Medical bulletin 13/ May/ 2024

According to research presented at the 26th European Congress of Endocrinology, individuals exposed to moderate and repeated stress during adolescence may have reduced fertility in adulthood.

Th study sheds light on the harmful effects that early-life stress has on health and could help to uncover future prevention strategies for children and adolescents.

During adolescence, stress triggers the release of hormones like cortisol, which can disrupt reproductive processes. Prolonged exposure to stress hormones can impair the development and function of reproductive organs, affecting fertility later in adulthood.

Additionally, chronic stress may disrupt menstrual cycles in females and sperm production in males, further compromising fertility. Moreover, stress-induced changes in behavior and lifestyle, such as poor diet and sleep patterns, can also contribute to fertility issues in adulthood.

In this study, researchers from the V.P. Komisarenko Institute of Endocrinology and Metabolism of the National Academy of Medical Science of Ukraine, examined male and female rats, aged 6 months, after individually placing about half of them in enclosed spaces for one hour every morning for two weeks during adolescence (30–45 days old).

They compared the rats who had been exposed to these stressful conditions to the control group and found that chronic stress during puberty delayed sexual maturity in females, and males gained weight more slowly. In adult males, sperm count fell by 25.9%, some sperm were abnormally shaped and sluggish or became immobile, and the breathing process by which sperm cells derive energy slowed down.

Additionally, males had almost two times lower levels of corticosterone – the main stress hormone in rats, equivalent to cortisol in humans.

“Our work is the first to show that even moderate and repetitive stress in adolescence has a long-lasting negative impact on the endocrine system of reproduction and adaptation of the body to changing living conditions,” said lead investigator, Professor Aleksander Reznikov.

“The results make it possible to predict the development of anomalies in reproduction and bodily adaptation systems and are the basis for finding methods for their prevention. We discovered for the first time that lipid peroxidation- a process in which oxidants, like free radicals attack lipid membranes of cells and eventually damage them- in the ovaries and testes, was significantly increased. This, however, needs further investigation,” he added.

Reference: Chronic stress during adolescence may reduce fertility in adulthood: EUROPEAN SOCIETY OF ENDOCRINOLOGY

A new research being presented at the European Congress on Obesity (ECO) and published in the International Journal of Obesity, explained why type 2 diabetes is more common in men than in women.

Previous research has indicated that men are more likely to develop type 2 diabetes (T2D) at a younger age and lower weight compared to women, suggesting a higher overall risk among men. One potential factor contributing to this difference is how adipose tissue responds to insulin.

Adipose tissue, responsible for storing excess energy as triglycerides, is regulated by insulin, which reduces triglyceride breakdown and increases storage. In insulin resistance, adipose cells become less sensitive to insulin, impairing these processes and leading to elevated fat levels in the bloodstream, increasing T2D risk.

If men exhibit more pronounced insulin resistance in adipose cells compared to women, it could explain the higher prevalence of T2D in men.

Lead researcher Dr. Daniel P. Andersson from the Department of Endocrinology at Karolinska University Hospital Huddinge and his team conducted the study by measuring the adipose insulin resistance index in 2,344 women and 787 men, with an average age of 44 years and a BMI of 35 kg/m².

The results showed that men had higher adipose insulin resistance index values than women, but this difference was observed only among individuals with obesity (BMI 30 kg/m² or higher). This pattern persisted regardless of physical activity level, presence of cardiometabolic disease, and nicotine use.

Additionally, in a subgroup consisting of 259 women and 54 men with obesity, the researchers conducted adipose tissue biopsies to examine the effect of insulin on isolated fat cells.

The findings revealed significant disparities between genders. In men, compared to women, a 10-fold higher insulin concentration was required to inhibit triglyceride breakdown into fatty acids, and this inhibition was less efficient in men. However, the storage capacity of fat cells was similar in both sexes.

“Men with obesity show increased adipose insulin resistance and higher blood levels of free fatty acids compared to women. This is primarily due to insulin's reduced ability to inhibit fatty acid breakdown in men's fat cells, rather than differences in storage capacity. Elevated fatty acids in the bloodstream can induce local insulin resistance in organs like the liver, muscles, and pancreas, potentially contributing to the development of type 2 diabetes over time,” explained Dr Andersson.

Reference: Daniel P. Andersson, Department of Endocrinology at Karolinska University Hospital, et al., Do sex differences in how adipose tissue responds to insulin explain why type 2 diabetes is more common in men? :EUROPEAN ASSOCIATION FOR THE STUDY OF OBESITY; International Journal of Obesity; MEETING: European Congress on Obesity (ECO2024)

New research being presented at the European Congress on Obesity (ECO) has found that poor muscle health is associated with a higher risk of an early death in people living with obesity.

Individuals with obesity often experience poor muscle health due to several factors. Excessive adipose tissue accumulation can lead to chronic low-grade inflammation, which contributes to muscle insulin resistance and impairs muscle function.

Additionally, increased fat mass can result in mechanical loading on muscles, leading to reduced muscle strength and endurance. Hormonal imbalances associated with obesity, such as elevated levels of adipokines and decreased levels of anabolic hormones, further exacerbate muscle dysfunction.

In their study, lead researcher Dr Jennifer Linge and colleagues utilized software to analyze scans from 56,109 participants enrolled in the UK Biobank study. They assessed muscle volume (indicating muscle quantity) and muscle fat (indicating muscle quality) and calculated personalized muscle volume z-scores to compare participants' muscle volume to the average for their sex and body size.

Participants were categorized into four groups based on their muscle composition: normal, high muscle fat only, low muscle volume z-score only, or adverse muscle composition (both high muscle fat and low muscle volume z-score).

Among the 9,840 participants with obesity, 2,001 (20.3%) had adverse muscle composition. Over an average follow-up period of 3.9 years, 174 participants died, with the most common causes of death being ischaemic disease and hypertensive disease.

The results showed that participants with adverse muscle composition were three times more likely to die during follow-up than those with normal muscle composition. Even after adjusting for factors such as hand grip strength, other diseases, lifestyle habits, as well as sex, age, type 2 diabetes, and smoking status, the association between poor muscle health and all-cause mortality remained significant. In this fully adjusted model, adverse muscle composition was linked to a 70% higher risk of early death.

The findings revealed that adverse muscle composition was common in individuals living with obesity and significantly associated with all-cause mortality. This emphasized the critical importance of evaluating both muscle volume and muscle fat when assessing muscle health.

Reference: Dr Jennifer Linge AMRA Medical, a health informatics company in Linköping, Sweden. Et al., Poor muscle health is common in people living with obesity – and increases the risk of an early death, Swedish study of people in UK finds; EUROPEAN ASSOCIATION FOR THE STUDY OF OBESITY; MEETING: European Congress on Obesity (ECO2024)