Aβ Oligomer Elimination Restores Cognition in Transgenic Alzheimer's Mice with Full-blown Pathology

Oligomers of the amyloid-β (Aβ) protein are suspected to be responsible for the development and progression of Alzheimer’s disease. Thus, the development of compounds that are able to eliminate already formed toxic Aβ oligomers is very desirable. Here, we describe the in vivo efficacy of the compound RD2, which was developed to directly and specifically eliminate toxic Aβ oligomers. In a truly therapeutic, rather than a preventive study, oral treatment with RD2 was able to reverse cognitive deficits and significantly reduce Aβ pathology in old-aged transgenic Alzheimer’s Disease mice with full-blown pathology and behavioral deficits. For the first time, we demonstrate the in vivo target engagement of RD2 by showing a significant reduction of Aβ oligomers in the brains of RD2-treated mice compared to placebo-treated mice. The correlation of Aβ elimination in vivo and the reversal of cognitive deficits in old-aged transgenic mice support the hypothesis that Aβ oligomers are relevant not only for disease development and progression, but also offer a promising target for the causal treatment of Alzheimer’s disease.

FGF21 regulates insulin sensitivity following long-term chronic stress

Objective

Post-traumatic stress disorder (PTSD) increases type 2 diabetes risk, yet the underlying mechanisms are unclear. We investigated how early-life exposure to chronic stress affects long-term insulin sensitivity.

Methods

C57Bl/6J mice were exposed to chronic variable stress for 15 days (Cvs) and then recovered for three months without stress (Cvs3m).

Results

Cvs mice showed markedly increased plasma corticosterone and hepatic insulin resistance. Cvs3m mice exhibited improved whole-body insulin sensitivity along with enhanced adipose glucose uptake and skeletal muscle mitochondrial function and fatty acid oxidation. Plasma FGF21 levels were substantially increased and associated with expression of genes involved in fatty acid oxidation and formation of brown-like adipocytes. In humans, serum FGF21 levels were associated with stress coping long time after the exposure.

Conclusions

Early-life exposure to chronic stress leads to long term improvements in insulin sensitivity, oxidative metabolism and adipose tissue remodeling. FGF21 contributes to a physiological memory mechanism to maintain metabolic homeostasis.

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Early-life exposure of mice to stress (CVS) causes acute insulin resistance but improves long-term insulin sensitivity.

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3 months after stress, mice had enhanced adipose glucose uptake and higher skeletal muscle mitochondrial function.

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Plasma FGF21 and gene expression for formation of brown-like adipocytes were substantially increased long after stress.

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In humans, serum FGF21 levels were associated with the ability to cope with stress long time after the exposure.

CDH13 abundance interferes with adipocyte differentiation and is a novel biomarker for adipose tissue health

BACKGROUND

CDH13, an atypical member of the cadherin superfamily, has been identified in adipocyte secretomes of lean mouse models. CDH13 abundance differs in mouse models according to their susceptibility to develop metabolic disorders, but the role of CDH13 in adipose tissue is unknown.

METHODS

Secreted CDH13 protein levels and mRNA levels in visceral adipose tissue were determined in lean and obese mouse models. In vitro studies were performed in 3T3-L1 adipocytes to determine the role of CDH13 in adipocyte differentiation. The pathophysiological impact of visceral adipose tissue CDH13 mRNA and circulating CDH13 levels were determined in humans (normal-weight men n = 37, obese men n = 109 including n = 51 type 2 diabetes patients) and in obese patients (n = 14) pre- and post-metabolic surgery.

RESULTS

This study shows that in visceral adipose tissue CDH13 protein secretion and mRNA levels were decreased in obese mouse models. Mechanistically, CDH13 affects lipid metabolism during adipogenesis but not in mature adipocytes. CDH13 knockdown during adipogenesis reduced fatty acid uptake and lipid content in developing adipocytes. Furthermore, CDH13 depletion during adipogenesis lowered the induction of PPARγ and C/EBPα expression. These observations are of pathophysiological impact since visceral adipose tissue CDH13 mRNA and circulating CDH13 levels were decreased in obese men compared to normal-weight controls. Weight loss induced by bariatric surgery restored circulating CDH13 to levels found in normal-weight controls.

CONCLUSIONS

CDH13 levels in adipose tissue and the circulation are affected by obesity in mouse models and humans and are restored by weight loss in humans. CDH13 interferes with the differentiation potential of adipocytes and therefore is a marker for plasticity of fat tissue that might reflect the health status of adipose tissue.

Protein levels of clusterin and glutathione synthetase in platelets allow for early detection of colorectal cancer

Colorectal cancer (CRC) is one of the most frequent malignancies in the Western world. Early tumor detection and intervention are important determinants on CRC patient survival. During early tumor proliferation, dissemination and angiogenesis, platelets store and segregate proteins actively and selectively. Hence, the platelet proteome is a potential source of biomarkers denoting early malignancy. By comparing protein profiles of platelets between healthy volunteers (n = 12) and patients with early- (n = 7) and late-stage (n = 5) CRCs using multiplex fluorescence two-dimensional gel electrophoresis (2D-DIGE), we aimed at identifying differentially regulated proteins within platelets. By inter-group comparisons, 94 differentially expressed protein spots were detected (p < 0.05) between healthy controls and patients with early- and late-stage CRCs and revealed distinct separations between all three groups in principal component analyses. 54 proteins of interest were identified by mass spectrometry and resulted in high-ranked Ingenuity Pathway Analysis networks associated with Cellular function and maintenance, Cellular assembly and organization, Developmental disorder and Organismal injury and abnormalities (p < 0.0001 to p = 0.0495). Target proteins were validated by multiplex fluorescence-based Western blot analyses using an additional, independent cohort of platelet protein samples [healthy controls (n = 15), early-stage CRCs (n = 15), late-stage CRCs (n = 15)]. Two proteins-clusterin and glutathione synthetase (GSH-S)-featured high impact and were subsequently validated in this independent clinical cohort distinguishing healthy controls from patients with early- and late-stage CRCs. Thus, the potential of clusterin and GSH-S as platelet biomarkers for early detection of CRC could improve existing screening modalities in clinical application and should be confirmed in a prospective multicenter trial.

Alteration of Liver Peroxisomal and Mitochondrial Functionality in the NZO Mouse Model of Metabolic Syndrome

PURPOSE

Metabolic syndrome (MetS) consists of five risk factors: elevated blood pressure and fasting glucose, visceral obesity, dyslipidemia, and hypercholesterinemia. The physiological impact of lipid metabolism indicated as visceral obesity and hepatic lipid accumulation on MetS is still under debate. One major cause of disturbed lipid metabolism might be dysfunction of cellular organelles controlling energy homeostasis, i.e., mitochondria and peroxisomes.

EXPERIMENTAL DESIGN

The New Zealand Obese (NZO) mouse model exhibits a polygenic syndrome of obesity, insulin resistance, triglyceridemia, and hypercholesterolemia that resembles human metabolic syndrome. We applied a multi-omics approach combining lipidomics with liver transcriptomics and top-down MS based organelle proteomics (2D-DIGE) of highly enriched mitochondria and peroxisomes in male mice, to investigate molecular mechanisms related to the impact of lipid metabolism in the pathophysiology of the metabolic syndrome.

CONCLUSIONS AND CLINICAL RELEVANCE

Proteome analyses of liver organelles indicate differences in fatty acid and cholesterol metabolism, mainly influenced by PG-C1α/PPARα and other nuclear receptor mediated pathways. These results are in accordance with altered serum lipid profiles and elevated organelle functionality. These data emphasize that metabolic syndrome is accompanied with increased mitochondria and peroxisomal activity to cope with dyslipidemia and hypercholesterinemia driven hepatic lipid overflow in developing a fatty liver.

Hyaluronan synthase 3 promotes plaque inflammation and atheroprogression

OBJECTIVE

Hyaluronan (HA) is a prominent component of the provisional extracellular matrix (ECM) present in the neointima of atherosclerotic plaques. Here the role of HA synthase 3 (HAS3) in atheroprogression was studied.

APPROACH AND RESULTS

It is demonstrated here that HAS isoenzymes 1, -2 and -3 are expressed in human atherosclerotic plaques of the carotid artery. In Apolipoprotein E (Apoe)-deficient mice Has3 expression is increased early during lesion formation when macrophages enter atherosclerotic plaques. Importantly, HAS3 expression in vascular smooth muscle cells (VSMC) was found to be regulated by interleukin 1 β (IL-1β) in an NFkB dependent manner and blocking antibodies to IL-1β abrogate Has3 expression in VSMC by activated macrophages. Has3/Apoe double deficient mice developed less atherosclerosis characterized by decreased Th1-cell responses, decreased IL-12 release, and decreased macrophage-driven inflammation.

CONCLUSIONS

Inhibition of HAS3-dependent synthesis of HA dampens systemic Th1 cell polarization and reduces plaque inflammation. These data suggest that HAS3 might be a promising therapeutic target in atherosclerosis. Moreover, because HAS3 is regulated by IL-1β, our results suggest that therapeutic anti-IL-1β antibodies, recently tested in human clinical trials (CANTOS), may exert their beneficial effects on inflammation in post-myocardial infarction patients in part via effects on HAS3. TOC categorybasic study TOC subcategoryarteriosclerosis.

Novel Insights into the Adipokinome of Obese and Obese/Diabetic Mouse Models

The group of adipokines comprises hundreds of biological active proteins and peptides released from adipose tissue. Alterations of those complex protein signatures are suggested to play a crucial role in the pathophysiology of multifactorial, metabolic diseases. We hypothesized that also the pathophysiology of type-2-diabetes is linked to the dysregulation of the adipocyte secretome. To test this, we investigated mouse models with monogenic defects in leptin signaling which are susceptible to adipositas (C57BL/6 Cg-Lep^ob (obob)) or adipositas with diabetes (C57BL/KS Cg-Lepr^db (dbdb)) according to their genetic background. At the age of 17 weeks, visceral fat was obtained and primary murine adipocytes were isolated to harvest secretomes. Quantitative proteome analyses (LC-ESI-MS/MS) identified more than 800 potential secreted proteins. The secretome patterns revealed significant differences connected to the pathophysiology of obese mice. Pathway analyses indicated that these differences focus on exosome modelling, but failed to provide more precise specifications. To investigate the relationship of secretome data to insulin sensitivity, we examined the content of diabetogenic lipids, i.e., diacylglycerols (DAGs), identified as key players in lipid-induced insulin resistance. In contrast to obob mice, fat tissue of dbdb mice showed elevated DAG content, especially of DAG species with saturated fatty acid C16:0 and C18:0, while unsaturated fatty acid C16:1 were only changed in obob. Furthermore, DAG signatures of the models specifically correlate to secreted regulated adipokines indicating specific pathways. In conclusion, our data further support the concept that the fat tissue is an endocrine organ that releases bioactive factors corresponding to adipose tissue health status.

Absence of the kinase S6k1 mimics the effect of chronic endurance exercise on glucose tolerance and muscle oxidative stress

Objective

Ribosomal protein S6 Kinase-1 (S6K1) has been linked to resistance exercise-mediated improvements in glycemia. We hypothesized that S6K1 may also play a role in regulating glycemic control in response to endurance exercise training.

Methods

S6k1-knockout (S6K1KO) and WT mice on a 60 cal% high-fat diet were trained for 4 weeks on treadmills, metabolically phenotyped, and compared to sedentary controls.

Results

WT mice showed improved glucose tolerance after training. In contrast, S6K1KO mice displayed equally high glucose tolerance already in the sedentary state with no further improvement after training. Similarly, training decreased mitochondrial ROS production in skeletal muscle of WT mice, whereas ROS levels were already low in the sedentary S6K1KO mice with no further decrease after training. Nevertheless, trained S6K1KO mice displayed an increased running capacity compared to trained WT mice, as well as substantially reduced triglyceride contents in liver and skeletal muscle. The improvements in glucose handling and running endurance in S6K1KO mice were associated with markedly increased ketogenesis and a higher respiratory exchange ratio.

Conclusions

In high-fat fed mice, loss of S6K1 mimics endurance exercise training by reducing mitochondrial ROS production and upregulating oxidative utilization of ketone bodies. Pharmacological targeting of S6K1 may improve the outcome of exercise-based interventions in obesity and diabetes.

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Absence of S6k1 upregulates oxidative substrate utilization under HFD consumption.

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S6k1 knockout mice show enhanced running performance and improved glycemia already in the sedentary state.

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Aerobic endurance exercise training of S6k1 knockout mice further improves running performance but not glycemia.

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Metabolic improvements are associated with lower rates of TCA-linked mitochondrial H₂O₂ production and increased ketogenesis.

Long-Term Cold Adaptation Does Not Require FGF21 or UCP1

Brown adipose tissue (BAT)-dependent thermogenesis and its suggested augmenting hormone, FGF21, are potential therapeutic targets in current obesity and diabetes research. Here, we studied the role of UCP1 and FGF21 for metabolic homeostasis in the cold and dissected underlying molecular mechanisms using UCP1-FGF21 double-knockout mice. We report that neither UCP1 nor FGF21, nor even compensatory increases of FGF21 serum levels in UCP1 knockout mice, are required for defense of body temperature or for maintenance of energy metabolism and body weight. Remarkably, cold-induced browning of inguinal white adipose tissue (iWAT) is FGF21 independent. Global RNA sequencing reveals major changes in response to UCP1- but not FGF21-ablation in BAT, iWAT, and muscle. Markers of mitochondrial failure and inflammation are observed in BAT, but in particular the enhanced metabolic reprogramming in iWAT supports the thermogenic role of UCP1 and excludes an important thermogenic role of endogenous FGF21 in normal cold acclimation.

Mechanisms of Insulin Resistance in Primary and Secondary Nonalcoholic Fatty Liver

Nonalcoholic fatty liver disease is associated with hepatic insulin resistance and may result primarily from increased hepatic de novo lipogenesis (PRIM) or secondarily from adipose tissue lipolysis (SEC). We studied mice with hepatocyte- or adipocyte-specific SREBP-1c overexpression as models of PRIM and SEC. PRIM mice featured increased lipogenic gene expression in the liver and adipose tissue. Their selective, liver-specific insulin resistance was associated with increased C18:1-diacylglycerol content and protein kinase Cε translocation. SEC mice had decreased lipogenesis mediated by hepatic cholesterol responsive element-binding protein and featured portal/lobular inflammation along with total, whole-body insulin resistance. Hepatic mitochondrial respiration transiently increased and declined with aging along with higher muscle reactive oxygen species production. In conclusion, hepatic insulin resistance originates from lipotoxicity but not from lower mitochondrial capacity, which can even transiently adapt to increased peripheral lipolysis. Peripheral insulin resistance is prevented during increased hepatic lipogenesis only if adipose tissue lipid storage capacity is preserved.

EB1 protein alteration characterizes sporadic but not ulcerative colitis associated colorectal cancer

Background

While carcinogenesis in Sporadic Colorectal Cancer (SCC) has been thoroughly studied, less is known about Ulcerative Colitis associated Colorectal Cancer (UCC). This study aimed to identify and validate differentially expressed proteins between clinical samples of SCC and UCC to elucidate new insights of UCC/SCC carcinogenesis and progression.

Results

Multiplex-fluorescence two-dimensional gel electrophoresis (2-D DIGE) and mass spectrometry identified 67 proteoforms representing 43 distinct proteins. After analysis by Ingenuity Pathway Analysis^® (IPA), subsequent Western blot validation proofed the differential expression of Heat shock 27 kDA protein 1 (HSPB1) and Microtubule-associated protein R/EB family, member 1 (EB1) while the latter one showed also expression differences by immunohistochemistry.

Materials and Methods

Fresh frozen tissue of UCC (n = 10) matched with SCC (n = 10) was investigated. Proteins of cancerous intestinal mucosal cells were obtained by Laser Capture Microdissection (LCM) and compared by 2-D DIGE. Significant spots were identified by mass spectrometry. After IPA, three proteins [EB1, HSPB1, and Annexin 5 (ANXA5)] were chosen for further validation by Western blotting and tissue microarray-based immunohistochemistry.

Conclusions

This study identified significant differences in protein expression of colorectal carcinoma cells from UCC patients compared to patients with SCC. Particularly, EB1 was validated in an independent clinical cohort.

Differential Patterns of Impaired Cardiorespiratory Fitness and Cardiac Autonomic Dysfunction in Recently Diagnosed Type 1 and Type 2 Diabetes

OBJECTIVE

Both impaired cardiorespiratory fitness (CRF) and heart rate variability (HRV) are predictors of mortality, but their relative roles in recent-onset diabetes are unknown. We determined to which extent CRF and HRV are reduced and interrelated in recent-onset diabetes.

RESEARCH DESIGN AND METHODS

Participants from the German Diabetes Study with type 1 (n = 163) or type 2 (n = 188) diabetes with known diabetes duration <1 year and two age-matched glucose-tolerant control groups (n = 40 each) underwent spiroergometry and HRV assessment during a hyperinsulinemic-euglycemic clamp.

RESULTS

Compared with control subjects, patients with type 2 diabetes showed reduced VO_2max (median [1st-3rd quartiles] 19.3 [16.5-22.9] vs. 25.6 [20.7-29.9] mL/kg body weight/min; P < 0.05), diminished VCO_2max (23.0 [19.1-26.8] vs. 30.9 [24.5-34.4] mL/kg body weight/min; P < 0.05), blunted heart rate recovery after 2 min (-29.0 [-35.0 to -23.0] vs. -36.0 [-42.8 to -28.0] beats/min; P < 0.05), and reduced HRV in four of nine indices, whereas patients with type 1 diabetes had unaltered CRF but reduced HRV in three of nine indices (P < 0.05), indicating diminished vagal and sympathetic HRV modulation. HRV measures correlated with VO_2max in patients with type 1 diabetes (r >0.34; P < 0.05) but not in those with type 2 diabetes.

CONCLUSIONS

CRF is reduced in recently diagnosed type 2 diabetes but preserved in type 1 diabetes, whereas cardiac autonomic function is reduced in both diabetes types but is strongly associated with CRF only in type 1 diabetes. These results support the therapeutic concept of promoting physical fitness in the early course of diabetes.

Impact of fibroblast growth factor 21 on the secretome of human perivascular preadipocytes and adipocytes: a targeted proteomics approach

CONTEXT

Perivascular adipose tissue (PVAT) is suggested to impact on vascular cells via humoral factors, possibly contributing to endothelial dysfunction and atherosclerosis.

OBJECTIVE

To address whether the hepatokine fibroblast growth factor (FGF) 21 affects the PVAT secretome.

METHODS

Human perivascular (pre)adipocytes were subjected to targeted proteomics and whole-genome gene expression analysis.

RESULTS

Preadipocytes, as compared to adipocytes, secreted higher amounts of inflammatory cytokines and chemokines. Adipocytes released higher amounts of adipokines [e.g. adipisin, visfatin, dipeptidyl peptidase 4 (DPP4), leptin; p < 0.05, all]. In preadipocytes, omentin 1 release was 1.28-fold increased by FGF-21 (p < 0.05). In adipocytes, FGF-21 reduced chemerin release by 5% and enhanced DPP4 release by 1.15-fold (p < 0.05, both). FGF-21 altered the expression of four secretory genes in preadipocytes and of 18 in adipocytes (p < 0.01, all).

CONCLUSION

The hepatokine FGF-21 exerts secretome-modulating effects in human perivascular (pre)adipocytes establishing a new liver-PVAT-blood vessel axis that possibly contributes to vascular inflammation and atherosclerosis.

Mass spectrometry in life science research

Investigating complex signatures of biomolecules by mass spectrometry approaches has become indispensable in molecular life science research. Nowadays, various mass spectrometry-based omics technologies are available to monitor qualitative and quantitative changes within hundreds or thousands of biological active components, including proteins/peptides, lipids and metabolites. These comprehensive investigations have the potential to decipher the pathophysiology of disease development at a molecular level and to monitor the individual response of pharmacological treatment or lifestyle intervention.

Oxygen and differentiation status modulate the effect of X-ray irradiation on physiology and mitochondrial proteome of human neuroblastoma cells

Cytotoxic effects, including oxidative stress, of low linear energy transfer (LET)-ionizing radiation are often underestimated and studies of their mechanisms using cell culture models are widely conducted with cells cultivated at atmospheric oxygen that does not match its physiological levels in body tissues. Also, cell differentiation status plays a role in the outcome of experiments. We compared effects of 2 Gy X-ray irradiation on the physiology and mitochondrial proteome of nondifferentiated and human neuroblastoma (SH-SY5Y) cells treated with retinoic acid cultivated at 21% and 5% O₂. Irradiation did not affect the amount of subunits of OxPhos complexes and other non-OxPhos mitochondrial proteins, except for heat shock protein 70, which was increased depending on oxygen level and differentiation status. These two factors were proven to modulate mitochondrial membrane potential and the bioenergetic status of cells. We suggest, moreover, that oxygen plays a role in the differentiation of human SH-SY5Y cells.

Untargeted mass spectrometric approach in metabolic healthy offspring of patients with type 2 diabetes reveals medium-chain acylcarnitine as potential biomarker for lipid induced glucose intolerance (LGIT)

Offspring of type 2 diabetes (T2D) patients have increased risk to develop diabetes, due to inherited genetic susceptibility that directly interferes with the individual adaption to environmental conditions. We characterise T2D offspring (OSP) to identify metabolic risk markers for early disease prediction. Plasma of metabolically healthy OSP individuals (n = 43) was investigated after an oral lipid tolerance test (oLTT) by an untargeted mass spectrometric approach for holistic metabolome analyses. Two subgroups of OSP probands can be separated by oLTT, although not differing in general clinical parameters. Analyses of the plasma metabolome revealed mainly medium-chain acylcarnitines and very long-chain fatty acids with differential abundance in the subgroups. The study presented indicates that metabolically healthy OSP of T2D patients differ upon metabolic challenging in serum metabolite composition, especially medium-chain acylcarnitines. The difference suggest that postprandial lipid induced glucose intolerance (LGIT) may serve as a further valuable marker for early diabetes prediction.

Specific Metabolic Profiles and Their Relationship to Insulin Resistance in Recent-Onset Type 1 and Type 2 Diabetes

CONTEXT

Insulin resistance reflects the inadequate insulin-mediated use of metabolites and predicts type 2 diabetes (T2D) but is also frequently seen in long-standing type 1 diabetes (T1D) and represents a major cardiovascular risk factor.

OBJECTIVE

We hypothesized that plasma metabolome profiles allow the identification of unique and common early biomarkers of insulin resistance in both diabetes types.

DESIGN, SETTING, AND PATIENTS

Two hundred ninety-five plasma metabolites were analyzed by mass spectrometry from patients of the prospective observational German Diabetes Study with T2D (n = 244) or T1D (n = 127) and known diabetes duration of less than 1 year and glucose-tolerant persons (CON; n = 129). Abundance of metabolites was tested for association with insulin sensitivity as assessed by hyperinsulinemic-euglycemic clamps and related metabolic phenotypes.

MAIN OUTCOMES MEASURES

Sixty-two metabolites with phenotype-specific patterns were identified using age, sex, and body mass index as covariates.

RESULTS

Compared with CON, the metabolome of T2D and T1D showed similar alterations in various phosphatidylcholine species and amino acids. Only T2D exhibited differences in free fatty acids compared with CON. Pairwise comparison of metabolites revealed alterations of 28 and 49 metabolites in T1D and T2D, respectively, when compared with CON. Eleven metabolites allowed differentiation between both diabetes types and alanine, α-amino-adipic acid, isoleucin, and stearic acid showed an inverse association with insulin sensitivity in both T2D and T1D combined.

CONCLUSION

Metabolome analyses from recent-onset T2D and T1D patients enables identification of defined diabetes type-specific differences and detection of biomarkers of insulin sensitivity. These analyses may help to identify novel clinical subphenotypes diabetes.