α-Amylase in Vaginal Fluid: Association With Conditions Favorable to Dominance of Lactobacillus

Abstract

Vaginal glycogen is degraded by host α-amylase and then converted to lactic acid by Lactobacilli. This maintains the vaginal pH at ≤4.5 and prevents growth of other bacteria. Therefore, host α-amylase activity may promote dominance of Lactobacilli. We evaluated whether the α-amylase level in vaginal fluid is altered in women with bacterial vaginosis (BV) and vulvovaginal candidiasis (VVC) and whether its concentration was associated with levels of lactic acid isomers and host mediators. Vaginal fluid was obtained from 43 women with BV, 50 women with VVC, and 62 women with no vulvovaginal disorders. Vaginal fluid concentrations of α-amylase, secretory leukocyte protease inhibitor (SLPI), hyaluronan, hyaluronidase-1, β-defensin, and elafin were measured by enzyme-linked immunosorbent assay (ELISA). Vaginal concentrations of neutrophil gelatinase-associated lipocalin (NGAL), matrix metalloproteinase (MMP) 8, and d- and l-lactic acid levels in these patients were previously reported. The median vaginal fluid α-amylase level was 1.83 mU/mL in control women, 1.45 mU/mL in women with VVC, and 1.07 mU/mL in women with BV. Vaginal levels of α-amylase were correlated with d-lactic acid (P = .003) but not with l-lactic acid (P > .05) and with SLPI (P < .001), hyaluronidase-1 (P < .001), NGAL (P = .001), and MMP-8 (P = .005). The exfoliation of glycogen-rich epithelial cells into the vaginal lumen by hyaluronidase-1 and MMP-8 may increase glycogen availability and promote α-amylase activity. The subsequent enhanced availability of glycogen breakdown products would favor proliferation of Lactobacilli, the primary producers of d-lactic acid in the vagina. Concomitant production of NGAL and SLPI would retard growth of BV-related bacteria.

Keywords: Lactobacilli; bacterial vaginosis; lactic acid; vaginal fluid; vulvovaginal candidiasis; α-amylase.