The relationship of androgenic and estrogenic receptor distribution and CD36 expression in gastroesophageal fat pad, subcutaneous, and omental adipose tissue obtained during laparoscopic sleeve gastrectomy surgery and gastric resection

Obesity is a significant public health issue for both the present and the future. The primary pathological mechanism involves adipose tissue, which cannot respond physiologically to increased energy intake and thus expands through hypertrophy. Central adiposity, particularly the accumulation of fat around internal organs, can lead to organ and system damage, eventually resulting in organ failure. During this process, several systemic diseases such as diabetes mellitus (DM), hypertension (HT), and metabolic syndrome (MS) may occur. Estrogens influence obesity through estrogen receptor-1 (ESR1) and estrogen receptor-2 (ESR2), androgens through the androgen receptor (AR), and CD36 through the CD36 receptor, all affecting adipose tissue and lipid metabolism. Factors such as gender differences, menopause, pregnancy, and medication use can modify the expression of these receptors, potentially leading to obesity. In this study, we aimed to elucidate the relationship between different adipose tissue regions, ESR1, ESR2, AR, and CD36, and gender differences in obesity, using samples from patients who underwent bariatric surgery. The study included 33 male and female patients with obesity. Preoperative anthropometric measurements and laboratory data were recorded. Based on the three different adipose tissue regions sampled during surgery, the 33 patients were grouped into peritoneal, periperitoneal, and subcutaneous categories. Biochemical parameters, receptor expression levels, adipocyte diameters, and gender comparisons were conducted. The obtained tissues were first processed histologically, and adipocyte diameters were measured in micrometers (μm) under a microscope. mRNA synthesis from adipose tissues was followed by real-time PCR using predetermined primer sequences, and receptor expression levels were expressed using the LIVAC method. Results showed that ESR1, ESR2, and CD36 expressions were highest in the peritoneal region, followed by periperitoneal, and lowest in the subcutaneous region (p<0.001). AR expressions differed, being highest in the periperitoneal region and decreasing in the peritoneal and subcutaneous regions (p<0.001). Adipocyte diameters in the periperitoneal tissue were larger in males (p=0.030). In the peritoneal group, there was a significant positive XI XII correlation between ESR1 expression and HOMA-IR (r=0.417, p=0.016) and insulin (r=0.352, p=0.044), a significant positive correlation between ESR2 expression and HDL (r=0.376, p=0.031), and a significant negative correlation between AR expression and creatinine (r=-0.354, p=0.043) and potassium (r=-0.356, p=0.042). In the periperitoneal group, there was a significant positive correlation between CD36 expression and sodium (Na) levels (r=0.459, p=0.007). In the subcutaneous group, there was a significant positive correlation between ESR2 expression and LDL (r=0.401, p=0.021), a significant negative correlation between CD36 expression and triglycerides (TG) (r=-0.355, p=0.043), a significant positive correlation between CD36 expression and insulin (r=0.355, p=0.043), and a significant negative correlation between AR expression and BMI (r=0.343, p=0.049), and a significant positive correlation between AR expression and cortisol (r=0.384, p=0.028). There is no precedent in the literature for a study evaluating the same parameters used in this study. The results include unique findings from subgroup analyses. Due to the limited number of patients and the absence of a control group, further studies with larger patient populations and balanced gender distributions are needed on this topic.