MAY 19, 2021 12:00 PM PDT

Intestinal Macrophages Promote Chronic Inflammation in Obesity

WRITTEN BY: Caroline Wallace

It is a well-known fact that obesity can lead to serious issues such as cardiovascular disease. This is partly due to the chronic low-grade inflammation that occurs in obese individuals. As scientists begin to understand what drives chronic inflammation in obesity, new treatment targets for metabolic diseases may be found.

A research group from Switzerland hypothesized that immune cells in the gut (gastrointestinal tract) must trigger chronic inflammation in obese individuals. Their discovery and characterization of the gut immune cells in obese versus non-obese individuals was published in early May in Frontiers Immunology.

The immune system in our gut is unique because it is constantly exposed to food, bacteria (microbiota), and metabolites. Immune cells are a vital part of the intestinal mucosa that form a barrier between the foreign products in our gut and the rest of our body. Monocytes are a type of innate immune cell in the blood, and they change into macrophages once they enter the gut tissues. Macrophages are the most common immune cell in a healthy gut.

The researchers characterized human intestinal macrophages in non-obese and obese individuals at different locations along the GI tract, since potential differences were not known before this study. The team also looked at how body composition, different lifestyle behaviors (nutrition and physical activity), and disease variables impacted innate immunity in the gut.

This study was a prospective, single-center observational study that enrolled 54 subjects. Obesity was determined based on the participants' body mass index (BMI). Biopsies were taken from obese and non-obese individuals during routine scheduled procedures such as screening colonoscopies, gastroscopy, or bariatric surgery. The immune cells were isolated from the biopsied tissues and flow cytometry was used to identify the immune cell sub-populations.

There is a delicate balance between the immune cell sub-populations: imbalance can lead to disease. In a healthy gut, most of the intestinal macrophages are more mature anti-inflammatory macrophages. Previous research has shown that in IBD, macrophages retain their immature pro-inflammatory phenotype, which drives the disease.

The research team identified five distinct macrophage subpopulations in the GI tract and three blood monocyte subpopulations. The monocyte subpopulations were present in both obese and non-obese individuals, and they replenish the intestinal macrophages.

However, obese individuals had more pro-inflammatory macrophages throughout their GI tract and they also had more intermediate blood monocytes. Additionally, the pro-inflammatory macrophage subpopulation P2 and the number of intermediate blood monocytes correlated with body weight and unhealthy lifestyle habits.

This data reveals a potential link between unhealthy lifestyle behaviors and changes in gut innate immunity. Since a role for the mucosal innate immune system in obese individuals is established, these biological mechanisms may be exploited to find new treatments for metabolic disorders such as obesity. Future studies, such as what triggers more pro-inflammatory macrophages in obesity, are necessary to fully complete the picture.

Source: Frontiers Immunology

About the Author
PhD
Caroline Wallace has a PhD in Biomedical Science with over 15 peer-reviewed publications. Her scientific writing areas of interest include immunology, nutritional immunology, immuno-oncology, cancer prevention, and general wellness through natural products.
You May Also Like
SEP 06, 2022
Genetics & Genomics
Reduced A-to-I Editing in RNA Linked to Autoimmune Disorder Risk
SEP 06, 2022
Reduced A-to-I Editing in RNA Linked to Autoimmune Disorder Risk
The genome contains the sequences for protein-coding genes, but before those seuquences are translated into protein, the ...
SEP 02, 2022
Coronavirus
Omicron-Specific Booster Shots Will be Available Soon
SEP 02, 2022
Omicron-Specific Booster Shots Will be Available Soon
Soon, vaccine booster shots that are specific to the Omicron variant will be available in many countries. The new Omicro ...
SEP 07, 2022
Drug Discovery & Development
An Oral Insulin Pill is Getting Closer
SEP 07, 2022
An Oral Insulin Pill is Getting Closer
Diabetes is a chronic disease that requires constant monitoring. Patients have to check the level of sugar, or glucose i ...
SEP 21, 2022
Immunology
Calorie Reduction Lowers Levels of Aging-Linked Proteins
SEP 21, 2022
Calorie Reduction Lowers Levels of Aging-Linked Proteins
A variety of studies have suggested that diets that restrict or reduce caloric intake can lengthen lifespan. Now, resear ...
OCT 23, 2022
Immunology
The Double-Edged Sword of Iron Deficiency
OCT 23, 2022
The Double-Edged Sword of Iron Deficiency
Iron is a crucial nutrient. Most of the iron in the body is contained in red blood cells, as part of hemoglobin, which i ...
OCT 27, 2022
Cardiology
Consistent Lack of Sleep Increases Risk of Heart Disease and Inflammatory Disorders
OCT 27, 2022
Consistent Lack of Sleep Increases Risk of Heart Disease and Inflammatory Disorders
Chronic sleep deprivation harms immune cells, which may lead to heart problems and inflammation.
Loading Comments...