Tag Archives: gut microbiome

Metal oxide nanoparticles and negative effects on gut health?

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A May 4, 2023 Binghamton University news release by Jillian McCarthy (also on EurekAlert but published on May 9, 2023) announces the research, Note: A link has been removed,

Common food additives known as metal oxide nanoparticles may have negative effects on your gut health, according to new research from Binghamton University, State University of New York and Cornell University. 

Gretchen Mahler, professor of biomedical engineering and interim vice provost and dean of the Graduate School, worked in collaboration with Cornell researchers to study five of these nanoparticles. Their findings were recently published in the Journal of Antioxidants.

“They’re all actual food additives,” said Mahler. “Titanium dioxide tends to show up as a whitening and brightening agent. Silicon dioxide tends to be added to foods to prevent it from clumping. Iron oxide tends to be added to meats, for example, to keep that red color. And zinc oxide can be used as a preservative because it’s antimicrobial.” [emphases mine]

In order to test these nanoparticles, Mahler and Elad Tako, senior author and associate professor of food science in the College of Agriculture and Life Sciences at Cornell, used the intestinal tract of chickens. A chicken’s intestinal tract is comparable to a human’s; the microbiota that they have and the bacterial components have a lot of overlap with the microbiota that you see in the human digestive system, said Mahler. 

“We’ve been testing a series of nanomaterials here at Binghamton, and we’ve been looking at things like nutrient absorption, enzyme expression and some of the more subtle, functional markers,” said Mahler.

The doses of nanoparticles that were tested reflect what is typically consumed by humans. The nanoparticles were injected into the amniotic sac of broiler chicken eggs, which are specifically bred and raised for their meat. These chickens get larger faster, so the effects of the nanoparticles are more obvious earlier in development. The amniotic sac at a certain stage of development flows through the chicken intestine.

“When they hatched, we harvested tissue from the small intestine, the microbiota and the liver,” said Mahler. “We looked at gene expression, microbiota composition and the structure of the small intestine.”

The researchers found more negative effects with silicone dioxide and titanium dioxide. They also found that the nanoparticles had affected the functioning of the chicken’s intestinal lining (called the brush border membrane), the balance of bacteria in their intestinal tract and the chickens’ ability to absorb minerals.

The other nanoparticles had more neutral, or even positive, effects. Zinc oxide appeared to support intestinal development or compensatory mechanisms due to intestinal damage. Iron oxide could potentially be used for iron fortification, but with potential alterations in intestinal functionality and health.

Mahler doesn’t want to suggest that these nanoparticles need to be removed from our diets completely. Their research is meant to provide some information, and allow people to have a better understanding of what’s really in the food they consume.

“We’re eating these things, so it’s important to consider what some of the more subtle effects could be,” said Mahler. “We develop these gut models around this problem to try to understand it, and this collaboration, where we have these complementary methods to try to look at the problem, has been successful.”

Here’s a link to and a citation for the paper,

Food-Grade Metal Oxide Nanoparticles Exposure Alters Intestinal Microbial Populations, Brush Border Membrane Functionality and Morphology, In Vivo (Gallus gallus) by Jacquelyn Cheng, Nikolai Kolba, Alba García-Rodríguez, Cláudia N. H. Marques, Gretchen J. Mahler and Elad Tako. Antioxidants 2023, 12(2), 431, DOI: https://doi.org/10.3390/antiox12020431 Published online : 9 February 2023 (This article belongs to the Special Issue Dietary Supplements and Oxidative Stress)

This paper is open access.

Could engineered nanoparticles be behind rise in obesity and metabolic disorders?

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The researchers haven’t published a study and they have used fruit flies as their testing mechanism (animal models) so, it’s a little difficult (futile) to analyze the work at this stage but it is intriguing. A June 9, 2015 news item on Azonano announces a research collaboration  designed to examine the impact engineered nanoparticles have on the gut and the gut microbiome,

Researchers at Binghamton University believe understanding nano particles’ ability to influence our metabolic processing may be integral to mediating metabolic disorders and obesity, both of which are on the rise and have been linked to processed foods.

Anthony Fiumera, associate professor of biological sciences, and Gretchen Mahler, assistant professor of biomedical engineering, are collaborating on a research project funded by a Binghamton University Transdisciplinary Areas of Excellence (TAE) grant to discover the role ingested nanoparticles play in the physiology and function of the gut and gut microbiome.

A June 8, 2015 Binghamton University news release, which originated the news item, describes the reasoning behind the research,

The gut microbiome is the population of microbes living within the human intestine, consisting of tens of trillions of microorganisms (including at least 1,000 different species of known bacteria). Nanoparticles, which are often added to processed foods to enhance texture and color, have been linked to changes in gut function. As processed foods become more common elements of our diet, there has been a significant increase in concentrations of these particles found in the human body.

Fiumera works in vivo with fruit flies while Mahler works in vitro using a 3-D cell-culture model of the gastrointestinal (GI) tract to understand how ingesting nanoparticles influences glucose processing and the gut microbiome. By using complementary research methods, the researchers have helped advance each other’s understanding of nanoparticles.

Using fruit flies, Fiumera looks at the effects of nanoparticles on development, physiology and biochemical composition, as well as the microbial community in the GI tract of the fly. The fly model offers two advantages: 1) research can be done on a wide range of traits that might be altered by changes in metabolism and 2) the metabolic processes within the fly are similar to those in humans. Fiumera also aims to investigate which genes are associated with responses to the nanoparticles, which ultimately may help us understand why individuals react differently to nanoparticles.

For this project, Mahler expanded her GI tract model to include a commensal intestinal bacterial species and used the model to determine a more detailed mechanism of the role of nanoparticle exposure on gut bacteria and intestinal function. Early results have shown that nanoparticle ingestion alters glucose absorption, and that the presence of beneficial gut bacteria eliminates these effects.

Mahler was already investigating nanoparticles when she reached out to Fiumera and proposed they combine their respective expertise. With the help of undergraduate students Gabriella Shull and John Fountain and graduate student Jonathan Richter, Fiumera and Mahler have begun to uncover some effects of ingesting nanoparticles. Since they are using realistic, low concentrations of nanoparticles, the effects are slight, but eventually may be additive.

The most interesting aspect of this research (to me) is the notion that the impact may be additive. In short, you might be able to tolerate a few more nanoparticles in your gut but as more engineered nanoparticles become part of our food and drink (including water) and your gut receives more and more that tolerance may no longer possible.

There is increasing concern about engineered nanoparticles as they cycle through environment and the US Environmental Protection Agency (EPA) funded a programed by Arizona State University (ASU), LCnano Network (part of the EPA’s larger Life Cycle of Nanomaterials project). You can find out more about the ASU program in my April 8, 2014 post (scroll down about 50% of the way).

Getting back to Binghamton, I look forward to hearing more about the research as it progresses.

Metal nanoparticles and gut microbiomes

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What happens when you eat or drink nanoparticles, metallic or otherwise? No one really knows. Part of the problem with doing research now is there are no benchmarks for the quantity we’ve been ingesting over the centuries. Nanoparticles do occur naturally, as well, people who’ve eaten with utensils made of or coated with silver or gold have ingested silver or gold nanoparticles that were shed by those very utensils. In short, we’ve been ingesting any number of nanoparticles through our food, drink, and utensils in addition to the engineered nanoparticles that are found in consumer products. So, part of what researchers need to determine is the point at which we need to be concerned about nanoparticles. That’s trickier than it might seem since we ingest our nanoparticles and recycle them into the environment (air, water, soil) to reingest (inhale, drink, eat, etc.) them at a later date. The endeavour to understand what impact engineered nanoparticles in particular will have on us as more are used in our products is akin to assembling a puzzle.

There’s a May 5, 2015 news item on Azonano which describes research into the effects that metallic nanoparticles have on the micriobiome (bacteria) in our guts,

Exposure of a model human colon to metal oxide nanoparticles, at levels that could be present in foods, consumer goods, or treated drinking water, led to multiple, measurable differences in the normal microbial community that inhabits the human gut. The changes observed in microbial metabolism and the gut microenvironment with exposure to nanoparticles could have implications for overall human health, as discussed in an article published in Environmental Engineering Science, a peer-reviewed journal from Mary Ann Liebert, Inc., publishers. The article is available free on the Environmental Engineering Science website until June 1, 2015.

A May 4, 2015 Mary Ann Liebert publisher news release on EurekAlert, which originated the news item, describes the research in more detail (Note: A link has been removed),

Alicia Taylor, Ian Marcus, Risa Guysi, and Sharon Walker, University of California, Riverside, individually introduced three different nanoparticles–zinc oxide, cerium dioxide, and titanium dioxide–commonly used in products such as toothpastes, cosmetics, sunscreens, coatings, and paints, into a model of the human colon. The model colon mimics the normal gut environment and contains the microorganisms typically present in the human microbiome.

In the article “Metal Oxide Nanoparticles Induce Minimal Phenotypic Changes in a Model Colon Gut Microbiota” the researchers described changes in both specific characteristics of the microbial community and of the gut microenvironment after exposure to the nanoparticles.

Here’s a link to and a citation for the paper,

Metal Oxide Nanoparticles Induce Minimal Phenotypic Changes in a Model Colon Gut Microbiota by Alicia A. Taylor, Ian M. Marcus Ian, Risa L., Guysi, and Sharon L. Walker. Environmental Engineering Science. DOI:10.1089/ees.2014.0518 Online Ahead of Print: April 24, 2015

I’ve taken a quick look at the research while it’s still open access (till June 1, 2015) to highlight the bits I consider interesting. There’s this about the nanoparticle (NP) quantities used in the study (Note: Links have been removed),

Environmentally relevant NP concentrations were chosen to emulate human exposures to NPs through ingestion of both food and drinking water at 0.01 μg/L ZnO NP, 0.01 μg/L CeO2 NP, and 3 mg/L TiO2 NP (Gottschalk et al., 2009; Kiser et al., 2009, 2013; Weir et al., 2012; Keller and Lazareva, 2013). Recent work has also indicated that adults in the USA ingest 5 mg TiO2 per day, half of which is in the nano-size range (Lomer et al., 2000; Powell et al., 2010). Exposure routes and reliable dosing information of NPs that are embedded in solid matrices are difficult to predict, and this is often a limitation of analytical techniques (Nowack et al., 2012; Yang and Westerhoff, 2014). The exposure levels used in this study were predominately selected from literature values that give predictions on amount of NPs in water and food sources (Gottschalk et al., 2009; Kiser et al., 2009; Weir et al., 2012; Keller and Lazareva, 2013; Keller et al., 2013).

For anyone unfamiliar with chemical notations, ZnO NP is zinc oxide nanoparticle, 0.01 μg/L is one/one hundredth of a microgram per litre,  CeO2 is cesisum dioxide NP, and TiO2 is titanium dioxide NP while 3 mg/L, is 3 milligrams per litre.

After assuring the quantities used in the study are the same as they expect humans to be ingesting on a regular basis, the researchers describe some of the factors which may affect the interaction between the tested nanoparticles and the bacteria (Note: Links have been removed),

It is essential to note that interactions between NPs and bacteria in the intestines may be dependent on numerous factors: the surface charge of the NPs and bacteria, the chemical composition and surface charge of the digested food, and variability in diet. These factors may ultimately correlate to effects seen in humans on an individual basis. In fact, similar work has demonstrated that exposing common NPs found in food to stomach-like conditions will change their surface chemistry from negative to neutral or positive, causing the NPs to interact with negatively charged mucus proteins in the gastrointestinal tract and, in turn, affecting the transport of NPs within the intestine (McCracken et al., 2013). The purpose of this work was to measure responses of the microbial community during the NP exposures. Based on previous research, it is anticipated that the NPs altered by stomach-like conditions would also cause changes in the gut environment (McCracken et al., 2013).

Here’s some of what they discovered,

Our initial hypothesis, that NPs induce phenotypic changes in a gut microbial community, was affirmed through significant measurable effects seen in the data. Tests that supported that NPs caused changes in the phenotype included hydrophobicity, EPM, sugar content of the EPS, cell size, conductivity, and SFCA (specifically butyric acid) production. Data for cell concentration and the protein content of the EPS demonstrated no significant results. Data were inconclusive for pH. With such a complex biological system, it is very likely that the phenotypic and biochemical changes observed are combinations of responses happening in parallel. The effects seen may be attributed to both changes induced by the NPs and natural phenomena associated with microbial community activity and other metabolic processes in a multifaceted environment such as the gut. Some examples of natural processes that could also influence the phenotypic and biochemical parameters are osmolarity, active metabolites, and electrolyte concentrations (Miller and Wood, 1996; Record et al., 1998).

Here’s the concluding sentence from the abstract,

Overall, the NPs caused nonlethal, significant changes to the microbial community’s phenotype, which may be related to overall health effects. [emphasis mine]

This research like the work I featured in a June 27, 2013 posting points to some issues with researching the impact that nanoparticles may have on our bodies. There was no cause for immediate alarm in 2013 and it appears that is still the case in 2015. However, that assumes quantities being ingested don’t increase significantly.