With the
increase in average life expectancy of women worldwide, it is estimated that 1.2
billion women will be menopausal or postmenopausal by the year 2030. About 85%
of whom will experience at-least one menopausal symptom in lifetime. In US
alone about 40 to 50 million women are estimated to suffer from vasomotor
symptoms.
A recent
review published in the forthcoming issue of Maturitas, The European menopause Journal compares the
changes in vaginal microbiome with approaching menopause, the role of
hormone replacement therapy in vaginal bacterial community and role of probiotics in reinstating the homeostasis.
The vaginal
microbiome plays an important role in women’s life, right from puberty to
menopause. The diversity, abundance and composition of the microbial species in
vagina varies dramatically. One of the original NIH-funded Human MicrobiomeProject (HMP) targeted sites for characterization of the microbiota was the
vagina.
The
relationship between the vaginal microbiome and menopause occurs predominantly
through estrogen. During reproductive years, production of lactic acid and
hydrogen peroxide by lactobacilli help maintain a strong barrier to pathogenic
bacteria by maintaining a vaginal pH of 3.8 to 4.5.
During the perimenopause
women experience hormonal fluctuations, with decline in estrogen levels leading
to a progressive decrease in acid-producing bacteria and pH rises >4.6 –
this disrupts the vaginal micro-habitat and can lead to problems such as bacterial vaginosis. Normal
flora has a dominance of various Lactobacilli, while in bacterial
vaginosis (BV) microbiota is dominated by Gardnerella vaginalis and
includes a number of anaerobic organisms.
In
reproductive age women the microbial species in vagina can be grouped in five
consistent groupings, referred to by Ravel et al as community state types (CSTs). Out of the 5 CSTs,
the first four have higher proportion of Lactobacillus species whereas the
fifth (CST IV) has lower proportions of Lactobacillus spp. and higher
proportions of anaerobic organisms including Mobiluncus spp.,
and Atopobium vaginae.
As women progress
towards premenopause and menopause, the composition of the VMB undergo
significant change and play an important role in vulvovaginal atrophy. Postmenopausal
hypoestrogenism causes a cascade of events that starts with thinning of the
vaginal epithelium, leading to a smaller contribution of glycogen and higher
alkaline pH that inhibits the growth of Lactobacillus.
Rebecca Brotman is an epidemiologist and infectious disease
expert by training has worked and researched extensively on Vaginal Microbiome
and its role in reproductive tract infection through various stages of women’s
life. She is interested in intervention in VMB in context of meeting many of
the challenges of premeopausal and menopausal life.
In a study by Brotman R.M et al significant association
was found between vaginal bacterial composition with menopause stage and signs
of vaginal atrophy. A distinctive community state type CST IV-A was identified
which was highly associated with signs of Vulvo Vagianl Atrophy (VVA) and was
predominant in post-menopausal women. CST IV-A is a low Lactobacillus state
and is known by a higher abundance of genera including Anaerococcus,
Peptoniphilus and Prevotella, which could be playing a pivotal role in the
clinical presentation of VVA.
It was also seen that compared to
women with no VVA, the odds of CST of women with atrophy being classified as CST
IV-A was 25 times more than being labellled as CST I.
This study
provides a valuable insight into further research and studies to modulate and
restore VMB homeostasis to understand and treat VVA in postmenopausal women.
It is well known that estrogen therapy is effective for the
treatment of VVA and concomitantly, hormonal replacement increases the
abundance of vaginal Lactobacillus species. Oral and
vaginal probiotics holds considerable promise as a therapeutic modality for
future in restoring the vaginal microbiome. However additional trials are required before
bacterial therapeutics can find its way into treatment armament species.
Several small RCTs have shown the effect of combination of ultra-low-dose
vaginal estriol 0.03 mg in combination with viable Lactobacillus acidophilus to
treat vaginal atrophy is superior to placebo. But, larger studies and
meta-analysis are still awaited.
To date, a 2 strain combination of Lactobacillus rhamnosus
GR-1 and Lactobacillus reuteri RC-14 have proved to be the most effective at
restoring and maintaining a normal vaginal microbiota.
Science has
yet not solved all the interactions between body and the microbiome. It is so
complex that it will take many more years to understand the implications of
this symbiosis and devising effective therapeutics.
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