Products of Mature Adipocytes in Visceral Fat of Obese Patients Impair Esophageal Epithelial Barrier Formation and Function

Abstract

ObjectiveVisceral obesity is associated with GERD and its complications of reflux esophagitis, Barrett’s esophagus and esophageal adenocarcinoma. A traditional explanation for these associations is that visceral fat causes pathological acid reflux by increasing intra‐abdominal pressure. However, for unknown reasons, the esophagus of obese patients who have normal esophageal acid exposure can exhibit evidence of impaired epithelial barrier function including dilated intercellular spaces (DIS) and reduced transepithelial resistance (TER). In this study, we explored our hypothesis that the visceral fat of obese individuals secretes substances that impair esophageal barrier function, thus predisposing to injury by GERD.MethodsWe obtained subcutaneous (SQ) and visceral (VIS) fat from 1 non‐obese (BMI 18) and 2 obese (BMIs 51& 42) patients having foregut surgery; VIS included both mesenteric fat and gastroesophageal junction (GEJ) fat pad. Fat contains both mature adipocytes (MAs) and adipocyte derived stem cells (ADSCs), which were isolated from adipocyte tissues by collagenase digestion and differential centrifugation; immunofluorescence (CD90+, CD44+, CD31−, CD45−) was used to confirm ADSC isolation. Telomerase‐immortalized normal, human esophageal squamous cells (NES‐B10T) were seeded into transwells and grown to confluence for 3 days. On day 4, the cells were raised to an air‐liquid interface (ALI) to allow for differentiation, stratification, and formation of an esophageal epithelial barrier. ALI cultures were exposed to conditioned media (CM) from MAs or ADSCs, or to control NES medium beginning at day 4. TER was measured (in Ω·cm2) on days 4, 6, and 8 using the EVOM2 Epithelial Volt/Ohm Meter (World Precision Instruments, Sarasota, FL). On day 10, ALI cultures were stained with H&E and imaged.ResultsCM from ADSCs of SQ and VIS fat from an obese patient did not reduce the TER of NES ALI cultures at any time point; CM from MAs of SQ fat from all 3 patients also did not reduce TER. In contrast, CM from MAs of VIS fat from both obese patients significantly reduced TER on day 6 compared with control medium; TER also remained lower than control on day 8 (Table 1). CM from MAs of VIS fat from the non‐obese patient did not reduce TER of NES ALI cultures at any time point (Table 1). H&E staining demonstrated DIS only in those ALI cultures grown with the CM from MAs of VIS fat from the obese patients.ConclusionsSubstances produced by MAs, but not by ADSCs, in the VIS fat of obese patients impair esophageal epithelial barrier integrity and cause morphologic changes of DIS. No such effects were found for substances produced by MAs in the SQ fat of any patient, or from those produced by MAs in VIS fat of the non‐obese patient. Moreover, VIS fat in the mesentery and at the GEJ exert similar functional and morphologic effects on esophageal barrier formation. We are conducting further investigations to identify the mechanisms underlying the impairment of esophageal barrier formation caused by visceral adiposity, specifically for the GEJ fat pad that surrounds the distal esophagus.Support or Funding InformationBaylor Scott & White Research Institute Transepithelial Resistance (Ω·cm2 ±SEM) of NES on Day 6 and Day 8 of ALI Culture Exposed to Conditioned Media from Mature Adipocytes from Subcutaneous (SQ), Mesenteric, and GEJ Adipocyte Tissues BMI Control Day 6 SQ Day 6 Mesenteric Day 6 GEJ Day 6 Control Day 8 SQ Day 8 Mesenteric Day 8 GEJ Day 8 18 241±2.1 242±2.0 234±2.0 235±2.5 245±3.8 256±2.2 243±4.2 248±7.2 51 212±2.0 204±3.5 194±3.0 * 192±0.5 ** 235±8.5 233±1.0 209±6.5 207±8.0 42 264±3.6 263±5.5 236±2.3 ** 239±3.3 ** 251±2.4 296±45 249±0.9 237±2.6 * *p≤0.05; **p≤0.01 compared with control