Peroxisome proliferator-activated receptors (PPARs) are a family of transcription factors with a key role in glucose and lipid metabolism. PPARs are expressed in many cell types including pancreatic beta cells and immune cells, where they regulate insulin secretion and T cell differentiation, respectively. Moreover, various PPAR agonists prevent diabetes in the non-obese diabetic (NOD) mouse model of type 1 diabetes. PPARs are thus of interest in type 1 diabetes (T1D) as they represent a novel approach targeting both the pancreas and the immune system. In this review, we examine the role of PPARs in immune responses and beta cell biology and their potential as targets for treatment of T1D.
Type 1 diabetes (T1D) is an autoimmune disease with rising incidence. Pre‐ and manifest T1D is associated with intestinal barrier dysfunction, skewed microbiota composition, and serum dyslipidemia. The intestinal mucus layer protects against pathogens and its structure and phosphatidylcholine (PC) lipid composition may be compromised in T1D, potentially contributing to barrier dysfunction. This study compared prediabetic Non‐Obese Diabetic (NOD) mice to healthy C57BL/6 mice by analyzing the intestinal mucus PC profile by shotgun lipidomics, plasma metabolomics by mass spectrometry and nuclear magnetic resonance, intestinal mucus production by histology, and cecal microbiota composition by 16 S rRNA sequencing. Jejunal mucus PC class levels were decreased in early prediabetic NOD vs C57BL/6 mice. In colonic mucus of NOD mice, the level of several PC species was reduced throughout prediabetes. In plasma, similar reductions of PC species were observed in early prediabetic NOD mice, where also increased beta‐oxidation was prominent. No histological alterations were found in jejunal nor colonic mucus between the mouse strains. However, the β‐diversity of the cecal microbiota composition differed between prediabetic NOD and C57BL/6 mice, and the bacterial species driving this difference were related to decreased short‐chain fatty acid (SCFA)‐production in the NOD mice. This study reports reduced levels of PCs in the intestinal mucus layer and plasma of prediabetic NOD mice as well as reduced proportions of SCFA‐producing bacteria in cecal content at early prediabetes, possibly contributing to intestinal barrier dysfunction and T1D.
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