Medical Bulletin 06/ July/ 2024

Here are the top medical news for the day:

Reducing Processed Meat Intake Linked to Health Benefits: Study

Reducing consumption of processed meat by around one-third could prevent more than 350,000 cases of diabetes in over 10 years, a study published in the journal The Lancet Planetary Health suggested.

Processed meats, which often contain high levels of salt, fat, and preservatives, have been linked to an increased risk of various health issues, including heart disease, type 2 diabetes, and certain cancers, particularly colorectal cancer. By cutting down on processed meats, individuals can lower their intake of harmful substances, leading to improved cardiovascular health, better blood sugar control, and a reduced risk of cancer.

A team from the University of Edinburgh and the University of North Carolina developed a simulation tool to estimate the health impacts of reducing processed and unprocessed red meat consumption. While many studies link high processed meat consumption with chronic diseases, fewer examine multiple health outcomes, and evidence on unprocessed red meat remains limited.

Using the Centres for Disease Control and Prevention health (CDC) survey data, researchers created a representative microsimulation of the adult population to estimate the effects of reducing meat consumption by 5% to 100% on diabetes, cardiovascular disease, colorectal cancer, and mortality.

The results showed that cutting processed meat intake by 30% could prevent over 350,000 diabetes cases, 92,500 cardiovascular disease cases, and 53,300 colorectal cancer cases over a decade. Reducing both processed and unprocessed red meat by 30% could lead to 1,073,400 fewer diabetes cases, 3,82,400 fewer cardiovascular disease cases, and 84,400 fewer colorectal cancer cases. Lowering unprocessed red meat intake alone by 30% could prevent over 7,32,000 diabetes cases, 2,91,500 cardiovascular disease cases, and 32,200 colorectal cancer cases.

The findings suggested that the greater impact of reducing unprocessed red meat is due to a higher average intake compared to processed meat. However, the researchers advise caution in interpreting these estimates and call for further research.

Reference: Kennedy, J., et al. (2024) Estimated effects of reductions in processed meat consumption and unprocessed red meat consumption on occurrences of type 2 diabetes, cardiovascular disease, colorectal cancer, and mortality in the USA: a microsimulation study. The Lancet Planetary Health. doi.org/10.1016/S2542-5196(24)00118-9.

Study Finds Link Between Semaglutide and a Rare

A new study led by investigators from Mass Eye and Ear has discovered that patients prescribed semaglutide (marketed as Ozempic or Wegovy) for diabetes or weight loss had a higher risk of developing a potentially blinding eye condition called Non-Arteritic Anterior Ischemic Optic Neuropathy (NAION) compared to similar patients who had not been prescribed these drugs.

The findings were published in the journal JAMA Ophthalmology.

NAION (Non-Arteritic Anterior Ischemic Optic Neuropathy) is a relatively rare condition, affecting up to 10 out of every 100,000 people. It is the second leading cause of optic nerve blindness, following glaucoma, and the most common cause of sudden optic nerve blindness. NAION occurs due to reduced blood flow to the optic nerve head, resulting in permanent vision loss in one eye. This condition causes painless visual loss, which may progress over several days before stabilizing. There are currently no effective treatments for NAION.

For the study, researchers examined the records of over 17,000 patients treated at Mass Eye and Ear over six years since the release of Ozempic. They divided the patients into groups diagnosed with either diabetes or overweight/obesity. They compared those who had been prescribed semaglutide with those taking other diabetes or weight loss medications.

The analysis revealed a significant increase in the risk of NAION diagnoses among patients using semaglutide.

Semaglutide was developed to treat type 2 diabetes. The drug encourages weight loss, and its use has snowballed since its launch as Ozempic for diabetes in 2017. The drug was also approved for weight management, branded as Wegovy, and released in 2021.

"Our findings should be viewed as being significant but tentative, as future studies are needed to examine these questions in a much larger and more diverse population. This is information we did not have before and it should be included in discussions between patients and their doctors, especially if patients have other known optic nerve problems like glaucoma or if there is preexisting significant visual loss from other causes,” said Joseph Rizzo, director of the Neuro-Ophthalmology Service at Mass Eye and Ear.

Reference: Hathaway, J et al. "Risk of Nonarteritic Anterior Ischemic Optic Neuropathy in Patients Prescribed Semaglutide" JAMA Ophthalmology DOI: 10.1001/jamaophthalmol.2024.2296

New Findings on Cellular Mechanism for Brain Energy May Improve Late-Life Brain Health

A key mechanism which detects when the brain needs an additional energy boost to support its activity has been identified in a study in mice and cells led by UCL scientists.

The findings, published in the journal Nature, could discover new therapies to maintain brain health and longevity, as other studies have found that brain energy metabolism can become impaired late in life and contribute to cognitive decline and the development of neurodegenerative disease.

Previous research has shown that astrocytes, a type of star-shaped brain cell, help supply energy to brain neurons. Astrocytes are glial cells, which are non-neuronal cells found in the central nervous system. When nearby neurons need more energy, astrocytes quickly activate their own glucose stores and metabolism. This process increases the production and release of lactate, which supplements the energy available for neurons in the brain.

In a series of experiments with mice and cell samples, researchers discovered specific receptors in astrocytes that detect and monitor neuronal activity. These receptors trigger a signalling pathway involving adenosine, a key molecule. They found that this pathway in astrocytes, which activates glucose metabolism to supply energy to neurons, is the same as the pathway that activates energy stores in muscles and the liver during exercise.

Adenosine helps astrocytes boost glucose metabolism and provide energy to neurons, ensuring that communication signals between brain cells continue smoothly, even under high energy demand or reduced energy supply.

When researchers deactivated these key astrocyte receptors in mice, the mice showed less effective brain activity, with significant impairments in overall brain metabolism, memory, and sleep. This demonstrated that the identified signalling pathway is crucial for learning, memory, and sleep.

"When our brain is active, like during mentally demanding tasks, it needs an immediate energy boost. However, the exact mechanisms ensuring this on-demand energy supply are not fully understood. Identifying this mechanism could help treat brain diseases where energy levels are low, such as neurodegeneration and dementia. Brain energy regulation declines with age and more rapidly in diseases like Alzheimer’s. Our study highlights a promising target for drugs to boost brain energy, protect brain function, maintain cognitive health, and promote brain longevity,” said the authors.

Reference: Theparambil, S.M., Kopach, O., Braga, A. et al. Adenosine signalling to astrocytes coordinates brain metabolism and function. Nature (2024). https://doi.org/10.1038/s41586-024-07611-w