Insulin activates Na(+)/H(+) exchanger 3: biphasic response and glucocorticoid dependence

Insulin Resistance and Hypertension: Mechanisms Involved and Modifying Factors for Effective Glucose Control

Factors such as aging, an unhealthy lifestyle with decreased physical activity, snacking, a standard Western diet, and smoking contribute to raising blood pressure to a dangerous level, increasing the risk of coronary artery disease and heart failure. Atherosclerosis, or aging of the blood vessels, is a physiological process that has accelerated in the last decades by the overconsumption of carbohydrates as the primary sources of caloric intake, resulting in increased triglycerides and VLDL-cholesterol and insulin spikes. Classically, medications ranging from beta blockers to angiotensin II blockers and even calcium channel blockers were used alone or in combination with lifestyle modifications as management tools in modern medicine to control arterial blood pressure. However, it is not easy to control blood pressure or the associated complications. A low-carbohydrate, high-fat (LCHF) diet can reduce glucose and insulin spikes, improve insulin sensitivity, and lessen atherosclerosis risk factors. We reviewed articles describing the etiology of insulin resistance (IR) and its impact on arterial blood pressure from databases including PubMed, PubMed Central, and Google Scholar. We discuss how the LCHF diet is beneficial to maintaining arterial blood pressure at normal levels, slowing down the progression of atherosclerosis, and reducing the use of antihypertensive medications. The mechanisms involved in IR associated with hypertension are also highlighted.

Empagliflozin and Renal Sodium-Hydrogen Exchange in Healthy Subjects

CONTEXT

Sodium glucose co-transporter-2 inhibitors exert clinically relevant cardiorenal protection. Among several mechanisms, inhibition of sodium-hydrogen exchanger-3 (NHE3) in proximal renal tubules has been proposed in rodents. Demonstration of this mechanism with the associated electrolyte and metabolic changes in humans is lacking.

OBJECTIVE

The present proof-of-concept study was designed to explore the involvement of NHE3 in modulating the response to sodium glucose co-transporter-2 inhibitors in humans.

METHODS

Twenty healthy male volunteers received 2 tablets of empagliflozin 25 mg during a standardized hydration scheme; freshly voided urines and blood samples were collected at timed intervals for 8 hours. Protein expression of relevant transporters was examined in exfoliated tubular cells.

RESULTS

Urine pH levels increased after empagliflozin (from 5.81 ± 0.5 to 6.16 ± 0.6 at 6 hours, P = .008) as did urinary output (from median, 1.7; interquartile range [IQR, 0.6; 2.5] to 2.5 [IQR, 1.7; 3.5] mL/min-1, P = .008) and glucose (from median, 0.03 [IQR, 0.02; 0.04] to 34.8 [IQR, 31.6; 40.2] %, P < .0001), and sodium fractional excretion rates (from median, 0.48 [IQR, 0.34; 0.65] to 0.71 [IQR, 0.55; 0.85] %, P = .0001), whereas plasma glucose and insulin concentrations decreased and plasma and urinary ketones increased. Nonsignificant changes in NHE3, phosphorylated NHE3, and membrane-associated protein 17 protein expression were detected in urinary exfoliated tubular cells. In a time-control study in 6 participants, neither urine pH nor plasma and urinary parameters changed.

CONCLUSIONS

In healthy young volunteers, empagliflozin acutely increases urinary pH while inducing a substrate shift toward lipid utilization and ketogenesis, without significant changes in renal NHE3 protein expression.

Insulin may promote SARS-CoV-2 cell entry and replication in diabetes patients

Patients with diabetes often have severe hyperglycemia triggered by novel coronavirus disease 2019 (COVID-19). Insulin treatment should be the main approach to the control of acute hyperglycemia in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, clinical investigation found that insulin treatment is associated with a significant increase in mortality risk in patients with diabetes and SARS-CoV-2 infection. The reason for this high mortality rate remains obscure. Previous studies have demonstrated that insulin is an activator of Na⁺/H⁺ exchanger (NHE) which could decrease extracellular pH and increase intracellular pH and glycolysis. Here, the author emphasizes insulin may contribute to SARS-CoV-2 cell entry and multiplication in host cells through activation of Na⁺/H⁺ exchange. Additionally, the inhibition of Na⁺ /H⁺ exchange activity or glycolytic flux can result in reduced mortality in patients with COVID-19 and diabetes mellitus during insulin treatment.

Evaluation of the effectiveness of two new strains of Lactobacillus on obesity-induced kidney diseases in BALB/c mice

Background

Kidney disease (KD) is a public health problem worldwide and is an important factor in peripheral vascular disease, arrhythmias, heart failure, acute myocardial infarction, stroke, and angina. Obesity has been indicated as an effective cause of kidney diseases. So, this study aims to use two new strains of Lactobacillus to reduce the metabolic disorders and kidney insufficiency associated with obesity.

Methods

Fifty BALB/c male mice were divided into five groups (control, obesity, obesity pro1, obesity pro2, and obesity mix). The bodyweight, cholesterol profile, urea, and creatinine levels in urine and serum were all measured. Histopathological analysis and expression of Opn, Vim, Ngal, Kim-1, and αKlotho genes for kidney tissues were performed.

Results

The results indicated that body weight, cholesterol profile, urea, and creatinine levels in serum and urine had the lowest significance (P ˂ 0.05) in the obesity mix group and the highest significance in the obesity group. HDL had the highest significance (P ˂ 0.05) in the obesity mix group and the lowest significance (P ˂ 0.05) in the obesity group. Expression of Opn, Vim, Ngal, and Kim-1 genes was the most upregulated in the obesity group compared with the other groups, and there were nonsignificant differences (P > 0.05) between the obesity pro1 and obesity mix groups and the control group. Expression of αKlotho gene was significantly reduced (P ˂ 0.05) in the obesity group compared with the control group.

Conclusion

This study demonstrated that the combination of pro1 and pro2 strains could reduce kidney inflammation and necrosis.

Insulin Resistance and High Blood Pressure: Mechanistic Insight on the Role of the Kidney

The metabolic effects of insulin predominate in skeletal muscle, fat, and liver where the hormone binds to its receptor, thereby priming a series of cell-specific and biochemically diverse intracellular mechanisms. In the presence of a good secretory reserve in the pancreatic islets, a decrease in insulin sensitivity in the metabolic target tissues leads to compensatory hyperinsulinemia. A large body of evidence obtained in clinical and experimental studies indicates that insulin resistance and the related hyperinsulinemia are causally involved in some forms of arterial hypertension. Much of this involvement can be ascribed to the impact of insulin on renal sodium transport, although additional mechanisms might be involved. Solid evidence indicates that insulin causes sodium and water retention, and both endogenous and exogenous hyperinsulinemia have been correlated to increased blood pressure. Although important information was gathered on the cellular mechanisms that are triggered by insulin in metabolic tissues and on their abnormalities, knowledge of the insulin-related mechanisms possibly involved in blood pressure regulation is limited. In this review, we summarize the current understanding of the cellular mechanisms that are involved in the pro-hypertensive actions of insulin, focusing on the contribution of insulin to the renal regulation of sodium balance and body fluids.

Changes in Proximal Tubular Reabsorption Modulate Microvascular Regulation via the TGF System

This review paper considers the consequences of modulating tubular reabsorption proximal to the macula densa by sodium–glucose co-transporter 2 (SGLT2) inhibitors, acetazolamide, and furosemide in states of glomerular hyperfiltration. SGLT2 inhibitors improve renal function in early and advanced diabetic nephropathy by decreasing the glomerular filtration rate (GFR), presumably by activating the tubuloglomerular feedback (TGF) mechanism. Central in this paper is that the renoprotective effects of SGLT2 inhibitors in diabetic nephropathy can only be partially explained by TGF activation, and there are alternative explanations. The sustained activation of TGF leans on two prerequisites: no or only partial adaptation should occur in reabsorption proximal to macula densa, and no or only partial adaptation should occur in the TGF response. The main proximal tubular and loop of Henle sodium transporters are sodium–hydrogen exchanger 3 (NHE3), SGLT2, and the Na-K-2Cl co-transporter (NKCC2). SGLT2 inhibitors, acetazolamide, and furosemide are the most important compounds; inhibiting these transporters would decrease sodium reabsorption upstream of the macula densa and increase TGF activity. This could directly or indirectly affect TGF responsiveness, which could oppose sustained TGF activation. Only SGLT2 inhibitors can sustainably activate the TGF as there is only partial compensation in tubular reabsorption and TGF response. SGLT2 inhibitors have been shown to preserve GFR in both early and advanced diabetic nephropathy. Other than for early diabetic nephropathy, a solid physiological basis for these effects in advanced nephropathy is lacking. In addition, TGF has hardly been studied in humans, and therefore this role of TGF remains elusive. This review also considers alternative explanations for the renoprotective effects of SGLT2 inhibitors in diabetic patients such as the enhancement of microvascular network function. Furthermore, combination use of SGLT2 inhibitors and angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARBs). in diabetes can decrease inflammatory pathways, improve renal oxygenation, and delay the progression of diabetic nephropathy.

The Post-Translational Modification Networking in WNK-Centric Hypertension Regulation and Electrolyte Homeostasis

The with-no-lysine (WNK) kinase family, comprising four serine-threonine protein kinases (WNK1-4), were first linked to hypertension due to their mutations in association with pseudohypoaldosteronism type II (PHAII). WNK kinases regulate crucial blood pressure regulators, SPAK/OSR1, to mediate the post-translational modifications (PTMs) of their downstream ion channel substrates, such as sodium chloride co-transporter (NCC), epithelial sodium chloride (ENaC), renal outer medullary potassium channel (ROMK), and Na/K/2Cl co-transporters (NKCCs). In this review, we summarize the molecular pathways dysregulating the WNKs and their downstream target renal ion transporters. We summarize each of the genetic variants of WNK kinases and the small molecule inhibitors that have been discovered to regulate blood pressure via WNK-triggered PTM cascades.

Salt-Sensitivity of Blood Pressure and Insulin Resistance

Salt sensitivity of blood pressure (SSBP) is an independent risk factor for cardiovascular morbidity and mortality that is seen in both hypertensive and normotensive populations. Insulin resistance (IR) strongly correlates with SSBP and affects nearly 50% of salt sensitive people. While the precise mechanism by which IR and SSBP relate remains elusive, several common pathways are involved in the genesis of both processes, including vascular dysfunction and immune activation. Vascular dysfunction associated with insulin resistance is characterized by loss of nitric oxide (NO)-mediated vasodilation and heightened endothelin-1 induced vasoconstriction, as well as capillary rarefaction. It manifests with increased blood pressure (BP) in salt sensitive murine models. Another common denominator in the pathogenesis of insulin resistance, hypertension, and salt sensitivity (SS) is immune activation involving pro-inflammatory cytokines like tumor necrosis factor (TNF)-α, IL-1β, and IL-6. In the last decade, a new understanding of interstitial sodium storage in tissues such as skin and muscle has revolutionized traditional concepts of body sodium handling and pathogenesis of SS. We have shown that interstitial Na⁺ can trigger a T cell mediated inflammatory response through formation of isolevuglandin protein adducts in antigen presenting cells (APCs), and that this response is implicated in salt sensitive hypertension. The peroxisome proliferator-activated receptor γ (PPARγ) is a transcription factor that modulates both insulin sensitivity and BP. PPARγ agonists increase insulin sensitivity and ameliorate salt sensitivity, whereas deficiency of PPARγ results in severe insulin resistance and hypertension. These findings suggest that PPARγ plays a role in the common pathogenesis of insulin sensitivity and salt sensitivity, perhaps via effects on the immune system and vascular function. The goal of this review is to discuss those mechanisms that may play a role in both SSBP and in insulin resistance.

Novel Treatments from Inhibition of the Intestinal Sodium-Hydrogen Exchanger 3

Plasma membrane sodium–hydrogen exchangers (NHE) transport Na⁺ into cells in exchange for H⁺. While there are nine isoforms of NHE in humans, this review focuses on the NHE3 isoform, which is abundantly expressed in the gastrointestinal tract, where it plays a key role in acid–base balance and water homeostasis. NHE3 inhibition in the small intestine results in luminal sodium and water retention, leading to a general decrease in paracellular water flux and diffusional driving force, reduced intestinal sodium absorption, and increased stool sodium excretion. The resulting softer and more frequent stools are the rationale for the development of tenapanor as a novel, first-in-class NHE3 inhibitor to treat irritable bowel syndrome with constipation. NHE3 also has additional therapeutic implications in nephrology. Inhibition of intestinal NHE3 also lowers blood pressure by reducing intestinal sodium absorption. Perhaps, the most novel effect is its ability to decrease intestinal phosphate absorption by inhibiting the paracellular phosphate absorption pathway. Therefore, selective pharmacological inhibition of NHE3 could be a potential therapeutic strategy to treat not only heart failure and hypertension but also hyperphosphatemia. This review presents an overview of the molecular and physiological functions of NHE3 and discusses how these functions translate to potential clinical applications in nephrology.

The recycling regulation of sodium-hydrogen exchanger isoform 3(NHE3) in epithelial cells

As the main exchanger of electroneutral NaCl absorption, sodium-hydrogen exchanger isoform 3 (NHE3) circulates in the epithelial brush border (BB) and intracellular compartments in a multi-protein complex. The size of the NHE3 complex changes during rapid regulation events. Recycling regulation of NHE3 in epithelial cells can be roughly divided into three stages. First, when stimulated by Ca²⁺, cGMP, and cAMP-dependent signaling pathways, NHE3 is converted from an immobile complex found at the apical microvilli (MV) into an easily internalized and mobile form that relocates to a compartment near the base of the MV. Second, NHE3 is internalized by clathrin and albumin-dependent pathways into cytoplasmic endosomal compartments, where the complex is reprocessed and reassembled. Finally, NHE3 is translocated from the recycling endosomes (REs) to the apex of epithelial cells, a process that can be stimulated by an increase in sodium-glucose cotransporter 1 (SGLT1) activity, epidermal growth factor receptor (EGFR) signaling, Ca²⁺ signaling, and binding to βPix and SH3 and multiple ankyrin repeat domains 2 (Shank2) proteins. This review describes the molecular steps and protein interactions involved in the recycling movement of NHE3 from the apex of epithelial cells, into vesicles, where it is reprocessed and reassembled, and returned to its original location on the plasma membrane, where it exerts its physiological function.

Insulin stimulates β-alanine uptake in skeletal muscle cells in vitro

We evaluated whether insulin could stimulate β-alanine uptake by skeletal muscle cells in vitro. Mouse myoblasts (C2C12) (n = 3 wells per condition) were cultured with β-alanine (350 or 700 µmol·L^-1), with insulin (100 µU·mL^-1) either added to the media or not. Insulin stimulated the β-alanine uptake at the lower (350 µmol·L^-1) but not higher (700 µmol·L^-1) β-alanine concentration in culture medium, indicating that transporter saturation might blunt the stimulatory effects of insulin.

Peptide Hormone Insulin Regulates Function, Expression, and SUMOylation of Organic Anion Transporter 3

Organic anion transporter 3 (OAT3) plays an important role in the disposition of various anionic drugs which impacts the pharmacokinetics and pharmacodynamics of the therapeutics, thus influencing the pharmacological effects and toxicity of the drugs. In this study, we investigated the effect of insulin on the regulation of OAT3 function, expression, and SUMOylation. We demonstrated that insulin induced an increase in OAT3 transport activity through a dose- and time-dependent manner in COS-7 cells. The insulin-induced elevation in OAT3 function was blocked by PKA inhibitor H89, which correlated well with OAT3 protein expression. Moreover, both PKA activator Bt2-cAMP-induced increase and insulin-induced increase in OAT3 function were blocked by PKB inhibitor AKTi1/2. To further investigate the involvement of SUMOylation, we treated OAT3-expressing cells with insulin in presence or absence of H89 or AKTi1/2 followed by examining OAT3 SUMOylation. We showed that insulin enhanced OAT3 SUMOylation, and such enhancement was abrogated by H89 and AKTi1/2. Lastly, insulin increased OAT3 function and SUMOylation in rat kidney slice. In conclusion, our investigations demonstrated that insulin regulated OAT3 function, expression, and SUMOylation through PKA/PKB signaling pathway. Graphical abstract.

Association between metabolic syndrome components and the risk of developing nephrolithiasis: A systematic review and bayesian meta-analysis

Background: There is increasing evidence that nephrolithiasis is a systemic disease, as opposed to an isolated urinary metabolic problem, after considerable links were found between nephrolithiasis and systemic diseases such as hypertension, obesity, dyslipidemia, and insulin resistance. The interplay between these four factors defines metabolic syndrome (MetS). In this review we aim to clarify the associations of MetS and its components to kidney stone incident. Methods: Online databases of EMBASE, MEDLINE, and Google Scholar were searched from January 1998 up to October 2020 to identify observational studies examining the association between metabolic syndrome components and kidney stone incident. Bayesian random-effects meta-analysis and meta-regression were performed to observe the association. Linear dose-response analysis was conducted to shape the direction of the association. Data analysis was performed using STATA, and R statistics. Results: A total of 25 potentially relevant studies (n = 934,588 participants) were eventually identified. The pooled results suggested that metabolic syndrome was associated with an increased risk of nephrolithiasis with an odds ratio (OR) of 1.769 (95% CI: 1.386 - 2.309).  The summary OR of hypertension and dyslipidemia for developing nephrolithiasis were 1.613 (95% CI: 1.213 - 2.169) and 1.586 (95% CI: 1.007 - 2.502) respectively. The presence of diabetes mellitus and obesity had an OR of 1.552 (95% CI: 1.027 - 2.344) and 1.531 (95% CI: 1.099 - 2.109) respectively. Our results revealed that the increasing number of MetS traits will increase the risk of developing nephrolithiasis, the higher the fasting plasma glucose, and body mass index, the higher the risk of kidney stones incident. Conclusions: Our results suggest that hypertension, diabetes, obesity and dyslipidemia are associated with increased risk of developing nephrolithiasis. Linear significant association between MetS components and nephrolithiasis were revealed in our study which reinforced the notion that should be considered a systemic disorder.

Higher Triglyceride-Glucose Index Is Associated With Increased Likelihood of Kidney Stones

AIMS

We aimed to assess the association between triglyceride-glucose (TyG) index and kidney stones in US adults.

METHODS

Data were obtained from the 2007-2014 National Health and Nutrition Examination Survey (NHANES). Participants aged ≥18 years who were not pregnant and provided complete data about TyG index and kidney stones were included in the analysis. Weighted multivariable regression analysis and subgroup analysis were preformed to estimate the independent relationship between TyG index and nephrolithiasis and recurrence.

RESULTS

A total of 20,972 participants were included with the mean TyG index of 8.71 ± 0.72. The prevalence rates of nephrolithiasis and recurrence were 9.30% and 3.17% overall and increased with the higher TyG index tertiles (Nephrolithiasis: Tertile 1, 6.98%; Tertile 2, 9.15%; Tertile 3, 11.98%, p < 0.01; Recurrence: Tertile 1, 1.84%; Tertile 2, 3.27%; Tertile 3, 4.50%, p < 0.01). Each unit increase in TyG index was associated with 12% and 26% higher odds of nephrolithiasis [odds ratio (OR) = 1.12; 95% CI: 1.02-1.22; p = 0.02] and recurrence (OR = 1.26; 95% CI: 1.08-1.46; p < 0.01). Interaction tests indicated no significant effect of gender, age, body mass index, hypertension, and diabetes on this association between TyG index and kidney stones.

CONCLUSIONS

Higher TyG index was associated with an increased likelihood of nephrolithiasis and recurrence. Considering TyG index is a reliable indicator of insulin resistance (IR). Treatment and management of IR at a younger age may improve or alleviate the occurrence and recurrence of kidney stones.

Sodium-coupled glucose transport, the SLC5 family, and therapeutically relevant inhibitors: from molecular discovery to clinical application

Sodium glucose transporters (SGLTs) belong to the mammalian solute carrier family SLC5. This family includes 12 different members in human that mediate the transport of sugars, vitamins, amino acids, or smaller organic ions such as choline. The SLC5 family belongs to the sodium symporter family (SSS), which encompasses transporters from all kingdoms of life. It furthermore shares similarity to the structural fold of the APC (amino acid-polyamine-organocation) transporter family. Three decades after the first molecular identification of the intestinal Na+-glucose cotransporter SGLT1 by expression cloning, many new discoveries have evolved, from mechanistic analysis to molecular genetics, structural biology, drug discovery, and clinical applications. All of these advances have greatly influenced physiology and medicine. While SGLT1 is essential for fast absorption of glucose and galactose in the intestine, the expression of SGLT2 is largely confined to the early part of the kidney proximal tubules, where it reabsorbs the bulk part of filtered glucose. SGLT2 has been successfully exploited by the pharmaceutical industry to develop effective new drugs for the treatment of diabetic patients. These SGLT2 inhibitors, termed gliflozins, also exhibit favorable nephroprotective effects and likely also cardioprotective effects. In addition, given the recent finding that SGLT2 is also expressed in tumors of pancreas and prostate and in glioblastoma, this opens the door to potential new therapeutic strategies for cancer treatment by specifically targeting SGLT2. Likewise, further discoveries related to the functional association of other SGLTs of the SLC5 family to human pathologies will open the door to potential new therapeutic strategies. We furthermore hope that the herein summarized information about the physiological roles of SGLTs and the therapeutic benefits of the gliflozins will be useful for our readers to better understand the molecular basis of the beneficial effects of these inhibitors, also in the context of the tubuloglomerular feedback (TGF), and the renin-angiotensin system (RAS). The detailed mechanisms underlying the clinical benefits of SGLT2 inhibition by gliflozins still warrant further investigation that may serve as a basis for future drug development.

Carbonic anhydrase influences asymmetric sodium and acetate transport across omasum of sheep

Objective

Omasum is an important site for the absorption of short chain fatty acids. The major route for the transport of acetate is via sodium hydrogen exchanger (NHE). However, a discrepancy in the symmetry of sodium and acetate transport has been previously reported, the mechanism of which is unclear. In this study, we investigated the possible role of carbonic anhydrase (CA) for this asymmetry.

Methods

Omasal tissues were isolated from healthy sheep (N = 3) and divided into four groups; pH 7.4 and 6.4 alone and in combination with Ethoxzolamide. Electrophysiological measurements were made using Ussing chamber and the electrical measurements were made using computer controlled voltage clamp apparatus. Effect(s) of CA inhibitor on acetate and sodium transport flux rate of Na²² and ¹⁴C-acetate was measured in three different flux time periods. Data were presented as mean±standard deviation and level of significance was ascertained at p≤0.05.

Results

Mucosal to serosal flux of Na (J_msNa) was greater than mucosal to serosal flux of acetate (J_msAc) when the pH was decreased from 7.4 to 6.4. However, the addition of CA inhibitor almost completely abolished this discrepancy (J_msNa ≈ J_msAc).

Conclusion

The results of the present study suggest that the additional protons required to drive the NHE were provided by the CA enzyme in the isolated omasal epithelium. The findings of this study also suggest that the functions of CA may be exploited for better absorption in omasum.

Glycemic Status, Insulin Resistance, and the Risk of Nephrolithiasis: A Cohort Study

RATIONALE & OBJECTIVE

The effect of glycemic status on nephrolithiasis risk remains controversial. This study sought to examine the association of glycemic status and insulin resistance with incident nephrolithiasis.

STUDY DESIGN

A retrospective cohort study.

SETTING & PARTICIPANTS

278,628 Korean adults without nephrolithiasis who underwent a comprehensive health examination between 2011 and 2017.

EXPOSURES

Glucose level, glycated hemoglobin level, and Homeostasis Model Assessment of Insulin Resistance (HOMA-IR).

OUTCOME

Nephrolithiasis ascertained using abdominal ultrasound.

ANALYTICAL APPROACH

A parametric proportional hazard model was used to estimate adjusted HRs and 95% CIs. We explored prespecified potential sex differences in the association of glycemic status and incident nephrolithiasis.

RESULTS

During a median follow-up of 4.2 years, 6,904 participants developed nephrolithiasis. Associations between levels of glycemic status and incident nephrolithiasis were examined separately in men and women (P for interaction = 0.003). Among men, multivariable-adjusted HRs for incident nephrolithiasis comparing glucose levels of 90-99, 100-125, and ≥ 126 mg/dL were 1.10 (95% CI, 1.01-1.19), 1.11 (95% CI, 1.02-1.21), and 1.27 (95% CI, 1.10-1.46), respectively, while HRs for incident nephrolithiasis comparing glycated hemoglobin levels of 5.7%-5.9%, 6.0%-6.4%, and 6.5%-<5.7% were 1.03 (95% CI, 0.96-1.10), 1.18 (95% CI, 1.07-1.31), and 1.20 (95% CI, 1.06-1.37), respectively. The HR for incident nephrolithiasis comparing the highest HOMA-IR quintile to the lowest quintile was 1.18 (95% CI, 1.06-1.31). Among women, no apparent association was found between glycemic status and nephrolithiasis risk.

LIMITATIONS

Glucose tolerance testing and computed tomography assessment for nephrolithiasis were not available.

CONCLUSIONS

Higher glycemic values, even within the normoglycemic range, and HOMA-IR were positively associated with increased risk for nephrolithiasis, associations that were only observed among men. Insulin resistance and hyperglycemia may contribute to the development of nephrolithiasis, particularly among men.

Low urine pH predicts new onset of diabetes mellitus during a 10-year period in men: BOREAS-DM1 study

Aims/Introduction

A low level of urine pH (U‐pH) has been reported to be associated with metabolic disorders. However, the relationship between the incidence of diabetes mellitus and U‐pH has not yet been fully addressed.

Materials and Methods

We investigated the relationship between U‐pH and the development of diabetes mellitus during a 10‐year period in a general population of individuals who received annual health examinations in 2006 (n = 28,990). After exclusion of individuals with missing data, and those with diabetes mellitus and/or chronic kidney disease at baseline, a total of 12,476 individuals (men/women: 8,027/4,449) who received health examinations at least once during the period from 2007 to 2016 were recruited. The recruited individuals were divided into four groups according to their U‐pH levels: groups of U‐pH ≤5.0, 5.5, 6.0 and ≥6.5.

Results

During a 10‐year period, 521 men (6.5%) and 132 women (3.0%) had new onset of diabetes mellitus. The cumulative incidence of diabetes mellitus was 7.5% (men/women: 9.3%/4.4%) per 100 person‐years. The hazard ratios (HRs) in the U‐pH ≤5.0 (HR 1.93) and U‐pH 5.5 groups (HR 1.46) were significantly higher than that in the U‐pH ≥6.5 group as a reference for men, but not for women. After adjustment of age, obesity, fasting glucose, smoking and alcohol drinking habits, family history of diabetes mellitus, and use of drugs for hypertension and dyslipidemia, HR in the U‐pH ≤5.0 group (HR 1.39) was significantly higher than that in the U‐pH ≥6.5 group for men, but not for women.

Conclusions

Low U‐pH predicts new onset of diabetes mellitus in a general population of men.

Insulin does not stimulate β-alanine transport into human skeletal muscle

To test whether high circulating insulin concentrations influence the transport of β-alanine into skeletal muscle at either saturating or subsaturating β-alanine concentrations, we conducted two experiments whereby β-alanine and insulin concentrations were controlled. In experiment 1, 12 men received supraphysiological amounts of β-alanine intravenously (0.11 g·kg−1·min−1for 150 min), with or without insulin infusion. β-Alanine and carnosine were measured in muscle before and 30 min after infusion. Blood samples were taken throughout the infusion protocol for plasma insulin and β-alanine analyses. β-Alanine content in 24-h urine was assessed. In experiment 2, six men ingested typical doses of β-alanine (10 mg/kg) before insulin infusion or no infusion. β-Alanine was assessed in muscle before and 120 min following ingestion. In experiment 1, no differences between conditions were shown for plasma β-alanine, muscle β-alanine, muscle carnosine and urinary β-alanine concentrations (all P > 0.05). In experiment 2, no differences between conditions were shown for plasma β-alanine or muscle β-alanine concentrations (all P > 0.05). Hyperinsulinemia did not increase β-alanine uptake by skeletal muscle cells, neither when substrate concentrations exceed the Vmaxof β-alanine transporter TauT nor when it was below saturation. These results suggest that increasing insulin concentration is not necessary to maximize β-alanine transport into muscle following β-alanine intake.

The SLC9A-C Mammalian Na+/H+ Exchanger Family: Molecules, Mechanisms, and Physiology

Na⁺/H⁺ exchangers play pivotal roles in the control of cell and tissue pH by mediating the electroneutral exchange of Na⁺ and H⁺ across cellular membranes. They belong to an ancient family of highly evolutionarily conserved proteins, and they play essential physiological roles in all phyla. In this review, we focus on the mammalian Na⁺/H⁺ exchangers (NHEs), the solute carrier (SLC) 9 family. This family of electroneutral transporters constitutes three branches: SLC9A, -B, and -C. Within these, each isoform exhibits distinct tissue expression profiles, regulation, and physiological roles. Some of these transporters are highly studied, with hundreds of original articles, and some are still only rudimentarily understood. In this review, we present and discuss the pioneering original work as well as the current state-of-the-art research on mammalian NHEs. We aim to provide the reader with a comprehensive view of core knowledge and recent insights into each family member, from gene organization over protein structure and regulation to physiological and pathophysiological roles. Particular attention is given to the integrated physiology of NHEs in the main organ systems. We provide several novel analyses and useful overviews, and we pinpoint main remaining enigmas, which we hope will inspire novel research on these highly versatile proteins.

Effect of renal tubule-specific knockdown of the Na+/H+ exchanger NHE3 in Akita diabetic mice

Na+/H+ exchanger isoform 3 (NHE3) contributes to Na+/bicarbonate reabsorption and ammonium secretion in early proximal tubules. To determine its role in the diabetic kidney, type 1 diabetic Akita mice with tubular NHE3 knockdown [Pax8-Cre; NHE3-knockout (KO) mice] were generated. NHE3-KO mice had higher urine pH, more bicarbonaturia, and compensating increases in renal mRNA expression for genes associated with generation of ammonium, bicarbonate, and glucose (phosphoenolpyruvate carboxykinase) in proximal tubules and H+ and ammonia secretion and glycolysis in distal tubules. This left blood pH and bicarbonate unaffected in nondiabetic and diabetic NHE3-KO versus wild-type mice but was associated with renal upregulation of proinflammatory markers. Higher renal phosphoenolpyruvate carboxykinase expression in NHE3-KO mice was associated with lower Na+-glucose cotransporter (SGLT)2 and higher SGLT1 expression, indicating a downward tubular shift in Na+ and glucose reabsorption. NHE3-KO was associated with lesser kidney weight and glomerular filtration rate (GFR) independent of diabetes and prevented diabetes-associated albuminuria. NHE3-KO, however, did not attenuate hyperglycemia or prevent diabetes from increasing kidney weight and GFR. Higher renal gluconeogenesis may explain similar hyperglycemia despite lower SGLT2 expression and higher glucosuria in diabetic NHE3-KO versus wild-type mice; stronger SGLT1 engagement could have affected kidney weight and GFR responses. Chronic kidney disease in humans is associated with reduced urinary excretion of metabolites of branched-chain amino acids and the tricarboxylic acid cycle, a pattern mimicked in diabetic wild-type mice. This pattern was reversed in nondiabetic NHE3-KO mice, possibly reflecting branched-chain amino acids use for ammoniagenesis and tricarboxylic acid cycle upregulation to support formation of ammonia, bicarbonate, and glucose in proximal tubule. NHE3-KO, however, did not prevent the diabetes-induced urinary downregulation in these metabolites.

Which Diet for Calcium Stone Patients: A Real-World Approach to Preventive Care

Kidney stone disease should be viewed as a systemic disorder, associated with or predictive of hypertension, insulin resistance, chronic kidney disease and cardiovascular damage. Dietary and lifestyle changes represent an important strategy for the prevention of kidney stone recurrences and cardiovascular damage. A full screening of risk factors for kidney stones and for cardiovascular damage should be recommended in all cases of calcium kidney stone disease, yet it is rarely performed outside of stone specialist clinics. Many patients have a history of kidney stone disease while lacking a satisfactory metabolic profile. Nonetheless, in a real-world clinical practice a rational management of kidney stone patients is still possible. Different scenarios, with different types of dietary approaches based on diagnosis accuracy level can be envisaged. The aim of this review is to give patient-tailored dietary suggestions whatever the level of clinical and biochemistry evaluation. This can help to deliver a useful recommendation, while avoiding excessive dietary restrictions especially when they are not based on a specific diagnosis, and therefore potentially useless or even harmful. We focused our attention on calcium stones and the different scenarios we may find in the daily clinical practice, including the case of patients who reported renal colic episodes and/or passed stones with no information on stone composition, urinary risk factors or metabolic cardiovascular risk factors; or the case of patients with partial and incomplete information; or the case of patients with full information on stone composition, urinary risk factors and metabolic cardiovascular profile.

Increased production and reduced urinary buffering of acid in uric acid stone formers is ameliorated by pioglitazone

Idiopathic uric acid nephrolithiasis is characterized by an overly acidic urine pH caused by the combination of increased acid production and inadequate buffering of urinary protons by ammonia. A large proportion of uric acid stone formers exhibit features of the metabolic syndrome. We previously demonstrated that thiazolidinediones improved the urinary biochemical profile in an animal model of the metabolic syndrome. In this proof-of-concept study, we examined whether the thiazolidinedione pioglitazone can also ameliorate the overly acidic urine in uric acid stone formers. Thirty-six adults with idiopathic uric acid nephrolithiasis were randomized to pioglitazone 30 mg/day or matching placebo for 24 weeks. At baseline and study end, participants underwent collection of blood and 24-hour urine in an inpatient research unit while consuming a fixed metabolic diet, followed by assessment of the ammoniagenic response to an acute oral acid load. Twenty-eight participants completed the study. Pioglitazone treatment improved features of the metabolic syndrome. Pioglitazone also reduced net acid excretion and increased urine pH (5.37 to 5.59), the proportion of net acid excreted as ammonium, and ammonium excretion in response to an acute acid load, whereas these parameters were unchanged with placebo. Treatment of patients with idiopathic uric acid nephrolithiasis with pioglitazone for 24 weeks led to a reduction in the acid load presented to the kidney and a more robust ammoniagenesis and ammonium excretion, resulting in significantly higher urine pH. Future studies should consider the impact of this targeted therapy on uric acid stone formation.

The mechanistic links between insulin and human organic anion transporter 4

Human organic anion transporter 4 (hOAT4) belongs to a class of organic anion transporters that exert critical function in the secretion, absorption, and distribution of numerous drugs in the body, such as anti-viral drugs, anti-cancer therapeutics, antibiotics, antihypertensive medicine, and anti-inflammatory drugs. hOAT4 is richly existent in the kidney and placenta. We previously established that serum- and glucocorticoid-inducible kinases (sgk) stimulate hOAT4 expression and transport activity by abrogating the inhibitory effect of a ubiquitin ligase Nedd4-2. Insulin is one of the upstream signaling molecules for sgk. We therefore investigated the effect of insulin on hOAT4 function. We showed that insulin stimulated hOAT4 expression and transport activity, and the action of insulin was abolished in cells overexpressing Nedd4-2-specific siRNA to knockdown the endogenous Nedd4-2. We further showed that insulin phosphorylated serine 327 on Nedd4-2 and weakened the interaction between hOAT4 and Nedd4-2. Interestingly, in cells overexpressing sgk2, the stimulatory effect of insulin on hOAT4 was diminished. In addition, the stimulatory effect of insulin on hOAT4 was blocked by wortmannin and buparlisib, two PI3K inhibitors. In conclusion, our study demonstrated that insulin stimulates hOAT4 expression and transport activity by abrogating the inhibition effect of Nedd4-2 on the transporter. Moreover, insulin regulates hOAT4 by competing with sgk2 rather than through sgk2.

Low urine pH is a risk for non-alcoholic fatty liver disease: A population-based longitudinal study

BACKGROUND

Low urine pH has a close association with insulin resistance. This study was aimed to investigate the association between urine pH and incident non-alcoholic fatty liver disease (NAFLD), which is associated with insulin resistance.

SUBJECTS AND METHODS

In this historical cohort study of 11,012 participants (5503 men and 5509 women), we investigated the effect of urine pH on incident NAFLD. NAFLD was defined as having fatty liver diagnosed by abdominal ultrasonography and excluding the participants consumed ethanol over 60g/day for men and 40g/day for women. We divided the participants into three groups according to urine pH; the lowest group (urine pH≤5.5), the middle group (urine pH=6.0) and the highest group (urine pH≥6.5). Cox proportional hazards models was performed to investigate the effect of urine pH on incident NAFLD, adjusting for age, sex, body mass index, smoking, exercise, alcohol consumption, alanine aminotransferase, triglycerides, systolic blood pressure, uric acid and fasting plasma glucose.

RESULTS

Over the median 6.8-year follow-up duration, 2023 participants developed NAFLD, and the crude proportions were 20.3% (case/N=1104/5447) in the lowest urine pH group, 16.3% (487/2989) in the middle urine pH group and 16.8% (432/2576) in the highest urine pH group. The lowest urine pH group showed a significantly higher risk for incident NAFLD than the highest urine pH group (adjusted hazard ratio 1.48, 95% confidence interval 1.31-1.66, P<0.001).

CONCLUSION

Low urine pH is associated with incident NAFLD. Our findings indicate that urine pH can be an additional data when considering further diagnostic investigation for NAFLD in patients who have other risk factors.

Renal tubular effects of prolonged therapy with the GLP-1 receptor agonist lixisenatide in patients with type 2 diabetes mellitus

Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) are well-established glucose-lowering drugs for type 2 diabetes mellitus (T2DM) management. Acute GLP-1RA administration increases urinary excretion of sodium and other electrolytes. However, the renal tubular effects of prolonged GLP-1RA treatment are largely unknown. In this secondary analysis of a randomized trial, we determined the renal tubular effects of 8-wk treatment with 20 μg lixisenatide, a short-acting (prandial) GLP-1RA, versus titrated once-daily insulin glulisine in 35 overweight T2DM-patients on stable insulin glargine background therapy (age: 62 ± 7 yr, glycated hemoglobin: 8.0 ± 0.9%, estimated glomerular filtration rate: >60 ml·min^-1·1.73 m^-2). After a standardized breakfast, lixisenatide increased absolute and fractional excretions of sodium, chloride, and potassium and increased urinary pH. In contrast, lixisenatide reduced absolute and fractional excretions of magnesium, calcium, and phosphate. At week 8, patients treated with lixisenatide had significantly more phosphorylated sodium-hydrogen exchanger isoform 3 (NHE3) in urinary extracellular vesicles than those on insulin glulisine treatment, which suggested decreased NHE3 activity in the proximal tubule. A rise in postprandial blood pressure with lixisenatide partly explained the changes in the urinary excretion of sodium, potassium, magnesium, and phosphate and the changes in urinary pH. In conclusion, lixisenatide affects postprandial urinary excretion of several electrolytes and increases urinary pH compared with insulin glulisine in T2DM patients after 8 wk of treatment. This is most likely explained by a drug-induced rise in blood pressure or direct inhibitory effects on NHE3 in the proximal tubule.

Low Urine pH Is Associated with Non-alcoholic Fatty Liver Disease: A Community-based Cross-sectional Study

Objective Low urine pH is associated with several metabolic diseases, such as dyslipidemia, diabetes, and metabolic syndrome. However, the association between low urine pH and non-alcoholic fatty liver disease (NAFLD) remains unknown. Therefore, we conducted a community-based cross-sectional study to investigate this association. Methods Between April 2013 and March 2014, the records of 4,945 Japanese subjects who had undergone annual health checkups were reviewed to identify subjects who met the diagnostic criteria for NAFLD. Patients Based on urine pH, the participants were classified into four groups; a low urine pH was defined as ≤5.5. Of the 3,411 subjects who qualified for enrollment, 1,028 met the diagnostic criteria for NAFLD. Results The prevalence of NAFLD was significantly increased with decreasing urine pH in both men and women (p<0.01 and p=0.02, respectively). A multivariate analysis, including adjustments for age, metabolic markers, and the renal function, showed a significant association between low urine pH and NAFLD in men and women (odds ratio, 1.37; 95% confidence interval, 1.01-1.85, p=0.04 and odds ratio, 1.73; 95% confidence interval, 1.15-2.62, p<0.01, respectively). Conclusion Our study indicates that NAFLD is associated with a low urine pH in both sexes, findings that might help clinicians identify patients at high risk for NAFLD.

Relationship between urine pH and abnormal glucose tolerance in a community-based study

AIMS/INTRODUCTION

The association between urine pH and abnormal glucose tolerance in men and women is unclear; therefore, we carried out a community-based, cross-sectional study to investigate sex-specific associations between these values, possible indicators of prediabetes and type 2 diabetes.

MATERIALS AND METHODS

We enrolled 4,945 Japanese individuals (2,490 men and 2,455 women), who had undergone annual health checkups. To investigate the relationship between low urine pH and abnormal glucose tolerance, participants were divided into three groups based on their fasting plasma glucose levels (<6.11 mmol/L, 6.11-6.99 mmol/L and ≥6.99 mmol/L), and three groups based on their glycated hemoglobin levels (≤44.3 mmol/mol, 44.3-47.5 mmol/mol and ≥47.5 mmol/mol). To examine the effects of urine pH on abnormal glucose tolerance, participants were categorized into five groups based on their urine pH (5.0, 5.5, 6.0, 6.5 and ≥7.0).

RESULTS

Multivariate analysis adjusted for age, body mass index, systolic blood pressure, triglycerides, high-density lipoprotein cholesterol, uric acid, creatinine and antidiabetic agent use showed significant associations between low urine pH and both high fasting plasma glucose and high glycated hemoglobin levels (P for trend = 0.0260, 0.0075) in men. Furthermore, after the same adjustments, prevalence rates of abnormal glucose tolerance (≥6.11 mmol/L and ≥6.99 mmol/L), increased significantly as urine pH levels decreased (P for trend = 0.0483, 0.0181) in men. In women, a similar trend was observed without a significant difference.

CONCLUSIONS

Low urine pH is significantly associated with abnormal glucose tolerance; therefore, measuring urine pH might prove useful for identifying patients at high risk for diabetes.

Obesity and kidney stone disease: a systematic review

INTRODUCTION

Currently, abdominal obesity has reached an epidemic stage and obesity represents an important challenge for worldwide health authorities. Epidemiologic studies have demonstrated that the stone risk incidence increases with Body Mass Index, through multiple pathways. Metabolic syndrome and diabetes are associated with an increased renal stones disease incidence. The aim of this systematic review was to investigate the prevalence, morbidity, risk factors involved in the association between obesity and urolithiasis.

EVIDENCE ACQUISITION

The search involved finding relevant studies from MEDLINE, EMBASE, Ovid, the Cochrane Central Register of Controlled Trials, CINAHL, Google Scholar, and individual urological journals between January 2001 and May 2017. The inclusion criteria were for studies written in the English language, reporting on the association between obesity and urinary stones.

EVIDENCE SYNTHESIS

The underlying pathophysiology of stone formation in obese patients is thought to be related to insulin resistance, dietary factors, and a lithogenic urinary profile. Uric acid stones and calcium oxalate stones are observed frequently in these patients. Insulin resistance is thought to alter the renal acid-base metabolism, resulting in a lower urine pH, and increasing the risk of uric acid stone disease. Obesity is also associated with excess nutritional intake of lithogenic substances and with an increase in urinary tract infection incidence. Recent studies highlighted that renal stone disease increases the risk of myocardial infarction, progression of chronic kidney disease, and diabetes. Contemporary, bariatric surgery has been shown to be associated with hyperoxaluria and oxalate nephropathy. Certainly, the many health risks of obesity, including nephrolithiasis, will add more burden on urologists and nephrologists.

CONCLUSIONS

Obesity related nephrolithiasis seems to necessitate weight loss as primary treatment, but the recognition of the associated complications is necessary to prevent induction of new and equally severe medical problems. The optimal approach to obesity control that minimizes stone risk needs to be determined in order to manage obesity-induced renal stones disease.

Obesity and kidney disease: Hidden consequences of the epidemic

Obesity has become a worldwide epidemic, and its prevalence has been projected to grow by 40% in the next decade. This increasing prevalence has implications for the risks of diabetes, cardiovascular disease and also for Chronic Kidney Disease. A high body mass index is one of the strongest risk factors for new-onset Chronic Kidney Disease. In individuals affected by obesity, a series of complex pathophysiologic changes occur that lead to the development of Chronic Kidney Disease. These include on the one hand effects mediated by the downstream consequences of obesity (such as diabetes mellitus and hypertension), but also direct effects of adipose tissue, via humoral factors such as leptin, adiponectin, resistin and visfatin). In obese individuals a compensatory hyperfiltration occurs to meet the heightened metabolic demands of the increased body weight, leading to glomerulomegaly and accompanied by deposition of adipose tissue in the glomerulus and the gradual development of focal segmental glomerulosclerosis. The incidence of obesity-related glomerulopathy has increased ten-fold in recent years. In addition to the development of Chronic Kidney Disease, obesity has also been shown to be a risk factor for nephrolithiasis, and for a number of malignancies including kidney cancer. Interventions to stem the tide of obesity are thus extremely important for preventing the development and progression of Chronic Kidney Disease and other disorders of the kidneys. This year the World Kidney Day promotes education on the harmful consequences of obesity and its association with kidney disease, advocating healthy lifestyle and health policy measures that makes preventive behaviors an affordable option.

Metabolic and Hypertensive Complications of Pregnancy in Women with Nephrolithiasis

BACKGROUND AND OBJECTIVES

Kidney stones are associated with future development of hypertension, diabetes, and the metabolic syndrome. Our objective was to assess whether stone formation before pregnancy was associated with metabolic and hypertensive complications in pregnancy. We hypothesized that stone formation is a marker of metabolic disease and would be associated with higher risk for maternal complications in pregnancy.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a retrospective cohort study of women who delivered infants at the Massachusetts General Hospital from 2006 to 2015. Women with abdominal imaging (computed tomography or ultrasound) before pregnancy were included in the analysis. Pregnancy outcomes in women with documented kidney stones on imaging (stone formers, n=166) were compared with those of women without stones on imaging (controls, n=1264). Women with preexisting CKD, hypertension, and diabetes were excluded.

RESULTS

Gestational diabetes and preeclampsia were more common in stone formers than nonstone formers (18% versus 6%, respectively; P<0.001 and 16% versus 8%, respectively; P=0.002). After multivariable adjustment, previous nephrolithiasis was associated with higher risks of gestational diabetes (adjusted odds ratio, 3.1; 95% confidence interval, 1.8 to 5.3) and preeclampsia (adjusted odds ratio, 2.2; 95% confidence interval, 1.3 to 3.6). Infants of stone formers were born earlier (38.7±2.0 versus 39.2±1.7 weeks, respectively; P=0.01); however, rates of small for gestational age offspring and neonatal intensive care admission were similar between groups (8% versus 7%, respectively; P=0.33 and 10% versus 6%, respectively; P=0.08). First trimester body mass index significantly influenced the association between stone disease and hypertensive complications of pregnancy: in a multivariable linear regression model, stone formation acted as an effect modifier of the relationship between maximum systolic BP in the third trimester and body mass index (P interaction <0.001).

CONCLUSIONS

In women without preexisting diabetes, hypertension, and CKD, a history of nephrolithiasis was associated with gestational diabetes and hypertensive disorders of pregnancy, especially in women with high first trimester body mass index.

Preservation of renal function in chronic diabetes by enhancing glomerular glucose metabolism

Diabetic nephropathy (DN) affects approximately 30-40% of patients with type 1 (T1DM) and type 2 diabetes (T2DM). It is a major cause of end-stage renal disease (ESRD) for the developed world. Hyperglycemia and genetics are major causal factors for the initiation and progression of DN. Multiple abnormalities in glucose and mitochondrial metabolism induced by diabetes likely contribute to the severity of DN. Recent clinical studies in people with extreme duration of T1DM (> 50 years, Joslin Medalist Study) have supported the importance of endogenous protective factors to neutralize the toxic effects of hyperglycemia on renal and other vascular tissues. Using renal glomeruli from these patients (namely Medalists) with and without DN, we have shown the importance of increased glycolytic flux in decreasing the accumulation of glucose toxic metabolites, improving mitochondrial function, survival of glomerular podocytes, and reducing glomerular pathology. Activation of a key glycolytic enzyme, pyruvate kinase M2 (PKM2), resulted in the normalization of renal hemodynamics and mitochondrial and glomerular dysfunction, leading to the mitigation of glomerular pathologies in several mouse models of DN.

The impact of body mass index on quantitative 24-h urine chemistries in stone forming patients: a systematic review and meta-analysis

To study the impact of body mass index (BMI) on quantitative 24-h urine chemistries in stone forming patients and to explore how overweight and obesity contribute to urolithiasis. A systematic search of PubMed, EMBASE, Cochrane Library, and Web of Science was performed in July 2017 and updated in October 2017 to detect relevant studies. After that, we screened all the relevant articles in accordance with the predetermined inclusion and exclusion criteria. Data of eligible studies were extracted, and then, a meta-analysis was conducted via RevMan 5.3 software. Nine studies, involving 5965 stone forming patients who underwent 24-h urine collection for chemistry analysis, were included in our analysis. BMI was used to clarify the body size. BMI ≥ 25 kg/m² group, including overweight and obesity patients, erected more calcium (WMD 34.44 mg; 95% CI 11.33-57.55; p = 0.003), oxalate (WMD 3.44 mg; 95% CI 1.40-5.49; p = 0.001), urate (WMD 97.71 mg; 95% CI 63.05-132.38; p < 0.00001), and sodium (WMD 26.64 mg; 95% CI 18.23-35.05; p < 0.00001) in 24 h than BMI < 25 kg/m² group. However, the BMI < 25 kg/m² group showed higher pH of urine (WMD 0.12; 95% CI 0.04-0.20; p = 0.004). There was no significant difference in 24-h urine volume (WMD - 29.30 ml; 95% CI - 122.03 to - 63.42; p = 0.54), citrate (WMD - 34.03 mg; 95% CI - 72.88 to 4.82; p = 0.09), magnesium (WMD - 4.50 mg; 95% CI - 10.48 to 1.48; p = 0.14), phosphate (WMD - 89.38 mg; 95% CI - 219.23 to 40.47; p = 0.18), and creatinine (WMD - 191.98 mg; 95% CI - 395.35 to 11.38; p = 0.06) between the two groups. All the results kept the same tendency when gender was taken in consideration. Sensitivity analysis generated similar results. The current evidence suggested that patients with BMI ≥ 25 kg/m² erected more promotions but not inhibitors of urolithiasis than those with BMI < 25 kg/m², which increased the risk of urolithiasis in overweight and obesity individuals.

Non-alcoholic fatty liver disease and the development of nephrolithiasis: A cohort study

Background

Non-alcoholic fatty liver disease (NAFLD), a hepatic manifestation or precursor of metabolic syndrome, may increase nephrolithiasis, a renal manifestation of insulin resistance, but the prospective association between NAFLD and incident nephrolithiasis has not been evaluated. We examined the association of NAFLD with the development of nephrolithiasis in a large cohort of Korean men and women.

Methods

We performed a cohort study of 208,578 Korean adults who underwent a health checkup examination between January 2002 and December 2014 and were followed-up annually or biennially through December 2014. NAFLD was defined as the presence of fatty liver in the absence of excessive alcohol use or other identifiable causes. Fatty liver and nephrolithiasis were determined based on ultrasonographic findings. We used a parametric Cox model to estimate the adjusted hazard ratios (HRs) of nephrolithiasis according to the presence of NAFLD.

Results

During 1,054,887.6 person-year of follow-up, 16,442 participants developed nephrolithiasis. After adjusting for age, center, year of screening exam, smoking status, alcohol intake, physical activity, education level, body mass index, history of hypertension and diabetes, HOMA-IR, uric acid and C-reactive protein, male participants with NAFLD had a significantly increased risk of nephrolithiasis than those without NAFLD (adjusted HR 1.17, 95% CI 1.06–1.30). However, no association between NAFLD and nephrolithiasis was observed in women (adjusted HR 0.97, 95% CI 0.81–1.16).

Conclusions

In this large cohort study of young and middle-aged Koreans, NAFLD was significantly associated with an increased incidence of nephrolithiasis in men but not in women.

Increases in the expression of Na+ /H+ exchanger 1 and 3 are associated with insulin signalling in the ruminal epithelium

Na⁺ /H⁺ exchanger (NHE), which catalyses the exchange of extracellular Na⁺ for intracellular H⁺ , is of importance in the maintenance of Na⁺ and pH homoeostasis for rumen epithelial cells. Studies in ruminants showed that high concentrate diets could increase the expression of NHE in ruminal epithelium. Results of recent studies further indicated that insulin, as an important hormone closely related to dietary concentrate, could enhance the expression of NHE. In this study, we have investigated the mechanisms of insulin regulating the expression of NHE in rumen epithelial cells and its potential role in dietary modulation of NHE expression in ruminal epithelium of cows. In primary culture, insulin increased phosphorylation of ERK 1/2 and AKT in rumen epithelial cells. However, this promotion was diminished by insulin receptor inhibitor. Insulin also stimulated NHE1 and NHE3 expression. But this increase was suppressed by insulin receptor inhibitor, ERK inhibitor and AKT inhibitor. In the present animal experiment, NHE1 and NHE3 expression increased in rumen epithelium of cows ingesting a high concentrate diet (HC, 60% concentrate), accompanied by increased insulin concentration in plasma, compared to those feeding a low concentrate diet (LC, 20% concentrate). Furthermore, the phosphorylation of ERK1/2 and AKT was higher in the rumen epithelium of the HC group than those in the LC group. Collectively, these results indicate that diet-dependent change of NHE1 and NHE3 abundance was mediated, at least in part, by plasma insulin through the ERK and AKT pathway.

Urinary pH is a predictor of diabetes in men; a population based large scale cohort study

AIMS

Previous cross-sectional studies revealed that patients with type 2 diabetes were associated with low urine pH. However, the association between urinary pH and incident type 2 diabetes is still unclear. Thus, we investigated the association between urinary pH and incident type 2 diabetes.

METHODS

This is a 5-year observational study of 3119men. We divided participants into four groups according to quartile of urinary pH. Multivariate logistic regression analysis was performed to calculate adjusted odds ratios (ORs) and 95% CIs for incident type 2 diabetes. We adjusted for age, body mass index, smoking, exercise, alcohol consumption, hypertension, hypertriglyceridemia, low high-density lipoprotein cholesterol levels and impaired fasting glycaemia.

RESULTS

In the follow-up examination, 113men diagnosed as diabetes. The proportion of incident diabetes was 6.9% (case/N=22/318) in the lowest urinary pH group (urinary pH = 5.0), 3.4% (46/1366) in the second lowest group (urinary pH = 5.5), 3.5% (30/856) in the third lowest group (urinary pH = 6.0) and 2.6% (15/579) in the highest group (urinary pH≥6.5). The lowest urinary pH group was associated with the increased risk of incident diabetes compared to the other urinary pH groups (multivariate OR=1.91, 95% CI 1.05-3.36, p=0.033 for the second lowest, multivariate OR=1.99, 95% CI 1.05-3.71, p=0.036 for the third lowest and multivariate OR 2.69, 95% CI 1.30-5.72, p=0.008 for the highest urinary pH groups).

CONCLUSIONS

Low urine pH is an independent predictor of diabetes. We suggest that the urine pH can be an easy practical marker for diabetes.

Obesity and kidney disease: Hidden consequences of the epidemic

Obesity has become a worldwide epidemic, and its prevalence has been projected to grow by 40% in the next decade. This increasing prevalence has implications for the risk of diabetes, cardiovascular disease, and also for chronic kidney disease (CKD). A high body mass index is one of the strongest risk factors for new-onset CKD. In individuals affected by obesity, a compensatory hyperfiltration occurs to meet the heightened metabolic demands of the increased body weight. The increase in intraglomerular pressure can damage the kidneys and raise the risk of developing CKD in the long-term. The incidence of obesity-related glomerulopathy has increased tenfold in recent years. Obesity has also been shown to be a risk factor for nephrolithiasis, and for a number of malignancies including kidney cancer. This year the World Kidney Day promotes education on the harmful consequences of obesity and its association with kidney disease, advocating healthy lifestyle, and health policy measures that makes preventive behaviors an affordable option.

Obesity and kidney disease: hidden consequences of the epidemic

Obesity has become a worldwide epidemic and its prevalence has been projected to grow by 40% in the next decade. This increasing prevalence has implications for the risk of diabetes, cardiovascular disease and also for chronic kidney disease (CKD). A high body mass index is one of the strongest risk factors for new-onset CKD. In individuals affected by obesity, a compensatory hyperfiltration occurs to meet the heightened metabolic demands of the increased body weight. The increase in intraglomerular pressure can damage the kidneys and raise the risk of developing CKD in the long-term. The incidence of obesity-related glomerulopathy has increased ten-fold in recent years. Obesity has also been shown to be a risk factor for nephrolithiasis, and for a number of malignancies including kidney cancer. This year, the World Kidney Day will promote education on the harmful consequences of obesity and its association with kidney disease, advocating healthy lifestyle and health policy measures that make preventive behaviors an affordable option.

Development of Nephrolithiasis in Asymptomatic Hyperuricemia: A Cohort Study

BACKGROUND

Although the association between gout and nephrolithiasis is well known, the relationship between asymptomatic hyperuricemia and the development of nephrolithiasis is largely unknown.

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

239,331 Korean adults who underwent a health checkup examination during January 2002 to December 2014 and were followed up annually or biennially through December 2014.

PREDICTOR

Baseline serum uric acid levels of participants.

OUTCOME

The development of nephrolithiasis during follow-up.

MEASUREMENTS

Nephrolithiasis is determined based on ultrasonographic findings. A parametric Cox model was used to estimate the adjusted HRs of nephrolithiasis according to serum uric acid level.

RESULTS

During 1,184,653.8 person-years of follow-up, 18,777 participants developed nephrolithiasis (incidence rate, 1.6/100 person-years). Elevated uric acid level was significantly associated with increased risk for nephrolithiasis in a dose-response manner (P for trend < 0.001) in men. This dose-response association was not observed in women. In male participants, multivariable-adjusted HRs for incident nephrolithiasis comparing uric acid levels of 6.0 to 6.9, 7.0 to 7.9, 8.0 to 8.9, 9.0 to 9.9, and ≥10.0mg/dL with uric acid levels < 6.0mg/dL were 1.06 (95% CI, 1.02-1.11), 1.11 (95% CI, 1.05-1.16), 1.21 (95% CI, 1.13-1.29), 1.31 (95% CI, 1.17-1.46), and 1.72 (95% CI, 1.44-2.06), respectively. This association was observed in all clinically relevant subgroups and persisted even after adjustment for homeostasis model assessment of insulin resistance and high-sensitivity C-reactive protein level.

LIMITATIONS

Dietary information and computed tomographic diagnosis of nephrolithiasis were unavailable.

CONCLUSIONS

In this large cohort study, increased serum uric acid level was modestly and independently associated with increased risk for the development of nephrolithiasis in a dose-response manner in apparently healthy men.

Obesity and Kidney Disease: Hidden Consequences of the Epidemic

Obesity has become a worldwide epidemic, and its prevalence has been projected to grow by 40% in the next decade. This increasing prevalence has implications for the risk of diabetes, cardiovascular disease, and also for chronic kidney disease (CKD). A high body mass index is one of the strongest risk factors for new-onset CKD. In individuals affected by obesity, a compensatory hyperfiltration occurs to meet the heightened metabolic demands of the increased body weight. The increase in intraglomerular pressure can damage the kidneys and raise the risk of developing CKD in the long term. The incidence of obesity-related glomerulopathy has increased 10-fold in recent years. Obesity has also been shown to be a risk factor for nephrolithiasis, and for a number of malignancies including kidney cancer. This year the World Kidney Day promotes education on the harmful consequences of obesity and its association with kidney disease, advocating healthy lifestyle and health policy measures that make preventive behaviors an affordable option.