Conjugated dienes & alcoholic liver disease (ALD)
In organic chemistry, we have been studying conjugated dienes and allylic systems. Many times, we have problems in relating the materials learned in an organic chemistry with real-world phenomena, especially for those interested in biomedical fields.
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| Folic Acid |
In 2011, Lee et al. published a study on alcoholic liver disease (ALD) and the use of folic acid to reduce oxidative stress & hepatic toxicity in an animal model. The article can be found in the hyperlink below:
One of the factors that they use to study the effects of chronic alcoholism on their subjects is the presence of conjugated dienes. In class, we are studying the unique properties of conjugated systems and how they have an increased stability compared to other alkyl systems. Is stability always a "good thing" though?
For extra credit, I want you to thoroughly read & critique this journal article. Do not just cursorily glance over the abstract & figures! One of my goals for my students is to help them be prepared for (and be more comfortable with) critically analyzing scientific literature. After reading this paper, I want you to post a 250-word minimum critique/response. First, briefly summarize the authors' findings. Second, briefly describe the role(s) of conjugated dienes with respect to the liver and/or hepatic toxicity. Finally, do you agree with the authors' findings? Are they discerning too much from their results? Are there any ways they could strengthen their paper?
You can add up to 5% bonus points for a good, well-thought critique. When responding to another person's post, don't just say, "good job!" or "I hadn't thought of that!" or anything of that ilk. I want a thoughtful discussion on this journal article, if possible.
It is fine with me if you use a moniker to remain anonymous; however, you will need to email me what moniker you are using so that I can accredit your exam score appropriately.
The purpose of the study performed was to study the in vivo effect of folic acid supplementation on oxidative stress and hepatic toxicity induced by chronic ethanol consumption. The results are as follows: chronic ethanol feeding to Wistar rats led to significantly elevated plasma Hcy, AST, ALT, and TG levels, while folic acid supplementation partially reduced plasma Hcy, AST, ALT, and TG in ethanol-fed rats. Thus these results indicate that folic acid supplementation appears to lower hepatic toxicity induced by chronic ethanol consumption possibly by decreasing oxidative stress.
ReplyDeleteHepatic toxicity can be caused by abnormal hepatic methionine metabolism, which leads to hyperhomocysteinemia which in-turn leads to alcohol-induced liver injury. Since plasma Hcy levels were reduced with addition of folic acid, it means that hepatic toxicity can be alleviated by supplementation of folic acid. Oxidative stress contributes to hepatic toxicity. Some markers of oxidative stress include conjugated dienes (CD) in isolated LDL. CD levels were found to be greater in high ethanol (HE) fed rats than the folic acid supplemented ones. Thus, one can conclude that folic acid supplementation partially prevents oxidative stress which in turn attenuates hepatic toxicity. Taking this into consideration, it makes sense to agree with the authors of the study. I don’t believe they discerned too much from their results unless there is something I’ve missed in the article.
The idea you present in your response seems to have enhanced my understanding of the role of conjugated dienes in liver or hepatic toxicity. I agree with the idea that folic acid likely reduces oxidative stress. it may have helped all the more if one can propose a likely mechanism through which folate reduces oxidative stress as the journal attempted to do. You reponse is great and informative.
DeleteThe purpose of the study was to determine how folic acid supplements affected rats that were fed ethanol; more specifically the hepatic toxicity and oxidative stress in the rats. The results were obtained by using 32 rats that were divided up into four groups. The first group was the control group which was fed a Lieber and DeCarli liquid diet that included dextrinmaltose, ethanol was slowly added to the diet in 5 days. The second group was called low ethanol and ethanol (12% of the calories) was added to the diet in place of dextrinmaltose. The third group was called high ethanol and ethanol (36% of the calories) was added to the diet. The final group was called FE which had ethanol (36% of the calories) and folic acid added to the diet. The groups were fed the diets for 5 weeks; after which were not fed overnight and then anesthetized. Liver tissue and blood samples were taken and the results were analyzed. The results indicated that folic acid has the ability to decrease hepatic toxicity, which is caused by ethanol consumption, by lowering homocysteine; this in turn lowers the oxidative stress.
ReplyDeleteThe presence and amount of conjugated dienes found in LDL represented the oxidative stress experienced in the plasma; high levels of oxidative stress cause hepatic toxicity.
I agree with the author’s findings. It seems that the experiment was well planned and the analyses of the results were in depth. One thing I think that could help strengthen the paper would be to make the experiment last longer than five weeks and to incorporate female rats in the experiment as well.
Besides only using male rats, they used rats in a specific weight range. I wonder what the results of the study would be if they had used rats from several different weight ranges. Also, they don’t mention the age of the rats. Could that also affect how the rats responded to the folic acid supplements?
DeleteAlcoholic liver disease (ALD) is a disease caused by alcohol consumption. The ethanol causes liver injury and hepatic oxidative stress from free radical formation. A folate deficiency is seen in ALD patients, and this study tested the in vivo effect of supplementing folic acid in ethanol-fed rats. Rats that received folic acid supplements had greatly reduced alanine transaminase and aspartate transaminase activity compared to those who did not receive the folic acid supplement. Because of the decrease in the activity of these two enzymes, the study concluded that folic acid supplements can reduce ethanol-induced liver injury.
ReplyDeleteThe results from this study seem very promising. A treatment to combat ethanol-induced liver injury would be very helpful, but this test does not prove beyond all doubt that folic acid will work. Though the authors seem very sure of their results throughout the paper, they do end by saying it is a potential treatment. More tests need to be performed. The paper does not mention how close the ethanol diet the rats received is to the types of alcohol people generally consume. Would there be any other ingredients that may cancel out the affects of the folic acid supplements? Also, at what point does the folic acid supplement stop working? Is there a certain amount of folic acid that acts as a limit, like no matter how much more you take, it will do the same amount of work as a smaller dose? While I do agree that these results are very promising, I would be interested to see what other studies are finding.
It would have been a much better study if the researchers had given the rats varying amounts of ethanol to simulate the varying amounts of alcohol that humans consume.I also wished the researchers gave an explanation as to why folic acid would be better than existing drugs. If the medical field is already using drugs that are agonists of folic acid and are very effective, why is so much attention being given to folic acid? Since folic acid is a trace element in the body, would an increase cause other and more hazardous side effects?
DeleteAccording to some quick research I did, an increase in folic acid in humans does lead to side effects such as diarrhea, confusion, and seizures. It may also increase the risk of heart attacks with people who have heart problems. In addition, it can increase the risk of lung and prostate cancer. Thinking about this, I wish they mentioned whether the rats had any side effects during and after their treatment.
DeleteResource: http://www.webmd.com/vitamins-supplements/ingredientmono-1017-FOLIC%20ACID.aspx?activeIngredientId=1017&activeIngredientName=FOLIC%20ACID
Another question that could be asked would be if exercise helped the folic acid in combating ethanol-induced liver injury. Perhaps the rats that were more active and took folic acid would have more of a decrease in liver damage than the rats that were simply given the supplement.
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ReplyDeleteThe purpose of the journal article was to see if taking folic acid reduces the severity of the effects of ethanol on the liver. The presence of plasma alanine transaminase (ALT), aspartate transaminase (AST), triglycerides, homocysteine, and low density lipoprotein conjugated dienes are the signs that the liver has succumbed to damage due to toxicity or apoptosis. In this study, the researchers analyzed four groups of rats which each group was subjected to a different type of meal.
ReplyDeleteThe first group (control group) was given a regular liquid diet. The second group, the low ethanol group, was given the same liquid diet but 12% of the meal consisted of ethanol. The third group, the high ethanol group, was given the liquid diet but 36% of the meal consisted of ethanol. The last group, ethanol + folic acid group, was given the same liquid diet as the third group but had the addition of 10 mg/L of folic acid. For five weeks, the rats were fed these diets and at the time of analysis, the rats had their blood extracted and centrifuged and liver tissue samples were taken and frozen in liquid nitrogen.
For body weight, the results showed that the third group’s body weight increased and the last group’s body weight significantly decreased. The liver folate concentration in the fourth group increased but stayed the same in the second and third groups. However, the plasma folate concentration decreased in the third group and increased significantly in the last group. The third group’s liver tissue samples showed ethanol-induced injury due to the significant increase in the plasma AST and ALT levels but the presence of injury in the last group’s tissue samples was significantly decreased due to the low levels of plasma AST and ALT. The samples also showed that the presence of conjugated dienes significantly increased in the third group and significantly decreased in the last group.
The presence of conjugated dienes in the plasma is seen as a sign of oxidative stress meaning that the diene acts as a radical. The increase of the diene directly increases the toxicity in the liver making it more prone to succumbing liver injury. At low levels, the detoxification of the radical is possible by TRAP (total radical-trapping antioxidant potential). However, in the event of a spike in conjugated dienes, the body’s natural defenses become ineffective at detoxification and keeping the conjugated dienes at low levels.
The researchers’ findings do make sense to me but I would like to read about the same study in humans. If the folic acid is shown to be very effective in humans as well, I know that this method could change the way ALD patients are treated in the emergency department. My concern in this study that would prove to be problematic in human patients is the length of time. It took five weeks in rats to see that folic acid was effective at reducing the toxicity in the liver but for human patients this is very impractical. I would suggest the researchers repeat same study but analyze the effects after increasing the amount of folic acid and also analyze the effects over a shorter period of time.
I agree with you in saying that a human study would be very interesting. I am sure that if the authors are granted further studies in this area a study with human subjects will eventually be inevitable. However, I would disagree in saying that a five week period to determine the effectiveness of folic acid supplementation in hepatic toxicity would be too long. Since patients would normally have to take medication for this problem already, I do not foresee the issue of having a five week trial period. This seems to fit well in the bounds of an experimental research time frame. I am sure in the near future this group will be conducting the very experiment we are discussing with human subjects and we will be able to see for ourselves the methods they decide to use.
DeleteI guess I didn't make myself clear as to why I thought a human study on this subject would be too long. In the case of someone who came to the emergency department because of acute ALD, you can't wait five weeks to see if folic acid is effective. Like other drugs, treatments need to begin to be effective in the shortest amount of time. If the researchers could replicate acute ALD in rats to test what is the shortest amount of time that folic acid quickly begin to reduce the effects of ALD, that would be a wise investment in my opinion in order to see if folic acid is better than synthetic drugs.
DeleteIn an effort to determine the mechanism between the linkages of chronic ethanol consumption to hepatic injury, the authors of this study conducted an experiment with ethanol-fed rats. Since chronic ethanol consumption increases oxidative stress and antioxidant potential the study was also aimed at the possibility of folic acid supplementation in the correction of these disturbances in normal hepatic behavior. What they found was that folic acid supplementation may lessen hepatic toxicity by preventing homocysteinemia, which is often a causative agent to hepatic toxicity, in the ethanol-fed rats tested.
ReplyDeleteConjugated dienes (CD) were used to identify the oxidation of low density lipoproteins (LDL). Because lipid conjugated dienes are part of an early lipid peroxidation stage, the LDL could be isolated at differing times of development when and CDs counted to observe the effect of folic acid supplementation on the plasma of the ethanol-fed rats. The number of CDs in plasma samples of rats from the highly concentrated ethanol diet group are much higher than the control group rats. This would suggest that a highly concentrated ethanol diet would produce oxygen free radicals. In turn, this would lead to lipid peroxidation and ultimately increasing hepatic toxicity.
Personally, I agree with the results of the study. The authors were very careful not to make any conclusive statements but made numerous suggestions as to what their results may or may not indicate with the correlation of folic acid supplementation to hepatic toxicity in ethanol consuming rats. Since there do seem to be connections between the mechanisms of hepatic toxicity and ethanol consumption, based on the results, I would suggest further studies to help narrow down the causative agents of major indicators of hepatic toxicity and/or abnormalities.
I feel that the study may have “bitten off more than it could chew.” By that I mean that the data did not conclusively state anything other than possible correlations of data. Also, the discussion and results of the data were very brief, leaving the reader with many questions. Therefore, more detail in the discussion section would be helpful in understanding why this data is relevant and important to the study.
The purpose of this experiment (briefly) was to observe the effect of folic acid on ethanol fed rats. The results of this experiment were interesting and a little broad in my opinion. First, the final weight gained with the rats that were fed the ethanol, in any percentage, was increased significantly. However there was the largest increase in the rats that were fed the high ethanol diets, which suggests that the liver can only metabolize a certain level of ethanol before a buildup occurs. Secondly, the levels of folic acid concentration didn’t vary to a significant amount in either the high ethanol or low ethanol diets, but did in the ethanol plus folic acid diet. Also, the high ethanol diet did raise the levels of plasma ALT which correlates to liver damage or toxicity. It also increased the levels of plasma TG, while the low ethanol diet didn’t have an effect on plasma TG.
ReplyDeleteI thought this study was well done for being a pioneer or breakthrough study. The experiment was well thought out and performed with a thorough understanding of how the folic acid process works. Although they are still a little uncertain of how the actual process of decreasing the oxidative stress of folic acid works, I feel like more testing and increased research in the area of folic acid’s mechanism would better lead to a cure for this disease for future generations. Finally, it seemed that the author was very adamant at the findings of the results, but they seemed a little too confident for me. I would like to see more studies before suggesting using it as a treatment as they did (this early on).
The overall purpose of this review was to further research how folic acid plays a role in alcoholic liver disease. The author conducted an experiment using Wistar rats that were induced by chronic ethanol consumption. Results from this experiment indicated that folate deficiency and hyperhomocysteinemia was the key to most alcoholic liver diseases. The author understood that there was a connection between high levels of oxidative stress and tissue injury. The article discusses how the oxidations of LDL were used to measure the conjugated dienes (CD). CD roles are performed by identifying the oxidation levels of LDL. Basically, the study indicates that folic acid supplementation appears to lower hepatic toxicity induced by chronic ethanol consumption possibly by decreasing oxidative stress. Additionally, folic acid has the ability to decrease hepatic toxicity; if this is decreased then the oxidative stress is lowered as well.
ReplyDeleteI believe that this article had a few uncertainties when it came to discussing the pathogenesis of alcohol liver disease. According to the article “practically nothing has been reported on the effects of exogenous administration of folic acid on oxidative stress and hepatic toxicity in ethanol-fed rats. This statement says that everything that they are concluding is all based upon this one study. I think that it takes more than one study to provide the information needed to declare these results. In order to strengthen this paper I would say that the author could broaden the study to a wider range of possibilities. For example, testing a different type of rat or gender to see if results would be similar. Also I believe that stability isn’t always a good thing but in this case I think that stability is needed. If folic acid deficiency is the cause of alcohol liver disease then the stability is a necessity in vivo.
Split into multiple posts for sake of room:
ReplyDeleteSince an aunt of mine died a few years back after decades of fighting alcoholism, I was particularly interested to read this article. Her death was due to cirrhosis of the liver, which marks the last stage of ALD (http://www.liverfoundation.org/abouttheliver/info/alcohol/).
The study linked in the blog post explored the effects of supplementing folate in the diets of rats given high-ethanol diets, and compared them to rats with high-ethanol and no-folate diets as well as controls and rats on low-ethanol diets (blog-linked study).
The researchers first observed that folate deficiency is common in alcoholics, which is problematic given its vital role in methionine production (blog-linked study). Depleted levels of methionine could lead to problems in protein production, and it is also considered helpful in preventing liver damage, which is the very thing that makes ALD problematic (http://www.webmd.com/vitamins-supplements/ingredientmono-42-METHIONINE.aspx?activeIngredientId=42&activeIngredientName=METHIONINE, http://www.liverfoundation.org/abouttheliver/info/alcohol/). Aside from lowered levels of methionine and molecules involving the amino acid, such as S-adenosyl methionine, a lack of the nutrient also leads to elevated levels of homocysteine (blog-linked study). Elevated homocysteine levels may also contribute to liver damage, inflammation, cellular suicide, and other disease responses (blog-linked study). In other words, too much of a given molecule is as bad as too little. All of these reasons explain why the researchers suspected that folate supplementation may alleviate some of the effects of ALD (blog-linked study).
The researchers discovered that folate was helpful in decreasing, in rats fed high-ethanol diets, the levels of plasma triglycerides, weight gain, homocysteine, and the levels of two compounds that correlated with liver damage [blog-linked study]. The decrease in those chemicals suggest that folate-supplemented rats experienced less liver damage than those on the high ethanol diet without folate [blog-linked study]. The levels of folate in the supplemented rats’ livers and blood plasma were also increased, although this did not extend to the levels of S-adenosyl methionine or S-adenosyl homocysteine [blog-linked study]. Folate supplementation was also found to increase the ability of blood plasma in ethanol-fed rats to trap free radicals [blog-linked study]. Conjugated dienes were at their lowest levels of any rat group in folate-supplemented rats [blog-linked study]. The researchers mentioned that higher levels of these molecules were correlated to free radical production and oxidative stress [blog-linked study].
ReplyDeleteAs far as the researcher’s conclusions, they seemed solid enough if the premises (conjugated dienes correlate to oxidative stress, etc.) held up, although further research would obviously be necessary in order to translate the results to something practically applicable. I decided to check their findings against those of related studies exploring the use of folate supplementation against ALD. A study involving micropigs concluded that “folate deficiency accelerates and folate sufficiency protects against the early development of ALD” (http://jn.nutrition.org/content/132/8/2367S.full). Similarly, the Mayo Clinic considers the use of folate supplementation in the diets of alcoholics to have ‘strong scientific evidence’ of being beneficial (http://www.mayoclinic.org/drugs-supplements/folate/evidence/HRB-20059475).
Thus, it seems unlikely that the researchers are reading too much into their study’s results. I wish I’d known more about the possible benefits of folate for alcoholics back when my aunt was still trying to beat the addiction, as perhaps it would have helped her body to better withstand the damage it suffered from the bouts of frequent drinking. Of course, these studies both examined the use of folate when given along with and throughout the consumption of alcohol and development of liver damage. In comparison, if this were to have been applied to my aunt, it would have been after her development of ALD. This leaves me wondering what a study involving the addition of folate to the diet of an animal after ALD symptoms had developed might do- would folate still result in benefits to liver health, or would it have no effect?
This was really interesting to me because prior to this I only associated folic acid with pregnancy, but it is interesting to know that it can be associated with alcoholism. Folate is involved in methionine metabolism. Interestingly, a deficiency in folate can exacerbate the oxidative stress and liver toxicity. This article was written in 2011 and ALD is still a prevalent problem 6 years later because alcohol is still readily available for consumption. I wonder if something can be done to use this research on folate to somehow create a supplemental drug that could curb or slow down the destruction of the liver long enough to help alcoholics get over their dependency.
ReplyDelete