability of bacterial community CE-SSCP profiles provided some evidence that the caecal microbiota develops progressively from a simple and unstable community after birth into a complex and climax community in subadult rabbits. Meanwhile, the microbial activity evolved with the progressive decrease of the propionate/butyrate ratio towards a rabbit-specific value <1.     

Cytogenetic findings in 4952 prenatal diagnoses. An Italian collaborative study

Summary The development of prenatal diagnosis in Italy was made difficult by the restrictions of the old abortion law and only in recent years has a consistent number of cases been investigated. We report the experience on prenatal chromosome diagnosis of ten Italian centers participating in a collaborative study on 4952 diagnoses performed from 1972 to 1980. The main indication groups were: advanced maternal age (2882 cases), previous child with chromosome anomaly from parents with normal karyotype (847 cases), and chromosome anomaly in one parent (97 cases). The other indications for amniocentesis, including cases without a cytogenetic risk, have been assembled into a miscellaneous group (1126 cases). We found 125 abnormal fetal karyotypes (2.5%) of which 89 were unbalanced (1.8%). The frequencies and types of chromosome anomalies are reported in detail for each indication group and are compared with the corresponding ones from the European Munich Conference. The great majority of these Italian data were not included in the Munich report.     

不同身体质量指数人群肠道菌群结构及共存网络解析

[背景] 人体能量稳态失衡表现为体重过轻、超重和肥胖,肠道菌群与人体能量稳态的维持有关,但不同身体质量指数（Body Mass Index,BMI）人群的肠道菌群特征仍需进一步探究。[目的] 基于美国肠道计划公开数据库,解析4类BMI人群肠道菌群的特征,并探究4类BMI人群肠道菌群共存网络特征及差异,为基于肠道菌群来干预肥胖及体重过轻等不健康状态提供新的理论依据。[方法] 从美国肠道计划数据集中筛选具有BMI信息的肠道菌群样本,并根据世界卫生组织规定的BMI划分标准将筛选后的样本分为4类：体重过轻（BMI<18.5 kg/m²）,正常体重（18.5 kg/m²2）,超重（25 kg/m²2）,肥胖（BMI>30 kg/m²）;通过计算和比较肠道菌群的α多样性和β多样性探究4类BMI人群肠道菌群的整体结构特征及差异;通过多元线性回归模型对不同BMI分类与肠道菌群进行相关性分析,并且将地域、年龄、性别因素作为混杂因素加入到模型中进行校正;采用SparCC分别计算4类BMI人群肠道菌群中菌属相关性,并分别构建肠道菌群共存网络。[结果] 经过Wilcoxon秩和检验,发现体重过轻、超重、肥胖人群的肠道菌群α多样性都显著低于正常体重人群;β多样性分析结果表明4类BMI人群肠道菌群的整体结构存在显著差异;4类BMI人群肠道中厚壁菌门（Firmicutes）和拟杆菌门（Bacteroidetes）的相对含量无显著差异;通过MaAsLin分析,并且将地域、年龄、性别因素作为混杂因素加入到模型中进行校正,共得到49个与BMI类型显著相关的物种;4类BMI人群肠道菌群共存网络的拓扑结构具有一定差异,体重过轻和正常体重人群肠道菌群共存网络的复杂度较高,超重和肥胖人群肠道菌群共存网络的复杂度较低。[结论] 4类BMI人群肠道菌群的多样性、整体结构和共存网络间均存在差异。     

Anthropometric and body composition characteristics in pre- and postmenopausal Asian Indian women: Santiniketan women study

The present cross-sectional study was aimed to investigate anthropometric and body composition characteristics in pre- and postmenopausal Asian Indian women. A total of 245 healthy women aged 25 to 65 years took part in the study. A random sampling procedure using a local voters' registration list was followed to select the participants. All participants belonged to the Bengalee population and were inhabitants of the Bolpur-Santiniketan area (lying in between 23 degrees 40' north latitude and 87degrees 43' east longitude) West Bengal, India. Before the actual commencement of the study, written information was communicated to select individuals, and an appointment was requested at their respective houses. Anthropometric measures, namely height, weight etc., were collected using standard techniques. Percentages of body fat (%BF) and body mass index (BMI) were measured using an Omron body fat analyser. All subjects were categorized into two groups: premenopausal (Group I; n = 145, mean age = 32.66 +/- 5.75 years) and postmenopausal (Group II; n = 100, mean age = 52.72 +/- 5.62 years). It was observed that 80.00% women were cohabited and 80.82% were housewife with 44.08% of them having an education up to secondary level. Furthermore, 62.45% subjects had monthly family expenditure of > or = 5000 Indian Rupees. One way ANOVA revealed that there was significant group difference for age, age at menarche, MWC, WHR, FM, FFM and %BF across the groups. Intercorrelation matrix (Pearson's correlation) showed that age had significantly positive association with MWC (p < 0.01), MHC (p < 0.05), WHR (p < 0.01), FM (p < 0.01), and %BF (p < 0.01), whereas FFM has had negative association with age. Most interestingly, it was observed that there was significant difference [chi2 (1) = 9.73] for central obesity status across the groups. It seems reasonable to argue that onset of menopause does play a vital role to alter body composition and in turn CVD risk factors.     

Use of stable isotopes to measure the metabolic activity of the human intestinal microbiota

The human intestinal microbiota is a complex biological system comprising a vast repertoire of microbes with considerable metabolic activity relevant to both bacterial growth and host health. Greater strides have been made in the analysis of microbial diversity than in the measurement of functional activity, particularly in vivo. Stable isotope probing offers a new approach by coupling measurements of metabolic activity with microbial identification. Using a low-enrichment labeling strategy in vitro, this study has identified metabolically active bacterial groups via magnetic-bead capture methodology and stable isotope ratio analysis. Using five probes (EUB338, Bac303, Bif164, EREC482, and Clep866), changes in the activities of key intestinal microbial groups were successfully measured by exploiting tracers of de novo RNA synthesis. Perturbation of the nutrient source with oligofructose generated changes in the activity of bifidobacteria as expected, but also in the Bacteroides-Prevotella group, the Eubacterium rectale-Clostridium coccoides group, and the Clostridium leptum subgroup. Changes in activity were also observed in response to the medium type. This study suggests that changes in the functional activity of the gut microbiota can be assessed using tracers of de novo nucleic acid synthesis combined with measurement of low isotopic enrichment in 16S rRNA. Such tracers potentially limit substrate bias because they are universally available to bacteria. This low-enrichment labeling approach does not depend on the commercial availability of specific labeled substrates and can be easily translated to in vivo probing experiments of the functional activity of the microbiota in the human gut.     

Similar bifidogenic effects of prebiotic-supplemented partially hydrolyzed infant formula and breastfeeding on infant gut microbiota

The aim of the study was to assess the quantitative and qualitative differences of the gut microbiota in infants. We evaluated gut microbiota at the age of 6 months in 32 infants who were either exclusively breast-fed, formula-fed, nursed by a formula supplemented with prebiotics (a mixture of fructo- and galacto-oligosaccharides) or breast-fed by mothers who had been given probiotics. The Bifidobacterium, Bacteroides, Clostridium and Lactobacillus/Enterococcus microbiota were assessed by the fluorescence in situ hybridization, and Bifidobacterium species were further characterized by PCR. Total number of bifidobacteria was lower among the formula-fed group than in other groups (P=0.044). Total amounts of the other bacteria were comparable between the groups. The specific Bifidobacterium microbiota composition of the breast-fed infants was achieved in infants receiving prebiotic supplemented formula. This would suggest that early gut Bifidobacterium microbiota can be modified by special diets up to the age of 6 months.     

The genetic structure of natural and reintroduced roe deer (Capreolus capreolus) populations in the Alps and central Italy,with reference to the mitochondrial DNA phylogeography of Europe

The first hypervariable fragment (HVI) of the mitochondrial DNA control region was sequenced in 90 individuals of the European roe deer (Capreolus capreolus) from the Alps, central Italy and Spain. Pooling these data with 70 published sequences from several European regions, we were able to identify patterns of divergence within the Italian peninsula, and in Europe in general. The results we obtained can be summarized as follows. First, the genetic structure of European roe deer populations is substantial (PhiST values around 0.6). Second, the divergence between some central Italian populations, the Alpine group (which is genetically close to the French, the Spanish and the Norwegian samples) and the Eastern European populations seems to reflect Upper Pleistocene subdivisions, possibly related to three southern European refugia. Third, a different group of central Italian individuals probably diverged more recently from the Alpine group, and their attribution to the subspecies C. c. italicus does not appear justified. Fourth, the analysis of mitochondrial DNA in the roe deer can be used to identify recently reintroduced animals in the western Alps which clearly cluster within the Eastern European group, thus providing an important tool for conservation and management strategies for this species.     

AKT1 polymorphisms are associated with risk for metabolic syndrome

Converging lines of evidence suggest that AKT1 is a major mediator of the responses to insulin,insulin-like growth factor 1 (IGF1), and glucose. AKT1 also plays a key role in the regulation of both muscle cell hypertrophy and atrophy. We hypothesized that AKT1 variants may play a role in the endophenotypes that makeup metabolic syndrome. We studied a 12-kb region including the ?rst exon of the AKT1 gene for association with metabolic syndrome-related phenotypes in four study populations [FAMUSS cohort (n = 574; age 23.7 ± 5.7 years), Strong Heart Study (SHS) (n = 2,134; age 55.5 ± 7.9 years), Dynamics of Health, Aging and Body Composition (Health ABC) (n = 3,075; age 73.6 ± 2.9 years), and Studies of a Targeted Risk Reduction Intervention through De?ned Exercise (STRRIDE)(n = 175; age 40–65 years)]. We identi?ed a three SNP haplotype that we call H1, which represents the ancestral alleles eles at the three loci and H2, which represents the derived alleles at the three loci. In young adult European Americans (FAMUSS), H1 was associated with higher fasting glucose levels in females. In middle age Native Americans (SHS), H1 carriers showed higher fasting insulin and HOMA in males, and higher BMI in females. Inolder African-American and European American subjects(Health ABC) H1 carriers showed a higher incidence of metabolic syndrome. Homozygotes for the H1 haplotype showed about twice the risk of metabolic syndrome in both males and females (p\0.001). In middle-aged European Americans with insulin resistance (STRRIDE) studied by intravenous glucose tolerance test (IVGTT), H1 carriers showed increased insulin resistance due to the Sg component (p = 0.021). The 12-kb haplotype is a risk factor for metabolic syndrome and insulin resistance that needs to be explored in further populations.     

Menarcheal age of Turkish girls in Bremen

Several studies have shown that there is a Northwest-Southeast gradient in menarcheal age of European girls, with menarche occurring on the average about one year earlier in girls living in the Southern parts of Europe as compared with those from the Northern and Northwestern European countries. Eveleth & Tanner (1976) as well as Danker-Hopfe (1986a) suggested that this gradient is due primarily to genetic differences rather than climatic or nutritional variation. To substantiate this hypothesis menarcheal age of Turkish girls who lived in Bremen for several years has been investigated. The mean age at menarche estimated by probit analysis based on status quo data from n = 494 girls aged from 9.0 to 16.5 years was 12.90 +/- 1.21 years. These results correspond very well to those reported by Neyzi et al. (1975) for girls from Istanbul. On the other hand mean menarcheal age of Turkish girls living in Bremen is distinctly lower than mean age at menarche of urban German girls, living in the same district. In summary the results of the present study support the hypothesis of a predominantly genetic cause for the observed Northwest-Southeast gradient in age at menarche in Europe.     

Self-reported ethnicity, genetic structure and the impact of population stratification in a multiethnic study

It is well-known that population substructure may lead to confounding in case–control association studies. Here, we examined genetic structure in a large racially and ethnically diverse sample consisting of five ethnic groups of the Multiethnic Cohort study (African Americans, Japanese Americans, Latinos, European Americans and Native Hawaiians) using 2,509 SNPs distributed across the genome. Principal component analysis on 6,213 study participants, 18 Native Americans and 11 HapMap III populations revealed four important principal components (PCs): the first two separated Asians, Europeans and Africans, and the third and fourth corresponded to Native American and Native Hawaiian (Polynesian) ancestry, respectively. Individual ethnic composition derived from self-reported parental information matched well to genetic ancestry for Japanese and European Americans. STRUCTURE-estimated individual ancestral proportions for African Americans and Latinos are consistent with previous reports. We quantified the East Asian (mean 27%), European (mean 27%) and Polynesian (mean 46%) ancestral proportions for the first time, to our knowledge, for Native Hawaiians. Simulations based on realistic settings of case–control studies nested in the Multiethnic Cohort found that the effect of population stratification was modest and readily corrected by adjusting for race/ethnicity or by adjusting for top PCs derived from all SNPs or from ancestry informative markers; the power of these approaches was similar when averaged across causal variants simulated based on allele frequencies of the 2,509 genotyped markers. The bias may be large in case-only analysis of gene by gene interactions but it can be corrected by top PCs derived from all SNPs.     

Glutathione S-transferase M1 and T1 polymorphisms in Brazilian African descendants

The glutathione S-transferase gene family has an important role in the biotransformation and detoxification of different xenobiotics and endogenous compounds. Two polymorphic genes of this family, GSTM1 and GSTT1, present null alleles that consequently do not produce the respective enzyme when the genotype is homozygous. These polymorphisms are also interesting for population dynamics studies because they have great frequency variations among different ethnic groups and have been reported worldwide. The distribution of these alleles in urban and Amerindian populations in Brazil has been described, but none of those studies reported on African-descended rural populations. The aim of this study was to analyze the genotype frequency distribution of the GSTM1 and GSTT1 null alleles in an urban sample from the Federal District (n = 91) and in four semi-isolated African-descended populations: Mocambo (n = 55), Rio das R?s (n = 117), Riacho de Sacutiaba (n = 34), and Kalunga (n = 68). The GSTM1 and GSTT1 null genotype frequencies in these populations range from 17% to 35% for GSTM1 and from 22% to 44% for GSTT1. These values are similar to those described in other African and African-descended populations. Despite this range, there is no distribution difference among the analyzed populations. Combined GSTM1 and GSTT1 null genotype frequencies range from 6% to 13% and are similar to European-derived populations, suggesting admixture with this ethnic group. This can be interpreted as a European contribution to these African-descended populations. Regarding the urban population in the Federal District, our results suggest an important African and European contribution.