A familial Danish dementia rat shows impaired presynaptic and postsynaptic glutamatergic transmission

Familial British dementia and familial Danish dementia are neurodegenerative disorders caused by mutations in the gene integral membrane protein 2B (ITM2b) encoding BRI2, which tunes excitatory synaptic transmission at both presynaptic and postsynaptic termini. In addition, BRI2 interacts with and modulates proteolytic processing of amyloid-β precursor protein (APP), whose mutations cause familial forms of Alzheimer''s disease (AD) (familial AD). To study the pathogenic mechanisms triggered by the Danish mutation, we generated rats carrying the Danish mutation in the rat Itm2b gene (Itm2b^D rats). Given the BRI2/APP interaction and the widely accepted relevance of human amyloid β (Aβ), a proteolytic product of APP, to AD, Itm2b^D rats were engineered to express two humanized App alleles and produce human Aβ. Here, we studied young Itm2b^D rats to investigate early pathogenic changes in these diseases. We found that periadolescent Itm2b^D rats not only present subtle changes in human Aβ levels along with decreased spontaneous glutamate release and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor–mediated responses but also had increased short-term synaptic facilitation in the hippocampal Schaeffer-collateral pathway. These alterations in excitatory interneuronal communication can impair learning and memory processes and were akin to those observed in adult mice producing rodent Aβ and carrying either the Danish or British mutations in the mouse Itm2b gene. Collectively, the data show that the pathogenic Danish mutation alters the physiological function of BRI2 at glutamatergic synapses across species and early in life. Future studies will determine whether this phenomenon represents an early pathogenic event in human dementia.     

The Osaka FAD mutation E22Δ leads to the formation of a previously unknown type of amyloid β fibrils and modulates Aβ neurotoxicity

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cerebral deposition of amyloid fibrils formed by the amyloid β (Aβ) peptide. Aβ has a length of 39-43 amino acid residues; the predominant Aβ isoforms are Aβ1-40 and Aβ1-42. While the majority of AD cases occur spontaneously, a subset of early-onset familial AD cases is caused by mutations in the genes encoding the Aβ precursor protein or presenilin 1/presenilin 2. Recently, a deletion of glutamic acid at position 22 within the Aβ sequence (E22Δ) was identified in Japanese patients with familial dementia, but the aggregation properties of the deletion variant of Aβ are not well understood. We investigated the aggregation characteristics and neurotoxicity of recombinantly expressed Aβ isoforms 1-40 and 1-42 with and without the E22Δ mutation. We show that the E22Δ mutation strongly accelerates the fibril formation of Aβ1-42 E22Δ compared to Aβ1-42 wild type (wt). In addition, we demonstrate that fibrils of Aβ1-40 E22Δ form a unique quaternary structure characterized by a strong tendency to form fibrillar bundles and a strongly increased thioflavin T binding capacity. Aβ1-40 E22Δ was neurotoxic in rat primary neuron cultures as compared to nontoxic Aβ1-40 wt. Aβ1-42 E22Δ was less toxic than Aβ1-42 wt, but it significantly decreased neurite outgrowth per cell in neuronal primary cultures. Because Aβ1-40 is the major Aβ form in vivo, the gain of toxic function caused by the E22 deletion may explain the development of familial AD in mutation carriers.     

Glucose transport and metabolism in the perfused hindquarters of lean and obese-hyperglecemic (db/db) mice effects of insulin and electrical stimulation

Changes in glucose transport and metabolism in skeletal muscles of the obese-diabetic mice (db/db) was characterized using the perfused mouse hindquarter preparation. Metabolism of [5-³H]glucose, uptake of 3-O-[methyl-³H]glucose (methylglucose) and [2-¹⁴C]deoxyglucose (deoxyglucose) was studied under resting, electrically stimulated contracting, and insulin-stimulated conditions. Basal rate of methylglucose uptake was 255 ± 18 and 180 ± 9 μl/15 min per ml intracellular fluid space for lean and db/db mice, respectively. The V_? of methylglucose transport was decreased with no change in K_m in the db/db mice. Both electrical stimulation and insulin (1/mU/ml) increased methylglucose uptake rate 2-fold in both lean and obese mice. We observed no significant change in insulin sensitivity in the db/db mice in stimulating methylglucose uptake which was subnormal under all conditions. Similar results were obtained using deoxyglucose. Likewise, uptake of glucose and ³H₂O production from [5-³H]glucose were significantly reduced, both at rest and during electrically stimulated contraction in the db/db mouse. However, lactate production in the electrically stimulated db/db mouse preparations was not significantly different from that in the lean mice. These data suggest a major contribution from an impaired glucose transport activity to the reduction in glucose metabolism in the db/db mouse skeletal muscle.     

Cardiac Fibroblast-Dependent Extracellular Matrix Accumulation Is Associated with Diastolic Stiffness in Type 2 Diabetes

Cardiovascular complications are a leading cause of death in patients with type 2 diabetes mellitus (T2DM). Diastolic dysfunction is one of the earliest manifestations of diabetes-induced changes in left ventricular (LV) function, and results from a reduced rate of relaxation and increased stiffness. The mechanisms responsible for increased stiffness are not completely understood. Chronic hyperglycemia, advanced glycation endproducts (AGEs), and increased levels of proinflammatory and profibrotic cytokines are molecular pathways known to be involved in regulating extracellular matrix (ECM) synthesis and accumulation resulting in increased LV diastolic stiffness. Experiments were conducted using a genetically-induced mouse model of T2DM generated by a point mutation in the leptin receptor resulting in nonfunctional leptin receptors (db/db murine model). This study correlated changes in LV ECM and stiffness with alterations in basal activation of signaling cascades and expression of profibrotic markers within primary cultures of cardiac fibroblasts from diabetic (db/db) mice with nondiabetic (db/wt) littermates as controls. Primary cultures of cardiac fibrobroblasts were maintained in 25 mM glucose (hyperglycemic-HG; diabetic db/db) media or 5 mM glucose (normoglycemic-NG, nondiabetic db/wt) media. The cells then underwent a 24-hour exposure to their opposite (NG; diabetic db/db) media or 5 mM glucose (HG, nondiabetic db/wt) media. Protein analysis demonstrated significantly increased expression of type I collagen, TIMP-2, TGF-β, PAI-1 and RAGE in diabetic db/db cells as compared to nondiabetic db/wt, independent of glucose media concentration. This pattern of protein expression was associated with increased LV collagen accumulation, myocardial stiffness and LV diastolic dysfunction. Isolated diabetic db/db fibroblasts were phenotypically distinct from nondiabetic db/wt fibroblasts and exhibited a profibrotic phenotype in normoglycemic conditions.     

Chronic stress aggravates glucose intolerance in leptin receptor-deficient (db/db) mice

Genetic predisposition and environmental challenges interact to determine individual vulnerability to obesity and type 2 diabetes. We previously established a mouse model of chronic subordination stress-induced hyperphagia, obesity, metabolic like-syndrome and insulin resistance in the presence of a high-fat diet. However, it remains to be established if social stress could also aggravate glucose intolerance in subjects genetically predisposed to develop obesity and type 2 diabetes. To answer this question, we subjected genetically obese mice due to deficiency of the leptin receptor (db/db strain) to chronic subordination stress. Over five weeks, subordination stress in db/db mice led to persistent hyperphagia, hyperglycemia and exacerbated glucose intolerance altogether suggestive of an aggravated disorder when compared to controls. On the contrary, body weight and fat mass were similarly affected in stressed and control mice likely due to the hyperactivity shown by subordinate mice. Stressed db/db mice also showed increased plasma inflammatory markers. Altogether our results suggest that chronic stress can aggravate glucose intolerance but not obesity in genetically predisposed subjects on the basis of a disrupted leptin circuitry.     

Novel frame-shift mutation in Slc5a2 encoding SGLT2 in a strain of senescence-accelerated mouse SAMP10

The senescence-accelerated mouse prone10 (SAMP10) strain, a model of aging, exhibits cognitive impairments and cerebral atrophy. We noticed that SAMP10/TaSlc mice, a SAMP10 substrain, have developed persistent glucosuria over the past few years. In the present study, we characterized SAMP10/TaSlc mice and further identified a spontaneous mutation in the Slc5a2 gene encoding sodium-glucose co-transporter (SGLT) 2. The mean concentration of urine glucose was high in SAMP10/TaSlc mice and increased further with advancing age, whereas other strains of senescence-accelerated mice, including SAMP1/SkuSlc, SAMP6/TaSlc and SAMP8/TaSlc or normal aging control SAMR1/TaSlc mice, exhibited no detectable glucose in urine. SAMP10/TaSlc mice consumed increasing amounts of food and water compared to SAMR1/TaSlc mice, suggesting the compensation of polyuria and the loss of glucose. Oral glucose tolerance tests showed decreased glucose reabsorption in the kidney of SAMP10/TaSlc mice. In addition, blood glucose levels decreased in an age-dependent fashion. The kidney was innately larger than that of control mice with no histological alterations. We examined the expression levels of glucose transporters in the kidney. Among SGLT1, SGLT2, glucose transporter (GLUT) 1 and GLUT2, we found a significant decrease only in the level of SGLT2. DNA sequencing of SGLT2 in SAMP10/TaSlc mice revealed a single nucleotide deletion of guanine at 1236, which resulted in a frameshift mutation that produced a truncated protein. We designate this strain as SAMP10/TaSlc-Slc5a2^slc (SAMP10-ΔSglt2). Recently, SGLT2 inhibitors have been demonstrated to be effective for the treatment of patients with type 2 diabetes (T2D). SAMP10-ΔSglt2 mice may serve as a unique preclinical model to study the link between aging-related neurodegenerative disorders and T2D.     

A deuterohemin peptide protects a transgenic Caenorhabditis elegans model of Alzheimer’s disease by inhibiting Aβ1–42 aggregation

Alzheimer’s disease (AD) is a progressive neurodegenerative brain disease and is the most common cause of dementia in the elderly. The main hallmark of AD is the deposition of insoluble amyloid (Aβ) outside the neuron, leading to amyloid plaques and neurofibrillary tangles in the brain. Deuterohemin-Ala-His-Thr-Val-Glu-Lys (DhHP-6), a novel porphyrin-peptide, has both microperoxidase activity and cell permeability. In the present study, DhHP-6 efficiently inhibited the aggregation of Aβ and reduced the β-sheet percentage of Aβ from 89.1% to 78.3%. DhHP-6 has a stronger affinity (K_D = 100 ± 12 μM) for binding with Aβ at Phe⁴, Arg⁵, Val¹⁸, Glu¹¹ and Glu²². In addition, DhHP-6 (100 μM) significantly prolonged lifespan, alleviated paralysis and reduced Aβ plaque formation in the Aβ_1–42 transgenic Caenorhabditis elegans CL4176 model of AD. Our results demonstrate that DhHP-6 is a potential drug candidate that efficiently protects a transgenic C. elegans model of Alzheimer’s disease by inhibiting Aβ aggregation.     

A high‐fat diet exacerbates the Alzheimer's disease pathology in the hippocampus of the App NL−F/NL−F knock‐in mouse model

Insulin resistance and diabetes mellitus are major risk factors for Alzheimer''s disease (AD), and studies with transgenic mouse models of AD have provided supportive evidence with some controversies. To overcome potential artifacts derived from transgenes, we used a knock‐in mouse model, App^{NL−F/NL−F} , which accumulates Aβ plaques from 6 months of age and shows mild cognitive impairment at 18 months of age, without the overproduction of APP. In the present study, 6‐month‐old male App^{NL−F/NL−F} and wild‐type mice were fed a regular or high‐fat diet (HFD) for 12 months. HFD treatment caused obesity and impaired glucose tolerance (i.e., T2DM conditions) in both wild‐type and App^{NL−F/NL−F} mice, but only the latter animals exhibited an impaired cognitive function accompanied by marked increases in both Aβ deposition and microgliosis as well as insulin resistance in the hippocampus. Furthermore, HFD‐fed App^{NL−F/NL−F} mice exhibited a significant decrease in volume of the granule cell layer in the dentate gyrus and an increased accumulation of 8‐oxoguanine, an oxidized guanine base, in the nuclei of granule cells. Gene expression profiling by microarrays revealed that the populations of the cell types in hippocampus were not significantly different between the two mouse lines, regardless of the diet. In addition, HFD treatment decreased the expression of the Aβ binding protein transthyretin (TTR) in App^{NL−F/NL−F} mice, suggesting that the depletion of TTR underlies the increased Aβ deposition in the hippocampus of HFD‐fed App^{NL−F/NL−F} mice.     

Brain-derived Neurotrophic Factor Regulates Energy Expenditure Through the Central Nervous System in Obese Diabetic Mice

It has been previously demonstrated that brain-derived neurotrophic factor (BDNF) regulates glucose metabolism and energy expenditure in rodent diabetic models such as C57BL/KsJ-lepr^db/lepr^db (db/db) mice. Central administration of BDNF has been found to reduce blood glucose in db/db mice, suggesting that BDNF acts through the central nervous system. In the present study we have expanded these investigations to explore the effect of central administration of BDNF on energy metabolism. Intracerebroventricular administration of BDNF lowered blood glucose and increased pancreatic insulin content of db/db mice compared with vehicle-treated pellet pair-fed db/db mice. While body temperatures of the pellet pair-fed db/db mice given vehicle were reduced because of restricted food supply in this pair-feeding condition, BDNF treatment remarkably alleviated the reduction of body temperature suggesting the enhancement of thermogenesis. BDNF enhanced norepinephrine turnover and increased uncoupling protein-1 mRNA expression in the interscapular brown adipose tissue. Our evidence indicates that BDNF activates the sympathetic nervous system via the central nervous system and regulates energy expenditure in obese diabetic animals.     

Bile acid sequestration reduces plasma glucose levels in db/db mice by increasing its metabolic clearance rate

Aims/Hypothesis

Bile acid sequestrants (BAS) reduce plasma glucose levels in type II diabetics and in murine models of diabetes but the mechanism herein is unknown. We hypothesized that sequestrant-induced changes in hepatic glucose metabolism would underlie reduced plasma glucose levels. Therefore, in vivo glucose metabolism was assessed in db/db mice on and off BAS using tracer methodology.

Methods

Lean and diabetic db/db mice were treated with 2% (wt/wt in diet) Colesevelam HCl (BAS) for 2 weeks. Parameters of in vivo glucose metabolism were assessed by infusing [U-¹³C]-glucose, [2-¹³C]-glycerol, [1-²H]-galactose and paracetamol for 6 hours, followed by mass isotopologue distribution analysis, and related to metabolic parameters as well as gene expression patterns.

Results

Compared to lean mice, db/db mice displayed an almost 3-fold lower metabolic clearance rate of glucose (p = 0.0001), a ∼300% increased glucokinase flux (p = 0.001) and a ∼200% increased total hepatic glucose production rate (p = 0.0002). BAS treatment increased glucose metabolic clearance rate by ∼37% but had no effects on glucokinase flux nor total hepatic or endogenous glucose production. Strikingly, BAS-treated db/db mice displayed reduced long-chain acylcarnitine content in skeletal muscle (p = 0.0317) but not in liver (p = 0.189). Unexpectedly, BAS treatment increased hepatic FGF21 mRNA expression 2-fold in lean mice (p = 0.030) and 3-fold in db/db mice (p = 0.002).

Conclusions/Interpretation

BAS induced plasma glucose lowering in db/db mice by increasing metabolic clearance rate of glucose in peripheral tissues, which coincided with decreased skeletal muscle long-chain acylcarnitine content.     

Supplementation with 9-cis β-carotene-rich alga Dunaliella improves hyperglycemia and adipose tissue inflammation in diabetic mice

Several species of the alga Dunaliella contain high levels of β-carotene. Low dietary β-carotene intake is associated with type 2 diabetes. Dunaliella contains high levels of all-trans and 9-cis isomers of β-carotene and is the best known naturally occurring nutritional source of 9-cis β-carotene. Since vitamin A has been suggested to play a role in glucose and lipid metabolism, we aimed to study the effect of Dunaliella supplementation on diabetes in mice. Ten diabetic db/db mice were fed chow diet fortified with 8 % 9-cis-rich Dunaliella powder. Ten db/db and heterozygous db/+ mice each served as controls and were fed chow diet alone. The control db/db mice developed severe hyperglycemia with fasting glucose levels reaching 400 mg dL^?1. Dunaliella significantly inhibited the elevation of plasma glucose (p?=?0.007). The area under the curve of the glucose tolerance test was 24 % lower in Dunaliella-treated mice than in the control db/db mice. Triglyceride elevation was significantly lower in the Dunaliella group than in the db/db group (p?=?0.007). The mRNA levels of several pro-inflammatory genes in adipose tissue, including monocyte chemotactic protein-1, intercellular adhesion molecule, vascular adhesion molecule-1, receptor-associated protein factor 6, and p-selectin, were elevated in the db/db group as compared to the db/+, whereas their levels were significantly lower in the Dunaliella-treated group. These results suggest that 9-cis β-carotene-rich Dunaliella may inhibit diabetes in db/db mice by reducing inflammation in adipose tissue. This study also emphasizes the importance of β-carotene isomers in our diet.     

Interplay between obesity and aging on myocardial geometry and function: Role of leptin-STAT3-stress signaling

BackgroundUncorrected obesity facilitates premature aging and cardiovascular anomalies. This study examined the interaction between obesity and aging on cardiac remodeling and contractile function. Methods: Cardiac echocardiographic geometry, function, morphology, intracellular Ca²⁺ handling, oxidative stress (DHE fluorescence), STAT3 and stress signaling were evaluated in young (3-mo) and old (12- and 18-mo) lean and leptin deficient ob/ob obese mice. Cardiomyocytes from young and old lean and ob/ob mice were treated with leptin (1 nM) for 4 h in vitro prior to assessment of mechanical and biochemical properties. High fat diet (45% calorie from fat) and the leptin receptor mutant db/db obese mice at young and old age were evaluated for comparison. Results: Our results displayed reduced survival in ob/ob mice. Obesity but less likely older age dampened echocardiographic, geometric, cardiomyocyte function and intracellular Ca²⁺ properties, elevated O₂^? and p^47phox NADPH oxidase levels with a more pronounced geometric change at older age. Immunoblot analysis revealed elevated p^47phox NADPH oxidase and dampened phosphorylation of STAT3, with a more pronounced response in old ob/ob mice, the effects were restored by leptin. Obesity and aging inhibited phosphorylation of Akt, eNOS, AMPK, and p38 while promoting phosphorylation of JNK and IκB. Leptin reconciled cardiomyocyte dysfunction, O₂^? yield, p^47phox upregulation, STAT3 dephosphorylation and stress signaling in ob/ob mice although its action on stress signaling cascades were lost at old age. High fat diet-induced and db/db obesity displayed aging-associated cardiomyocyte anomalies reminiscent of ob/ob model albeit lost leptin response.ConclusionsOur data suggest disparate age-associated obesity response in cardiac remodeling and contractile dysfunction due to phosphorylation of Akt, eNOS and stress signaling-related oxidative stress.     

The low density lipoprotein receptor modulates the effects of hypogonadism on diet-induced obesity and related metabolic perturbations

Here, we investigated how LDL receptor deficiency (Ldlr^−/−) modulates the effects of testosterone on obesity and related metabolic dysfunctions. Though sham-operated Ldlr^−/− mice fed Western-type diet for 12 weeks became obese and showed disturbed plasma glucose metabolism and plasma cholesterol and TG profiles, castrated mice were resistant to diet-induced obesity and had improved glucose metabolism and reduced plasma TG levels, despite a further deterioration in their plasma cholesterol profile. The effect of hypogonadism on diet-induced weight gain of Ldlr^−/− mice was independent of ApoE and Lrp1. Indirect calorimetry analysis indicated that hypogonadism in Ldlr^−/− mice was associated with increased metabolic rate. Indeed, mitochondrial cytochrome c and uncoupling protein 1 expression were elevated, primarily in white adipose tissue, confirming increased mitochondrial metabolic activity due to thermogenesis. Testosterone replacement in castrated Ldlr^−/− mice for a period of 8 weeks promoted diet-induced obesity, indicating a direct role of testosterone in the observed phenotype. Treatment of sham-operated Ldlr^−/− mice with the aromatase inhibitor exemestane for 8 weeks showed that the obesity of castrated Ldlr^−/− mice is independent of estrogens. Overall, our data reveal a novel role of Ldlr as functional modulator of metabolic alterations associated with hypogonadism.     

Hepatic deficiency of selenoprotein S exacerbates hepatic steatosis and insulin resistance

Nonalcoholic fatty liver disease (NAFLD) is closely associated with insulin resistance (IR) and type 2 diabetes mellitus (T2DM), which are all complex metabolic disorders. Selenoprotein S (SelS) is an endoplasmic reticulum (ER) resident selenoprotein involved in regulating ER stress and has been found to participate in the occurrence and development of IR and T2DM. However, the potential role and mechanism of SelS in NAFLD remains unclear. Here, we analyzed SelS expression in the liver of high-fat diet (HFD)-fed mice and obese T2DM model (db/db) mice and generated hepatocyte-specific SelS knockout (SelS^H-KO) mice using the Cre-loxP system. We showed that hepatic SelS expression levels were significantly downregulated in HFD-fed mice and db/db mice. Hepatic SelS deficiency markedly increased ER stress markers in the liver and caused hepatic steatosis via increased fatty acid uptake and reduced fatty acid oxidation. Impaired insulin signaling was detected in the liver of SelS^H-KO mice with decreased phosphorylation levels of insulin receptor substrate 1 (IRS1) and protein kinase B (PKB/Akt), which ultimately led to disturbed glucose homeostasis. Meanwhile, our results showed hepatic protein kinase Cɛ (PKCɛ) activation participated in the negative regulation of insulin signaling in SelS^H-KO mice. Moreover, the inhibitory effect of SelS on hepatic steatosis and IR was confirmed by SelS overexpression in primary hepatocytes in vitro. Thus, we conclude that hepatic SelS plays a key role in regulating hepatic lipid accumulation and insulin action, suggesting that SelS may be a potential intervention target for the prevention and treatment of NAFLD and T2DM.Subject terms: Metabolic syndrome, Obesity     

SORL1 and SIRT1 mRNA expression and promoter methylation levels in aging and Alzheimer’s Disease

Alzheimer’s Disease (AD) is a neurodegenerative disorder and the most common cause of dementia among the elderly. Efforts have been made to understand the genetic and epigenetic mechanisms involved in the development of this disease. As SORL1 (sortilin-related receptor) and SIRT1 (sirtuin 1) genes have been linked to AD pathogenesis, we aimed to investigate their mRNA expression and promoter DNA methylation in post mortem brain tissues (entorhinal and auditory cortices and hippocampus) from healthy elderly subjects and AD patients. We also evaluated these levels in peripheral blood leukocytes from young, healthy elderly and AD patients, investigating whether there was an effect of age on these profiles. The comparative CT method by Real Time PCR and MALDI-TOF mass spectrometry were used to analyze gene expression and DNA methylation, respectively. SORL1 gene was differently expressed in the peripheral blood leukocytes and might act as a marker of aging in this tissue. Furthermore, we found that SORL1 promoter DNA methylation might act as one of the mechanisms responsible for the differences in expression observed between blood and brain for both healthy elderly and AD patients groups. The impact of these studied genes on AD pathogenesis remains to be better clarified.     

Effect of canagliflozin on renal threshold for glucose, glycemia, and body weight in normal and diabetic animal models

Background

Canagliflozin is a sodium glucose co-transporter (SGLT) 2 inhibitor in clinical development for the treatment of type 2 diabetes mellitus (T2DM).

Methods

¹⁴C-alpha-methylglucoside uptake in Chinese hamster ovary-K cells expressing human, rat, or mouse SGLT2 or SGLT1; ³H-2-deoxy-d-glucose uptake in L6 myoblasts; and 2-electrode voltage clamp recording of oocytes expressing human SGLT3 were analyzed. Graded glucose infusions were performed to determine rate of urinary glucose excretion (UGE) at different blood glucose (BG) concentrations and the renal threshold for glucose excretion (RT_G) in vehicle or canagliflozin-treated Zucker diabetic fatty (ZDF) rats. This study aimed to characterize the pharmacodynamic effects of canagliflozin in vitro and in preclinical models of T2DM and obesity.

Results

Treatment with canagliflozin 1 mg/kg lowered RT_G from 415±12 mg/dl to 94±10 mg/dl in ZDF rats while maintaining a threshold relationship between BG and UGE with virtually no UGE observed when BG was below RT_G. Canagliflozin dose-dependently decreased BG concentrations in db/db mice treated acutely. In ZDF rats treated for 4 weeks, canagliflozin decreased glycated hemoglobin (HbA1c) and improved measures of insulin secretion. In obese animal models, canagliflozin increased UGE and decreased BG, body weight gain, epididymal fat, liver weight, and the respiratory exchange ratio.

Conclusions

Canagliflozin lowered RT_G and increased UGE, improved glycemic control and beta-cell function in rodent models of T2DM, and reduced body weight gain in rodent models of obesity.     

Genomic modulation of diabetes (<Emphasis Type="Italic">db/db)</Emphasis> and obese (<Emphasis Type="Italic">ob/ob</Emphasis>) mutation-induced hypercytolipidemia: cytochemical basis of female reproductive tract involution

Infertility and hypercytolipidemic utero-ovarian involution are recognized consequences of the diabetes-obesity syndrome (DOS) in C57BL mice with either obese (ob/ob) or diabetes (db/db) single gene mutations. We have evaluated the interdependent deleterious influences of both mutation types and differences in the genomic background on utero-ovarian dysfunction in C57BL mice. Control (+/?) C57BL mice were matched with littermate ob/ob and db/db mutants expressed on either the /KsJ or /6 background. Both ob/ob and db/db mutations increased body weights of /KsJ and /6 background strains relative to +/? groups. In contrast, uterine and ovarian weights were depressed by ob/ob and db/dbmutations relative to +/?, regardless of the background strain, but especially when expressed on the /KsJ background. Functionally, both ob/ob and db/db mutations induced hyperglycemic-hyperinsulinemic states coupled with depressed serum estradiol-17-β and progesterone concentrations when expressed on a /KsJ background. Microscopic analysis of utero-ovarian tissue samples revealed marked hypercytolipidemia in the follicular granulosa and endometrial epithelial tissue layers of both ob/oband db/db mutant groups relative to normal +/? cytoarchitecture. The db/db mutation consistently promoted more severe hypercytolipidemic profiles than the ob/obmutation, regardless of background strain. Thus, the severity of utero-ovarian hypercytolipidemia following the expression ofob/ob and db/db mutations in C57BL mice is influenced, or moderated, by the genomic background on which the mutation is expressed.     

Enhanced Phospholipase A2 Group 3 Expression by Oxidative Stress Decreases the Insulin-Degrading Enzyme

Oxidative stress has a ubiquitous role in neurodegenerative diseases and oxidative damage in specific regions of the brain is associated with selective neurodegeneration. We previously reported that Alzheimer disease (AD) model mice showed decreased insulin-degrading enzyme (IDE) levels in the cerebrum and accelerated phenotypic features of AD when crossbred with alpha-tocopherol transfer protein knockout (Ttpa ^-/-) mice. To further investigate the role of chronic oxidative stress in AD pathophysiology, we performed DNA microarray analysis using young and aged wild-type mice and aged Ttpa ^-/- mice. Among the genes whose expression changed dramatically was Phospholipase A2 group 3 (Pla2g3); Pla2g3 was identified because of its expression profile of cerebral specific up-regulation by chronic oxidative stress in silico and in aged Ttpa ^-/- mice. Immunohistochemical studies also demonstrated that human astrocytic Pla2g3 expression was significantly increased in human AD brains compared with control brains. Moreover, transfection of HEK293 cells with human Pla2g3 decreased endogenous IDE expression in a dose-dependent manner. Our findings show a key role of Pla2g3 on the reduction of IDE, and suggest that cerebrum specific increase of Pla2g3 is involved in the initiation and/or progression of AD.     

No correlation between time-linked plasma and CSF Aβ levels

Plasma β-amyloid protein (Aβ) isoforms are considered potential biomarkers for Alzheimer's disease (AD) and dementia. The relation between plasma and cerebrospinal fluid (CSF) levels of Aβ isoforms remains unclear. In order to identify possible correlations between Aβ levels in plasma and CSF we determined Aβ levels in time-linked plasma and CSF samples. Aβ concentrations in plasma (Aβ_1–42 and Aβ_N–42) and CSF (Aβ_1–42) samples from 49 AD patients, 47 non-Alzheimer's disease dementia (NONAD) patients, 39 MCI patients and 29 controls were determined using a multi-parameter fluorimetric bead-based immunoassay using xMAP^® technology (for plasma) and a conventional single-parameter ELISA (for CSF). Plasma Aβ_1–42 concentrations did not correlate with CSF Aβ_1–42 concentrations in the total study population, or in the different diagnostic groups. No correlations between plasma Aβ_N–42 and CSF Aβ_1–42 levels were found either. The CSF/serum albumin index did not show any significant differences between AD, NONAD, MCI and controls.These results suggest that the Aβ levels in plasma are independent of the Aβ levels in CSF both in dementia and controls. The fact that CSF and plasma Aβ do not correlate in patients as well as controls and no significant differences in plasma Aβ_1–42 or Aβ_N–42 between patients and controls can be detected hampers the diagnostic utility of the plasma Aβ levels as biomarkers for dementia.