Anterior Pituitary Transcriptomics Following a High Fat Diet:  Impact of oxidative stress on organelle pathology
Anterior pituitary cells are highly active with regards to protein synthesis and secretion, processes which depend heavily on mitochondrial ATP production and functional endoplasmic reticula.  It is well known that obesity adds an allostatic overload to tissues, requiring them to adapt to inflammation and oxidative stress.  Therefore, we hypothesized that the pituitary is highly vulnerable to the stress of high fat diet-induced weight gain. In this study, we utilized a 10-15 week high fat diet (HFD, 60%) plus a thermoneutral housing paradigm, testing both male and female FVB.129P mice. We quantified serum hormones and cytokines, characterized the metabolic phenotype, and defined changes in the pituitary transcriptome using single-cell RNA-seq. Weight gain was significant by 3 weeks in HFD mice, and by 10 weeks all HFD groups had gained 20 g.  HFD females (15 weeks) had increased energy expenditure and decreased activity. All HFD groups showed increases in serum leptin, Il-6, resistin, MCP-1, and TNFa. HFD males had increased insulin; both HFD males and females had increased TSH, and HFD females had decreased serum prolactin and growth hormone (GH) pulse amplitude.  Pituitary scRNA-seq revealed modest or no changes in pituitary cell gene expression in the different cell types from HFD males after 10 or 15 weeks or HFD females after 10 weeks.  However, females exposed to a HFD for 15 weeks showed significant numbers of differentially expressed genes in lactotropes and stem cells.  Pathway analyses identified a reduction in pathways that supported protein translation, ribosome biogenesis, and oxidative phosphorylation, indicating mitochondrial dysfunction.  Collectively, these studies reveal that pituitary cells from males are more resilient to the oxidative stress of obesity than females and identify the most vulnerable pituitary cell populations in females. Overall design: In this study, we utilized a 10-15 week high fat diet (HFD, 60%) plus a thermoneutral housing paradigm, testing both male and female FVB.129P mice. We quantified serum hormones and cytokines, characterized the metabolic phenotype, and defined changes in the pituitary transcriptome using single-cell RNA-seq.