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Biomedical subjects

George Jerums

Publications and source records attributed to George Jerums.

At least 37 records · Page 2Linked to original sources

Nonalbuminuric renal insufficiency in type 2 diabetes.

OBJECTIVE: To determine the prevalence and characteristics of patients with type 2 diabetes who have impaired renal function, defined as a glomerular filtration rate (GFR) <60 ml. min(-1). 1.73 m(-2), and normoalbuminuria. RESEARCH DESIGN AND METHODS: A cross-sectional survey of 301 outpatients attending a single tertiary referral center using the plasma disappearance of isotopic (99m)Tc-diethylene-triamine-penta-acetic acid to measure GFR and at least two measurements of urinary albumin excretion rate (AER) over 24 h to determine albuminuria. RESULTS: A total of 109 patients (36%) had a GFR <60 ml. min(-1). 1.73 m(-2). The overall prevalence of normo-, micro-, and macroalbuminuria was 43 of 109 (39%), 38 of 109 (35%), and 28 of 109 (26%), respectively. Compared with patients with macroalbuminuria, those with normoalbuminuria were more likely to be older and female. After excluding patients whose normoalbuminuric status was possibly related to the initiation of a renin-angiotensin system (RAS) inhibitor before the start of the study, the prevalence of a GFR <60 ml. min(-1). 1.73 m(-2) and normoalbuminuria was 23%. Temporal changes in GFR in a subset of 34 of 109 (32%) unselected patients with impaired renal function were available for comparison over a 3- to 10-year period. The rates of decline in GFR (ml. min(-1). 1.73 m(-2). year(-1)) of -4.6 +/- 1.0, -2.8 +/- 1.0, and -3.0 +/- 07 were not significantly different for normo- (n = 12), micro- (n = 12), and macroalbuminuric (n = 10) patients, respectively. CONCLUSIONS: These results suggest that patients with type 2 diabetes can commonly progress to a significant degree of renal impairment while remaining normoalbuminuric.

Age of Onset↗

3: Preventing complications of diabetes.

Diabetes complications are common and almost triple the annual cost of managing diabetes. Microvascular complications are the major risk in type 1 diabetes, while macrovascular complications are the major cause of morbidity and mortality in type 2 diabetes. Control of hyperglycaemia (target HbA(1c) level < or = 7%) and hypertension (target blood pressure < or = 130/80 mmHg) prevents microvascular complications in both types of diabetes; a multifactorial approach, comprising behaviour modification and pharmacological therapy for all risk factors, reduces the development of micro- and macrovascular complications in type 2 diabetes. The benefit of treating dyslipidaemia is at least as great in the diabetic population as in the non-diabetic population. Angiotensin-converting enzyme inhibitors and low-dose aspirin are indicated in people with diabetes and other cardiovascular risk factors. Regular annual screening for diabetes complications allows treatable disease to be identified. Aggressive management of hyperglycaemia and other risk factors can prevent many complications

Adult↗

Evolving concepts in advanced glycation, diabetic nephropathy, and diabetic vascular disease.

Advanced glycation endproducts (AGEs) have been postulated to play a role in the development of both nephropathy and large vessel disease in diabetes. However, it is still not clear which AGE subtypes play a pathogenetic role and which of several AGE receptors mediate AGE effects on cells. This review summarises the renoprotective effect of inhibitors of AGE formation, including aminoguanidine, and of cross-link breakers, including ALT-711, on experimental diabetic nephropathy and on mesenteric vascular hypertrophy. It also demonstrates similar effects of aminoguanidine and ramipril (an angiotensin converting enzyme inhibitor) on fluorescent and immunoassayable AGE levels, renal protein kinase C activity, nitrotyrosine expression, lysosomal function, and protein handling in experimental diabetes. These findings indicate that inhibition of the renin angiotensin system blocks both upstream and downstream pathways leading to tissue injury. We postulate that the chemical pathways leading to advanced glycation endproduct formation and the renin angiotensin systems may interact through the generation of free radicals, induced both by glucose and angiotensin II. There is also evidence to suggest that AGE-dependent pathways may play a role in the development of tubulointerstitial fibrosis in the diabetic kidney. This effect is mediated through RAGE and is TGF-beta and CTGF-dependent.

Albuminuria↗

The breakdown of preexisting advanced glycation end products is associated with reduced renal fibrosis in experimental diabetes.

Renal accumulation of advanced glycation end products (AGEs) has been linked to the progression of diabetic nephropathy. Cleavage of pre-formed AGEs within the kidney by a cross-link breaker, such as ALT-711, may confer renoprotection in diabetes. STZ diabetic rats were randomized into a) no treatment (D); b) treatment with the AGE cross-link breaker, ALT-711, weeks 16-32 (DALT early); and c) ALT-711, weeks 24-32 (DALT late). Treatment with ALT-711 resulted in a significant reduction in diabetes-induced serum and renal AGE peptide fluorescence, associated with decreases in renal carboxymethyllysine and RAGE immunostaining. Cross-linking of tail tendon collagen seen in diabetic groups was attenuated only by 16 weeks of ALT-711 treatment. ALT-711, independent of treatment duration, retarded albumin excretion rate (AER), reduced blood pressure, and renal hypertrophy. It also reduced diabetes-induced increases in gene expression of transforming growth factor beta1 (TGF-beta1), connective tissue growth factor (CTGF), and collagen IV. However, glomerulosclerotic index, tubulointerstitial area, total renal collagen, nitrotyrosine, protein expression of collagen IV, and TGF-beta1 only showed improvement with early ALT treatment alone. This study demonstrates the utility of a cross-link breaker as a treatment for diabetic nephropathy and describes effects not only on renal AGEs but on putative mediators of renal injury, such as prosclerotic cytokines and oxidative stress.

Albuminuria↗

The amino-terminal domains of the ezrin, radixin, and moesin (ERM) proteins bind advanced glycation end products, an interaction that may play a role in the development of diabetic complications.

The presence of advanced glycation end products (AGEs) formed because of hyperglycemia in diabetic patients has been strongly linked to the development of diabetic complications and disturbances in cellular function. In this report, we describe the isolation and identification of novel AGE-binding proteins from diabetic rat kidneys. The proteins were purified by cation exchange and AGE-modified bovine serum albumin (AGE-BSA) affinity chromatography. NH2-terminal and internal sequencing identified the proteins as the NH2-terminal domains of ezrin, radixin, and moesin (ERM proteins). Using BIAcore biosensor analysis, human N-ezrin-(1-324) bound to immobilized AGE-BSA with a KD of 5.3 +/- 2.1 x 10 -7 m, whereas full-length ezrin-(1-586) and C-ezrin-(323-586) did not bind. Other glycated proteins such as AGE-RNase, N in -carboxymethyllysine (CML)-BSA, and glycated human serum albumin isolated from hyperglycemic diabetic sera competed with the immobilized AGE-BSA for binding to N-ezrin, but non-glycated BSA and RNase did not. Thus N-ezrin binds to AGEs in a glycation- and concentration-dependent manner. Phosphorylated ezrin plays a crucial role in cell shape changes, cell attachment, and cell adhesion. The effect of AGE-BSA on ezrin function was studied in a tubulogenesis model in which LLC-PK1 cell tubule formation is dependent on phosphorylated ezrin. Addition of AGE-BSA completely inhibited the ability of the cells to produce tubules. Furthermore, in vitro tyrosine phosphorylation of N-ezrin and ezrin was also inhibited by AGE-BSA. These proteins represent a novel family of intracellular binding molecules for glycated proteins and provide a potential new target for therapeutic intervention in the prevention or treatment of diabetic complications.

Animals↗

Ramipril prevents microtubular changes in proximal tubules from streptozotocin diabetic rats.

This study has investigated the microtubular cytoskeleton in rat glomerular and proximal tubule cells in experimental diabetes. The effect of treatment with ramipril on the relationship between microtubule organization and albuminuria in diabetes has also been examined. Diabetes was induced in male Sprague-Dawley rats by administration of streptozotocin (50 mg/kg, i.v.). Rats were treated with or without ramipril in their drinking water for 12 weeks. Diabetes was characterized by an increase in blood glucose level, glomerular filtration rate, and albumin excretion rate. Treatment of diabetic rats with ramipril did not affect glycaemic control, but reduced systolic blood pressure and prevented the rise in albuminuria and glomerular filtration rate. Immunohistochemistry was performed by using the ARK Peroxidase method with alpha-tubulin antibody. The regular, grainy staining pattern of the microtubules present in the renal proximal tubules from control kidneys was altered in diabetic animals, and appeared fragmented and striated. This was prevented by treatment with ramipril. Quantitative morphometric analysis revealed an increase in the percent proportional staining for alpha-tubulin in the proximal tubules of untreated diabetic rats (33.3 +/- 3.3%, n = 8, P < 0.05 vs control) compared with control rats (11.7 +/- 1.7%, n = 6), which was reduced by ramipril treatment (26.7 +/- 2.1%, n = 6, P < 0.05 vs untreated diabetic). Staining for alpha-tubulin in glomerular cells was unchanged in all groups. There was no significant difference in renal alpha-tubulin expression among all groups, as determined by real-time reverse transcription-polymerase chain reaction. These results raise the possibility that diabetes-induced changes in microtubules in the renal proximal tubules may contribute, in part, to the increase in albuminuria observed in diabetes.

Angiotensin-Converting Enzyme Inhibitors↗

Reduced tubular cation transport in diabetes: prevented by ACE inhibition.

BACKGROUND: The renal clearance of organic cations is important for the homeostasis of a number of exogenous and endogenous compounds. The organic cation transporters (OCTs) situated on the basolateral surface of proximal tubular cells mediate active cation excretion. Alterations of cation transport may occur in diabetes, although the role of the OCTs has not been previously assessed. METHODS: Experimental diabetes was induced in rats with streptozotocin (55 mg/kg) and animals were randomly assigned to receive ramipril (3 mg/mL) in drinking water for 24 weeks. In a second protocol, rats were infused with angiotensin II (Ang II) at a dose of 58.3 ng/kg/min for 2 weeks via an implanted osmotic pump. Expression of the OCTs and renal clearance of the endogenous cation N-methyl-nicotinamide (NMN) was assessed. RESULTS: Diabetes was associated with a reduction in gene and protein expression of both OCT-1 and OCT-2 and a reduction in NMN clearance. These effects were prevented by ramipril, associated with the prevention of albuminuria and tubular injury as demonstrated by the expression of osteopontin and glutathione peroxidase 3 (GPX-3). An infusion of Ang II also reduced NMN clearance but without altering the renal expression of OCTs. CONCLUSION: We hypothesize that reduced expression of OCTs in diabetes may be a marker of tubular injury. However, Ang II may also directly augment renal cation clearance independent of changes in transporter expression. Together these effects may provide additional mechanism to explain treatment-related improvements in creatinine clearance and renoprotection in diabetes following blockade of the renin-angiotensin system (RAS).

Angiotensin-Converting Enzyme Inhibitors↗

High prevalence of immuno-unreactive intact albumin in urine of diabetic patients.

BACKGROUND: Intact albumin in urine may exist in two forms, immunoreactive and immuno-unreactive. Previous estimates of albuminuria in diabetic urine have only detected immunoreactive forms. METHODS: High performance liquid chromatography (HPLC) was used in this study to measure both forms of intact albumin (termed total intact albumin) to provide a more accurate measurement of albuminuria compared with radioimmunoassay (RIA) on 97 fresh urine samples from patients with diabetes. Eighty-six control urine samples from volunteers without diabetes were also tested. RESULTS: There was no significant difference between the two methods for nondiabetic controls. For diabetic urine samples, 91.6% of samples showed a greater concentration of albumin measured by HPLC than RIA. For normoalbuminuric diabetic samples, HPLC gave a mean albumin excretion rate of 12.5 +/- 4.4 microgram/min (SD), whereas RIA gave a rate of 8.0 +/- 6.7 microgram/min (P = 0.004; N = 28). For microalbuminuric samples, there also was a statistically significant difference: HPLC albumin excretion rate, 82.0 +/- 49.9 microgram/min, and RIA, 49.0 +/- 34.6 microgram/min (P = 0.004; N = 30). Thirty-two urine samples were normoalbuminuric by RIA (albumin, 11.4 +/- 3.9 microgram/min), but in the microalbuminuric range as determined by HPLC (albumin, 38.5 +/- 14.4 microgram/min). For urine samples in the macroalbuminuric range, there was no statistically significant difference between HPLC and RIA. Immuno-unreactive albumin was confirmed as albumin, analyzed by two-dimensional electrophoresis and matrix-assisted laser desorption ionization mass spectrometry. CONCLUSION: These studies show that to determine microalbuminuria accurately, there is a need to assess urinary total intact albumin, rather than simply immunoreactive albumin. Am J Kidney Dis 41:336-342.

Adult↗

The effect of ramipril on albumin excretion in diabetes and hypertension: the role of increased lysosomal activity and decreased transforming growth factor-beta expression.

OBJECTIVES: Albumin excretion is modulated post-filtration by lysosomal processing that produces a spectrum of albumin-derived material in urine, much of which is not detected by conventional immunoassays. This study aimed to determine the efficacy of ramipril treatment (+ RAM) after 24 weeks on total albumin excretion (intact plus albumin-derived peptides) in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats with (d) and without (c) diabetes. METHODS: Intact albumin excretion was analysed by radioimmunoassay and total albumin excretion was analysed by measuring radioactivity derived from circulating [ C]albumin. Renal lysosomal activity was determined by urinary [ H]dextran sulphate desulphation. Renal transforming growth factor-beta 1 (TGF-beta 1), TGF-beta inducible gene-h3 (beta ig-h3) and angiotensinogen mRNA production were analysed by real time reverse transcriptase-polymerase chain reaction. RESULTS: Hypertension (SHR-c and SHR-d) resulted in a significant increase in intact albumin excretion, which was significantly reduced by ramipril treatment (P < 0.05 for SHR-c + RAM and 0.001 for SHR-d + RAM compared to non-treated). This was accompanied by a significant decrease in blood pressure (P < 0.001 for SHR-c + RAM and SHR-d + RAM), renal beta ig-h3 mRNA production (P < 0.05 for SHR-c + RAM and SHR-d + RAM), and an increase in lysosomal activity. Diabetes (WKY-d and SHR-d) primarily caused a significant increase in total albumin excretion, predominantly in the form of albumin-derived fragments in the WKY-d group and intact albumin in the SHR-d group. Ramipril treatment reduced total albumin excretion in the WKY-d + RAM group (P < 0.001). CONCLUSIONS: Ramipril prevents increases in both intact albumin and total albumin excretion in hypertensive and diabetic states, respectively.

Albuminuria↗

Additive effects of hypertension and diabetes on renal cortical expression of PKC-alpha and -epsilon and alpha-tubulin but not PKC-beta 1 and -beta 2.

OBJECTIVE: This study examined the separate and combined effects of hypertension and diabetes on renal cortical expression of protein kinase C (PKC) isoforms -beta 1, -beta 2, -alpha and -epsilon, to determine whether albuminuria is the result of an increase in the expression of one or a combination of PKC isoforms. Corresponding changes in renal microtubules were also assessed. METHODS: Diabetes (D) was induced in Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) by streptozotocin. After 24 weeks, PKC expression was determined by Western blot and microtubules were assessed by immunohistochemistry for alpha-tubulin protein. RESULTS: Diabetes was characterized by significant increases in glycated haemoglobin (HbA1c) as compared to controls (C). There was a significant increase of three- to four-fold in PKC protein content for all four isoforms in renal cortex from SHR-C and WKY-D, and similar and significant levels of albuminuria (approximately 10 mg/24 h) observed in these groups in comparison to WKY-C (approximately 1 mg/24 h). Interestingly, PKC-alpha and -epsilon but not PKC-beta 1 and -beta 2 protein content was doubled in SHR-D, and albuminuria increased tenfold (approximately 100 mg/24 h) in comparison to SHR-C and WKY-D. These changes were paralleled by a significant decrease in alpha-tubulin protein content of approximately 50% in SHR-C and approximately 33% in WKY-D compared to WKY-C, with a further decrease of approximately 67% in SHR-D compared to WKY-C. CONCLUSION: These findings indicate that PKC expression can be increased by either diabetes or hypertension, and that there are further specific increases in the expression of PKC isoforms -alpha and -epsilon in the model of combined diabetes and hypertension. In addition, the degree of disruption in microtubular cytoskeleton appears to be correlated with PKC activation and levels of albuminuria.

Albuminuria↗

Reversible angiotensin II-mediated albuminuria in rat kidneys is dynamically associated with cytoskeletal organization.

Angiotensin II (ANG II) is intimately involved in normal renal function, and is estimated to exist at a normal physiological range of 6-10 nM within the renal tubules. The potential role that intrarenal ANG II may play in renal disease was assessed by perfusing isolated rat kidneys with or without excess intratubular levels of ANG II, which may mimic changes in the intrarenal RAS under pathological conditions. The effects of increased systemic ANG II were also determined by infusing rats with ANG II by osmotic pump. In isolated perfused kidneys, ANG II significantly and specifically increased the fractional clearance of albumin to clinical levels, as determined by using radiolabelled albumin. This effect was reversible, as removing ANG II from the perfusate caused the albumin fractional clearance to decrease to pre-ANG II exposure levels. The increase in fractional clearance of albumin was not correlated with renal hemodynamic changes, nor glomerular permeability alterations as measured by the fractional clearance of 36 A Ficoll and immunoglobulin G. Immunochemical analysis using anti-alpha-tubulin antibody of perfused kidney sections revealed that ANG II caused a marked disruption of tubular epithelial cytoskeletal components, through disassembly and reorganization of alpha-tubulin. This disruption was reversible. In vivo, osmotic pump delivery of ANG II at less potent dosage caused a proteinuria (Biuret) and an albuminuria (radioimmunoassay) in rats, from as early as 2 days after pump implantation. These results demonstrate that ANG II may reversibly induce clinical levels of albuminuria. These data point to an important role for renal tubules and the intratubular lumen concentrations of ANG II in the renal processing of albumin.

Albuminuria↗

Unrecognized anemia in patients with diabetes: a cross-sectional survey.

OBJECTIVE: Anemia is common in diabetes, potentially contributing to the pathogenesis of diabetes complications. This study aims to establish the prevalence and independent predictors of anemia in a cross-sectional survey of 820 patients with diabetes in long-term follow-up in a single clinic. RESEARCH DESIGN AND METHODS: A full blood count was obtained in addition to routine blood and urine test results for all patients over a 2-year period to encompass all patterns of review. Predictors of the most recent Hb concentration and anemia were identified using multiple and logistic regression analysis. RESULTS: A total of 190 patients (23%) had unrecognized anemia (Hb <12 g/dl for women and <13 g/dl for men). This prevalence is two to three times higher than for patients with comparable renal impairment and iron stores in the general population. Independent predictors for Hb were transferrin saturation, glomerular filtration rate (GFR), sex, albumin excretion rate, and HbA(1c) level (all P < 0.0001). Microalbuminuric patients were >2 times (odds ratio [OR] 2.3) and macroalbuminuric patients >10 times (OR 10.1) as likely to have anemia than normoalbuminuric patients with preserved renal function (GFR >80 ml/min). CONCLUSIONS: Anemia is a common accompaniment to diabetes, particularly in those with albuminuria or reduced renal function. Additional factors present in diabetes may contribute to the development of increased risk for anemia in patients with diabetes.

Albuminuria↗

Urinary connective tissue growth factor excretion in patients with type 1 diabetes and nephropathy.

OBJECTIVE: Excretion of growth factors in the urine has been implicated in the pathogenesis of tubulointerstitial disease that characterizes proteinuric renal disease. In this cross-sectional study, we sought to examine the urinary excretion of the profibrotic cytokine connective tissue growth factor (CTGF) in type 1 diabetic patients with incipient and overt diabetic nephropathy. RESEARCH DESIGN AND METHODS: We recruited 31 subjects with type 1 diabetes from a hospital diabetes outpatient clinic. Of these, 10 subjects were normoalbuminuric, 8 were microalbuminuric and not receiving ACE inhibitor treatment, and 13 were macroalbuminuric, 8 of whom were receiving ACE inhibitor treatment. Urinary CTGF NH(2)-terminal fragment (CTGF-N) was determined by enzyme-linked immunosorbent assay and expressed relative to urinary creatinine. RESULTS: Urinary CTGF-N was closely correlated with the degree of albuminuria (r = 0.76, P < 0.001). In comparison with normoalbuminuric subjects, urinary CTGF-N was increased 10- and 100-fold in micro- and untreated macroalbuminuric subjects, respectively (CTGF-N-to-creatinine ratio: normoalbuminuria 0.23 x// 1.3 ng/mg, microalbuminuria 2.1 x// 1.7 ng/mg, untreated macroalbuminuria 203 x// 3.8 ng/mg, and geometric mean x// tolerance factor; P < 0.05 for normoalbuminuria versus microalbuminuria, P < 0.001 for microalbuminuria versus macroalbuminuria). Urinary CTGF-N was lower (<30-fold) in macroalbuminuric subjects treated with ACE inhibitors (6.5 x// 1.7 ng/mg; P < 0.01 vs. untreated macroalbuminuria) compared with their untreated counterparts. CONCLUSIONS: In this cross-sectional study, the magnitude of urinary CTGF-N excretion was related to the severity of diabetic nephropathy. In the context of its known profibrotic actions, these findings suggest that CTGF may contribute to the chronic tubulointerstitial fibrosis that accompanies proteinuric renal disease. Prospective and interventional studies will be needed to determine whether urinary CTGF-N may provide a reliable surrogate marker of renal injury and a meaningful indicator of response to therapy.

Adult↗

Albumin to creatinine ratio: a screening test with limitations.

The aim of this study is to assess the effects of age on (1) the ability of a spot albumin-creatinine ratio (ACR) to accurately predict 24-hour albumin excretion rate (AER), and (2) the performance of spot ACR as a screening test for microalbuminuria. Three hundred fourteen patients with diabetes aged 18 to 84 years attending a tertiary outpatient clinic underwent one 24-hour urine collection and, immediately after completion, provided one fasting spot morning urine sample. Twenty-four-hour AER and spot ACR were determined. Performance of spot ACR was assessed according to age and sex. Fifty-three percent of men and 32% of women had an AER of 20 microg/min or greater. Multiple regression analysis showed age was an independent predictor of spot ACR. For an AER of 20 microg/min for patients in the age range of 40 to 80 years, there was an increase in corresponding values for spot ACR from 18.2 mg/g (95% confidence interval [CI], 15.6 to 21.3) to 32.5 mg/g (95% CI, 27.5 to 38.4) in men and from 22.1 mg/g (95% CI, 18.0 to 27.1) to 56.4 mg/g (95% CI, 47.2 to 67.4) in women. Using ACR cutoff values of 22.1 mg/g or greater and 30.9 mg/g or greater in conventional units (equivalent to > or =2.5 and > or =3.5 mg/mmol in SI units) in men and women, the spot ACR provided high sensitivities (men, 95.7%; women, 93.35%) and had excellent receiver operator characteristic curves, respectively. However, the spot ACR false-positive rate increased with age from 15.9% (age, 40 to 65 years) to 31.8% (>65 years) in men and from 10.5% (age, 45 to 65 years) to 28.3% (>65 years) in women. Spot ACR is a good screening test for microalbuminuria, but a poor predictor of quantitative AER, and should not be used as a diagnostic test. The increase in spot ACR relative to 24-hour AER with age supports the use of sex- and age-adjusted ACR cutoff values.

Adolescent↗

The influence of diabetes mellitus and hyperglycaemia on stroke incidence and outcome.

Diabetes mellitus is a complex metabolic syndrome with significant effects on the systemic and cerebral vasculature. The incidence and severity of ischaemic stroke are increased by the presence of diabetes, and outcome from stroke is poorer. More than one third of patients admitted with acute stroke are hyperglycaemic at presentation. Reasons for the altered prognosis in diabetes associated stroke are multifactorial. A direct influence of hyperglycaemia at the time of ischaemia is likely to be important. The use of novel methods to delineate stroke topography and pathophysiology such as MR spectroscopy, diffusion and perfusion weighted MRI appear helpful in delineating the effects of hyperglycaemia on stroke pathophysiology. Randomised clinical trials to determine optimal management for patients with hyperglycaemia following stroke are ongoing. Such trials will determine if aggressive control of acute hyperglycaemia following stroke has similar benefits to that observed following acute myocardial infarction. Clinicians responsible for stroke patients should be aware of the importance of adequate glycaemic control in both primary and secondary prevention of stroke.

Diabetes Mellitus↗