Association between Advanced Glycation End-Products and Sarcopenia in Patients with Chronic Kidney Disease

Dietary advanced glycation end-products exacerbate sarcopenia onset by activating apoptosis through PRMT1-mediated CRTC3 arginine methylation

BACKGROUND

Sarcopenia, the age-related decline in muscle mass and function, poses a major health risk to the elderly population. Although dietary advanced glycation end-products (AGEs) have been implicated in worsening sarcopenia, the precise molecular mechanisms remain unclear.

METHODS

A sarcopenia animal model was established by feeding a high AGE diet to C57BL/6 mice. Muscle function and mass were assessed using grip strength tests, and rotarod tests. Proteomic analysis was used to identify differentially expressed proteins. Immunoprecipitation, mass spectrometry, and co-immunoprecipitation were employed to investigate protein interactions both in vivo and in vitro. Quantitative reverse transcription PCR and Western blotting were conducted to measure gene and protein expression levels.

RESULTS

Our results revealed that dietary AGEs accelerated the onset of sarcopenia in mice by triggering apoptosis. Proteomic analysis showed a marked upregulation of protein arginine methyltransferase 1 (PRMT1) in the muscle tissues of mice fed a high AGE diet. PRMT1 mediated the arginine methylation of CREB-regulated transcription coactivator 3 (CRTC3) at the R534 site within its transactivation domain, leading to CRTC3 activation. The activated CRTC3, together with Forkhead box O3a (FOXO3a), transactivated the BAX (BCL2 associated X) gene, initiating Bax downstream signaling, promoting apoptosis in muscle cells, and contributing to muscle atrophy. Inhibition of PRMT1 prevented CRTC3 methylation and suppressed Bax-mediated apoptotic signaling in vitro. Moreover, in vivo treatment with PRMT1 and Bax inhibitors significantly attenuated AGE-induced sarcopenia in mice.

CONCLUSION

PRMT1-mediated CRTC3 arginine methylation plays a critical role in AGE-induced sarcopenia and suggests potential therapeutic targets for preventing sarcopenia progression.

Osteosarcopenia in Chronic Kidney Disease: An Overlooked Syndrome?

BACKGROUND

Healthy ageing relies on maintaining physiological systems, particularly the musculoskeletal system (MKS). After 50, declines in bone density, muscle mass and strength increase the risk of osteoporosis and sarcopenia, leading to frailty, fractures and higher healthcare costs. Osteosarcopenia, combining osteoporosis and sarcopenia, is rising because of the ageing population. Chronic kidney disease (CKD) exacerbates this condition through disruptions in mineral metabolism, hormonal imbalances and inflammation, further compromising musculoskeletal health.

AIMS

This review examines the pathophysiology of osteosarcopenia associated with CKD, focusing on the role of mineral and hormonal disturbances, chronic inflammation and endocrine dysfunction. It aims to increase clinical awareness and highlight the need for early diagnosis and intervention to mitigate the burden of osteosarcopenia on the quality of life and healthcare systems in ageing CKD populations.

METHODS

A narrative review of the current literature was conducted, summarising evidence on the mechanisms underlying osteosarcopenia in CKD, including mineral metabolism alterations, inflammatory processes and hormonal imbalances.

RESULTS

Osteosarcopenia is a recognised consequence of CKD, contributing to increased morbidity and mortality. The pathophysiology of osteosarcopenia in CKD is multifactorial, involving disruptions in mineral metabolism, inflammation, endocrine dysfunction and physical inactivity. CKD-mineral and bone disorder (CKD-MBD) leads to alterations in calcium, phosphate, parathyroid hormone (PTH), fibroblast growth factor 23 (FGF-23) and vitamin D metabolism, resulting in impaired bone mineralisation and increased fracture risk. Simultaneously, CKD accelerates muscle wasting through systemic inflammation, anabolic resistance and metabolic derangements, increasing the risk of sarcopenia. Sarcopenic obesity, inflammaging and hormonal dysregulation further exacerbate bone muscle deterioration. Emerging evidence suggests that osteosarcopenia in CKD is a consequence of interconnected pathophysiological pathways rather than isolated conditions. Diagnosis remains challenging because of overlapping clinical features, necessitating integrated assessment tools. Targeted therapeutic strategies, including mineral metabolism correction, resistance exercise and anabolic interventions, are essential to mitigate osteosarcopenia's progression and improve patient outcomes in CKD.

CONCLUSIONS

Osteosarcopenia is a growing concern in ageing CKD populations. Early diagnostic strategies and targeted interventions are essential to mitigate the impact of osteosarcopenia on patient outcomes and reduce associated healthcare costs. Increased clinical awareness and research into effective therapies are crucial for improving the quality of life for individuals affected by CKD and osteosarcopenia.

Frailty Is Associated with Malnutrition-Inflammation Syndrome in Older CKD Patients

Patients affected by chronic kidney disease (CKD) are generally considered to be frailer than those with preserved renal function. We cross-sectionally evaluated the associations between frailty, malnutrition-inflammation syndrome and circulating inflammatory cytokines in 115 older individuals with advanced CKD. As for frailty definition, we adopted Fried's frailty phenotype (FP), while malnutrition-inflammation syndrome was assessed using the Malnutrition-Inflammation Score (MIS) and circulating inflammatory cytokines (IL-6; TNFα; MCP-1). A total of 48 patients were frail, and mean eGFR was comparable in both frail and non-frail patients (24 ± 10 vs. 25 ± 11 mL/min/1.73 m2; p = 0.63). Frail patients had higher MIS (6 [4-11] vs. 4 [3-5]; p < 0.0001) but cytokine concentrations were comparable in both groups. At multivariate regression, FP was independently associated with MIS, age, gender and pre-albumin but not with cytokines. However, we found some associations between inflammatory cytokines and some specific frailty criteria: weight loss and slowness were associated with MCP-1 (respectively p = 0.049 and p < 0.0001) and weakness with IL-6 (p = 0.005); in conclusion, in older patients with advanced CKD, frailty is strictly associated with malnutrition-inflammation syndrome but not with circulating inflammatory cytokines.

Oxytocin transported from the blood across the blood-brain barrier by receptor for advanced glycation end-products (RAGE) affects brain function related to social behavior

Oxytocin (OT) is a neuropeptide that primarily functions as a hormone controlling female reproductive processes. Since numerous recent studies have shown that single and repetitive administrations of OT increase trust, social interaction, and maternal behaviors in humans and animals, OT is considered a key molecule that regulates social memory and behavior. Furthermore, OT binds to receptors for advanced glycation end-products (RAGE), and it has been demonstrated that loss of RAGE in the brain vascular endothelial cells of mice fails to increase brain OT concentrations following peripheral OT administration. This leads to the hypothesis that RAGE is involved in the direct transport of OT, allowing it access to the brain by transporting it across the blood-brain barrier; however, this hypothesis is only based on limited evidence. Herein, we review the recent results related to this hypothesis, such as the mode of transport of OT in the blood circulation to the brain via different forms of RAGE, including membrane-bound full-length RAGE and soluble RAGE. We further review the modulation of brain function and social behavior, which seem to be mediated by RAGE-dependent OT. Overall, this review mostly confirms that RAGE enables the recruitment of circulating OT to the brain, thereby influencing social behavior. The requirement for further studies considering the physiological aspects of RAGE is also discussed.

Editorial for the Special Issue: Pathophysiology of Chronic Kidney Disease and Its Complications

Chronic kidney disease (CKD) is a risk factor for end-stage kidney disease, requiring renal replacement therapy [...].

Association of Autofluorescent Advanced Glycation End Products (AGEs) with Frailty Components in Chronic Kidney Disease (CKD): Data from a Single-Center Cohort Study

BACKGROUND

Chronic kidney disease (CKD) is characterized by an overproduction and accumulation of advanced glycation end products (AGEs). Because AGEs may play a role in the development of malnutrition and sarcopenia, two essential components of frailty, we evaluated whether they may also contribute to the onset of frailty in CKD patients.

METHODS

We performed a cross-sectional analysis of 117 patients. AGEs were quantified using a fluorescence spectrophotometer and soluble receptor for AGE (sRAGE) isoforms by ELISA. We defined frailty according to the frailty phenotype (FP) proposed by Fried.

RESULTS

The average age of patients was 80 ± 11 years, 70% were male, and the mean eGFR was 25 + 11 mL/min/1.73m². Frailty was diagnosed in 51 patients, and 40 patients were classified as pre-frail. AGEs and RAGE isoforms seem not to correlate with overall frailty. Instead, AGEs were associated with specific frailty domains, inversely associated with BMI (R = -0.22, p = 0.016) and directly associated with gait test time (R = 0.17, p = 0.049). AGEs were also associated with involuntary weight loss (OR 1.84 p = 0.027), independent of age and sex.

CONCLUSIONS

AGEs are associated with some pivotal components of the frailty phenotype, although they are not associated with frailty overall.