Medical Bulletin 04/August/2026

The AQP4 gene helps regulate fluid movement in the brain and supports the brain's natural waste-clearing system, which becomes most active during sleep. This system helps remove harmful proteins, including those associated with Alzheimer's disease.

The researchers examined 13 common AQP4 gene variants, along with participants' self-reported sleep habits, brain MRI scans, and cognitive test results.

They found that people carrying certain AQP4 variants experienced faster loss of grey matter when they reported shorter sleep duration. Grey matter contains many of the brain cells responsible for memory, learning, decision-making, and movement. Reduced grey matter volume is considered an early sign of structural brain changes.

In some participants, taking longer to fall asleep was also associated with lower brain volume. Cognitive performance changed differently depending on both sleep quality and the specific AQP4 variant an individual carried. Some gene variants appeared to make poor sleep more harmful, while others showed different patterns of brain and cognitive change.

The findings suggest that genetics may influence how strongly poor sleep affects the brain, meaning two people with similar Alzheimer's risk could respond differently to the same sleep habits.

The researchers emphasize that the results do not support routine genetic testing at this stage. Instead, they highlight the need for larger studies to confirm the findings and determine whether improving sleep can reduce genetically driven Alzheimer's risk. If confirmed, the research could pave the way for personalized Alzheimer's prevention.

REFERENCE: Tenielle Porter, Ayeisha Milligan Armstrong, et al.; Evidence for direct and sleep‐moderated relationships between aquaporin‐4 genetic variants and Alzheimer\'s disease phenotypes. Alzheimer\'s, 2026; 22 (6) DOI: 10.1002/alz.71516

Researchers Debunk 42-Year-Old Theory Behind Childhood Obesity

What if your child's rising BMI isn't a warning sign—but proof they're growing stronger?

A long-held belief about childhood weight gain may need a major rethink. New research suggests the well-known "adiposity rebound"—the rise in body mass index (BMI) that begins around age 5 to 6—may not reflect increasing body fat after all. Instead, it could simply represent healthy muscle and lean tissue growth. The study was presented at the European Congress on Obesity and published in The Journal of Nutrition.

For more than 40 years, doctors have believed that children's BMI rises again after early childhood because body fat "rebounds." Earlier rebound has even been linked to a higher risk of obesity later in life. However, Agbaje argues that this interpretation is based on BMI alone—a measure that cannot distinguish between fat, muscle, and bone.

To investigate further, researchers analyzed data from 2,410 children and adolescents aged 2–19 years who participated in the US National Health and Nutrition Examination Survey (NHANES) 2021–2023.

While BMI followed the familiar pattern of declining after infancy and rising again by age six, a more accurate measure of body fat—the waist-to-height ratio (WHtR)—told a different story. Body fat continued to decline until around age seven and never returned to the higher levels seen at age two.

The findings suggest the increase in BMI is largely driven by muscle and lean mass development, not fat accumulation.

The researchers say this challenges the decades-old adiposity rebound theory and questions whether the BMI rise should be treated as an early warning sign requiring intervention. Instead, they propose that the waist-to-height ratio may be a more reliable tool for identifying excess body fat in children.

Although further research is needed, the study suggests many children may simply be experiencing normal, healthy growth—not an early obesity problem.

REFERENCE: Andrew O Agbaje. Adiposity Rebound or Fat-Free Mass Anabolism in Children—Challenging a 42-Year-Old BMI Puzzle with Waist-to-Height Ratio: The ASNF-NNF 2025 Inaugural Flemming Quaade Award for Innovation in Childhood Obesity Lecture. The Journal of Nutrition, 2026; 156 (5): 101437 DOI: 10.1016/j.tjnut.2026.101437

Study Links Daily Tomato Consumption to Lower Liver Fat Marker in MASLD

Can a simple tomato a day help your liver shed fat? A new study suggests it just might.

Eating tomatoes every day may help reduce fat buildup in the liver, according to a new exploratory randomized controlled trial published in Nutrients. The findings suggest that adding tomatoes to the diet could support liver health in people with metabolic dysfunction-associated steatotic liver disease (MASLD), even without significant weight loss.

MASLD is the most common chronic liver disease worldwide and is closely linked to obesity, insulin resistance, and metabolic disorders. While current treatment mainly focuses on weight loss and healthy eating patterns, researchers wanted to know whether one specific food—tomatoes—could directly improve liver fat.

To investigate this, scientists in Italy enrolled 79 adults with MASLD and a body mass index (BMI) of 30 kg/m² or lower. Participants were randomly assigned to either consume 200 grams of raw tomatoes plus 50 grams of tomato sauce daily or follow a tomato-free diet for six weeks while maintaining their usual lifestyle.

Researchers assessed liver fat using the controlled attenuation parameter (CAP), a non-invasive ultrasound-based technique that estimates fat accumulation in the liver.

Both groups showed some reduction in liver fat, but the improvement was significantly greater among those eating tomatoes. The tomato group recorded a median CAP reduction of 35 dB/m, compared with 18 dB/m in the control group.

Interestingly, the benefits occurred without major changes in body weight, BMI, body fat, blood sugar, cholesterol, liver enzymes, or inflammatory markers.

Researchers believe tomatoes' rich supply of lycopene and other antioxidant compounds may help reduce oxidative stress and influence liver fat metabolism.

However, because the study was relatively small, lasted only six weeks, and assessed liver fat indirectly, the findings are considered preliminary. Larger, longer-term clinical trials are needed to determine whether regular tomato consumption can provide lasting and clinically meaningful benefits for people with MASLD.

REFERENCE: Tatoli, R., et al. (2026). Effect of Tomato Consumption on Liver Steatosis in MASLD: A Randomized Controlled Trial (POMOSANO Study). Nutrients, 18(15), 2476. DOI: 10.3390/nu18152476