Wen Dong

Effect of caloric restriction on the SIRT1/mTOR signaling pathways in senile mice

AIMS To determine the effects and underlying molecular mechanisms of caloric restriction (CR) in C57BL/6 mice. METHODS Thirty-six 6-week-old male C57BL/6 mice were assigned to a normal control group (NC, n=12), a high energy group (HE, n=12), and a CR group (n=12), and received a normal diet, a high-calorie diet, or a calorie-restricted diet, respectively, for 44 weeks. Body weight and serum glucose concentration were regularly recorded, and animals were sacrificed and hippocampus tissues were collected for immunohistochemistry (n=6 per group), western blotting (n=3 per group) and real-time polymerase chain reaction (n=3 per group) analysis at the end of the 44-week experimental period. Immunohistochemistry, western blotting and real-time polymerase chain reaction were used to detect changes in hippocampal proteins may be involved in the SIRT1/mTOR pathways. RESULTS Body weight and serum glucose over the 44 weeks in animals from the CR group were lower than those of HE group. The number of SIRT1-immunoreactive cells in the CR group was significantly higher than in the NC and HE groups, and SIRT1 mRNA expression in the CR group was significantly higher than that in the HE group, but there was no difference in SIRT1 protein expression among the three groups. mTOR and S6K1 protein activation and mTOR and S6K1 mRNA were significantly lower in the CR group than in the NC group. CONCLUSIONS Our findings suggest that a CR diet could lead to activation of SIRT1 and suppression of mTOR and S6K1 activation in C57BL/6 mice. We have shown that the SIRT1/mTOR signaling pathways may be involved in the neuroprotective effect of CR.

The level of Alzheimer-associated neuronal thread protein in urine may be an important biomarker of mild cognitive impairment

Increased levels of Alzheimer-associated neuronal thread protein (AD7c-NTP) are often detected in urine in the early course of Alzheimers disease (AD), which makes it a promising biomarker for AD. However, whether the concentration of urinary AD7c-NTP is increased in patients with mild cognitive impairment (MCI) remains unclear. The aim of this study was to explore the value of urinary AD7c-NTP to assist in the diagnosis of cognitive impairment by comparing differences in urinary AD7c-NTP among normal controls, MCI patients and AD patients. One hundred and seventy patients from the Xuan wu Hospital, Capital Medical University were divided into three groups according to their clinical diagnosis: an AD group (n=45), an MCI group (n=60) and a normal group (n=65). The Mini Mental State Examination and the Montreal Cognitive Assessment scale were used to screen for the diagnosis of AD and MCI, and patients met the diagnostic criteria of the National Institute of Neurological Disorders and Stroke and the Alzheimers Disease and Related Disorders Association. The level of urinary AD7c-NTP was determined using the enzyme-linked immunosorbent assay method. The urinary levels of AD7c-NTP in the AD group (median 2.14 [range 0.49-6.39] ng/ml) and the MCI group (median 1.57 [range 0.4-4.15] ng/ml) were significantly higher than those of the normal group (median 0.53 [range 0.04-2.07] ng/ml). To our knowledge our study is the first to show that the level of urinary AD7c-NTP in MCI patients is higher than in healthy people, which suggests that the level of urinary AD7c-NTP may be an important biomarker for early diagnosis of MCI.

Rosiglitazone Improves Learning and Memory Ability in Rats With Type 2 Diabetes Through the Insulin Signaling Pathway

Abstract:Diabetes mellitus (DM) is associated with moderate cognitive deficits and neurophysiologic and structural changes in the brain, a condition that is referred to as diabetic encephalopathy. This study was performed to investigate the effect of rosiglitazone (RSG) on learning and memory in rats with DM and elucidate possible mechanisms underlying this condition. Thirty-two male Sprague-Dawley rats were randomly divided into 4 groups: control (C, n = 8), DM (n = 8), RSG-administered control (C + RSG, n = 8) and RSG-administered DM groups (DM + RSG, n = 8). At 8 weeks after drug administration, Morris water maze was used to perform a training and probe trial to detect spatial learning and memory abilities. Western blot and immunohistochemistry were also used to detect changes in proteins involved in the insulin signal transduction pathway, such as the insulin receptor, insulin receptor substrate-1, protein kinase B, phosphorylated cAMP response element–binding protein and B-cell lymphoma 2, in the hippocampus of the rats. This study found that RSG could normalize the impaired insulin signal transduction in type 2 DM. The authors showed that RSG modulated the central insulin signaling axis.

Alzheimer-associated urine neuronal thread protein level increases with age in a healthy Chinese population.

Alzheimer-associated neuronal thread protein (AD7c-NTP) has been found to be a biomarker for Alzheimers disease (AD) with elevated levels in the cerebrospinal fluid and urine from AD patients in the early stage of the disease. Whether the urine level of AD7c-NTP in healthy people is age-related is still unclear. We aimed to measure the level of urine AD7c-NTP in a healthy Chinese population of different ages. Urine samples of 294 subjects were collected from the Department of Health Examination Center at Xuanwu Hospital of Capital Medical University, China. The samples were divided into five groups by age: Group 1 (20-29 years), Group 2 (30-39 years), Group 3 (40-49 years), Group 4 (50-59 years) and Group 5 (⩾ 60 years). The Mini Mental State Examination and Montreal Cognitive Assessment were carried out. The level of AD7c-NTP in the urine specimen was detected by enzyme-linked immunosorbent assay. The urine AD7c-NTP levels in Group 1, 2, 3, 4 and 5 were 0.3012 ± 0.2373, 0.3702 ± 0.2422, 0.3914 ± 0.2442, 0.4844 ± 0.2908 and 0.5880 ± 0.2638 ng/ml (mean ± standard error of the mean), respectively. The urine AD7c-NTP levels among the five groups differed significantly (F=6.181, p=0.00). Females had a higher urine AD7c-NTP content than males, and the urine AD7c-NTP level increased with age (r=0.28, p=0.00). To our knowledge this study is the first to show that urine AD7c-NTP level increases with age in a healthy Chinese population without cognitive dysfunction. This study suggests that different cut-off values aimed at different age groups should be established for diagnosing cognitive impairments in clinical practice.

Short-term caloric restriction exerts neuroprotective effects following mild traumatic brain injury by promoting autophagy and inhibiting astrocyte activation

HighlightsCaloric restriction (CR) can ameliorate mild traumatic brain injury (mTBI).We demonstrated improved cognitive dysfunction in a mouse model of mTBI after CR.CR decreased the number of GFAP‐positive astrocytes in the hippocampus after mTBI.CR increased LC3b and Beclin1 expression and decreased mTOR expression.Short‐term CR may alleviate mTBI by promoting autophagy and suppressing astrocytes. Abstract Cognitive deficits may occur after mild traumatic brain injury (mTBI), but effective treatment modalities are presently unavailable. Caloric restriction (CR) has beneficial effects on neurodegenerative diseases and brain injury. However, the underlying mechanisms have not yet been clearly defined. Therefore, the aim of the present study was to investigate the short‐term effects of CR treatment on cognitive function in mice after mTBI. Forty‐five 12‐week‐old C57/BL6 mice were subjected to closed‐head mTBI using a weight drop device. The mice were then randomly divided into three groups according to their diet for 30 days: the normal calorie group (mTBI + NC group, n = 15), the caloric restriction group (mTBI + CR group, n = 15), and the high energy group (mTBI + HE group, n = 15). After 30 days, the Morris water maze test was performed to evaluate learning abilities. Nissl staining, immunohistochemistry, and western blotting were used to monitor pathological changes and changes in autophagy‐associated proteins in the hippocampus. The average escape latency was significantly shorter in the mTBI + CR group than in the mTBI + NC and mTBI + HE groups, and the number of target platform crossings in the mTBI + CR group was significantly higher than in the other two groups. In the hippocampus, the expression of GFAP and mTOR was increased in the mTBI + HE group and decreased in the mTBI + CR group. Conversely, the expression of LC3B was decreased in the mTBI + HE group and increased in the mTBI + CR group. Our findings suggest that short‐term CR after mTBI may ameliorate cognitive dysfunction induced by mTBI by increasing the level of autophagy and suppressing astrocyte activation.

Caloric restriction can improve learning and memory in C57/BL mice probably via regulation of the AMPK signaling pathway

&NA; Caloric restriction (CR) is effective in slowing aging and delaying aging‐related diseases in many species, but the mechanism is complex and not fully elucidated. This study aimed to evaluate the beneficial effects of a caloric restriction diet on learning and memory, and further to elucidate the mechanisms. Thirty‐six week‐old male C57/BL mice were randomly divided into three groups: normal control (NC group), high‐energy (HE group) and CR group. After 44 weeks, the Morris water maze was used to examine learning and memory abilities. Western blotting and immunohistochemistry were used to detect changes in proteins involved in the adenosine monophosphate‐activated protein kinase (AMPK) pathway in the mouse hippocampus. Compared with NC group, the swimming distance and escape latency were shorter in the CR group. The protein and mRNA expression of AMPK and glucose transporter type 4 (GLUT4) in the CR group were significantly higher than that in HE group. CR increased serum insulin‐like growth factor, adiponectin and vaspin, decreased blood glucose and serum malondialdehyde, and improved insulin sensitivity. Our findings demonstrate that a CR diet may improve hippocampus‐dependent spatial learning ability of C57/BL mice, accompanied with an increase in AMPK and GLUT4 expression, which indicates AMPK pathway was associated with the neuroprotective effect of CR in mice. HighlightsCR may improve hippocampus‐dependent spatial learning ability.CR increased AMPK and GLUT4 expression.AMPK pathway might play a role in cognitive performance.

Long-term caloric restriction in mice may prevent age-related learning impairment via suppression of apoptosis.

Caloric restriction (CR) is the most reliable intervention to extend lifespan and prevent age-related disorders in various species from yeast to rodents. However, the underlying mechanisms have not yet been clearly defined. Therefore, we aimed to identify the underlying mechanisms of long-term CR on age-related learning impairment in C57/BL mice. Thirty six-week-old male C57/BL mice were randomly divided into three groups: normal control group (NC group, n=10), high energy group (HE group, n=10), and CR group (n=10). After 10 months, the Morris water maze test was performed to monitor learning abilities. Western blotting, immunohistochemistry and real-time polymerase chain reaction were used to monitor changes in protein and mRNA levels associated with apoptosis-related proteins in the hippocampus. The average escape latency was lower in the CR group compared with the NC group, and the average time taken to first cross the platform in the CR group was significantly shorter than the HE group. Both Bcl-2 protein and mRNA expression levels in the CR group were significantly higher than those of the NC group and HE group. The expression of Bax, Caspase-3 and PARP protein in the CR group was significantly lower than the NC group. Our findings demonstrate that long-term CR may prevent age-related learning impairments via suppressing apoptosis in mice.