Ethnic-specific differences in abdominal subcutaneous adipose tissue compartments

Central and local arterial stiffness in White Europeans compared to age-, sex-, and BMI-matched South Asians

BACKGROUND

Ethnicity impacts cardiovascular disease (CVD) risk, and South Asians demonstrate a higher risk than White Europeans. Arterial stiffness is known to contribute to CVD, and differences in arterial stiffness between ethnicities could explain the disparity in CVD risk. We compared central and local arterial stiffness between White Europeans and South Asians and investigated which factors are associated with arterial stiffness.

METHODS

Data were collected from cohorts of White Europeans (the Netherlands) and South Asians (India). We matched cohorts on individual level using age, sex, and body mass index (BMI). Arterial stiffness was measured with ARTSENS® Plus. Central stiffness was expressed as carotid-femoral pulse wave velocity (cf-PWV, m/s), and local carotid stiffness was quantified using the carotid stiffness index (Beta) and pressure-strain elastic modulus (Epsilon, kPa). We compared arterial stiffness between cohorts and used multivariable linear regression to identify factors related to stiffness.

RESULTS

We included n = 121 participants per cohort (age 53±10 years, 55% male, BMI 24 kg/m2). Cf-PWV was lower in White Europeans compared to South Asians (6.8±1.9 vs. 8.2±1.8 m/s, p<0.001), but no differences were found for local stiffness parameters Beta (5.4±2.4 vs. 5.8±2.3, p = 0.17) and Epsilon (72±35 vs. 70±31 kPa, p = 0.56). Age (standardized β, 95% confidence interval: 0.28, 0.17-0.39), systolic blood pressure (0.32, 0.21-0.43), and South Asian ethnicity (0.46, 0.35-0.57) were associated with cf-PWV; associations were similar between cohorts (p>0.05 for interaction). Systolic blood pressure was associated with carotid stiffness in both cohorts, whereas age was associated to carotid stiffness only in South Asians and BMI only in White Europeans.

CONCLUSION

Ethnicity is associated with central but not local arterial stiffness. Conversely, ethnicity seems to modify associations between CVD risk factors and local but not central arterial stiffness. This suggests that ethnicity interacts with arterial stiffness measures and the association of these measures with CVD risk factors.

Liver, visceral and subcutaneous fat in men and women of South Asian and white European descent: a systematic review and meta-analysis of new and published data

AIMS/HYPOTHESIS

South Asians have a two- to fivefold higher risk of developing type 2 diabetes than those of white European descent. Greater central adiposity and storage of fat in deeper or ectopic depots are potential contributing mechanisms. We collated existing and new data on the amount of subcutaneous (SAT), visceral (VAT) and liver fat in adults of South Asian and white European descent to provide a robust assessment of potential ethnic differences in these factors.

METHODS

We performed a systematic review of the Embase and PubMed databases from inception to August 2021. Unpublished imaging data were also included. The weighted standardised mean difference (SMD) for each adiposity measure was estimated using random-effects models. The quality of the studies was assessed using the ROBINS-E tool for risk of bias and overall certainty of the evidence was assessed using the GRADE approach. The study was pre-registered with the OSF Registries ( https://osf.io/w5bf9 ).

RESULTS

We summarised imaging data on SAT, VAT and liver fat from eight published and three previously unpublished datasets, including a total of 1156 South Asian and 2891 white European men, and 697 South Asian and 2271 white European women. Despite South Asian men having a mean BMI approximately 0.5-0.7 kg/m² lower than white European men (depending on the comparison), nine studies showed 0.34 SMD (95% CI 0.12, 0.55; I²=83%) more SAT and seven studies showed 0.56 SMD (95% CI 0.14, 0.98; I²=93%) more liver fat, but nine studies had similar VAT (-0.03 SMD; 95% CI -0.24, 0.19; I²=85%) compared with their white European counterparts. South Asian women had an approximately 0.9 kg/m² lower BMI but 0.31 SMD (95% CI 0.14, 0.48; I²=53%) more liver fat than their white European counterparts in five studies. Subcutaneous fat levels (0.03 SMD; 95% CI -0.17, 0.23; I²=72%) and VAT levels (0.04 SMD; 95% CI -0.16, 0.24; I²=71%) did not differ significantly between ethnic groups in eight studies of women.

CONCLUSIONS/INTERPRETATION

South Asian men and women appear to store more ectopic fat in the liver compared with their white European counterparts with similar BMI levels. Given the emerging understanding of the importance of liver fat in diabetes pathogenesis, these findings help explain the greater diabetes risks in South Asians.

FUNDING

There was no primary direct funding for undertaking the systematic review and meta-analysis.

Ultrasound estimated subcutaneous and visceral adipose tissue thicknesses and risk of pre-eclampsia

Early identification of high-risk pregnancies enables identification of those who would benefit from aspirin prophylaxis and increased surveillance for pre-eclampsia. A high body mass index (BMI) is a well-known predictor for pre-eclampsia. However, if abdominal adipose tissue distribution is associated with pre-eclampsia is limited investigated. Subcutaneous adipose tissue (SAT) thickness and visceral adipose tissue (VAT) thickness were measured by ultrasound on 3777 women at around 18 gestational weeks. SAT thickness was measured from the skin to linea alba and VAT from linea alba to the anterior aortic wall. The risk of developing pre-eclampsia (de novo hypertension at ≥ 20 gestational weeks in combination with proteinuria) was evaluated by logistic regression and expressed as odds ratio (OR) with 95% confidence intervals (CI). The risk of pre-eclampsia increased by 79% for every cm in SAT thickness (OR 1.79; 95% CI 1.48–2.17) and by 23% for every cm VAT thickness (OR 1.23; 95% CI 1.11–1.35). After adjustment for maternal age, parity, BMI, smoking and country of birth, the association between SAT thickness and pre-eclampsia remained (AOR 1.35; 95% CI 1.02–1.79). Greater SAT thickness measured with second trimester ultrasound is associated with increased risk of developing pre-eclampsia. The measurement may improve prediction models for pre-eclampsia.

Energy Metabolism in Relation to Diet and Physical Activity: A South Asian Perspective

The prevalence of overweight and obesity is on the rise around the world, not only in the West, but also in Asian countries. South Asian countries in particular are experiencing a rapid increase in overweight and obesity, that coexists with the rapid increase in non-communicable diseases linked to obesity such as diabetes and cardiovascular disease than any other country in Asia. The phenomena observed in South Asian countries are due to the size of the population, the ageing of the population, the high degree of urbanization and the lifestyle changes in favor of increased energy consumption and reduced physical activity. The imbalance between energy consumption and energy expenditure results in the development of a positive energy balance that, over time, accumulates in higher body fat. South Asians were reported to have a more unfavorable body composition with a higher percentage of body fat than Caucasians with an equivalent BMI. Body composition is a major determinant of resting energy expenditure. It has been reported that South Asians have a lower resting energy expenditure than Caucasians with the same BMI. Resting energy expenditure accounts for the majority of total daily energy expenditure and, therefore, plays a crucial role in achieving the balance between energy intake and expenditure.

The contribution of obesity to the population burden of high metabolic cardiovascular risk among different ethnic groups. The HELIUS study

BACKGROUND

The burden of cardiovascular risk is distributed unequally between ethnic groups. It is uncertain to what extent this is attributable to ethnic differences in general and abdominal obesity. Therefore, we studied the contribution of general and abdominal obesity to metabolic cardiovascular risk among different ethnic groups.

METHODS

We used data of 21 411 participants of Dutch, South-Asian Surinamese, African-Surinamese, Ghanaian, Turkish or Moroccan origin in Healthy Life in an Urban Setting (Amsterdam, the Netherlands). Obesity was defined using body-mass-index (general) or waist-to-height-ratio (abdominal). High metabolic risk was defined as having at least two of the following: triglycerides ≥1.7 mmol/l, fasting glucose ≥5.6 mmol/l, blood pressure ≥130 mmHg systolic and/or ≥85 mmHg diastolic and high-density lipoprotein cholesterol <1.03 mmol/l (men) or <1.29 mmol/l (women).

RESULTS

Among ethnic minority men, age-adjusted prevalence rates of high metabolic risk ranged from 32 to 59% vs. 33% among Dutch men. Contributions of general obesity to high metabolic risk ranged from 7.1 to 17.8%, vs. 10.1% among Dutch men, whereas contributions of abdominal obesity ranged from 52.1 to 92.3%, vs. 53.9% among Dutch men. Among ethnic minority women, age-adjusted prevalence rates of high metabolic risk ranged from 24 to 35% vs. 12% among Dutch women. Contributions of general obesity ranged from 14.6 to 41.8%, vs. 20% among Dutch women, whereas contributions of abdominal obesity ranged from 68.0 to 92.8%, vs. 72.1% among Dutch women.

CONCLUSIONS

Obesity, especially abdominal obesity, contributes significantly to the prevalence of high metabolic cardiovascular risk. Results suggest that this contribution varies substantially between ethnic groups, which helps explain ethnic differences in cardiovascular risk.

The Effects of Asthma on the Association Between Pulmonary Function and Obesity: A 16-Year Longitudinal Study

Background

Asthma and obesity are important public health issues around the world. Obesity is considered a risk factor associated with the severity and incidence of asthma. We investigated the relationships between poor pulmonary function (defined by forced vital capacity (FVC) and percentage of predicted FVC (FVC%)) and obesity.

Methods

This is a retrospective longitudinal study using the MJ health examination database in Taiwan from 2000 to 2015. There were 160,609 participants aged ≥20 years with complete obesity indicators and lung function data, and having at least two visits. A generalized estimation equation (GEE) model was applied to estimate the association between lung function and obesity.

Results

BMI was the best indicator to predict poor pulmonary function for our participants. Results of BMI are presented as an example: Obesity (body mass index (BMI) ≥27.0 kg/m²) is significantly associated with lower FVC [adjusted coefficients (β) for asthmatics: -0.11 L (95% CI: -0.14, -0.08); adjusted β for non-asthmatics: -0.08 L (-0.09, -0.08)] and FVC% [adjusted β for asthmatics: -1.91% (95% CI: -2.64, -1.19); adjusted β for non-asthmatics: 1.48% (-1.63, -1.33)]. Annual change of BMI (ΔBMI/year) is an independent risk factor for decreased FVC [adjusted β for asthmatics: -0.030 L (-0.048, -0.013); adjusted β for non-asthmatics: -0.019 L (-0.022, -0.016)] and FVC% [adjusted β for non-asthmatics: -0.603% (-1.063, -0.142); adjusted β for non-asthmatics: -0.304% (-0.393, -0.214)], and is significantly associated with accelerated FVC decline [adjusted β of ΔFVC/year and ΔFVC %/year for asthmatics: -0.038 L (-0.054, -0.022) and -0.873% (-1.312, -0.435); adjusted β of ΔFVC/year and ΔFVC %/year for non-asthmatics: -0.033 L (-0.042, -0.024) and -0.889% (-1.326, -0.452)].

Conclusion

Obesity is significantly associated with decreased lung function, and asthmatics had a higher risk than non-asthmatics.

Adiposity Phenotypes and Subclinical Atherosclerosis in Adults from Sub-Saharan Africa: An H3Africa AWI-Gen Study

Background:

Obesity and adipose tissue distribution contribute to an increased risk of cardiovascular disease (CVD) by promoting atherosclerosis. This association has been poorly studied in sub–Saharan Africa (SSA) despite the rising prevalence of cardiovascular disease.

Objectives:

We determined the association between various adiposity phenotypes and carotid intima–media thickness (CIMT), a proxy of subclinical atherosclerosis, in a large SSA population.

Methods:

A population–based cross–sectional study was performed from 2013–2016 in Burkina Faso, Ghana, Kenya and South Africa. Body mass index (BMI), waist (WC), hip circumferences (HC), visceral (VAT) and subcutaneous adipose tissue (SCAT) using B-mode ultrasound were measured. Ultrasonography of left and right far wall CIMT of the common carotid artery was used as an indicator of subclinical atherosclerosis. Individual participant data meta–analyses were used to determine the associations between adiposity phenotypes and CIMT in the pooled sample while adjusted multivariable linear regression analyses were used for site specific analyses.

Results:

Data were obtained from 9,010 adults (50.3% women and a mean age of 50± 6years). Men had higher levels of visceral fat than women while women had higher BMI, waist and hip circumference and subcutaneous fat than men at all sites except Burkina Faso. In the pooled analyses, BMI (β–value [95% CIs]: 19.5 [16.8, 22.3] μm) showed the strongest relationship with CIMT followed by VAT (5.86 [4.65, 7.07] μm), SCAT (5.00 [2.85, 7.15] μm), WC (1.27 [1.09, 1.44] μm) and HC (1.23 [1.04, 1.42] μm). Stronger associations were observed in men than in women.

Conclusion:

Obesity within SSA will likely result in higher levels of atherosclerosis and promote the occurrence of cardio- and cerebrovascular events, especially in males, unless addressed through primary prevention of obesity in both rural and urban communities across Africa. The inverse association of VAT with CIMT in Burkina Faso and Ghana requires further investigation.

Highlights

Clinical profile of non-alcoholic fatty liver disease in nonobese patients

BACKGROUND AND AIM

Non-alcoholic fatty liver disease (NAFLD) is associated with metabolic syndrome. Worryingly, it has been increasingly reported among nonobese patients. This study aims to analyse patient characteristics of biopsy-proven NAFLD in an Asian cohort and explore differences stratified by body mass index (BMI).

METHODS

Clinical, laboratory, and histological data were collected from 263 adults with biopsy-proven NAFLD. Patients with and without obesity (BMI cut-off 25) were compared. The ability to predict advanced liver fibrosis with three non-invasive scores, the NAFLD Fibrosis score (NFS), Fibrosis-4 (FIB4), and the aspartate aminotransferase to platelet ratio index (APRI), was compared.

RESULTS

Obese subjects had a lower mean age (49.5 ± 12.5 vs 54.0 ± 12.9 years, P = 0.017), a higher prevalence of diabetes (52.4% vs 36.8%, P = 0.037), and a higher waist circumference (113.9 ± 16.0 cm vs 87.0 ± 18.4 cm, P = 0.022). The prevalence of dyslipidaemia (68.0% vs 61.4%, P = 0.353) and hypertension (61.7% vs 49.1%, P = 0.190) was comparable between the two groups. The distribution of non-alcoholic steatohepatitis (NASH) (63.1% versus 61.4%, P = 0.710) and advanced fibrosis (31.6% versus 26.3%, P = 0.447) were also similar in both groups. All three non-invasive scores (NFS, FIB4, and APRI) performed poorly in predicting advanced fibrosis in nonobese patients with NAFLD. The FIB4 was the most accurate non-invasive score in predicting advanced fibrosis in the obese group.

CONCLUSIONS

Obese and nonobese patients are equally at risk of NASH and advanced fibrosis. While the FIB4 is the most accurate non-invasive score in predicting advanced fibrosis among obese individuals, further research is warranted to develop a nonobese specific score to correctly identify nonobese NAFLD patients with advanced fibrosis.

Comparison of anthropometric indices as predictors of the risk factors for cardiovascular disease in Iran: The PERSIAN Guilan Cohort Study

OBJECTIVE

This study was conducted to assess the prevalence of central and general obesity and compare nine anthropometric indices as predictors of the risk factors for cardiovascular disease (CVD) in Iranian adults.

METHODS

A total of 10,520 adults between ages 35 and 70 years old who were referred to the PERSIAN Guilan Cohort Study were included in this study. Anthropometric indices, including body mass index (BMI), waist circumference (WC), waist to height ratio (WHtR), waist to hip ratio (WHR), conicity index, hip circumference (HC), waist to hip to height ratio (WHHR), body adiposity index, and a body shape index (ABSI), were measured using the standard methods. The risk factors for CVD (diabetes mellitus, hypertension, and out of range lipid profiles) were defined by laboratory tests and medical history. The odds ratio of the risk factors based on a unit increase in anthropometric indices was examined by an adjusted logistic model.

RESULTS

The mean of all anthropometric indices was higher in women than in men (p<0.01). After adjusting for confounders, the risk of diabetes mellitus, hypertension, and hypertriglyceridemia increased with an increase in all anthropometric indices. The highest risk of diabetes mellitus and hypertriglyceridemia was found in higher WHHR. The highest risk of low high density lipoprotein cholesterol (HDL C) and high low density lipoprotein cholesterol (LDL C) was found in an increase in the WHR and ABSI, respectively.

CONCLUSION

Our findings emphasize higher levels of general and central obesity in adults in the north of Iran. The WHHR and WHtR seem to be more valuable indices than BMI and WC for predicting distinct risk factors for CVD. However, the WHR was the strongest index for the prediction of high LDL C/HDL C ratio.

Interrogation of nonconserved human adipose lincRNAs identifies a regulatory role of linc-ADAL in adipocyte metabolism

Long intergenic noncoding RNAs (lincRNAs) have emerged as important modulators of cellular functions. Most lincRNAs are not conserved among mammals, raising the fundamental question of whether nonconserved adipose-expressed lincRNAs are functional. To address this, we performed deep RNA sequencing of gluteal subcutaneous adipose tissue from 25 healthy humans. We identified 1001 putative lincRNAs expressed in all samples through de novo reconstruction of noncoding transcriptomes and integration with existing lincRNA annotations. One hundred twenty lincRNAs had adipose-enriched expression, and 54 of these exhibited peroxisome proliferator-activated receptor γ (PPARγ) or CCAAT/enhancer binding protein α (C/EBPα) binding at their loci. Most of these adipose-enriched lincRNAs (~85%) were not conserved in mice, yet on average, they showed degrees of expression and binding of PPARγ and C/EBPα similar to those displayed by conserved lincRNAs. Most adipose lincRNAs differentially expressed (n = 53) in patients after bariatric surgery were nonconserved. The most abundant adipose-enriched lincRNA in our subcutaneous adipose data set, linc-ADAL, was nonconserved, up-regulated in adipose depots of obese individuals, and markedly induced during in vitro human adipocyte differentiation. We demonstrated that linc-ADAL interacts with heterogeneous nuclear ribonucleoprotein U (hnRNPU) and insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2) at distinct subcellular locations to regulate adipocyte differentiation and lipogenesis.

Association between risk factors of metabolic syndrome with lung function

BACKGROUND/OBJECTIVES

Increased evidence suggests that metabolic syndrome (MetS) is correlated with lung function impairment. This study aimed to explore the associations between MetS risk factors and the lung function.

SUBJECTS/METHODS

The cross-sectional study included 6945 participants attending health examination between 2010 and 2012 in Taiwan. MetS was assessed according to the criteria of National Cholesterol Education Program III. Spirometric parameters were measured to define lung function. The relationships were tested using multiple linear regression and logistic regression analyses.

RESULTS

The prevalence of MetS was significantly higher in males (16.2%) than females (3.8%). Although the prevalence of restrictive lung disease (RLD) was comparable between genders (20.7 and 21.0%), males with co-existent MetS had a higher prevalence of RLD than females (27.4 vs. 18.0%). Abdominal obesity, indicated by waist circumference (WC) and weight-to-height ratio (WHtR), was the most significant factor associated with lung function decline. Other components of MetS also showed statistically significant relationships, but very weak, with lung function. There was a trend toward an increased prevalence of RLD with the increasing number of MetS scores in males, independent of age, smoking, and body mass index.

CONCLUSIONS

Abdominal obesity was the key component of MetS associated with mechanical effect on lung function impairment in a prime-age adult population. Although RLD was not associated with increased probability of having MetS, the participants with more MetS scores were at a higher risk of losing lung function.

Genetics of metabolic traits in Greenlanders: lessons from an isolated population

In this review, we describe the extraordinary population of Greenland, which differs from large outbred populations of Europe and Asia, both in terms of population history and living conditions. Many years in isolation, small population size and an extreme environment have shaped the genetic composition of the Greenlandic population. The unique genetic background combined with the transition from a traditional Inuit lifestyle and diet, to a more Westernized lifestyle, has led to an increase in the prevalence of metabolic conditions like obesity, where the prevalence from 1993 to 2010 has increased from 16.4% to 19.4% among men, and from 13.0% to 25.4% among women, type 2 diabetes and cardiovascular diseases. The genetic susceptibility to metabolic conditions has been explored in Greenlanders, as well as other isolated populations, taking advantage of population-genetic properties of these populations. During the last 10 years, these studies have provided examples of loci showing evidence of positive selection, due to adaption to Arctic climate and Inuit diet, including TBC1D4 and FADS/CPT1A, and have facilitated the discovery of several loci associated with metabolic phenotypes. Most recently, the c.2433-1G>A loss-of-function variant in ADCY3 associated with obesity and type 2 diabetes was described. This locus has provided novel biological insights, as it has been shown that reduced ADCY3 function causes obesity through disrupted function in primary cilia. Future studies of isolated populations will likely provide further genetic as well as biological insights.

Physical Activity and Abdominal Fat Distribution in Greenland

PURPOSE

We examined how total volume of physical activity and reallocation of time spent at various objectively measured intensities of physical activity (PA) were associated with overall and abdominal fat distribution in adult Inuit in Greenland.

METHODS

Data were collected as part of a countrywide cross-sectional health survey in Greenland. A combined accelerometer and HR monitor measured total physical activity energy expenditure (PAEE) and intensities of PA (N = 1536). Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were assessed by ultrasonography. Isotemporal substitution modeling was used to analyze the association between substitution of 1 h of sedentary time to light- or moderate-intensity PA and 1 h light-intensity PA to moderate- or vigorous-intensity PA in relation to body mass index (BMI), waist circumference (WC), SAT, and VAT.

RESULTS

A negative linear association was found for total PAEE and BMI, WC, VAT, and SAT. Exchanging 1 h of sedentary time with light-intensity PA was associated with lower WC (-0.6 cm, P = 0.01), SAT (-0.08 cm, P < 0.001), and VAT (-0.04 cm, P = 0.359). Exchanging light-intensity PA with vigorous-intensity PA resulted in -6.1-cm lower WC (P < 0.001), -0.7-cm lower VAT (P = 0.018) and -0.7-cm lower SAT (P < 0.001). When further adjusting for BMI, the associations were attenuated; however, most of them remained significant, and the directions were mostly unchanged. All 1-, 5-, and 10-min bouts of MVPA were negatively associated with overall and abdominal fat distribution.

CONCLUSION

Physical activity energy expenditure is associated with lower BMI, WC, and abdominal fat among Greenland Inuit. The importance of promoting an upward shift of the whole PA intensity distribution and to spur even short bouts of MVPA to limit excessive accumulation of SAT and VAT is highlighted.

Ethnic differences in coronary plaque and epicardial fat volume quantified using computed tomography

Epidemiological studies observed a higher prevalence of coronary atherosclerosis in South Asians when compared to Caucasians, but quantitative computed tomography differences in aggregate plaque volume (APV) and epicardial fat volume (EFV) between South Asians, Southeast or East Asians (SEEAs) and Caucasians remain unknown. We aimed to compare APV and EFV quantified on computed-tomographic-coronary-angiography (CTCA) between South Asian, SEEA and Caucasian populations residing in Australia. Age, gender and body-mass-index matched subjects from three ethnic groups who underwent clinically indicated 320-detector CTCA were retrospectively analysed. Percentage APV in the first 5 cm of the left anterior descending artery (LAD) and EFV were quantified using dedicated software (Vital Images, USA). One-hundred-and-fifty subjects (average age = 57.7 years, 56 % male, n = 50 in each ethnic group) were analysed. Mean LAD percentage APV was highest in South Asians (44.5 ± 8.4 % vs. 37.5 ± 6.5 % in SEEAs and 39.5 ± 6.4 % in Caucasians, P = 0.00001). South Asian ethnicity predicted LAD APV above traditional risk factors on multivariate analysis (P = 0.000002). EFV was significantly higher in both South Asians (103.2 ± 41.7 cm³ vs. 85.8 ± 39.4 cm³, P = 0.035) and SEEAs (110.8 ± 36.9 cm³ vs. 85.8 ± 39.4 cm³, P = 0.001) when compared with Caucasians. In this cohort LAD percentage APV and EFV, as quantified on CTCA, differs between South Asians, SEEA and Caucasian populations, with higher LAD APV observed in South Asians and lower EFV in Caucasians. Atherosclerotic volume in LAD was best predicted by South Asian ethnicity above traditional risk factors and EFV. Further research is required to establish whether APV and EFV quantification can improve cardiac risk prediction in the South Asian population.

Investigation of Genetic Variation Underlying Central Obesity amongst South Asians

South Asians are 1/4 of the world's population and have increased susceptibility to central obesity and related cardiometabolic disease. Knowledge of genetic variants affecting risk of central obesity is largely based on genome-wide association studies of common SNPs in Europeans. To evaluate the contribution of DNA sequence variation to the higher levels of central obesity (defined as waist hip ratio adjusted for body mass index, WHR) among South Asians compared to Europeans we carried out: i) a genome-wide association analysis of >6M genetic variants in 10,318 South Asians with focused analysis of population-specific SNPs; ii) an exome-wide association analysis of ~250K SNPs in protein-coding regions in 2,637 South Asians; iii) a comparison of risk allele frequencies and effect sizes of 48 known WHR SNPs in 12,240 South Asians compared to Europeans. In genome-wide analyses, we found no novel associations between common genetic variants and WHR in South Asians at P<5x10-8; variants showing equivocal association with WHR (P<1x10-5) did not replicate at P<0.05 in an independent cohort of South Asians (N = 1,922) or in published, predominantly European meta-analysis data. In the targeted analyses of 122,391 population-specific SNPs we also found no associations with WHR in South Asians at P<0.05 after multiple testing correction. Exome-wide analyses showed no new associations between genetic variants and WHR in South Asians, either individually at P<1.5x10-6 or grouped by gene locus at P<2.5x10-6. At known WHR loci, risk allele frequencies were not higher in South Asians compared to Europeans (P = 0.77), while effect sizes were unexpectedly smaller in South Asians than Europeans (P<5.0x10-8). Our findings argue against an important contribution for population-specific or cosmopolitan genetic variants underlying the increased risk of central obesity in South Asians compared to Europeans.

Type 2 diabetes in migrant south Asians: mechanisms, mitigation, and management

South Asians, particularly when living in high-income countries, are at a substantially elevated risk of type 2 diabetes compared with white Europeans, and typically develop the disease 5-10 years earlier and at a lower BMI. Migrant south Asians seem to be more insulin resistant than white Europeans across the life course and potentially experience β-cell exhaustion at a younger age. Differences in adiposity (high percentage of body fat and high proportion of deep subcutaneous and visceral fat) and skeletal muscle (low percentage of lean mass and low cardiorespiratory fitness) are likely to contribute these factors. No clear evidence is available suggesting genetic factors make a major contribution to the increased risk of diabetes in south Asians, but epigenetic factors might have a role. Irrespective of future mechanistic discoveries, south Asians need to be encouraged and helped-by various culturally appropriate methods--to maintain a high physical activity level and low bodyweight across the life course to prevent diabetes. In clinical terms, cardiovascular risks have attenuated over time in migrant south Asians with diabetes but retinopathy and renal complication risks remain high because of the high levels of glycaemia and rapid glycaemic deterioration noted in this population. We review these aspects and suggest areas for future research.

Associations of body mass index, smoking, and alcohol consumption with prostate cancer mortality in the Asia Cohort Consortium

Many potentially modifiable risk factors for prostate cancer are also associated with prostate cancer screening, which may induce a bias in epidemiologic studies. We investigated the associations of body mass index (weight (kg)/height (m)(2)), smoking, and alcohol consumption with risk of fatal prostate cancer in Asian countries where prostate cancer screening is not widely utilized. Analysis included 18 prospective cohort studies conducted during 1963-2006 across 6 countries in southern and eastern Asia that are part of the Asia Cohort Consortium. Body mass index, smoking, and alcohol intake were determined by questionnaire at baseline, and cause of death was ascertained through death certificates. Analysis included 522,736 men aged 54 years, on average, at baseline. During 4.8 million person-years of follow-up, there were 634 prostate cancer deaths (367 prostate cancer deaths across the 11 cohorts with alcohol data). In Cox proportional hazards analyses of all cohorts in the Asia Cohort Consortium, prostate cancer mortality was not significantly associated with obesity (body mass index >25: hazard ratio (HR) = 1.08, 95% confidence interval (CI): 0.85, 1.36), ever smoking (HR = 1.00, 95% CI: 0.84, 1.21), or heavy alcohol intake (HR = 1.00, 95% CI: 0.74, 1.35). Differences in prostate cancer screening and detection probably contribute to differences in the association of obesity, smoking, or alcohol intake with prostate cancer risk and mortality between Asian and Western populations and thus require further investigation.

Body Composition in Asians and Caucasians: Comparative Analyses and Influences on Cardiometabolic Outcomes

Within the last four decades Asia has witnessed major transformation in its population demographics, which gave rise to changes in food availability, food habits and lifestyle. A significant consequence of these changes has been the continuing rise in overweight and obesity across Asia. In parallel, there has been a significant rise in Asians in the incidence of the major chronic diseases, particularly in cardiometabolic disorders such as metabolic syndrome, type 2 diabetes, hypertension, and other cardiovascular diseases. Given that the majority of the evidence, to date, investigating the associations between adiposity and cardiometabolic disorder risk have been obtained from studies undertaken either in European or in North American Caucasians, in this chapter, we have reviewed differences in body fat content and distribution between East Asians, South Asians, and Caucasians. The evidence is consistent that the content and distribution of body fat are markedly different between the various ethnic groups. We found that Asians have a greater predisposition towards adiposity at higher BMI than in Caucasians. Moreover, at any given level of adiposity, Asians have a much greater predisposition to risk of cardiometabolic disorders than Caucasians. We therefore strongly endorse the need for different adiposity cutoffs in Asians as compared to the Caucasians. We have also reviewed the predictive abilities of the various body composition/adiposity measures in determining risk of cardiometabolic disorders in Asians.

Relationship between serum osteocalcin levels and non-alcoholic fatty liver disease in Chinese men

The present study was designed to investigate the relationship between serum osteocalcin levels and non-alcoholic fatty liver disease (NAFLD) in Chinese men. In all, 1558 men (21-78 years old) were recruited to the study. Serum osteocalcin, glucose and lipid profiles were determined. Demographic and clinical characteristics were recorded. All participants underwent hepatic ultrasonographic examination. Serum osteocalcin levels were significantly lower in subjects with NAFLD than those without (P < 0.01). All study subjects were divided into four subgroups according to quartiles of serum osteocalcin levels. The frequency of NAFLD increased progressively with declining serum osteocalcin levels (P(trend) < 0.01). Serum osteocalcin levels were inversely correlated with NAFLD (P < 0.01). However, the significant association between serum osteocalcin levels and NAFLD disappeared in logistic regression analyses. Furthermore, multiple stepwise regression analysis showed that serum osteocalcin levels were independently associated with serum alanine aminotransferase levels in Chinese men (P < 0.01). The findings of the present study suggest that serum osteocalcin levels are not directly correlated with NAFLD.

Individual contributions of visceral fat and total body fat to subclinical atherosclerosis: The NEO study

BACKGROUND

Both overall and abdominal adiposity are established risk factors for cardiovascular disease. Visceral adipose tissue (VAT) and total body fat (TBF) are strongly correlated and previous studies did not make this distinction.

OBJECTIVE

We aimed to distinguish individual contributions of TBF, VAT, and the ratio of VAT to abdominal subcutaneous adipose tissue (VAT/SAT) to subclinical atherosclerosis in men and women.

METHODS

In this cross-sectional analysis of the Netherlands Epidemiology of Obesity (NEO) study, we assessed VAT and SAT with magnetic resonance imaging, TBF with bio-electrical impendence analysis, and carotid Intima-Media Thickness (cIMT) with ultrasound. We performed linear regression analyses of standardized values of TBF, VAT, VAT/SAT with cIMT. We adjusted the models for confounding factors (age, sex, ethnicity, education, smoking, alcohol, physical activity), and either for VAT or TBF.

RESULTS

This analysis included 2451 participants, 53% men with mean (SD) cIMT of 615 (91)μm. After adjustment for confounding factors, the difference in cIMT (95% CI) per SD in VAT was 14 (8,21)μm in men and 18 (13,24)μm in women. After adjustment for TBF, this attenuated to 5 (-3,13)μm in men and 13 (5,20)μm in women. In the full model, differences in cIMT (95% CI) per SD of TBF were 14 (6,22)μm in men and 8 (0,16)μm in women, and per SD of VAT/SAT were 7 (-1,15)μm and 9 (3,16)μm respectively.

CONCLUSIONS

In this population-based study, VAT contributed beyond overall adiposity to subclinical atherosclerosis, particularly in women. This implies a specific role of VAT in the early development of atherosclerosis.

Clinical usefulness of lipid ratios to identify men and women with metabolic syndrome: a cross-sectional study

Background

Waist circumference, a metabolic syndrome (MetSy) criterion, is not routinely measured in clinical practice making early identification of individuals with MetSy challenging. It has been argued that ratios of commonly measured parameters such as lipids and lipoproteins may be an acceptable alternative for identifying individuals with MetSy. The objective of our study was to explore clinical utility of lipid ratios to identify men and women with MetSy; and to explore the association between lipid ratios and the number of MetSy components.

Methods

Men and women (N = 797) of Aboriginal, Chinese, European, and South Asian origin (35–60 years), recruited across ranges of body mass index (BMI), with no diagnosed cardiovascular disease (CVD) or on medications to treat CVD risk factors were assessed for anthropometrics, family history of CVD, MetSy components (waist circumference, blood pressure, glucose, triglycerides (TG), high-density-lipoprotein-cholesterol (HDL-C)), low-density-lipoprotein-cholesterol (LDL-C), nonHDL-C, and health-related behaviours.

Results

Mean levels of lipid ratios significantly increased with increasing number of MetSy components in men and women (p < 0.05). After adjustment for age, ethnicity, smoking, alcohol consumption, physical activity, family history of CVD and BMI, (and menopausal status in women), all lipid ratios were associated with the number of MetSy components in men and women (Poisson regression, p < 0.001). Compared to the rest of the lipid ratios (ROC curve analysis), TG/HDL-C was best able to discriminate between individuals with and without MetSy (AUC = 0.869 (95% CI: 0.830, 0.908) men; AUC = 0.872 (95% CI: 0.832, 0.912) women). The discriminatory power of TC/HDL-C and nonHDL-C/HDL-C to identify individuals with MetSY was the same (for both ratios, AUC = 0.793 (95% CI: 0.744, 0.842) men; 0.818 (95% CI: 0.772, 0.864) women). Additionally, LDL-C/HDL-C was a good marker for women (AUC = 0.759 (95% CI: 0.706, 0.812)), but not for men (AUC = 0.689 (95% CI: 0.631, 0.748)). Based on a multiethnic sample, we identified TG/HDL-C cut-off values of 1.62 in men and 1.18 in women that were best able to discriminate between men and women with and without MetSY.

Conclusions

Our results indicate that TG/HDL-C is a superior marker to identify men and women with MetSy compared to TC/HDL-C, LDL-C/HDL-C, and nonHDL-C/HDL-C.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-511X-13-159) contains supplementary material, which is available to authorized users.

Cardiovascular risk among South Asians living in Canada: a systematic review and meta-analysis

BACKGROUND

South Asians represent about 3% of the Canadian population and have a higher burden of certain cardiovascular risk factors and cardiovascular disease (CVD) compared with white people. The objective of this study was to review the literature to compare cardiovascular risk factors and disease management practices among adult South Asian and white Canadians.

METHODS

We searched MEDLINE, Embase, Cochrane and Cumulative Index to Nursing and Allied Health Literature databases from their inception through Feb. 17, 2014 and the reference lists of the selected articles. English-language studies of interventions and observational studies of biological mechanisms underlying CVD risk in South Asians conducted in Canada were eligible for inclusion. Where appropriate, we used random-effects meta-analyses to integrate results comparing the CVD risk profiles of South Asian and white Canadians.

RESULTS

We included 50 articles (n = 5 805 313 individuals) in this review. Compared with white Canadians, South Asian Canadians had a higher prevalence and incidence of CVD, an increased prevalence of diabetes (odds ratio [OR] 2.25, 95% confidence interval [CI] 1.81 to 2.80, p < 0.001) and hypertension (OR 1.11, 95% CI 1.02 to 1.22, p = 0.02), lower high-density lipoprotein cholesterol levels (mean difference -0.19 mmol/L, 95% CI -0.25 to -0.13 mmol/L, p < 0.001) and a higher percentage of body fat (men: absolute mean difference 3.23%, 95% CI 0.83% to 5.62%, p = 0.008; women: absolute mean difference 4.09%, 95% CI 3.46% to 4.72%, p < 0.001). South Asian people are also more sedentary, consume higher levels of carbohydrates and are less likely to smoke tobacco (OR 0.38, 95% CI 0.24 to 0.60, p < 0.001]) than white Canadians. No differences in access to diagnostic tests, outcomes following cardiovascular surgery or use of cardiac rehabilitation programs were apparent.

INTERPRETATION

Compared with white people, South Asian people living in Canada have a higher prevalence and incidence of CVD and possess a unique cardiovascular risk profile.

Ethnicity and the association between anthropometric indices of obesity and cardiovascular risk in women: a cross-sectional study

OBJECTIVES

The objectives of this study were to determine whether the cross-sectional associations between anthropometric obesity measures, body mass index (BMI), waist circumference (WC) and waist-to-hip ratio (WHR), and calculated 10-year cardiovascular disease (CVD) risk using the Framingham and general CVD risk score models, are the same for women of Australian, UK and Ireland, North European, South European and Asian descent. This study would investigate which anthropometric obesity measure is most predictive at identifying women at increased CVD risk in each ethnic group.

DESIGN

Cross-sectional data from the National Heart Foundation Risk Factor Prevalence Study.

SETTING

Population-based survey in Australia.

PARTICIPANTS

4354 women aged 20-69 years with no history of heart disease, diabetes or stroke. Most participants were of Australian, UK and Ireland, North European, South European or Asian descent (97%).

OUTCOME MEASURES

Anthropometric obesity measures that demonstrated stronger predictive ability of identifying women at increased CVD risk and likelihood of being above the promulgated treatment thresholds of various risk score models.

RESULTS

Central obesity measures, WC and WHR, were better predictors of cardiovascular risk. WHR reported a stronger predictive ability than WC and BMI in Caucasian women. In Northern European women, BMI was a better indicator of risk using the general CVD (10% threshold) and Framingham (20% threshold) risk score models. WC was the most predictive of cardiovascular risk among Asian women.

CONCLUSIONS

Ethnicity should be incorporated into CVD assessment. The same anthropometric obesity measure cannot be used across all ethnic groups. Ethnic-specific CVD prevention and treatment strategies need to be further developed.

Forty-five year trends in overweight and obesity in an indigenous arctic Inuit Society in transition and spatiotemporal trends

OBJECTIVES

Overweight and obesity associate with increased morbidity and premature death. Westernization of societies heralds rising obesity rates. A steep increase in body mass index (BMI) and overweight in Greenland from 1963 to 1998 led us to follow-up on height, weight, BMI, and rates of overweight among populations in Greenland and assess time trends between different stages of transition.

METHODS

BMI was calculated from height and weight measured on Inuit and non-Inuit aged 50 through 69 years surveyed in 1963, 1998, and 2008 in Ammassalik district in East Greenland and in 1998 and 2008 in the capital Nuuk in West Greenland.

RESULTS

A total of 1,186 were surveyed in 1963 (52 men/63 women), 1998 (309/226), and 2008 (297/239). BMI increased with time (P < 0.001; 1963/1998/2008 23.3/24.3/26.2 kg/m(2) ). In addition, BMI increased with urbanization in Inuit men (P = 0.001; settlements/town/city, in 1998, 23.9/24.9/25.5 kg/m(2) ; in 2008, 25.0/26.0/27.0 kg/m(2) ) while not in Inuit women (P = 0.18). The number of overweight Inuit (BMI >27 kg/m(2) ) increased with time in men (4.0/25.6/33.2% in 1963/1998/2008, P = 0.001) and in women (13.6/30.7/37.3%, P = 0.001). BMI was above 30 kg/m(2) in 2.0/10.8/17.5% of all Inuit men in 1963/1998/2008 (P = 0.003) and in 8.3%/23.0/24.5% of all Inuit women (P = 0.02) respectively.

CONCLUSIONS

Overweight and obesity rates rise with time and with societal transition in Greenland. Settlements and town are catching up with the city where the rate of increase is diminishing, although there were gender differences.

Elevated cholesteryl ester transfer protein (CETP) activity, a major determinant of the atherogenic dyslipidemia, and atherosclerotic cardiovascular disease in South Asians

AIMS

Why South Asians are at increased risk of premature atherosclerotic cardiovascular diseases compared with other ethnic groups is not fully understood. Atherogenic dyslipoproteinemia - hypertriglyceridemia, elevated numbers of low-density lipoprotein (LDL) particles and low high-density lipoprotein cholesterol (HDL-C) - is more common in South Asians but the mechanisms responsible have not been explicated. Here we examined whether the circulating lipid transfer protein, cholesteryl ester transfer protein (CETP), plays a role in the pathogenesis of the atherogenic dyslipoproteinemia among South Asians.

METHODS AND RESULTS

CETP activity was determined by exogenous substrate assay in the serum of healthy, metabolically well-characterized individuals of South Asian and European descent (N = 244 and 238, respectively). Serum and lipoprotein lipids and apolipoproteins were measured and lipoprotein particle number and size were quantified via nuclear magnetic resonance spectroscopy. All the elements of the atherogenic dyslipoproteinemia were more severe in South Asians and CETP activity was significantly greater by 30% in South Asians compared with Europeans, adjusted for age, sex, body mass index and waist circumference (p < 0.0001). CETP activity was directly associated with serum triglycerides and inversely with HDL-C in the whole population. CETP activity was also directly related to apoB and LDL particle number. Finally, increased CETP activity was associated with pro-atherogenic reductions in HDL and LDL particle size.

CONCLUSIONS

We identified novel associations between elevated CETP activity and the triad of quantitative and qualitative lipoprotein abnormalities in the atherogenic dyslipidemia in South Asians, a major contributor of increased atherosclerotic cardiovascular diseases in South Asians.

The association between "hypertriglyceridemic waist" and sub-clinical atherosclerosis in a multiethnic population: a cross-sectional study

Background

"Hypertriglyceridemic waist" (HTGW) phenotype, an inexpensive early screening tool for detection of individuals at risk for type 2 diabetes and cardiovascular disease was found to be associated with subclinical atherosclerosis in various patient populations such as those with diabetes mellitus, chronic kidney disease, and those infected with human immunodeficiency virus. However, less is known regarding an association between HTGW and subclinical atherosclerosis in the apparently healthy, multiethnic population. Therefore, the aim of the study was to explore the association between HTGW and sub-clinical atherosclerosis in an apparently healthy, multiethnic population; and to investigate whether the effect of HTGW on sub-clinical atherosclerosis persists over and above the traditional atherosclerosis risk factors.

Methods

We studied 809 individuals of Aboriginal, Chinese, European and South Asian origin who were assessed for indices of sub-clinical atherosclerosis (intima-media thickness (IMT), total area and presence of carotid plaques), socio-demographic and lifestyle characteristics, anthropometrics, lipids, glucose, blood pressure, and family history of cardiovascular disease.

Results

We found that, compared to individuals without HTGW and after adjusting for age, ethnicity, smoking, and physical activity; men and women with HTGW had a significantly higher: IMT (men: B (95%CI = 0.084 (0.037, 1.133), p < 0.001; women: B (95%CI) = 0.041 (0.006, 0.077), p = 0.020); and total area (men: B (95%CI = 0.202 (0.058, 0.366), p = 0.005; women: B (95%CI) = 0.115 (0.006, 0.235), p = 0.037). The association between HTGW waist and presence of plaques was significant for men (OR (95%CI) = 1.904 (1.040, 3.486), p = 0.037 vs. men without HTGW), but not for women (p = 0.284). Once analyses were adjusted for additional, traditional risk factors for atherosclerosis, the effect of HTGW on sub-clinical atherosclerosis was no longer significant.

Conclusions

In conclusion, HTGW may serve as an early marker of subclinical atherosclerosis in men and women, irrespective of ethnicity. However, once individuals are assessed for all traditional risk factors for atherosclerosis, the additional assessment for HTGW is not warranted.

Ethnic differences in serum adipokine and C-reactive protein levels: the multiethnic cohort

BACKGROUND

Ethnic disparities in metabolic disease risk may be the result of differences in circulating adipokines and inflammatory markers related to ethnic variations in obesity and body fat distribution.

SUBJECTS/METHODS

In a cross-sectional design, we compared serum levels of leptin, adiponectin, C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in control subjects (321 men and 930 women) from two nested case-control studies conducted within the Multiethnic Cohort Study consisting of whites, Japanese Americans (JA), Latinos, African Americans (AA) and Native Hawaiians (NH). General linear models were applied to evaluate ethnic differences in log-transformed serum biomarker levels before and after adjusting for body mass index (BMI) at cohort entry.

RESULTS

In comparison to whites, significant ethnic differences were observed for all biomarkers except TNF-α. JA men and women had significantly lower leptin and CRP levels than whites, and JA women also had lower adiponectin levels. Leptin was significantly higher in AA women (P < 0.01), adiponectin was significantly lower in AA men and women (P = 0.02 and P < 0.001), and CRP and IL-6 were significantly higher in AA men and women. Lower adiponectin (P < 0.0001) and CRP (P = 0.03) levels were the only biomarkers in NH women that differed from whites; no statistically significant differences were seen for NH men and for Latino men and women. When adjusted for BMI at cohort entry, the differences between the lowest and the highest values across ethnic groups decreased for all biomarkers except adiponectin in men indicating that ethnic differences were partially due to weight status.

CONCLUSIONS

These findings demonstrate the ethnic variations in circulating adipokine and CRP levels before and after adjustment for BMI. Given the limitation of BMI as a general measure of obesity, further investigation with visceral and subcutaneous adiposity measures are warranted to elucidate ethnicity-related differences in adiposity in relation to disparities in obesity-related disease risk.

Metabolic basis of ethnic differences in diabetes risk in overweight and obese youth

The global pandemic of childhood obesity has led to increased risk for prediabetes and type 2 diabetes mellitus (T2DM). Studies have shown decreased insulin sensitivity and/or secretion with increasing adiposity and consistently observed greater risk for T2DM in obese, non-Caucasian youth. In the current review we describe recent advances in understanding how obesity and metabolic status in children and adolescents confers various risk profiles for T2DM among Latinos, African Americans, Caucasians, Asians, and Native Americans. These possible determinants include ectopic fat distribution, adipose tissue inflammation and fibrosis, and elevated plasma levels of nonesterified free fatty acids. Future work should aim to elucidate the ethnic-specific pathophysiology of T2DM in order to develop and implement appropriate prevention and treatment strategies based on different ethnic profiles of diabetes risk.

Structural and functional properties of deep abdominal subcutaneous adipose tissue explain its association with insulin resistance and cardiovascular risk in men

OBJECTIVE

Fat distribution is an important variable explaining metabolic heterogeneity of obesity. Abdominal subcutaneous adipose tissue (SAT) is divided by the Scarpa's fascia into a deep subcutaneous adipose tissue (dSAT) and a superficial subcutaneous adipose tissue (sSAT) layer. This study sought to characterize functional differences between the two SAT layers to explore their relative contribution to metabolic traits and cardiovascular risk (CVR) profile.

RESEARCH DESIGN AND METHODS

We recruited 371 Caucasians consecutively from a local random, population-based screening project in Oxford and 25 Asian Indians from the local community. The depth of the SAT layers was determined by ultrasound (US), and adipose tissue (AT) biopsies were performed under US guidance in a subgroup of 43 Caucasians. Visceral adipose tissue (VAT) mass was quantified by dual-energy X-ray absorptiometry scan.

RESULTS

Male adiposity in both ethnic groups was characterized by a disproportionate expansion of dSAT, which was strongly correlated with VAT mass. dSAT depth was a strong predictor of global insulin resistance (IR; homeostatic model assessment of IR), liver-specific IR (insulin-like growth factor binding protein-1), and Framingham risk score independently of other measures of adiposity in men. Moreover, dSAT had higher expression of proinflammatory, lipogenic, and lipolytic genes and contained higher proportions of saturated fatty acids. There was increased proportion of small adipocytes in dSAT.

CONCLUSIONS

SAT is heterogeneous; dSAT expands disproportionally more than sSAT with increasing obesity in Caucasian males (confirmed also in Asian Indians). Its expansion is related to increased CVR independent of other adiposity measures, and it has biological properties suggestive of higher metabolic activity contributing to global IR.

Molecular and morphologic characterization of superficial- and deep-subcutaneous adipose tissue subdivisions in human obesity

OBJECTIVE

Human abdominal subcutaneous white adipose tissue (SAT) is composed of two different subcompartments: a "superficial" SAT (SSAT), located between the skin and a fibrous-fascia plane; and a deeper SAT, located under this fibrous fascia plane, indicated as "deep" SAT (DSAT).

DESIGN AND METHODS

In order to investigate whether SSAT and DSAT have different molecular and morphological features, paired SSAT/DSAT biopsies were collected from 10 female obese patients and used for microarray and morphologic analysis. The stroma-vascular fraction cells were also isolated from both depots and cultured in vitro to assess the lipid accumulation rate.

RESULTS

SSAT and DSAT displayed different patterns of gene expression, mainly for metabolic and inflammatory genes, respectively. Detailed gene expression analysis indicated that several metabolic genes, including adiponectin, are preferentially expressed in SSAT, whereas inflammatory genes are over-expressed in DSAT. Despite a similar lipid accumulation rate in vitro, in vivo SSAT showed a significant adipocyte hypertrophy together with a significantly lower inflammatory infiltration and vascular vessel lumen mean size, when compared to DSAT.

CONCLUSIONS

These data show that, SSAT and DSAT are functionally and morphologically different and emphasize the importance of considering independent these two adipose depots when investigating SAT biology and obesity complications.

Pathogenesis of type 2 diabetes in South Asians

The risk of developing type 2 diabetes mellitus (T2DM) is exceptionally high among both native and migrant South Asians. T2DM occurs more often and at a younger age and lower BMI, and the risk of coronary artery and cerebrovascular disease, and renal complications is higher for South Asians compared with people of White Caucasian descent. The high prevalence of T2DM and its related complications in South Asians, which comprise one-fifth of the total world's population, poses a major health and socioeconomic burden. The underlying cause of this excess risk, however, is still not completely understood. Therefore, gaining insight into the pathogenesis of T2DM in South Asians is of great importance. The predominant mechanism, in this ethnicity seems to be insulin resistance (IR) rather than an impaired β-cell function. In this systematic review, we describe several possible mechanisms that may underlie or contribute to the increased IR observed in South Asians.

Lean NASH: distinctiveness and clinical implication

INTRODUCTION

Non-alcoholic fatty liver (NAFL) in the absence of overweight and/or obesity, defined by the anthropometric parameter, body mass index (BMI), has been designated as 'lean NASH.' While maintaining a close pathophysiological link with metabolic syndrome (MS) and insulin resistance (IR), the presence of subtle alterations in measures of total body and regional adiposity not exceeding the designed cut-offs, are hallmarks of 'lean NASH.'

MATERIAL AND METHODS

Available literature related to non-alcoholic steatohepatitis (NASH) in lean or non-obese individuals and its pathogenesis in general published in English language journals till the time of manuscript preparation were reviewed and critically analysed.

ANALYSIS

Being a closely related but variant phenotype of NASH, its features metabolically resemble the well-characterized entity 'metabolically obese normal weight (MONW)' individuals. Apart from total body adiposity, distribution of fat in different body compartments has assumed greater pathophysiologic relevance in characterizing 'lean NASH'. Detection of NASH in stringently defined non-obese individuals, by both BMI and waist circumference indices, indicates existence of a subset of NASH in which fat compartmentalization at ectopic sites is not picked up by the anthropometric yardsticks used. Volume [Quantity] and biological behavior of the visceral and deep subcutaneous adipose tissues contribute to this variant of NASH in non-obese subjects. Genetic predisposition to IR and MS along with the environmental influences like childhood nutritional status, dietary composition and gut microbiome possibly play pathogenetic role.

CONCLUSION

The most important concern is in the principles of nomenclature within syndromes where clinical dissimilarities exist despite biological similarities. Till a uniformly acceptable pathophysiological and/or etiology-based classification emerges, the term "lean NASH" would continue to provide us an opportunity to ponder over and refine this subset of fatty liver in non-obese people and potentially significant liver disease.

Raised BMI cut-off for overweight in Greenland Inuit--a review

Background

Obesity is associated with increased morbidity and premature death. Obesity rates have increased worldwide and the WHO recommends monitoring. A steep rise in body mass index (BMI), a measure of adiposity, was detected in Greenland from 1963 to 1998. Interestingly, the BMI starting point was in the overweight range. This is not conceivable in a disease-free, physically active, pre-western hunter population.

Objective

This led us to reconsider the cut-off point for overweight among Inuit in Greenland.

Design and findings

We found 3 different approaches to defining the cut-off point of high BMI in Inuit. First, the contribution to the height by the torso compared to the legs is relatively high. This causes relatively more kilograms per centimetre of height that increases the BMI by approximately 10% compared to Caucasian whites. Second, defining the cut-off by the upper 90-percentile of BMI from height and weight in healthy young Inuit surveyed in 1963 estimated the cut-off point to be around 10% higher compared to Caucasians. Third, if similar LDL-cholesterol and triglycerides are assumed for a certain BMI in Caucasians, the corresponding BMI in Inuit in both Greenland and Canada is around 10% higher. However, genetic admixture of Greenland Inuit and Caucasian Danes will influence this difference and hamper a clear distinction with time.

Conclusion

Defining overweight according to the WHO cut-off of a BMI above 25 kg/m² in Greenland Inuit may overestimate the number of individuals with elevated BMI.

Different associations of subscapular and triceps skinfold thicknesses with pathogen load: an ecogeographical analysis

OBJECTIVES

The dominant evolutionary perspective on adipose tissue has considered it a relatively inert energy store. However, variability in adipose tissue distribution has recently been associated with age, parity, thermal environment and immune function. Genes regulating the innate immune system are more strongly expressed in deep-lying than peripheral adipose tissue. We hypothesized that central adiposity would correlate more strongly than peripheral adiposity with pathogen load across populations.

METHODS

Primary outcomes were subscapular and triceps skinfolds from 133 male and 106 female populations. National values for disability-adjusted life years lost, attributable to infectious diseases, were used to index pathogen load. Linear mixed-effects models were fitted, including a random effect term by country to investigate the association of each skinfold with pathogen load, adjusting for the other skinfold, mean annual temperature and clustering of the populations across countries.

RESULTS

Adjusting for subscapular skinfold, triceps skinfold was not associated with pathogen load in either sex. Adjusting for triceps skinfold, subscapular skinfold was negatively associated with pathogen load in both sexes (P < 0.02). These associations were independent of variability in annual temperature. Adjusting for pathogen load and temperature, Oceanic populations had a different fat distribution compared to other populations.

CONCLUSIONS

Across populations, higher pathogen load was associated with reduced central but not peripheral skinfolds, supporting the hypothesis that central adiposity is more closely associated with immune function. This scenario might explain why some populations increase disproportionately in central adiposity when the environment shifts from low-energy high-pathogen status to high-energy low-pathogen status.

Sex hormone-binding globulin and the risk for metabolic syndrome in children of South Asian Indian origin

OBJECTIVE

To determine whether the plasma level of sex hormone-binding globulin (SHBG) identifies South Asian Indian children at risk for metabolic syndrome.

METHODS

Adults and their children aged 5 to 9 years were recruited at the annual health fair at the Hindu temple serving the South Asian Indian community in Louisville, Kentucky. Anthropometric data were collected in adults and children, and blood pressure, lipid, and glucose levels were measured in adults. SHBG levels were measured in children using a fingerstick blood sample. In adults, metabolic syndrome was diagnosed according to the International Diabetes Federation criteria. Twelve months later, follow-up anthropometric data were obtained for a portion of the children.

RESULTS

The study included 30 sets of parents and 30 children. The prevalence of metabolic syndrome among 310 adults attending the health fair was 42% in men and 39% in women. Children with 1 parent with metabolic syndrome had 24% lower SHBG levels that increased to 55% if both parents had metabolic syndrome. SHBG levels were inversely related to waist circumference and to body mass index percentile. Both SHBG and waist circumference predicted weight gain over 1 year in children. CONCLUSIONS Low SHBG levels were found in South Asian Indian children whose parents had attributes of metabolic syndrome. The dose dependency of SHBG is consistent with inheritance of a genetic trait, and if the results are applicable to other racial/ethnic groups, SHBG may be a useful marker to identify at-risk children for early intervention.

Ratio of waist circumference to chest circumference is inversely associated with lung function in Chinese children and adolescents

BACKGROUND AND OBJECTIVE

In White children, waist circumference (WC) is positively correlated with forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV(1)). Because fat distribution differs among different races, the relationship between WC and lung function in Asian children may differ from that in White children. The present study aimed to examine the effect of WC on ventilatory function in Chinese children.

METHODS

A cross-sectional study was performed on 1572 healthy subjects aged 9-18 years. Height, weight, chest circumference (CC), WC and lung function (FVC, FEV(1), peak expiratory flow (PEF) and maximal mid-expiratory flow (MMEF)) were measured. To avoid the problem of colinearity, a model that combined CC and WC as the waist-to-chest ratio (WCR) was used. The relative contributions of WCR and body mass index (BMI) to spirometric parameters were determined by linear regression analysis.

RESULTS

WCR was inversely associated with all spirometric parameters. On average, each 0.01 increase in WCR was associated with decreases of 8.14 mL for FVC, 9.36 mL for FEV(1), 6.54% for FEV(1)/FVC, 19.81 mL/s for PEF and 17.25 mL/s for MMEF. BMI was positively associated with all spirometric parameters except FEV(1)/FVC. These results suggest that WC was inversely associated with lung function parameters.

CONCLUSIONS

Inverse associations were identified between WCR, as well as WC, and lung function in a population of Chinese children. The underlying mechanisms need to be further explored.

A four-stage model explaining the higher risk of Type 2 diabetes mellitus in South Asians compared with European populations

With approximately 1.5 billion people at risk, the staggeringly high risk of Type 2 diabetes in South Asians comprises a global problem. The causes of this high risk are complex, with 23 major risk factors identified in a Lancet seminar. This paper proposes a four-stage explanatory model: (1) the birth of a small, adipose, lowlean mass South Asian baby--the phenotype tracking through life; (2) in childhood and early adulthood, the deposition of any excess energy intake preferentially in upper body and ectopic fat stores rather than in the lower body or superficial subcutaneous fat stores; (3) as a consequence of points 1 and 2, and exacerbated by an environment of low physical activity and excess calories, the accelerated appearance of high levels of plasma insulin, triglycerides and glucose, and the fatty-liver vicious cycle; (4) β-cell failure as a result of fewer β-cells at birth, exposure to apoptotic triggers such as fat in the pancreas, and high demand from insulin resistance, which causes diabetes. Other risk factors--especially energy-dense hyperglycaemic diet and low physical activity--play into this pathway. The recommended behavioural changes fit with this model, which brings clarity to guide future research, policy, practice and health promotion.

Ethnic influences on the relations between abdominal subcutaneous and visceral adiposity, liver fat, and cardiometabolic risk profile: the International Study of Prediction of Intra-Abdominal Adiposity and Its Relationship With Cardiometabolic Risk/Intra-Abdominal Adiposity

BACKGROUND

Ethnic differences in cardiometabolic risk (CMR) may be related to patterns of ethnic-specific body fat distribution.

OBJECTIVE

We aimed to identify differences across ethnic groups in interrelations between BMI, abdominal adiposity, liver fat, and CMR profile.

DESIGN

In the International Study of Prediction of Intra-Abdominal Adiposity and Its Relationship With Cardiometabolic Risk/Intra-Abdominal Adiposity, 297 physicians recruited 4504 patients (from 29 countries). In the current cross-sectional analyses, 2011 whites, 166 African Caribbean blacks, 381 Hispanics, 1192 East Asians, and 347 Southeast Asians were included. Computed tomography was used to assess abdominal fat distribution and to estimate liver fat content. Anthropometric variables and CMR profile were measured.

RESULTS

Higher ranges of BMI were associated with higher levels of visceral [visceral adipose tissue (VAT)] and deep subcutaneous [deep subcutaneous adipose tissue (DSAT)] adiposity, with significant ethnic differences regarding the slope of these relations. Despite lower absolute BMI values, East Asians presented the largest accumulation of VAT but the lowest accumulation of DSAT with increasing adiposity. The association of BMI with liver fat did not differ between ethnic groups. Liver fat and DSAT were positively correlated with VAT with no ethnic variation. All ethnic groups had a similar association between a 1-SD increase in VAT, DSAT, or liver fat with hypertension, type 2 diabetes, hypertriglyceridemia, low HDL-cholesterol concentration, or high C-reactive protein concentration.

CONCLUSIONS

Ethnicity significantly affects abdominal adiposity and liver fat partitioning, and East Asians have the most deleterious abdominal fat distribution. Irrespective of ethnicity, abdominal and hepatic fat depots are strongly interrelated and increased with obesity. Higher amounts of VAT or liver fat are associated with a more deteriorated CMR profile in all ethnic groups.

The association between triglyceride to high-density-lipoprotein cholesterol ratio and insulin resistance in a multiethnic primary prevention cohort

The objective was to explore the clinical utility of triglyceride (TG) to high-density lipoprotein cholesterol (HDL-C) ratio in predicting insulin resistance (IR) in 4 ethnic groups and the relationship between IR and TG/HDL-C in comparison to that with other lipid measures. Apparently healthy Aboriginals, Chinese, Europeans, and South Asians (N = 784) were assessed for sociodemographics, lifestyle, anthropometry, lipids, glucose, and insulin. The homeostasis model assessment of IR was used as a measure of IR. Compared with other lipid parameters, TG/HDL-C was the highest correlate of the homeostasis model assessment of IR (age and sex adjusted) in Aboriginals (r = 0.499, P < .001), Chinese (r = 0.432, P < .001), Europeans (r = 0.597, P < .001), and South Asians (0.372, P < .001). For a 1-unit increase in TG/HDL-C, the odds of being insulin resistant increased about 4 times (odds ratio [OR], 3.95; 95% confidence interval [CI], 1.86-8.42; P < .001) in Aboriginals, 3.4 times in Chinese (OR, 3.44; 95% CI, 1.79-6.62; P < .001), 1.9 times in Europeans (OR, 1.94; 95% CI, 1.00-3.75; P = .049), and 1.8 times in South Asians (OR, 1.77; 95% CI, 0.91-3.45; P = .094) (age, sex, smoking, physical activity, body mass index, and waist circumference adjusted). Receiver operating characteristic curve analyses revealed areas under the curve (95% CI) of 0.777 (0.707-0.847) in Aboriginals, 0.723 (0.647-0.798) in Chinese, 0.752 (0.675-0.828) in Europeans, and 0.676 (0.590-0.762) in South Asians. Optimal cutoffs (sensitivity, specificity) of TG/HDL-C for identifying individuals with IR were 0.9 (93.0%, 51.9%), 1.1 (71.7%, 61.5%), 1.1 (73.5%, 70.9%), and 1.8 (52.0%, 77.9%) in Aboriginal, Chinese, European, and South Asian individuals, respectively. The TG/HDL-C ratio may be a good marker to identify insulin-resistant individuals of Aboriginal, Chinese, and European, but not South Asian, origin.

The influence of childhood and adolescent environmental exposure to a westernized environment on the relation between body mass index and adiposity in young Asian American women

BACKGROUND

Asians who have a healthy body mass index (BMI) range have been observed to have higher levels of obesity and risk of cardiovascular disease than whites, which suggests that the relation between BMI and adiposity may be different for Asians.

OBJECTIVE

The primary aim of this study was to investigate the influence of childhood and adolescent exposure to a westernized environment on the relation between BMI and percentage body fat in young Asian American women.

DESIGN

Secondary data from 129 Asian women, aged 20-25 y, with variable lengths of residence in the United States and 327 white women of comparable ages who had participated in the Latina and Asian Bone Health Study (1999-2000) and the Berkeley Bone Health Study (1998-2000), respectively, were analyzed by using multiple linear regression with percentage body fat as the outcome variable and place of birth, ethnicity, length of US residency, and BMI as predictor variables.

RESULTS

Asians who lived in the United States <12 y showed the same relation between BMI and percentage body fat as did whites. In contrast, Asians who had lived in the United States ≥12 y had higher percentage body fat than did whites for BMIs (in kg/m(2)) <20.5 and lower percentage body fat for BMIs in the overweight and obese range.

CONCLUSIONS

Our findings suggest that childhood environments may influence the relation between BMI and adiposity. Research is warranted on the role that childhood environments play in the accumulation and distribution of body fat and hence metabolic disease risk later in life.

Body composition phenotypes in pathways to obesity and the metabolic syndrome

Dynamic changes in body weight have long been recognized as important indicators of risk for debilitating diseases. While weight loss or impaired growth can lead to muscle wastage, as well as to susceptibility to infections and organ dysfunctions, the development of excess fat predisposes to type 2 diabetes and cardiovascular diseases, with insulin resistance as a central feature of the disease entities of the metabolic syndrome. Although widely used as the phenotypic expression of adiposity in population and gene-search studies, body mass index (BMI), that is, weight/height(2) (H(2)), which was developed as an operational definition for classifying both obesity and malnutrition, has considerable limitations in delineating fat mass (FM) from fat-free mass (FFM), in particular at the individual level. After an examination of these limitations within the constraints of the BMI-FM% relationship, this paper reviews recent advances in concepts about health risks related to body composition phenotypes, which center upon (i) the partitioning of BMI into an FM index (FM/H(2)) and an FFM index (FFM/H(2)), (ii) the partitioning of FFM into organ mass and skeletal muscle mass, (iii) the anatomical partitioning of FM into hazardous fat and protective fat and (iv) the interplay between adipose tissue expandability and ectopic fat deposition within or around organs/tissues that constitute the lean body mass. These concepts about body composition phenotypes and health risks are reviewed in the light of race/ethnic variability in metabolic susceptibility to obesity and the metabolic syndrome.