Identification of a subgroup of black South Africans with type 1 diabetes who are older at diagnosis but have lower levels of glutamic acid decarboxylase and islet antigen 2 autoantibodies

AIMS

To compare the age at diagnosis and prevalence of islet autoantibody [glutamic acid decarboxylase (65 kDa) 65 and islet antigen 2] positivity in black and white participants with type 1 diabetes in South Africa, and to analyse the relationship between age at diagnosis and the presence of autoantibodies.

METHODS

Participants were recruited from diabetes outpatient departments and autoantibodies to glutamic acid decarboxylase (65 kDa) and islet antigen 2 were measured by enzyme-linked immunosorbent assay.

RESULTS

We recruited 472 (353 black and 119 white) participants with type 1 diabetes. Age at diagnosis of diabetes was later in black (19.7 ± 10.5) than in white participants (12.7 ± 10.8 years; P < 0.001) with a median (interquartile range) disease duration of 5.0 (2.0-10.0) and 8.5 (4.0-20.0) years (P < 0.001), respectively. An older age at diagnosis (≥ 21 years) was more frequent in black (152 of 340, 45%) than in white participants (24 of 116, 21%; P < 0.001). The prevalence of islet antigen 2 autoantibodies was 19% (66/352) in black and 41% in white participants (48/118; P < 0.001). There was no significant difference in glutamic acid decarboxylase (65 kDa) autoantibody positivity between black (212/353, 60%) and white participants (77/117, 66%; P = 0.269). In black, but not white, participants the prevalence of both glutamic acid decarboxylase (65 kDa) and islet antigen 2 autoantibody positivity was significantly lower in participants diagnosed at age ≥ 21 years (P < 0.001 for both comparisons).

CONCLUSIONS

The older age at diagnosis, lower prevalence of islet antigen 2 autoantibodies and a distinct subgroup of participants with type 1 diabetes with age at diagnosis of > 20 years in the black compared to white population suggest a difference in the immunological aetiology of type 1 diabetes in these two population groups.

Cardiovascular disease management in people with diabetes outside North America and Western Europe in 2006 and 2015

AIM

Optimal treatment of cardiovascular disease is essential to decrease mortality among people with diabetes, but information is limited on how actual treatment relates to guidelines. We analysed changes in therapeutic approaches to anti-hypertensive and lipid-lowering medications in people with Type 2 diabetes from 2006 and 2015.

METHODS

Summary data from clinical services in seven countries outside North America and Western Europe were collected for 39 684 people. Each site summarized individual-level data from outpatient medical records for 2006 and 2015. Data included: demographic information, blood pressure (BP), total cholesterol levels and percentage of people taking statins, anti-hypertensive medication (angiotensin-converting enzyme inhibitors, calcium channel blockers, angiotensin II receptor blockers, thiazide diuretics) and antiplatelet drugs.

RESULTS

From 2006 to 2015, mean cholesterol levels decreased in six of eight sites (range: -0.5 to -0.2), whereas the proportion with BP levels > 140/90 mmHg increased in seven of eight sites. Decreases in cholesterol paralleled increases in statin use (range: 3.1 to 47.0 percentage points). Overall, utilization of anti-hypertensive medication did not change. However, there was an increase in the use of angiotensin II receptor blockers and a decrease in angiotensin-converting enzyme inhibitors. The percentage of individuals receiving calcium channel blockers and aspirin remained unchanged.

CONCLUSIONS

Our findings indicate that control of cholesterol levels improved and coincided with increased use of statins. The percentage of people with BP > 140/90 mmHg was higher in 2015 than in 2006. Hypertension treatment shifted from using angiotensin-converting enzyme inhibitors to angiotensin II receptor blockers. Despite the potentially greater tolerability of angiotensin II receptor blockers, there was no associated improvement in BP levels.

HIV treatment is associated with a two-fold higher probability of raised triglycerides: Pooled Analyses in 21 023 individuals in sub-Saharan Africa

BACKGROUND

Anti-retroviral therapy (ART) regimes for HIV are associated with raised levels of circulating triglycerides (TG) in western populations. However, there are limited data on the impact of ART on cardiometabolic risk in sub-Saharan African (SSA) populations.

METHODS

Pooled analyses of 14 studies comprising 21 023 individuals, on whom relevant cardiometabolic risk factors (including TG), HIV and ART status were assessed between 2003 and 2014, in SSA. The association between ART and raised TG (>2.3 mmol/L) was analysed using regression models.

FINDINGS

Among 10 615 individuals, ART was associated with a two-fold higher probability of raised TG (RR 2.05, 95% CI 1.51-2.77, I2=45.2%). The associations between ART and raised blood pressure, glucose, HbA1c, and other lipids were inconsistent across studies.

INTERPRETATION

Evidence from this study confirms the association of ART with raised TG in SSA populations. Given the possible causal effect of raised TG on cardiovascular disease (CVD), the evidence highlights the need for prospective studies to clarify the impact of long term ART on CVD outcomes in SSA.

Deriving an optimal threshold of waist circumference for detecting cardiometabolic risk in sub-Saharan Africa

BACKGROUND

Waist circumference (WC) thresholds derived from western populations continue to be used in sub-Saharan Africa (SSA) despite increasing evidence of ethnic variation in the association between adiposity and cardiometabolic disease and availability of data from African populations. We aimed to derive a SSA-specific optimal WC cut-point for identifying individuals at increased cardiometabolic risk.

METHODS

We used individual level cross-sectional data on 24 181 participants aged ⩾15 years from 17 studies conducted between 1990 and 2014 in eight countries in SSA. Receiver operating characteristic curves were used to derive optimal WC cut-points for detecting the presence of at least two components of metabolic syndrome (MS), excluding WC.

RESULTS

The optimal WC cut-point was 81.2 cm (95% CI 78.5-83.8 cm) and 81.0 cm (95% CI 79.2-82.8 cm) for men and women, respectively, with comparable accuracy in men and women. Sensitivity was higher in women (64%, 95% CI 63-65) than in men (53%, 95% CI 51-55), and increased with the prevalence of obesity. Having WC above the derived cut-point was associated with a twofold probability of having at least two components of MS (age-adjusted odds ratio 2.6, 95% CI 2.4-2.9, for men and 2.2, 95% CI 2.0-2.3, for women).

CONCLUSION

The optimal WC cut-point for identifying men at increased cardiometabolic risk is lower (⩾81.2 cm) than current guidelines (⩾94.0 cm) recommend, and similar to that in women in SSA. Prospective studies are needed to confirm these cut-points based on cardiometabolic outcomes.International Journal of Obesity advance online publication, 31 October 2017; doi:10.1038/ijo.2017.240.

Sustaining diabetes prevention and care interventions: A multiple case study of translational research projects

BACKGROUND

This study identifies the barriers and enablers for sustainability of interventions in primary and secondary prevention of diabetes. In the context of translational research, sustainability is defined as the continued use of program components and activities for the continued achievement of desirable program and population outcomes.

METHODS

In this study, eleven translational research projects, supported by the BRIDGES program of the International Diabetes Federation, were investigated. By theoretically-informed semi-structured interviews and analyses of project reports, qualitative data was collected on the sustainability outcomes and the barriers and enablers.

RESULTS

The sustainability outcomes can be grouped in three main areas: (1) sustainability at the intervention site(s); (2) diffusion to the wider community; and (3) replication of the intervention at other site(s). Each of the outcomes has their own set of enablers and barriers, and thus requires consideration for a different sustainability strategy.

CONCLUSIONS

This study is the first international study that relates the sustainability outcomes of translational research project to specific barriers and enablers, and develops an evidence-based framework which provides practical advice on how to ensure the sustainability of health interventions.

The need for an integrated approach for chronic disease research and care in Africa

With the changing distribution of infectious diseases, and an increase in the burden of non-communicable diseases, low- and middle-income countries, including those in Africa, will need to expand their health care capacities to effectively respond to these epidemiological transitions. The interrelated risk factors for chronic infectious and non-communicable diseases and the need for long-term disease management, argue for combined strategies to understand their underlying causes and to design strategies for effective prevention and long-term care. Through multidisciplinary research and implementation partnerships, we advocate an integrated approach for research and healthcare for chronic diseases in Africa.

H3Africa multi-centre study of the prevalence and environmental and genetic determinants of type 2 diabetes in sub-Saharan Africa: study protocol

The burden and aetiology of type 2 diabetes (T2D) and its microvascular complications may be influenced by varying behavioural and lifestyle environments as well as by genetic susceptibility. These aspects of the epidemiology of T2D have not been reliably clarified in sub-Saharan Africa (SSA), highlighting the need for context-specific epidemiological studies with the statistical resolution to inform potential preventative and therapeutic strategies. Therefore, as part of the Human Heredity and Health in Africa (H3Africa) initiative, we designed a multi-site study comprising case collections and population-based surveys at 11 sites in eight countries across SSA. The goal is to recruit up to 6000 T2D participants and 6000 control participants. We will collect questionnaire data, biophysical measurements and biological samples for chronic disease traits, risk factors and genetic data on all study participants. Through integrating epidemiological and genomic techniques, the study provides a framework for assessing the burden, spectrum and environmental and genetic risk factors for T2D and its complications across SSA. With established mechanisms for fieldwork, data and sample collection and management, data-sharing and consent for re-approaching participants, the study will be a resource for future research studies, including longitudinal studies, prospective case ascertainment of incident disease and interventional studies.

Retinopathy in subjects with type 2 diabetes at a tertiary diabetes clinic in Durban, South Africa: Clinical, biochemical and genetic factors

Aim

To determine the prevalence of clinical and laboratory variables and genetic polymorphisms in association with diabetic retinopathy (DR) in subjects with type 2 diabetes attending a tertiary referral diabetes clinic in Durban, South Africa.

Methods

Cross-sectional study on 292 Indian and African patients with type 2 diabetes (71.5% women). The presence of DR was determined by direct ophthalmoscopy. Clinical and laboratory data were collected and polymorphisms in the NOS3 (rs61722009, rs2070744, rs1799983) and VEGF (rs35569394, rs2010963) genes were determined.

Results

DR was present in 113 (39%) subjects. Those with DR were older (60.6 ± 9.6 vs. 55.4 ± 12.9 years, p = 0.005), had longer duration diabetes (18.5 ± 8.8 vs. 11.9 ± 9.2 years, p < 0.0001), higher HbA_1c (9.2 ± 1.8 vs. 8.8 ± 1.7%, p = 0.049), serum creatinine (106.3 ± 90.2 vs. 75.2 ± 33.4 μmol/l), triglycerides (2.1 ± 1.2 vs. 1.9 ± 1.6 mmol/l, p = 0.042), proteinuria (72% vs. 28%, p = 0.001), and used more insulin (78% vs. 39% p = 0.0001), anti-hypertensive (95% vs. 80%, p = 0.0003) and lipid-lowering therapy (70% vs. 56%, p = 0.023). There was no association between DR and any of the NOS3 or VEGF gene polymorphisms studied, although there were ethnic differences. After adjustment, diabetes duration (OR 1.05, 95% CI 1.01–1.08), presence of proteinuria (OR 4.15, 95% CI 1.70–10.11) and use of insulin therapy (OR 3.38, 95% CI 1.60–7.12) were associated with DR.

Conclusion

Hyperglycemia, duration of diabetes and proteinuria are associated with DR in Indian and African patients in South Africa, whereas NOS3 and VEGF gene polymorphisms were not associated with DR.

Toll-like receptor 3 gene polymorphisms in South African Blacks with type 1 diabetes

Type 1 diabetes is the consequence of exposure of genetically susceptible individuals to specific environmental precipitants. The innate immune system provides the initial response to exogenous antigen and links with the adaptive immune system. The aim of this study was to assess the role of polymorphisms occurring in the cytoplasmic region of toll-like receptor (TLR) 3 gene and immediate 5' sequence, in subjects of Zulu descent with type 1 diabetes in KwaZulu-Natal, South Africa. Seventy-nine subjects with type 1 diabetes and 74 healthy normal glucose tolerant gender-matched control subjects were studied. Parts of exon 4 and exon 3/intron 3 of the TLR3 gene were studied by polymerase chain reaction, direct sequencing and restriction enzyme digestion with Bts 1. Of the nine polymorphisms studied, a significant association with type 1 diabetes was found for the major allele in the 2593 C/T polymorphism and for the minor alleles in the 2642 C/A and 2690 A/G polymorphisms, which were found to be in complete linkage disequilibrium. Correction of the P-values for the number of alleles studied, however, rendered the results no longer significant. These results suggest that polymorphisms in the TLR3 gene, which is part of the innate immune system, may be associated with type 1 diabetes in this population.

Distribution of HLA class II (DRB1/DQB1) alleles and haplotypes among Bahraini and Lebanese Arabs

The genetic relationship between Bahraini and Lebanese Arabs in terms of HLA class II (DRB1 and DQB1) gene and haplotype frequencies was investigated in a group of 90 Lebanese and 52 Bahraini Arabs. Subjects of both sexes were unrelated and HLA-DRB1 and DQB1 genes were genotyped using the polymerase chain reaction-sequence specific primer (PCR-SSP) technique. Analysis of the HLA-DRB1 alleles showed that the DRB1*040101 and DRB1*110101 alleles were more common among Lebanese, whereas DRB1*030101, DRB1*130701/1327, and DRB1*160101 alleles were more common among Bahrainis. Similarly, of the 7 HLA-DQB1 alleles analyzed, the presence of DQB1*0201 was higher among Bahrainis, whereas DQB1*030101 was higher among Lebanese. The DRB1*160101-DQB1*050101 (23.08%) and DRB1*030101-DQB1*0201 (21.15%) haplotypes were more frequent among Bahrainis, while the DRB1*110101-DQB1*030101 (56.67%), DRB1*040101-DQB1*0302 (28.89%) and DRB1*040101/DQB1*030101 (25.56%) haplotypes were more frequent in Lebanese subjects. Our results underline significant differences between these two populations in HLA class II distribution, and provide basic information for further studies of MHC heterogeneity among Arab-speaking countries, and as a reference for further anthropologic studies.

High incidence of Type 2 diabetes mellitus in South African Indians: a 10-year follow-up study

AIMS

Previous cross-sectional studies have established that South African Indians have a high prevalence of Type 2 diabetes mellitus. A prospective community study was undertaken to determine the incidence of Type 2 diabetes and the risk factors associated with its development in a cohort of South African Indians who had been studied 10 years previously.

METHODS

This is a report on 563 subjects who participated both at baseline and at the 10-year follow-up study. In the baseline study, 2479 subjects (> 15 years) were studied; using 1985 World Health Organization criteria for glucose tolerance based on 75 g oral glucose tolerance tests (OGTT), the crude prevalence of diabetes mellitus (Diabetes) was 9.8% and of impaired glucose tolerance (IGT) 5.8% (age and sex-adjusted prevalence 13% and 6.9%, respectively).

RESULTS

At the 10-year follow-up study, 563 of the subjects who could be traced consented to a repeat OGTT; of these, 91 (16.2%) were classified as Diabetes and 41 (7.3%) as IGT. Of the subjects who did not have diabetes at baseline (n = 517), 49 (9.5%) progressed to diabetes (PTD) and 40 (7.7%) had IGT. The crude cumulative incidence of diabetes was 9.5% (rate of progression 0.95% per annum; incidence density 9.5/1000 person years) with an age and sex-adjusted cumulative incidence of 8.3% (rate of progression 0.95% per annum; incidence density 8.3/1000 person years). Examination of risk factors predictive of subsequent diabetes development was undertaken by analysis of baseline (year 0) variables in the 517 subjects who did not have diabetes at baseline. In multivariate analysis using a logistic regression model, the significant predictive risk factors for future diabetes included 2-h post load plasma glucose (2 PG) (P < 0.0001, odds ratio (OR) 1.7, 95% confidence interval (CI) 1.4-2.1), body mass index (BMI) (P < 0.006, OR 1.1, 95% CI 1.0-1.3) and obesity (P < 0.01, OR 4.6, 95% CI 1.4-14.7).

CONCLUSIONS

This long-term study has shown that in South African Indians there is a high incidence of Type 2 diabetes, and in this population significant predictors include higher baseline blood glucose, BMI and obesity.

Asymptomatic hyperparathyroidism caused by a giant parathyroid adenoma

On routine investigation a 57-year-old woman was found to have primary hyperparathyroidism caused by a giant parathyroid gland. The gland was removed successfully and histological examination proved it to be a parathyroid adenoma.

Microvascular complications in South African patients with long-duration diabetes mellitus

OBJECTIVE

To determine the prevalence of microvascular complications in South African black and Indian patients with long-duration diabetes mellitus (DM).

DESIGN

A retrospective analysis was undertaken of clinical records of 219 DM patients (132 black, 87 Indian) with long-duration DM (over 10 years) attending a diabetes clinic in Durban. Data recorded on each subject included demographic details (age, gender, ethnic group, type of diabetes, age of onset and duration of diabetes), presence of retinopathy, markers of nephropathy and biochemical variables. The prevalence of complications and the clinical and biochemical parameters were evaluated for type 1 and type 2 diabetes and for each ethnic group.

RESULTS

Of the 219 patients, 47 had type 1 DM (36 blacks, 11 Indians) and 172 were classified as type 2 DM (96 blacks, 76 Indians). The mean age of onset of DM was later in blacks than Indians, both for type 1 (P < 0.05) and type 2 DM (P < 0.01). In patients with type 1 DM, the prevalence of retinopathy was 53.2% (blacks 55.6%, Indians 45.5%), persistent proteinuria was found in 23.4% (blacks 25%, Indians 18.2%) and hypertension in 34%. No ethnic difference was found except for the prevalence of hypertension which was higher in blacks than Indians (41.7% v. 9.1%, P < 0.5). Onset of retinopathy from time of diabetes diagnosis occurred earlier in blacks than Indians (13.0 +/- 4.6 yrs v. 18.0 +/- 4.6 yrs, P < 0.05). For the type 2 DM group, retinopathy was found in 64.5% (black v. Indian 68.8 v. 59.2%) and persistent proteinuria in 25% (black v. Indian 30.2 v. 18.4%). Hypertension was observed in 68% and was more prevalent in blacks (84.4 v. 47.4%, P < 0.01) There was an earlier onset of retinopathy (P < 0.05) and hypertension (P < 0.01) from time of diabetes diagnosis in blacks than Indians. In the type 1 DM group retinopathy was associated with a significantly longer duration of diabetes (P < 0.05) and higher glycated haemoglobin (HbA1) (P < 0.05). For type 2 DM subjects there was a significant association between retinopathy and longer duration of diabetes (P < 0.05) and higher systolic blood pressure (P < 0.05).

CONCLUSION

This study has shown that there is a high prevalence of microvascular complications in South African patients with long-duration diabetes mellitus.

HLA class II antigens in South African Blacks with type I diabetes

Type 1 diabetes mellitus is poorly characterised in many African communities, including South Africa, where little is known of the disease epidemiology. This study aimed to identify the HLA class II alleles associated with type 1 diabetes in a group of Zulu subjects in Durban, KwaZulu-Natal by PCR-SSP. The HLA alleles associated with type 1 diabetes included HLA-DQB*0302 (P<0.0001), DRB1*O9 (P<0.0001), DRB1*04 (P=0.002), DRB1*0301 (P=0.003), DQB*02 (P=0.004) and DQA*03 (P=0.035). Estimated haplotypes positively associated with type 1 diabetes included HLA-DRB1 *0301-DQA*0501, DRB1*04-DQA*03, DRB1*04-DQB*0302, DRB1*0301-DQB*0201, DQA*0501-DQB*0201 and DQA*03-DQB*0302. These findings are similar to those reported from Zimbabwe and other populations with type 1 diabetes.

Application of the new ADA criteria for the diagnosis of diabetes to population studies in sub-Saharan Africa. American diabetes association

AIMS

To examine the implications for epidemiological studies of the American Diabetes Association (ADA) recommendation that the fasting blood glucose at a lowered level becomes the main diagnostic test for diabetes on cross-sectional-based data from sub-Saharan Africa.

METHODS

Data from 11 surveys conducted in rural, peri-urban and urban Cameroon (n = 1804), South Africa (n = 3799) and Tanzania (n = 10013) which measured fasting (ADA criteria) and 2-h blood glucose concentrations during a standard 75 g OGTT (old WHO criteria) were analysed.

RESULTS

The prevalence of diabetes was higher in eight of the 11 surveys when applying the new ADA compared to the old WHO criteria. With the exception of one population (Mara, Tanzania) the absolute difference in prevalence between the two classifications tended to be small (< 2%). There was considerable variation in the categorization of individuals using the ADA and old WHO criteria. The level of agreement between the two ranged from fair to good (Kappa statistic 0.17-0.86). The prevalence of impaired fasting glycaemia (IFG) was lower than that of impaired glucose tolerance (IGT) in 10 of the surveys and the agreement between the two was fair, < or = 0.26 in all the surveys.

CONCLUSIONS

Although the use of the new ADA fasting criteria for prevalence surveys is an attractive and practical option, particularly in Africa, further information is required on the characteristics and prognosis of individuals classified as IFG or diabetic by the fasting criteria, prior to wide adoption of the ADA criteria. Ideally measurement of both fasting and two low glucose concentrations should remain the standard for epidemiological studies.

Transient impaired glucose tolerance in South African Indians does not carry a risk for progression to NIDDM

OBJECTIVE

To evaluate the significance of transient impaired glucose tolerance (IGT) in terms of the risk of progression to NIDDM and the serum insulin response during oral glucose tolerance test (OGTT) in a prospective study on the natural history of IGT in South African Indians.

RESEARCH DESIGN AND METHODS

This is a report on 87 subjects who formed part of a 4-year prospective study in 128 subjects classified with IGT at baseline (year 0) using World Health Organization criteria for glucose tolerance. Subjects were reexamined at years 1 and 4. At year 1, based on OGTT results, the subjects were divided into three groups: transient IGT (normal glucose tolerance [trIGT], n = 40), persistent IGT (pIGT, n = 47), and diabetes (n = 41). Analysis was performed on the 87 subjects who were classified as IGT at year 0, but who had not progressed to NIDDM by year 1 of the study At baseline (year 0), a modified OGTT was performed; between years 1 and 4, the OGTT included timed midtest samples for plasma glucose and serum insulin. Analysis of predictive factors for progression to diabetes or reversion to normal glucose tolerance was undertaken using year 0 as baseline.

RESULTS

By year 4, 72 subjects (82.8%) completed the study Of the 32 subjects in the trIGT group, none (0%) had progressed to NIDDM, 11 (34.4%) had reverted to IGT (N-IGT), and 21 (65.6%) had persisted with normal glucose tolerance (N-N); of the 40 subjects in the pIGT group, 16 (40%) had progressed to NIDDM (IGT-D), 17 (42.5%) had persisted with IGT (IGT-IGT), and 7 (17.5%) had reverted to normal glucose tolerance (IGT-N). Significant predictive factors for reversion to normal glucose tolerance included absence of obesity (P = 0.0131, odds ratio [OR] 4.2, 95% CI 1.4-13.1) and 2-h plasma glucose level (P = 0.027, OR 2.4, 95% CI 1.11-5.13) at baseline (year 0). Intergroup (cross-sectional) analysis showed that the serum insulin response was higher in the pIGT than in the trIGT subgroup (fasting serum insulin: IGT-N vs. N-IGT and N-N, 16.9 +/- 1.9 vs. 6.8 +/- 2.1 and 6.1 +/- 2.4 microU/ml, respectively, P < 0.001; 2-h postload serum insulin: IGT-IGT vs. N-IGT, 116.8 +/- 2.2 vs. 60.3 +/- 1.7 microU/ml, P < 0.05). By contrast, the insulinogenic index was higher in the trIGT subgroups both at year 1 (90-min: N-N vs. IGT-D, 48.9 +/- 3.9 vs. 14.1 +/- 2.5; P < 0.05) and at year 4 (N-N vs. remaining four subgroups, P < 0.01 at 60 min and 90 min). Intragroup (prospective) comparisons showed that in the N-IGT subgroup, the mean 2-h insulinogenic index was lower at year 4 than at year 1 (19.9 +/- 1.7 vs. 66.0 +/- 2.7; P < 0.05).

CONCLUSIONS

In this 4-year prospective study in South African Indians, transient IGT carries no risk of progression to NIDDM. The significant predictive factors for reversion to normal glucose tolerance include lower baseline obesity prevalence and 2-h postload plasma glucose level. Moreover, in this group, beta-cell secretory function appeared to deteriorate with worsening of glucose tolerance.

The significance of a positive family history in South African Indians with non-insulin-dependent diabetes (NIDDM)

A group of South African Indians with NIDDM participated in a study to evaluate the frequency of positive family histories of the disease and to determine the relative contribution of maternal or paternal genetic determinants. Information was elicited by means of an interview and recorded. Of the 1098 diabetic subjects studied 70% gave a positive family history of a first degree relative suffering from NIDDM. Three-generation transmission was recorded in 5.3% of the subjects. A significantly greater proportion of probands (40%) had a mother with NIDDM than those with a father (26%). A positive family history in an offspring was more common in female probands (10.6%) than males (5.5%). Twice as many probands with 3 generation transmission had a maternal grandmother suffering from NIDDM (2.5%) compared with those who had a paternal grandmother afflicted (1.2%) (P < 0.05), whereas the frequencies in the maternal (0.9%) and paternal (0.8%) grandfathers were similar. This study has highlighted, not only the high prevalence of a positive family history in South African Indians with NIDDM, but also a stronger maternal contribution to the putative gene responsible for the disease.

Evidence for impaired pancreatic beta cell function in South African Indians with impaired glucose tolerance

In a prospective study of South African Indians with impaired glucose tolerance (IGT), the serum insulin response during a 75 g oral glucose tolerance test (OGTT) was examined in 128 subjects who were classified as IGT 1 year previously (year 0) and in 60 matched control subjects. Based on the results at year 1, study subjects were divided into three groups, using World Health Organization criteria for glucose tolerance: IGT (n = 47), diabetes (n = 41), and transient IGT (normal glucose tolerance) (n = 40). When compared with the control group, despite higher plasma glucose concentrations, the IGT group showed similar fasting insulin, but lower 30-min insulin response (57.4 +/- 1.9 mUl-1 vs 86.5 +/- 1.8, p < 0.001) and lower 30-min insulin/glucose ratio (7.4 +/- 5.2 vs 13.3 +/- 8.7, p < 0.001). The insulinogenic index was lower in the IGT group than in the control group at 30, 60, 90, and 120 min (p < 0.01, p < 0.001, p < 0.001, p < 0.001, respectively). The 2-h insulin response was higher in the IGT group (106.7 +/- 1.9 mUl-1 vs 59.2 +/- 1.9, p < 0.01). The IGT group displayed a delayed pattern of insulin response with maximum levels only at 2-h. Insulin area was similar in the two groups. In the transient IGT group, despite similar plasma glucose levels, the insulin responses at 0, 15, 30, and 60 min (p < 0.01, p < 0.001, p < 0.001, p < 0.001, respectively) were lower than in the control group; the 30-min insulin/glucose ratio (7.1 +/- 5.1 vs 13.3 +/- 8.7, p < 0.001) and 60-min insulinogenic index (46.9 +/- 86.3 vs 123.4 +/- 206.3, p < 0.001) were also lower in the transient IGT group.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of WHO and NDDG criteria for impaired glucose tolerance

A 4-year prospective study on the natural history of IGT in South African Indians has allowed for the evaluation of the WHO and NDDG criteria for IGT, using the five groups for non-diabetic glucose tolerance recently recommended and relating these to the risk of diabetes development. Using WHO criteria, 128 subjects were classed IGT in a baseline survey (Year 0). The five recommended categories were applied to the OGTTs done between Year 1 and Year 4 of the study, when mid-test plasma (MPG) samples were also obtained. These categories included N-N (Normal by WHO and NDDG); N-ND1 (Normal by WHO, non-diagnostic level 1 by NDDG); N-ND2 (Normal by WHO, non-diagnostic level 2 by NDDG); I-ND3 (IGT by WHO, non-diagnostic level 3 by NDDG) and I-I (IGT by WHO and NDDG). The risk of diabetes development and the significance of the non-diagnostic category were evaluated by comparing the glucose tolerance status at Year 4 with the status at Year 1. In the cross-sectional evaluation at Year 1, of the 87 non-diabetic OGTTs analysed, 31% (n = 27) were classified I-I, 34.5% (n = 30) were classed N-N and 34.5% (n = 30) were classified non-diagnostic [I-ND3 (23.1%); N-ND2 (8%); N-ND1 (3.4%)]. In the prospective analysis, of the 72 subjects who completed the study, 16 subjects developed NIDDM by Year 4; of these 13 subjects were classed I-I and 3 subjects I-ND3 at Year 1.(ABSTRACT TRUNCATED AT 250 WORDS)

South African Indians show a high prevalence of NIDDM and bimodality in plasma glucose distribution patterns

OBJECTIVE

To determine the prevalence of diabetes mellitus and impaired glucose tolerance (IGT) and to test for bimodality in the plasma glucose distribution in South African Indians.

RESEARCH DESIGN AND METHODS

Subjects were selected by systematic cluster sampling in various areas of Durban. They underwent a modified glucose tolerance test whereby fasting and 2-h postglucose (75 g) plasma glucose levels were measured. The program MIX was used to test for bimodality in the plasma glucose distribution.

RESULTS

We tested 2,479 subjects (1,441 women and 1,038 men). Based on the revised World Health Organization criteria, the crude prevalence of diabetes mellitus was 9.8%, and the crude prevalence of IGT was 5.8%; the age- and sex-adjusted prevalence was 13.0 and 6.9%, respectively. IGT was significantly more common in men (7.6%) than in women (4.4%). Obesity was a feature of both diabetes mellitus and IGT, particularly in women. Both fasting and 2-h plasma glucose values did not conform to a single normal distribution pattern in any age-group, whereas unequivocal evidence of bimodality was seen in the 55- to 74-year age-group of both sexes for fasting and 2-h glucose and also in the 2-h levels of men in the 25- to 34-year age-group.

CONCLUSIONS

This study has highlighted a high prevalence of non-insulin-dependent diabetes mellitus in South African Indians and bimodality in the plasma glucose distribution.

The prevalence of diabetes mellitus and impaired glucose tolerance in a group of urban South African blacks

The prevalence of diabetes mellitus and impaired glucose tolerance (IGT) was determined in 479 urbanised South African blacks (141 men and 338 women) of Zulu descent selected by cluster sampling in a suburb of Durban. All subjects underwent a modified glucose tolerance test whereby fasting and 2-hour post-glucose (75 g) plasma glucose levels were measured. On the basis of the revised World Health Organisation criteria, the overall prevalence of diabetes was 4.2% and of IGT 6.9%; the age- and sex-adjusted prevalences were 5.3% and 7.7% respectively. Diabetes mellitus was more common in women (5.2% v. 2.3%), while the reverse was true of IGT (5.5% v. 11.5%). The mean age-adjusted body mass indices (BMIs) of diabetic (31.3 +/- 1.9) and IGT (29.7 +/- 1.9) subjects were significantly higher than those of the group with normal glucose tolerance (28 +/- 0.5). Female subjects with all types of glucose tolerance had significantly higher mean BMIs than men. There was a significant correlation between BMI and both fasting glucose (r = 0.16; P = 0.0039) and 2-hour plasma levels (r = 0.15; P = 0.0065) in the women, while in men only the fasting levels showed such a relationship (r = 0.21; P = 0.01719).

High risk of progression to NIDDM in South-African Indians with impaired glucose tolerance

A four-yr prospective study was undertaken to examine the natural history of IGT in 128 South-African Indians classified as such at year 0 of the study, based on WHO criteria. Subjects were reexamined at year 1 and year 4. Of the 113 subjects who completed the study, 50.4% progressed to NIDDM (rate of progression 12.6%/yr), 24.8% persisted with IGT, and 24.8%, reverted to NGT. The majority (72%) who progressed to NIDDM did so in year 1. At year 1, 47 subjects were still classified as IGT; of the 40 subjects completing the study, 16 subjects (40%) progressed to NIDDM, 17 subjects (42.5%) persisted with IGT, and 7 subjects (17.5%) reverted to NGT. Examination of risk factors predictive of subsequent progression to NIDDM was undertaken by analysis of baseline variables in two ways: When year 0 was used as baseline (in 113 IGT0 subjects), significant predictive risk factors were the FPG and 2-h plasma glucose concentrations. All subjects who at year 0 had 2-h plasma glucose > or = 10.2 and < 11.1 mM or FPG > or = 7.3 but < 7.8 mM, subsequently progressed to NIDDM. When year 1 was used as baseline (40 IGT1 subjects), 90-min plasma glucose concentration (midtest level) was found to be a significant risk factor for development of NIDDM. In conclusion, this study has demonstrated that in South-African Indians with IGT, the majority (50.4%) progress to NIDDM within 4 yr; significant predictors of subsequent diabetes are the baseline fasting and 2-h plasma glucose concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of insulin therapy on blood pressure in NIDDM patients with secondary failure

OBJECTIVE

To assess the effect of insulin therapy on blood pressure in NIDDM patients with secondary failure.

RESEARCH DESIGN AND METHODS

The influence of insulin treatment on blood pressure was assessed retrospectively in a group of 80 NIDDM patients with secondary failure to diet and maximum doses of oral hypoglycemic agents. Weight, blood glucose, and blood pressure were recorded over a 3-mo period before and after the initiation of insulin therapy.

RESULTS

There was a significant rise in systolic (131.8 +/- 1.7 to 148 +/- 1.9 mmHg, P less than 0.05) and diastolic (80.9 +/- 0.9 to 89.2 +/- 1.0 mmHg, P less than 0.02) blood pressures with insulin treatment. Insulin treatment was associated with a significant decrease in blood glucose (18.36 +/- 0.28 to 10.4 +/- 0.34 mM, P less than 0.01) and an increase in weight (72.1 +/- 1.6 to 78 +/- 1.7 kg, P = 0.01). A control group of 80 NIDDM patients matched for age, weight, BMI, and duration of diabetes demonstrated no significant change in blood pressure over a matched period of follow-up.

CONCLUSIONS

This study has shown that insulin therapy is associated with significant elevation of both systolic and diastolic blood pressures.

The value of glycosylated haemoglobin as a substitute for the oral glucose tolerance test in the detection of impaired glucose tolerance (IGT)

In a prospective study of South African Indian subjects with IGT, glycosylated hemoglobin [specifically HbA1 (HbA1(a+b+c)] and its relationship to the oral glucose tolerance test (OGTT) was studied in 128 study subjects who were classified IGT a year previously (Year 0 of study) and in 64 control subjects. At Year 1 of the study, the standard 75-g OGTT was performed on all subjects; study subjects were further divided into three groups based on World Health Organisation criteria [Normal (N), impaired glucose tolerance (IGT), diabetes mellitus (D)]. HbA1, a glycosylated hemoglobin (GHb), was measured by a cation-exchange microchromatographic method. Based on OGTT results, 47 of the 128 study subjects were classified IGT, 41 diabetes (newly-diagnosed diabetes) and 40 subjects had normal glucose tolerance. Mean GHb was significantly higher in the D group (7.61 +/- 1.76%) compared to the control group (6.99 +/- 1.22%) and the N group (6.9 +/- 1.12%), respectively (P less than 0.05); there was no significant difference between the IGT group (7.48 +/- 1.44%) and each of the other three groups. Compared to the OGTT, GHb was relatively insensitive in the diagnosis of IGT or diabetes mellitus: only 17% of the IGT group and 26.8% of the D group has elevated GHb values; the specificity of GHb as a measure of normal glucose tolerance was 85.9%. The majority of subjects, irrespective of the category of glucose tolerance, had GHb levels within the normal range and there was marked overlap between the four groups.(ABSTRACT TRUNCATED AT 250 WORDS)

HLA class I and II antigens in South African blacks with Graves' disease

A study was done to evaluate the relationship between Graves' disease and the HLA system in South African Blacks of Zulu descent. One hundred and three patients with Graves' disease and 1416 control subjects were typed for HLA A, B, and C antigens while HLA DR antigens were done on 63 of the former and 330 of the latter. There was a significant increase in the frequency of HLA DR3 in patients compared to control subjects (57.1% vs 36.1%; P corrected = 0.014). A relationship was also seen at the DR1 locus (14.3% vs 4.6%; P corrected = 0.023).

Diabetes and hypertension in South African Indians. A community study

A community survey was done to assess the prevalence of diabetes and hypertension in Indians living in Durban. Each subject, selected by systematic cluster sampling, had blood pressure measured and a glucose tolerance test. Diagnoses of diabetes mellitus and of hypertension were based on World Health Organization criteria. Of the 1,064 subjects studied 9% had diabetes and 14.2% hypertension; diabetes mellitus was more common in women (10.5%) than men (7%), whereas the prevalence of hypertension was similar in both sexes (women 13.5%, men 14.7%). Hypertension was found in 45.8% of the diabetic subjects, 31.4% of those with impaired glucose tolerance and 9.9% of those with normal glucose tolerance. Although hypertension was more common in women (63.3%) than men (37.9%) in the diabetic group, there was no significant difference in the sex distribution in the subjects with impaired glucose tolerance and those with normal glucose tolerance. Of the subjects with hypertension, 29.1% had diabetes; there was no significant difference in the sex distribution. The mean age-adjusted body mass indices were significantly higher in the hypertensive subjects with all degrees of glucose tolerance than in normotensive subjects. There was a trend towards elevation of both systolic and diastolic blood pressure with increasing degrees of glucose intolerance and increasing age.

HLA class I and II antigens in South African Indians with NIDDM

The relationship between the HLA system and non-insulin-dependent diabetes mellitus (NIDDM) in South African Indians, a migrant Indian group, was evaluated by testing HLA-A, -B, and -C antigens in 184 patients and 1444 control subjects and HLA-DR antigens in 104 patients and 330 control subjects. There was a significant increase in the frequency of HLA-Bw61 in patients compared with control subjects (27.7 vs. 18%, P = .00155), although the degree of association was not very strong (relative risk 1.7). A similar association has been noted in Fiji Indians, another migrant Indian group. However, no relationship could be established at the DR locus. It is suggested that the relatively high frequency of the Bw61 allele in South African Indians could, in the presence of some environmental factor like obesity, confer increased susceptibility to NIDDM.

Management of diabetes mellitus

The management of diabetes mellitus involves patient education and dietary modifications, both of which play a key role in determining the success of therapy. Other therapeutic measures include oral hypoglycaemic agents and insulin. In type II diabetic patients not responding to diet alone the second-generation sulphonylureas are preferred. Biguanides are indicated in the very obese type II diabetic, provided there are no contraindications. Where insulin therapy is indicated (e.g. type 1 diabetes mellitus), the trend is to use a human preparation because it evokes a very weak antibody response. Optimal diabetes control, as gauged by home blood glucose monitoring and glycosylated haemoglobin levels or, in the case of type II diabetics, fasting blood glucose levels, prevents the acute symptoms of diabetes mellitus as well as coma and in addition appears to minimise the risk of vascular complications.

Microvascular complications and non-insulin-dependent diabetes of the young in South African Indians

103 Indians (74 females, 29 males) with NIDDM diagnosed before age 30 yr on the basis of the revised WHO diagnostic criteria were studied in order to assess the prevalence of microvascular complications. The mean duration of NIDDM in the subjects was 11 yr (range 2-38 yr). 24 patients (23%) eventually required insulin therapy for control after a mean interval of 11.8 yr (range 5-38 yr). Diabetic retinopathy was present in 37 patients (35.9%), of whom 6 had proliferative retinopathy. Nephropathy was found in 16 patients (15.5%). The mean GFR of these patients was 46.8 ml/min, compared to a mean of 97.1 ml/min in 12 of the patients without nephropathy who had a similar mean duration of disease. The mean duration of disease in patients with retinopathy and nephropathy was 14.9 yr and 14.8 yr respectively. In the patients who eventually required insulin therapy both retinopathy (75%) and nephropathy (41%) were more common but the mean duration of disease in these patients was longer (16 yr vs 9 yr). This study has underlined the heterogeneity of NIDDM in the young, as microvascular complications are by no means uncommon in South African Indians with the disease.

The prevalence of diabetes mellitus in a large group of South African Indians

The prevalences of diabetes mellitus and impaired glucose tolerance (IGT) among 866 Indians living in the Chatsworth area of Durban were determined. The study group was selected by cluster sampling and the participants underwent a modified glucose tolerance test (GTT) (determination of fasting and 2-hour plasma glucose levels after a 75 g glucose load). On the basis of the revised World Health Organization criteria the overall prevalence of diabetes mellitus was 11% and of IGT 5,8%. Of the 368 men, 7,6% were found to have diabetes mellitus and 7,1% IGT; the prevalence of diabetes mellitus was much greater among women (13,5%), while there was less IGT (4,8%). Subjects with diabetes mellitus were significantly older (mean 50,7 years) than those with a normal GTT (mean 30,9 years), but of similar age distribution compared with the IGT group (mean 46 years). Subjects with a normal GTT had a significantly lower mean body mass index (22,1 +/- 2,8) compared with diabetic subjects (26,1 +/- 5,2) or the IGT group (25,8 +/- 6,6). Obesity was commonly associated with both diabetes mellitus and IGT, particularly among women.