title: Osteoprotegerin in relation to insulin resistance and blood lipids in sub-Saharan African women with and without abdominal obesity.
abstract: BACKGROUND
  Osteoprotegerin (OPG), a soluble member of the tumor necrosis factor receptor superfamily that inhibits bone resorption, has been suggested as a potential marker of cardiovascular risk. This study aimed to assess the relationship between insulin resistance, lipid profile and OPG levels in obese and non-obese sub-Saharan African women.
  
  
  METHODS
  Sixty obese (44) and non-obese (16) volunteer women aged 18 to 40 years were recruited in this cross-sectional study. Their clinical (age, height, weight, waist circumference, systolic and diastolic blood pressures) and biochemical parameters (fasting blood glucose, total cholesterol, high density lipoprotein-cholesterol (HDL-C)) were measured using standard methods. Insulin levels were measured using an electrochemiluminescence immunoassay, while OPG levels were measured using the ELISA technique. Low density lipoprotein-cholesterol (LDL-C), body mass index (BMI) and Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) were calculated using standard methods. Abdominal obesity was defined as a waist circumference ≥ 80 cm.
  
  
  RESULTS
  OPG levels were higher in obese than in normal subjects, though the difference was not significant (p = 0.9). BMI, waist circumference, percent body fat and systolic blood pressure were significantly higher in obese than in non-obese subjects (p < 0.05). In these subjects, only age significantly correlated with OPG levels (r = 0.831, p = 0.003), while none of the anthropometric nor metabolic parameter did, even after adjustment for age. In obese subjects, OPG levels fairly correlated with HDL-C (r = 0.298, p = 0.058), and significantly correlated with HOMA-IR (r = -0.438, p = 0.018). After adjustment for age, OPG levels remained negatively correlated to HOMA-IR (r = -0.516, p = 0.020) and LDL-C (r = -0.535, p = 0.015) and positively correlated to HDL-C (r = 0.615, p = 0.004). In multiple linear regression analysis, age was a main determinant of OPG levels in non-obese (β = 0.647, p = 0.006) and obese (β = 0.356, p = 0.044) women. HDL-C was also associated to OPG levels in obese women (β = 0.535, p = 0.009).
  
  
  CONCLUSIONS
  The positive correlation of OPG with HDL-C and HOMA-IR, and its negative correlation with LDL-C suggest that it may be a marker of insulin sensitivity/resistance and atherogenic risk in obese African women.
authors.affiliation: Department of Animal Science, Faculty of Science, University of Douala, Douala, Cameroon.
authors.forename: Clarisse Noël
authors.initials: CN
authors.lastname: Ayina Ayina
authors.affiliation: Department of Internal Medicine and Specialties, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon ; Laboratory for Molecular Medicine and Metabolism, Biotechnology Center, University of Yaoundé I, Yaoundé, Cameroon ; National Obesity Center, Yaoundé Central Hospital, Yaoundé, Cameroon.
authors.forename: Eugene
authors.initials: E
authors.lastname: Sobngwi
authors.affiliation: Department of Internal Medicine and Specialties, Faculty of Medicine and Biomedical Sciences, University of Yaoundé I, Yaoundé, Cameroon.
authors.forename: Mickael
authors.initials: M
authors.lastname: Essouma
authors.affiliation: Department of Medicine, Groote Schuur Hospital and University of Cape Town, Cape Town, South Africa ; Medical Diagnostic Center, Yaoundé, Cameroon.
authors.forename: Jean Jacques N
authors.initials: JJ
authors.lastname: Noubiap
authors.affiliation: Department of Hormonal Biology, Saint-Louis Hospital, Public Assistance - Paris Hospitals, University Paris-Diderot Paris-7, Paris, France ; Department of Diabetes and Endocrinology, Saint-Louis Hospital, Public Assistance - Paris Hospitals, University Paris-Diderot Paris-7, Paris, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Boudou
authors.affiliation: Department of Animal Science, Higher Teacher's Training College, University of Yaoundé I, Yaoundé, Cameroon.
authors.forename: Laurent Serge
authors.initials: LS
authors.lastname: Etoundi Ngoa
authors.affiliation: Department of Diabetes and Endocrinology, Saint-Louis Hospital, Public Assistance - Paris Hospitals, University Paris-Diderot Paris-7, Paris, France ; INSERM UMRS 1138, Cordeliers Research Centre, University Pierre et Marie Curie-Paris 6, Paris, France.
authors.forename: Jean François
authors.initials: JF
authors.lastname: Gautier
keywords: Insulin resistance; Lipids; Obesity; Osteoprotegerin; Sub-Saharan Africans