Tag: inflammation

Intermittent Fasting Triggers an Anti-inflammatory Response

Credit: Intermountain Healthcare

Intermittent fasting may not only be a hot dieting trend, but it also has broader health benefits, including helping to fight inflammation, according to a new study. The new research shows that intermittent fasting raises the levels of galectin-3, a protein tied to inflammatory response.

Intermittent fasting has previously been shown to possibly improve health markers not related to weight. 

“Inflammation is associated with higher risk of developing multiple chronic diseases, including diabetes and heart disease. We’re encouraged to see evidence that intermittent fasting is prompting the body to fight inflammation and lowering those risks,” said Benjamin Horne, PhD, principal investigator of the study and director of cardiovascular and genetic epidemiology at the Intermountain Healthcare Heart Institute.

The findings of the study were presented at the American Heart Association’s Scientific Sessions 2021.

These results form part of Intermountain’s WONDERFUL Trial which is studying intermittent fasting. It found that intermittent fasting causes drops in metabolic syndrome score (MSS) and insulin resistance.  

This particular study followed 67 patients aged 21 to 70 who all had at least one metabolic syndrome feature or type 2 diabetes, and were also not taking anti-diabetic or statin medication, and had raised LDL cholesterol levels.

Of the 67 patients studied, 36 were prescribed an intermittent fasting schedule: twice a week water-only 24-hour fasting for four weeks, then once a week water-only 24 hour-fasting for 22 weeks. Fasts could not be done on consecutive days. The remaining 31 participants continued their routines.

After 26 weeks, participants’ galectin-3 was measured, and found to be higher in the intermittent fasting group. Lower rates of HOMA-IR (insulin resistance) and MSS (metabolic syndrome) were found, which researchers believe may be similar to the reported effects of SGLT-2 inhibitors.

“In finding higher levels of galectin-3 in patients who fasted, these results provide an interesting mechanism potentially involved in helping reduce the risk of heart failure and diabetes,” said Dr Horne, who added that a few members of the trial team completed the same regime before the study started to make sure that it was doable and not overly onerous for participants.

“Unlike some IF diet plans that are incredibly restrictive and promise magic weight loss, this isn’t a drastic form of fasting. The best routine is one that patients can stick to over the long term, and this study shows that even occasional fasting can have positive health effects,” he added.

Source: EurekAlert!

New Type of Skin Cell Reveals Secrets of Inflammation

The surprise discovery of a new type of cell explains how distress to the skin early in life may prime a person for inflammatory skin disease later, according to a new study in Nature. This finding will likely lead to treatments for autoimmune disorders like scleroderma, and inform understanding of inflammatory disease.

“The results reinforce the idea that what you’re exposed to initially may have lasting ramifications,” said lead researcher Michael Rosenblum, MD, PhD. “It appears that early exposure to inflammation can, through these cells we discovered, imprint an ability for tissues to develop inflammatory disease later in life.”

The team came across this new type of cell while investigating the effects of certain actions known to evoke immune response in mice. One of these actions involved knocking out a group of skin cells that suppress the immune system. Without that regulation, said Dr Rosenblum, a unique cell was observed that seemed to act as a shelter for pathogenic immune cells not typically seen in skin tissues.

“We had to knock out one cell population to see that they were controlling the growth and capacity of these other, unknown cells,” he said, noting that the new cells only became apparent in the tissue exposed to inflammatory triggers. “What normally would be a deserted island on the skin was now inhabited by all these strangers,” he said.

The team dubbed these strangers ‘TIFFs’ (Th2-interacting fascial fibroblasts) after the Th2 immune cells that they help to house. The location of TIFFs in the skin suggests that they belong to a group of cells that make up the fibrous connective tissue that is fascia, said lead author Ian Boothby, a graduate student in Dr Rosenblum’s lab.

“Because most organs have fascia of some sort, what we’re learning about TIFFs in skin may well be widely applicable to the rest of the body, meaning that these cells may play a role in a huge number of inflammatory diseases,” he said.

Boothby and Dr Rosenblum when skin without regulatory cells receives inflammatory triggers, the TIFFs spread like wildfire and become a sort of holding pen for the Th2 immune cells. Later in life, when there is even a small insult to the skin, Dr Rosenblum said, the TIFFs open their floodgates, unleashing the Th2 cells.

It seems that, through these cells, early exposure to inflammalation can leave a life-long imprint.

“All you need to do is push the immune system just a little bit, with a wound or with stress, to unleash all the pathogenic cells living in these TIFFs and create an exaggerated inflammatory response,” he said.

The researchers hypothesise that the exaggerated response may manifest as the creation of fibroses in the fascia, the driving force behind inflammatory skin diseases such as scleroderma.

To confirm the presence of TIFFs in human skin, the team obtained samples from volunteers with eosinophilic fasciitis (EF), a rare inflammatory disorder in which eosinophils build up in the skin fascia, the fibrous tissue between the skin and the muscles below it.

Comparing the EF samples to those of healthy skin, the researchers found TIFFs in both, but looked completely different. In healthy skin, the fascia forms a thin, spidery network between fat cells, while in the EF skin sample, the cells had expanded to form thick bands of fibrous tissue.

Revealing the mysteries of inflammation
TIFFs appear to be present in every organ, said Dr Rosenblum, usually found in the fascia surrounding major organs and serve a role in maintaining structure. They’re also prone to interacting with immune cells. He postulates that TIFFs might have evolved as a sort of emergency brigade in case of injury, able to jump-start repair in the case of internal injury.

“In patients with scleroderma or other fibrosing diseases like EF, that repair program may be kind of co-opted, resulting in this chronic wound-healing response,” said Dr Rosenblum. “If we can understand the biology of these cells, we can come in with drugs that revert them back to what they’re supposed to be doing.”

Source: University of California San Francisco

Distinct Lower Airways Bacterial Profile inChildren with Cystic Fibrosis

Phot by Ben Wicks on Unsplash

In children with cystic fibrosis (CF), their lower airways have a higher burden of infection, more inflammation and lower diversity of microorganisms, compared to children with other illnesses who also have lung issues, researchers have found. They noted a clear divergence in these bacterial communities in toddlers, before progressive lung disease manifests in CF patients. 

Their findings, published in the journal PLOS ONE, could help providers target specific pathogens earlier, treat them and potentially prevent more severe lung disease.

As lead author Jack O’Connor, at Ann & Robert H. Lurie Children’s Hospital of Chicago explained, “We compared lower airway samples from bronchoscopy in children with CF and disease controls across the age spectrum, and used genetic sequencing to identify microorganisms, finding that a few common cystic fibrosis pathogens begin to dominate at very early ages. Such a clear split from disease controls in this young age group has not been shown before. Our findings deepen our understanding of the disease trajectory in cystic fibrosis and could help improve outcomes through earlier intervention.”

Chronic airway infection and inflammation which leads to progressive, obstructive lung disease is the main cause of illness and death in people with cystic fibrosis.

Researchers tested lower airway samples from 191 patients (63 with cystic fibrosis) aged 0-21 years. The disease controls included patients with diverse conditions, such as cancer, immune deficiency and pneumonia. Using genetic sequencing, researchers were able to identify distinct pathogens that are more dominant at different ages in patients with cystic fibrosis.

“Establishing key age-related differences in lower airway bacterial communities and inflammation in patients with CF, especially during early childhood, may give us a window of opportunity for earlier and more precise treatment,” said senior author Theresa Laguna, MD, MSCS, Division Head of Pulmonary and Sleep Medicine at Lurie Children’s and Associate Professor of Pediatrics at Northwestern University Feinberg School of Medicine. “If we can prevent worse infections, we could improve the quality of life and potentially expand the life expectancy of patients with CF.”

Source: News-Medical.Net

Gut Microbes and Antibiotics Impact Inflammatory Pain

C difficile. Source: CDC

A study in rats showed that gut microbiomes and antibiotic use could modulate inflammatory pain.

Published in The Journal of Pain, the study examined the impact of antibiotics on the gut microbiome and how antibiotic use can alter inflammatory pain in subjects with or without access to exercise.

According to Glenn Stevenson, Ph.D., professor of psychology within the School of Social and Behavioral Sciences, this is the first publication to assess how antibiotic-induced changes to the gut microbiome impact inflammatory pain distal to the gut (in the limbs, for example).

The study determined the effects of vancomycin on inflammatory pain-stimulated and pain-depressed behaviours in rats, which was induced with formalin. Oral vancomycin administered in drinking water attenuated pain-stimulated behaviour, and prevented formalin pain-depressed wheel running. Faecal microbiota transplantation produced a non-significant trend toward reversal of vancomycin’s effect on pain-stimulated behaviour. Vancomycin depleted Firmicutes and Bacteroidetes gut populations while partially sparing Lactobacillus species and Clostridiales. The vancomycin treatment effect was associated with an altered profile in amino acid concentrations in the gut.

The results indicate that manipulation of the gut microbiome may be one method to attenuate inflammatory pain amplitude. Additionally, results indicated that the antibiotic-induced shift in gut amino acid concentrations may be a causal mechanism for this reduction in pain.

The research for this study took four years to complete, Prof Stevenson said, adding that the link between amino acids and pain reduction is “highly novel.”

Source: University of New England

Histamine Involvement in Depression Revealed

Image by Falkurian Design on Unsplash

Histamine from inflammation dampens serotonin levels and antidepressants’ ability to boost them, according to experiments in mice models.

The findings, published in The Journal of Neuroscience add to mounting evidence that inflammation, and the accompanying release of the molecule histamine, affects serotonin, a key molecule responsible for mood in the brain.

Inflammation triggers the release of histamine in the body, increasing blood flow to affected areas to flood them with immune cells. While these effects help the body fight infections, both long-term and acute inflammation is increasingly linked to depression. There is already strong evidence that patients with both depression and severe inflammation are the ones most likely not to respond to antidepressants.

Dr Parastoo Hashemi, Lead Author, Imperial’s Department of Bioengineering, said: “Our work shines a spotlight on histamine as a potential key player in depression. This, and its interactions with the ‘feel-good molecule’ serotonin, may thus be a crucial new avenue in improving serotonin-based treatments for depression.”

Chemical messengers
Serotonin is a key target for depression-tackling drugs, and selective serotonin reuptake inhibitors (SSRIs) inhibit the re-absorption of serotonin in the brain, allowing it to circulate for longer and improve mood.

However, although SSRIs bring relief to many who take them, an increasing number of people are resistant to it. This could be due to the specific interactions between chemical messengers, or neurotransmitters, including serotonin and histamine.

With this in mind, researchers set out to investigate the relationship between histamine, serotonin, and SSRIs. They created tiny serotonin-measuring microelectrodes and put them into the hippocampus of the brains of live mice, an area known to regulate mood. The technique, known as fast scan cyclic voltammetry (FSCV), allowed them to measure brain serotonin levels in real time..

After placing the microelectrodes, they injected half the mice with lipopolysaccharide (LPS), an inflammation-causing toxin found in some bacteria, and half the mice with a saline solution as a control.

Within minutes of LPS injection, brain serotonin levels dropped, whereas they remained the same in control mice, demonstrating the rapid action of inflammatory responses on the brain and serotonin. Since LPS cannot cross the blood-brain barrier, it could not cause the drop in serotonin.
The inflammatory response triggered histamine in the brain which directly inhibited the release of serotonin by attaching to inhibitory receptors. 

To counter this, the researchers administered SSRIs to the mice, but they were much less able to boost serotonin levels than in control mice. They posited that this is because the SSRIs directly increased the amount of histamine in the brain, cancelling out its serotonin boosting action.

The researchers then administered histamine reducing drugs alongside the SSRIs to counter histamine’s inhibitory effects, and saw serotonin levels rise back to control levels. This appears to confirm the theory that histamine directly dampens serotonin release in the mouse brain. These histamine reducing drugs cause a whole-body reduction in histamine and are distinct from antihistamines taken for allergies, which block histamine’s effects on neurons.

A new molecule of interest
More work is needed before progressing to human studies. However, it is not currently feasible to use microelectrodes to make similar measurements in human brains, so the researchers are now looking at other ways to get a snapshot of the brain by looking at other organs which use serotonin and histamine, like the gut.

Source: Imperial College London

New Insights into Gum Disease and Inflammatory Response

Photo by Caroline LM on Unsplash
Photo by Caroline LM on Unsplash

A team of researchers has identified how different people respond to the accumulation of dental plaque, helping us understand the vulnerability of some to serious conditions that lead to tooth loss and other problems. 

The study was led by University of Washington researchers and recently published in the journal Proceedings of the National Academy of Sciences (PNAS). 

Buildup of plaque, the sticky biofilm covering teeth and gums, can induce gingivitis, or gum inflammation if left unchecked. Gingivitis, in turn, can lead to periodontitis, a serious infection that can damage and destroy the gum and bones supporting teeth. As well as causing tooth loss, this chronic inflammation can also trigger heart disease, diabetes, cancer, arthritis, and bowel diseases.

The researchers also discovered a range of inflammatory responses to oral bacterial accumulation. When bacteria build up on tooth surfaces, it generates inflammation as the body responds. Two known major oral inflammation phenotypes were known: a high or strong clinical  response and a low clinical response. The team identified a third phenotype, which they dubbed ‘slow’: a delayed strong inflammatory response in the wake of the bacterial buildup.

The study also found that subjects with low clinical response also showed a low inflammatory response for a variety of inflammation signals.  “Indeed, this study has revealed a heterogeneity in the inflammatory response to bacterial accumulation that has not been described previously,” said Dr Richard Darveau of the UW School of Dentistry, one of the study’s authors.

Study co-author Dr Jeffrey McLean said, “We found a particular group of people that have a slower development of plaque as well as a distinct microbial community makeup prior to the start of the study.” The authors wrote that understanding the variations in gum inflammation could help screen for higher periodontitis risk. In addition, it is possible that this variation in the inflammatory response among the human population may be related to the susceptibility to other chronic bacterial-associated inflammatory conditions such as inflammatory bowel disease.

Additionally, the researchers found a novel protective response by the body, triggered by plaque accumulation, that can save tissue and bone during inflammation. This mechanism, which was apparent among all three phenotypes, utilises white blood cells known as neutrophils. In the mouth, they act something like cops on the beat, patrolling and regulating the bacterial population to maintain a stable condition known as healthy homeostasis.

In this instance, plaque is not a villain. To the contrary, the researchers said that the proper amount and makeup of plaque supports normal tissue function. Studies in mice have also shown that plaque also provides a pathway for neutrophils to migrate from the bloodstream through the gum tissue and into the crevice between the teeth and gums.

When healthy homeostasis exists and everything is working right, the neutrophils promote colonization resistance, a low-level protective inflammatory response that helps the mouth fend off an excess of unhealthy bacteria and resist infection. At the same time, the neutrophils help ensure the proper microbial composition for normal periodontal bone and tissue function.

The researchers’ findings underscore why dentists preach the virtues of regular brushing and flossing, which prevent too much plaque buildup. “The idea of oral hygiene is to in fact recolonise the tooth surface with appropriate bacteria that participate with the host inflammatory response to keep unwanted bacteria out,” Dr Darveau explained. The bacteria start repopulating the mouth’s surfaces spontaneously and almost immediately afterward, Dr Darveau said.

Source: University of Washington School of Dentistry

Journal information: Bamashmous, S., et al. (2021) Human variation in gingival inflammation. PNASdoi.org/10.1073/pnas.2012578118.

Chronic Inflammation Ages the Pituitary Gland in Mice

Photo by Robina Weermeijer on Unsplash

Researchers have discovered that the pituitary gland in mice ages due to an age-related form of chronic inflammation — which raises the possibility of slowing or even partially repairing this process. 

The pituitary gland is a small, globular gland located underneath the brain that plays a major role in the hormonal system, explained Professor Hugo Vankelecom, a stem cell biologist from the Department of Development and Regeneration at KU Leuven. “My research group discovered that the pituitary gland ages as a result of a form of chronic inflammation that affects tissue and even the organism as a whole,” he said. “This natural process usually goes unnoticed and is referred to as ‘inflammaging’ — a contraction of inflammation and ageing. Inflammaging has previously been linked to the ageing of other organs.”

Because of the pituitary’s pivotal role in the body, its ageing may contribute to the reduction of hormonal processes and hormone levels in our body – such as in menopause.

The study also provides significant insight into the stem cells in the ageing pituitary gland. In 2012, Prof Vankelecom and colleagues showed that a prompt reaction of these stem cells to injury in the gland leads to repair of the tissue, even in adult animals.

“As a result of this new study, we now know that stem cells in the pituitary do not lose this regenerative capacity when the organism ages. In fact, the stem cells are only unable to do their job because, over time, the pituitary becomes an ‘inflammatory environment’ as a result of the chronic inflammation. But as soon as the stem cells are taken out of this environment, they show the same properties as stem cells from a young pituitary.”

Could damage be repaired?

This insight opens up a number of potential therapeutic avenues: would it be possible to reactivate the pituitary? This wouldn’t just involve slowing down hormonal ageing processes, but also repairing the damage caused by a tumour in the pituitary, for example. 

“No fewer than one in every 1000 people is faced with this kind of tumour — which causes damage to the surrounding tissue — at some point.

“The quality of life of many of these patients would be drastically improved if we could repair this damage. We may be able to do so by activating the stem cells already present — for which our present study also provides new indications — or even by transplanting cells. That said, these new treatment options are not quite around the corner just yet, as the step from fundamental research to an actual therapy can take years to complete. For the time being, our study sets out a potential direction for further research.”

The study also brings up another interesting approach: using anti-inflammatory drugs to slow down pituitary ageing or even rejuvenate an ageing pituitary. “Several studies have shown that anti-inflammatory drugs may have a positive impact on some ageing organs. No research has yet been performed on this effect in relation to the pituitary.”

From mice to humans

Since Prof Vankelecom and colleagues studied the pituitary of mice, further research is required to demonstrate whether their findings also apply to humans. Prof Vankelecom cautioned, however: “Mice have a much greater regeneration capacity than humans.

“They can repair damaged teeth, for instance, while humans have lost this ability over the course of their evolution. Regardless, there are plenty of signs suggesting that pituitary processes in mice and humans are similar, and we have recent evidence to hand that gene expression in the pituitaries of humans and mice is very similar. As such, it is highly likely that the insights we gained will equally apply to humans.”

Source: KU Leuven

Journal information: Vennekens, A., et al. (2021) Interleukin-6 is an activator of pituitary stem cells upon local damage, a competence quenched in the aging gland. Proceedings of the National Academy of Sciences. doi.org/10.1073/pnas.2100052118.

Inflammation a Predictor of Future Depression in Widowed Spouses

Researchers at Rice University have found that future depression in widowed spouses can be predicted by bodily inflammation after the death of their partners.

The study will be published in the June 2021 edition of the journal Psychoneuroendocrinology. The study was led by lead author Lydia Wu, a Rice psychology graduate student, and Christopher Fagundes, associate professor of psychology and principal investigator for the Biobehavioral Mechanisms Explaining Disparities (BMED) lab at Rice. The researchers recruited 99 participants who had lost their spouses within 2-3 months of the study, and evaluated them on a number of factors, including physical and mental health, over three months.

“Prior research has already linked bodily inflammation to a host of health issues, including cancer, memory issues, heart problems and depression,” Wu said. “We were interested in how systemic inflammation affects the mental health of spouses after losing a loved one. In particular, can inflammation help us identify who will experience clinical levels of depression at a future point in time?”

The researchers found that widowed spouses with higher levels of bodily inflammation immediately after the loss of their partners had more severe symptoms of depression three months later compared to those with lower inflammation levels. This was even more pronounced if they didn’t experience significant depression initially.

Prof Fagundes said that it is normal to experience depression following the death of a spouse, and research shows that undergoing psychotherapy right after the event can actually interfere with people’s natural coping ability.

“We know that most people are remarkably resilient,” he said.

In the case of persistent depression, or depression occurring six or more months after a spouse’s death, it may be a sign that clinical intervention is needed, Prof Fagundes said.

“Until this study, it was difficult to know who was at risk for these persistently high levels of depression and grief until the six-month mark,” he said. “This study identifies a potential biomarker that could help us predict who is at greatest risk for long-term repercussions of loss.”

“This information makes early intervention possible,” Wu said. “We can identify at-risk bereaved persons and introduce them to interventions early on to improve their mental health.”

The researchers said more research is needed to determine who might be at greatest risk.

Source: Rice University

Journal information: E. Lydia Wu et al, Inflammation and future depressive symptoms among recently bereaved spouses, Psychoneuroendocrinology (2021). DOI: 10.1016/j.psyneuen.2021.105206

Tropical Ginger Can Block Inflammation

A piece of ginger. Photo by Lawrence Aritao on Unsplash

New research has shown how compound found in the tropical ginger plant, 1′-acetoxychavicol acetate, or ACA, can have an anti-inflammatory effect.

Researchers found that ACA reduces mitochondrial damage by lowering levels of mitochondrial reactive oxygen species (ROS), blocking activation of a crucial protein complex known as the NLRP3 inflammasome. A number of inflammatory diseases, like inflammatory bowel disease, display improper and chronic activation of this complex.

It has been suggested by previous studies that the NLRP3 inflammasome plays a significant role in promoting inflammation by secreting a molecule called IL-1β. This molecule works as a messenger, sending various immune cells to the site of injury or infection. Further studies detailed how production of ROS can help to trigger the NLRP3 inflammasome. Because other groups showed that the ginger compound ACA can reduce ROS production in certain immune cells, the researchers wondered how this compound would affect the way NLRP3 inflammasome worked.

“Many disease pathogeneses involve dysregulation of the inflammasome,” commented Daisuke Ori, co-lead author on the study. “Blood cells from people suffering from rheumatoid arthritis or other autoimmune disorders frequently have increased levels of inflammasome-derived IL-1β. Therefore, targeting the NLRP3 inflammasome with a compound like ACA may be a promising therapeutic strategy.”

The researchers took immune cells from mouse bone marrow, and also used a mouse model of colitis. ACA was added to the growing cells and the compound was added to their mice’s food. The researchers then looked at the effects on ROS production, secretion of IL-1β, and other markers of inflammation.

“Cells treated with ACA had significantly reduced IL-1β production, as well as lower levels of ROS,” explained senior author Taro Kawai. “ACA could also inhibit NLRP3 inflammasome activation in the colitis mouse model.” These in vivo results are promising, as they suggest ACA has the potential to treat or prevent the development of inflammatory diseases. “Interestingly, we did not observe high levels of immune cell death when using ACA, which means that it may be relatively safe,” continued Ori.

The study provided novel evidence for a specific molecular mechanism governing the previously observed anti-inflammatory properties of ACA. The study also showed the potential of ACA for therapeutic use in diseases mediated by IL-1β molecules, or associated with cytokine storms, as seen in patients suffering from severe COVID.

Source: Medical Xpress

Journal information: Sophia P M Sok et al. 1′-acetoxychavicol acetate inhibits NLRP3-dependent inflammasome activation via mitochondrial ROS suppression, International Immunology (2021). DOI: 10.1093/intimm/dxab016

Mitochondria Dump DNA into Cells, Triggering Inflammation

Researchers have discovered that when building blocks for DNA in cells are in short supply, mitochondria— the powerhouses of cells — release their own DNA, triggering an inflammatory response. Targeting this process can now open up new avenues of treatment into ageing-related diseases.

Mitochondria, the producers of energy for cells, , have their own genetic material: mitochondrial DNA. In certain situations, however, mitochondria are known to release their DNA into the interior of the cell, provoking a reaction from the cell’s own immune system. Some cardiac and neurodegenerative diseases as well as the ageing process are associated with the mitochondrial genome.

To find out when mitochondria release their DNA, the researchers have focused on the mitochondrial protein YME1L. “In cells lacking YME1L, we observed the release of mitochondrial DNA into the cell interior and a related immune response in the cells,” explained Thomas MacVicar, one of the study’s two first authors.  
“If the cells lack YME1L, there is a deficiency of DNA building blocks inside the cell,” he continued. “This deficiency triggers the release of mitochondrial DNA, which in turn causes an inflammatory response in the cell: the cell stimulates similar inflammatory reactions as it does during a bacterial or viral infection. If we add DNA building blocks to the cells from the outside, that also stops the inflammation.”

This newly discovered link between cellular inflammatory response and the metabolism of DNA building blocks could have far-reaching consequences, MacVicar explained. “Some viral inhibitors stop the production of certain DNA building blocks, thereby triggering an inflammatory response. The release of mitochondrial DNA could be a crucial factor in this, contributing to the effect of these inhibitors,” he said. 
Mitochondrial DNA is associated with a number of ageing-associated inflammatory diseases, including cardiac and neurodegenerative diseases, as well as obesity and cancer. The authors hope that new therapeutic opportunities in such diseases can be created by modulating the metabolism of DNA building blocks.

Source: Medical Xpress

Journal information: Hans-Georg Sprenger et al, Cellular pyrimidine imbalance triggers mitochondrial DNA–dependent innate immunity, Nature Metabolism (2021). DOI: 10.1038/s42255-021-00385-9