Melanocortin-4 receptor (MC4R)-induced anorexigenic signaling in the hypothalamus controls body weight and energy homeostasis. So far, MC4R-induced signaling has been exclusively attributed to its coupling to G s proteins. In line with this monogamous G protein coupling profile, most MC4R mutants isolated from obese individuals showed a reduced ability to activate G s . However, some mutants displayed enhanced G s coupling, suggesting that signaling pathways independent of G s may be involved in MC4R-mediated anorexigenic signaling. Here we report that the G s signaling-deficient MC4R-D90N mutant activates G proteins in a pertussis toxin-sensitive manner, indicating that this mutant is able to selectively interact with G i/o proteins. Analyzing a hypothalamic cell line (GT1-7 cells), we observed activation of pertussis toxin-sensitive G proteins by the wild-type MC4R as well, reflecting multiple coupling of the MC4R to G s and G i/o proteins in an endogenous cell system. Surprisingly, the agouti-related protein, which has been classified as a MC4R antagonist, selectively activates G i/o signaling in GT1-7 cells. Thus, the agouti-related protein antagonizes melanocortin-dependent G s activation not only by competitive antagonism but additionally by initiating G i/o protein-induced signaling as a biased agonist.The melanocortin system has been shown to play a pivotal role in food intake and energy homeostasis. Therefore, dysfunction of the melanocortin system inevitably leads to an obese phenotype in mammals. Accordingly, targeted disruption of the melanocortin-4 receptor (MC4R) 2 gene in mice causes an obesity-diabetes syndrome characterized by hyperphagia, hyperinsulinemia, and hyperglycemia (1). The importance of MC4R signaling in the regulation of human metabolism has been highlighted by the finding that mutations in the MC4R gene are the most frequent monogenic cause of severe obesity (2-7).Signaling pathways involved in MC4R-mediated regulation of energy homeostasis have been attributed to its coupling to G s proteins and the resulting activation of the protein kinase A pathway (8, 9). Agouti and agouti-related protein (AGRP) are the only known endogenously occurring neuropeptides that block GPCR activity and are, therefore, classified as MCR antagonists. AGRP has been shown to block melanocortin signaling at MC3R and MC4R subtypes (10). In addition, it has been proposed that AGRP decreases basal as well as forskolinpromoted adenylyl cyclase activity, thus also acting as an inverse agonist on basal MCR activity (11). However, recent studies revealed that the effects of AGRP on appetite control are independent of melanocortin signaling (12, 13). For example, in mice deficient of the melanocortin precursor proopiomelanocortin starvation after AGRP neuron ablation is independent of melanocortin signaling (13). Thus, the orexigenic effects induced by AGRP appear to be mediated in a melanocortin-independent manner by a so far unknown mechanism.Interestingly, the aforementioned MC4R mutants isolated from obese pat...

Prognosis of patients with advanced extrahepatic cholangiocarcinoma (eCCA) is poor. The current standard first-line treatment is systemic chemotherapy (CT) with gemcitabine and a platinum derivate. Additionally, endobiliary radiofrequency ablation (eRFA) can be applied to treat biliary obstructions. This study aimed to evaluate the additional benefit of scheduled regular eRFA in a real-life patient cohort with advanced extrahepatic cholangiocarcinoma under standard systemic CT. All patients with irresectable eCCA treated at University Hospital Bonn between 2010 and 2020 were eligible for inclusion. Patients were stratified according to treatment: standard CT (n = 26) vs. combination of eRFA with standard CT (n = 40). Overall survival (OS), progression free survival (PFS), feasibility and toxicity were retrospectively analyzed using univariate and multivariate approaches. Combined eRFA and CT resulted in significantly longer median OS (17.3 vs. 8.6 months, p = 0.004) and PFS (12.9 vs. 5.7 months, p = 0.045) compared to the CT only group. While groups did not differ regarding age, sex, tumor stage and chemotherapy treatment regimen, mean MELD was even higher (10.1 vs. 6.7, p = 0.015) in the eRFA + CT group. The survival benefit of concomitant eRFA was more evident in the subgroup with locally advanced tumors. Severe hematological toxicities (CTCAE grades 3 – 5) did not differ significantly between the groups. However, therapy-related cholangitis occurred more often in the combined treatment group (p = 0.031). Combination of eRFA and systemic CT was feasible, well-tolerated and could significantly prolong survival compared to standard CT alone. Thus, eRFA should be considered during therapeutic decision making in advanced eCCA.

Background Endoscopic vacuum therapy (EVT) has become a standard treatment method for esophageal perforations in adults. However, experience with EVT in infants is scarce. In this retrospective case series, we report on four very young infants who were successfully treated with EVT for esophageal perforations of different etiology. Methods Four infants were diagnosed with esophageal perforations on day 7, 32, 35 and 159 of life, respectively. The youngest one was prematurely born in the 31st week of pregnancy weighing 980 g only. Three infants had perforations due to foreign body insertion (nasogastric tube or pulling through of percutaneous endoscopic gastrostomy (PEG) tube through the esophagus). One child had an anastomotic dehiscence after Foker’s surgery for atresia. In three children EVT was applied as first-line therapy for perforation, in one child EVT was a rescue therapy due to persisting leakage after surgical closure involving thoracotomy. Depending on the esophageal diameter, either an open-pore drainage film or polyurethane sponge was attached to a single-lumen 8 Fr suction catheter, endoscopically (or fluoroscopically by wire-guidance) placed into the esophagus (intraluminal EVT) and supplied with continuous negative pressure (ranging between 75 and 150 mmHg). The EVT system was exchanged twice per week. Results Complete closure of the perforation/leakage could be achieved in all four infants (100%) after 22 days of continuous EVT (median value; range 7–39) and 4.5 EVT exchanges (median value; range 1–12). No serious adverse events occurred. Conclusions EVT is an effective and safe addition to our therapeutic armamentarium in the management of esophageal perforations irrespective of its etiology. Here we prove the feasibility of EVT even in very young infants. The use of an extra thin vacuum open-pore drainage film is helpful to cope with the small esophageal diameter. EVT settings and exchange rates similar to those known from adult treatment were used.

Backround and study aims Duodenal cancer is the cancer most often seen in patients with familial adenomatous polyposis (FAP) who have undergone risk-reducing colonic surgery. Almost all patients with FAP eventually develop duodenal adenomas and risk for duodenal cancer is up to 12 % with poor prognosis. In addition, there is a rising concern regarding increased gastric cancer risk in patients with FAP. Our aim was to enhance polyp detection by using CE (CE) with the application of indigo carmine dye. Patient and methods We conducted a prospective, blinded study of patients with FAP undergoing endoscopic examination of the upper gastrointestinal tract. First, a standard white-light examination (WLE) was done followed by an examination performed by an endoscopist who was blinded to the previous examination, using chromoendoscopy (CE) (0.4 % indigo carmine dye). Results Fifty patients were included in the study. Using WLE, a median number of 13 adenomas (range 0–90) was detected compared to 23 adenomas/patient (range 0–150; P < 0.0001) detected after staining, leading to a higher Spigelman stage in 16 patients (32 %; P = 0.0003). CE detected significantly more larger adenomas (> 10 mm) than WLE (12 vs. 19; P = 0.0391). In the gastric antral region, a median number of 0 adenomas (range 0–6) before and 0.5 adenomas (range 0–7) after staining (P = 0.0025) were detected. Conclusion This prospective endoscopic trial, to our knowledge the largest in patients with FAP, showed a significant impact of CE on adenoma detection and therapeutic management in the upper gastrointestinal tract. This leads to more intensive surveillance intervals.