Dear senior citizens, are you walking extra slowly? You may be at risk of dementia. 


People, who developed slow walking, showed shrinkage of their right hippocampus, the area of the brain primarily associated with memory and the ability to maintain posture.

Senior citizens
People who slow by 0.1 seconds more per year are 47% more likely to struggle cognitively, says study.

Beware! If your grandma’s walking pace has suddenly slowed down more than usual, then you may have to rush her to the doctor as it could be an early indicator of dementia, warns a study. The results suggested that participants, who walked slower over time, but those who slowed by 0.1 seconds more per year than their peers were 47 percent more likely to struggle cognitively.

Researchers from the University of Pittsburgh in Pennsylvania, US found that people, who developed slow walking, showed shrinkage of their right hippocampus. This area of the brain, which is similar in shape to a seahorse, is primarily associated with memory and the ability to maintain posture, in relation to the physical space around you when at rest and during motion.

The findings suggested that dementia could be treated earlier if doctors regularly measure the walking speeds of older patients and watch for changes over time. “Prevention and early treatment may hold the key to reducing the global burden of dementia, but the current screening approaches are too invasive and costly to be widely used,” said a researcher Andrea Rosso.

The team looked at 175 people, aged 70 to 79, who had good health and normal mental function, at the start, for 14 years. The participants were regularly assessments over the years, involving the participants walking an 18-foot stretch of hallway while they were timed.

The study found that dementia could be treated earlier if doctors regularly measure the walking speeds of older patients and looked for changes over time.

The results revealed that the right hippocampus was the only area of the brain found to shrink in relation to both gait slowing and cognitive impairment. The finding held even when the researchers took into account slowing caused by muscle weakness, knee pain and diseases, including diabetes, heart disease and hypertension.

“What we’re finding is that physicians also should consider that there may be a brain pathology driving the slowing gait and refer the patient for a cognitive evaluation,” Rosso noted.

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Here’s How 23andMe Hopes to Make Drugs From Your Spit Samples


On March 12, 23andMe, the genetic testing company best known for analyzing your DNA from a sample of spit, announced the creation of a new therapeutics group. The group’s mission: to find and develop drugs from the world’s largest database of human genetic material.

That’s a huge shift for the company, which must now build a research and development arm from scratch. Richard Scheller, formerly of the biotechnology corporation Genentech, will lead the group and will also be 23andMe’s chief science officer.

 Scheller admits that for now, he’s the therapeutics group’s only member. But soon after he starts on April 1, he anticipates that things will move quickly, as they do in the genetics world. That’s what attracted him to 23andMe after overseeing early drug development at Genentech for 14 years. “I’ve seen over the last couple of years how human genetics has impacted the way Genentech does drug discovery, and I thought it might be fun and interesting to work in an unrestricted way with the world’s largest human genetic database,” he says. “The questions we will ask are research based, but we could identify a drug target extremely quickly. I believe there is the real possibility to do really, really great things for people with unmet medical needs.”

More than 850,000 people have paid 23andMe to sequence their DNA since the company launched in 2006 until 2013, when the Food and Drug Administration requested that the company stop selling its medical genetic information services over concerns that their marketing claims weren’t supported by strong enough evidence about how the genetic information influenced human health. The company still retains that genetic information and continues to sell kits, but provides only non-medical information now while it continues to work with the FDA on further regulatory issues.

 That experience “transformed” the company, as CEO Anne Wojcicki said to TIME earlier this year. Since then, the company has expanded its collaborations with pharmaceutical companies to access its database. The latest addition of drug development is a further evolution in the company’s identity.

Of those who have sent in samples, 80% have agreed to allow their genetic information to be used for research purposes. That’s the database that Scheller is eager to investigate. While at Genentech, he helped broker a collaboration between the biotech firm and 23andMe in which Genentech would have access just to the genetic testing company’s Parkinson’s disease patients, to search for any genetic clues to new therapies. Now, he says, “I plan on asking hundreds or maybe thousands of times more questions of the database than any pharmaceutical partner.”

He will be looking, for example, at whether patients who develop a certain disease tend to have specific hallmark genetic changes in their DNA, which could serve as potential launching points for new drugs. Or he might focus on the extreme outliers: people who have advanced cancer, for example, but somehow survive, or those who seem to succumb early. Mining their genomes might yield valuable information about what makes diseases more or less aggressive, and might become targets for drugs as well.

To do this, Scheller will have to create a drug development team from the ground up. The company is not divulging how much it intends to invest in this effort, but is soliciting another round of financing in the coming months. Initially, Scheller anticipates that even before the company has labs set up, he and his team will take advantage of labs-for-hire, or contract research organizations, to start doing experiments within weeks. Because his drug candidates will be more targeted and designed to address specific mutations or processes in the body, he anticipates that the cost of developing drugs that patients might eventually benefit from may be “substantially reduced” from the average $1 to $2 billion most pharmaceutical companies now spend.

As for which disorders or medical issues he will tackle first, Scheller is being democratic. “We are going to be opportunistic,” he says. “That’s the nice thing about being part of 23andMe. We don’t really have a say. We can look generally at the database, and try and let it teach us what we should be working on.” In other words, anything is game.

Stephen Hawking Says Trump’s Climate Policy Could “Push Earth Over The Brink”


The legendary physicist Stephen Hawking is celebrating his 75th year on this planet with a grand cosmology conference in his honour held this week at the University of Cambridge, UK.

Ahead of this event Hawking spoke to BBC News, sharing his grave disappointment and concern with the direction Earth’s climate is taking, especially in light of US President Donald Trump’s decision to pull out of the Paris climate agreement.

 “We are close to the tipping point where global warming becomes irreversible,” Hawking told BBC’s Pallab Ghosh.

“Trump’s action could push the Earth over the brink, to become like Venus, with a temperature of two hundred and fifty degrees, and raining sulphuric acid.”

Now, the famous scientist was certainly being a touch hyperbolic here, as is wont for someone who has spent his career in the public eye, making headlines with every new discovery and popular science book.

While our planet is without a doubt undergoing the effects of anthropogenic climate change, the kind of runaway greenhouse gas effect that is actually happening on Earth’s ‘evil twin’ Venus is not really our most immediate concern.

A 2013 study did predict that a runaway greenhouse effect on Earth “could in theory be triggered by increased greenhouse forcing”, but added that, based on the available data, emissions wouldn’t be enough to cause this.

But even if we’re not about to be melted down to our skeletons in sulphuric acid rain, Hawking still has a point.

 

“By denying the evidence for climate change, and pulling out of the Paris Climate Agreement, Donald Trump will cause avoidable environmental damage to our beautiful planet, endangering the natural world, for us and our children,” he added.

It’s already too late to prevent the full effect that climate change is going to have on our planet. Over the course of the 20th century, Earth’s average temperature increased by about 1 degree Fahrenheit (0.6 degrees Celsius), which may not sound like much, but actually amounts to huge environmental changes.

As that average temperature climbs even higher, temperature anomalies are going to swing all over the shop, with weather extremes hot on their heels. There will be more hurricanes, more heat waves, more record temperatures, loss of sea ice and changing seasonal patterns everywhere.

For people who accept the reality of scientific consensus on climate change, it’s now become a question of how best to mitigate all these effects, and the Paris Climate Agreement was the result of 195 countries coming together to say “let’s finally do this”.

When a major world power decides to renege on these international efforts, it’s natural to feel pessimistic – although Professor Hawking has seemed to be pessimistic about humanity’s prospects for a while now.

Just last month he reiterated that if humans are to persist as a species, our only choice is to explore other planets as quickly as possible, so that we can one day travel beyond our own Solar System.

“Spreading out may be the only thing that saves us from ourselves. I am convinced that humans need to leave Earth,” Hawking said at a science festival in Norway.

The leap to a backup plan off world is a lot harder than fixing this one Goldilocks planetwe’ve got. But at least for worst case scenario planning, it’s good to know NASAJapan, and China are all working on new lunar missions as a stepping stone to putting spaceboots on Mars.

There’s Now Very Strong Evidence We Really Are Killing Our Bees


Two industry-funded studies have finally provided sound evidence that vastly popular pesticides called neonicotinoids are horrible for the pollinators that keep our food production system running.

We’ve suspected for a while that these pesticides might be affecting bees, but it’s a tricky subject to study in the lab, where bees might be given unrealistically high doses of pesticide. Now scientists have conducted the largest-ever field trials in Europe and Canada, and the news is bad.

 

Neonicotinoids are the most widely used class of insecticides in the world. They are chemically similar to nicotine, the compound that plants in the nightshade family have evolved to protect themselves from pests.

Invented in the 1980s, neonicotinoids quickly became a popular crop treatment because they are systemic, which means they circulate through the whole plant and kill bugs as soon as they feast on the crop. And because they linger in the plant’s system, one application – sometimes just on the seeds – can be plenty to offer long-term protection.

But these attractive properties for farmers are what makes neonicotinoids such a concern for bee welfare, because a systemic insecticide easily makes its way to the nectar and pollen of a flowering plant.

To measure this potential harm, a team of European researchers established 33 sites growing rapeseed in Germany, Hungary and the UK. These were randomly assigned to either be treated with one of two choice nicotinoids, or none at all.

The team looked at honeybees and two wild bee species – bumblebees and solitary bees. Results differed between locations and species, but overall they discovered that honeybee hives were less likely to survive over winter, while the wild bees reproduced less.

It’s not that the pesticides directly kill bees, the scientists note. Instead, it appears that low-level exposure makes them more vulnerable, especially if there are other environmental factors or diseases already affecting the hive.

 “Neonicotinoid applications are thus a kind of reproductive roulette for bees,” biodiversity researcher Jeremy Kerr notes in a related perspectives article in Science.

The huge study was actually largely funded by the pesticide industry itself. The companies Bayer Crop Science and Syngenta put up US$3 million for the trial, and both have panned the scientists’ conclusions that it would be better to restrict neonicotinoid use.

But these are important results nonetheless, and are likely to inform the European Union’s upcoming decision on a potential blanket ban of these pesticides. A temporary ban has already been in place since 2013.

“Our results suggest that even if their use were to be restricted, as in the recent EU moratorium, continued exposure to neonicotinoid residues resulting from their previous widespread use has the potential to impact negatively wild bee persistence in agricultural landscapes,” the researchers write in the study.

And that’s not even all.

Another field study by researchers in Canada was published in the same issue ofScience, also showing negative effects on bees.

The team studied honey bees that either lived close to neonicotinoid-treated corn fields, or far away from agriculture. The results suggested that chronically exposed bees had lower life expectancies and poorer hygiene conditions in the hive.

Additionally, they also discovered that bees collected pollen tainted with the pesticides, but this pollen didn’t even come from the treated crops themselves.

“This indicates that neonicotinoids, which are water soluble, spill over from agricultural fields into the surrounding environment, where they are taken up by other plants that are very attractive to bees,” says one of the researchers, Nadia Tsvetkov.

The work done by both teams goes a long way to demonstrate that we really are contributing to the worldwide bee decline, way more dramatically than we’d like to admit.

“It’s reached a point where it’s just not plausible to keep denying these things harm bees in realistic studies,” bee researcher Dave Goulson from the University of Sussex told Daniel Cressey at Nature News.

“I’d say it’s the final nail in the coffin.”

Human Emotions Really Are Affected by Gut Bacteria, New Study Suggests


The more we find out about the bacteria that live in our gut, the more we’re coming to realise how these microbiota could have an impact on every facet of our lives – and not just our physical health and well-being, but our thoughts and emotions too.

A new study has identified associations between two kinds of gut microbiota and how they affect people’s emotional responses, and the researchers say it’s the first evidence of behavioural differences related to microbial composition in healthy humans.

 

Up until now, most research looking into how gut organisms influence emotions has been conducted on animals, with scientists finding that the bacterial composition of rodent guts can have an effect on the animals’ behaviour.

Now, a team led by gastroenterologist Kirsten Tillisch at UCLA has shown that the same kind of associations appear to be affecting human emotional reactions.

The researchers took faecal samples from 40 healthy women between the ages of 18 and 55. When the samples were analysed, the participants were divided into two groups based on their microbiota composition.

One of the groups showed a greater abundance of a bacterium genus called Bacteroides, while the other group demonstrated more clusters of a genus called Prevotella.

Next, the team scanned the brains of the participants via functional magnetic resonance imaging, while showing them images designed to provoke a positive, negative, or neutral emotional response.

What the researchers found was that the group with greater abundance of Bacteroidesin their gut bacteria showed greater thickness of the grey matter in the frontal cortexand insula – brain regions which process complex information – and also a larger volume of the hippocampus, which is involved with memory.

In contrast, the women with higher levels of Prevotella demonstrated lower volume in these areas, and demonstrated greater connections between emotional, attentional and sensory brain regions.

When shown the negative images, the Prevotella participants showed lower activity in the hippocampus – but reported higher levels of anxiety, distress and irritability after looking at the photos.

According to the researchers, this could be because the hippocampus helps us to regulate our emotions, and so with less hippocampal volume – which is possibly related somehow to the makeup of our gut microbiota – negative imagery may pack a greater emotional wallop.

“Reduced hippocampal engagement to negative imagery may be associated with increased emotional arousal,” the authors write in their paper.

“Such changes have been suggested to result in less specificity of encoding the contextual details of incoming stimuli, a deficit seen in the setting of several psychiatric disorders, including depression, post traumatic stress disorder, and borderline personality disorder. While the subjects in this study were healthy, it is possible that the patterns which emerge from the microbial clustering represent vulnerability factors.”

It’s important to bear in mind that the sample studied here was very small – a point the researchers freely admit in their paper, acknowledging that further research with larger numbers of participants will be needed before we can really understand what’s going on here.

But it’s clear that there’s something going on between the organisms in our gut and the thoughts and feelings we experience, and the sooner we delve into this, the sooner we’ll comprehend just how emotionally powerful our ‘second brain‘ really is.

Men Experience Their Own Biological Clock, IVF Study Shows


Male fertility doesn’t last forever.

 

While it’s well known that women start to experience a decline in fertility in their thirties, scientists have found new evidence suggesting men also have a ‘biological clock‘ that limits their ability to reproduce as they get older.

A new study shows that in vitro fertilisation (IVF) delivery rates are affected by the age of the male partner, with successful IVF procedures becoming less likely as would-be fathers get older.

 The research, led by reproductive biologist Laura Dodge from Harvard University, shows that when it comes to producing babies through IVF, it’s not just the age of the woman that matters, even though that may be the dominating factor affecting successful outcomes.

Dodge’s team analysed 15 years’ worth of IVF treatments conducted in Boston between 2000 and 2014, encompassing some 19,000 IVF cycles performed for almost 8,000 couples.

What they found is that as the males in the couples got older, the chances of live birth were reduced – but the effect was only apparent in couples where the woman wasn’t older than 40.

From the data set, the researchers divided the IVF participants (both male and female) into four age bands: under 30, 30–35 years old, 35–40, and 40–42.

The cumulative live birth rate – measured from up to six cycles of IVF treatment – was lowest in couples where the female partner was aged 40–42, which wasn’t a surprise, given what we know about decreasing female fertility as women age.

In this band, where females were aged 40–42, the age of the male partner had no impact on birth rate, but in the younger female bands, cumulative live birth rates were found to decline as male partners grew older.

 “Generally, we saw no significant decline in cumulative live birth when women had a male partner the same age or younger,” says Dodge.

“However, women aged 35–40 did significantly benefit from having a male partner who is under age 30, in that they see a nearly 30 percent relative improvement in cumulative incidence of live birth when compared to women whose partner is 30–35 – from 54 percent to 70 percent.”

And just as birth outcomes were more successful when older females paired with younger males, they stood a greater chances of failure when younger females attempted IVF with older males.

In the study, couples where the female partner was under 30 and the male was aged 40–42 had a cumulative birth rate of 46 percent, but if the male partner’s age was 30–35, this improved significantly to 73 percent.

“Where we see significant decreases in the cumulative incidence of live birth is among women with male partners in the older age bands,” says Dodge.

“For women age 30–35, having a partner who is older than they are is associated with approximately 11 percent relative decreases in cumulative incidence of live birth – from 70 percent to 64 percent – when compared to having a male partner within their same age band.”

As for why older males enjoy less success with IVF, the researchers aren’t entirely sure and intend to pursue the question further, but suggest it could be related to damaged sperm that affect fertility prospects as men get older.

While the effects reported here are significant, it’s worth pointing out that the study – which is being presented this week at the annual meeting of the European Society of Reproduction and Embryology in Switzerland – hasn’t yet been peer-reviewed by other scientists, so we should bear that in mind when considering the findings.

But in the meantime, researchers say these preliminary results could help would-be parents to consider the broader range of factors that may affect their family prospects – and which aren’t simply limited to how old the female partner is.

“The value of this is not only in counselling couples,” obstetrician Nick Macklon from the University of Southampton in the UK, who was not involved in the study, told Ian Sample at The Guardian.

“It may help women to encourage their male partners to get a move on. We know from a number of studies that one of the reasons why women are having babies later is because men are sometimes slow to support the idea. This reminds us that it takes two to tango and it’s not just down to the age of the woman.”

UK to launch 100,000 genomes project as Obama backs DNA drive


Gene research is getting a boost on both sides of the Atlantic, with scientists in England set to launch a project on Feb. 2 to analyse 100,000 entire human genomes and U.S. President Barack Obama backing a big new DNA data drive.

The twin projects show the accelerating work by researchers to understand the underlying basis of diseases and develop medicines targeted to the genetic profile of individual patients.

Obama will announce the U.S. plan to analyse genetic information from more than 1 million American volunteers on Friday as a central part of an initiative to promote so-called precision medicine, officials said.

The 100,000 genomes project in England, meanwhile, was first unveiled by the British government two years ago — but the 11 centres charged with collecting samples will only begin full-scale recruitment from next week. The aim is to complete the programme by the end of 2017.

Such large-scale genomic research has become possible because the cost of genome sequencing has plummeted in recent years to around $1,000 per genome. That is a far cry from 15 years ago when it cost some $3 billion to get the first human genome.

In the case of the British project, all the sequencing will be carried out by U.S. biotech company Illumina, which has pioneered fast and cheap technology to read genetic code.

The 100,000 genomes project is focussing on patients with rare diseases, and their families, as well as people with common cancers. The idea is to tease out the common drivers of disease to help develop better drugs and diagnostic tests.

The project will actually recruit around 75,000 participants, rather than 100,000, since people with cancer will provide two genomes — one derived from the healthy cells in their body and one from their tumour. By comparing the two, experts hope to find the exact genetic changes causing cancer.

Constructing the cyber-troll: Psychopathy, sadism, and empathy


Highlights

Trolling is an online antisocial behaviour with negative psychological outcomes.

Current study predicted trolling perpetration from gender and personality.

Trolls more likely to be male with high levels of trait psychopathy and sadism

Trolls have lower affective empathy, and psychopathy moderates cognitive empathy.

Results have implications for establishing education and prevention programs.


Abstract

Online trolling is of particular concern due to the harmful negative outcomes its victims experience. The current study sought to explore and extend the personality profile of Internet trolls. After gender was controlled for, psychopathy, sadism, and empathy (affective empathy, cognitive empathy, and social skills) were examined for their predictive utility of trolling behaviour. A sample of 415 participants (36% men, 63% women, 1% other) with a mean age of 23.37 years (SD = 7.19) completed an online questionnaire. Results showed that men were more likely than women to engage in trolling, and higher levels of trait psychopathy and sadism predicted trolling behaviour. Lower levels of affective empathy predicted perpetration of trolling, and trait psychopathy moderated the association between cognitive empathy and trolling. Results indicate that when high on trait psychopathy, trolls employ an empathic strategy of predicting and recognising the emotional suffering of their victims, while abstaining from the experience of these negative emotions. Thus, trolls appear to be master manipulators of both cyber-settings and their victims’ emotions.

Contraceptive pills reduces general well being of healthy woman , study says.


Researchers suggested although moods and energy levels among women taking the pill were negatively affected, there was no significant increase of depressive symptoms.

The contraceptive pill can reduce the general well-being of healthy women, a study has claimed.

Researchers at the Karolinska Institutet in Sweden and the Stockholm School of Economics studied 340 healthy women aged between 18 and 35. The women were either given prescriptions for a combined contraceptive pill containing ethniylestradoil and levonorgestrel (the most common type of contraceptive pill in the country and many others) or a placebo pill and the results were published in the journal of fertility and sterility.

Neither group knew which pill they were taking but the women who were given contraceptive pills estimated their quality of life to be “significantly lower” than those taking the placebos. The women said their general well-being, along with their moods, self-control, vitality and energy levels, were all negatively affected by the pill.

However, despite these side effects the study suggested there was no significant increase in depressive symptoms as when specific questions about depression and depressed moods were given to both groups they did not significantly change.

The researchers emphasised that as the changes were relatively small, the results must be interpreted with caution but said the negative effects on the quality of life in individual women may be of clinical importance.

“We do not want women to stop using oral contraceptives due to our results but if a woman is worried about negative influence on mood and life quality she should discuss this with a doctor,” lead author Angelica Hirschberg told The Independent. “There may be better alternatives for her.”

 

“This might in some cases be a contributing cause of low compliance and irregular use of contraceptive pills,” the study’s co-author Niklas Zethraeus said. “This possible degradation of quality of life should be paid attention to and taken into account in conjunctions with prescribing of contraceptive pills and when choosing a method of contraception.”

Professor Hirschberg added: “All types of hormonal contraception have advantages and disadvantages. The possible effect on life quality adds to this knowledge and could be of particular importance for women who have experienced negative mood symptoms previously.”

The authors said the findings could not be generalised to other kinds of combined contraceptive pills as they may have a different risk profile and side-effects.

Last year, a particularly large study suggested a link between women who take the pill and an increased risk of developing depression. The study analysed one million Danish women and found the combined oral contraceptive increased the risk of a woman aged between 20 and 34 being prescribed antidepressants by 23 per cent. For teenage women aged between 15 and 19, the risk of depression was 80 per cent and 120 per cent for those taking the progestogen-only pill (mini pill).

Regulation of the sperm calcium channel CatSper by endogenous steroids and plant triterpenoids


Abstract

The calcium channel of sperm (CatSper) is essential for sperm hyperactivated motility and fertility. The steroid hormone progesterone activates CatSper of human sperm via binding to the serine hydrolase ABHD2. However, steroid specificity of ABHD2 has not been evaluated. Here, we explored whether steroid hormones to which human spermatozoa are exposed in the male and female genital tract influence CatSper activation via modulation of ABHD2. The results show that testosterone, estrogen, and hydrocortisone did not alter basal CatSper currents, whereas the neurosteroid pregnenolone sulfate exerted similar effects as progesterone, likely binding to the same site. However, physiological concentrations of testosterone and hydrocortisone inhibited CatSper activation by progesterone. Additionally, testosterone antagonized the effect of pregnenolone sulfate. We have also explored whether steroid-like molecules, such as the plant triterpenoids pristimerin and lupeol, affect sperm fertility. Interestingly, both compounds competed with progesterone and pregnenolone sulfate and significantly reduced CatSper activation by either steroid. Furthermore, pristimerin and lupeol considerably diminished hyperactivation of capacitated spermatozoa. These results indicate that (i) pregnenolone sulfate together with progesterone are the main steroids that activate CatSper and (ii) pristimerin and lupeol can act as contraceptive compounds by averting sperm hyperactivation, thus preventing fertilization.

Discussion

Our results demonstrate that testosterone, estrogen, and hydrocortisone alone did not activate CatSper but that they reduce or prevent CatSper activation by progesterone (P4). In the case of testosterone and hydrocortisone, the effects were the strongest with a significant inhibition of P4-mediated CatSper stimulation under physiological concentrations of either steroid. One possibility for this effect could be that testosterone binds with a much higher affinity to ABHD2 than P4, thereby preventing CatSper activation. The blood serum concentration of P4 in men is about 2 nM (22), whereas the minimum concentration needed for CatSper activation is 10 pM, with an EC50 of 7.7 nM (3). Testosterone blocked CatSper activation even in the presence of 1 µM P4 with an IC50 of 429 nM, which is within the physiological range, as testosterone concentrations reach 2 µM in the blood plasma of men (23). CatSper can also be activated by PregS, which can reach high concentrations in male reproductive tissues. However, testosterone also inhibits CatSper response to PregS by shifting its EC50 10-fold to 172 nM. Therefore, even if sperm are exposed to elevated concentrations of PregS, high concentrations of testosterone in the male genital tract prevent premature CatSper activation by P4, or even PregS. It is therefore possible that testosterone acts as an anticapacitation factor by preventing CatSper activation until it is removed in the female reproductive tract, presumably by chelation with albumin.

Resting serum E2 levels in women are about 110 pM, which peak at ovulation to concentrations of around 403 pM (24). Therefore, sperm encounter an E2-enriched milieu in the uterus and the fallopian tube. Our results show that E2 did not alter resting CatSper currents but that it also did not allow full channel activation by P4. We assume that elevated levels of E2 during ovulation render CatSper in its closed state to prevent premature calcium influx and thus sperm activation. However, the significantly weaker IC50 for E2 of 833 nM indicates that E2 acts as a much less potent P4 antagonist. Right after ovulation, E2 levels decrease, whereas P4 concentrations surge to ∼7 nM (24) in the blood. Because cumulus cells surrounding the oocyte also secrete P4 (2528), sperm travel through a P4 gradient with maximal concentrations in close proximity to the egg. It is therefore possible that P4 outcompetes E2, leading to CatSper activation, as P4 is the natural E2 antagonist (29).

Various conditions, such as stress and elevated levels of glucocorticoids, particularly hydrocortisone, are known to impair male fertility (16) by either inhibiting spermatogenesis (30) or reducing sperm counts and sperm motility (31). Stress and elevated hydrocortisone levels can also affect female fertility. One study shows that in women who underwent in vitro fertilization, baseline urine cortisol levels increased from ∼230 nM to ∼500 nM (32). According to our results, hydrocortisone blocked CatSper activation by P4 with an IC50 of 153 nM. It is therefore possible that elevated levels of stress hormones in the female genital tract impair not only early stages but also late stages of sperm acquisition of their fertilizing potential, thus significantly contributing to infertility.

Another interesting candidate among the hormones tested in this study was the sulfated neurosteroid PregS, as it stimulates CatSper currents via the P4-related pathway. Although significant, the response to PregS was not as pronounced as the response to P4 and the EC50 of PregS was twofold higher than the EC50 of P4 [15 nM vs. 7 nM (3)]. Nevertheless, we show that PregS acted via an ABHD2 mechanism to activate CatSper—the same mechanism of channel activation as demonstrated for P4 (7). These findings identify PregS as the third steroid hormone to exert nongenomic actions on CatSper apart from P4 and its close analog 17-OH-P4 (3533) and demonstrate the importance of sulfated steroids to regulate physiological processes in human sperm. Even though the concentrations of PregS in human testes are higher than those of pregnenolone (51 μg/100 g tissue) (34), it is unclear whether elevated concentrations of PregS exist within the entire testis or only in specific domains. Because testosterone inhibits the response to PregS with an IC50 of 172 nM, it will prevent CatSper activation by PregS even if sperm cells are exposed to high PregS concentrations. Interestingly, the plasma concentration of PregS in women is about 14 nM (35). This concentration matches the EC50 we determined for PregS to activate CatSper. It is therefore possible that once testosterone is removed from sperm cells within the female genital tract, both P4 and PregS can bind to ABHD2, resulting in CatSper activation. These two compounds indeed compete for the ABHD2 binding site(s), but further studies are needed to reveal whether PregS and P4 act synergistically or independently to activate CatSper.

Our earlier findings identified the acylglycerol lipase ABHD2 as the P4 binding partner (7). Therefore, we tested whether the monoacylglycerol lipase inhibitor pristimerin, a plant triterpenoid (18), can inhibit both the P4- and the PregS-mediated activation of CatSper of human sperm. Although basal CatSper currents were not affected, both P4 and PregS-mediated CatSper potentiation was significantly reduced. Lupeol, another plant triterpenoid, had similar effects on ICatSper as pristimerin. It is possible that both triterpenoids occupy the steroid binding site of ABHD2, thus preventing CatSper activation by P4 via a competitive antagonist-type mechanism. Both compounds were also able to inhibit sperm hyperactivation and slightly reduced basal motility of capacitated sperm cells, as evident from computer-assisted sperm analyses (CASAs). Interestingly, pristimerin and lupeol had no effect on sperm motility of noncapacitated cells, which indicates their low toxicity effect toward spermatozoa. These results correlate with our electrophysiological data, which showed a significant reduction of ICatSper with pristimerin + P4 and lupeol + P4, respectively. Because CatSper is indispensable for hyperactivated sperm motility (3640), it is evident that the reduction of sperm hyperactivation by both triterpenoids may significantly impair sperm ability to fertilize an egg.

CASA experiments also revealed that although P4 increased hyperactivated motility, PregS failed to do so. This could be due to the fact that PregS is a charged molecule, which cannot pass the plasma membrane (41). It is therefore possible that the nonpolar P4 can activate additional intracellular pathways, contributing to a more pronounced activation of CatSper. Indeed, for full sperm hyperactivation in vitro, two events must be met at the same time: (i) CatSper must be relieved from inhibition by 2-AG, and (ii) the sperm plasma membrane needs to be depolarized. Because CatSper is a voltage-dependent channel, it requires at least +30 mV for half-activation (3). The latter can be achieved via the P4-mediated inhibition of the potassium channel KSper (6), which creates membrane depolarization required for full CatSper activation. If P4 inhibits KSper from the intracellular side, which PregS fails to do, as it cannot cross plasma membrane, then P4 is able to cause a more pronounced hyperactivation.

In conclusion, our findings show that apart from P4, PregS is another steroid hormone that can activate CatSper via ABHD2 in human spermatozoa, whereas testosterone, E2, and HC may bind to ABHD2 competitively to modulate the response to P4 and PregS. In addition, we describe two plant triterpenoids that can serve as promising candidates for contraception, as they reduce the number of hyperactive spermatozoa, thus preventing sperm from reaching and fertilizing an egg.

Materials and Methods

Reagents.

Progesterone and pristimerin were purchased from Calbiochem (EMD Millipore). MAFP was from Cayman Chemical Company, and NNC 55–0396 was from Tocris. All other compounds were from Sigma Aldrich. Testosterone was purchased in accordance with the controlled substance protocol (CS084484), as a collaborative effort with Yuriy Kirichok (University of California, San Francisco).

Donors and Purification of Human Ejaculated Spermatozoa.

The participation of four healthy human sperm donor volunteers was approved by the Committee on Human Research at the University of California, Berkeley (protocol number 2013–06-5395). All donors provided informed consent. Freshly ejaculated semen samples were obtained by masturbation. Sperm were purified with the swim-up technique (3) using artificial human tubal fluid solution (HTF), containing (in mM) 21 Hepes, 21 lactic acid, 98 NaCl, 4.7 KCl, 3 glucose, 2 CaCl2, 0.3 KH2PO4, 0.3 sodium pyruvate, and 0.2 MgSO4, pH 7.4 (adjusted with NaOH).

Electrophysiology.

All recordings were performed as described in ref. 3. Briefly, gigaohm seals between patch pipette and spermatozoa were formed at the cytoplasmic droplet in high saline (HS) solution containing (in mM) 135 NaCl, 20 Hepes, 10 lactic acid, 5 KCl, 5 glucose, 2 CaCl2, 1 MgSO4, 1 sodium pyruvate, pH 7.4 (adjusted with NaOH), and ∼320 mOsm/L. Transition into whole-cell mode was achieved by applying suction and short voltage pulses. For CatSper recordings, the divalent-free bath solution contained (in mM) 140 Cs-methanesulfonate, 40 Hepes, 1 EDTA, pH 7.4 (adjusted with CsOH), and ∼325 mOsm/L. Pipettes (10–15 MΩ) were filled with 130 mM Cs-methanesulfonate, 70 mM Hepes, 3 mM EGTA, 2 mM EDTA, 0.5 mM Tris·HCl, pH 7.4 (adjusted with CsOH), and ∼335 mOsm/L. Access resistance was 42–60 MΩ. Cells were stimulated every 5 s, and data were sampled at 2–5 kHz and filtered at 1 kHz. All experiments were performed at room temperature and currents elicited by a voltage ramp from –80 mV to 80 mV with a holding potential of 0 mV. Data were analyzed with Clampfit 9.2 and OriginPro 9.0. To build dose–response curves, data were fitted with the Hill-based equation: y = Imin + (Imax – Imin)/(1 + (x/IC50)k), where Imax is close to 100% activation, Imin is close to inactivation, and k is the Hill slope factor.

CASA.

Purified human spermatozoa were capacitated for 3.5 h at 37 °C and 5% CO2 in capacitation media (HS supplemented with 15 mM NaHCO3 and 5% BSA) as reported in ref. 7. Aliquots of the cell suspension were preincubated for 15 min with 3 μM pristimerin or 3 μM lupeol before exposure to steroids (3 μM progesterone or 3 μM PregS). Sperm motility was analyzed at 37 °C with an HTM-IVOS sperm analysis system (version 12.3, Hamilton Thorne Biosciences). We pipetted 10 μL of sperm suspension into a two-chamber slide (Leja), and sperm movement of a minimum of 300 cells was recorded. Parameters measured were the four motility classes (A–D), average path velocity (VAP, μm/s), straight line velocity (VSL, μm/s), and VCL (μm/s). Measurements on a given day were performed in duplicates and defined as one experiment.

Data Analysis.

Statistical data were calculated as the mean ± SEM, and n indicates number of individual cells analyzed unless stated otherwise. Statistical significance (unpaired t test) is indicated by *P < 0.05, **P < 0.005, ***P < 0.001, and ****P < 0.0001.

Source:http://www.pnas.org