Dietary n-3 polyunsaturated fatty acids intervention ameliorates cognitive dysfunction in db/db mice by mitigating cortical insulin resistance, mitochondrial dysfunction, and energy metabolism impairment

Introduction

Cognitive dysfunction is a prevalent complication associated with Type 2 Diabetes Mellitus (T2DM). Cognitive dysfunction in patients with T2DM not only severely impacts their quality of life but also imposes a substantial burden on their families and society. Despite the increasing prevalence of T2DM and its associated cognitive dysfunction, the underlying mechanisms remain incompletely understood, and effective treatment strategies are still lacking. This creates an urgent need for in-depth research to clarify these mechanisms and develop novel therapeutic approaches.

Objectives

This study aims to investigate the ameliorating effects of dietary n-3 polyunsaturated fatty acids (n-3 PUFA) on diabetes-related cognitive dysfunction and its underlying mechanisms.

Methods

In this study, we employed multiple mouse models of diabetes and cognitive impairment to explore the impact of disrupted glucose metabolism on central insulin signaling pathways and mitochondrial function. Furthermore, we treated db/db mice with n-3 PUFA-enriched diets and assessed the effects of n-3 PUFA on insulin signaling pathways, mitochondrial function, and cognitive function to elucidate the mechanisms by which n-3 PUFA mitigate diabetes-related cognitive dysfunction. The expression levels of target proteins and genes were detected using western blot, immunohistochemistry, and reverse transcription-polymerase chain reaction. Cognitive function was evaluated using the Morris water maze test, while damage of brain structure and neurons was analyzed through diffusion tensor imaging and Nissl staining. Mitochondrial morphology was examined by transmission electron microscopy, and energy metabolism alterations were investigated using metabolomics.

Results

db/db mice exhibited pronounced insulin resistance and mitochondrial dysfunction in the brain cortex. Abnormalities in brain mitochondrial energy metabolism and disruptions in the glutamate-glutamine circulation constitute the pathological basis for diabetes-related cognitive dysfunction. Dietary n-3 PUFA intervention alleviated insulin resistance, neuronal loss, mitochondrial structural abnormalities, energy metabolism disorders, glutamate-glutamine cycling disorders and cognitive dysfunction in db/db mice.

Conclusion

n-3 PUFA facilitated the recovery of cognitive function in T2DM mice by regulating cortical mitochondrial energy metabolism and enhancing the glutamate-glutamine cycle.