Ghrelin Is Produced in Taste Cells and Ghrelin Receptor Null Mice Show Reduced Taste Responsivity to Salty (NaCl) and Sour (Citric Acid) Tastants

Abstract

BackgroundThe gustatory system plays a critical role in determining food preferences, food intake and energy balance. The exact mechanisms that fine tune taste sensitivity are currently poorly defined, but it is clear that numerous factors such as efferent input and specific signal transduction cascades are involved.Methodology/Principal FindingsUsing immunohistochemical analyses, we show that ghrelin, a hormone classically considered to be an appetite-regulating hormone, is present within the taste buds of the tongue. Prepro-ghrelin, prohormone convertase 1/3 (PC 1/3), ghrelin, its cognate receptor (GHSR), and ghrelin-O-acyltransferase (GOAT , the enzyme that activates ghrelin) are expressed in Type I, II, III and IV taste cells of mouse taste buds. In addition, ghrelin and GHSR co-localize in the same taste cells, suggesting that ghrelin works in an autocrine manner in taste cells. To determine a role for ghrelin in modifying taste perception, we performed taste behavioral tests using GHSR null mice. GHSR null mice exhibited significantly reduced taste responsivity to sour (citric acid) and salty (sodium chloride) tastants.Conclusions/SignificanceThese findings suggest that ghrelin plays a local modulatory role in determining taste bud signaling and function and could be a novel mechanism for the modulation of salty and sour taste responsivity.

The alcohol-induced locomotor stimulation and accumbal dopamine release is suppressed in ghrelin knockout mice

“…One final explanation for the lack of a basal alcohol-drinking phenotype in the ghrelin knockout mice addresses the possibility that alcohol intake may involve taste and homeostatic regulation rather than rewardrelated regulation. However this appears less likely since GHS-R1A knockout mice, despite having normal basal alcohol consumption (presumably reflecting a normal taste experience to alcohol), show reduced taste responsively to other (salty and sour) tastants (Shin et al, 2010).…”

Taste perception, associated hormonal modulation, and nutrient intake

“…Hormones that bind to receptors on taste cells alter the palatability of food and, therefore, intake. Current knowledge of the hormonal modulation of taste function is summarized in Table 1 [60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77] and described in greater detail below.…”

“…G protein-coupled growth hormone secretagogue receptor-null mice are less responsive to sodium chloride and citric acid (but not sweet or bitter stimuli) relative to wild-type controls. 76 …”

Expression of NUCB2/nesfatin-1 in the taste buds of rats

“…Nesfatin-1 is a gastrointestinal tract hormone classically considered to be associated with appetite control, glucose homeostasis, and slimness. Recent reports have indicated that many peptides in the gastrointestinal tract that regulate appe- tite are co-expressed in taste bud cells [9][10][11][12], where they may play a modulatory role in fine tuning taste perception. Therefore, it is reasonable to speculate that nesfatin-1 is expressed in taste bud cells.…”

“…Recently, a number of reports have shown that many gastrointestinal acting peptides, such as cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1), and ghrelin that are classically considered to regulate appetite, also exist in taste cells and may play a role in the gustatory system [9][10][11][12]. Of these peptides, ghrelin is the only known hormone originating from gastric X/Alike cells that can stimulate food intake centrally [13].…”