Inter-individual variability in the production of flavan-3-ol colonic metabolites: preliminary elucidation of urinary metabotypes.

PURPOSE: There is much information on the bioavailability of (poly)phenolic compounds following acute intake of various foods. However, there are only limited data on the effects of repeated and combined exposure to specific (poly)phenol food sources and the inter-individual variability in their bioavailability. This study evaluated the combined urinary excretion of (poly)phenols from green tea and coffee following daily consumption by healthy subjects in free-living conditions. The inter-individual variability in the production of phenolic metabolites was also investigated. METHODS: Eleven participants consumed both tablets of green tea and green coffee bean extracts daily for 8 weeks and 24-h urine was collected on five different occasions. The urinary profile of phenolic metabolites and a set of multivariate statistical tests were used to investigate the putative existence of characteristic metabotypes in the production of flavan-3-ol microbial metabolites. RESULTS: (Poly)phenolic compounds in the green tea and green coffee bean extracts were absorbed and excreted after simultaneous consumption, with green tea resulting in more inter-individual variability in urinary excretion of phenolic metabolites. Three metabotypes in the production of flavan-3-ol microbial metabolites were tentatively defined, characterized by the excretion of different amounts of trihydroxyphenyl-γ-valerolactones, dihydroxyphenyl-γ-valerolactones, and hydroxyphenylpropionic acids. CONCLUSIONS: The selective production of microbiota-derived metabolites from flavan-3-ols and the putative existence of characteristic metabotypes in their production represent an important development in the study of the bioavailability of plant bioactives. These observations will contribute to better understand the health effects and individual differences associated with consumption of flavan-3-ols, arguably the main class of flavonoids in the human diet.

Ethnic differences in beta-cell function, dietary intake and expression of the metabolic syndrome among UK adults of South Asian, black African-Caribbean and white-European origin at high risk of metabolic syndrome.

A cross-sectional analysis of ethnic differences in dietary intake, insulin sensitivity and beta-cell function, using the intravenous glucose tolerance test (IVGTT), was conducted on 497 healthy adult participants of the 'Reading, Imperial, Surrey, Cambridge, and Kings' (RISCK) study. Insulin sensitivity (Si) was significantly lower in African-Caribbean (AC) and South Asian (SA) participants [IVGTT-Si; AC: 2.13 vs SA: 2.25 vs white-European (WE): 2.84 (×10(-4) mL µU min)(2), p < 0.001]. AC participants had a higher prevalence of anti-hypertensive therapy (AC: 19.7% vs SA: 7.5%), the most cardioprotective lipid profile [total:high-density lipoprotein (HDL); AC: 3.52 vs SA: 4.08 vs WE: 3.83, p = 0.03] and more pronounced hyperinsulinaemia [IVGTT-acute insulin response (AIR)] [AC: 575 vs SA: 428 vs WE: 344 mL/µU/min)(2), p = 0.002], specifically in female participants. Intake of saturated fat and carbohydrate was lower and higher in AC (10.9% and 50.4%) and SA (11.1% and 52.3%), respectively, compared to WE (13.6% and 43.8%, p < 0.001). Insulin resistance in ACs is characterised by 'normal' lipid profiles but high rates of hypertension and pronounced hyperinsulinaemia.

VEGF is indirectly associated with NO production and acutely increases in response to hyperglycaemia(1).

BACKGROUND: Increased levels of vascular endothelial growth factor (VEGF) have been observed in patients with metabolic syndrome (MetS). Nitric oxide (NO) formation is reduced in MetS, but its relationship to VEGF production remains poorly defined. We evaluated the association between VEGF/NO synthesis and insulin sensitivity in obese subjects and investigated the secretory response of VEGF to an acute elevation of glucose. MATERIALS AND METHODS: Seven healthy normal-weight subjects, seven obese subjects without MetS and seven obese subjects with MetS were recruited. Anthropometry, body composition and cardiometabolic functions (blood pressure, glucose, insulin, triglycerides, total cholesterol, HDL-C and VEGF) were measured, and a novel stable isotope method was used to assess in vivo rates of NO production. A frequent sampling intravenous glucose tolerance test was performed to study the dynamics of VEGF release. RESULTS: Fasting VEGF levels were significantly higher in the two obese groups compared to the control group (P for trend = 0·02), but the difference was not significant after adjustment for age. Vascular endothelial growth factor levels were associated with systolic blood pressure (ρ = 0·54; P = 0·01) and NO production (ρ = -0·44; P = 0·04). Vascular endothelial growth factor levels increased in response to acute hyperglycaemia in normal-weight and obese subjects (P < 0·001). CONCLUSIONS: Vascular endothelial growth factor levels rapidly increase during hyperglycaemia and are inversely related to NO production at steady state. The potential link between the acute secretion of VEGF and atherosclerotic risk in subjects with poorly controlled glycaemia as well as the potential of lowering elevated VEGF levels by increasing NO production and/or availability warrants further investigation.

Measuring energy expenditure after stroke: validation of a portable device.

BACKGROUND AND PURPOSE: Current means of assessing physical activity and energy expenditure have restrictions in stroke, limiting our understanding of its role in therapeutic management. This study validates a portable multisensor array for measuring free-living total energy expenditure compared with a gold standard method (doubly labeled water) in individuals with stroke. METHODS: Daily energy expenditure was measured in 9 participants with stroke (73 ± 8 years) over a 10-day period with 2 techniques: a portable multisensor array and doubly labeled water. RESULTS: Bland-Altman analysis revealed a mean difference of 94 kcal/day (3.8%) in total energy expenditure measures given by the multisensor array in comparison to doubly labeled water with lower and upper limits of agreement of -276 to 463.8 kcal/day (2473 ± 468 versus 2380 ± 551, P=0.167). There was strong agreement between the multisensor array and labeled water methods of capturing total daily energy expenditure (r=0.850, P=0.004). CONCLUSIONS: The multisensor array is a portable and accurate method of capturing daily energy expenditure and may assist in understanding how stroke influences free-living energy expenditure and aid in clinical management.

Genetic predisposition to type 2 diabetes is associated with impaired insulin secretion but does not modify insulin resistance or secretion in response to an intervention to lower dietary saturated fat.

Genome-wide association studies have identified SNPs reproducibly associated with type 2 diabetes (T2D). We examined the effect of genetic predisposition to T2D on insulin sensitivity and secretion using detailed phenotyping in overweight individuals with no diagnosis of T2D. Furthermore, we investigated whether this genetic predisposition modifies the responses in beta-cell function and insulin sensitivity to a 24-week dietary intervention. We genotyped 25 T2D-associated SNPs in 377 white participants from the RISCK study. Participants underwent an IVGTT prior to and following a dietary intervention that aimed to lower saturated fat intake by replacement with monounsaturated fat or carbohydrate. We composed a genetic predisposition score (T2D-GPS) by summing the T2D risk-increasing alleles of the 25 SNPs and tested for association with insulin secretion and sensitivity at baseline, and with the change in response to the dietary intervention. At baseline, a higher T2D-GPS was associated with lower acute insulin secretion (AIRg 4% lower/risk allele, P = 0.006) and lower insulin secretion for a given level of insulin sensitivity, assessed by the disposition index (DI 5% lower/risk allele, P = 0.002), but not with insulin sensitivity (Si). T2D-GPS did not modify changes in insulin secretion, insulin sensitivity or the disposition index in response to the dietary interventions to lower saturated fat. Participants genetically predisposed to T2D have an impaired ability to compensate for peripheral insulin resistance with insulin secretion at baseline, but this does not modify the response to a reduction in dietary saturated fat through iso-energetic replacement with carbohydrate or monounsaturated fat.

In vivo nitric oxide synthesis, insulin sensitivity, and asymmetric dimethylarginine in obese subjects without and with metabolic syndrome.

Metabolic syndrome (MetSyn) is associated with impaired endothelial function. Here the association between nitric oxide (NO) production and insulin sensitivity (Si) in obese subjects with and without MetSyn was evaluated. The relationship between NO production and asymmetric dimethylarginine (ADMA) was also explored. Seven healthy normal-weight subjects (male/female [M/F], 3/4; age, 27.4 ± 10.9 years; body mass index [BMI], 21.9 ± 2.2 kg/m(2)), 7 obese subjects without MetSyn (M/F, 1/6; age, 48.0 ± 8.0 years; BMI, 34.5 ± 2.3 kg/m(2)), and 7 with MetSyn (M/F, 3/4; age, 48.0 ± 10.7 years; BMI, 33.4 ± 2.9 kg/m(2)) were recruited. Body composition and cardiometabolic functions (blood pressure, glucose, insulin, triglycerides, total cholesterol, high-density lipoprotein, ADMA) were measured. A frequent sampling intravenous glucose tolerance test was performed to measure Si. A novel stable isotopic method was used to measure in vivo rates of NO production. The NO production was lower in obese subjects with MetSyn compared with normal-weight subjects and obese subjects without MetSyn. Similarly, Si was significantly lower in obesity, both without and with MetSyn, compared with the control group. A significant direct association was found between NO synthesis and Si (ρ = 0.47, P = .03). Circulating levels of ADMA were significantly higher in the obese group with MetSyn. A nonsignificant negative trend between ADMA and NO synthesis was observed. The association between Si and NO production suggests a close mechanistic link between endothelial function and insulin signaling. The results may be highly informative for the development of controlled longitudinal interventions to improve endothelial and metabolic regulation.

The effect of food preparation on the bioavailability of carotenoids from carrots using intrinsic labelling.

A strategy to reduce the incidence of vitamin A deficiency is to improve precursor bioavailability from meals. Since vitamin A precursors are fat-soluble, we noted that carotenoids are more easily absorbed from food if prepared in such a way that the food matrix containing provitamin A (ß-carotene) is sufficiently fat rich. To quantify this effect, we have developed a stable isotope methodology. By regular watering with 2H-labelled water, we were able to produce several kg of intrinsically labelled carrots, with carotenoids labelled to 0.63 % excess 2H. These were divided into 100 g portions and fed to a small group of healthy subjects both raw and stir-fried. To normalise for inter-individual variation in absorption and subsequent metabolism, small quantities of extrinsically 13C-labelled ß-carotene and 2H-labelled retinol acetate were also incorporated into the meal. After ingestion of the carrots, blood lipids were monitored for a period of 3 d in order to determine the kinetics of ß-carotene and retinol. From kinetic data, it was estimated that the bioavailability of carrot-derived ß-carotene compared with pure ß-carotene was about 11 % for raw carrots, but 75 % when the carrots were stir-fried. Conversely, there was a slight reduction in the bioconversion to retinol from ß-carotene when the latter was derived from the stir-fried meal compared with that from raw carrots. When these two factors are combined, the yield of retinol from the carotene in carrots was found to be enhanced by a factor of 6.5 by stir-frying.

Plasma appearance and disappearance of an oral dose of 25-hydroxyvitamin D2 in healthy adults.

25-Hydroxyvitamin D (25(OH)D) half-life is a potential biomarker for investigating vitamin D metabolism and requirements. We performed a pilot study to assess the approach and practical feasibility of measuring 25(OH)D half-life after an oral dose. A total of twelve healthy Gambian men aged 18-23 years were divided into two groups to investigate the rate and timing of (1) absorption and (2) plasma disappearance after an 80 nmol oral dose of 25(OH)D2. Fasting blood samples were collected at baseline and, in the first group, every 2 h post-dose for 12 h, at 24 h, 48 h and on day 15. In the second group, fasting blood samples were collected on days 3, 4, 5, 6, 9, 12, 15, 18 and 21. Urine was collected for 2 h after the first morning void at baseline and on day 15. 25(OH)D2 plasma concentration was measured by ultra-performance liquid chromatography-tandem MS/MS and corrected for baseline. Biomarkers of vitamin D, Ca and P metabolism were measured at baseline and on day 15. The peak plasma concentration of 25(OH)D2 was 9·6 (sd 0·9) nmol/l at 4·4 (sd 1·8) h. The terminal slope of 25(OH)D2 disappearance was identified to commence from day 6. The terminal half-life of plasma 25(OH)D2 was 13·4 (sd 2·7) d. There were no significant differences in plasma 25(OH)D3, total 1,25(OH)2D, parathyroid hormone, P, Ca and ionised Ca and urinary Ca and P between baseline and day 15 and between the two groups. The present study provides data on the plasma response to oral 25(OH)D2 that will underpin and contribute to the further development of studies to investigate 25(OH)D half-life.

In-vivo nitric oxide synthesis is reduced in obese patients with metabolic syndrome: application of a novel stable isotopic method.

OBJECTIVES: Nitric oxide synthesis is declined in cardiovascular and metabolic diseases associated with endothelial dysfunction such as type 2 diabetes, hypertension or congestive heart failure. The objectives were to validate a novel stable isotopic method for the determination of in-vivo nitric oxide synthesis and to evaluate differences in nitric oxide synthesis in obese patients with and without metabolic syndrome (MetSyn). METHODS: The new method, called oral nitrate test (ONT), measured the decay in saliva or urine samples of an oral dose of labelled sodium nitrate. The ONT method was compared to a validated method (frequent sampling arginine test, FSAT method) in 10 healthy adult volunteers (BMI range = 20.8-27.3 kg/m). The accuracy of the saliva ONT method was then tested by measuring nitric oxide synthesis in seven healthy, normal weight individuals, seven obese patients without MetSyn and seven obese patients with MetSyn. RESULTS: The estimated rate of nitric oxide synthesis was 0.63 ±â€Š0.20 µmol/h per kg from the data obtained from saliva, and 0.50 ±â€Š0.14 µmol/h per kg from urine. The agreement of the saliva ONT method with the FSAT method (Δ = +0.02 ±â€Š0.24; P = 0.79) was superior to the urine ONT method (Δ = -0.11 ±â€Š0.20; P = 0.13). Obese patients with MetSyn had a significantly lower nitric oxide production rate (0.21 ±â€Š0.13 µmol/h per kg; P = 0.009) than healthy normal weight individuals (0.63 ±â€Š0.30 µmol/h per kg), whereas nitric oxide production rate was intermediate in obese patients without MetSyn (0.49 ±â€Š0.22 µmol/h per kg; P = 0.33). CONCLUSION: The advantages of the new saliva ONT method are its accuracy, sensitivity and lack of invasiveness, which could make it a reference method for the assessment of in-vivo rates of whole-body nitric oxide synthesis.

Variation in the FFAR1 gene modifies BMI, body composition and beta-cell function in overweight subjects: an exploratory analysis.

BACKGROUND: FFAR1 receptor is a long chain fatty acid G-protein coupled receptor which is expressed widely, but found in high density in the pancreas and central nervous system. It has been suggested that FFAR1 may play a role in insulin sensitivity, lipotoxicity and is associated with type 2 diabetes. Here we investigate the effect of three common SNPs of FFAR1 (rs2301151; rs16970264; rs1573611) on pancreatic function, BMI, body composition and plasma lipids. METHODOLOGY/PRINCIPAL FINDINGS: For this enquiry we used the baseline RISCK data, which provides a cohort of overweight subjects at increased cardiometabolic risk with detailed phenotyping. The key findings were SNPs of the FFAR1 gene region were associated with differences in body composition and lipids, and the effects of the 3 SNPs combined were cumulative on BMI, body composition and total cholesterol. The effects on BMI and body fat were predominantly mediated by rs1573611 (1.06 kg/m(2) higher (P = 0.009) BMI and 1.53% higher (P = 0.002) body fat per C allele). Differences in plasma lipids were also associated with the BMI-increasing allele of rs2301151 including higher total cholesterol (0.2 mmol/L per G allele, P = 0.01) and with the variant A allele of rs16970264 associated with lower total (0.3 mmol/L, P = 0.02) and LDL (0.2 mmol/L, P<0.05) cholesterol, but also with lower HDL-cholesterol (0.09 mmol/L, P<0.05) although the difference was not apparent when controlling for multiple testing. There were no statistically significant effects of the three SNPs on insulin sensitivity or beta cell function. However accumulated risk allele showed a lower beta cell function on increasing plasma fatty acids with a carbon chain greater than six. CONCLUSIONS/SIGNIFICANCE: Differences in body composition and lipids associated with common SNPs in the FFAR1 gene were apparently not mediated by changes in insulin sensitivity or beta-cell function.

Health, fitness, and responses to military training of officer cadets in a Gulf Cooperation Council country.

OBJECTIVE: To quantify the health, fitness, and physiological responses to military training of Officer Cadets from a Gulf Cooperation Council country. METHODS: One hundred and nineteen Officer Cadets volunteered; body composition, core body temperature, aerobic fitness, hydration status (urine osmolality), cardiovascular strain, physical activity (3-dimensional accelerometry), and energy expenditure (doubly labelled water) were measured over 5-days of Basic Training (BT), Army Training (AT), Navy Training (NT), and Air Force Training (AFT). RESULTS: There were no differences between courses for body mass index (mean all courses: 24.1 +/- 4.1 kg x m2) or peak core body temperature (mean all courses: 38.1 +/- 0.4 degrees C) (p > 0.05). AT body fat (19.8 +/- 3.6%) and BT VO2 max (36.8 +/- 11.6 mL x kg(-1) x min(-1)) were lower than the other courses (BT, 26.1 +/- 8.1; NT, 26.0 +/- 6.0; AFT, 24.7 +/- 6.1%) and (AT, 44.8 +/- 9.6; NT, 45.0 +/- 7.5; AFT, 44.6 +/- 5.2 mL x kg(-1) x min(-1)), respectively (p < 0.05). NT urine osmolality (979 +/- 90 mOsmol x kg(-1)) was similar to BT (946 +/- 181 mOsmol x kg(-1) p > 0.05) but lower in AT (868 +/- 144 mOsmol x kg(-1), p < 0.05) and AFT (883 +/- 121 mOsmol x kg(-1), p < 0.05). Cardiovascular strain during NT (22 +/- 5% HRR) was lower than other courses (range, 25 +/- 4-29 +/- 3% Heart Rate Reserve) (p < 0.05). Physical activity level during AFT (1.70 +/- 0.18 AU) was lower than other courses (range, 1.86 +/- 0.21-1.92 +/- 0.18 AU) (p > 0.05). CONCLUSION: Positive developments were apparent from BT leading into other courses. Potential exists to increase physical training volume on all courses, which may improve participants' aerobic fitness, body composition, and health.

Effect of changing the amount and type of fat and carbohydrate on insulin sensitivity and cardiovascular risk: the RISCK (Reading, Imperial, Surrey, Cambridge, and Kings) trial.

BACKGROUND: Insulin sensitivity (Si) is improved by weight loss and exercise, but the effects of the replacement of saturated fatty acids (SFAs) with monounsaturated fatty acids (MUFAs) or carbohydrates of high glycemic index (HGI) or low glycemic index (LGI) are uncertain. OBJECTIVE: We conducted a dietary intervention trial to study these effects in participants at risk of developing metabolic syndrome. DESIGN: We conducted a 5-center, parallel design, randomized controlled trial [RISCK (Reading, Imperial, Surrey, Cambridge, and Kings)]. The primary and secondary outcomes were changes in Si (measured by using an intravenous glucose tolerance test) and cardiovascular risk factors. Measurements were made after 4 wk of a high-SFA and HGI (HS/HGI) diet and after a 24-wk intervention with HS/HGI (reference), high-MUFA and HGI (HM/HGI), HM and LGI (HM/LGI), low-fat and HGI (LF/HGI), and LF and LGI (LF/LGI) diets. RESULTS: We analyzed data for 548 of 720 participants who were randomly assigned to treatment. The median Si was 2.7 × 10(-4) mL · µU(-1) · min(-1) (interquartile range: 2.0, 4.2 × 10(-4) mL · µU(-1) · min(-1)), and unadjusted mean percentage changes (95% CIs) after 24 wk treatment (P = 0.13) were as follows: for the HS/HGI group, -4% (-12.7%, 5.3%); for the HM/HGI group, 2.1% (-5.8%, 10.7%); for the HM/LGI group, -3.5% (-10.6%, 4.3%); for the LF/HGI group, -8.6% (-15.4%, -1.1%); and for the LF/LGI group, 9.9% (2.4%, 18.0%). Total cholesterol (TC), LDL cholesterol, and apolipoprotein B concentrations decreased with SFA reduction. Decreases in TC and LDL-cholesterol concentrations were greater with LGI. Fat reduction lowered HDL cholesterol and apolipoprotein A1 and B concentrations. CONCLUSIONS: This study did not support the hypothesis that isoenergetic replacement of SFAs with MUFAs or carbohydrates has a favorable effect on Si. Lowering GI enhanced reductions in TC and LDL-cholesterol concentrations in subjects, with tentative evidence of improvements in Si in the LF-treatment group. This trial was registered at clinicaltrials.gov as ISRCTN29111298.

The effect of different meals on the absorption of stable isotope-labelled phylloquinone.

Few studies have investigated the absorption of phylloquinone (vitamin K1). We recruited twelve healthy, non-obese adults. On each study day, fasted subjects took a capsule containing 20 microg of 13C-labelled phylloquinone with one of three meals, defined as convenience, cosmopolitan and animal-oriented, in a three-way crossover design. The meals were formulated from the characteristics of clusters identified in dietary pattern analysis of data from the National Diet and Nutrition Survey conducted in 2000-1. Plasma phylloquinone concentration and isotopic enrichment were measured over 8 h. Significantly more phylloquinone tracer was absorbed when consumed with the cosmopolitan and animal-oriented meals than with the convenience meal (P = 0.001 and 0.035, respectively). Estimates of the relative availability of phylloquinone from the meals were: convenience meal = 1.00; cosmopolitan meal = 0.31; animal-oriented meal = 0.23. Combining the tracer data with availability estimates for phylloquinone from the meals provides overall relative bioavailability values of convenience = 1.00, cosmopolitan = 0.46 and animal-oriented = 0.29. Stable isotopes provide a useful tool to investigate further the bioavailability of low doses of phylloquinone. Different meals can affect the absorption of free phylloquinone. The meal-based study design used in the present work provides an approach that reflects more closely the way foods are eaten in a free-living population.

Intramyocellular lipid levels are associated with peripheral, but not hepatic, insulin sensitivity in normal healthy subjects.

Increased levels of IMCL (intramyocellular lipid) have been shown to be associated with reduced steady-state glucose infusion rates during a hyperinsulinaemic-euglycaemic clamp (M-value). The aim of the present study was to explore how IMCL levels relate to the insulin-mediated suppression of endogenous glucose production [hepatic SI (insulin sensitivity)] and increase in glucose disposal (peripheral SI). In the present study, 11 healthy young adults (7 male, 4 female; aged 21-31 years) undertook, in random order, an hyperinsulinaemic-euglycaemic clamp combined with stable glucose isotope enrichment to measure peripheral and hepatic SI, a 1H-MRS (proton-magnetic resonance spectroscopy) scan to determine IMCL levels and a DXA (dual-energy X-ray absorptiometry) scan to assess body composition. IMCL levels (range, 3.2-10.7) were associated with whole-body fat mass (r=0.787, P=0.004), fat mass corrected for height (r=0.822, P=0.002) and percentage of central fat mass (r=0.694, P=0.02), but were not related to whole-body FFM (fat-free mass; r=-0.472, P=0.1). IMCL levels correlated closely with the M-value (r=-0.727, P=0.01) and FFM-corrected peripheral SI (r=-0.675, P=0.02), but were not related to hepatic SI adjusted for body weight (r=0.08, P=0.8). The results of the present study suggest that IMCL accumulation may be a sensitive marker for attenuations in peripheral, but not hepatic, SI in normal populations. Given the close relationship of IMCL levels to whole-body and central abdominal fat mass, relative increases in the flux of lipids from adipose tissue to the intramyocellular compartment may be an integral part of the mechanisms underlying reductions in SI.