From:  Disruption of the transsulfuration pathway as a sulfur-driven etiology of insulin resistance: proinsulin misfolding, disulfide bond deformation, and PDI dysregulation

 PDI dysregulation, ER stress, and inflammatory signaling in T2DM.

YearStudy (authors)Sample/ModelFindingsQuantitative DataInterpretation
2022Su et al. [106]553 adults (225 T2DM, 159 NGT)↑ PDIA4 in T2DMCorrelation: FPG r = 0.62; BMI r = 0.58; CRP r = 0.55; ISI r = –0.67PDI upregulation linked to T2DM severity
2022Lee et al. [107]C2C12 cells, palmitatePDIA4 ↑ inflammation & resistanceTNF-α, IL-6 ↑ 2.5× (P < 0.01); knockdown ↓ IR 40%PDI mediates lipotoxic resistance
2023Tseng et al. [108]db/db mice, PS1 inhibitor↓ ROS, ↑ glucose tolerance, ↓ HbA1cROS ↓ 50% (P < 0.01); HbA1c –1.2% (P < 0.05); β-cell survival +30%Targeting PDIA4 restores insulin action
2022Zhou et al. [109]Biochemical reviewS-nitrosylation of cysteine residues↓ IRS-1 phosphorylationCompetes w/disulfide formation, impairs signaling
2016Lei et al. [110]45 men, PBMCsObesity ↑ ER stress & inflammatory markers↑ GRP78, CHOP, XBP-1, TLR2/4, APP (P < 0.05)ER stress linked to obesity & diabetes
2024Luo et al. [111]Adipose snRNA-seqMaladaptive macrophage subpopulation PDIA3hisiRNA liposomes ↓ inflammation, ↓ obesity (P < 0.05)PDI-driven inflammation worsens T2DM
2019Jang et al. [112]β-cell-specific PDIA1 KO mice↑ Proinsulin/insulin ratio, ↓ insulin granules, ↑ ER vesiculationP < 0.01PDI is critical for proinsulin folding

ER: endoplasmic reticulum; IL-6: interleukin-6; IR: insulin receptor; IRS-1: IR substrate-1; PBMCs: peripheral blood mononuclear cells; PDI: protein disulfide isomerase; PDIA4: PDI family A, member 4; ROS: reactive oxygen species; T2DM: type 2 diabetes mellitus; TLR4: toll-like receptor 4; TNF-α: tumor necrosis factor-alpha; APP: amyloid precursor protein; CHOP: CCAAT/enhancer-binding protein homologous protein; GRP78: glucose-regulated protein 78; HbA1c: hemoglobin A1c; PS1: presenilin 1; XBP-1: X-box binding protein 1.