The effects of nutritional supplements on postprandial nitric oxide bioactivity in abdominally obese men

Obese people have a disturbed postprandial metabolism and thereby a decreased
postprandial vascular function. Nitric oxide plays an important role in the
postprandial vascular function. Multiple studies already focused on various
nutritional compounds to improve the postprandial vascular function by
increasing the nitric oxide bioactivity. However, the vast majority of the
trials has been performed with relatively high doses of the individual
components, which are problematic to convert into daily food measures, thereby
preventing translation of these findings. Well-designed trails studying the
effect of feasible amounts of nutritional supplements on the bioactivity of
nitric oxide and vascular function are missing.

The primary objective of the proposed study is to evaluate the effect of the
high dose or L-arginine (3.0 gram) and a lower dose of L-arginine (1.5 gram)
compared with a placebo supplement on postprandial vascular function, assessed
by brachial artery flow-mediated vasodilation (FMD), in abdominally obese male
volunteers. Secondary objectives are to examine postprandial effects on retinal
vascular function, plasma cGMP (as indicator of nitric oxide bioactivity),
plasma markers for low-grade systemic inflammation and endothelial dysfunction,
blood pressure, and serum lipid and plasma glucose metabolism.

The proposed study will have a randomized, double-blind cross-over design. The
total study duration will be at least 8 weeks, including one baseline test day
and five experimental test days, each separated by a washout period of at least
1 week.

At the start of the study, the participants will have a baseline test day. On
this test day, the subjects will only receive a high fat milkshake and the 3
hours after ingestion of the milkshake will be studied. After completion of the
baseline test day the subjects will take a daily supplement with co-factors
(i.e. vitamins and minerals) for the entire study period. After 4 weeks, the
participants will start with the five experimental test days, each separated
with at least one week. On the five experimental test days, the subjects will
receive in random order one of the five interventional products and a high fat
milkshake. The postprandial response of the ingestion of the interventional
product and the high fat milkshake will be studied for 4 hours. The five
interventional products are: (1) co-factors*, (2) co-factors, 0.2 g nitrate and
1.2 mg nitrite, (3) co-factors, 0.2 g nitrate, 1.2 mg nitrite and 0.8 g
L-arginine, (4) co-factors, 0.2 g nitrate, 1.2 mg nitrite and 1.5 g L-arginine,
(5) co-factors and 3.0 g L-arginine.

* Co-factors: a supplement containing vitamins and minerals in a dose lower
than the Recommended Daily Intake. This subjects will take this supplement with
co-factors during the complete study period (after the baseline test day till
the final experimental test day).

Subjects will be screened to determine eligibility during one visit of 15
minutes. During these screening visits, anthropometric measurements will be
performed and blood pressure will be determined. In addition, a venous blood
sample (5.5 mL) will be drawn. Subjects will take a daily supplement with
vitamins and minerals during the complete study period. During the study there
will be five experimental test days in which subjects receive in random order
one of the five interventional products ((1) co-factors, (2) co-factors, 0.2 g
nitrate and 1.2 mg nitrite, (3) co-factors, 0.2 g nitrate, 1.2 mg nitrite and
0.8 g L-arginine, (4) co-factors, 0.2 g nitrate, 1.2 mg nitrite and 1.5 g
L-arginine, (5) co-factors and 3.0 g L-arginine). At the start of the study
there will be a baseline test day in which the subjects only receive a high fat
milkshake. No direct health benefit for the study participants is expected.
Investigational products are safe and all ingredients to prepare the high fat
milkshake are commercially available and approved for human consumption. There
are no side effects for the investigation products or the high fat milkshake.
On the baseline test day and the five experimental test days a postprandial
test will take place and blood will be sampled (6 x 76.0 mL with an interval of
at least one week inter-between). During the 3-hour postprandial period,
participants are allowed to drink one glass of water and are free to
walk-around. Some study subjects may report pain during venipuncture. Insertion
of the cannula can cause some discomfort and possible a hematoma or bruise.
Some men may also report pain during the insertion of the cannula. Vascular
measurements will be performed before and two hours after meal intake. These
measurements are routine and are not expected to lead to physical side effects.
Time investment for the participants is approximately 24 hours, excluding
travel time.