Acute effects of dietary proteins, that differ in amino acid composition, on blood pressure-related mechanisms

There is growing evidence for a beneficial effect of dietary protein on BP. We
previously showed that intake of a mixture of four proteins reduced BP compared
to maltodextrin intake, and induced postprandial vasodilation and changes in
markers of endothelial function. It is hypothesized that the individual protein
sources of the mixture might differentially influence postprandial
vasodilation, the factors that might be responsible for these differences, and
vascular function parameters due to differences in amino acid composition. In
addition, we found that postprandial and 24-hour urinary sodium excretion were
lower after protein intake compared to maltodextrin intake. This in
contradiction with findings in published literature.

The primary objective is to investigate if there are differences in the acute
postprandial vasodilating effect between different protein sources and if these
differences are associated with differences in the responses of vasodilating
factors. Secondary objectives are to investigate (1) if there are differences
in postprandial vascular function changes and renal sodium excretion between
different protein sources, (2) if there are differences in the acute
postprandial vasodilating effect, response of vasodilating factors, renal
sodium excretion and vascular function changes between these proteins and
maltodextrin, and (3) if there are differences in the acute postprandial
vasodilating effect, response of vasodilating factors, renal sodium excretion
and vascular function changes between maltodextrin and sucrose, another source
of carbohydrate.

The study has a double-blind randomized 6-arm cross-over design. The total
study period comprises 8 weeks consisting of a 2-week run-in period, followed
by a 6-week treatment period. Subjects will be randomized to one of 6 treatment
orders at the end of the run-in period if they meet the inclusion criteria with
respect to BP. Treatments consist of a single dosage of a protein or
carbohydrate and will be separated by a wash-out of at least 1 week.

During the 8 week study period, dietary intake of the subjects will be
standardized with respect to macronutrient composition (15% protein, 30% fat
(<10% saturated fat), 55% carbohydrates (recommended diet according to the
Dutch Health Council, 2006)). All foods will be provided to the subjects the
day before each of the 6 clinical investigation days (CID*s). During the CID*s
subjects receive a supplement in liquid form containing 0.6 gram protein per
kilogram body weight or an isocaloric amount of carbohydrate for breakfast.
Measurements of hemodynamics and vascular function will be performed and venous
blood samples will be collected at regular time intervals before breakfast and
over a 4-hour postprandial period.

The total study period comprises 8 weeks with a total of 8 visits and 6 CID*s.
A total of 80 ml blood will be taken on each CID. Urine will be collected over
the 4-hour postprandial period. No harm from the dietary intervention is to be
expected. All supplements used during this study are cleared for human use and
are prepared according to GMP regulations. The administration of the amount of
0.6 gram protein per kilogram body weight for breakfast will not have any
health risks and is performed previously without any side effects in the study
of Claessens et al. The amount of 0.6 gram per kilogram body weight for
breakfast is within the range of the RDA of proteins according to the WHO. All
measurements will be executed by trained personnel. The use of cuffs during
different measurements can feel uncomfortable but is only for a short period of
time and not harmful. Placement of catheters may be associated with some
bruising.