A period of 10 weeks of increased protein consumption does not alter faecal microbiota or volatile metabolites in healthy older men: a randomised controlled trial.

Diet has a major influence on the composition and metabolic output of the gut microbiome. Higher-protein diets are often recommended for older consumers; however, the effect of high-protein diets on the gut microbiota and faecal volatile organic compounds (VOC) of elderly participants is unknown. The purpose of the study was to establish if the faecal microbiota composition and VOC in older men are different after a diet containing the recommended dietary intake (RDA) of protein compared with a diet containing twice the RDA (2RDA). Healthy males (74⋅2 (sd 3⋅6) years; n 28) were randomised to consume the RDA of protein (0⋅8 g protein/kg body weight per d) or 2RDA, for 10 weeks. Dietary protein was provided via whole foods rather than supplementation or fortification. The diets were matched for dietary fibre from fruit and vegetables. Faecal samples were collected pre- and post-intervention for microbiota profiling by 16S ribosomal RNA amplicon sequencing and VOC analysis by head space/solid-phase microextraction/GC-MS. After correcting for multiple comparisons, no significant differences in the abundance of faecal microbiota or VOC associated with protein fermentation were evident between the RDA and 2RDA diets. Therefore, in the present study, a twofold difference in dietary protein intake did not alter gut microbiota or VOC indicative of altered protein fermentation.

Inflexibility of the plasma miRNA response following a high-carbohydrate meal in overweight insulin-resistant women.

CONTEXT: Metabolic inflexibility is a characteristic of insulin resistance, limiting the ability to transiently regulate oxidative metabolism and gene expression in response to nutrient availability. Little is known of the flexibility of post-transcriptional regulation, including circulatory miRNAs (c-miRNAs). DESIGN: The abundances of targeted c-miRNAs, with reported functions in metabolic regulation, were analysed in response to a high-carbohydrate meal in healthy weight insulin-sensitive (IS) and overweight insulin-resistant (IR) women. PARTICIPANTS: Age-matched healthy weight IS (n = 20, BMI = 24.3 ± 0.70) and overweight IR (n = 20, BMI = 28.6 ± 0.67) women. METHODS: An abundance of c-miRNAs was quantified prior to and following a high-carbohydrate breakfast meal (2500 kJ; 50% carbohydrate, 20% fat and 27% protein). Target genes of the differentially regulated c-miRNA were measured in RNA extracted from circulatory peripheral blood mononuclear cells (PBMCs). RESULTS: In healthy weight IS women, both miR-15a-5p (p = 0.03) and miR-17-5p (p < 0.01) levels were halved at 4 h post-meal. These miRNA remained unaltered following the same meal in the overweight IR women. Furthermore, amongst genes targeted by these miRNA, CPT1A (p = 0.01) and IL8 (p = 0.03) had also reduced expression 4 h post-meal only in the healthy weight IS women. CONCLUSIONS: The study findings provide preliminary evidence for a possible extension of metabolic inflexibility to include c-miRNAs. TRIAL REGISTRATION: The clinical trial is registered with Australian New Zealand Clinical Trials Registry under Trial registration: ANZCTR: ACTRN12615001108505. Registered on 21 October 2015.

Circulatory miRNA biomarkers of metabolic syndrome.

AIMS: Circulatory microRNAs (c-miRNAs) exert important roles in the molecular dysregulation of cardio-metabolic diseases. However, little is known whether dysregulated miRNA expression occurs when risk factors are elevated, as in the metabolic syndrome (MetS). This study quantified c-miRNA expression in individuals with MetS compared to healthy, further examining the relationship of gene pathways with the underlying pathogenesis. METHODS: Expression of 26 miRNAs was quantified in plasma from 40 women (20 healthy and 20 MetS) and 39 men (20 healthy and 19 MetS) by qPCR. In silico analysis was performed to investigate biological effects of the dysregulated miRNAs. Dysregulated miRNA expression was further validated in an independent cohort of 20 women (10 healthy and 10 MetS). RESULTS: Regression model adjusted for age and sex identified miR-15a-5p, miR-17-5p, miR-370-3p and miR-375 as important predictors of MetS presence. Analysis of predictive miRNAs in the validation cohort strengthened the relationship with miR-15a-5p and miR-17-5p expression. These miRNAs share genes involved in the regulation of metabolic pathways including insulin, wnt, fatty acid metabolism and AMPK. CONCLUSIONS: miR-15a-5p and miR-17-5p were identified as predictive biomarkers of MetS, irrespective of sexes, further demonstrating the relationship of c-miRNAs to known pathways of metabolic disturbances present in cardio-metabolic diseases.

Regulation of Amino Acid Transporters and Sensors in Response to a High protein Diet: A Randomized Controlled Trial in Elderly Men.

BACKGROUND: The mammalian target of rapamycin complex 1 (mTORC1) is fundamental for many cellular processes, yet it is often dysregulated with aging. Increased amino acid (AA) availability is correlated with the expression of AA transporters (AAT) and mTORC1 activity. Although many AA sensors and mediators have been proposed to relay the AA signal to mTORC1, it has not yet been determined if chronic dietary intervention affects the expression of AAT, sensors and mediators and their relationships with mTORC1 activity. OBJECTIVE AND DESIGN: This study investigated whether the consumption of a diet containing either the current recommended daily allowance (RDA) of protein intake (0.8 g/kg/d) or twice the RDA (2RDA) for ten weeks affected the expression of targets associated with AA transport, sensing and mTORC1 regulation in 26 older men (70-81 years). METHOD: Muscle biopsies were collected before and after the intervention under fasting conditions. Diets were controlled by providing fully prepared meals and snacks. Western blot and quantitative polymerase chain reaction were used to measure protein and gene expression respectively. RESULTS: Consumption of 2RDA reduced the protein expression of L-type amino acid transporter 1 (LAT1). However, plasma leucine concentration and basal mTORC1 activity were unaltered. The downregulation of LAT1 did not affect the expression of AA sensors and mediators, including leucyl tRNA synthetase (LRS), cytosolic arginine sensor for mTORC1 (CASTOR1), Sestrin2 and Rag proteins. Instead, total ribosomal protein S6 (RPS6) was upregulated with 2RDA. CONCLUSION: Ten weeks of 2RDA diet did not affect the fasting mTORC1 signaling, but increased total RPS6 might suggest improved muscular translational capacity to maintain muscular mass.

Short communication: Muscle protein synthetic response to microparticulated whey protein in middle-aged men.

Whey protein concentrate (WPC) is a high-quality dairy ingredient that is often included in formulated food products designed to stimulate muscle anabolism. Whey protein concentrate can be affected by UHT processing, and its sensory properties are not compatible with some formulated food products. Microparticulated WPC (mWPC) is a novel ingredient that is resistant to heat treatment and has enhanced sensory properties. When 16 healthy middle-aged men consumed 20 g of either WPC or mWPC, both proteins increased plasma essential AA and leucine concentrations with no detectable difference in curve kinetics. Myofibrillar protein synthesis was increased in both groups for 90 min after ingestion with no difference between groups. Ingestion of mWPC resulted in a muscle anabolic response that was equivalent to that of WPC over the full 210-min measurement period. Formulated products incorporating mWPC or standard WPC would provoke equivalent anabolic responses.

Older Adults Have Delayed Amino Acid Absorption after a High Protein Mixed Breakfast Meal.

OBJECTIVES: To measure the postprandial plasma amino acid appearance in younger and older adults following a high protein mixed meal. DESIGN: Cross-sectional study. SETTING: Clinical research setting. PARTICIPANTS: Healthy men and women aged 60-75 (n=15) years, and young controls aged 20-25 years (n=15) matched for body mass index and insulin sensitivity based on the homeostatic model assessment of insulin resistance. INTERVENTION: High protein mixed meal of complete food products. MEASUREMENTS: Circulating amino acid concentrations were determined hourly before and for 5 hours after meal ingestion. RESULTS: There was no difference between cohorts in postprandial appearance of non-essential amino acids, or area under the curve of any individual amino acid or amino acid class. However, older adults had higher baseline concentrations of aspartic acid, glutamic acid, glycine, ornithine, threonine and tyrosine and lower baseline concentrations of hydroxyproline, isoleucine, leucine, methionine and valine compared to younger adults. Younger adults showed peak essential (EAA) and branched-chain amino acid (BCAA) concentrations at 1 hour post meal while older adults' peak EAA and BCAA concentration was at 3 hours. Similarly, peak total amino acid concentrations were at 3 hours in older adults. CONCLUSION: Older adults digested and absorbed the protein within a mixed meal more slowly than younger adults. Delayed absorption of AA following a mixed meal of complete food products may suppress or delay protein synthesis in senescent muscle.

Relationship between serum ferritin, hepatic iron staining, diabetes mellitus and fibrosis progression in patients with chronic hepatitis C.

BACKGROUND: Chronic infection with the hepatitis C virus affects over 170 million individuals worldwide and 20% of patients develop cirrhosis after 20 years. Increased iron stores and hepatic iron content have been suggested to be important in fibrosis progression. The increased prevalence of diabetes mellitus has been associated with increased iron deposits in patients with chronic hepatitis C. AIM: To assess the potential relationship between serum ferritin and hepatic iron staining and liver fibrosis in patients with chronic hepatitis C virus infection and whether these factors are increased in diabetic patients with hepatitis C virus. METHODS: This was a cross-sectional, multi-centre study involving hospitals in the north-east of London between 1992 and 2003. Chronic hepatitis C patients with a liver biopsy and data concerning age, sex, basal metabolic index, diabetes mellitus or impaired glucose tolerance, alcohol intake, serum ferritin level and ethnicity were enrolled. Each biopsy was scored for fibrosis and stained for hepatic iron. RESULTS: Three hundred and thirty nine patients (200 Caucasian; 139 Asian) were enrolled. Fifty three patients had no fibrosis, 131 had mild fibrosis (stage one to two Modified Ishak), 68 moderate fibrosis (stage three to four) and 87 cirrhosis (stage five to six). 4.4% of patients had elevations in serum ferritin, whilst 11% had increased hepatic iron staining. The serum ferritin and hepatic iron staining were unrelated to the degree of fibrosis. Serum ferritin was significantly higher in patients with diabetes or impaired glucose tolerance compared to non-diabetics. No association was seen between diabetes and hepatic iron staining. CONCLUSIONS: Many patients with chronic hepatitis C virus infection may have elevated serum ferritin and/or iron deposition within the liver. However, both played no significant role in the progression of hepatitis C virus related liver injury. The association between chronic hepatitis C virus infection and type II diabetes mellitus exists, however the biological mechanism of this association still remains to be elucidated.

Knowledge of chronic hepatitis C among East London primary care physicians following the Department of Health's educational campaign.

BACKGROUND: In August 2002, the Department of Health (DH) wrote to all general practitioners (GPs) in England about hepatitis C, enclosing an educational booklet. AIM: To assess hepatitis C knowledge among East London GPs in June 2003. DESIGN: Postal questionnaire and face-to-face interviews. METHODS: A questionnaire was mailed to 250 (South-East) and 600 (North-East) London GPs, with reminders where needed. We randomly selected 10 GPs for face-to-face standardized interviews. RESULTS: Overall questionnaire response was 56% (South-East) and 57% (North-East), with little difference between the groups. Some 86% knew that hepatitis C was common in people who inject drugs, and that its prevalence was higher than HIV. However, 14% believed that antibodies to the virus indicated that the patient no longer had active disease. Some 49% thought that materno-fetal transmission was common, and 50% believed that blood transfusion in the 1990s carried a high risk of infection. Only 23% knew that 20% of patients develop cirrhosis after 20 years, and only 58% were aware that therapy was effective in > 50% of cases. Responses among the interviewed GPs were similar. DISCUSSION: Knowledge of hepatitis C among GPs remains poor. Every GP surveyed wished to be better informed. We hope the DH will produce and audit further educational campaigns.