Micronutrient Status of Critically Ill Patients with COVID-19 Pneumonia

Micronutrient deficiencies can develop in critically ill patients, arising from factors such as decreased intake, increased losses, drug interactions, and hypermetabolism. These deficiencies may compromise important immune functions, with potential implications for patient outcomes. Alternatively, micronutrient blood levels may become low due to inflammation-driven redistribution rather than consumption. This explorative pilot study investigates blood micronutrient concentrations during the first three weeks of ICU stay in critically ill COVID-19 patients and evaluates the impact of additional micronutrient administration. Moreover, associations between inflammation, disease severity, and micronutrient status were explored. We measured weekly concentrations of vitamins A, B6, D, and E; iron; zinc; copper; selenium; and CRP as a marker of inflammation state and the SOFA score indicating disease severity in 20 critically ill COVID-19 patients during three weeks of ICU stay. Half of the patients received additional (intravenous) micronutrient administration. Data were analyzed with linear mixed models and Pearson's correlation coefficient. High deficiency rates of vitamins A, B6, and D; zinc; and selenium (50-100%) were found at ICU admission, along with low iron status. After three weeks, vitamins B6 and D deficiencies persisted, and iron status remained low. Plasma levels of vitamins A and E, zinc, and selenium improved. No significant differences in micronutrient levels were found between patient groups. Negative correlations were identified between the CRP level and levels of vitamins A and E, iron, transferrin, zinc, and selenium. SOFA scores negatively correlated with vitamin D and selenium levels. Our findings reveal high micronutrient deficiency rates at ICU admission. Additional micronutrient administration did not enhance levels or expedite their increase. Spontaneous increases in vitamins A and E, zinc, and selenium levels were associated with inflammation resolution, suggesting that observed low levels may be attributed, at least in part, to redistribution rather than true deficiencies.

The Reliability of Patient-Performed Fecal Calprotectin Testing in Inflammatory Bowel Disease

BACKGROUND

Home use of a buffer-containing extraction device for fecal calprotectin determination can bypass the labor-intensive extraction procedure and potentially prevent degradation at room temperature.

METHODS

In this prospective cross-sectional observational study, 2 CALiaGold tubes (extraction device) and one native tube were filled from the same bowel movement by patients with inflammatory bowel disease. Afterwards patients completed a questionnaire including whether they preferred the extraction device or the normal sampling method. All tubes were sent to the laboratory and when they arrived, 2 more CALiaGold tubes were filled at the laboratory from the native sample. The fecal calprotectin concentrations in all tubes were measured by a particle-enhanced turbidimetric immunoassay.

RESULTS

Fifty-three patients were included in the study. Fecal calprotectin levels were significantly higher in samples extracted by the patient compared to the analyst-performed extractions. When patients were divided into 3 groups (i.e., fecal calprotectin levels <50 ug/g, 50 to 200 µg/g, and >200 µg/g) a substantial concordance was found (Cohen kappa 0.654). Patients sampling imprecision was higher (P < 0.018, median CV 16%) compared to the analyst. Most patients preferred this extraction device.

CONCLUSIONS

Patient-performed fecal calprotectin extraction seems a realistic alternative sampling method and is preferred by most patients.

Salivary Calprotectin Is not a Useful Biomarker to Monitor Disease Activity in Patients with Inflammatory Bowel Disease

BACKGROUND AND AIMS

Non-invasive biomarkers are gaining interest for monitoring disease activity in patients with inflammatory bowel diseases (IBD). Fecal calprotectin is a reliable biomarker but patients often report the collection of feces being unpleasant and cumbersome. In this study, we aimed to assess if salivary calprotectin could be used as a non-invasive biomarker to determine disease activity instead of fecal calprotectin.

METHODS

In this cross-sectional explorative cohort study, stimulated saliva was collected from patients with an established IBD diagnosis and healthy controls. The concentration of calprotectin in saliva was determined by a particle-enhanced turbidimetric immunoassay. Intestinal disease activity was assessed with fecal calprotectin levels and the Harvey-Bradshaw Index (HBI) or Simple Clinical Colitis Activity Index (SCCAI). Missing data were handled using multiple imputation.

RESULTS

Sixty-three patients (41 Crohn's disease and 22 ulcerative colitis) and 11 controls were included. Patients had a mean fecal calprotectin of 138.78 µg/g and a median salivary calprotectin of 1.87 mg/L. No significant correlation was found between salivary calprotectin and fecal calprotectin levels (p=0.495). When patients were stratified in two subgroups based on a fecal calprotectin cut-off value of 250 µg/g, there were no significant differences in salivary calprotectin levels between both patient groups (p=0.641) and between patients and healthy controls (p=0.248). Also, salivary, and fecal calprotectin levels were not significantly different when stratifying patients in two subgroups, active disease and remission, using HBI/SCCAI scores.

CONCLUSIONS

Salivary calprotectin does not correlate to fecal calprotectin and disease activity scores in patients, making it unreliable for assessing IBD activity.

Impact of Preanalytical Factors on Calprotectin Concentration in Stool: A Multiassay Comparison

Background

Measuring calprotectin concentration in stool is increasingly important in monitoring disease activity and treatment response in inflammatory bowel disease. This study evaluates the impact of preanalytical storage conditions on reliability of calprotectin testing using 5 different calprotectin immunoassays.

Methods

Aliquots of homogenized fresh fecal samples in untreated or extracted form were stored at room temperature or 4°C. Calprotectin concentration was measured day 0 to 4 and 8. Five different immunoassays and accompanying extraction buffers were used (CALiaGold, Phadia EliA, Bühlmann fCal turbo, ELISA Bühlmann, Inova Quanta Flash). Repeated measurements of change from baseline calprotectin levels over time were analyzed using a mixed model analysis.

Results

Calprotectin concentrations declined over time under all preanalytical conditions with all assays, except for extracted feces stored at 4°C. The rate of decline was greatest in untreated stool kept at room temperature, reaching significant difference from baseline already after 1 day (P &lt; 0.001). In extracted feces kept at room temperature, significant difference from baseline was reached after 2 days, and in untreated feces at 4°C, after 4 days. However, the results differed significantly between assays. After 4 days of storage at room temperature, the mean calprotectin decline from baseline differed between 30% and 60%, dependent on the assay used.

Conclusions

Fecal calprotectin concentration in stool samples declines over time, and the rate of decline is greater at higher temperatures. In extracted feces stored at 4°C, calprotectin is most stable. It is assay-dependent how long extracted feces stored at 4°C give reliable test results.

Diagnostic accuracy of four different D-dimer assays: A post-hoc analysis of the YEARS study

INTRODUCTION

For exclusion of pulmonary embolism (PE) clinical decision rules in combination with a D-dimer assay are applied. Currently available D-dimer assays are not standardized and it is unknown whether these differences have an impact on diagnostic management of suspected PE. Therefore, the aim is to explore differences between D-dimer assays and their impact on diagnostic outcome.

METHODS

Data from all patients included in the YEARS study were collected. The YEARS study is a prospective, multicentre, cohort outcome study evaluating 3462 patients with suspected PE in which four different D-dimer assays were applied (Liatest, Innovance, Tinaquant, Vidas). Median D-dimer concentrations were calculated for each D-dimer assay. Sensitivity, specificity, PPV and NPV for detection of PE of all four assays were determined in patients without YEARS items and in those with ≥1 YEARS items (i.e. symptomatic deep vein thrombosis, haemoptysis, and whether PE is the most likely diagnosis).

RESULTS

A total of 1323, 1100, 768 and 271 D-dimer concentrations were collected using the Liatest Innovance, Tinaquant and Vidas assay, respectively. Median D-dimer concentrations differed significantly between assays, with lowest values in the Tinaquant assay. In patients without YEARS items using a cutoff level of 1000 ng/mL, the NPV varied from 99,5 to 100%. In patients with ≥1 YEARS items using a 500 ng/mL cutoff, the NPV varied from 97,0 to 100% depending on the assay.

CONCLUSIONS

The overall high NPV for all assays demonstrates the clinical value of the D-dimer assay. However, these results confirm differences between D-dimer assays, which have an impact on follow-up imaging. This emphasizes the need for standardization of D-dimer assays.

Empagliflozin restores chronic kidney disease-induced impairment of endothelial regulation of cardiomyocyte relaxation and contraction

Chronic kidney disease (CKD) promotes development of cardiac abnormalities and is highly prevalent in patients with heart failure, particularly in those with preserved ejection fraction. CKD is associated with endothelial dysfunction, however, whether CKD can induce impairment of endothelium-to-cardiomyocyte crosstalk leading to impairment of cardiomyocyte function is not known. The sodium-glucose co-transporter 2 inhibitor, empagliflozin, reduced cardiovascular events in diabetic patients with or without CKD, suggesting its potential as a new treatment for heart failure with preserved ejection fraction. We hypothesized that uremic serum from patients with CKD would impair endothelial control of cardiomyocyte relaxation and contraction, and that empagliflozin would protect against this effect. Using a co-culture system of human cardiac microvascular endothelial cells with adult rat ventricular cardiomyocytes to measure cardiomyocyte relaxation and contraction, we showed that serum from patients with CKD impaired endothelial enhancement of cardiomyocyte function which was rescued by empagliflozin. Exposure to uremic serum reduced human cardiac microvascular endothelial cell nitric oxide bioavailability, and increased mitochondrial reactive oxygen species and 3-nitrotyrosine levels, indicating nitric oxide scavenging by reactive oxygen species. Empagliflozin attenuated uremic serum-induced generation of endothelial mitochondrial reactive oxygen species, leading to restoration of nitric oxide production and endothelium-mediated enhancement of nitric oxide levels in cardiomyocytes, an effect largely independent of sodium-hydrogen exchanger-1. Thus, empagliflozin restores the beneficial effect of cardiac microvascular endothelial cells on cardiomyocyte function by reducing mitochondrial oxidative damage, leading to reduced reactive oxygen species accumulation and increased endothelial nitric oxide bioavailability.

The Muscle Protein Synthetic Response to Whey Protein Ingestion Is Greater in Middle-Aged Women Compared With Men

RATIONALE

Muscle mass maintenance is largely regulated by the postprandial rise in muscle protein synthesis rates. It remains unclear whether postprandial protein handling differs between women and men.

METHODS

Healthy men (43 ± 3 years; body mass index, 23.4 ± 0.4 kg/m2; n = 12) and women (46 ± 2 years; body mass index, 21.3 ± 0.5 kg/m2; n = 12) received primed continuous infusions of l-[ring-2H5]-phenylalanine and l-[ring-3,5-2H2]-tyrosine and ingested 25 g intrinsically l-[1-13C]-phenylalanine-labeled whey protein. Blood samples and muscle biopsies were collected to assess dietary protein digestion and amino acid absorption kinetics as well as basal and postprandial myofibrillar protein synthesis rates.

RESULTS

Plasma phenylalanine and leucine concentrations rapidly increased after protein ingestion (both P < 0.001), with no differences between middle-aged women and men (Time × Sex, P = 0.307 and 0.529, respectively). The fraction of dietary protein-derived phenylalanine that appeared in the circulation over the 5-hour postprandial period averaged 56 ± 1% and 53 ± 1% in women and men, respectively (P = 0.145). Myofibrillar protein synthesis rates increased (Time, P = 0.010) from 0.035 ± 0.004%/h and 0.030 ± 0.002%/h in the postabsorptive state (t test, P = 0.319) to 0.045 ± 0.002%/h and 0.034 ± 0.002%/h in the 5-hour postprandial phase in middle-aged women and men, respectively, with higher postprandial myofibrillar protein synthesis rates in women compared with men (t test, P = 0.005). Middle-aged women showed a greater increase in myofibrillar protein synthesis rates during the early (0 to 2 hours) postprandial period compared with men (Time × Sex, P = 0.001).

CONCLUSIONS

There are no differences in postabsorptive myofibrillar protein synthesis rates between middle-aged women and men. The myofibrillar protein synthetic response to the ingestion of 25 g whey protein is greater in women than in men.

C11-oxy C19 and C11-oxy C21 steroids in neonates: UPC2-MS/MS quantification of plasma 11β-hydroxyandrostenedione, 11-ketotestosterone and 11-ketoprogesterone

The purpose of this study was to identify the C11-oxy C₁₉ and C11-oxy C₂₁ steroids in male and female neonate plasma. At birth, the most abundant C11-oxy steroids detected in neonatal plasma were 11β-hydroxyandrostenedione, ∼13 nM, and 11-ketoprogesterone, ∼23 nM. C11-oxy C₁₉ steroids were higher than C₁₉ steroids in neonatal plasma, 22.2 nM vs 5.4 nM. The inclusion of C11-oxy C₁₉ and C₂₁ steroid reference ranges in routine steroid analyses will assist the characterization of disorders associated with impaired steroidogenic enzyme expression and the identification of potential biomarkers.

[Haemolysis: role of the direct antiglobulin test and eluate]

Haemolytic anaemia is the result of an abnormal breakdown of red blood cells. The direct antiglobulin test (DAT), also known as the direct Coombs test, can be used to determine the cause of the haemolysis. The DAT distinguishes between immune and non-immune causes of haemolysis. However, the DAT should not be used in screening for haemolysis. When the DAT is performed without an indication for in vivo haemolysis, there is a high risk of false-positive results. To increase the specificity of the DAT, the eluate can be tested to determine the specificity of the autoantibodies. In this article we present two cases of haemolytic anaemia in which the DAT gives further indication of the cause of haemolysis.

Increasing Insulin Availability Does Not Augment Postprandial Muscle Protein Synthesis Rates in Healthy Young and Older Men

CONTEXT

Skeletal muscle protein synthesis is highly responsive to food intake. It has been suggested that the postprandial increase in circulating insulin modulates the muscle protein synthetic response to feeding.

OBJECTIVE

The objective of the study was to investigate whether a greater postprandial rise in circulating insulin level increases amino acid uptake in muscle and augments postprandial muscle protein synthesis rates.

PARTICIPANTS AND DESIGN

Forty-eight healthy young (age 22 ± 1 y; body mass index 22.0 ± 0.3 kg/m²) and older males (age 68 ± 1 y; body mass index 26.3 ± 0.4 kg/m²) ingested 20 g intrinsically L-[1-¹³C]-leucine- and L-[1-¹³C]-phenylalanine-labeled casein protein with or without local insulin infusion. Primed continuous infusions of L-[1-¹³C]-leucine and L-[ring-²H₅]-phenylalanine were applied, with arterial and venous blood samples and muscle biopsies being collected during a 5-hour postprandial period.

RESULTS

Insulin administration did not increase overall leg blood flow (P = .509) but increased amino acid uptake over the leg in both young and older subjects (P = .003). The greater amino acid uptake over the leg did not further increase postprandial muscle protein synthesis rates (0.050% ± 0.006% and 0.037% ± 0.004% per hour vs 0.044% ± 0.004% and 0.037% ± 0.002% per hour in the insulin-stimulated vs control condition in the young and older groups, respectively; P = .804) and did not affect postprandial deposition of dietary protein-derived amino acids in de novo muscle protein (P = .872).

CONCLUSION

Greater postprandial plasma insulin availability stimulates amino acid uptake over the leg but does not further augment postprandial muscle protein synthesis rates or stimulate the postprandial deposition of protein derived amino acids into de novo muscle protein in healthy young and older men.

Both basal and post-prandial muscle protein synthesis rates, following the ingestion of a leucine-enriched whey protein supplement, are not impaired in sarcopenic older males

BACKGROUND

Studying the muscle protein synthetic response to food intake in elderly is important, as it aids the development of interventions to combat sarcopenia. Although sarcopenic elderly are the target group for many of these nutritional interventions, no studies have assessed basal or post-prandial muscle protein synthesis rates in this population.

OBJECTIVE

To assess the basal and post-prandial muscle protein synthesis rates between healthy and sarcopenic older men.

DESIGN

A total of 15 healthy (69 ± 1 y) and 15 sarcopenic (81 ± 1 y) older men ingested a leucine-enriched whey protein nutritional supplement containing 21 g of protein, 9 g of carbohydrate, and 3 g of fat. Stable isotope methodology combined with frequent collection of blood and muscle samples was applied to assess basal and post-prandial muscle protein fractional synthetic rates. Handgrip strength, muscle mass, and gait speed were assessed to identify sarcopenia, according to international criteria.

RESULTS

Basal mixed muscle protein fractional synthetic rates (FSR) averaged 0.040 ± 0.005 and 0.032 ± 0.003%/h (mean ± SEM) in the sarcopenic and healthy group, respectively (P = 0.14). Following protein ingestion, FSR increased significantly to 0.055 ± 0.004 and 0.053 ± 0.004%/h in the post-prandial period in the sarcopenic (P = 0.003) and healthy groups (P < 0.001), respectively, with no differences between groups (P = 0.45). Furthermore, no differences were observed between groups in muscle protein synthesis rates during the early (0.058 ± 0.007 vs 0.060 ± 0.008%/h, sarcopenic vs healthy, respectively) and late (0.052 ± 0.004 vs 0.048 ± 0.003%/h) stages of the post-prandial period (P = 0.93 and P = 0.34, respectively).

CONCLUSIONS

Basal muscle protein synthesis rates are not lower in sarcopenic older men compared to healthy older men. The ingestion of 21 g of a leucine-enriched whey protein effectively increases muscle protein synthesis rates in both sarcopenic and healthy older men. Public trial registry number: NTR3047.

Systemic availability and metabolism of colonic-derived short-chain fatty acids in healthy subjects: a stable isotope study

KEY POINTS

The short-chain fatty acids (SCFAs) are bacterial metabolites produced during the colonic fermentation of undigested carbohydrates, such as dietary fibre and prebiotics, and can mediate the interaction between the diet, the microbiota and the host. We quantified the fraction of colonic administered SCFAs that could be recovered in the systemic circulation, the fraction that was excreted via the breath and urine, and the fraction that was used as a precursor for glucose, cholesterol and fatty acids. This information is essential for understanding the molecular mechanisms by which SCFAs beneficially affect physiological functions such as glucose and lipid metabolism and immune function.

ABSTRACT

The short-chain fatty acids (SCFAs), acetate, propionate and butyrate, are bacterial metabolites that mediate the interaction between the diet, the microbiota and the host. In the present study, the systemic availability of SCFAs and their incorporation into biologically relevant molecules was quantified. Known amounts of ¹³ C-labelled acetate, propionate and butyrate were introduced in the colon of 12 healthy subjects using colon delivery capsules and plasma levels of ¹³ C-SCFAs ¹³ C-glucose, ¹³ C-cholesterol and ¹³ C-fatty acids were measured. The butyrate-producing capacity of the intestinal microbiota was also quantified. Systemic availability of colonic-administered acetate, propionate and butyrate was 36%, 9% and 2%, respectively. Conversion of acetate into butyrate (24%) was the most prevalent interconversion by the colonic microbiota and was not related to the butyrate-producing capacity in the faecal samples. Less than 1% of administered acetate was incorporated into cholesterol and <15% in fatty acids. On average, 6% of colonic propionate was incorporated into glucose. The SCFAs were mainly excreted via the lungs after oxidation to ¹³ CO₂ , whereas less than 0.05% of the SCFAs were excreted into urine. These results will allow future evaluation and quantification of SCFA production from ¹³ C-labelled fibres in the human colon by measurement of ¹³ C-labelled SCFA concentrations in blood.

[Impact of early benefit assessment on patients with epilepsy in Germany: Current healthcare provision and therapeutic needs]

Epilepsy is one of the most common chronic neurological diseases and represents a significant burden for patients, their families and society. In more than 75 % of patients anticonvulsant therapy consists of valproate, carbamazepine, lamotrigine or levetiracetam. There is a need for polytherapy in drug-refractory patients and they suffer from negative effects on quality of life and employment that is associated with high indirect costs. To allow a comprehensive treatment in this patient group, access to new anticonvulsants with novel modes of action is needed; however, all applications for new antiepileptic drugs failed to prove added benefits during the Pharmaceutical Market Restructuring Act (AMNOG) in Germany. One of the main reasons is the mandatory definition of a standard comparative therapy. It remains unclear whether there will be studies in the future which will fulfill the requirements of the current version of AMNOG. Observational studies after approval and marketing of new antiepileptic drugs could be better alternatives to prove added benefits for individual patients in the current German healthcare system.

Adjunctive retigabine in refractory focal epilepsy: Postmarketing experience at four tertiary epilepsy care centers in Germany

PURPOSE

Retigabine (RTG, ezogabine) is the first potassium channel-opening anticonvulsant drug approved for adjunctive treatment of focal epilepsies. We report on the postmarketing clinical efficacy, adverse events, and retention rates of RTG in adult patients with refractory focal epilepsy.

METHODS

Clinical features before and during RTG treatment were retrospectively collected from patients treated at four German epilepsy centers in 2011 and 2012.

RESULTS

A total of 195 patients were included. Daily RTG doses ranged from 100 to 1500 mg. Retigabine reduced seizure frequency or severity for 24.6% and led to seizure-freedom in 2.1% of the patients but had no apparent effect in 43.1% of the patients. Seizure aggravation occurred in 14.9%. The one-, two-, and three-year retention rates amounted to 32.6%, 7.2%, and 5.7%, respectively. Adverse events were reported by 76% of the patients and were mostly CNS-related. Blue discolorations were noted in three long-term responders. Three possible SUDEP cases occurred during the observation period, equalling an incidence rate of about 20 per 1000 patient years.

CONCLUSIONS

Our results are similar to other pivotal trials with respect to the long-term, open-label extensions and recent postmarketing studies. Despite the limitations of the retrospective design, our observational study suggests that RTG leads to good seizure control in a small number of patients with treatment-refractory seizures. However, because of the rather high percentage of patients who experienced significant adverse events, we consider RTG as a drug of reserve.

Post-Prandial Protein Handling: You Are What You Just Ate

Background

Protein turnover in skeletal muscle tissue is highly responsive to nutrient intake in healthy adults.

Objective

To provide a comprehensive overview of post-prandial protein handling, ranging from dietary protein digestion and amino acid absorption, the uptake of dietary protein derived amino acids over the leg, the post-prandial stimulation of muscle protein synthesis rates, to the incorporation of dietary protein derived amino acids in de novo muscle protein.

Design

12 healthy young males ingested 20 g intrinsically [1-¹³C]-phenylalanine labeled protein. In addition, primed continuous L-[ring-²H₅]-phenylalanine, L-[ring-²H₂]-tyrosine, and L-[1-¹³C]-leucine infusions were applied, with frequent collection of arterial and venous blood samples, and muscle biopsies throughout a 5 h post-prandial period. Dietary protein digestion, amino acid absorption, splanchnic amino acid extraction, amino acid uptake over the leg, and subsequent muscle protein synthesis were measured within a single in vivo human experiment.

Results

55.3±2.7% of the protein-derived phenylalanine was released in the circulation during the 5 h post-prandial period. The post-prandial rise in plasma essential amino acid availability improved leg muscle protein balance (from -291±72 to 103±66 μM·min^-1·100 mL leg volume^-1; P<0.001). Muscle protein synthesis rates increased significantly following protein ingestion (0.029±0.002 vs 0.044±0.004%·h^-1 based upon the muscle protein bound L-[ring-²H₅]-phenylalanine enrichments (P<0.01)), with substantial incorporation of dietary protein derived L-[1-¹³C]-phenylalanine into de novo muscle protein (from 0 to 0.0201±0.0025 MPE).

Conclusion

Ingestion of a single meal-like amount of protein allows ~55% of the protein derived amino acids to become available in the circulation, thereby improving whole-body and leg protein balance. About 20% of the dietary protein derived amino acids released in the circulation are taken up in skeletal muscle tissue following protein ingestion, thereby stimulating muscle protein synthesis rates and providing precursors for de novo muscle protein synthesis.

Trial Registration

trialregister.nl 3638

Impact of the Macronutrient Composition of a Nutritional Supplement on Muscle Protein Synthesis Rates in Older Men: A Randomized, Double Blind, Controlled Trial

CONTEXT

An impaired muscle protein synthetic response to feeding likely contributes to muscle loss with aging. There are few data available on the effect of the macronutrient composition of clinical supplements on the postprandial muscle protein synthetic response in older subjects.

OBJECTIVE

The objective of the study was to determine the impact of the macronutrient composition of a nutritional supplement on the postprandial muscle protein synthetic response in older men.

METHODS

A total of 45 nonsarcopenic older men (aged 69 ± 1 y; body mass index 25.7 ± 0.3 kg/m(2)) were randomly assigned to ingest 21 g of leucine-enriched whey protein with carbohydrate (9 g) and fat (3 g) (Pro-En), an isonitrogenous amount of 21 g of leucine-enriched whey protein without carbohydrate and fat (Pro), or an isocaloric mixture (628 kJ) containing carbohydrate and fat only (En). Stable isotope tracer methodology was applied to assess the basal as well as the postprandial muscle protein synthesis rates in the three groups.

RESULTS

Ingestion of protein in the Pro-En and Pro groups significantly increased muscle protein synthesis rates when compared with the basal rates (from 0.032 ± 0.003%/h to 0.05%/h 3 ± 0.004%/h and 0.040%/h ± 0.003%/h to 0.049%/h ± 0.003%/h, respectively; P < .05), whereas ingestion of carbohydrate and fat did not increase muscle protein synthesis rates in the En group (from 0.039%/h ± 0.004%/h to 0.040%/h ± 0.003%/h; P = .60). Despite the greater postprandial rise in circulating insulin concentration in the Pro-En group, no significant differences were observed in postprandial muscle protein synthesis rates between the Pro-En and Pro groups (P = .32). Postprandial muscle protein synthesis rates were higher in the Pro-En vs En group (P = .01).

CONCLUSION

The ingestion of a nutritional supplement containing 21 g of leucine-enriched whey protein significantly raises muscle protein synthesis rates in nonsarcopenic older men, but coingestion of carbohydrate and fat does not modulate the postprandial muscle protein synthetic response to protein ingestion in older men.

Prolonged Adaptation to a Low or High Protein Diet Does Not Modulate Basal Muscle Protein Synthesis Rates - A Substudy

Background

Based on controlled 36 h experiments a higher dietary protein intake causes a positive protein balance and a negative fat balance. A positive net protein balance may support fat free mass accrual. However, few data are available on the impact of more prolonged changes in habitual protein intake on whole-body protein metabolism and basal muscle protein synthesis rates.

Objective

To assess changes in whole-body protein turnover and basal muscle protein synthesis rates following 12 weeks of adaptation to a low versus high dietary protein intake.

Methods

A randomized parallel study was performed in 40 subjects who followed either a high protein (2.4 g protein/kg/d) or low protein (0.4 g protein/kg/d) energy-balanced diet (30/35/35% or 5/60/35% energy from protein/carbohydrate/fat) for a period of 12 weeks. A subgroup of 7 men and 8 women (body mass index: 22.8±2.3 kg/m², age: 24.3±4.9 y) were selected to evaluate the impact of prolonged adaptation to either a high or low protein intake on whole body protein metabolism and basal muscle protein synthesis rates. After the diet, subjects received continuous infusions with L-[ring-²H₅]phenylalanine and L-[ring-²H₂]tyrosine in an overnight fasted state, with blood samples and muscle biopsies being collected to assess post-absorptive whole-body protein turnover and muscle protein synthesis rates in vivo in humans.

Results

After 12 weeks of intervention, whole-body protein balance in the fasted state was more negative in the high protein treatment when compared with the low protein treatment (-4.1±0.5 vs -2.7±0.6 μmol phenylalanine/kg/h;P<0.001). Whole-body protein breakdown (43.0±4.4 vs 37.8±3.8 μmol phenylalanine/kg/h;P<0.03), synthesis (38.9±4.2 vs 35.1±3.6 μmol phenylalanine/kg/h;P<0.01) and phenylalanine hydroxylation rates (4.1±0.6 vs 2.7±0.6 μmol phenylalanine/kg/h;P<0.001) were significantly higher in the high vs low protein group. Basal muscle protein synthesis rates were maintained on a low vs high protein diet (0.042±0.01 vs 0.045±0.01%/h;P = 0.620).

Conclusions

In the overnight fasted state, adaptation to a low-protein intake (0.4 g/kg/d) does not result in a more negative whole-body protein balance and does not lower basal muscle protein synthesis rates when compared to a high-protein intake.

Trial Registration

Clinicaltrials.gov NCT01551238.

MECHANISMS IN ENDOCRINOLOGY: Exogenous insulin does not increase muscle protein synthesis rate when administered systemically: a systematic review

BACKGROUND

Though it is well appreciated that insulin plays an important role in the regulation of muscle protein metabolism, there is much discrepancy in the literature on the capacity of exogenous insulin administration to increase muscle protein synthesis rates in vivo in humans.

OBJECTIVE

To assess whether exogenous insulin administration increases muscle protein synthesis rates in young and older adults.

DESIGN

A systematic review of clinical trials was performed and the presence or absence of an increase in muscle protein synthesis rate was reported for each individual study arm. In a stepwise manner, multiple models were constructed that excluded study arms based on the following conditions: model 1, concurrent hyperaminoacidemia; model 2, insulin-induced hypoaminoacidemia; model 3, supraphysiological insulin concentrations; and model 4, older, more insulin resistant, subjects.

CONCLUSIONS

From the presented data in the current systematic review, we conclude that: i) exogenous insulin and amino acid administration effectively increase muscle protein synthesis, but this effect is attributed to the hyperaminoacidemia; ii) exogenous insulin administered systemically induces hypoaminoacidemia which obviates any insulin-stimulatory effect on muscle protein synthesis; iii) exogenous insulin resulting in supraphysiological insulin levels exceeding 50, 000  pmol/l may effectively augment muscle protein synthesis; iv) exogenous insulin may have a diminished effect on muscle protein synthesis in older adults due to age-related anabolic resistance; and v) exogenous insulin administered systemically does not increase muscle protein synthesis in healthy, young adults.

Ingestion of Casein in a Milk Matrix Modulates Dietary Protein Digestion and Absorption Kinetics but Does Not Modulate Postprandial Muscle Protein Synthesis in Older Men

BACKGROUND

The slow digestion and amino acid absorption kinetics of isolated micellar casein have been held responsible for its relatively lower postprandial muscle protein synthetic response compared with rapidly digested proteins such as isolated whey. However, casein is normally consumed within a milk matrix. We hypothesized that protein digestion and absorption kinetics and the subsequent muscle protein synthetic response after micellar casein ingestion are modulated by the milk matrix.

OBJECTIVE

The aim of this study was to determine the impact of a milk matrix on casein protein digestion and absorption kinetics and postprandial muscle protein synthesis in older men.

METHODS

In a parallel-group design, 32 healthy older men (aged 71 ± 1 y) received a primed continuous infusion of L-[ring-(2)H5]-phenylalanine, L-[ring-3,5-(2)H2]-tyrosine, and L-[1-(13)C]-leucine, and ingested 25 g intrinsically L-[1-(13)C]-phenylalanine and L-[1-(13)C]-leucine labeled casein dissolved in bovine milk serum (Cas+Serum) or water (Cas). Plasma samples and muscle biopsies were collected in the postabsorptive state and for 300 min in the postprandial period to examine whole-body and skeletal muscle protein metabolism.

RESULTS

Casein ingestion increased plasma leucine and phenylalanine concentrations and L-[1-(13)C]-phenylalanine enrichments, with a more rapid rise after Cas vs. Cas+Serum. Nonetheless, dietary protein-derived phenylalanine availability did not differ between Cas+Serum (47 ± 2%, mean ± SEM) and Cas (46 ± 3%) when assessed over the 300-min postprandial period (P = 0.80). The milk matrix did not modulate postprandial myofibrillar protein synthesis rates from 0 to 120 min (0.038 ± 0.005 vs. 0.031 ± 0.007%/h) or from 120 to 300 min (0.052 ± 0.004 vs. 0.067 ± 0.005%/h) after Cas+Serum vs. Cas. Similarly, no treatment differences in muscle protein-bound L-[1-(13)C]-phenylalanine enrichments were observed at 120 min (0.003 ± 0.001 vs. 0.002 ± 0.001) or 300 min (0.015 ± 0.002 vs. 0.016 ± 0.002 mole percent excess) after Cas+Serum vs. Cas.

CONCLUSIONS

Casein ingestion in a milk matrix delays protein digestion and absorption but does not modulate postprandial muscle protein synthesis when compared to the ingestion of micellar casein only in healthy older men. This trial was registered at Nederlands Trial Register as NTR4429.

Carbohydrate coingestion delays dietary protein digestion and absorption but does not modulate postprandial muscle protein accretion

BACKGROUND

Dietary protein digestion and absorption is an important factor modulating muscle protein accretion. However, there are few data available on the effects of coingesting other macronutrients with protein on digestion and absorption kinetics and the subsequent muscle protein synthetic response.

OBJECTIVE

The objective of the study was to determine the impact of carbohydrate coingestion with protein on dietary protein digestion and absorption and muscle protein accretion in healthy young and older men.

DESIGN

Twenty-four healthy young (aged 21± 1 y, body mass index 21.8 ±0.5 kg/m(2)) and 25 older (aged 75 ± 1 y, body mass index 25.4 ± 0.6 kg/m(2)) men received a primed continuous L-[ring-(2)H5]-phenylalanine and L-[ring-3,5-(2)H2]-tyrosine infusion and ingested 20 g intrinsically L-[1-(13)C]-phenylalanine-labeled protein with (Pro+CHO) or without (Pro) 60 g carbohydrate. Plasma samples and muscle biopsies were collected in a postabsorptive and postprandial state.

RESULTS

Carbohydrate coingestion delayed the appearance of exogenous phenylalanine in the circulation (P = .001). Dietary protein-derived phenylalanine availability over the 5-hour postprandial period was lower in the older (62 ± 2%) when compared with the young subjects (74 ± 2%; P = .007), with no differences between conditions (P = .20). Carbohydrate coingestion did not modulate postprandial muscle protein synthesis rates (0.035 ± 0.003 vs 0.043 ± 0.004 and 0.033 ± 0.002 vs 0.035 ± 0.003%/h after Pro vs Pro+CHO in the young and older group, respectively). In accordance, no differences in muscle protein-bound L-[1-(13)C]-phenylalanine enrichments were observed between conditions (0.020 ± 0.002 vs 0.020 ± 0.002 and 0.019 ± 0.003 vs 0.022 ± 0.004 mole percent excess after Pro vs Pro+CHO in the young and older subjects, respectively).

CONCLUSION

Carbohydrate coingestion with protein delays dietary protein digestion and absorption but does not modulate postprandial muscle protein accretion in healthy young or older men.

Skeletal muscle capillary density and microvascular function are compromised with aging and type 2 diabetes

Adequate muscle perfusion is required for the maintenance of skeletal muscle mass. Impairments in microvascular structure and/or function with aging and type 2 diabetes have been associated with the progressive loss of skeletal muscle mass. Our objective was to compare muscle fiber type specific capillary density and endothelial function between healthy young men, healthy older men, and age-matched type 2 diabetes patients. Fifteen healthy young men (24 ± 1 yr), 15 healthy older men (70 ± 2 yr), and 15 age-matched type 2 diabetes patients (70 ± 1 yr) were selected to participate in the present study. Whole body insulin sensitivity, muscle fiber type specific capillary density, sublingual microvascular density, and dimension of the erythrocyte-perfused boundary region were assessed to evaluate the impact of aging and/or type 2 diabetes on microvascular structure and function. Whole body insulin sensitivity was significantly lower at a more advanced age, with lowest values reported in the type 2 diabetic patients. In line, skeletal muscle capillary contacts were much lower in the older and older type 2 diabetic patients when compared with the young. Sidestream darkfield imaging showed a significantly greater thickness of the erythrocyte perfused boundary region in the type 2 diabetic patients compared with the young. Skeletal muscle capillary density is reduced with aging and type 2 diabetes and accompanied by impairments in endothelial glycocalyx function, which is indicative of compromised vascular function.

Perioperative changes in cortical excitability, mood, and quality of life in patients with primary hyperparathyroidism: a pilot study using transcranial magnetic stimulation

OBJECTIVE

Serum calcium (Ca(2)(+)) and parathyroid hormone (PTH), amongst others, modify cortical excitability. Alterations in cortical excitability were shown in patients with epilepsy as well as hyper- or hypoparathyroidism. In patients with primary hyperparathyroidism (pHPT), preoperative elevated serum calcium and parathyroidectomy (PTx) may affect mood and quality of life. We hypothesized that perioperative changes in Ca(2)(+) and PTH in pHPT will affect cortical excitability and improve subjective health.

DESIGN AND METHODS

Transcranial magnetic stimulation (TMS) was performed before and after surgery in 15 pHPT patients. We measured resting motor threshold, cortical silent period (CSP), short intracortical inhibition, and intracortical facilitation. Health questionnaires were administered before, 1 day and 6 months after PTx, along with the disease-specific Pasieka's parathyroid assessment of symptoms (PAS), which was, to our knowledge, its first use in German.

RESULTS

SURGERY WAS SUCCESSFUL IN ALL PATIENTS. TMS-MEASUREMENTS REMAINED UNCHANGED WHEN ANALYZING ALL PATIENTS IN THIS PILOT STUDY. POSTOPERATIVELY, DEPRESSION DECLINED (P=0.05) AND QUALITY OF LIFE IMPROVED SIGNIFICANTLY (P=0.001) IN THE SF-36-SUBSCALES: vitality, social functioning, mental health and subjective health transition (post-hoc analysis). The PAS proved early relief of disease-specific symptoms (P<0.001).

CONCLUSIONS

We found unchanged cortical excitability comparing pre- and post-PTx in this pilot study. Mood and quality of life improved postoperatively. The German PAS is valuable in detecting disease-specific changes early after PTx.

The muscle protein synthetic response to the combined ingestion of protein and carbohydrate is not impaired in healthy older men

Aging is associated with a progressive decline in skeletal muscle mass. It has been hypothesized that an attenuated muscle protein synthetic response to the main anabolic stimuli may contribute to the age-related loss of muscle tissue. The aim of the present study was to compare the muscle protein synthetic response following ingestion of a meal-like amount of dietary protein plus carbohydrate between healthy young and older men. Twelve young (21 ± 1 years) and 12 older (75 ± 1 years) men consumed 20 g of intrinsically L-[1-(13)C]phenylalanine-labeled protein with 40 g of carbohydrate. Ingestion of specifically produced intrinsically L-[1-(13)C]phenylalanine-labeled protein allowed us to assess the subsequent incorporation of casein-derived amino acids into muscle protein. Blood samples were collected at regular intervals, with muscle biopsies obtained prior to and 2 and 6 h after protein plus carbohydrate ingestion. The acute post-prandial rise in plasma glucose and insulin concentrations was significantly greater in the older compared with the younger males. Plasma amino acid concentrations increased rapidly following drink ingestion in both groups. However, plasma leucine concentrations were significantly lower at t = 90 min in the older when compared with the young group (P < 0.05). Muscle protein-bound L-[1-(13)C]phenylalanine enrichments increased to 0.0071 ± 0.0016 and 0.0072 ± 0.0013 mole percent excess (MPE) at 2 h and 0.0229 ± 0.0016 and 0.0213 ± 0.0024 MPE at 6 h following ingestion of the intrinsically labeled protein in the young and older males, respectively, with no differences between groups (P > 0.05). We conclude that the use of dietary protein-derived amino acids for muscle protein synthesis is not impaired in healthy older men following intake of protein plus carbohydrate.

Substantial Differences between Organ and Muscle Specific Tracer Incorporation Rates in a Lactating Dairy Cow

We aimed to produce intrinsically L-[1-(13)C]phenylalanine labeled milk and beef for subsequent use in human nutrition research. The collection of the various organ tissues after slaughter allowed for us to gain insight into the dynamics of tissue protein turnover in vivo in a lactating dairy cow. One lactating dairy cow received a constant infusion of L-[1-(13)C]phenylalanine (450 µmol/min) for 96 h. Plasma and milk were collected prior to, during, and after the stable isotope infusion. Twenty-four hours after cessation of the infusion the cow was slaughtered. The meat and samples of the various organ tissues (liver, heart, lung, udder, kidney, rumen, small intestine, and colon) were collected and stored. Approximately 210 kg of intrinsically labeled beef (bone and fat free) with an average L-[1-(13)C]phenylalanine enrichment of 1.8±0.1 mole percent excess (MPE) was obtained. The various organ tissues differed substantially in L-[1-(13)C]phenylalanine enrichments in the tissue protein bound pool, the highest enrichment levels were achieved in the kidney (11.7 MPE) and the lowest enrichment levels in the skeletal muscle tissue protein of the cow (between 1.5-2.4 MPE). The estimated protein synthesis rates of the various organ tissues should be regarded as underestimates, particularly for the organs with the higher turnover rates and high secretory activity, due to the lengthened (96 h) measurement period necessary for the production of the intrinsically labeled beef. Our data demonstrates that there are relatively small differences in L-[1-(13)C]phenylalanine enrichments between the various meat cuts, but substantial higher enrichment values are observed in the various organ tissues. We conclude that protein turnover rates of various organs are much higher when compared to skeletal muscle protein turnover rates in large lactating ruminants.

Alterations in mucosal neuropeptides in patients with irritable bowel syndrome and ulcerative colitis in remission: a role in pain symptom generation?

BACKGROUND

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterized by chronic abdominal pain. The transient receptor potential vanilloid 1 (TRPV1) channel, which is involved in visceral pain signalling, has been shown to be up-regulated in IBS. Activation of TRPV1 leads to the release of neuropeptides, such as somatostatin and substance P (SP). We hypothesized that increased pain perception in IBS could be explained by increased transcription in TRPV1 and/or altered levels of neuropeptides. We therefore assessed the transcription of TRPV1 and the mucosal concentration of somatostatin and SP in IBS in comparison to healthy volunteers and patients with ulcerative colitis (UC) in remission as disease controls, and to ascertain their relationship to pain symptoms.

METHOD

Sigmoid colonic mucosal samples were collected from 12 patients with IBS, 34 patients with UC in remission and 9 healthy volunteers, in which groups TRPV1 mRNA levels were determined using quantitative polymerase chain reaction and neuropeptide concentrations by radioimmunoassay. Pain symptom intensity was determined by questionnaires.

RESULTS

Transcription of TRPV1 as well as the concentration of neuropeptides were significantly higher in IBS, but only the former correlated with pain symptom severity.

CONCLUSION

Increased transcription of TRPV1 may provide a possible explanation for pain generation in IBS. While the neuropeptides SP and somatostatin were both found to be increased in IBS, these changes are not sufficient to explain pain generation. Pain generation in IBS is probably explained by a complex redundancy in the regulation of local nociceptive mechanisms, which remains a subject of intensive investigation.

Carbohydrate co-ingestion with protein does not further augment post-prandial muscle protein accretion in older men

Background

A blunted muscle protein synthetic response to protein ingestion may contribute to the age related loss of muscle tissue. We hypothesized that the greater endogenous insulin release following co-ingestion of carbohydrate facilitates post-prandial muscle protein accretion after ingesting a meal-like bolus of protein in older males.

Methods

Twenty-four healthy older men (75±1 y) were randomly assigned to ingest 20 g intrinsically L-[1-¹³C] phenylalanine-labeled casein protein with (PRO-CHO) or without (PRO) 40 g carbohydrate. Ingestion of specifically produced intrinsically L-[1-¹³C] phenylalanine labeled protein allowed us to assess post-prandial incorporation of dietary protein derived amino acids into muscle protein. Blood samples were collected at regular intervals, with muscle biopsies being obtained prior to and 2 and 6 h after protein ingestion.

Results

Plasma glucose and insulin concentrations showed a greater increase in PRO-CHO compared with PRO (P<0.001). Muscle protein-bound L-[1-¹³C] phenylalanine enrichments tended to increase to a greater extent in PRO-CHO compared with PRO during the first 2 h after protein ingestion (0.0072±0.0013 vs 0.0046±0.010 MPE, respectively; P=0.13). However, 6 h after protein ingestion, differences in muscle protein-bound L-[1-¹³C] phenylalanine enrichments were no longer observed between experiments (0.0213±0.0024 vs 0.0185±0.0010 MPE, respectively; P=0.30).

Conclusions

This study shows that carbohydrate ingestion may accelerate, but does not further augment post-prandial incorporation of dietary protein derived amino acids into muscle protein in healthy elderly men.

Functional analysis of colonic bacterial metabolism: relevant to health?

With the use of molecular techniques, numerous studies have evaluated the composition of the intestinal microbiota in health and disease. However, it is of major interest to supplement this with a functional analysis of the microbiota. In this review, the different approaches that have been used to characterize microbial metabolites, yielding information on the functional end products of microbial metabolism, have been summarized. To analyze colonic microbial metabolites, the most conventional way is by application of a hypothesis-driven targeted approach, through quantification of selected metabolites from carbohydrate (e.g., short-chain fatty acids) and protein fermentation (e.g., p-cresol, phenol, ammonia, or H(2)S), secondary bile acids, or colonic enzymes. The application of stable isotope-labeled substrates can provide an elegant solution to study these metabolic pathways in vivo. On the other hand, a top-down approach can be followed by applying metabolite fingerprinting techniques based on (1)H-NMR or mass spectrometric analysis. Quantification of known metabolites and characterization of metabolite patterns in urine, breath, plasma, and fecal samples can reveal new pathways and give insight into physiological regulatory processes of the colonic microbiota. In addition, specific metabolic profiles can function as a diagnostic tool for the identification of several gastrointestinal diseases, such as ulcerative colitis and Crohn's disease. Nevertheless, future research will have to evaluate the relevance of associations between metabolites and different disease states.

[Neuropathology and etiology of focal epilepsy]

In 2010 the International League against Epilepsy published a new classification of epilepsies. A major advance of this classification system is the acknowledgment of a genetic or pathologic-anatomic basis of epilepsy as important predictors of outcome (cause matters). This applies in particular to structural-metabolic lesions, which were frequently recognized in surgical specimens obtained from patients with drug-resistant focal epilepsy, i.e. hippocampal sclerosis, glioneuronal tumors, focal cortical dysplasias, vascular malformations, ischemia, intracerebral hemorrhage, glial scars or inflammation. A better understanding and classification of the etiopathology as well as the underlying molecular mechanisms will help to anticipate and appreciate the clinical course of a disease as well as to develop new and targeted drug treatment. Surgically available human brain tissue will be most helpful to support this approach but will also need careful neuropathological evaluation with accurate classification systems and use of terminology.

The prebiotic, oligofructose-enriched inulin modulates the faecal metabolite profile: an in vitro analysis

SCOPE

Health benefits of prebiotic administration have been judged mainly from the increased numbers of bifidobacteria and the enhanced production of short-chain fatty acids in the colon. Only a few studies have focused on the capacity of prebiotics to decrease the proteolytic fermentation, which might contribute to health as well.

METHODS AND RESULTS

The influence of the prebiotic oligofructose-enriched inulin (OF-IN) on the pattern of volatile organic compounds was characterized using an in vitro faecal model. Faecal slurries, obtained from healthy subjects, were anaerobically incubated at 37 °C with and without different doses of OF-IN (2.5, 5, 10, or 20 mg) and changes in the metabolite pattern and pH were evaluated. A total of 107 different volatile organic compounds were identified and classified according to their chemical classes. The concentration of esters and acids significantly increased with increasing doses of OF-IN. Similar effects were observed for some aldehydes. To the contrary, OF-IN dose-dependently inhibited the formation of S-compounds. Also, the generation of other protein fermentation metabolites such as phenolic compounds was inhibited in the presence of OF-IN.

CONCLUSION

Our results confirmed a clear dose-dependent stimulation of saccharolytic fermentation. Importantly, a significant decrease in toxic protein fermentation metabolites such as sulphides attended these effects.

[Primary brain tumors and brain metastases. Symptomatic epilepsy and driving ability - systematic review and expert opinion]

PURPOSE

Primary brain tumors and metastases are common causes of symptomatic epilepsy. Seizures, neurological and neuropsychological deficits can interfere with driving ability. The present paper aims to systematically review the incidence of epileptic seizures in brain tumor patients and to discuss driving ability in the context of the current German guidelines and expert opinions.

METHODS

To evaluate the incidence of epileptic seizures which occur at the beginning and in the course of the disease, we performed a systematic literature research in PubMed from 1960 to 2007. Additionally on the basis of this data we performed a survey collecting expert opinions regarding the driving ability of brain tumor patients from members of the German working groups "Arbeitsgemeinschaft für prächirurgische Epilepsiediagnostik und operative Epilepsietherapie" (Working Group for Presurgical Epilepsy Diagnostics and Operative Epileptic Therapy) and "Neuroonkologische Arbeitsgemeinschaft" (Neuro-oncological Working Group).

RESULTS

The incidence of epileptic seizures depends on the entity, dignity and localization of the tumor. The driving ability of brain tumor patients is not explicitly regulated in Germany. Of the interviewed experts 72% judged the guidelines to be precise enough and 44% did not want to deprive the patients of their driving ability without a first seizure, independent of the individual risk.

DISCUSSION

The available studies are methodologically insufficient and show that a further evaluation is necessary to assess the driving ability. Possible restrictions of the driving ability in patients with a high risk of seizures in the course of the disease have to take into account the balance between individual rights and the interests of the general public.

The impact of pre- and/or probiotics on human colonic metabolism: does it affect human health?

Since many years, the role of the colonic microbiota in maintaining the host's overall health and well-being has been recognized. Dietary modulation of the microbiota composition and activity has been achieved by the use of pre-, pro- and synbiotics. In this review, we will summarize the available evidence on the modification of bacterial metabolism by dietary intervention with pre-, pro- and synbiotics. Enhanced production of SCFA as a marker of increased saccharolytic fermentation is well documented in animal and in vitro studies. Decreased production of potentially toxic protein fermentation metabolites, such as sulfides, phenolic and indolic compounds, has been less frequently demonstrated. Besides, pre-, pro- and synbiotics also affect other metabolic pathways such as the deconjugation of secondary bile acids, bacterial enzyme activities and mineral absorption. Data from human studies are less conclusive. The emergence of new analytical techniques such as metabolite profiling has revealed new pathways affected by dietary intervention. However, an important challenge for current and future research is to relate changes in bacterial metabolism to concrete health benefits. Potential targets and expected benefits have been identified: reduced risk for the metabolic syndrome and prevention of colorectal cancer.

Men and women are different: diffusion tensor imaging reveals sexual dimorphism in the microstructure of the thalamus, corpus callosum and cingulum

INTRODUCTION

Numerous magnetic resonance imaging (MRI) studies have addressed the question of morphological differences of the brain of men and women, reporting conflicting results regarding brain size and the ratio of gray and white matter. In the present study, we used diffusion tensor imaging (DTI) to delineate sex differences of brain white matter.

METHODS

We investigated brain microstructure in 25 male and 25 female healthy subjects using a 3T MRI scanner. Whole-head DTI scans were analyzed without a-priori hypothesis using Tract-Based Spatial Statistics (TBSS) calculating maps of fractional anisotropy (FA), radial diffusivity (RD, a potential marker of glial alteration and changes in myelination) and axial diffusivity (AD, a potential marker of axonal changes).

RESULTS

DTI revealed regional microstructural differences between the brains of male and female subjects. Those were prominent in the thalamus, corpus callosum and cingulum. Men showed significantly (p<0.0001) higher values of fractional anisotropy and lower radial diffusivity in these areas, suggesting that the observed differences are mainly due to differences in myelination.

DISCUSSION

As a novel finding we showed widespread differences in thalamic microstructure that have not been described previously. Additionally, the present study confirmed earlier DTI studies focusing on sexual dimorphism in the corpus callosum and cingulum. All changes appear to be based on differences in myelination. The sex differences in thalamic microstructure call for further studies on the underlying cause and the behavioral correlates of this sexual dimorphism. Future DTI group studies may carefully control for gender to avoid confounding.

Quantification of (15)N-nitrate in urine with gas chromatography combustion isotope ratio mass spectrometry to estimate endogenous NO production

The use of stable isotope labeled substrates and subsequent analysis of urinary nitrate, forms a noninvasive test for evaluation of the in vivo NO metabolism. The present paper describes a new method for simultaneous quantification of (15)N-nitrate and total nitrate with gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS). Nitrate, isolated from urine with a nitrate selective resin, was reduced to nitrite using copperized cadmium. Subsequently, Sudan I was formed by diazotation. Sudan II was added as internal standard, and both molecules were analyzed with GC-C-IRMS as tert-butyldimethylsilyl derivatives. The accuracy was determined during a recovery study of two different known nitrate concentrations and two (15)N-enrichments. A recovery of 101.6% and 103.9% for total nitrate and 107.6% and 91.2% for (15)N-nitrate was obtained, respectively. The validated method was applied on complete 72 h urine collections after intravenous administration of (15)N-nitrate and (15)N-arginine in humans. On average, 51.8% (47.0-71.0%) of administered (15)N-nitrate was excreted, while 0.68% (0.44-1.17%) of (15)N-arginine was metabolized to nitrate. In conclusion, this method can be used for accurate simultaneous determination of (15)N-nitrate and total nitrate concentrations in urine and can be applied in clinical studies for noninvasive evaluation of NO metabolism in vivo.

The effects of butyrate enemas on visceral perception in healthy volunteers

Fermentation of dietary fibres by colonic microbes leads to the production of short chain fatty acids (mainly propionate, butyrate and acetate), which are utilized by the colonic mucosa. Previous studies showed positive effects of butyrate on parameters of oxidative stress, inflammation and apoptosis. Recent studies in rats, however, showed that butyrate increased visceral sensitivity. The aim of this study was to determine the effects of physiologically relevant concentrations of butyrate on visceral perception in healthy human subjects. Eleven healthy volunteers participated in this randomized double-blind, placebo controlled cross-over study. The study consisted of three periods of 1 week each, in which the volunteers daily self-administered rectal enemas containing 100, 50 mmol L(-1) butyrate, or placebo (saline) prior to sleeping. A rectal barostat measurement was performed at the start and the end of each test period for the measurement of pain, urge and discomfort. Butyrate treatment resulted in a dose-dependent reduction of pain, urge and discomfort throughout the entire pressure range of the protocol. At a pressure of 4 mmHg, 50 and 100 mmol L(-1) butyrate concentrations resulted in a 23.9% and 42.1% reduction of pain scores, respectively, and the discomfort scores decreased by 44.2% and 69.0% respectively. At a pressure of 67 mmHg, 50 and 100 mmol L(-1) of butyrate decreased the pain scores by 23.8% and 42%, respectively, and discomfort scores 1.9% and 5.2% respectively. Colonic administration of butyrate, at physiologically relevant concentrations, dose-dependently decreases visceral sensitivity in healthy volunteers.

Butyrate-induced transcriptional changes in human colonic mucosa

Background

Fermentation of dietary fiber in the colon results in the production of short chain fatty acids (mainly propionate, butyrate and acetate). Butyrate modulates a wide range of processes, but its mechanism of action is mostly unknown. This study aimed to determine the effects of butyrate on the transcriptional regulation of human colonic mucosa in vivo.

Methodology/Principal Findings

Five hundred genes were found to be differentially expressed after a two week daily butyrate administration with enemas. Pathway analysis showed that the butyrate intervention mainly resulted in an increased transcriptional regulation of the pathways representing fatty acid oxidation, electron transport chain and oxidative stress. In addition, several genes associated with epithelial integrity and apoptosis, were found to be differentially expressed after the butyrate intervention.

Conclusions/Significance

Colonic administration of butyrate in concentrations that can be achieved by consumption of a high-fiber diet enhances the maintenance of colonic homeostasis in healthy subjects, by regulating fatty acid metabolism, electron transport and oxidative stress pathways on the transcriptional level and provide for the first time, detailed molecular insight in the transcriptional response of gut mucosa to butyrate.

Butyrate modulates oxidative stress in the colonic mucosa of healthy humans

BACKGROUND & AIMS

Butyrate, a short-chain fatty acid produced by colonic microbial fermentation of undigested carbohydrates, has been implicated in the maintenance of colonic health. This study evaluates whether butyrate plays a role in oxidative stress in the healthy colonic mucosa.

METHODS

A randomized, double blind, cross-over study with 16 healthy volunteers was performed. Treatments consisted of daily rectal administration of a 60 ml enema containing 100 mM sodium butyrate or saline for 2 weeks. After each treatment, a blood sample was taken and mucosal biopsies were obtained from the sigmoid colon. In biopsies, the trolox equivalent antioxidant capacity, activity of glutathione-S-transferase, concentration of uric acid, glutathione (GSH), glutathione disulfide and malondialdehyde, and expression of genes involved in GSH and uric acid metabolism was determined. Secondary outcome parameters were CRP, calprotectin and intestinal fatty acid binding protein in plasma and histological inflammatory scores.

RESULTS

Butyrate treatment resulted in significantly higher GSH (p<0.05) and lower uric acid (p<0.01) concentrations compared to placebo. Changes in GSH and uric acid were accompanied by increased and decreased expression, respectively, of their rate limiting enzymes determined by RT-PCR. No significant differences were found in other parameters.

CONCLUSIONS

This study demonstrated that butyrate is able to beneficially affect oxidative stress in the healthy human colon.