The ability to distinguish between odours declines steadily with age, and age-related smell loss can have a substantial impact on lifestyle and wellbeing for the elderly.

“Smells impact how foods taste. Many people with smell deficits lose the joy of eating. They make poor food choices, get less nutrition. They can’t tell when foods have spoiled or detect odours that signal danger, like a gas leak or smoke. They may not notice lapses in personal hygiene,” said Jayant M. Pinto, MD, an associate professor of surgery at the University of Chicago who specializes in the genetics and treatment of olfactory and sinus disease.

“Of all human senses,” he said, “smell is the most undervalued and underappreciated—until it’s gone.”

And for older adults, being unable to identify scents is also a strong predictor of death within five years, according to a study. Thirty-nine percent of study subjects who failed a simple smelling test died during that period, compared to 19 percent of those with moderate smell loss and just 10 percent of those with a healthy sense of smell.

The hazards of smell loss were “strikingly robust,” the researchers note, above and beyond most chronic diseases. Olfactory dysfunction was better at predicting mortality than a diagnosis of heart failure, cancer or lung disease. Only severe liver damage was a more powerful predictor of death. For those already at high risk, lacking a sense of smell more than doubled the probability of death.

 “We think loss of the sense of smell is like the canary in the coal mine,” said Pinto, the study’s lead author. “It doesn’t directly cause death, but it’s a harbinger, an early warning that something has gone badly wrong, that damage has been done. Our findings could provide a useful clinical test, a quick and inexpensive way to identify patients most at risk.”

The study was part of the National Social Life, Health and Aging Project (NSHAP), the first in-home study of social relationships and health in a large, nationally representative sample of men and women ages 57 to 85. University of Chicago Medicine and Biological Sciences

A new intermediate step and unexpected enzymatic activity in a metabolic pathway in the body, which could lead to new drug design for psychiatric and neurodegenerative diseases, has been discovered by researchers at Georgia State University.

The research team has been studying a metabolic pathway called the tryptophan kynurenine pathway, which is linked to psychiatric and neurodegenerative disorders, including depression, anxiety, Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, AIDS dementia complex, asphyxia in newborns and epilepsy. The medical potential of this pathway warrants detailed study to provide information about the pathway’s enzymes and their regulation.

This pathway produces several neurotransmitter regulators and is responsible for metabolizing nearly 99 percent of the tryptophan in the body. Tryptophan is a precursor of serotonin, the neurotransmitter responsible for mood.

The researchers determined the structure and mechanism of an enzyme in the kynurenine pathway, AMSDH.

To better understand the rapid chemical reaction catalysed by this enzyme, Dr. Aimin Liu, professor in the Department of Chemistry and core member of the Center for Diagnostics and Therapeutics at Georgia State, organized a research team, including graduate students Lu Huo, Ian Davis, Fange Liu and Shingo Esaki, and researchers at Brookhaven National Laboratory and Kansai University in Osaka, Japan. They used new scientific techniques, including time-lapse crystallography and single-crystal spectroscopy, to slow down the reaction rate by nearly 10,000 times. This allowed them to observe a new intermediate step, the thiohemiacetal intermediate, and discover an unexpected isomerase activity in AMSDH.

‘By doing this, we find new chemistry, and we also open up avenues for others to design specific drugs to target this pathway,’ Liu said. ‘This pathway is highly associated with neurodegenerative diseases and depression.’

The researchers took a high concentration of the purified protein, grew single crystals, mixed them with their substrate and froze them at different time points in liquid nitrogen at 77 Kelvin to stop all molecular activity. They sent the crystals to Argonne National Laboratory for remote data collection. The X-ray diffraction patterns collected there were used to create an electron density map, a 3-D, atomic-level resolution of the molecule’s shape. The researchers used time-lapse crystallography and single-crystal spectroscopy to observe intermediate steps of the reaction.

‘This is the first absorbance spectrum of this intermediate,’ Davis said. ‘When we look for this in solution assays, we don’t see this absorbance band because this intermediate is very short-lived in solution. But by doing it in crystal and freezing it down, you can actually see it in the crystalline state.

‘Enzymes work by stabilizing reactive intermediates. Through this isomerization mechanism, we found a new reactive intermediate stabilized by this enzyme. So if you want to design a drug, your best bet is to try and make something that looks very similar to this so that it will bind to the enzyme. That’s a general strategy for drug design. You want to try and make drugs that look very similar to transition states. Basically, we found a new transition state in this work.’

Information from the study has been deposited in the protein database, which can be accessed by other scientists. EurekAlert

A protein has been shown to have a surprising role in regulating the ‘glue’ that holds heart cells together, a finding that may explain how a gene defect could cause sudden cardiac death.

A team led by Oxford University researchers was looking at how a protein, iASPP, might be involved in the growth of tumours. However, serendipitously they found that mice lacking this gene died prematurely of sudden cardiac death. More detailed investigations showed that these mice had an irregular conductance in the right side of the heart, a condition known as arrhythmogenic right ventricular cardiomyopathy (ARVC).

The researchers discovered that iASPP had a previously unknown role in controlling desmosomes – one of the main structures that ‘glue’ individual heart muscle cells (cardiomyocytes) together. The genetic defect was shown to weaken desmosome function at the junctions of heart muscle cells: this affected the structural integrity of the heart, making mice lacking iASPP prone to ARVC.

Further studies of heart tissue from human patients who had died from ARVC showed that some of them have similar defects in desmosomes as in the mice suggesting that the faulty iASPP gene could also be responsible for ARVC deaths in humans. This finding also explains why a previously reported cattle herd with spontaneous iASPP gene deletion died of sudden cardiac death.

‘We set out to investigate how this protein might cause cancer and found by chance that it could play a key role in this rare genetic heart condition,’ said Professor Xin Lu, Director of the Ludwig Institute for Cancer Research at Oxford University, the lead investigator of the report. ‘It took my DPhil student Mario Notari, the lead author of the study, over two years of further detective work, in collaboration with our colleagues in Oxford and London, to show how a single faulty gene can affect the function of desmosomes, one of the main structures that ‘glue’ heart muscle cells together. Our studies suggest that these changes can threaten the structural integrity of the heart and predispose humans and animals to AVRC.’

ARVC is uncommon in humans, affecting around 1 in 2000 people in the UK [1], and is a leading cause of sudden cardiac death, which is estimated to kill around 100,000 people a year in the UK [2]. Whilst approximately 50% of human ARVC cases are related to known genetic defects in desmosomes, the cause of the other 50% of cases still remains unknown. The new study suggests that mutations in the gene encoding the iASPP protein may contribute to the development of ARVC in these previously-unexplained cases. University of Oxford

A team of scientists, led by researchers at The Wistar Institute, has identified a possible explanation for why middle-aged adults were hit especially hard by the H1N1 influenza virus during the 2013-2014 influenza season. The findings offer evidence that a new mutation in H1N1 viruses potentially led to more disease in these individuals. Their study suggests that the surveillance community may need to change how they choose viral strains that go into seasonal influenza vaccines, the researchers say.

“We identified a mutation in recent H1N1 strains that allows viruses to avoid immune responses that are present in a large number of middle-aged adults,” said Scott Hensley, Ph.D., a member of Wistar’s Vaccine Center and an assistant professor in the Translational Tumour Immunology program of Wistar’s Cancer Center.

Historically, children and the elderly are most susceptible to the severe effects of the influenza viruses, largely because they have weaker immune systems.  However, during the 2013-2014 physicians saw an unusually high level of disease due to H1N1 viruses in middle-aged adults—those who should have been able to resist the viral assault. Although H1N1 viruses recently acquired several mutations in the haemagglutinin (HA) glycoprotein, standard serological tests used by surveillance laboratories indicate that these mutations do not change the viruses’ antigenic properties.

However, Wistar researchers have shown that, in fact, one of these mutations is located in a region of HA that allows viruses to avoid antibody responses elicited in some middle-aged adults. Specifically, they found that 42 percent of individuals born between 1965 and 1979 possess antibodies that recognize the region of HA that is now mutated. The Wistar researchers suggest that new viral strains that are antigenically matched in this region should be included in future influenza vaccines.

“Our immune systems are imprinted the first time that we are exposed to influenza virus,” Hensley said. “Our data suggest that previous influenza exposures that took place in the 1970s and 1980s influence how middle-aged people respond to the current H1N1 vaccine.”

The researchers noted that significant antigenic changes of influenza viruses are mainly determined using anti-sera isolated from ferrets recovering from primary influenza infections. However humans are typically re-infected with antigenically distinct influenza strains throughout their life.  Therefore, antibodies that are used for surveillance purposes might not be fully reflective of human immunity. Wistar Institute

Damage to DNA is an issue for all cells, particularly in cancer, where the mechanisms that repair damage typically fail. The same agents that damage DNA also damage its sister molecule messenger RNA (mRNA), which ferries transcripts of the genes to the tens of thousands of ribosomes in each cell. But little attention has been paid to this damage.

 “There may be cases where messenger RNA is just as important as DNA,” said Carrie Simms, PhD, a postdoctoral associate in Zaher’s lab. “Clearly oxidative damage to RNA is somehow involved in neurodegenerative diseases, such as Alzheimer’s and ALS. It’s not necessarily causing the disease; it may just be some sort of by-product; but it’s in the mix.”

“Under normal conditions only about 1 percent of the cellular mRNAs are oxidized,” Zaher said, “but if you have oxidative stress, for whatever reason, a higher percentage can be damaged.

One of the hallmarks of Alzheimer’s is oxidative stress, and studies have shown that in people with advanced Alzheimer’s, half of the RNA molecules in the neurons may be oxidized.

Zaher, Simms and their colleagues report that when they fed oxidized mRNA to ribosomes, the nanomachines that convert mRNA to protein, the ribosomes jammed and stopped.

A stuck ribosome could be rescued by factors that released it from the mRNA and chewed up the damaged transcipt. But if the factors involved in this quality-control system were absent, damaged mRNA accumulated in the cell, just as it does in Alzheimer’s.

The three cellular processes essential to life—making copies of DNA, copying DNA into mRNA, and translating the mRNA into protein—have been penalized for billions of years by evolution, are astonishingly accurate, because evolution has heavily penalized any sloppiness.

Errors in DNA copying occur only once every billion events. When DNA is transcribed to mRNA, there is a mistake about once every ten thousand events .and when the mRNA is translated to protein, there might be an error once every thousand events.

To test the robustness of translation, the Zaher lab set out to break it, by giving faulty mRNA transcripts to ribosomes. They damaged one letter in a three-letter mRNA coding unit, oxidizing a G (the base guanine), to create what is called 8-oxo-G.

“We chose this oxidized base,” he said,” because we knew that when DNA is copied, an oxidized G causes a mistake. Instead of pairing with a C, as it normally would, 8-oxo-G will pair with an A.”

He thought the ribosome would read the three-letter codon C[8-oxo-G]C not as CGC but rather as CAC and conseqeuntly put the wrong amino acid in the protein chain it was making.

But when 8-oxo-G was added to a soup that contained all the factors needed to translate mRNA into protein, something surprising happened.

“We expected that we might get aberrant proteins,“ Simms said. “But the ribosome didn’t make mistakes.  It just stopped. It couldn’t deal with the mRNA at all”

The scientsts could tell it was stuck because levels of the protein the faulty mRNA encodes plummeted.

To make sure it was the presence rather than the position of the 8-oxo-G that mattered, Simms made mRNAs with the 8-oxo-G in each of the three positions of the three-letter coding unit. Each time the ribosome stalled.

Knowing they had found something interesting, the scientists upped their game. Simms built a longer 300-nucleotide mRNA to use as a probe. And instead of adding the damaged mRNA to a reconstituted bacterial system, she put it in extracts of plant and animal cells.

“We couldn’t look at ribosomes in the extracts,” Simms said, “but we could look at the proteins they made. They made short proteins, exactly the length you’d expect if the ribosome were stopping at the damaged base. “

A single mRNA typically has several ribosomes traveling along it, all simultaneously translating this transcript into protein. When the first ribosome stops, the others pile up behind it.

“You get this small product that is telling you the ribosome cannot go through the 8-oxo-G and then you get even smaller products that are telling you there are multiple ribosomes stuck behind the first ribosome. So the backed up ribosomes make a ladder of peptides,” Zaher said.

“This is a problem,” he said. “Among other things, the ribosome is an expensive machine that the cell has invested a lot of energy in making, and now it’s stuck on an mRNA. You need those ribosomes back.”

Fortunately ribosomes have three quality-control systems that keep watch for errors in the mRNA and rescue the ribosome if spot serious mistakes. One of these systems is “no-go decay.” When ribosomes are stuck and can’t go forward, they recruit factors that come in to pry open the ribosome, chew up the mRNA and add a tag to the defective peptide  that marks it for degradation.”

But no-go decay was originally discovered by throwing artificial roadblocks in the ribosome’s way: mRNAs with large hairpin turns in them that the ribosome could not unwind or plow through.

“Four billion years of evolution has made sure your genome does not have sequences that make hairpins, so these are clearly not the intended targets for no-go decay,” Zaher said.

To find out, the scientists turned to yeast cells. If the yeast’s ribosomes jammed on the oxidized mRNA but were rescued by no-go decay, very little damaged mRNA would accumulate in the cell. This proved to be the case.

Simms then deleted the gene for a factor that releases the ribosome from the mRNA when it jams. In these knockout yeast the level of oxidized mRNA went up. Then she deleted the gene for a factor that is recruited to degrade the mRNA after the ribosome is released, and again the level of oxidized mRNA rose. Without no-go decay, the cells were clearly in trouble.

“The system that translates mRNA into protein is highly conserved, so what’s true for yeast is probably true for people as well,” said Zaher. Washington University in St. Louis.