Department of Endocrinology, Drum Tower Hospital Affiliated to Nanjing University Medical School, Nanjing, China.
Department of Radiology, Drum Tower Hospital Affiliated to Nanjing University Medical School, Nanjing, China.
Diabetes. 2018 May;67(5):994-1006. doi: 10.2337/db17-1274. Epub 2018 Mar 2.
Type 2 diabetes is reported to be associated with olfactory dysfunction and cognitive decline. However, whether and how olfactory neural circuit abnormalities involve cognitive impairment in diabetes remains uncovered. This study thus aimed to investigate olfactory network alterations and the associations of odor-induced brain activity with cognitive and metabolic parameters in type 2 diabetes. Participants with normal cognition, including 51 patients with type 2 diabetes and 41 control subjects without diabetes, underwent detailed cognitive assessment, olfactory behavior tests, and odor-induced functional MRI measurements. Olfactory brain regions showing significantly different activation between the two groups were selected for functional connectivity analysis. Compared with the control subjects, patients with diabetes demonstrated significantly lower olfactory threshold score, decreased brain activation, and disrupted functional connectivity in the olfactory network. Positive associations of the disrupted functional connectivity with decreased neuropsychology test scores and reduced pancreatic function were observed in patients with diabetes. Notably, the association between pancreatic function and executive function was mediated by olfactory behavior and olfactory functional connectivity. Our results suggested the alteration of olfactory network is present before clinically measurable cognitive decrements in type 2 diabetes, bridging the gap between the central olfactory system and cognitive decline in diabetes.
2 型糖尿病与嗅觉功能障碍和认知能力下降有关。然而，糖尿病患者的嗅觉神经回路异常是否以及如何导致认知障碍仍未被揭示。因此，本研究旨在探讨 2 型糖尿病患者嗅觉网络改变以及气味诱导的大脑活动与认知和代谢参数的相关性。参与者包括认知正常的 51 名 2 型糖尿病患者和 41 名无糖尿病的对照组，他们接受了详细的认知评估、嗅觉行为测试和气味诱导的功能磁共振测量。选择两组之间激活存在显著差异的嗅觉脑区进行功能连接分析。与对照组相比，糖尿病患者的嗅觉阈值评分明显较低，大脑激活降低，嗅觉网络的功能连接中断。在糖尿病患者中，功能连接的中断与神经心理学测试分数的降低和胰腺功能的降低呈正相关。值得注意的是，胰腺功能与执行功能之间的关联是由嗅觉行为和嗅觉功能连接介导的。我们的研究结果表明，在 2 型糖尿病出现临床可测量的认知能力下降之前，嗅觉网络就已经发生了改变，这为糖尿病患者的中枢嗅觉系统和认知能力下降之间架起了桥梁。
