Waist circumference has heterogeneous impact on development of diabetes in different populations : Longitudinal comparative study between Australia and Iran

Aims : Comparing waist circumference (WC) role in diabetes risk prediction and diagnosis of metabolic syndrome (MS) in different populations.

Methods : Population-based samples from Australia (n = 9026) and Iran (n = 8259) were studied in 2000 and followed for 4 years. Follow-up attendance was 58% and mean age was 51 vs. 47. Pearson correlations calculated between WC and other MS components. ROC for the role of WC in the prediction of incident diabetes was used.

Results : Prevalences of MS (48% vs. 28%), an increased WC (58.5% vs. 54.5%), low HDL-C (35% vs. 11.2%), high triglyceride (52.2% vs. 29.6%) were significantly higher in Iran. Fasting glucose ≥5.6 mmol/L was higher in Australia (26% vs. 23%). Hypertension was no different (38%). Pearson correlations between WC and other MS components were stronger in Australians: FPG (0.32 vs. 0.2), HDL (0.47 vs. 0.16), TG (0.38 vs. 0.30) and SBP (0.38 vs. 0.36). Among women, area under ROC curve for WC as a predictor for diabetes was significantly higher for Australians (0.76 vs. 0.68, p < 0.001) with no difference among men (0.69 vs. 0.71, p = 0.4).

Conclusion : WC was more strongly related to other components of MS in Australia. Association between WC and MS or incident diabetes varies between ethnicities.

Oxygen (O2) kinetics during early recovery from peak exercise in patients with type 2 diabetes

Aims To examine the oxygen (O₂) kinetics during early recovery from peak exercise in patients with Type 2 diabetes and to examine whether oxygen O₂ recovery is associated with fasting glucose and HbA_1c in this population.

Methods Eighty-nine participants (52 men) aged 51.8 ± 7.1 years (mean ± sd) were divided into three groups: normal weight (BMI ≤ 25.0 kg/m²), overweight/obese without diabetes (BMI ≥ 26 kg/m²) and overweight/obese with Type 2 diabetes. Participants were assessed for their aerobic power (VO_2peak) on a cycle ergometer, provided a fasting blood sample and underwent a series of anthropometric measurements. Early recovery period was measured for 60 s from cessation of exercise and expressed as percentage of VO_2peak (higher percentage represents slower recovery).

Results No significant differences were observed for age between the three study groups. Both the overweight/obese groups without diabetes and with Type 2 diabetes had higher BMI than the normal weight group, with no significant differences between overweight/obese participants without diabetes and those with diabetes. Participants with Type 2 diabetes had lower VO_2peak than overweight/obese participants without diabetes and normal weight individuals (19.6 ± 4.8, 22.6 ± 5.4 and 25.7 ± 5.3 ml kg⁻¹ min⁻¹, respectively, P < 0.004 for overall trends). Participants with Type 2 diabetes also had slower recovery in oxygen O₂ kinetics after exercise, compared with both normal weight and overweight/obese individuals without diabetes (56.5 ± 7.7, 49.2 ± 7.2, 47.7 ± 7.4%, P < 0.004 for overall trends). Multiple regression analysis revealed that percentage of oxygen O₂ recovery was a stronger predictor than VO_2peak, BMI or age for fasting glucose and HbA_1c.

Conclusions Patients with Type 2 diabetes have lower VO_2peak and prolonged oxygen O₂ recovery from peak exercise. However, only prolonged oxygen O₂ recovery was associated with fasting glucose and HbA_1c.

Association between hyperglycaemia and fracture risk in non-diabetic middle-aged and older Australians : a national, population-based prospective study (AusDiab)

Summary : The association between pre-diabetes and fracture risk remains unclear. In this large cohort of middle-aged and older Australian men and women without diabetes, elevated 2-h plasma glucose and pre-diabetes were associated with a reduced 5-year risk of low trauma and all fractures in women, independently of BMI, fasting insulin and other lifestyle factors.

Introduction : We aimed to (1) examine associations between fasting and 2-h plasma glucose (FPG and 2-h PG), fasting insulin and risk of low trauma and all fractures in non-diabetic adults and (2) compare fracture risk between adults with pre-diabetes (impaired glucose tolerance or impaired fasting glucose) and those with normal glucose tolerance (NGT).

Methods : Six thousand two hundred fifty-five non-diabetic men and women aged ≥40 years with NGT (n = 4,855) and pre-diabetes (n = 1,400) were followed for 5 years in the AusDiab Study. Fractures were self-reported.

Results : Five hundred thirty-nine participants suffered at least one fracture (368 women, 171 men), of which the majority (318) occurred after a low-energy trauma (258 women, 60 men). In women, a 2-h PG ≥7.2 mmol/L (highest quartile) was associated with a decreased risk of low trauma and all fractures independent of age and BMI [OR (95% CI) for low trauma fractures, 0.59 (0.40–0.88)], but also fasting insulin, smoking, physical activity, history of fracture, dietary calcium and alcohol intake or menopausal status. There was no effect of 2-h PG on fracture risk in men [OR (95% CI), 1.39 (0.60–3.26)] or any relationship between fracture risk and quartiles of FPG or insulin in either sex. Compared to women with NGT, those with pre-diabetes had a reduced risk of fracture [OR (95% CI) for all fractures, 0.70 (0.52–0.95); for low trauma fractures, 0.75 (0.53–1.05)].

Conclusion : Elevated 2-h PG levels and pre-diabetes were inversely associated with low trauma and/or all fractures in non-diabetic women, independent of BMI and fasting insulin levels.

Lifestyle factors fail to explain the variation in plasma leptin concentrations in women

To assess the relationship between circulating leptin concentrations, metabolic parameters, and lifestyle factors such as alcohol intake, physical activity level, smoking habits, and reproductive history, a cohort of 359 women was drawn from a population-based study conducted in Victoria, Australia. The parameters measured included body mass index (BMI); waist and hip circumference; blood pressure; and fasting glucose, insulin, triacylglycerol, cholesterol, and leptin concentrations. In addition, a self-administered questionnaire was used to assess reproductive history, physical activity level, alcohol intake, and smoking habits. Our results demonstrated that BMI, body weight, waist circumference, and hip circumference were all strongly correlated with circulating leptin concentrations in this population (r > 0.56, P < 0.001 in all cases). Waist/hip ratio, triacylglycerols, insulin, glucose, and cholesterol were also associated with leptin (P < 0.05), but there was no association between leptin and age, height, or blood pressure. When these associations were adjusted for BMI, age, glucose, and waist circumference were significantly associated with leptin. The lifestyle factors examined did not help to explain the observed variation in leptin concentrations between individuals when results were adjusted for degree of adiposity and age.

Predicting changes in lifestyle and clinical outcomes in preventing diabetes : The Greater Green Triangle Diabetes Prevention Project

Objectives : To analyse how psychosocial determinants of lifestyle changes targeted in the Greater Green Triangle Diabetes Prevention Project conducted in Southeast Australia in 2004–2006 predict changes in dietary behaviour and clinical risk factors.

Methods : A longitudinal pre-test and post-test study design was used. The group program was completed by 237 people at high risk of type 2 diabetes. Associations between changes in the variables were examined by structural equation modelling using a path model in which changes in psychological determinants for lifestyle predicted changes in dietary behaviours (fat and fibre intake), which subsequently predicted changes in waist circumference and other clinical outcomes. Standardised regression weights are presented, with β = ± 0.1 and β = ± 0.3 representing small and medium associations, respectively.

Results : Improvements in coping self-efficacy and planning predicted improvements in fat (β = − 0.15, p < 0.05 and β = − 0.32, p < 0.001, respectively) and fibre intake (β = 0.15, p < 0.05 and β = 0.23, p < 0.001, respectively) which in turn predicted improvements in waist circumference (β = 0.18, p < 0.01 and β = − 0.16, p < 0.05, respectively). Improvements in waist circumference predicted improvements in diastolic blood pressure (β = 0.13, p < 0.05), HDL (β = − 0.16, p < 0.05), triglycerides (β = 0.17, p < 0.01), and fasting glucose (β = 0.15, p < 0.05).

Conclusions : Psychological changes predicted behaviour changes, resulting in 12-month biophysical changes. The findings support the theoretical basis of the interventions.

Low serum 25-hydroxyvitamin D is associated with increased risk of the development of the metabolic syndrome at five years : results from a national, population-based prospective study (the Australian Diabetes, Obesity and Lifestyle Study : AusDiab)

Context: Serum 25-hydroxyvitamin D [25(OH)D] concentration has been inversely associated with the prevalence of metabolic syndrome (MetS), but the relationship between 25(OH)D and incident MetS remains unclear.

Objective: We evaluated the prospective association between 25(OH)D, MetS, and its components in a large population-based cohort of adults aged 25 yr or older.

Design: We used baseline (1999–2000) and 5-yr follow-up data of the Australian Diabetes, Obesity, and Lifestyle Study (AusDiab).

Participants: Of the 11,247 adults evaluated at baseline, 6,537 returned for follow-up. We studied those without MetS at baseline and with complete data (n = 4164; mean age 50 yr; 58% women; 92% Europids).

Outcome Measures: We report the associations between baseline 25(OH)D and 5-yr MetS incidence and its components, adjusted for age, sex, ethnicity, season, latitude, smoking, family history of type 2 diabetes, physical activity, education, kidney function, waist circumference (WC), and baseline MetS components.

Results: A total of 528 incident cases (12.7%) of MetS developed over 5 yr. Compared with those in the highest quintile of 25(OH)D (≥34 ng/ml), MetS risk was significantly higher in people with 25(OH)D in the first (<18 ng/ml) and second (18–23 ng/ml) quintiles; odds ratio (95% confidence interval) = 1.41 (1.02–1.95) and 1.74 (1.28–2.37), respectively. Serum 25(OH)D was inversely associated with 5-yr WC (P < 0.001), triglycerides (P < 0.01), fasting glucose (P < 0.01), and homeostasis model assessment for insulin resistance (P < 0.001) but not with 2-h plasma glucose (P = 0.29), high-density lipoprotein cholesterol (P = 0.70), or blood pressure (P = 0.46).

Conclusions: In Australian adults, lower 25(OH)D concentrations were associated with increased MetS risk and higher WC, serum triglyceride, fasting glucose, and insulin resistance at 5 yr. Vitamin D supplementation studies are required to establish whether the link between vitamin D deficiency and MetS is causal.

Takeaway food consumption and cardio-metabolic risk factors in young adults

Background/objectives: Takeaway food consumption is positively associated with adiposity. Little is known about the associations with other cardio-metabolic risk factors. This study aimed to determine whether takeaway food consumption is associated with fasting glucose, insulin, lipids, homeostasis model assessment (HOMA) and blood pressure.

Subjects/methods: A national sample of 1896, 26–36 year olds completed a questionnaire on socio-demographics, takeaway food consumption, physical activity and sedentary behaviour. Waist circumference and blood pressure were measured, and a fasting blood sample was taken. For this analysis, takeaway food consumption was dichotomised to once a week or less and twice a week or more. Linear regression was used to calculate differences in the adjusted mean values for fasting lipids, glucose, insulin, HOMA and blood pressure. Models were adjusted for age, employment status, leisure time physical activity and TV viewing.

Results: Compared with women who ate takeaway once a week or less, women who ate takeaway twice a week or more had significantly higher adjusted mean fasting glucose (4.82 vs 4.88 mmol/l, respectively; P=0.045), higher HOMA scores (1.27 vs 1.40, respectively, P=0.034) and tended to have a higher mean fasting insulin (5.95 vs 6.45 mU/l, respectively, P=0.054). Similar associations were observed for men for fasting insulin and HOMA score, but the differences were not statistically significant. For both women and men adjustment for waist circumference attenuated the associations.

Conclusion: Consuming takeaway food at least twice a week was associated with cardio-metabolic risk factors in women but less so in men. The effect of takeaway food consumption was attenuated when adjusted for obesity.

Differential effect of inbred mouse strain (C57BL/6, DBA/2, 129T2) on insulin secretory function in response to a high fat diet

The increasing production of genetically-modified mouse models has necessitated studies to determine the inherent physiological characteristics of commonly used mouse strains. In this study we examined insulin secretory function in response to an intravenous bolus of glucose or glucose plus arginine in anesthetized C57BL/6, DBA/2 and 129T2 mice fed either a control or high fat diet for 6 weeks. The results show that 129T2 mice had higher fasting plasma glucose levels and lower fasting plasma insulin levels compared with C57BL/6 and DBA/2 mice regardless of diet. Furthermore, 129T2 mice were glucose intolerant and secreted significantly less insulin in response to glucose and glucose plus arginine irrespective of diet compared with the other two strains of mice. DBA/2 mice hypersecreted insulin in response to glucose and glucose plus arginine compared with C57BL/6 and 129T2 mice. Moreover while first phase insulin secretion was appropriately increased in response to the high fat diet in C57BL/6 and 129T2 mice, this was not the case for DBA/2 mice. Mean islet area was decreased in response to a high fat diet in DBA/2 mice, while there was no dietary effect on the other two strains. This study highlights the inherent genetic differences that exist among seemingly normal strains of mice that are commonly used to make transgenic and knockout mice. Understanding these differences will provide researchers with the information to choose the appropriate genetic background on which to express their particular genetic alteration.

The effect of obesity on polycystic ovary syndrome : a systematic review and meta-analysis

While many women with polycystic ovary syndrome (PCOS) are overweight, obese or centrally obese, the effect of excess weight on the outcomes of PCOS is inconsistent. The review aimed to assess the effects of overweight, obesity and central obesity on the reproductive, metabolic and psychological features of PCOS. MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials (CENTRAL) and PSYCINFO were searched for studies reporting outcomes according to body mass index categories or body fat distribution. Data were presented as mean difference or risk ratio (95% confidence interval). This review included 30 eligible studies. Overweight or obese women with PCOS had decreased sex hormone-binding globulin (SHBG), increased total testosterone, free androgen index, hirsutism, fasting glucose, fasting insulin, homeostatic model assessment-insulin resistance index and worsened lipid profile. Obesity significantly worsened all metabolic and reproductive outcomes measured except for hirsutism when compared to normal weight women with PCOS. Overweight women had no differences in total testosterone, hirsutism, total-cholesterol and low-density lipoprotein-cholesterol compared to normal weight women and no differences in SHBG and total testosterone compared to obese women. Central obesity was associated with higher fasting insulin levels. These results suggest that prevention and treatment of obesity is important for the management of PCOS.

Daily eating frequency and cardiometabolic risk factors in young Australian adults : cross-sectional analyses

Eating frequency may be important in the development of overweight and obesity and other cardiometabolic risk factors; however, the evidence is inconsistent. The aim of the present study was to examine the associations between the number of eating occasions and cardiometabolic risk factors in a national population-based sample of young adults. A cohort of 1273 men and 1502 women, aged 26–36 years, completed a meal pattern chart to record when they had eaten during the previous day (in hourly intervals). The total number of eating occasions was calculated. Diet quality was assessed, waist circumference was measured and a fasting blood sample was taken. Dietary intake was compared with the Australian Guide to Healthy Eating. The associations between the number of eating occasions and cardiometabolic risk factors were calculated using linear regression. Analyses were adjusted for age, education and physical activity. Most men ate three to five times per d and most women ate four to six times. The proportion of participants meeting dietary recommendations increased with the number of eating occasions. For men, an additional eating occasion was associated with reductions in mean values for waist circumference ( − 0·75 cm), fasting glucose ( − 0·02 mmol/l), fasting insulin ( − 0·34 mU/l; 2·04 pmol/l), TAG ( − 0·03 mmol/l), total cholesterol ( − 0·08 mmol/l) and LDL-cholesterol ( − 0·06 mmol/l). Adjustment for waist circumference attenuated the results. Significant trends were not observed for women. In conclusion, a higher number of eating occasions were associated with reduced cardiometabolic risk factors in men. Many associations were mediated by waist circumference.

A systematic review and meta-analysis of diabetes and risk of physical disability and functional impairment - protocol

Background
Diabetes and increased age are known risk factors for physical disability. With the increasing prevalence of diabetes within our aging population, the future burden of disability is expected to increase. To date, there has not been a pooled estimate of the risk for disability associated with diabetes or its precursor states, impaired glucose tolerance and impaired fasting glucose. We aim to conduct a systematic review and meta-analysis of the association between prediabetes and diabetes with disability, and quantify the risk of association.

Methods/design
We will search for relevant studies in Medline via Pubmed, Embase, Cochrane library and Cumulative Index to Nursing and Allied Health Literature (CINAHL), as well as scan reference lists from relevant reviews and publications included in our review. We will review all publications that include studies on human adults (18 years and older) where information is included on diabetes status and at least one measure of disability (Activities of Daily Living (ADL), Instrumental ADL (IADL) or functional/mobility limitation), and where a risk association is available for the relationship between diabetes and/or prediabetes with disability, with reference to those without diabetes.

We will further conduct a meta-analysis to pool estimates of the risk of disability associated with prediabetes and diabetes. Sensitivity analysis will be conducted to assess for publication bias and study quality.Findings from this systematic review and meta-analysis will be widely disseminated through discussions with stake-holders, publication in a peer-reviewed journal and conference presentation.

Reducing office workers' sitting time: rationale and study design for the Stand Up Victoria cluster randomized trial

Background
Excessive time spent in sedentary behaviours (sitting or lying with low energy expenditure) is associated with an increased risk for type 2 diabetes, cardiovascular disease and some cancers. Desk-based office workers typically accumulate high amounts of daily sitting time, often in prolonged unbroken bouts. The Stand Up Victoria study aims to determine whether a 3-month multi-component intervention in the office setting reduces workplace sitting, particularly prolonged, unbroken sitting time, and results in improvements in cardiometabolic biomarkers and work-related outcomes, compared to usual practice.

Methods/design
A two-arm cluster-randomized controlled trial (RCT), with worksites as the unit of randomization, will be conducted in 16 worksites located in Victoria, Australia. Work units from one organisation (Department of Human Services, Australian Government) will be allocated to either the multi-component intervention (organisational, environmental [heightadjustable workstations], and individual behavioural strategies) or to a usual practice control group. The recruitment target is 160 participants (office-based workers aged 18–65 years and working at least 0.6 full time equivalent) per arm. At each assessment (0- [baseline], 3- [post intervention], and 12-months [follow-up]), objective measurement via the activPAL3 activity monitor will be used to assess workplace: sitting time (primary outcome); prolonged sitting time (sitting time accrued in bouts of ≥30 minutes); standing time; sit-to-stand transitions; and, moving time. Additional outcomes assessed will include: non-workplace activity; cardio-metabolic biomarkers and health indicators (including fasting glucose, lipids and insulin; anthropometric measures; blood pressure; and, musculoskeletal symptoms); and, work-related outcomes (presenteeism, absenteeism, productivity, work performance). Incremental cost-effectiveness and identification of both workplace and individual-level mediators and moderators of change will also be evaluated.

Coronary heart disease risk in volunteer firefighters in Victoria, Australia

Coronary heart disease (CHD) is a major problem for firefighters, even when considering the healthy worker effect (HWE). Although volunteer firefighters outnumber paid personnel, previous research has focused on paid US firefighters. By contrast, no CHD data for Australian firefighters exist. Risk factor data were collected from 2,943 Australian volunteer firefighters and CHD risk was compared with reference "low-risk" and Australian population data. Predicted CHD risk for male and female firefighter was 19.2% and 5.1%, respectively. Female firefighters high blood pressure and fasting glucose was significantly lower than the general population, whereas all other risk factors was similar to the general population. Firefighters' CHD risk was greater than other volunteer and paid emergency services, but the prevalence for most risk factors was similar to the general population. Therefore, Australian volunteer firefighters may not benefit from the HWE.

Shining the light on sunshine: a systematic review of the influence of sun exposure on type 2 diabetes mellitus-related outcomes

Prospective observational studies uniformly link vitamin D deficiency with the incidence of type 2 diabetes mellitus (T2DM), yet trials supplementing participants at risk of T2DM with vitamin D to reduce progression to T2DM have yielded inconsistent results. Inconsistencies between supplementation trials may be due to insufficient dosing or small sample sizes. Observational studies may also have reported spurious associations due to uncontrolled confounding by lifestyle or genetic factors. Alternatively, observational and intervention studies may not be entirely comparable. Observational studies show an association between higher vitamin D status, which is predominantly derived from sun exposure, and decreased incidence of T2DM. Trials intervene with vitamin D supplementation, and therefore may be missing alternate causes of the effect of sun exposure, as seen in observational studies. We propose that sun exposure may be the driving force behind the associations seen in observational studies; sun exposure may have additional benefits beyond increasing serum 25-hydroxyvitamin D (25OHD) levels. We performed an electronic literature search to identify articles that examined associations between sun exposure and T2DM and/or glucose metabolism. A best evidence synthesis was then conducted using outcomes from analyses deemed to have high methodological quality. Ten eligible full-text articles were identified, yielding 19 T2DM-related outcomes. The best evidence analysis considered 11 outcomes which were grouped into six outcome types: T2DM, fasting glucose, glucose tolerance, fasting insulin, insulin secretion and insulin sensitivity. There was moderate evidence to support a role of recreational sun exposure in reducing odds of T2DM incidence. High-level evidence was lacking; evidence presented for other outcomes was of low or insufficient level. This review highlights significant gaps in research pertaining to sun exposure and T2DM-related outcomes. Further research is encouraged as we aim to identify novel preventative strategies for T2DM.