Background/Objectives: There is increasing evidence linking circulating neurotoxic lipids to the progression of chronic neuroinflammatory diseases in the peripheral and central nervous systems. Strategies to modify lipid profiles, such as docosahexaenoic acid (DHA)-rich supplementation, may aid in managing conditions like painful diabetic neuropathy (pDN). In a previous study, we demonstrated that three months of DHA supplementation significantly altered the metabolomic profile of patients with painful diabetic neuropathy (pDN), resulting in symptom improvement. This study investigates whether DHA-rich supplementation reduces neurotoxic lipid mediators associated with pDN in individuals with type 2 diabetes mellitus (T2DM). Methods: Forty individuals with type 2 diabetes participated in the “En Balance-PLUS” study, attending weekly lifestyle and nutrition education sessions while receiving daily supplementation of 1000 mg DHA and 200 mg EPA. Pain levels were assessed using the Short-Form McGill Pain Questionnaire (SF-MPQ) at baseline and after three months. Blood serum samples collected at these time points underwent untargeted lipidomic analyses, with ELISA used to evaluate biomarkers of necrosis (MLKL), autophagy (ATG5), and lipid chaperone protein (FABP5). Results: Untargeted lipidomic analysis revealed that several neurotoxic-associated lipids significantly decreased after DHA-rich supplementation. Also, circulating levels of MLKL were reduced, while protein levels of ATG5 and FABP5 significantly increased. Conclusions: The reduction of circulating neurotoxic lipids and increase in neuroprotective lipids following DHA-rich supplementation are consistent with the reported roles of omega-3 polyunsaturated fatty acids (PUFAs) in reducing adverse symptoms associated with neuroinflammatory diseases and painful neuropathy.

Neuropathic pain (NP) arises from diverse conditions, including peripheral nerve injury, spinal cord injury (SCI), and painful diabetic neuropathy, yet these disorders share oxidative stress, mitochondrial dysfunction, lipid dysregulation, and altered neuronal excitability. We investigated whether dietary omega-3 polyunsaturated fatty acids modulate ferroptotic stress-associated pathways, defined as lipid peroxidation susceptibility and impaired antioxidant defense rather than overt ferroptotic cell death. Female Sprague–Dawley rats received either a soy oil control diet (SOD) or fish oil omega-3-enriched diet (FOD) before chronic constriction injury (CCI). Behavioral outcomes were assessed using Hargreaves and CatWalk testing, followed by dorsal root ganglion (DRG) RNA sequencing, RT-PCR, and GPX4 ELISA. Previously generated SCI metabolomics and human diabetic serum metabolomic/lipidomic datasets were re-analyzed for shared pathways. FOD attenuated CCI-induced thermal hypersensitivity and improved gait parameters. DRG transcriptomics showed reduced injury-associated transcriptional disruption, enrichment of selenoamino acid metabolism, nonsense-mediated decay, and ribosomal quality-control pathways, and reduced mitochondrial dysfunction pathway activity. Omega-3 increased Gpx1/Gpx4 expression and GPX4 protein, reduced pain-associated genes including Scn10a, Piezo2, Trpa1, and Oprm1, and aligned with selenoamino acid enrichment in SCI and human datasets. Human lipidomics showed MG/DG/PC/PE pathway remodeling. These findings support ferroptotic stress as a plausible shared downstream mechanism modulated by omega-3 supplementation across NP models.

A growing body of evidence indicates a link between circulating neurotoxic lipids and the development of chronic neuroinflammatory diseases in the peripheral and central nervous systems. Therefore, strategies to modify circulating lipid profiles may complement the management of neuroinflammatory diseases, including neuropathic pain. In a previous study, we observed a sig-nificant shift in the metabolomic profile of patients' plasma with symptoms of painful diabetic neuropathy (pDN) following three months of docosahexaenoic acid (DHA)-rich supplementation, leading to improved pDN symptoms. However, it is important to identify the specific lipid mediators responsible for this therapeutic effect and elucidate potential mechanism(s). This study investigates whether DHA-rich supplementation reduces neurotoxic lipid mediators associated with pDN in individuals with type 2 diabetes mellitus (T2DM). Forty volunteers diagnosed with type 2 diabetes were enrolled in the "En Balance-PLUS" diabetes education study. The volunteers participated in weekly lifestyle/nutrition education and daily supplementation with 1000 mg DHA and 200 mg eicosapentaenoic acid. The Short-Form McGill Pain Questionnaire validated the clinical determination of baseline and post-intervention pain complaints. Untargeted Lipidomic analyses were conducted using blood serum collected at baseline and after three months of participation in the dietary regimen. The lipidomic data were analyzed using a non-parametric paired Wilcoxon rank-sum test and random forest analysis. ELISA further eval-uated participant serum samples to investigate associated biomarkers of necrosis (MLKL), autophagy (ATG5), and lipid chaperone protein (FABP5). Untargeted lipidomic analysis revealed that several neurotoxic-associated lipids significantly decreased after DHA-rich supplementation. Also, circulating levels of MLKL were reduced, while protein levels of ATG5 and FABP5 significantly increased. The reduction of circulating neurotoxic lipids and increase of neuroprotective lipids following DHA-rich supplementation is consistent with the reported roles of omega-3 polyunsaturated fatty acids (PUFAs) in reducing adverse symptoms associated with neuroinflammatory diseases and painful neuropathy.