title: Vitamin A: potential misclassification of vitamin A status among patients with type 2 diabetes and hypertension in urban Ghana.
abstract: BACKGROUND
  Sub-Saharan Africa is facing a double burden of malnutrition: vitamin A deficiency (VAD) prevails, whereas the nutrition-related chronic conditions type 2 diabetes (T2D) and hypertension are emerging. Serum retinol—a VAD marker—increases in kidney disease and decreases in inflammation, which can partly be attributed to alterations in the vitamin A-transport proteins retinol-binding protein 4 (RBP4) and prealbumin. Kidney dysfunction and inflammation commonly accompany T2D and hypertension.
  
  
  OBJECTIVE
  Among urban Ghanaians, we investigated the associations of T2D and hypertension with serum retinol as well as the importance of kidney function and inflammation in this regard.
  
  
  METHODS
  A hospital-based, case-control study in individuals for risk factors of T2D, hypertension, or both was conducted in Kumasi, Ghana (328 controls, 197 with T2D, 354 with hypertension, and 340 with T2D plus hypertension). In 1219 blood samples, serum retinol, RBP4, and prealbumin were measured. Urinary albumin and estimated glomerular filtration rate (eGFR) defined kidney function. C-reactive protein (CRP) >5 mg/L indicated inflammation. We identified associations of T2D and hypertension with retinol by linear regression and calculated the contribution of RBP4, prealbumin, urinary albumin, eGFR, and CRP to these associations as the percentages of the explained variance of retinol.
  
  
  RESULTS
  VAD (retinol <1.05 μmol/L) was present in 10% of this predominantly female, middle-aged, overweight, and deprived population. Hypertension, but not T2D, was positively associated with retinol (β: 0.12; 95% CI: 0.08, 0.17), adjusted for age, sex, socioeconomic factors, anthropometric measurements, and lifestyle. In addition to RBP4 (72%) and prealbumin (22%), the effect of increased retinol on individuals with hypertension was mainly attributed to impaired kidney function (eGFR: 30%; urinary albumin: 5%) but not to inflammation.
  
  
  CONCLUSIONS
  In patients with hypertension, VAD might be underestimated because of increased serum retinol in the context of kidney dysfunction. Thus, the interpretation of serum retinol in sub-Saharan Africa should account for hypertension status.
authors.affiliation: Department of Molecular Epidemiology, German Institute of Human Nutrition Potsdam-Rebruecke, Nuthetal, Germany; ina.danquah@dife.de.
authors.forename: Ina
authors.initials: I
authors.lastname: Danquah
authors.affiliation: Department of Physiology and Pathophysiology, Institute of Nutritional Science, University of Potsdam, Potsdam, Germany;
authors.forename: C Lydia
authors.initials: CL
authors.lastname: Dobrucky
authors.affiliation: Department of Molecular Epidemiology, German Institute of Human Nutrition Potsdam-Rebruecke, Nuthetal, Germany;
authors.forename: Laura K
authors.initials: LK
authors.lastname: Frank
authors.affiliation: Department of Physiology and Pathophysiology, Institute of Nutritional Science, University of Potsdam, Potsdam, Germany;
authors.forename: Andrea
authors.initials: A
authors.lastname: Henze
authors.affiliation: School of Medical Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana; and.
authors.forename: Yaw A
authors.initials: YA
authors.lastname: Amoako
authors.affiliation: School of Medical Science, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana; and.
authors.forename: George
authors.initials: G
authors.lastname: Bedu-Addo
authors.affiliation: Department of Physiology and Pathophysiology, Institute of Nutritional Science, University of Potsdam, Potsdam, Germany;
authors.forename: Jens
authors.initials: J
authors.lastname: Raila
authors.affiliation: Department of Molecular Epidemiology, German Institute of Human Nutrition Potsdam-Rebruecke, Nuthetal, Germany;
authors.forename: Matthias B
authors.initials: MB
authors.lastname: Schulze
authors.affiliation: Institute of Tropical Medicine and International Health, Charité-Universitaetsmedizin Berlin, Berlin, Germany.
authors.forename: Frank P
authors.initials: FP
authors.lastname: Mockenhaupt
authors.affiliation: Department of Physiology and Pathophysiology, Institute of Nutritional Science, University of Potsdam, Potsdam, Germany;
authors.forename: Florian J
authors.initials: FJ
authors.lastname: Schweigert
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D002097:C-Reactive Protein / Q000378:metabolism; D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000150:complications; D005260:Female; D005869:Ghana; D005919:Glomerular Filtration Rate; D006801:Humans; D006973:Hypertension / Q000097:blood*; D007674:Kidney Diseases / Q000097:blood / Q000150:complications; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011228:Prealbumin / Q000378:metabolism; D054839:Retinol-Binding Proteins, Plasma / Q000378:metabolism; D012307:Risk Factors; D012959:Socioeconomic Factors; D014505:Urban Population; D014801:Vitamin A / Q000097:blood*; D014802:Vitamin A Deficiency / Q000097:blood* / Q000150:complications
chemical_list: D015415:Biomarkers; D011228:Prealbumin; C101326:RBP4 protein, human; D054839:Retinol-Binding Proteins, Plasma; D014801:Vitamin A; D002097:C-Reactive Protein
keywords: hypertension; inflammation; kidney dysfunction; type 2 diabetes; vitamin A deficiency