Type 2 Diabetes Mellitus Treatment

  Diabetes mellitus (DM) is a complex metabolic disorder affecting more than 400 million people worldwide.^8,11 There are currently two types of diabetes, designated Type 1 and Type 2. Type 1 diabetes mellitus (T1DM) is characterized by deficient insulin production within the body due to the autoimmune destruction of pancreatic insulin-producing β-cells. ^8,11 Type 2 diabetes mellitus (T2DM) is defined by hyperglycemia in individuals due to a myriad of pathological changes within the body, the three key defects being increased hepatic glucose production, diminished insulin production and development of insulin resistance. ^{5, 8} Insulin resistance is defined as suppressed or delayed responses to insulin, and generally refers to “post-receptor” effects, meaning the complication lies in cellular response to insulin in contrast to insulin production. ⁵ A major point of diversion between the two forms of diabetes pertains to the production of insulin. T2DM patients retain the ability to naturally produce insulin, though production declines as the disease progresses, while T1DM patients are physically incapable of producing their own insulin following the loss of pancreatic β-cells. ^{8, 11}

T2DM accounts for the vast majority of people diagnosed with DM, and this disease takes a massive toll on patients and healthcare systems alike. ^8,9 Patients with T2DM have a 15% increase in all-cause mortality, along with complications that include macrovascular and microvascular diseases, such as cardiovascular disease, stroke, retinopathy, nephropathy, neuropathy and others (see Figure 1). ^2,13 The medical and socioeconomic burden on healthcare systems is enormous due to the need for persistent care arising from the numerous associated pathological complications, not to mention the immense cost to patients and insurance companies paying for these treatments. ^8,9

     

Figure 1 Symptoms and Affected Areas of Diabetes.¹³

The current understanding of T2DM pathophysiology involves several organs that contribute to the development and progression of the disease, summarized in Figure 2.^{5, 8} The most prevalent risk factors contributing to the development of T2DM are obesity, an unhealthy diet and physical inactivity.⁸

Figure 2: Current theories contributing to pathogenesis of T2DM.⁵ 

In the early and intermediate disease stages of T2DM, hyperglycemia occurs in the presence of hyperinsulinemia, which indicates that insulin resistance is the driving force of this disease.⁹ The current treatment guidelines, per the American Diabetes Association (ADA), highlight glycemic control as the main criteria to determine efficacy of therapy, stating that “clinical trials…support decreasing glycemia as an effective means of reducing long-term microvascular and neuropathic complications.” ⁷ The core initial treatment for patients diagnosed with T2DM is lifestyle intervention and metformin administration, followed by insulin or sulfonylurea medication.⁷ These are considered well-validated treatment options by the ADA and are the first line of therapy following diagnosis. The ADA also states that it is uncommon for lifestyle interventions to achieve or maintain metabolic goals, thus metformin is the immediate pharmacological treatment option in addition to lifestyle intervention strategies.⁷ If lifestyle and metformin treatment fail, the next step is insulin administration.⁷ If the disease continues to progress, there are a multitude of other pharmacological agents that can be introduced and tested in different combinations.

Despite the introduction of new classes of medications along with numerous combination therapies, techniques that target glycemic control for treatment have ultimately failed to produce positive health outcomes or prevent progression of the disease.^{7, 3} This is where Dr. Jason Fung and his idea of therapeutic fasting for T2DM patients come into play. Dr. Fung states that the prevailing view of insulin resistance theorizes a pathology within the cell that derails the normal mechanism of glucose absorption. As stated earlier, T2DM patients still produce insulin. In early and intermediate stages of the disease, this production is at normal, or even excessive, levels.⁹ In a healthy individual, increased blood glucose levels – for example, following a meal – cause an increase in insulin levels, which interact with insulin receptors on the surface of cells within tissues in the liver, muscle and fat. This signal relays that high concentrations of glucose within the blood need to be absorbed into cells for use as fuel or packaged and stored for later use, as demonstrated in Figure 3 (Upper panel).¹²

Cells then respond by presenting glucose transporters at the cell membrane to allow glucose entry. In insulin-resistant individuals, the cells no longer elicit a response to normal levels of circulating insulin, thus the cells must be resistant to the insulin, shown in Figure 3 (Lower panel).¹² Dr. Fung terms this the “lock-and-key paradigm,” where the insulin receptor is a “locked” door and insulin-binding is a “key” that unlocks and open the door, allowing glucose to exit the bloodstream and enter the cell.¹ There is evidence that supports regular function of the insulin receptor and normal insulin composition and action in T2DM – so the “lock” and “key” are both unaffected. Thus, it is assumed that there must be something jamming the lock, arresting glucose entry into the cell, and causing an internal starvation state within. To counteract this, insulin is administered to T2DM patients as a way to force the door open and allow glucose entry.

Figure 3.  (Upper) Normal glucose response.  (Lower) T2DM insulin resistance.¹²

Herein lies a paradox: insulin has many functions within the body, only one of which contributes to glucose absorption.¹ For example, insulin is also responsible for lipogenesis within the liver, a process that takes excess carbohydrates (i.e. glucose), packages it into fat molecules and stores it for later use. However, lipogenesis is not reduced in T2DM patients, despite a supposed starvation state within the cells, and it is even well supported that lipogenesis in T2DM is in fact hyperactive.¹ This means that in the same liver tissue, there is a contradictory state of both resistance and super-sensitivity to the same hormone, creating the paradox wherein insulin-resistant patients are accomplishing the process of insulin-mediated fat production despite apparent cellular starvation as a result of insulin resistance.¹ Going back to the lock-and-key paradigm, there could be another, more fitting explanation for the blockage of glucose entry: either the lock is jammed shut, or the space behind the door is jammed too full.¹ In other words, the cells may have already reached their limit for glucose storage and cannot let any more in. This perspective resolves the paradox within the currently accepted view of insulin resistance. That is, the problem is not actually insulin resistance, but hyperinsulinemia.¹ Thus, the administration of insulin as a core treatment method for T2DM is a lot like filling a suitcase that has space for 20 t-shirts with 40 t-shirts, then coming back with a t-shirt cannon and blasting in 40 more, when only 10 t-shirts were needed for the trip in the first place. One novel way to solve this dilemma of needing to manage the cardiovascular risks of hyperglycemia without forcing an already overloaded liver to process more glucose, is to naturally reset the entire process through fasting.

Therapeutic fasting as a treatment for T2DM is a relatively new, and not widely accepted, option for diabetic patients. Revisiting the suitcase analogy, fasting is like dumping out all 80 t-shirts, packing the required 10 and enjoying a nice vacation. The idea is that there is already so much excess energy stored within the abundant adipose tissue of obese diabetic patients, that constantly eating is not really necessary. The body is not only able to easily utilize fat as energy, but it possesses a remarkable ability to readily do so when entering a fasted state. Dr. Fung published a case study on three T2DM patients that underwent therapeutic fasting therapy, defined as “the controlled and voluntary abstinence from all calorie-containing food and drinks [for] a specified period of time”.³ All patients within this trial not only had subjective reports of positive affect and higher energy levels during fasting periods, they also had reductions in serum A1C levels and waist circumference, and experienced 10-18% weight loss over the course of 10 months.³ Additionally, Patients 1 and 3 were able to discontinue all diabetic medications, and Patient 2 discontinued 3 out of 4.³ All patients were able to discontinue insulin therapy within the first 20 days of their fasting regiment, one patient in as little as five days, with no occurrences of symptomatic hypoglycemia reported.³ The results of this trial demonstrated that the therapeutic fasting can significantly reverse or eliminate the need for diabetic medication, as well as improve other clinically significant health measures such as serum A1C levels, body mass index and waist circumference.³ Therapeutic fasting may be a viable therapy for T2DM patients, aiding in the remission of the disease, reduction of cardiovascular risk factors through weight loss, decrease the need for glycemic control medication and possibly improve additional diabetic-related complications, reducing the need for those medications as well.³ This would not only improve patient outcomes but lighten the socioeconomic burden on the healthcare system contributed by diabetic patients due to the wide range of subsidiary pathologies arising from the disease.⁹

By Andrew Yakzan, A Post Baccalaureate Student at the University of Kentucky

References

¹Attia, Peter, and Jason Fung. “#59 - Jason Fung, M.D.: Fasting as a Potent Antidote to Obesity, Insulin Resistance, Type 2 Diabetes, and the Many Symptoms of Metabolic Illness.” Edited by Gary et al., Peter Attia MD, Peter Attia, MD, 24 June 2019, peterattiamd.com/jasonfung/.

²Chatterjee, Sudesna, et al. “Type 2 Diabetes.” The Lancet, vol. 389, no. 10085, 2017, pp. 2239–2251., doi:10.1016/s0140-6736(17)30058-2.

³Furmli, Suleiman, et al. “Therapeutic Use of Intermittent Fasting for People with Type 2 Diabetes as an Alternative to Insulin.” BMJ Case Reports, 2018, doi:10.1136/bcr-2017-221854.

⁴Kalra, Sanjay, et al. “Defining Disease Progression and Drug Durability in Type 2 Diabetes Mellitus.” European Endocrinology, vol. 15, no. 2, 2019, p. 67., doi:10.17925/ee.2019.15.2.67.

⁵Lin, Yi, and Zhongjie Sun. “Current Views on Type 2 Diabetes.” Journal of Endocrinology, vol. 204, no. 1, 2009, pp. 1–11., doi:10.1677/joe-09-0260.

⁶Madenidou, Anastasia-Vasiliki, et al. “Comparative Benefits and Harms of Basal Insulin Analogues for Type 2 Diabetes.” Annals of Internal Medicine, vol. 169, no. 3, 2018, p. 165., doi:10.7326/m18-0443.

⁷Nathan, D. M., et al. “Medical Management of Hyperglycemia in Type 2 Diabetes: A Consensus Algorithm for the Initiation and Adjustment of Therapy: A Consensus Statement of the American Diabetes Association and the European Association for the Study of Diabetes.” Diabetes Care, vol. 32, no. 1, 2008, pp. 193–203., doi:10.2337/dc08-9025.

⁸Roglic, Gojka. Global Report on Diabetes. World Health Organization, 2016.

⁹Stumvoll, Michael, et al. “Type 2 Diabetes: Principles of Pathogenesis and Therapy.” The Lancet, vol. 365, no. 9467, 2005, pp. 1333–1346., doi:10.1016/s0140-6736(05)61032-x.

¹⁰Weir, G. C., and S. Bonner-Weir. “Five Stages of Evolving Beta-Cell Dysfunction During Progression to Diabetes.” Diabetes, vol. 53, no. Supplement 3, 2004, doi:10.2337/diabetes.53.suppl_3.s16.

¹¹Zaccardi, Francesco, et al. “Pathophysiology of Type 1 and Type 2 Diabetes Mellitus: a 90-Year Perspective.” Postgraduate Medical Journal, vol. 92, no. 1084, 2015, pp. 63–69., doi:10.1136/postgradmedj-2015-133281.

¹²Harvard Health Publishing. “Type 2 Diabetes Mellitus.” Harvard Health, Dec. 2018, www.health.harvard.edu/a_to_z/type-2-diabetes-mellitus-a-to-z.

¹³Gulati, Martha, et al. “Diabetes (Type 2 Diabetes).” Global, Mar. 2019, www.cardiosmart.org/diabetes.

Golden Blood

Red blood cell antigens are best known as A, B, AB, and O, however, up to 342 identified independent antigens can be present on a single red blood cell.¹ The present antigens on an individual’s red blood cells are recognized and processed by their immune system as originating from themselves.⁵ When an antigen that is not typically present is found by an immune cell, the immune system deems the red blood cell as foreign and proceeds to attack it and others with the same antigen.⁵ For this reason, when an individual needs a blood transfusion, they must receive their donation from someone who has compatible antigens on their red blood cells.⁵ This can become difficult when the individual has a more rare pattern of blood antigens on their blood cells or in other words, a rare blood type. 

Figure 1.  The common blood types with their coinciding alloantibodies.

When blood types such as A or AB are discussed, they are mentioned in the context of if the individual is positive or negative for them. When the individual is negative for the antigen, they can donate to an individual that is positive or negative for the antigen but can only receive a donation from an individual negative for it.⁵ The most discussed blood types are A+, B+, AB+, O+, A-, B-, AB-, and O-.⁵ The most well recognized flexible blood donor group is O- which is known as the universal donor because they are able to donate to all previously mentioned blood types.⁵ The most widely compatible blood group is known as golden blood and individuals with this extremely rare blood type are inherently able to donate to all rare blood types from the Rh antigen system and even common blood types.^6,11

Rh-deficiency syndrome, an autosomal recessive genetic disorder characterized by red blood cells that lack all 61 antigens known as Rh system antigens, can occur in both a complete (Rhnull) or significantly reduced phenotype (Rhmod) .^2,6 The syndrome is extremely rare, it has been reported less than 50 times since its discovery in 1960.¹¹ Other rare blood types from the Rh antigen system can lack any one or more of the Rh antigens but less than all. The low prevalence of the Rhnull phenotype and the potential complexity of the other Rh system blood types makes finding a blood donor for a patient with these blood types extremely hard. This is where the coined term ‘golden blood’ is derived. Afflicted individuals are classified into two subgroups based on their specific genetic defect; regulatory when the mutation is in a suppressor gene and amorph when it is at the Rh gene locus.^2,9 Patients with Rhnull syndrome are found to have stomatocytes which are osmotically fragile red blood cells that undergo hemolysis when in a hypotonic environment.^2,3,8 This is a result of their abnormal shape that seems to coincide with the lack of the cell membrane antigens.³ As a result of this the patients also suffer from chronic hemolytic anemia to some degree.^2,3 This is a condition in which the patients’ blood cells are broken down via hemolysis faster than they are made.⁷ Individuals with hemolytic anemia have symptoms such as fatigue, pale skin, chills, fever, heart palpitations, confusion, and more.¹⁰ Clinically Rh deficient patients readily produce alloantibodies when exposed to Rh antigens and in certain situations such as pregnancy can be very dangerous.^2,4

Figure 2.  Stomatocytes in culture.

When a Rhnull mother is pregnant with a fetus with the Rh antigens (Rh+) the mother's immune system may create antibodies against the fetus’s red blood cells and destroy them.¹ This can cause hemolytic anemia in the fetus and the severity of the anemia can induce brain damage, severe illness, or even death of the fetus.¹ Expecting mothers whose red blood cells are lacking any of the Rh system antigens and have not yet produced antibodies towards her growing fetus may be put on Rh immunoglobulin (Rhlg) at around the 28^th week of pregnancy.¹ This can prevent the mother from starting to produce antibodies to the fetal blood cells for the remainder of the pregnancy.¹ The mother is also given another dose of the Rhlg post-birth to prevent any Rh+ cells left in the mother from producing an immunological reaction.¹ Any Rh- mothers that produced antibodies to Rh+ fetal blood will not be helped by Rhlg treatment.¹ While this condition may only affect a select few expecting mothers however, it can make their pregnancy very difficult and scary. 

Figure 3.  Illustration of fetal hemolytic disease development

As previously mentioned, individuals with golden blood are able to donate to anyone with common or specific rare Rh system blood types without their blood generating an immune response in the recipient.⁶ Before Rhnull blood was first discovered it was thought an individual without these antigens would not survive utero.⁶ Since its discovery, golden blood has been sought after by researchers and physicians alike for its rare properties, however, in 2017 there were only 9 active donors.¹¹ This makes finding a single bag of the blood extremely difficult which has made blood transfusions for these patients complicated and slowed the progression of studies on the blood.¹¹  Despite this, with all of its very special characterizations, these individuals’ blood holds an extraordinary place in the healthcare and scientific communities.⁶

References:

1. Rh Factor. American Pregnancy Association. https://americanpregnancy.org/pregnancy-complications/rh-factor/. Published October 9, 2019.

2. Journal Of Pakistan Medical Association. JPMA. https://jpma.org.pk/article-details/2399.

3. Stomatocyte. Stomatocyte - an overview | ScienceDirect Topics. https://www.sciencedirect.com/topics/medicine-and-dentistry/stomatocyte.

4. Glossary: Alloantibody - Blood Bank Guy Glossary. Blood Bank Guy. https://www.bbguy.org/education/glossary/gla17/.

5. Blood: the basics. Professional Education. https://professionaleducation.blood.ca/en/transfusion/publications/blood-basics. Published February 11, 2019.

6. Bailey P. Wellcome. The man with the golden blood. https://mosaicscience.com/story/man-golden-blood/.

7. Hemolytic Anemia. Johns Hopkins Medicine. https://www.hopkinsmedicine.org/health/conditions-and-diseases/hemolytic-anemia.

8. Osmotic fragility test: MedlinePlus Medical Encyclopedia. MedlinePlus. https://medlineplus.gov/ency/article/003641.htm.

9. Cartron, Jean-Pierre. "Rh-deficiency syndrome." The Lancet 358 (2001): S57.

10. Hemolytic Anemia. National Heart Lung and Blood Institute. https://www.nhlbi.nih.gov/health-topics/hemolytic-anemia.

11. Rhnull, the Rarest Blood Type on Earth, Has Been Called the "Golden Blood". Curiosity.com. https://curiosity.com/topics/rhnull-the-rarest-blood-type-on-earth-has-been-called-the-golden-blood-curiosity/.

By Cheyenne Cook, A Master’s of Medical Sciences Student at the University of Kentucky

What a Headache!

Migraines are the most common cause of neurological disability in the world affecting nearly 15% of the global population. Some migraines initially present with prodromes or warning signs, which may include: Fatigue, euphoria, depression, irritability, food cravings, constipation, neck stiffness, increased yawning, and/or abnormal sensitivity to light, sound, and smell.² The prodrome phase is often followed by the aura phase. Auras are transient neurological pathologies that manifest as scintillating light and blurred field of vision and progress to loss of peripheral vision creating tunnel vision. Not all who suffer from migraines get auras, though prodromes are very common. The headache phase, the final phase, proceeds the aura when present, typically pulses; this increases intracranial pressure, and may present in association with nausea, vomiting, and abnormal sensitivity to light, noise, and smell. It may also be accompanied by abnormal skin sensitivity and muscle tenderness.²

Adding another layer to the difficulty of this disease is the fact that it can worsen over time as it transitions from acute to chronic manifestation. Multiple factors that contribute to this chronification are shown in Figure 1. Migraines should be viewed as a complex disorder with a strong genetic basis involving cortical, subcortical and brainstem regions that account for the pain and wide variation of symptoms¹. The extent and diversity of symptoms strongly suggest that migraines are more than just headaches. Treatment options are complex, broad, and often countercurrent with rational thinking; successful pharmacological treatment for one person, may be a trigger and detriment for another. The diversity in symptoms of migraines is reflected in the diversity of pharmacological treatments for them; and largely follow one of two paths: Prophylactic or therapeutic. Two of the most promising pharmacological treatments of migraines, Triptans and Onabotulinumtoxin A, will be discussed in more detail below.

Figure 1: Contributing Factors in Migraine Chronification (3)

                The Triptans, introduced nearly 30 years ago, are still considered the gold standard of migraine treatment. These drugs are selective serotonin receptor agonists, and because of their effectiveness have largely replaced older drugs in this category like the ergot derivatives. The Triptans are potent vasoconstrictors and are thought to target 5-HT1B/1D receptors (trigeminovascular afferents and trigeminal nucleus caudalis), to inhibit the release of neurotransmitters.⁴ The pharmacokinetic properties of the most prominent Triptans are shown in Figure 2. All of the drugs in this class are indicated for the acute treatment of mild to severe migraines that respond poorly to nonsteroidal anti-inflammatory drugs with or without the addition of additional analgesics, and mild to severe migraines in patients with contraindications, intolerance or hypersensitivity to other analgesics. Most Triptans are available in various formulations including: Subcutaneous injection, oral tablet, nasal spray, and oral dispersible tablet. The choice of formulation is determined by a number of patient factors that include headache features, side effect preference, convenience and cost. The single patient’s response to a Triptan cannot be predicted, but most show highest effectivity if they are taken at the very onset of the headache phase.⁴ All of the Triptans show similar side effects: Paresthesia, flushing, tingling of hands and feet, and mild, fleeting chest pressure. 1 in 1,000,000 patients experience cardiovascular complications of arrhythmia, stroke, and heart attack.

Figure 2: Pharmacokinetics of Triptans (4)

            Central and peripheral nerve sensitization occurs during the progression of migraines. This refers to the nerve response threshold decreasing and their response magnitude increasing. It stands to reason then – by paralyzing the muscle at the neuromuscular junction, one can mitigate some of the effects of migraines. That is precisely the mechanism behind the use of Botulinum neurotoxins (BoNTs). First used as a cosmetic enhancement to prevent wrinkles, BoNTs are now known to be effective in preventing migraines. BoNTs are produced by seven serotypes (A-G) of bacillus bacteria, Clostridium botulinum, and consist of a heavy chain and a light chain. The heavy chain facilitates the uptake of the whole molecule into the cytosol, and the light chain then cleaves soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex in the motor neurons.⁵ SNARE molecules are critical to this mechanism because they fuse synaptic vesicles containing neurotransmitters like acetylcholine with the pre-synaptic membrane; which results in the release of the neurotransmitter back into the pre-synaptic cell; without transmission to the post-synaptic cell, paralysis will occur. Onabotulinumtoxin A (onaBoNTA), approved by the FDA in 2010, represents the only agent specifically approved for the prevention of chronic migraines. In addition to modulating the function of motor neurons, uptake of onaBoNTA in sensory neurons that innervate the skin and muscles is thought to inhibit the release of inflammatory mediators at several sites within the sensory neuron.⁵ OnaBoNTA is administered in accordance with the PREEMPT regimen at 12-week intervals. 31 sites across frontal, temporal, occipital and neck muscles are injected with 5 units per injection, totaling 155 units; the injection scheme can be seen in Figure 3. A Botox unit is a measure of a defined amount of biological activity and corresponds to a fixed number of botulinum toxin molecules. 

Figure 3: Injection Sites for OnaBoNTA (9)

  Migraines are highly heterogeneous, and their treatment should be tailored to the individual patient. The variability in migraine etiology informs the numerous pharmacological treatments; Triptans and OnaBoNTA only scratch the surface of available options. After explaining the diagnosis, the provider should encourage the patient to actively participate in assessing his/her lifestyle and behaviors; diet, sleep, stress and exercise, may all contribute to the individual’s condition and subsequent response to pharmaceutical intervention.

References

1.      Puledda, Francesca et al. “An update on migraine: current understanding and future directions.” Journal of neurology vol. 264,9 (2017): 2031-2039. doi:10.1007/s00415-017-8434-y

2.      Burstein, Rami et al. “Migraine: multiple processes, complex pathophysiology.” The Journal of neuroscience : the official journal of the Society for Neuroscience vol. 35,17 (2015): 6619-29. doi:10.1523/JNEUROSCI.0373-15.2015

3.      May, Arne, and Laura H. Schulte. “Chronic Migraine: Risk Factors, Mechanisms and Treatment.” Nature News, Nature Publishing Group, 8 July 2016, https://www.nature.com/articles/nrneurol.2016.93.

4.       Antonaci, Fabio et al. “Recent advances in migraine therapy.” SpringerPlus vol. 5 637. 17 May. 2016, doi:10.1186/s40064-016-2211-8

5.      Gooriah, Rubesh, and Fayyaz Ahmed. “OnabotulinumtoxinA for chronic migraine: a critical appraisal.” Therapeutics and clinical risk management vol. 11 1003-13. 29 Jun. 2015, doi:10.2147/TCRM.S76964

6.      Silberstein, Stephen D., et al. “OnabotulinumtoxinA for Treatment of Chronic Migraine: PREEMPT 24-Week Pooled Subgroup Analysis of Patients Who Had Acute Headache Medication Overuse at Baseline.” Journal of the Neurological Sciences, vol. 331, no. 1-2, 2013, pp. 48–56., doi:10.1016/j.jns.2013.05.003.

7.      Goadsby, Peter J et al. “Pathophysiology of Migraine: A Disorder of Sensory Processing.” Physiological reviews vol. 97,2 (2017): 553-622. doi:10.1152/physrev.00034.2015

8.      Akerman, Simon, et al. “Current and Novel Insights into the Neurophysiology of Migraine and Its Implications for Therapeutics.” Pharmacology & Therapeutics, vol. 172, 2017, pp. 151–170., doi:10.1016/j.pharmthera.2016.12.005.

9.      “Botox For Migraine.” MigrainePal, 21 Jan. 2019, https://migrainepal.com/botox-for-migraine/.

10.  Sutherland, Heidi G., et al. “Advances in Genetics of Migraine.” The Journal of Headache and Pain, vol. 20, no. 1, 2019, doi:10.1186/s10194-019-1017-9.

By Danny Craig, A Master’s of Medical Science Student at the University of Kentucky

Caloric Restriction: Can it help you increase your rate of living?

          In the past few years, dieting has become such an important part of society. Society is addicted to losing weight, gaining muscle, attaining better health, and trying to live longer. In Caloric restriction (CR),  in the absence of malnutrition, has shown to extend lifespan in many animal models and decrease age-related oxidative stress in multiple tissues & organs ¹. Furthermore, recent studies show CR extends the lifespan and reduces a number of adverse effects associated with aging. The principal theory on caloric restriction is a combination of “rate of living” and “oxidative stress” theories, which emphasize the importance that metabolic rate and reactive oxygen species have on lifespan ⁴. The ‘rate of living’ theory claims that the higher an organism’s metabolism, the shorter its life span, thus explaining the effects of caloric restriction on longevity ⁴. The ‘oxidative stress’ theory claims that caloric restriction reduces oxidative stress, which in turn reduces damage to tissues and organs (Figure 1) ^3,4.  Researchers in the caloric restriction field have examined how age-related changes in physiological and endocrine systems play a role in metabolic functions, which may be correlated with health and lifespan benefits ⁴.

Figure 1.  CR enhances resting energy efficiency to decease systemic oxidative damage (3).

An example of ongoing work investing how CR may benefit overall health is a study by Redman et al ². Here, it was hypothesized that maintaining patients on CR diets for a period of two years would reduce energy expenditure (EE) of endocrine mediators and oxidative stress in energetically active tissues ². Finally, the authors conducted this study to provide scientific validity for the biological aging hypothesis; which explains that a prolonged use of CR diet enhances energy efficiency, reduces reactive oxygen species, and reduces oxidative damage to tissues and organs ³.

The researchers recruited 53 people, of which only 19 people were assigned to the control group and 34 people were randomized to the caloric restriction group ³. In order to see how CR plays a role the amount of weight each group lost was examined ³. The CR group lost about 9.4 kg on average and a 16.5% reduction in energy intake ³. In year two the CR group only maintained their weight loss and had a 14.8% reduction in energy intake (Figure 2) ³. The weight loss in the CR group was primarily fat mass loss, but some fat-free mass loss was observed as well ³. This study explains the idea that changes in metabolic adaptation of energy expenditure show reductions in oxidative stress ³. This implies that metabolic adaptation may be related to energy conservation, and in turn may delay biological aging, which in turn enhance lifespan ³.

 Fat mass loss was observed in the CR group and to understand how this effects energy metabolism, aging, and metabolic changes ³. To examine these effects the researchers attained blood samples from both groups ³. The blood samples were tested for T3, T4, TSH, leptin, and insulin ³.  It was found that leptin levels drastically decreased in the CR group and the control group had no changes ³. When examining T3 and T4 levels the CR group had significant reductions in the concentration of these hormones over the two years ³. When examining TSH there was not a considerable impact on the thyroid axis and does not explain how TSH plays a role in mediating metabolic adaption ³.  Finally, insulin concentration were significantly lowered in the CR group at year one but not in year two, and in the control group insulin levels were maintained for both years ³. 

Figure 2.  Calorie Restriction and Change in Body Composition.  Percent of calorie restriction (A) achieved after 1 and 2 years of calorie restriction and the resulting change in fat mas (FM) and fat-free mass (FFM) (B).  N=53: 34 CR, 19 controls.  The p value for statistically significant treatment group effects, adjusted for multiple comparisons, is shown.  The changes in weight, FM and FFM were all significantly different between the CR and control group (p<0.0001 for all, treatment main effect)(3).

Oxidative stress was measured to understand how the biological aging hypothesis. The participants gave urine samples, which were used to measure urinary 2,3-dinor-iPF(2α)-II by liquid chromatography to see oxidative stress ³. The urinary F2-isoprostane excretion showed a significant reduction in the CR group but no changes in the control group ³. When analyzing the urinary data, it was found that urinary 2,3-dinor-iPF(2α)-II concentrations where significantly lower for the CR group than the control group at year two ³. These changes in the urinary 2,3-dinor-iPF(2α)-II concentration show a drop in oxidative stress, but these findings need to be studied long-term ³.

Redman et al, explain that patients who were put on a caloric restriction diet for two years had an impact on biological aging ³. This study shows that the use of CR does have some beneficial aspects to human life span due to efficiency in energy metabolism, fat loss, and reducing systemic oxidative stress. CR’s effectiveness is important as it indicates weight loss to be safe and tolerable, as well as a reduction in systemic oxidative stress to live longer. Overall, caloric restriction is important for people’s health, people’s lifespan benefits, and allow people to live longer.  

By Cocanut Suhail, a Master's of Medical Science Student at the  University of Kentucky

References:

1.      Il’yasova, D., Fontana, L., Bhapkar, M., Pieper, C., Spasojevic, I., Redman, L., Das, S.K., Huffman, K., and Kraus, W. (2018). Effects of 2 years of caloric restriction on oxidative status assessed by urinary F2-isoprostanes: The CALERIE 2 randomized clinical trial. Aging Cell. 17: e127109.

2.      Ravussin, E., Redman, L., Rochon,J., Das, S.K., Fontana, L., Kraus, W.,  Romashkan, S., Williamson, D., Meydani, S., Villareal, D.T., Smith, S., Stein, R., Scott, T., Stewart, T.,Saltzman, E., Klein, S., Bhapkar, M., Martin, C., Gilhooly,  Holloszy, J., Hadley, E., Roberts, S., and Kritchevsky, S.  (2015). A 2-Year Randomized Controlled Trial of Human Caloric Restriction: Feasibility and Effects on Predictors of Health Span and Longevity, The Journals of Gerontology: Series A. 70 (9), 1097–1104.

3.      Redman, L. M., Smith, S. R., Burton, J. H., Martin, C. K., Il'yasova, D., & Ravussin, E. (2018). Metabolic slowing and reduced oxidative damage with sustained caloric restriction support the rate of living and oxidative damage theories of aging. Cell Metabolism. 27(4), 805-815.

4.      Speakman, J., and Mitchell, S. (2011). Caloric restriction. Molecular Aspects of Medicine. 32: 159-221.

To Die or not to Die

        Everything and everyone that is living has a limit to life, down to the single unit of living things our cells go through the same fate, death. During development, many regulatory mechanisms help direct and promote either cell differentiation and growth or the opposite cell death. Imagine trillions and trillions of cells accumulating.  If they  happened to live forever, it would cause many mechanisms that regulate physiological homeostasis to fail. We would all have high blood pressure and massive edema and eventually death if certain cells did not have a regulatory control mechanism. Cell death is necessary and specifically controlled. Three  main ways a cell can undergo cell death are apoptosis, necrosis, or autophagy. All three of these play vital roles in controlling many processes in development, the development and progression of major diseases and basic, daily functions. These cell death processes are also essential therapeutic targets to treat disease a variety of disease states.  Promoting death of cancer cells or preventing death of neurons  in neurodegenerative diseases like  Parkinson’s disease or  other tauopathies may be beneficial.

        During the development of cancer, defects in apoptosis pathway results in an accumulation of cells leads formation of a tumor. A crucial step in apoptosis involves activation of caspases (i.e., caspases 3, 7 and 9) by signaling and activating MEK through dimerization of the receptor which activates the ERK and MAPK which can phosphorylate caspase 9. Another way to phosphorylate caspase 9 is through mitosis and buildup of CDK1 and Cyclin B. Apaf-1 is also needed to form a complex with caspase 9 in order to activate caspase 3 and 7. This occurs by the BH3 pro cytochrome c activator and Bcl-2 a anti cytochrome c activator to bind to Apaf-1. After Caspases 3 and 7 are activated, apoptosis can be initiated (Fig. 1).  Overall apoptosis does not cause toxic build up at the site of cell death and has a very rapid turnover.

Figure 1: Caspase-9 is activates by formation of the apoptosome and by forming a multimeric complex with Apaf-1. When cytochrome c is released. This can be enhanced by proapoptotic signal BH3 or inhibited Bcl-2 an antiapoptotic protein class². 

        Like apoptosis, necrosis, is also a clinically important process of cell death.  Necrosis is involved in tissue damage that occurs during traumatic brain injury, myocardial infarctions, strokes and some liver diseases.  While it is also initiated following DNA fragmentation and dysregulate mitochondrial function, it fails to be subject to processed by lysosomal degradation.  Instead, necrotic cells spill their  toxic contents out into the extracellular space aiding in an increase in tissue damage and inflammation brought on by cytokines. Assays to distinguish different forms of cell death are used, including use of  a deoxynucleotidyl transferase-mediated biotin-dUTP nick-end labeling assay to detect DNA fragmentation³. Ischemia and hypoxia are important triggers of cell necrosis. While necrosis also has tightly regulated features, targeting these has limited  therapeutic value, since the damage is already done such as many agents in Spinal cord injuries have been related to inhibiting further necrosis and reducing inflammation through the process of apoptosis. Energy starvation or oxygen starvation, ROS production can generate pro-necrotic signals which consist of inflammatory mediators and their ligands. Cellular calcium overload accompanies depletion of intracellular adenosine triphosphate (ATP), since calcium pumps that sequester cytosolic calcium are energy dependent. Calcium overload is a potent inducer of cell death³. An indirect therapy suggests that activating protein kinase (MAP) turns necrosis signaling into stress activates induced apoptosis. Inhibition of p38 is another way to also reduce cellular necrosis. A common pathology associated with necrosis is pyknotic cells which degrade and increase toxicities to surrounding cells (Fig 1). This displays the importance of a balancing act of pro and antiapoptotic signals.

Figure 2: Distinctive features of the CSC (cancer stem cell) niche, including hypoxia, reduced nutrient availability and acidity (H⁺), promote high levels of basal autophagy in CSCs⁴. This figure explains the Basal autophagy pathway in different cancer cells that are self-renewing rapidly. These cells can undergo basil autophagy if high acidity, low glucose or oxygen is present acutely, this initiates different signaling mechanisms such as inhibition of ROS build up, migration leading to metastasis. And even further cell differentiation.

        Autophagy is the third natural cell death process and occurs when the body undergoes extreme change in pH, glucose deficiency, and hypoxic conditions. This pathway has the most potential for being targeted for the development of new therapies to treat  cancer. Autophagy can occur during fasting and inhibit production of reactive oxygen species and cell death.  Mechanistically it is controlled/initiated by the mTOR pathway and activates through the ATG/ULK1 and Class III PI3K complex. Next the autophagosome formation is meditated by ATG7,10,5,12. It them fuses with a lysosome degrades the waste into amino acids, lipids and nucleotides to be recycled to a new cell system. In a way autophagy cleanses the body to a degree and is a reset for cellular processes and resulting in a less toxic and efficient/stable cellular enviorment⁵.

        Taking all cell death pathways into account, we can better understand the pros and cons of cell death mechanisms therapeutically  for each specified disease whether its cancer and for example Hotchkiss et al classified that decreased apoptosis is associated with diseases in over half of neoplasms. Enhancing apoptosis TP53 guardian can reduce the risk of cancer by 8-fold. Also stated in a table Leukemia and multiple myeloma and colorectal cancers have been treated with obatoclax which induces apoptosis by inhibiting antiapoptotic Bcl-2 family members. Or activates death receptors for treating Hodgkin’s lymphoma⁶. Another example is giving hydroxychloroquine to inhibit autophagy in breast cancer and prostate cancer, which can ultimately inhibit the progression and metastasis of early stages of these cancers. It is important to look at death as good at times and appreciate the amount of interplay of genes and signaling cascades there are for normal biochemical processes within our complex systems. This all concludes the importance apoptosis is for normal function and health to our biological systems.

References:

(1)    Reed, J. C. (2000). Mechanisms of Apoptosis. The American Journal of Pathology, 157(5), 1415–1430. doi: 10.1016/s0002-9440(10)64779-7

(2)    Allan, Lindsey & Clarke, Paul. (2008). Allan LA, Clarke PRA mechanism coupling cell division and the control of apoptosis. SEB Exp Biol Ser 59: 257-265. SEB experimental biology series. 59. 257-65.

(3)    Szabó, C. (2005). Mechanisms of cell necrosis. Critical Care Medicine, 33(Suppl). doi: 10.1097/01.ccm.0000187002.88999.cf

(4)    Boya, P., Codogno, P., & Rodriguez-Muela, N. (2018). Autophagy in stem cells: repair, remodelling and metabolic reprogramming. Development, 145(4). doi: 10.1242/dev.146506

(5)    Yang, Z., & Klionsky, D. J. (2009). An Overview of the Molecular Mechanism of Autophagy. Current Topics in Microbiology and Immunology Autophagy in Infection and Immunity, 1–32. doi: 10.1007/978-3-642-00302-8_1

(6)    Hotchkiss, R. S., Strasser, A., McDunn, J. E., & Swanson, P. E. (2009). Cell death. The New England journal of medicine, 361(16), 1570–1583. doi:10.1056/NEJMra0901217

Amal Agarwal University of Kentucky MSMS student Class of 2019

Biologic Drugs: From Crohn’s Disease to Cancer

            Biologics are a wide class of drugs that in recent decades, have become incredibly common and desirable due to their specificity and subsequent decreased potential for side effects. All biologics originate from or are modified forms of biomolecules. In contrast to traditional small molecule drugs such as lipitor or aspirin, biologics are quite large and are substantially more specific in the treatment of small groups of diseases through targeted modification of cellular pathways (Chan and Chan, 2017). This is by design, as most new biologic drugs are synthetic and rely on exploiting the principles of established physiological actions. Many believe that the healthcare industry is only just beginning to understand and utilize this powerful class of drugs and in fact they may allow for the treatment of many diseases that current lack effective therapies (Riley, 2018).

            One common example of a disease that is preferentially treated with biologic drugs is Crohn’s disease or CD for short. CD is a chronic inflammatory disease of the gastrointestinal tract that is caused by dysregulation of inflammatory pathways within the walls of the digestive system (Binion, 2019). This disease has been on the rise in recent decades.  It is now estimated that more than 1.6 million individuals have been diagnosed with CD in the United States (Shivashankar et al, 2017). Prior to the advent of biologics, CD was treated in much the same way as other inflammatory conditions, with repeated administration of corticosteroids and eventual surgery. The corticosteroids would down regulate and maintain low levels of inflammation, while surgery would remove the areas of the GI tract that were inevitably destroyed by the disease (Binion, 2010). It is not difficult to imagine that the prospects for life with CD were not great at that time. Now, CD is treated using biologics such as infliximab and adalimumab which modulate tumor necrosis factor or TNF which is a major cytokine that is crucial for maintenance of the inflammatory pathway. By binding and removing TNF, inflammation is halted in patients with CD and remission is commonly achieved and maintained (Jauregui-Amezaga et al, 2017).

            Despite the success of biologics, however, it is not uncommon for some patients to become unresponsive to the drug or to develop resistance over time (Riley, 2018). Because of this, a patient may have to switch between drugs throughout the course of their lifetime. Interestingly, more and more biologics are made each year, and the newest generation of biologics are designed to be more efficient and less likely to lose effectiveness. One such CD drug is ustekinumab which was originally used for psoriatic arthritis but is now evaluated for other applications like CD. In CD, ustekinumab, a monoclonal antibody, targets the p40 subunits of cytokines IL-12 and IL-23 to downregulate the immune response and shut down inflammation. Of note, these pathways also prohibit TNF and their downstream activity in the Th17 and Th1 response pathways (Jauregui-Amezaga et al, 2017).

Figure 1. An illustration of the action of ustekinumab on p40 and cytokine activation (Jauregui-Amezaga et al, 2017)

            Many patients with CD benefit from biologics, but the applications of these drugs are far more diverse with uses in treating several forms of arthritis, asthma, lupus, diabetes, heart attack, cystic fibrosis, osteoporosis, and several more. Several more diseases have the potential to benefit from future biologics that are not even yet made such as multiple sclerosis and cancer (Riley, 2018). Cancers are of particular interest because of the horrible side effects that are typically associated with chemotherapy, the current standard of cancer treatment. The principles that are guiding research efforts into the development of biologic cancer drugs rely on targeting markers specific to a cancerous cell using antibodies.  These antibodies may then arm immune cells to destroy cancer cells directly using the host immune system. They can also act to destroy cancer cells by introducing cytotoxic agents by binding a target marker and entering the cell with the toxin (NIH National Cancer Institute, 2018). Regardless, this could be far more specific than traditional chemotherapy that indiscriminately destroys cells and tissues leading to side effects like hair loss, soft tissue damage, and neuropathies.

Figure 2. An illustration of endocytosis of biologic drugs conjugated to cytotoxic agents in cancer cells (Riley, 2018).

             There is now a sort of mad dash to develop these drugs because of how potentially lucrative producing biologics can be. More than 37% of net drug spending since 2014 was on biologics, and more than 93% of the drug market growth can be attributed to an increase in their sales and production (Forbes, 2019). It is quite easy to forecast that the market will continue to demand more biologics as time goes on. More importantly, many diseases that could not be managed before will likely have biologics developed for them to improve the quality of life for patients and enrich our knowledge about disease processes and treatment at large. As such, the healthcare industry and patients will no doubt continue to benefit from biologic drugs as they evolve and improve.

By Bradley Wright, Master's of Medical Science Student, University of Kentucky

References:

Binion, D. G. (2010). Biologic Therapies for Crohn's Disease Update from the 2009 ACG Meeting. Gastroenterology and Hepatology, 6(1), 4–16. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2886448/

Riley, M. (2018, March 13). The ever-increasing attraction of biologics. Retrieved October 26, 2019, from https://www.chemistryworld.com/health-tech/the-ever-increasing-attraction-of-biologics/3008719.article.

Chan, J. C., & Chan, A. T. (2017). Biologics and biosimilars: what, why and how? ESMO Open, 2(1). doi: 10.1136/esmoopen-2017-000180

Jauregui-Amezaga, A., Somers, M., Schepper, H. D., & Macken, E. (2017). Next generation of biologics for the treatment of Crohn’s disease: an evidence-based review on ustekinumab. Clinical and Experimental Gastroenterology, Volume 10, 293–301. doi: 10.2147/ceg.s110546

NIH National Cancer Institute. (2018, April 26). Biological Therapies for Cancer. Retrieved October 26, 2019, from https://www.cancer.gov/about-cancer/treatment/types/immunotherapy/bio-therapies-fact-sheet.

Forbes. (2019, July 3). Biologic Medicines: The Biggest Driver Of Rising Drug Prices. Retrieved October 26, 2019, from https://www.forbes.com/sites/theapothecary/2019/03/08/biologic-medicines-the-biggest-driver-of-rising-drug-prices/#61afc63718b0.

Shivashankar, R., Tremaine, W. J., Harmsen, W. S., & Loftus, E. V. (2017). Incidence and Prevalence of Crohn’s Disease and Ulcerative Colitis in Olmsted County, Minnesota From 1970 Through 2010. Clinical Gastroenterology and Hepatology, 15(6), 857–863. doi: 10.1016/j.cgh.2016.10.039