Bacteria and Fat: A 'Perfect Storm' for Inflammation

From ScienceDaily website (see original article)

Oct. 30, 2013 — Making fat cells immortal might seem like a bad idea to most people, but for a team of University of Iowa scientists it was the ideal way to study how the interaction between bacteria and fat cells might contribute to diabetes.

The connection between fat, bacteria, and diabetes is inflammation, which is the body's normal reaction to infection or injury.
Inflammation is beneficial in small, controlled doses but can be extremely harmful when it persists and becomes chronic.

"The idea is that when fat cells (adipocytes) interact with environmental agents -- in this case, bacterial toxins -- they then trigger a chronic inflammatory process," says Patrick Schlievert, Ph.D., UI professor and head of microbiology and co-senior author of a new study published in the journal PLOS ONE.
"We know that chronic inflammation leads to insulin resistance, which can then lead to diabetes.
So people are very interested in the underlying causes of chronic inflammation."

The UI researchers used immortalized fat cells to show that bacterial toxins stimulate fat cells to release molecules called cytokines, which promote inflammation.
By immortalizing fat cells the UI team created a stockpile of continuously dividing, identical cells that are necessary for repeat experiments to validate results, explains Al Klingelhutz, Ph.D., UI microbiologist and co-senior author of the study.

Previous studies have shown that a toxin called lipopolysaccharide (LPS) produced by E. coli bacteria that reside in the human gut, triggers fat cells to produce pro-inflammatory cytokines, and this interaction has been proposed to contribute to the development of diabetes.

The UI team focused on a different bacterium, Staphylococcus aureus (staph), which appears to be important in the context of diabetes for two reasons. First, as people become obese and then progress into diabetes they become very heavily colonized with staph bacteria.
Secondly, staph is the most common microbe isolated from diabetic foot ulcers, one of the most common and health-threatening complications of diabetes.

All staph bacteria make toxins called superantigens -- molecules that disrupt the immune system.
Schlievert's research has previously shown that superantigens cause the deadly effects of various staph infections, such as toxic shock syndrome, sepsis, and endocarditis.

The new UI study shows that superantigens from staph bacteria trigger fat cells to produce pro-inflammatory molecules.
Moreover, the study found that superantigens synergized with LPS from E. coli to magnify fat cells' cytokine responses, amplifying the inflammation, which could potentially boost the likelihood of developing diabetes.

"The E. coli that resides in our gut produces LPS and every day a small amount of this toxin gets into our circulation, but it is generally cleared from the circulation by the liver.
However, people colonized by staph bacteria are also chronically exposed to superantigens, which shut down the LPS detoxification pathway," Schlievert explains.
"That creates a synergy between the 'uncleared' LPS and the superantigen.
All these two molecules do is cause inflammation and cytokine production. So in essence, their presence together creates a perfect storm for inflammation."

The findings suggest that by promoting chronic inflammation through their effect on fat cells, staph superantigens may play a role in the development of diabetes.
In addition, the chronic inflammation caused by the superantigens may also hinder wound healing in diabetic foot ulcers.
The ulcers, which affect 15 to 25 percent of people with diabetes, are notoriously difficult to heal and can often lead to amputation.

Why immortalize fat cells?

The UI team created immortalized fat cells for their research because primary fat cells (taken directly from fat tissue) are not very useful for lab experiments.
Once the primary cells are grown in a dish, they quickly stop dividing and can't be used for repeated experiments.
In contrast, the immortalized fat cells allow experiments to be repeated multiple times on identical cells ensuring consistent, reproducible results.

Klingelhutz and his team immortalized immature precursor fat cells by adding in two genes from HPV (the virus that causes cervical cancer) along with a gene for part of an enzyme that controls the length of cells' telomeres -- the pieces of DNA that protect chromosome tips from deterioration.
These immortal precursor cells could then be "grown up" in petri dishes and differentiated into normal fat cells.

"The immortal fat cells are a great experimental tool that will allow us to investigate the mechanisms of the inflammation and allow us to test ways to potentially inhibit the response," says Klingelhutz. "That would be a goal in the future."

Connection Between Inflammatory Stimulus and Parkinson's Disease Examined

From ScienceDaily website

Apr. 29, 2013 — Parkinson's disease (PD) is a progressive degenerative disease affecting a person's ability to coordinate and control their muscle movement.
What starts out as a tremor in a finger will eventually lead to difficulty in writing and speaking, and ultimately the inability to walk without assistance.
Since the 1950s research has shown that people with Parkinson's have decreased levels of the chemical dopamine in their brains, which is involved in sending messages to the part of the brain that controls coordination and movement.
Subsequent research has found that dopamine-generating cells, known as dopaminergic neurons, are also absent in a specific area of the brain in those with PD.

The precise cause or causes of PD is unknown, but there is a consensus that an inflammatory event or episode is involved in the initiation of neurodegeneration, and that chronic neuroinflammation is a sustaining and exacerbating reason for the loss of the dopaminergic neurons.
A new study conducted by a team of Texas researchers brings the understanding of inflammation's role a step further.
They have found that a single, high-dose exposure of an experimental inflammatory agent in an animal model causes changes in brain tissue that are similar to those associated with the development of the disease.

The study was conducted by Roger Bick and his colleagues Marie-Francoise Doursout, Michael S. Schurdell, Lauren M. Young, Uzondu Osuagwu, Diana M. Hook, Brian J. Poindexter, Mya C. Schiess, and Diane L. M. Bick, all at The University of Texas Health Science Center at Houston (UTHealth), Houston, TX.
Dr. Schiess presented the team's findings at last week's Experimental Biology 2013 meeting, held at the Boston Convention and Exhibition Center, Boston, Mass.
Their poster presentation was entitled, "Inflammatory cells and cytokines in the olfactory bulb of a rat model of neuroinflammation; Insights into neurodegeneration?" The full study will appear in an upcoming edition of the Journal of Interferon & Cytokine Research.

Methodology

In the study, the researchers examined inflammatory cell and cytokine production in brain tissue from a lipopolysaccharide (LPS)-treated rat model that mimics many of the neuropathologic changes associated with PD.
Concurrently, they monitored the appearance of glial cell line-derived neurotrophic factor (GDNF), a neuronal protective agent, and circulating nitric oxide (NO) levels. They also examined the immune system associated cells in the olfactory bulb of the brain. It is known that Parkinson's starts with this mechanism.

Twelve male Sprague-Dawley rats were treated with intravenous LPS in saline, 12 control rats were treated with saline, and all were maintained for up to 48 hours before euthanasia and brain removal.
Brains were removed from both groups at defined times, blood and other tests were conducted, and images of various sections of the brain, including the olfactory bulb, cortex and cerebellum, were taken using fluorescent microscopy.

Results and Conclusions

In general, the researchers found that a single injection of LPS elicited a systemic inflammatory response in the rats, as indicated by an elevation in certain circulatory cytokines. Tissue taken from the olfactory bulb showed the presence of immune associated cells.
Individual cytokines within the olfactory bulb showed an increase in certain types of cytokines.
Taken together, the complete analysis indicated that the single dose of LPS stimulated an inflammatory response that closely resembled the hallmarks of the development of the disease.

The results suggest an involvement of both the peripheral and the central nervous system immune components in response to inflammation and inflammatory episodes.

As a result, the researchers suggest:

(1) inflammation initiates an immune response;

(2) the presence of continuing and increasing pro-inflammatory mechanisms results in a process whereby cellular protective mechanisms are overcome and the more susceptible cells, such as the dopaminergic neurons, enter into cell death pathways; and

(3) this leads to a series of events that are a key part of the progression of PD.

Next Steps

Neuroinflammation is a significant problem for those with PD, and it persists throughout the course of this debilitating illness.
Understanding of the essential processes behind it is the best pathway to finding therapeutic approaches to address it.
This study highlights an opportunity to better understand the role inflammation plays in the process.