Abnormal glucose tolerance and other coronary heart disease risk factors in an isolated aboriginal community in central Australia

Noncoding Variations in the Gene Encoding Ceramide Synthase 6 are Associated with Type 2 Diabetes in a Large Indigenous Australian Pedigree

Type 2 diabetes (T2D) is a chronic disease that disproportionately affects Indigenous Australians. We have previously reported the localization of a novel T2D locus by linkage analysis to chromosome 2q24 in a large admixed Indigenous Australian pedigree (Busfield et al. (2002). American Journal of Human Genetics, 70, 349-357). Here we describe fine mapping of this region in this pedigree, with the identification of SNPs showing strong association with T2D: rs3845724 (diabetes p = 7 × 10-4), rs4668106 (diabetes p = 9 × 10-4) and rs529002 (plasma glucose p = 3 × 10-4). These associations were successfully replicated in an independent collection of Indigenous Australian T2D cases and controls. These SNPs all lie within the gene encoding ceramide synthase 6 (CERS6) and thus may regulate ceramide synthesis.

Evidence for low high-density lipoprotein cholesterol levels in Australian indigenous peoples: a systematic review

Background

Low plasma high-density lipoprotein cholesterol (HDL-C) levels are a strong, independent, but poorly understood risk factor for cardiovascular disease (CVD). Although this atherogenic lipid abnormality has been widely reported in Australia’s Indigenous peoples, Aboriginal and Torres Strait Islanders, the evidence has not come under systematic review. This review therefore examines published data for Indigenous Australians reporting 1) mean HDL-C levels for both sexes and 2) factors associated with low HDL-C.

Methods

PubMed, Medline and Informit ATSI Health databases were systematically searched between 1950 and 2012 for studies on Indigenous Australians reporting mean HDL-C levels in both sexes. Retrieved studies were evaluated by standard criteria. Low HDL-C was defined as: <1.0 mmol/L. Analyses of primary data associating measures of HDL-C with other CVD risk factors were also performed.

Results

Fifteen of 93 retrieved studies were identified for inclusion. These provided 58 mean HDL-C levels; 29 for each sex, most obtained in rural/regional (20%) or remote settings (60%) and including 51–1641 participants. For Australian Aborigines, mean HDL-C values ranged between 0.81-1.50 mmol/L in females and 0.76-1.60 mmol/L in males. Two of 15 studies reported HDL-C levels for Torres Strait Islander populations, mean HDL-C: 1.00 or 1.11 mmol/L for females and 1.01 or 1.13 mmol/L for males. Low HDL-C was observed only in rural/regional and remote settings - not in national or urban studies (n = 3) in either gender. Diabetes prevalence, mean/median waist-to-hip ratio and circulating C-reactive protein levels were negatively associated with HDL-C levels (all P < 0.05). Thirty-four per cent of studies reported lower mean HDL-C levels in females than in males.

Conclusions

Very low mean HDL-C levels are common in Australian Indigenous populations living in rural and remote communities. Inverse associations between HDL-C and central obesity, diabetes prevalence and inflammatory markers suggest a particularly adverse CVD risk factor profile. An absence of sex dichotomy in HDL-C levels warrants further investigation.

Dietary factors related to the increase of cardiovascular risk factors in traditional Tepehuanos communities from Mexico. A 10 year follow-up study

BACKGROUND AND AIMS

Tepehuanos Indians, a traditional Mexican ethnic group, followed a vegetarian diet exhibiting a low prevalence of obesity and the absence of diabetes. However, from the year 2000 the traditional diet of the Tepehuanos was modified by the introduction of western food. In this study we examine the changes in their customary diet and its impact on the prevalence of cardiovascular risk factors in this group.

METHODS AND RESULTS

Individuals from 12 Tepehuanos communities were randomly enrolled during 1995-1996 and 2006-2007. Using a 64-item semiquantitative food frequency questionnaire macronutrient intakes were calculated from values of Mexican food-composition tables. Cardiovascular risk factors such as obesity, hypertension, hyperglycemia and dyslipidemia were determined. The median (25, 75 percentile) of total caloric intake (1476 [1083, 1842]-2100 [1366, 2680]kcal/day, p<0.001) as well as the percentage of energy consumed from saturated fat (3.0 [2.7,4.1]-7.2 [3.9,7.4], p<0.0001) and protein (8.2 [7.8,8.9]-16.8 [16.3,17.1], p<0.0001) increased, whereas the percentage of total calorie intake from carbohydrates (66.4 [61.3,69.5]-61.3 [61,68.8], p<0.0001), polyunsaturated fat (11.2 [10.3,12.1]-4.0 [3.9,4.3], p<0.0001), and the polyunsaturated:saturated fat ratio (3.84-0.53%, p<0.0001) decreased during the period of study. The prevalence of obesity (11.1-21.9%, p=0.04), impaired fasting glucose (5.9-14.9%, p=0.04), diabetes (0.0-0.88%, p=0.48), hypertension (1.7-3.4%, p=0.43), triglycerides (2.6-16.7%, p=0.0006), and low HDL-cholesterol (10.2-71.1%, p<0.0001) increased.

CONCLUSIONS

Changes in the customary diet introduced in the Tepehuanos communities are related to the increase of cardiovascular risk factors.

Diabetes and cardiovascular risk factors in urban Indigenous adults: Results from the DRUID study

INTRODUCTION

Little is known about the burden of diabetes and related conditions among urban Indigenous Australians. The DRUID study was established to address this important information gap.

SUBJECTS

Eligible participants were Aboriginal and Torres Strait Islander adult volunteers aged 15 years and over who had lived in a defined region in and around Darwin, NT for at least 6 months.

MATERIALS AND METHODS

Participants underwent a health examination based on the AusDiab protocol, including blood and urine collection, clinical and anthropometric measurements and questionnaires, in 2003-2005.

RESULTS

Among 861 participants included in the analysis (approximately 14% of the target population), diabetes and other cardiovascular risk factors were common and increased with age. Almost one-third of those aged >or=35 years (31.7%) and over half of those >or=55 years (52.4%) had diabetes. Of 48 participants with newly diagnosed diabetes, half would not have been diagnosed without OGTT. Cardiovascular risk factors were common even among young people without diabetes-45% had >or=2 risk factors and only 18% had none.

CONCLUSIONS

This study indicates a very high burden of current disease and high risk of future disease, even among young people. Both primary prevention and better management of known risk factors and existing disease are urgently required.

Differential association of C-reactive protein with adiposity in men and women in an Aboriginal community in northeast Arnhem Land of Australia

OBJECTIVE

To examine the relationship between C-reactive protein (CRP), adiposity and other metabolic abnormalities in an Aboriginal community in Northern Australia.

DESIGN

Cross-sectional analysis of data obtained between 2001 and 2003 from 379 Aboriginal people residing in a geographically isolated community.

RESULTS

Mean (95% CI) CRP in women and men was 4.06 cholesterol (3.53, 4.66) mg/l and 3.42 (2.94, 3.97) mg/l, respectively (P=NS). The prevalence of the metabolic syndrome (US National Cholesterol Education [corrected] Program (NCEP) definition) was significantly higher for women than men (41 vs 18%, chi (2)=20.94, P<0.001). C-reactive protein correlated strongly with adiposity in women (waist circumference, waist to hip ratio and body mass index; r>/=0.514, P<0.01) but much less strongly in men (r</=0.221, P<0.05). In a multivariate stepwise linear regression model, waist circumference was the strongest independent predictor explaining 35% of CRP concentration variance in women, but only 5.4% in men (WHR). Incremental increases in CRP concentration across four BMI categories were significant in women (P (linear trend)<0.001) but not in men.

CONCLUSIONS

High CRP levels in the surveyed population are consistent with the high prevalence of vascular disease morbidity and mortality in Aboriginal Australians. The relationship of CRP with increasing body fat was strong and consistent in women but not in men. Prospective studies are needed to elucidate the role of CRP (if any) as a predictive marker for cardiovascular events in this high-risk population.

Uncovering the determinants of cardiovascular disease among Indigenous people

OBJECTIVE

This paper attempts to delineate an appropriate methodology for research into cardiovascular diseases (CVD) in the context of the Australian Indigenous population.

DESIGN

Our argument proceeds in three main stages of critical analysis of the appropriate literature. First we demonstrate the extremely complex aetiology of CVD and also argue that, in any population, exposure to many of the more important risk factors at an individual or group level is generated through social and behavioural factors whose causation, persistence and reproduction are both complex and multilayered. Secondly, and having established that the aetiology and morbidity of CVD in various populations is a product of a complex and interactive hierarchy of biomedical, social and political processes, we argue that only research methodologies capable of encompassing the complete span of this hierarchy can be expected to generate results which are efficacious as a basis for intervention. Thirdly, and most importantly, we argue that in the Indigenous context a central and essential feature in the development of an appropriate methodology must be to centre Indigenous people themselves as the dominant partner in setting the research agenda and the conduct of research.

RESULTS/CONCLUSIONS

We conclude that an appropriate methodology for the elucidation of the aetiology, and sequelae of CVD in Indigenous people, would go far beyond 'black box' epidemiology, would recognise the essentially social nature of chronic disease by deploying appropriate social theory within a transdisciplinary framework and would centre Indigenous people as the dominant partner in the research process.

Leanness and type 2 diabetes in a population of indigenous Australians

OBJECTIVE

To determine the prevalence of type 2 diabetes and its risk factors in a population of indigenous Australians.

RESEARCH DESIGN AND METHODS

A cross-sectional study of 332 indigenous community residents aged 15 years and over with fasting blood samples and anthropometric measurements.

RESULTS

Almost half of the study population (47.3%) was extremely lean (BMI<22 kg/m(2)). Leanness was particularly pronounced in the youngest age group (15<20 years), 78% of which had a BMI<22 kg/m(2). The prevalence of diabetes was 12%. It was highest in those 45-54 years and declined in older aged people. No cases of diabetes were detected in those aged less than 30 years. Diabetes prevalence was strongly linked to BMI and age (age-adjusted odds ratio=24.1, 95% CI 6.0-96.5, p<0.001) for BMI>or=25 kg/m(2) versus BMI<22 kg/m(2). Those with the lowest diabetes risk profile are lean (BMI<22 kg/m(2)) and/or young (age 15-34 years).

CONCLUSIONS

These results highlight that strategies to prevent or delay the onset of diabetes should focus on the maintenance of leanness from adolescence and throughout adult life whilst young people are still in the process of forming lifelong habits.

Animal evidence for the transgenerational development of diabetes mellitus

The mammalian fetus develops inside the uterus of its mother and is completely dependent on the nutrients supplied by its mother. Disturbances in the maternal metabolism that alter this nutrient supply from mother to fetus can induce structural and functional adaptations during fetal development, with lasting consequences for growth and metabolism of the offspring throughout life. This effect has been investigated, by several research groups, in different experimental models where the maternal metabolism during pregnancy was experimentally manipulated (maternal diabetes and maternal malnutrition) and the effect on the offspring was investigated. The altered maternal/fetal metabolism appears to be associated with a diabetogenic effect in the adult offspring, including gestational diabetes. This diabetic pregnancy in the offspring again induces a diabetogenic effect into the next generation, via adaptations during fetal development. These experimental data in laboratory animals are confirmed by epidemiological studies on infants of mothers suffering from diabetes or malnutrition during pregnancy. It can be concluded that fetal development in an abnormal intra-uterine milieu can induce alterations in the fetal metabolism, with lasting consequences for the glucose tolerance of the offspring in adult life. The most marked effect is the development of gestational diabetes, thereby transmitting the diabetogenic tendency to the next generation again. The concept of fetal origin of adult diabetes therefore is of major significance for public health in the immediate and the far future.

So far and yet so close: quality of management of diabetes in Australian and Canadian Indigenous communities

OBJECTIVES

To compare quality of clinical management of Indigenous people with diabetes in remote areas of Australia and Canada.

DESIGN

Clinical audit of diabetes management.

SETTING

The Kimberley region of Western Australia and Northern Saskatchewan in Canada.

SUBJECTS

One hundred and two Saskatchewan and 142 Kimberley patients from seven and 11 primary health services, respectively.

MAIN OUTCOME MEASURES

Indicators of quality of diabetes clinical management during the preceding two years.

RESULTS

Overall quality of management was poor. Retinopathy screening was better in the Kimberley than Saskatchewan (58% screened in the preceding two years cf 30%). Glycemic control of Saskatchewan patients was better than that of Kimberley patients (16% with optimal control vs. 9%).

CONCLUSIONS

Continuing efforts at the level of health service organisation, patient and staff education, and creative ways to reduce barriers to access, as well as primary prevention initiatives, are required to counter the devastating effect of diabetes on Indigenous communities.

Current incidence, treatment patterns and outcome of end-stage renal disease among indigenous groups in Australia and New Zealand

The changes in rates of treated end-stage renal disease (ESRD) among indigenous populations have profound consequences for those individuals affected and for health-care providers. By using data from the Australia and New Zealand Dialysis and Transplant (ANZDATA) Registry, we examined the current incidence, treatment and outcomes of ESRD among indigenous groups in Australia and New Zealand. All patients who began renal replacement therapy (RRT) in Australia or New Zealand between October 1991 and September 2000 were included. Rates of ESRD, RRT modalities, renal transplantation and mortality were the outcomes examined. End-stage renal disease rates among indigenous groups in Australia and New Zealand exceeded non-indigenous rates up to eightfold. The median age of indigenous ESRD patients was younger (51 vs 60 years, P < 0.0001), and there was an excess of comorbidities, particularly diabetes. For Australian Aboriginal and Torres Strait Islanders, and New Zealand Maori patients, mortality rates across all modalities of RRT were 70% higher than non-indigenous rates. Indigenous people were less likely to receive a renal transplant prior to dialysis treatment, less likely to be accepted onto the cadaveric transplant waiting list, and less likely to receive a well-matched transplant. The poorer outcomes among Australian Aboriginal and Torres Strait Islanders, and New Zealand Maori patients did not appear to be explained by the different comorbid conditions or age. Whether the outcomes reflect unmeasured differences in disease burden or treatment differences is not known. Tackling this problem will involve a spectrum of people and approaches, from tertiary care providers and RRT to local staff and preventative programs.

A genomewide search for type 2 diabetes-susceptibility genes in indigenous Australians

The prevalence of type 2 diabetes among Australian residents is 7.5%; however, prevalence rates up to six times higher have been reported for indigenous Australian communities. Epidemiological evidence implicates genetic factors in the susceptibility of indigenous Australians to type 2 diabetes and supports the hypothesis of the "thrifty genotype," but, to date, the nature of the genetic predisposition is unknown. We have ascertained clinical details from a community of indigenous Australian descent in North Stradbroke Island, Queensland. In this population, the phenotype is characterized by severe insulin resistance. We have conducted a genomewide scan, at an average resolution of 10 cM, for type 2 diabetes-susceptibility genes in a large multigeneration pedigree from this community. Parametric linkage analysis undertaken using FASTLINK version 4.1p yielded a maximum two-point LOD score of +2.97 at marker D2S2345. Multipoint analysis yielded a peak LOD score of +3.9 <1 cM from marker D2S2345, with an 18-cM 3-LOD support interval. Secondary peak LOD scores were noted on chromosome 3 (+1.8 at recombination fraction [theta] 0.05, at marker D3S1311) and chromosome 8 (+1.77 at theta=0.0, at marker D8S549). These chromosomal regions are likely to harbor novel susceptibility genes for type 2 diabetes in the indigenous Australian population.

The impact of diabetes on cardiovascular risk factors and outcomes in a native Canadian population

We measured cardiovascular disease (CVD) risk factors and their relationship to glucose intolerance in a Native Canadian population with very high rates of Type 2 diabetes mellitus. Five hundred and twenty five study-eligible Ojibwa-Cree individuals age 18 and over in the community of Sandy Lake, Canada who had participated in a population-based survey were studied. Diabetes status, plasma concentrations of total cholesterol (TC), triglycerides (TG), high density lipoprotein cholesterol (HDL-C), calculated low density lipoprotein-cholesterol (LDL-C), waist/hip ratio (WHR), BMI, systolic and diastolic BP, and history of smoking were compared to a standard national population. Extremely high rates of obesity (BMI and WHR) were identified in the study population and were associated with increasing glucose intolerance for both males and females. Rates of smoking exceeded 70 and 80% in females and males, respectively. Interestingly, despite obesity individuals who had normal glucose tolerance had significantly lower rates of high risk TC, TG, LDL-C, and HDL-C levels compared to a national Canadian population survey. However, with worsening glucose intolerance, TC, TG, LDL-C and HDL-C dramatically deteriorated in comparison to nationally published levels. These changes in cardiovascular risk factors, as a consequence of diabetes, appear to result in increased clinical outcomes. Admission to hospital for Ischemic Heart Disease (IHD) for Sandy Lake residents increased from a rate of 34.8/10,000 to 109.1/10,000 in 15 years. Although this and similar populations have historically reported low rates of CVD, the impact of diabetes on lipid risk factor is having devastating consequences on cardiovascular outcomes. This trend is expected to continue unless the high rates of diabetes can be modified.

Increase in prevalence of obesity and diabetes and decrease in plasma cholesterol in a central Australian aboriginal community

OBJECTIVE

To document change in prevalence of obesity, diabetes and other cardiovascular disease (CVD) risk factors, and trends in dietary macronutrient intake, over an eight-year period in a rural Aboriginal community in central Australia.

DESIGN

Sequential cross-sectional community surveys in 1987, 1991 and 1995.

SUBJECTS

All adults (15 years and over) in the community were invited to participate. In 1987, 1991 and 1995, 335 (87% of eligible adults), 331 (76%) and 304 (68%), respectively, were surveyed.

MAIN OUTCOME MEASURES

Body mass index and waist: hip ratio; blood glucose level and glucose tolerance; fasting total and high density lipoprotein (HDL) cholesterol and triglyceride levels; and apparent dietary intake (estimated by the store turnover method).

INTERVENTION

A community-based nutrition awareness and healthy lifestyle program, 1988-1990.

RESULTS

At the eight-year follow-up, the odds ratios (95% CIs) for CVD risk factors relative to baseline were obesity, 1.84 (1.28-2.66); diabetes, 1.83 (1.11-3.03); hypercholesterolaemia, 0.29 (0.20-0.42); and dyslipidemia (high triglyceride plus low HDL cholesterol level), 4.54 (2.84-7.29). In younger women (15-24 years), there was a trembling in obesity prevalence and a four- to fivefold increase in diabetes prevalence. Store turnover data suggested a relative reduction in the consumption of refined carbohydrates and saturated fats.

CONCLUSIONS

Interventions targeting nutritional factors alone are unlikely to greatly alter trends towards increasing prevalences of obesity and diabetes. In communities where healthy food choices are limited, the role of regular physical activity in improving metabolic fitness may also need to be emphasised.

Women living with type II diabetes: the intrusion of illness

This study is part of a larger research project which aimed to create an understanding of how people with type II diabetes incorporated chronic illness into their lives. We aimed to find wellness in the context of a chronic illness. The participatory action-orientated research (PAR) approach is consumer based and managed, and six women with diabetes and the research team met for eight two-hour sessions in August and September 1998. The objectives were to contribute to understanding of the health of adults who live with chronic illness by providing greater insight and understanding into the worlds of people who live with a chronic illness and allowing the voices of people with diabetes to be clearly heard in relation to their health. There was a wellness theme around taking time out, but considering the other dominant negative experiences, this study can only be considered as an attempt to find wellness in the context of chronic illness. The PAR process, built upon sharing, listening and reconstructing stories, worked toward the women being heard and having a voice for the first time. Listening and acting upon the voices of the women has implications for the practice of health care professionals.

The epidemiology of Type 2 diabetes and its current measurement

Type 2 diabetes is globally increasing in prevalence and is widely recognized as a major cause of morbidity and mortality, as well as being a burden to the health-care services. Planning for current and future diabetes services requires up-to-date prevalence information. The enumeration of Type 2 diabetes is, however, surprisingly difficult. Large numbers of people are undiagnosed, and those known cases have variable loci of care. Traditional techniques include cross-sectional diagnostic surveys, postal or house-to-house surveys and cohort surveys. All are time-consuming and expensive, and may potentially undercount. The use of multiple patient lists (e.g. hospital clinic data, general practitioner (GP) lists, prescribing information, etc.) can, however, increase accuracy and, if the data are computerized, may be rapid and inexpensive. A new and potentially exciting tool to utilize multiple lists in Type 2 diabetes prevalence assessment is known as 'capture-recapture'. In this, statistical models are used to estimate prevalence from the degree of overlap between lists. Capture-recapture is emerging as a valuable tool in the epidemiological assessment of Type 2 diabetes.

Beneficial impact of the homelands movement on health outcomes in central Australian aborigines

OBJECTIVE

This study compares prevalence of obesity, hypertension and diabetes in two groups of Aboriginal adults: those living in homelands versus centralised communities in central Australia. It also compares weight gain, incidence of diabetes, mortality and hospitalisation rates between the groups over a seven-year period.

METHODS

Baseline survey of 826 Aboriginal adults in rural central Australian communities in 1987-88 with a follow-up survey of 416 (56% response rate, excluding deaths). Each time, they had a 75 g oral glucose tolerance test (OGTT), and blood pressure and anthropometry measurement. Deaths and hospitalisations for all of the original cohort were recorded for the seven-year period.

RESULTS

Homelands residents had a lower baseline prevalence of diabetes (risk ratio [RR] = 0.77, 0.59-1.00), hypertension (RR = 0.66, 0.54-0.80) and overweight/obesity (RR = 0.70, 0.59-0.83). The incidence of diabetes was lower among homelands residents (RR = 0.70, 0.46-1.06). They were less likely to die than those living in centralised communities (RR = 0.56, 0.37-0.85) and less likely to be hospitalised for any cause (RR = 0.79, 0.71-0.87), particularly infections (RR = 0.70, 0.61-0.80), injury involving alcohol (RR = 0.61, 0.47-0.79) and other injury (RR = 0.75, 0.60-0.93). Mean age at death was 58 and 48 years for residents of homelands and centralised communities respectively.

CONCLUSION

Aboriginal people who live in homelands communities appear to have more favourable health outcomes with respect to mortality, hospitalisation, hypertension, diabetes and injury, than those living in more centralised settlements in Central Australia. These effects are most marked among younger adults.

Insulin resistance syndrome in Australian aboriginal people

1. Like many indigenous populations, Australian Aboriginal people have developed high rates of obesity, non-insulin-dependent diabetes mellitus (NIDDM) and cardiovascular and renal disease following the transition from a traditional to an 'urbanized' lifestyle. These conditions tend to cluster as part of the insulin resistance syndrome. 2. The prevalence of overweight people and obesity in Australian Aboriginal populations ranges from 0% in communities with a traditionally orientated lifestyle to well over 50% in the worst affected communities. There is a predominantly central pattern of fat deposition in both men and women, which is associated with greater insulin resistance and cardiovascular risk than is peripheral fat deposition. 3. Data from four previously published, population-based surveys in Aboriginal communities were combined to give a cohort of 1079 subjects of 15 years and older. Several conditions of the insulin resistance syndrome had a strong, positive association with increasing body mass index (BMI): NIDDM (both cross-sectionally and longitudinally), hypertension, dyslipidaemia and albuminuria. Remaining lean (BMI < 20 kg/m2) protected even older Aboriginal people from these conditions to a large extent. 4. Community based programmes to increase physical activity and improve dietary quality are likely to be the major means by which conditions associated with insulin resistance can be prevented in Aboriginal populations.