Taste receptor cells use multiple signaling pathways to detect chemicals in potential food items. These cells are functionally grouped into different types: Type I cells act as support cells and have glial-like properties; Type II cells detect bitter, sweet, and umami taste stimuli; and Type III cells detect sour and salty stimuli. We have identified a new population of taste cells that are broadly tuned to multiple taste stimuli including bitter, sweet, sour, and umami. The goal of this study was to characterize these broadly responsive (BR) taste cells. We used an IP 3 R3-KO mouse (does not release calcium (Ca 2+) from internal stores in Type II cells when stimulated with bitter, sweet, or umami stimuli) to characterize the BR cells without any potentially confounding input from Type II cells. Using live cell Ca 2+ imaging in isolated taste cells from the IP 3 R3-KO mouse, we found that BR cells are a subset of Type III cells that respond to sour stimuli but also use a PLCβ signaling pathway to respond to bitter, sweet, and umami stimuli. Unlike Type II cells, individual BR cells are broadly tuned and respond to multiple stimuli across different taste modalities. Live cell imaging in a PLCβ3-KO mouse confirmed that BR cells use this signaling pathway to respond to bitter, sweet, and umami stimuli. Short term behavioral assays revealed that BR cells make significant contributions to taste driven behaviors and found that loss of either PLCβ3 in BR cells or IP 3 R3 in Type II cells caused similar behavioral deficits to bitter, sweet, and umami stimuli. Analysis of c-Fos activity in the nucleus of the solitary tract (NTS) also demonstrated that functional Type II and BR cells are required for normal stimulus induced expression.

Original Article OBESITY BIOLOGY AND INTEGRATED PHYSIOLOGY Study ImportanceWhat is already known?► Obesity is often associated with impaired taste. ► The mechanisms associating obesity and taste are poorly understood. What does this study add?► Our study on diet-induced obese mice demonstrates that high-fat diet and excess weight can each contribute to impaired taste. ► There is selectivity in the effects of diet and weight that varies by stimulus.Objective: Previous studies have reported that individuals with obesity have reduced taste perception, but the relationship between obesity and taste is poorly understood. Earlier work has demonstrated that diet-induced obesity directly impairs taste. Currently, it is not clear whether these changes to taste are due to obesity or to the high-fat diet exposure. The goal of the current study was to determine whether diet or excess weight is responsible for the taste deficits induced by diet-induced obesity.Methods: C57BL/6 mice were placed on either high-fat or standard chow in the presence or absence of captopril. Mice on captopril did not gain weight when exposed to a high-fat diet. Changes in the responses to different taste stimuli were evaluated using live cell imaging, briefaccess licking, immunohistochemistry, and real-time polymerase chain reaction.Results: Diet and weight gain each affected taste responses, but their effects varied by stimulus. Two key signaling proteins, α-gustducin and phospholipase Cβ2, were significantly reduced in the mice on the highfat diet with and without weight gain, identifying a potential mechanism for the reduced taste responsiveness to some stimuli. Conclusions: Our data indicate that, for some stimuli, diet alone can cause taste deficits, even without the onset of obesity.Obesity (2020) 28, 284-292.

Invasive fungal infections are a leading global cause of human mortality. Only three major classes of antifungal drugs are widely used, and resistance to all three classes can arise rapidly. The most widely prescribed antifungal drug, fluconazole, disseminates rapidly and reaches a wide range of concentrations throughout the body. The impact of drug concentration on the spectrum and effect of mutations acquired during adaptation is not known for any fungal pathogen, and how the specific level of a given stress influences the distribution of beneficial mutations has been poorly explored in general. We evolved 144 lineages from three genetically distinct clinical isolates of Candida albicans to four concentrations of fluconazole (0, 1, 8, and 64 μg/ml) and performed comprehensive phenotypic and genomic comparisons of ancestral and evolved populations. Adaptation to different fluconazole concentrations resulted in distinct adaptive trajectories. In general, lineages evolved to drug concentrations close to their MIC50 (the level of drug that reduces growth by 50% in the ancestor) tended to rapidly evolve an increased MIC50 and acquired distinct segmental aneuploidies and copy number variations. By contrast, lineages evolved to drug concentrations above their ancestral MIC50 tended to acquire a different suite of mutational changes and increased in drug tolerance (the ability of a subpopulation of cells to grow slowly above their MIC50). This is the first evidence that different concentrations of drug can select for different genotypic and phenotypic outcomes in vitro and may explain observed in vivo drug response variation.

Objective Previous studies have reported that individuals with obesity have reduced taste perception, but the relationship between obesity and taste is poorly understood. Earlier work has demonstrated that diet‐induced obesity directly impairs taste. Currently, it is not clear whether these changes to taste are due to obesity or to the high‐fat diet exposure. The goal of the current study was to determine whether diet or excess weight is responsible for the taste deficits induced by diet‐induced obesity. Methods C57BL/6 mice were placed on either high‐fat or standard chow in the presence or absence of captopril. Mice on captopril did not gain weight when exposed to a high‐fat diet. Changes in the responses to different taste stimuli were evaluated using live cell imaging, brief‐access licking, immunohistochemistry, and real‐time polymerase chain reaction. Results Diet and weight gain each affected taste responses, but their effects varied by stimulus. Two key signaling proteins, α‐gustducin and phospholipase Cβ2, were significantly reduced in the mice on the high‐fat diet with and without weight gain, identifying a potential mechanism for the reduced taste responsiveness to some stimuli. Conclusions Our data indicate that, for some stimuli, diet alone can cause taste deficits, even without the onset of obesity.

Aim Loss of dystrophin causes oxidative stress and affects nitric oxide synthase‐mediated vascular function in striated muscle. Because tetrahydrobiopterin is an antioxidant and co‐factor for nitric oxide synthase, we tested the hypothesis that tetrahydrobiopterin would be low in mdx mice and humans deficient for dystrophin. Methods Tetrahydrobiopterin and its metabolites were measured at rest and in response to exercise in Duchenne and Becker muscular dystrophy patients, age‐matched male controls as well as wild‐type, mdx and mdx mice transgenically overexpressing skeletal muscle‐specific dystrophins. Mdx mice were also supplemented with tetrahydrobiopterin and pathophysiology was assessed. Results Duchenne muscular dystrophy patients had lower urinary dihydrobiopterin + tetrahydrobiopterin/specific gravity1.020 compared to unaffected age‐matched males and Becker muscular dystrophy patients. Mdx mice had low urinary and skeletal muscle dihydrobiopterin + tetrahydrobiopterin compared to wild‐type mice. Overexpression of dystrophins that localize neuronal nitric oxide synthase restored dihydrobiopterin + tetrahydrobiopterin in mdx mice to wild‐type levels while utrophin overexpression did not. Mdx mice and Duchenne muscular dystrophy patients did not increase tetrahydrobiopterin during exercise and in mdx mice tetrahydrobiopterin deficiency was likely because of lower levels of sepiapterin reductase in skeletal muscle. Tetrahydrobiopterin supplementation improved skeletal muscle strength, resistance to fatiguing and injurious contractions in vivo, increased utrophin and capillary density of skeletal muscle and lowered cardiac muscle fibrosis and left ventricular wall thickness in mdx mice. Conclusion These data demonstrate that impaired tetrahydrobiopterin synthesis is associated with dystrophin loss and treatment with tetrahydrobiopterin improves striated muscle histopathology and skeletal muscle function in mdx mice.