A unified classification approach rating clinical utility of protein biomarkers across neurologic diseases

A major evolution from purely clinical diagnoses to biomarker supported clinical diagnosing has been occurring over the past years in neurology. High-throughput methods, such as next-generation sequencing and mass spectrometry-based proteomics along with improved neuroimaging methods, are accelerating this development. This calls for a consensus framework that is broadly applicable and provides a spot-on overview of the clinical validity of novel biomarkers. We propose a harmonized terminology and a uniform concept that stratifies biomarkers according to clinical context of use and evidence levels, adapted from existing frameworks in oncology with a strong focus on (epi)genetic markers and treatment context. We demonstrate that this framework allows for a consistent assessment of clinical validity across disease entities and that sufficient evidence for many clinical applications of protein biomarkers is lacking. Our framework may help to identify promising biomarker candidates and classify their applications by clinical context, aiming for routine clinical use of (protein) biomarkers in neurology

Nutrimetabolomics: An Integrative Action for Metabolomic Analyses in Human Nutritional Studies

The life sciences are currently being transformed by an unprecedented wave of developments in molecular analysis, which include important advances in instrumental analysis as well as biocomputing. In light of the central role played by metabolism in nutrition, metabolomics is rapidly being established as a key analytical tool in human nutritional studies. Consequently, an increasing number of nutritionists integrate metabolomics into their study designs. Within this dynamic landscape, the potential of nutritional metabolomics (nutrimetabolomics) to be translated into a science, which can impact on health policies, still needs to be realized. A key element to reach this goal is the ability of the research community to join, to collectively make the best use of the potential offered by nutritional metabolomics. This article, therefore, provides a methodological description of nutritional metabolomics that reflects on the state‐of‐the‐art techniques used in the laboratories of the Food Biomarker Alliance (funded by the European Joint Programming Initiative "A Healthy Diet for a Healthy Life" (JPI HDHL)) as well as points of reflections to harmonize this field. It is not intended to be exhaustive but rather to present a pragmatic guidance on metabolomic methodologies, providing readers with useful "tips and tricks" along the analytical workflow

Acylcarnitine Profiles in Plasma and Tissues of Hyperglycemic NZO Mice Correlate with Metabolite Changes of Human Diabetes

The New Zealand obese (NZO) mouse is a polygenic model for obesity and diabetes with obese females and obese, diabetes-prone males, used to study traits of the metabolic syndrome like type 2 diabetes mellitus (T2DM), obesity, and dyslipidaemia. By using LC-MS/MS, we here examine the suitability of this model to mirror tissue-specific changes in acylcarnitine (AC) and amino acid (AA) species preceding T2DM which may reflect patterns investigated in human metabolism. We observed high concentrations of fatty acid-derived ACs in 11 female mice, high abundance of branched-chain amino acid- (BCAA-) derived ACs in 6 male mice, and slight increases in BCAA-derived ACs in the remaining 6 males. Principal component analysis (PCA) including all ACs and AAs confirmed our hypothesis especially in plasma samples by clustering females, males with high BCAA-derived ACs, and males with slight increases in BCAA-derived ACs. Concentrations of insulin, blood glucose, NEFAs, and triacylglycerols (TAGs) further supported the hypothesis of high BCAA-derived ACs being able to mirror the onset of diabetic traits in male individuals. In conclusion, alterations in AC and AA profiles overlap with observations from human studies indicating the suitability of NZO mice to study metabolic changes preceding human T2DM

ACYLCARNITINE AND AMINO ACID PROFILING IN PLASMA AND TISSUES OF NZO MICE AS A MODEL FOR OBESITY-INDUCED TYPE 2 DIABETES

Metabolomics has identified biomarkers in human plasma with a predictive quality for type 2 diabetes (T2D) development. Amongst these markers are various acylcarnitine species, most prominently those derived from branched-chain amino acid (BCAA) breakdown. The metabolic perturbations in tissues underlying these changes in plasma are often unknown and hard to assess in humans. Thus, animal models are used to have access to the different tissues. In contrast to diet-induced obesity models or monogenetic mouse models of obesity and diabetes, the New Zealand Obese (NZO) mouse is a prototypical polygenic model for obesity, with a male-specific susceptibility to developing diabetes. We have used this model to study the metabolic alterations in obesity-induced diabetes for changes in tissue-specific acylcarnitine and amino acid profiles. Twelve male and 11 female NZO mice at an age of 8 weeks were fed a chemically-defined high carbohydrate diet for 12 weeks. Acylcarnitine and amino acid profiles were obtained from plasma, skeletal muscle, heart muscle, liver, kidney and adipose tissues, using a high-resolution LC-MS/MS method. This method covered around 35 amino acids and 43 acylcarnitine species originating from fatty acids and amino acids, as well as odd-numbered and dicarboxylic acylcarnitines. Furthermore, blood glucose, plasma insulin, non-esterified fatty acids (NEFA), triglyceride and urea concentrations were measured. Hierarchical cluster analysis of principle components derived from plasma samples revealed a grouping of normoglycemic females, normoglycemic males and hyperglycemic males and this originated mainly from differences in concentrations of acylcarnitines derived from BCAAs and odd-numbered short- and medium-chain fatty acids. Hyperglycemic males were characterized by high insulin levels and low levels of NEFAs. These findings largely match with findings in humans. Comparison of metabolite profiles in diabetic and non-diabetic male mice revealed the largest overlap of significant metabolite changes between plasma and liver, including longer-chain odd-numbered acylcarnitine species. In conclusion, the alterations in acylcarnitine and amino acid profiles in NZO mice largely overlap with findings in humans, suggesting similar underlying metabolic perturbations in this diabetes model as compared to humans. The metabolite profiling of individual tissues in this model suggests a specific role of the liver in the generation of odd-numbered fatty acylcarnitines

Plasma concentrations of anserine, carnosine and pi-methylhistidine as biomarkers of habitual meat consumption

BACKGROUND/OBJECTIVES Dietary intake of red and processed meat has been associated with disease risk. Since dietary intake assessment methods are prone to measurement errors, identifying biomarkers of meat intake in bio-samples could provide more valid intake estimates. We examined associations of habitual red and processed meat, poultry, fish, and dairy products consumption with plasma concentrations of anserine, carnosine, pi-methylhistidine (Π-MH), tau-methylhistidine (T-MH), and the ratio of T-MH to Π-MH in a cross-sectional study. SUBJECTS/METHODS Plasma anserine, carnosine, Π-MH, and T-MH concentrations were measured using ion-pair LC-MS/MS in 294 participants in the second Bavarian Food Consumption Survey (BVS II). Habitual food consumption was assessed using three 24-h dietary recalls. Associations between plasma metabolites concentrations and meat, fish, eggs, and dairy products consumption were assessed by fitting generalized linear model, adjusted for age, sex, and BMI. RESULTS Total meat intake was associated with plasma concentrations of anserine, carnosine, Π-MH and, the ratio of T-MH to Π-MH. Red meat intake was related to carnosine (p-trend = 0.0028) and Π-MH plasma levels (p-trend = 0.0493). Poultry (p-trend = 0.0006) and chicken (p-trend = 0.0003) intake were associated with Π-MH. The highest anserine concentrations were observed in individuals consuming processed meat or turkey. For T-MH we did not observe any association with meat intake. CONCLUSIONS Our results indicate an association between habitual meat consumption and plasma concentrations of anserine, carnosine, Π-MH and the ratio of T-MH to Π-MH. Intervention studies should clarify whether the analyzed plasma metabolites are indicative for a specific type of meat before proposing them as biomarkers of habitual meat intake in epidemiologic studies

Effects of Intragastric Administration of Tryptophan on the Blood Glucose Response to a Nutrient Drink and Energy Intake, in Lean and Obese Men

Tryptophan stimulates plasma cholecystokinin and pyloric pressures, both of which slow gastric emptying. Gastric emptying regulates postprandial blood glucose. Tryptophan has been reported to decrease energy intake. We investigated the effects of intragastric tryptophan on the glycaemic response to, and gastric emptying of, a mixed-nutrient drink, and subsequent energy intake. Lean and obese participants (n = 16 each) received intragastric infusions of 1.5 g (“Trp-1.5g”) or 3.0 g (“Trp-3.0g”) tryptophan, or control, and 15 min later consumed a mixed-nutrient drink (56 g carbohydrates). Gastric emptying (13C-acetate breath-test), blood glucose, plasma C-peptide, glucagon, cholecystokinin and tryptophan concentrations were measured (t = 0–60 min). Energy intake was assessed between t = 60–90 min. In lean individuals, Trp-3.0g, but not Trp-1.5g, slowed gastric emptying, reduced C-peptideAUC and increased glucagonAUC (all P < 0.05), but did not significantly decrease the blood glucose response to the drink, stimulate cholecystokinin or reduce mean energy intake, compared with control. In obese individuals, Trp-3.0g, but not Trp-1.5g, tended to slow gastric emptying (P = 0.091), did not affect C-peptideAUC, increased glucagonAUC (P < 0.001) and lowered blood glucose at t = 30 min (P < 0.05), and did not affect cholecystokinin or mean energy intake. In obese individuals, intragastrically administered tryptophan may reduce postprandial blood glucose by slowing gastric emptying; the lack of effect on mean energy intake requires further investigation

Chronic High Phosphate Intake in Mice Affects Macronutrient Utilization and Body Composition

SCOPE: In the last decades, dietary phosphate intake has increased due to a higher consumption of ultraprocessed food. This higher intake has an impact on body composition and health state. Recently, this study finds that a high chronic phosphate diet leads to no major renal alterations, but negatively affects parameters of bone health probably due to the chronic acid load. Here the effect of high phosphate consumption on parameters of energy metabolism is assessed. METHODS AND RESULTS: Healthy mature adult mice are fed for 1 year or 4 months with either a standard (0.6 % w/w) or a high phosphate (1.2 % w/w) diet. Males and females of two different genetic backgrounds are investigated. Mice feed the high phosphate diet show an attenuated body-weight gain, lower respiratory exchange ratio, decreased body fat mass, and increased lean-to-fat mass ratio. Moreover, the high phosphate diet leads to fasting hypoglycemia with no differences in the glucose response to an oral glucose tolerance test. Triglycerides and cholesterol in blood are similar independently of dietary phosphate content. However, 1-methylhistidine is lower in animals feed a chronic high phosphate intake. CONCLUSIONS: High phosphate diet attenuates body weight gain, but induces hypoglycemia and may alter muscle homeostasis

Allergen‐free extracts from birch, ragweed, and hazel pollen activate human and guinea‐pig submucous and spinal sensory neurons

Background Non-allergenic, low molecular weight components of pollen grains are suspected to trigger changes in gut functions, sometimes leading to inflammatory conditions. Based on extensive neuroimmune communication in the gut wall, we investigated the effects of aqueous pollen extracts (APE) on enteric and spinal sensory neurons. Methods Using Ca2+ and fast potentiometric imaging, we recorded the responses of guinea-pig and human submucous and guinea-pig dorsal root ganglion (DRG) neurons to microejection of low (<3 kDa) and high (≥3 kDa) molecular weight APEs of birch, ragweed, and hazel. Histamine was determined pharmacologically and by mass spectrometry (LC–MS/MS). Key Results Birch APE<3kDa evoked strong [Ca+2]i signals in the vast majority of guinea-pig DRG neurons, and in guinea-pig and human enteric neurons. The effect of birch APE≥3kDa was much weaker. Fast neuroimaging in human enteric neurons revealed an instantaneous spike discharge after microejection of birch, ragweed, and hazel APE<3kDa [median (interquartile range) at 7.0 Hz (6.2/9.8), 5.7 Hz (4.4/7.1), and 8.4 Hz (4.3/12.5), respectively]. The percentage of responding neurons per ganglion were similar [birch 40.0% (33.3/100.0), ragweed 50.8% (34.4/85.6), and hazel 83.3% (57.1/100.0)]. A mixture of histamine receptor (H1–H3) blockers significantly reduced nerve activation evoked by birch and ragweed APEs<3kDa, but was ineffective on hazel. Histamine concentrations in ragweed, birch and hazel APE's < 3 kDa were 0.764, 0.047, and 0.013 μM, respectively. Conclusions Allergen-free APEs from birch, ragweed, and hazel evoked strong nerve activation. Altered nerve-immune signaling as a result of severe pollen exposure could be a pathophysiological feature of allergic and non-allergic gut inflammation