pregnancy
Fundamental Knowledge of Microbes Shedding New Light on Human Health
Posted on by Dr. Francis Collins
Basic research in biology generates fundamental knowledge about the nature and behavior of living systems. It is generally impossible to predict exactly where this line of scientific inquiry might lead, but history shows that basic science almost always serves as the foundation for dramatic breakthroughs that advance human health. Indeed, many important medical advances can be traced back to basic research that, at least at the outset, had no clear link at all to human health.
One exciting example of NIH-supported basic research is the Human Microbiome Project (HMP), which began 12 years ago as a quest to use DNA sequencing to identify and characterize the diverse collection of microbes—including trillions of bacteria, fungi, and viruses—that live on and in the healthy human body.
The HMP researchers have subsequently been using those vast troves of fundamental data as a tool to explore how microbial communities interact with human cells to influence health and disease. Today, these explorers are reporting their latest findings in a landmark set of papers in the Nature family of journals. Among other things, these findings shed new light on the microbiome’s role in prediabetes, inflammatory bowel disease, and preterm birth. The studies are part of the Integrative Human Microbiome Project.
If you’d like to keep up on the microbiome and other basic research journeys, here’s a good way to do so. Consider signing up for basic research updates from the NIH Director’s Blog and NIH Research Matters. Here’s how to do it: Go to Email Updates, type in your email address, and enter. That’s it. If you’d like to see other update possibilities, including clinical and translational research, hit the “Finish” button to access Subscriber Preferences.
As for the recent microbiome findings, let’s start with the prediabetes study [1]. An estimated 1 in 3 American adults has prediabetes, detected by the presence of higher than normal fasting blood glucose levels. If uncontrolled and untreated, prediabetes can lead to the more-severe type 2 diabetes (T2D) and its many potentially serious side effects [2].
George Weinstock, The Jackson Laboratory for Genomic Medicine, Farmington, CT, Michael Snyder, Stanford University, Palo Alto, CA, and colleagues report that they have assembled a rich new data set covering the complex biology of prediabetes. That includes a comprehensive analysis of the human microbiome in prediabetes.
The data come from monitoring the health of 106 people with and without prediabetes for nearly four years. The researchers met with participants every three months, drawing blood, assessing the gut microbiome, and performing 51 laboratory tests. All this work generated millions of molecular and microbial measurements that provided a unique biological picture of prediabetes.
The picture showed specific interactions between cells and microbes that were different for people who are sensitive to insulin and those whose cells are resistant to it (as is true of many of those with prediabetes). The data also pointed to extensive changes in the microbiome during respiratory viral infections. Those changes showed clear differences in people with and without prediabetes. Some aspects of the immune response also appeared abnormal in people who were prediabetic.
As demonstrated in a landmark NIH study several years ago [2], people with prediabetes can do a lot to reduce their chances of developing T2D, such as exercising, eating healthy, and losing a modest amount of body weight. But this study offers some new leads to define the biological underpinnings of T2D in its earliest stages. These insights potentially point to high value targets for slowing or perhaps stopping the systemic changes that drive the transition from prediabetes to T2D.
The second study features the work of the Inflammatory Bowel Disease Multi’omics Data team. It’s led by Ramnik Xavier and Curtis Huttenhower, Broad Institute of MIT and Harvard, Cambridge, MA. [4]
Inflammatory bowel disease (IBD) is an umbrella term for chronic inflammations of the body’s digestive tract, such as Crohn’s disease and ulcerative colitis. These disorders are characterized by remissions and relapses, and the most severe flares can be life-threatening. Xavier, Huttenhower, and team followed 132 people with and without IBD for a year, collecting samples of their gut microbiomes every other week along with biopsies and blood samples for a total of nearly 3,000 samples.
By integrating DNA, RNA, protein, and metabolic analyses, they followed precisely which microbial species were present. They could also track which biochemical functions those microbes were capable of performing, and which functions they actually were performing over the course of the study.
These data now offer the most comprehensive view yet of functional imbalances associated with changes in the microbiome during IBD flares. These data also show how those imbalances may be altered when a person with IBD goes into remission. It’s also noteworthy that participants completed questionnaires on their diet. This dataset is the first to capture associations between diet and the gut microbiome in a relatively large group of people over time.
The evidence showed that the gut microbiomes of people with IBD were significantly less stable than the microbiomes of those without IBD. During IBD activity, the researchers observed increases in certain groups of microbes at the expense of others. Those changes in the microbiome also came with other telltale metabolic and biochemical disruptions along with shifts in the functioning of an individual’s immune system. The shifts, however, were not significantly associated with people taking medications or their social status.
By presenting this comprehensive, “multi-omic” view on the microbiome in IBD, the researchers were able to single out a variety of new host and microbial features that now warrant further study. For example, people with IBD had dramatically lower levels of an unclassified Subdoligranulum species of bacteria compared to people without the condition.
The third study features the work of The Vaginal Microbiome Consortium (VMC). The study represents a collaboration between Virginia Commonwealth University, Richmond, and Global Alliance to Prevent Prematurity and Stillbirth (GAPPS). The VMC study is led by Gregory Buck, Jennifer Fettweis, Jerome Strauss,and Kimberly Jefferson of Virginia Commonwealth and colleagues.
In this study, part of the Multi-Omic Microbiome Study: Pregnancy Initiative, the team followed up on previous research that suggested a potential link between the composition of the vaginal microbiome and the risk of preterm birth [5]. The team collected various samples from more than 1,500 pregnant women at multiple time points in their pregnancies. The researchers sequenced the complete microbiomes from the vaginal samples of 45 study participants, who gave birth prematurely and 90 case-matched controls who gave birth to full-term babies. Both cases and controls were primarily of African ancestry.
Those data reveal unique microbial signatures early in pregnancy in women who went on to experience a preterm birth. Specifically, women who delivered their babies earlier showed lower levels of Lactobacillus crispatus, a bacterium long associated with health in the female reproductive tract. Those women also had higher levels of several other microbes. The preterm birth-associated signatures also were associated with other inflammatory molecules.
The findings suggest a link between the vaginal microbiome and preterm birth, and raise the possibility that a microbiome test, conducted early in pregnancy, might help to predict a woman’s risk for preterm birth. Even more exciting, this might suggest a possible way to modify the vaginal microbiome to reduce the risk of prematurity in susceptible individuals.
Overall, these landmark HMP studies add to evidence that our microbial inhabitants have important implications for many aspects of our health. We are truly a “superorganism.” In terms of the implications for biomedicine, this is still just the beginning of what is sure to be a very exciting journey.
References:
[1] Longitudinal multi-omics of host-microbe dynamics in prediabetes. Zhou W, Sailani MR, Contrepois K, Sodergren E, Weinstock GM, Snyder M, et. al. Nature. 2019 May 29.
[2] National Diabetes Statistics Report, 2017, Center for Disease Control and Prevention (Atlanta, GA)
[3] Long-term effects of lifestyle intervention or metformin on diabetes development and microvascular complications over 15-year follow-up: the Diabetes Prevention Program Outcomes Study. Diabetes Prevention Program Research Group.Lancet Diabetes Endocrinol.2015 Nov;3(11):866-875.
[4] Multi-omics of the gut microbial ecosystem in inflammatory bowel disease. Lloyd-Price J, Arze C. Ananthakrishnan AN, Vlamakis H, Xavier RJ, Huttenhower C, et. al. Nature. 2019 May 29.
[5] The vaginal microbiome and preterm birth. Fettweis JM, Serrano MG, Brooks, JP, Jefferson KK, Strauss JF, Buck GA, et al. Nature Med. 2019 May 29.
Links:
Insulin Resistance & Prediabetes (National Institute of Diabetes and Digestive and Kidney Diseases/NIH)
Crohn’s Disease (NIDDK/NIH)
Ulcerative colitis (NIDDK/NIH)
Preterm Labor and Birth: Condition Information (Eunice Kennedy Shriver National Institute of Child Health and Human Development/NIH)
Global Alliance to Prevent Prematurity and Stillbirth (Seattle, WA)
NIH Integrative Human Microbiome Project
NIH Support:
Prediabetes Study: Common Fund; National Institute of Dental and Craniofacial Research; National Institute of Diabetes and Digestive and Kidney Diseases; National Institute of Human Genome Research; National Center for Advancing Translational Sciences
Inflammatory Bowel Disease Study: Common Fund; National Institute of Diabetes and Digestive and Kidney Diseases; National Center for Advancing Translational Sciences; National Institute of Human Genome Research; National Institute of Dental and Craniofacial Research
Preterm Birth Study: Common Fund; National Institute of Allergy and Infectious Diseases; Eunice Kennedy Shriver National Institute of Child Health and Human Development
Preeclampsia: Study Highlights Need for More Effective Treatment, Prevention
Posted on by Dr. Francis Collins
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It’s well known that preeclampsia, a condition characterized by a progressive rise in a pregnant woman’s blood pressure and appearance of protein in the urine, can have negative, even life-threatening impacts on the health of both mother and baby. Now, NIH-funded researchers have documented that preeclampsia is also taking a very high toll on our nation’s economic well-being. In fact, their calculations show that, in 2012 alone, preeclampsia-related care cost the U.S. health care system more than $2 billion.
These findings are especially noteworthy because preeclampsia rates in the United States have been steadily rising over the past 30 years, fueled in part by increases in average maternal age and weight. This highlights the urgent need for more research to develop new and more effective strategies to protect the health of all mothers and their babies.
Could Zika Virus Have Lasting Impact on Male Fertility?
Posted on by Dr. Francis Collins
Caption: Immunofluorescence staining showing that the testes of Zika-free mice (left) are full of developing sperm (pink), while the testes of Zika-infected mice (right) contain very few sperm.
Credit: Prabagaran Esakky, Washington University School of Medicine, St. Louis
Recent research has shown that the mosquito-borne Zika virus has the potential to cause serious health problems, including severe birth defects in humans. But the damaging effects of Zika might not end there: results of a new mouse study show that the virus may also have an unexpected negative—and possibly long-lasting—impact on male fertility.
In work published in the journal Nature, an NIH-funded research team found that Zika infections can persist for many weeks in the reproductive systems of male mice [1]. As a result of this infection, levels of testosterone and other sex hormones drop, sperm counts fall, and, in some animals, the testicles shrink to 1/10th of their normal size, possibly irreversibly. All of this adds up to Zika-infected male mice that are significantly less fertile than their healthy counterparts—producing about a quarter as many viable offspring as normal when mated with female mice. While mice are certainly not humans, the results underscore the urgent need for additional research to examine the full spectrum of Zika’s health effects in men, women, and children of both sexes.
Morning Sickness Associated with Lower Miscarriage Risk
Posted on by Dr. Francis Collins
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During the first trimester of pregnancy, many women experience what’s commonly known as “morning sickness.” As distressing as this nausea and vomiting can be, a team of NIH researchers has gathered some of the most convincing evidence to date that such symptoms may actually be a sign of something very positive: a lower risk of miscarriage.
In fact, when the researchers studied a group of women who had suffered one or two previous miscarriages, they found that the women who felt nauseous during their subsequent pregnancies were 50 to 75 percent less likely to miscarry than those without nausea. While it’s not yet exactly clear what’s going on, the findings lend support to the notion that morning sickness may arise from key biological factors that reflect an increased likelihood of a successful pregnancy.
Largest Study Yet Shows Mother’s Smoking Changes Baby’s Epigenome
Posted on by Dr. Francis Collins
Credit: Daniel Berehulak/Getty Images
Despite years of public health campaigns warning of the dangers of smoking when pregnant, many women are unaware of the risk or find themselves unable to quit. As a result, far too many babies are still being exposed in the womb to toxins that enter their mothers’ bloodstreams when they inhale cigarette smoke. Among the many infant and child health problems that have been linked to maternal smoking are premature birth, low birth weight, asthma, reduced lung function, sudden infant death syndrome (SIDS), and cleft lip and/or palate.
Now, a large international study involving NIH-supported researchers provides a biological mechanism that may explain how exposure to cigarette toxins during fetal development can produce these health problems [1]. That evidence centers on the impact of the toxins on the epigenome of the infant’s body tissues. The epigenome refers to chemical modifications of DNA (particularly methylation of cytosines), as well as proteins that bind to DNA and affect its function. The genome of an individual is the same in all cells of their body, but the epigenome determines whether genes are turned on or off in particular cells. The study found significant differences between the epigenetic patterns of babies born to women who smoked during pregnancy and those born to non-smokers, with many of the differences affecting genes known to play key roles in the development of the lungs, face, and nervous system.
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