Human Microbiome and its Association With Health and Diseases

Human microbiota are distinct communities of microorganisms that resides at different body niches. Exploration of the human microbiome has become a reality due to the availability of powerful metagenomics and metatranscriptomic analysis technologies. Recent advances in sequencing and bioinformatics over the past decade help provide a deep insight into the nature of the host-microbial interactions and identification of potential deriver genes and pathways associated with human health, well-being, and predisposition to different diseases. In the present review, we outline recent studies devoted to elucidate the possible link between the microbiota and various type of diseases. The present review also highlights the potential utilization of microbiota as a potential therapeutic option to treat a wide array of human diseases.

Humans are viewed as composites of human and microbial cells. Human microbiota are complex and dynamic microbial communities composed mainly of bacteria, but also includes protozoa, archaea, viruses, and fungi that resides in and on different body niches such as oral cavity, throat, esophagus, stomach, colon, urogenital tract, respiratory tract, and skin. The number of microbial cells inhabiting human body is estimated to exceed the H.sapiens cells by 10-fold and estimated at 350 trillion microbial cells.

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Microbiome-host interactions. Schematic representation showing the perplexed microbial-host
interactions due to different triggering factors on microbiota and their genetic material constitute;
the human microbiome.

Source: Wiley

The Theory of Disappearing Microbiota and the Epidemics of Chronic Diseases.

In the present era, medical scientists have been confounded by the increasing incidence of multiple diseases across the world, beginning first in developed countries, and gradually spreading to other areas as they develop. These include the rises in cases of obesity, asthma, hay fever, food allergies, inflammatory bowel disease, juvenile (type 1) diabetes and autism, among many others. Are these diseases, which affect different body systems, unrelated or can a unified theory explain the increased incidence of all of these?

I believe that the latter possibility is true, and that the central theory to explain why these diseases have arisen and by what mechanism is based on modern changes in early life events that are related to the human microbiome. According to this theory, the microbiome of humans and of other animals is not accidental, but has been selected over long time periods to optimize host reproductive success through interactions between the microbiota and host physiology. Early life is the crucial period during which the adult microbiome becomes established, and development of the host and of the microbiota occur together in a conjoined manner through a dynamic equilibrium that follows a well-choreographed path. In early life, the context is set for the important developmental decisions that are required for the immune system to distinguish between what is self and what is not self, for metabolic organs to partition how much energy to expend or to save, and for the brain to determine how to respond socially to a person who might be either a friend or a foe.

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Figure 1: A model for the interaction of the inherited microbiota with
early life immunological development in past and present children.

Source: NATURE REVIEWS IMMUNOLOGY

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Short-Chain Fatty Acids In Control Of Body Weight And Insulin Sensitivity

The connection between the gut microbiota and the etiology of obesity and cardiometabolic disorders is increasingly being recognized by clinicians. Our gut microbiota might affect the cardiometabolic phenotype by fermenting indigestible dietary components and thereby producing short-chain fatty acids (SCFA). These SCFA are not only of importance in gut health and as signaling molecules, but might also enter the systemic circulation and directly affect metabolism or the function of peripheral tissues.

In this Review, we discuss the effects of three SCFA (acetate, propionate and butyrate) on energy homeostasis and metabolism, as well as how these SCFA can beneficially modulate adipose tissue, skeletal muscle and liver tissue function.

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Short-Chain Fatty Acids (SCFA) and liver function.

Source: NatureReviewsEndocrinology

Cesarean Delivery May Increase Risk of Childhood Obesity

Children born by cesarean delivery may have an increased risk of becoming obese, compared with their siblings born by vaginal delivery, says study. This finding may have significant implications for the almost 1.3 million cesarean births per year in the United States.

Cesarean delivery is the most common U.S. surgical procedure and accounts for one third of deliveries nationwide.

The most common risk to children born via cesarean delivery is respiratory problems, while increasing evidence suggests children may also have an increased risk of other adverse health outcomes as adults.

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Cesarean delivery can increase a child's risk of obesity into adulthood, study finds.

Source: medicalnewstoday

Antibiotics In Early Life Could Raise Children's Food Allergy Risk

Infection in the first year of life can be deadly for an infant, and antibiotic treatment is often the first port of call. But such treatment may have a downside; new research from the University of South Carolina finds early antibiotic exposure could raise a child's risk of food allergies.

While the study did not investigate the reasons behind this association, the researchers say it is likely down to changes in gut microbiota as a result of antibiotic treatment.

Lead author Dr. Bryan Love, of the Department of Clinical Pharmacy and Outcomes Sciences at the South Carolina College of Pharmacy, and colleagues report their results in the journal Allergy, Asthma & Clinical Immunology.

Previous research has suggested that changes to the composition of gut bacteria in early life can have negative implications for health, and antibiotics are known to do just that.

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Early antibiotic exposure could raise children's risk of food allergies.

Source: medicalnewstoday

High-Fat Diet in Pregnancy Reduces Beneficial Gut Microbiota for Offspring

Eating a high-fat diet during pregnancy could alter the population of gut microbiota in offspring, which may have negative implications for nutrition and development. This is the conclusion of a new study published in the journal Genome Medicine.

It is well established that what women eat and drink during pregnancy can influence the health and development of their child.

For example, it is recommended that expectant mothers consume 0.4 milligrams of folic acid every day in order to help prevent certain birth defects, and current advice says a healthy, balanced diet is best for both mother and baby.

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Women who eat a high-fat diet in pregnancy may be putting their offspring's health and development at risk,
say researchers.

Source: medicalnewstoday

Mother's microbiome influence her offspring's immune system during gestation.

During gestation, a mother's microbiome shapes the immune system of her offspring, a new study in mice suggests. While it's known that a newborn's gut microbiota can affect its own immune system, the impact of a mother's microbiota on her offspring has largely been unexplored.

Here, Mercedes Gomez de Agüero et al. infected the guts of pregnant mice with E.coli engineered to dwindle over time, allowing the mothers to become germ-free again around the time they gave birth.

This temporary colonization of E.coli in the mother affected the immune system of her offspring; after birth, the offspring harbored more innate lymphoid and mononuclear cells in their intestines compared to mice born to microbe-free pregnant mothers. Similar results were seen when pregnant mothers were temporarily colonized with a cocktail of eight other microbes.

An RNA analysis of offspring born to gestation-only colonized mothers compared with controls revealed greater expression of numerous genes, including those that influence cell division and differentiation, mucus and ion channels, and metabolism and immune function.

By transferring serum from bacteria-colonized pregnant mice to non-colonized pregnant mice, the researchers found that maternal antibodies likely facilitate the transmission and retention of microbial molecules from a mother to her offspring.

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Shaping of the immune system starts with the maternal microbiota.

Source: sciencedaily