Adipose Tissue, Bile Acids, and Gut Microbiome Species Associated With Gallstones After Bariatric Surgery.

Several risk factors are associated with gallstone disease after bariatric surgery, but the underlying pathophysiological mechanisms of gallstone formation are unclear. We hypothesize that gallstone formation after bariatric surgery is induced by different pathways compared with gallstone formation in the general population, since postoperative formation occurs rapidly in patients who did not develop gallstones in preceding years. To identify both pathophysiological and potentially protective mechanisms against postoperative gallstone formation, we compared the preoperative fasting metabolome, fecal microbiome, and liver and adipose tissue transcriptome obtained before or during bariatric surgery of obese patients with and without postoperative gallstones. In total, 88 patients were selected from the BARIA longitudinal cohort study. Within this group, 32 patients had postoperative gallstones within 2 years. Gut microbiota metagenomic analyses showed group differences in abundance of 41 bacterial species, particularly abundance of Lactobacillaceae and Enterobacteriaceae in patients without gallstones. Subcutaneous adipose tissue transcriptomic analyses revealed four genes that were suppressed in gallstone patients compared with patients without gallstones. These baseline gene expression and gut microbiota composition differences might relate to protective mechanisms against gallstone formation after bariatric surgery. Moreover, baseline fasting blood samples of patients with postoperative gallstones showed increased levels of several bile acids. Overall, we revealed different genes and bacteria associated with gallstones than those previously reported in the general population, supporting the hypothesis that gallstone formation after bariatric surgery follows a different trajectory. Further research is necessary to confirm the involvement of the bile acids, adipose tissue activity, and microbial species observed here.

Differences in the prevalence of intermediate hyperglycaemia and the associated incidence of type 2 diabetes mellitus by ethnicity: The HELIUS study.

AIMS: We aimed to describe differences in the prevalence of intermediate hyperglycaemia (IH) between six ethnic groups. Moreover, to investigate differences in the association of the classifications of IH with the incidence of T2DM between ethnic groups. METHODS: We included 3759 Dutch, 2826 African Surinamese, 1646 Ghanaian, 2571 Turkish, 2691 Moroccan and 1970 South Asian Surinamese origin participants of the HELIUS study. IH was measured by fasting plasma glucose (FPG) and HbA1c. We calculated age-, BMI and physical-activity-adjusted prevalence of IH by sex, and calculated age and sex-adjusted hazard ratios (HR)for the association between IH and T2DM in each ethnic group. RESULTS: The prevalence of IH was higher among ethnic minority groups (68.6-41.7%) than the Dutch majority (34.9%). The prevalence of IH categories varied across subgroups. Combined increased FPG and HbA1c was most prevalent in South-Asian Surinamese men (27.6%, 95 %CI: 24.5-30.9%), and in Dutch women (4.2%, 95 %CI: 3.4-5.1%). The HRs for T2DM for each IH-classification did not differ significantly between ethnic groups. HRs were highest for the combined classification, e.g., HR = 8.1, 95 %CI: 2.5-26.6 in the Dutch. CONCLUSION: We found a higher prevalence of IH in ethnic minority versus majority groups, but did not find evidence for a differential association of IH with incident T2DM.

Plasma oxyphytosterols most likely originate from hepatic oxidation and subsequent spill-over in the circulation.

We evaluated oxyphytosterol (OPS) concentrations in plasma and various tissues of two genetically modified mouse models with either increased cholesterol (apoE KO mice) or increased cholesterol and plant sterol (PS) concentrations (apoExABCG8 dKO mice). Sixteen female apoE KO and 16 dKO mice followed the same standard, low OPS-chow diet. Animals were euthanized at 36 weeks to measure PS and OPS concentrations in plasma, brain, liver and aortic tissue. Cholesterol and oxysterol (OS) concentrations were analyzed as reference for sterol oxidation in general. Plasma campesterol (24.1 ± 4.3 vs. 11.8 ± 3.0 mg/dL) and sitosterol (67.4 ± 12.7 vs. 4.9 ± 1.1 mg/dL) concentrations were severely elevated in the dKO compared to the apoE KO mice (p < 0.001). Also, in aortic and brain tissue, PS levels were significantly elevated in dKO. However, plasma, aortic and brain OPS concentrations were comparable or even lower in the dKO mice. In contrast, in liver tissue, both PS and OPS concentrations were severely elevated in the dKO compared to apoE KO mice (sum OPS: 7.4 ± 1.6 vs. 4.1 ± 0.8 ng/mg, p < 0.001). OS concentrations followed cholesterol concentrations in plasma and all tissues suggesting ubiquitous oxidation. Despite severely elevated PS concentrations, OPS concentrations were only elevated in liver tissue, suggesting that OPS are primarily formed in the liver and plasma concentrations originate from hepatic spill-over into the circulation.

Fecal Microbiota Transplantation from Overweight or Obese Donors in Cachectic Patients with Advanced Gastroesophageal Cancer: A Randomized, Double-blind, Placebo-Controlled, Phase II Study.

PURPOSE: Cachexia is a multifactorial syndrome, associated with poor survival in patients with cancer, and is influenced by the gut microbiota. We investigated the effects of fecal microbiota transplantation (FMT) on cachexia and treatment response in patients with advanced gastroesophageal cancer. EXPERIMENTAL DESIGN: In a double-blind randomized placebo-controlled trial performed in the Amsterdam University Medical Center, we assigned 24 cachectic patients with metastatic HER2-negative gastroesophageal cancer to either allogenic FMT (healthy obese donor) or autologous FMT, prior to palliative chemotherapy (capecitabine and oxaliplatin). Primary objective was to assess the effect of allogenic FMT on satiety. Secondary outcomes were other features of cachexia, along with disease control rate (DCR), overall survival (OS), progression-free survival (PFS), and toxicity. Finally, exploratory analyses were performed on the effect of FMT on gut microbiota composition (metagenomic sequencing) and metabolites (untargeted metabolomics). RESULTS: Allogenic FMT did not improve any of the cachexia outcomes. Patients in the allogenic group (n = 12) had a higher DCR at 12 weeks (P = 0.035) compared with the autologous group (n = 12), longer median OS of 365 versus 227 days [HR = 0.38; 95% confidence interval (CI), 0.14-1.05; P = 0.057] and PFS of 204 versus 93 days (HR = 0.50; 95% CI, 0.21-1.20; P = 0.092). Patients in the allogenic group showed a significant shift in fecal microbiota composition after FMT (P = 0.010) indicating proper engraftment of the donor microbiota. CONCLUSIONS: FMT from a healthy obese donor prior to first-line chemotherapy did not affect cachexia, but may have improved response and survival in patients with metastatic gastroesophageal cancer. These results provide a rational for larger FMT trials.

A systems biology approach to understand gut microbiota and host metabolism in morbid obesity: design of the BARIA Longitudinal Cohort Study.

INTRODUCTION: Prevalence of obesity and associated diseases, including type 2 diabetes mellitus, dyslipidaemia and non-alcoholic fatty liver disease (NAFLD), are increasing. Underlying mechanisms, especially in humans, are unclear. Bariatric surgery provides the unique opportunity to obtain biopsies and portal vein blood-samples. METHODS: The BARIA Study aims to assess how microbiota and their metabolites affect transcription in key tissues and clinical outcome in obese subjects and how baseline anthropometric and metabolic characteristics determine weight loss and glucose homeostasis after bariatric surgery. We phenotype patients undergoing bariatric surgery (predominantly laparoscopic Roux-en-Y gastric bypass), before weight loss, with biometrics, dietary and psychological questionnaires, mixed meal test (MMT) and collect fecal-samples and intra-operative biopsies from liver, adipose tissues and jejunum. We aim to include 1500 patients. A subset (approximately 25%) will undergo intra-operative portal vein blood-sampling. Fecal-samples are analyzed with shotgun metagenomics and targeted metabolomics, fasted and postprandial plasma-samples are subjected to metabolomics, and RNA is extracted from the tissues for RNAseq-analyses. Data will be integrated using state-of-the-art neuronal networks and metabolic modeling. Patient follow-up will be ten years. RESULTS: Preoperative MMT of 170 patients were analysed and clear differences were observed in glucose homeostasis between individuals. Repeated MMT in 10 patients showed satisfactory intra-individual reproducibility, with differences in plasma glucose, insulin and triglycerides within 20% of the mean difference. CONCLUSION: The BARIA study can add more understanding in how gut-microbiota affect metabolism, especially with regard to obesity, glucose metabolism and NAFLD. Identification of key factors may provide diagnostic and therapeutic leads to control the obesity-associated disease epidemic.

Short chain fatty acids in human gut and metabolic health.

Evidence is accumulating that short chain fatty acids (SCFA) play an important role in the maintenance of gut and metabolic health. The SCFA acetate, propionate and butyrate are produced from the microbial fermentation of indigestible carbohydrates and appear to be key mediators of the beneficial effects elicited by the gut microbiome. Microbial SCFA production is essential for gut integrity by regulating the luminal pH, mucus production, providing fuel for epithelial cells and effects on mucosal immune function. SCFA also directly modulate host metabolic health through a range of tissue-specific mechanisms related to appetite regulation, energy expenditure, glucose homeostasis and immunomodulation. Therefore, an increased microbial SCFA production can be considered as a health benefit, but data are mainly based on animal studies, whereas well-controlled human studies are limited. In this review an expert group by ILSI Europe's Prebiotics Task Force discussed the current scientific knowledge on SCFA to consider the relationship between SCFA and gut and metabolic health with a particular focus on human evidence. Overall, the available mechanistic data and limited human data on the metabolic consequences of elevated gut-derived SCFA production strongly suggest that increasing SCFA production could be a valuable strategy in the preventing gastro-intestinal dysfunction, obesity and type 2 diabetes mellitus. Nevertheless, there is an urgent need for well controlled longer term human SCFA intervention studies, including measurement of SCFA fluxes and kinetics, the heterogeneity in response based on metabolic phenotype, the type of dietary fibre and fermentation site in fibre intervention studies and the control for factors that could shape the microbiome like diet, physical activity and use of medication.

Distinct differences in gut microbial composition and functional potential from lean to morbidly obese subjects.

INTRODUCTION: The gut microbiome may contribute to the development of obesity. So far, the extent of microbiome variation in people with obesity has not been determined in large cohorts and for a wide range of body mass index (BMI). Here, we aimed to investigate whether the faecal microbial metagenome can explain the variance in several clinical phenotypes associated with morbid obesity. METHODS: Caucasian subjects were recruited at our hospital. Blood pressure and anthropometric measurements were taken. Dietary intake was determined using questionnaires. Shotgun metagenomic sequencing was performed on faecal samples from 177 subjects. RESULTS: Subjects without obesity (n = 82, BMI 24.7 ± 2.9 kg m-2 ) and subjects with obesity (n = 95, BMI 38.6 ± 5.1 kg m-2 ) could be clearly distinguished based on microbial composition and microbial metabolic pathways. A total number of 52 bacterial species differed significantly in people with and without obesity. Independent of dietary intake, we found that microbial pathways involved in biosynthesis of amino acids were enriched in subjects with obesity, whereas pathways involved in the degradation of amino acids were depleted. Machine learning models showed that more than half of the variance in body fat composition followed by BMI could be explained by the gut microbiome, composition and microbial metabolic pathways, compared with 6% of variation explained in triglycerides and 9% in HDL. CONCLUSION: Based on the faecal microbiota composition, we were able to separate subjects with and without obesity. In addition, we found strong associations between gut microbial amino acid metabolism and specific microbial species in relation to clinical features of obesity.

Plant-based sterols and stanols in health & disease: "Consequences of human development in a plant-based environment?"

Dietary plant sterols and stanols as present in our diet and in functional foods are well-known for their inhibitory effects on intestinal cholesterol absorption, which translates into lower low-density lipoprotein cholesterol concentrations. However, emerging evidence suggests that plant sterols and stanols have numerous additional health effects, which are largely unnoticed in the current scientific literature. Therefore, in this review we pose the intriguing question "What would have occurred if plant sterols and stanols had been discovered and embraced by disciplines such as immunology, hepatology, pulmonology or gastroenterology before being positioned as cholesterol-lowering molecules?" What would then have been the main benefits and fields of application of plant sterols and stanols today? We here discuss potential effects ranging from its presence and function intrauterine and in breast milk towards a potential role in the development of non-alcoholic steatohepatitis (NASH), cardiovascular disease (CVD), inflammatory bowel diseases (IBD) and allergic asthma. Interestingly, effects clearly depend on the route of entrance as observed in intestinal-failure associated liver disease (IFALD) during parenteral nutrition regimens. It is only until recently that effects beyond lowering of cholesterol concentrations are being explored systematically. Thus, there is a clear need to understand the full health effects of plant sterols and stanols.

Differential metabolic effects of oral butyrate treatment in lean versus metabolic syndrome subjects.

BACKGROUND: Gut microbiota-derived short-chain fatty acids (SCFAs) have been associated with beneficial metabolic effects. However, the direct effect of oral butyrate on metabolic parameters in humans has never been studied. In this first in men pilot study, we thus treated both lean and metabolic syndrome male subjects with oral sodium butyrate and investigated the effect on metabolism. METHODS: Healthy lean males (n = 9) and metabolic syndrome males (n = 10) were treated with oral 4 g of sodium butyrate daily for 4 weeks. Before and after treatment, insulin sensitivity was determined by a two-step hyperinsulinemic euglycemic clamp using [6,6-2H2]-glucose. Brown adipose tissue (BAT) uptake of glucose was visualized using 18F-FDG PET-CT. Fecal SCFA and bile acid concentrations as well as microbiota composition were determined before and after treatment. RESULTS: Oral butyrate had no effect on plasma and fecal butyrate levels after treatment, but did alter other SCFAs in both plasma and feces. Moreover, only in healthy lean subjects a significant improvement was observed in both peripheral (median Rd: from 71 to 82 µmol/kg min, p < 0.05) and hepatic insulin sensitivity (EGP suppression from 75 to 82% p < 0.05). Although BAT activity was significantly higher at baseline in lean (SUVmax: 12.4 ± 1.8) compared with metabolic syndrome subjects (SUVmax: 0.3 ± 0.8, p < 0.01), no significant effect following butyrate treatment on BAT was observed in either group (SUVmax lean to 13.3 ± 2.4 versus metabolic syndrome subjects to 1.2 ± 4.1). CONCLUSIONS: Oral butyrate treatment beneficially affects glucose metabolism in lean but not metabolic syndrome subjects, presumably due to an altered SCFA handling in insulin-resistant subjects. Although preliminary, these first in men findings argue against oral butyrate supplementation as treatment for glucose regulation in human subjects with type 2 diabetes mellitus.

The effects of amoxicillin and vancomycin on parameters reflecting cholesterol metabolism.

BACKGROUND: Changes in the microbiota composition have been implicated in the development of obesity and type 2 diabetes. However, not much is known on the involvement of gut microbiota in lipid and cholesterol metabolism. In addition, the gut microbiota might also be a potential source of plasma oxyphytosterol and oxycholesterol concentrations (oxidation products of plant sterols and cholesterol). Therefore, the aim of this study was to modulate the gut microbiota by antibiotic therapy to investigate effects on parameters reflecting cholesterol metabolism and oxyphytosterol concentrations. DESIGN: A randomized, double blind, placebo-controlled trial was performed in which 55 obese, pre-diabetic men received oral amoxicillin (broad-spectrum antibiotic), vancomycin (antibiotic directed against Gram-positive bacteria) or placebo (microcrystalline cellulose) capsules for 7days (1500mg/day). Plasma lipid and lipoprotein, non-cholesterol sterol, bile acid and oxy(phyto)sterol concentrations were determined at baseline and after 1-week intervention. RESULTS: Plasma secondary bile acids correlated negatively with cholestanol (marker for cholesterol absorption, r=-0.367; P<0.05) and positively with lathosterol concentrations (marker for cholesterol synthesis, r=0.430; P<0.05). Fasting plasma secondary bile acid concentrations were reduced after vancomycin treatment as compared to placebo treatment (-0.24±0.22µmol/L vs. -0.08±0.29µmol/L; P<0.01). Vancomycin and amoxicillin treatment did not affect markers for cholesterol metabolism, plasma TAG, total cholesterol, LDL-C or HDL-C concentrations as compared to placebo. In addition, both antibiotic treatments did not affect individual isoforms or total plasma oxyphytosterol or oxycholesterol concentrations. CONCLUSION: Despite strong correlations between plasma bile acid concentrations and cholesterol metabolism (synthesis and absorption), amoxicillin and vancomycin treatment for 7days did not affect plasma lipid and lipoprotein, plasma non-cholesterol sterol and oxy(phyto)sterol concentrations in obese, pre-diabetic men.

Maternal-fetal cholesterol transport in the second half of mouse pregnancy does not involve LDL receptor-related protein 2.

AIM: LDL receptor-related protein type 2 (LRP2) is highly expressed on both yolk sac and placenta. Mutations in the corresponding gene are associated with severe birth defects in humans, known as Donnai-Barrow syndrome. We here characterized the contribution of LRP2 and maternal plasma cholesterol availability to maternal-fetal cholesterol transport and fetal cholesterol levels in utero in mice. METHODS: Lrp2+/- mice were mated heterozygously to yield fetuses of all three genotypes. Half of the dams received a 0.5% probucol-enriched diet during gestation to decrease maternal HDL cholesterol. At E13.5, the dams received an injection of D7-labelled cholesterol and were provided with 1-13 C acetate-supplemented drinking water. At E16.5, fetal tissues were collected and maternal cholesterol transport and fetal synthesis quantified by isotope enrichments in fetal tissues by GC-MS. RESULTS: The Lrp2 genotype did not influence maternal-fetal cholesterol transport and fetal cholesterol. However, lowering of maternal plasma cholesterol levels by probucol significantly reduced maternal-fetal cholesterol transport. In the fetal liver, this was associated with increased cholesterol synthesis rates. No indications were found for an interaction between the Lrp2 genotype and maternal probucol treatment. CONCLUSION: Maternal-fetal cholesterol transport and endogenous fetal cholesterol synthesis depend on maternal cholesterol concentrations but do not involve LRP2 in the second half of murine pregnancy. Our results suggest that the mouse fetus can compensate for decreased maternal cholesterol levels. It remains a relevant question how the delicate system of cholesterol transport and synthesis is regulated in the human fetus and placenta.

Beyond the genetics of HDL: why is HDL cholesterol inversely related to cardiovascular disease?

There is unequivocal evidence that high-density lipoprotein (HDL) cholesterol levels in plasma are inversely associated with the risk of cardiovascular disease (CVD). Studies of families with inherited HDL disorders and genetic association studies in general (and patient) population samples have identified a large number of factors that control HDL cholesterol levels. However, they have not resolved why HDL cholesterol and CVD are inversely related. A growing body of evidence from nongenetic studies shows that HDL in patients at increased risk of CVD has lost its protective properties and that increasing the cholesterol content of HDL does not result in the desired effects. Hopefully, these insights can help improve strategies to successfully intervene in HDL metabolism. It is clear that there is a need to revisit the HDL hypothesis in an unbiased manner. True insights into the molecular mechanisms that regulate plasma HDL cholesterol and triglycerides or control HDL function could provide the handholds that are needed to develop treatment for, e.g., type 2 diabetes and the metabolic syndrome. Especially genome-wide association studies have provided many candidate genes for such studies. In this review we have tried to cover the main molecular studies that have been produced over the past few years. It is clear that we are only at the very start of understanding how the newly identified factors may control HDL metabolism. In addition, the most recent findings underscore the intricate relations between HDL, triglyceride, and glucose metabolism indicating that these parameters need to be studied simultaneously.

From genome to phenome-Simple inborn errors of metabolism as complex traits.

Sporadically, patients with a proven defect in either mFAO or OXPHOS are described presenting with a metabolic profile and clinical phenotype expressing concurrent defects in both pathways. Biochemical linkages between both processes are tight. Therefore, it is striking that concurrent dysfunction of both systems occurs so infrequent. In this review, the linkages between OXPHOS and mFAO and the hypothesized processes responsible for concurrent problems in both systems are reviewed, both from the point of view of primary biochemical connections and secondary cellular responses, i.e. signaling pathways constituting nutrient-sensing networks. We propose that affected signaling pathways may play an important role in the phenomenon of concurrent defects. Recent data indicate that interference in the affected signaling pathways may resolve the pathological phenotype even though the primary enzyme deficiency persists. This offers new (unexpected) prospects for treatment of these inborn errors of metabolism. This article is part of a Special Issue entitled: From Genome to Function.

Maternal western diet primes non-alcoholic fatty liver disease in adult mouse offspring.

AIM: Metabolic programming via components of the maternal diet during gestation may play a role in the development of different aspects of the metabolic syndrome. Using a mouse model, we aimed to characterize the role of maternal western-type diet in the development of non-alcoholic fatty liver disease (NAFLD) in the offspring. METHODS: Female mice were fed either a western (W) or low-fat control (L) semisynthetic diet before and during gestation and lactation. At weaning, male offspring were assigned either the W or the L diet, generating four experimental groups: WW, WL, LW and LL offspring. Biochemical, histological and epigenetic indicators were investigated at 29 weeks of age. RESULTS: Male offspring exposed to prenatal and post-weaning western-style diet (WW) showed hepatomegaly combined with accumulation of hepatic cholesterol and triglycerides. This accumulation was associated with up-regulation of de novo lipid synthesis, inflammation and dysregulation of lipid storage. Elevated hepatic transaminases and increased expression of Tnfa, Cd11, Mcp1 and Tgfb underpin the severity of liver injury. Histopathological analysis revealed the presence of advanced steatohepatitis in WW offspring. In addition, alterations in DNA methylation in key metabolic genes (Ppara, Insig, and Fasn) were detected. CONCLUSION: Maternal dietary fat intake during early development programmes susceptibility to liver disease in male offspring, mediated by disturbances in lipid metabolism and inflammatory response. Long-lasting epigenetic changes may underlie this dysregulation.

Intestinal cholesterol secretion: future clinical implications.

Together with the liver, the intestine serves as a homeostatic organ in cholesterol metabolism. Recent evidence has substantiated the pivotal role of the intestine in reverse cholesterol transport (RCT). RCT is a fundamental antiatherogenic pathway, mediating the removal of cholesterol from tissues in the body to the faeces. In humans, faecal cholesterol elimination via the RCT pathway is considered to be restricted to excretion via the hepatobiliary route. Recently, however, direct trans-intestinal excretion of plasma-derived cholesterol (TICE) was shown to contribute substantially to faecal neutral sterol (FNS) excretion in mice. TICE was found to be amenable to stimulation by various pharmacological and dietary interventions in mice, offering new options to target the intestine as an inducible, cholesterol-excretory organ. The relevance of TICE for cholesterol elimination in humans remains to be established. There is, however, emerging evidence for the presence of TICE in human (patho) physiology. This review discusses our current understanding of TICE and its novel therapeutic potential for individuals at increased risk of cardiovascular disease.

The effect of organelle discovery upon sub-cellular protein localisation.

Prediction of protein sub-cellular localisation by employing quantitative mass spectrometry experiments is an expanding field. Several methods have led to the assignment of proteins to specific subcellular localisations by partial separation of organelles across a fractionation scheme coupled with computational analysis. Methods developed to analyse organelle data have largely employed supervised machine learning algorithms to map unannotated abundance profiles to known protein-organelle associations. Such approaches are likely to make association errors if organelle-related groupings present in experimental output are not included in data used to create a protein-organelle classifier. Currently, there is no automated way to detect organelle-specific clusters within such datasets. In order to address the above issues we adapted a phenotype discovery algorithm, originally created to filter image-based output for RNAi screens, to identify putative subcellular groupings in organelle proteomics experiments. We were able to mine datasets to a deeper level and extract interesting phenotype clusters for more comprehensive evaluation in an unbiased fashion upon application of this approach. Organelle-related protein clusters were identified beyond those sufficiently annotated for use as training data. Furthermore, we propose avenues for the incorporation of observations made into general practice for the classification of protein-organelle membership from quantitative MS experiments. BIOLOGICAL SIGNIFICANCE: Protein sub-cellular localisation plays an important role in molecular interactions, signalling and transport mechanisms. The prediction of protein localisation by quantitative mass-spectrometry (MS) proteomics is a growing field and an important endeavour in improving protein annotation. Several such approaches use gradient-based separation of cellular organelle content to measure relative protein abundance across distinct gradient fractions. The distribution profiles are commonly mapped in silico to known protein-organelle associations via supervised machine learning algorithms, to create classifiers that associate unannotated proteins to specific organelles. These strategies are prone to error, however, if organelle-related groupings present in experimental output are not represented, for example owing to the lack of existing annotation, when creating the protein-organelle mapping. Here, the application of a phenotype discovery approach to LOPIT gradient-based MS data identifies candidate organelle phenotypes for further evaluation in an unbiased fashion. Software implementation and usage guidelines are provided for application to wider protein-organelle association experiments. In the wider context, semi-supervised organelle discovery is discussed as a paradigm with which to generate new protein annotations from MS-based organelle proteomics experiments.

A novel approach to monitor glucose metabolism using stable isotopically labelled glucose in longitudinal studies in mice.

The aetiology of insulin resistance is still an enigma. Mouse models are frequently employed to study the underlying pathology. The most commonly used methods to monitor insulin resistance are the HOMA-IR, glucose or insulin tolerance tests and the hyperinsulinemic euglycaemic clamp (HIEC). Unfortunately, these tests disturb steady state glucose metabolism. Here we describe a method in which blood glucose kinetics can be determined in fasted mice without noticeably perturbing glucose homeostasis. The method involves an intraperitoneal injection of a trace amount of [6,6-(2)H2]glucose and can be performed repeatedly in individual mice. The validity and performance of this novel method was tested in mice fed on chow or high-fat diet for a period of five weeks. After administering the mice with [6,6-(2)H2]glucose, decay of the glucose label was followed in small volumes of blood collected by tail tip bleeding during a 90-minute period. The total amount of blood collected was less than 120 µL. This novel approach confirmed in detail the well-known increase in insulin resistance induced by a high-fat diet. The mice showed reduced glucose clearance rate, and reduced hepatic and peripheral insulin sensitivity. To compensate for this insulin resistance, ß-cell function was slightly increased. We conclude that this refinement of existing methods enables detailed information of glucose homeostasis in mice. Insulin resistance can be accurately determined while mechanistic insight is obtained in underlying pathology. In addition, this novel approach reduces the number of mice needed for longitudinal studies of insulin sensitivity and glucose metabolism.

The therapeutic potential of manipulating gut microbiota in obesity and type 2 diabetes mellitus.

Obesity and type 2 diabetes mellitus (T2DM) are attributed to a combination of genetic susceptibility and lifestyle factors. Their increasing prevalence necessitates further studies on modifiable causative factors and novel treatment options. The gut microbiota has emerged as an important contributor to the obesity--and T2DM--epidemic proposed to act by increasing energy harvest from the diet. Although obesity is associated with substantial changes in the composition and metabolic function of the gut microbiota, the pathophysiological processes remain only partly understood. In this review we will describe the development of the adult human microbiome and discuss how the composition of the gut microbiota changes in response to modulating factors. The influence of short-chain fatty acids, bile acids, prebiotics, probiotics, antibiotics and microbial transplantation is discussed from studies using animal and human models. Ultimately, we aim to translate these findings into therapeutic pathways for obesity and T2DM in humans.