Furthermore, post-menopausal women (POST-M) had significantly higher levels of pro-inflammatory marker tumour necrosis factor-α, suggesting higher levels of inflammation.
"Reduced oestradiol (E2) and dietary protein intake in POST-M women occurs in conjunction with increased levels of biomarkers of NMJ [neuromuscular junction] degradation, inflammation and muscle proteolysis, which may be associated with reduced motor unit activation and muscle quality," researchers from the University of Mary Hardin-Baylor in Belton, TX wrote in the journal Nutrients.
Menopause and muscle
Menopause is accompanied by decreased production of the female oestrogenic hormone E2, which plays an essential role in the maintenance of neuromuscular function through its antioxidant properties. Thus, menopause has been associated with increased sarcopenia risk, as well as increased oxidative stress and production of pro-inflammatory mediators, which also negatively impact muscle mass and function.
Deterioration of muscle is common as people age, yet it has also been associated with inadequate protein consumption in older adults.
As such, the researchers sought to investigate further the effects of lower circulating levels of E2 in POST-M compared to PRE-M women to evaluate axonal and NMJ degeneration, pro-inflammatory status and protein degeneration.
The study included 12 healthy women within a cross-sectional design, six of whom were pre-menopausal and six post-menopausal. Blood, urine and dietary data were collected from the participants, in addition to measures of body composition, motor unit activation and muscle performance.
The researchers reported that POST-M women had significantly lower levels of E2, motor unit activity, muscle quality and muscle performance compared to PRE-M women. In addition, they noted that POST-M women consumed inadequate amounts of protein at 0.81 g/kg/day, considerably less than the 1.47 g/kg/day consumed in the PRE-M group.
In contrast, levels of c-terminal fragment of agrin and urinary titin were higher in the POST-M group, however, inflammatory marker tumour necrosis factor-α was also significantly elevated.
"We conclude that reductions in E2, protein intake and antioxidant effects most likely up-regulated TNF-α levels, which subsequently (1) increased the activity of NT to degrade agrin to CAF and (2) up-regulated the activity of NF-кB to instigate muscle proteolysis, thereby resulting in increased TNTF," the researchers explained.
"We also conclude that the culminating effects of this inflammatory and proteolytic cascade conceivably had a detrimental impact on NMJ integrity, motor unit activation and [muscle quality] compared to the pre-menopausal women, who displayed normal levels of E2," they added.
The study called for further research to validate the findings in a larger sample of women more representative of the overall population.
“Decreased Neuromuscular Function and Muscle Quality along with Increased Systemic Inflammation and Muscle Proteolysis Occurring in the Presence of Decreased Estradiol and Protein Intake in Early to Intermediate Post-Menopausal Women”
Authors: Darryn S. Willoughby et al.