Abstract
Saccharin sodium and rebaudioside A are extensively used as non-nutritive sweeteners (NNSs) in daily life. NNSs elicit a multitude of endocrine influences on animals, differing across species and chemically distinct sweeteners, whose exposure induce activation of sweet taste receptors in oral and extra-oral tissues with consequences of metabolic changes. To evaluate the influence of NNSs on histologic change and expression of sweet taste receptors in testis and epididymis of young male guinea pigs, thirty 4-week-old male guinea pigs with body weight 245.73 ± 6.02 g were randomly divided into five groups (n = 6) and received normal water (control group) and equivalent sweetness low dose or high dose of sodium saccharin (L-SS, 1.5 mM or H-SS, 7.5 mM) or rebaudioside A (L-RA, 0.5 mM or H-RA, 2.5 mM) solution for 28 consecutive days. The results showed that the relative testis weight in male guinea pig with age of 56 days represented no significant difference among all groups; in spite of heavier body weight in L-SS and H-RA, NNS contributes no significant influence on serum testosterone and estradiol level. Low-dose 0.5 mM rebaudioside A enhanced testicular and epididymal functions by elevating the expressions of taste receptor 1 subunit 2 (T1R2) and gustducin α-subunit (GNAT3), and high-dose 7.5 mM sodium saccharin exerted adverse morphologic influences on testis and epididymis with no effect on the expression of T1R2, taste receptor 1 subunit 2 (T1R3), and GNAT3. In conclusion, these findings suggest that a high dose of sodium saccharin has potential adverse biologic effects on the testes and epididymis, while rebaudioside A is a potential steroidogenic sweetener for enhancing reproductive functions.
Highlights
Taste or gustation is one of the five traditional senses including hearing, sight, touch, and smell, and the sense of taste has classically been limited to the five basic taste qualities: sweet, salty, sour, bitter, and umami or savory [1]
We found that the immunoreactions of anti-T1R2 and anti-GNAT3 antibodies on germ cells and Sertoli cells in LRA and H-RA were stronger than those in control, L-SS, and HSS (Figures 6A1–E1,A3–E3)
The mechanisms are likely synergistic and may differ across species [for example, genetic variants of sweet taste receptor gene associated with food intake [22] and chemically distinct non-nutritive sweeteners [14]]; we uncovered that dose-response metabolic manners to the equivalent sweetness NNS with artificial sodium saccharin and natural rebaudioside A were different in male guinea pigs
Summary
Taste or gustation is one of the five traditional senses including hearing, sight, touch, and smell, and the sense of taste has classically been limited to the five basic taste qualities: sweet, salty, sour, bitter, and umami or savory [1]. The percentage ratio of sweet taste to bitter taste may be a better gauge of the broadly conceived food value of a plant than sweetness alone [3]. Sweet and bitter and taste-receptor cells provide instructive signals to sweet and bitter target neurons via different guidance molecules [4]. Taste signal-modifying factors, such as serum components, may have a contributing role in agingrelated changes in taste sensitivity [6]. Taste perception has been investigated in “taste” and “no-taste” tissues, and components of taste transduction cascade in the testis are found to be involved in spermatogenesis [7], but functional implications of taste senses in the field of male reproduction remain unclear despite recent advances
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