Sampling Thoracic Duct Lymph After Esophagectomy: A Pilot Study Investigating the "Gut-Lymph" Concept.

Background: Gut-lymph in animal models of acute disease is altered by intestinal ischemia and contributes to the development of systemic inflammation and organ dysfunction. Investigating gut-lymph in humans is hampered difficulty in accessing the thoracic duct (TD) for lymph sampling. The aims of this study were to develop and pilot a technique of intraoperative TD cannulation with delayed embolization to serially measure TD lymph pressure, flow, and composition (including markers of intestinal injury) during the early postoperative period and in response to enteral feeding and vasopressor treatment. Methods: A Seldinger technique was used for percutaneous TD cannulation during an Ivor Lewis esophagogastrectomy. Lymph flow rate and pressure were measured. TD lymph and plasma were sampled at 12 hourly intervals for up to 120 hours after surgery and before TD embolization. Biochemistry, lipids, cytokines, and markers of intestinal injury were measured before and after enteral feeding commenced at 36 hours. Results: Intraoperative TD cannulation was technically feasible in three of four patients. Delayed TD embolization was only successful in one of three patients, with two patients requiring a re-thoracotomy to treat chylothorax. Profound changes in TD composition, but not flow rate, occurred over time and in response to enteral feeding and vasopressors. TD lymph compared with plasma had significantly higher lipase (1.4-17 × ), interleukin-6 (8-108 × ), tumor necrosis factor-α (2.7-17 × ), d-lactate (0.3-23 × ), endotoxin (0.1-41 × ), and intestinal fatty acid binding protein (1.1-853 × ). Conclusions: Although TD cannulation and lymph sampling were successful, TD embolization failed in two of three patients. The composition of sampled TD lymph changed dramatically in response to enteral feeding, indicating intestinal ischemia that could be exacerbated by nonselective vasopressors. The higher concentration of proinflammatory cytokines and gut injury markers in TD lymph, compared with plasma, lends support to the gut-lymph concept.

Mesenteric lymphatic dysfunction promotes insulin resistance and represents a potential treatment target in obesity.

Visceral adipose tissue (VAT) encases mesenteric lymphatic vessels and lymph nodes through which lymph is transported from the intestine and mesentery. Whether mesenteric lymphatics contribute to adipose tissue inflammation and metabolism and insulin resistance is unclear. Here we show that obesity is associated with profound and progressive dysfunction of the mesenteric lymphatic system in mice and humans. We find that lymph from mice and humans consuming a high-fat diet (HFD) stimulates lymphatic vessel growth, leading to the formation of highly branched mesenteric lymphatic vessels that 'leak' HFD-lymph into VAT and, thereby, promote insulin resistance. Mesenteric lymphatic dysfunction is regulated by cyclooxygenase (COX)-2 and vascular endothelial growth factor (VEGF)-C-VEGF receptor (R)3 signalling. Lymph-targeted inhibition of COX-2 using a glyceride prodrug approach reverses mesenteric lymphatic dysfunction, visceral obesity and inflammation and restores glycaemic control in mice. Targeting obesity-associated mesenteric lymphatic dysfunction thus represents a potential therapeutic option to treat metabolic disease.

Intestinal Lymph Flow, and Lipid and Drug Transport Scale Allometrically From Pre-clinical Species to Humans.

The intestinal lymphatic system transports fluid, immune cells, dietary lipids, and highly lipophilic drugs from the intestine to the systemic circulation. These transport functions are important to health and when dysregulated contribute to pathology. This has generated significant interest in approaches to deliver drugs to the lymphatics. Most of the current understanding of intestinal lymph flow, and lymphatic lipid and drug transport rates, comes from in vitro studies and in vivo animal studies. In contrast, intestinal lymphatic transport studies in human subjects have been limited. Recently, three surgical patients had cannulation of the thoracic lymph duct for collection of lymph before and during a stepwise increase in enteral feed rate. We compared these data to studies where we previously enterally administered controlled quantities of lipid and the lipophilic drug halofantrine to mice, rats and dogs and collected lymph and blood (plasma). The collected lymph was analyzed to compare lymph flow rate, triglyceride (TG) and drug transport rates, and plasma was analyzed for drug concentrations, as a function of enteral lipid dose across species. Lymph flow rate, TG and drug transport increased with lipid administration in all species tested, and scaled allometrically according to the equation A = aM E where A is the lymph transport parameter, M is animal body mass, a is constant and E is the allometric exponent. For lymph flow rate and TG transport, the allometric exponents were 0.84-0.94 and 0.80-0.96, respectively. Accordingly, weight normalized lymph flow and TG mass transport were generally lower in larger compared to smaller species. In comparison, mass transport of drug via lymph increased in a greater than proportional manner with species body mass with an exponent of ∼1.3. The supra-proportional increase in lymphatic drug transport with species body mass appeared to be due to increased partitioning of drug into lymph rather than blood following absorption. Overall, this study proposes that intestinal lymphatic flow, and lymphatic lipid and drug transport in humans is most similar to species with higher body mass such as dogs and underestimated by studies in rodents. Notably, lymph flow and lipid transport in humans can be predicted from animal data via allometric scaling suggesting the potential for similar relationships with drug transport.

Surgical detachment of Descemet's membrane and endothelium imaged over time by in vivo confocal microscopy.

A 90-year-old woman developed a large circular capsulorhexis-like defect in Descemet's membrane as a complication of small incision cataract surgery. Nine months post-surgery, in vivo confocal microscopic examination of the temporal mid-peripheral cornea revealed an endothelial cell density of 934 +/- 69 cells/mm2 (normal range 1566-3088 cells/mm2). Endothelial pigmented deposits were visible as scattered hyper-reflective areas on the posterior endothelial surface. Descemet's folds were also noted. In vivo confocal microscopy performed 3 years later showed the temporal mid-peripheral corneal endothelial density (in the region of the break) was 948 +/- 66 cells/mm2. A reduction of endothelial polymegathism and pleomorphism was observed. Imaging in the region of the temporal portion of the original Descemet's defect showed well-defined linear structures with hyper-reflective edges. Compared to 3 years previously, the cornea at the level of Descemet's membrane appeared to have greater reflectivity. This case demonstrates how microstructural changes in the cornea can be described and analysed over time with the assistance of in vivo confocal microscopy.