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Glucose Metabolism in the Kidney: Neurohormonal Activation and Heart Failure Development.
Gronda, E, Jessup, M, Iacoviello, M, Palazzuoli, A, Napoli, C
Journal of the American Heart Association. 2020;(23):e018889
Abstract
The liver is not the exclusive site of glucose production in humans in the postabsorptive state. Robust data support that the kidney is capable of gluconeogenesis and studies have demonstrated that renal glucose production can increase systemic glucose production. The kidney has a role in maintaining glucose body balance, not only as an organ for gluconeogenesis but by using glucose as a metabolic substrate. The kidneys reabsorb filtered glucose through the sodium-glucose cotransporters sodium-glucose cotransporter (SGLT) 1 and SGLT2, which are localized on the brush border membrane of the early proximal tubule with immune detection of their expression in the tubularized Bowman capsule. In patients with diabetes mellitus, the renal maximum glucose reabsorptive capacity, and the threshold for glucose passage into the urine, are higher and contribute to the hyperglycemic state. The administration of SGLT2 inhibitors to patients with diabetes mellitus enhances sodium and glucose excretion, leading to a reduction of the glycosuria threshold and tubular maximal transport of glucose. The net effects of SGLT2 inhibition are to drive a reduction in plasma glucose levels, improving insulin secretion and sensitivity. The benefit of SGLT2 inhibitors goes beyond glycemic control, since inhibition of renal glucose reabsorption affects blood pressure and improves the hemodynamic profile and the tubule glomerular feedback. This action acts to rebalance the dense macula response by restoring adenosine production and restraining renin-angiotensin-aldosterone activation. By improving renal and cardiovascular function, we explain the impressive reduction in adverse outcomes associated with heart failure supporting the current clinical perspective.
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Perioperative glutamine supplementation restores disturbed renal arginine synthesis after open aortic surgery: a randomized controlled clinical trial.
Brinkmann, SJ, Buijs, N, Vermeulen, MA, Oosterink, E, Schierbeek, H, Beishuizen, A, de Vries, JP, Wisselink, W, van Leeuwen, PA
American journal of physiology. Renal physiology. 2016;(3):F567-75
Abstract
Postoperative renal failure is a common complication after open repair of an abdominal aortic aneurysm. The amino acid arginine is formed in the kidneys from its precursor citrulline, and citrulline is formed from glutamine in the intestines. Arginine enhances the function of the immune and cardiovascular systems, which is important for recovery after surgery. We hypothesized that renal arginine production is diminished after ischemia-reperfusion injury caused by clamping of the aorta during open abdominal aortic surgery and that parenteral glutamine supplementation might compensate for this impaired arginine synthesis. This open-label clinical trial randomized patients who underwent clamping of the aorta during open abdominal aortic surgery to receive a perioperative supplement of intravenous alanyl-glutamine (0.5 g·kg(-1)·day(-1); group A, n = 5) or no supplement (group B, n = 5). One day after surgery, stable isotopes and tracer methods were used to analyze the metabolism and conversion of glutamine, citrulline, and arginine. Whole body plasma flux of glutamine, citrulline, and arginine was significantly higher in group A than in group B (glutamine: 391 ± 34 vs. 258 ± 19 μmol·kg(-1)·h(-1), citrulline: 5.7 ± 0.4 vs. 2.8 ± 0.4 μmol·kg(-1)·h(-1), and arginine: 50 ± 4 vs. 26 ± 2 μmol·kg(-1)·h(-1), P < 0.01), as was the synthesis of citrulline from glutamine (4.8 ± 0.7 vs. 1.6 ± 0.3 μmol·kg(-1)·h(-1)), citrulline from arginine (2.3 ± 0.3 vs. 0.96 ± 0.1 μmol·kg(-1)·h(-1)), and arginine from glutamine (7.7 ± 0.4 vs. 2.8 ± 0.2 μmol·kg(-1)·h(-1)), respectively (P < 0.001 for all). In conclusion, the production of citrulline and arginine is severely reduced after clamping during aortic surgery. This study shows that an intravenous supplement of glutamine increases the production of citrulline and arginine and compensates for the inhibitory effect of ischemia-reperfusion injury.
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Rosuvastatin preserves renal function and lowers cystatin C in HIV-infected subjects on antiretroviral therapy: the SATURN-HIV trial.
Longenecker, CT, Hileman, CO, Funderburg, NT, McComsey, GA
Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 2014;(8):1148-56
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Abstract
BACKGROUND In chronic human immunodeficiency virus (HIV) infection, plasma cystatin C may be influenced by factors other than glomerular filtration rate such as inflammation. Statins may improve cystatin C by improving glomerular function or by decreasing inflammation. METHODS The Stopping Atherosclerosis and Treating Unhealthy Bone With Rosuvastatin in HIV (SATURN-HIV) trial randomized 147 patients on stable antiretroviral therapy (ART) with low-density lipoprotein cholesterol ≤130 mg/dL to blinded 10 mg daily rosuvastatin or placebo. We analyzed relationships of baseline and 0- to 24-week changes in plasma cystatin C concentration with measures of vascular disease, inflammation, and immune activation. RESULTS Median age was 46 (interquartile range, 40-53) years; 78% were male, 68% African American. Tenofovir and protease inhibitors were used in 88% and 49% of subjects, respectively. Baseline cystatin C was associated with higher carotid intima-media thickness and epicardial adipose tissue independent of age, sex, and race. Biomarkers of endothelial activation and inflammation were associated with cystatin C in a multivariable model independent of creatinine-based estimated glomerular filtration rate (eGFRcr). After 24 weeks, statin use slowed mean eGFRcr decline (1.61 vs -3.08 mL/minute/1.73 m(2) for statin vs placebo; P = .033) and decreased mean cystatin C (-0.034 mg/L vs 0.010 mg/L; P = .008). Within the statin group, changes in cystatin C correlated with changes in endothelial activation, inflammation, and T-cell activation. CONCLUSIONS Rosuvastatin 10 mg daily reduces plasma cystatin C and slows kidney function decline in HIV-infected patients on ART. Reductions in cystatin C with statin therapy correlate with reductions in inflammatory biomarkers. Relationships between cystatin C, kidney function, and cardiovascular risk in HIV may be mediated in part by inflammation. Clinical Trials Registration. NCT01218802.
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Emerging functions of autophagy in kidney transplantation.
Pallet, N, Livingston, M, Dong, Z
American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons. 2014;(1):13-20
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Abstract
In response to ischemic, toxic or immunological insults, the more frequent injuries encountered by the kidney, cells must adapt to maintain vital metabolic functions and avoid cell death. Among the adaptive responses activated, autophagy emerges as an important integrator of various extracellular and intracellular triggers (often related to nutrients availability or immunological stimuli), which, as a consequence,may regulate cell viability, and also immune functions,both innate or adaptive. The aim of this review is to make the synthesis of the recent literature on the implications of autophagy in the kidney transplantation field and to discuss the future directions for research.
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An attempt to understand kidney's protein handling function by comparing plasma and urine proteomes.
Jia, L, Zhang, L, Shao, C, Song, E, Sun, W, Li, M, Gao, Y
PloS one. 2009;(4):e5146
Abstract
BACKGROUND With the help of proteomics technology, the human plasma and urine proteomes, which closely represent the protein compositions of the input and output of the kidney, respectively, have been profiled in much greater detail by different research teams. Many datasets have been accumulated to form "reference profiles" of the plasma and urine proteomes. Comparing these two proteomes may help us understand the protein handling aspect of kidney function in a way, however, which has been unavailable until the recent advances in proteomics technology. METHODOLOGY/PRINCIPAL FINDINGS After removing secreted proteins downstream of the kidney, 2611 proteins in plasma and 1522 in urine were identified with high confidence and compared based on available proteomic data to generate three subproteomes, the plasma-only subproteome, the plasma-and-urine subproteome, and the urine-only subproteome, and they correspond to three groups of proteins that are handled in three different ways by the kidney. The available experimental molecular weights of the proteins in the three subproteomes were collected and analyzed. Since the functions of the overrepresented proteins in the plasma-and-urine subproteome are probably the major functions that can be routinely regulated by excretion from the kidney in physiological conditions, Gene Ontology term enrichment in the plasma-and-urine subproteome versus the whole plasma proteome was analyzed. Protease activity, calcium and growth factor binding proteins, and coagulation and immune response-related proteins were found to be enriched. CONCLUSION/SIGNIFICANCE The comparison method described in this paper provides an illustration of a new approach for studying organ functions with a proteomics methodology. Because of its distinctive input (plasma) and output (urine), it is reasonable to predict that the kidney will be the first organ whose functions are further elucidated by proteomic methods in the near future. It can also be anticipated that there will be more applications for proteomics in organ function research.