Agouti-related protein promoter variant associated with leanness and decreased risk for diabetes in West Africans

OBJECTIVE

The role of the central melanocortin system in the development of obesity has been extensively studied. Single-nucleotide polymorphisms (SNPs) within several candidate genes have been associated with food intake and obesity-related phenotypes; however, few of these associations have been replicated. SNPs in the agouti-related protein (AGRP) gene coding (Ala67Thr, 199G/A) and promoter (-38C/T) have been reported to be associated with body mass index (BMI), fat mass (FM) and percent body fat, in populations of European and African descent. In this study, we evaluated the association between the functional AGRP -38C/T promoter SNP and weight-related traits, namely BMI, FM and fat-free mass (FFM), as well as diabetes status.

DESIGN

An association study of the AGRP -38C/T SNP and indices of obesity and diabetes status.

SUBJECTS

A well-characterized population of 538 West Africans from Ghana and Nigeria recruited in the AADM (Africa America Diabetes Mellitus) study (mean age 52 years, 41.3% males, 71% diabetic).

MEASUREMENTS

Genotyping of the AGRP -38C/T SNP, BMI, FM, FFM and fasting plasma glucose.

RESULTS

Women carrying two copies of the variant T allele had significantly lower BMI (OR=0.47; 95% CI, 0.25-0.87). Also, men with at least one copy of the variant T allele were over two times less likely to be diabetic than other men (OR=0.44; 95% CI, 0.22-0.89).

CONCLUSION

Our results replicate previous findings and implicate the AGRP -38C/T SNP in the regulation of body weight in West Africans.

A genome-wide scan for quantitative trait loci linked to obesity phenotypes among West Africans

OBJECTIVE

To identify quantitative trait loci (QTL) for three obesity phenotypes: body mass index (BMI), fat mass (FM) and percent body fat (PBF) in West Africans with type 2 diabetes (T2DM).

DESIGN

An affected sibling pair (ASP) design, in which both siblings had T2DM. Obesity was analyzed as a quantitative trait using a variance components approach.

SUBJECTS

Sib-pairs affected with T2DM from the Africa America Diabetes Mellitus (AADM) study, comprising 321 sibling pairs and 36 half-sibling pairs.

MEASUREMENTS

Weight was measured on an electronic scale to the nearest 0.1 kg, and height was measured with a stadiometer to the nearest 0.1 cm. Body composition was estimated using bioelectric impedance analysis (BIA). Genotyping was carried out at the Center for Inherited Disease Research (CIDR) with a panel of 390 trinucleotide and tetranucleotide repeats.

RESULTS

The obesity-related phenotype showing the strongest linkage evidence was PBF on chromosome 2 (LOD 3.30 at 72.6 cM, marker D2S739). Suggestive linkage to FM was found on chromosomes 2 (LOD 2.56 at 80.4 cM) and 5 (LOD 2.25 at 98 cM, marker D5S1725). The highest LOD score for BMI was 1.68 (chromosome 4, 113.8 cM). The areas of linkage for the three phenotypes showed some clustering as all three phenotypes were linked to the same regions of 2p13 and 5q14, and our study replicated linkage evidence for several regions previously reported in other studies.

CONCLUSION

We obtained evidence for several QTLs on chromosome 2, 4 and 5 to three obesity phenotypes. This study provides data on the genetics of obesity in populations that are currently under represented in the global effort directed at understanding the pathophysiology of excess adiposity in free living individuals.

A national diabetes care and education programme: the Ghana model

An account is given of how a national diabetes care and education programme was developed in Ghana, a developing country, through international collaboration of medical schools, industry and government health care institutions. The approach is by way of trained diabetes teams consisting of physicians, dietitians and nurse educators at two tertiary institutional levels (teaching hospitals) who in turn trained teams consisting of physicians, dietitians or diettherapy nurses, nurse educators and pharmacists at regional and district/sub-regional levels to offer care and education to patients and the community. In three years all regional and about 63% of sub-regional/district health facilities had trained diabetes health care teams, run diabetes services and had diabetes registers at these institutions. Additionally a set of guidelines for diabetes care and education was produced. All programme objectives with the exception of one (deployment of diabetes kits) were met. Distances to be travelled by persons with diabetes to receive diabetes care had been reduced considerably. The success of the project has given an impetus to the collaborators to extend the programme to the primary health care level. The continuing prohibitive prices of diabetes medications and supplies however, could be addressed by removing taxes on such supplies. The Ghana diabetes care model, a 'top-down' approach, initially involving two diabetes centres is recommended to other developing countries, which intend to incorporate diabetes care and education into their health care system.