Intranasal metformin treatment ameliorates cognitive functions via insulin signaling pathway in ICV-STZ-induced mice model of Alzheimer's disease

AIMS

The relationship between type 2 diabetes and Alzheimer's disease (AD) provides evidence that insulin and insulin sensitizers may be beneficial for the treatment of AD. The present study investigated the effect and mechanism of action of intranasal metformin treatment on impaired cognitive functions in an experimental mice model of AD.

MAIN METHODS

Intracerebroventricularly (ICV) streptozotocin (STZ)-injected mice were treated with intranasal or oral metformin for 4 weeks. Learning and memory functions were evaluated using Morris water maze. Metformin and Aβ42 concentrations were determined by liquid chromatography tandem mass spectrometry and ELISA respectively. The expressions of insulin receptor, Akt and their phosphorylated forms were determined in the hippocampi and cerebral cortices of mice.

KEY FINDINGS

ICV-STZ-induced AD mice displayed impaired learning and memory functions which were improved by metformin treatment. ICV-STZ injection or intranasal/oral metformin treatments had no effect on blood glucose concentrations. Intranasal treatment yielded higher concentration of metformin in the hippocampus and lower in the plasma compared to oral treatment. ICV-STZ injection and metformin treatments did not change amyloid β-42 concentration in the hippocampus of mice. In hippocampal and cortical tissues of ICV-STZ-induced AD mice, insulin receptor (IR) and Akt expressions were unchanged, while phosphorylated insulin receptor (pIR) and pAkt expressions decreased compared to control. Metformin treatments did not change IR and Akt expressions but increased pIR and pAkt expressions.

SIGNIFICANCE

The present study showed for the first time that intranasal metformin treatment improved the impaired cognitive functions through increasing insulin sensitivity in ICV-STZ-induced mice model of AD.

Recombinant AhpC antigen from Mycobacterium bovis boosts BCG-primed immunity in mice

Tuberculosis (TB) is still one of the most common infectious diseases around the world despite the widespread use of BCG (bacille Calmette-Guerin) strain of Mycobacterium bovis as a vaccine. This vaccine does not always protect people from TB, and, thus, new effective vaccines or vaccination strategies are being investigated. In this study, alkyl hydroperoxide reductase (AhpC) from M. bovis was evaluated as a new candidate vaccine antigen against TB in BALB/c mice model. The ahpC gene was amplified from M.bovis genome, cloned, and expressed in Escherichia coli. Vaccine antigen AhpC was formulated with Montanide ISA 61 VG, an oil-based emulsion adjuvant. Both IgG and IL-12 responses were observed in mice after administering the formulation both as a subunit vaccine alone and also as a booster vaccine for BCG immunization. However, a long-lasting response was observed when AhpC formulation was used as a booster (for BCG-primed immunization) as compared to being used as a subunit vaccine alone. In short, these findings suggested that AhpC has the potential to be used as a booster vaccine candidate for BCG-primed immunization.

The effects of 5-hydroxytryptophan on carrageenan-induced mouse paw oedemas

ABSTRACT Objective 5-Hydroxytryptophan is the precursor compound of serotonin biosynthesis. The oral absorption of 5-Hydroxytryptophan is close to 100% and, unlike serotonin, it crosses the blood-brain barrier freely. 5-Hydroxytryptophan has been used as a food supplement for many years to treat anxiety and depression. Recent studies have shown that 5-Hydroxytryptophan suppresses the pro-inflammatory mediators and is effective in some inflammatory diseases, such as arthritis and allergic asthma. However, the role of 5-Hydroxytryptophan supplements on acute peripheral inflammation has not been investigated yet. In this study, the in vivo anti-inflammatory activity of 5-Hydroxytryptophan was evaluated with a carrageenan-induced paw oedema test in mice. Methods For the investigation of the acute antiinflammatory activity, single oral doses of 5-Hydroxytryptophan (1.5, 5 and 20mg/kg) were given to mice 1.5 hours prior to the carrageenan test. For chronic activity, the same oral doses were administered daily for two weeks prior to the carrageenan test on the 14th day. To induce inflammation, 0.01mL of 2% carrageenan was injected into the paws of mice. Results Supplementation with 5-Hydroxytryptophan significantly reduced inflammation in a dose-independent manner which was irrespective of the duration of exposure (per cent inhibition in acute experiments was 35.4%, 20.9%, 24.0%, and per cent inhibition in chronic experiments was 29.5%, 35.3%, 40.8% for the doses of 1.5, 5, and 20mg/kg, respectively). Conclusion Our findings demonstrate for the first time that 5-HTP supplements have the potential of suppressing the measures of acute peripheral inflammation. It is suggested that, apart from several diseases where serotonin is believed to play an important role, including depression, patients with inflammatory conditions may also benefit from 5-HTP.

Design and Synthesis of 1,2,4-Triazolo[3,2-b]-1,3,5-thiadiazine Derivatives as a Novel Template for Analgesic/Anti-Inflammatory Activity

Previously, we demonstrated that certain heterocyclic compounds derived from 3-substituted-1,2,4-triazole-5-thiones had promising analgesic/anti-inflammatory activities together with low ulcerogenic properties. Therefore, we sought to design and synthesize new derivatives of triazol-5-thiones-fused heterocycles. In the present study, a series of novel bis-Mannich bases, namely 2,6-disubstituted-6,7-dihydro-5H-1,2,4-triazolo[3,2-b]-1,3,5-thiadiazines (1a-d, 2a-c, and 3a-d), were synthesized and characterized to assess their possible anti-inflammatory/analgesic properties. Additionally, their ability to induce gastric toxicity was also evaluated. Several of the condensed compounds produced a degree of analgesic activity comparable to reference drugs in both the hot plate and tail-flick tests. A strong anti-inflammatory effect was observed for the derivatives carrying a benzyl group at the second position (2a-c). The majority of the prepared compounds caused comparatively less gastrointestinal (GI) side effects than the reference drugs naproxen and indomethacin did. These results showed that 1,2,4-triazolo[3,2-b]-1,3,5-thiadiazine derivatives might afford a safer alternative to currently available analgesic/anti-inflammatory agents for the treatment and management of inflammatory disease and pain.

Lack of insulin results in reduced seladin-1 expression in primary cultured neurons and in cerebral cortex of STZ-induced diabetic rats

Several studies demonstrated that Diabetes mellitus (DM) enhances the risk for Alzheimer's disease (AD). Although hyperglycemia and perturbed function of insulin signaling have been proposed to contribute to AD pathogenesis, the molecular mechanisms behind this association is not clear yet. Seladin-1 is an enzyme catalyzing the last step in cholesterol biosynthesis converting desmosterol to cholesterol. The neuroprotective function of seladin-1 has gained interest in AD research recently. Seladin-1 has anti-apoptotic properties and regulates the expression of β-secretase (BACE-1). Here we measured seladin-1 mRNA and protein expressions in rat primary cultured neurons under diabetic conditions and also in the brains of rats with streptozotocine (STZ)-induced diabetes. We show that constant lack of insulin for 5days decreased seladin-1 levels in cultured rat primary neurons. Similarly, a decrease in seladin-1 was found in the brains of rats with STZ-induced diabetes. However, if the lack of insulin and/or high glucose treatment was intermittent, neuronal seladin-1 levels were not affected in vitro. On the other hand, treatment of neurons with metformin resulted in a significant increase in seladin-1. Constant lack of insulin for 5days, as well as high glucose treatment, increased the neuronal expression of BACE-1 in vitro, but not in the in vivo model. Our study defines insulin as a regulator of seladin-1 expression for the first time. The relevance of these findings for the association of DM with AD is discussed.

Novel thiazolo[3,2-b]-1,2,4-triazoles derived from naproxen with analgesic/anti-inflammatory properties: Synthesis, biological evaluation and molecular modeling studies

3-Substituted-1,2,4-triazole-5-thiones are versatile synthetic intermediates for the preparation of several biologically active N-bridged heterocyclic compounds, given that they have two reactive sites, thiocarbonyl and an amine nitrogen (N1/N4). For several years, our interest has focused on the synthesis of novel heterocyclic systems derived from 3-substituted-1,2,4-triazole-5-thiones having analgesic/anti-inflammatory activity. In this study, a series of novel thiazolo[3,2-b]-1,2,4-triazole-6(5H)-one derivatives bearing naproxen was synthesized and evaluated for their in vivo analgesic and anti-inflammatory properties in acute experimental pain and inflammation models. The compounds were also tested for their ulcerogenic potential. Our findings showed that all the newly synthesized derivatives attenuate nociception and inflammation compared with a control. All the synthesized compounds exhibited much lower ulcerogenic risk than the standard drugs indomethacin and naproxen. Some compounds with significant analgesic and/or anti-inflammatory activities as well as low ulcer scores were further evaluated for in vitro COX-1 and COX-2 inhibitory potential in a COX-catalyzed prostaglandin biosynthesis assay. Among the tested compounds, compound 1q showed the highest selectivity index (SI) of 4.87. The binding mode for some of the tested compounds to the cyclooxygenase (COX) enzymes was predicted using docking studies.

Effects of experimental diabetes on C/EBP proteins in rat hippocampus, sciatic nerve and ganglia

Neurodegeneration is one of the most important complications of diabetes mellitus (DM). The exact mechanisms underlying neurodegeneration related to diabetic complications such as cognitive deficits and peripheral neuropathy are not clarified yet. Due to the fact that CCAAT/enhancer binding proteins (C/EBPs) have roles in cognitive functions, memory, synaptic plasticity, inflammation, lipid storage, and response to neurotrophic factors, it is possible to suggest that these transcription factors could have roles in neurodegeneration. Hence, in this study, the effects of experimental diabetes on C/EBPs in the hippocampus, sciatic nerve, and ganglia tissues were examined. After experimentally induced diabetes, immunoreactivity of related proteins was measured by western blotting. C/EBPα immunoreactivity in the hippocampus was not altered at 4-weeks but significantly decreased at 12-weeks of diabetes. C/EBPβ immunoreactivity was not altered at 4-weeks whereas significantly increased at 12-weeks of diabetes. In the ganglion, C/EBPα immunoreactivity was significantly decreased in diabetes, but C/EBPβ immunoreactivity was not affected. In the sciatic nerve, C/EBPα and β immunoreactivities were significantly decreased in diabetic rats. Furthermore, insulin therapy prevented diabetes-induced alterations in C/EBPα and β immunoreactivities. This study indicated, for the first time, that DM altered the immunoreactivity of C/EBPs in the nervous system. C/EBPs might be one of the important molecular targets which are responsible for neurodegeneration seen in diabetes.