Abstract
The reproductive phase-dependent and sex-related differential expression of leptin (lep) and its receptor (lepr) in primary and secondary lymphoid organs of a highly nutritive economically important Channa punctata preempts the involvement of sex steroids in modulating intra-immuno-leptin system. This hypothesis was strengthened when plasma testosterone (T) and estradiol (E2) levels in male and female fish of reproductively active spawning and quiescent phases were correlated with lep and lepr expression in their immune organs. Splenic lep and lepr showed a negative correlation with T in both male and female, while with E2 there was a positive correlation in male and negative in female C. punctata. In head kidney, a contrasting correlation was observed as compared to spleen. To validate the implication of sex steroids in regulating leptin system in immune organs, in vivo and in vitro experiments were performed with DHT and E2. Upon administration, lep and lepr expression in tissues of either sex was downregulated. In addition, in vitro results with either of the sex steroids exemplified their direct involvement. Overall, this study, for the first time, reports correlation between sex steroids and transcript expression of leptin system in immune organs of a seasonally breeding vertebrate.
Highlights
This hypothesis was strengthened when plasma testosterone (T) and estradiol (E2) levels in male and female fish of reproductively active spawning and quiescent phases were correlated with lep and lepr expression in their immune organs
The present study aimed to investigate the reproductive phase-dependent and sex-related variations in expression of leptin and leptin receptor in primary and secondary lymphoid organs, head kidney and spleen, respectively, of an adult Channa punctata
The expression of lep and lepr in immune organs of C. punctata preempts the direct role of leptin in regulation of immune system in fishes
Summary
This hypothesis was strengthened when plasma testosterone (T) and estradiol (E2) levels in male and female fish of reproductively active spawning and quiescent phases were correlated with lep and lepr expression in their immune organs. Sexual dimorphism is unveiled in levels of leptin in blood plasma[16,17] and adipose tissue[18,19] in mammals, being significantly higher in females than males. These sex-related differences in leptin protein and mRNA levels exist regardless of the amount of body fat[16]. The data is represented as mean fold change ± standard error of mean (SEM)
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