الملخص الإنجليزي
Background: Two types of white adipose tissue are found in humans that differ in
siological properties, namely, subcutaneous fat and visceral fat. Abdominal visceral obesity, in particular, has been found to contribute to increased cardiometabolic risk. Abdominal obesity becomes more prevalent in women as they age. During menopause, women become at higher cardiometabolic risk. This is partly attributed to increased visceral fat accumulation where visceral adipose tissue secretes inflammatory markers and adipocytokines, which may contribute to this cardiometabolic risk manifestation. Retinol binding protein (RBP4) is one of the adipokines that transport retinol in blood. RBP4 has been linked to visceral fat accumulation and its metabolic consequences. Although linked to metabolic risk, studies on the association of RBP4 with hormones, fat storage and metabolic risk in women are limited. A major limitation is the effect of hormonal alterations during the menstrual cycle in women. Aim: The main aim of this study is to investigate the association between circulating RBP4, body fat composition, and metabolic risk parameters and its relation with female hormone levels in healthy women.
Subjects and methods: This is a prospective cross sectional study involving 411 apparently healthy women (283 reproductive and 128 menopausal), age range (18-73 years). Subjects with any metabolic disorder, taking medications, alcoholics, smokers and pregnant were excluded from the study, Anthropometric measures including weight, height, waist circumference, hip, fat percentage, visceral fat and skin fold thickness were recorded for all subjects. Blood samples were collected during the beginning of follicular phase to overcome the limitation of hormonal variation. In this study, RBP4, major fat storage factors, lipids, HbAlc and other metabolic parameters were measured by specialized kits and clinical biochemistry auto-analyzer. Finally, all data obtained were analyzed by SPSS program version 23.
Results: We found a significant positive correlation of RBP4 with metabolic risk factors namely visceral fat, total fat percent, BMI, waist, total cholesterol, TG, LDL C, VLDL-C, glucose and HbAlc. Also, RBP4 had a negative correlation with HDL-C and muscle percent. Among all fat anthropometric measures, the most significant correlation of RBP4 was with visceral fat (p<0.001). Multiple regression analysis revealed that TG along with RBP4 were the major positive predictors of visceral fat accumulation (R?= 0.219, p<0.001) followed by insulin. On the other hand, insulin was the major predictor of subcutaneous fat, represented by abdominal subcutaneous fat (RP=0.142, p<0.001) and arm subcutaneous fat (R=0.104, p<0.001). RBP4 significantly correlated with decreased progesterone and estradiol levels, which may explain the significant difference in RBP4 levels between reproductive and menopausal women. This association was not found with any other lipogenic factors in this study. Conclusion: This study highlights the significance of RBP4 as a significant metabolic risk marker linked to visceral fat accumulation. Visceral fat was mainly predicted by RBP4 followed by insulin levels. On the other hand, subcutaneous fat was determined by insulin levels only. These results point out the clinical importance of RBP4 as an early marker of metabolic risk and visceral fat distribution in women.
