Vitamin A Status under Type 2 Diabetes Mellitus and Hypertension in Urban Ghanaians

Abstract

Objectives: Sub-Saharan Africa (SSA) is affected by a double burden of malnutrition: While vitamin A deficiency (VAD) still prevails, type 2 diabetes mellitus (DM2) and hypertension (HTN) are emerging. Serum retinol, retinol binding protein-4 (RBP4), transthyretin (TTR) and their ratios are potent biomarkers for vitamin A status which are influenced by metabolic disorders. This study investigated the associations of DM2 and HTN with these biomarkers. Methods: A case-control study on risk factors of DM2 and HTN was conducted in Kumasi, Ghana. 1219 samples (328 controls, 197 DM2, 354 HTN, 340 DM2+HTN) were analyzed for serum retinol by rpHPLC and RBP4 and TTR by ELISA. Retinol-RBP4-ratio and RBP4-TTR-ratio were calculated and group differences analyzed by non-parametric tests. Multiple-adjusted linear regression evaluated the associations of DM2 and HTN with Ln-normalized biomarkers. Results: Among the predominantly female study population, 10% were affected by VAD (retinol<1.05µmol/L) with the highest prevalence in the control group (19%) and the lowest in the DM2+HTN group (4%; p<0.01). Retinol-RBP4-ratio and RBP4-TTR-ratio were significantly higher in DM2 (0.98±0.26 and 0.67±0.99, respectively) and HTN (0.95±0.28 and 0.64±0.28, respectively) than in controls (0.90±0.26 and 0.58±0.27, respectively; p<0.001). These associations were most pronounced for DM2, remaining statistically significant after multiple adjustment in linear regression analyses. Conclusions: Our findings may have additional implications for retinol-RBP4- and RBP4-TTR-ratios as diagnostic markers for vitamin A status among patients with DM2 and HTN in SSA as they run the risk of overestimated serum retinol due to altered metabolic dysfunction.