The complexity of kidney disease and diagnosing it - cystatin C, selective glomerular hypofiltration syndromes and proteome regulation.

Estimation of kidney function is often part of daily clinical practice, mostly done by using the endogenous glomerular filtration rate (GFR)-markers creatinine or cystatin C. A recommendation to use both markers in parallel in 2010 has resulted in new knowledge concerning the pathophysiology of kidney disorders by the identification of a new set of kidney disorders, selective glomerular hypofiltration syndromes. These syndromes, connected to strong increases in mortality and morbidity, are characterized by a selective reduction in the glomerular filtration of 5-30 kDa molecules, such as cystatin C, compared to the filtration of small molecules <1 kDa dominating the glomerular filtrate, for example water, urea and creatinine. At least two types of such disorders, shrunken or elongated pore syndrome, are possible according to the pore model for glomerular filtration. Selective glomerular hypofiltration syndromes are prevalent in investigated populations, and patients with these syndromes often display normal measured GFR or creatinine-based GFR-estimates. The syndromes are characterized by proteomic changes promoting the development of atherosclerosis, indicating antibodies and specific receptor-blocking substances as possible new treatment modalities. Presently, the KDIGO guidelines for diagnosing kidney disorders do not recommend cystatin C as a general marker of kidney function and will therefore not allow the identification of a considerable number of patients with selective glomerular hypofiltration syndromes. Furthermore, as cystatin C is uninfluenced by muscle mass, diet or variations in tubular secretion and cystatin C-based GFR-estimation equations do not require controversial race or sex terms, it is obvious that cystatin C should be a part of future KDIGO guidelines.

Variation of Complement Protein Levels in Maternal Plasma and Umbilical Cord Blood during Normal Pregnancy: An Observational Study.

The complement system constitutes a crucial part of the innate immunity, mediating opsonization, lysis, inflammation, and elimination of potential pathogens. In general, there is an increased activity of the complement system during pregnancy, which is essential for maintaining the host's defense and fetal survival. Unbalanced or excessive activation of the complement system in the placenta is associated with pregnancy complications, such as miscarriage, preeclampsia, and premature birth. Nonetheless, the actual clinical value of monitoring the activation of the complement system during pregnancy remains to be investigated. Unfortunately, normal reference values specifically for pregnant women are missing, and for umbilical cord blood (UCB), data on complement protein levels are scarce. Herein, complement protein analyses (C1q, C3, C4, C3d levels, and C3d/C3 ratio) were performed in plasma samples from 100 healthy, non-medicated and non-smoking pregnant women, collected during different trimesters and at the time of delivery. In addition, UCB was collected at all deliveries. Maternal plasma C1q and C3d/C3 ratio showed the highest mean values during the first trimester, whereas C3, C4, and C3d had rising values until delivery. We observed low levels of C1q and C4 as well as increased C3d and C3d/C3 ratio, particularly during the first trimester, as a sign of complement activation in some women. However, the reference limits of complement analyses applied for the general population appeared appropriate for the majority of the samples. As expected, the mean complement concentrations in UCB were much lower than in maternal plasma, due to the immature complement system in neonates.

Pregnancy outcome in women with gestational diabetes - A longitudinal study of changes in demography and treatment modalities.

INTRODUCTION: Gestational diabetes is on the rise and demographics are changing in many countries due to increased migration. Simultaneously, the treatment of gestational diabetes in our clinic has shifted towards metformin with substantially less insulin treatment. The aim was to study the impact of these changes on metabolic control and pregnancy outcome by comparing women diagnosed with gestational diabetes during 2012-2013 and 2016-2017. MATERIAL AND METHODS: Our universal Oral Glucose Tolerance Test screening program for gestational diabetes diagnosed 199 women with singleton pregnancies during 2012-2013 and 203 during 2016-2017. Treatment and achieved metabolic control in the two different time periods were compared. Pregnancy outcome data related to gestational diabetes were retrieved from case notes and compared between the different time periods. RESULTS: When comparing results from 2016-2017 with 2012-2013 there was no difference in maternal weight or weight gain. There was a higher frequency of heredity (52.6 vs 35.4%; P = 0.001) and non-Scandinavian ethnicity (46.5 vs 33.8%; P = 0.011).The frequency of smoking during pregnancy was significantly lower (2.6 vs 7.7%; P = 0.023) There was an improved metabolic control as measured by median glucose in 2016-2017 compared with 2012-2013 (5.8 vs 6.2 mmol/L; P < 0.001). Insulin was less frequently used in 2016-2017 than in 2012-2013 (32.5 vs 44.7%; P = 0.012). There was a significant increase in the use of metformin (14.8 vs 0%; P < 0.001). There were no differences regarding the frequency of large-for-gestational-age infants (8.2% vs 7.3%; P = 0.762) or macrosomia (16.3 vs 15.1%; P = 0.745), median birthweight (3510 vs 3521; P = 0.879), frequency of cesarean section (28.1 vs 27.8%; P = 0.951) or Apgar scores at 10 minutes (10 [3-10] vs 10 [7-10]; P = 0.290). CONCLUSIONS: In an increasing but changing population of gestational diabetes women in our region, with more hereditary and non-Scandinavian origins, but with fewer smokers, metabolic control has improved with maintained favorable pregnancy outcomes, with more frequent use of metformin and substantially less use of insulin treatment.

Evidence of Augmented Intrarenal Angiotensinogen Associated With Glomerular Swelling in Gestational Hypertension and Preeclampsia: Clinical Implications.

Background AGT (angiotensinogen) synthesis occurs in renal proximal tubular epithelial cells, independent from systemic AGT , as a component of the intrarenal renin-angiotensin system. We investigated urinary AGT , as a biomarker for renin-angiotensin system activation, and electrolyte concentrations, in relation to glomerular volume, as a proxy for glomerular endotheliosis in renal biopsy tissue from pregnant normotensive control and hypertensive women. Methods and Results Urine samples were collected from normotensive control (n=10), gestational hypertensive (n=6), and pre-eclamptic (n=16) women at the time a renal biopsy was obtained. Samples were collected from Lund University Hospital between November 1999 and June 2001. Urinary AGT , potassium, and sodium were measured, normalized to urinary creatinine. Mean glomerular volume was estimated from biopsy sections. AGT protein expression and localization were assessed in renal biopsies by immunohistochemistry. Urinary AGT concentrations were higher in hypertensive pregnancies (median, gestational hypertension: 11.3 ng/mmol [interquartile range: 2.8-13.6]; preeclampsia: 8.4 ng/mmol [interquartile range: 4.2-29.1]; normotensive control: 0.6 ng/mmol [interquartile range: 0.4-0.8]; P<0.0001) and showed a positive relationship with estimated mean glomerular volume. Urinary potassium strongly correlated with urinary AGT ( P<0.0001). Although numbers were small, AGT protein was found in both glomeruli and proximal tubules in normotensive control but was present only in proximal tubules in women with hypertensive pregnancy. Conclusions This study shows that pregnant women with gestational hypertension or preeclampsia have increased urinary AGT and potassium excretion associated with signs of glomerular swelling. Our data suggest that the kidneys of women with hypertensive pregnancies and endotheliosis have inappropriate intrarenal renin-angiotensin system activation, which may contribute toward the pathogenesis of hypertension and renal injury.

Soluble CD163 and TWEAK in early pregnancy gestational diabetes and later glucose intolerance.

Gestational diabetes mellitus (GDM) is today universally diagnosed during late pregnancy. Treating hyperglycaemia during pregnancy reduces the risk of complications, the effect of interventions is however limited due to the late diagnosis. It is thus important to identify biomarkers reaching a high precision for GDM development in early pregnancy. Here we aim to investigate soluble CD163 (sCD163) and soluble tumour necrosis factor-like weak inducer of apoptosis (sTWEAK) in early pregnancy GDM and their association to the development of later glucose intolerance. In this case-control study, women diagnosed with GDM in early pregnancy (n = 70) at Lund University Hospital, Lund, Sweden in 2011-2015 were age- and BMI matched to pregnant volunteers without diabetes (n = 70) recruited in early pregnancy from maternal health care centres in 2014-2015. Plasma levels of sCD163 and sTWEAK were analysed using commercial ELISA. Plasma levels of sCD163 did not differ between patients with and without GDM in early pregnancy (p = 0.86), plasma levels of sTWEAK however was decreased in women with GDM (0.71 [0.4-1.75] ng/ml) compared to controls (1.38 [0.63-4.86] ng/ml; p = 0.003). Women with sTWEAK levels in the lowest tertile had an increased risk of GDM in early pregnancy (p = 0.014). Neither sCD163 nor sTWEAK were associated with later glucose intolerance in women with GDM. This study reports decreased levels of sTWEAK in women with early pregnancy GDM, independent of age and BMI. Neither sCD163 nor sTWEAK were found to be associated to later glucose intolerance.

PP038. Renal ETK/BMX activation decreased in preeclampsia.

INTRODUCTION: Vascular endothelial growth factors (VEGF's) are essential to angiogenesis and play a central role in the pathophysiology of preeclampsia. Specifically, antagonists of VEGFR2 cause a preeclampsia-like syndrome, in humans and rats[1]. ETK/BMX is a receptor tyrosine kinase (RTK) which induces VEGF expression and forms a complex with VEGFR2, whereby VEGF and TNF can induce a reciprocal activation of both kinases. OBJECTIVES: To determine the levels of phosphorylation, and thus activation, of VEGFR2 and ETK/BMX in renal tissue from women with preeclampsia and with healthy pregnancies. METHODS: Renal tissue was obtained with consent from six preeclamptic and six healthy pregnant women included in a previous renal needle biopsy study[2] and a RayBio® Phosphorylation Antibody Array was used according to instructions. RESULTS: Phosphorylated ETK/BMX was significantly reduced in the preeclamptic women compared to in the healthy pregnant women. There was no difference in phosphorylated VEGFR2 between groups. CONCLUSION: These data suggest that ETK/BMX could be an important mediator of VEGF function in healthy pregnancy, in the kidneys more so than VEGFR2, and that absence of the positive feedforward signalling that ETK/BMX and VEGF together accomplish, and/or a TNF induced activation of this, may play a role in the pathophysiology of preeclampsia.

The vascular endothelial growth factor receptor inhibitor sunitinib causes a preeclampsia-like syndrome with activation of the endothelin system.

Angiogenesis inhibition is an established treatment for several tumor types. Unfortunately, this therapy is associated with adverse effects, including hypertension and renal toxicity, referred to as "preeclampsia." Recently, we demonstrated in patients and in rats that the multitarget tyrosine kinase inhibitor sunitinib induces a rise in blood pressure (BP), renal dysfunction, and proteinuria associated with activation of the endothelin system. In the current study we investigated the effects of sunitinib on rat renal histology, including the resemblance with preeclampsia, as well as the roles of endothelin 1, decreased nitric oxide (NO) bioavailability, and increased oxidative stress in the development of sunitinib-induced hypertension and renal toxicity. In rats on sunitinib, light and electron microscopic examination revealed marked glomerular endotheliosis, a characteristic histological feature of preeclampsia, which was partly reversible after sunitinib discontinuation. The histological abnormalities were accompanied by an increase in urinary excretion of endothelin 1 and diminished NO metabolite excretion. In rats on sunitinib alone, BP increased (ΔBP: 31.6±0.9 mm Hg). This rise could largely be prevented with the endothelin receptor antagonist macitentan (ΔBP: 12.3±1.5 mm Hg) and only mildly with Tempol, a superoxide dismutase mimetic (ΔBP: 25.9±2.3 mm Hg). Both compounds could not prevent the sunitinib-induced rise in serum creatinine or renal histological abnormalities and had no effect on urine nitrates but decreased proteinuria and urinary endothelin 1 excretion. Our findings indicate that both the endothelin system and oxidative stress play important roles in the development of sunitinib-induced proteinuria and that the endothelin system rather than oxidative stress is important for the development of sunitinib-induced hypertension.

How should women with pre-eclampsia be followed up? New insights from mechanistic studies.

Understanding of the maternal syndrome of pre-eclampsia has greatly improved over the past 5 years. Specifically, the notion has emerged that the placenta is a source of antiangiogenic factors, such as soluble fms-like tyrosine kinase 1, that can progressively impair the mother's vascular and glomerular function throughout pregnancy. This impairment can be harmless during normal pregnancy, but in cases of defective placentation, concentrations of antiangiogenic factors increase to a level that compromises vital vascular functions in the short term and jeopardizes long-term maternal and fetal outcomes. In both pre-eclamptic and healthy pregnancies, the transient imbalance between angiogenic and antiangiogenic factors elicited by pregnancy acts as a 'stress test' for the endothelium, particularly in the glomerular capillary bed. Women who do not pass this test (i.e. those who develop pre-eclampsia or gestational hypertension) should be screened for glomerular disease, and their cardiovascular risk should be carefully monitored throughout life.

Serum cystatin C reflects glomerular endotheliosis in normal, hypertensive and pre-eclamptic pregnancies.

OBJECTIVE: To study the correlation between serum cystatin C levels and renal structural changes in normal, hypertensive and pre-eclamptic pregnancy to evaluate it as a marker of the degree of renal involvement in pre-eclampsia. DESIGN: An observational prospective study. SETTING: University Hospital of Lund, Sweden. SAMPLE: Thirty-six women with hypertensive disease in pregnancy and 12 healthy pregnant women in the third trimester recruited from maternal health care centres in the catchment area of the hospital. METHODS: Renal biopsy samples were obtained from all participants and the degree of endotheliosis as well as the mean glomerular volume was evaluated by light microscopy in silver methenamin-stained sections. Serum cystatin C levels were measured and correlated to the structural changes. MAIN OUTCOME MEASURES: Correlation among degree of glomerular endotheliosis, glomerular volume and serum cystatin C. RESULTS: Serum cystatin C levels differed between the different degrees of endotheliosis, showing a highly significant increasing linear trend. They also correlated significantly with glomerular volume (r = 0.60, P < 0.001). Mean serum urate and creatinine levels also increased with the degree of endotheliosis, but not above the reference interval for normal term pregnancy, even in pre-eclamptic women. CONCLUSION: Serum cystatin C may be used as a marker, not only for impaired renal function, but also for the degree of glomerular endotheliosis and increase in glomerular volume in pregnancy. It may be of value in the monitoring of pregnancies complicated by pre-eclampsia.

Glomerular endotheliosis in normal pregnancy and pre-eclampsia.

OBJECTIVE: To investigate the proportion of women with findings characteristic for pre-eclampsia, as opposed to renal disease, in a controlled study of hypertensive pregnant women undergoing antepartum renal biopsy. DESIGN: An observational prospective controlled study. SETTING: University Hospital of Lund, Sweden. SAMPLE: Thirty-six previously healthy women with hypertensive disease in pregnancy, consecutively admitted to the antenatal ward at onset of disease during a 20 month period and giving informed consent, as well as 12 voluntary healthy pregnant controls. METHODS: Renal biopsy samples were obtained from all participants and evaluated by light microscopy, electron microscopy and immunofluorescence techniques. MAIN OUTCOME MEASURES: Presence and degree of glomerular endotheliosis. RESULTS: Glomerular endotheliosis was present in all women with pre-eclampsia and gestational hypertension, and in 5 of the 12 controls, although significant differences in the degree of endotheliosis were found between the groups. Clinically undetected renal disease was not diagnosed in any of the women. CONCLUSION: Glomerular endotheliosis was found in women with normal pregnancy as well as in both non-proteinuric and proteinuric hypertension and is consequently not, as earlier believed, pathognomonic for pre-eclampsia. The transition between normal term pregnancy, gestational hypertension and pre-eclampsia appears to be a continuous process, perhaps of increasing adaptation to pregnancy. Pre-eclampsia may be the extreme of the adaptational process, rather than a separate abnormal condition. Clinically undetected renal disease could be a rare cause of hypertension in pregnancy.

Blood pressure patterns through consecutive pregnancies are influenced by body mass index.

OBJECTIVE: The purpose of this study was to analyze the impact of parity and baseline body mass index on blood pressure levels in pregnancy. STUDY DESIGN: We studied a longitudinal historic cohort of 166 healthy pregnant women who gave birth in 2000 to a third child at the University Hospital of Lund; blood pressure measurements were obtained at each antenatal visit during the three consecutive pregnancies. RESULTS: The mean systolic and diastolic blood pressure levels were consistently higher during the first pregnancy at comparable weeks of gestation, significantly so during the third trimester. The body mass index correlated with diastolic blood pressure levels only in the first pregnancy, and the impact of parity on third trimester blood pressure levels was greatest in the women with a high body mass index. Age, smoking, change of paternity, or a short time interval between pregnancies did not influence blood pressure levels. CONCLUSION: The interrelationship among blood pressure levels, parity, and body mass index in normal pregnancy resembles the situation in hypertensive pregnancies, which implies common adaptive mechanisms.