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Title: Gut hormones and adiponectin : receptors and effects in bone-related cells
Author: Pacheco-Pantoja, Elda Leonor
ISNI:       0000 0004 2702 0773
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2010
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In recent years, the relationship of gut hormones and adipocytokines with bone processes has received increased attention. It represents one aspect of the current skeletal investigation. The understanding of these interactions between bone metabolism and gastrointestinal or adipose tissue function must take into account homeostasis, appetite, neural system, and lifestyle. The proportion of bone mass to soft tissue is a relationship that seems to be controlled by delicate and subtle regulations that imply "cross-talks" between the nutrient intake and tissues like fat. Thus, recognition of the mechanisms that integrate a gastrointestinal-fat-bone axis and its application to a number of aspects of human health is vital for improving treatments related to bone diseases. This thesis analysed some of the aspects of experimental research regarding the effects of gut hormones and adiponectin when they were present in cell cultures of osteoblastic cell lines. mRNA expression levels of five gut hormone receptors were analysed in three osteoblastic cell lines (Saos-2, TE-85 and MG-63) using molecular biology techniques (reverse transcription and real time polymerase chain reaction, RT-qPCR). The gut hormone receptor mRNA expression was positive for GIPr, GHSr and GPR39 in the three cell lines whereas GLP-I r and GLP-2r were only expressed in the least mature cell lines (MG-63 and TE-8S). The responses to the gut peptides were studied finding significant changes in viability, and biochemical bone markers like alkaline phosphatase (ALP), procollagen type 1 amino-terminal propeptides (P 1NP), and osteocalcin production. Other experiments included the study of induction of e-fos in presence or absence of extracellular nucleotides using a luciferase assay and RT-qPCR. Adiponectin receptors and effects were investigated in one of the osteoblastic cell lines, Saos-2, finding the presence of the receptors in these cells. Functional studies revealed that adiponectin caused significant changes in viability, ALP and PI NP production. Significant changes were also observed in osteoprotegerin expression. The adiponectin receptors were additionally investigated in peripheral blood mononuclear cell (PBMC) cultures since they are the precursor for osteoclasts. The experiments were carried out in the presence or absence of cytokines (M-CSF, RANKL) which stimulate PBMC to commit to differentiation to osteoclastic cells. The levels of AdipoRI were higher than AdipoR2 when evaluated by qPCR. Immunofluorescence using anti-AdipoR 1 and -AdipoR2, displayed specific green emission in foci located mainly in the periphery of the cells but also in the cytosol in cells that were cultured up to 21 days with M-CSF and RANKL. These observations in immunofluorescence suggest that the adiponectin receptor could be undergoing redistribution in the osteoclastic cells. Taking together all the results it is enticing to speculate that the distribution of bone and soft masses is regulated by the direct effects of the hormones involved in the absorption of nutrients (gut hormones) and those produced in soft tissues like fat, as in the case of adiponectin.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available