Medical Bulletin 06/February/2024

Here are the top medical news of the day:

Gut microbiota influence severity of respiratory viral infection

The composition of microbiota found in the gut influences how susceptible mice are to respiratory virus infections and the severity of these infections, according to researchers from the Center for Translational Antiviral Research in the Institute for Biomedical Sciences at Georgia State University.

The findings, published in the journal Cell Host & Microbe, report that segmented filamentous bacteria, a bacterial species found in the intestines, protected mice against influenza virus infection when these bacteria were either naturally acquired or administered.

This protection against infection also applied to respiratory syncytial virus (RSV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes COVID-19. To maintain this protection, the study noted that segmented filamentous bacteria required immune cells in the lungs called basally resident alveolar macrophages.

In this study, the researchers investigated how differences in specific microbial species can impact outcomes of respiratory virus infections and how they might do so, which hasn't been well defined previously.

They studied mice with discrete microbiome differences and mice differing in only the presence or absence of segmented filamentous bacteria. Viral titers in the lung were measured several days after infection and varied significantly depending on the nature of the microbiome of the different animal groups.

These findings uncover complex interactions that mechanistically link the intestinal microbiota with the functionality of basally resident alveolar macrophages and severity of respiratory virus infection," said Dr. Andrew Gewirtz, co-senior author of the study and Regents' Professor in the Institute for Biomedical Sciences at Georgia State.

The study found that in segmented filamentous bacteria-negative mice, basally resident alveolar macrophages were quickly depleted as respiratory virus infection progressed. However, in segmented filamentous bacteria-colonized mice, basally resident alveolar macrophages were altered to resist influenza virus infection depletion and inflammatory signaling.

Reference: Vu L. Ngo, Carolin M. Lieber, Hae-ji Kang, Kaori Sakamoto, Michal Kuczma, Richard K. Plemper, Andrew T. Gewirtz. Intestinal microbiota programming of alveolar macrophages influences severity of respiratory viral infection. Cell Host & Microbe, 2024; DOI: 10.1016/j.chom.2024.01.002.

Cold water swimming may reduce anxiety and symptoms of menopause

Cold water swimming may reduce anxiety and symptoms of menopause suggests a new study published in the Post Reproductive Health.

This study aimed to determine how women felt cold water swimming affected their menstrual and perimenopausal symptoms. An online survey that asked women who regularly swim in cold water about their experiences. The survey was advertised for 2 months on social media. Questions related to cold water swimming habits and menstrual and perimenopausal symptoms were analysed. Quantitative and qualitative data including; frequency of menstrual and menopause symptoms, the effect of cold water swimming on these symptoms were measured.

A total of 1114 women completed the survey. Women reported that cold water swimming reduced their menstrual symptoms, notably psychological symptoms such as anxiety (46.7%), mood swings (37.7%) and irritability (37.6%). Perimenopausal women reported a significant improvement in anxiety (46.9%), mood swings (34.5%), low mood (31.1%) and hot flushes (30.3%). The majority of women with symptoms swam specifically to reduce these symptoms (56.4% for period and 63.3% for perimenopause symptoms). Women said they felt it was the physical and mental effects of the cold water that helped their symptoms. For the free text question, five themes were identified: the calming and mood-boosting effect of the water, companionship and community, period improvements, an improvement in hot flushes and an overall health improvement.

Women felt that cold water swimming had a positive overall effect on menstrual and perimenopause symptoms. Studies on other forms of exercise to relieve menstrual and perimenopause symptoms may show similar findings.

Reference: Pound M, Massey H, Roseneil S, et al. How do women feel cold water swimming affects their menstrual and perimenopausal symptoms? Post Reproductive Health. 2024;0(0). doi:10.1177/20533691241227100

Protein intake before exercise may cut risk of hypoglycemia

Protein intake before exercise may cut risk of hypoglycemia suggests a new study published in Diabetes, Obesity and Metabolism.

Secondary analyses were conducted from a randomised trial of an adaptive behavioural intervention to assess the relationship between protein intake (g and g/kg) consumed within 4 h before moderate-to-vigorous physical activity (MVPA) bouts and glycaemia during and following MVPA bouts among adolescents with type 1 diabetes (T1D).

A total of 112 Adolescents with T1D, 14.5 (13.8, 15.7) years of age and 36.6% overweight/obese, provided measures of glycaemia using continuous glucose monitoring [percentage of time above range (>180 mg/dl), time in range (70-180 mg/dl), time below range (TBR; <70 mg/dl)], self-reported physical activity (previous day physical activity recalls), and 24 h dietary recall data at baseline and 6 months post-intervention.

Pre-exercise protein intakes of 10-19.9 g and >20 g were associated with an absolute reduction of -4.41% (p = .04) and -4.83% (p = .02) TBR during physical activity compared with those who did not consume protein before moderate-to-vigorous physical activity. Similarly, relative protein intakes of 0.125-0.249 g/kg and ≥0.25 g/kg were associated with -5.38% (p = .01) and -4.32% (p = .03) absolute reductions in TBR during physical activity.

We did not observe a significant association between protein intake and glycaemia measures following moderate-to-vigorous physical activity bouts. Among adolescents with T1D, a dose of ≥10 g or ≥0.125 g/kg of protein within 4 h before moderate-to-vigorous physical activity may promote reduced time in hypoglycaemia during, but not following, physical activity.

Reference: Muntis FR, Crandell JL, Evenson KR, Maahs DM, Seid M, Shaikh SR, Smith-Ryan AE, Mayer-Davis E. Pre-exercise protein intake is associated with reduced time in hypoglycaemia among adolescents with type 1 diabetes. Diabetes Obes Metab. 2024 Jan 15. doi: 10.1111/dom.15438. Epub ahead of print. PMID: 38221862.