Gender-associated differences in oral microbiota and salivary biochemical parameters in response to feeding

Saliva plays a key role in food absorption and digestion mainly due to both its enzymes and microbiota. The main objective of this study was to compare the oral microbiota and salivary parameters between men and women in response to feeding. To answer this question, we set up a pilot study on 10 male and 10 female subjects to examine the role of saliva in glycaemia physiology. Biological parameters and the microbiotal composition of saliva were analyzed in fasted and fed states. The results show that the level of blood glucose was not different between men and women in the fasted state (88.00 mg/dL ± 6.38 vs 87.00 mg/dL ±8.07, p = 0.9149) or in the fed state (102.44 mg/dL ± 14.03 vs 116.9 mg/dL ± 25, p = 0.1362). Free fatty acids (FFA 0.15 mmol/L ± 0.15 vs 0.07 mmol/L ± 0.07, p = 0,0078), cholesterol (0.53 mmol/L ± 0.30 vs 0.15 mmol/L ± 0.14, p < 0.0001), and total saliva proteins (13.2 g/L ± 4.31 vs 9.02 g/L ± 6.98, p = 0.0168) were decreased after feeding, as well as the saliva lipase (27.89 U/L ± 25.7 vs 12.28 U/L ± 4.85, p = 0.0126). A very significant increase in the relative abundance of Streptococcaceae (24.56 ± 9.32 vs 13.53 ± 7.47, p = 0.00055) and a decrease in Prevotellaceae (34.45 ± 9.30 vs 17.43 ± 9.03, p = 0.00055) were observed in the fed condition. When investigating gender-related differences in the fasted state, men showed higher levels of cholesterol (0.71 mmol/L ± 0.26 vs 0.40 mmol/L ± 0.27, p = 0.0329), FFA (0.25 mmol/L ± 0.18 vs 0.08 mmol/L ± 0.06, p = 0.0049), and triglycerides (0.24 mmol/L ± 0.15 vs 0.09 mmol/L ± 0.04, p = 0.006) than women. Finally, differences could be observed in saliva microbiota between men and women in the fasted condition but even more in the fed condition, where Porphyromonas and Capnocytophaga were overrepresented in the male salivary samples compared with female saliva. Thus, biological parameters and microbiota in saliva could be the signatures of the feeding conditions and sex gender status.