Bisphosphonate affects the behavioral responses to HCl by disrupting farnesyl diphosphate synthase in mouse taste bud and tongue epithelial cells

Diagnosis and treatment of taste disorders in Japan

Though 270,000 patients with complaints of taste abnormalities visited medical institutions annually in 2019 survey, there are no drugs for the treatment of taste disorders that are covered by health insurance in Japan. In the survey, the number of patients with taste disorders was correlated with age, and the need for medical treatment for taste disorders is expected to increase in the future because of the super-aging society. The pathophysiology of taste disorders varies widely. There is an obvious need to decide the site and the causes of the disorder and understand the mechanism, by performing various examinations. It needs to first adjust the causative systemic diseases and medications in the treatment for taste disorder. Damage of taste cells due to zinc deficiency is the main pathophysiological mechanism of taste disorders, and zinc supplementation is a standard treatment in Japan. Oral zinc therapy is the treatment for taste disorders due to zinc deficiency or idiopathic taste disorder; though a double-blind study was conducted, it was considered low-level evidence in a clinical review. In Japan, the off-label use of polaprezinc for taste disorders was approved in 2011, and zinc acetate hydrate was approved for hypozincemia in March 2017, making it easier to use oral zinc therapy in general. In some cases, psychotherapy or herbal medicine therapy has been used with remarkable success, although its effectiveness has not been clearly tested. It might be expected to offer some help to patients. In the treatment of elderly patients with taste disorders, physicians need to consider the difference between "age-related changes in taste in healthy people" and "taste disorders in elderly persons", and they should separate them. Aggressive treatment is desirable regardless of age, because no significant difference in the efficacy of various treatments was found between patients older and younger than 65 years.

Cellular mechanisms of taste disturbance induced by the non-steroidal anti-inflammatory drug, diclofenac, in mice

Drug-induced taste disorders are a serious problem in an aging society. This study investigated the mechanisms underlying taste disturbances induced by diclofenac, a non-steroidal anti-inflammatory drug that reduces pain and inflammation by inhibiting the synthesis of prostaglandins by cyclooxygenase enzymes (COX-1 and COX-2). RT-PCR analyses demonstrated the expression of genes encoding arachidonic acid pathway components such as COX-1, COX-2 and prostaglandin synthases in a subset of mouse taste bud cells. Double-staining immunohistochemistry revealed that COX-1 and cytosolic prostaglandin E synthase (cPGES) were co-expressed with taste receptor type-1 member-3 (T1R3), a sweet/umami receptor component, or gustducin, a bitter/sweet/umami-related G protein, in a subset of taste bud cells. Long-term administration of diclofenac reduced the expression of genes encoding COX-1, gustducin and cPGES in mouse taste buds and suppressed both the behavioral and taste nerve responses to sweet and umami taste stimuli but not to other tastants. Furthermore, diclofenac also suppressed the responses of both mouse and human sweet taste receptors (T1R2/T1R3, expressed in HEK293 cells) to sweet taste stimuli. These results suggest that diclofenac may suppress the activation of sweet and umami taste cells acutely via a direct action on T1R2/T1R3 and chronically via inhibition of the COX/prostaglandin synthase pathway inducing down-regulated expression of sweet/umami responsive components. This dual inhibition mechanism may underlie diclofenac-induced taste alterations in humans.