Insulin resistance status and four-year changes in other cardiometabolic risk factors in West-African adults: the Benin study

Correlation between insulin-based and C-peptide based homeostatic model assessment of insulin resistance in adults without diabetes in a sub-Saharan African setting: a cross-sectional study

OBJECTIVE

To assess the correlation between the insulin-based and C-peptide based HOMA-IR in the general population without diabetes in sub-Saharan Africa as well as to identify factors associated with IR.

RESULTS

This was a cross-sectional study in urban settings in Yaoundé, Cameroon. We included 84 people with a body mass index (BMI) ≥ 18.5 Kg/m² and without diabetes (females: 72.6%; mean age: 37 years). IR was assessed using the following formulae: HOMA-IR_INS = fasting insulin (mU/ml) x fasting plasma glucose (FPG) (mmol/L)/ 22.5; HOMA-IR_CP1 = fasting C-peptide (mU/ml) x FPG (mmol/L)/ 22.5; and HOMA-IR_CP2 = 1.5 + (FPG (mg/dl) x fasting C-peptide (ng/ml))/ 2800. Correlation (rho) between HOMA-IR_INS and C-peptide based HOMA-IR was investigated using the Spearman rank test. The median (25th -75th percentiles) HOMA-IR_INS, HOMA-IR_CP1, and HOMA-IR_CP2 were: 1.94 (1.36-3.50), 0.18 (0.11-0.27) and 9.91 (6.81-14.52), respectively. There was no correlation between the insulin-based and C-peptide-based HOMA-IR indices: rho = 0.043, p = 0.697. IR (HOMA-IR_INS ≥ 2.8) was associated with obesity: A BMI ≥ 30 Kg/m² (adjusted odds ratio (aOR): 16.9, 95% confidence intervals (CI): 3.1-92.5) and being a student (aOR: 8.9, 95%CI: 2.1-38.2) were associated with IR.

Interethnic Differences in Serum Lipids and Implications for Cardiometabolic Disease Risk in African Ancestry Populations

African Americans generally have a healthier lipid profile (lower triglycerides and higher high-density lipoprotein cholesterol concentration) compared with those of other ethnicities. Paradoxically, African Americans do not experience a decreased risk of the cardiometabolic diseases that serum lipids are expected to predict. This review explores this mismatch between biomarker and disease among African ancestry individuals by investigating the presence of interethnic differences in the biological relationships underlying the serum lipids-disease association. This review also discusses the physiologic and genomic factors underlying these interethnic differences. Additionally, because of the importance of serum lipids in assessing disease risk, interethnic differences in serum lipids have implications for identifying African ancestry individuals at risk of cardiometabolic disease. Where possible, data from Africa is included, to further elucidate these ancestral differences in the context of a different environmental background.

Early insulin resistance predicts weight gain and waist circumference increase in first-episode psychosis--A one year follow-up study

First-episode psychosis (FEP) is associated with weight gain during the first year of treatment, and risk of abdominal obesity is particularly increased. To identify early risk markers of weight gain and abdominal obesity, we investigated baseline metabolic differences in 60 FEP patients and 27 controls, and longitudinal changes during the first year of treatment in patients. Compared to controls at baseline, patients had higher low-density lipoprotein, triglyceride and apolipoprotein B levels, and lower levels of high-density lipoprotein and apolipoprotein A-I but no difference in body mass index or waist circumference. At 12-month follow-up, 60.6% of patients were overweight or obese and 58.8% had abdominal obesity. No significant increase during follow-up was seen in markers of glucose and lipid metabolism or blood pressure, but increase in C-reactive protein between baseline and 12-month follow-up was statistically significant. Weight increase was predicted by baseline insulin resistance and olanzapine use, while increase in waist circumference was predicted by baseline insulin resistance only. In conclusion, insulin resistance may be an early marker of increased vulnerability to weight gain and abdominal obesity in young adults with FEP. Olanzapine should be avoided as a first-line treatment in FEP due to the substantial weight increase it causes. In addition, the increase in the prevalence of overweight and abdominal obesity was accompanied by the emergence of low-grade systemic inflammation.

Specific cut-off points for waist circumference and waist-to-height ratio as predictors of cardiometabolic risk in Black subjects: a cross-sectional study in Benin and Haiti

PURPOSE

Waist circumference (WC) and waist-to-height ratio (WHtR) are widely used as indicators of abdominal adiposity and the cut-off values have been validated primarily in Caucasians. In this study we identified the WC and WHtR cut-off points that best predicted cardiometabolic risk (CMR) in groups of African (Benin) and African ancestry (Haiti) Black subjects.

METHODS

This cross-sectional study included 452 apparently healthy subjects from Cotonou (Benin) and Port-au-Prince (Haiti), 217 women and 235 men from 25 to 60 years. CMR biomarkers were the metabolic syndrome components. Additional CMR biomarkers were a high atherogenicity index (total serum cholesterol/high density lipoprotein cholesterol ≥4 in women and ≥5 in men); insulin resistance set at the 75th percentile of the calculated Homeostasis Model Assessment index (HOMA-IR); and inflammation defined as high-sensitivity C-reactive protein (hsCRP) concentrations between 3 and 10 mg/L. WC and WHtR were tested as predictors of two out of the three most prevalent CMR biomarkers. Receiver operating characteristic (ROC) curves, Youden's index, and likelihood ratios were used to assess the performance of specific WC and WHtR cut-offs.

RESULTS

High atherogenicity index (59.5%), high blood pressure (23.2%), and insulin resistance (25% by definition) were the most prevalent CMR biomarkers in the study groups. WC and WHtR were equally valid as predictors of CMR. Optimal WC cut-offs were 80 cm and 94 cm in men and women, respectively, which is exactly the reverse of the generic cut-offs. The standard 0.50 cut-off of WHtR appeared valid for men, but it had to be increased to 0.59 in women.

CONCLUSION

CMR was widespread in these population groups. The present study suggests that in order to identify Africans with high CMR, WC thresholds will have to be increased in women and lowered in men. Data on larger samples are needed.