Causes of nephrotic syndrome in Sweden: The relevance of clinical presentation and demographics.

Background: Many pathological processes can disrupt the integrity of the glomerular capillary wall and cause a massive leakage of protein, resulting in nephrotic syndrome (NS). Clinical parameters such as age, sex, renal function, presence of diabetes, and how NS is defined influence the spectrum of underlying diseases. In this study, we examine how these parameters interact. Methods: Age, sex, hematuria, proteinuria, plasma creatinine plasma albumin levels, and final diagnosis were retrieved for all adult patients with NS as an indication for biopsy and/or massive albuminuria in conjunction with low plasma albumin from the biopsy module of the Swedish Renal Registry (SRR) between 2014 and 2019. A basic calculator was developed to demonstrate the importance of clinical presentation in relation to the likelihood of having a specific diagnosis. Results: A total of 913 unique patients were included in the study. Diabetic nephropathy (DN) and membranous nephropathy (MN) (both found in 17% of patients) were the most common diagnoses. With a stringent definition of NS, MN and minimal change nephropathy (MCN) increased in proportion. Among the cohort as a whole, MCN was the most frequent diagnosis in women and those < 50 years of age (found in 21% and 17%, respectively). In the case of patients aged between 50 and 70 years, those with chronic kidney disease stage 4, and those with negative dipstick tests for hematuria, the most common underlying disease was DN (in 23%, 30%, and 21% of cases, respectively). Among those with high-grade hematuria (dipstick grade 3 or 4), membranoproliferative glomerulonephritis was the most common diagnosis (14%), closely followed by IgA nephropathy (13%). Focal segmental glomerulosclerosis (9.7%) was less common than in many comparable studies. Conclusion: Clinical parameters have a profound impact on the likelihood of different diagnoses in adult patients with NS. Differences in clinical practice and study inclusion criteria may be more important than genetic background and environmental factors when explaining differences between studies in different parts of the world.

Increased mortality in non-alcoholic fatty liver disease with chronic kidney disease is explained by metabolic comorbidities.

BACKGROUND: There is a close association between non-alcoholic fatty liver disease (NAFLD) and prevalent chronic kidney disease (CKD). Few longitudinal studies exist. No previous study has investigated to what extent CKD affects mortality in biopsy-proven NAFLD. Our aim was to investigate the long-term risk of developing CKD in biopsy-proven NAFLD and its effect on mortality. METHODS: Patients with biopsy-proven NAFLD diagnosed in 1978-2006 in Malmö, Sweden were included. Estimated glomerular filtration rate (eGFR) at baseline and last follow-up was calculated with the CKD-EPI equation. CKD 3-5 (< 60 mL/min/1.73 m2) was classified as CKD. Hospital medical records were extensively scrutinized from inclusion to endpoint (death or end of 2016). The prevalence of CKD was compared to a control group from the population-based prospective cohort Malmö Preventive Project (MPP). RESULTS: 120 patients with biopsy-proven NAFLD were included. Mean age was 52.5 years and mean follow-up time 19.5 years. At baseline CKD prevalence in NAFLD was only significantly higher in the highest age group compared to controls (> 55 years, 25% vs. 9.5%, P = 0.003), and no significant difference was seen at follow-up (in total 37.5% vs. 30.8%, P = 0.124). NAFLD patients with long-term CKD had significantly higher crude overall mortality rate than NAFLD patients without CKD (P < 0.001). Regression analyses revealed that this increased mortality risk was explained by an increased prevalence of metabolic comorbidities (including diabetes mellitus), not CKD. CONCLUSION: Mortality risk is significantly increased in NAFLD patients with long-term CKD due to metabolic comorbidities, not influenced by CKD per se.

Influence of mitochondrial inhibition on global and local [Ca(2+)](I) in rat tail artery.

Inhibition of oxidative metabolism is often found to decrease contractility of systemic vascular smooth muscle, but not to reduce global [Ca(2+)](i). In the present study, we probe the hypothesis that it is associated with an altered pattern of intracellular Ca(2+) oscillations (waves) influencing force development. In the rat tail artery, mitochondrial inhibitors (rotenone, antimycin A, and cyanide) reduced alpha(1)-adrenoceptor-stimulated force by 50% to 80%, but did not reduce global [Ca(2+)](i). Less relaxation (about 30%) was observed after inhibition of myosin phosphatase activity with calyculin A, suggesting that part of the metabolic sensitivity involves the regulation of myosin 20-kDa light chain phosphorylation, although no decrease in phosphorylation was found in freeze-clamped tissue. Confocal imaging revealed that the mitochondrial inhibitors increased the frequency but reduced the amplitude of asynchronous cellular Ca(2+) waves elicited by alpha(1) stimulation. The altered wave pattern, in association with increased basal [Ca(2+)](i), accounted for the unchanged global [Ca(2+)](i). Inhibition of glycolytic ATP production by arsenate caused similar effects on Ca(2+) waves and global [Ca(2+)](i), developing gradually in parallel with decreased contractility. Inhibition of wave activity by the InsP(3) receptor antagonist 2-APB correlated closely with relaxation. Furthermore, abolition of waves with thapsigargin in the presence of verapamil reduced force by about 50%, despite unaltered global [Ca(2+)](i), suggesting that contraction may at least partly depend on Ca(2+) wave activity. This study therefore indicates that mitochondrial inhibition influences Ca(2+) wave activity, possibly due to a close spatial relationship of mitochondria and the sarcoplasmic reticulum and that this contributes to metabolic vascular relaxation.

Cholesterol depletion impairs vascular reactivity to endothelin-1 by reducing store-operated Ca2+ entry dependent on TRPC1.

The reactivity of the vascular wall to endothelin-1 (ET-1) is influenced by cholesterol, which is of possible importance for the progression of atherosclerosis. To elucidate signaling steps affected, the cholesterol acceptor methyl-beta-cyclodextrin (mbetacd, 10 mmol/L) was used to manipulate membrane cholesterol and disrupt caveolae in intact rat arteries. In endothelium-denuded caudal artery, contractile responsiveness to 10 nmol/L ET-1 (mediated by the ETA receptor) was reduced by mbetacd and increased by cholesterol. Neither ligand binding nor colocalization of ETA and caveolin-1 was affected by mbetacd. Ca2+ inflow via store-operated channels after depletion of intracellular Ca2+ stores was reduced in mbetacd-treated caudal arteries, as shown by Mn2+ quench rate and intracellular [Ca2+] response. Expression of TRPC1, 3, and 6 was detected by reverse transcriptase-polymerase chain reaction, and colocalization of TRPC1 with caveolin-1 was reduced by mbetacd, as seen by immunofluorescence. Part of the contractile response to ET-1 was inhibited by Ni2+ (0.5 mmol/L) and by a TRPC1 blocking antibody. In the basilar artery, exhibiting less store-operated channel activity than the caudal artery, ET-1-induced contractions were insensitive to the TRPC1 blocking antibody and to mbetacd. Increased store-operated channel activity in basilar arteries after organ culture correlated with increased sensitivity of ET-1 contraction to mbetacd. These results suggest that cholesterol influences vascular reactivity to ET-1 by affecting the caveolar localization of TRPC1.

Cholesterol depletion disrupts caveolae and differentially impairs agonist-induced arterial contraction.

OBJECTIVE: This study assessed the role of cholesterol-rich membrane regions, including caveolae, in the regulation of arterial contractility. Methods and Results- Rat tail artery devoid of endothelium was treated with the cholesterol acceptor methyl-beta-cyclodextrin, and the effects on force and Ca2+ handling were evaluated. In cholesterol-depleted preparations, the force responses to alpha1-adrenergic receptors, membrane depolarization, inhibition of myosin light chain phosphatase, and activation of G proteins with a mixture of 20 mmol/L NaF and 60 micro mol/L AlCl3 were unaffected. In contrast, responses to 5-hydroxytryptamine (5-HT), vasopressin, and endothelin were reduced by >50%. The rise in global intracellular free Ca2+ concentration in response to 5-HT was attenuated, as was the generation of Ca2+ waves at the cellular level. By electron microscopy, cholesterol depletion was found to disrupt caveolae. The 5-HT response could be restored by exogenous cholesterol, which also restored caveolae. Western blots showed that the levels of 5-HT2A receptor and of caveolin-1 were unaffected by cholesterol extraction. Sucrose gradient centrifugation showed enrichment of 5-HT2A receptors, but not alpha1-adrenergic receptors, in the caveolin-1-containing fractions, suggesting localization of the former to caveolae. CONCLUSIONS: These results show that a subset of signaling pathways that regulate smooth muscle contraction depends specifically on cholesterol. Furthermore, the cholesterol-dependent step in serotonergic signaling occurs early in the pathway and depends on the integrity of caveolae.

Plasticity of TRPC expression in arterial smooth muscle: correlation with store-operated Ca2+ entry.

Loss of the smooth muscle contractile phenotype is critical in atherosclerosis and in restenosis after angioplasty, but its early signals are incompletely understood. In this study, we have explored the role of transient receptor potential canonical (TRPC) proteins, which have been suggested to mediate store-operated Ca2+ entry (SOCE). Contractility of rat cerebral arteries in organ culture is preserved for several days, whereas SOCE is increased. In correlation with this increase is that nifedipine-insensitive whole cell current, activated by depletion of intracellular Ca2+ stores, was increased by 50% in cells isolated from arteries cultured for 3 days. TRPC1 and TRPC6 mRNA were more than fivefold increased in cells isolated after organ culture, whereas TRPC3 was decreased. Immunofluorescent staining and/or Western blotting of arteries and isolated cells showed upregulation of TRPC1 and TRPC6 proteins during organ culture. In intact arteries, TRPC4 expression correlated with the amount of endothelium present. Ca2+ addition after store depletion caused a contraction in cultured, but not in freshly dissected, arteries. A polyclonal TRPC1 antibody directed against an extracellular epitope inhibited this contraction by approximately 50%. To investigate the basis of the TRPC upregulation and assess its possible clinical significance, segments of human internal mammary artery were organ cultured for 24 h and then exposed to balloon dilatation in vitro, followed by further culturing for up to 48 h. After dilatation, TRPC1 and TRPC6 mRNA were progressively increased compared with undilated control segments. The results of this study indicate that vascular injury enhances plasticity in TRPC expression, that TRPC expression correlates with cellular Ca2+ handling, and that TRPC1 is a subunit of upregulated store-operated Ca2+ channels.

Effects of oxygen tension on energetics of cultured vascular smooth muscle.

Chronic hypoxia is a clinically important condition known to cause vascular abnormalities. To investigate the cellular mechanisms involved, we kept rings of a rat tail artery for 4 days in hypoxic culture (HC) or normoxic culture (NC) (PO(2) = 14 vs. 110 mmHg) and then measured contractility, oxygen consumption (JO(2)), and lactate production (J(lac)) in oxygenated medium. Compared with fresh rings, basal ATP turnover (J(ATP)) was decreased in HC, but not in NC, with a shift from oxidative toward glycolytic metabolism. JO(2) during mitochondrial uncoupling was reduced by HC but not by NC. Glycogen stores were increased 40-fold by HC and fourfold by NC. Maximum tension in response to norepinephrine and the JO(2) versus tension relationship (JO(2) vs. high K(+) elicited force) were unaffected by either HC or NC. Force transients in response to caffeine were increased in HC, whereas intracellular Ca(2+) wave activity during adrenergic stimulation was decreased. Protein synthesis rate was reduced by HC. The results show that long-term hypoxia depresses basal energy turnover, impairs mitochondrial capacity, and alters Ca(2+) homeostasis, but does not affect contractile energetics. These alterations may form a basis for vascular damage by chronic hypoxia.