Vitamin A Status under Type 2 Diabetes Mellitus and Hypertension in Urban Ghanaians
Ina M. Ott *
Institute of Nutritional Sciences, University of Potsdam, Potsdam, Germany.
Ina Danquah
Department of Molecular Epidemiology, German Institute of Human Nutrition Potsdam-Rehbrücke, Potsdam, Germany.
George Bedu-Addo
Kwame Nkrumah University of Sciences and Technology, Kumasi, Ghana.
Frank P. Mockenhaupt
Institute of Tropical Medicine and International Health, Charité, Berlin, Germany
Andrea Henze
Institute of Nutritional Sciences, University of Potsdam, Potsdam, Germany.
Jens Raila
Institute of Nutritional Sciences, University of Potsdam, Potsdam, Germany.
Florian J. Schweigert
Institute of Nutritional Sciences, University of Potsdam, Potsdam, Germany.
*Author to whom correspondence should be addressed.
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.