̽��ֱ�� of Cambridge - Fondation Botnar

Genetic study points to oxytocin as possible treatment for obesity and postnatal depression

cjb250 — Tue, 02 Jul 2024 15:00:18 +0000

Obesity and postnatal depression are significant global health problems. Postnatal depression affects more than one in 10 women within a year of giving birth and is linked to an increased risk of suicide, which accounts for as many as one in five maternal deaths in high income countries. Meanwhile, obesity has more than doubled in adults since 1990 and quadrupled in adolescents, according to the World Health Organization.

While investigating two boys from different families with severe obesity, anxiety, autism, and behavioural problems triggered by sounds or smells, a team led by scientists at the ̽��ֱ�� of Cambridge, UK, and Baylor College of Medicine, Houston, USA, discovered that the boys were missing a single gene, known as TRPC5, which sits on the X chromosome.

Further investigation revealed that both boys inherited the gene deletion from their mothers, who were missing the gene on one of their X chromosomes. ̽��ֱ��mothers also had obesity, but in addition had experienced postnatal depression.

To test if it was the TRPC5 gene that was causing the problems in the boys and their mothers, the researchers turned to animal models, genetically-engineering mice with a defective version of the gene (Trpc5 in mice).

Male mice with this defective gene displayed the same problems as the boys, including weight gain, anxiety, a dislike of social interactions, and aggressive behaviour. Female mice displayed the same behaviours, but when they became mothers, they also displayed depressive behaviour and impaired maternal care. Interestingly, male mice and female mice who were not mothers but carried the mutation did not show depression-like behaviour.

Dr Yong Xu, Associate Director for Basic Sciences at the USDA/ARS Children’s Nutrition Research Center at Baylor College of Medicine, said: “What we saw in those mice was quite remarkable. They displayed very similar behaviours to those seen in people missing the TRPC5 gene, which in mothers included signs of depression and a difficulty caring for their babies. This shows us that this gene is causing these behaviours.”

TRPC5 is one of a family of genes that are involved in detecting sensory signals, such as heat, taste and touch. This particular gene acts on a pathway in the hypothalamus region of the brain, where it is known to control appetite.

When the researchers looked in more detail at this brain region, they discovered that TRPC5 acts on oxytocin neurons – nerve cells that produce the hormone oxytocin, often nicknamed the ‘love hormone’ because of its release in response to displays of affection, emotion and bonding.

Deleting the gene from these oxytocin neurons led to otherwise healthy mice showing similar signs of anxiety, overeating and impaired sociability, and, in the case of mothers, postnatal depression. Restoring the gene in these neurons reduced body weight and symptoms of anxiety and postnatal depression.

In addition to acting on oxytocin neurons, the team showed that TRPC5 also acts on so-called POMC neurons, which have been known for some time to play an important role in regulating weight. Children in whom the POMC gene is not working properly often have an insatiable appetite and gain weight from an early age.

Professor Sadaf Farooqi from the Institute of Metabolic Science at the ̽��ֱ�� of Cambridge said: “There's a reason why people lacking TRPC5 develop all of these conditions. We’ve known for a long time that the hypothalamus plays a key role in regulating ‘instinctive behaviours’ – which enable humans and animals to survive – such as looking for food, social interaction, the flight or fight response, and caring for their infants. Our work shows that TRPC5 acts on oxytocin neurons in the hypothalamus to play a critical role in regulating our instincts.”

While deletions of the TRPC5 gene are rare, an analysis of DNA samples from around 500,000 individuals in UK Biobank revealed 369 people – around three-quarters of whom were women – that carried variants of the gene and had a higher-than-average body mass index.

̽��ֱ��researchers say their findings suggests that restoring oxytocin could help treat people with missing or defective TRPC5 genes, and potentially mothers experiencing postnatal depression.

Professor Farooqi said: “While some genetic conditions such as TRPC5 deficiency are very rare, they teach us important lessons about how the body works. In this instance, we have made a breakthrough in understanding postnatal depression, a serious health problem about which very little is known despite many decades of research. And importantly, it may point to oxytocin as a possible treatment for some mothers with this condition.”

There is already evidence in animals that the oxytocin system is involved in both depression and in maternal care and there have been small trials into the use of oxytocin as a treatment. ̽��ֱ��team say their work provides direct proof of oxytocin’s role, which will be crucial in supporting bigger, multi-centre trials.

Professor Farooqi added: “This research reminds us that many behaviours which we assume are entirely under our control have a strong basis in biology, whether that’s our eating behaviour, anxiety or postnatal depression. We need to be more understanding and sympathetic towards people who suffer with these conditions.”

This work was supported by Wellcome, the National Institute for Health and Care Research (NIHR), NIHR Cambridge Biomedical Research Centre, Botnar Fondation and Bernard Wolfe Health Neuroscience Endowment.

Reference
Li, Y, Cacciottolo, TM & Yin, N. Loss of Transient Receptor Potential Channel 5 Causes Obesity and Postpartum Depression. Cell; 2 July 2024; DOI: 10.1016/j.cell.2024.06.001

Scientists have identified a gene which, when missing or impaired, can cause obesity, behavioural problems and, in mothers, postnatal depression. ̽��ֱ��discovery, reported on 2 July in Cell, may have wider implications for the treatment of postnatal depression, with a study in mice suggesting that oxytocin may alleviate symptoms.

This research reminds us that many behaviours which we assume are entirely under our control have a strong basis in biology. We need to be more understanding and sympathetic towards people who suffer with these conditions

Sadaf Farooqi

Olli Turho (Getty Images)

Illustration of a tired African American mother crying

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Widely-used COVID-19 antiviral could be helping SARS-CoV-2 to evolve

cjb250 — Mon, 25 Sep 2023 15:00:41 +0000

̽��ֱ��drug works by disrupting the virus’s genome, causing it to develop random mutations as it replicates, weakening the virus to prevent replication, thereby enabling clearance of infection.

But in research published today in Nature, scientists have shown that in some cases, mutated forms of the virus have been able to be transmitted from patients treated with molnupiravir and spread within the community.

Dr Christopher Ruis from the Department of Medicine at the ̽��ֱ�� of Cambridge said: “Molnupiravir is one of a number of drugs being used to fight COVID-19. It belongs to a class of drugs that can cause the virus to mutate so much that it is fatally weakened. But what we’ve found is that in some patients, this process doesn’t kill all the viruses, and some mutated viruses can spread. This is important to take into account when assessing the overall benefits and risks of molnupiravir and similar drugs.”

Molnupiravir, marketed under the brand name Lagevrio, is licensed for the treatment of COVID-19 in several countries, including the UK, USA and Japan. It has been used to treat the disease since late 2021.

In the body, molnupiravir is converted into a molecule that disrupts the genome of the SARS-CoV-2 virus, introducing some nucleotide mutations in its RNA – randomly changing some Cs to Ts and some Gs to As. These changes mean that as the virus replicates, its progeny get weaker, reducing how quickly the virus is able to replicate and ridding the body of the virus.

However, concern has been expressed that in some cases, a number of mutated viruses may not be killed off quickly enough and so are able to infect other individuals, potentially allowing new mutated viruses to spread.

During the COVID-19 pandemic, a number of countries – spearheaded by the Cambridge-led COVID-19 Genomics UK Consortium – sequenced virus samples, depositing the information in databases such as the Global Initiative on Sharing All Influenza Data (GISAID) and the International Nucleotide Sequence Database Collaboration (INSDC). This allowed scientists and public health agencies to track the evolution and spread of the virus, and in particular to look out for so-called ‘variants of concern’ – versions of the virus with mutations that might make them more transmissible, more lethal, or able to evade the immune system of vaccinated individuals, such as the Delta and Omicron variants.

A team of researchers from the UK and South Africa noticed a number of viral genomes that contained a large number of mutations, particularly where Cs had changed to Ts and Gs to As. While C-to-T mutations are relatively common overall in SARS-CoV-2 evolution, G-to-A mutations occur much less frequently, and a higher proportion of G-to-A mutations is associated with molnupiravir treatment.

̽��ֱ��team then analysed a family tree of more than 15 million SARS-CoV-2 sequences in the GISAID and INSDC databases looking for which mutations had occurred at each point in the virus’s evolutionary history. They found that viruses with this signature of mutations had begun to emerge almost exclusively from 2022 onwards and in countries and age groups where molnupiravir was being widely used to treat COVID-19.

To confirm the link, the researchers examined treatment records in England and found that at least one in three of viruses showing the mutational signature involved the use of molnupiravir.

̽��ֱ��researchers also saw small clusters of patients infected with mutated viruses, which suggests that these new viruses were being passed from one person to another. However, none of the known variants of concern has so far been linked to the use of molnupiravir.

Dr Theo Sanderson from the Francis Crick Institute, said: “COVID-19 is still having a major effect on human health, and some people have difficulty clearing the virus, so it’s important we develop drugs which aim to cut short the length of infection. But our evidence shows that a specific antiviral drug, molnupiravir, also results in new mutations, increasing the genetic diversity in the surviving viral population.

“Our findings are useful for ongoing assessment of the risks and benefits of molnupiravir treatment. ̽��ֱ��possibility of persistent antiviral-induced mutations needs to be taken into account for the development of new drugs which work in a similar way.”

̽��ֱ��research was funded by Wellcome, Cancer Research UK, the Medical Research Council, National Institute for Health and Care Research, Fondation Botnar, UK Cystic Fibrosis Trust and the Oxford Martin School.

Reference
Sanderson, T et al. A molnupiravir-associated mutational signature in global SARS-CoV-2 genomes. Nature; 25 Sept 2023: DOI: 10.1038/s41586-023-06649-6

Molnupiravir, an antiviral drug used to treat patients with COVID-19, appears to be driving SARS-CoV-2 to mutate and evolve, with some of these new viruses being transmitted onwards, a new study has shown. It is not clear, however, whether these mutated viruses pose an increased risk to patients or are able to evade the vaccine.

Molnupiravir belongs to a class of drugs that can cause the virus to mutate so much that it is fatally weakened. But what we’ve found is that in some patients, this process doesn’t kill all the viruses

Christopher Ruis

visuals3Dde

SARS-CoV-2 viruses

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Ability of multi-drug resistant infection to evolve within cystic fibrosis patients highlights need for rapid treatment

cjb250 — Thu, 29 Apr 2021 18:00:25 +0000

Around one in 2,500 children in the UK is born with cystic fibrosis, a hereditary condition that causes the lungs to become clogged up with thick, sticky mucus. ̽��ֱ��condition tends to decrease life expectancy among patients.

In recent years, M. abscessus, a species of multi-drug resistant bacteria, has emerged as a significant global threat to individuals with cystic fibrosis and other lung diseases. It can cause a severe pneumonia leading to accelerated inflammatory damage to the lungs, and may prevent safe lung transplantation. It is also extremely difficult to treat – fewer than one in three cases is treated successfully.

In a study published today in Science, a team led by scientists at the ̽��ֱ�� of Cambridge examined whole genome data for 1,173 clinical M. abscessus samples taken from 526 patients to study how the organism has evolved – and continues to evolve. ̽��ֱ��samples were obtained from cystic fibrosis clinics in the UK, as well as centres in Europe, the USA and Australia.

̽��ֱ��team found two key processes that play an important part in the organism’s evolution. ̽��ֱ��first is known as horizontal gene transfer – a process whereby the bacteria pick up genes or sections of DNA from other bacteria in the environment. Unlike classical evolution, which is a slow, incremental process, horizontal gene transfer can lead to big jumps in the pathogen’s evolution, potentially allowing it to become suddenly much more virulent.

̽��ֱ��second process is within-host evolution. As a consequence of the shape of the lung, multiple versions of the bacteria can evolve in parallel – and the longer the infection exists, the more opportunities they have to evolve, with the fittest variants eventually winning out. Similar phenomena have been seen in the evolution of new SARS-CoV-2 variants in immunocompromised patients.

Professor Andres Floto, joint senior author from the Centre for AI in Medicine (CCAIM) and the Department of Medicine at the ̽��ֱ�� of Cambridge and the Cambridge Centre for Lung Infection at Royal Papworth Hospital, said: “What you end up with is parallel evolution in different parts of an individual’s lung. This offers bacteria the opportunity for multiple rolls of the dice until they find the most successful mutations. ̽��ֱ��net result is a very effective way of generating adaptations to the host and increasing virulence.

“This suggests that you might need to treat the infection as soon as it is identified. At the moment, because the drugs can cause unpleasant side effects and have to be administered over a long period of time – often as long as 18 months – doctors usually wait to see if the bacteria cause illness before treating the infection. But what this does is give the bug plenty of time to evolve repeatedly, potentially making it more difficult to treat.”

Professor Floto and colleagues have previously advocated routine surveillance of cystic fibrosis patients to check for asymptomatic infection. This would involve patients submitting sputum samples three or four times a year to check for the presence of M. abscessus infection. Such surveillance is carried out routinely in many centres in the UK.

Using mathematical models, the team have been able to step backwards through the organism’s evolution in a single individual and recreate its trajectory, looking for key mutations in each organism in each part of the lung. By comparing samples from multiple patients, they were then able to identify the key set of genes that enabled this organism to change into a potentially deadly pathogen.

These adaptations can occur very quickly, but the team found that their ability to transmit between patients was constrained: paradoxically, those mutations that allowed the organism to become a more successful pathogen within the patient also reduced its ability to survive on external surfaces and in the air – the key mechanisms by which it is thought to transmit between people.

Potentially one of the most important genetic changes witnessed by the team was one that contributed towards M. abscessus becoming resistant to nitric oxide, a compound naturally produced by the human immune system. ̽��ֱ��team will shortly begin a clinical trial aimed at boosting nitric oxide in patients’ lung by using inhaled acidified nitrite, which they hope would become a novel treatment for the devastating infection.

̽��ֱ��researchers say their findings highlight the need to treat patients with Mycobacterium abscessus infection immediately, counter to current medical practice.

Examining the DNA taken from patient samples is also important in helping understand routes of transmission. Such techniques are used routinely in Cambridge hospitals to map the spread of infections such as MRSA and C. difficile – and more recently, SARS-CoV-2. Insights into the spread of M. abscessus helped inform the design of the new Royal Papworth Hospital building, opened in 2019, which has a state-of-the-art ventilation system to prevent transmission. ̽��ֱ��team recently published a study showing that this ventilation system was highly effective at reducing the amount of bacteria in the air.

Professor Julian Parkhill, joint senior author from the Department of Veterinary Medicine at the ̽��ֱ�� of Cambridge, added: “M. abscessus can be a very challenging infection to treat and can be very dangerous to people living with cystic fibrosis, but we hope insights from our research will help us reduce the risk of transmission, stop the bug evolving further, and potentially prevent the emergence of new pathogenic variants.”

̽��ֱ��team have used their research to develop insights into the evolution of M. tuberculosis – the pathogen that causes TB about 5,000 years ago. In a similar way to M. abscessus, M. tuberculosis likely started life as an environmental organism, acquired genes by horizontal transfer that made particular clones more virulent, and then evolved through multiple rounds of within-host evolution. While M. abscessus is currently stopped at this evolutionary point, M. tuberculosis evolved further to be able to jump directly from one person to another.

Dr Lucy Allen, Director of Research at the Cystic Fibrosis Trust, said: “This exciting research brings real hope of better ways to treat lung infections that are resistant to other drugs. Our co-funded Innovation Hub with the ̽��ֱ�� of Cambridge really shows the power of bringing together world-leading expertise to tackle a health priority identified by people with cystic fibrosis. We’re expecting to see further impressive results in the future coming from our joint partnership.”

̽��ֱ��study was funded by the Wellcome Trust, Cystic Fibrosis Trust, NIHR Cambridge Biomedical Research Centre and Fondation Botnar.

Reference
Bryant, JM et al. Stepwise pathogenic evolution of Mycobacterium abscessus. Science; 30 Apr 2021

Scientists have been able to track how a multi-drug resistant organism is able to evolve and spread widely among cystic fibrosis patients – showing that it can evolve rapidly within an individual during chronic infection.

We hope insights from our research will help us reduce the risk of transmission, stop the bug evolving further, and potentially prevent the emergence of new pathogenic variants

Julian Parkhill

Jon Sneddon

Patient with cystic fibrosis

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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