Short-term peaks in glucose promote renal fibrogenesis independently of total glucose exposure

High levels of blood glycemic indicators are associated with chronic kidney disease prevalence in non-diabetic adults: Cross-sectional data from the national health and nutrition examination survey 2005-2016

Objective

Hyperglycemia in individuals with diabetes is associated with chronic kidney disease (CKD); however, little is known about its association with those without diabetes. Our goal was to investigate the association between glycemic indicators and CKD in individuals without diabetes.

Methods

This cross-sectional study included 9610 participants without diabetes who participated in the Health and Nutrition Examination Survey between 2005 and 2016. Exposures included postprandial glucose dip (PGD), fasting blood glucose (FBG), oral glucose tolerance test two-hour blood glucose (OGTT-2HBG), and glycated hemoglobin (HbA1C) levels. Moreover, CKD was defined as an estimated glomerular filtration rate below 60 mL/min per 1.73 m2 or a urinary albumin-creatinine ratio of ≥ 30 mg/g. Two multivariate models were constructed. Interaction effects were also explored.

Results

The mean age of the participants was 46.0 years, with 50.3 % being females. The prevalence of CKD was 12.6 %. In the final multivariable models, the odds ratios (ORs) for CKD were 1.51 (95 % confidence interval [CI]: 1.22,1.88, p < 0.001) for participants in the highest quartile of PGD,1.46 (95 %CI: 1.13,1.87, p = 0.004) for OGTT-2HBG, and 1.33 (95 %CI: 1.04,1.70, p = 0.020) for HbA1C, when compared with the quartile 1. No significant association was observed between FBG levels and CKD in the final model. Additionally, interactions were observed between PGD and body mass index, as well as between PGD and alcohol consumption in relation to CKD.

Conclusion

The study identified that high levels of PGD, OGTT-2HBG, and HBA1C were significantly associated with a high prevalence of CKD in individuals without diabetes.

Auricular Acupuncture for Lowering Blood Glucose in Type 2 Diabetes: A Pilot Study

Objective

Although type 2 diabetes mellitus (T2DM) is a major health epidemic, little research on auricular acupuncture for reducing blood glucose levels has been published. In Guatemala, where this study was conducted, the prevalence of T2DM is high and access to care is limited. The purpose of this pilot study was to determine if an auricular acupuncture protocol could be a feasible, effective treatment for reducing blood glucose, thus offering another potential accessible treatment.

Materials and Methods

Utilizing a self-controlled design approach, 28 participants diagnosed with T2DM were recruited and received 2 weeks of treatment consisting of a set protocol of 5 points in each ear. Pre- and post-treatment surveys were used to assess patients' health status, treatment expectations, and quality of life. Paired t-tests were used to measure pre- to post-treatment glucose levels.

Results

Treatment produced significant reduction in the patients' fasting and postprandial blood glucose levels, averaging 45.35 (n = 19; P = 0.014) and 109.45 points (n = 10; P = 0.008), respectively. Surveys indicated that all participants would be interested in using the treatment again to help manage their blood glucose.

Conclusions

An auricular protocol may provide a low-cost, effective treatment for lowering blood glucose in patients with T2DM. The results of this study are promising, suggesting that further investigation is warranted.

Effect of high glucose supplementation on pulmonary fibrosis involving reactive oxygen species and TGF-β

This study explored the profibrotic impact of high glucose in the lung and potential mechanisms using latent TGF-β1-induced human epithelial cell pulmonary fibrosis and bleomycin (BLM)-induced pulmonary fibrosis models. Results demonstrated that high glucose administration induced epithelial–mesenchymal transition (EMT) in human epithelial cells in a dose-dependent manner via activating latent TGF-β1, followed by increased expression of mesenchymal-related proteins and decreased expression of epithelial marker protein E-cadherin. Further mechanism analysis showed that administration of high glucose dose-dependently promoted total and mitochondrial reactive oxygen species (ROS) accumulation in human epithelial cells, which promoted latent TGF-β1 activation. However, N-acetyl-L-cysteine, a ROS eliminator, inhibited such effects. An in vivo feed study found that mice given a high-glucose diet had more seriously pathological characteristics of pulmonary fibrosis in BLM-treated mice, including increasing infiltrated inflammatory cells, collagen I deposition, and the expression of mesenchymal-related proteins while decreasing the expression of the epithelial marker E-cadherin. In addition, high glucose intake further increased TGF-β1 concentration and upregulated p-Smad2/3 and snail in lung tissues from BLM-treated mice when compared to BLM-treated mice. Finally, supplementation with high glucose further increased the production of lipid peroxidation metabolite malondialdehyde and decreased superoxide dismutase activity in BLM-treated mice. Collectively, these findings illustrate that high glucose supplementation activates a form of latent TGF-β1 by promoting ROS accumulation and ultimately exacerbates the development of pulmonary fibrosis.

Age and sex-specific associations of visit-to-visit variability of glycated hemoglobin A1c with all-cause mortality in patients with diabetes

BACKGROUND

Visit-to-visit variability (VVV) of glycated hemoglobin (HbA1c) levels have been found to be associated with prognosis of diabetes. However, little is known about whether or to what extent sex and age may modify the effects of VVV.

METHODS

To investigate age- and sex-specific rates of mortality from all causes and relative hazards of mortality in association with VVV of HbA1c levels, 47,145 patients with diabetes and prescription of any antidiabetic agents >6 months were identified from outpatient visits of a tertiary medical center in northern Taiwan during 2003-2018. VVV of HbA1c was measured by quartiles of standard deviation (SD), coefficient of variation (CV), and average real variability (ARV), respectively. The study subjects were linked to Taiwan's National Death Registry to identify all-cause mortality. The person-year approach with the Poisson assumption was used to assess the all-cause mortality rates, and Cox proportional hazard regression model was used to evaluate the relative hazards of all-cause mortality concerning various levels of VVV of HbA1c.

RESULTS

The lowest all-cause mortality rate was found in either the first or second quartile of various measures for VVV of HbA1c, but the highest mortality rate was consistently observed in the fourth quartile of VVV, regardless of SD, CV, or ARV across ages and sexes. Increased hazards of overall all-cause mortality were noticed from the second to fourth quartile of VVV of HbA1c. In detailed age- and sex-stratified analyses, elevated risk of mortality was seen in the fourth quartile of those aged <50 years while in those aged >69 years, increased risk of mortality was noticed in the third and fourth quartiles of any VVV of HbA1c irrespective of sex. In those aged 50-69 years, incremental increased hazards of mortality were consistently observed in the second to fourth quartiles of VVV of HbA1c.

CONCLUSION

HbA1c variability whether it was SD, CV, or ARV could strongly predict the risks of all-cause mortality. The extent of the relationship between VVV of HbA1c and all-cause mortality in different age groups was comparable between both sexes. Given the importance of long-term glucose fluctuation, the inclusion of HbA1c variability calculated from the standardized method should be considered by clinical guideline policymakers as part of the biochemical panel in daily diabetes management.

Glucose Variability: How Does It Work?

A growing body of evidence points to the role of glucose variability (GV) in the development of the microvascular and macrovascular complications of diabetes. In this review, we summarize data on GV-induced biochemical, cellular and molecular events involved in the pathogenesis of diabetic complications. Current data indicate that the deteriorating effect of GV on target organs can be realized through oxidative stress, glycation, chronic low-grade inflammation, endothelial dysfunction, platelet activation, impaired angiogenesis and renal fibrosis. The effects of GV on oxidative stress, inflammation, endothelial dysfunction and hypercoagulability could be aggravated by hypoglycemia, associated with high GV. Oscillating hyperglycemia contributes to beta cell dysfunction, which leads to a further increase in GV and completes the vicious circle. In cells, the GV-induced cytotoxic effect includes mitochondrial dysfunction, endoplasmic reticulum stress and disturbances in autophagic flux, which are accompanied by reduced viability, activation of apoptosis and abnormalities in cell proliferation. These effects are realized through the up- and down-regulation of a large number of genes and the activity of signaling pathways such as PI3K/Akt, NF-κB, MAPK (ERK), JNK and TGF-β/Smad. Epigenetic modifications mediate the postponed effects of glucose fluctuations. The multiple deteriorative effects of GV provide further support for considering it as a therapeutic target in diabetes.

HbA1c variability in adults with type 1 diabetes on continuous subcutaneous insulin infusion (CSII) therapy compared to multiple daily injection (MDI) treatment

OBJECTIVE

To determine if continuous subcutaneous insulin infusion (CSII) therapy is associated with lower glycated haemoglobin (HbA1c) variability (long-term glycaemic variability; GV) relative to multiple daily injection (MDI) treatment in adults with type 1 diabetes mellitus (T1DM).

DESIGN

Retrospective audit.

SETTING AND PARTICIPANTS

Clinic records from 506 adults with T1DM from two tertiary Australian hospitals.

OUTCOME MEASURES

Long-term GV was assessed by HbA1c SD and coefficient of variation (CV) in adults on established MDI or CSII therapy, and in a subset changing from MDI to CSII.

RESULTS

Adults (n=506, (164 CSII), 50% women, mean±SD age 38.0±15.3 years, 17.0±13.7 years diabetes, mean HbA1c 7.8%±1.2% (62±13 mmol/mol) on CSII, 8.0%±1.5% (64±16 mmol/mol) on MDI) were followed for 4.1±3.6 years. CSII use was associated with lower GV (HbA1c SD: CSII vs MDI 0.5%±0.41% (6±6 mmol/mol) vs 0.7%±0.7% (9±8 mmol/mol)) and CV: CSII vs MDI 6.7%±4.6% (10±10 mmol/mol) vs 9.3%±7.3% (14±13 mmol/mol), both p<0.001. Fifty-six adults (73% female, age 36±13 years, 16±13 years diabetes, HbA1c 7.8%±0.8% (62±9 mmol/mol)) transitioned from MDI to CSII. Mean HbA1c fell by 0.4%. GV from 1 year post-CSII commencement decreased significantly, HbA1c SD pre-CSII versus post-CSII 0.7%±0.5% (8±5 mmol/mol) vs 0.4%±0.4% (5±4 mmol/mol); p<0.001, and HbA1c CV 9.2%±5.5% (13±8 mmol/mol) vs 6.1%±3.9% (9±5 mmol/mol); p<0.001.

CONCLUSIONS

In clinical practice with T1DM adults relative to MDI, CSII therapy is associated with lower HbA1c GV.

The early detection of atherosclerosis in type 1 diabetes: why, how and what to do about it

The major cause of morbidity and often premature mortality in people with type I diabetes (T1D) is cardiovascular disease owing to accelerated atherosclerosis. We review publications relating to the rationale behind, and clinical tests for, detecting and treating early atherosclerosis in people with T1D. Currently available tools for atherosclerosis assessment include risk equations using vascular risk factors, arterial intima-media thickness, the ankle-brachial index, coronary artery calcification and angiography, and for more advanced lesions, intravascular ultrasound and optical coherence tomography. Evolving research tools include risk equations incorporating novel clinical, biochemical and molecular tests; vascular MRI and molecular imaging. As yet there is little information available to quantify early atherosclerosis. With better means to control the vascular risk factors, such as hypertension, dyslipidaemia and glycaemic control, and emerging therapies to control novel risk factors, further epidemiologic and clinical trials are merited to facilitate the translation into clinical practice of robust means to detect, monitor and treat early atherosclerosis in those with T1D.

Insulin Prevents Hyperfiltration and Proteinuria but Not Glomerular Hypertrophy and Increases Mesangial Matrix Expansion in Diabetic Rats

OBJECTIVE

The aim of this work was to study the effect of 7 days of strict glycemic control with insulin on glomerular function and structure in streptozotocin (STZ)-diabetic rats.

MATERIALS AND METHODS

Three groups of adult male Fischer rats were studied: controls (n = 15), diabetics (n = 15), and insulin-treated diabetics (n = 15). Diabetes was induced by treating the rats with STZ (55 mg/kg i.p.). One week after the induction of diabetes, blood glucose, protein excretion rate (PER), glomerular filtration rate (GFR), and renal plasma flow (RPF) were estimated in each group. Furthermore, morphometric analysis was performed to estimate the tuft volume and changes in mesangial matrix area. The results are expressed as the mean ± SEM.

RESULTS

STZ diabetes caused significant increases in GFR (0.89 ± 0.1 to 1.21 ± 0.1 mL/min/100 g; p < 0.01) and RPF (1.78 ± 0.37 to 3.32 ± 0.6 mL/min/100 g; p < 0.05). Furthermore, the diabetic rats had higher glomerular volumes but mesangial matrix areas similar to controls. Insulin treatment prevented the increases in blood glucose (4.5 ± 0.2 mM), PER (66.1 ± 7.8 mg/day), GFR (0.6 ± 0.07 mL/min/100 g), and RPF (1.72 ± 0.36 mL/min/100 g), but did not prevent glomerular hypertrophy (21.7% increase), but induced mesangial matrix expansion (25% increase).

CONCLUSIONS

Insulin prevented the diabetes-induced hyperfiltration and proteinuria, but did not prevent glomerular growth, and induced mesangial expansion. Hyperglycemic episodes could be partly responsible for persistent glomerular growth and accelerated mesangial growth.

Tubulointerstitial disease in diabetic nephropathy

Diabetes mellitus is the major cause of end stage renal disease (ESRD). We cannot predict which patient will be affected. ESRD patients suffer an extremely high mortality rate, due to a very high incidence of cardiovascular disease. Several randomized, prospective studies have been conducted to quantify the impact of strict glycemic control on morbidity and mortality, and have consistently demonstrated an association between strict glycemic control and a reduction in ESRD. Within the past 20 years, despite the implementation of treatments that were presumed to be renoprotective, diabetes mellitus has continued to rank as the leading cause of ESRD, which clearly indicates that we are still far from understanding the mechanisms involved in the initiation of ESRD. Progressive albuminuria has been considered as the sine qua non of diabetic nephropathy, but we know now that progression to diabetic nephropathy may well happen in the absence of initial microalbuminuria. The search for new biomarkers of early kidney damage has received increasing interest, since early identification of the pathways leading to kidney damage may allow us to adopt measures to prevent the development of ESRD. Most of these biomarkers are deeply influenced by environment, genetics, sex differences, and so on, making it extremely difficult to identify the ideal biomarker to target. At present, there are no new drugs that come close to providing the solutions we desire for our patients (ie, reducing complications). Even when used in combination with standard care, renal complications are, at best, only modestly reduced, at the considerable expense of additional pill burden and exposure to serious off-target effects. In this review, some of the hypothesized mechanisms of this heterogeneous disease will be considered, with particular attention to the tubule–interstitial compartment.

Combined acute hyperglycemic and hyperinsulinemic clamp induced profibrotic and proinflammatory responses in the kidney

Increase in matrix protein content in the kidney is a cardinal feature of diabetic kidney disease. While renal matrix protein content is increased by chronic hyperglycemia, whether it is regulated by acute elevation of glucose and insulin has not been addressed. In this study, we aimed to evaluate whether short duration of combined hyperglycemia and hyperinsulinemia, mimicking the metabolic environment of prediabetes and early type 2 diabetes, induces kidney injury. Normal rats were subjected to either saline infusion (control, n = 4) or 7 h of combined hyperglycemic-hyperinsulinemic clamp (HG+HI clamp; n = 6). During the clamp, plasma glucose and plasma insulin were maintained at about 350 mg/dl and 16 ng/ml, respectively. HG+HI clamp increased the expression of renal cortical transforming growth factor-β (TGF-β) and renal matrix proteins, laminin and fibronectin. This was associated with the activation of SMAD3, Akt, mammalian target of rapamycin (mTOR) complexes, and ERK signaling pathways and their downstream target events in the initiation and elongation phases of mRNA translation, an important step in protein synthesis. Additionally, HG+HI clamp provoked renal inflammation as shown by the activation of Toll-like receptor 4 (TLR4) and infiltration of CD68-positive monocytes. Urinary F2t isoprostane excretion, an index of renal oxidant stress, was increased in the HG+HI clamp rats. We conclude that even a short duration of hyperglycemia and hyperinsulinemia contributes to activation of pathways that regulate matrix protein synthesis, inflammation, and oxidative stress in the kidney. This finding could have implications for the control of short-term rises in blood glucose in diabetic individuals at risk of developing kidney disease.

Cardiac fibroblast-dependent extracellular matrix accumulation is associated with diastolic stiffness in type 2 diabetes

Cardiovascular complications are a leading cause of death in patients with type 2 diabetes mellitus (T2DM). Diastolic dysfunction is one of the earliest manifestations of diabetes-induced changes in left ventricular (LV) function, and results from a reduced rate of relaxation and increased stiffness. The mechanisms responsible for increased stiffness are not completely understood. Chronic hyperglycemia, advanced glycation endproducts (AGEs), and increased levels of proinflammatory and profibrotic cytokines are molecular pathways known to be involved in regulating extracellular matrix (ECM) synthesis and accumulation resulting in increased LV diastolic stiffness. Experiments were conducted using a genetically-induced mouse model of T2DM generated by a point mutation in the leptin receptor resulting in nonfunctional leptin receptors (db/db murine model). This study correlated changes in LV ECM and stiffness with alterations in basal activation of signaling cascades and expression of profibrotic markers within primary cultures of cardiac fibroblasts from diabetic (db/db) mice with nondiabetic (db/wt) littermates as controls. Primary cultures of cardiac fibrobroblasts were maintained in 25 mM glucose (hyperglycemic-HG; diabetic db/db) media or 5 mM glucose (normoglycemic-NG, nondiabetic db/wt) media. The cells then underwent a 24-hour exposure to their opposite (NG; diabetic db/db) media or 5 mM glucose (HG, nondiabetic db/wt) media. Protein analysis demonstrated significantly increased expression of type I collagen, TIMP-2, TGF-β, PAI-1 and RAGE in diabetic db/db cells as compared to nondiabetic db/wt, independent of glucose media concentration. This pattern of protein expression was associated with increased LV collagen accumulation, myocardial stiffness and LV diastolic dysfunction. Isolated diabetic db/db fibroblasts were phenotypically distinct from nondiabetic db/wt fibroblasts and exhibited a profibrotic phenotype in normoglycemic conditions.

Can we target tubular damage to prevent renal function decline in diabetes?

The glomerulus has been at the center of attention as the primary site of injury in diabetic nephropathy (DN). Although there is no question that there are changes seen in the glomerulus, it is also well known that tubulointerstitial changes are a prominent component of the disease, especially in patients with type 2 diabetes. The level of albuminuria and DN disease progression best correlate with tubular degeneration and interstitial fibrosis. Nephrotoxicity studies in animals reveal that albuminuria is a highly sensitive marker of early tubular toxicity even in the absence of glomerular pathology. Urinary biomarker data in human beings support the view that proximal tubule injury contributes in a primary way, rather than in a secondary manner, to the development of early DN. I present a model in which very specific injury to the proximal tubule in vivo in the mouse results in severe inflammation, loss of blood vessels, interstitial fibrosis, and glomerulosclerosis. Increased glucose levels, free glycation adducts, reactive oxygen species, and oxidized lipids result in toxicity to tubule epithelia. This results in loss of cells with a stimulus to repair the epithelium. However, because of sublethal injury there is cell-cycle arrest in epithelial cells attempting to replace damaged cells. This leads to epithelial secretion of both profibrogenic growth factors, collagens, and factors that cause pericytes to proliferate and differentiate into myofibroblasts, leading to endothelial destabilization and capillary rarefaction. Local ischemia ensues with further injury to the tubules, more profibrogenic mediators, matrix protein deposition, fibrosis, and glomerulosclerosis.

Both ERK/MAPK and TGF-Beta/Smad signaling pathways play a role in the kidney fibrosis of diabetic mice accelerated by blood glucose fluctuation

BACKGROUND

The notion that diabetic nephropathy is the leading cause of renal fibrosis prompted us to investigate the effects of blood glucose fluctuation (BGF) under high glucose condition on kidney in the mice.

METHODS

The diabetic and BGF animal models were established in this study. Immunohistochemistry, Western blot, and RT-PCR analysis were applied to detect the expression of type I collagen, matrix metalloproteinase-1 (MMP1), metalloproteinase inhibitor 1 (TIMP1), transforming growth factor beta 1 (TGF- β 1), phosphorylated-ERK, p38, smad2/3, and Akt.

RESULTS

BGF treatment increased type I collagen synthesis by two times compared with the control. The expression of MMP1 was reduced markedly while TIMP1 synthesis was enhanced after BGF treatment. ERK phosphorylation exhibits a significant increase in the mice treated with BGF. Furthermore, BGF can markedly upregulate TGF- β 1 expression. The p-smad2 showed 2-fold increases compared with the only diabetic mice. However, p-AKT levels were unchanged after BGF treatment.

CONCLUSIONS

These data demonstrate that BGF can accelerate the trend of kidney fibrosis in diabetic mice by increasing collagen production and inhibiting collagen degradation. Both ERK/MAPK and TGF- β /smad signaling pathways seem to play a role in the development of kidney fibrosis accelerated by blood glucose fluctuation.

Matrix metalloproteinases in type 2 diabetes and non-diabetic controls: effects of short-term and chronic hyperglycaemia

INTRODUCTION

The role of matrix metalloproteinases (MMPs) in type 2 diabetes mellitus (DM) is not clear as increased activation of MMPs in the vasculature contrasts with decreased activity of MMPs in the kidneys, contributing to development of nephropathy.

MATERIAL AND METHODS

We measured serum MMP-2 and MMP-9 in 22 subjects with type 2 DM age (mean ± SD) 56.7 ±16.8 years, BMI 31.8 ±4.6 kg/m(2), HbA(1c) 8.45 ±1.78% and in 32 controls, age 39.2 ±16.0 years, BMI 35.2 ±8.5 kg/m(2). In 15 subjects with 2 DM we also measured MMP-2 and MMP-9 at discharge from hospital and after 3 months (n = 8). In controls, MMP-2 and -9 were also measured during 75 g oral glucose tolerance test (OGTT).

RESULTS

Concentrations of MMP-2 and MMP-9 were lower in subjects with type 2 DM (219 ±62 ng/ml vs. 305 ±63 ng/ml and 716 ±469 ng/ml vs. 1285 ±470 ng/ml, for MMP-2 and MMP-9, respectively, p < 0.05). MMP-9 concentrations fell at 120 min of OGTT from 1675 ±372 ng/ml to 1276 ±422 ng/ml (p < 0.05). In diabetic subjects there was a correlation between MMP-9 and HbA(1c) (r = 0.51, p< 0.05). In subjects with diabetes there was a fall of HbA(1c) from 9.77 ±1.76% to 8.36 ±1.54% (p < 0.01), at three months post-discharge. There was no difference in MMP-2, but there was a fall in MMP-9 at three months post-discharge in comparison to concentrations observed at admission (854 ±560 ng/ml vs. 500 ±235 ng/ml, p= 0.02).

CONCLUSIONS

Matrix metalloproteinases in type 2 and MMP-9 concentrations were lower in subjects with 2 DM than in non-diabetic controls. Regulation of MMPs appears to be complex as hyperglycaemia during OGTT results in a decrease in MMP-9, while chronic hyperglycaemia, reflected by HbA(1c), correlates with MMP-9 concentrations in subjects with 2 DM.

Intermittent high glucose promotes expression of proinflammatory cytokines in monocytes

OBJECTIVE AND DESIGN

The aim of this study was to examine expression of proinflammatory cytokines in monocytes under fluctuating glucose conditions.

MATERIAL AND TREATMENT

Monocytic cells (THP-1) were divided into four groups and cultured in the presence of 5 or 15 mmol/L glucose or in fluctuating conditions (12 h exposure to 15 mmol/L glucose or mannitol medium followed by 12 h exposure to 5 mmol/L glucose or mannitol medium) respectively.

METHODS

Levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α in the supernatants and surface expression of CD11b in monocytes were measured after 72 h culture. Paired Student's t tests were used to compare two groups and ANOVA for multiple comparisons.

RESULTS

Activation of monocytes was most pronounced in the fluctuating glucose conditions, as measured by concentrations of IL-6 and TNF-α in cultured supernatants and surface expression of CD11b in monocytes (P < 0.05). Fluctuating mannitol also induced a proinflammatory profile, but to a lesser extent than fluctuating glucose.

CONCLUSIONS

The results indicated that exposure to fluctuating glucose concentrations enhanced activation of monocytes compared with stable elevation of glucose concentrations. The effects were partly attributable to the inherent osmotic changes.

Regression of microalbuminuria in type 1 diabetes is associated with lower levels of urinary tubular injury biomarkers, kidney injury molecule-1, and N-acetyl-β-D-glucosaminidase

Elevated urinary albumin excretion in patients with type 1 diabetes reverts to normoalbuminuria in a majority of patients but advances toward proteinuria in some. In order to gain valuable insights into the early pathophysiology of diabetic nephropathy we evaluated the association of kidney tubular injury biomarkers with changes in albuminuria in patients with type 1 diabetes mellitus. Urine levels of kidney injury molecule-1 (KIM-1), N-acetyl-β-D-glucosaminidase (NAG), and some inflammatory markers were determined in 38 healthy individuals and 659 patients with type 1 diabetes mellitus having varying degrees of albuminuria. Urinary interleukin-6, CXCL10/IP-10, NAG, and KIM-1 levels were very low in healthy individuals, increased in type 1 patients with normoalbuminuria, and were highest in diabetic patients that had microalbuminuria. Low baseline concentrations of urinary KIM-1 and NAG both individually and collectively were significantly associated with the regression of microalbuminuria over the subsequent 2 years; an effect independent of clinical characteristics. Progression and regression of microalbuminuria were unrelated to urinary levels of interleukins 6 and 8, CXCL10/IP-10, and monocyte chemoattractant protein-1. Thus our results show that lower urinary KIM-1 and NAG levels were associated with the regression of microalbuminuria in type 1 diabetes mellitus. Hence, tubular dysfunction is a critical component of the early course of diabetic nephropathy.

'Glycaemic variability': a new therapeutic challenge in diabetes and the critical care setting

Much attention has been paid recently to the possibility that oscillating glucose may superimpose on glycated haemoglobin (HbA(1c)) in determining the risk for diabetes complications. Furthermore, recent evidence suggests that glucose variability, particularly if accompanied by frequent hypoglycaemic episodes, may adversely alter the prognosis of acutely ill patients. In vitro and animal studies confirm that oscillating glucose is more dangerous than stable constant high glucose, particularly in activating the pathways involved in the pathogenesis of diabetes complications. The production of free radicals, accompanied by an insufficient increase in intracellular antioxidant defences, seems to account for this phenomenon. In humans, studies also confirm that fluctuating glucose levels produce an increase in free radicals as well as endothelial dysfunction, and that these changes are greater than those produced by stable high glucose. Avoiding glucose fluctuations in diabetic patients and in critically ill patients seems to be an emerging therapeutic challenge.

Glycaemic variability using continuous glucose monitoring and endothelial function in the metabolic syndrome and in Type 2 diabetes

AIMS

Subjects who are at increased risk of developing diabetes may have increased glycaemic variability associated with endothelial dysfunction and possibly subclinical atherosclerosis, which may lead to increased cardiovascular risk observed at the time of diabetes diagnosis. To investigate this hypothesis, we measured endothelial function, carotid intima-media thickness and glycaemic variability using 48-h continuous subcutaneous glucose monitoring in 3 groups of overweight or obese subjects--those without the metabolic syndrome, and those with the metabolic syndrome with or without newly diagnosed Type 2 diabetes.

METHODS

Consecutive subjects, aged 30-65 years with a body mass index >or= 25 kg/m(2) were recruited. Patients were classified as with or without the metabolic syndrome,or as metabolic syndrome with newly diagnosed Type 2 DM. Glycaemic variability was calculated in terms of the coefficient of variation. Endothelial function was measured using brachial artery flow-mediated dilation.

RESULTS

We identified 75 subjects. Mean flow mediated dilation decreased (P < 0.001) and carotid intima-media thickness increased (P < 0.05) across groups. Flow mediated dilation predictors included mean 48-h continuous subcutaneous glucose monitoring values (beta = -0.022; P < 0.005) and the coefficient of variation (beta = -0.10; P = 0.01). Carotid intima-media thickness predictors included age (beta = 0.009; P < 0.001) and flow mediated dilation (beta = -0.014; P = 0.076). Patients re-stratified according to cut-offs for mean 48-h glycaemia and variability demonstrated that subjects with high mean glycaemia but low coefficient of variability had similar flow mediated dilation and carotid intima-media thickness to subjects with low mean glycaemia but high coefficient of variation.

CONCLUSIONS

This study suggests that glycaemic variability influences endothelial function even in non-diabetic subjects. Such variability may explain the increased cardiovascular risk observed in patients prior to developing overt Type 2 diabetes.

A1C variability predicts incident cardiovascular events, microalbuminuria, and overt diabetic nephropathy in patients with type 1 diabetes

OBJECTIVE

Recent data from the Diabetes Control and Complications Trial (DCCT) indicated that A1C variability is associated with the risk of diabetes microvascular complications. However, these results might have been influenced by the interventional study design. Therefore, we investigated the longitudinal associations between A1C variability and diabetes complications in patients with type 1 diabetes in the observational Finnish Diabetic Nephropathy (FinnDiane) Study.

RESEARCH DESIGN AND METHODS

A total of 2,107 patients in the FinnDiane Study had complete data on renal status and serial measurements of A1C from baseline to follow-up (median 5.7 years), and 1,845 patients had similar data on cardiovascular disease (CVD) events. Intrapersonal SD of serially measured A1C was considered a measure of variability.

RESULTS

During follow-up, 10.2% progressed to a higher albuminuria level or to end-stage renal disease, whereas 8.6% had a CVD event. The SD of serial A1C was 1.01 versus 0.75 (P < 0.001) for renal status and 0.87 versus 0.79 (P = 0.023) for CVD in progressors versus nonprogressors, respectively. In a Cox regression model, SD of serial A1C was independently associated with progression of renal disease (hazard ratio 1.92 [95% CI 1.49-2.47]) and of a CVD event (1.98 [1.39-2.82]) even when adjusting for mean A1C and traditional risk factors. Interestingly for CVD, mean serial A1C itself was not predictive even though SD of A1C was.

CONCLUSIONS

In patients with type 1 diabetes, A1C variability was not only predictive of incident microalbuminuria and progression of renal disease but also of incident CVD events.

Essential role of TGF-beta signaling in glucose-induced cell hypertrophy

In multicellular organisms, cell size is tightly controlled by nutrients and growth factors. Increasing ambient glucose induces enhanced protein synthesis and cell size. Continued exposure of cells to high glucose in vivo, as apparent under pathological conditions, results in cell hypertrophy and tissue damage. We demonstrate that activation of TGF-beta signaling has a central role in glucose-induced cell hypertrophy in fibroblasts and epithelial cells. Blocking the kinase activity of the TbetaRI receptor or loss of its expression prevented the effects of high glucose on protein synthesis and cell size. Exposure of cells to high glucose induced a rapid increase in cell surface levels of the TbetaRI and TbetaRII receptors and a rapid activation of TGF-beta ligand by matrix metalloproteinases, including MMP-2 and MMP-9. The consequent autocrine TGF-beta signaling in response to glucose led to Akt-TOR pathway activation. Accordingly, preventing MMP-2/MMP-9 or TGF-beta-induced TOR activation inhibited high glucose-induced cell hypertrophy.

Rapid 'glycaemic swings' induce nitrosative stress, activate poly(ADP-ribose) polymerase and impair endothelial function in a rat model of diabetes mellitus

AIM/HYPOTHESIS

Postpandrial hyperglycaemia is a significant risk factor for the development of macrovascular diseases. There is no clear agreement in the field whether these alterations result from hyperglycaemic episodes or from exaggerated alterations ('glycaemic swings') in blood glucose. We compared the effect of stable high glucose with a model of poorly maintained insulin-controlled diabetes (on average lower glucose, but with large glycaemic swings) on the development of endothelial dysfunction in rats.

METHODS

Intermediate- or long-acting insulin was used to reduce mean blood glucose levels. One group of animals had stable low glucose levels, while animals in the other group exhibited rapid changes ('swings') in their blood glucose concentration. Acetylcholine-induced endothelium-dependent vascular relaxation of the thoracic aorta was measured. Immunohistochemistry, western blot analysis and flow cytometry were used to determine nitrotyrosine formation and poly(ADP-ribose) accumulation in the aorta, in circulating leucocytes and in bone marrow cells.

RESULTS

Steady normalisation of blood glucose levels (a model of well-controlled diabetes) protected against the development of endothelial dysfunction, poly(ADP-ribose) polymerase (PARP) activation and nitrotyrosine production. However, impairment of endothelium-dependent relaxation was found in the animals undergoing glycaemic swings, even though the fructosamine levels in these animals were lower than in the untreated diabetic rats. This was associated with elevated PARP activation in the aorta and in bone marrow cells that was similar to or even more pronounced than that seen in the untreated diabetic animals.

CONCLUSIONS/INTERPRETATION

Large glycaemic swings exert deleterious cardiovascular effects in diabetes mellitus, in part via enhanced activation of the PARP pathway.

Integrin-associated protein association with SRC homology 2 domain containing tyrosine phosphatase substrate 1 regulates igf-I signaling in vivo

OBJECTIVE

Smooth muscle cell (SMC) maintained in medium containing normal levels of glucose do not proliferate in response to IGF-I, whereas cells maintained in medium containing 25 mmol/l glucose can respond. The aim of this study was to determine whether signaling events that have been shown to be required for stimulation of SMC growth were regulated by glucose concentrations in vivo.

RESEARCH DESIGN AND METHODS

We compared IGF-I-stimulated signaling events and growth in the aortic smooth muscle cells from normal and hyperglycemic mice.

RESULTS

We determined that, in mice, hyperglycemia was associated with an increase in formation of the integrin-associated protein (IAP)/Src homology 2 domaine containing tyrosine phosphatase substrate 1 (SHPS-1) complex. There was a corresponding increase in Shc recruitment to SHPS-1 and Shc phosphorylation in response to IGF-I. There was also an increase in mitogen-activated protein kinase activation and SMC proliferation. The increase in IAP association with SHPS-1 in hyperglycemia appeared to be due to the protection of IAP from cleavage that occurred during exposure to normal glucose. In addition, we demonstrated that the protease responsible for IAP cleavage was matrix metalloprotease-2. An anti-IAP antibody that disrupted the IAP-SHPS-1 association resulted in complete inhibition of IGF-I-stimulated proliferation.

CONCLUSIONS

Taken together, our results support a model in which hyperglycemia is associated with a reduction in IAP cleavage, thus allowing the formation of the IAP-SHPS-1 signaling complex that is required for IGF-I-stimulated proliferation of SMC.

Do high blood glucose peaks contribute to higher HbA1c? Results from repeated continuous glucose measurements in children

BACKGROUND

HbA1c levels are influenced by the glycemic control of previous 2-3 months. Sometimes patients have surprisingly low HbA1c in spite of many correctly measured high blood glucose values, which is difficult to explain. As glucose sensors give an objective picture based on glucose readings several times per minute over 24 hours, we used the area under the curve (AUC) of such subcutaneous glucose profiles to evaluate their relationship with HbA1c.

METHODS

Thirty-two patients were randomized into two study arms, one open and the other blinded. Both arms had 8 pump users and 8 patients with multiple daily injections (MDI). After three months the two arms crossed over. Both study arms wore a continuous glucose monitoring system (CGMS) for 3 days every 2 weeks. HbA1c was determined before and after each 3-month study period.

RESULTS

There was no relationship between HbA1c and s.c. glucose AUC or between HbA1c and the number of peaks >15.0 mmol/L when all CGMS profiles during the 6 months were taken together. Children on MDI showed a positive relationship between HbA1c and AUC (P<0.01) as well as the number of peaks (P<0.01). Children with a negative relationship between HbA1c and AUC generally had fewer fluctuations in blood glucose values, whereas children with a positive relationship had wide fluctuations. between s.c. glucose AUC and HbA1c, the results indicate that wide blood glucose fluctuations may be related to high HbA1c values. Therefore, complications and therapeutic interventions should aim at reducing such fluctuations.

CONCLUSIONS

Although there was no relationship between s.c. glucose AUC and HbA1c, the results indicate that wide blood glucose fluctuations may be related to high HbA1c values. Therefore, complications and therapeutic interventions should aim at reducing such fluctuations.

Sourdough-leavened bread improves postprandial glucose and insulin plasma levels in subjects with impaired glucose tolerance

Sourdough bread has been reported to improve glucose metabolism in healthy subjects. In this study postprandial glycaemic and insulinaemic responses were evaluated in subjects with impaired glucose tolerance (IGT) who had a meal containing sourdough bread leavened with lactobacilli, in comparison to a reference meal containing bread leavened with baker yeast. Sixteen IGT subjects (age range 52-75, average BMI 29.9 +/- 4.2 kg/ m2) were randomly given a meal containing sourdough bread (A) and a meal containing the reference bread (B) in two separate occasions at the beginning of the study and after 7 days. Sourdough bread was leavened for 8 h using a starter containing autochthonous Saccharomyces cerevisiae and several bacilli able to produce a significant amount of D-and L-lactic acid, whereas the reference bread was leavened for 2 h with commercial baker yeast containing Saccharomyces cerevisiae. Plasma glucose and insulin levels were measured at time 0, 30, 60, 120, and 180 min. In IGT subjects sourdough bread induced a significantly lower plasma glucose response at 30 minutes (p = 0.048) and a smaller incremental area under curve (AUC) delta 0-30 and delta 0-60 min (p = 0.020 and 0.018 respectively) in comparison to the bread leavened with baker yeast. Plasma insulin response to this type of bread showed lower values at 30 min (p = 0.045) and a smaller AUC delta 0-30 min (p = 0.018). This study shows that in subjects with IGT glycaemic and insulinaemic responses after the consumption of sourdough bread are lower than after the bread leavened with baker yeast. This effect is likely due to the lactic acid produced during dough leavening as well as the reduced availability of simple carbohydrates. Thus, sour-dough bread may potentially be of benefit in subjects with impaired glucose metabolism.

Oscillating glucose is more deleterious to endothelial function and oxidative stress than mean glucose in normal and type 2 diabetic patients

OBJECTIVE

To explore the possibility that oscillating glucose may outweigh A1C levels in determining the risk for cardiovascular diabetes complications.

RESEARCH DESIGN AND METHODS

A euinsulinemic hyperglycemic clamp at 5, 10, and 15 mmol/l glucose was given in increasing steps as a single "spike" or oscillating between basal and high levels over 24 h in normal subjects and type 2 diabetic patients. Flow-mediated dilatation, a marker of endothelial function, and plasma 3-nitrotyrosine and 24-h urinary excretion rates of free 8-iso PGF2 alpha, two markers of oxidative stress, were measured over 48 h postclamp.

RESULTS

Glucose at two different levels (10 and 15 mmol/l) resulted in a concentration-dependent fasting blood glucose-independent induction of both endothelial dysfunction and oxidative stress in both normal and type 2 diabetic patients. Oscillating glucose between 5 and 15 mmol/l every 6 h for 24 h resulted in further significant increases in endothelial dysfunction and oxidative stress compared with either continuous 10 or 15 mmol/l glucose.

CONCLUSIONS

These data suggest that oscillating glucose can have more deleterious effects than constant high glucose on endothelial function and oxidative stress, two key players in favoring cardiovascular complications in diabetes. Concomitant vitamin C infusion can reverse this impairment.

Neonatal streptozotocin-induced glucose intolerance: different consequences in Lyon normotensive and hypertensive rats

BACKGROUND

Lyon hypertensive (LH) rats exhibit a mild hypertension associated with excessive body weight, spontaneous hyperlipidemia, elevated insulin/glucose ratio and exaggerated urinary protein excretion.

AIMS

We aimed to develop, in LH rats and their normotensive control (LL) rats, a moderate non-insulin-dependent diabetic model to study the different consequences on metabolic and renal functions.

METHODS

Non-insulin-dependent diabetes was induced by intraperitoneal injection of streptozotocin (STZ) at 2 days of age (50, 75 or 100 mg/kg for LH and 75, 100 or 125 mg/kg for LL rats). The evolution, with age, of glycemia, glucose tolerance (glucose 2 g/kg by gavage), blood pressure, plasma lipids and urinary protein and albumin excretions were studied in control and STZ-treated LH and LL rats.

RESULTS

Although fasting glycemia was not significantly changed, the neonatal administration of STZ increased non-fasting glycemia and induced a marked glucose intolerance that were comparable between LH rats receiving 75 mg/kg and LL rats receiving 100 mg/kg of STZ. Interestingly, in treated LH rats only, the impaired glucose tolerance was accompanied by further metabolic and renal dysfunctions characterized by additional increases in plasma cholesterol (+28%) and triglycerides (+105%) and accelerated progression of proteinuria (+36%) and albuminuria (+48%).

CONCLUSIONS

These observations indicate that susceptibility to diabetic metabolic disorders and renal diseases may be linked to the genetic predisposition to hypertension. This new model offers a reasonable reflection of the human situation, where hypertension and non-insulin-dependent diabetes often coincide, suitable for molecular, biochemical and pharmacological investigations.

High glucose, high insulin, and their combination rapidly induce laminin-beta1 synthesis by regulation of mRNA translation in renal epithelial cells

Laminin is a glycoprotein that contributes to renal extracellular matrix expansion in diabetes. We investigated regulation of laminin-beta1 synthesis in murine renal proximal tubular epithelial cells by 30 mmol/l glucose (high glucose), 1 nmol/l insulin (high insulin), and their combination (high glucose+high insulin), simulating conditions observed during progression of type 2 diabetes. Compared with 5 mmol/l glucose and no insulin (control), high glucose alone, high insulin alone, or high glucose+high insulin together increased laminin-beta1 chain protein synthesis within 5 min, lasting for up to 60 min with no change in laminin-beta1 mRNA levels. Cycloheximide, but not actinomycin-D, abrogated increased laminin-beta1 synthesis. High glucose, high insulin, and high glucose+high insulin stimulated phosphorylation of 4E-BP1, a repressor binding protein for eukaryotic initiation factor 4E (eIF4E), that was dependent on activation of phosphatidylinositol 3-kinase, Akt, and mammalian target of rapamycin. High glucose, high insulin, and high glucose+high insulin also promoted release of eIF4E from 4E-BP1, phosphorylation of eIF4E, and increase in eIF4E association with eIF4G, critical events in the initiation phase of mRNA translation. High glucose, high insulin, and high glucose+high insulin increased Erk phosphorylation, which is an upstream regulator of eIF4E phosphorylation, and PD098059, which is a MEK inhibitor that blocks Erk activation, abolished laminin-beta1 synthesis. This is the first demonstration of rapid increment in laminin-beta1 synthesis by regulation of its mRNA translation by cells exposed to high glucose, high insulin, or high glucose+high insulin.

Constant and intermittent high glucose enhances endothelial cell apoptosis through mitochondrial superoxide overproduction

BACKGROUND

It has been previously shown that hyperglycemia enhances free radical production, inducing oxidative damage, which in its turn activates the death pathways implicated in cell apoptosis and necrosis. But the possible involvement of this pathway in the hyperglycemia-induced apoptosis of endothelial cells has not yet been reported.

METHODS

To verify a possible connection between mitochondrial ROS production and apoptosis induced by both stable and oscillating high glucose, SOD, MnTBAP and TTFA was added to HUVEC cell culture medium. We measured nitrotyrosine and 8OHdG as oxidative stress parameters and Bcl-2 expression and Caspase-3 expression and activity as apoptosis indicators.

RESULTS

Our results show that hyperglycemia, both stable or oscillating, increases oxidative stress and endothelial cell apoptosis through ROS overproduction at the mitochondrial transport chain level.

CONCLUSION

The prevention of mitochondrial oxidative damage seems to be a future important therapeutic strategy in diabetes.

Pioglitazone inhibits cell growth and reduces matrix production in human kidney fibroblasts

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists are increasingly used in patients with diabetes, and small studies have suggested a beneficial effect on renal function, but their effects on extracellular matrix (ECM) turnover are unknown. The aims of this study were to investigate the effects of the PPAR-gamma agonist pioglitazone on growth and matrix production in human cortical fibroblasts (CF). Cell growth and ECM production and turnover were measured in human CF in the presence and absence of 1 and 3 muM pioglitazone. Exposure of CF to pioglitazone caused an antiproliferative (P < 0.0001) and hypertrophic (P < 0.0001) effect; reduced type IV collagen secretion (P < 0.01), fibronectin secretion (P < 0.0001), and proline incorporation (P < 0.0001); decreased MMP-9 activity (P < 0.05); and reduced tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2 secretion (P < 0.001 and P < 0.0001, respectively). These effects were independent of TGF-beta1. A reduction in ECM production was similarly observed when CF were exposed to a selective PPAR-gamma agonist (L-805645) in concentrations that caused no toxicity, confirming the antifibrotic effects of pioglitazone were mediated through a PPAR-gamma-dependent mechanism. Exposure of CF to high glucose conditions induced an increase in the expression of collagen IV (P < 0.05), which was reversed both in the presence of pioglitazone (1 and 3 muM) and by L-805645. In summary, exposure of human CF to pioglitazone causes an antiproliferative effect and reduces ECM production through mechanisms that include reducing TIMP activity, independent of TGF-beta1. These studies suggest that the PPAR-gamma agonists may have a specific role in ameliorating the course of progressive tubulointerstitial fibrosis under both normoglycemic and hyperglycemic states.

Cellular oxidative processes in relation to renal disease

This article summarizes the biochemical processes that produce reactive oxygen species (ROS) and other mediators that account for 'oxidative stress'. Formation of ROS in signal transduction cascades is illustrated from studies of kidney cell systems. The pathophysiological implications for the nephrologist are then reviewed.