DL-3-n-butylphthalide (NBP) ameliorates cognitive deficits and CaMKII-mediated long-term potentiation impairment in the hippocampus of diabetic db/db mice

ABSTRACT

Objective: Diabetes-associated cognitive deficits is characterized by long-term potentiation (LTP) decline in the hippocampus. DL-3-n-butylphthalide (NBP) is a novel agent exerting protective effect against ischemic brain. However, the effects of NBP on diabetes-associated cognitive deficits and underlying mechanisms are not fully clear. This study was designed to evaluate the effects of NBP on the cognitive deficits through activating CaMKII-mediated LTP process and protecting neuron structure of hippocampus in diabetic db/db mice.

Methods: Male db/db mice were randomly divided into db/db group (n = 8) and db/db+NBP group (n = 8, 120mg/Kg NBP by gavage). Male db/m mice (n = 8) were included as control group. All animals were treated for 6 weeks. Morris Water Maze test was carried out to evaluate cognitive function. Electrophysiological recordings were performed to test LTP level. HE-staining and electron microscopy of hippocampus were used to observe structure change of neurons and synapse. RT-PCR and Western blot were used to assess the expression of CaMKII, NR2B, and GluR1.

Results: Type 2 diabetes mellitus caused LTP decline, and significantly decreased NR2B, CaMKII, and GluR1 expression. Histological analysis showed that disorganized pyramidal cells, as well as degraded neuron and synapse ultrastructure in db/db mice. NBP treatment restored LTP and its associated proteins in db/db mice. The structure changes of hippocampal cells were partly reversed by NBP intervention.

Conclusion: These results suggest that NBP ameliorates cognitive deficits induced by type 2 diabetes mellitus through improving CaMKII-mediated LTP and cell ultrastructure in the hippocampus. NBP is a potential therapeutic agent for diabetes-associated cognitive deficits.

Abbreviations: NBP: DL-3-n-butylphthalide; LTP: long-term potentiation; CaMKII: calcium/calmodulin-dependent protein kinase II; NR2B: N-methyl-D-aspartic acid receptor subtype 2B; GluR1: α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subtype 1.

KEYWORDS:

• Type 2 diabetes mellitus
• DL-3-n-butylphthalide
• long-term potentiation
• cognitive deficits
• CaMKII

Authors’ Contributions

Songyun Zhang participated in designing the experiments. Ming Gao and Suxiao Ji participated in performing the research and writing the manuscript. Jie Li participated in preparing the research and analyzing the data. All authors have approved the final article.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The project was supported by the Natural Science Foundation of Hebei Province [H2014206390] and Science Foundation of Hebei Province Health and Family Planning Commission [#20180323].

Notes on contributors

Ming Gao

Ming Gao, M.D. Attending physician, Endocrinology Department, The Second Hospital of Hebei Medical University.

Suxiao Ji

Suxiao Ji, Resident physician, Endocrinology Department, Handan First Hospital.

Jie Li

Jie Li, Resident physician, Endocrinology Department, The Second Hospital of Hebei Medical University.

Songyun Zhang

Songyun Zhang, M.D, Chief physician, Professor, Endocrinology Department, The Second Hospital of Hebei Medical University.