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- Dunder, Linda
(författare)
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Exposure to Bisphenol A (BPA) and Metabolic Disruption
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Metbolic disorders such as obesity, type 2 diabetes, liver lipid disorders and metabolic syndrome are increasing rapidly and have largely been attributed to genetic background and changes in diet, exercise and aging. However, there is now considerable evidence showing that other environmental factors, including environmental chemicals, may contribute to the rapid increase in the incidence of these metabolic diseases. Of particular growing concern is low-dose developmental exposure to endocrine disrupting chemicals (EDCs). The developing period is an extremely sensitive window of exposure to environmental stressors, including EDCs, and early life exposure has been linked to metabolic disorders later in life. Consistent with hormones, EDCs can act at very low serum concentrations and even small changes in the endocrine system may lead to extensive effects. The overall aim of this thesis has been to investigate potential metabolic disruption following exposure to Bisphenol A (BPA), which is a known EDC. The experimental animal study demonstrated that male and female rat offspring generally exhibited differential susceptibility to developmental exposure to BPA (0.5 µg/kg BW/day or 50 µg/kg BW/day). The main results showed that the lowest dose of BPA induced increased plasma triglyceride levels and increased adipocyte cell density in inguinal white adipose tissue in female offspring. Further, this low dose increased fatty acid indices and altered the fatty acid composition in male offspring and enhanced insulin secretion in pancreatic islets from male and female offspring and dams. Contrastingly, the higher BPA-dose decreased insulin secretion in pancreatic islets from male and female offspring and dams. The increased fatty acid indices, and the altered fatty acid composition together with enhanced insulin secretion may be early risk factors for insulin resistance. Furthermore, depending on the tissue, dose and sex, BPA altered the expression of genes involved in lipid and adipocyte homeostasis.The epidemiological study with a meta-analysis of data from the National Health and Nutrition Survey (NHANES) did not disclose any associations between urinary BPA and dyslipidemia. However, considering the cross-sectional nature of the present study, this should rather be investigated in carefully designed prospective cohort studies with repeated BPA measurements. Nonetheless, we hope that this paper can encourage researchers to evaluate NHANES data using meta-analyses instead of pooling of data.This thesis concludes that exposure to BPA, which is a known EDC, most likely is a contributor, along with genetic, social and behavioral factors, to the development of metabolic disorders.
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| 2. |
- Halin Lejonklou, Margareta, 1966-
(författare)
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The MEN 1 Pancreas : Tumor Development and Haploinsufficiency
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Multiple Endocrine Neoplasia Type I Syndrome (MEN 1) is a monogenic autosomal dominantly inherited cancer syndrome caused by a heterozygous loss of the MEN1 gene, predisposing for endocrine cell proliferation and tumor formation. MEN 1 carriers classically develop tumors in endocrine organs; the parathyroids, the endocrine pancreas, and the pituitary. Other organs, endocrine and non-endocrine, may also be affected. The most common cause of death in MEN 1 is pancreatic endocrine tumor (PNET), which exhibit inactivation of both MEN1 alleles. The increased proliferation prior to loss of the wild-type allele indicates haploinsufficiency, and little is known concerning the mechanisms behind MEN 1 PNET development. The MEN1 protein, menin, lacking homology with other known proteins, is involved in several aspects of transcriptional regulation and chromatin organization.We report differential expression and subcellular localization of transcription factors important in pancreatic development, in human and mouse MEN 1 pancreas, compared to non-MEN 1 pancreas. A predominantly cytoplasmic localization of Neurogenin3 and NeuroD1 was observed in tumors as well as in MEN 1 non-tumorous pancreas.Notch signaling factor expression and localization were examined in the pancreas of a heterozygous Men1 mouse model, and compared with that of wild-type littermates. Nuclear Hes1 was lost in tumors, concomitant to weaker Notch1 NICD expression, and further, analyzed using qPCR, it was shown that Notch1 was less expressed in heterozygous islets compared to wild-type islets.Performing a global gene expression array, we identified differential gene expression in five-week-old heterozygous Men1 mouse islets, compared to islets from wild-type littermates. The array results for a subset of the differentially regulated genes were corroborated using qPCR, western blotting and in situ PLA. We additionally observed significantly accelerated proliferation in islets from young heterozygous animals.It is often problematic to determine prognosis for individual patients with PNET. This is especially true in the group of patients with well differentiated endocrine carcinomas. In the absence of metastases, morphological signs of malignancy are frequently lacking. We evaluated the expression of nuclear and cytoplasmic survivin in a clinically characterized patient material (n=111), and a high nuclear survivin expression proved to be a significant negative prognostic factor for survival.
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| 3. |
- Lind, Thomas, Docent, 1965-, et al.
(författare)
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Developmental low-dose exposure to bisphenol A induces chronic inflammation, bone marrow fibrosis and reduces bone stiffness in female rat offspring only
- 2019
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Ingår i: Environmental Research. - : Elsevier BV. - 0013-9351 .- 1096-0953. ; 177
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Tidskriftsartikel (refereegranskat)abstract
- Background: Developmental exposure to low doses of the endocrine disruptor bisphenol A (BPA) is known to alter bone tissue in young rodents, although how bone tissue is affected in aged animals is not well known. We have recently shown that low-dose developmental exposure to BPA increases procollagen type I N-terminal propeptide (P1NP) levels, a peptide formed during type 1 collagen synthesis, in plasma of 5-week-old female rat offspring while male offspring showed reduced bone size.Objective: To analyze offspring bone phenotype at 52 weeks of age and clarify whether the BPA-induced increase in P1NP levels at 5 weeks is an early sign of bone marrow fibrosis development.Methods: As in our 5-week study, pregnant Fischer 344 rats were exposed to BPA via drinking water corresponding to 0.5 mu g/kg BW/day (BPA0.5), which is in the range of human daily exposure, or 50 mu g/kg BW/day (BPA50) from gestational day 3.5 until postnatal day 22. Controls were given only vehicle. The offspring were sacrificed at 52 weeks of age. Bone effects were analyzed using peripheral quantitative and micro-computed tomography (microCT), 3-point bending test, plasma markers and histological examination.Results: Compared to a smaller bone size at 5 weeks, at the age of 52 weeks, femur size in male offspring had been normalized in developmentally BPA-exposed rats. The 52-week-old female offspring showed, like the 5-week-old siblings, higher plasma P1NP levels compared to controls but no general increasing bone growth or strength. However, 2 out of 14 BPA-exposed female offspring bones developed extremely thick cortices later in life, discovered by systematic in vivo microCT scanning during the study. This was not observed in male offspring or in female controls. Biomechanical testing revealed that both doses of developmental BPA exposure reduced femur stiffness only in female offspring. In addition, histological analysis showed an increased number of fibrotic lesions only in the bone man ow of female rat offspring developmentally exposed to BPA. In line with this, plasma markers of inflammation, Tnf (in BPA0.5) and Timpl (in BPA50) were increased exclusively in female offspring.Conclusions: Developmental BPA exposure at an environmentally relevant concentration resulted in female specific effects on bone as well as on plasma biomarkers of collagen synthesis and inflammation. Even a dose approximately eight times lower than the current temporary EFSA human tolerable daily intake of 4 mu g/kg BW/day, appeared to induce bone stiffness reduction, bone man ow fibrosis and chronic inflammation in female rat offspring later in life.
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