Jan-Dirk Raguse

The human TAS2R16 receptor mediates bitter taste in response to beta-glucopyranosides.

Bitter taste generally causes aversion, which protects humans from ingesting toxic substances. But bitter flavors also contribute to the palatability of food and beverages, thereby influencing nutritional habits in humans. Although many studies have examined bitter taste, the underlying receptor mechanisms remain poorly understood. Anatomical, functional and genetic data from rodents suggest the existence of a family of receptors that are responsive to bitter compounds. Here we report that a human member of this family, TAS2R16, is present in taste receptor cells on the tongue and is activated by bitter β-glucopyranosides. Responses to these phytonutrients show a similar concentration dependence and desensitization in transfected cells and in experiments assessing taste perception in humans. Bitter compounds consisting of a hydrophobic residue attached to glucose by a β-glycosidic bond activate TAS2R16. Thus, TAS2R16 links the recognition of a specific chemical structure to the perception of bitter taste. If the ability of TAS2R16 to detect substances with common molecular properties is typical of the bitter receptor family, it may explain how a few receptors permit the perception of numerous bitter substances.

Gustatory Expression Pattern of the Human TAS2R Bitter Receptor Gene Family Reveals a Heterogenous Population of Bitter Responsive Taste Receptor Cells

Human bitter taste is mediated by ∼25 members of the human TAS2 receptor (hTAS2R) gene family. The hTAS2R genes are expressed in taste buds of gustatory papillae on the tongue surface. Because many naturally occurring bitter compounds are toxic, bitter taste receptors are believed to serve as warning sensors against the ingestion of toxic food compounds. An important question is whether bitter taste receptor cells are a homogeneous, broadly tuned population of cells, which uniformly express all bitter taste receptor genes, or not. Gene expression analyses in rodents demonstrated an essentially overlapping expression of TAS2R genes indicating a broad tuning, whereas functional in vivo analyses suggest a narrow tuning. The present study demonstrates the expression of all 25 human TAS2R genes in taste receptor cells of human circumvallate papillae. As shown by in situ hybridization experiments, the expression of hTAS2R genes differs in both the apparent level of expression and the number of taste receptor cells expressing these genes, suggesting a heterogeneous bitter taste receptor cell population. Differences in gene expression levels were verified by quantitative reverse transcription-PCR experiments for a subset of hTAS2R genes. Direct evidence for the heterogeneity of bitter taste receptor cells is provided by dual-labeling in situ hybridizations with selected pairs of hTAS2R gene-specific probes. Functional coexpression experiments in heterologous cells show competition among hTAS2Rs, indicating a possible biological reason for the observed expression pattern. From the data, we conclude that human bitter taste receptor cells are tuned to detect a limited subset of bitter stimuli.

The role of lipolysis in human orosensory fat perception

Taste perception elicited by food constituents and facilitated by sensory cells in the oral cavity is important for the survival of organisms. In addition to the five basic taste modalities, sweet, umami, bitter, sour, and salty, orosensory perception of stimuli such as fat constituents is intensely investigated. Experiments in rodents and humans suggest that free fatty acids represent a major stimulus for the perception of fat-containing food. However, the lipid fraction of foods mainly consists of triglycerides in which fatty acids are esterified with glycerol. Whereas effective lipolysis by secreted lipases (LIPs) liberating fatty acids from triglycerides in the rodent oral cavity is well established, a similar mechanism in humans is disputed. By psychophysical analyses of humans, we demonstrate responses upon stimulation with triglycerides which are attenuated by concomitant LIP inhibitor administration. Moreover, lipolytic activities detected in minor salivary gland secretions directly supplying gustatory papillae were correlated to individual sensitivities for triglycerides, suggesting that differential LIP levels may contribute to variant fat perception. Intriguingly, we found that the LIPF gene coding for lingual/gastric LIP is not expressed in human lingual tissue. Instead, we identified the expression of other LIPs, which may compensate for the absence of LIPF.

Rehabilitation of irradiated patients with modified and conventional sandblasted acid‐etched implants: preliminary results of a split‐mouth study

PURPOSE The aim of this study was to evaluate the success rate of chemically modified and conventional sandblasted acid-etched surface (SLA) titanium implants in irradiated oral squamous cell carcinoma patients. MATERIAL AND METHODS Twenty patients with a mean age of 61.1 years were treated with dental implants after ablative surgery and radio-chemotherapy of oral cancer. All patients were non-smokers. The placement of SLA and modSLA implants was performed bilaterally according to a split-mouth design. All 102 implants (50 SLA, 52 modSLA) placed showed an unloaded healing time of 6 weeks in the mandible and 10 weeks in the maxilla. Mean crestal bone changes using standardized orthopantomographies and clinical parameters like pocket depths, mPII and mBI were evaluated. RESULTS Of 102 implants, 55 implants (27 SLA implants, 28 modSLA) were located in the maxilla and 47 implants (23 SLA, 24 modSLA) in the mandible. The average observation period was 14.4 months. The amount of bone loss at the implant shoulder of SLA implants was 0.4 mm mesial and 0.4 mm distal. The modSLA implants displayed a bone loss of mesial 0.3 mm and distal 0.3 mm. Two SLA implants were lost resulting in a success rate of 96%. The success rate of modSLA implants was 100%. CONCLUSION Regarding the data found in this investigation, we can conclude that implants with chemically modified and conventional SLA titanium surface show high success rates in irradiated patients. SLA implants with or without a chemically modified surface regardless of the location can be restored with a high predictability of success at least in the short time range observed.

A comprehensively characterized large panel of head and neck cancer patient-derived xenografts identifies the mTOR inhibitor everolimus as potential new treatment option

Patient‐derived xenograft (PDX) models have shown to reflect original patient tumors better than any other preclinical model. We embarked in a study establishing a large panel of head and neck squamous cell carcinomas PDX for biomarker analysis and evaluation of established and novel compounds. Out of 115 transplanted specimens 52 models were established of which 29 were characterized for response to docetaxel, cetuximab, methotrexate, carboplatin, 5‐fluorouracil and everolimus. Further, tumors were subjected to sequencing analysis and gene expression profiling of selected mTOR pathway members. Most frequent response was observed for docetaxel and cetuximab. Responses to carboplatin, 5‐fluorouracil and methotrexate were moderate. Everolimus revealed activity in the majority of PDX. Mutational profiling and gene expression analysis did not reveal a predictive biomarker for everolimus even though by trend RPS6KB1 mRNA expression was associated with response. In conclusion we demonstrate a comprehensively characterized panel of head and neck cancer PDX models, which represent a valuable and renewable tissue resource for evaluation of novel compounds and associated biomarkers.

Detection of circulating tumor cells for prediction of recurrence after adjuvant chemoradiation in locally advanced squamous cell carcinoma of the head and neck

BACKGROUND The prognostic role of persistence of circulating tumor cells (CTC) after upfront tumor surgery for outcome of adjuvant (chemo)radiation in locally advanced squamous cell carcinoma of the head and neck (LASCCHN) was evaluated. PATIENTS AND METHODS In this prospective study, peripheral blood samples from 144 patients with LASCCHN presenting after tumor resection for adjuvant treatment were analyzed for CTC. Their detection was correlated with tumor site, clinical risk factors, disease-free (DFS) and overall survival (OS). RESULTS CTC were detected in 42 of 144 patients (29%). CTC detection was higher in cases with nodal involvement and in carcinomas located at the tonsil or base of tongue but was not influenced by age, smoking history, T stage, extracapsular lymph node extension, surgical margins or the human papillomavirus status. Overall, the presence of CTC was not predictive for OS or DFS. However, while in oropharyngeal carcinomas (OPC, n = 63), the detection of CTC was associated per trend with improved DFS [CTC+ versus CTC- (% of patients without evidence of disease at 2 years): 100% versus 79%; log rank: P = 0.059]; the reverse was observed for carcinomas from other sites (non-OPC, n = 81; CTC+ versus CTC-: 29% versus 75%; P = 0.001). In multivariate analysis, CTC remained an independent prognostic marker for DFS [hazard ratio (HR) 4.3, 95% confidence interval (CI) 1.7-10.9, P = 0.002] and OS (HR 2.7, 95% CI 1.2-6.3, P = 0.016) in non-OPC. CONCLUSIONS Assessment of CTC in non-OPC should prove useful for identification of patients who benefit from treatment intensification. The basis for the good prognostic value of CTC in OPC has to be elucidated in future studies.

Immunohistochemical detection of TAS2R38 protein in human taste cells.

The sense of taste plays an important role in the evaluation of the nutrient composition of consumed food. Bitter taste in particular is believed to serve a warning function against the ingestion of poisonous substances. In the past years enormous progress was made in the characterization of bitter taste receptors, including their gene expression patterns, pharmacological features and presumed physiological roles in gustatory as well as in non-gustatory tissues. However, due to a lack in TAS2R-specifc antibodies the localization of receptor proteins within gustatory tissues has never been analyzed. In the present study we have screened a panel of commercially available antisera raised against human bitter taste receptors by immunocytochemical experiments. One of these antisera was found to be highly specific for the human bitter taste receptor TAS2R38. We further demonstrate that this antibody is able to detect heterologously expressed TAS2R38 protein on Western blots. The antiserum is, however, not able to interfere significantly with TAS2R38 function in cell based calcium imaging analyses. Most importantly, we were able to demonstrate the presence of TAS2R38 protein in human gustatory papillae. Using double immunofluorescence we show that TAS2R38-positive cells form a subpopulation of PLCbeta2 expressing cells. On a subcellular level the localization of this bitter taste receptor is neither restricted to the cell surface nor particularly enriched at the level of the microvilli protruding into the pore region of the taste buds, but rather evenly distributed over the entire cell body.

Patient and treatment-related risk factors for osteoradionecrosis of the jaw in patients with head and neck cancer

OBJECTIVE The purpose of this study was to evaluate risk factors for and the incidence of osteoradionecrosis (ORN) of the jaw in patients with head and neck cancer. STUDY DESIGN This study was a retrospective analysis of the risk for ORN and outcome for 149 of 540 patients with head and neck cancer of the oral cavity (65%), oropharynx (26%), or other head and neck sites (9%) treated with radiotherapy between 2004 and 2009. ORN was graded according to Late Effects of Normal Tissues/Somatic Objective Management Analytic Scale (LENT/SOMA) criteria. RESULTS Within a median follow-up of 41 months (95% confidence interval: 27.4-54.6), 38 patients (25.5%) had developed ORN, 37 patients (25%) had a local recurrence, and 53 patients (36%) had died. The median time to diagnosis of ORN was 14.5 months (range: 3-80), and 79% were diagnosed within 2 years of RT. Eleven of these patients had undergone previous mandibular surgery. Univariate significant risk factors for ORN were any comorbidity, poor oral hygiene, pre-radiotherapy osteotomy, close tumor-to-bone proximity, post-radiotherapy dentoalveolar surgery (DAS), DAS without sufficient wound closure, alcohol consumption, and denture pressure sores. In multivariate analysis, comorbidities, pre-radiotherapy mandibular surgery, poor oral hygiene, and insufficient DAS remained significant. CONCLUSIONS Reducing the risk of ORN calls for maintaining optimal oral hygiene, ensuring good denture fit, receiving proper training in DAS, and helping patients to stop drinking and smoking.

Long-term retrospective evaluation of the peri-implant bone level in onlay grafted patients with iliac bone from the anterior superior iliac crest

OBJECTIVE The purpose of the present study was to evaluate crestal bone level changes around dental implants after iliac bone augmentation in the long term. MATERIAL AND METHODS A total of 32 partially edentulous/edentulous patients (mean age, 52 years; range, 22-70 years) and a remaining bone volume of less than 5 mm of the alveolar ridge underwent maxillary or mandibular iliac bone graft augmentation. All patients received spaced standardized radiological examination for evaluation of peri-implant crestal bone loss. RESULTS The grafting procedure was successfully performed in all patients. A total of 150 implants were placed. The mean observation period was 69 months (range, 12-165 months; success rate for maxilla, 96%; success rate for mandible, 92%). The mean amount of crestal bone loss after 10 years was 1.8 mm. A significant difference between gender and crestal bone loss was shown, but no influence was found regarding the implant system, diameter of implant, and age of the patients. CONCLUSION In patients with atrophic jaws, a sufficient long-term reconstruction can be achieved with the combination of iliac onlay grafting and dental implants. The results demonstrate high success rates and a stable peri-implant bone level in the long term.

Incidence and management of severe odontogenic infections—A retrospective analysis from 2004 to 2011

The management of odontogenic infections is a typical part of the spectrum of maxillofacial surgery. Normally these infections can be managed in a straight forward way however under certain conditions severe and complicated courses can arise which require interdisciplinary treatment including intensive care. A retrospective analysis of all patients affected by an odontogenic infection that received surgical therapy from 2004 to 2011 under stationary conditions was performed. Surgical treatment consisted in incision and drainage of the abscess supported by additional i.v. antibiotic medication in all patients. Detailed analysis of all patients that required postoperative intensive medical care was additionally performed with respect to special risk factors. During 8 years 814 patients affected by odontogenic infections received surgical treatment under stationary conditions representing 4% of all patients that have been treated during that period (n = 18981). In 14 patients (1.7%) intensive medical therapy after surgery was required, one lethal outcome was documented (0.12%). In all of these 14 patients a history of typical risk factors was present. According to these results two patients per week affected by an odontogenic infection required stationary surgical treatment, about two patients per year were likely to require additional intensive medical care. If well-known risk factors are present in patients affected by odontogenic infection appropriate interdisciplinary management should be considered as early as possible.