Is miRNA-30d a good pharmological target for treatment of diabetes?

Summary of: Zhao, X., Mohan, R., Ozcan, S., and Tang, X. (2012). MicroRNA-30d Induces Insulin Transcription Factor MafA and Insulin Production by Targeting Mitogen-activated Protein 4 Kinase 4 (MAP4K4) in Pancreatic β-Cells. The Journal of Biological Chemistry. Vol. 287, No. 37, pp. 31155 – 31164.

(written by Emma Frair and Yeana Jang)

What is diabetes? Diabetes is a metabolic condition in which a person’s body is either unable to produce or properly use insulin. A small organ near the stomach called the pancreas is responsible for producing and secreting all the insulin in one’s body.

Why is insulin so important? So… what’s the big deal if we don’t have insulin or if it doesn’t function properly? Well, we all know that the cells in our body that need a source of energy to funciton properly. That energy comes from food, which a majority of is turned into glucose or sugar serving as the source of our cell’s energy. Insulin is responsible for conducting and getting the glucose into the cells. Without proper insulin function one’s cells are not able to maintain energy in the necessary places.

What are these different types of diabetes?

Type 1- Only 5-10% of those diagnosed with diabetes have Type 1 diabetes. The type 1 diabetic patient’s pancrease produce little to no insulin. TREATMENT- These patients will have to have a daily injection or permanent pump to deliver his or her insulin. The blood glucose levels will have to be checked at least 4 to 5 times a day.

Type 2- Type 2 can also be a result from the depletion of insulin secretion; however, the difference from type 1 is that even if the patient’s pancreas is producing insulin his or her body has become resistant to its effects. TREATMENT- Type 2 diabetes can be treated with healthier eating and daily exercise. While the body remains resistant to insulin patients must treat it the same way as type 1 diabetics.

What do high glucose levels in the blood actually do?  Diabetes can still lead to serious health problems including: heart disease, blindness, kidney failure, and loweer-extremity amputations. Diabetes is also the seventh leading cause of death in the United Sates.

How is this related to the study of the inflammatory system? The β-cells in the pancreas are responsible for exclusively expressing and secreting the insulin transcription factors, PDX-1 and MafA. The inflammatory cytokine, TNF-⍺, is also secreted from the β-cells in the pancreas.

How do microRNAs work? microRNAs are a class of small non-coding RNAs that regulate function of a gene by binding the untranslated (UTR) end of the target gene and inhibiting the translation or secretion of that gene. It has been found that the relative high levels of mRNA-375 is responsible for inhibiting the glucose-induced insulin secretion. High levels of miRNA-375 (and any levels of miRNA-21, 34A, and 146) lead to negative regulation of insulin transcription factors made in the β-cells of the pancreas, resulting in a decrease of insulin production.

This is where the story begins…

It was hypothesized that the upregulation of miRNA-30d results in insulin production, which protects any β-cell functions that are impaired by the TNF-α cytokines. Intentional overexpression of miR-30d is beneficial in the prevention of diabetes.

In order to test this hypothesis, an insulin-secreting cell line MIN6 was transfected with siRNA against MAP4K4 compared with the negative control. This was analyzed by real-time PCR after incubation of TNF-α. The protein and mRNA levels of insulin increased when the levels of miR-30d and MafA were also increased, but there was a reduction of both TNF-α and MAP4K4. The expression of MafA and IRS2 could effectively inhibit TNF-α by silencing MAP4K4 (Figure 6).

Furthermore, pancreas of 10-week-old diabetic mice and heterozygous (normal) mice were isolated to analyze by MAP4K4 antisense LNA probe. Western blog and real-time PCR were used to further analyze. The normal mice had increased expression of miR-30d whereas the diabetic mice had decreased expression, and it was vice versa with M4P4K4 (Figure 7).

Overall, it is important to understand the signaling pathway of insulin production in β-cells by observing the roles of miRNA and MafA. Studying this mechanism could potentially provide new therapeutic agents for diabetes.

13 thoughts on “Is miRNA-30d a good pharmological target for treatment of diabetes?”

  1. One thing that I am especially interested in is the role of stress in the occurrence of Diabetes Types I and II. Chronic stress can lead to many adverse side effects, including myopathy, fatigue, and plaque formation. This last concept is very important, as the increased fat and glucose levels in the bloodstream of chronically stressed individuals can lead to atherosclerosis. In Type I diabetics stress can also cause increased insulin resistance, leading patients to require higher and higher insulin doses for the same effect. Stress can also predispose patients to developing Type I and II diabetes, due to the overactivation of the HPA axis.
    However, one question that I have about the two types of diabetes is in respect to the fact that Type II diabetics can develop Type I diabetes when their immune system begins to target pancreatic cells. What is the underlying mechanism behind this shift to both types of diabetes?

  2. It is interesting that the researchers found that miR-30D protects B-cells against the effects of pro-inflammatory cytokines. In light of the other diseases involving inflammation that we have been studying, it would be interesting to study the effects of miR-30D on other cell types. Based on your understanding of the molecule, do you think it likely that miR-30D would interact with other important cell types and potentially have an impact on the phenotypes of other inflammatory diseases?

  3. The paper states that expression of MafA, which both promotes insulin transcription and activates insulin secretion, is significantly increased by over-expression of miR-30d. However, over-expression of miR-30d did not affect insulin secretion under normal growth conditions. Though the authors address a potential explanation for this result in that it could indicate that miR-30d may target more than one negative regulator, I am curious as to how much is known at that point. Are these other negative regulators something we understand or is it just a ‘black box’? I just think this could be an important aspect to experiment with and test in the future, especially if miR-30d has potential to be a pharmacological target for treatment.

  4. I really like the layout of the blog entry. It allows for a clear and concise outline of the paper. Furthermore, the paper on Diabetes is always interesting to read because this disease affects so many people and also has a lot determining factors to its development. I personally am predisposed to developing diabetes because of my families history and genetics. I think that this paper really supported some of the current research that states that miRNAs control the intricate network of transcriptional repressors and activators that regulate insulin production in B-cells. It would be interesting to investigate the role of other miRNAs like miRNA-24 and 26 in insulin production and pancreatic processes. Its also interesting to see that there were gender differences to observe when studying MKD and the inflammatory immune system but it seems that the pancreas and diabetes don’t seem to have noticeable gender differences in its severity.

  5. My last comment was incorrect in saying that MKD was the disease that displayed a gender difference. It was Influenza and Respiratory disease.

  6. I was not previously aware that miRNAs had such a defining role in regulating the transcriptional players that determine insulin production. While I think this paper really dives into miR-30d, I’m intrigued to see how other miRNAs may play into insulin regulation as well. Multiple other miRNAs were mentioned, but experiments regarding their involvement were not discussed. The paper also suggests that miR-30 may target more than one negative regulator depending on the growth condition. I’d be interested to see this develop and more experiments to be done concerning the observation that over-expression of miR-30d did not effect insulin secretions within normal conditions. While diabetes is known to have genetic pre-dispositions in certain individuals, I wonder if there is something that can be found on the miRNA level contributing to ‘what goes wrong’ in insulin secretion in diabetic individuals.

  7. In the second section of results, the authors present the following hypothesis: “The induction of insulin gene transcription by miR-30d may be involved through the up-regulation of insulin transcription factors, such as PDX-1 and NeuroD-1.” However, they conclude that neither PDX-1 expression nor NeuroD-1 expression influence miR-30d overexpression. Of course, they do find that miR-30d induces insulin gene transcription through activation of MafA. I’m curious to know why there is a propensity for targets of miR-30d to specifically repress MafA, but not the other major insulin transcription factors. Since PDX-1 and NeuroD-1 don’t seem to be influencing miR-30d, follow up studies could also begin to tease out their true interactions and functions.

  8. I would be curious to see the effects of miRNA-30d overexpressison in humans with both Type I and Type II diabetes. This paper examines the many effects miR-30d has on beta-cell function and transcription of insulin. I am wondering what would happen if MafA was blocked following over expression of miR-30d. Would the other transcription factors overcompensate for the loss of MafA or would transcription be inhibited completely?

  9. I found this article to be very interesting, particularly because I do not have much background knowledge of miRNA. This article showed that they are crucial to the correct functioning of Beta pancreas cells. One section of the results said that TNF alpha inhibited insulin transcription and secretion and that over-expression of miR-30d only partially rescued the cells. Are there any proposed treatments that could fully rescue the cells and return them to normal function? Are there any known inhibitors of TNF alpha?

  10. First of all, I found the methods used in this study to be really interesting! I especially liked the experiments where they used an Adenovirus vector to introduce miR-30d, and where they used a luciferase reporter gene to measure the effect of mutation on miR-30d knockdowns of MAP4K4. The latter experiment was a new method for me, and I liked it, even though the authors reported that inhibiting miR-30d did not increase wild type MAP4K4 reporter activity. That was a little weird, but otherwise I thought the paper did a great job of telling the story that the researchers have produced! Nice selection!

  11. This article was very interesting and important in thinking about more targeted and specific therapies for diabetes, a disorder that is really lacking in a successful treatment plan or cure at this time in modern medicine. I found it especially amazing that the researchers were able to use an “online target prediction program” to decide to study the relation between miR-30d and MAP4K4. Since MAP4K4 was screened as a potential target because of its complementary 3’UTRs to miR-30d, MAP4K4 was further studied and results indicated that MAP4K4 levels decreased by 40% as compared to the control with the introduction of miR-30d. This online bioinformatics analysis was able to point them in the direction of a successful target gene worth studying.

  12. Is this microRNA actually a potential therapeutic target for diabetes?? For either Type I or Type II?? The db/db diabetic mice are a model of Type II diabetes. However, Type I diabetes is an autoimmune disorder where pancreatic beta cells are destroyed. miR-30d levels are decreased and Map4K4 levels are increased in islets of db/db mice indicating a role for this pathway in Type II diabetes. It would have been interesting to see if treatment of db/db mice with this microRNA would lead to improved symptoms. Why didn’t they do this? Ultimately, I think that many factors are involved with the use of this microRNA as a therapeutic target. What role does Map4K4 play in normal cellular functions? Are there other targets for miR-30d? If a microRNA is used as a drug, how can you target delivery to the correct cells (beta cells in this case)? The effects in this paper were pretty small…is the effect on Map4K4 enough to see a difference in beta cell function in vivo? While miR-30d seems to be one piece of the puzzle, much more work needs to be done before we can claim it is a potential therapy.

  13. In the discussion, several other microRNAs were mentioned miR-21, miE-34a and miR-146a. While the had a different function than miR-30d, the did seem to have a role in cytokine triggered reduction of insulin production. While a lot is understood about miRNAs, there is still much to learn. I would be interested to see different combinations of the miRNAs examined, similar to experiments in this paper to see if there are any synergistic effects on various elements of insulin promotion and production.

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