(18)F-fluorodeoxyglucose uptake in brown adipose tissue during insulin-induced hypoglycemia and mild cold exposure in non-diabetic adults

OBJECTIVE

Hypoglycemia is associated with increased heat production and, despite of this, hypothermia. Heat production is likely to be mediated by sympathetic innervation. Brown adipose tissue is activated by cold exposure and stimulated by the sympathetic nervous system. We therefore examined the effect of hypoglycemia on uptake of the labeled glucose analogue (18)F-fluorodeoxyglucose in brown adipose tissue using positron emission tomography and computer tomography.

METHODS

In nine healthy adults (18)F-fluorodeoxyglucose uptake as measure of brown adipose tissue activity was assessed in a cold environment (17 °C) during euglycemia (blood glucose 4.5 mmol/L) and hypoglycemia (2.5 mmol/L) using a hyperinsulinemic glucose clamp.

RESULTS

Brown adipose tissue activity was observed in all participants. No difference was observed in the median (range) maximal standardized uptake values of (18)F-fluorodeoxyglucose in brown adipose tissue between euglycemia and hypoglycemia: 4.2 (1.0-7.7) versus 3.1 (2.2-12.5) g/mL (p=0.7). Similarly there were no differences in mean standardized (18)F-fluorodeoxyglucose uptake values or total brown adipose tissue volume between euglycemia and hypoglycemia. Body temperature dropped by 0.6 °C from baseline during the hypoglycemic condition and remained unchanged during the euglycemic condition. There was no correlation between the maximal standardized uptake values of (18)F-fluorodeoxyglucose in brown adipose tissue and levels of counterregulatory hormones.

CONCLUSIONS

This study shows that there is a similar amount of (18)F-fluorodeoxyglucose uptake in brown adipose tissue during hypoglycemia when compared to euglycemia, which makes a role for systemic catecholamines in brown adipose tissue activation and a role for brown adipose tissue thermogenesis in hypoglycemia associated hypothermia unlikely. Future studies in humans should determine whether hypoglycemia indeed increases energy expenditure, and if so which alternative source can explain this increase.

Ethnicity influences weight loss 1 year after bariatric surgery: a study in Turkish, Moroccan, South Asian, African and ethnic Dutch patients

Several studies conducted in the USA have demonstrated that the effectiveness of bariatric surgery differs between patients from African and European origin. However, little is known on differences in outcomes after bariatric surgery between individuals from other ethnic backgrounds. In this retrospective study, we found that, in terms of weight loss, gastric bypass surgery is less effective in African, South Asian, Turkish and Moroccan patients than in their ethnic Dutch counterparts. Our results underscore that ethnic differences in the effectiveness of bariatric surgery are not limited to those between patients of African and European origin, but extend to other minority groups as well. Therefore, it is important that prospective studies both determine ethnic differences in weight loss-related improvement of co-morbidities and elucidate the exact reasons for these ethnic disparities.

Ethnic disparities in the association of impaired fasting glucose with the 10-year cumulative incidence of type 2 diabetes

AIMS

Evidence of ethnic disparities in the conversion of prediabetes to type 2 diabetes is scarce. We studied the association of impaired fasting glucose (IFG) and fasting plasma glucose (FPG) with the 10-year cumulative incidence of type 2 diabetes in three ethnic groups.

METHODS

We analyzed data for 90 South-Asian Surinamese, 190 African-Surinamese, and 176 ethnic Dutch that were collected in the periods 2001-2003 and 2011-2012. We excluded those with type 2 diabetes or missing FPG data. We defined baseline IFG as FPG of 5.7-6.9 mmol/L. We defined type 2 diabetes at follow-up as FPG ≥ 7.0 mmol/L, HbA1c ≥ 48 mmol/mol (6.5%), or self-reported type 2 diabetes.

RESULTS

10-Year cumulative incidences of type 2 diabetes were: South-Asian Surinamese, 18.9%; African-Surinamese, 13.7%; ethnic Dutch, 4.5% (p<0.05). The adjusted association of baseline IFG and FPG with the 10-year cumulative incidence of type 2 diabetes was stronger for South-Asian Surinamese than for African-Surinamese and ethnic Dutch. The IFG (compared to normoglycaemia) ORs were 11.1 [3.0-40.8] for South-Asian Surinamese, 5.1 [2.0-13.3] for African-Surinamese, and 2.2 [0.5-10.1] for ethnic Dutch.

CONCLUSIONS

The 10-year cumulative incidence of type 2 diabetes was higher and associations with baseline IFG and FPG were stronger among South-Asian Surinamese and African-Surinamese than among ethnic Dutch. Our findings confirm the high risk of type 2 diabetes in South-Asians and suggest more rapid conversion in populations of South-Asian origin and (to a lesser extent) African origin than European origin.

Cold-induced activity of brown adipose tissue in young lean men of South-Asian and European origin

AIMS/HYPOTHESIS

South Asians have a disproportionately high risk of developing abdominal obesity, insulin resistance and type 2 diabetes. Brown adipose tissue (BAT) has been identified as a possible target to fight obesity and protect against metabolic disturbance. We explored whether lower BAT activity in South Asians compared with Europids may contribute to the high risk of metabolic disturbance.

METHODS

We studied 20 healthy men (ten Europids/ten South Asians, BMI 19-25 kg/m(2), age 18-32 years). Following 2 h of cold exposure (16-18°C) after an overnight fast, (18)F-fluorodeoxyglucose ((18)F-FDG) positron-emission tomography-computed tomography (CT) and (123)I-metaiodobenzylguanidine ((123)I-MIBG) single-photon emission computed tomography-CT were performed to visualise metabolic BAT activity and sympathetic stimulation of BAT. Metabolic BAT activity was defined as maximal standardised uptake value (SUV(max)) of (18)F-FDG, and sympathetic stimulation of BAT as semiquantitative uptake value (SQUV) of (123)I-MIBG. We performed hyperinsulinaemic-euglycaemic clamps to assess insulin sensitivity. Spearman's correlations for SUV(max) of (18)F-FDG and both SQUV of (123)I-MIBG and insulin sensitivity were determined.

RESULTS

The median (interquartile range) SUV(max) of (18)F-FDG in South Asians (7.5 [2.2-10.6] g/ml) was not different from the median SUV(max) obtained in Europids (4.5 [2.2-8.4] g/ml; p = 0.59). There was no correlation between BAT activity and insulin sensitivity. Correlations between SQUV of (123)I-MIBG and SUV(max) of (18)F-FDG were positive, both in the total population (ρ = 0.80, p < 0.001) and after stratification by ethnicity (Europids, ρ = 0.65, p = 0.04; South Asians, ρ = 0.83, p = 0.01).

CONCLUSIONS/INTERPRETATION

This is the first study to prospectively investigate ethnic differences in metabolic BAT activity during cold exposure. We did not find differences in BAT activity between South Asians and Europids. Therefore, it seems unlikely that BAT plays an important role in the development of unfavourable metabolic profiles in South Asians.

Intensive lifestyle intervention in general practice to prevent type 2 diabetes among 18 to 60-year-old South Asians: 1-year effects on the weight status and metabolic profile of participants in a randomized controlled trial

Aim

To study 1-year effectiveness of an intensive, culturally targeted lifestyle intervention in general practice for weight status and metabolic profile of South-Asians at risk of type 2 diabetes.

Methods

536 South-Asians at risk of type 2 diabetes were randomized to an intervention (n = 283) or control (n = 253) group. The intervention, which was targeted culturally to the South-Asian population, consisted of individual lifestyle counselling, a family session, cooking classes, and supervised physical activity programme. All components of the intervention were carried out by professionals as part of their daily clinical practice. The control group received generic lifestyle advice. Change in weight status and metabolic profile were assessed after 1 year.

Results

After 1 year, 201 participants were lost to follow-up. Remaining participants in intervention (n = 177) and control (n = 158) group had similar baseline characteristics. Weight loss in the intervention group was 0.2±3.3 kg, weight gain in the control group was 0.4±3.1 kg (p = 0.08). Changes in other weight-related measurements did not differ significantly between groups. Furthermore, there were no differences between groups in changes of metabolic profile. All results remained similar after repeating analyses in a multiple imputed dataset.

Discussion

An intensive, culturally targeted, lifestyle intervention of 1 year did not improve weight status and metabolic profile of South-Asians at risk of type 2 diabetes. The laborious recruitment, high drop-out, and lack of effectiveness emphasise the difficulty of realising health benefits in practice and suggest that this strategy might not be the optimal approach for this population.

Trial Registration

Nederlands Trial Register NTR1499

Screening South Asians for type 2 diabetes and prediabetes: (1) comparing oral glucose tolerance and haemoglobin A1c test results and (2) comparing the two sets of metabolic profiles of individuals diagnosed with these two tests

BACKGROUND

The glycated haemoglobin A1c (HbA1c) level may be used for screening for type 2 diabetes and prediabetes instead of a more burdensome oral glucose tolerance test (OGTT). However, among the high-risk South Asian population, little is known about the overlap of the methods or about the metabolic profiles of those disconcordantly diagnosed.

METHODS

We included 944 South Asians (18-60 years old), whom we screened with the HbA1c level and the OGTT in The Hague, the Netherlands. We calculated the area under the receiver-operator characteristic curve (AUROC) with a 95% confidence interval of HbA1c using the American Diabetes Association classifications, and determined the sensitivity and specificity with 95% confidence intervals at different thresholds. Moreover, we studied differences in metabolic characteristics between those identified by HbA1c and by the OGTT alone.

RESULTS

The overlap between HbA1c and OGTT classifications was partial, both for diabetes and prediabetes. The AUROC of HbA1c for OGTT defined diabetes was 0.86 (0.79-0.93). The sensitivity was 0.46 (0.29-0.63); the specificity 0.98 (0.98-0.99). For prediabetes, the AUROC was 0.73 (0.69-0.77). Each of the 31 individuals with diabetes and 353 with prediabetes identified with the HbA1c level had a high body mass index, large waist circumference, high blood pressure, and low insulin sensitivity, all of which were similar to the values shown by those among the 19 with diabetes or 62 with prediabetes who only met the OGTT criteria, but not the HbA1c criteria.

CONCLUSIONS

The HbA1c level identified a partially different group than the OGTT did. However, both those identified with the HbA1c level and those identified with the OGTT alone were at increased metabolic risk.

TRIAL REGISTRATION

Dutch Trial Register: NTR1499.

[Lifestyle-recommendations on weight loss in type 2 diabetes--useful, or not?]

Weight loss is recommended for overweight or obese patients with type 2 diabetes on the basis of short-term studies, but the long-term effects of weight loss on cardiovascular disease are unknown. The recently published Look AHEAD (Action for health in diabetes) study investigated the 10-year effect of an intensive lifestyle intervention designed to achieve weight loss on cardiovascular morbidity and mortality among overweight or obese adults with type 2 diabetes. In this commentary, we discuss the results and clinical implications of this study.

The Diabetes Pearl: Diabetes biobanking in The Netherlands

Background

Type 2 diabetes is associated with considerable comorbidity and severe complications, which reduce quality of life of the patients and require high levels of healthcare. The Diabetes Pearl is a large cohort of patients diagnosed with type 2 diabetes, covering different geographical areas in the Netherlands. The aim of the study is to create a research infrastructure that will allow the study of risk factors, including biomarkers and genetic determinants for severe diabetes complications.

Methods/design

Baseline examinations began November 2009 and will continue through 2012. By the end of 2012, it is expected that 7000 patients with type 2 diabetes will be included in the Diabetes Pearl cohort. To ensure quality of the data collected, standard operation procedures were developed and used in all 8 recruitment centers. From all patients who provide informed consent, the following information is collected: personal information, medication use, physical examination (antropometry, blood pressure, electrocardiography (ECG), retina photographs, ankle-brachial index, peripheral vibration perception), self-report questionnaire (socio-economic status, lifestyle, (family) history of disease, and psychosocial well-being), laboratory measurements (glucose, A1c, lipid profile, kidney function), biobank material (storage of urine and blood samples and isolated DNA). All gathered clinical data and biobank information is uploaded to a database for storage on a national level. Biobanks are maintained locally at all recruitment centers.

Discussion

The Diabetes Pearl is large-scale cohort of type 2 diabetes patients in the Netherlands aiming to study risk factors, including biomarkers and genetic markers, for disease deterioration and the development of severe diabetes complications. As a result of the well-designed research design and the national coverage, the Diabetes Pearl data can be of great value to national and international researchers with an interest in diabetes related research.

Ethnic differences in weight loss and diabetes remission after bariatric surgery: a meta-analysis

OBJECTIVE

It has been postulated that the effectiveness of bariatric surgery varies between ethnic groups. However, data regarding this topic are inconclusive, as most studies included few patients from minority groups. We conducted a meta-analysis to determine the difference in percentage of excess weight loss (%EWL) 1-2 years after bariatric surgery in people of African and Caucasian descent. We also studied differences in diabetes mellitus (DM) remission.

RESEARCH DESIGN AND METHODS

We performed a MEDLINE and EMBASE search for studies reporting %EWL and/or DM remission after bariatric surgery and including both African Americans and Caucasians. The 613 publications obtained were reviewed. We included 14 studies (1,087 African Americans and 2,714 Caucasians); all provided data on %EWL and 3 on DM remission. We extracted surgery type, %EWL, and DM remission 1-2 years after surgery. After analyzing %EWL for any surgery type, we performed subanalyses for malabsorptive and restrictive surgery.

RESULTS

The overall absolute mean %EWL difference between African Americans and Caucasians was -8.36% (95% CI -10.79 to -5.93) significantly in favor of Caucasians. Results were similar for malabsorptive (-8.39% [-11.38 to -5.40]) and restrictive (-8.46% [-12.95 to -3.97]) surgery. The remission of DM was somewhat more frequent in African American patients than in Caucasian patients (1.41 [0.56-3.52]). However, this was not statistically significant.

CONCLUSIONS

In %EWL terms, bariatric surgery is more effective in Caucasians than in African Americans, regardless of procedure type. Further studies are needed to investigate the exact mechanisms behind these disparities and to determine whether ethnic differences exist in the remission of comorbidities after bariatric surgery.

The association of physical inactivity with Type 2 diabetes among different ethnic groups

AIMS

To study differences in the association between physical inactivity and Type 2 diabetes among subjects from different ethnic groups.

METHODS

We analysed data on 508 Caucasian, 596 African-Surinamese and 339 Hindustani-Surinamese participants, aged 35-60 years, in the population-based, cross-sectional Surinamese in the Netherlands Study on Health and Ethnicity (SUNSET) study. Physical inactivity was defined as the lowest quartile of reported activity, measured with the validated Short Questionnaire to Assess Health-Enhancing Physical Activity. Type 2 diabetes was defined as fasting plasma glucose levels ≥7.0 mmol/l or self-reported diagnosis.

RESULTS

Physical inactivity was associated with Type 2 diabetes (OR 1.63, 95% CI 1.12-2.38) in the total group after adjustment for sex, age, BMI, ethnicity, resting heart rate, hypertension, smoking, history of cardiovascular disease, having a first-degree relative with Type 2 diabetes and educational level. However, this association was only significant in Caucasians (OR 3.17, 95% CI 1.37-7.30). Moreover, it appeared stronger in Caucasians than in Hindustani-Surinamese (OR 1.43, 95% CI 0.78-2.63) and African-Surinamese (OR 1.13, 95% CI 0.58-2.19), although the P-value for interaction was not significant.

CONCLUSIONS

Physical inactivity was associated with Type 2 diabetes in the total group after adjustment for multiple risk factors, but this association was only significant in Caucasians. Also, it appeared stronger in Caucasians than in Hindustani and African-Surinamese, but formal testing for interaction provided no further evidence. These findings confirm the importance of exercise, but suggest that potential health gain may differ between ethnic groups. However, it should be noted that, in general, promotion of physical activity in populations with an increased a priori risk of Type 2 diabetes, remains of the utmost importance.