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Differential effects of polyamine depletion by DENSpm and DFMO on beta cell stress reponses and type 1 diabetes outcomes in mice

ABSTRACT: Type 1 diabetes (T1D) is an autoimmune disease leading to dysfunction and loss of insulin-secreting β cells. In β cells, polyamines have been implicated in causing cellular stress and dysfunction. An inhibitor of polyamine biosynthesis, difluoromethylornithine (DFMO), has been shown to delay T1D in mouse models and preserve β cell function in humans with recent-onset T1D. Another small molecule, N1,N11-diethylnorspermine (DENSpm), both inhibits polyamine biosynthesis and accelerates polyamine metabolism and is currently being tested for efficacy in cancer clinical trials. In this study, we show that DENSpm depletes intracellular polyamines as effectively as DFMO in mouse β cells. RNA sequencing analysis, however, suggests that the cellular reponses to DENSpm and DFMO differ, with the two sharing similar effects on cellular proliferation, but the latter showing greater effects on mRNA translation and protein folding pathways. In the low-dose streptozotocin-induced mouse model of T1D, DENSpm administration did not prevent or delay diabetes outcome, but did result in improvements in glucose tolerance and reductions in islet oxidative stress. In non-obese diabetic (NOD) mice, short-term DENSpm administration resulted in slight reduction in insulitis and proinflammatory Th1 cells in the pancreatic lymph nodes. Longer term treatment resulted in a dose-dependent increase in mortality. Notwithstanding the efficacy of both DFMO and DENSpm in reducing potentially toxic polyamine levels in β cells, our results highlight the discordant T1D outcomes that result from differing mechanisms of polyamine depletion and, more importantly, that toxic effects of DENSpm may limit its utility in T1D treatment.

ORGANISM(S): Mus musculus

PROVIDER: GSE242725 | GEO | 2024/01/01

REPOSITORIES: GEO

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Project description:Streptococcus pneumoniae (Spn), a Gram-positive bacterium, poses a significant threat to human health, causing mild respiratory infections to severe invasive conditions. Despite availability of vaccines, challenges persist due to serotype replacement and antibiotic resistance, emphasizing the need for alternative therapeutic strategies. This study explores the intriguing role of polyamines, ubiquitous, small organic cations, in modulating virulence factors, especially the capsule, a crucial determinant of Spn's pathogenicity. Utilizing chemical inhibitors, difluoromethylornithine (DFMO) and AMXT 1501, this research unveils distinct regulatory effects on the gene expression of Spn D39 serotype in response to altered polyamine homeostasis. DFMO inhibits polyamine biosynthesis, disrupting pathways associated with glucose import and interconversion of sugars. In contrast, AMXT 1501, targeting polyamine transport, enhances the expression of polyamine and glucose biosynthesis genes, presenting a novel avenue for regulating the capsule independent of glucose availability. Despite ample glucose availability, AMXT 1501 treatment downregulates glycolytic pathway, fatty acid synthesis and ATP synthase, crucial for energy production while upregulating two-component systems responsible for stress management. This suggests a potential shutdown of energy production and capsule biosynthesis, redirecting resources towards stress management. Following DFMO and AMXT 1501 treatments, countermeasures such as upregulation of stress response genes and ribosomal protein were observed but appear to be insufficient to overcome the deleterious effects on capsule production. This study highlights the complexity of polyamine-mediated regulation in S. pneumoniae, particularly, capsule biosynthesis. Our findings offer valuable insights into potential therapeutic targets for modulation of capsule in a polyamine dependent manner, a promising avenue for intervention against S. pneumoniae infections.

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Differential effects of polyamine depletion by DENSpm and DFMO on beta cell stress reponses and type 1 diabetes outcomes in mice

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