Modulation of the Cellular Expression of Circulating Advanced Glycation End-Product Receptors in Type 2 Diabetic Nephropathy

Background. Advanced glycation end-products (AGEs) and their receptors are prominent contributors to diabetic kidney disease. Methods. Flow cytometry was used to measure the predictive capacity for kidney impairment of the AGE receptors RAGE, AGE-R1, and AGE-R3 on peripheral blood mononuclear cells (PBMCs) in experimental models of type 2 diabetes (T2DM) fed varied AGE containing diets and in obese type 2 diabetic and control human subjects. Results. Diets high in AGE content fed to diabetic mice decreased cell surface RAGE on PBMCs and in type 2 diabetic patients with renal impairment (RI). All diabetic mice had elevated Albumin excretion rates (AERs), and high AGE fed dbdb mice had declining Glomerular filtration rate (GFR). Cell surface AGE-R1 expression was also decreased by high AGE diets and with diabetes in dbdb mice and in humans with RI. PBMC expression of AGE R3 was decreased in diabetic dbdb mice or with a low AGE diet. Conclusions. The most predictive PBMC profile for renal disease associated with T2DM was an increase in the cell surface expression of AGE-R1, in the context of a decrease in membranous RAGE expression in humans, which warrants further investigation as a biomarker for progressive DN in larger patient cohorts

An engineered nanosugar enables rapid and sustained glucose-responsive insulin delivery in diabetic mice

Glucose-responsive insulin-delivery platforms that are sensitive to dynamic glucose concentration fluctuations and provide both rapid and prolonged insulin release have great potential to control hyperglycemia and avoid hypoglycemia diabetes. Here, biodegradable and charge-switchable phytoglycogen nanoparticles capable of glucose-stimulated insulin release are engineered. The nanoparticles are "nanosugars" bearing glucose-sensitive phenylboronic acid groups and amine moieties that allow effective complexation with insulin (approximate to 95% loading capacity) to form nanocomplexes. A single subcutaneous injection of nanocomplexes shows a rapid and efficient response to a glucose challenge in two distinct diabetic mouse models, resulting in optimal blood glucose levels (below 200 mg dL(-1)) for up to 13 h. The morphology of the nanocomplexes is found to be key to controlling rapid and extended glucose-regulated insulin delivery in vivo. These studies reveal that the injected nanocomplexes enabled efficient insulin release in the mouse, with optimal bioavailability, pharmacokinetics, and safety profiles. These results highlight a promising strategy for the development of a glucose-responsive insulin delivery system based on a natural and biodegradable nanosugar

Effect of vitamin D supplementation on inflammation and nuclear factor kappa-B activity in overweight/obese adults: a randomized placebo-controlled trial

In-vitro studies suggest that vitamin D reduces inflammation by inhibiting nuclear factor kappa-B (NF kappa B) activity. Yet, no trials have examined the effects of vitamin D supplementation on NF kappa B activity in-vivo in humans. We conducted a double-blind randomized trial (RCT) examining effects of vitamin D supplementation on inflammatory markers and NF kappa B activity in peripheral blood mononuclear cells (PBMCs). Sixty-five overweight/obese, vitamin D-deficient (25-hydroxyvitamin D [25(OH) D] <= 50 nmol/L) adults were randomized to a single 100,000 IU bolus followed by 4,000 IU daily cholecalciferol or matching placebo for 16 weeks. We measured BMI, % body fat, serum 25(OH) D, high-sensitivity C-reactive protein (hsCRP), tumour necrosis factor (TNF), monocyte chemoattractant protein-1 (MCP-1), interferon-gamma (IFN-gamma), several interleukins, and NF kappa B activity in PBMCs. Fifty-four participants completed the study. Serum 25(OH) D concentrations increased with vitamin D supplementation compared to placebo (p < 0.001). Vitamin D and placebo groups did not differ in any inflammatory markers or NF kappa B activity (all p > 0.05). Results remained non-significant after adjustment for age, sex, and % body fat, and after further adjustment for sun exposure, physical activity, and dietary vitamin D intake. Although in-vitro studies report anti-inflammatory effects of vitamin D, our RCT data show no effect of vitamin D supplementation on inflammatory markers or NF kappa B activity in-vivo in humans

c-Jun NH2-Terminal Kinase Activity in Subcutaneous Adipose Tissue but Not Nuclear Factor-κB Activity in Peripheral Blood Mononuclear Cells Is an Independent Determinant of Insulin Resistance in Healthy Individuals

OBJECTIVE Chronic low-grade activation of the immune system (CLAIS) predicts type 2 diabetes via a decrease in insulin sensitivity. Our study investigated potential relationships between nuclear factor-κB (NF-κB) and c-Jun NH2-terminal kinase (JNK) pathways—two pathways proposed as the link between CLAIS and insulin resistance. RESEARCH DESIGN AND METHODS Adiposity (dual-energy X-ray absorptiometry), waist-to-hip ratio (WHR), and insulin sensitivity (M, hyperinsulinemic-euglycemic clamp) were measured in 22 healthy nondiabetic volunteers (aged 29 ± 11 years, body fat 28 ± 11%). NF-κB activity (DNA-binding assay) and JNK1/2 activity (phosphorylated JNK) were assessed in biopsies of the vastus lateralis muscle and subcutaneous adipose tissue and in peripheral blood mononuclear cell (PBMC) lysates. RESULTS NF-κB activities in PBMCs and muscle were positively associated with WHR after adjustment for age, sex, and percent body fat (both P 0.1), although it was inversely related to M (r = −0.54, P < 0.05) and explained 29% of its variance. When both NF-κB and JNK1/2 were examined statistically, only JNK1/2 activity in adipose tissue was a significant determinant of insulin resistance (P = 0.02). CONCLUSIONS JNK1/2 activity in adipose tissue but not NF-κB activity in PBMCs is an independent determinant of insulin resistance in healthy individual

Altered Mitochondrial Function, Mitochondrial DNA and Reduced Metabolic Flexibility in Patients With Diabetic Nephropathy.

The purpose of this study was to determine if mitochondrial dysfunction plays a role in diabetic nephropathy (DN), a kidney disease which affects > 100 million people worldwide and is a leading cause of renal failure despite therapy. A cross-sectional study comparing DN with diabetes patients without kidney disease (DC) and healthy controls (HCs); and renal mesangial cells (HMCs) grown in normal and high glucose, was carried out. Patients with diabetes (DC) had increased circulating mitochondrial DNA (MtDNA), and HMCs increased their MtDNA within 24 h of hyperglycaemia. The increased MtDNA content in DCs and HMCs was not functional as transcription was unaltered/down-regulated, and MtDNA damage was present. MtDNA was increased in DC compared to HC, conversely, patients with DN had lower MtDNA than DC. Hyperglycaemic HMCs had fragmented mitochondria and TLR9 pathway activation, and in diabetic patients, mitophagy was reduced. Despite MtDNA content and integrity changing within 4 days, hyperglycaemic HMCs had a normal bio-energetic profile until 8 days, after which mitochondrial metabolism was progressively impaired. Peripheral blood mononuclear cells (PBMCs) from DN patients had reduced reserve capacity and maximal respiration, loss of metabolic flexibility and reduced Bioenergetic Health Index (BHI) compared to DC. Our data show that MtDNA changes precede bioenergetic dysfunction and that patients with DN have impaired mitochondrial metabolism compared to DC, leading us to propose that systemic mitochondrial dysfunction initiated by glucose induced MtDNA damage may be involved in the development of DN. Longitudinal studies are needed to define a potential cause-effect relationship between changes in MtDNA and bioenergetics in DN

Mapping Time-course Mitochondrial Adaptations in the Kidney in Experimental Diabetes

Abstract Oxidative phosphorylation drives ATP production by mitochondria, which are dynamic organelles, constantly fusing and dividing to maintain kidney homeostasis. In diabetic kidney disease, mitochondria appear dysfunctional, but the temporal development of diabetes-induced adaptations in mitochondrial structure and bioenergetics, have not been previously documented. Here, we map the changes in mitochondrial dynamics and function in rat kidney mitochondria at 4, 8, 16 and 32 weeks of diabetes. Our data reveal that changes in mitochondrial bioenergetics and dynamics precede the development of albuminuria and renal histological changes. Specifically, in early diabetes (4 weeks) a decrease in ATP content and mitochondrial fragmentation within proximal tubule epithelial cells of diabetic kidneys were clearly apparent, but no change urinary albumin excretion or glomerular morphology were evident at this time. By 8 weeks of diabetes, there was increased capacity for mitochondrial permeability transition (mPT) by pore opening, which persisted over time and correlated with mitochondrial hydrogen peroxide generation and glomerular damage. Late in diabetes, by week 16, tubular damage was evident with increased urinary Kidney injury molecule (Kim)-1 excretion, where an increase in Complex I-linked oxygen consumption rate, in the context of a decrease in kidney ATP, indicated mitochondrial uncoupling. Taken together, these data show that changes in mitochondrial bioenergetics and dynamics may precede the development of the renal lesion in diabetes, and this supports the hypothesis that mitochondrial dysfunction is a primary cause of diabetic kidney disease. Summary statement We identified that dysfunction of cellular power stations, mitochondria, may precede the development of kidney disease in diabetes. This suggests that mitochondrial dysfunction is a primary cause of diabetic nephropathy, which could be targeted to improve the burden of this disease. Short title: Mitochondrial adaptations in diabetic nephropath

Clearance kinetics and matrix binding partners of the receptor for advanced glycation end products

Elucidating the sites and mechanisms of sRAGE action in the healthy state is vital to better understand the biological importance of the receptor for advanced glycation end products (RAGE). Previous studies in animal models of disease have demonstrated that exogenous sRAGE has an anti-inflammatory effect, which has been reasoned to arise from sequestration of pro-inflammatory ligands away from membrane-bound RAGE isoforms. We show here that sRAGE exhibits in vitro binding with high affinity and reversibly to extracellular matrix components collagen I, collagen IV, and laminin. Soluble RAGE administered intratracheally, intravenously, or intraperitoneally, does not distribute in a specific fashion to any healthy mouse tissue, suggesting against the existence of accessible sRAGE sinks and receptors in the healthy mouse. Intratracheal administration is the only effective means of delivering exogenous sRAGE to the lung, the organ in which RAGE is most highly expressed; clearance of sRAGE from lung does not differ appreciably from that of albumin. Copyright: © 2014 Milutinovic et al

Mapping time-course mitochondrial adaptations in the kidney in experimental diabetes

Abstract Oxidative phosphorylation (OXPHOS) drives ATP production by mitochondria, which are dynamic organelles, constantly fusing and dividing to maintain kidney homoeostasis. In diabetic kidney disease (DKD), mitochondria appear dysfunctional, but the temporal development of diabetes-induced adaptations in mitochondrial structure and bioenergetics have not been previously documented. In the present study, we map the changes in mitochondrial dynamics and function in rat kidney mitochondria at 4, 8, 16 and 32 weeks of diabetes. Our data reveal that changes in mitochondrial bioenergetics and dynamics precede the development of albuminuria and renal histological changes. Specifically, in early diabetes (4 weeks), a decrease in ATP content and mitochondrial fragmentation within proximal tubule epithelial cells (PTECs) of diabetic kidneys were clearly apparent, but no changes in urinary albumin excretion or glomerular morphology were evident at this time. By 8 weeks of diabetes, there was increased capacity for mitochondrial permeability transition (mPT) by pore opening, which persisted over time and correlated with mitochondrial hydrogen peroxide (H 2 O 2 ) generation and glomerular damage. Late in diabetes, by week 16, tubular damage was evident with increased urinary kidney injury molecule-1 (KIM-1) excretion, where an increase in the Complex I-linked oxygen consumption rate (OCR), in the context of a decrease in kidney ATP , indicated mitochondrial uncoupling. Taken together, these data show that changes in mitochondrial bioenergetics and dynamics may precede the development of the renal lesion in diabetes, and this supports the hypothesis that mitochondrial dysfunction is a primary cause of DKD

Vitamin D supplementation for the prevention of type 2 diabetes in overweight adults: study protocol for a randomized controlled trial

Despite Australia's sunny climate, low vitamin D levels are increasingly prevalent. Sun exposure is limited by long working hours, an increase in time spent indoors, and sun protection practices, and there is limited dietary vitamin D fortification. While the importance of vitamin D for bone mineralization is well known, its role as a protective agent against chronic diseases, such as type 2 diabetes and cardiovascular disease, is less understood. Observational and limited intervention studies suggest that vitamin D might improve insulin sensitivity and secretion, mainly via its anti-inflammatory properties, thereby decreasing the risk of development and progression of type 2 diabetes. The primary aim of this trial is to investigate whether improved plasma concentrations of 25-hydroxyvitamin D (25(OH)D), obtained through vitamin D supplementation, will increase insulin sensitivity and insulin secretion. A secondary aim is to determine whether these relationships are mediated by a reduction in underlying subclinical inflammation associated with obesity.Fifty overweight but otherwise healthy nondiabetic adults between 18 and 60 years old, with low vitamin D levels (25(OH)D < 50 nmol/l), will be randomly assigned to intervention or placebo. At baseline, participants will undergo a medical review and anthropometric measurements, including dual X-ray absorptiometry, an intravenous glucose tolerance test, muscle and fat biopsies, a hyperinsulinemic euglycemic clamp, and questionnaires assessing diet, physical activity, sun exposure, back and knee pain, and depression. The intervention group will receive a first dose of 100,000 IU followed by 4,000 IU vitamin D (cholecalciferol) daily, while the placebo group will receive apparently identical capsules, both for a period of 16 weeks. All measurements will be repeated at follow-up, with the primary outcome measure expressed as a change from baseline in insulin sensitivity and secretion for the intervention group compared with the placebo group. Secondary outcome measures will compare changes in anthropometry, cardiovascular risk factors, and inflammatory markers.The trial will provide much needed clinical evidence on the impact of vitamin D supplementation on insulin resistance and secretion and its underlying mechanisms, which are relevant for the prevention and management of type 2 diabetes.Clinicaltrials.gov ID: NCT02112721 .Barbora de Courten, Aya Mousa, Negar Naderpoor, Helena Teede, Maximilian P J de Courten and Robert Scrag