Metabolic syndrome (MetS) is a cluster of cardiovascular risk factors that includes obesity, diabetes, and dyslipidemia. Accumulating evidence implies that MetS contributes to the development and progression of Alzheimer's disease (AD); however, the factors connecting this association have not been determined. Insulin resistance (IR) is at the core of MetS and likely represent the key link between MetS and AD. In the central nervous system, insulin plays key roles in learning and memory, and AD patients exhibit impaired insulin signaling that is similar to that observed in MetS. As we face an alarming increase in obesity and T2D in all age groups, understanding the relationship between MetS and AD is vital for the identification of potential therapeutic targets. Recently, several diabetes therapies that enhance insulin signaling are being tested for a potential therapeutic benefit in AD and dementia. In this review, we will discuss MetS as a risk factor for AD, focusing on IR and the recent progress and future directions of insulin-based therapies.
Alzheimer Disease/etiology/metabolism ; Amyloid beta-Peptides/metabolism ; Animals ; Brain/metabolism ; Cognition Disorders/*etiology/*metabolism ; Humans ; Insulin/metabolism ; *Insulin Resistance ; Metabolic Syndrome X/complications/drug therapy/*metabolism ; Molecular Targeted Therapy ; Signal Transduction/drug effects ; tau Proteins/metabolism

OBJECTIVETo study the effect of Sailuotong capsule (Sailuotong) on learning and memory functions of multi-infarct dementia (MID) rats and its mechanism.

METHODAll SD rats were divided into five groups, namely the sham operation group, the model group, the positive group, the low dosage Sailuotong-treated group and the high dosage Sailuotong-treated group. The multi-infarct dementia model was established by injecting the micro-sphere vascular occlusive agent. On the 10th day after the successful operation, the rats were administered intragastrically with distilled water, memantine hydrochloride (20 mg x kg(-1)) and Sailuotong (16.5 mg x kg(-1) and 33.0 mg x kg(-1)) once a day for 60 days respectively, in order to detect the effect of Sailuotong in different doses on the latent period and route length in Morris water maze and the activities of choline acetyltransferase (ChAT) and acetylcholinesterase (AchE) in brain tissues.

RESULTCompared with the sham operation rats, it had been observed that the latent period and route length of MID rats in Morris water maze were significantly increased (P < 0.05 or P < 0.01), and the activity of ChAT in brain tissues was significantly decreased (P < 0.05). After the intervention with Sailuotong for sixty days, the latent period and route length of MID rats in Morris water maze significantly shrank (P < 0.05 or P < 0.01). Additionally, Sailuotong decreased AchE activity, while increasing ChAT activity in brain tissues of MID rats (P < 0.05 or P < 0.01).

CONCLUSIONSailuotong capsule can improve cognitive dysfunction of MID rats to some extent. Its mechanism may be related to its different regulation of activities of ChAT and AchE in brain tissues.

Acetylcholinesterase ; metabolism ; Animals ; Brain ; metabolism ; pathology ; Choline O-Acetyltransferase ; metabolism ; Cognition Disorders ; drug therapy ; etiology ; metabolism ; Dementia, Multi-Infarct ; complications ; metabolism ; Drugs, Chinese Herbal ; administration & dosage ; pharmacology ; Male ; Maze Learning ; drug effects ; Rats ; Rats, Sprague-Dawley

OBJECTIVENitric oxide (NO) was speculated to play an important role in the pathophysiology of cerebral ischemia. Minocycline, a tetracycline derivative, reduced inflammation and protected against cerebral ischemia. To study the neuroprotection mechanism of minocycline for vascular dementia, the influences of minocycline on expressions of inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) were observed in the brains of Wistar rats.

METHODSThe vascular dementia rat model was established by permanent bilateral common carotid arteries occlusion (BCCAO). Wistar rats were divideded into 3 groups randomly: sham-operation group (S group), vascular dementia model group (M group), and minocycline treatment group (MT group). The behaviour was tested with Morris water maze and open-field task. Expressions of iNOS and eNOS were measured by immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR). The optical density value was measured by imaging analysis. Percentage of positive cells with iNOS and eNOS expression was analyzed with optical microscope.

RESULTSMinocycline attenuated cognitive impairment. Inducible NOS was significantly down-regulated in MT group, compared with that in M group (P < 0.01), while eNOS was significantly up-regulated, compared with that in M group (P < 0.01). The expressions of iNOS and eNOS in M and MT groups were higher than those in S group (P < 0.01).

CONCLUSIONMinocycline can down-regulate the expression of iNOS and up-regulate the expression of eNOS in vascular dementia, which restrains apoptosis and oxidative stress to protect neural function.

Animals ; Behavior, Animal ; drug effects ; Carotid Artery Diseases ; complications ; Carotid Artery, Common ; Cognition Disorders ; drug therapy ; etiology ; pathology ; Disease Models, Animal ; Exploratory Behavior ; drug effects ; Female ; Hippocampus ; drug effects ; physiopathology ; Maze Learning ; drug effects ; Minocycline ; therapeutic use ; Nitric Oxide Synthase Type II ; metabolism ; Nitric Oxide Synthase Type III ; metabolism ; Oxidative Stress ; drug effects ; Rats ; Rats, Wistar ; Reaction Time ; drug effects ; Time Factors