Medical Bulletin 14/July/2026

Here are the top medical news for today:

Researchers Discover Surprising Brain Changes During a Woman's Second Pregnancy

No two pregnancies shape the brain in exactly the same way, a new study has suggested.

Researchers from Amsterdam UMC have found that a second pregnancy reshapes the mother's brain differently from the first, creating new changes that may help women care for a growing family. The findings, published in Nature Communications, also provide new clues about maternal mental health and postpartum depression.

In the study, researchers followed 110 women over time. Some were pregnant with their first child, others were expecting their second, while a third group had never been pregnant. Using repeated brain scans, the team tracked how the brain changed before, during, and after pregnancy.

The results showed that both first and second pregnancies alter the brain, but in different ways. During a first pregnancy, the largest changes occurred in the brain's Default Mode Network, which is involved in self-reflection, social thinking, and understanding others.

During a second pregnancy, this same network changed again, but less dramatically. Instead, the biggest changes appeared in brain regions responsible for attention and processing sensory information. Researchers believe these adaptations may help mothers respond more effectively to the needs of multiple children.

The study also found that pregnancy-related brain changes were linked to the emotional bond between mother and baby. This connection was stronger after a first pregnancy than after a second.

Importantly, researchers identified an association between structural brain changes and peripartum depression during both first and second pregnancies. However, the timing differed. Among first-time mothers, these changes became more evident after childbirth, while in women expecting a second child, they were more noticeable during pregnancy.

The researchers say the findings improve understanding of how the maternal brain adapts to pregnancy and motherhood. They hope this knowledge will help scientists better identify women at risk of maternal mental health problems and eventually improve prevention and treatment strategies for postpartum depression.

REFERENCE: M. Straathof, S. Halmans, P. J. W. Pouwels, E. A. Crone, E. Hoekzema. The effects of a second pregnancy on women’s brain structure and function. Nature Communications, 2026; 17 (1) DOI: 10.1038/s41467-026-69370-8

New Study Explores Gut Microbiota's Role in Eating Behavior and Obesity

What if your gut microbes are quietly influencing when, what, and how much you eat?

A new review published in the British Journal of Pharmacology suggests that the gut microbiome plays a much bigger role in obesity and eating disorders than previously thought, offering potential new targets for future treatments.

Researchers explained that food intake is controlled by two systems in the brain: the homeostatic system, which regulates hunger and energy needs, and the hedonic system, which drives eating for pleasure. Hormones such as ghrelin, GLP-1, PYY, and leptin constantly communicate with the brain to control appetite, meal size, and energy balance. When this communication breaks down, it can contribute to obesity, binge eating, anorexia, or bulimia.

The review highlights the importance of the gut-brain axis—a two-way communication network linking the gut microbiome with the brain through immune, hormonal, metabolic, and nerve signals. Beneficial gut bacteria produce short-chain fatty acids, which help regulate inflammation, protect the blood-brain barrier, and support healthy brain function.

When the gut microbiome becomes imbalanced, a condition known as dysbiosis, harmful bacterial products can leak into the bloodstream, triggering chronic inflammation and altering brain regions involved in hunger and food reward. This may increase cravings for high-calorie foods and promote overeating.

Researchers also reviewed microbiome-based therapies. Prebiotics, probiotics, synbiotics, postbiotics, and fecal microbiota transplantation (FMT) have all shown promise in early studies. Certain probiotic strains, including A. muciniphila, B. lactis, and L. plantarum, have been linked to modest improvements in weight and metabolic health. However, the evidence is still limited, and these approaches are not yet established treatments.

The researchers conclude that although the gut microbiome is an exciting target for tackling obesity and eating disorders, larger, long-term human studies are needed before microbiome-based therapies or biomarkers can become part of routine clinical care.

REFERENCE: Samulėnaitė, S., Mathis, V., Darcq, E., Burokas, A., Martín-García, E., & Maldonado, R. (2026). Gut microbiota as a novel therapeutic target for eating disorders and obesity. British Journal of Pharmacology, 1-30. DOI: 10.1111/bph.70547

Researchers Uncover Surprising Memory Role of Alzheimer's Tau Protein

What if the same protein linked to Alzheimer's disease is also the key to forming lasting memories?

A new study published in Nature Communications has found that tau, a protein long associated with Alzheimer's disease, is also essential for creating long-lasting memories. The discovery sheds new light on how healthy memory works and could help researchers develop better treatments for dementia in the future.

Scientists from Flinders University, the University of New South Wales, and Macquarie University studied memory formation in mice. They found that tau is not required for learning new information or recalling it shortly afterward. Instead, it plays a critical role in turning short-term experiences into stable, long-term memories.

The researchers focused on specialized brain cells called engram cells, which store memories. They discovered that tau helps select which of these cells will preserve a new experience. It also reduces unnecessary "background noise" in the brain, allowing only the right cells to form a clear and lasting memory.

The team also identified that tau undergoes a normal chemical change, called phosphorylation, during learning. While abnormal tau phosphorylation is a hallmark of Alzheimer's disease, this study shows that low, controlled levels of the process are actually essential for healthy memory formation.

Interestingly, even without tau, memory traces still existed in the brain and could be recovered by directly stimulating engram cells. This suggests tau is not needed to store memories but is crucial for linking natural cues, such as sights or sounds, to memory recall.

When disease-related forms of tau were present during learning, they disrupted the formation of new memories. If abnormal tau appeared after memories had already formed, it interfered with their retrieval.

Although the findings come from mouse studies and need confirmation in humans, they suggest that memory problems in Alzheimer's may result from disrupted organization and access to memories, rather than memories simply disappearing.

REFERENCE: Renée Kosonen, Kristie Stefanoska, Yijun Lin, Samantha Edwards, Emmanuel Prikas, Josefine Bertz, Anne Poljak, Lars M. Ittner, Arne Ittner. Tau T205 phosphorylation modulates engram cell recruitment and remote memory in mice. Nature Communications, 2026; DOI: 10.1038/s41467-026-73207-9