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.

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.

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.