Ethnic differences in glycemic markers in patients with type 2 diabetes

Family Model of Diabetes Education With a Pacific Islander Community

PURPOSE

The purpose of the study was to use a community-based participatory research approach to pilot-test a family model of diabetes education conducted in participants' homes with extended family members.

METHODS

The pilot test included 6 families (27 participants) who took part in a family model of diabetes self-management education (DSME) using an intervention-driven pre- and posttest design with the aim of improving glycemic control as measured by A1C. Questionnaires and additional biometric data were also collected. Researchers systematically documented elements of feasibility using participant observations and research field reports.

RESULTS

More than three-fourths (78%) of participants were retained in the study. Posttest results indicated a 5% reduction in A1C across all participants and a 7% reduction among those with type 2 diabetes. Feasibility of an in-home model with extended family members was documented, along with observations and recommendations for further DSME adaptations related to blood glucose monitoring, physical activity, nutrition, and medication adherence.

CONCLUSIONS

The information gained from this pilot helps to bridge the gap between knowledge of an evidence-based intervention and its actual implementation within a unique minority population with especially high rates of type 2 diabetes and significant health disparities. Building on the emerging literature of family models of DSME, this study shows that the family model delivered in the home had high acceptance and that the intervention was more accessible for this hard-to-reach population.

HbA1c for diagnosis and prognosis of gestational diabetes mellitus

AIMS

HbA1c is a widely used marker in diagnosing type 2 diabetes mellitus (DM), but its clinical utility in diagnosing gestational diabetes mellitus (GDM) is not established. Here, we evaluated the clinical usefulness of HbA1c in diagnosing GDM and predicting the risk of future type 2 DM development among GDM patients.

METHODS

This retrospective, cross-sectional study included 321 subjects who underwent 100-g oral glucose tolerance tests (OGTT) during pregnancy. HbA1c and other variables were analyzed to evaluate their diagnostic performance for GDM. To evaluate the clinical usefulness of HbA1c in predicting future type 2 DM development, we classified GDM subjects who had more than 3 months of follow-up data into two subgroups: those who developed postpartum type 2 DM (PDM) and those who did not.

RESULTS

HbA1c was significantly higher in the GDM group than in the normal control group. With the 100-g OGTT as reference, HbA1c showed 91.3% sensitivity and 62% specificity at a cut-off value of 5.05% (32 mmol/mol) for GDM diagnosis. At a cut-off value of 5.25% (34 mmol/mol), sensitivity was 73.6% and specificity was 77.2%. HbA1c levels during pregnancy were higher in those with PDM than in those without PDM (5.91 [41 mmol/mol] vs. 5.44% [36 mmol/mol], p<0.001). The prognostic value of HbA1c for PDM was evaluated by ROC curve analysis, with sensitivity of 78.6% and specificity of 72.5% at a cut-off value of 5.55% (37 mmol/mol).

CONCLUSIONS

HbA1c showed high sensitivity with relatively low specificity for diagnosis of GDM in pregnant women and was a potential predictor of PDM. HbA1c may be able to be used as a simple and less invasive alternative screening test for OGTT in GDM patients.

Shortfalls of the use of HbA1C-derived eAG in older adults with diabetes

AIMS

The hemoglobin HbA1C (HbA1C) value, translated into estimated average glucose concentration (eAG), is commonly used to assess glycaemic control and manage treatment regimens in people with diabetes. However, the relationships among HbA1C-derived eAG, and mean glucose concentration derived from continuous glucose monitoring (CGM) in different populations have not been well studied. We examined this relationship in older people with diabetes and compared the results to those currently used in clinical practice.

METHODS

Data from three studies evaluating CGM in older adults (≥70 years of age), with stable glycaemic control were analyzed retrospectively. Mean glucose and mean amplitude of glucose excursion (MAGE) were calculated from CGM data and correlated with HbA1C and HbA1C-derived eAG using the ADAG study formula.

RESULTS

HbA1C and CGM data were analyzed from 90 patients with mean age 76±5 years, HbA1C 7.9±1.2% (63±13 mmol/mol) and 77% with Type 2 diabetes. The HbA1C and HbA1C-derived eAG correlated significantly with CGM-measured mean glucose (r(2)=0.30, p<0.0001) and MAGE (r(2)=0.16, p=0.00013) in this population and all its subgroups, but the slopes of the relationship between HbA1C and eAG or CGM-measured mean glucose were significantly different.

CONCLUSIONS

HbA1C-derived eAG values may not accurately reflect CGM-measured mean glucose or MAGE in older adults with diabetes. Wide glucose excursions should be considered and HbA1C should be interpreted cautiously when making treatment changes based on HbA1C.

HbA1c alone is a poor indicator of cardiometabolic risk in middle-aged subjects with pre-diabetes but is suitable for type 2 diabetes diagnosis: a cross-sectional study

Objectives

Glycated haemoglobin A_1c (HbA_1c) measurement is recommended as an alternative to fasting plasma glucose (FPG) for the diagnosis of pre-diabetes and type 2 diabetes. However, evidence suggests discordance between HbA_1c and FPG. In this study we examine a range of metabolic risk features, pro-inflammatory cytokines, acute-phase response proteins, coagulation factors and white blood cell counts to determine which assay more accurately identifies individuals at increased cardiometabolic risk.

Materials and Methods

This was a cross-sectional study involving a random sample of 2,047 men and women aged 46-73 years. Binary and multinomial logistic regression were employed to examine risk feature associations with pre-diabetes [either HbA_1c levels 5.7-6.4% (39-46 mmol/mol) or impaired FPG levels 5.6-6.9 mmol/l] and type 2 diabetes [either HbA_1c levels >6.5% (>48 mmol/mol) or FPG levels >7.0 mmol/l]. Receiver operating characteristic curve analysis was used to evaluate the ability of HbA_1c to discriminate pre-diabetes and diabetes defined by FPG.

Results

Stronger associations with diabetes-related phenotypes were observed in pre-diabetic subjects diagnosed by FPG compared to those detected by HbA_1c. Individuals with type 2 diabetes exhibited cardiometabolic profiles that were broadly similar according to diagnosis by either assay. Pre-diabetic participants classified by both assays displayed a more pro-inflammatory, pro-atherogenic, hypertensive and insulin resistant profile. Odds ratios of having three or more metabolic syndrome features were also noticeably increased (OR: 4.0, 95% CI: 2.8-5.8) when compared to subjects diagnosed by either HbA_1c (OR: 1.4, 95% CI: 1.2-1.8) or FPG (OR: 3.0, 95% CI: 1.7-5.1) separately.

Conclusions

In middle-aged Caucasian-Europeans, HbA_1c alone is a poor indicator of cardiometabolic risk but is suitable for diagnosing diabetes. Combined use of HbA_1c and FPG may be of additional benefit for detecting individuals at highest odds of type 2 diabetes development.

Effects of Glucocorticoid Treatment on β- and α-Cell Mass in Japanese Adults With and Without Diabetes

The aim of this study was 1) to clarify β-cell regenerative capacity in the face of glucocorticoid (GC)-induced insulin resistance and 2) to clarify the change in β- and α-cell mass in GC-induced diabetes in humans. We obtained the pancreases from 100 Japanese autopsy case subjects. The case subjects were classified according to whether or not they had received GC therapy before death and the presence or absence of diabetes. Fractional β-cell area (%BCA) and α-cell area (%ACA) were quantified, and the relationship with GC therapy was evaluated. As a result, in case subjects without diabetes, there was no significant difference in %BCA between case subjects with and without GC therapy (1.66 ± 1.05% vs. 1.21 ± 0.59%, P = 0.13). %ACA was also not significantly different between the two groups. In case subjects with type 2 diabetes, %BCA and %ACA were both significantly reduced compared with control subjects without diabetes; however, neither %BCA nor %ACA was significantly decreased in case subjects with GC-induced diabetes. There was a significant negative correlation between %BCA and HbA1c measured before death; however, this relationship was attenuated in case subjects with GC therapy. In conclusion, the current study suggests that β- and α-cell mass remain largely unchanged in the face of GC-induced insulin resistance in Japanese individuals, implying limited capacity of β-cell regeneration in adult humans. The absence of apparent β-cell deficit in case subjects with GC-induced diabetes suggests that GC-induced diabetes is mainly caused by insulin resistance and/or β-cell dysfunction, but not necessarily a deficit of β-cell mass.

Guiding diabetes screening and prevention: rationale, recommendations and remaining challenges

Advances made in diabetes management are not sufficient to reduce morbidity, mortality and cost without making prevention efforts at various levels imperative for substantial impact. Research has demonstrated the efficacy of lifestyle intervention and medications in preventing type 2 diabetes among diverse high-risk groups commonly identified with oral glucose tolerance testing. Efficacy, sustainability and safety data are most comprehensive for lifestyle and metformin, with other medications also demonstrating efficacy and potential in the pharmacoprevention of diabetes. Subsequent implementation studies have demonstrated feasibility of lifestyle intervention programs at health centers, communities, and at local and national government levels. Challenges remain in widespread translation and reaching and engaging at-risk individuals and populations.

The hemoglobin glycation index identifies subpopulations with harms or benefits from intensive treatment in the ACCORD trial

OBJECTIVE

This study tested the hypothesis that intensive treatment in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial disproportionately produced adverse outcomes in patients with diabetes with a high hemoglobin glycation index (HGI = observed HbA1c - predicted HbA1c).

RESEARCH DESIGN AND METHODS

ACCORD was a randomized controlled trial of 10,251 patients with type 2 diabetes assigned to standard or intensive treatment with HbA1c goals of 7.0% to 7.9% (53 to 63 mmol/mol) and less than 6% (42 mmol/mol), respectively. In this ancillary study, a linear regression equation (HbA1c = 0.009 × fasting plasma glucose [FPG] [mg/dL] + 6.8) was derived from 1,000 randomly extracted participants at baseline. Baseline FPG values were used to calculate predicted HbA1c and HGI for the remaining 9,125 participants. Kaplan-Meier and Cox regression were used to assess the effects of intensive treatment on outcomes in patients with a low, moderate, or high HGI.

RESULTS

Intensive treatment was associated with improved primary outcomes (composite of cardiovascular events) in the low (hazard ratio [HR] 0.75 [95% CI 0.59-0.95]) and moderate (HR 0.77 [95% CI 0.61-0.97]) HGI subgroups but not in the high HGI subgroup (HR 1.14 [95% CI 0.93-1.40]). Higher total mortality in intensively treated patients was confined to the high HGI subgroup (HR 1.41 [95% CI 1.10-1.80]). A high HGI was associated with a greater risk for hypoglycemia in the standard and intensive treatment groups.

CONCLUSIONS

HGI calculated at baseline identified subpopulations in ACCORD with harms or benefits from intensive glycemic control. HbA1c is not a one-size-fits-all indicator of blood glucose control, and taking this into account when making management decisions could improve diabetes care.

Association between Self-Reported Smoking and Hemoglobin A1c in a Korean Population without Diabetes: The 2011-2012 Korean National Health and Nutrition Examination Survey

Background

Several Western studies have revealed that among non-diabetics, glycosylated hemoglobin A1c (HbA1c) levels are higher in smokers than non-smokers. While studies conducted in Western populations consistently support this association, a recent meta-analysis reported that studies carried out in non-Western populations, including studies of Chinese, Egyptian, and Japanese-Americans, did not detect any significant differences in HbA1c levels between smokers and non-smokers.

Objectives

We assessed the association between smoking habits and HbA1c levels in the general Korean adult population using data from the Korean National Health and Nutrition Examination Survey (KNHANES) performed in 2011–2012.

Methods

A total of 10,241 participants (weighted n=33,946,561 including 16,769,320 men and 17,177,241 women) without diabetes were divided into four categories according to their smoking habits: never smokers (unweighted n/ weighted n= 6,349/19,105,564), ex-smokers (unweighted n/ weighted n= 1,912/6,207,144), current light smokers (<15 cigarettes per day, unweighted n/ weighted n=1,205/5,130,073), and current heavy smokers (≥15 cigarettes per day, unweighted n/ weighted n=775/3,503,781).

Results

In age- and gender-adjusted comparisons, the HbA1c levels of each group were 5.52 ± 0.01% in non-smokers, 5.49 ± 0.01% in ex-smokers, 5.53 ± 0.01% in light smokers, and 5.61 ± 0.02% in heavy smokers. HbA1c levels were significantly higher in light smokers than in ex-smokers (p = 0.033), and in heavy smokers compared with light smokers (p < 0.001). The significant differences remained after adjusting for age, gender, fasting plasma glucose, heavy alcohol drinking, hematocrit, college graduation, and waist circumference. Linear regression analyses for HbA1c using the above-mentioned variables as covariates revealed that a significant association between current smoking and HbA1c (coefficient 0.021, 95% CI 0.003–0.039, p = 0.019).

Conclusions

Current smoking was independently associated with higher HbA1c levels in a cigarette exposure-dependent manner in a representative population of Korean non-diabetic adults. In this study, we have observed an association between smoking status and HbA1c levels in non-diabetics drawn from a non-Western population, consistent with previous findings in Western populations.

Association between the presence of iron deficiency anemia and hemoglobin A1c in Korean adults: the 2011-2012 Korea National Health and Nutrition Examination Survey

Few studies have investigated the clinical effect of iron deficiency anemia (IDA) on the use of the Hemoglobin A1c (HbA1c) as a screening parameter for diabetes or prediabetes. We investigated the association between IDA and HbA1c levels in Korean adults.Among the 11,472 adults (≥19 years of age) who participated in the 2011-2012 Korea National Health and Nutrition Examination Survey (a cross-sectional and nationally representative survey conducted by the Korean Center for Disease Control for Health Statistics), 807 patients with diabetes currently taking anti-diabetes medications were excluded from this study. We compared the weighted HbA1c levels and weighted proportion (%) of HbA1c levels of ≥5.7%, ≥6.1%, and ≥6.5% according to the range of fasting plasma glucose (FPG) levels and the presence of IDA.Among 10,665 participants (weighted n = 35,229,108), the prevalence of anemia and IDA was 7.3% and 4.3%, respectively. The HbA1c levels were higher in participants with IDA (5.70% ± 0.02%) than in normal participants (5.59% ± 0.01%; P < 0.001), whereas there was no significant difference in FPG levels. In participants with an FPG level of <100 mg/dL and 100 to 125 mg/dL, the weighted HbA1c level was higher in those with IDA (5.59% ± 0.02% and 6.00% ± 0.05%) than in normal participants (5.44% ± 0.01% and 5.82% ± 0.01%) after adjusting for confounders such as age, sex, FPG level, heavy alcohol drinking, waist circumference, and smoking status as well as after exclusion of an estimated glomerular filtration rate of <60 mL/min/1.73 m (P < 0.001, <0.01). The weighted proportions (%) of an HbA1c level of ≥5.7% and ≥6.1% were also higher in participants with IDA than in normal participants (P < 0.001, <0.05). However, the weighted HbA1c levels in individuals with an FPG level ≥126 mg/dL and a weighted proportion (%) of an HbA1c level of ≥6.5% showed no significant differences according to the presence of IDA.In conclusion, the presence of IDA shifted the HbA1c level upward only in the normoglycemic and prediabetic ranges, not in the diabetic range. Therefore, IDA should be considered before using HbA1c as a screening test for prediabetes.

Ethnicity and risk of cardiovascular disease (CVD): 4.8 year follow-up of patients with type 2 diabetes living in Scotland

AIMS/HYPOTHESIS

Potential differences in cardiovascular risk by ethnicity remain uncertain. We evaluated the association of ethnicity with cardiovascular disease (CVD) incidence in a large cohort of people with type 2 diabetes living in Scotland.

METHODS

Data from Scottish Care Information-Diabetes (SCI-Diabetes) were linked to Scottish Morbidity Records (SMR01) and National Records of Scotland data for mortality for dates between 2005 and 2011. Of 156,991 people with type 2 diabetes with coded ethnicity, 121,535 (77.4%) had no CVD at baseline (White: 114,461; Multiple Ethnic: 2,554; Indian: 797; Other Asian: 319; Pakistani: 2,250; Chinese: 387; African-Caribbean: 301 and Other: 466) and were followed up (mean ± SD: 4.8 ± 2.3 years) for the development of fatal and non-fatal CVD.

RESULTS

During follow-up, 16,265 (13.4%) patients developed CVD (ischaemic heart or cerebrovascular diseases). At baseline, Pakistanis were younger and had developed diabetes earlier, had higher HbA1c and longer duration of diabetes, but had lower BP, BMI, creatinine, proportion of smokers and proportion on antihypertensive therapy than whites. The age and sex adjusted HRs for CVD were HR 1.31 (CI 1.17, 1.47), p < 0.001 in Pakistanis and HR 0.66 (CI 0.47, 0.92), p = 0.014 in Chinese compared with whites. Adjusting additionally for an area measure of deprivation, duration of diabetes, conventional CVD and other risk factors, the HR for Pakistanis (HR 1.45 [CI 1.14, 1.85], p = 0.002) was significantly higher, and that for Chinese (HR = 0.58 [CI 0.24, 1.40], p = 0.228) lower, compared with whites.

CONCLUSIONS/INTERPRETATION

Compared with whites with type 2 diabetes, those of Pakistani ethnicity in Scotland were at increased risk of CVD, whereas Chinese were at lower risk, with these differences unexplained by known risk factors.

The efficacy and safety of canagliflozin across racial groups in patients with type 2 diabetes mellitus

OBJECTIVE

Canagliflozin, a sodium-glucose co-transporter 2 inhibitor, enhances urinary glucose excretion through an insulin-independent mode of action, and improves glycemic control in patients with type 2 diabetes mellitus (T2DM). This study assessed the efficacy and safety of canagliflozin across racial groups.

METHODS

The efficacy of canagliflozin 100 mg and 300 mg was evaluated by racial group using data pooled from four placebo-controlled phase 3 studies and two placebo-controlled sub-studies of a population of patients with inadequately controlled T2DM (N = 4158). Least-squares mean changes from baseline were calculated for hemoglobin A1c (HbA1c), systolic blood pressure (SBP), body weight (BW), cholesterol, and triglycerides. Safety/tolerability evaluation included reporting of general and prespecified adverse events (AEs).

RESULTS

A total of 75% of patients were White, 13% were Asian, 4% were Black/African American, and 8% were 'Other' (American Indian, Alaskan Native, mixed race, Native Hawaiian or other Pacific Islander, not reported, and unknown). Baseline demographics were similar for these groups. Dose-related reductions in HbA1c, BW, and SBP were observed with both canagliflozin doses in all racial groups. Canagliflozin was generally safe and well tolerated. Treatment with canagliflozin was associated with an increased rate of genital mycotic infections (GMIs) and urinary tract infections (UTIs) in all racial groups. GMIs were observed more often in Black/African American males and males from the 'Other' racial group, whereas UTIs and osmotic diuresis-related AEs were less common in Asians. Key study limitations include the high proportion of White patients compared with other racial groups and the fact that included studies were not powered to evaluate racial differences.

CONCLUSION

Canagliflozin was generally well tolerated and consistently associated with reductions in HbA1c, BW, and SBP in patients with T2DM independent of racial background. (ClinicalTrials.gov numbers: NCT01081834; NCT01106677; NCT01106625; NCT01106690; and NCT01032629.).

Diet and glycaemia: the markers and their meaning. A report of the Unilever Nutrition Workshop

Consumption of carbohydrate-containing foods leads to transient postprandial rises in blood glucose concentrations that vary between food types. Higher postprandial glycaemic exposures have particularly been implicated in the development of chronic cardiometabolic diseases. Reducing such diet-related exposures may be beneficial not only for diabetic patients but also for the general population. A variety of markers have been used to track different aspects of glycaemic exposures, with most of the relevant knowledge derived from diabetic patients. The assessment of glycaemic exposures among the non-diabetic population may require other, more sensitive markers. The present report summarises key messages of presentations and related discussions from a workshop organised by Unilever intended to consider currently applied markers of glycaemic exposure. The particular focus of the meeting was to identify the potential applicability of glycaemic exposure markers for studying dietary effects in the non-diabetic population. Workshop participants concluded that markers of glycaemic exposures are sparsely used in intervention studies among non-diabetic populations. Continuous glucose monitoring remains the optimal approach to directly assess glycaemic exposure. Markers of glycaemic exposure such as glycated Hb, fructosamine, glycated albumin, 1,5-anhydroglucitol and advanced glycation end products can be preferred dependent on the aspect of interest (period of exposure and glucose variability). For all the markers of glycaemia, the responsiveness to interventions will probably be smaller among the non-diabetic than among the diabetic population. Further validation and acceptance of existing glycaemic exposure markers applied among the non-diabetic population would aid food innovation and better design of dietary interventions targeting glycaemic exposure.

Monitoring HIV-infected Patients with Diabetes: Hemoglobin A1c, Fructosamine, or Glucose?

BACKGROUND

Published studies report inappropriately low hemoglobin A1C (HbA1c) values that underestimate glycemia in HIV patients.

METHODS

We reviewed the charts of all HIV patients with diabetes mellitus (DM) at our clinic. Fifty-nine patients had HbA1c data, of whom 26 patients also had fructosamine data. We compared the most recent HbA1c to finger-stick (FS) glucose averaged over three months, and fructosamine to FS averaged over six weeks. Predicted average glucose (pAG) was calculated as reported by Nathan et al: pAG (mg/dL) = 28.7 × A1C% − 46.7. Data were analyzed using the Statistical Analysis System (SAS) and Kruskal–Wallis test.

RESULTS

HbA1c values underestimated (UE) actual average glucose (aAG) in 19% of these patients and overestimated (OE) aAG in 27%. HbA1c estimated aAG within the established range in only 54% of the patients. There were no statistical differences in the types of HIV medication used in patients with UE, OE, or accurately estimated (AE) glycemia. A Spearman correlation coefficient between HbA1c and aAG was r = 0.53 (P < 0.0001). Correlation between fructosamine and aAG was r = 0.47 (P = 0.016).

CONCLUSIONS

The correlations between HbA1c and aAG and between fructosamine and aAG were weaker than expected, and fructosamine was not more accurate than HbA1c.

Glycemic Allostasis during Mental Activities on Fasting in Non-alcohol Users and Alcohol Users with Different Durations of Abstinence

Glycemic allostasis is the process by which blood glucose stabilization is achieved through the balancing of glucose consumption rate and release into the blood stream under a variety of stressors. This paper reviews findings on the dynamics of glycemic levels during mental activities on fasting in non-alcohol users and alcohol users with different periods of abstinence. Referred articles for this review were searched in the databases of PubMed, Scopus, DOAJ and AJOL. The search was conducted in 2013 between January 20 and July 31. The following keywords were used in the search: alcohol action on glycemia OR brain glucose OR cognitive functions; dynamics of glycemia, dynamics of glycemia during mental activities; dynamics of glycemia on fasting; dynamics of glycemia in non-alcohol users OR alcohol users; glycemic regulation during sobriety. Analysis of the selected articles showed that glycemic allostasis during mental activities on fasting is poorly regulated in alcohol users even after a long duration of sobriety (1-4 weeks after alcohol consumption), compared to non-alcohol users. The major contributor to the maintenance of euglycemia during mental activities after the night's rest (during continuing fast) is gluconeogenesis.

Performance of glycated haemoglobin (HbA1c) as a screening test for diabetes and impaired glucose tolerance (IGT) in a high risk population--the Brazilian Xavante Indians

AIMS

To examine the properties of HbA1c to detect diabetes and IGT in adult Brazilian Xavante Indians, a high risk population for diabetes.

METHODS

The survey was carried out between October 2010 and January 2012 and based on a 75 g oral glucose tolerance test (OGTT). Basal and 2h capillary glycaemia were measured by HemoCue Glucose 201+; HbA1c using an automated high-performance liquid chromatography analyzer (Tosoh G7).

RESULTS

630 individuals aged ≥ 20 years were examined and 80 had a previous diagnosis of diabetes. Sensitivity, specificity and accuracy for HbA1c ≥ 6.5% (≥ 48 mmol/mol) were 71.3%, 90.5% and 87.2%. The areas under the ROC curve (AUC) was 0.88 (95%CI: 0.83-0.93). To identify IGT, HbA1c values between 5.7% and 6.4% (39-47 mmol/mol) presented sensitivity, specificity and accuracy of 87.2%, 24.7% and 51.4%, with an AUC of 0.62 (95%CI: 0.57-0.67).

CONCLUSIONS

The ADA/WHO proposed cut-off of 6.5% (48 mmol/mol) for HbA1c was adequate to detect diabetes among the Xavante. However, the performance of the ADA proposed cut-off points for pre-diabetes, when used to detect IGT was inadequate and should not be recommended.

Update on the American Diabetes Association Standards of Medical Care

The diagnosis and management of diabetes in primary care has increased immensely over the past several years. The focus of this article is on the latest substantive revisions in the diagnosis, treatment, and management of diabetes, which was presented in the January 2014 issue of the ADA's journal Diabetes Care.

Multiple nonglycemic genomic loci are newly associated with blood level of glycated hemoglobin in East Asians

Glycated hemoglobin A1c (HbA1c) is used as a measure of glycemic control and also as a diagnostic criterion for diabetes. To discover novel loci harboring common variants associated with HbA1c in East Asians, we conducted a meta-analysis of 13 genome-wide association studies (GWAS; N = 21,026). We replicated our findings in three additional studies comprising 11,576 individuals of East Asian ancestry. Ten variants showed associations that reached genome-wide significance in the discovery data set, of which nine (four novel variants at TMEM79 [P value = 1.3 × 10(-23)], HBS1L/MYB [8.5 × 10(-15)], MYO9B [9.0 × 10(-12)], and CYBA [1.1 × 10(-8)] as well as five variants at loci that had been previously identified [CDKAL1, G6PC2/ABCB11, GCK, ANK1, and FN3KI]) showed consistent evidence of association in replication data sets. These variants explained 1.76% of the variance in HbA1c. Several of these variants (TMEM79, HBS1L/MYB, CYBA, MYO9B, ANK1, and FN3K) showed no association with either blood glucose or type 2 diabetes. Among individuals with nondiabetic levels of fasting glucose (<7.0 mmol/L) but elevated HbA1c (≥6.5%), 36.1% had HbA1c <6.5% after adjustment for these six variants. Our East Asian GWAS meta-analysis has identified novel variants associated with HbA1c as well as demonstrated that the effects of known variants are largely transferable across ethnic groups. Variants affecting erythrocyte parameters rather than glucose metabolism may be relevant to the use of HbA1c for diagnosing diabetes in these populations.

Islet number rather than islet size is a major determinant of β- and α-cell mass in humans

OBJECTIVE

The objective of the study was to clarify the relative contribution of islet number and islet size to β- and α-cell mass in humans.

RESEARCH DESIGN AND METHODS

We obtained the pancreas at autopsy from 72 Japanese adults with no history of diabetes or pancreatitis (aged 47 ± 12 years, body mass index 24.1 ± 5.0 kg/m(2)). Pancreatic sections were stained for insulin or glucagon, and fractional β-cell area (%BCA) and α-cell area (%ACA) were measured. Islet number and islet size as well as β-cell turnover were also quantified. Glycosylated hemoglobin measured within 1 year prior to death was obtained in 38 individuals.

RESULTS

There was considerable interindividual variation in islet density and mean islet size, with a significant negative correlation between the two (r = -0.25, P = .03). There were significant positive correlations between islet density and %BCA or %ACA (r = 0.63, P < .001, and r = 0.41, P = .001), whereas mean islet size correlated with neither of them. Islet density as well as %BCA, but not mean islet size, was negatively correlated with glycosylated hemoglobin (r = -0.37, P = .02, and r = -0.36, P = .03).

CONCLUSION

The present study suggests that islet number rather than islet size is a major determinant of β- and α-cell mass in humans. Interindividual difference in islet number may contribute to susceptibility to development of glucose intolerance.

Racial/ethnic differences in dementia risk among older type 2 diabetic patients: the diabetes and aging study

OBJECTIVE Although patients with type 2 diabetes have double the risk of dementia, potential racial/ethnic differences in dementia risk have not been explored in this population. We evaluated racial/ethnic differences in dementia and potential explanatory factors among older diabetic patients. RESEARCH DESIGN AND METHODS We identified 22,171 diabetic patients without preexisting dementia aged ≥60 years (14,546 non-Hispanic whites, 2,484 African Americans, 2,363 Latinos, 2,262 Asians, 516 Native Americans) from the Kaiser Permanente Northern California Diabetes Registry. We abstracted prevalent medical history (1 January 1996 to 31 December 1997) and dementia incidence (1 January 1998 to 31 December 2007) from medical records and calculated age-adjusted incidence densities. We fit Cox proportional hazards models adjusted for age, sex, education, diabetes duration, and markers of clinical control. RESULTS Dementia was diagnosed in 3,796 (17.1%) patients. Age-adjusted dementia incidence densities were highest among Native Americans (34/1,000 person-years) and African Americans (27/1,000 person-years) and lowest among Asians (19/1,000 person-years). In the fully adjusted model, hazard ratios (95% CIs) (relative to Asians) were 1.64 (1.30-2.06) for Native Americans, 1.44 (1.24-1.67) for African Americans, 1.30 (1.15-1.47) for non-Hispanic whites, and 1.19 (1.02-1.40) for Latinos. Adjustment for diabetes-related complications and neighborhood deprivation index did not change the results. CONCLUSIONS Among type 2 diabetic patients followed for 10 years, African Americans and Native Americans had a 40-60% greater risk of dementia compared with Asians, and risk was intermediate for non-Hispanic whites and Latinos. Adjustment for sociodemographics, diabetes-related complications, and markers of clinical control did not explain observed differences. Future studies should investigate why these differences exist and ways to reduce them.