Changes in serum glucose and lipids, and liver glycogen and phosphorylase during vitellogenesis in nature in the flounder (Platichtys flesus, L.)

Metabolic Changes During Growth and Reproductive Phases in the Liver of Female Goldfish (Carassius auratus)

Hormones of the brain-pituitary-peripheral axis regulate metabolism, gonadal maturation, and growth in vertebrates. In fish, reproduction requires a significant energy investment to metabolically support the production of hundreds of eggs and billions of sperms in females and males, respectively. This study used an LC-MS-based metabolomics approach to investigate seasonally-related changes in metabolic profile and energy allocation patterns in female goldfish liver. We measured basal metabolic profile in female goldfish at three phases of the reproductive cycle, including 1) Maximum growth period in postovulatory regressed phase, 2) mid recrudescence in fish with developing follicles, and 3) late recrudescence when the ovary contains mature ovulatory follicles. We also investigated changes in the liver metabolism following acute treatments with GnRH and GnIH, known to be involved in controlling reproduction and growth in goldfish. Chemometrics combined with pathway-driven bioinformatics revealed significant changes in the basal and GnRH/GnIH-induced hepatic metabolic profile, indicating that metabolic energy allocation is regulated to support gonadal development and growth at different reproductive cycles. Overall, the findings support the hypothesis that hormonal control of reproduction involves accompanying metabolic changes to energetically support gonadotropic and somatotropic activities in goldfish and other oviparous vertebrates.

Comparative metabolomics analysis of ovarian developmental stages in Macrobrachium nipponense

Rapid sexual maturity of female Macrobrachium nipponense is a severe problem for the aquaculture industry. To date, there have been only transcriptome studies investigating ovarian development, and studies using other tools, such as metabolomics are lacking. Metabolomics reveals changes in the level of metabolites in tissues in relation to current physiological characteristics, and can yield valuable insight into the growth and development of organisms. In this study, we systematically analyzed 15 samples from five different ovarian developmental stages in M. nipponense to learn more about how metabolites change over reproduction. Gas chromatography/time-of-flight mass spectroscopy revealed an array of different compounds and 83-162 pathways depending on the stage. Furthermore, 89 metabolites and 14 pathways were significantly different across stages. It is hypothesized that N-acetyl-N-formyl-5-methoxykynurenamine, ascorbate, fructose-2,6-bisphosphate, cortexolone and other metabolites that significantly differed by stage are regulated by hormones and are closely related to ovarian development. However, for other metabolites that changed with development, such as cytidine and xanthine, an association with ovarian development has yet to be revealed. Quantitative polymerase chain reaction was used to correlate gene changes to metabolites in the pathway for biosynthesis of plant secondary metabolites. We found that the TCA cycle rate may be the cause of female miniaturization during the reproductive period, and that the control of fatty acid content via aquaculture nutrition may be an exogenous tool for regulatory control of maturation. This study provides a systematic and comprehensive metabolomics analysis of ovarian development in M. nipponense and lays a foundation for addressing the problem of rapid sexual maturity.

Effects of 17 beta-estradiol and methyl testosterone on the activity of the thyroid gland in rainbow trout, Salmo gairdneri Richardson

Methyl testosterone (MT) and 17 beta-estradiol (E2), suspended either in sesame oil (and injected on alternate days) or in warm hydrogenated coconut oil (and injected once in the form of an "implant"), were administered intraperitoneally to nonvitellogenic rainbow trout (Salmo gairdneri Richardson). When given as sesame oil injections E2 significantly reduced plasma triiodo-L-thyronine (T3) levels and thyroid epithelial cell height (TEH), but had no apparent effect on plasma L-thyroxine (T4) levels. When given as a coconut oil "implant" E2 significantly reduced both plasma T3 and T4 levels. E2 also elevated the hepatosomatic index (HSI), plasma Ca2+, Mg2+, protein, triglyceride, and alkali-labile phosphoprotein (ALP) and hepatic lipid concentration, decreased hepatic glycogen levels, but was without effect on plasma Na+ and glucose levels. MT given via sesame oil injections significantly lowered plasma T3 levels, but was without effect on plasma T4 concentrations or TEH; the T3-lowering effect of MT was not evident when the steroid was given in the form of a coconut oil "implant." MT also effected a lowering of plasma Mg2+ and protein and hepatic lipid concentrations, but had no significant effect on HSI, plasma Na+, glucose triglyceride and ALP concentration, or hepatic glycogen levels. MT given as a series of injections lowered plasma Ca2+ levels, but was without effect when given as an "implant" and had no significant effect on plasma Ca2+. Intraperitoneal injections of ovine thyrotropin (TSH) (2 micrograms/g body wt) elicited an increase in both plasma T4 and T3 levels within 24 hr in E2-, MT-, and oil-injected groups. The TSH-stimulated increase in plasma T4 level was significantly less in the E2-treated fish compared with oil- or MT-treated groups. The TSH-stimulated increase in plasma T3 levels in both groups of steroid-treated fish was significantly less than that of the oil-injected controls.