Minocycline reverses diabetes-associated cognitive impairment in rats

Effectiveness of pharmacotherapies for diabetes on nicotine, food, and water intake in insulin-resistant rats

The intersectionality between diabetes medications and nicotine consumption was assessed in female and male rats. Briefly, the rats were fed a high-fat diet (HFD) or regular diet (RD) for 4 weeks. Then separate groups received vehicle or a low dose of streptozotocin (STZ; 25 mg/kg). Three days later, insulin resistance was assessed by measuring plasma glucose levels for 180 min following an injection of insulin (0.75 U/kg). The rats were then prepared with jugular catheters, and they were given 23 h access to nicotine intravenous self-administration (IVSA) in 4 days cycles with 3 days of forced abstinence in their home cages where they consumed their respective diet. During the IVSA sessions, operant responses for food and water and changes in body weight were recorded. Prior to administration of the pharmacotherapies, the rats were given access to two doses of nicotine (0.015 then 0.03 mg/kg for the remainder of the study). Then, daily injections of the pharmacotherapies were given at the onset of dark cycle (6 p.m.) in the following order: 1) dapagliflozin (3.0 then 10.0 mg/kg), 2) insulin (0.75 U/kg twice), and 3) bromocriptine (3.0 then 10.0 mg/kg). The results suggest that our HFD+STZ regiment induced insulin resistance in female and male rats. Also, the HFD-fed rats displayed higher nicotine intake than RD controls, regardless of sex. Administration of insulin, but not dapagliflozin or bromocriptine, normalized nicotine intake in HFD-fed rats to control levels. These results have clinical implications regarding the potential efficacy of insulin to control excessive nicotine intake in persons with diabetes.

Minocycline alleviated scopolamine-induced amnesia by regulating antioxidant and cholinergic function

Background and aim

Minocycline, a tetracycline derivative, has been found to exert neuroprotective properties. The current project aimed to assess the antioxidant status and cholinergic function in the amnesia induced by scopolamine.

Methods

We evaluated the passive avoidance performance, acetylcholine esterase (AChE) enzyme activity, and the oxidative stress indicators in the following groups: Normal control, scopolamine, and the treatment groups (the animals were given minocycline (10-30 mg/kg)).

Results

Scopolamine (intraperitoneal) injection was associated with impairment of passive avoidance performance and neurotoxicity. Minocycline pronouncedly ameliorated scopolamine injury as presented by the increased latency time to darkness and stay time in lightness along with the decreased darkness entry. Moreover, minocycline decreased lipid peroxidation, while it elevated the levels of superoxide dismutase, AChE enzymes, and thiol groups in both the cortex and hippocampus.

Conclusion

Our data suggested that minocycline modulated the antioxidant status and AChE in the brains, which may contribute to its protective effects against scopolamine-induced amnesia.

Minocycline, a classic antibiotic, exerts psychotropic effects by normalizing microglial neuroinflammation-evoked tryptophan-kynurenine pathway dysregulation in chronically stressed male mice

The dysregulation of tryptophan-kynurenine pathway (TKP) is extensively involved in the pathophysiology of Alzheimer's disease, depression, and neurodegenerative disorders. Minocycline, a classic antibiotic, may exert psychotropic effects associated with the modulation of TKP. In this study, we examined the effects of minocycline in improving behaviour and modulating TKP components in chronically stressed male mice. Following repeated treatment with 22.5 mg/kg and 45 mg/kg minocycline for 27 days, the stressed mice particularly with higher dose displayed significant improvement on cognitive impairment, depression- and anxiety-like behaviour. Minocycline suppressed stress-induced overexpression of pro-inflammatory cytokines and restored anti-inflammatory cytokines. Chronic stress dramatically suppressed blood and prefrontal cortical levels of the primary substrate tryptophan (TRP), the neuroprotective metabolite kynurenic acid (KYNA), and KYNA/KYN ratio, but increased the intermediate kynurenine (KYN), 3-hydroxykynurenine (3-HK), KYN/TRP ratio, and the neurotoxic metabolite quinolinic acid (QUIN). Minocycline partially or completely reversed changes in these components. Minocycline also inhibited stress-induced overexpression of QUIN-related enzymes, indoleamine 2, 3-dioxygenase 1(iDO-1), kynureninase (KYNU), kynurenine 3-monooxygenase (KMO), 3-hydroxyanthranilate 3,4-dioxygenase (3-HAO), but rescued the decreased expression of kynurenine aminotransferase (KAT) in brain regions. Behavioral improvements were correlated with multiple TKP metabolites and enzymes. These results suggest that the psychotropic effects of minocycline are mainly associated with the restoration of biodistribution of the primary substrate in the brain and normalization of neuroinflammation-evoked TKP dysregulation.

Electroacupuncture improves cognitive impairment in diabetic cognitive dysfunction rats by regulating the mitochondrial autophagy pathway

Background

Diabetes-associated cognitive dysfunction has become a major public health concern. However, the mechanisms driving this disease are elusive. Herein, we explored how electroacupuncture improves learning and memory function in diabetic rats.

Methods

The diabetic model was established by intraperitoneal injection of streptozotocin (STZ) in adult Sprague–Dawley rats. Rats were fed on high-fat and high-sugar diets. Learning and memory functions were assessed using behavioral tests. The hematoxylin and eosin (H&E) staining, Western blotting, real-time PCR, ELISA, immunohistochemistry, and transmission electronic microscopy (TEM) was performed to test related indicators.

Results

High-fat and high-sugar diets impaired learning and memory function in rats, while electroacupuncture treatment reversed these changes. The model group presented highly prolonged escape latency compared to the control group, indicating impaired learning and memory functions. The TEM examination showed that electroacupuncture enhanced Aβ clearance and mitochondrial autophagy in hippocampal neuronal cells by increasing DISC1 expression.

Conclusions

Electroacupuncture improves learning and memory function in diabetic rats by increasing DISC1 expression to promote mitophagy. This enhanced Aβ clearance, alleviating cytotoxicity in hippocampal neuronal cells.

Minocycline attenuates cholinergic dysfunction and neuro-inflammation-mediated cognitive impairment in scopolamine-induced Alzheimer's rat model

OBJECTIVE

Minocycline, a semisynthetic tetracycline-derived antibiotic, has various pharmacological effect such as anti-inflammatory, anti-oxidative stress, and anti-apoptotic effects. The current study investigated the involvement of neuro-inflammatory, oxidative stress, and cholinergic markers in neuroprotection by minocycline against scopolamine-induced brain damage.

METHODS

Minocycline was administered (oral, 10, 15, and 30 mg/kg, daily) to groups of amnesic rats for 21 days. Passive avoidance memory and spatial learning and memory were assessed. Following that, oxidative stress, cholinergic function, and neuro-inflammation markers were evaluated in the brain tissue.

RESULTS

According to our biochemical data, treatment of the scopolamine-injured rats with minocycline decreased the levels of malondialdehyde and acetylcholinesterase (AChE) as well as mRNA expression of AChE and neuro-inflammation markers (tumor necrosis factor-α, interleukin (IL)-1β, IL-6). It also increased the total thiol levels and superoxide dismutase activity as well as mRNA expression of cholinergic receptor M1 (ChRM1). Moreover, minocycline modified distance and latencies in Morris water maze, prolonged latency to enter the black zone and light time while decreasing time spent and frequency of entries to darkness.

CONCLUSION

Taken together, the data indicate that treatment with minocycline improved memory dysfunction mediated possibly through restoring AChE and ChRM1 levels, oxidant/antioxidant balance, as well as inhibiting inflammatory responses.

Tetramethylpyrazine Attenuates Cognitive Impairment Via Suppressing Oxidative Stress, Neuroinflammation, and Apoptosis in Type 2 Diabetic Rats

Cognitive dysfunction is an important complication observed in type 2 diabetes mellitus (T2DM) patients. Tetramethylpyrazine (TMP) is known to exhibit anti-diabetic and neuroprotective properties. Therefore, the present study aimed to investigate the possible therapeutic effects of TMP against type 2 diabetes-associated cognitive impairment in rats. High-fat diet (HFD) followed by a low dose of streptozotocin (35 mg/kg) was used to induce diabetes in Sprague-Dawley rats. TMP (20, 40, and 80 mg/kg) and Pioglitazone (10 mg/kg) were administered for 4 weeks. The Morris water maze (MWM) and novel objective recognition task (NOR) tests were used to assess memory function. Fasting blood glucose (FBG), lipid profile, HOMA-IR, glycosylated hemoglobin (HbA1c), and glucose tolerance were measured. Acetylcholinesterase (AChE) and choline acetytransferase (ChAT) activity, acetylcholine (ACh) levels, oxidative stress, apoptotic (Bcl-2, Bax, caspase-3), and inflammatory markers (TNF-α, IL-1β, and NF-kβ) were assessed. BDNF, p-AKT, and p-CREB levels were also measured. In the present work, we observed that treatment of diabetic rats with TMP alleviated learning and memory deficits, improved insulin sensitivity, and attenuated hyperglycemia and dyslipidemia. Furthermore, treatment with TMP increased BDNF, p-Akt, and p-CREB levels, normalized cholinergic dysfunction, and suppressed oxidative, inflammatory, and apoptotic markers in the hippocampus. Collectively, our results suggest that the TMP may be an effective neuroprotective agent in alleviating type 2 diabetes-associated cognitive deficits.

Oligosaccharide and Flavanoid Mediated Prebiotic Interventions to Treat Gut Dysbiosis Associated Cognitive Decline

Oligosaccharides are potential prebiotic which maintains gut microbiota and improves gut health. The association of gut and brain is named as gut-brain-axis. Gut dysbiosis disrupts gut-brain-axis and effectively contributes to psychiatric disorders. In the present study, Xylo-oligosaccharide (XOS) and Quercetin were used as therapeutic interventions against gut dysbiosis mediated cognitive decline. Gut dysbiosis was established in mice through administration of Ampicillin Sodium, orally for 14 days. XOS and quercetin were administered separately or in combination along with antibiotic. Gene expression studies using mice faecal samples showed both XOS and quercetin could revive Lactobacillus, Bifidobacterium, Firmicutes and Clostridium which were reduced due to antibiotic treatment. FITC-dextran concentration in serum revealed XOS and quercetin protected intestinal barrier integrity against antibiotic associated damage. This was verified by histopathological studies showing restored intestinal architecture. Moreover, intestinal inflammation which increased after antibiotic treated animals was reduced upon XOS and quercetin treatment. Behavioural studies demonstrated that gut dysbiosis reduced fear conditioning, spatial and recognition memory which were reversed upon XOS and quercetin treatment. XOS and quercetin also reduced inflammation and acetylcholine esterase which were heightened in antibiotic treated animal brain. They also reduced oxidative stress, pro-inflammatory cytokines and chemokines and protected hippocampal neurons. In conclusion, XOS and quercetin effectively reduced antibiotic associated gut dysbiosis and prevented gut dysbiosis associated cognitive decline in mice.

Saccharomyces boulardii ameliorates gut dysbiosis associated cognitive decline

Saccharomyces boulardii, a probiotic yeast is well prescribed for various gastrointestinal disorders accompanied by gut dysbiosis such as inflammatory bowel disease, bacterial diarrhea and antibiotic associated diarrhea. Gut dysbiosis has been associated with central nervous system via gut brain axis primarily implied in the modulation of psychiatric conditions. In the current study we use Saccharomyces boulardii as a therapeutic agent against gut dysbiosis associated cognitive decline. In mice, gut dysbiosis was induced by oral Ampicillin Na (250 mg/kg twice-daily) for 14 days. While in the treatment group S. boulardii (90 mg/kg once a day) was administered orally for 21 days along with 14 days of antibiotic treatment. Gene expression studies revealed antibiotic mediated decrease in the Lactobacillus, Bifidobacterium, Firmicutes and Clostridium which were restored by S. boulardii treatment. Cognitive behavioral studies showed a parallel reduction in fear conditioning, spatial as well as recognition memory which were reversed upon S. boulardii treatment in these animals. S. boulardii treatment reduced myeloperoxidase enzyme, an inflammatory marker, in colon as well as brain which was increased after antibiotic administration. Similarly, S. boulardii reduced the brain acetylcholine esterase, oxidative stress and inflammatory cytokines and chemokines which were altered due to antibiotic treatment. S. boulardii treatment also protected hippocampal neuronal damage and restored villus length and crypt depth thus normalizing gut permeability in antibiotic treated animals. Hence, we conclude that S. boulardii prevented antibiotic associated gut dysbiosis leading to reduced intestinal and brain inflammation and oxidative stress thus preventing hippocampal neuronal damage and eventually reversing gut dysbiosis associate cognitive decline in mice.

Probiotics protect against gut dysbiosis associated decline in learning and memory

Gut-Brain-Axis imbalance due to gut dysbiosis by antibiotics may lead to neurobehavioral changes. Here we determine neuroprotective effect of probiotic against gut dysbiosis associated decline in learning and memory. Oral Ampicillin was used to induce gut dysbiosis while probiotic was administered along with antibiotic as treatment in Swiss albino mice. Antibiotic decreased Lactobacillus, Bifidobacterium, Firmicutes and Clostridium level. This was followed by reduced cognition, hippocampal neuronal density, intestinal crypt depth, villus length and increased corticohippocampal acetylcholinesterase, myeloperoxidase activity and oxidative stress which were partially reversed by probiotic treatment. Probiotic protected hippocampal neurons from gut dysbiosis associated inflammatory and oxidative damage in mice.

Ginseng Extracts, GS-KG9 and GS-E3D, Prevent Blood-Brain Barrier Disruption and Thereby Inhibit Apoptotic Cell Death of Hippocampal Neurons in Streptozotocin-Induced Diabetic Rats

Type 1 diabetes mellitus is known to be linked to the impairment of blood–brain barrier (BBB) integrity following neuronal cell death. Here, we investigated whether GS-KG9 and GS-E3D, bioactive ginseng extracts from Korean ginseng (Panax ginseng Meyer), inhibit BBB disruption following neuronal death in the hippocampus in streptozotocin-induced diabetic rats showing type 1-like diabetes mellitus. GS-KG9 and GS-E3D (50, 150, or 300 mg/kg, twice a day for 4 weeks) administered orally showed antihyperglycemic activity in a dose-dependent manner and significantly attenuated the increase in BBB permeability and loss of tight junction proteins. GS-KG9 and GS-E3D also inhibited the expression and activation of matrix metalloproteinase-9 and the infiltration of macrophages into the brain parenchyma, especially into the hippocampal region. In addition, microglia and astrocyte activation in the hippocampus and the expression of proinflammatory mediators such as tnf-α, Il-1β, IL-6, cox-2, and inos were markedly alleviated in GS-KG9 and GS-E3D-treated group. Furthermore, apoptotic cell death of hippocampal neurons, especially in CA1 region, was significantly reduced in GS-KG9 and GS-E3D-treated groups as compared to vehicle control. These results suggest that GS-KG9 and GS-E3D effectively prevent apoptotic cell death of hippocampal neurons by inhibiting BBB disruption and may be a potential therapy for the treatment of diabetic patients.