Randomized placebo-controlled pilot study to determine the effect of probiotics on vitamin K status in renal transplant recipients

Since its discovery in 1929, vitamin K has been primarily considered for its
role as a coagulation cofactor, but the last decades it became clear that
vitamin K insufficiency plays a significant role in cardiovascular health as
well as in bone health. Vitamin K insufficiency is highly prevalent in the
Western general population, particularly in older individuals and in certain
patient groups, including patients with type 2 diabetes and kidney disease.
With respect to the latter patient group, we have found that more than 90% of
renal transplant recipients have a vitamin K deficiency independent of adequate
dietary intake, which likely adds to the very high rate of cardiovascular
events and high frequency of osteopenic fractures in these patients. Also, we
recently found that renal transplant recipients suffer from gut microbial
dysbiosis, which might contribute to an impaired vitamin K status. Vitamin K is
a fat-soluble vitamin, present in two forms in our diet, namely phylloquinone
(vitamin K1), which is mainly provided by green leafy vegetables and
menaquinone (vitamin K2), mainly provided by fermented food such as cheese,
yoghurt and buttermilk. In addition to dietary sources, vitamin K2 is produced
by gut bacteria. Recently it has been discovered that certain probiotic strains
that are already on the market have the ability to produce vitamin K2 in vitro.
These probiotics are currently approved as over-the-counter supplements and are
safe according to EFSA. We aim to administer probiotic formulations with
vitamin K2-producing bacteria to renal transplant recipients to investigate
whether this improves vitamin K status. The aim of the project is to better
understand the potential of these newly developed formulations in vivo, by
assessing whether vitamin K production can be stimulated by probiotic bacteria
in renal transplant recipients. This probiotic has the potential to improve
vitamin K status, gut health in general and improve cardiovascular and bone
health.

To investigate the effect of a daily sachet of probiotics for 12 weeks vs
placebo on vitamin K status in renal transplant recipients.

This intervention study is a double-blind, randomized, placebo-controlled pilot
study. During 12 weeks, participants will either take a probiotic or a placebo.
Participants will be randomized into two equal groups, of which one group will
receive a probiotic with bacteria that produce vitamin K2. The duration of the
present study is 12 weeks, study visits will take place at baseline, after 6
weeks and after 12 weeks.

Participants will take one dose of oral probiotic or placebo daily for 12
weeks. The daily dose will consist of 1 sachet of 4 gram probiotics or placebo
per day dissolved in 200 ml luke warm water.

Before the start of the study, subjects will attend the research facilities for
a screening visit. During this visit, anthropometric measurements (weight,
length, body mass index) will be performed and blood pressure will be
determined. For the study, 3 visits to the UMCG will take a total time of 3
hours. Before each test day, 24-hour urine samples and faecal samples will be
collected. After 6 and 12 weeks, measurements will be repeated. No direct
health benefit for the participants is expected. Subjects assigned to active
treatment will receive probiotics with strains that are thoroughly tested and
are currently approved as over-the-counter supplements and safe according to
EFSA. The probiotics can induce changes in bowel frequency and bowel movement,
which will likely stabilize after 2 weeks. At each visit a total amount of up
to 18 ml blood will be collected by means of vena puncture. Vena puncture can
cause discomfort and can result in bruising that continues up to a few days
after the examinations. Also during the visits, participants will hand in a
24-hour urine collection and a frozen stool sample. Participants gain no
individual benefit from their participation in the study. The study will
provide pilot data for the design of a larger intervention study, which is
expected to contribute to reducing the high prevalence of vitamin K deficiency
and thereby the high burden of cardiovascular disease and osteopenic fractures
in renal transplant recipients.