Ersilia Satta

Pain in end-stage renal disease: a frequent and neglected clinical problem

Pain is a major health problem in end-stage renal disease (ESRD) affecting half of the dialysis patients; most of them experience a moderate to severe degree of pain. Nevertheless, the impact of chronic pain and its consequences are often underestimated. Sources of pain related to the uremic environment are renal bone disease (osteitis fibrosa cystica, amyloidosis, osteomalacia), osteoarthritis, calcific uremic arteriolopathy and peripheral neuropathy. Moreover, comorbid conditions such as ischemic peripheral artery disease, diabetic neuropathy, osteopenia/ osteoporosis (due to long-standing hypertension, diabetes, or old age) result in various kinds of pain. Also the primary kidney disease (e.g. autosomal dominant polycystic kidney disease (ADPKD)) as well as performance of hemodialysis or peritoneal dialysis are important causes of pain. Potential consequences of persistent pain are disturbed sleep, weakened memory/attention, altered mood (anxiety and depressive disorder), impotence, poorer physical state, less social activities and consideration of withdrawal from dialysis. Consequently the health-related-quality of life (HRQOL) is diminished, associated with a higher morbidity and mortality. In the therapy of pain the WHO three-step analgesic ladder adapted for ESRD, was shown to be effective in dialysis patients. Of fundamental importance are various forms of non-pharmacological strategies including electrotherapy. Recently the so-called high tone external muscle stimulation (HTEMS) was very effective in the management of neuropathic pain in ESRD patients.

Plasma Protein Aspartyl Damage Is Increased in Hemodialysis Patients: Studies on Causes and Consequences

Plasma proteins in hemodialysis patients display a significant increase in deamidated/isomerized Asx (asparagine and aspartic acid) content, a marker of protein fatigue damage. This has been linked to the toxic effects of hyperhomocysteinemia in uremic erythrocytes; however, treatment aimed at abating homocysteine levels did not lead to significant reductions in plasma protein damage. The hypothesis that lack of reduction in protein damage could be due to protein increased intrinsic instability, as result of interference with the uremic milieu rather than to hyperhomocysteinemia, was put forward. The deamidated/isomerized Asx content of normal plasma incubated with several uremic toxins for 24 h, 72 h, and 7 d was measured, identifying a group of toxins that were able to elicit this kind of damage. Uremic toxins were also incubated with purified human albumin, and dose-response experiments with the two most toxic agents in terms of protein damage (guanidine and guanidinopropionic acid) were carried out. The effect of the hemodialysis procedure on protein damage was evaluated. For investigating also the consequences of these alterations, human albumin was treated in vitro to produce an increase in deamidated/isomerized Asx residues, and the effects of albumin deamidation on protein binding were evaluated. Among the uremic toxins that are able to elicit protein damage, guanidine produced a dose-dependent increase in protein damage. No difference was found after a hemodialysis session. Deamidated albumin shows normal binding capacity to warfarin, salicylic acid, or diazepam but reduced binding to homocysteine. In conclusion, uremic toxins, especially guanidine, display an ability to induce significant protein damage, which can in turn have functional consequences.

Vitamin D Status and Mortality Risk in Patients with Chronic Kidney Disease

Several studies have shown that mineral metabolism disorders play a major role in determining a higher mortality rate for end-stage renal disease patients. Vitamin D deficiency is associated with cardiovascular events in hemodialysis patients. Recently, an association between vitamin D insufficiency and cardiovascular or renal events has been found, in patients with chronic renal failure who have not started renal replacement therapy yet. To further investigate this issue, we evaluated the relationship between blood levels of 25-hydroxyvitamin D (25-OH D; > or ≤30 ng/mL) and mortality or dialysis dependence in 104 incident consecutive patients with chronic kidney disease stages 3–5, over a period of 17 months, with a follow-up of 2 years in a cross-sectional analysis. The correlation between different levels of vitamin D and the risk of events has been estimated by using a probit model. Explanatory variables employed concerned age, sex, blood pressure, BMI, and number of co-morbid factors. The average 25-OH D concentration was of 30.13 ng/mL. During follow-up (>16 months), each patient experienced an average of 1.28 events. Vitamin D has been shown to reduce the probability of cardiovascular or renal events. Vitamin D intake for more than 12 months can reduce the probability of such events by 11.42%. Each co-morbid factor, instead, raises the probability of events by 29%. Lower probabilities of experiencing an adverse cardiovascular event might depend on higher levels of vitamin D. The influence of 25-OH D on survival in chronic kidney disease patients may be related to unrecognized factors that need to be further explored.

Hyperhomocysteinemia and macromolecule modifications in uremic patients.

Abstract Hyperhomocysteinemia is present in the majority of well-nourished chronic renal failure and uremic patients. Most observations reported in the literature come from studies carried out in end-stage renal disease patients treated with hemodialysis. The underlying mechanisms of the toxic effects of homocysteine in uremia related to cardiovascular disease and other disturbances are still under scrutiny. As a consequence, macromolecules (i.e., proteins and DNA) have been found to be altered to various extents. One of the mechanisms of homocysteine toxicity is related to the action of its metabolic precursor, S-adenosylhomocysteine, a powerful methyltransferase competitive inhibitor. Disruption of DNA methylation has been demonstrated to occur as a result of hyperhomocysteinemia, and/or is associated with vascular damage. DNA hypomethylation has been found in the mononuclear cell fraction of uremic patients with hyperhomocysteinemia. Proteins are also targets of homocysteine-dependent molecular damage. The formation of oxidative products with free cysteinyl residue thiol groups has been demonstrated to occur in blood. The latter also represents a mechanism for the transport of homocysteine in plasma. In addition, homocysteine thiolactone has been shown to react with free amino groups in proteins to form isopeptide bonds, in particular at the lysine residue level. Another type of isopeptide bond in proteins may result from the deamidation and isomerization of asparaginyl residues, yielding abnormal isoaspartyl residues, which have been demonstrated to be increased in uremic patients. Folate treatment exerts a partial, but significant, homocysteine-lowering effect in uremic patients and has been shown to improve the changes in macromolecules induced by high homocysteine levels. In conclusion, both DNA and proteins are structurally modified in uremia as a consequence of high homocysteine levels. The role of these macromolecule changes in inducing the clinical complications of hyperhomocysteinemia in these patients, although still conjectural in some respects, is at present sustained by several pieces of evidence.

Endothelial Dysfunction in Chronic Renal Failure

Cardiovascular disease is a very early phenomenon in the course of chronic renal failure, and increases continuously with decrease of renal function. Endothelial dysfunction seems to be a starting point in vascular changes leading to atherosclerosis and artery calcification. Endothelium, considered the largest organ in the body, has many functions. It senses mechanical and hormonal stimuli and in response the endothelial cells secrete a range of compounds which modulate vascular tone, coagulation, cell proliferation, and inflammation. The central role of endothelium in the development of vascular disease has led to identification of new relevant biomarkers and methods to estimate endothelial function and injury. Arterial stiffness, which is not an early phenomenon in endothelial dysfunction but a common complication of chronic renal failure may be evaluated through Pulse Wave Velocity and Augmentation Index obtained by pulse-wave analysis. Aortic stiffness is an independent predictor of cardiovascular morbidity and mortality in patients with hypertension. A new fascinating aspect of research in endothelial function is rising through the studies on endothelial progenitor cells. These are primitive bone marrow cells that have the ability to mature into endothelial cells and have a physiologic role in the repair of endothelial lesions.

Plasma protein homocysteinylation in uremia

Abstract Protein homocysteinylation is proposed as one of the mechanisms of homocysteine toxicity. It occurs through various means, such as the post-biosynthetic acylation of free amino groups (protein-N-homocysteinylation, mediated by homocysteine thiolactone) and the formation of a covalent -S-S- bond found primarily with cysteine residues (protein-S-homocysteinylation). Both protein modifications are a cause of protein functional derangements. Hemodialysis patients in the majority of cases are hyperhomocysteinemic, if not malnourished. Protein-N-homocysteinylation and protein-S-homocysteinylation are significantly increased in hemodialysis patients compared to controls. Oral folate treatment normalizes protein-N-homocysteinylation levels, while protein-S-homocysteinylation is significantly reduced. Albumin binding experiments after in vitro homocysteinylation show that homocysteinylated albumin is significantly altered at the diazepam, but not at the warfarin and salicilic acid binding sites. Clin Chem Lab Med 2007;45:1678–82.

Sexual Dysfunction in Women with Diabetic Kidney

Few studies address alteration of sexual function in women with diabetes and chronic kidney disease (CKD). Quality of life surveys suggest that discussion of sexual function and other reproductive issues are of psychosocial assessment and that education on sexual function in the setting of chronic diseases such as diabetes and CKD is widely needed. Pharmacologic therapy with estrogen/progesterone and androgens along with glycemic control, correction of anemia, ensuring adequate dialysis delivery, and treatment of underlying depression are important. Changes in lifestyle such as smoking cessation, strength training, and aerobic exercises may decrease depression, enhance body image, and have positive impacts on sexuality. Many hormonal abnormalities which occur in women with diabetes and CKD who suffer from chronic anovulation and lack of progesterone secretion may be treated with oral progesterone at the end of each menstrual cycle to restore menstrual cycles. Hypoactive sexual desire disorder (HSDD) is the most common sexual problem reported by women with diabetes and CKD. Sexual function can be assessed in women, using the 9-item Female Sexual Function Index, questionnaire, or 19 items. It is important for nephrologists and physicians to incorporate assessment of sexual function into the routine evaluation protocols.

Sexual Dysfunction in Chronic Kidney Disease

Several factors contribute to sexual dysfunction (SD) in patients with chronic kidney disease (CKD) and some of them are less frequent in general population. Hormonal alterations along with vascular, neurologic, and psychosocial factors and drugs contribute to the development of SD. Low levels of testosterone in men with CKD can be responsible to alterations in libido, erectile function, spermatogenesis, and sperm motility. Erectile dysfunction (ED) is the persistent inability to achieve and/or maintain an erection sufficient for satisfactory sexual intercourse. Risk factors for ED can be grouped into those that have an effect upon the vasculature, those in which the mode of action is nonvascular in nature, and age.

Pain in renal disease.

ABSTRACT Pain is the presenting symptom in 20 to 30% of patients with autosomal dominant polycystic kidney disease (ADPKD) and occurs in 50 to 60% of patients at some stage of the disease process, but its frequency increases with age and size of the cysts. Back pain is caused by kidney enlargement as well as rupture, hemorrhage, or infection of cysts. Other causes of pain include nephrolithiasis and urinary tract infections (UTIs). Analgesic options for patients with ADPKD include transcutaneous electrical nerve stimulation (TENS), spinal cord stimulation, low-dose opioids, and local anesthetics.