Nacre extract improves insulin resistance and cognitive functions in diabetic mice

Abstract

Objective: To investigate whether nacre extract improves insulin sensitivity, brain glucose metabolism, and cognitive function in diabetic mice.

Methods: Diabetic KK-Ay mice (n=5/group) were fed a standard diet or diets supplemented with nacre extract (125 or 250 mg/kg) for 13 weeks. Metabolic status was assessed by measuring fasting glucose and insulin levels, HOMA-IR, glucose tolerance, and insulin tolerance. The expression of IRS-1, IRS-2, and GLUT4 in the brain was analyzed by qPCR, Western blotting, and immunohistochemistry. Cognitive and anxiety-like behaviors were evaluated using the Y-maze, novel object recognition, Barnes maze, and open field tests.

Results: Nacre extract significantly reduced fasting glucose and insulin levels, improved HOMA-IR, and enhanced glucose and insulin tolerance (P<0.05) in diabetic mice. It also restored GLUT4 expression and significantly upregulated SIRT1 and BDNF. Behavioral assessments showed significant improvements in memory and reduced anxiety-like behaviors.

Conclusions: Nacre extract enhances insulin sensitivity, improves brain glucose metabolism, and alleviates cognitive and emotional dysfunction in diabetic mice. Further studies are warranted to verify the exact molecular mechanisms and efficacy of nacre extract in diabetes-associated metabolic and neurocognitive dysfunction.

Keywords

Nacre extract / Diabetes mellitus / Cognitive dysfunction / Insulin resistance / BDNF

Conflict of interest statement

The authors declare no conflict of interest.

Funding

This study received no extramural funding.

Data availability statement

The data supporting the findings of this study are available from the corresponding author upon request.

Authors’ contributions

ZH contributed to the methodology, investigation, formal analysis, and writing of the manuscript. YY and TO were involved in the methodology and investigation. YH was responsible for writing the original draft and project administration.

Publisher’s note

The Publisher of the Journal remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Acknowledgments

We are grateful to Kaneko Pearl Farming Company Limited for supplying the pearl oyster shells used in this study. We also thank the Department of Molecular Medicine, Akita University, for assistance with immunohistochemistry.

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