Type 1 diabetes (T1D) is a chronic autoimmune disorder manifested with elevated blood glucose levels, which is attributed to insulin deficiency evoked by loss of the pancreatic islet β-cells [1]. Globally, T1D has been estimated to have a growing incidence, with an overall annual increase of approximately 2–3% [2]. Impaired immune regulation has been regarded as a feature of a subgroup of T1D patients, and the onset of T1D correlates with immune-mediated selective disruption of pancreatic insulin-producing β-cells [3]. An existing study has expounded that activation of β cell-reactive T cells, pro-inflammatory response, and failed immune modulation of auto-reactive responses are three prerequisites of the T1D progression [4]. Although recent innovations in techniques such as glucose sensing and insulin delivery have shown great benefit in managing diabetes, reducing the burden of self-care, and facilitating prognosis improvement [5], there remains a challenge for the treatment and prevention of T1D due to complicated mechanisms underpinning the immune regulation in this disease.

Recently, increasing evidence has illustrated that the gut microbiota is associated with the immune system in the development of T1D [6,7]. Their abundance, stability, and connectivity all have associations with the progression of T1D, which is potentially linked to the modulations of intestinal permeability and immunity [8,9]. It has been unveiled that microbes may exert pro- and anti-autoimmunity roles through different receptors, such as toll-like receptors (TLRs) [10]. On the one hand, the microbiota can up-regulate self-reactive T cells, polarize Th1 and Th17 to stimulate the activation of inflammation-promoting, self-reactive T cells, and reduce the anti-inflammatory metabolites to trigger the failure of autoimmune response [11]. On the other hand, live, non-pathogenic microbes (such as probiotics) or microbial components show the potential to affect the immune system through activating immune receptors or anti-inflammatory cytokines within the intestinal environment, which hold great promise for the management and prevention of T1D [12].

Paeoniflorin (PF) is a water-soluble monoterpene glycoside derived from Shaoyao (known as Paeonia lactiflora Pall). It's well known that PF possesses multiple medicinal properties, encompassing anti-inflammatory, antioxidant, and anti-depressive effects, immune-modulatory role as well as cardio-, neuro-, hepato-protective functions, etc. [13]. Interestingly, the anti-depressive activity of PF is reported to be achieved possibly through altering the gut microbiota compositions and increasing the abundance of probiotics [14]. A recent study has suggested that PF plays an anti-diabetic role through disrupting the p38 MAPK and JNK pathways [15], yet the anti-diabetic mechanism of PF remains largely elusive. Given the crucial significance of TLRs in the immune system during the progression of T1D [16]. This study principally aims to explore whether PF could modulate microbiota-mediated TLR pathways to control the activity of immune cells in T1D, thereby affecting the onset and progression of T1D.