The research described in this thesis has, using the zebrafish as a model system, shed new light on the intricate relationship between TB and DM2, in particular on the role of leptin, SHP-1 and... Show moreThe research described in this thesis has, using the zebrafish as a model system, shed new light on the intricate relationship between TB and DM2, in particular on the role of leptin, SHP-1 and glucocorticoids.Leptin plays an important role during TB infection and has a huge impact on insulin sensitivity in zebrafish larvae. Similarly to what has been observed in the murine model, leptin deficiency in zebrafish increased the bacterial burden and mortality during the infection, leading to hyperglycemia and the development of insulin resistance. In addition, a novel SHP-1/SHP-2 inhibitor, NSC-87877, was shown to represent a promising anti-diabetic drug that can be used for further DM2 research, as it is able to rescue the phenotype of the leptin-deficient zebrafish and to restore glucose transport to the tissues. In contrast to metformin, NSC-87877 can act at very early developmental stages and inhibits the function of SHP-1 and factors that underlay impaired glucose metabolism, whereas metformin is mostly known to improve insulin sensitivity. Additionally, treatment with the glucocorticoid beclomethasone attenuates the metabolic changes associated with the infection, and transcriptional alterations induced by beclomethasone treatment suggest that genes involved in glucose metabolism, insulin and leptin signaling all play an important role in the modulation of the metabolism.Our data show that zebrafish larvae represent an interesting model system to investigate the complex pathology of TB, and the studies described in this thesis in which this model has been used have provided novel insights into the molecular mechanisms underlying wasting syndrome and the possibilities for adjunctive glucocorticoid therapy to alleviate this metabolic state. Show less
Background Leptin plays a critical role in the regulation of metabolic homeostasis. However, the molecular mechanism and cross talks between leptin and metabolic pathways leading to metabolic... Show moreBackground Leptin plays a critical role in the regulation of metabolic homeostasis. However, the molecular mechanism and cross talks between leptin and metabolic pathways leading to metabolic homeostasis across different species are not clear. This study aims to explore the effects of leptin in mice and zebrafish larvae by integration of metabolomics and transcriptomics. Different metabolomic approaches including mass spectrometry, nuclear magnetic resonance (NMR) and high-resolution magic-angle-spinning NMR spectrometry were used to investigate the metabolic changes caused by leptin deficiency in mutant ob/ob adult mice and lepb(-/-) zebrafish larvae. For transcriptome studies, deep RNA sequencing was used. Results Thirteen metabolites were identified as common biomarkers discriminating ob/ob mice and lepb(-/-) zebrafish larvae from their respective wild type controls: alanine, citrulline, ethanolamine, glutamine, glycine, histidine, isoleucine, leucine, methionine, phenylalanine, putrescine, serine and threonine. Moreover, we also observed that glucose and lipid levels were increased in lepb(-/-) zebrafish larvae compared to the lepb(+/+) group. Deep sequencing showed that many genes involved in proteolysis and arachidonic acid metabolism were dysregulated in ob/ob mice heads and lepb mutant zebrafish larvae compared to their wild type controls, respectively. Conclusions Leptin deficiency leads to highly similar metabolic alterations in metabolites in both mice and zebrafish larvae. These metabolic changes show similar features as observed during progression of tuberculosis in human patients, mice and zebrafish larvae. In addition, by studying the transcriptome, we found similar changes in gene regulation related to proteolysis and arachidonic acid metabolism in these two different in vivo models. Show less
