Changes in hippocampal volume, synaptic plasticity and amylin sensitivity in an animal model of type 2 diabetes are associated with increased vulnerability to amyloid-beta in advancing age.

Type-2 diabetes (T2D) is a metabolic disorder that is considered a risk factor for Alzheimer's disease (AD). Cognitive impairment can arise due to hypoglycemia associated with T2D, and hyperamylinemia associated with insulin resistance can enhance AD pathology. We explored whether changes occur in the hippocampus in aging (6-12 months old) female V-Lep○b-/- transgenic (tg) mice, comprising an animal model of T2D. We also investigated whether an increase in vulnerability to Aß (1-42), a known pathological hallmark of AD, is evident. Using magnetic resonance imaging we detected significant decreases in hippocampal brain volume in female tg-mice compared to wild-type (wt) littermates. Long-term potentiation (LTP) was impaired in tg compared to wt mice. Treatment of the hippocampus with Aß (1-42) elicited a stronger debilitation of LTP in tg compared to wt mice. Treatment with an amylin antagonist (AC187) significantly enhanced LTP in wt and tg mice, and rescued LTP in Aß (1-42)-treated tg mice. Taken together our data indicate that a T2D-like state results in an increased vulnerability of the hippocampus to the debilitating effects of Aß (1-42) and that effects are mediated in part by changes in amylin receptor signaling.

Starvation in Mice Induces Liver Damage Associated with Autophagy.

Anorexia nervosa (AN) induces organ dysfunction caused by malnutrition, including liver damage leading to a rise in transaminases due to hepatocyte damage. The underlying pathophysiology of starvation-induced liver damage is poorly understood. We investigate the effect of a 25% body weight reduction on murine livers in a mouse model and examine possible underlying mechanisms of starvation-induced liver damage. Female mice received a restricted amount of food with access to running wheels until a 25% weight reduction was achieved. This weight reduction was maintained for two weeks to mimic chronic starvation. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were measured spectrophotometrically. Liver fat content was analyzed using an Oil Red O stain, and liver glycogen was determined using a Periodic acid-Schiff (PAS) stain. Immunohistochemical stains were used to investigate macrophages, proliferation, apoptosis, and autophagy. Starvation led to an elevation of AST and ALT values, a decreased amount of liver fat, and reduced glycogen deposits. The density of F4/80+ macrophage numbers as well as proliferating KI67+ cells were decreased by starvation, while apoptosis was not altered. This was paralleled by an increase in autophagy-related protein staining. Increased transaminase values suggest the presence of liver damage in the examined livers of starved mice. The observed starvation-induced liver damage may be attributed to increased autophagy. Whether other mechanisms play an additional role in starvation-induced liver damage remains to be investigated.

[18F]GE-180-PET and Post Mortem Marker Characteristics of Long-Term High-Fat-Diet-Induced Chronic Neuroinflammation in Mice.

Obesity is characterized by immoderate fat accumulation leading to an elevated risk of neurodegenerative disorders, along with a host of metabolic disturbances. Chronic neuroinflammation is a main factor linking obesity and the propensity for neurodegenerative disorders. To determine the cerebrometabolic effects of diet-induced obesity (DIO) in female mice fed a long-term (24 weeks) high-fat diet (HFD, 60% fat) compared to a group on a control diet (CD, 20% fat), we used in vivo PET imaging with the radiotracer [18F]FDG as a marker for brain glucose metabolism. In addition, we determined the effects of DIO on cerebral neuroinflammation using translocator protein 18 kDa (TSPO)-sensitive PET imaging with [18F]GE-180. Finally, we performed complementary post mortem histological and biochemical analyses of TSPO and further microglial (Iba1, TMEM119) and astroglial (GFAP) markers as well as cerebral expression analyses of cytokines (e.g., Interleukin (IL)-1ß). We showed the development of a peripheral DIO phenotype, characterized by increased body weight, visceral fat, free triglycerides and leptin in plasma, as well as increased fasted blood glucose levels. Furthermore, we found obesity-associated hypermetabolic changes in brain glucose metabolism in the HFD group. Our main findings with respect to neuroinflammation were that neither [18F]GE-180 PET nor histological analyses of brain samples seem fit to detect the predicted cerebral inflammation response, despite clear evidence of perturbed brain metabolism along with elevated IL-1ß expression. These results could be interpreted as a metabolically activated state in brain-resident immune cells due to a long-term HFD.

Leptin deficiency-caused behavioral change - A comparative analysis using EthoVision and DeepLabCut.

Introduction: Obese rodents e.g., the leptin-deficient (ob/ob) mouse exhibit remarkable behavioral changes and are therefore ideal models for evaluating mental disorders resulting from obesity. In doing so, female as well as male ob/ob mice at 8, 24, and 40 weeks of age underwent two common behavioral tests, namely the Open Field test and Elevated Plus Maze, to investigate behavioral alteration in a sex- and age dependent manner. The accuracy of these tests is often dependent on the observer that can subjectively influence the data. Methods: To avoid this bias, mice were tracked with a video system. Video files were further analyzed by the compared use of two software, namely EthoVision (EV) and DeepLabCut (DLC). In DLC a Deep Learning application forms the basis for using artificial intelligence in behavioral research in the future, also with regard to the reduction of animal numbers. Results: After no sex and partly also no age-related differences were found, comparison revealed that both software lead to almost identical results and are therefore similar in their basic outcomes, especially in the determination of velocity and total distance movement. Moreover, we observed additional benefits of DLC compared to EV as it enabled the interpretation of more complex behavior, such as rearing and leaning, in an automated manner. Discussion: Based on the comparable results from both software, our study can serve as a starting point for investigating behavioral alterations in preclinical studies of obesity by using DLC to optimize and probably to predict behavioral observations in the future.

The effect of different weight loss strategies to treat non-alcoholic fatty liver disease focusing on fibroblast growth factor 21.

Objective: Obesity, often associated with non-alcoholic fatty liver disease (NAFLD), is characterized by an imbalance between energy expenditure and food intake, which is also reflected by desensitization of fibroblast growth factor 21 (FGF21). FGF21 is strongly influenced, among others, by TNFα, which is known to be upregulated in obesity-induced inflammation. Successful long-term treatments of NAFLD might be dietary modification, exercise, or fasting. Materials and methods: Whether succeeded NAFLD recovery is linked with improved FGF21 sensitivity and finally reverted FGF21 resistance was the focus of the present study. For this purpose, mice received a high-fat diet (HFD) for 6 months to establish obesity. Afterward, the mice were subjected to three different weight loss interventions, namely, dietary change to low-fat diet (LFD), treadmill training, and/or time-restricted feeding for additional 6 months, whereas one group remained on HFD. Results: In addition to the expected decrease in NAFLD activity with dietary change, this was also observed in the HFD group with additional time-restricted feeding. There was also an associated decrease in hepatic TNFα and FGF21 expression and an increase in ß-klotho expression, demonstrated mainly by using principal component analysis. Pearson correlation analysis shows that independent of any intervention, TNFα expression decreased with improved NAFLD recovery. This was accompanied with higher FGF21 sensitivity, as expressed by an increase in ß-klotho and FGFR1c expression and concomitantly decreased FGF21 levels. Conclusion: In summary, we conclude that successful NAFLD therapy is associated with a reversion of the TNFα-triggered FGF21-resistant state or desensitization.

Dietary intervention improves health metrics and life expectancy of the genetically obese Titan mouse.

Suitable animal models are essential for translational research, especially in the case of complex, multifactorial conditions, such as obesity. The non-inbred mouse (Mus musculus) line Titan, also known as DU6, is one of the world's longest selection experiments for high body mass and was previously described as a model for metabolic healthy (benign) obesity. The present study further characterizes the geno- and phenotypes of this non-inbred mouse line and tests its suitability as an interventional obesity model. In contrast to previous findings, our data suggest that Titan mice are metabolically unhealthy obese and short-lived. Line-specific patterns of genetic invariability are in accordance with observed phenotypic traits. Titan mice also show modifications in the liver transcriptome, proteome, and epigenome linked to metabolic (dys)regulations. Importantly, dietary intervention partially reversed the metabolic phenotype in Titan mice and significantly extended their life expectancy. Therefore, the Titan mouse line is a valuable resource for translational and interventional obesity research.

A Role for Peripheral Anandamide and 2-Arachidonoylglycerol in Short-Term Food Intake and Orexigenic Hypothalamic Responses in a Species with Continuous Nutrient Delivery.

The endocannabinoid system (ECS) plays a pivotal role in the complex control and regulation of food intake. Pharmacological ECS activation could improve health in energy-deficient stages by increasing food intake, at least in intermittent feeders. However, knowledge of the mechanism regulating appetite in species with continued nutrient delivery is incomplete. The objectives of this pilot study were to investigate the effect of the intraperitoneal (i.p.) administration of the endocannabinoids (ECs) anandamide (AEA) and 2-arachidonoylglycerol (2-AG) on food intake, plasma EC concentrations and hypothalamic orexigenic signaling, and to study how the circulatory EC tone changes in response to short-term food deprivation in dairy cows, a species with continuous nutrient delivery. The administration of EC resulted in higher food intake during the first hour after treatment. Plasma AEA concentrations were significantly increased 2.5 h after AEA injection, whereas plasma 2-AG concentrations remained unchanged 2.5 h after 2-AG injection. The hypothalamic immunoreactivity of cannabinoid receptor 1, agouti-related protein, and orexin-A was not affected by either treatment; however, neuropeptide Y and agouti-related protein mRNA abundances were downregulated in the arcuate nucleus of AEA-treated animals. Short-term food deprivation increased plasma 2-AG, while plasma AEA remained unchanged. In conclusion, i.p.-administered 2-AG and AEA increase food intake in the short term, but only AEA accumulates in the circulation. However, plasma 2-AG concentrations are more responsive to food deprivation than AEA.

Fibroblast Growth Factor 21 as a Potential Biomarker for Improved Locomotion and Olfaction Detection Ability after Weight Reduction in Obese Mice.

Obesity is one of the most challenging diseases of the 21st century and is accompanied by behavioural disorders. Exercise, dietary adjustments, or time-restricted feeding are the only successful long-term treatments to date. Fibroblast growth factor 21 (FGF21) plays a key role in dietary regulation, but FGF21 resistance is prevalent in obesity. The aim of this study was to investigate in obese mice whether weight reduction leads to improved behaviour and whether these behavioural changes are associated with decreased plasma FGF21 levels. After establishing a model for diet-induced obesity, mice were subjected to three different interventions for weight reduction, namely dietary change, treadmill exercise, or time-restricted feeding. In this study, we demonstrated that only the combination of dietary change and treadmill exercise affected all parameters leading to a reduction in weight, fat, and FGF21, as well as less anxious behaviour, higher overall activity, and improved olfactory detection abilities. To investigate the interrelationship between FGF21 and behavioural parameters, feature selection algorithms were applied designating FGF21 and body weight as one of five highly weighted features. In conclusion, we concluded from the complementary methods that FGF21 can be considered as a potential biomarker for improved behaviour in obese mice after weight reduction.

Neuronal Hyperexcitability in APPSWE/PS1dE9 Mouse Models of Alzheimer's Disease.

Transgenic mouse models serve a better understanding of Alzheimer's disease (AD) pathogenesis and its consequences on neuronal function. Well-known and broadly used AD models are APPswe/PS1dE9 mice, which are able to reproduce features of amyloid-ß (Aß) plaque formations as well as neuronal dysfunction as reflected in electrophysiological recordings of neuronal hyperexcitability. The most prominent findings include abnormal synaptic function and synaptic reorganization as well as changes in membrane threshold and spontaneous neuronal firing activities leading to generalized excitation-inhibition imbalances in larger neuronal circuits and networks. Importantly, these findings in APPswe/PS1dE9 mice are at least partly consistent with results of electrophysiological studies in humans with sporadic AD. This underscores the potential to transfer mechanistic insights into amyloid related neuronal dysfunction from animal models to humans. This is of high relevance for targeted downstream interventions into neuronal hyperexcitability, for example based on repurposing of existing antiepileptic drugs, as well as the use of combinations of imaging and electrophysiological readouts to monitor effects of upstream interventions into amyloid build-up and processing on neuronal function in animal models and human studies. This article gives an overview on the pathogenic and methodological basis for recording of neuronal hyperexcitability in AD mouse models and on key findings in APPswe/PS1dE9 mice. We point at several instances to the translational perspective into clinical intervention and observation studies in humans. We particularly focus on bi-directional relations between hyperexcitability and cerebral amyloidosis, including build-up as well as clearance of amyloid, possibly related to sleep and so called glymphatic system function.

Long-Term Caloric Restriction Attenuates ß-Amyloid Neuropathology and Is Accompanied by Autophagy in APPswe/PS1delta9 Mice.

Caloric restriction (CR) slows the aging process, extends lifespan, and exerts neuroprotective effects. It is widely accepted that CR attenuates ß-amyloid (Aß) neuropathology in models of Alzheimer's disease (AD) by so-far unknown mechanisms. One promising process induced by CR is autophagy, which is known to degrade aggregated proteins such as amyloids. In addition, autophagy positively regulates glucose uptake and may improve cerebral hypometabolism-a hallmark of AD-and, consequently, neural activity. To evaluate this hypothesis, APPswe/PS1delta9 (tg) mice and their littermates (wild-type, wt) underwent CR for either 16 or 68 weeks. Whereas short-term CR for 16 weeks revealed no noteworthy changes of AD phenotype in tg mice, long-term CR for 68 weeks showed beneficial effects. Thus, cerebral glucose metabolism and neuronal integrity were markedly increased upon 68 weeks CR in tg mice, indicated by an elevated hippocampal fluorodeoxyglucose [18F] ([18F]FDG) uptake and increased N-acetylaspartate-to-creatine ratio using positron emission tomography/computer tomography (PET/CT) imaging and magnet resonance spectroscopy (MRS). Improved neuronal activity and integrity resulted in a better cognitive performance within the Morris Water Maze. Moreover, CR for 68 weeks caused a significant increase of LC3BII and p62 protein expression, showing enhanced autophagy. Additionally, a significant decrease of Aß plaques in tg mice in the hippocampus was observed, accompanied by reduced microgliosis as indicated by significantly decreased numbers of iba1-positive cells. In summary, long-term CR revealed an overall neuroprotective effect in tg mice. Further, this study shows, for the first time, that CR-induced autophagy in tg mice accompanies the observed attenuation of Aß pathology.

Neuroprotective Effects of the FGF21 Analogue LY2405319.

BACKGROUND: To date, there are no effective treatments for Alzheimer's disease (AD). Thus, a significant need for research of therapies remains. OBJECTIVE: One promising pharmacological target is the hormone fibroblast growth factor 21 (FGF21), which is thought to be neuroprotective. A clinical candidate for medical use could be the FGF21 analogue LY2405319 (LY), which has a specificity and potency comparable to FGF21. METHODS: The present study investigated the potential neuroprotective effect of LY via PPARγ/apoE/abca1 pathway, which is known to degrade amyloid-ß (Aß) plaques by using primary glial cells and hippocampal organotypic brain slice cultures (OBSCs) from 30- and 50-week-old transgenic APPswe/PS1dE9 (tg) mice. By LY treatment of 52-week-old tg mice with advanced Aß deposition, we further aimed to elaborate the effect of LY on AD pathology in vivo. RESULTS: LY application to primary glial cells caused an upregulation of pparγ, apoE, and abca1 mRNA expression and significantly decreased number and area of Aß plaques in OBSCs. LY treatment in tg mice increased cerebral [18F] FDG uptake and N-acetylaspartate/creatine ratio indicating enhanced neuronal activity and integrity. Although LY did not reduce the number of Aß plaques in tg mice, the number of iba1-positive cells was significantly decreased indicating reduced microgliosis. CONCLUSION: These data identified LY in vitro as an activator of Aß degrading genes leading to cerebral Aß load amelioration in early and late AD pathology. Although Aß plaque reduction by LY failed in vivo, LY may be used as therapeutic agent to treat AD-related neuroinflammation and impaired neuronal integrity.

Dietary-Induced Low-Grade Inflammation in the Liver.

The literature describes a close correlation between metabolic disorders and abnormal immune responses, like low-grade inflammation (LGI), which may be one mechanistic link between obesity and various comorbidities, including non-alcoholic fatty liver disease (NAFLD). In our study, we investigated the influence of dietary composition on obesity-derived LGI in the liver. We used a dietary induced obesity mouse model of C57BL/6J mice fed with high fat diet (HFD, 60% fat, 20% protein, 20% carbohydrates) and two different controls. One was rich in carbohydrates (10% fat, 20% protein, 70% carbohydrates), further referred to as the control diet (CD), and the other one is referred to as the standard diet (SD), with a more balanced macronutrient content (9% fat, 33% protein, 58% carbohydrates). Our results showed a significant increased NAFLD activity score in HFD compared to both controls, but livers of the CD group also differed in their macroscopic appearance from healthy livers. Hepatic fat content showed significantly elevated cholesterol concentrations in the CD group. Histologic analysis of the cellular immune response in the liver showed no difference between HFD and CD and expression analysis of immunologic mediators like interleukin (IL)-1ß, IL-6, IL-10 and tumor necrosis factor alpha also point towards a pro-inflammatory response to CD, comparable to LGI in HFD. Therefore, when studying diet-induced obesity with a focus on inflammatory processes, we encourage researchers to carefully select controls and not use a control diet disproportionally rich in carbohydrates.

Longitudinal [18F]FDG-PET/CT analysis of the glucose metabolism in ApoE-deficient mice.

BACKGROUND: Strong line of evidence suggests that the increased risk to develop AD may at least be partly mediated by cholesterol metabolism. A key regulator of cholesterol transport is the Apolipoprotein E4 (ApoE4), which plays a fundamental role in neuronal maintenance and repair. Impaired function of ApoE4 may contribute to altered cerebral metabolism leading to higher susceptibility to neurodegeneration. METHODS: To determine a possible link between ApoE function and alterations in AD in the brain of Apolipoprotein E-deficient mice (ApoE-/-) in a longitudinal manner metabolic and neurochemical parameters were analyzed. Cortical metabolism was measured by 2-deoxy-2-[18F]fluoroglucose ([18F]FDG)-PET/CT and proton magnetic resonance spectroscopy (1H-MRS) served to record neurochemical status. RESULTS: By using [18F]FDG-PET/CT, we showed that brain metabolism declined significantly stronger with age in ApoE-/- versus wild type (wt) mice. This difference was particularly evident at the age of 41 weeks in almost each analyzed brain region. In contrast, the 1H-MRS-measured N-acetylaspartate to creatine ratio, a marker of neuronal viability, did not decline with age and did not differ between ApoE-/- and wt mice. CONCLUSION: In summary, this longitudinal in vivo study shows for the first time that ApoE-/- mice depict cerebral hypometabolism without neurochemical alterations.

Involvement of Plasma Endocannabinoids and the Hypothalamic Endocannabinoid System in Increasing Feed Intake after Parturition of Dairy Cows.

The endocannabinoids (ECs) N-arachidonylethanolamide (anandamide; AEA) and 2-arachidonoylglycerol (2-AG) participate in the control of feed intake and energy metabolism. Most mammals increase their feed intake after parturition to cope with the increased energy and nutrient requirements for milk synthesis, thereby increasing their metabolic rate. Here we investigated in experiment 1 the regulation of plasma AEA and 2-AG concentrations during the transition from late pregnancy to early lactation in dairy cows, and analyzed in experiment 2 the expression of the EC system in the paraventricular nucleus (PVN) and the arcuate nucleus (ARC) of the hypothalamus of late and early lactating cows using immunohistochemistry. Cows in experiment 1 were retrospectively grouped based on peak plasma fatty acid concentrations to a high (H) or low (L) group. Feed intake was not different between groups before parturition, but was lower in H than L cows during early lactation. Plasma AEA and 2-AG concentrations increased 2.2- to 2.4-fold during early lactation, in which time plasma AEA concentrations rose faster in H cows than in L cows postpartum. Upregulation of N-acyl phosphatidylethanolamine-specific phospholipase D together with tending increased cannabinoid receptor 1 (CB1) expression, and downregulation of fatty acid amide hydrolase in early lactating cows suggested an increased PVN AEA tone. The abundance of CB1 in the ARC and diacylglycerol lipase-alpha was not different between late and early lactating cows, but PVN monoacylglycerol lipase expression was 30% higher in early lactating cows, indicating diminished PVN 2-AG concentrations. The results show a potential involvement of AEA in stimulating feed intake and of 2-AG in regulating energy metabolism of early lactating cows.

Defining body-weight reduction as a humane endpoint: a critical appraisal.

In many animal experiments scientists and local authorities define a body-weight reduction of 20% or more as severe suffering and thereby as a potential parameter for humane endpoint decisions. In this study, we evaluated distinct animal experiments in multiple research facilities, and assessed whether 20% body-weight reduction is a valid humane endpoint criterion in rodents. In most experiments (restraint stress, distinct models for epilepsy, pancreatic resection, liver resection, caloric restrictive feeding and a mouse model for Dravet syndrome) the animals lost less than 20% of their original body weight. In a glioma model, a fast deterioration in body weight of less than 20% was observed as a reliable predictor for clinical deterioration. In contrast, after induction of chronic diabetes or acute colitis some animals lost more than 20% of their body weight without exhibiting major signs of distress. In these two animal models an exclusive application of the 20% weight loss criterion for euthanasia might therefore result in an unnecessary loss of animals. However, we also confirmed that this criterion can be a valid parameter for defining the humane endpoint in other animal models, especially when it is combined with additional criteria for evaluating distress. In conclusion, our findings strongly suggest that experiment and model specific considerations are necessary for the rational integration of the parameter 'weight loss' in severity assessment schemes and humane endpoint criteria. A flexible implementation tailored to the experiment or intervention by scientists and authorities is therefore highly recommended.

Liver-specific Bid silencing inhibits APAP-induced cell death in mice.

Acetaminophen (APAP)-induced acute liver failure (ALF) is a life-threatening disease with only a few treatment options available. Though extensive research has been conducted for more than 40 years, the underlying pathomechanisms are not completely understood. Here, we studied as to whether APAP-induced ALF can be prevented in mice by silencing the BH3-interacting domain death agonist (Bid) as a potential key player in APAP pathology. For silencing Bid expression in mice, siRNABid was formulated with the liver-specific siRNA delivery system DBTC and administered 48 h prior to APAP exposure. Mice which were pre-treated with HEPES (vehicleHEPES) and siRNALuci served as siRNA controls. Hepatic pathology was assessed by in vivo fluorescence microscopy, molecular biology, histology and laboratory analysis 6 h after APAP or PBS exposure. Application of siRNABid caused a significant decrease of mRNA and protein expression of Bid in APAP-exposed mice. Off-targets, such as cytochrome P450 2E1 and glutathione, which are known to be consumed under APAP intoxication, were comparably reduced in all APAP-exposed mice, underlining the specificity of Bid silencing. In APAP-exposed mice non-sterile inflammation with leukocyte infiltration and perfusion failure remained almost unaffected by Bid silencing. However, the Bid silencing reduced hepatocellular damage, evident by a remarkable decrease of DNA fragmented cells in APAP-exposed mice. In these mice, the expression of the pro-apoptotic protein Bax, which recently gained importance in the cell death pathway of regulated necrosis, was also significantly reduced, in line with a decrease in both, necrotic liver tissue and plasma transaminase activities. In addition, plasma levels of HMGB1, a marker of sterile inflammation, were significantly diminished. In conclusion, the liver-specific silencing of Bid expression did not protect APAP-exposed mice from microcirculatory dysfunction, but markedly protected the liver from necrotic cell death and in consequence from sterile inflammation. The study contributes to the understanding of the molecular mechanism of the APAP-induced pathogenic pathway by strengthening the importance of Bid and Bid silencing associated effects.

Current Challenges in Understanding the Cellular and Molecular Mechanisms in Niemann-Pick Disease Type C1.

Rare diseases are a heterogeneous group of very different clinical syndromes. Their most common causes are defects in the hereditary material, and they can therefore be passed on to descendants. Rare diseases become manifest in almost all organs and often have a systemic expressivity, i.e., they affect several organs simultaneously. An effective causal therapy is often not available and can only be developed when the underlying causes of the disease are understood. In this review, we focus on Niemann-Pick disease type C1 (NPC1), which is a rare lipid-storage disorder. Lipids, in particular phospholipids, are a major component of the cell membrane and play important roles in cellular functions, such as extracellular receptor signaling, intracellular second messengers and cellular pressure regulation. An excessive storage of fats, as seen in NPC1, can cause permanent damage to cells and tissues in the brain and peripheral nervous system, but also in other parts of the body. Here, we summarize the impact of NPC1 pathology on several organ systems, as revealed in experimental animal models and humans, and give an overview of current available treatment options.

Metformin Therapy Aggravates Neurodegenerative Processes in ApoE-/- Mice.

Epidemiological studies suggest that individuals with diabetes mellitus are at greater risk of developing Alzheimer's disease. A well-known insulin-sensitizing drug and the most widely prescribed oral medication for diabetes is metformin. There is evidence that metformin acts in a neuroprotective manner via the AMPK/mTOR pathway by inhibiting the tau phosphorylation. In addition, it is known that metformin upregulates Fgf21, which in turn activates the AMPK/mTOR pathway and mediates neuroprotection. Thus, metformin-induced Fgf21 release may be involved in AMPK/mTOR activation. However, some studies reported that metformin causes cognition impairment. Due to the controversial data on the neuroprotective properties of metformin, we treated Apolipoprotein E deficient (ApoE- /-) mice, a mouse model of tauopathy, with metformin for 18 weeks. Metformin-treated mice revealed increased expression of lipogenic genes, i.e., lxrα and srebp1c. In line with this, metformin caused an increase in plasma triglyceride leading to enhanced gliosis as indicated by an increase of GFAP-positive cells. Although the systemic Fgf21 concentration was increased, metformin did not activate the FgfR1c/AMPK/mTOR pathway suggesting a Fgf21-resistant state. Further, metformin-treated mice showed increased tau phosphorylation and reduced numbers of NeuN-and PSD95-positive cells. Thus, metformin-associated lipogenesis as well as inflammation aggravated neurodegenerative processes in ApoE- /- mice. Consequently, this study supports previous observations showing that metformin causes impairment of cognition.

Evaluation of Two Liver Treatment Strategies in a Mouse Model of Niemann-Pick-Disease Type C1.

Niemann-Pick-disease type C1 (NPC1) is an autosomal-recessive cholesterol-storage disorder. Besides other symptoms, NPC1 patients develop liver dysfunction and hepatosplenomegaly. The mechanisms of hepatomegaly and alterations of lipid metabolism-related genes in NPC1 disease are still poorly understood. Here, we used an NPC1 mouse model to study an additive hepatoprotective effect of a combination of 2-hydroxypropyl-ß-cyclodextrin (HPßCD), miglustat and allopregnanolone (combination therapy) with the previously established monotherapy using HPßCD. We examined transgene effects as well as treatment effects on liver morphology and hepatic lipid metabolism, focusing on hepatic cholesterol transporter genes. Livers of Npc1-/- mice showed hepatic cholesterol sequestration with consecutive liver injury, an increase of lipogenetic gene expression, e.g., HMG-CoA, a decrease of lipolytic gene expression, e.g., pparα and acox1, and a decrease of lipid transporter gene expression, e.g., acat1, abca1 and fatp2. Both, combination therapy and monotherapy, led to a reduction of hepatic lipids and an amelioration of NPC1 liver disease symptoms. Monotherapy effects were related to pparα- and acox1-associated lipolysis/ß-oxidation and to fatp2-induced fatty acid transport, whereas the combination therapy additionally increased the cholesterol transport via abca1 and apoE. However, HPßCD monotherapy additionally increased cholesterol synthesis as indicated by a marked increase of the HMG-CoA and srebp-2 mRNA expression, probably as a result of increased hepatocellular proliferation.

Association between serum neuron-specific enolase, age, overweight, and structural MRI patterns in 901 subjects.

Serum neuron-specific enolase (sNSE) is considered a marker for neuronal damage, related to gray matter structures. Previous studies indicated its potential as marker for structural and functional damage in conditions with adverse effects to the brain like obesity and dementia. In the present study, we investigated the putative association between sNSE levels, body mass index (BMI), total gray matter volume (GMV), and magnetic resonance imaging-based indices of aging as well as Alzheimer's disease (AD)-like patterns. SUBJECTS/METHODS: sNSE was determined in 901 subjects (499 women, 22-81 years, BMI 18-48 kg/m2), participating in a population-based study (SHIP-TREND). We report age-specific patterns of sNSE levels between males and females. Females showed augmenting, males decreasing sNSE levels associated with age (males: p = 0.1052, females: p = 0.0363). sNSE levels and BMI were non-linearly associated, showing a parabolic association and decreasing sNSE levels at BMI values >25 (p = 0.0056). In contrast to our hypotheses, sNSE levels were not associated with total GMV, aging, or AD-like patterns. Pathomechanisms discussed are: sex-specific hormonal differences, neuronal damage/differentiation, or impaired cerebral glucose metabolism. We assume a sex-dependence of age-related effects to the brain. Further, we propose in accordance to previous studies an actual neuronal damage in the early stages of obesity. However, with progression of overweight, we assume more profound effects of excess body fat to the brain.