RNA silencing. Computer artwork showing a length of RNA (yellow with red rings) bound to an RNA-induced silencing complex (RISC). © Medi-Mation Ltd / Photo Researchers, Inc

RNA interference, with its powerful promise of therapy for many diseases, may also act as a master regulator of most—if not all—cellular processes

The-Scientist.com, April 2010, by Judy Lieberman – One of the biggest surprises in biology in the past decades was the discovery that humans have about the same number of protein coding genes as a worm. That puzzling finding began to make sense when we realized that we were missing a big part of the picture: a lot of DNA is transcribed into RNA but never into proteins. The more we learn about these RNAs, the more we realize how much complexity they add. Some of these noncoding RNAs, called microRNAs because of their small size, interfere with protein expression by chopping up protein coding transcripts or inhibiting their translation into proteins. Their effect on cell fate and function is far wider than we initially thought. In recent years, it has become clear that microRNAs can act as master switches by regulating large networks of genes.

I came to work on microRNAs by a circuitous path. I started as a theoretical high-energy particle physicist, but after 8 years decided to go to medical school to do work that more directly helped people. As part of my medical training in hematology and oncology, I began a postdoc at MIT in the lab of Herman Eisen in the early eighties when molecular biology was just coming into its own: The T-cell receptor had just been discovered (work to which the Eisen lab contributed), and HIV was about to be identified as the cause of AIDS. With no therapy available then, AIDS patients died a truly gruesome death. The Eisen lab studied the cytotoxic T cells that were supposed to protect us against viral infections like HIV.

After my postdoc, I was offered a job at Tufts–New England Medical Center that combined clinical work in hematology with running a lab. I decided that my new lab would work on understanding the T-cell response to HIV and why these cells fail to control the infection, with an eye towards developing immune-based therapy. We also investigated how cytotoxic T cells activate programmed cell death (apoptosis) in virally infected cells.

I was immersed in HIV and T-cell immunology work in 1998 when I read the Fire and Mello paper1 describing one of the first examples of RNA interference (RNAi) in C. elegans. I was intrigued and perplexed by the paper: how could a double-stranded RNA possibly silence gene expression? I would periodically ask a colleague working on worms, Keith Blackwell, if there was an explanation for this strange phenomenon.

Liver saver
Liver damage, by infection with hepatitis B or C virus (1) or other causes, doesn’t usually result from the first insult. In the case of infection, for example, the virus initiates an inflammatory response, which upregulates Fas receptors on liver cells (2), and attracts T lymphocytes. T cells express the ligand for Fas on their surface and when they enter the liver they bind the Fas receptors (3), initiating the apoptosis pathway that leads to tissue scarring (4). When the small interfering RNAs (siRNA) were taken up by liver cells, they degraded the RNA message for the Fas receptor, preventing even the most deadly and acute liver damage.

My curiosity was thus piqued when 3 years later Carl Novina, a postdoc in Phillip Sharp’s lab whom I had known when he was a graduate student at Tufts, came to me with the still-unpublished news that RNA silencing also functions in mammalian cells. Tom Tuschl had found that genes could be silenced by introducing small double-stranded RNAs into a cell. Carl wanted to find out if this method could be used to inhibit HIV infection of immune cells. The prospect was tantalizing. What if we could use small interfering RNA to block HIV infection in humans?

Because T cells—the natural target of HIV in the body—are difficult to transfect, we started by trying to block infection in an epithelial cell line that was engineered to express CD4 and CCR5, two receptors required for HIV infection. Transfecting the cells with a small interfering RNA (siRNA) designed to degrade the messenger RNA (mRNA) for CD4 indeed blocked HIV infection by 4- to 10-fold. Encouraged by these results, we used RNA silencing to target an HIV gene that encodes for the viral capsid, and found that we could knock down both the host mRNA and the viral mRNA within the host cell. Knocking down either gene could stop the spread of the infection in cell culture. It was no small achievement. Our paper was one of the first in the field to show the potential of RNAi in treating human disease.2 Of course, at the time, no one understood that RNAi is actually a very basic antiviral mechanism. Organisms, like plants and more primitive animals that don’t have adaptive immune systems, use RNAi to attack and degrade viral mRNAs. In retrospect, it made a lot of sense that our HIV experiment would work.

RNA interference is much more than just a cell’s antiviral technique. This mechanism acts as a master regulator of gene expression, directing a cell’s response to developmental and environmental cues.

I was excited about translating our promising in vitro results into therapies, but in 2001 there were still no good small animal models of HIV infection. Without my knowledge, my postdocs, led by Erwei Song, decided to test the concept of using RNAi to protect against a different disease in mice—hepatitis.3 Two groups had shown that rapid intravenous injection of siRNAs in a large volume (so-called “hydrodynamic injection”) in mice was able to knock down expression of a simultaneously injected luciferase transgene in some organs in the mouse. The most effective knockdown was in liver cells. Using RNAi to prevent hepatitis might work. Erwei and his friends in China, who were skilled at performing the exceedingly tricky hydrodynamic injections, tried to silence a transcript for one of the caspases. This enzyme triggers programmed cell death in liver cells in virtually all forms of hepatitis. However, it didn’t work and all the mice died. When Erwei finally told me what had happened, I thought the approach was promising, but suggested trying to knock down a different target.

The RNA interference mechanism acts as a master regulator of gene expression, directing a cell’s response to developmental and environmental cues.

Because of my research on apoptosis in the immune system and antiviral immunity, I knew that liver cell death in hepatitis, no matter what the cause, is triggered by activating a death receptor called Fas on liver cells. Infection with hepatitis B and C viruses, for example, does not kill liver cells directly. Rather, the inflammation they cause induces Fas expression on liver cells and attracts killer lymphocytes bearing the counter-receptor for Fas (called Fas ligand) to infiltrate the liver, where they attack Fas-bearing liver cells (see graphic above). Triggering Fas is the common pathway for liver damage. Therefore knocking down Fas at the beginning of the pathway seemed like a good idea.

After hydrodynamic injection of siRNAs to knock down expression of the Fas receptor, Fas expression was reduced by 80% throughout the liver. As a consequence, there was a dramatic reduction in liver-cell damage. The technique could prevent liver damage not only in models of chronic hepatitis, but also in an acute liver damage model, in which all mice normally die within 3 days.4 After knocking down Fas in the liver, most mice survived the lethal challenge and recovered. It was clear that knocking down the Fas receptor could potentially block damage from any kind of hepatitis insult. What was more impressive was how easy it was to get these experiments to work. Once we started looking at Fas, we finished all of the experiments in the study in a month or two. When things work that well, it gives you the sense that you’re looking at a really fundamental process, rather than a curious side pathway. I was very excited and optimistic that small RNAs could be the basis for a new type of drug.

Research soon emerged showing that developing RNAi drugs wouldn’t be quite so easy. The active small RNAs, called small interfering RNAs or siRNAs, mediate RNAi silence genes by binding to a matching messenger RNA (mRNA) sequence and cutting it. But researchers found that a single siRNA could silence other mRNAs—not just the ones being targeted. These off-target effects could arise from one of two mechanisms: siRNAs were either hitting unintended genes that share partial sequence complementarity, or they were triggering the intracellular immune sensors that recognize viral double-stranded RNAs, causing inflammation and widespread immune stimulation. These potential problems were rapidly addressed by others who found that chemical modifications of the siRNA sugar backbone could block most off-target effects without jeopardizing gene knockdown. The other obstacle, which is still a major problem, was the incredible difficulty getting cells to take up naked RNAs. Hepatocytes were relatively easy because the liver is the filtering organ of the body, with a rich blood supply that routinely takes up particulates.

We tried to address some of these issues while working on an RNAi-based microbicide to prevent sexual transmission of viral infection (and ultimately HIV) in mice. Because of the lack of a small animal model for HIV transmission at the time, we decided to first try to block herpes transmission in mice. We developed a way of getting siRNAs into epithelial cells by either mixing them with a transfection lipid used to introduce exogenous nucleic acids into cells in the lab or by adding a cholesterol tag to the end of the RNA sequence that allowed the RNA to be taken up into cells. The result: effective gene silencing of an epithelial cell receptor that the herpes virus uses to enter the cell. The method could actually protect mice from a lethal vaginal dose of HSV-2 without causing immune recognition of the siRNA.5 However, neither of these methods was effective at transducing the T cells that HIV infects; we are still testing ways to modify siRNAs that could prevent HIV transmission, with some promising leads.

Erwei Song finished his postdoc in my lab in 2004, and returned to China to work as a breast cancer surgeon. When I visited China in 2005 for the annual meeting of a US–Sino comprehensive HIV research program in Beijing that I had helped organize, Song came to see me with exciting news. He had been working at Sun Yat Sen University in Guangzhou on his own projects and told me that he had discovered a method for culturing cancer stem cells from breast tumors. At the time, the cancer stem-cell hypothesis, which posits that breast cancer is initiated by a rare population of cancer stem cells, was controversial (and still is), in part because these cells are hard to identify and because the mouse models for human cancer might not accurately reflect how cancers originate in a human. These cells are relatively resistant to current chemotherapy and radiation therapy. They survive after cancer therapy and replenish the cancerous mass, leading to relapse. Although some tumors may be formed by initiating cells that do not resemble stem cells, it is likely that stem cell–like tumor cells are more aggressive at forming tumors, with a higher likelihood of relapse and metastasis.

It appeared that we had found not only a potential therapeutic mediator, but also a factor that controlled cancer cell “stemness”.

With his success at culturing these elusive cells, I couldn’t help but wonder what their microRNA expression profile looked like in comparison to other cells. microRNAs, the small endogenous RNAs that mediate RNAi naturally, were first identified in seminal studies by Victor Ambros and Gary Ruvkun in 1993, 5 years before the Fire and Mello paper. Their work suggested that small RNAs are instrumental in regulating development, as would later be confirmed by studies in several model organisms. I had a hunch based on this work that microRNA expression would be different in breast cancer stem cells than in more differentiated tumor cells or normal tissue and that it would change as the stem cells differentiated to form a tumor.

Our collaborative effort revealed that the breast cancer stem cells expressed far fewer microRNAs than their more differentiated counterparts. One family of microRNAs stood out: the let-7 family containing 11 related sequences in humans. let-7 is one of the most evolutionarily ancient microRNAs that Ruvkun’s lab had shown regulates the larval-to-adult transition in worms. The more we looked at this microRNA in functional assays, the more interesting it became. let-7 was not expressed in cancer stem cells, but its expression increased as the cell differentiated. When we infected cancer stem cells with a lentivirus expressing let-7, we could force their differentiation into treatment-susceptible cancer cells. Surprisingly, forced expression of let-7 also reduced the number of tumors formed in the mouse and reduced their metastases.

Master of the cell
Current computer algorithms used to search the genome for mRNA targets of microRNAs rely on the idea of a perfect sequence match between the mRNA and the seed region (nucleotides 2—8) of the microRNA. In reality, some targets are “seedless” and may have good pairing elsewhere in the sequence. By looking at the mRNA sequences that were downregulated when miR-24 was expressed, we found not only that this miRNA targeted major transcription factors in the cell cycle pathway like MYC and E2F2, but it also regulated genes that were transcriptionally regulated by MYC and E2F2.

It appeared that we had found not only a potential therapeutic mediator, but also a factor that controlled cancer cell “stemness.” In fact, let-7 controlled a number of stem cell properties, including the ability to self-renew and differentiate into different cell types (or “multipotency”). It accomplished this task by regulating the expression of more than one gene. Frank Slack had previously identified the oncogene RAS as a target of let-7 and David Bartel’s group had identified another oncogene, HMGA2, as a target. We found that let-7 regulation of RAS contributed to loss of self-renewal, while knockdown of HMGA2 led to loss of multipotency. Our study suggested that let-7 might be a master regulator of defining cancer stem cell properties.6 Together with the earlier studies in worms, this suggested that let-7 might be a master regulator of “stemness” more generally. At the time, researchers regarded small RNAs as rheostats that fine tune gene expression and cellular function; they were thought to only make small adjustments in expression. When I wrote the let-7 paper and called it a “master regulator,” controlling the very identity of a stem cell, I was asked to change the wording. However, I was convinced that these small RNAs are more powerful than the field had acknowledged.

While we were examining microRNAs in breast cancer stem cells, we were also looking at their role in blood cell differentiation from immature progenitor cells—somewhat more familiar territory for me. We became especially interested in one microRNA—miR-24—that stood out because it is upregulated as multipotent blood cells differentiate into a wide variety of mature blood cells. These mature cells are no longer capable of proliferating. Introducing miR-24 into proliferating normal and tumor cells also stopped them from further cell division. To understand how miR-24 worked, we wanted to identify the genes it regulated. It was a challenge, as microRNAs are only ~22 nucleotides long and bind to their targets by matching their sequence to a sequence in the target mRNA. But it’s a loose match at best—not every base pair matches its complementary nucleic acid. The algorithms used to predict which mRNA targets will be regulated by a particular microRNA are based on sequence matching. This often identifies thousands of potential targets and sometimes misses important ones like the oncogene RAS as a target of let-7. The algorithms place a lot of emphasis on target mRNAs that contain an exact 7 or 8 nucleotide match in their 3´ untranslated region (UTR) to residues 2–8 of the miRNA, called the “seed” region. Instead, we looked at all mRNAs that were downregulated when miR-24 was expressed in cells that don’t normally express it. We found 248 downregulated mRNAs, which did not overlap much with those found by the prediction algorithms.

I am optimistic that RNAi will be harnessed to produce a new class of drugs to treat many diseases.

To make sense of the large list of potential targets and choose a small number of genes to test experimentally, we collaborated with Winston Hide, a bioinformatician at the Harvard School of Public Health. Not only did miR-24 suppress major transcription factors that regulate the cell cycle—E2F2 and MYC—it micromanaged the expression of many of the transcripts that E2F2 and MYC activated (see graphic above). Most of the downstream genes we looked at experimentally were regulated by miR-24 recognition of “seedless” complementary sequences.7 We now think that miR-24 is another example of a “master regulator” of the cell, which acts by directly suppressing the expression of many genes that act in interconnected pathways.

Introducing microRNAs, such as let-7 or miR-24, that force cancer stem cells to differentiate or cause cells to stop dividing could be used for cancer therapy. Let-7 could make tumors more susceptible to standard cancer chemotherapy or radiation. Targeting cancer stem cells, especially, might address this highly malignant and refractory source of recurrent tumors. This is an approach we are now working on.

Jumping into RNAi research as it was just beginning has been extraordinarily rewarding. As I move into new fields, however, I’ve never given up on trying to understand the questions that I asked when I started my lab. Although I completely abandoned theoretical particle physics, I am still deeply involved in understanding how HIV manipulates and overcomes antiviral immunity, and how antiviral killer lymphocytes destroy their targets. As a physician, I hope that solving these questions and understanding how microRNAs work can be used to improve treatments for HIV and cancer. In my work on RNAi, and indeed during the 25 years I have been engaged in biomedical research, I have had one foot in basic research and the other in translational work, seeking to apply new understanding of biology to improving patient treatment. I am optimistic that RNAi will be harnessed to produce a new class of drugs to treat many diseases.

Judy Lieberman is a senior investigator at the Immune Disease Institute and Program in Cellular and Molecular Medicine, Children’s Hospital Boston and a professor of pediatrics at the Harvard Medical School.

References

1. A. Fire, et al., “Potent and specific genetic interference by double-stranded RNA in Caenorhabditis elegans,” Nature, 391:806–11, 1998.

2. C.D. Novina et al., “siRNA-directed inhibition of HIV-1 infection,” Nat Med, 8:681–86, 2002.

3. E. Song et al., “RNA interference targeting Fas protects mice from fulminant hepatitis,” Nat Med, 9:347–51, 2003.

4. P. Hamar et al., ”Small interfering RNA targeting Fas protects mice against renal ischemia-reperfusion injury,” Proc Natl Acad Sci USA, 101:14883–88, 2004.

5. D. Palliser et al., “An siRNA-based microbicide protects mice from lethal herpes simplex virus 2 infection,” Nature, 439:89–94, 2006.

6. F. Yu et at., “let-7 regulates self renewal and tumorigenicity of breast cancer cells,” Cell, 131:1109–23, 2007.

7. A. Lal et al., “miR-24 Inhibits cell proliferation by targeting E2F2, MYC, and other cell-cycle genes via binding to “seedless” 3´UTR microRNA recognition elements,” Mol Cell, 35:610–25, 2009.

From Medscape Medical News

Emma Hitt, PhD

April 22, 2010 — Dietary intakes of folate and vitamin B6 reduce the risk for mortality from stroke and any cardiovascular disease in women and may reduce the risk for heart failure in men, according to a study conducted in Japan.

The findings were reported online April 15 in Stroke by Renzhe Cui, MD, from the Graduate School of Medicine at Osaka University, in Osaka, Japan, and colleagues.

“This study is the first to show that high dietary intakes of folate and vitamin B6 were associated with a reduced risk of heart failure mortality for men,” the authors note.

Data from 23,119 men and 35,611 women (aged 40 – 79 years) who completed food frequency questionnaires as part of the Japan Collaborative Cohort study were analyzed. At a median 14 years of follow-up, 986 participants died from stroke, 424 died from coronary heart disease, and 2087 died from any cardiovascular disease.

Participants’ intake of folate, vitamin B6, and vitamin B12 were classified into quintiles. Comparing the lowest vs the highest quintiles for each nutrient, the researchers found that higher consumption of folate and vitamin B6 was associated with significantly fewer deaths from heart failure in men, and significantly fewer deaths from stroke, heart disease, and any cardiovascular diseases in women. By contrast, vitamin B12 intake was not associated with reduced mortality risk.

The protective effects of folate and vitamin B6 remained significant after adjustment for the presence of cardiovascular risk factors and also after exclusion of supplement users (n = 7334) from the analysis.

The hazard ratios (HRs) of coronary heart disease for the highest vs the lowest quintiles were 0.62 (95% confidence interval [CI], 0.42 – 0.89) for folate, 0.51 (95% CI, 0.29 – 0.91) for vitamin B6, and 1.35 (95% CI, 0.80 – 2.27) for vitamin B12. The HRs of heart failure for the highest vs the lowest quintiles were 0.76 (95% CI, 0.51 – 1.13) for folate, 0.60 (95% CI, 0.32 – 1.13) for vitamin B6, and 1.57 (95% CI, 0.90 – 2.73) for vitamin B12.

“Mechanisms for these observed associations may involve the effects of these vitamin intakes on reduction of blood homocysteine concentrations,” the researchers suggest.

This study has received grant funding from the Ministry of Education, Science, Sports and Culture of, Japan (Monbusho), Japanese Ministry of Education, Culture, Sports, Science, and Technology. The study authors have disclosed no relevant financial relationships.

Stroke. Published online April 15, 2010.

A new technique might help doctors foresee suicidal thoughts before a patient even has them

MIT Technology Review, April 22, 2010, by Lauren Gravitz  –  Over the past five years, an increasing number of studies have pointed to the rare but serious risk of suicidal thoughts that can accompany new antidepressant treatments. Close monitoring is currently the only clinical option, but a new technique–one that measures and analyzes electrical activity of the brain–could one day predict which people might be most susceptible to antidepressant-induced suicide.

While uncommon, the gravity of suicide risk was enough to prompt the U.S. Food and Drug Administration to place a “black box” warning on multiple antidepressant labels. So in order to tease out those individuals at highest risk, researchers at the University of California at Los Angeles’s Laboratory of Brain, Behavior, and Pharmacology are using an approach called quantitative EEG (QEEG).

Electroencephalography (EEG) uses a cap of electrodes placed at multiple locations across the scalp, each of which measures electrical activity coming from the brain at that particular spot. Neurologists frequently use EEG readouts to diagnose conditions such as epilepsy or brain injury. But instead of using the raw data–a set of jerky, squiggly lines, with each line corresponding to a single electrode–UCLA researchers employ an algorithm that mathematically analyzes data from all of the electrodes to transform the results into a map of brain activity.

The lab is using this quantitative EEG to determine how different individuals’ brains respond to different antidepressants, trying to find early markers that indicate whether a new therapy will be effective. But in addition to efficacy, research psychologist Aimee Hunter is also interested in side effects, since those often appear long before any improvement in mood. “And with all the increased press about antidepressants causing suicidal ideation, I began looking for brain changes that might specifically be related to that,” says Hunter, who is the lead author of a paper about the research, which was published in the April issue of Acta Psychiatrica Scandinavica.

An earlier study by Hunter and her colleagues, in which healthy volunteers were placed on either placebo or antidepressants, pinpointed the midline-and-right-frontal (MRF) portion of the brain as a region of interest. Those on medication showed moderately decreased activity in this area after just a week, while placebo-takers exhibited a slight increase. Focusing on the MRF region, Hunter then examined QEEGs from 72 adult patients who had been randomly assigned to take either medication or placebo for eight weeks. At multiple time points–48 hours, one week, two weeks, four weeks, and eight weeks after starting their therapy–the patients returned for QEEG measurements and a mood-assessment questionnaire.

When Hunter examined the results, she found a striking effect: Those patients on antidepressants who indicated any increase in suicidal thoughts also showed a drastic decrease in activity in their MRF region just 48 hours after starting their meds–six times the decrease shown in subjects with no change in suicidal thoughts. But after one week, the two groups were nearly identical again.

“It was very strange: There was a very large downward spike, and then … nothing,” Hunter says. “But the suicidal worsening isn’t happening at 48 hours–it’s happening at some later point over the next eight weeks.” She was seeing what appeared to be a harbinger of future response.

“They’re onto something important,” says Barry Lebowitz, a professor of psychiatry at the University of California at San Diego, who was not involved with the research. “This is clearly a first step in trying to personalize antidepressant treatment.”

Lebowitz, who has worked with the UCLA group on prior projects, notes that other techniques that could potentially predict a patient’s response to antidepressants are incredibly expensive, and not practical for widespread use. “But the kind of physiological measure this group is talking about is something people can use. An EEG machine is something that every doctor could have in the office for relatively small amounts of money.”

The results may also prove helpful in determining underlying physiology, says Ira Lesser, a professor of psychiatry at the Harbor-UCLA Medical Center who was not involved in the current work. “It begins to let people think neurochemically about what might be involved in the genesis of suicidal thinking. Heuristically, it could lead to whole other areas of study.”

Dan Iosifescu, who directs the translational neuroscience program at Boston’s Massachusetts General Hospital, performed similar QEEG experiments with similar results in 2008. “I think it’s interesting, but it’s too early to tell whether [the effect] is real or whether it’s an artifact,” he says. “Worsening of suicidal ideation is not a frequent event, and it happens in less than 10 percent of people. So you typically need very large data sets to study it adequately.”

Hunter’s next step is to determine whether a similar effect can be seen using abbreviated EEG monitors, which require far fewer electrodes and can be completed in just 10 minutes (as opposed to the hour required with the full electrode array), and she’ll be examining this using a much larger group of patients. “Further development needs to be done, but we’re hoping this would allow us to provide a tool that could make antidepressant use happen in a safer way,” she says.

Barefoot Running

       Harvard evolutionary biologist Dan Lieberman believes

that modern running shoes may explain why fifty percent of serious

runners are injured at least once a year (Nature, January 2010).

Modern running shoes have features that cause runners to land on

their heels with forces of at least three times body weight at

6-minute mile pace.  The faster a runner runs, the greater the

force, which causes stress fractures of the feet and lower legs,

shin splints, tears in the fascia on the bottom of the feet, knee

and hip pain, tendon and joint damage and more.

       Hitting the ground with the heel first generates

tremendous force because it stops the foot suddenly.  On the other

hand, landing on the front of the foot allows the foot to keep on

moving as the heel is lowered toward the ground to distribute the

forces throughout the entire lower leg.  If you drop a pen on its

tip, it hits with tremendous force because it stops when it hits

the ground and then falls forward.  However, if the pen were dropped

on the side of one end, it would hit the ground with much less force

because after hitting on that side, the force would be distributed

as the pen falls backward to the other end.

       In the 1960s doctors thought that most running injuries

were caused by excessive pronation, a rolling inward of the foot

after the heal strikes the ground.  They felt that the foot rolled

inward toward the arch to dissipate the tremendous heel strike

forces. This, in turn, caused the lower leg to twist inward and they

blamed the frequent running injuries on the inward twisting motion

of the leg after heel strike.  So they invented running shoes with

special arch supports to limit inward rolling, and with padded

heels to cushion some of the shock of the heel hitting the ground.

However, these features reinforce the runners’ habit of landing on

their heels.

       Dr. Lieberman has shown that barefoot runners are more

likely to land on their forefoot or mid-foot.  He has shown in

elegant experiments that landing on the front part of the foot

reduces the force of the foot strike very significantly. However,

he has no data to show that running injuries can be prevented by

running barefoot. Furthermore, stones and cut glass can cause

injuries, and most runners have such thin skin on the bottom of

their feet that they couldn’t possibly run barefoot.

        New on the market are running shoes with very thin soles

and minimal heels called Vibram FiveFingers shoe and the Dunlop

Volley.  Vibram is supporting Dr. Lieberman’s studies.  Dr.

Lieberman has shown only *that modern running shoes tend to

encourage a runner to land on his heels and * heel strike

generates more force than front foot strike.  He has not yet

shown that: *modern running shoes cause injuries or that  *injuries

can be treated or prevented  by running barefoot or in thin-soled

shoes.  His website is www.barefootrunning.fas.harvard.edu

Dear Dr. Mirkin: Can diet help to prevent senility and

Alzheimer’s disease?

       Probably.  A study from Columbia University in New York

shows that those least likely to develop Alzheimer’s disease eat

a diet rich in omega-3 fatty acids, omega-6 fatty acids, vitamin E,

vitamin B12 and folate, in foods such as nuts, fish, tomatoes,

olive oil, poultry, broccoli and other cruciferous vegetables,

fruits, and dark green leafy vegetables.  They eat less red meat,

organ meats and high-fat dairy products (Archives of Neurology,

April 2010).

       Alzheimer’s disease is associated with an overactive

immunity called inflammation. Your immunity is good for you

because it prevents germs from invading your body. However if

your immunity is overactive, it uses the same chemicals that it

uses to destroy invading bacteria to punch holes in your arteries

and damage your brain (Nature Medicine, August 2009).  The

foods recommended in the Columbia study reduce inflammation, while

red meat and high fat dairy products may increase inflammation.

Being overweight also increases risk for Alzheimer’s disease because

full fat cells release hormones that cause inflammation

(Biochimica et Biophysica Acta, May 2009).

Dear Dr. Mirkin: What can I do about very high triglycerides and

low HDL cholesterol?

        These blood test results mean that you have metabolic

syndrome, a form of pre-diabetes or diabetes that puts you at

high risk for heart attacks (JAMA, April 15, 2010).   When you

eat foods with added sugars, those made from flour, and sugar in

liquid form (including fruit juice), your blood sugar rises to high

levels. This causes your pancreas to release large amounts of

insulin that converts sugar to triglycerides (high triglycerides).

Then you use up your good HDL cholesterol in carrying triglycerides

from your bloodstream into your liver (low HDL cholesterol).

       You should avoid the refined carbohydrates that cause

the highest rises in blood sugar, except when you exercise.  When

muscles rest, they cannot remove sugar from the bloodstream without

insulin. However when muscles contract, they draw sugar rapidly

from the bloodstream without needing insulin.  This effect lasts

while you exercise and for up to an hour afterwards, and then

tapers off to zero in the next 17 hours.  That’s why you must

exercise every day to reap this major benefit of exercise.

       You can avoid diabetes by exercising daily, losing body

fat, gaining muscle, eating lots of vegetables, and making sure

that your blood level of vitamin D is normal. Lack of vitamin D

increases risk for diabetes by blocking insulin receptors and

preventing your body from responding to insulin. If your vitamin

D3 level is below 75 nmol/L, you are deficient and need more

sunlight or vitamin D pills.

http://www.drmirkin.com