Adiponectin-mimetic novel nonapeptide rescues aberrant neuronal metabolic-associated memory deficits in Alzheimer's disease.

BACKGROUND: Recently, we and other researchers reported that brain metabolic disorders are implicated in Alzheimer's disease (AD), a progressive, devastating and incurable neurodegenerative disease. Hence, novel therapeutic approaches are urgently needed to explore potential and novel therapeutic targets/agents for the treatment of AD. The neuronal adiponectin receptor 1 (AdipoR1) is an emerging potential target for intervention in metabolic-associated AD. We aimed to validate this hypothesis and explore in-depth the therapeutic effects of an osmotin-derived adiponectin-mimetic novel nonapeptide (Os-pep) on metabolic-associated AD. METHODS: We used an Os-pep dosage regimen (5 µg/g, i.p., on alternating days for 45 days) for APP/PS1 in amyloid ß oligomer-injected, transgenic adiponectin knockout (Adipo-/-) and AdipoR1 knockdown mice. After behavioral studies, brain tissues were subjected to biochemical and immunohistochemical analyses. In separate cohorts of mice, electrophysiolocal and Golgi staining experiments were performed. To validate the in vivo studies, we used human APP Swedish (swe)/Indiana (ind)-overexpressing neuroblastoma SH-SY5Y cells, which were subjected to knockdown of AdipoR1 and APMK with siRNAs, treated with Os-pep and other conditions as per the mechanistic approach, and we proceeded to perform further biochemical analyses. RESULTS: Our in vitro and in vivo results show that Os-pep has good safety and neuroprotection profiles and crosses the blood-brain barrier. We found reduced levels of neuronal AdipoR1 in human AD brain tissue. Os-pep stimulates AdipoR1 and its downstream target, AMP-activated protein kinase (AMPK) signaling, in AD and Adipo-/- mice. Mechanistically, in all of the in vivo and in vitro studies, Os-pep rescued aberrant neuronal metabolism by reducing neuronal insulin resistance and activated downstream insulin signaling through regulation of AdipoR1/AMPK signaling to consequently improve the memory functions of the AD and Adipo-/- mice, which was associated with improved synaptic function and long-term potentiation via an AdipoR1-dependent mechanism. CONCLUSION: Our findings show that Os-pep activates AdipoR1/AMPK signaling and regulates neuronal insulin resistance and insulin signaling, which subsequently rescues memory deficits in AD and adiponectin-deficient models. Taken together, the results indicate that Os-pep, as an adiponectin-mimetic novel nonapeptide, is a valuable and promising potential therapeutic candidate to treat aberrant brain metabolism associated with AD and other neurodegenerative diseases.

Co-Treatment with Anthocyanins and Vitamin C Ameliorates Ethanol- Induced Neurodegeneration via Modulation of GABAB Receptor Signaling in the Adult Rat Brain.

Chronic ethanol exposure is known to cause neuronal damage in both humans and experimental animal models. Ethanol treatment induces neurotoxicity via the generation of reactive oxygen species (ROS), while anthocyanins (extracted from black soybean) and ascorbic acid (vitamin C) are free radical scavengers that can be used as neuroprotective agents against ROS. In this study the underlying neuroprotective potential of black soybean anthocyanins and vitamin C was determined. For this purpose, adult rats were exposed to 10% (v/v) ethanol for 8 weeks, followed by co-treatment with anthocyanins (24 mg/kg) and vitamin C (100 mg/kg) during the last 4 weeks. Our results showed that ethanol administration increased the expression of γ -aminobutyric acid B1 receptor (GABAB1R) and induced neuronal apoptosis via alterations to the Bax/Bcl-2 ratio, release of cytochrome C and activation of caspase-3 and caspase-9. Anthocyanins alone and supplementation with vitamin C showed an additive effect in reversing the trend of apoptotic signals induced by ethanol in the cortex and hippocampus. Consequently, anthocyanins also decreased the expression of poly (ADP ribose) polymerase-1 induced by ethanol and prevented DNA damage. Furthermore, anthocyanins and vitamin C reversed the ethanol-induced expression of GABAB1R and its downstream signaling molecule phospho-cAMP response element binding protein. Moreover, histopathology and immunohistochemistry results showed that anthocyanins and vitamin C significantly reduced ethanol-induced neuronal cell death. Our study revealed a neuroprotective role of anthocyanins and vitamin C via modulation of GABAB1R expression in the adult brain. Hence, we suggest that anthocyanins or co-treatment with anthocyanins and vitamin C may be a new and potentially effective neuroprotective agent for alcohol abuse.

Thymoquinone and vitamin C attenuates pentylenetetrazole-induced seizures via activation of GABAB1 receptor in adult rats cortex and hippocampus.

Epilepsy is a common neurological disorder that leads to neuronal excitability and provoke various forms of cellular reorganization in the brain. In this study, we investigate the anti-convulsant and neuroprotective effects of thymoquinone (TQ) and vitamin C against pentylenetetrazole (PTZ)-induced generalized seizures. Epileptic seizures were induced in adult rats using systemic intraperitoneal injections of PTZ (50 mg/kg) for 7 days. Animals pretreated with either TQ or vitamin C or in combination attenuated PTZ-induced seizures and mortality in rats as well neurodegeneration in the cells. Compared to PTZ, TQ and vitamin C significantly prolonged the onset of seizures (p > 0.05) as well decrease the high-grade seizures. Analysis of electroencephalogram (EEG) recordings revealed that TQ or vitamin C supplementation significantly reduced polyspike and epileptiform discharges. Epileptic seizures caused a decline in expression of gamma-aminobutyric acid B1 receptor (GABAB1R) (p > 0.05), unchanged expression of protein kinase A (PKA), decreased calcium/calmodulin-dependent protein kinase II (CaMKII) (p > 0.05) and inhibit the phosphorylation of cAMP response element-binding protein (CREB) (p > 0.05) in cortex and hippocampus, respectively, compared with control. Changes in expression of GABAB1R, CaMKII and CREB by PTZ were reversed by TQ and vitamin C supplementation. Moreover, PTZ significantly increased Bax, decreased Bcl-2 expression and finally the activation of caspase-3. TQ and vitamin C pretreatment reversed all these deleterious effects induced by PTZ. TQ and vitamin C showed anticonvulsant effects via activation of GABAB1R/CaMKII/CREB pathway and suggest a potential therapeutic role in epilepsy.

Anthocyanins attenuate body weight gain via modulating neuropeptide Y and GABAB1 receptor in rats hypothalamus.

Anthocyanins in a variety of plant species have been identified and are known for its hypolipidemic and anti-obesity effects. The effect of anthocyanins extracted from black soybean on body weight and daily food intake in adult rats raised on normal diet were studied. Male Sprague-Dawley rats were daily intra-gastric administered water or anthocyanins 6 mg/kg and 24 mg/kg for 40 days. During this period daily food intake and body weight were measured prior to anthocyanins treatment. These findings showed that anthocyanins treatment resulted in significantly lowered body weight and food intake compared with water treated rats. In addition, anthocyanins dose dependently reduced the adipose tissue size compared with control group. Western blot analysis showed that high dose of anthocyanins treatment significantly reduced the expression of neuropeptide Y (NPY) and increased γ-amino butyric acid receptor (GABAB1R) in hypothalamus. Furthermore, these events were followed by a decreased in expression of GABAB1R downstream signaling molecules protein kinase A-α (PKA) and phosphorylated cAMP-response element binding protein (p-CREB) in hypothalamus. These data support the concept that anthocyanins even in normal circumstances have the capability to reduce body weight and food intake through its modulatory effect on NPY and GABAB1R in hypothalamus. These results suggest that anthocyanins from black soybean seed coat might have a novel role in preventing obesity in rats on normal diet.