Sunday, May 21, 2017

A New Outbreak of the Ebola Virus in 2017

On April 22 a 45-year-old man in a remote area of the Democratic Republic of the Congo (DRC) was diagnosed with the Ebola virus; call him the new "patient zero". In less than a month there were 20 more suspected cases and three deaths. Is this the start of a new outbreak? And if so, what is being done to prevent another outbreak like the 2014-2016 outbreak that killed over 11,000 people in Guinea, Sierra Leone, and Liberia?

It would be encouraging to think that "it'll be different this time", and maybe it will. For one thing, Merck has developed a vaccine that appears to be effective against the 2014-2016 strain of Ebola. There are already stockpiles of the vaccine on ice. But the vaccine is still considered "experimental". It has not yet been approved by the FDA, and so it can only be used in carefully monitored clinical study protocols designed to document the vaccine's safety and effectiveness. The DRC does not yet have an approved clinical study protocol on file, according to an article in Science. The government will need to decide whether standard containment strategies are likely to suffice, or whether it can establish an approved study protocol quickly enough to be able to vaccinate people at risk before the outbreak gets much worse.

You might think it would be a no-brainer to establish a clinical study protocol. It is not. Requirements would include the ability to keep the vaccine refrigerated the vaccine at all times - no small task in remote region of the country. Furthermore, an approved clinical study protocol would require extensive record-keeping, including follow-up of all vaccine recipients for an extended period of time. There's even a requirement for ethical oversight and for obtaining informed consent from all vaccine recipients.

And so we wait. We wait to see what the DRC does about this latest outbreak, and whether the outbreak spreads.

Friday, May 19, 2017

Creating Eggs From Skin Cells

Some day it may be possible to produce human babies from skin cells, according to an editorial in Science Translational Medicine.  It's all due to a new technique called in vitro gametogenesis (IVG).

IVG refers to the technique for producing eggs or sperm (gametogenesis) outside the body (in vitro). The technique only became possible because, a decade or so ago, scientists learned how to produce undifferentiated stem cells known as induced pluripotent stem cells (iPSPs) from mature somatic cells.  Since that time iPSCs have been used to create various kinds of specialized somatic cells, including neurons to heart muscle cells.  And just recently, iPSCs derived from mouse tail cells were used to create fully functional gametes (eggs).  When fertilized with sperm, these eggs created by IVG were able to develop into healthy baby mice.  Sperm have not yet been fully developed from iPSCs, but surely they will be.

The ability to produce eggs and/or sperm from somatic cells raises all kinds of possibilities for how the procedure might be used (or misused, depending on your perspective).  If an egg could be grown from a male's skin cell and then fertilized by IVF with sperm from a male partner, gay couples could have babies that were genetically related to both of the males.  Of course a female surrogate mother would be necessary to carry the embryo to term, but surrogate mothers are not uncommon these days. Taking it one step further, if both eggs and sperm could be created from a male's skin cells, the male could (again, with the help of a surrogate) have a child that was entirely genetically his. These are scenarios that may need to be dealt with in your lifetime.  (Note that since females have no Y chromosome, IVG could only produce eggs from a female; never sperm.)

On the positive side, the ability to produce eggs from skin cells could mean that overcoming infertility would become easier and cheaper.  Right now, women undergoing an IVF procedure must undergo a complicated cycle of ovary stimulation and egg retrieval; with IVG, that would be unnecessary.  Furthermore, IVG could be used to produce an almost infinite supply of eggs, whereas only a few eggs are produced with each IVF cycle.

How do you think IVG should be used?

Thursday, May 11, 2017

A Second Drug is Approved to Treat ALS

The FDA has approved a second drug to treat amyotropic lateral sclerosis (ALS), also known as Lou Gehrig's disease. ALS is a progressive, debilitating, neurodegenerative disease that is usually fatal within 3-5 years. The new drug, called Radicava, slows the progression of the disease somewhat after six months of use; apparently that was enough for the FDA to approve the drug.

Before you get too excited, though, here are some facts about the new drug; 1) It must be given intravenously. That means that the patient must have a permanent IV port installed, which poses an infection risk. 2) The drug is only partially effective. Patients using the drug won't feel better; their health will just decline less rapidly. 3) It's expensive - $146,000 a year, according to its manufacturer.

The first drug to treat ALS, called riluzole, costs only about a tenth as much as Radicava.  Riluzole extends the life of ALS patients by 2 or 3 months; whether Radicava does the same isn't yet known.

If you had a fatal disease and were expected to live only 5 more years, would you pay $146,000 per year to slow the rate of disease progression just a little, or to live an extra 2-3 months? That's a judgment call only you can make. But your insurance company might balk at the price of this drug, considering its minimal effectiveness.

Sunday, May 7, 2017

When Did Humans Reach the Americas?

Until now, the best available evidence had indicated that humans probably reached the Americas about 20,000 years ago.  But now a new paper published in Nature raises the possibility that humans reached the Americas as early as 130,000 years ago.  The new findings could force a re-thinking of when, how, and by whom the Americas were colonized.

The new paper focuses on an archaeological site in California, where smashed and broken bones of a mastodon were found intermingled with what are reported to be crude stone tools.  Uranium/thorium dating shows that the bones are a whopping 130,000 years old.  The authors propose that the bones were deliberately smashed, leading to the conclusion that humans must have been in California at least as early as 130,000 years ago.

The findings are intriguing, but we'll probably have to wait for corroborating evidence before everyone accepts the new date.  For starters, it would help if we could find human bones that old; so far, no human bones older than about 20,000 years have ever been found in the Americas.  And then there's the question of how they could have gotten to the Americas in the first place.  The humans who colonized the Americas about 20,000 years ago crossed over from Asia via a land bridge that existed at the time between current-day Russia and Alaska.  That land bridge probably didn't exist 130,000 years ago.  They could have arrived by boat, but that would presume a higher degree of sophistication than implied by primitive stone tools.

Finally, there's the question of who these people were, if indeed they ever existed.  DNA evidence indicates that Native Americans can trace their ancestry back to a common ancestor who lived about 20,000 years ago.  If a band of humans arrived more than 110,000 years before that, they must have died out without leaving a continuous line of descendants.

Thursday, May 4, 2017

An artificial Womb

A baby that is born at 23 weeks of gestation (about halfway through the normal gestation period) has only about a 50% chance of surviving. The main problem for babies born prematurely ("preemies") is that they struggle to breathe, for their lungs are not yet fully developed. Their underdeveloped hearts, too, have a hard time pumping all of the blood that the baby requires outside of the womb. In the womb, the baby's still-developing lungs are filled with amniotic fluid, and so the baby doesn't breathe at all. Oxygen is delivered to the baby (and CO2 is removed) by the blood circulating between mother and baby via the umbilical cord.

In an effort to increase the chances of survival of very premature preemies, scientists are now working to develop an artificial womb. So far, the artificial womb has only been tried with premature lambs in an experimental setting, but the early results look promising. The artificial womb looks a bit like a large re-sealable bag. Upon delivery, a premature lamb is put into the bag, and the bag is then filled with artificial amniotic fluid and sealed to prevent infections. Ports provide access to the umbilical cord and allow for exchange of amniotic fluid. The umbilical artery and vein are cannulated so that blood can be exchanged with the lamb, just as it would be in the womb. Premature lambs have been kept alive in the artificial womb for four weeks; long enough to dramatically increase their chances of survival outside the womb.

It may be awhile before you'll see artificial wombs for human use. But perhaps some day, you'll have a grandchild that was delivered at 19 weeks of gestation then grown for four weeks or more in a plastic bag!

Friday, April 28, 2017

Are Vitamin D Supplements Effective in Preventing Disease?

Are you one of the millions of people who are taking vitamin D supplements? People take vitamin D supplements to prevent depression, muscle weakness, cancer, heart disease, and who knows what else. And yet, there is a lack of evidence that vitamin D supplements will prevent any of these conditions.

The trend to test for and treat alleged vitamin D deficiencies took off in 2011 with the publication of a book entitled The Vitamin D Solution - A 3-Step Strategy to Cure Our Most Common Health Problems. The suggestion by the book's author that vitamin D levels of 21-29 ng/ml are insufficient for good health were a bit of a shocker, since blood levels of vitamin D of greater than 20 ng/ml are considered normal.  The book and several studies that seemed to support its thesis led to an increase in vitamin D screening blood tests, and to recommendations by many physicians that their patients consider taking vitamin D supplements.

However, the Institute of Medicine says that there is no evidence that people who have vitamin D levels above 20 ng/ml (i.e. normal vitamin D levels) will benefit from taking additional vitamin D.  In addition, two studies published this year show that vitamin D supplements don't prevent heart attacks and don't protect women against cancer. An ambitious 5-year study is now underway to try to determine once and for all whether vitamin D supplements are of any use in preventing cancer, heart disease, and stroke.

I don't know about you, but I'm taking vitamin D deficiency off my list of things to worry about, at least for now.

Tuesday, April 25, 2017

'Subclinical' Hypothyroidism is Being Over-treated

What was the most prescribed drug in 2016?   If you guessed a blood pressure medication, a cholesterol-lowering drug, insulin for diabetes, or even a painkiller such as oxycodone, you'd have been wrong.  It was levothyroxine, a drug used to treat hypothyroidism. But not all physicians are using this drug correctly; many are using it to treat 'subclinical' hypothyroidism.

Subclinical hypothyroidism is generally defined as a slightly elevated TSH (thyroid-stimulating hormone; indicating perhaps an under-responsive thyroid gland), accompanied by a number of vague and highly subjective symptoms such as tiredness, lack of motivation, and muscle aches and pains. It's called 'subclinical' hypothyroidism because levels of the two thyroid hormones, T3 and T4, are still normal, as opposed to true hypothyroidism in which there is a clear deficiency in these two hormones.

The problem is that many of the physical symptoms of hypothyroidism, such as tiredness and muscle aches and pains, are common complaints in older people.  So if their TSH levels are just a little over the normal level (which also often happens with age), physicians are increasingly putting their older patients on levothyroxine, regardless of what their T3 and T4 levels are.  As a result, fully 15% of older Americans are taking levothyroxine to treat their alleged symptoms.

However, recent evidence shows that other than lowering TSH levels to normal, levothyroxine doesn't have any effect on the actual "symptoms" patients are complaining about - no effect at all.  If this new evidence is correct, physicians could stop prescribing levothyroxine to treat 'subclinical' hypothyroidism entirely.  The proper use of levothyroxine is to treat patients with true hypothyroidism, in which T3 and T4 are demonstrably low.