Food scarcity under long photoperiod suppresses Tshβ expression in
the pars tuberalis
To test at what level of the signaling cascade metabolic cues act to
modify PNES output signals, we measured gene expression levels in the
posterior and anterior hypothalamus. Because the posterior hypothalamic
block did not contain the pars distalis, Tshβ expression can be
exclusively attributed to the pars tuberalis. Tshβ expression was
significantly reduced (50% reduction) in male voles at high workloads
(Fig. 2A,C; Table S4). In males, this effect is stronger in common voles
than in tundra voles (Fig. 2A,C, Table S4). In females, this effect was
only observed in common voles at 10°C (Fig. 2B,D; Table S4). Temperature
did not affect Tshβ expression, but a significant reduction was
found only in female common voles at 10°C (Fig. 2A-D; Table S4).
Overall, Tshβ and gonadal weight show a positive relationship
(Fig. 3A-D), indicating that Tshβ is involved in suppressing
gonadal development when food is scarce.
After translation, TSHβ and αGSU locally dimerize to form active TSH,
which can bind to its receptor (TSHr) located in the tanycytes around
the third ventricle of the brain. Workload did not affect Tshrexpression in both sexes of both species (Fig. 2A-D, Table S4). Although
common vole females show slightly elevated Tshr expression at
10°C, general Tshr levels were lower in common voles than in
tundra voles (Fig. 2A-D, Table S4).
Although TSH generally leads to increased Dio2 levels, workload
induced changes in Tshβ are not reflected in Dio2expression (Fig. 2A-D), suggesting that modifying factors other than TSH
can affect posterior hypothalamic Dio2 expression.
Kiss1 expressing neurons are located in the ARC nucleus in the posterior
hypothalamus and are involved in metabolic regulation and food intake.
For this reason, it was unexpected that workload and temperature did not
affect Kiss1 expression in the posterior hypothalamus (Fig. 2A-D,
Table S4).
The DMH and VMH of the posterior hypothalamus are nuclei that are
involved in the regulation of feeding behavior and both these areas are
capable of expressing Rfrp3 . Although overall Rfrp3expression was higher at 21°C, no effects of workload on Rfrp3expression were observed (Fig. 2A-D, Table S4).