A Two-Way Path to Health: Environmental Influences on Skeletal Muscle Endocrine Function

To date, PFAS exposure has been linked to disturbances in lipid and cholesterol metabolism, oxidative stress, and endocrine dysfunction, including alterations in thyroid and steroid hormone regulation. However, there is a lack of data regarding the effects of PFAS-chemicals widely used in numerous industrial and consumer applications and ubiquitous in the environment-on exercise-induced adaptive responses.

Over the past two decades, research has demonstrated the critical role of specific proteins released by skeletal muscle (myokines) and other organs, including the brain, heart, and liver (collectively referred to as exerkines), in mediating physiological adaptations to exercise. The extent to which PFAS influence these signaling pathways remains unknown. The limited evidence available from animal studies suggests that PFAS may adversely affect the metabolic potential of skeletal muscle. Given the widespread presence of PFAS in the environment and their accumulation within the human body, the research proposed in this project has substantial societal and public health relevance.

Scientific evidence indicates that PFAS bioaccumulate in critical organs, including the liver, kidneys, and placenta, potentially affecting fetal development and long-term metabolic health. PFAS have been detected in multiple tissues and are characterized by prolonged biological half-lives ranging from several months to as long as six years. PFAS are known to disrupt lipid metabolism and vascular function, potentially contributing to the development of metabolic syndrome and type 2 diabetes mellitus. They have also been identified as compounds capable of altering lipid storage and energy metabolism, thereby promoting obesity. Available evidence further suggests that PFAS exposure is associated with an increased risk of cardiovascular diseases, including hypertension, atherosclerosis, and heart failure. These adverse health effects may be amplified in urban populations exposed to high levels of environmental pollution and characterized by sedentary lifestyles with limited physical activity. Consequently, both elevated PFAS exposure and physical inactivity may independently and synergistically contribute to the burden of chronic diseases.

Given the well-established anti-inflammatory effects of physical activity and its recognized role as a non-pharmacological strategy for health promotion and rehabilitation, it is essential to determine whether PFAS accumulation limits exercise-induced adaptations and impairs the endocrine function of skeletal muscle. Recent studies suggest that environmental pollutants may influence exercise responses and PFAS clearance dynamics. However, the mechanisms regulating exercise-induced PFAS redistribution remain largely unknown. A limited number of animal studies have demonstrated potential adverse effects of PFAS on skeletal muscle cells and their regenerative capacity, whereas comparable human studies are lacking.

In recent years, myokines and exerkines have emerged as key mediators of health-promoting adaptations to exercise. Nevertheless, little is known about how persistent environmental pollutants modulate their secretion and biological activity. In our previous studies, we observed substantial interindividual variability in exercise-induced responses of several key myokines and exerkines, including interleukin-6 (IL-6), soluble IL-6 receptor, gp130, irisin, decorin, follistatin, myostatin, IL-15, N-lactoyl-phenylalanine (Lac-Phe), and brain-derived neurotrophic factor (BDNF). Given the ubiquitous presence of PFAS and their potential impact on public health, further research is urgently needed to elucidate the mechanisms of PFAS bioaccumulation, elimination, and potential mitigation strategies.

According to national cancer statistics from 2022, breast cancer accounted for 23.6% of all female cancer cases in Poland (N = 21,554; ASW = 60.6; ESP2013 = 103.9). In the Greater Poland region, the corresponding figure was 25.5% (N = 2,221; ASW = 71.8; ESP2013 = 122.2). Despite substantial improvements in oncological treatment outcomes, women diagnosed with estrogen receptor-positive (ER+) breast cancer, which represents the majority of cases, typically receive adjuvant endocrine therapy with aromatase inhibitors (AIs) for a period of 5-10 years. Although such treatment significantly improves survival, it is associated with numerous adverse effects, leading 20-50% of patients to discontinue therapy prematurely. These treatment-related consequences often result in hypokinesia and fear of physical activity, thereby promoting the development of sarcopenia and osteopenia. Disturbances in glucose homeostasis, overweight and obesity, and impaired cardiovascular and respiratory function are also frequently observed. Recent epidemiological findings published in 2025, based on data from the UK Biobank (n = 315,457 participants, including 48.1% women; mean age 56.1 ± 8.2 years) and more than 10 years of follow-up, demonstrated that failure to meet World Health Organization (WHO) recommendations for waist circumference was associated with an 11% increase in overall cancer risk, whereas failure to meet WHO physical activity recommendations was associated with a 5% increase in cancer risk. From a preventive medicine perspective, it is difficult to establish a hierarchy among the numerous factors influencing women's health. Importantly, not only body composition but also optimal cardiovascular and cardiac function appear to be central determinants of health outcomes. It may be hypothesized that hypokinesia, overweight, obesity, low muscle and bone mass, reduced concentrations of myokines, hormonal alterations, and cancer collectively impair cardiovascular function. Although numerous studies have demonstrated the beneficial effects of physical activity on health, a key unanswered question is whether physical activity influences PFAS distribution within the human body and facilitates their elimination. While considerable attention has been devoted to chronic PFAS exposure and the long-term consequences of accumulation, relatively little is known about the effects of acute physiological stressors, such as high-intensity exercise, on PFAS distribution within the circulation. Therefore, the development of evidence-based exercise programs and the identification of previously unrecognized factors regulating adaptive responses are of considerable importance for women's health. Collectively, the available evidence strongly supports the need for further research and preventive actions in this area.

The project will address the following research questions:

• To determine and compare baseline concentrations of PFAS and selected myokines/exerkines (proteins released in response to skeletal muscle contraction) in women entering the study. Which factors determine cardiorespiratory fitness, cardiovascular function, and the capacity for PFAS redistribution and elimination from the body?
• To determine changes in circulating concentrations of selected myokines/exerkines in relation to PFAS concentrations following two supervised 6-month exercise interventions. Does exercise intensity and regularity influence PFAS redistribution and elimination, thereby improving women's health outcomes? Which exercise program is more effective in promoting PFAS elimination from the body?
• To determine the role of physical activity in PFAS redistribution and elimination. The findings may provide an additional rationale for promoting long-term engagement in regular physical activity among women. For this reason, participants will undergo a further assessment six months after completion of the intervention. PFAS concentrations will be assessed in both blood and urine and correlated with changes in exercise-induced proteins.
• To develop and validate a method for PFAS determination in urine samples in order to characterize patterns of PFAS redistribution and elimination.

To determine whether previous cancer treatment combined with aromatase inhibitor therapy affects the endocrine potential of skeletal muscle in physically active women, and whether PFAS burden attenuates the regenerative capacity of skeletal muscle.

Milestone I The results obtained during the first stage of the project will allow to determine how PFAS concentrations, lifestyle factors, health literacy, dietary habits, and physical activity influence the endocrine function of skeletal muscle, circulating concentrations of myokines/exerkines, arginine metabolites, and overall health status in participating women.

The collected data and subsequent analyses will provide insights into the concept of the "endocrine potential" of skeletal muscle. Traditionally, body composition and health status have often been assessed using body mass index (BMI) alone. However, increasing evidence highlights the importance of skeletal muscle not only as a locomotor and stabilizing tissue but also as a key endocrine organ.

The application of advanced methods for assessing circulating myokines/exerkines and PFAS concentrations will enable a more precise characterization of skeletal muscle function and the role of health-related behaviors. The interdisciplinary nature of the proposed research, focusing on the relationship between PFAS exposure and skeletal muscle endocrine function-an area not previously investigated-constitutes the innovative aspect of the project.

Milestone II The objective of this stage is to determine how previous cancer treatment in women who have undergone breast cancer therapy affects the endocrine potential of skeletal muscle. Thee investigators will also establish whether cancer treatment is associated with increased PFAS concentrations as a consequence of impaired skeletal muscle endocrine function.

Milestone III To identify the most effective form of physical activity for promoting PFAS redistribution and elimination from the body. Following the six-month intervention period, implementation of the exercise programs, and completion of the planned biochemical analyses, it will be possible to determine which training modality provides greater health benefits.

The investigators hypothesize that resistance-type exercise will be more effective in facilitating PFAS elimination due to the greater involvement of skeletal muscle mass and consequently how that both exercise interventions will improve cardiovascular function and cardiorespiratory fitness.

Milestone IV To evaluate whether maintaining a daily physical activity level of approximately 8,000 steps is sufficient to promote PFAS elimination in women who have completed cancer treatment and are receiving aromatase inhibitor therapy.

In addition, the impact of PFAS and myokines/exerkines concentrations on the immune potential of CD8⁺ T cells and CD3⁺ T cells will be assess.

Milestone V To develop evidence-based recommendations regarding PFAS redistribution and elimination in women, with particular emphasis on breast cancer survivors.

The final outcome of this stage will be the determination of how the implemented exercise interventions improve cardiovascular function through alterations in arginine metabolite profiles, improvements in exercise-test parameters, and modulation of the endocrine function of skeletal muscle.

Milestone VI Dissemination of the developed recommendations in the form of practical guidelines entitled: "Myths and Facts of the Two-Way Path to Health: Muscles and the Environment."

Inclusion criteria

(HICT, IWT and Control groups):

• Women,
• aged 35-75 years
• qualified by a physician for participation in the study and with no contraindications to the training intervention (e.g., heart failure, asthma, chronic obstructive pulmonary disease [COPD], or arthritis)

Inclusion criteria

(Onco Group):

• Women ,
• aged 35-75 years,
• Diagnosed with invasive breast cancer, Stage I-III disease according to the TNM classification,
• Estrogen receptor-positive (ER+) breast cancer, defined as expression in at least 10% of tumor cell nuclei,
• Adjuvant hormone therapy with an aromatase inhibitor for at least 6 months,
• BMI between 18.5 and 32 kg/m².
• Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.
• No chronic diseases limiting the possibility of oncological treatment.
• No contraindications to daily physical activity.
• Willingness to maintain a daily step count of 8,000 steps.

Exclusion criteria

(HICT, IWT and Control groups):

• history of cardiovascular disease,
• previous hospitalization for cardiovascular conditions,
• ongoing cardiovascular treatment, or recent cardiovascular symptoms,
• advanced osteoporosis

Exclusion criteria

(Onco Group):

• Stage IV invasive breast cancer according to the TNM classification.
• ECOG performance status ≥2.
• Unstable ischemic heart disease.
• Cardiac arrhythmias.
• Advanced degenerative joint disease.
• Rheumatic disorders (including rheumatoid arthritis, osteoarthritis, or fibromyalgia).
• Progression of chronic diseases.
• Pregnancy.
• BMI <18.5 or >32 kg/m².
• Uncontrolled hypothyroidism or hyperthyroidism.