SLC35 Transporters: The Missing Link Between Glycosylation and Type 2 Diabetes

Type 2 diabetes mellitus (T2D) affects hundreds of millions worldwide, with recent estimates indicating approximately 589 million adults living with diabetes, most with type 2 disease. Beyond classical insulin signaling pathways, increasing evidence implicates altered protein glycosylation in metabolic dysfunction. The solute carrier 35 (SLC35) family of nucleotide sugar transporters mediates the import of activated sugars into the endoplasmic reticulum and Golgi lumen, thereby influencing global glycosylation patterns. Dysregulation of these transporters can perturb glucose homeostasis, insulin responsiveness, and nutrient-sensing pathways through changes in glycosylation flux. In this review, we dissect the molecular mechanisms by which these transporters modulate glucose homeostasis, insulin signaling pathways, protein O-GlcN acylation, and broader glycosylation processes. We integrate findings from human genetic studies, rodent models, and in vitro functional analyses to characterize how altered SLC35 activity is associated with T2D and metabolic syndrome. Four members demonstrate particularly compelling evidence: SLC35B4 modulates hepatic glucose metabolism, SLC35D3 mutations impair dopaminergic signaling and energy balance, and SLC35F3 variants interact with high-carbohydrate intake to increase metabolic-syndrome risk. SLC35A3, though less studied, may influence glycosylation-dependent insulin signaling through its role in N-glycan biosynthesis. Beyond these characterized transporters, this review identifies potential metabolic roles for understudied family members, suggesting broader implications across the entire SLC35 family. We also discuss how such alterations can lead to disrupted hexosamine flux, impaired glycoprotein processing, aberrant cellular signaling, and micronutrient imbalances. Finally, we evaluate the therapeutic potential of targeting SLC35 transporters, outlining both opportunities and challenges in translating these insights into novel T2D treatments.