Nourish’s Research

Background

Dietary stipulations, which influence gut microbiota composition, form patterns throughout geographical regions. Certain microbial species are associated with populations from specific areas, and gut bacteria are synthesizers of amino acids such as arginine, a critical aspect of maternal nutrition. As such, there may be diverse gut microbiota populations in pregnant women from different regions with impacts on arginine synthesis. My research focused on evaluating these differences by measuring the pH–an indicator of arginine synthesis–of agar plates incubated with different bacterial species to determine their impacts on arginine metabolism and evaluate the potential of dietary modulation of the gut microbiome. 

Why is arginine important?

  • Arginine is a conditionally essential amino acid

  • Arginine is a crucial determinant of proper maternal nutrition

    • Pregnancy requires increased tissue deposition from mothers to fully develop a fetus; arginine is crucial for this process of protein synthesis. 

    • Lower maternal arginine availability is strongly associated with lower birth weight.

Hypotheses

Null Hypothesis:

There is no significant difference between the level of arginine flux in the presence of the bacterial species Bacillus megaterium, Lactobacillus acidophilus, Escherichia coli, and Clostridium sporogenes.

Alternate Hypothesis:

The level of arginine flux in the presence of the bacterial species B. megaterium is significantly higher than in the presence of the species Lactobacillus acidophilus, Escherichia coli, and Clostridium sporogenes.

Experimental Layout

Results

After the 1-week incubation period, the changes in the pH values of the agar plates treated with C. sporogenes and those treated with B. megaterium were significantly different from the changes of the other experimental groups (p<0.0001). 

Conclusions

  • Arginine is a basic amino acid (pH range of 10.5 - 12.5). B. megaterium and C. sporogenes had significantly higher pH values after the incubation period; the shifts in pH toward a higher, less acidic value indicate greater de novo synthesis of arginine from the precursor compound citrulline.  

  • The most significant spike in these pH values occurred within 24 hours of incubation; after this period, the pH values stayed comparatively constant for the rest of the incubation period. This indicates that the bacterial species were able to rapidly synthesize arginine from citrulline within 24 hours of incubation and then mainly worked to maintain these levels of arginine flux for the duration of the incubation period.

  • An abundance of B. megaterium is associated with the intestinal microbiota of populations adhering to a traditional Western diet. An abundance of C. sporogenes is associated with the intestinal microbiota of populations adhering to a traditional Mediterranean diet. Hence, both the Western and Mediterranean diets offer potential natural means of modulation of the gastrointestinal microbiome into an environment conducive to arginine synthesis.

Why This Matters

  • Arginine is a crucial determinant of proper maternal nutrition; as such, lower maternal arginine availability is strongly associated with lower birth weight. Fetal growth restriction (FGR) occurs in approximately 3% to 7% of pregnancies worldwide, and in developing countries, the prevalence of FGR is 6 times higher. These results concerning arginine metabolism and the possibilities for dietary gut microbiome modulation could reduce the occurrence of growth-related fetal deaths. 

    • Roughly 20% of infants are of low birth weight in countries with lower incomes; the fatality rate is around 25% for these infants

  • Decreased levels of arginine in maternal diets are associated with intrauterine growth restriction (IUGR) and fetal resorption. IUGR causes 50% of nonmalformed infant deaths. IUGR also impacts fetal propensity for genetic and metabolic disorders as well as chronic diseases later on in life.

  • Applications of this research to find low-cost and beneficial dietary alternatives could improve nutritional maternal and fetal health in low-income countries that are disproportionately impacted by nutritional disorders.

  • The most impactful future direction for this research is its potential for life-saving applications regarding nutrition in the fields of maternal-fetal medicine and neonatology.