Leukocytes Negative Effects After Ischemic Stroke

Leukocyte Accumulation and Hemodynamic Changes in the Cerebral Microcirculation During Early Reperfusion After Stroke by Leslie S. Ritter, Jose A. Orozco, Bruce M. Coull, Paul F. McDonagh and William I. Rosenblum

This week’s peer-reviewed article is about the role of leukocyte accumulation and the changes in the flow of blood after an ischemic stroke, specifically a middle cerebral artery occlusion reperfusion (MCAO-R).

How were they able to model an MCA stroke?

They used a technique called intraluminal filament method (IFM). The animal model of choice was the male Sprague-Dawley rats at 250-300g mass, which were separated into two groups, namely, the sham group (n=7) and the experimental or MCAO-R group (n=7). They took the rats and anesthetized them and visualized the right carotid artery by making an incision on the rat’s neck. The IFM as described on the paper was confusing at first, so I searched for how this technique is done. I found a video (link below) that showed how the procedure is done. Basically, once they’ve visualized the common carotid artery, they tie ligatures on the external carotid artery (ECA) and the common carotid artery (CCA) to prevent the bleeding. Then they make an incision by the internal carotid artery (ICA) and insert the nylon filament. For the sham surgery, they did the exact same thing, but withdrew the nylon filament immediately. However, for the MCAO-R group, the filament was left for two hours then was removed. They took a piece of the dura and observed the hemodynamic changes using a fluorescent microscope.

What did they find out?
- There were no significant statistical difference between the sham and MCAO-R group with regards to gases, blood pressure, body temperature, and body weight.
- In the venules, there were presence of leukocyte adhesion after MCAO-R compared to sham group
- In the arterioles, there were presence of leukocyte adhesions in the MCAO-R only at 30 minutes but not after 15 or 60 minutes
- In the capillaries, leukocyte trapping was greater in the MCAO-R group at 15 and 30 minutes
- Rolling leukocytes were significantly higher in the MCAO-R group compared to the sham group

• They talked about the reason why there were high numbers of rolling leukocytes in the MCAO-R group. A part of it was that selectin adhesion molecules and integrins +ICAM-1 ligands are upregulated during an ischemic episode.
• In the case of an ischemic stroke, the endothelial cells of the vessels are stimulated to express selectin surface proteins and leukocytes bind to these with a weak affinity and cause the leukocytes to basically roll. The link below shows a great video of how leukocytes roll. It’s pretty cool!

- With regards to shear rates, the sham group had a decreasing trend while the MCAO-R group was significantly lower

• Leukocyte plugging in the capillaries could be responsible for the low shear in the MCAO-R group, but it’s still a controversial concept.

Their study was able to show that there are leukocytes at high levels present during an ischemic stroke, and they do cause damage once they are activated by releasing toxic mediators, which will eventually hinder the process of healing. I feel like it's not a surprise that leukocytes are recruited in the ischemic area because it is part of what they do. It was surprising to see and know that they were also responsible to injury after an MCAO-R. 

Can you think of other way leukocytes can be dangerous during recovery from a stroke and reperfusion?

Journal Article Link

http://www.ncbi.nlm.nih.gov/pubmed/10797180

Filament MCAO

http://www.jove.com/video/2423/modeling-stroke-mice-middle-cerebral-artery-occlusion-with-filament

Leukocyte Rolling

http://www.youtube.com/watch?v=WEGGMaRX8f0

Hamartin: The Protector of Neurons

As I was doing research for this week, a lay science article caught my eye.  An article was published by the BBC last week describing a possible new technique in treating stroke.  In it, the author summarizes the results of a recent study called "Tsc1 (hamartin) confers neuroprotection against ischemia by inducing autophagy," published in the journal Nature Medicine, which was examining the methods by which certain cells in the brain are able to survive extended periods without oxygen during stroke, while other cells die quickly.

It appears that the key to cell survival in these hypoxic conditions is the production of a protein called hamartin.  Hamartin, or Tsc1, is a protein produced by hippocampus cells in the brain when they lack oxygen.  Hamartin appears to cause the cells to stop producing other proteins and instead break-down those it already has, thus temporarily halting its use of oxygen.  In the study, researchers were able to isolate the gene that regulates hamartin expression in rats, and turn it off.  This caused a 38% increase in the rate of cell death in stroke in the animals, compared to those with an active hamartin gene, indicating the protective role that harmartin plays.

The goal of the researchers is to be able to find a way to turn on the genes to produce hamartin in other brain cells.  The BBC article suggests that an additional, long-term goal is to produce a drug that could be given to a patient in the early stages of stroke, in order to cause their own cells to produce enough hamartin to allow them to survive.  Of course, this is highly reliant on the ability of stroke to be detected in its early stages; administration of hemartin significantly after the onset of stroke would have negligible benefits.  It should additionally be noted though that other experts contacted by the journalist indicate that this may be a long way off.  Nevertheless, the prospect is certainly an exciting one.

Picky Details

This week I took a look at the article Effects of Cholesterol and Inflammation-Sensitive Plasma Proteins on Incidence of Mycardial Infarction and Stroke in Men (downloadable here http://circ.ahajournals.org/).

All too often I find myself reading articles similar to this one, who find a correlation between two things and think to myself "le awesome so glad we figured this out" (or if it isn't totally figured out at least we know a little more than we did before). Then I start to think about the results a little more and the possibilites for outside factors and errors start piling up in my mind. Particularly in health related studies, I find myself asking well what if these people smoke versus people who don't smoke, or work out 7 days a week versus watching CSI 7 days a week, or eat McDonald's for every meal like the guy on Super Size Me? More often than not I find that researchers aren't necessarily ignoring these details but they just don't mention them in their results and I find myself asking well do these relate to a soccer playing 16 year old or a 35 year old code monkey?

Personally I'd say that 7/10 of the articles leave me unhappy with just a little bit of the population details missing. By details I mean I want to know more about the people who were in the study, are we sure that these statements can be applied across the board, or does it only work for qualified individuals with certain risk factors etc. This article in Circulation, did a great job, imho, of separating risk factor groups and determining just how universal their results were. By dividing their subjects in to categories from smokers to non-smokers, (even a subset of how many cigarettes per day) level of physical activity, pre-existing conditions, and current physical health the study can more accurately declare their results, stating that elevated ISP levels, not hypercholesterolemia alone can give men a higher risk of ischemic stroke. This slight differentiation in detail could lead to much more efficient and successful follow up work.

Do you guys think that when looking at studies such as this one there should be a certain number of characteristic groups defined and studied before publishing results, particularly with studies that look at inflammatory factors, their origins, and effects? Is it possible that this would just be another hoop researchers would have to go through in order to get possible life saving results out in to the world or do you think it's more of a precautionary measure that would save a lot of time and trouble from unnecessary treatments?

I think it could be argued that it needs to be thought of on a case to case basis but for the most part definitive guidelines of different characteristics represented per group would usually be more helpful. Especially when you consider, like many inflammatory diseases, that there are so many risk factors and characteristics that can make one person more prone to susceptibility than others.

E-Selectin Tolerance Protects Against Stroke

E-Selectin is a cell surface glycoprotein cell adhesion molecule that is inducible by cytokines. It was used in this study because it is not constitutive and its expression is limited to the endothelium that becomes activated in response to an inflammatory stimuli. In this case, E-Selectin serves as a molecular target for regulatory T cells to activating blood vessels where they can release anti-inflammatory cytokines, suppressing vessel activation, and therefore preventing thrombosis and hemorrhage seen with strokes.

Previous studies have determined that mucosal tolerance to E- Selectin, meaning that the immune system does not see it as a foreign antigen, has the effect of preventing both hemorrhagic and ischemic strokes in spontaneously hypertensive, genetically stroke prone rats. This study was a continuation of that to determine whether tolerance to E-Selectin has protective effects in ischemic brain damage after permanent middle cerebral artery occlusion(MCAO) in SHR-SP rats, and whether those effects are regulated through the generation of regulatory T cells.

The study utilized a total of 35 male and female rats from SHR-SP breeders that were divided into 4 groups. These four groups were PBS(control) and E-Selectin tolerized groups that were each divided into single-tolerization and booster tolerization groups. The single tolerization groups received the PBS or E-Selectin nasally every other day for a total of 10 days and 5 administrations. The booster-tolerization received the intranasal installation on the same schedule, but was repeated once after 11 days. The tests for this study included Delayed Type Hypersensitivity(DTH) reaction, ELISA, assessment of infarct volume, as well as an adoptive transfer test. In the adoptive transfer test, the spleens were removed from rats 48 hours after their final dose of the tolerizing agent on the booster tolerization schedule. The spleens were used to make a suspension and culture cells to inject into SHR-SP rats before the MCAO.

The results of this study showed that E-Selectin mucosal booster tolerization had a significant decrease in infarct size in rats at both 6 and 48 hours after the onset of ischemia. Single tolerization experiments were not as significant and showed only a slight  decrease in  infarct size and minimal trend toward benefit in stroke outcome. The results from the DTH test showed that the responses to E-Selectin were repressed in rats that were tolerized to it, indicating that there were antigen specific regulatory T cells produced in tolerized rats, also implying a cell mediated response in protection against stroke. Additionally, the adoptive transfer of splenocytes from tolerized rats resulted in a similar level of protection in normal rats as seen in rats that were on the booster tolerization schedule, also supporting the finding that this reaction is cell mediated. Finally, the ELISA test showed an increase in IL-10 in tolerized splenocytes when compared to control splenocytes, showing again that there was a substantial involvement of regulatory T cells in the protection against the effects of stroke. Overall, the mechanism for this type of protection against the effects of a stroke still remains unknown and leaves room for future research in this area.

Does the utilization of E-Selectin seem like a reasonable option to prevent the effects associated with strokes?

Do you see any potential issues in using this type of therapy in humans?



Chen Y, Ruetzler C, Spatz S, et al. Mucosal Tolerance to E-Selectin provides cell-mediated protection against ischemic Brain Injury. Proceedings of the National Academy of Sciences. 2003:100(25);15107-15112

Hypothermia used as a neuroprotectant for treatment after an acute stroke.

Hypothermia used as a neuroprotectant for treatment after an acute stroke.  

Article Link: http://www.medscape.com/viewarticle/744579

For the past few years researchers have been testing the effects of hypothermia treatments to decrease damage caused by an acute stroke. This method is done by intentionally inducing controlled reductions in a patient’s core temperature to mild-moderate degrees of 30-34 degrees Celsius. Researchers hypothesized that by inducing hypothermia, it will act effectively by inhibit toxic effects and stimulating important repair mechanisms.

Patients who experience Ischemia are seen to undergo various tissue damages such as apoptosis and cellular death, which are caused by various ischemia-induced pathways. Based on the experiment animal studies performed by the researchers, they believe that hypothermia can inhibit these detrimental pathways caused by ischemia and thus reduce cellular injury.  They concluded that hypothermia can inhibit energy depletion, ion shifts, free radical formation, EAA release and inflammation processes which would otherwise be detrimental to the human body. Furthermore, it was noted that hypothermia reduces cerebral O2 consumption rate by 6% per 1 degree Celsius. This was great news for researchers for brain tissue could be preserved for longer periods of time.

Questions:

Do you think hypothermia is a viable option for treating patients following an acute stroke?

What would you consider the pros and cons to be to this treatment?

Reviewing back to the article, based on the methods of inducing hypothermia, what would you consider (based on your own thoughts) to be the potential side effects or complications of hypothermia treatment? (without reading further ahead into the article)

I previously wrote a blog about magnet therapy to treat stroke. Would you find hypothermia treatment to be a better alternative to treating stroke?

Magnet Therapy May Help Stroke Survivors Recover

http://www.webmd.com/stroke/news/20111213/magnet-therapy-may-help-some-stroke-survivors-recover

Magnet Therapy May Help Stroke Survivors Recover

It has been observed that stroke survivors who have experiences a decrease in the use of one hemisphere of their brain have experienced an increase in nerve cell stimulation to the defective hemisphere through magnet therapy. Magnet therapy (TMS) enables the stimulation of nerve cells by an electrical current which is produced when the physician places a large magnetic against the patients scalp. The article clams that this magnet therapy can be effective after a stroke because it allows for the electrical activity within the brain to become rebalanced between the two hemispheres. Researchers claim that when a stroke occurs and half the hemisphere becomes defective then the other hemisphere that is active becomes overactive in an attempt to compensate for the loss. So by using this magnet therapy, it will allow the brain to return to a more balanced state.

The study performed:

Ten out of 20 people who faced this problem following a stroke received the magnet therapy daily for two weeks. The other 10 received a fake treatment. All participants also did standard brain retraining. Everyone took tests that measured their abilities after the study and then again two weeks later. The tests measured line crossing and figure- and shape-copying ability. The tests also measured activities of daily living affected by neglect, such as dialing numbers on a phone, reading a menu, and sorting coins.

Overall, participants who received the magnet therapy improved by 16.3% immediately following treatment and by 22.6% two weeks later. There were no improvements seen in test scores of those who got the other treatment.

The overactive brain circuits also improved among people who got the TMS treatment, the study showed. Researcher Giacomo Koch, MD, PhD, of the Santa Lucia Foundation in Rome, Italy, and colleagues point out that the changes could be the combined effects of the mental tasks and the TMS.

Just based off of this article what do you guys think about Magnetic therapy.  What can you conclude would be the pros and cons of this therapy and would you find it to be valid and useful in aiding stroke victim recovery or is this method to extreme for the average person?

Chocolate Lowers Stroke Risks!

The last disease we talked about was obesity and diabetes, and for the next couple of weeks, we will be talking about stroke, which is also a disease that is very much related to obesity and diabetes. This week is all about media and review articles, and the topic I got was about chocolate and its beneficial effects on lowering stroke risk and lowering heart disease incidence.

First of all, we should be able to define what is stroke. Stroke is like a heart attack but in the brain. It is divided into two types: (1) Ischemic stroke and (2) hemorrhagic stroke. Ischemic stroke is when an artery in the brain is blocked and causes restriction of blood and oxygen in the brain while hemorrhagic stroke is when a vessel in the brain bursts and spills the blood in the brain.

The paper discusses about the health benefits of chocolate in women. It has been in the news before and a lot people seem to know about the benefits of chocolate. But it is not chocolate in general, it is dark chocolate. Dark chocolate is the type of chocolate that is rich in cocoa, and cocoa is the vital substance that has anti-inflammatory and antioxidant properties.

The author did not say much about what makes cocoa good for you. I did some research on cocoa and the main substance that reduces heart disease and stroke risks is flavonoids. Sounds familiar? Yes it does! Flavonoid was one of the plant metabolites we discussed when we talked about the review articles regarding onions. Flavonoids suppress oxidation of low density lipoproteins or LDL cholesterol. This explains the reason on why dark chocolate is better compared to milk or white chocolate. Dark chocolate has more cocoa in it, so the more the cocoa, the more flavonoids it has.

It seems like a delicious way to fight off heart disease and stroke. The question I have for you is whether or not this is an ideal lifestyle change to have? With all the obesity, diabetes, etc. diseases we have talked about, is adding chocolate good for you? Also, does this have the same effects in men? The paper and research only talked about women, and it made me wonder on whether or not the anatomical makeup of men versus women play a role here.


Reference: http://www.naturalnews.com/034077_chocolate_stroke_risk.html

NO, Ischemia, and Brain Inflammation

The main focus of this article was to highlight the effect that NOS-2 plays in the role of stroke caused by cerebral ischemia and to look at experimental studies that examined the therapeutic utility of NO donors as well as NOS inhibitors.

Some of the main components of stroke include excitotoxicity, cell death, and compensatory neurogenesis often as a result of the activation of Nitric Oxide through Nitric Oxide Synthase. Nitric Oxide is a free radical and known vasodilator and is a crucial component of the activation of transcriptionally regulated genes, cell signaling proteins, and the initiation of apoptosis. There are also three different isoforms of the NOS enzyme including NOS-1 (neuronal NOS), NOS-2 (inducible NOS), and NOS-3 (endothelial NOS) with each enzyme being controlled by a single copy gene and different with the respect that each has a different binding domain to target different proteins.

Although it has been seen that all three isoforms of NOS are increased in response to ischemia, NOS-2 occurs later than the other isoforms and does not contribute to early injury related to strokes. This was supported with data that differences in infarct volume  were not seen between wildtype mice and mice lacking the NOS-2 gene after only 24 hours; however, after 48 hours, the NOS-2 deficient mice had a decreased infarct volume following cerebral ischemia. The infarct volume refers to the area of dead tissue from the failure of blod supply caused by the stroke. It was also noted that the NOS-2 deficient mice experienced less impairment related to motor performance following ischemia than the mice expressing the NOS-2 gene. Because NOS-2 is activated by transcription, it is assumed that the pro-inflammatory cytokines such as IL-1Beta and TNF-alpha trigger this activation and that the expression of NOS-2 increases with time when ischemia is present. It was also concluded that even though there is often an association with neutrophil action in response to NO from pro-inflammatory cytokines and adhesion molecules, no connection could be made between neutrophils and ischemia.

The therapeutic research that the article presented was related to both the inhibition of NOS as well as Nitric Oxide donors. It is suggested that the Nitric Oxide produced through NOS-1 and NOS-2 are detrimental, while the NO produced through NOS-3 is beneficial. It was found that in relation to NOS inhibitors, specific inhibitors were found to reduce infarct volume, however, when non-selective inhibitors were used, did not alter infarct volume. This was most likely due to the beneficial benefits of NOS-3 being inhibited as well. Similarly, NO donors  including L-arginine encountered the same problem as they could not differentiate between detrimental and beneficial routes. One postitive aspect of NO donors was that neurogenesis increased following ischemia and improved functional outcome. This was important because this neurogenic response was not seen in mice lacking NOS-2. Additionally it was concluded that the production of NO through NOS-3 has a protective effect through preconditioning. There was also evidence that supported the steroidal regulation of NOS-2 through items such as estrogen and progesterone, which actually blocks increased NOS-2 expression and reduces infarct volume.

Nitric Oxide: Helpful or Harmful?

Something that stood out to me as I was reading one of the articles for this week was the role that nitric oxide (NO) plays during stroke.  The review article “Pathobiology of an ischemic stroke,” notes that the actions of NO seem to contradict each other, showing that  while NO synthesized by a Ca²⁺ -dependent enzyme can react to form, “the highly reactive species, peroxynitrate, that promotes tissue damage,” it also has therapeutic effects, acting to improve the affected area’s microcirculation to increase oxygen delivery and clean out other reactive species.  The article “Nitric oxide, ischaemia and brain inflammation,” also notes a similar contradiction.

References to these beneficial effects made me curious as to whether it would be possible to use NO therapeutically in stroke cases, or if some substitute could be used that mimics NO’s vasodialatory abilities without causing an increase in the amount of damaging reactive species.  From a quick PubGet search it appears as though little is being done in this area, as the majority of research is focused on reducing the production of neuronal nitric-oxide synthase (NOS), the form of NO that reacts to become the reactive species.  One article though did grab my attention.  Entitled, “Inhaled nitric oxide reduces secondary brain damage after traumatic brain injury in mice,” from the Journal of Cerebral Blood Flow and Metabolism, it describes how researchers used a mouse model to study the effects of immediate post-injury inhalation of NO on the brain.  

Their results were quite promising, specifically noting that NO inhalation had no effect on NOS levels in the brain, and that secondary lesion growth was significantly reduced compared to the control group.  Now, it should be noted that the mice were subjected to traumatic brain injury (an injury from an external source), rather than an embolus as seen in stroke, but as the main effect of both is ischemia, their results should be relatively transferable.  A larger concern would be the ability to replicate their results in a human study.  This is certainly an area worth further research.

Check Your Facts Before You Tell Everyone to Carry Listerine 24/7

If you google search the definition of science you'll find something to the likes of this in response, 

"sci-ence noun 1. The intellectual and practical activity encompassing the systematic study of the structure and behavior of the physical and natural world through observation and experiment."

Being science majors ourselves we know experiments don't always go as planned, there's a lot of trial and error in the process of these major scientific breakthroughs. Health sciences are particularly difficult because one person may react to some illness or ailment differently than another person or animal making these studies very difficult at times. What it boils down to is science isn't always 100%, we might be 99.99999999% sure but you can't always say with absolute certainty that something is so (even if you cross your heart and swear to die or stick a needle in your eye).

My article (under the content section as "stroke lay article" titled Gum Disease Linked to Stroke from RedOrbit) was published in 2009 and states that based on a study of over 1,000 men in Boston researchers were confident in stating that they found a link between periodontal disease, which would indicated inflammation, and cerebrovascular disease in men. 

Two years later the same website posted this article, Heart Disease, Cancer, Diabetes, Stroke Signs Can be Found in Mouth Says Atlanta Dentist. GREAT! We had this great idea a few years ago, now we've got some people supporting our idea saying that "sore, red or swollen and bleeding gums could be the gum disease periodontitis, which can increase the risk of stroke ". As you may suspect though, this isn't the end to our story.

Just a little over a year later, the same website posted this article No Proof That Gum Disease Causes Heart Disease Or Stroke. You may be asking yourself, "But how is this possible?!? They JUST told me I've got to keep my mouth clean or I might have a stroke?" Well, as I told you before, science isn't always 100% absolutely positively certain about pretty much anything. For all we know in the next year maybe someone will discover that the key to fixing all the cerebrovascular accidents (strokes) in the world really is to just make sure you're flossing twice a day (I'd say the chances of that are PRETTY slim to say the least but you never know). I guess what I'm saying is just make sure you're well informed about all possibilities and scenarios before you start preaching that everyone should carry a bottle of Listerine with them 24/7. Science is an ever changing field with new innovations and ideas every day and that's what makes it so awesome, albeit rather annoying when years of work could be for not but to say that the idea didn't work, we've just got to make sure we're well informed and on top of our research game!

The "Cure" for Diabetes

The lay article from last week discussed weight loss surgery, such as gastric bypass or stomach band surgery, as a cure for diabetes. I was taken aback at first when thinking of a cure for diabetes because it seems that Type II diabetes has only been "treated" with diet and exercise. I'm not sure why I hadn't realized this before, but with the proper diet and exercise some people are actually able to reverse their Type II diabetes. I found a few bloggers who even swear by their "5 easy steps to curing diabetes." So it is an interesting concept that weight loss surgery may be marketed as a treatment for Type II diabetes instead. As we discussed in class, we all generally believed that prevention of diabetes is really the best "cure" and that diet and exercise should be the first choice for patients looking to reverse their diabetes. One of the reasons for using surgery as a last option is because it is invasive and requires a recovery period. An interesting alternative I found to lap band surgery can be found on this website, http://rocalabs.com/answers/ask-the-doctor/medical-answers/past-weight-loss-surgery-patients/. It is an edible formula that fills the majority of your stomach. Any thoughts on how effective the study discussed in the lay article would be if this formula was used instead of the stomach banding surgery?

Mice and Menopause

This week I studied the paper “Effects of high fat diet on plasma lipids, adiposity, and inflammatory markers in ovariectomized mice.” This article pointed out that the combination of a high fat diet along with an ovariectomized mouse correlated with increased body weight, increased adipocyte diameter, and an increase in pro-inflammatory markers such as leptin, IL-6, and TNF-alpha. These ovariectomized mice can be compared to women going through menopause or who are post-menopausal because they also experience weight gain, shift in fat distribution throughout the body, along with other frustrating side effects. For reference, menopause is a time in a woman’s life where her ovaries stop making eggs and produce less estrogen and progesterone, leading to the termination of her menstrual cycle.

So why are estrogen and progesterone so important to the female body? This article shows that women with their ovaries (non- menopausal) seem to have “hormonal protection” against weight gain and are less at risk for inflammation related diseases such as diabetes. It is not completely clear what estrogen’s role is because oddly it seems to down regulate levels of adiponectin. It can be concluded, however, that it is very important for menopausal women to avoid a high fat diet because they no longer have this hormonal protection.

What I found most intriguing during our discussion of this article in class was our thoughts on the age at which menopause occurs. Is it possible that the age is decreasing? Years ago menopause was considered to take place around 60 years of age, but now it can be anywhere between 40-58 years of age, with an average age of 51.  Sometimes menopause can even occur before 35 and this is called premature menopause (http://www.webmd.com/sexual-conditions/sexual-health-your-guide-to-menopause) or premature ovarian failure. I thought it would be interesting to research if and why menopause is occurring earlier in women’s lives and how that might relate to obesity, diabetes, or inflammation.

Studies seem to show that there is a relationship between obesity in children and early puberty. One possible explanation for this is that the levels of leptin are increased in obese children, and leptin, along with other hormones, play a role in the onset of puberty. I thought there might be a connection between early puberty and early menopause, but it seems there is no evidence in the literature to support this. Although I read somewhere that poor diet is a possible explanation.  

Some other possible explanations for premature menopause may include thyroid dysfunction, autoimmune disorder, and genetics (http://www.earlymenopause.com/causes.htm)

 I’d be interested to see what you guys are able to find in terms of obesity, inflammation, and premature menopause!

IL-6, Diabetes and Cardiovascular Disease in Women

Hello again everyone! For week 2 of obesity/diabetes, I focused on the paper that discussed the supposed increase in proinflammatory cytokines in diabetic women with some sort of cardiovascular disease, which included a heart attack, coronary artery bypass surgery, stroke, or coronary angioplasty. The paper looked specifically at IL-6, TNF-alpha, and IL-1 beta.  The study itself consisted of four different groups: 1) the healthy control group without diabetes or cardiovascular disease, 2) women with only cardiovascular disease, 3) women with only diabetes, and 4) women with diabetes and cardiovascular disease, (which was the group of interest).  Blood samples were taken from the subjects, and ELISA was used to measure the amount of the 3 different cytokines in the blood.

They found that IL-6 levels were significantly increased in women with diabetes and cardiovascular disease. TNF-alpha was also highest in the group with diabetes and cardiovascular disease, BUT the increase was not statistically significant. IL-1 beta showed no significant pattern or increase so the authors concluded that it is not one of the cytokines that is chronically higher in patients with diabetes and cardiovascular disease.

 

One very important point that Dr. Cohen brought up in class was the significance of significance!! The data for TNF-alpha did not show a statistically significant increase in any of the groups over the control. And yet, the authors discussed the effects and mechanisms of TNF-alpha at length, and treated their data as if it was significantly increased in subjects with diabetes and cardiovascular disease. We cannot make claims from data without them being significant, because that data doesn't officially prove or support the hypothesis.

In my opinion, the article should have been entirely focused on IL-6, since it did show a statistically significant increase in the subjects. IL-6 drives B cell differentiation and stimulation, as well as promotes inflammation and fever. In addition to its immunoregulatory actions, IL-6 has been proposed to affect glucose homeostasis and metabolism directly and indirectly by action on skeletal muscle cells, adipocytes, hepatocytes, pancreatic beta-cells, and neuroendocrine cells. Genetic studies have shown type 2 diabetes may be associated with an over-expression of the gene for the IL-6 receptor, which means increased levels of IL-6 would be able to effectively bind and promote inflammatory processes. The paper mentions a study that was done where IL-6 was given exogenously to mice and it was shown to enhance fatty lesion buildup in atherosclerosis. IL-6 was also increased after a heart attack and is associated with a lower ejection fraction, which is a measurement of how well the heart is pumping out blood.

The article also brings up the point that the increased cytokines, such as IL-6, in diabetes are primarily secreted from cells not in the circulation, such as adipocytes and endothelial cells in blood vessels, not from immune cells. Last week, we talked about adipocytes’ role in promoting inflammation with their secretion of leptin and adiponectin. I think this just goes to show the damaging role that obesity plays in inflammation, since adipocyte hyperplasia and hypertrophy can lead to such damaging inflammatory effects. 

The article also makes the point that diabetes is a stronger risk factor for coronary heart disease in women than in men. Diabetes is associated with a 3-7 times greater cardiovascular disease risk among women compared with a 2-3 times greater risk among men. So I wanted to ask you guys, why do you think that is? What would make diabetes so much worse for women in terms of acquiring cardiovascular disease? As a woman with cardiovascular disease and diabetes running in my family, this is particularly relevant to me!

Alcohol...helpful or not?

"Young adult obese subjects with and without insulin resistance; what is the role of chronic inflammation and how to weigh it non-invasively?"

Giovanni Tarantino*1, Patrizia Colicchio1, Paolo Conca1, Carmine Finelli1,

Matteo Nicola Dario Di Minno1, Marianna Tarantino2, Domenico Capone3

and Fabrizio Pasanisi1

In the above titled paper, the authors claim that both increased spleen diameter and CRP (C-reactive Protein) are valid tools to utilize in diagnosing insulin resistance. While the authors affirm that obesity is the leading risk factor for metabolic syndrome which further expresses into non-alcoholic fatty liver disease, they are sure to keep their experimental population within a range of people that do NOT drink alcohol. They mention that this was strictly enforced by utilizing the MAST (Michigan Alcohol Screening Test) and CAGE (Cut down, Annoyed, Guilty, and Eye Opener) so that alcohol abused fatty liver acid would be ruled out according to DSM-IV diagnostic criteria.

Since the authors were so strict in enforcing the non-alcoholic form of fatty liver disease (NAFLD), it came to my attention to question if the alcoholic form of fatty liver disease (ALFD) was a better or less severe form of the disease, or if it was indeed worse. Searching through some valid research articles, I found this one to be helpful, yet with some grey areas still:

http://www.biomedcentral.com/content/pdf/1471-2458-10-237.pdf

 Do you think that it actually convinces us that one is better than the other depending on the health situation of the person? Also, correlating to our theme of obesity/diabetes, which type of fatty liver disease is more "favorable" to have?

Leptin + Adiponectin = Inflammation!!

Hi everyone! As you all know, our topic this week is the inflammatory processes involved with obesity and diabetes. The rate of obesity in the U.S. has increased dramatically since the 1990's and has contributed to many metabolic disorders, especially diabetes. Diabetes is marked by chronically high levels of glucose in the blood due to the insensitivity of our cells to insulin. People with diabetes are unable to take up glucose into their cells because they have acquired insulin resistance.

The paper I focused on this week was the review article on inflammation and metabolic disorders. It covered obesity and diabetes along with a slew of other metabolic disorders including hypertension and atherosclerosis. One of the things about the article that I found intriguing was the discussion of two key regulatory hormones involved in obesity: leptin and adiponectin. Obesity itself is mediated by leptin, which is a hormone that controls food intake and body weight through its binding and activation of leptin receptors (OBR). High levels of leptin usually promote weight loss, but in obese people, high levels of leptin have no effect. This is referred to as leptin resistance and is associated with diabetes. 

In regard to inflammation, leptin regulates components of innate and adaptive immunity, including T lymphocytes and monocytes. Leptin also has structural and functional resemblance to proinflammatory cytokines, such as IL-6 and may regulate C-reactive protein (CRP). It is referred to as an adipocytokine. Leptin has been found to be an insulin-sensitizing hormone, but increased amounts of non-functional leptin in the circulation of obese people is associated with hyperinsulinemia and insulin resistance.

Adiponectin is a hormone secreted from fat tissue that increases insulin sensitivity. However, as body mass increases, serum adiponectin levels decrease. Less circulating adiponectin means that insulin sensitivity is decreased, which can lead to diabetes. Adiponectin also normally inhibits the expression of proinflammatory cytokines such as TNF-alpha, but with less adiponectin being produced, these cytokines are more highly expressed, leading to an inflammatory state.

  

The article also briefly discussed the role of lipid oxidation in inflammation, but they didn't do a very thorough job in explaining it. So, I thought this would be a great question to pose to all you bloggers! How does the process of lipid oxidation work? How are reactive oxygen and nitrogen species involved? And what are the consequences of having these oxidized lipids in our circulation? How does the process promote inflammation??

Hopefully this will give everyone some food for thought!

Inflammation and Chocolate

Hey guys! Last week I opened my browser and this article was on the front page of MSN. I thought it was very applicable to what we were talking about in class last week regarding lay articles and basic inflammation. Here is a link:
http://longevity.about.com/od/lifelongnutrition/a/The-Healthiest-Chocolate.htm

The article first points out a population that has distinctively low blood pressure and low incidence rates of cardiovascular disease. The Kuna Indians are not genetically lucky, as shown by their increased blood pressure when they moved into the city. Researchers determined a main factor in their cardiovascular health was their consumption of cocoa. The researchers cite the flavinoids in chocolate as an antioxidant as well as an anti inflammatory agent. This is only mentioned in one sentence, so I would like to see more studies on how exactly flavinoids can affect inflammation and by what mechanism. Unfortunately, the cocoa that the Kuna Indians consume is unprocessed and not very similar to what we can buy in the store. That probably won't stop me from rationalizing why I can have some chocolate- it could be anti inflammatory!

Macrophage-mediated Inflammation in Metabolic Disease

Chawla, Ajay, Khoa Nguyen, and Y.P. Sharon Goh. "Macrophage-mediated inflammation in metabolic disease." Nature Reviews: Immunology. 11. (2011): n. page. Print. <www.nature.com/reviews/immunol>.

Okay so reading the article cited above, a couple of ideas struck me as interesting that were aside from the original objective of the paper...I wanted to elaborate on one specific one and will momentarily. Throughout the paper they address the world-wide dilemma (and especially in the United States) of obesity. They offer new evidence to support the idea that there is indeed a connection between our immune system responses and various metabolic diseases, such as obesity and diabetes. They tell us in explicit detail that macrophages take on the role of a liasion for cross-talk between the metabolic and immune systems in metazoans.

Obesity-induced insulin resistance was a major point in the paper that was found to be caused by classically activated macrophages in adipose tissue that contain the receptors TLR2 and TLR4. When obesity occurs, saturated fatty acids are more prevalent and bind to these receptors, activating the macrophages to produce pro-inflammatory cytokines such as TNF (tumor necrosis factor) and IL-1beta. These leads to various inflammation in adipose tissue by multiple cascade pathways involving inflammasomes, pro-inflammatory genes, alternative activation genes, etc. Figure 1 in the paper does an exceptional job in explaining this cross-talk.

On to the point of this post...the authors mentioned in the second half of the paper that although it is evident macrophages aid in the pathogenesis of metabolic disease such as obesity, the cross-talk found between the immune and metabolic systems most likely evolved to a mechanism to aid immunity. This is interesting because the macrophages in the adipose tissue are most likely required to be alternatively activated macrophages rather than the classically activated ones described above. An example they give in which the cross-talk between the two systems may be beneficial is an acute bacterial infection. This bacterial infection promototes glycogenolysis in muscle tissue, gluconeogenesis in liver tissue, and lipolysis in adipose tissue. As a result glucose and free fatty acid levels are increased and said to support the metabollic demands of macrophages and non-immune cells. As the authors claim that this cross-talk "probably evolved to modulate insulin action and nutrient availability during times of infection." This made me wonder then if the alternatively activated macrophages aided the immune system when bacterial infection is present, will the benefits of taking anti-biotics during bacterial infection nullify or decrease the positive effects of the macrophages when a bacterial infection is present? I understand that antibiotics potentially kill the bacterial infection before it can produce nutrients for immune system cells such as macrophages, but I was wondering if there are any indirect side effects when this occurs? I went through the attached paper, but still am a little unclear on the situation. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2896384/