A rodent model of partial intestinal diversion: a novel metabolic operation

Vitamin D enhances the therapeutic effect of TNF-α antibodies through lipid metabolism in overweight IBD patients

The inhibitory effects of the tumor necrosis factor-α (TNF-α) antibody infliximab (IFX) on colitis are well established. Since IFX dosing is weight-based and associated with various side effects, there is a growing interest in identifying combination therapies that can enhance its efficacy, particularly in overweight inflammatory bowel disease (IBD) patients, to maximize the anti-inflammatory effect while minimizing the required dose. Our research revealed that overweight IBD patients present decreased vitamin D levels in the intestinal epithelium alongside elevated TNF-α levels. In mice fed a high-fat diet (HFD) for four weeks, treatment with the vitamin D analog palicalcitol (PAL) reduced lipid synthesis and TNF-α production in intestinal epithelial cells (IECs). In a 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced experimental colitis model, PAL treatment mitigated TNF-α-induced damage to the intestinal epithelial barrier and reduced the activation of Th1 and Th17 cells in the lamina propria, thereby reducing colitis development in HFD-fed mice. Notably, the combination of IFX and PAL was more effective than IFX alone in treating colitis in these mice. Overall, our findings suggest that vitamin D inhibits TNF-α production by reducing lipid synthesis in IECs, thereby enhancing IFX therapy in overweight IBD patients.

The Phantom Satiation Hypothesis of Bariatric Surgery

The excitation of vagal mechanoreceptors located in the stomach wall directly contributes to satiation. Thus, a loss of gastric innervation would normally be expected to result in abrogated satiation, hyperphagia, and unwanted weight gain. While Roux-en-Y-gastric bypass (RYGB) inevitably results in gastric denervation, paradoxically, bypassed subjects continue to experience satiation. Inspired by the literature in neurology on phantom limbs, I propose a new hypothesis in which damage to the stomach innervation during RYGB, including its vagal supply, leads to large-scale maladaptive changes in viscerosensory nerves and connected brain circuits. As a result, satiation may continue to arise, sometimes at exaggerated levels, even in subjects with a denervated or truncated stomach. The same maladaptive changes may also contribute to dysautonomia, unexplained pain, and new emotional responses to eating. I further revisit the metabolic benefits of bariatric surgery, with an emphasis on RYGB, in the light of this phantom satiation hypothesis.