Open Access
Refine
Has Fulltext
- yes (29)
Document Type
- Postprint (29) (remove)
Language
- English (29)
Is part of the Bibliography
- yes (29)
Keywords
- inflammation (3)
- oxidative stress (3)
- LC-MS/MS (2)
- NASH (2)
- carotenoids (2)
- cholesterol (2)
- disease (2)
- kidney transplantation (2)
- retinol (2)
- Biomarker (1)
Institute
- Institut für Ernährungswissenschaft (29) (remove)
Gut bacteria exert beneficial and harmful effects in metabolic diseases as deduced from the comparison of germfree and conventional mice and from fecal transplantation studies. Compositional microbial changes in diseased subjects have been linked to adiposity, type 2 diabetes and dyslipidemia. Promotion of an increased expression of intestinal nutrient transporters or a modified lipid and bile acid metabolism by the intestinal microbiota could result in an increased nutrient absorption by the host. The degradation of dietary fiber and the subsequent fermentation of monosaccharides to short-chain fatty acids (SCFA) is one of the most controversially discussed mechanisms of how gut bacteria impact host physiology. Fibers reduce the energy density of the diet, and the resulting SCFA promote intestinal gluconeogenesis, incretin formation and subsequently satiety. However, SCFA also deliver energy to the host and support liponeogenesis. Thus far, there is little knowledge on bacterial species that promote or prevent metabolic disease. Clostridium ramosum and Enterococcus cloacae were demonstrated to promote obesity in gnotobiotic mouse models, whereas bifidobacteria and Akkermansia muciniphila were associated with favorable phenotypes in conventional mice, especially when oligofructose was fed. How diet modulates the gut microbiota towards a beneficial or harmful composition needs further research. Gnotobiotic animals are a valuable tool to elucidate mechanisms underlying diet-host-microbe interactions.
As an essential trace element, copper plays a pivotal role in physiological body functions. In fact, dysregulated copper homeostasis has been clearly linked to neurological disorders including Wilson and Alzheimer’s disease. Such neurodegenerative diseases are associated with progressive loss of neurons and thus impaired brain functions. However, the underlying mechanisms are not fully understood. Characterization of the element species and their subcellular localization is of great importance to uncover cellular mechanisms. Recent research activities focus on the question of how copper contributes to the pathological findings. Cellular bioimaging of copper is an essential key to accomplish this objective. Besides information on the spatial distribution and chemical properties of copper, other essential trace elements can be localized in parallel. Highly sensitive and high spatial resolution techniques such as LA-ICP-MS, TEM-EDS, S-XRF and NanoSIMS are required for elemental mapping on subcellular level. This review summarizes state-of-the-art techniques in the field of bioimaging. Their strengths and limitations will be discussed with particular focus on potential applications for the elucidation of copper-related diseases. Based on such investigations, further information on cellular processes and mechanisms can be derived under physiological and pathological conditions. Bioimaging studies might enable the clarification of the role of copper in the context of neurodegenerative diseases and provide an important basis to develop therapeutic strategies for reduction or even prevention of copper-related disorders and their pathological consequences.
Sphingolipids are a class of lipids that share a sphingoid base backbone. They exert various effects in eukaryotes, ranging from structural roles in plasma membranes to cellular signaling. De novo sphingolipid synthesis takes place in the endoplasmic reticulum (ER), where the condensation of the activated C₁₆ fatty acid palmitoyl-CoA and the amino acid L-serine is catalyzed by serine palmitoyltransferase (SPT). The product, 3-ketosphinganine, is then converted into more complex sphingolipids by additional ER-bound enzymes, resulting in the formation of ceramides. Since sphingolipid homeostasis is crucial to numerous cellular functions, improved assessment of sphingolipid metabolism will be key to better understanding several human diseases. To date, no assay exists capable of monitoring de novo synthesis sphingolipid in its entirety. Here, we have established a cell-free assay utilizing rat liver microsomes containing all the enzymes necessary for bottom-up synthesis of ceramides. Following lipid extraction, we were able to track the different intermediates of the sphingolipid metabolism pathway, namely 3-ketosphinganine, sphinganine, dihydroceramide, and ceramide. This was achieved by chromatographic separation of sphingolipid metabolites followed by detection of their accurate mass and characteristic fragmentations through high-resolution mass spectrometry and tandem-mass spectrometry. We were able to distinguish, unequivocally, between de novo synthesized sphingolipids and intrinsic species, inevitably present in the microsome preparations, through the addition of stable isotope-labeled palmitate-d₃ and L-serine-d₃. To the best of our knowledge, this is the first demonstration of a method monitoring the entirety of ER-associated sphingolipid biosynthesis. Proof-of-concept data was provided by modulating the levels of supplied cofactors (e.g., NADPH) or the addition of specific enzyme inhibitors (e.g., fumonisin B₁). The presented microsomal assay may serve as a useful tool for monitoring alterations in sphingolipid de novo synthesis in cells or tissues. Additionally, our methodology may be used for metabolism studies of atypical substrates – naturally occurring or chemically tailored – as well as novel inhibitors of enzymes involved in sphingolipid de novo synthesis.
Plasma carotenoids, tocopherols, and retinol in the age-stratified (35–74 years) general population
(2016)
Blood micronutrient status may change with age. We analyzed plasma carotenoids, α-/γ-tocopherol, and retinol and their associations with age, demographic characteristics, and dietary habits (assessed by a short food frequency questionnaire) in a cross-sectional study of 2118 women and men (age-stratified from 35 to 74 years) of the general population from six European countries. Higher age was associated with lower lycopene and α-/β-carotene and higher β-cryptoxanthin, lutein, zeaxanthin, α-/γ-tocopherol, and retinol levels. Significant correlations with age were observed for lycopene (r = −0.248), α-tocopherol (r = 0.208), α-carotene (r = −0.112), and β-cryptoxanthin (r = 0.125; all p < 0.001). Age was inversely associated with lycopene (−6.5% per five-year age increase) and this association remained in the multiple regression model with the significant predictors (covariables) being country, season, cholesterol, gender, smoking status, body mass index (BMI (kg/m2)), and dietary habits. The positive association of α-tocopherol with age remained when all covariates including cholesterol and use of vitamin supplements were included (1.7% vs. 2.4% per five-year age increase). The association of higher β-cryptoxanthin with higher age was no longer statistically significant after adjustment for fruit consumption, whereas the inverse association of α-carotene with age remained in the fully adjusted multivariable model (−4.8% vs. −3.8% per five-year age increase). We conclude from our study that age is an independent predictor of plasma lycopene, α-tocopherol, and α-carotene.
Background: The relative dose response (RDR) test, which quantifies the increase in serum retinol after vitamin A administration, is a qualitative measure of liver vitamin A stores. Particularly in preterm infants, the feasibility of the RDR test involving blood is critically dependent on small sample volumes. Objectives: This study aimed to assess whether the RDR calculated with retinol-binding protein 4 (RBP4) might be a substitute for the classical retinol-based RDR test for assessing vitamin A status in very preterm infants. Methods: This study included preterm infants with a birth weight below 1,500 g (n = 63, median birth weight 985 g, median gestational age 27.4 weeks) who were treated with 5,000 IU retinyl palmitate intramuscularly 3 times a week for 4 weeks. On day 3 (first vitamin A injection) and day 28 of life (last vitamin A injection), the RDR was calculated and compared using serum retinol and RBP4 concentrations. Results: The concentrations of retinol (p < 0.001) and RBP4 (p < 0.01) increased significantly from day 3 to day 28. On day 3, the median (IQR) retinol-RDR was 27% (8.4-42.5) and the median RBP4-RDR was 8.4% (-3.4 to 27.9), compared to 7.5% (-10.6 to 20.8) and -0.61% (-19.7 to 15.3) on day 28. The results for retinol-RDR and RBP4-RDR revealed no significant correlation. The agreement between retinol-RDR and RBP4-RDR was poor (day 3: Cohen's κ = 0.12; day 28: Cohen's κ = 0.18). Conclusion: The RDR test based on circulating RBP4 is unlikely to reflect the hepatic vitamin A status in preterm infants.
Wheat is one of the most consumed foods in the world and unfortunately causes allergic reactions which have important health effects. The α-amylase/trypsin inhibitors (ATIs) have been identified as potentially allergen components of wheat. Due to a lack of data on optimization of ATI extraction, a new wheat ATIs extraction approach combining solvent extraction and selective precipitation is proposed in this work. Two types of wheat cultivars (Triticum aestivum L.), Julius and Ponticus were used and parameters such as solvent type, extraction time, temperature, stirring speed, salt type, salt concentration, buffer pH and centrifugation speed were analyzed using the Plackett-Burman design. Salt concentration, extraction time and pH appeared to have significant effects on the recovery of ATIs (p < 0.01). In both wheat cultivars, Julius and Ponticus, ammonium sulfate substantially reduced protein concentration and inhibition of amylase activity (IAA) compared to sodium chloride. The optimal conditions with desirability levels of 0.94 and 0.91 according to the Doehlert design were: salt concentrations of 1.67 and 1.22 M, extraction times of 53 and 118 min, and pHs of 7.1 and 7.9 for Julius and Ponticus, respectively. The corresponding responses were: protein concentrations of 0.31 and 0.35 mg and IAAs of 91.6 and 83.3%. Electrophoresis and MALDI-TOF/MS analysis showed that the extracted ATIs masses were between 10 and 20 kDa. Based on the initial LC-MS/MS analysis, up to 10 individual ATIs were identified in the extracted proteins under the optimal conditions. The positive implication of the present study lies in the quick assessment of their content in different varieties especially while considering their allergenic potential.
The current study was undertaken to investigate the relation between serum C-reactive protein (CRP) concentrations and parameters of renal function in dogs with naturally occurring renal disease. Dogs were assigned to groups according to plasma creatinine concentration, urinary protein-to-creatinine ratio (UP/UC), and exogenous plasma creatinine clearance (P-Cl(Cr)) rates. Group A (healthy control dogs; n = 8): non-azotemic (plasma creatinine <125 mu mol/l) and nonproteinuric (UP/UC <0.2), with P-Cl(Cr) rates >90 ml/min/m(2); group B (n = 11): non-azotemic, nonproteinuric dogs with reduced P-Cl(Cr) rates (50-89 ml/min/m(2)); group C (n = 7): azotemic, borderline proteinuric dogs (P-Cl(Cr) rates: 22-67 ml/min/m(2)); and group D (n = 6): uremic, proteinuric dogs (not tested for P-Cl(Cr)). The serum CRP concentrations were measured via commercial enzyme-linked immunosorbent assay. The CRP concentrations in the clinically healthy dogs (group A) ranged from 2.09 mg/l to 8.60 mg/l (median: 3.21 mg/l). In comparison with dogs of group A, median CRP concentrations were significantly (P < 0.01) elevated in dogs of group B (17.6 mg/l, range: 17.0-19.2 mg/l), group C (24.8 mg/l, range: 18.0-32.5 mg/l), and group D (59.7 mg/l, range: 17.7-123 mg/l). Serum CRP was significantly related to P-Cl(Cr) (r = -0.83; P < 0.001), plasma creatinine (r = 0.81; P < 0.001), UP/UC (r = 0.70; P < 0.001), and leukocytes (r = 0.49; P < 0.01). The significant relations between serum CRP concentrations and biochemical parameters of kidney function in plasma and urine suggest that a stimulation of the acute phase response is implicated in the pathogenesis of canine renal disease.
Background: Plasma concentration of retinol is an accepted indicator to assess the vitamin A (retinol) status in cattle. However, the determination of vitamin A requires a time consuming multi-step procedure, which needs specific equipment to perform extraction, centrifugation or saponification prior to high-performance liquid chromatography (HPLC).
Methods: The concentrations of retinol in whole blood (n = 10), plasma (n = 132) and serum (n = 61) were measured by a new rapid cow-side test (iCheck™ FLUORO) and compared with those by HPLC in two independent laboratories in Germany (DE) and Japan (JP).
Results: Retinol concentrations in plasma ranged from 0.033 to 0.532 mg/L, and in serum from 0.043 to 0.360 mg/L (HPLC method). No significant differences in retinol levels were observed between the new rapid cow-side test and HPLC performed in different laboratories (HPLC vs. iCheck™ FLUORO: 0.320 ± 0.047 mg/L vs. 0.333 ± 0.044 mg/L, and 0.240 ± 0.096 mg/L vs. 0.241 ± 0.069 mg/L, lab DE and lab JP, respectively). A similar comparability was observed when whole blood was used (HPLC vs. iCheck™ FLUORO: 0.353 ± 0.084 mg/L vs. 0.341 ± 0.064 mg/L). Results showed a good agreement between both methods based on correlation coefficients of r2 = 0.87 (P < 0.001) and Bland-Altman blots revealed no significant bias for all comparison.
Conclusions: With the new rapid cow-side test (iCheck™ FLUORO) retinol concentrations in cattle can be reliably assessed within a few minutes and directly in the barn using even whole blood without the necessity of prior centrifugation. The ease of the application of the new rapid cow-side test and its portability can improve the diagnostic of vitamin A status and will help to control vitamin A supplementation in specific vitamin A feeding regimes such as used to optimize health status in calves or meat marbling in Japanese Black cattle.
Cell-Based Reporter Release Assay to Determine the Potency of Proteolytic Bacterial Neurotoxins
(2018)
Despite the implementation of cell-based replacement methods, the mouse lethality assay is still frequently used to determine the activity of botulinum toxin (BoNT) for medical use. One explanation is that due to the use of neoepitope-specific antibodies to detect the cleaved BoNT substrate, the currently devised assays can detect only one specific serotype of the toxin. Recently, we developed a cell-based functional assay, in which BoNT activity is determined by inhibiting the release of a reporter enzyme that is liberated concomitantly with the neurotransmitter from neurosecretory vesicles. In theory, this assay should be suitable to detect the activity of any BoNT serotype. Consistent with this assumption, the current study shows that the stimulus-dependent release of a luciferase from a differentiated human neuroblastoma-based reporter cell line (SIMA-hPOMC1-26-GLuc cells) was inhibited by BoNT-A and-C. Furthermore, this was also inhibited by BoNT-B and tetanus toxin to a lesser extent and at higher concentrations. In order to provide support for the suitability of this technique in practical applications, a dose–response curve obtained with a pharmaceutical preparation of BoNT-A closely mirrored the activity determined in the mouse lethality assay. In summary, the newly established cell-based assay may represent a versatile and specific alternative to the mouse lethality assay and other currently established cell-based assays.
Soils in Germany are commonly low in selenium; consequently, a sufficient dietary supply is not always ensured. The extent of such provision adequacy is estimated by the optimal effect range of biomarkers, which often reflects the physiological requirement. Preceding epidemiological studies indicate that low selenium serum concentrations could be related to cardiovascular diseases. Inter alia, risk factors for cardiovascular diseases are physical inactivity, overweight, as well as disadvantageous eating habits. In order to assess whether these risk factors can be modulated, a cardio-protective diet comprising fixed menu plans combined with physical exercise was applied in the German MoKaRi (modulation of cardiovascular risk factors) intervention study. We analyzed serum samples of the MoKaRi cohort (51 participants) for total selenium, GPx activity, and selenoprotein P at different timepoints of the study (0, 10, 20, 40 weeks) to explore the suitability of these selenium-associated markers as indicators of selenium status. Overall, the time-dependent fluctuations in serum selenium concentration suggest a successful change in nutritional and lifestyle behavior. Compared to baseline, a pronounced increase in GPx activity and selenoprotein P was observed, while serum selenium decreased in participants with initially adequate serum selenium content. SELENOP concentration showed a moderate positive monotonic correlation (r = 0.467, p < 0.0001) to total Se concentration, while only a weak linear relationship was observed for GPx activity versus total Se concentration (r = 0.186, p = 0.021). Evidently, other factors apart from the available Se pool must have an impact on the GPx activity, leading to the conclusion that, without having identified these factors, GPx activity should not be used as a status marker for Se
Zinc deficiency has a fundamental influence on the immune defense, with multiple effects on different immune cells, resulting in a major impairment of human health. Monocytes and macrophages are among the immune cells that are most fundamentally affected by zinc, but the impact of zinc on these cells is still far from being completely understood. Therefore, this study investigates the influence of zinc deficiency on monocytes of healthy human donors. Peripheral blood mononuclear cells, which include monocytes, were cultured under zinc deficient conditions for 3 days. This was achieved by two different methods: by application of the membrane permeable chelator N,N,N0´,N0´-tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN) or by removal of zinc from the culture medium using a CHELEX 100 resin. Subsequently, monocyte functions were analyzed in response to Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. Zinc depletion had differential effects. On the one hand, elimination of bacterial pathogens by phagocytosis and oxidative burst was elevated. On the other hand, the production of the inflammatory cytokines tumor necrosis factor (TNF)-a and interleukin (IL)-6 was reduced. This suggests that monocytes shift from intercellular communication to basic innate defensive functions in response to zinc deficiency. These results were obtained regardless of the method by which zinc deficiency was achieved. However, CHELEX-treated medium strongly augmented cytokine production, independently from its capability for zinc removal. This side-effect severely limits the use of CHELEX for investigating the effects of zinc deficiency on innate immunity.
Background: Transport of methylmercury (MeHg) across the blood-brain barrier towards the brain side is well discussed in literature, while ethylmercury (EtHg) and inorganic mercury are not adequately characterized regarding their entry into the brain. Studies investigating a possible efflux out of the brain are not described to our knowledge.
Methods: This study compares, for the first time, effects of organic methylmercury chloride (MeHgCl), EtHg-containing thiomersal and inorganic Hg chloride (HgCl2) on as well as their transfer across a primary porcine in vitro model of the blood-brain barrier.
Results: With respect to the barrier integrity, the barrier model exhibited a much higher sensitivity towards HgCl2 following basolateral incubation (brain-facing side) as compared to apical application (blood-facing side). These HgCl2 induced effects on the barrier integrity after brain side incubation are comparable to that of the organic species, although MeHgCl and thiomersal exerted much higher cytotoxic effects in the barrier building cells. Hg transfer rates following exposure to organic species in both directions argue for diffusion as transfer mechanism. Inorganic Hg application surprisingly resulted in a Hg transfer out of the brain-facing compartment.
Conclusions: In case of MeHgCl and thiomersal incubation, mercury crossed the barrier in both directions, with a slight accumulation in the basolateral, brain-facing compartment, after simultaneous incubation in both compartments. For HgCl2, our data provide first evidence that the blood-brain barrier transfers mercury out of the brain.
Background:
First metabolomics studies have indicated that metabolic fingerprints from accessible tissues might
be useful to better understand the etiological links between metabolism and cancer. However, there is still a lack
of prospective metabolomics studies on pre-diagnostic metabolic alterations and cancer risk.
Methods:
Associations between pre-diagnostic levels of 120 circulating metabolites (acylcarnitines, amino acids,
biogenic amines, phosphatidylcholines, sphingolipids, and hexoses) and the risks of breast, prostate, and colorectal
cancer were evaluated by Cox regression analyses using data of a prospective case-cohort study including 835
incident cancer cases.
Results:
The median follow-up duration was 8.3 years among non-cases and 6.5 years among incident cases of
cancer. Higher levels of lysophosphatidylcholines (lysoPCs), and especially lysoPC a C18:0, were consistently related
to lower risks of breast, prostate, and colorectal cancer, independent of background factors. In contrast, higher
levels of phosphatidylcholine PC ae C30:0 were associated with increased cancer risk. There was no heterogeneity
in the observed associations by lag time between blood draw and cancer diagnosis.
Conclusion:
Changes in blood lipid composition precede the diagnosis of common malignancies by several years.
Considering the consistency of the present results across three cancer types the observed alterations point to a
global metabolic shift in phosphatidylcholine metabolism that may drive tumorigenesis.
Background: Gestational diabetes mellitus (GDM) is associated with adverse pregnancy outcomes. It is known that GDM is associated with an altered placental function and changes in placental gene regulation. More recent studies demonstrated an involvement of epigenetic mechanisms. So far, the focus regarding placental epigenetic changes in GDM was set on gene-specific DNA methylation analyses. Studies that robustly investigated placental global DNA methylation are lacking. However, several studies showed that tissue-specific alterations in global DNA methylation are independently associated with type 2 diabetes. Thus, the aim of this study was to characterize global placental DNA methylation by robustly measuring placental DNA 5-methylcytosine (5mC) content and to examine whether differences in placental global DNA methylation are associated with GDM.
Methods: Global DNA methylation was quantified by the current gold standard method, LC-MS/MS. In total, 1030 placental samples were analyzed in this single-center birth cohort study.
Results: Mothers with GDM displayed a significantly increased global placental DNA methylation (3.22 ± 0.63 vs. 3.00 ± 0.46 %; p = 0.013; ±SD). Bivariate logistic regression showed a highly significant positive correlation between global placental DNA methylation and the presence of GDM (p = 0.0009). Quintile stratification according to placental DNA 5mC levels revealed that the frequency of GDM was evenly distributed in quintiles 1–4 (2.9–5.3 %), whereas the frequency in the fifth quintile was significantly higher (10.7 %; p = 0.003). Bivariate logistic models adjusted for maternal age, BMI, ethnicity, recurrent miscarriages, and familiar diabetes predisposition clearly demonstrated an independent association between global placental DNA hypermethylation and GDM. Furthermore, an ANCOVA model considering known predictors of DNA methylation substantiated an independent association between GDM and placental DNA methylation.
Conclusions: This is the first study that employed a robust quantitative assessment of placental global DNA methylation in over a thousand placental samples. The study provides large scale evidence that placental global DNA hypermethylation is associated with GDM, independent of established risk factors.
Background: The biological properties of oxidized and non-oxidized PTH are substantially different. Oxidized PTH (oxPTH) loses its PTH receptor-stimulating properties, whereas non-oxidized PTH (n-oxPTH) is a full agonist of the receptor. This was described in more than 20 well published studies in the 1970(s) and 80(s). However, PTH oxidation has been ignored during the development of PTH assays for clinical use so far. Even the nowadays used third generation assay systems do not consider oxidation of PTH. We recently developed an assay to differentiate between oxPTH and n-oxPTH. In the current study we established normal values for this assay system. Furthermore, we compare the ratio of oxPTH to n-oxPTH in different population with chronic renal failure: 620 children with renal failure stage 2-4 of the 4C study, 342 adult patients on dialysis, and 602 kidney transplant recipients. In addition, we performed modeling of the interaction of either oxPTH or n-oxPTH with the PTH receptor using biophysical structure approaches. Results: The children had the highest mean as well as maximum n-oxPTH concentrations as compared to adult patients (both patients on dialysis as well as kidney transplant recipients). The relationship between oxPTH and n-oxPTH of individual patients varied substantially in all three populations with renal impairment. The analysis of n-oxPTH in 89 healthy control subjects revealed that n-oxPTH concentrations in patient with renal failure were higher as compared to healthy adult controls (2.25-fold in children with renal failure, 1.53-fold in adult patients on dialysis, and 1.56-fold in kidney transplant recipients, respectively). Computer assisted biophysical structure modeling demonstrated, however, minor sterical- and/or electrostatic changes in oxPTH and n-oxPTH. This indicated that PTH oxidation may induce refolding of PTH and hence alters PTH-PTH receptor interaction via oxidation induced three-dimensional structure alteration of PTH. Conclusion: A huge proportion of circulating PTH measured by current state-of-the-art assay systems is oxidized and thus not biologically active. The relationship between oxPTH and n-oxPTH of individual patients varied substantially. Non-oxidized PTH concentrations are 1.5 - 2.25 fold higher in patients with renal failure as compared to health controls. Measurements of n-oxPTH may reflect the hormone status more precise. The iPTH measures describes most likely oxidative stress in patients with renal failure rather than the PTH hormone status. This, however, needs to be demonstrated in further clinical studies.
Background
The kidneys are essential for the metabolism of vitamin A (retinol) and its transport proteins retinol-binding protein 4 (RBP4) and transthyretin. Little is known about changes in serum concentration after living donor kidney transplantation (LDKT) as a consequence of unilateral nephrectomy; although an association of these parameters with the risk of cardiovascular diseases and insulin resistance has been suggested. Therefore we analyzed the concentration of retinol, RBP4, apoRBP4 and transthyretin in serum of 20 living-kidney donors and respective recipients at baseline as well as 6 weeks and 6 months after LDKT.
Results
As a consequence of LDKT, the kidney function of recipients was improved while the kidney function of donors was moderately reduced within 6 weeks after LDKT. With regard to vitamin A metabolism, the recipients revealed higher levels of retinol, RBP4, transthyretin and apoRBP4 before LDKT in comparison to donors. After LDKT, the levels of all four parameters decreased in serum of the recipients, while retinol, RBP4 as well as apoRBP4 serum levels of donors increased and remained increased during the follow-up period of 6 months.
Conclusion
LDKT is generally regarded as beneficial for allograft recipients and not particularly detrimental for the donors. However, it could be demonstrated in this study that a moderate reduction of kidney function by unilateral nephrectomy, resulted in an imbalance of components of vitamin A metabolism with a significant increase of retinol and RBP4 and apoRBP4 concentration in serum of donors.
The visceral protein transthyretin (TTR) is frequently affected by oxidative post-translational protein modifications (PTPMs) in various diseases. Thus, better insight into structure-function relationships due to oxidative PTPMs of TTR should contribute to the understanding of pathophysiologic mechanisms. While the in vivo analysis of TTR in mammalian models is complex, time- and resource-consuming, transgenic Caenorhabditis elegans expressing hTTR provide an optimal model for the in vivo identification and characterization of drug-mediated oxidative PTPMs of hTTR by means of matrix assisted laser desorption/ionization – time of flight – mass spectrometry (MALDI-TOF-MS). Herein, we demonstrated that hTTR is expressed in all developmental stages of Caenorhabditis elegans, enabling the analysis of hTTR metabolism during the whole life-cycle. The suitability of the applied model was verified by exposing worms to D-penicillamine and menadione. Both drugs induced substantial changes in the oxidative PTPM pattern of hTTR. Additionally, for the first time a covalent binding of both drugs with hTTR was identified and verified by molecular modelling.
In a subset of patients, non-alcoholic fatty liver disease (NAFLD) is complicated by cell death and inflammation resulting in non-alcoholic steatohepatitis (NASH), which may progress to fibrosis and subsequent organ failure. Apart from cytokines, prostaglandins, in particular prostaglandin E-2 (PGE(2)), play a pivotal role during inflammatory processes. Expression of the key enzymes of PGE(2) synthesis, cyclooxygenase 2 and microsomal PGE synthase 1 (mPGES-1), was increased in human NASH livers in comparison to controls and correlated with the NASH activity score. Both enzymes were also induced in NASH-diet-fed wild-type mice, resulting in an increase in hepatic PGE(2) concentration that was completely abrogated in mPGES-1-deficient mice. PGE(2) is known to inhibit TNF-alpha synthesis in macrophages. A strong infiltration of monocyte-derived macrophages was observed in NASH-diet-fed mice, which was accompanied with an increase in hepatic TNF-alpha expression. Due to the impaired PGE(2) production, TNF-alpha expression increased much more in livers of mPGES-1-deficient mice or in the peritoneal macrophages of these mice. The increased levels of TNF-alpha resulted in an enhanced IL-1 beta production, primarily in hepatocytes, and augmented hepatocyte apoptosis. In conclusion, attenuation of PGE(2) production by mPGES-1 ablation enhanced the TNF-alpha-triggered inflammatory response and hepatocyte apoptosis in diet-induced NASH.
Non-alcoholic fatty liver diseases (NAFLD) including the severe form with steatohepatitis (NASH) are highly prevalent ailments to which no approved pharmacological treatment exists. Dietary intervention aiming at 10% weight reduction is efficient but fails due to low compliance. Increase in physical activity is an alternative that improved NAFLD even in the absence of weight reduction. The underlying mechanisms are unclear and cannot be studied in humans. Here, a rat NAFLD model was developed that reproduces many facets of the diet-induced NAFLD in humans. The impact of endurance exercise was studied in this model. Male Wistar rats received control chow or a NASH-inducing diet rich in fat, cholesterol, and fructose. Both diet groups were subdivided into a sedentary and an endurance exercise group. Animals receiving the NASH-inducing diet gained more body weight, got glucose intolerant and developed a liver pathology with steatosis, hepatocyte hypertrophy, inflammation and fibrosis typical of NAFLD or NASH. Contrary to expectations, endurance exercise did not improve the NASH activity score and even enhanced hepatic inflammation. However, endurance exercise attenuated the hepatic cholesterol overload and the ensuing severe oxidative stress. In addition, exercise improved glucose tolerance possibly in part by induction of hepatic FGF21 production.