Personalized microbial substrates to prevent type 2 diabetes

Evidence is increasing that the gut microbiota is a key player in the aetiology
of insulin resistance and type 2 diabetes mellitus (T2DM). The gut microbiota
is able to transform fermentable dietary fibres into short-chain fatty acids
(SCFA). In previous clinical trials we demonstrated that acute distal colonic
SCFA infusions resulted in increased energy expenditure, fat oxidation and
satiety hormones, and decreased inflammatory markers and lipolysis in men.
These results suggest a beneficial role of increased distal colonic SCFA in
insulin sensitivity. A straightforward approach to translate these promising
SCFA-related acute effects into long-term metabolic benefits would be the
supplementation of specific fermentable fibres. However, well-controlled
long-term human studies supplementing one specific fibre (e.g.
galacto-oligosaccharides (GOS), fructo-oligosaccharides (FOS)) failed to show
enhanced microbial SCFA production and did not induce beneficial metabolic
effects.
From these studies, it can be concluded that the lack of metabolic effects is
mainly caused by (1) the stimulation of only few specific bacteria genera,
thereby decreasing the abundance of other essential SCFA-producing microbes,
and (2) the lack of these studies to take into account the individual*s initial
microbiome and its capacity to produce SCFA.
Therefore, in this project we hypothesize
(1) that a mixture of fermentable fibres, which differ in degree of
polymerization and side chains, will stimulate a broad range of SCFA-producing
bacterial genera, resulting in enhanced chronic SCFA production with a large
variation between individuals; (2) that providing personalized fibre mixtures,
selected based on the individuals* initial microbial capacity for SCFA
production, is crucial to successfully improve host insulin sensitivity and
metabolic health.

In this project we intends to study the therapeutic potential of a personalized
fibre mixture in individuals at high risk of developing T2DM, and aims to
address the following key objectives:
1. To investigate whether a mixture of fermentable fibres, which differ in DP
and side chains, will stimulate a broad range of SCFA-producing bacterial
genera, resulting in enhanced chronic SCFA production throughout the whole
colon with a large variation between individuals;
2. To unravel whether providing personalized fibre mixtures, selected based on
the individuals* initial microbiota and capacity for SCFA production is crucial
to successfully improve host insulin sensitivity and metabolic health

Double blind, controlled, randomized, parallel design.

First, a fibre mixture that yields the highest amounts of SCFA in the distal
colon will be determined for each individual in the in vitro model. Food-grade
fibres will be used, which allows me to apply them directly in the human in
vivo study. In total 4 fibre mixtures will be tested for each individual
microbiota. The fibre mixtures will be a combination of 3 fibres that differ in
DP and branching (each 4 g). Each fibre mixture will include a rapidly
fermentable oligosaccharide (FOS or GOS), a more complex fibre (resistant
starches (RS2)) and slowly fermentable, high DP fibres pectin, corn bran
arabinoxylans). The 4 fibre mixtures will contain:
1. 4 g FOS + 4 g RS2 + 4 g pectin
2. 4 g GOS + 4 g RS2 + 4 g pectin
3. 4 g FOS + 4 g RS2 + 4 g corn bran arabinoxylans
4. 4 g GOS + 4 g RS2 + 4 g corn bran arabinoxylans
The individual fibre mixture will then be provided to 22 participants who will
receive in the first two weeks of the intervention period 12 g of the fibre
mixture daily and thereafter for ten weeks 24 g daily. The control group will
receive in the first two weeks 12 g GOS daily and in the last 10 weeks 24 g GOS
daily.

All participants will be screened before participation and thereby receive
information about their health status. In the future there can be general
health benefits for the public. Participants receiving the personalized dietary
fibers may have personal health benefits if intervention effects are according
to expectations. The general interest of this study is to investigate how
manipulating the gut microbiota, increasing SCFA production and shifting
colonic SCFA ratios by the intake of dietary fiber mixtures will influence
human peripheral insulin sensitivity and substrate and energy metabolism.
Burdens that volunteers can experience, such as the time spent with the
study (participants will have to invest approximately 14.5 hours in the study,
divided among 2 clinical investigation days (CIDs) interim visits for feces
collection and questionnaires and a screening visit (see for an overview table
1 and figure 1)). In addition, the participants will fill in diet and physical
activity records and will fill in with an intake record of the supplements,
which are also time consuming. Also the collection of faecal samples can be
experienced as a burden, because they have to handle them themselves and have
to store them at home. Also the 12-week intake of the dietary fiber can be seen
as a burden for the participants.
During the CIDs, blood will be collected via a venous catheter.
Venepunctures can occasionally cause a local hematoma or bruise to occur. Some
participants report pain during venepuncture. During CID 1 and 2 the total
amount of blood sampled is 140 ml per CID, totaling 315 ml (35ml screening)
during the whole test period. During CID 1 and 2, adipose tissue and skeletal
muscle biopsies will be taken. The adipose tissue biopsy might cause local
hematoma as well. After the muscle biopsy, some participants report pain, which
is experienced as muscle pain. More often the muscle feels stiff for a couple
of days after the biopsy. To minimize the risk for a hematoma, the biopsy place
will be compressed for approximately 5 minutes after biopsy. The place of
incision will leave a small scar (* 3 mm for adipose tissue biopsy and * 8 mm
for skeletal muscle biopsy). To promote good wound healing, the incision will
be sealed with sterile steristrips and a waterproof band-aid. The site of the
muscle biopsy will, in addition, be sealed with a compression bandage. During
the hyperinsulinaemic-euglycemic clamp there is a small risk of hypo- or
hyperglycemia. However, from our own extensive experience, these conditions do
not occur very often and can be reversed immediately. A medical doctor is
always available during the clamp. In addition, participants will undergo for
two times a DEXA scan. Thereby, they will receive a radiation of circa 20
microSievert (calculated by Radiation Experts, Randwyck, Maastricht). The
average doses of each person in the Netherlands is 2,5 miliSievert per year
(thus a factor 125 higher), therefore the risk of the radiation is considered
negligible.