Lipopolysaccharides or LPS are bacterial toxins that can cause inflammation and health issues if they reach the bloodstream. Normally housed safely in the gut, lipopolysaccharides become toxic by entering the blood if you have an infection, “leaky gut”, or eat too many fatty foods.

Read on to learn how lipopolysaccharides cause inflammation and how you can test for them.

What Are LPS?

Definition

Lipopolysaccharides (LPS) are one of the main causes of systemic, low-grade inflammation. In fact, intravenous LPS is often used in research experiments to cause inflammation [1].

Exposure to LPS causes both rodents and people to display “sickness behavior,” including depression, impaired cognitive function, and social withdrawal [1].

LPS are also considered a key link between Western diets, inflammation, and obesity and metabolic disorders [2].

LPS are normally present in the blood at very low levels. In certain infections, LPS levels increase substantially, causing sepsis. LPS can also enter the blood during leaky gut or with certain types of fat [3].

Where Are They Found?

LPS are found on the outer membrane of Gram-negative bacteria. Gram-negative bacteria, such as E. coli and Salmonella, are a type of bacteria that often cause health problems and resist antibiotics (many probiotics, on the other hand, are gram-positive bacteria).

Gram-negative bacteria colonize the respiratory, urinary, and GI tracts, including the mouth and gut. The largest concentrations are found in the gut.

Structure

LPS are large molecules that are composed of three distinct sections [4]:

• O-antigen or O-specific chain (chain of many simple sugars, capable of being recognized by the immune system)
• Core oligosaccharide (a small chain of simple sugars)
• Lipid A (two glucosamine molecules bound to many fatty acids)

The fat component of LPS, called lipid A, is responsible for the toxic and inflammatory properties of LPS.

Lipid A is anchored to the cell membrane, while the rest of the LPS projects from the cell surface into the surrounding environment. However, once the bacteria dies, and the cell membrane falls apart, the lipid A is exposed and can cause damage [4].

How They Disrupt the Immune System

LPS are potent stimulators of the immune system. If LPS remain in the gut, they don’t activate the immune system and cause harm. The ability of LPS to promote inflammation depends on their ability to enter the blood [5].

Besides infection, the