Metabolic characteristics of African descendants: a comparative study of African-Americans and Ghanaian immigrants using minimal model analysis

The Cardiometabolic Health of African Immigrants in High-Income Countries: A Systematic Review

In recent decades, the number of African immigrants in high-income countries (HICs) has increased significantly. However, the cardiometabolic health of this population remains poorly examined. Thus, we conducted a systematic review to examine the prevalence of cardiometabolic risk factors among sub-Saharan African immigrants residing in HICs. Studies were identified through searches in electronic databases including PubMed, Embase, CINAHL, Cochrane, Scopus, and Web of Science up to July 2021. Data on the prevalence of cardiometabolic risk factors were extracted and synthesized in a narrative format, and a meta-analysis of pooled proportions was also conducted. Of 8655 unique records, 35 articles that reported data on the specific African countries of origin of African immigrants were included in the review. We observed heterogeneity in the burden of cardiometabolic risk factors by African country of origin and HIC. The most prevalent risk factors were hypertension (27%, range: 6-55%), overweight/obesity (59%, range: 13-91%), and dyslipidemia (29%, range: 11-77.2%). The pooled prevalence of diabetes was 11% (range: 5-17%), and 7% (range: 0.7-14.8%) for smoking. Few studies examined kidney disease, hyperlipidemia, and diagnosed cardiometabolic disease. Policy changes and effective interventions are needed to improve the cardiometabolic health of African immigrants, improve care access and utilization, and advance health equity.

Exploring the Experiences of West African Immigrants Living with Type 2 Diabetes in the UK

The increasing prevalence and poorer management of Type 2 diabetes among West African immigrants in the UK is a public health concern. This research explored the experiences of West African immigrants in the management of Type 2 diabetes in the UK using a constructivist grounded theory approach. In-depth individual interviews were conducted with thirty-four West African immigrants living with Type 2 diabetes in the London area. Fifteen male and nineteen female adult West African immigrants with age range from 33-82 years participated in the study. Participants were recruited from five diabetes support groups and community settings. Initial, focused and theoretical coding, constant comparison and memos were used to analyse collected data. Three concepts emerged: Changing dietary habits composed of participants' experiences in meeting dietary recommendations, improving physical activity concerned with the experience of reduced physical activity since moving to the UK and striving to adapt which focus on the impact of migration changes in living with Type 2 diabetes in the UK. These address challenges that West African immigrants experience in the management of Type 2 diabetes in the UK. The findings of this research provide a better understanding of the influencing factors and can be used to improve the support provided for West Africans living with Type 2 diabetes in the UK, presenting a deeper understanding of socio-cultural factors that contribute to supporting individuals from this population.

Postprandial Insulin Response and Clearance Among Black and White Women: The Federal Women's Study

CONTEXT

Postprandial hyperinsulinemia might be an important cardiometabolic risk determinant in black compared with white women. However, the contributions of insulin clearance and β-cell function to racial differences in postprandial insulin response are unknown.

OBJECTIVE

To compare, by race and menopause, early insulin response to oral and intravenous glucose and to measure postprandial intact glucagon-like peptide 1 (GLP-1) concentrations, insulin clearance, and β-cell function.

DESIGN AND PARTICIPANTS

119 federally employed women without diabetes [87 premenopausal (52 black, 35 white) and 32 postmenopausal (19 black, 13 white)] underwent an oral glucose tolerance test, insulin-modified frequently sampled intravenous glucose test (IM-FSIGT), and mixed meal tolerance test (MMTT).

OUTCOME MEASURES

Early insulin response was measured as follows: (i) insulinogenic index (oral glucose tolerance test); (ii) acute insulin response to glucose (IM-FSIGT); and (iii) ratio of incremental insulin/glucose area under the curve in the first 30 minutes of the MMTT. Insulin clearance was assessed during the IM-FSIGT and MMTT. During the MMTT, intact GLP-1 was measured and β-cell function assessed using the insulin secretion rate and β-cell responsivity indexes.

RESULTS

Black pre-menopausal and postmenopausal women had a greater insulin response and lower insulin clearance and greater dynamic β-cell responsivity (P ≤ 0.05 for all). No differences were found in the total insulin secretion rates or intact GLP-1 concentrations.

CONCLUSIONS

Greater postprandial hyperinsulinemia in black pre-menopausal and postmenopausal women was associated with lower hepatic insulin clearance and heightened β-cell capacity to rapid changes in glucose, but not to higher insulin secretion. The relationship of increased β-cell secretory capacity, reduced insulin clearance, and ambient hyperinsulinemia to the development of cardiometabolic disease requires further investigation.

Gluconeogenesis and risk for fasting hyperglycemia in Black and White women

Black women, compared with White women, have high rates of whole-body insulin resistance but a lower prevalence of fasting hyperglycemia and hepatic steatosis. This dissociation of whole-body insulin resistance from fasting hyperglycemia may be explained by racial differences in gluconeogenesis, hepatic fat, or tissue-specific insulin sensitivity. Two groups of premenopausal federally employed women, without diabetes were studied. Using stable isotope tracers, [2H2O] and [6,62-H2]glucose, basal glucose production was partitioned into its components (gluconeogenesis and glycogenolysis) and basal whole-body lipolysis ([2H5]glycerol) was measured. Indices of insulin sensitivity, whole-body (SI), hepatic (HISIGPR), and adipose tissue, were calculated. Hepatic fat was measured by proton magnetic resonance spectroscopy. Black women had less hepatic fat and lower fractional and absolute gluconeogenesis. Whole-body SI, HISIGPR, and adipose tissue sensitivity were similar by race, but at any given level of whole-body SI, Black women had higher HISIGPR. Therefore, fasting hyperglycemia may be a less common early pathological feature of prediabetes in Black women compared with White women, because gluconeogenesis remains lower despite similar whole-body SI.

The global dynamics of diabetes and tuberculosis: the impact of migration and policy implications

The convergence between tuberculosis (TB) and diabetes mellitus (DM) will represent a major public health challenge in the near future. DM increases the risk of developing TB by two to three times and also increases the risk of TB treatment failure, relapse, and death. The global prevalence of DM is predicted to rise significantly in the next two decades, particularly in some of the low- and middle-income countries with the highest TB burden. Migration may add further complexity to the effort to control the impact on TB of the growing DM pandemic. Migration may increase the risk of DM, although the magnitude of this association varies according to country of origin and ethnic group, due to genetic factors and lifestyle differences. Migrants with TB may have an increased prevalence of DM compared to the native population, and the risk of TB among persons with DM may be higher in migrants than in autochthonous populations. Screening for DM among migrants, screening migrants with DM for active and latent TB, and improving access to DM care, could contribute to mitigate the effects of DM on TB.

Cardiometabolic Health in African Immigrants to the United States: A Call to Re-examine Research on African-descent populations

In the 20th century, Africans in Sub-Saharan Africa had lower rates of cardiometabolic disease than Africans who migrated. However, in the 21st century, beyond infectious diseases, the triple epidemics of obesity, diabetes and hypertension have taken hold in Africa. Therefore, Africans are acquiring these chronic diseases at different rates and different intensity prior to migration. To ensure optimal care and health outcomes, the United States practice of grouping all African-descent populations into the "Black/African American" category without regard to country of origin masks socioeconomic and cultural differences and needs re-evaluation. Overall, research on African-descent populations would benefit from a shift from a racial to an ethnic perspective. To demonstrate the value of disaggregating data on African-descent populations, the epidemiologic transition, social, economic, and health characteristics of African immigrants are presented.

comparative study of glucose homeostasis, lipids and lipoproteins, HDL functionality, and cardiometabolic parameters in modestly severely obese African Americans and White Americans with prediabetes: implications for the metabolic paradoxes

OBJECTIVE

To determine whether modestly severe obesity modifies glucose homeostasis, levels of cardiometabolic markers, and HDL function in African Americans (AAs) and white Americans (WAs) with prediabetes.

RESEARCH DESIGN AND METHODS

We studied 145 subjects with prediabetes (N = 61 WAs, N = 84 AAs, mean age 46.5 ± 11.2 years, mean BMI 37.8 ± 6.3 kg/m(2)). We measured fasting levels of lipids, lipoproteins, and an inflammatory marker (C-reactive protein [CRP]); HDL functionality (i.e., levels of paraoxonase 1 [PON1]); and levels of oxidized LDL, adiponectin, and interleukin-6 (IL-6). We measured serum levels of glucose, insulin, and C-peptide during an oral glucose tolerance test. Values for insulin sensitivity index (Si), glucose effectiveness index (Sg), glucose effectiveness at zero insulin (GEZI), and acute insulin response to glucose (AIRg) were derived using a frequently sampled intravenous glucose tolerance test (using MINMOD software).

RESULTS

Mean levels of fasting and incremental serum glucose, insulin, and C-peptide tended to be higher in WAs versus AAs. The mean Si was not different in WAs versus AAs (2.6 ± 2.3 vs. 2.9 ± 3.0 × 10(-4) × min(-1) [μU/mL](-1)). Mean values for AIRg and disposition index as well as Sg and GEZI were lower in WAs than AAs. WAs had higher serum triglyceride levels than AAs (116.1 ± 55.5 vs. 82.7 ± 44.2 mg/dL, P = 0.0002). Mean levels of apolipoprotein (apo) A1, HDL cholesterol, PON1, oxidized LDL, CRP, adiponectin, and IL-6 were not significantly different in obese AAs versus WAs with prediabetes.

CONCLUSIONS

Modestly severe obesity attenuated the ethnic differences in Si, but not in Sg and triglyceride levels in WAs and AAs with prediabetes. Despite the lower Si and PON1 values, AAs preserved paradoxical relationships between the Si and HDL/apoA1/triglyceride ratios. We conclude that modestly severe obesity has differential effects on the pathogenic mechanisms underlying glucose homeostasis and atherogenesis in obese AAs and WAs with prediabetes.

Worse cardiometabolic health in African immigrant men than African American men: reconsideration of the healthy immigrant effect

BACKGROUND

The healthy immigrant effect is a phrase that has been used for decades to describe better cardiometabolic health in African immigrants than African Americans. The recent global increase in cardiometabolic diseases raises the possibility that immigrant health may be changing. Therefore, a new assessment of cardiometabolic health in African immigrants is warranted.

METHODS

Glucose tolerance status, blood pressure, and visceral adipose tissue (VAT) volume were compared in 214 self-identified healthy men comprised of 138 African immigrants, 76 African Americans, mean age 36±9 years [mean±standard deviation (SD); range 20-64 years]. Insulin resistance was defined by the lowest quartile of the insulin sensitivity index (SI≤2.28 mU/L(-1)·min(-1)). The waist circumference (WC) which predicts insulin resistance was determined using receiver operating characteristic curves and the Youden index.

RESULTS

Body mass index (BMI) and WC were lower in African immigrants than African Americans (BMI, 27.4±3.8 vs. 29.3±5.5 kg/m(2), P<0.01; WC, 91±11 vs. 97±16 cm, P<0.01). However, blood pressure, fasting glucose, and 2-hr glucose were higher in the African immigrants (all P<0.01). In addition, African immigrants had a higher prevalence of previously undiagnosed diabetes (8% vs. 0%, P<0.01) and prediabetes (35% vs. 22%, P<0.01). After adjusting for WC, African immigrants had more visceral adipose tissue (VAT) than African Americans (P<0.01). Consequently, the WC that predicted insulin resistance was 92 cm in African immigrants but 102 cm in African Americans.

CONCLUSION

African immigrants were less obese than African Americans but had worse cardiometabolic health, specifically higher glucose levels, more hypertension, and greater visceral adiposity. Overall, the healthy immigrant effect may no longer be valid.

Influence of migration on characteristics of type 2 diabetes in sub-Saharan Africans

AIM

This study compared the clinical and biochemical characteristics and microvascular complications found in three groups of type 2 diabetes (T2D) patients: Africans living in Africa; African immigrants living in France; and Caucasians living in France.

METHODS

Diagnosed T2D Africans living in Cameroon (n=100) were compared with 98 African migrants diagnosed with T2D after having moved to France, and a group of 199 T2D Caucasian patients living in France. All underwent clinical and biochemical evaluations, and all were assessed for microvascular complications.

RESULTS

The median duration of stay of the migrants in France was 15years before being diagnosed with diabetes. Despite similar durations of diagnosis, they were 8.9years younger at the time of diagnosis than Africans living in Cameroon (P<0.001). Caucasians and African immigrants in France had lower HbA1c values than Africans in Cameroon (P<0.001); they were also more aggressively treated for hypertension and dyslipidaemia and, therefore, had significantly lower blood pressure levels and better lipid profiles. Diabetic nephropathy and retinopathy rates were higher in Cameroon than in the two other groups. After adjusting for age, diabetes duration, HbA1c, hypertension and other covariates, only the prevalence of diabetic nephropathy (OR: 5.61, 95% CI: 2.32-13.53; P<0.0001) was higher in Cameroon compared with those living in France.

CONCLUSION

Our results suggest that Africans who emigrate to France may develop diabetes earlier than those staying in their home country. However, the latter may be a reflection of late diagnosis of diabetes. Also, the less adequate diabetes and hypertension control in the latter would explain their higher rates of nephropathy. Large-scale cohorts are now warranted to substantiate these observations.

Metabolic syndrome does not detect metabolic risk in African men living in the U.S

OBJECTIVE

Metabolic risk and metabolic syndrome (MetSyn) prevalence were compared in Africans who immigrated to the U.S. and African Americans. If MetSyn were an effective predictor of cardiometabolic risk, then the group with a worse metabolic risk profile would have a higher rate of MetSyn.

RESEARCH DESIGN AND METHODS

Cross-sectional analyses were performed on 95 men (39 Africans, 56 African Americans, age 38 ± 6 years [mean ± SD]). Glucose tolerance was determined by oral glucose tolerance test, visceral adipose tissue (VAT) was determined by computerized tomography, and MetSyn was determined by the presence of three of five factors: central obesity, hypertriglyceridemia, low levels of HDL cholesterol, hypertension, and fasting hyperglycemia.

RESULTS

MetSyn prevalence was similar in Africans and African Americans (10 vs. 13%, P = 0.74), but hypertension, glycemia (fasting and 2-h glucose), and VAT were higher in Africans.

CONCLUSIONS

African immigrants have a worse metabolic profile than African Americans but a similar prevalence of MetSyn. Therefore, MetSyn may underpredict metabolic risk in Africans.

First phase release coefficient of insulin in subjects with normal glucose tolerance on glucose infusion analyzed by computer simulation

We report here a mathematical model using computer simulation to solve the phase fractionation coefficient (f) of instantaneous insulin release on glucose infusion. By extensive model testing with the cited parameters obtained from the literature, the values of the factor f were shown to lie in range of 0.93+/-0.02 (mean+/-2S.D., n=15), indicating that the high pulsatile bolus of glucose by i.v. infusion may trigger acute insulin release (AIR) corresponding to a fraction of more than 90% of the stored insulin release in the first phase from the secretory granules of pancreatic beta cells. In addition, the value of the factor f was shown to be independent of both the glucose infusion method and the non-insulin-dependent uptake of glucose.

Impaired insulin sensitivity, insulin secretion, and glucose effectiveness predict future development of impaired glucose tolerance and type 2 diabetes in pre-diabetic African Americans: implications for primary diabetes prevention

OBJECTIVE

We examined the determinants of impaired glucose tolerance (IGT) and type 2 diabetes in first-degree relatives of African-American type 2 diabetic patients over 5-8 years (median 6).

RESEARCH DESIGN AND METHODS

A total of 81 healthy subjects (age 41.5 +/- 4.8 years; BMI 31.3 +/- 3.6 kg/m(2)) participated in the study. Each subject underwent an oral glucose tolerance test (OGTT) and a frequently sampled intravenous glucose tolerance test at baseline. Insulin sensitivity index (S(i)) and glucose effectiveness index (S(g)) were determined by the minimal model method. Homeostasis model assessment (HOMA) was used to estimate insulin resistance (HOMA-IR) and beta-cell function (HOMA-%B). A total of 18 subjects progressed to either IGT or type 2 diabetes (progressors), whereas 19 subjects maintained normal glucose tolerance (nonprogressors).

RESULTS

Comparing the progressors and nonprogressors, mean fasting serum glucose levels (95 +/- 8 vs. 80 +/- 14 mg/dl, P < 0.01) and 2-h serum glucose levels (149 +/- 27 vs. 100 +/- 60 mg/dl, P < 0.01) as well as 2-h serum insulin levels (117 +/- 81 vs. 72 +/- 87 microU/ml, P < 0.01) during OGTT were higher at baseline. Mean acute first-phase insulin secretion (205 +/- 217 vs. 305 +/- 230 microU/ml), HOMA-%B (148 +/- 60 vs. 346 +/- 372, P < 01), S(i) (1.61 +/- 1.13 vs. 2.48 +/- 1.25 x 10(-4). min(-1) [microU/ml](-1)), and S(g) (1.48 +/- 0.61 vs. 2.30 +/- 0.97 x 10(-2). min(-1)) were lower in the progressors than in the nonprogressors at baseline. Mean HOMA-IR (3.31 +/- 1.64 vs. 2.36 +/- 1.64) was significantly greater in the progressors than the nonprogressors. At the time of diagnosis of glucose intolerance (IGT + diabetes), HOMA-%B (101 +/- 48 vs. 148 +/- 60, P < 0.001) and HOMA-IR (5.44 +/- 2.55 vs. 3.31 +/- 1.64, P < 0.003) deteriorated in the progressors versus baseline.

CONCLUSIONS

We conclude that nondiabetic, first-degree relatives of African-American type 2 diabetic patients who progressed to IGT and type 2 diabetes manifest triple defects (decreased insulin secretion, insulin action, and glucose effectiveness) that antecede the disease.

Fatty acids, diet, and body indices of type II diabetic American whites and blacks and Ghanaians

OBJECTIVE

This research was designed to study the diet, lipid profile, and metabolic and body indices of type II diabetic and non-diabetic subjects among American white and black and Ghanaian populations.

METHODS

Fifty-one type II diabetic and non-diabetic volunteers were recruited through medical clinics. Data collected included food intake and anthropometric measurement. Blood samples were taken for glucose and serum lipid analyses. Serum non-esterified fatty acids, very low-density lipoproteins, low-density lipoproteins, high-density lipoproteins, total cholesterol, and triacylglycerols levels were measured.

RESULTS

The Ghanaian subjects had lower body mass indexes than did the American white and black subjects (P < 0.01), although they recorded the highest carbohydrate intake. Dietary fat intake was not significantly correlated with body fat level or body mass index among the different observational groups. The serum ratio of saturated to polyunsaturated fat was higher in all diabetics than in controls and higher in Ghanaians than in Americans. Total cholesterol, triacylglycerols, and lipoproteins were within normal ranges for diabetic and non-diabetic subjects. The ratio of total cholesterol to high-density lipoprotein cholesterol was slightly elevated among the white diabetics (P < 0.05).

CONCLUSIONS

The data showed a higher metabolism of carbohydrate for energy in the Ghanaian group than in the other groups. In addition, fat metabolism may differ between Americans and Ghanaians. For many variables, black Americans were more similar to white Americans than to Ghanaians. These observations imply that cultural factors may contribute more than ethnic origin to the etiology of diabetes.

Insulin sensitivity and cardiovascular risk factors in hypertensive and normotensive native Ghanaians

AIMS/HYPOTHESIS

The objective of this study was to examine the relationships among insulin and insulin sensitivity and risk factors for cardiovascular diseases in native Ghanaians with and without hypertension.

METHODS

We measured the anthropometric parameters, systolic and diastolic blood pressure, fasting serum triglycerides, cholesterol and high-density lipoprotein cholesterol and fasting and stimulated glucose, insulin and C-peptide of 200 Ghanaian subjects, who were between 25 to 74 years of age, and residing in the Accra Metropolitan area. Serum glucose, C-peptide and insulin concentrations were measured at baseline (fasting) and also 2 h after 75 gm oral glucose drink. Homeostasis model assessment was used to measure insulin resistance. Hypertension was defined as a blood pressure higher than 140/90 mmHg.

RESULTS

There were 53 subjects with hypertension (HBP) and 147 subjects with normal blood pressure (NBP). The mean BMI, waist circumference and waist-to-hip circumference ratio for HBP and NBP subjects were 27.4+/-0.8, 24.8+/-0.4 kg/m(2); 89.8+/-11.7, 81.1+/-0.9 cm; and 0.87+/-0.08, 0.82+/-0.08 respectively, (p<0.05). The fasting and 2-h plasma glucose concentrations in HBP and NBP subjects were 5.5+/-0.2, 7.2+/-0.3 mmol/l and 5.2+/-01, 6.8+/-0.2 mmol/l respectively (p>0.05). The corresponding fasting and 2-h insulin concentrations were 10.0+/-0.7, 8.0+/-0.4 uU/ml and 47.3+/-3.7, 37.3+/-2.5 uU/ml respectively (p<0.05). The insulin resistance index (HOMA-IR) in the HBP and the NBP groups were 2.49+/-0.2 and 1.95+/-0.13 (p<0.05). The two groups had similar fasting and stimulated C-peptide, lipids and HDL concentrations. Correlations were found between blood pressure and the concentrations of lipids, HDL, fasting and stimulated insulin and C-peptide, and between fasting insulin and HOMA-IR with lipids and HDL concentrations. On multiple regression analysis, fasting insulin and HOMA-IR did not influence blood pressure variations significantly.

CONCLUSIONS/INTERPRETATION

We found clustering of hyperinsulinaemia, insulin resistance and truncal obesity in hypertensive Ghanaian subjects but dissociation between insulin resistance, hypertension and atherogenic lipid and lipoprotein profile.

Differences in insulin secretion and sensitivity of Caucasian and African American prepubertal children

OBJECTIVE

To investigate whether differences in body composition of African American children (AA) and Caucasian children (C) explain differences in insulin sensitivity and secretion.

STUDY DESIGN

Prepubertal nondiabetic children (31 AA and 54 C) were studied; 84% were overweight. Participants underwent a 2-hour hyperglycemic clamp, to estimate insulin sensitivity (SI(clamp)) and secretion, and dual energy x-ray absorptiometry, to assess body composition.

RESULTS

AA had greater total body fat mass (P =.01), fasting, 1st phase, 2nd phase, and steady state insulin levels (P <.05). AA and C had similar glucose disposal rates, but AA had lower SI(clamp) (P <.05). Fasting, 1st phase, and steady state C-peptide were less in C (P <.05), whereas corresponding C-peptide/insulin ratios were higher (all P <.005). Insulin levels and SI(clamp) remained different in AA and C after adjustment for body fat or lean mass differences. Analyses restricted to only overweight AA and C showed similar trends.

CONCLUSION

Prepubertal African American children have higher baseline and glucose-stimulated insulin and C-peptide levels, as well as reduced insulin sensitivity that is not entirely explained by differences in adiposity. The lower C-peptide/insulin molar ratio in AA suggests that they probably have lower hepatic insulin clearance than Caucasian children.

Clinical, biophysical and biochemical variables from African-heritage subjects with type 2 diabetes

We compared the metabolic profile of two ethnic populations with type 2 diabetes, one from Bantu (n = 23; Ban) and the other from Belgian (n = 314) extraction followed at St Luc Hospital. Further comparison with a Belgian sub-cohort (n = 64; Be) matched for age (52 yrs) and sex distribution (M/F: 61/39%) showed no significant difference between Belgian and Bantu subjects with regards to diabetes duration (9 and 11 yrs; Ban and Be respectively), age at diabetes diagnosis (43 and 42 yrs), HbA1c (8.1 +/- 1.9 vs. 8.5 +/- 1.9%; NS), and achieved education level. BMI was lower in Ban (29 +/- 4 vs. 32 +/- 7 in Be; p < 0.02), as were body fat (33 +/- 12 vs. 37 +/- 11 kg; NS) and waist diameter (99 +/- 9 vs. 106 +/- 16 cm; p < 0.02). Forty-eight and 72% of Ban and Be were on metformin (p < 0.05), while insulin was given to 39 and 34%. Daily insulin dose was lower in Ban (0.31 +/- 0.20 vs. 0.47 +/- 0.18 IU.kg-1.24 h-1; p < 0.001). There was no difference in beta-cell function (% beta; normal: 100%) or insulin sensitivity (%S; normal: 100%) as determined with HOMA between groups. % beta (median [perc 25-75]) was 51 [23-119] and 67 [45-84] in Ban and Be, while %S was 32 [29-37] and 37 [27-45]. Smoking (past & current) prevalence was 5 and 47% in Ban and Be (p < 0.0001). Prevalence of micro- and macroangiopathy did not differ between groups, although Ban had more macroalbuminuria (29 vs. 9%; p < 0.05), and were more often treated with Ca(2+)-channel- and beta-blockers than Be subjects (36 and 39% vs. 16 and 8%; p = 0.07 and < 0.05, respectively). Fasting (F) and interprandial (IP) triglycerides (TG) were lower in Ban: 115 [81-149] vs. 189 [155-325] mg.dL-1 for F-TG and 127 [81-160] vs. 170 [128-305] mg.dL-1 for IP-TG (p < 0.0001), as was total cholesterol (201 +/- 53 vs. 223 +/- 40 mg.dL-1 (p < 0.05), despite lower use of hypolipidaemic drug (13 vs. 44%; p < 0.01). African-heritage subjects with type 2 diabetes have similar degree of diabetes control and complications, in the presence of leaner biophysical status, minimal tobacco exposure and lower fasting and interprandial triglycerides.

Associação da cor da pele com diabetes mellitus tipo 2 e intolerância à glicose em mulheres obesas de Salvador, Bahia

Fora do Brasil a prevalência de diabetes mellitus (DM) tipo 2 é maior em negros do que em brancos. Mulheres do ambulatório de obesidade do Hospital Universitário Professor Edgard Santos, Salvador - BA, foram estudadas para avaliar se a cor de pele escura tem prevalência mais alta de DM tipo 2 e de intolerância à glicose (ITG), com diagnóstico baseado nos critérios da Organização Mundial da Saúde, independentemente da idade e do índice de massa corporal (IMC). A cor da pele foi classificada como clara (n= 166), intermediária (n= 186) ou escura (n= 128). Determinou-se o nível de glicose plasmática pelo método da glicose-oxidase. O teste de tolerância à glicose oral foi realizado em todas as pacientes, com exceção de 14 que já sabiam ser diabéticas. Pacientes com pele clara, intermediária e escura foram semelhantes em idade, IMC e relação cintura/quadril. A prevalência de DM, contudo, foi significantemente maior (p< 0,05) nas de pele escura (13,3%) quando comparadas com as de pele clara (7,2%). A prevalência de ITG foi também maior, embora estatisticamente não significante (p= 0,088), nas de pele escura (18,8%) do que nas de pele clara (12,7%). A relação entre o número de pacientes com e sem o diagnóstico de DM ou ITG foi 1,9 vezes maior no grupo pele escura, comparado com clara [odds ratio (OR)= 1,9; intervalo de confiança (IC) 95%= 1,1-3,2; p< 0,05]. Esta associação não foi alterada (OR= 1,7; IC 95%= 1,0-2,9) e permaneceu moderadamente significante (p= 0,069), mesmo após o ajuste para idade e IMC, através de regressão logística. Neste estudo, as mulheres obesas com pele escura tiveram maior associação com DM e ITG, independentemente da idade e IMC.

Insulin sensitivity in normal and diabetic cats

Estimates of in vivo insulin sensitivity (S(I)) can be derived from minimal model analysis of a frequently sampled intravenous glucose tolerance test (FSIVGTT). Modification of the FSIVGTT by the injection of insulin allows insulin sensitivity to be measured in diabetics. To establish and compare reference values for insulin sensitivity in clinically normal and diabetic cats, we subjected 10 clinically normal cats and five diabetic cats to the insulin-modified FSIVGTT with minimal model analysis. Diabetic cats had a significantly lower insulin sensitivity than clinically normal cats (P<0.05). Mean insulin sensitivity in clinically normal cats was 3.22x10(-4)/min/microU/ml (range 1.71-5.23x10(-4)/min/microU/ml). In contrast, the mean insulin sensitivity in diabetic cats was 0.58x10(-4)/min/microU/ml (range 0.136-0.88x10(-4)/min/microU/ml), or approximately six times less insulin sensitive than clinically normal cats. Mean glucose effectiveness in clinically normal cats was 0.030/min (range 0.021-0.045/min). Mean glucose effectiveness in diabetic cats was 0.014/min (range 0.008-0.021/min). Our data demonstrate that insulin resistance is a feature of feline diabetes mellitus and that diabetic cats have a similar relative decrease in insulin sensitivity to humans with type 2 diabetes.

Clinical classification of diabetes in tropical west Africa

The objective of this work was to classify and describe the different types of diabetic patients detected in West Africa. In four health centres (three in Ivory Coast, one in Niger) 310 new cases were detected and followed up over 1 year. Classification was based on age at diagnosis, BMI, ketonuria, basal and stimulated C-peptide levels at inclusion, and response to antidiabetic therapy. In this population, males were predominant (sex ratio = 2.40), and random blood glucose levels very high at screening (mean +/- SE, 18.6 +/- 0.4 mmol/l). Only one case of fibrocalculous pancreatic diabetes and one possible case of diabetes mellitus related to malnutrition were detected. IDDM was diagnosed in 11.3% of the patients, half of them above 35 years. Leanness was observed in 59% of the patients with NIDDM. A dramatic decrease of fasting blood glucose was observed in all groups after 2 months of treatment, especially in NIDDM. As IDDM and non-obese NIDDM presented great similarities before treatment, even for C-peptide levels, a point score system is proposed to classify these two groups at baseline. In conclusion, it is confirmed that the form of diabetes previously defined as related to malnutrition is a very rare entity in black African populations. In contrast, African diabetes is characterised by the high proportion of NIDDM patients with low BMI, and reduced beta-cell function, rarely associated to ketonuria. This form of diabetes seems to be adequately controlled with oral hypoglycaemic drugs and/or diet in the year following diagnosis.

Glucose effectiveness assessed under dynamic and steady state conditions. Comparability of uptake versus production components

Glucose tolerance is determined by both insulin action and insulin-independent effects, or "glucose effectiveness," which includes glucose-mediated stimulation of glucose uptake (Rd) and suppression of hepatic glucose output (HGO). Despite its importance to tolerance, controversy surrounds accurate assessment of glucose effectiveness. Furthermore, the relative contributions of glucose's actions on Rd and HGO under steady state and dynamic conditions are unclear. We performed hyperglycemic clamps and intravenous glucose tolerance tests in eight normal dogs, and assessed glucose effectiveness by two independent methods. During clamps, glucose was raised to three successive 90-min hyperglycemic plateaus by variable labeled glucose infusion rate; glucose effectiveness (GE) was quantified as the slope of the dose-response relationship between steady state glucose and glucose infusion rate (GE[CLAMP(total)]), Rd (GE[CLAMP(uptake)]) or HGO (GE[CLAMP(HGO)]). During intravenous glucose tolerance tests, tritiated glucose (1.2 microCi/kg) was injected with cold glucose (0.3 g/kg); glucose and tracer dynamics were analyzed using a two-compartment model of glucose kinetics to obtain Rd and HGO components of glucose effectiveness. All experiments were performed during somatostatin inhibition of islet secretion, and basal insulin and glucagon replacement. During clamps, Rd rose from basal (2.54+/-0.20) to 3.95+/-0.54, 6.76+/-1.21, and 9.48+/-1.27 mg/min per kg during stepwise hyperglycemia; conversely, HGO declined to 2.06+/-0.17, 1.17+/-0.19, and 0.52+/-0.33 mg/min per kg. Clamp-based glucose effectiveness was 0.0451+/-0.0061, 0.0337+/-0.0060, and 0.0102+/-0.0009 dl/min per kg for GE[CLAMP(total)], GE[CLAMP(uptake)], and GE[CLAMP(HGO)], respectively. Glucose's action on Rd dominated overall glucose effectiveness (72.2+/-3.3% of total), a result virtually identical to that obtained during intravenous glucose tolerance tests (71.6+/-6.1% of total). Both methods yielded similar estimates of glucose effectiveness. These results provide strong support that glucose effectiveness can be reliably estimated, and that glucose-stimulated Rd is the dominant component during both steady state and dynamic conditions.

The prevalence of insulin resistance and other cardiovascular disease risk factors in healthy elderly southwestern Nigerians

We assessed the prevalence of coronary heart disease (CHD) risk factors including insulin resistance in 500 (205 males, 295 females) healthy elderly (age > 55 years) indigenous, low socioeconomic group Yorubas residents in either an urban slum (n = 240) or a rural town (n = 260) in southwestern Nigeria. Anthropometric indices, blood pressure and fasting plasma levels of glucose, lipids, insulin and insulin resistance were measured. The results indicated that: (i) gross obesity (4.4%), diabetes (1.6%), hyperlipidaemia (0.2%) and cigarette smoking (4.8%) were relatively uncommon in the population, although the prevalence of hypertension (30%) was higher than previously reported from this population; (ii). the subjects had a relatively high prevalence of multiple CHD risk factors (about 20% had > 4 risk factors), an observation considered paradoxical in view of the reportedly low CHD prevalence in this population; (iii) these CHD risk factors (increased body mass and blood pressure (BP), hyperinsulinaemia and insulin resistance) were more prevalent in the women and in urban residents; (iv) hyperinsulinaemia (20%) and insulin resistance (35%) were common in the population, and were associated, on regression analyses, to such other CHD risk factors as BP and body mass, particularly in women, suggesting, as in Caucasians, that insulin resistance could be an important index of CHD risk; and (v) the excess of multiple CHD risk factors in the women, is due at least in part, to their increased tendency to obesity (8%) and reduced physical activity (83%). This study concludes that: (i) despite the high prevalence of multiple risk factors in this population, CHD prevalence is low, indicating the supremacy of such major risk factors as diabetes and hyperlipidaemia (relatively uncommon here) in the development of CHD; and (ii) potentially the greatest CHD risk is in the elderly women especially if relatively overweight, physically inactive and resident in an urban centre. While further confirmatory studies are necessary in younger subjects and across societal socioeconomic strata, our results nonetheless suggest that attempts to maintain the CHD prevalence at low levels in this population should include efforts directed at reducing excess body weight particularly in women, and advice on maintenance of a traditional diet to keep lipid levels and diabetes prevalence low.

Race and ethnicity determine serum insulin and C-peptide concentrations and hepatic insulin extraction and insulin clearance: comparative studies of three populations of West African ancestry and white Americans

We examined the importance of ethnicity in terms of beta-cell secretion and hepatic insulin extraction (HIE) and insulin clearance (IC) to peripheral insulin levels before and after stimulation in three populations of West African ancestry, namely African-Americans, Ghanaian immigrants, and native Ghanaians living in diverse environments, and white Americans. Following 10 to 12 hours of overnight fasting, each subject ingested a 75-g oral glucose load. Blood samples for determination of serum glucose, insulin, and C-peptide were obtained at baseline and after the oral glucose load at 30-minute intervals for 240 minutes. Basal HIE and IC were calculated as the molar ratios of C-peptide and insulin concentrations at basal steady state, and postprandial values as molar ratios of the incremental integrated C-peptide and insulin areas. Clinical characteristics of the patients were not significantly different among the four groups. During the fasting and postprandial state, serum glucose levels were not significantly different among the four groups. Surprisingly, the mean fasting insulin concentration was significantly greater in native Ghanaians (21.19 +/- 0.93 microU/mL, P < .05) than in African-Americans (11.90 +/- 1.02,microU/ML), Ghanaian immigrants (8.14 +/- 0.96 microU/mL), and white Americans (7.03 +/- 0.78 microU/mL). Following the oral glucose load, the mean serum peak and incremental integrated areas of insulin were significantly (P < .05) greater in native Ghanaians, African-Americans, and Ghanaian immigrants compared with white Americans. In contrast, there were no significant differences in postprandial serum insulin responses among the three groups of West African ancestry, irrespective of country of origin or residence. Despite the higher insulin concentrations in blacks of West African ancestry compared with whites, the corresponding basal and postprandial serum C-peptide levels were not significantly different among the four groups. Mean basal and postprandial HIE and IC were significantly (P < .05 to .01) reduced (25% to 52%) in the three populations of West African ancestry compared with the white Americans, but these values were not significantly different among the West African descendants. When comparing metabolic responses in obese (body mass index [BMI] > 27 kg/m2) and non-obese (BMI < 27 kg/m2) native Ghanaians, we found no significant differences in fasting insulin, C-peptide, and basal HIE or IC. Also, there were no significant relations between fasting and postprandial serum insulin, obesity indices, and HIE and IC in any of the groups. In summary, our study demonstrates that glucose-tolerant native Ghanaians, Ghanaian immigrants, and African-Americans of West African ancestry manifest hyperinsulinemia and a decreased HIE and IC compared with white Americans. We conclude that race and ethnicity may be the major determinants of the mechanism(s) of beta-cell secretion, insulin action, and peripheral insulin levels and HIE or IC in humans. We speculate that the lower HIE and IC in blacks of West African descent appears to be a highly conserved metabolic trait irrespective of the country of residence.