Kazumi Natsuhara

FTO polymorphisms in oceanic populations

AbstractIt has been suggested that Neels “thrifty genotype” model may account for high body weights in some Oceanic populations, which presumably arose in modern times. In European populations, common variants (rs1421085-C, rs17817449-G, and rs9939609-A) in the fat mass and obesity (FTO associated) were recently found to be associated with body mass index (BMI) or obesity. In this study, we investigated the population frequencies of these variants in six Oceanic populations (Melanesians, Micronesians, and Polynesians) and tested for an association with BMI. Unlike European populations, the Oceanic populations displayed no significant association between the FTO polymorphisms and BMI. These variants were in strong linkage disequilibrium. The population frequencies ranged between 4.2 and 30.3% in the six Oceanic populations, and were similar to those in southeast and east Asian populations. Our study of the FTO polymorphisms has generated no evidence to support the thrifty genotype hypothesis for Oceanic populations.

Polymorphisms in the ABO blood group gene in three populations in the New Georgia group of the Solomon Islands

AbstractTo examine genetic affinity among Oceanian populations, polymorphisms of exons six and seven of the ABO blood group gene (ABO) were investigated in three populations—Munda town, Paradise village, and Rawaki village—in the New Georgia group of the Solomon Islands. The Munda and Paradise populations consist of Austronesian (AN)-speaking Melanesians; the Rawaki population consists of AN-speaking Micronesians who migrated from the Gilbert Islands to the New Georgia Islands approximately 30 years ago. We recently described the polymorphisms of ABO in three other Oceanian populations—Balopa Islanders (AN-speaking Melanesians), Gidra (non-AN-speaking Melanesians), and Tongans (AN-speaking Polynesians). The results from these six Oceanian populations suggest: (1) the main alleles in Oceanian populations are ABO*A101, ABO*A102, ABO*B101, ABO*O01, and ABO*O02, among which the most predominant is ABO*O01, and (2) there are marked differences in the ABO allele frequency spectrum among Oceanian populations. The different geographical distribution of ABO alleles provides insight into the migration history of AN-speaking populations in Oceania.

Cardiovascular risk factors of migrants in Port Moresby from the highlands and island villages, Papua New Guinea.

This study examined cardiovascular disease (CVD) risk factors, i.e., obesity, blood pressures, and serum lipoproteins and apoproteins, in relation to sociocultural characteristics in two rural–urban migrant populations (n = 173 adult males and females) in Port Moresby, the capital of Papua New Guinea. Tari migrants from the highlands and Balopa migrants from the islands differ genetically. More importantly, the lifestyle of the latter is more Westernized than that of the former in both Port Moresby and their homelands. The results demonstrate that CVD risk factors vary markedly among the origin/sex groups and that the length of stay in Port Moresby on CVD risk factors was significant only in Balopa males, most of whom had professional or skilled full‐time jobs and were considered to have more stress. This study identified different CVD risk factors in the migrant groups: obesity or fatness for the Balopa migrants, and serum lipoproteins and apoproteins, particularly lipoprotein(a), for the Tari migrants. Am. J. Hum. Biol. 12:655–664, 2000.

Development, validation, and use of a semi-quantitative food frequency questionnaire for assessing protein intake in Papua New Guinean Highlanders

The aim of this article was to develop a semi‐quantitative food frequency questionnaire (FFQ) and evaluate its validity to estimate habitual protein intake, and investigate current dietary protein intakes of Papua New Guinea (PNG) Highlanders.

The serum leptin level and body mass index in Melanesian and Micronesian Solomon Islanders: Focus on genetic factors and urbanization

Objectives: This study examined the association between the serum leptin level and body mass index (BMI) and the effects of urbanization and polymorphisms of leptin (LEP) or leptin receptor (LEPR) genes on the leptin level in three Solomon Islands populations.

A missense variant, rs373863828-A (p.Arg457Gln), of CREBRF and body mass index in Oceanic populations

It has been suggested that a ‘thrifty’ genotype hypothesis can account for high prevalence of obesity in the island populations of Oceania. A recent genome-wide association study revealed that a missense variant, rs373863828-A (p.Arg457Gln), of the CREBRF gene (encoding CREB3 regulatory factor) was associated with an excessive increase in body mass index (BMI) in Samoans. In the present study, the association of rs373863828-A with an increase in BMI was examined in four Austronesian (AN)-speaking populations in Oceania. We found that rs373863828-A was frequently observed (frequency of 0.15) in Tongans (Polynesians), and was strongly associated with higher BMI (P=6.1 × 10−4). A single copy of the rs373863828-A allele increased BMI by 3.09 kg m−2 after adjustment of age and sex. No significant association was detected in the other three AN-speaking populations (Melanesians and Micronesians) living in Solomon Islands. This was probably due to the low allele frequency (0.02–0.06) of rs373863828-A as well as small sample size. The rs373863828-A allele was not found in both AN-speaking and non-AN-speaking Melanesians living in Papua New Guinea. Our results suggest that rs373863828-A of CREBRF, a promising thrifty variant, arose in recent ancestors of AN-speaking Polynesians.

Association of protein intakes and variation of diet-scalp hair nitrogen isotopic discrimination factor in Papua New Guinea highlanders.

OBJECTIVES We present new nitrogen isotopic discrimination factor between diets and scalp hairs (Δ(15) NHair-Diet : δ(15) NHair - δ(15) NDiet ) for indigenous residents in three communities in the Papua New Guinea Highlands who consumed various amounts and qualities of protein. The Δ(15) N is important for precise evaluation of the dietary habits of human populations; in both contemporary and traditional lifestyles. Several hypotheses have been proposed regarding factors that affect Δ(15) N values, based largely on observations from animal feeding experiments. However, variations and factors controlling Δ(15) N in humans are not well understood, mainly due to the difficulty of controlling the diets of participants. MATERIALS AND METHODS These residents were studied because they have maintained relatively traditional dietary habits, which allow quantitative recording of diets. Δ(15) N was estimated by comparing hair δ(15) N values to mean dietary δ(15) N values calculated from the recorded intake of each food item and their δ(15) N values. RESULTS The results showed that: i) there was a significant difference in Δ(15) N among study locations (3.9 ± 0.9‰ for most urbanized, 5.2 ± 1.0‰ for medium and 5.0 ± 0.9‰ for least urbanized communities; range = 1.2-7.3‰ for all participants); and ii) estimated Δ(15) N values were negatively correlated with several indicators of animal protein intake (% nitrogen in diet: range = 0.9-7.6%). DISCUSSION We hypothesize that a combination of several factors, which presumably included urea recycling and amino acid and protein recycling and/or de novo synthesis during metabolic processes, altered the Δ(15) N values of the participants.

Protein content and amino acid scores of sweet potatoes in Papua New Guinea Highlands

Protein content and amino acid scores of sweet potatoes were determined in Papua New Guinea Highlands where sweet potatoes contributed approximately 50% of the total protein intake. Major cultivars of sweet potatoes in the Tari basin and the Asaro valley, 15 in total, were sampled and their nitrogen and amino acid contents were analyzed. Sweet potatoes in the Tari basin and the Asaro valley contained, respectively, 1.4% and 0.8% of protein in fresh weight basis. The concentration was 1.7 times higher in the former than in the latter (t‐test, p < .01). The first limiting amino acid was leucine in the samples from both areas and amino acid scores were 87 in the Tari samples and 85 in the Asaro samples, using values of FAO/WHO (1973). Protein content and amino acid scores of sweet potatoes in the Tari basin were higher than those previously reported in Papua New Guinea Highlands probably because of introduction of new cultivars in recent decades, and thus protein intake of the inhabitants may have been increased.

Characterization of the gut microbiota of Papua New Guineans using reverse transcription quantitative PCR.

There has been considerable interest in composition of gut microbiota in recent years, leading to a better understanding of the role the gut microbiota plays in health and disease. Most studies have been limited in their geographical and socioeconomic diversity to high-income settings, and have been conducted using small sample sizes. To date, few analyses have been conducted in low-income settings, where a better understanding of the gut microbiome could lead to the greatest return in terms of health benefits. Here, we have used quantitative real-time polymerase chain reaction targeting dominant and sub-dominant groups of microorganisms associated with human gut microbiome in 115 people living a subsistence lifestyle in rural areas of Papua New Guinea. Quantification of Clostridium coccoides group, C. leptum subgroup, C. perfringens, Bacteroides fragilis group, Bifidobacterium, Atopobium cluster, Prevotella, Enterobacteriaceae, Enterococcus, Staphylococcus, and Lactobacillus spp. was conducted. Principle coordinates analysis (PCoA) revealed two dimensions with Prevotella, clostridia, Atopobium, Enterobacteriaceae, Enterococcus and Staphylococcus grouping in one dimension, while B. fragilis, Bifidobacterium and Lactobacillus grouping in the second dimension. Highland people had higher numbers of most groups of bacteria detected, and this is likely a key factor for the differences revealed by PCoA between highland and lowland study participants. Age and sex were not major determinants in microbial population composition. The study demonstrates a gut microbial composition with some similarities to those observed in other low-income settings where traditional diets are consumed, which have previously been suggested to favor energy extraction from a carbohydrate rich diet.

A functional SNP upstream of the beta-2 adrenergic receptor gene ( ADRB2 ) is associated with obesity in Oceanic populations

OBJECTIVE:Obesity is a growing health concern in the Oceanic populations. To investigate the genetic factors associated with adult obesity in the Oceanic populations, the association of single nucleotide polymorphisms (SNPs) of the beta-2 adrenergic receptor (ADRB2) gene with obesity was examined in 694 adults living in Tonga and Solomon Islands.RESULTS:A screening for variation in 16 Oceanic subjects detected 17 SNPs in the entire region of ADRB2, of which nine SNPs including two non-synonymous ones, rs1042713 (Arg16Gly) and rs1042714 (Gln27Glu), were further genotyped for all subjects. The rs34623097-A allele, at a SNP located upstream of ADRB2, showed the strongest association with risk for obesity in a logistic regression analysis adjusted for age, sex, and population (P=5.6 × 10−4, odds ratio [OR]=2.5, 95% confidence interval [CI]=1.5–4.2). The 27Glu was also significantly associated with obesity in the single-point association analysis (P=0.013, OR=2.0, 95%CI=1.2–3.4); however, this association was no longer significant after adjustment for rs34623097 since these SNPs were in linkage disequilibrium with each other. A copy of the obesity-risk allele, rs34623097-A, led to a 1.6 kg/m2 increase in body mass index (BMI; defined as weight in kilograms divided by height in meters squared) (P=0.0019). A luciferase reporter assay indicated that rs34623097-A reduced the transcriptional activity of the luciferase reporter gene by approximately 10% compared with rs34623097-G. An electrophoretic mobility shift assay demonstrated that rs34623097 modulated the binding affinity with nuclear factors. An evolutionary analysis implies that a G>A mutation at rs34623097 occurred in the Neandertal genome and then the rs34623097-A allele flowed into the ancestors of present-day humans.CONCLUSION:The present results suggest that rs34623097-A, which would lead to lower expression of ADRB2, contributes to the onset of obesity in the Oceanic populations.