In the past, little attention had been paid to the intestine and its microbial flora as a potential source of systemic inflammation in chronic kidney disease(CKD). Systemic inflammation plays a central role in progression of CKD and its cardiovascular and various other complications. The gastrointestinal tract houses a large community of microbes that have a symbiotic relationship with the host. The normal microbial flora protects the host against pathogenic microorganisms. It also contributes to the energy metabolism, micronutrient homeostasis and nitrogen bal- ance. Recent studies have revealed significant changes in the composition and function of the microbial flora in CKD patients and animals. These changes are driven by altered intestinal bio- chemical environment caused by: I-heavy influx of urea and uric acid from body fluids into the gastrointestinal tract, II- restrictions of potassium-rich food including fruits and vegetables which as the main source of indigestible complex carbohydrates are the essential nutrients for the guts' symbiotic microbial com- munity, and III- various medications such as phosphate binders, antibiotics etc. Together the changes in intestinal milieu and the resultant microbial dysbiosis play a major role in systemic inflammation and uremic toxicity by several mechanisms : I-generation of several microbial derived uremic toxins such as indoxyl sulfate, p-cresol sulfate and trimethylamine-N-oxide etc. II-reduction of microbial derived micronutrients such a short chain fatty acids (SCFA) which are the main source of nutrients for colonocytes. This is caused by diminished substrates (indigestible complex carbohydrates) which leads to depletion of SCFA-making bacteria. In addition, III-Disruption of the intestinal epithelial barrier by ammonia and ammonium hydroxide generated from hydrolysis of urea by urease-possessing microbial species which are common complications of CKD, and bowel ischemia caused by excessive use of diuretics (in CKD patients) and aggressive ultrafiltration by hemodialysis (in ESRD patients) can impair gastrointestinal epithelial barrier. The resulting breakdown of the gut epithelial barrier (tight junction complex) leads to influx of endotoxin, microbial fragments, and other noxious luminal products in the sub-epithelial tissue and systemic circulation leading to local and systemic inflammation and oxidative stress which are the major cause of morbidity and mortality in CKD population. This review is intended to provide an overview of the effects of CKD on the gut microbiome and intestinal epithelial barrier structure and the potential interventions aimed at mitigating these abnormalities.

Normal HDL activity confers cardiovascular and overall protection by mediating reverse cholesterol transport and through its potent anti-inflammatory, antioxidant, and antithrombotic functions. Serum lipid profile, as well as various aspects of HDL metabolism, structure, and function can be profoundly altered in patients with nephrotic range proteinuria or chronic kidney disease (CKD). These abnormalities can, in turn, contribute to the progression of cardiovascular complications and various other comorbidities, such as foam cell formation, atherosclerosis, and/or glomerulosclerosis, in affected patients. The presence and severity of proteinuria and renal insufficiency, as well as dietary and drug regimens, pre-existing genetic disorders of lipid metabolism, and renal replacement therapies (including haemodialysis, peritoneal dialysis, and renal transplantation) determine the natural history of lipid disorders in patients with kidney disease. Despite the adverse effects associated with dysregulated reverse cholesterol transport and advances in our understanding of the underlying mechanisms, safe and effective therapeutic interventions are currently lacking. This Review provides an overview of HDL metabolism under normal conditions, and discusses the features, mechanisms, and consequences of HDL abnormalities in patients with nephrotic syndrome or advanced CKD.

Nephrotic syndrome results in hyperlipidemia and profound alterations in lipid and lipoprotein metabolism. Serum cholesterol, triglycerides, apolipoprotein B (apoB)-containing lipoproteins (very low-density lipoprotein [VLDL], immediate-density lipoprotein [IDL], and low-density lipoprotein [LDL]), lipoprotein(a) (Lp[a]), and the total cholesterol/high-density lipoprotein (HDL) cholesterol ratio are increased in nephrotic syndrome. This is accompanied by significant changes in the composition of various lipoproteins including their cholesterol-to-triglyceride, free cholesterol-to-cholesterol ester, and phospholipid-to-protein ratios. These abnormalities are mediated by changes in the expression and activities of the key proteins involved in the biosynthesis, transport, remodeling, and catabolism of lipids and lipoproteins including apoproteins A, B, C, and E; 3-hydroxy-3-methylglutaryl-coenzyme A reductase; fatty acid synthase; LDL receptor; lecithin cholesteryl ester acyltransferase; acyl coenzyme A cholesterol acyltransferase; HDL docking receptor (scavenger receptor class B, type 1 [SR-B1]); HDL endocytic receptor; lipoprotein lipase; and hepatic lipase, among others. The disorders of lipid and lipoprotein metabolism in nephrotic syndrome contribute to the development and progression of cardiovascular and kidney disease. In addition, by limiting delivery of lipid fuel to the muscles for generation of energy and to the adipose tissues for storage of energy, changes in lipid metabolism contribute to the reduction of body mass and impaired exercise capacity. This article provides an overview of the mechanisms, consequences, and treatment of lipid disorders in nephrotic syndrome.

Intravenous iron products are essential for the treatment of anemia in end-stage renal disease patients maintained on hemodialysis. Although proper use of these compounds is necessary for the prevention of iron deficiency, their indiscriminate use could potentially cause insidious adverse consequences. Iron overload can intensify the chronic kidney disease-associated oxidative stress, inflammation, and cardiovascular disease; increase the risk of infections; worsen the severity of type 2 diabetes; and exacerbate neurologic and cognitive dysfunction. These and other adverse effects largely are mediated by iron-catalyzed generation of reactive oxygen species. Unlike conventional oral iron products, the newly released iron-containing phosphate binder ferric citrate has been shown to increase iron stores in end-stage renal disease patients. Therefore, iron indices should be monitored in patients receiving this product. Two published studies have shown a high prevalence of hepatic iron loading among hemodialysis patients treated with erythropoiesis-stimulating agents and intravenous iron compounds. Given the potential risks related to iron treatment in this vulnerable population, studies to better understand safety are needed.

Loss of blood associated with hemodialysis procedures and laboratory testing, together with impaired iron absorption due to elevation of hepcidin, invariably cause iron deficiency in end-stage renal disease patients. For this reason, nearly all ESRD patients require intravenous iron to replete iron stores. Unfortunately, intravenously administered iron is often used routinely with inadequate attention to the body iron stores or severity of systemic inflammation. This has led to an epidemic of iron overload in the ESRD population. Only a minute amount (3-4 mg) of the total body iron (3-4 g in an adult man) resides in the plasma bound to transferrin, which serves as a safe vehicle for iron transport in the circulation. IV iron products are generally administered as bolus injections of 100 to 1000 mg, which far exceeds the available pool of free transferrin and represents a huge quantity compared to the intestinal iron absorption of 1 to 2 mg/day in the course of 3 to 4 meals. Administration of these products results in an increased plasma level of catalytically active non-transferrin bound iron and the rise in the biomarkers of oxidative stress and inflammation. IV iron bypasses the biological safeguards for the transport and handling of iron and helps to intensify chronic kidney disease-associated oxidative stress and inflammation. As briefly described in this review, indiscriminate use of IV iron can accelerate cardiovascular disease, promote microbial infections, aggravate viral hepatitis, and worsen diabetes and diabetic complications in such patients. For these reasons IV iron should be used judiciously in this vulnerable population.