Liraglutide is a type of glucagon‑like‑peptide 1 receptor agonist, which has been reported as a novel type of antidiabetic agent with numerous benefits, including cardiovascular and neuroprotective effects. To the best of our knowledge, few studies to date have reported the potential mechanism underlying the neuroprotective effects of liraglutide on rats with type 2 diabetes mellitus (T2DM). The present study aimed to investigate the neuroprotective actions of liraglutide in diabetic rats and to determine the mechanisms underlying these effects. A total of 30 male T2DM Goto‑Kakizaki (GK) rats (age, 32 weeks; weight, 300‑350 g) and 10 male Wistar rats (age, 32 weeks; weight, 300‑350 g) were used in the present study. Wistar rats received vehicle treatment, and GK rats randomly received treatment with vehicle, low dose of liraglutide (75 µg/kg) or high dose of liraglutide (200 µg/kg) for 28 days. Cognitive deficits were evaluated using the Morris water maze test. The expression levels of phosphoinositide 3‑kinase (PI3K), protein kinase B (Akt), phosphorylated (p)‑Akt, AMP‑activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), Beclin‑1, microtubule‑associated protein light chain 3 (LC)‑3 II, caspase‑3, B‑cell lymphoma 2 (Bcl‑2)‑associated X protein and Bcl‑2 were assessed by western blot analysis. The results demonstrated that diabetic GK rats exhibited cognitive dysfunction, whereas treatment with liraglutide alleviated the learning and memory deficits, particularly in the high‑dose liraglutide group. The expression levels of Beclin‑1 and LC‑3 II were decreased in GK rats; however, this decrease was alleviated in the presence of liraglutide. Liraglutide also reversed T2DM model‑induced increases in mTOR, and decreases in p‑AMPK, PI3K and p‑Akt expression, and modulated the expression of apoptosis‑associated proteins. Furthermore, the administration of liraglutide inhibited apoptosis and exerted a protective effect against cognitive deficits via the activation of autophagy. In conclusion, the protective effects of liraglutide may be associated with increased mTOR expression via activation of the AMPK and PI3K/Akt signaling pathways.
Background/Aims: To explore the effects of sulforaphane (SFN) on neuronal apoptosis in hippocampus and memory impairment in diabetic rats. Methods: Thirty male rats were randomly divided into normal control, diabetic model and SFN treatment groups (N = 10 in each group). Streptozotocin (STZ) was applied to establish diabetic model. Water Morris maze task was applied to test learning and memory. Tunel assaying was used to detect apoptosis in hippocampus. The expressions of Caspase-3 and myeloid cell leukemia 1(MCL-1) were detected by western blotting. Neurotrophic factor levels and AKT/GSK3β pathway were also detected. Results: Compared with normal control, learning and memory were apparently impaired, with up-regulation of Caspase-3 and down-regulation of MCL-1 in diabetic rats. Apoptotic neurons were also found in CA1 region after diabetic modeling. By contrast, SFN treatment prevented the memory impairment, decreased the apoptosis of hippocampal neurons. SFN also attenuated the abnormal expression of Caspase-3 and MCL-1 in diabetic model. Mechanically, SFN treatment reversed diabetic modeling-induced decrease of p-Akt, p-GSK3β, NGF and BDNF expressions. Conclusion: SFN could prevent the memory impairment and apoptosis of hippocampal neurons in diabetic rat. The possible mechanism was related to the regulation of neurotropic factors and Akt/GSK3β pathway.
Background and aimsType 2 diabetes (T2DM) is associated with cognitive deficits. However, their pathophysiological mechanisms are still unknown. Recent study suggests that brain-derived neurotrophic factor (BDNF) is correlated with cognitive deficits in T2DM patients. This study was to determine whether altered serum BDNF levels and cognitive deficits depended on the BDNF Val66Met polymorphism in T2DM.ResultsThe BDNF Val66Met polymorphism may not contribute directly to the susceptibility to T2DM. The total and nearly all index scores (all p < 0.01) except for the attention and visuospatial/constructional indexes (both p > 0.05) of RBANS were markedly decreased in T2DM compared with healthy controls. Serum BDNF levels were significantly lower in patients than that in controls (p < 0.001), and BDNF was positively associated with delayed memory in patients (p < 0.05). The Met variant was associated with worse delayed memory performance among T2DM patients but not among normal controls. Moreover, serum BDNF was positively associated with delayed memory among Met homozygote patients (β = 0.29, t = 2.21, p = 0.033), while serum BDNF was negatively associated the RBANS total score (β = –0.92, t = –3.40, p = 0.002) and language index (β = −1.17, t = –3.54, p = 0.001) among Val homozygote T2DM patients.ConclusionsBDNF gene Val66Met variation may be associated with cognitive deficits in T2DM, especially with delayed memory. The association between lower BDNF serum levels and cognitive impairment in T2DM is dependent on the BDNF Val66Met polymorphism.MethodsWe recruited 311 T2DM patients and 346 healthy controls and compared them on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), serum BDNF levels, and the BDNF Val66Met polymorphism.
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