The implication of adipocyte ATP-binding cassette A1 and G1 transporters in metabolic complications of obesity.

Obesity is characterised by imbalance in lipid metabolism manifested by high concentrations of circulating triacylglycerols and total cholesterol as well as low high-density lipoprotein (HDL) levels. Abnormalities related to these lipids lead to metabolic complications such as type 2 diabetes, arterial hypertension and cardiovascular disease. Despite extensive research, it is still unclear why a subset of obese subjects develop metabolic syndrome, while others do not. The aim of our work was to assess total and plasma membrane expressions of cholesterol transport proteins: adipocyte ATP-binding cassette A1 (ABCA1), adipocyte ATP-binding cassette G1 (ABCG1), class B scavenger receptor (SR-BI) in visceral and subcutaneous adipose tissue of obese subjects with and without metabolic syndrome. To keep our preliminary study group uniform, we focused on women, who constitute the majority of bariatric patients. The study was performed on 34 patients: 24 morbidly obese women subjected to bariatric surgery, half of whom had metabolic syndrome; and 10 lean subjects undergoing elective laparoscopic cholecystectomy. Total and plasma membrane expressions of cholesterol transport proteins (SR-BI, ABCA1 and ABCG1) were assessed in samples of both visceral and subcutaneous adipose and analysed in relation to other clinical and laboratory parameters. We demonstrated lower plasma membrane expressions of ABCG1 in visceral adipose tissue of obese patients with metabolic syndrome as compared to lean ones. In addition, total ABCG1 expressions in both types of adipose tissue were lower in morbidly obese patients with metabolic syndrome compared to those without metabolic syndrome. Plasma membrane ABCA1 expressions in visceral adipose tissue were lower in the group of morbidly obese patients without metabolic syndrome, compared to lean patients. We did not find any significant differences in SR-BI expressions. Because of ABCG1 is responsible for cholesterol efflux to HDL, reduced plasma membrane expression of ABCG1 in VAT of morbidly obese women with metabolic syndrome may leads to a significantly decreased concentration of HDL in serum. This may be also confirmed by high positive correlation between both parameters.