In recent years, the existence of a wheat-related disorder, in patients who do not suffer from celiac disease (CD) or wheat allergy (WA), has been definitively ascertained and defined as non-celiac wheat sensitivity (NCWS). Its prevalence in the general population is unknown but self-reported NCWS is around 10%. Conflicting data have been reported about the underlying physiopathology. It has been known for years how exposure to gliadin, both in CD and in healthy patients (albeit with reduced levels in the latter), is able to alter intestinal permeability acting on zonulin release and signalling mechanisms. More recently, it has been shown that wheat has high concentrations of wheat amylase-trypsin inhibitors (ATIs), proteins able to activate innate immunity via toll-like receptor-4 (TLR-4) on myeloid cells. Orally ingested ATIs increase intestinal inflammation by activating gut and mesenteric lymphnode myeloid cells.~An increasing number of data have shown that patients with NCWS could have an association with autoimmune diseases, including thyroiditis, undifferentiated connective tissue disease, psoriatic arthritis, spondylarthritis, and Sjogren's syndrome (SS).~SS is an autoimmune disease characterized by an infiltrate of mononuclear cells, mainly lymphocytes, in the exocrine glands, especially the salivary and lacrimal glands. Some preliminary data suggested that a GFD can reduce sialadenitis and increase salivary flow in SS and CD patients. Furthermore, some SS patients have an inflammatory response (release of nitric oxide) to a rectal gluten challenge.~Based on these evidences, as well as on the ability of gluten/wheat to increase intestinal permeability, altering zonulin mechanisms of regulation and signalling, and the ability of some of its components (ATIs, but not only) to activate a local inflammatory response, it could be hypothesized that gluten/wheat may represents one of the pathogenetic environmental factors of SS and that its intake may be able to worsen symptoms in affected patients. In our hypothesis, exposure to gluten/wheat would cause a release of zonulin, which, binding to the surface of the intestinal epithelial cells, is able to modify cell cytoskeleton and to cause the loss of normal occludins function, ultimately leading to an increased monolayer permeability. This increase in permeability would result in greater exposure of the immune system cells to gluten/wheat molecules via activation of TLR-4, with an increase in the infiltration and activation of myeloid cells in the intestinal mucosa and an augmented activity of lymphnode dendritic cells. Such local inflammatory response would have systemic repercussions with alteration of normal cytokine pattern and infiltration of monocytes/macrophages and T cells in the salivary and lacrimal glands, thus being able to contribute, as an environmental factor, to the onset and exacerbation of the clinical manifestations of SS.~Therefore, the investigators hypothesize that a wheat-free diet (WFD) can reduce the inflammatory state and ameliorate the clinical symptoms in SS patients. This hypothesis will be evaluated in both SS patients with associate GI symptoms and in those without GI symptoms. The successive clinical and immunologic reaction to the re-exposure to wheat ingestion, performed by an open challenge, will be also evaluated to confirm a wheat-dependent mechanism and to understand the underlining mechanisms. The project results will provide data about a possible therapeutic role of a WFD in SS and will improve the knowledges about the axis between the intestinal permeability and the systemic inflammation in SS.~More specifically, the investigators aim to:~identify the prevalence of self-reported NCWS in SS patients;~assess the overall effect that a WFD plus cow's milk products free diet (CMPFD) determines in symptoms control of the patients affected with SS; the investigators decided to include a CMPFD in association with a WFD because, according to several authors, including our previous studies, NCWS, and more generally gluten-related disorders, are often associated with multiple foods intolerance, first of all cow's milk products intolerance;~evaluate, by an open wheat challenge, the real frequency of a coexistent NCWS condition;~assess the possible role played by wheat ingestion in the pathogenesis and molecular mechanisms of SS and NCWS by analysing the variation of intestinal permeability and gut microbiota, in association with cytokines and lymphocytes pattern typical of SS.
Recent data show that some foods can increase intestinal mucosa permeability and immune activation of subjects with gastrointestinal (GI) symptoms. Wheat seems the most frequent food which activates this inflammatory response and can cause both GI and extra-intestinal symptoms. Patients suffering from wheat-related troubles, in absence of celiac disease diagnosis, can suffer from non-celiac wheat sensitivity (NCWS) and our previous studies showed that about 25% of them are also affected by autoimmune diseases (AD). A gluten-free diet (GFD) can influence inflammatory pattern of AD, including Sjogren's syndrome (SS). Thus, the investigators would enquire if SS patients may also suffer from NCWS and how a wheat-free diet (WFD) modifies their clinical features, and inflammatory and cytokine pattern. The investigators will also assess how wheat reintroduction, by an open challenge, modifies their clinical parameters, intestinal permeability, and both local and systemic inflammatory response.