Apocynin ameliorates cognitive deficits in streptozotocin-induced diabetic rats.

AIMS: The aim was to investigate the improvement properties of apocynin and its potential mechanism on diabetes-associated cognitive decline. METHODS: In this study, the model of diabetic rat was established by STZ (50 mg/kg) and treated with apocynin (16 mg/kg/d for 12 weeks). The cognitive ability was evaluated by Morris water maze test. The indicators of oxidative stress (SOD and MDA) were analyzed by spectrophotometer. The inflammatory cytokines were measured by real time-PCR and ELISA. The protein expressions of Nrf-2, HO-1, Bcl-2 and Bax were determined by Western blot. RESULTS: Treatment with apocynin ameliorated diabetes-related learning and memory injury, as represented by decreasing escape latency and enhancement of the number of times of crossing platform, in the Morris water maze test. In hippocampus, apocynin markedly augmented SOD activity and inhibited MDA level to alleviate oxidative stress. Moreover, apocynin obviously relieved inflammatory reaction by suppressing TNF-α, IL-1ß and IL-6 concentrations. Concomitantly, apocynin also statistically enhanced Nrf-2 and HO-1 protein expression to improve DACD. Lastly, apocynin notably ameliorated Bax/Bcl-2 ratio by regulating Bax and Bcl-2 protein expression to mitigate apoptosis. CONCLUSION: Our results have shown that apocynin may be a valid therapeutic agent against DACD via modulation of antioxidant, anti-inflammatory, and anti-apoptosis (Tab. 1, Fig. 18, Ref. 35).

The D-alanyl-d-alanine carboxypeptidase enzyme is essential for virulence in the Schu S4 strain of Francisella tularensis and a dacD mutant is able to provide protection against a pneumonic challenge.

Low molecular mass penicillin binding proteins (LMM PBP) are bacterial enzymes involved in the final steps of peptidoglycan biosynthesis. In Escherichia coli, most LMM PBP exhibit dd-carboxypeptidase activity, are not essential for growth in routine laboratory media, and contributions to virulent phenotypes remain largely unknown. The Francisella tularensis Schu S4 genome harbors the dacD gene (FTT_1029), which encodes a LMM PBP with homology to PBP6b of E. coli. Disruption of this locus in the fully virulent Schu S4 strain resulted in a mutant that could not grow in Chamberlain's Defined Medium and exhibited severe morphological defects. Further characterization studies demonstrated that the growth defects of the dacD mutant were pH-dependent, and could be partially restored by growth at neutral pH or fully restored by genetic complementation. Infection of murine macrophage-like cells showed that the Schu S4 dacD mutant is capable of intracellular replication. However, this mutant was attenuated in BALB/c mice following intranasal challenge (LD50 = 603 CFU) as compared to mice challenged with the parent (LD50 = 1 CFU) or complemented strain (LD50 = 1 CFU). Additionally, mice that survived infection with the dacD mutant showed significant protection against subsequent challenge with the parent strain. Collectively, these results indicate that the DacD protein of F. tularensis is essential for growth in low pH environments and virulence in vivo. These results also suggest that a PBP mutant could serve as the basis of a novel, live attenuated vaccine strain.

Puerarin ameliorates cognitive deficits in streptozotocin-induced diabetic rats.

Previous research has indicated that Diabetes is a high risk of learning and memory deficits. Puerarin, an isoflavonoid extracted from Kudzu roots, has been reported to possess antioxidant, anti-inflammatory, anti-apoptotic and anti-diabetic properties which are useful in the treatment of various diseases. Recently, Puerarin was found to have the effects on learning and memory performances in humans and animal models. However, up to now, there is no detailed evidence on the effect of Puerarin on diabetes-associated cognitive decline (DACD). In this study, we designed to assess the effects of Puerarin on diabetes-associated cognitive decline (DACD) using a streptozotocin (STZ)-injected rat model and exploring its potential mechanism. Diabetic rats were treated with Puerarin (100 mg/kg per d) for 7 days. The learning and memory function was evaluated by morris water maze test. The acetylcholinesterase (AChE), choline acetylase (ChAT), oxidative indicators [malondialdehyde (MDA) and superoxide dismutase (SOD)] and inflammatory cytokine (TNF-a, IL-1ß and IL-6) were measured in hippocampus by using corresponding commercial kits. mRNA and Protein levels of Bcl-2 were analyzed by RT-PCR and Westernblot. The results showed that supplementation of Puerarin improved the learning and memory performances compared with the STZ group by the morris water maze test. In addition, Puerarin supplement significantly prevented AChE and MDA activities, increased ChAT and SOD activities, and alleviated the protein level of TNF-α, IL-1ß and IL-6 in the hippocampus compared with the STZ group. Moreover, the pretreatment with Puerarin also significantly increased the Bcl-2 expression. It is concluded that Puerarin possesses neuroprotection to ameliorate cognitive deficits in streptozotocin-induced diabetic rats by anti-inflammatory, antioxidant and antiapototic effects.

ZiBu PiYin recipe prevents diabetes-associated cognitive decline in rats: possible involvement of ameliorating mitochondrial dysfunction, insulin resistance pathway and histopathological changes.

BACKGROUND: Disturbance in energy metabolism, as a key factor in diabetes-associated cognitive decline (DACD), has become a promising therapeutic target of Chinese medicine ZiBu PiYin Recipe (ZBPYR). However, it is still not clear how ZBPYR affects the mitochondrial function in DACD rats' brains, which is considered as the crucial cell organelle to supply energy for the brain. METHODS: Type 2 diabetes mellitus (T2DM) rat models were established by using high fat diet and streptozotocin (STZ) (30 mg/kg, ip). The evaluation of insulin sensitivity was performed by oral glucose tolerance and insulin tolerance test. After 7 weeks, the T2DM rats were treated with vehicle or ZBPYR for 11 weeks and morris water maze (MWM) test were used to evaluate memory function. The ultra structural changes of prefrontal cortex (PFC) and hippocampus were examined by transmission electron microscopy (TEM). The mitochondrial membrane potential (ΔΨm) and reactive oxygen species (ROS) were measured with JC-1 and DCFDA assay. The levels of insulin proteins were quantified by Western Blot analysis and the markers of histopathological changes were detected by immunohistochemistry. RESULTS: ZBPYR could alleviate learning and memory impairment of DACD rats. TEM showed that ZBPYR prevented mitochondrial ultra-structural alterations and number changes in the PFC and hippocampus of the DACD rats. In addition, ZBPYR significantly increased ΔΨm and lowered the levels of ROS. Further investigation indicated that ZBPYR suppressed the release of cytochrome c from mitochondria, strengthened insulin signaling and inhibited GSK3ß over-expression. These positive effects were associated with reduced Aß1-42 deposition and restored expression levels of microtubule-associated protein MAP2. CONCLUSION: ZBPYR showed excellent protective effect against DACD via ameliorating mitochondrial dysfunction, insulin resistance and histopathological changes.

Augmented Mitochondrial Transfer Involved in Astrocytic PSPH Attenuates Cognitive Dysfunction in db/db Mice.

Diabetes-associated cognitive dysfunction (DACD) has ascended to become the second leading cause of mortality among diabetic patients. Phosphoserine phosphatase (PSPH), a pivotal rate-limiting enzyme in L-serine biosynthesis, has been documented to instigate the insulin signaling pathway through dephosphorylation. Concomitantly, CD38, acting as a mediator in mitochondrial transfer, is activated by the insulin pathway. Given that we have demonstrated the beneficial effects of exogenous mitochondrial supplementation on DACD, we further hypothesized whether astrocytic PSPH could contribute to improving DACD by promoting astrocytic mitochondrial transfer into neurons. In the Morris Water Maze (MWM) test, our results demonstrated that overexpression of PSPH in astrocytes alleviated DACD in db/db mice. Astrocyte specific-stimulated by PSPH lentivirus/ adenovirus promoted the spine density both in vivo and in vitro. Mechanistically, astrocytic PSPH amplified the expression of CD38 via initiation of the insulin signaling pathway, thereby promoting astrocytic mitochondria transfer into neurons. In summation, this comprehensive study delineated the pivotal role of astrocytic PSPH in alleviating DACD and expounded upon its intricate cellular mechanism involving mitochondrial transfer. These findings propose that the specific up-regulation of astrocytic PSPH holds promise as a discerning therapeutic modality for DACD.

Levels of serum S100B are associated with cognitive dysfunction in patients with type 2 diabetes.

OBJECTIVE: Previous studies have provided robust evidence that cognitive impairment exists in patients with type 2 diabetes. The predictive role of S100B in a variety of neurodegenerative diseases such as Alzheimer's disease, has been shown to be closely related to cognitive function. The purpose of this study was to investigate the correlation between serum S100B levels and cognitive function in type 2 diabetes patients. RESULTS: The type 2 diabetes group scored lower than the healthy control group in all domains of cognitive function except language and attention, and the former group also had lower serum levels of S100B. Besides, serum S100B levels were lower in the type 2 diabetes patients with impaired cognition than in those with normal cognition. In addition, the moderate to severe cognitive impairment group had significantly lower levels than that in mild cognitive impairment group. After adjusting for confounding factors, serum S100B levels were positively correlated with cognitive function in type 2 diabetes patients. CONCLUSIONS: Serum S100B levels were positively correlated with cognitive function in type 2 diabetes patients with cognitive impairment. It is suggested that S100B may be involved in the occurrence and development of cognitive dysfunction in type 2 diabetes patients and play a protective role. METHODS: The clinical data and biochemical indexes of ninety-six patients with type 2 diabetes and sixty-eight healthy subjects were collected. The levels of serum S100B were detected by enzyme-linked immunosorbent assay. Ninety-six type 2 diabetes patients were divided into a cognitive dysfunction group and a normal cognition group according to Mini-mental State Examination scores. To better understand the differences in various aspects of cognition, we used the Repeatable Battery for the Assessment of Neuropsychological Status scale for further evaluation. To study the relationship between serum S100B levels and cognitive impairment, the cognitive dysfunction group was divided into a mild cognitive impairment group and a moderate to severe cognitive impairment group for further study.

Autophagy Activation is Associated with Neuroprotection in Diabetes-associated Cognitive Decline.

Autophagy is a lysosome-dependent cellular catabolic mechanism that mediates the turnover of dysfunctional organelles and aggregated proteins. It has a neuroprotective role on neurodegenerative diseases. Here, we hypothesized that autophagy may also have a neuroprotective role in diabetes-associated cognitive decline (DACD). In current study, we found that db/db mice display cognitive decline with inferior learning and memory function. The accumulation of ß-amyloid1-42 (Aß1-42), which is a characteristic of Alzheimer's disease (AD), was markedly higher in the prefrontal cortex (PFC), cornu ammon1 (CA1), and dentate gyrus (DG) areas of the hippocampus in db/db mice. Moreover, BDNF and microtubule associated protein 2 (MAP2) levels were lower in the hippocampus of db/db mice. However, there was no noticeable differences in the level of apoptosis in the hippocampus between control (CON) mice and db/db mice. Markers of autophagy in the hippocampus were elevated in db/db mice. The expression levels of ATG5, ATG7, and LC3B were higher, and the level of P62 was lower. An autophagy inhibitor, 3-MA, and ATG7 siRNA significantly reversed the activation of autophagy in vitro, which was accompanied with a higher level of apoptosis. Taken together, our current study suggests that diabetes is associated with cognitive decline, and activation of autophagy has a neuroprotective role in DACD.

Francisella tularensis D-Ala D-Ala Carboxypeptidase DacD Is Involved in Intracellular Replication and It Is Necessary for Bacterial Cell Wall Integrity.

D-alanyl-D-alanine carboxypeptidase, product of dacD gene in Francisella, belongs to penicillin binding proteins (PBPs) and is involved in remodeling of newly synthetized peptidoglycan. In E. coli, PBPs are synthetized in various growth phases and they are able to substitute each other to a certain extent. The DacD protein was found to be accumulated in fraction enriched in membrane proteins from severely attenuated dsbA deletion mutant strain. It has been presumed that the DsbA is not a virulence factor by itself but that its substrates, whose correct folding and topology are dependent on the DsbA oxidoreductase and/or isomerase activities, are the primary virulence factors. Here we demonstrate that Francisella DacD is required for intracellular replication and virulence in mice. The dacD insertion mutant strain showed higher sensitivity to acidic pH, high temperature and high osmolarity when compared to the wild-type. Eventually, transmission electron microscopy revealed differences in mutant bacteria in both the size and defects in outer membrane underlying its SDS and serum sensitivity. Taken together these results suggest DacD plays an important role in Francisella pathogenicity.

Naringin ameliorates cognitive deficits in streptozotocin-induced diabetic rats.

OBJECTIVES: Previous research demonstrated that diabetes is one of the leading causes of learning and memory deficits. Naringin, a bioflavonoid isolated from grapefruits and oranges, has potent protective effects on streptozotocin (STZ)-induced diabetic rats. Recently, the effects of naringin on learning and memory performances were monitored in many animal models of cognitive impairment. However, to date, no studies have investigated the ameliorative effects of naringin on diabetes-associated cognitive decline (DACD). In this study, we investigated the effects of naringin, using a STZ-injected rat model and explored its potential mechanism. MATERIALS AND METHODS: Diabetic rats were treated with naringin (100 mg/kg/d) for 7 days. The learning and memory function were assessed by Morris water maze test. The oxidative stress indicators [superoxide dismutase (SOD) and malondialdehyde (MDA)] and inflammatory cytokines (TNF-a, IL-1ß, and IL-6) were measured in hippocampus using corresponding commercial kits. The mRNA and protein levels of PPARγ were evaluated by real time (RT)-PCR and Western blot analysis. RESULTS: The results showed that supplementation of naringin improved learning and memory performances compared with the STZ group. Moreover, naringin supplement dramatically increased SOD levels, reduced MDA levels, and alleviated TNF-α, IL-1ß, and IL-6 compared with the STZ group in the hippocampus. The pretreatment with naringin also significantly increased PPARγ expression. CONCLUSION: Our results showed that naringin may be a promising therapeutic agent for improving cognitive decline in DACD.