Altered immune and metabolic molecular pathways drive islet cell dysfunction in human type 1 diabetes.

Type 1 diabetes (T1D) is characterized by the autoimmune destruction of most insulin-producing β cells, along with dysregulated glucagon secretion from pancreatic α cells. We conducted an integrated analysis that combines electrophysiological and transcriptomic profiling, along with machine learning, of islet cells from T1D donors. The few surviving β cells exhibit altered electrophysiological properties and transcriptomic signatures indicative of increased antigen presentation, metabolic reprogramming, and impaired protein translation. In α cells, we observed hyperresponsiveness and increased exocytosis, which are associated with upregulated immune signaling, disrupted transcription factor localization, and lysosome homeostasis, as well as dysregulation of mTORC1 complex signaling. Notably, key genetic risk signals for T1D were enriched in transcripts related to α cell dysfunction, including MHC class I, which were closely linked with α cell dysfunction. Our data provide what we believe are novel insights into the molecular underpinnings of islet cell dysfunction in T1D, highlighting pathways that may be leveraged to preserve residual β cell function and modulate α cell activity. These findings underscore the complex interplay between immune signaling, metabolic stress, and cellular identity in shaping islet cell phenotypes in T1D.