Age trajectories of glycaemic traits in non-diabetic South Asian and white individuals: the Whitehall II cohort study

Hepatic insulin resistance affects the efficacy of metformin in patients with newly diagnosed type 2 diabetes: A Sub-Analysis of the MARCH trial

AIM

Our study aimed to analyze how hepatic insulin resistance (IR) influences the efficacy of 48 weeks of metformin treatment in newly diagnosed type 2 diabetes patients.

METHODS

We chose 291 participants who were allocated to a 48-week metformin treatment in the "Metformin and Acarbose in Chinese as initial Hypoglycemic treatment" (MARCH) trial and calculated their hepatic insulin resistance indexes (HIRI). We equally grouped the subjects into tertiles: low, medium, and high HIRI groups based on baseline HIRI; Low, medium, and high ΔHIRI groups based on the decreasing extent of HIRI after a 48-week metformin treatment.

RESULTS

Multiple linear regression showed that baseline HIRI was positively associated with the rising degree of Matsuda index and the falling range of fasting blood glucose, fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), and HIRI. Furthermore, baseline fasting insulin, homeostatic model assessment of β cell function (HOMA-β), HOMA-IR, and HIRI were positively associated with the decreasing extent of HIRI, while baseline Matsuda index had a negative association with the falling extent of HIRI.

CONCLUSIONS

Patients with higher levels of hepatic IR obtained better curative effects from metformin in terms of glycemic control, insulin saving, insulin sensitivity enhancement, and IR improvement. Higher fasting blood glucose, fasting insulin, HOMA-β, IR, and lower Matsuda index were indicators of better hepatic IR improvement.

Insulin resistance levels predicted metabolic improvement and weight loss after metabolic surgery in Chinese patients with type 2 diabetes

BACKGROUND

The causes for failure of metabolic improvement and inadequate weight loss after metabolic surgery (MS) in Chinese patients with type 2 diabetes (T2D) have not been fully elucidated. The effect of insulin resistance (IR) on the outcome of T2D, hypertension, hyperlipidemia, and obesity after MS in Chinese patients with T2D and a body mass index (BMI) of 25-32.5 kg/m2 warrants further study.

OBJECTIVES

Patients with T2D and a BMI of 25-32.5 kg/m2 who underwent MS between July 2019 and June 2021 were included.

SETTING

University hospital, China.

METHODS

IR levels were evaluated with the glucose disposal rate (GDR). Improvement of T2D, hypertension, and hyperlipidemia was assessed with the composite triple endpoint (CTEP), and weight loss was assessed with the percent of total weight loss (%TWL). Partial correlation analysis, binary logistic regression analysis, multiple linear regression analysis, receiver operating characteristic curve (ROC) analysis, and subgroup analysis were used to analyze the relationship between the CTEP, %TWL at 1 year postoperative, and GDR preoperative.

RESULTS

This study analyzed the data of 51 patients with T2D and a BMI of 25-32.5 kg/m2 (30 men and 21 women) with a mean preoperative GDR of 3.72 ± 1.48 mg/kg/min. Partial correlation coefficients between CTEP, %TWL, and GDR were .303 (P = .041) and .449 (P = .001), respectively. The preoperative GDR was significantly positively correlated with CTEP (OR = 1.610, P = .024) and %TWL (β = 1.38, P = .003). The preoperative GDR predicted cutoff values of 4.36 and 5.35 mg/kg/min for CTEP attainment and %TWL ≥ 20%, respectively.

CONCLUSION

IR levels predicted metabolic improvement and weight loss 1 year after MS in Chinese patients with T2D and a BMI of 25-32.5 kg/m2.

Disentangling Dual Threats: Premature Coronary Artery Disease and Early-Onset Type 2 Diabetes Mellitus in South Asians

South Asian individuals (SAs) face heightened risks of premature coronary artery disease (CAD) and early-onset type 2 diabetes mellitus (T2DM), with grave health, societal, and economic implications due to the region's dense population. Both conditions, influenced by cardiometabolic risk factors such as insulin resistance, hypertension, and central adiposity, manifest earlier and with unique thresholds in SAs. Epidemiological, demographic, nutritional, environmental, sociocultural, and economic transitions in SA have exacerbated the twin epidemic. The coupling of premature CAD and T2DM arises from increased obesity due to limited adipose storage, early-life undernutrition, distinct fat thresholds, reduced muscle mass, and a predisposition for hepatic fat accumulation from certain dietary choices cumulatively precipitating a decline in insulin sensitivity. As T2DM ensues, the β-cell adaptive responses are suboptimal, precipitating a transition from compensatory hyperinsulinemia to β-cell decompensation, underscoring a reduced functional β-cell reserve in SAs. This review delves into the interplay of these mechanisms and highlights a prediabetes endotype tied to elevated vascular risk. Deciphering these mechanistic interconnections promises to refine stratification paradigms, surpassing extant risk-prediction strategies.

β-Cell Function, Hepatic Insulin Clearance, and Insulin Sensitivity in South Asian and Nordic Women After Gestational Diabetes Mellitus

South Asian women have a higher risk of type 2 diabetes after gestational diabetes mellitus (GDM) than Nordic women; however, the mechanisms behind this difference remain unclear. We investigated insulin sensitivity, β-cell function, and hepatic insulin clearance in 179 South Asian and 108 Nordic women ∼17 months after GDM (mean age 35.3 years, BMI 29.1 kg/m2) by oral glucose tolerance test using deconvolution of C-peptide kinetics. Thirty-one percent of South Asian and 53% of Nordic participants were normoglycemic at the time of measurement. South Asian women had higher areas under the curve (AUCs) for glucose, prehepatic insulin, and peripheral insulin and lower insulin sensitivity, disposition index, and fasting hepatic insulin clearance than Nordic women. In the group with prediabetes or diabetes, South Asian women had similar AUCs for glucose and prehepatic insulin but a higher AUC for peripheral insulin, lower disposition index, and lower fasting hepatic insulin clearance than Nordic women. The waist-to-height ratio mediated ∼25-40% of the ethnic differences in insulin sensitivity in participants with normoglycemia. Overall, our novel data revealed that South Asian women with normoglycemia after GDM showed lower insulin secretion for a given insulin resistance and lower hepatic insulin clearance than Nordic women. South Asian women are at high risk of developing type 2 diabetes after GDM, and preventive efforts should be prioritized.

Age-specific prevalence, subtypes and risk factors of metabolic diseases in Chinese adults and the different patterns from other racial/ethnic populations

Background

Age has substantial influence on metabolic diseases patterns. Ethnic disparities of metabolic characteristics between Chinese and other populations also exist. Large-scale investigations of age-specific prevalence, subtypes and modifiable risk factors of metabolic disorders are essential to promote individualized strategies for the control and prevention of metabolic diseases in multi-ethnic populations. The study aims to address the age-specific prevalence, subtype characteristics and risk factor profiles of metabolic diseases among different races/ethnicities.

Methods

We analyzed data from the China Noncommunicable Disease Surveillance 2010 and the National Health and Nutrition Evaluation Survey (NHANES). We examined the prevalence and subtypes of hypertension, diabetes and hyperlipidemia across age groups in four ethnic populations. We also investigated the odds ratios (ORs) of metabolic diseases associated with 11 classical risk factors in the young and the elder Mainland Chinese.

Results

The sex and BMI standardized prevalence of hypertension in Chinese aged 18–40 years was 18.5% and was the highest among the four populations. The main pathophysiologic subtype of diabetes was characterized by insulin resistance, instead of β-cell dysfunction in Mainland Chinese, and this pattern was more evident in obese subjects. The major subtype of hyperlipidemia in Mainland Chinese was hypertriglyceridemia, while Non-Hispanic Whites and Blacks were more prone to high low-density lipoprotein cholesterol. For risk of hypertension, diabetes and hyperlipidemia, young Chinese adults were more prone to general and central obesity than older ones. The other factors showed similar effects on the young and the old.

Conclusions

The age-specific prevalence, subtypes and risk factors of metabolic diseases were substantially different in Chinese and other ethnic/racial populations.

South Asian ethnicity: What can we do to make this risk enhancer a risk equivalent?

South Asians account for around 25% of the global population and are the fastest-growing ethnicity in the US. This population has an increasing burden of atherosclerotic cardiovascular disease (ASCVD) which is also seen in the diaspora. Current risk prediction equations underestimate this risk and consider the South Asian ethnicity as a risk-enhancer among those with borderline-intermediate risk. In this review, we discuss why the South Asian population is at a higher risk of ASCVD and strategies to mitigate this increased risk.

Pathophysiology, phenotypes and management of type 2 diabetes mellitus in Indian and Chinese populations

Nearly half of all adults with type 2 diabetes mellitus (T2DM) live in India and China. These populations have an underlying predisposition to deficient insulin secretion, which has a key role in the pathogenesis of T2DM. Indian and Chinese people might be more susceptible to hepatic or skeletal muscle insulin resistance, respectively, than other populations, resulting in specific forms of insulin deficiency. Cluster-based phenotypic analyses demonstrate a higher frequency of severe insulin-deficient diabetes mellitus and younger ages at diagnosis, lower β-cell function, lower insulin resistance and lower BMI among Indian and Chinese people compared with European people. Individuals diagnosed earliest in life have the most aggressive course of disease and the highest risk of complications. These characteristics might contribute to distinctive responses to glucose-lowering medications. Incretin-based agents are particularly effective for lowering glucose levels in these populations; they enhance incretin-augmented insulin secretion and suppress glucagon secretion. Sodium-glucose cotransporter 2 inhibitors might also lower blood levels of glucose especially effectively among Asian people, while α-glucosidase inhibitors are better tolerated in east Asian populations versus other populations. Further research is needed to better characterize and address the pathophysiology and phenotypes of T2DM in Indian and Chinese populations, and to further develop individualized treatment strategies.

Risk Classification for Metabolic Syndrome and the Incidence of Cardiovascular Disease in Japan With Low Prevalence of Obesity: A Pooled Analysis of 10 Prospective Cohort Studies

Background It is uncertain whether risk classification under the nationwide program on screening and lifestyle modification for metabolic syndrome captures well high-risk individuals who could benefit from lifestyle interventions. We examined the validity of risk classification by linking the incidence of cardiovascular disease (CVD). Methods and Results Individual-level data of 29 288 Japanese individuals aged 40 to 74 years without a history of CVD from 10 prospective cohort studies were used. Metabolic syndrome was defined as the presence of high abdominal obesity and/or overweight plus risk factors such as high blood pressure, high triglyceride or low high-density lipoprotein cholesterol levels, and high blood glucose levels. The risk categories for lifestyle intervention were information supply only, motivation-support intervention, and intensive support intervention. Sex- and age-specific hazard ratios and population attributable fractions of CVD, which were also further adjusted to consider non-high density lipoprotein cholesterol levels, were estimated with reference to nonobese/overweight individuals, using Cox proportional hazard regression. Since the reference category included those with risk factors, we set a supernormal group (nonobese/overweight with no risk factor) as another reference. We documented 1023 incident CVD cases (565 men and 458 women). The adjusted CVD risk was 60% to 70% higher in men and women aged 40 to 64 years receiving an intensive support intervention, and 30% higher in women aged 65 to 74 years receiving a motivation-support intervention, compared with nonobese/overweight individuals. The population attributable fractions in men and women aged 40 to 64 years receiving an intensive support intervention were 17.7% and 6.6%, respectively, while that in women aged 65 to 74 years receiving a motivation-support intervention was 9.4%. Compared with the supernormal group, nonobese/overweight individuals with risk factors had similar hazard ratios and population attributable fractions as individuals with metabolic syndrome. Conclusions Similar CVD excess and attributable risks among individuals with metabolic syndrome components in the absence and presence of obesity/overweight imply the need for lifestyle modification in both high-risk groups.

Comparison of islet cell function, insulin sensitivity, and incretin axis between Asian-Indians with either impaired fasting glucose or impaired glucose tolerance, and normal healthy controls

AIMS

The objective of this study was to compare the islet cell function, insulin sensitivity, and incretin axis between Asian-Indian subjects with either impaired fasting glucose (IFG), or impaired glucose tolerance (IGT), and normal glucose tolerance (NGT).

MATERIALS AND METHODS

Prediabetes subjects underwent a mixed meal tolerance test(MMTT) after overnight fasting. Samples for glucose, insulin, glucagon, and glucagon-like peptide-1 (GLP-1) were collected at 0, 30, 60, and 120 min. Insulin secretion sensitivity index -2 (ISSI-2) for beta-cell function and Matsuda index for insulin sensitivity were assessed. Alpha cell function was assessed by measuring the area under the curve (AUC) _0-120 glucagon/AUC_0-120 glucose.

RESULTS

A total of sixty subjects were recruited with 20 in each group. The beta-cell function represented by ISSI-2 was impaired in prediabetes subjects as compared to NGT group (IFG: 2.09 ± 0.44 vs. NGT: 3.04 ± 0.80, P < 0.0001, and IGT: 2.33 ± 0.59 vs. NGT: 3.04 ± 0.80, P = 0.002). Similarly, AUC_0-120 glucagon/AUC_0-120 glucose was also lower in prediabetes group as compared to healthy controls (IFG: 0.41(0.54) vs. NGT: 1.07(0.39), P = 0.003 and IGT: 0.57(0.38) vs. NGT: 1.07(0.39), P = 0.001).

CONCLUSION

Asian-Indian prediabetes subjects have reduced beta-cell function with lesser glucagon secretion during MMTT as compared to normal healthy controls.

Incidence of diabetes in South Asian young adults compared to Pima Indians

INTRODUCTION

South Asians (SA) and Pima Indians have high prevalence of diabetes but differ markedly in body size. We hypothesize that young SA will have higher diabetes incidence than Pima Indians at comparable body mass index (BMI) levels.

RESEARCH DESIGN AND METHODS

We used prospective cohort data to estimate age-specific, sex, and BMI-specific diabetes incidence in SA aged 20-44 years living in India and Pakistan from the Center for Cardiometabolic Risk Reduction in South Asia Study (n=6676), and compared with Pima Indians, from Pima Indian Study (n=1852).

RESULTS

At baseline, SA were considerably less obese than Pima Indians (BMI (kg/m²): 24.4 vs 33.8; waist circumference (cm): 82.5 vs 107.0). Age-standardized diabetes incidence (cases/1000 person-years, 95% CI) was lower in SA than in Pima Indians (men: 14.2, 12.2-16.2 vs 37.3, 31.8-42.8; women: 14.8, 13.0-16.5 vs 46.1, 41.2-51.1). Risk of incident diabetes among 20-24-year-old Pima men and women was six times (relative risk (RR), 95% CI: 6.04, 3.30 to 12.0) and seven times (RR, 95% CI: 7.64, 3.73 to 18.2) higher as compared with SA men and women, respectively. In those with BMI <25 kg/m², however, the risk of diabetes was over five times in SA men than in Pima Indian men. Among those with BMI ≥30 kg/m², diabetes incidence in SA men was nearly as high as in Pima men. SA and Pima Indians had similar magnitude of association between age, sex, BMI, and insulin secretion with diabetes. The effect of family history was larger in SA, whereas that of insulin resistance was larger in Pima Indians CONCLUSIONS: In the background of relatively low insulin resistance, higher diabetes incidence in SA is driven by poor insulin secretion in SA men. The findings call for research to improve insulin secretion in early natural history of diabetes.

Sex and ethnic differences in the cardiovascular complications of type 2 diabetes

Diabetes mellitus represents a global health concern affecting 463 million adults and is projected to rapidly rise to 700 million people by 2045. Amongst those with type 2 diabetes (T2D), there are recognised differences in the impact of the disease on different sex and ethnic groups. The relative risk of cardiovascular complications between individuals with and without T2D is higher in females than males. People of South Asian heritage are two to four times more likely to develop T2D than white people, but conversely not more likely to experience cardiovascular complications. Differences in the pathophysiological responses in these groups may identify potential areas for intervention beyond glycaemic control. In this review, we highlight key differences of diabetes-associated cardiovascular complications by sex and ethnic background, with a particular emphasis on South Asians. Evidence assessing therapeutic efficacy of new glucose lowering drugs in minority groups is limited and many major cardiovascular outcomes trials do not report ethnic specific data. Conversely, lifestyle intervention and bariatric surgery appear to have similar benefits regardless of sex and ethnic groups. We encourage future studies with better representation of women and ethnic minorities that will provide valuable data to allow better risk stratification and tailored prevention and management strategies to improve cardiovascular outcomes in T2D.

Pathophysiological Mechanisms Underlying Excess Risk for Diabetes and Cardiovascular Disease in South Asians: The Perfect Storm

BACKGROUND

South Asians are at a significantly increased risk of type 2 diabetes (T2D) and cardiovascular disease (CVD), are diagnosed at relatively younger ages, and exhibit more severe disease phenotypes as compared with other ethnic groups. The pathophysiological mechanisms underlying T2D and CVD risk in South Asians are multifactorial and intricately related.

METHODS

A narrative review of the pathophysiology of excess risk of T2D and CVD in South Asians.

RESULTS

T2D and CVD have shared risk factors that encompass biological factors (early life influences, impaired glucose metabolism, and adverse body composition) as well as behavioral and environmental risk factors (diet, sedentary behavior, tobacco use, and social determinants of health). Genetics and epigenetics also play a role in explaining the increased risk of T2D and CVD among South Asians. Additionally, South Asians harbor several lipid abnormalities including high concentration of small-dense low-density lipoprotein (LDL) particles, elevated triglycerides, low high-density lipoprotein (HDL)- cholesterol levels, dysfunctional HDL particles, and elevated lipoprotein(a) that predispose them to CVD.

CONCLUSION

In this comprehensive review, we have discussed risk factors that provide insights into the pathophysiology of excess risk of T2D and CVD in South Asians.

Validation of the Swedish Diabetes Re-Grouping Scheme in Adult-Onset Diabetes in China

CONTEXT

This study applied the Swedish novel data-driven classification in Chinese newly diagnosed diabetic patients and validated its adoptability.

OBJECTIVE

This study aimed to validate the practicality of the Swedish diabetes regrouping scheme in Chinese adults with newly diagnosed diabetes.

DESIGN

Patients were classified into 5 subgroups by K-means and Two-Step methods according to 6 clinical parameters.

SETTING

Ambulatory care.

PATIENTS

A cross-sectional survey of 15 772 patients with adult-onset newly diagnosed diabetes was conducted in China from April 2015 to October 2017.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Six parameters including glutamate decarboxylase antibodies (GADA), age of onset, body mass index (BMI), glycated hemoglobin A1c (HbA1c), homoeostatic model assessment 2 estimates of β-cell function (HOMA2-B) and insulin resistance (HOMA2-IR) were measured to calculate the patient subgroups.

RESULTS

Our patients clustered into 5 subgroups: 6.2% were in the severe autoimmune diabetes (SAID) subgroup, 24.8% were in the severe insulin-deficient diabetes (SIDD) subgroup, 16.6% were in the severe insulin-resistance diabetes (SIRD) subgroup, 21.6% were in the mild obesity-related diabetes (MOD) subgroup and 30.9% were in the mild age-related diabetes (MARD) subgroup. When compared with the Swedish population, the proportion of SIDD subgroup was higher. In general, Chinese patients had younger age, lower BMI, higher HbA1c, lower HOMA2-B and HOMA2-IR, and higher insulin use but lower metformin usage than the Swedish patients.

CONCLUSION

The Swedish diabetes regrouping scheme is applicable to adult-onset diabetes in China, with a high proportion of patients with the severe insulin deficient diabetes. Further validations of long-term diabetes complications remain warranted in future studies.

Association of change in alcohol consumption on fasting serum glucose, insulin resistance, and beta cell function among Korean men

We aimed to determine the association between alcohol consumption change on fasting serum glucose, insulin resistance, and beta cell function. The study population consisted of 55,858 men from the Kangbuk Samsung Health Study. Participants were divided into non-, light, moderate, and heavy drinkers for each of the first and second health examinations based on a self-reported questionnaire on alcohol consumption. The adjusted mean values for change in fasting serum glucose (FSG), homeostatic model assessment of insulin resistance (HOMA-IR), and beta cell function (HOMA-β) levels were determined according to alcohol consumption change by linear regression. Compared to sustained initial drinkers, those who increased alcohol intake to moderate (p < 0.001) and heavy (p < 0.001) levels had increased FSG levels. In contrast, reduction in alcohol intake to light levels among initial heavy drinkers was associated with reduced change in FSG levels (p = 0.007) compared to sustained heavy drinkers. No significant associations were observed between changes in alcohol intake with HOMA-IR levels. Compared to sustained light drinkers, those who increased alcohol intake to moderate (p < 0.001) and heavy (p = 0.009) levels had lower increases in HOMA-β levels. Finally, compared to sustained heavy drinkers, those who reduced alcohol consumption to light levels had greater increases in HOMA-β levels (p = 0.002). Increases in alcohol consumption were associated with higher blood glucose levels and worsened beta cell function. Heavy drinkers who reduce alcohol intake could benefit from improved blood glucose control via improved beta cell function.

Why are South Asians prone to type 2 diabetes? A hypothesis based on underexplored pathways

South Asians have a high prevalence of type 2 diabetes, even at a lower BMI. This review sets out our perspective and hypothesis on the reasons for this. Emerging data from epidemiological studies indicate that South Asians may have a lower ability to secrete insulin, and thus may have less compensatory reserves when challenged with unhealthy lifestyles. Thus, insulin resistance may not be the primary driver of type 2 diabetes in this population. Furthermore, data also suggest that South Asians, on average, have lower muscle mass, and may have a specific propensity to ectopic hepatic fat accumulation and for intramyocellular fat deposition, which cause further disruption in insulin action. We hypothesise that the high diabetes susceptibility in South Asians is evolutionarily set through dual parallel and/or interacting mechanisms: reduced beta cell function and impaired insulin action owing to low lean mass, which is further accentuated by ectopic fat deposition in the liver and muscle. These areas warrant further research.

Tale of two Indians: Heterogeneity in type 2 diabetes pathophysiology

AIMS

Type 2 diabetes is a heterogeneous disease and may manifest from multiple disease pathways. We examined insulin secretion and insulin resistance across two ethnicities with particularly high risk for diabetes yet with widely different distributions of weight class.

MATERIALS AND METHODS

In this population-based, cross-sectional study, Pima Indians from Southwestern United States (n = 865) and Asian Indians from Chennai, India (n = 2374) had a 75-g oral glucose tolerance test. We analysed differences in plasma glucose, plasma insulin, insulin resistance (HOMA-IR), and insulin secretion (ΔI0-30 /ΔG0-30 ) across categories of body mass index (BMI) and glycemic status per American Diabetes Association criteria.

RESULTS

Pima Indians were younger (mean 27.4 ± SD 6.6, Asian: 33.9 ± 6.7 years) and had higher BMI (33.6 ± 8.1, Asian: 25.7 ± 4.9 kg/m2 ). Among normal weight participants (mean BMI: Pima 22.4 SE 0.2; Asian 22.2 SE 0.06 kg/m2 ), fasting glucose was higher in Asian Indians (5.2 vs Pima: 4.8 mmol/L, P = .003), adjusted for age and sex. Pima Indians were three times as insulin resistant as Asian Indians (HOMA-IR: 7.7 SE 0.1, Asian: 2.5 SE 0.07), while Asian Indians had three times less insulin secretion (Pima: 2.8 SE 1.0 vs Asian: 0.9 SE 1.0 pmol/mmol), a pattern evident across age, BMI, and glycemic strata.

CONCLUSIONS

Metabolic differences between Pima and Asian Indians suggest heterogeneous pathways of type 2 diabetes in the early natural history of disease, with emphasis of insulin resistance in Pima Indians and emphasis of poor insulin secretion in Asian Indians.

South Asians: why are they at a higher risk for cardiovascular disease?

PURPOSE OF REVIEW

We comment on the high prevalence of cardiovascular disease (CVD) in South Asians (SA). The effect of various risk factors, for example biochemical, genetic, lifestyle, socioeconomic factors and psychosocial stress on CVD risk is discussed.

RECENT FINDINGS

'Prediabetes' is common in SA, but its relationship with coronary artery disease (CAD) is not significant unlike for the white population. At the same time, 'prediabetes' in SA is associated with an increased risk for cerebrovascular disease (CeVD). The differentiating factor could be the high lipids in Europeans and their relationship to CAD. Likewise, higher diastolic blood pressure in SA may explain the risk of CeVD. Small, dense, low-density lipoprotein (LDL), low high-density lipoprotein-cholesterol (HDL-C) concentration and high triglycerides may contribute to atherosclerosis. Thrombotic factors such as increased levels of plasminogen activator inhibitor, fibrinogen, lipoprotein (a) and homocysteine have been shown to be associated with increased CVD. Impaired cerebrovascular autoregulation and sympathovagal activity, increased arterial stiffness and endothelial dysfunction may increase CVD risk further. In addition, environmental and dietary factors may exaggerate the unfavourable cardiovascular profile through genetic factors.

SUMMARY

The implications of the findings suggest comprehensive screening of SA for CVD. Cultural differences should be considered while designing prevention strategies specifically targeting barriers for uptake of preventive service.

Diabetes in South Asians: Phenotype, Clinical Presentation, and Natural History

PURPOSE OF REVIEW

South Asia is one of the epicenters of the global diabetes pandemic. Diabetes in south Asians has certain peculiar features with respect to its pathophysiology, clinical presentation, and management. This review aims to summarize some of the recent evidence pertaining to the distinct diabetes phenotype in south Asians.

RECENT FINDINGS

South Asia has high incidence and prevalence rates of diabetes. The progression from "pre-diabetes" to diabetes also occurs faster in this population. Pancreatic beta cell dysfunction seems to be as important as insulin resistance in the pathophysiology of diabetes in south Asians. Recent evidence suggests that the epidemic of diabetes in south Asia is spreading to rural areas and to less affluent sections of society. Diabetes in south Asians differs significantly from that in white Caucasians, with important implications for prevention, diagnosis, and management.

Association between alcohol consumption pattern and the incidence risk of type 2 diabetes in Korean men: A 12-years follow-up study

Moderate alcohol consumption is generally associated with reduced risk of type 2 diabetes. However, this beneficial effects of alcohol intake remains controversial due to inconsistent results across studies. The analysis was performed using data from the Ansung-Ansan cohort study. We categorized the participants into four groups-based on the baseline (one-point measure; non-drinking, <5 g/day, ≥5, <30 g/day, and ≥30 g/day) and follow-up (consumption pattern; never-drinking, light, moderate, and heavy drinking) measurement. At baseline, ≥30 g/day alcohol consumption increased the risk of incident diabetes (HR: 1.42; 95% CI, 1.10-1.85), but ≥5, <30 g/day alcohol consumption had no effects on the incident diabetes. Meanwhile, when using the alcohol consumption pattern, a heavy-drinking pattern increased the risk of incident diabetes (HR = 1.32, 1.01-1.73), but the light and moderate consumption pattern was associated with a reduced risk of type 2 diabetes (HR: 0.66; 0.50-0.87 and HR: 0.74; 0.57-0.95, respectively). At the end point of follow-up, the insulinogenic index (IGI), but not the insulin sensitivity index (ISI), differed among the groups. Alcohol consumption pattern had a J-shaped association with the incident type 2 diabetes in Korean men. The IGI showed an inverted J-shaped association according to alcohol drinking pattern, but the ISI was not a J-shape.

Trajectories of glycaemia, insulin sensitivity and insulin secretion in South Asian and white individuals before diagnosis of type 2 diabetes: a longitudinal analysis from the Whitehall II cohort study

AIMS/HYPOTHESIS

South Asian individuals have reduced insulin sensitivity and increased risk of type 2 diabetes compared with white individuals. Temporal changes in glycaemic traits during middle age suggest that impaired insulin secretion is a particular feature of diabetes development among South Asians. We therefore aimed to examine ethnic differences in early changes in glucose metabolism prior to incident type 2 diabetes.

METHODS

In a prospective British occupational cohort, subject to 5 yearly clinical examinations, we examined ethnic differences in trajectories of fasting plasma glucose (FPG), 2 h post-load plasma glucose (2hPG), fasting serum insulin (FSI), 2 h post-load serum insulin (2hSI), HOMA of insulin sensitivity (HOMA2-S) and secretion (HOMA2-B), and the Gutt insulin sensitivity index (ISI0,120) among 120 South Asian and 867 white participants who developed diabetes during follow-up (1991-2013). We fitted cubic mixed-effects models to longitudinal data with adjustment for a wide range of covariates.

RESULTS

Compared with white individuals, South Asians had a faster increase in FPG before diagnosis (slope difference 0.22 mmol/l per decade; 95% CI 0.02, 0.42; p = 0.03) and a higher FPG level at diagnosis (0.27 mmol/l; 95% CI 0.06, 0.48; p = 0.01). They also had higher FSI and 2hSI levels before and at diabetes diagnosis. South Asians had a faster decline and lower HOMA2-S (log e -transformed) at diagnosis compared with white individuals (0.33; 95% CI 0.21, 0.46; p < 0.001). HOMA2-B increased in both ethnic groups until 7 years before diagnosis and then declined; the initial increase was faster in white individuals. ISI0,120 declined steeply in both groups before diagnosis; levels were lower among South Asians before and at diagnosis. There were no ethnic differences in 2hPG trajectories.

CONCLUSIONS/INTERPRETATION

We observed different trajectories of plasma glucose, insulin sensitivity and secretion prior to diabetes diagnosis in South Asian and white individuals. This might be due to ethnic differences in the natural history of diabetes. South Asian individuals experienced a more rapid decrease in insulin sensitivity and faster increases in FPG compared with white individuals. These findings suggest more marked disturbance in beta cell compensation prior to diabetes diagnosis in South Asian individuals.

Type 2 Diabetes: Demystifying the Global Epidemic

Type 2 diabetes (T2D) has attained the status of a global pandemic, spreading from affluent industrialized nations to the emerging economies of Asia, Latin America, and Africa. There is significant global variation in susceptibility to T2D, with Pacific Islanders, Asian Indians, and Native Americans being considerably more prone to develop the disorder. Although genetic factors may play a part, the rapidity with which diabetes prevalence has risen among these populations reflects the far-ranging and rapid socioeconomic changes to which they have been exposed over the past few decades. Traditionally, obesity and its correlate, insulin resistance, have been considered the major mediators of T2D risk; however, recent evidence shows that early loss of β-cell function plays an important role in the pathogenesis of T2D, especially in nonobese individuals such as South Asians. Knowledge of the modifiable risk factors of T2D is important, as it forms the basis for designing cost-effective preventive and therapeutic strategies to slow the epidemic in populations at increased risk. Lessons learned from randomized prevention trials need to be implemented with appropriate cultural adaptations, accompanied by empowerment of the community, if the diabetes epidemic is to be slowed or halted.

Stroke recurrence among South Asians with diabetes in Ontario, Canada

Background South Asians have more vascular risk factors, earlier cardiovascular disease onset, and higher stroke mortality than non-South Asians. However, ethnic differences in long-term outcomes post-stroke in diabetics are unclear. Aims We compared cardiovascular outcome risk after first ischemic stroke between South Asian and non-South Asian diabetics. Methods Using population-based health care databases in Ontario, Canada, we selected all patients with diabetes hospitalized with first ischemic stroke between 1 April 2002 and 31 March 2012, and assigned South Asian versus non-South Asian ethnicity using a validated surname algorithm. Kaplan-Meier survival analysis estimated survival functions, and competing risk models estimated hazards of death, stroke, and myocardial infarction. The primary predictor was ethnicity, and models were adjusted for demographics and vascular risk factors. Sensitivity analysis including adjustment for medication use was performed in those aged ≥65 years. Results There were 25,495 diabetics with first ischemic stroke; 840 were South Asian. South Asians were younger, more often male, had lower income, and had shorter Ontario residency compared to non-South Asians. South Asians had higher incidence and cumulative risk of recurrent stroke. In fully adjusted competing risk models, recurrent stroke rate was increased among South Asians compared to non-South Asians (HR 1.17 [95% CI 1.00-1.38]) in the whole cohort and in those aged ≥65 years, both with adjustment for medication use (HR 1.23 [1.01-1.50]) and without (1.27 [1.04-1.54]). Conclusions In this large population-based study, South Asian diabetic stroke patients had higher recurrent stroke rates compared to non-South Asians, despite a younger age profile. Further research is needed to reduce stroke burden in South Asians.

Diabetes mellitus and its complications in India

India is one of the epicentres of the global diabetes mellitus pandemic. Rapid socioeconomic development and demographic changes, along with increased susceptibility for Indian individuals, have led to the explosive increase in the prevalence of diabetes mellitus in India over the past four decades. Type 2 diabetes mellitus in Asian Indian people is characterized by a young age of onset and occurrence at low levels of BMI. Available data also suggest that the susceptibility of Asian Indian people to the complications of diabetes mellitus differs from that of white populations. Management of this disease in India faces multiple challenges, such as low levels of awareness, paucity of trained medical and paramedical staff and unaffordability of medications and services. Novel interventions using readily available resources and technology promise to revolutionise the care of patients with diabetes mellitus in India. As many of these challenges are common to most developing countries of the world, the lessons learnt from India's experience with diabetes mellitus are likely to be of immense global relevance. In this Review, we discuss the epidemiology of diabetes mellitus and its complications in India and outline the advances made in the country to ensure adequate care. We make specific references to novel, cost-effective interventions, which might be of relevance to other low-income and middle-income countries of the world.

Type 2 Diabetes: Why We Are Winning the Battle but Losing the War? 2015 Kelly West Award Lecture

Diabetes is among the biggest of the 21st-century global health challenges. In the U.S. and other high-income countries, thanks to investments in science, dedication to implementing these findings, and measurement of quality of care, there have been improvements in diabetes management and declines in rate of diabetes complications and mortality. This good news, however, is overshadowed by the ever-increasing absolute numbers of people with diabetes and its complications and the unprecedented growth of diabetes in low- and middle-income countries of the world. To comprehensively win the war against diabetes requires 1) concerted attention to prevention and 2) expansion of global research to better inform population-level policies to curb diabetes but also to better understand individual- and population-level variations in pathophysiology and phenotypes globally so that prevention and treatment can be tailored. For example, preliminary data show that thin people in low- and middle-income countries such as India commonly experience type 2 diabetes. Global studies comparing these thin Asian Indians with other high-risk groups such as Pima Indians, a population with a high mean BMI, suggest that type 2 diabetes may not be a single pathophysiological entity. Pima Indians may represent the well-studied phenotype of poor insulin action (type 2A), whereas Asian Indians represent the grossly understudied phenotype of poor insulin secretion (type 2B). This has major implications for diagnosis, prevention, and treatment and highlights the mismatch between where diabetes burdens occur (i.e., low- and middle-income countries) and where research happens (i.e., high-income countries). Correcting this imbalance will advance our knowledge and arsenal to win the global war against diabetes.

Ethnic differences in cross-sectional associations between impaired glucose regulation, identified by oral glucose tolerance test or HbA1c values, and cardiovascular disease in a cohort of European and South Asian origin

AIMS

We contrasted impaired glucose regulation (prediabetes) prevalence, defined according to oral glucose tolerance test or HbA1c values, and studied cross-sectional associations between prediabetes and subclinical/clinical cardiovascular disease (CVD) in a cohort of European and South Asian origin.

METHODS

For 682 European and 520 South Asian men and women, aged 58-85 years, glycaemic status was determined by oral glucose tolerance test or HbA1c thresholds. Questionnaires, record review, coronary artery calcification scores and cerebral magnetic resonance imaging established clinical plus subclinical coronary heart and cerebrovascular disease.

RESULTS

Prediabetes was more prevalent in South Asian participants when defined by HbA1c rather than by oral glucose tolerance test criteria. Accounting for age, sex, smoking, systolic blood pressure, triglycerides and waist-hip ratio, prediabetes was associated with coronary heart disease and cerebrovascular disease in European participants, most obviously when defined by HbA1c rather than by oral glucose tolerance test [odds ratios for HbA1c -defined prediabetes 1.60 (95% CI 1.07, 2.39) for coronary heart disease and 1.57 (95% CI 1.00, 2.51) for cerebrovascular disease]. By contrast, non-significant associations were present between oral glucose tolerance test-defined prediabetes only and coronary heart disease [odds ratio 1.41 (95% CI 0.84, 2.36)] and HbA1c -defined prediabetes only and cerebrovascular disease [odds ratio 1.39 (95% CI 0.69, 2.78)] in South Asian participants. Prediabetes defined by HbA1c or oral glucose tolerance test criteria was associated with cardiovascular disease (defined as coronary heart and/or cerebrovascular disease) in Europeans [odds ratio 1.95 (95% CI 1.31, 2.91) for HbA1c prediabetes criteria] but not in South Asian participants [odds ratio 1.00 (95% CI 0.62, 2.66); ethnicity interaction P = 0.04].

CONCLUSIONS

Prediabetes appeared to be less associated with cardiovascular disease in the South Asian than in the European group. These findings have implications for screening, and early cardiovascular prevention strategies in South Asian populations.

10-year trajectory of β-cell function and insulin sensitivity in the development of type 2 diabetes: a community-based prospective cohort study

BACKGROUND

The relative contributions of β-cell function and insulin sensitivity in the pathogenesis of type 2 diabetes are not fully understood. We investigated the longitudinal change in β-cell function and insulin sensitivity in the development of diabetes and the role of genetic variants in deterioration of glucose tolerance.

METHODS

We followed up 4106 participants with normal glucose tolerance (NGT) from the Korean Genome and Epidemiology Study with oral glucose tolerance tests every 2 years for 10 years. We estimated pancreatic β-cell function with the 60 min insulinogenic index (IGI60) and insulin sensitivity with the composite (Matsuda) insulin sensitivity index (ISI). We investigated the association of 66 known type 2 diabetes genetic variants with risk of prediabetes or diabetes and impaired β-cell function and insulin sensitivity.

FINDINGS

During 10 years of follow-up, 1093 (27%) of 4106 participants developed prediabetes and 498 (12%) participants developed diabetes. Compared with participants who remained NGT, those who progressed to diabetes had a lower IGI60 (unadjusted data 5·1 μU/mmol [95% CI 0·5-56·1] vs 7·9 μU/mmol [0·5-113·8]; p<0·0001) and lower ISI (unadjusted data 8·2 [2·6-26·0] vs 10·0 [3·2-31·6]; p<0·0001) at baseline. Participants who had NGT at 10 years showed a decrease in ISI (adjusted data 10·1 [9·9-10·3] vs 7·4 [7·3-7·6]; p<0·0001) but a compensatory increase in IGI60 (adjusted data 6·9 μU/mmol [6·5-7·2] vs 11·7 μU/mmol [11·2-12·1]; p<0·0001) compared with baseline. By contrast, participants who developed diabetes showed a decrease in ISI (adjusted data 8·4 [8·0-8·7] vs 3·0 [2·8-3·2]; p<0·0001) but no significant compensatory increase (p=0·95) in IGI60. A genetic variant near the glucokinase gene (rs4607517) was significantly associated with progression to prediabetes or diabetes (hazard ratio 1·27, 1·16-1·38; p=1·70 × 10(-7)).

INTERPRETATION

Decreased β-cell function, which might be determined partly by genetic factors, and impaired β-cell compensation for progressive decline in insulin sensitivity are crucial factors in the deterioration of glucose tolerance.

FUNDING

South Korean Ministry of Health & Welfare.

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.