Cattini, P. A. | bioRxiv Science

bioRxiv2024

A Locus Control Region Generates Distinct Active Placental Lactogen And Inactive Growth Hormone Gene Domains In Term Placenta That Are Disrupted With Obesity

A Placental villi include an outer layer of syncytiotrophoblasts (STBs) and an inner layer of cytotrophoblasts (CTBs) that fuse to generate STBs in pregnancy. While activation of the single locus containing the human (h) placental lactogen (hPL) genes (hPL-A/CSH1 and hPL-B/CSH2) begins in the CTBs, their expression in STBs requires further epigenetic modifications as well as interactions between locus control region (LCR) and gene regulatory sequences. No transcription factor that limits or facilitates hPL LCR/gene interactions for locus activation is reported but the paternally-expressed gene 3 (PEG3/PW1) transcription factor is a candidate. PEG3 is expressed by villous CTBs but not STBs, and putative PEG3 sites were identified in the hPL LCR and promoter sequences. Furthermore, dysregulation of both hPL and PEG3 gene expression have been linked to peripartum depression. Using CTB-like JEG-3 cells, we show PEG3 binding to hypersensitive sites (HS III-V) within the LCR, and that hPL transcript levels increase with PEG-3 knockdown. In term placenta, PEG3 binding at placenta-specific HS IV was increased with maternal obesity, where a decrease in hPL RNA levels is seen, while PEG3 binding was reduced in women with obesity who develop insulin-treated gestational diabetes mellitus (O/GDM+Ins), where increased hPL gene expression is observed. Chromatin conformation capture revealed distinct hPL gene domain interactions that are modified with maternal obesity but largely reversed in O/GDM+Ins, correlating with PEG3 binding. Thus, decreased PEG3 binding may be required for hPL domain generation and expression during CTB to STB transition.

molecular biology↗

bioRxiv2024

Increased capacity to maintain glucose homeostasis in a transgenic mouse expressing human but not mouse growth hormone with developing high fat diet-related insulin resistance, steatosis and adipose dysfunction

ObjectiveDifferences in primate and non-primate growth hormone (GH) genes can affect their regulation and function. This includes the ability of human (h) but not mouse (m) GH to bind the prolactin (PRL) receptor (PRLR) as well as the GH receptor (GHR). Potential differential effects were assessed in male hGH- or mGH-expressing mice and fed high fat diet (HFD) versus regular chow diet (RCD). Pancreas and epididymal white adipose tissue (eWAT) gene expression and/or related function were targeted as the pancreas responds to both PRLR and GHR signaling and catabolic effects like lipolytic activity are more directly attributable to GH and GHR signaling. DesignA transgenic CD-1 mouse expressing hGH but not mGH under hypothalamic control was generated to compare with wild type CD-1 mice and size and bone density determined. Glucose clearance, islet area, insulin and insulin-like growth factor (IGF) -2 gene expression were assessed as well as serum glucose and insulin levels in mice fed a HFD versus RCD for 8 and 24 weeks. Adiposity, liver and serum triglycerides as well as eWAT cell area, cytokine (leptin and adiponectin) and senescence-related marker (p21CIP1 and p16INK4a) RNA levels were also assessed. ResultsMale hGH-expressing transgenic CD-1[{Delta}mGH.hGH] mice have significantly lower liver IGF-1 RNA levels and are smaller based on length and weight than wild type CD-1[mGH] mice. They also have [~]1.5-fold higher total body fat and serum triglyceride levels. However, CD-1[{Delta}mGH.hGH] and CD-1[mGH] mice grow at the same rate with similar cortical and trabecular bone densities. Unlike CD-1[mGH] mice, there was no significant delay in glucose clearance in CD-1[{Delta}mGH.hGH] mice after 8 weeks on a HFD versus RCD; while basal (RCD) serum insulin levels were similar, fasting glucose levels were lower and pancreas IGF-2 RNA levels were increased in CD-1[{Delta}mGH.hGH] mice. However, both CD-1[{Delta}mGH.hGH] and CD-1[mGH] showed evidence of increased insulin resistance after 24 weeks on HFD, including delayed glucose clearance in spite of increased pancreatic islet area and insulin production as well as signs of liver steatosis and increased hepatic triglyceride levels. These increases correlated with elevated PRLR but not GHR RNA levels. Assessment of eWAT revealed >2-fold larger adipocytes in CD-1[{Delta}mGH.hGH] compared to CD-1 [mGH] mice fed RCD at both 12 and 28 weeks. This was associated with an [~]2.6-fold increase in leptin RNA levels at 12 weeks and [~]58% lower adiponectin RNA levels at 28 weeks. A >2-fold increase in p21CIP1 transcript levels was also detected in eWAT from both CD-1[{Delta}mGH.hGH] and CD-1 [mGH] mice fed RCD with age (28 versus 12 weeks) but were unaffected by diet. However, a >2-fold increase in p16INK4a RNA levels was observed after 24 weeks on HFD. ConclusionsWhile limited to observations in the male, transgenic CD-1[{Delta}mGH.hGH] mice exhibit signs of GH insufficiency and eWAT adipocyte dysfunction. These mice also show an initial resistance to the negative effects of HFD on glucose clearance when compared to CD-1[mGH] mice, which is potentially related to a differential effect of hGH versus mGH on pancreas development and/or function.

physiology↗