The effects of plant sterols and stanol on cytokine production by mononucleair blood cells isolated out of blood from asthma patients

Western diets provide daily about 160 to 460 mg dietary plant sterols, of which
campesterol, sitosterol and stigmasterol are the most common [1]. Plant stanols
are the saturated derivatives of plant sterols. These sterols and stanols are
structurally related to cholesterol, but have a different side-chain
configuration. Additionally, plant stanols are lacking the double bond at C-5.
Due to this structural similarity, these compounds lower intestinal cholesterol
absorption. Although this reduction in cholesterol absorption induces
endogenous cholesterol synthesis, the overall effect is that diets enriched
with plant sterol or stanol esters lower fasting serum low-density lipoprotein
(LDL) cholesterol concentrations [2]. These effects have been found in many
patient groups (e.g. slightly hypercholesterolemic people, subjects treated
with statins, patients with familial hypercholesterolemia, and diabetic
subjects), and do hardly depend on the composition of the food matrix or
background [3]. As both plant sterol and stanol esters are generally recognized
as safe (GRAS), these dietary agents have therefore a great potential in the
prevention of coronary heart disease. In fact, functional foods enriched with
plant sterol or stanol esters are nowadays widely available for the general
population in many European countries, the U.S.A. and Australia.

Till now, there is little evidence for plant sterols and stanol effects other
than improving lipid profiles. However, we have very recently found strong
indications in ex vivo models using isolated human peripheral mononuclear blood
cells (PBMCs) from healthy volunteers that plant sterols and stanols have the
capacity to improve immune function. More into detail, plant stanols shifted
the differentiation of naive T-cells into the Th1 direction. In our hands, this
effect was mediated via activating a specific receptor present on the Antigen
presenting cells (APCs) and T-cells both present in the PBMC mixtures. These in
vitro effects are in line with findings presented in the literature in mouse
models (4) and in human HIV patients (5). However, mice are not men and the
study in HIV patients is not a real valid model since the cytokines used to
determine the Th1/Th2 balance are in fact produced by CD4+ T-helper cells which
are almost completely absent in HIV patients. Therefore, this finding needs to
be confirmed in other patient groups, just like HIV patients characterized by a
th2 skewing based on their cytokine profiles. Asthma is a typical example of a
disease characterized by th2 skewing which in theory could benefit from Th1
activation to restore the th1/Th2 balance. However before starting a
well-controlled intervention study providing plant sterol or stanol ester based
products to asthma patients we here describe a pilot experiment to show that
(1) asthma patients are indeed characterized by a th2 skewing, (2) that their
PBMCs respond towards plant sterols or stanols by a th1 skewing and (3) we will
compare different outcome parameters to find the parameters that is most
responsive in this respect. We will use this parameter in an upcomming
intervention study, which is now in development.
If true, the effect of plant sterols or stanols might ultimately be helpful in
other situations in which the Th1/Th2 helper cell balance is disturbed into a
Th2 over-responsiveness. By activating the Th1 response, the disturbed balance
may be restored. This is for example a possibility in the treatment or
prevention of asthma, food allergies or HIV in susceptible subjects.

The major research objectives are (1) to prove that PBMCs isolated from asthma
patients are indeed characterized by a Th2 phenotype and (2) that this
disturbed balance can be restored by adding plant sterols or stanols during in
vitro culturing and stimulation, and (3) which cytokine is most sensitive in
this response.

A pilot study using PBMCs isolated from 10 asthma patients and 10 matched
controls. These cells will be cultured in vitro with and without plant sterols
/ stanols and cytokines produced will be evaluated. This will be done twice
with 4 weeks interval to obtain information regarding reproducibility of the
disturbed Th2 shift in asthma patients, the responsiveness of the PBMCs from
these patients for plant sterols / stanols and the most sensitive parameter to
evaluate this.

During the study, 2 blood samples (each 20 mL) will be taken. Total time
investment for the subjects will be 80 min. Occasionally, a heamatoma or bruise
can occur during venepuncture. The results of this study will show whether
plant sterols and stanols have the capacity - at least in vitro - to restore
the disturbed th1/Th2 balance seen in asthma patients. The ultimate aim is to
test this effect - if present in this in vitro study - in an in vivo
intervention study in asthma patients, which is however not part of this
proposal.