Defective peroxisomal catabolism of branched fatty acyl coenzyme A in mice lacking the sterol carrier protein-2/sterol carrier protein-x gene function

Gene targeting in mice was used to investigate the unknown function of Scp2, encoding sterol carrier protein-2 (SCP2; a peroxisomal lipid carrier) and sterol carrier protein-x (SCPx; a fusion protein between SCP2 and a peroxisomal thiolase). Complete deficiency of SCP2 and SCPx was associated with marked alterations in gene expression, peroxisome proliferation, hypolipidemia, impaired body weight control, and neuropathy. Along with these abnormalities, catabolism of methyl-branched fatty acyl CoAs was impaired. The defect became evident from up to 10-fold accumulation of the tetramethyl-branched fatty acid phytanic acid in Scp2(−/−) mice. Further characterization supported that the gene disruption led to inefficient import of phytanoyl-CoA into peroxisomes and to defective thiolytic cleavage of 3-ketopristanoyl-CoA. These results corresponded to high-affinity binding of phytanoyl-CoA to the recombinant rat SCP2 protein, as well as high 3-ketopristanoyl-CoA thiolase activity of the recombinant rat SCPx protein.     

Hippocampal metabolic abnormalities in mild cognitive impairment and Alzheimer's disease

Mild cognitive impairment (MCI) defines a group of otherwise healthy elderly subjects with a markedly elevated risk of developing Alzheimer's disease (AD). In the search for biomarkers of MCI, we assessed whether MCI shares neurochemical abnormalities with AD in areas affected early in the course of the disease. As a secondary study aim, we tested to what extent neurochemical findings reflect neuropsychological deficits. Proton spectroscopy was performed in 19 MCI patients, 18 AD patients and 22 age and gender matched controls (CON) within the parietal gray and white matter (PWM and PGM) and the hippocampus (HIP). The cognitive test battery used included measures compiled by the Consortium to Establish a Registry for Alzheimer's Disease (CERAD). The N-acetyl-aspartate to creatine ratio (NAA/Cr) was significantly reduced in the HIP of MCI and AD compared with CON (p < 0.05). Only AD patients showed parietal abnormalities, namely significantly elevated myoinositol (mI/Cr and mI/NAA) in PGM, reduced NAA/Cr and elevated mI/NAA in PWM. MCI subjects were significantly impaired in categorical verbal fluency (VF) (p < 0.001) and delayed verbal recall (DVR) (p < 0.001). VF was positively correlated with hippocampal NAA/Cr (p < 0.05) and parietal mI/NAA (p < 0.05). In summary, this study demonstrates shared neurobiological hippocampal abnormalities in MCI and AD, whereas parietal lobe neurochemical profiles and functions were normal in MCI. Thus, biological evidence is provided that MCI represents a precursor stage of AD. Moreover, multivoxel 1H MRS may enable an objective staging of the neurodegenerative process underlying the age-dependent cognitive deficits eventually leading to dementia.     

Ambiguous Role of Interleukin-12 in Yersinia enterocolitica Infection in Susceptible and Resistant Mouse Strains

Endogenous interleukin-12 (IL-12) mediates protection against Yersinia enterocolitica in C57BL/6 mice by triggering gamma interferon (IFN-γ) production in NK and CD4⁺ T cells. Administration of exogenous IL-12 confers protection against yersiniae in Yersinia-susceptible BALB/c mice but exacerbates yersiniosis in resistant C57BL/6 mice. Therefore, we wanted to dissect the different mechanisms exerted by IL-12 during Yersinia infections by using different models of Yersinia-resistant and -susceptible mice, including resistant C57BL/6 mice, susceptible BALB/c mice, intermediate-susceptible wild-type 129/Sv mice, 129/Sv IFN-γ-receptor-deficient (IFN-γR^−/−) mice and C57BL/6 tumor necrosis factor (TNF) receptor p55 chain-deficient (TNFR p55^−/−) mice. IFN-γR^−/− mice turned out to be highly susceptible to infection by Y. enterocolitica compared with IFN-γR^+/+ mice. Administration of IL-12 was protective in IFN-γR^+/+ mice but not in IFN-γR^−/− mice, suggesting that IFN-γR-induced mechanisms are essential for IL-12-induced resistance against yersiniae. BALB/c mice could be rendered Yersinia resistant by administration of anti-CD4 antibodies or by administration of IL-12. In contrast, C57BL/6 mice could be rendered more resistant by administration of transforming growth factor β (TGF-β). Furthermore, IL-12-triggered toxic effects in C57BL/6 mice were abrogated by coadministration of TGF-β. While administration of IL-12 alone increased TNF-α levels, administration of TGF-β or TGF-β plus IL-12 decreased both TNF-α and IFN-γ levels in Yersinia-infected C57BL/6 mice. Moreover, IL-12 did not induce toxicity in Yersinia-infected TNFR p55^−/− mice, suggesting that TNF-α accounts for IL-12-induced toxicity. Taken together, IL-12 may induce different effector mechanisms in BALB/c and C57BL/6 mice resulting either in protection or exacerbation. These results are important for understanding the critical balance of proinflammatory and regulatory cytokines in bacterial infections which is decisive for beneficial effects of cytokine therapy.     

Experimental pneumococcal meningitis: impaired clearance of bacteria from the blood due to increased apoptosis in the spleen in Bcl-2-deficient mice

Necrotic and apoptotic neuronal cell death can be found in pneumococcal meningitis. We investigated the role of Bcl-2 as an antiapoptotic gene product in pneumococcal meningitis using Bcl-2 knockout (Bcl-2(-/-)) mice. By using a model of pneumococcal meningitis induced by intracerebral infection, Bcl-2-deficient mice and control littermates were assessed by clinical score and a tight rope test at 0, 12, 24, 32, and 36 h after infection. Then mice were sacrificed, the bacterial titers in blood, spleen, and cerebellar homogenates were determined, and the brain and spleen were evaluated histologically. The Bcl-2-deficient mice developed more severe clinical illness, and there were significant differences in the clinical score at 24, 32, and 36 h and in the tight rope test at 12 and 32 h. The bacterial titers in the blood were greater in Bcl-2-deficient mice than in the controls (7.46 +/- 1.93 log CFU/ml versus 5.16 +/- 0.96 log CFU/ml [mean +/- standard deviation]; P < 0.01). Neuronal damage was most prominent in the hippocampal formation, but there were no significant differences between groups. In situ tailing revealed only a few apoptotic neurons in the brain. In the spleen, however, there were significantly more apoptotic leukocytes in Bcl-2-deficient mice than in controls (5,148 +/- 3,406 leukocytes/mm2 versus 1,070 +/- 395 leukocytes/mm2; P < 0.005). Bcl-2 appears to counteract sepsis-induced apoptosis of splenic lymphocytes, thereby enhancing clearance of bacteria from the blood.     

Direct interaction of the Fanconi anaemia protein FANCG with BRCA2/FANCD1

Fanconi anaemia (FA) is an autosomal recessive genetic disorder characterized by progressive bone marrow failure, multiple congenital abnormalities, and an increased risk of cancer. FA cells are characterized by chromosomal instability and hypersensitivity to DNA interstrand crosslinking agents. At least eight complementation groups exist (FA-A to G), and the genes for all of these except FA-B have been cloned. Functional linkage between the FA pathway and genes involved in susceptibility to breast cancer has been demonstrated by the interaction of the FANCA and FANCD2 proteins with BRCA1, and the discovery that the FANCD1 gene is identical to BRCA2. Here we have used the yeast two-hybrid system to test for direct interaction between BRCA2 or its effector RAD51 and the FANCA, FANCC and FANCG proteins. We found that FANCG was capable of binding to two separate sites in the BRCA2 protein, located either side of the BRC repeats. Furthermore, FANCG could be co-immunoprecipitated with BRCA2 from human cells, and FANCG co-localized in nuclear foci with both BRCA2 and RAD51 following DNA damage with mitomycin C. These results demonstrate that BRCA2 is directly connected to a pathway that is deficient in interstrand crosslink repair, and that at least one other FA protein is closely associated with the homologous recombination DNA repair machinery.     

Synaptic transmission in ammonia intoxication

Ammonia intoxication allegedly plays a significant role in the pathophysiology of hepatic encephalopathy. In order to understand the pathogenesis of this encephalopathy it is necessary to know the effects of ammonia on the mechanisms by which neurons communicate, i.e., excitatory and inhibitory synaptic transmissions. NH ₄ ⁺ decreases excitatory synaptic transmission mediated by glutamate. Possibly, this effect is related to a depletion of glutamate in presynaptic terminals. NH ₄ ⁺ decreases inhibitory synaptic transmission mediated by hyperpolarizing Cl^?-dependent inhibitory postsynaptic potentials. This effect is related to the inactivation of the extrusion of Cl^? from neurons by NH ₄ ⁺ . By the very same action, NH ₄ ⁺ also decreases the hyperpolarizing action of Ca²⁺-and voltage-dependent Cl^? currents. These currents may modify the efficacy of the synaptic input to neurons and increase neuronal excitability. Estimates derived from experimental observations suggest that an increase of CNS tissue NH ₄ ⁺ to 0.5 μmol/g is sufficient to disturb excitatory and inhibitory synaptic transmission and to initiate the encephalopathy related to acute ammonia intoxication. Chronic portasystemic shunting of blood, as in hepatic encephalopathy, significantly changes the relation between CNS NH ₄ ⁺ and function of synaptic transmission. A portacaval shunt increases the tissue NH ₄ ⁺ necessary to disturb synaptic transmission. However, after a portasystemic shunt, synaptic transmission becomes extremely sensitive to any acute increase of NH ₄ ⁺ in the CNS.     

A Log Ratio-Based Analysis of Individual Changes in the Composition of the Oral Microbiota in Different Dietary Phases

Background: Investigating the influence of nutrition on oral health has a long scientific history. Due to recent technical advances like sequencing techniques for the oral microbiota, this topic has gained scientific interest again. A basic challenge is to understand the influence of nutrition on the oral microbiota and on the interaction between the oral bacteria, which is also statistically challenging. Methods: Log-transformed ratios of two bacteria concentrations are introduced as the basic analytic tool. The framework is illustrated by application in an experimental study exposing eleven participants to different nutrition schemes in five consecutive phases. Results: The method could be sufficiently used to analyse the interrelation between the bacteria and to identify some bacterial groups with the same as well as different reactions to additional dietary components. It was found that the strongest changes in bacterial concentrations were achieved by the additional consumption of dairy products. Conclusion: A log ratio-based analysis offers insights into the relation of different bacteria while taking specific features of compositional data into account. The presented methods allow becoming independent of the behaviour of other bacteria, which is a disadvantage of common analysis methods of compositions. The results indicate that modulations of the oral biofilm microbiota due to nutrition change can be attained.     

Relative Validity of MijnEetmeter: A Food Diary App for Self-Monitoring of Dietary Intake

This study aimed to evaluate the relative validity of intake of energy, nutrients and food groups assessed with MijnEetmeter food diary as compared to 24-h dietary recalls, and if this differed between experienced and new users. One hundred men and women aged 18–70 y participated, of whom 47 had prior experience with the tool. Participants kept MijnEetmeter on three days. Trained dietitians called them three times for a 24-h dietary recall interview, once recalling food consumption on the same day as the food recording in MijnEetmeter. Systematic differences and correlations were assessed, and Bland–Altman plots were created; both for 3-day mean intakes and for intakes on the same day. Relative to 24-h dietary recalls, MijnEetmeter underestimated consumption of drinks, added fat, cereal products, and potatoes. Relative underestimation was observed for energy intake (6%) and about half of the nutrients. Experienced MijnEetmeter users underestimated intake the least. For intake of energy and six key nutrients, correlations between 3-day mean intakes were above 0.7 except for sodium intake. In conclusion, MijnEetmeter moderately underestimates intakes of energy and some nutrients and food groups. To improve the self-monitoring of dietary intake, it is recommended that the users record food consumption for several days and that the apps probes for easily forgotten foods and drinks.     

Markers of Intestinal Permeability Are Rapidly Improved by Alcohol Withdrawal in Patients with Alcohol-Related Liver Disease

Changes in intestinal microbiome and barrier function are critical in the development of alcohol-related liver disease (ALD). Here, we determined the effects of a one-week alcohol withdrawal on parameters of intestinal barrier function in heavy drinkers with ALD in comparison to healthy non-drinkers (controls). In serum samples of 17 controls (m = 10/f = 7) and 37 age-matched ALD patients (m = 26/f = 11) undergoing a one-week alcohol withdrawal, markers of liver health and intestinal barrier function were assessed. Liver damage, e.g., fibrosis and hepatic steatosis, were assessed using FibroScan. Before alcohol withdrawal, markers of liver damage, lipopolysaccharide binding protein (LBP) and overall TLR4/TLR2 ligands in serum were significantly higher in ALD patients than in controls, whereas intestinal fatty acid binding protein (I-FABP) and zonulin protein concentrations in serum were lower. All parameters, with the exception of LBP, were significantly improved after alcohol withdrawal; however, not to the level of controls. Our data suggest that one-week of abstinence improves markers of intestinal barrier function and liver health in ALD patients.     

Modifiable Determinants of Postpartum Weight Loss in Women with Obesity: A Secondary Analysis of the UPBEAT Trial

Pregnancy can alter a woman’s weight gain trajectory across the life course and contribute to the development of obesity through retention of weight gained during pregnancy. This study aimed to identify modifiable determinants associated with postpartum weight retention (PPWR; calculated by the difference in pre-pregnancy and 6 month postpartum weight) in 667 women with obesity from the UPBEAT study. We examined the relationship between PPWR and reported glycaemic load, energy intake, and smoking status in pregnancy, excessive gestational weight gain (GWG), mode of delivery, self-reported postpartum physical activity (low, moderate, and high), and mode of infant feeding (breast, formula, and mixed). At the 6 month visit, 48% (n = 320) of women were at or above pre-pregnancy weight. Overall, PPWR was negative (−0.06 kg (−42.0, 40.4)). Breastfeeding for ≥4 months, moderate or high levels of physical activity, and GWG ≤9 kg were associated with negative PPWR. These three determinants were combined to provide a modifiable factor score (range 0–3); for each added variable, a further reduction in PPWR of 3.0 kg (95% confidence interval 3.76, 2.25) occurred compared to women with no modifiable factors. This study identified three additive determinants of PPWR loss. These provide modifiable targets during pregnancy and the postnatal period to enable women with obesity to return to their pre-pregnancy weight.