Nicotinamide Riboside (NR) Supplementation Exerts Neuroprotective Effects in db/db Mouse Model of Type 2 Diabetes

Type 2 diabetes is linked to neuropsychiatric complications such as anxiety-like behaviors, disrupted brain metabolism, neuroinflammation, and impaired mitochondrial function. Nicotinamide riboside (NR) has emerged as a potential therapeutic agent for these complications due to its role in NAD + biosynthesis and neuroprotective properties. In this study, we assessed whether NR supplementation can ameliorate anxiety-like behavior in a mouse model of type 2 diabetes by modulating the hippocampal inflammatory response. 8-week-old db/db mice on the BKS background were used as a model of type 2 diabetes, and db/m mice were used as non-diabetic controls. Four groups, consisting of non-diabetic and diabetic mice, were fed with a control diet or a diet supplemented with NR at 500 mg/kg dosage for 20 weeks. The open field test and nesting behavioral assessments were conducted to evaluate anxiety-related behaviors and overall well-being. After animals were euthanized, biochemical analyses were performed on hippocampal samples using RT-qPCR, Western blotting, and immunohistochemistry. Behavioral assessments revealed increased anxiety and reduced nest-building motivation in db/db mice compared with control mice. These effects were ameliorated by NR treatment. Biochemical analyses revealed that NR attenuated markers of inflammation, including astrocytosis and microglial activation, activation of inflammatory signaling via STING and NF-kB, and pro-inflammatory cytokines. Our findings show that NR supplementation reduces anxiety-like symptoms and neuroinflammation in diabetic mice, highlighting the potential therapeutic relevance of NR in mitigating neuropsychiatric complications associated with diabetes mellitus.