Cutaneous adaptive immunity and uraemia: a narrative review

Chronic kidney disease affects 1 in 10 people globally, with a prevalence twenty times that of cancer. A subset of individuals will progress to end-stage renal disease (ESRD) where renal replacement therapy is required to maintain health. Cutaneous disease, including xerosis and pruritus, are endemic amongst patients with ESRD. In the uraemia-associated immune deficiency of ESRD, impaired circulating immune responses contribute to increased infection risk and poorer vaccination response. Clinical manifestations of dysregulated adaptive immunity within the skin have been well-described and have been posited to play a role in cutaneous features of ESRD. However, our understanding of the mechanisms by which adaptive immunity within the skin is affected by uraemia is relatively limited. We provide an overview of how the cutaneous adaptive immune system is impacted both directly and indirectly by uraemia, highlighting that much work has been extrapolated from the circulating immune system and often has not been directly evaluated in the skin compartment. We identify knowledge gaps which may be addressed by future research. Ultimately, greater understanding of these pathways may facilitate novel therapeutic approaches to ameliorate widespread cutaneous symptomatology in ESRD.

Prospective Study of Change in Skin Autofluorescence Over Time and Mortality in People Receiving Hemodialysis

Introduction

Elevated skin autofluorescence (SAF), a measure of tissue accumulation of advanced glycation end products (AGEs), is a strong predictor of all-cause and cardiovascular mortality in the hemodialysis population. However, prospective studies investigating the association between changes in SAF over time and mortality are scarce. We therefore aimed to investigate the prognostic value of SAF trend for predicting mortality in a hemodialysis population.

Methods

We enrolled 120 patients on hemodialysis in a 5-year observational, prospective study. SAF was measured at baseline, 3, 6, 9, 12, and 24 months. Rate of change in SAF (i.e., SAF trend) was calculated using linear regression. Time to event was the number of days from baseline to death, kidney transplantation, or March 31, 2022.

Results

Mean age, mean baseline SAF, and median SAF trend were 65 ± 14 years, 3.4 ± 0.9 arbitrary units (AU), and an increase of 0.1 (-0.1 to 0.4) AU/yr, respectively. Median observation time was 42 months, during which 59 participants (49%) died. Univariable analysis identified age, history of smoking, lower serum albumin, higher baseline SAF, and increase in SAF as significant predictors of higher mortality. In multivariable analysis, higher baseline SAF (hazard ratio: 1.45; 95% confidence interval: 1.08-1.94; P = 0.01) and increasing SAF trend (2.37 [1.43-3.93]; P < 0.001) were independent predictors of increased mortality.

Conclusion

An increasing SAF trend and higher baseline SAF were independent predictors of all-cause mortality in this hemodialysis population, suggesting that monitoring of SAF may have clinical utility. Strategies to improve outcomes by reducing or preventing the increase in SAF should now be investigated in prospective studies.

Malnutrition as a potential predictor of mortality in chronic kidney disease patients on dialysis: A systematic review and meta-analysis

BACKGROUND & AIMS

Malnutrition, a significant problem in patients with chronic kidney disease (CKD), is linked to lower health-related quality of life, longer and more frequent hospital admissions, worse functional capacity, and higher levels of morbidity. However, the extent of its impact on mortality is poorly elucidated. This systematic review and meta-analysis aimed to investigate the impact of malnutrition on mortality among CKD patients on dialysis.

METHODS

This meta-analysis was designed and performed in accordance with the PRISMA guidelines (CRD42023394584). A systematic electronic literature search was conducted in PubMed, ScienceDirect, and Embase to identify relevant cohort studies. The studies that reported nutritional status and its impact on mortality in patients were considered for analysis. The generic inverse variance method was used to pool the hazard ratio effect estimates by employing a random effects model. The Newcastle-Ottawa scale was used for the quality assessment. The statistical analysis was performed by utilizing RevMan and CMA 2.0.

RESULTS

A total of 29 studies that comprised 11,063 patients on dialysis whose nutritional status was evaluated were eligible for quantitative analysis. Based on a comparison between the "malnutrition" category and the reference "normal nutrition status" category, the results showed that the overall pooled hazard risk (HR) for mortality was (HR 1.49, 95% CI: 1.36-1.64, p < 0.0001). According to the subgroup analysis, the hemodialysis subgroup had greater mortality hazards (HR 1.53; 95% CI 1.38-1.70, p < 0.0001), compared to the peritoneal dialysis subgroup (HR 1.26; 95% CI 1.15-1.37, p < 0.00001). Additionally, the overall incidence of mortality was explored but the authors were unable to combine the results due to limitations with the data.

CONCLUSION

The findings conclude that malnutrition is a strong predictor of mortality among patients on dialysis, with the hemodialysis subgroup having a higher mortality hazard compared to the peritoneal dialysis subgroup. The results of this study will advocate for early nutritional evaluation and timely dietary interventions to halt the progression of CKD and death.

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.

Is the measurement of tissue advanced glycosylation products by skin autofluorescence associated with mortality in patients treated by peritoneal dialysis?

BACKGROUND

Advanced glycosylated end-products (AGEs) have been shown to cause cardiovascular disease, and tissue AGE accumulation can be measured by skin autofluorescence (SAF). AGEs are cleared by the kidney, and thus accumulate in dialysis patients. However, as the results of SAF measurements in peritoneal dialysis patients (PD) have been ambiguous, we examined the association between mortality and SAF.

METHODS

We reviewed SAF measurements in PD patients attending a university associated PD program, along with standard measurements of dialysis adequacy and peritoneal membrane function.

RESULTS

We studied 341 prevalent PD patients, 61.9% male, mean age 61.2 ± 16 years, and 31.4% of all patients died during a median follow-up of 27.2 (23.3-36.3) months. Patients who died were older, mean age 72 ± 10.5 years, were more often diabetic (60.7%), and had higher median SAF 3.8 (3.2-4.5) AU. On logistic regression, mortality was independently associated with age (odds ratio (OR) 1.1 (95% confidence limits 1.06-1.16), diabetes OR 10.1 (3.1-33.4), SAF OR 3.3 (1.8-6.2), all p < 0.001, and male gender OR 5.2 (1.6-17.4), p = 0.007; and negatively associated with weight OR 0.91 (0.86-0.95), p < 0..001, normalised nitrogen appearance rate (nPNA) OR 0.05 (0.01-0.4), p = 0.005 and mean arterial blood pressure (MAP) OR 0.96 (0.93-0.96), p = 0.03.

CONCLUSIONS

In this observational study, SAF was independently associated with mortality. However, other factors were also associated with mortality, including age, diabetes and malnutrition which have all been reported to affect SAF measurements. Thus, the additional predictive value of measuring SAF compared to standard risk factors for mortality remains to be determined.

Role of skin autofluorescence in managing renal and cardiac diseases in outpatient dermatology

INTRODUCTION

The accumulation of tissue-advanced glycation end products in skin results from complex and consecutive reactions and can be measured by skin autofluorescence (SAF) reader devices. This overview discusses studies evaluating the utilization of SAF in screening renal and cardiac disease.

MATERIALS AND METHODS

Literature search was performed using Google Scholar, PubMed, Springer, Ovid, and ScienceDirect.

RESULTS

SAF was an independent predictor of progression of chronic kidney disease (CKD) and was elevated in subjects on hemodialysis and peritoneal dialysis. Furthermore, SAF was significantly associated with cardiovascular events, cardiovascular mortality, and all-cause mortality in CKD patients. Other studies revealed a correlation between SAF and arterial stiffness, vascular damage, and subclinical atherosclerosis. A vegetarian diet was associated with lower SAF levels, whereas malnutrition was correlated with higher levels and increased mortality.

CONCLUSIONS

SAF measurement may be useful in managing renal and cardiac disease. Future studies are needed to clarify the specific role of SAF in the management of CKD and its noninvasive office utilization to identify comorbidities in inflammatory diseases, such as psoriasis.

Associations between Advanced Glycation End Products, Body Composition and Mediterranean Diet Adherence in Kidney Transplant Recipients

There is limited evidence on the associations between dietary patterns, body composition, and nonclassical predictors of worse outcomes such as advanced glycation end products (AGE) in kidney transplant recipients (KTRs). The aim of this cross-sectional study was to determine the level of AGE-determined cardiovascular (CV) risk in Dalmatian KTRs and possible associations between AGE, adherence to the Mediterranean diet (MeDi), and nutritional status. Eighty-five (85) KTRs were enrolled in this study. For each study participant, data were collected on the level of AGE, as measured by skin autofluorescence (SAF), Mediterranean Diet Serving Score (MDSS), body mass composition, anthropometric parameters, and clinical and laboratory parameters. Only 11.76% of the participants were adherent to the MeDi. Sixty-nine percent (69%) of KTRs had severe CV risk based on AGE, while 31% of KTRs had mild to moderate CV risk. The results of the LASSO regression analysis showed that age, dialysis type, dialysis vintage, presence of CV and chronic kidney disease, C- reactive protein level, urate level, percentage of muscle mass, and adherence to recommendations for nuts, meat, and sweets were identified as positive predictors of AGE. The negative predictors for AGE were calcium, phosphate, cereal adherence according to the MeDi, and trunk fat mass. These results demonstrate extremely low adherence to the MeDi and high AGE levels related CV risk in Dalmatian KTRs. Lifestyle interventions in terms of CV risk management and adherence to the MeDi of KTRs should be taken into consideration when taking care of this patient population.

In Patients with Chronic Kidney Disease Advanced Glycation End-Products Receptors Isoforms (sRAGE and esRAGE) Are Associated with Malnutrition

Background: in patients with chronic kidney disease (CKD), the inflammatory and pro-oxidant milieu may contribute to malnutrition development. In this study, we investigated the relationship between inflammation, advanced glycation end-products (AGEs), and their receptors (RAGEs) with malnutrition in CKD patients. Methods: we evaluated 117 patients. AGEs were quantified by fluorescence intensity using a fluorescence spectrophotometer, soluble RAGEs isoforms, and inflammatory interleukins by ELISA. Malnutrition was assessed by a malnutrition inflammation score. Results: mean age was 80 ± +11 years, eGFR was 25 ± +11 mL/min/1.73 m2 and BMI was 28 ± 5 Kg/m2. Malnourished individuals were older, had lower estimated protein intake (nPCR 0.65 ± 0.2 vs. 0.8 ± 0.2 vs. 0.8 ± 0.3, p = 0.01), higher C reactive protein (CRP 0.6 ± 1 vs. 0.6 ± 0.7 vs. 0.17 ± 0.13, p = 0.02) and tumor necrosis factor α (TNF α 14.7 ± 8.7 vs. 15.6 ± 8 vs. 11.8 ± 5.8, p = 0.029). Malnourished patients had higher sRAGE (2813 ± 1477 vs. 2158 ± 1236 vs. 2314 ± 1115, p = 0.035) and esRAGE (648 [408–1049] vs. 476 [355–680] vs. 545 [380–730] p = 0.033). In the multivariate analysis, only sRAGE maintained its association with malnutrition (p = 0.02) independently of aging and inflammation. Conclusions: in CKD patients, RAGEs isoforms, but not AGEs, are associated with malnutrition, irrespective of systemic inflammation, aging, and renal function.

Impact of malnutrition on health-related quality of life in persons receiving dialysis: a prospective study

Health-related quality of life (HRQoL) is severely impaired in persons receiving dialysis. Malnutrition has been associated with some measures of poor HRQoL in cross-sectional analyses in dialysis populations, but no studies have assessed the impact of malnutrition and dietary intake on change in multiple measures of HRQoL over time. We investigated the most important determinants of poor HRQoL and the predictors of change in HRQoL over time using several measures of HRQoL. We enrolled 119 haemodialysis and thirty-one peritoneal dialysis patients in this prospective study. Nutritional assessments (Subjective Global Assessment (SGA), anthropometry and 24-h dietary recalls) and HRQoL questionnaires (Short Form-36 (SF-36) mental (MCS) and physical component scores (PCS) and European QoL-5 Dimensions (EQ5D) health state (HSS) and visual analogue scores (VAS)) were performed at baseline, 6 and 12 months. Mean age was 64 (14) years. Malnutrition was present in 37 % of the population. At baseline, malnutrition assessed by SGA was the only factor independently (and negatively) associated with all four measures of HRQoL. No single factor was independently associated with decrease in all measures of HRQoL over 1 year. However, prevalence/development of malnutrition over 1 year was an independent predictor of 1-year decrease in EQ5D HSS, and 1-year decrease in fat intake independently predicted the 1-year decline in SF-36 MCS and PCS, and EQ5D VAS. These findings strengthen the importance of monitoring for malnutrition and providing nutritional advice to all persons on dialysis. Future studies are needed to evaluate the impact of nutritional interventions on HRQoL and other long-term outcomes.

A Systematic Review of Handgrip Strength Measurement in Clinical and Epidemiological Studies of Kidney Disease: Toward a Standardized Approach

In chronic kidney disease (CKD), handgrip strength (HGS) is recommended as a surrogate measure of protein-energy status and functional status. However, it is not routinely used because of inconsistencies such as the optimal timing of the HGS measurement and unclear guidance regarding technique. We aimed to determine the extent of variation in the protocols and methods of HGS assessment. We aimed to identify clinical and epidemiological studies conducted on CKD that reported on the use of HGS as an outcome. A systematic literature search identified n = 129 studies with a total participant population of n = 35,192. We identified large variations in all aspects of the methodology including body and arm position, repetitions, rest time, timing, familiarization, and how scores were calculated. The heterogeneous methodologies used reinforce the need to standardize HGS measurement. After reviewing previously employed methodology in the literature, we propose a comprehensive HGS assessment protocol for use in CKD.