SALivAry biomarkers of MediterraneAN Diet associated with long-tERm protection against type 2 diabetes mellitus
Background and aim
The SALAMANDER project aimed at defining salivary signatures indicative of healthy dietary choices (adherence to a Mediterranean diet: MeDi) with a positive long-term health outcome (protection against type 2 diabetes: T2DM).
In a discovery phase, 214 subjects were selected in two cohorts of elderly people (3-C Bordeaux in France, Seniors-ENRICA in Spain) following a case-control design (cases: T2DM). Saliva samples were obtained and their microbiome, metabolome and proteome compositions were analyzed by 1H-NMR, 16SrRNA gene analyses and nano-LC MS/MS, respectively. This generated three datasets of 78 metabolites, 450 unique amplicon sequence variants and 246 proteins. Each dataset was first analyzed separately. There were differences in microbial diversity with some food groups defining MeDi. For example, subjects who ate more butter showed increased alpha diversity and differences in the presence of some genera including Prevotella, Porphyrmonas and Fusobacterium. Eating more vegetables resulted in a lower presence of Porphyrmonas, Peptostreptococcaceae and Saccharibacteria. For proteome, three food groups were explained by a model comprising proteins: eating vegetables (cohort + 5 proteins), butter (cohort + 4 proteins) and sweets & pastries (diabetic status, sex + 2 proteins).
The datasets of the discovery phase were also analyzed jointly. The microbiome and metabolome datasets shared much information: 60% of the variability in metabolome was explained by microbiome. In contrast, proteome was largely independent of microbiome (<10% of the variability in proteome explained by microbiome). Biomarkers of T2DM were sought in each cohort separately and in a meta-analysis : 5 proteins, ethanol and Coriobacteriia were significantly different between cases and controls. Interestingly, two of the proteins (Q96DA0, Q96DR5) were also significantly different between high and low consumers of butter.
As a validation, 121 new Seniors-ENRICA participants were selected. 116 saliva samples were obtained and analyzed with the same methods as in the discovery phase for microbiome and proteome. Ethanol concentration was also measured. Overall, none of the T2DM biomarker candidates identified in the discovery phase (5 proteins, ethanol, Coriobacteriia) were confirmed. Only one protein was near significance both in the meta-analysis of the discovery phase and in the validation phase (gene CTBS).
The validation phase nonetheless provided interesting results. It first confirmed that variability in microbiome did not explain variability in proteome. Second, there were statistically significant differences in both alpha and beta diversities between participants who visit the dentist frequently (at least once a year) or not. This was particulary true for T2DM patients.
Overall, it was not possible to identify a signature of T2DM across both a discovery and a validation phase. However, the results strongly suggest that saliva reflects some aspects of usual diet.
First, the saliva proteome analytical conditions were systematically optimized and the results have been presented in a scientific congress. This optimized method may serve as a reference in future research on salivary biomarkers.
Second, the identification of a multimarker signature of “healthy nutrition” (especially consumption levels of vegetables, butter and sweets & pastries) may be a useful addition to ‘personalized healthcare’ planning and offers the longer-term prospect of developing a point-of-care objective tool, that can be used to influence an individual experience by encouraging healthy nutrition or a change in diet and lifestyle. This tool would be useful for physicians and carers.
Since the project is focused on a non-invasively obtained fluid, it is realistic that a device can be ultimately designed for at-home self-use . This development is clearly beyond the scope of SALAMANDER. Nevertheless, there is likely a market for this “healthy nutrition” monitoring device, among consumers who have health-conscious eating habits. Additionally, it would be used as a motivation tool for subjects who have been advised for medical or quality-of-life reasons to improve their dietary habits.
|Université de Bordeaux
|King's College London
|Universidad Autonoma de Madrid
In view of identifying biomarkers of diet and health, we analyzed the microbiome, metabolome and proteome of saliva samples. Two key findings should be pointed out :
- Coordination between the three omics studied was evaluated. We found coordinated profiles of saliva microbiome and metabolome : how individuals are grouped is quite similar considering the profile of either saliva microbiome or metabolome. In contrast, saliva proteome has little information shared with the other two omics. This suggests that identification of biomarkers in saliva may benefit from the combined analysis of proteome on one hand and microbiome or metabolome on the other hand, since these two groups convey complementary information.
- The microbiome diversity and proteome composition were altered by the usual consumption of specific food groups such as vegetables or butter & cream. Although this should be confirmed, this opens the way of utilizing saliva (an easily accessible biofluid) as a source of objective markers of usual diet.
Author: Proctor GB, André P, Lopez-Garcia E , Gomez Cabrero Lopez D, Neyraud E, Feart C, Rodriguez Artalejo F, García García-Esquinas E & Morzel M
Author: André P, Proctor G, Driollet B, Garcia-Esquinas E, Lopez-Garcia E, Gomez-Cabrero D, Neyraud E, Rodriguez-Artalejo F, Morzel M & Féart C.
The SALAMANDER project aimed at defining salivary signatures indicative of healthy dietary choices (adherence to a Mediterranean diet : MeDi) with a positive long-term health outcome (protection against type 2 diabetes: T2DM).
Saliva microbiome, metabolome and proteome datasets were used to identify markers of T2DM. A key finding is that some protein marker candidates of T2DM were also significantly linked to the usual consumption of some food groups (vegetables and butter in particular). However, the validation data did not confirm the validity of biomarkers of T2DM.
It was also not possible to find a salivary signature linked to a global score translating adherence to the Mediterranean diet (MEDAS score), but in the discovery phase of the project, we identified microbiome and proteome markers indicative of usual consumption of some food groups (vegetables, butter, sweets & pastries). These were valid in our study sample (seniors in two European countries). This finding should be confirmed in our own validation data first, and in other studies. This would open the way of utilizing saliva (an easily accessible biofluid) as a source of objective markers of usual diet.