It is hypothesized that viruses play an important role in the pathogenesis of Type I Diabetes (T1DM). Viral infection of beta (b) cells can initiate disease by direct cell damage, b-cell toxicity from the acute antiviral response, or release/induction of b-cell self-antigens triggering autoimmune destruction. Viruses and viral products such as synthetic double stranded (dsRNA), a viral replication intermediate, and polyinosinic-polycytidylic Acid (poly I:C), a synthetic dsRNA, both trigger abnormal expression of Toll-Like Receptor 3 (TLR3) and TLR3 signaling, triggering insulitis/b-cell apoptosis in BALB/c mice, and accelerating the onset of T1DM in the NOD mouse model.

We examined whether C10 was effective at inhibiting poly(I:C)-induction of insulitis and b-cell apoptosis and determine if this was a TLR3 mediated process. Specifically, we transfected NIT-1 and TC-6 b-cell lines with poly(I:C) to investigate the effects on viability and cytokine production in the presence or absence of C10. While poly(I:C) induced b-cell death within 48 hrs. in both cell lines, it was prevented by C10. Using Real-time PCR arrays we demonstrated that poly(I:C) stimulated the expression of numerous genes related to TLR3 signaling and inflammatory response pathways involved in b-cell destruction (e.g., CXCL10 and IFN-b) whereas C10 suppressed the expression of most of the increased genes implicated in the pathogenesis of T1DM. Secondly, we induced insulitis with poly(I:C) in the BALB/c mouse and this too was prevented by C10 treatment. These results suggest that C10 may be a potential novel therapeutic useful to treat or prevent viral induction of T1DM.

Visceral adipocytes and associated macrophages produce and release excessive amounts of biologically active inflammatory cytokines via the portal and systemic vascular system which can induce insulin resistance in insulin target tissues such as liver and muscle. Free fatty acids (FFAs) absorbed via the portal system or released from adipocytes also induce insulin resistance.

We have shown that phenylmethimazole (C10) blocks basal IL-6 and Leptin production, as well as basal Socs-3 expression, in fully differentiated 3T3L1 cells (3T3L1 adipocytes) without affecting insulin-stimulated AKT signaling. More importantly, C10 inhibits palmitate-induced IL-6 and iNOS upregulation in both 3T3L1 adipocytes and RAW264.7 macrophages, LPS-induced NF-κb & Type I Interferon (IFNb) activation in 3T3L1 cells, and LPS-induced iNOS, Ifnb, Il-1b, CXCL10, & IL-6 expression in RAW264.7 macrophages. C10 also blocks palmitate-induced Socs-3 upregulation and IRS-1 serine 307 phosphorylation in 3T3L1 adipocytes. Additionally, we show for the first time that although palmitate increases IRS-1 serine 307 phosphorylation in 3T3L1 adipocytes, AKT serine 473 phosphoryaltion is enhanced, not reduced, by palmitate. These results suggest that through inhibition of FFA-mediated signaling in adipocytes and associated macrophages, as well as possibly other insulin target cells/tissues (i.e. non-immune cells), C10 might be efficacious to prevent or reverse cytokine-induced insulin resistance seen in obesity-related insulin resistance and T2DM.