Gary E. Striker

Advanced Glycation End Products in Foods and a Practical Guide to Their Reduction in the Diet

Modern diets are largely heat-processed and as a result contain high levels of advanced glycation end products (AGEs). Dietary advanced glycation end products (dAGEs) are known to contribute to increased oxidant stress and inflammation, which are linked to the recent epidemics of diabetes and cardiovascular disease. This report significantly expands the available dAGE database, validates the dAGE testing methodology, compares cooking procedures and inhibitory agents on new dAGE formation, and introduces practical approaches for reducing dAGE consumption in daily life. Based on the findings, dry heat promotes new dAGE formation by >10- to 100-fold above the uncooked state across food categories. Animal-derived foods that are high in fat and protein are generally AGE-rich and prone to new AGE formation during cooking. In contrast, carbohydrate-rich foods such as vegetables, fruits, whole grains, and milk contain relatively few AGEs, even after cooking. The formation of new dAGEs during cooking was prevented by the AGE inhibitory compound aminoguanidine and significantly reduced by cooking with moist heat, using shorter cooking times, cooking at lower temperatures, and by use of acidic ingredients such as lemon juice or vinegar. The new dAGE database provides a valuable instrument for estimating dAGE intake and for guiding food choices to reduce dAGE intake.

Screening and management of microalbuminuria in patients with diabetes mellitus: recommendations to the scientific advisory board of the nationals Kidney Foundation from an Ad Hoc Committee of the council on diabetes mel of the national kidney foundation

All individuals with diabetes mellitus should be screened yearly with a spot urine albumin:creatinine ratio to identify those who are at increased risk for the development of complications of diabetes mellitus, including nephropathy, retinopathy, and cardiovascular disease. Once these high-risk individuals are appropriately identified, it is recommended that therapy with an angiotensin-converting enzyme (ACE) inhibitor be initiated. In addition, cardiovascular risk factors should be investigated, and when appropriate, therapeutic interventions should be initiated according to existing recommendations.

Restriction of Advanced Glycation End Products Improves Insulin Resistance in Human Type 2 Diabetes Potential role of AGER1 and SIRT1

OBJECTIVE Increased oxidative stress (OS) and impaired anti-OS defenses are important in the development and persistence of insulin resistance (IR). Several anti-inflammatory and cell-protective mechanisms, including advanced glycation end product (AGE) receptor-1 (AGER1) and sirtuin (silent mating-type information regulation 2 homolog) 1 (SIRT1) are suppressed in diabetes. Because basal OS in type 2 diabetic patients is influenced by the consumption of AGEs, we examined whether AGE consumption also affects IR and whether AGER1 and SIRT1 are involved. RESEARCH DESIGN AND METHODS The study randomly assigned 36 subjects, 18 type 2 diabetic patients (age 61 ± 4 years) and 18 healthy subjects (age 67 ± 1.4 years), to a standard diet (>20 AGE equivalents [Eq]/day) or an isocaloric AGE-restricted diet (<10 AGE Eq/day) for 4 months. Circulating metabolic and inflammatory markers were assessed. Expression and activities of AGER1 and SIRT1 were examined in patients’ peripheral blood mononuclear cells (PMNC) and in AGE-stimulated, AGER1-transduced (AGER1+), or AGER1-silenced human monocyte-like THP-1 cells. RESULTS Insulin and homeostasis model assessment, leptin, tumor necrosis factor-α and nuclear factor-κB p65 acetylation, serum AGEs, and 8-isoprostanes decreased in AGE-restricted type 2 diabetic patients, whereas PMNC AGER1 and SIRT1 mRNA, and protein levels normalized and adiponectin markedly increased. AGEs suppressed AGER1, SIRT-1, and NAD+ levels in THP-1 cells. These effects were inhibited in AGER1+ but were enhanced in AGER1-silenced cells. CONCLUSIONS Food-derived pro-oxidant AGEs may contribute to IR in clinical type 2 diabetes and suppress protective mechanisms, AGER1 and SIRT1. AGE restriction may preserve native defenses and insulin sensitivity by maintaining lower basal OS.

Mouse Embryonic Stem Cell–Derived Embryoid Bodies Generate Progenitors That Integrate Long Term into Renal Proximal Tubules In Vivo

The metanephric kidney is a mesodermal organ that develops as a result of reciprocal interactions between the ureteric bud and the blastema. The generation of embryonic stem (ES) cell-derived progenitors offers potential for regenerative therapies but is often limited by development of tumor formation. Because brachyury (T) denotes mesoderm specification, a mouse ES cell line with green fluorescence protein (GFP) knocked into the functional T locus as well as lacZ in the ROSA26 locus (LacZ/T/GFP) was used in cell selection and lineage tracing. In the absence of leukemia inhibitory factor, mouse ES cells give rise to embryoid bodies that can differentiate into mesoderm. Culture conditions were optimized (4 d, 10 ng/ml Activin-A) to generate maximal numbers of renal progenitor populations identified by expression of the specific combination of renal markers cadherin-11, WT-1, Pax-2, and Wnt-4. LacZ/T/GFP+ cells were further enriched by FACS selection. Five days after injection of LacZ/T/GFP+ cells into embryonic kidney explants in organ culture, beta-galactosidase immunohistochemistry showed incorporation into blastemal cells of the nephrogenic zone. After a single injection into developing live newborn mouse kidneys, co-localization studies showed that the LacZ/T/GFP+ cells were stably integrated into proximal tubules with normal morphology and normal polarization of alkaline phosphatase and aquaporin-1 for 7 mo, without teratoma formation. It is concluded that defined differentiation of ES cells into embryoid bodies with Activin-A and selection for T expression provides a means to isolate and purify renal proximal tubular progenitor cells with the potential for safe use in regenerative therapies.

Maternally Transmitted and Food-Derived Glycotoxins A factor preconditioning the young to diabetes?

OBJECTIVE Proinflammatory advanced glycation end products (AGEs) found in thermally processed foods correlate with serum AGEs (sAGEs) and promote type 1 and type 2 diabetes in mice. Herein we assess the relationship of maternal blood and food AGEs to circulating glycoxidants, inflammatory markers, and insulin levels in infants up to age 1 year. RESEARCH DESIGN AND METHODS AGEs (Nε-carboxymethyllysine [CML] and methylglyoxal derivatives) were tested in sera of healthy mothers in labor (n = 60), their infants, and infant foods. Plasma 8-isoprostane, fasting glucose, insulin, leptin, and adiponectin levels were assessed in 12-month-old infants. RESULTS Significant correlations were found between newborn and maternal serum CML (sCML) (r = 0.734, P = 0.001) serum methylglyoxal derivatives (sMGs) (r = 0.593, P = 0.001), and 8-isoprostanes (r = 0.644, P = 0.001). Infant adiponectin at 12 months negatively correlated with maternal sCML (r = −0.467, P = 0.011), whereas high maternal sMGs predicted higher infant insulin or homeostasis model assessment (P = 0.027). Infant sAGEs significantly increased with the initiation of processed infant food intake, raising daily AGE consumption by ∼7.5-fold in year 1. CONCLUSIONS Maternal blood and food-derived AGEs prematurely raise AGEs in children to adult norms, preconditioning them to abnormally high oxidant stress and inflammation and thus possibly to early onset of disease, such as diabetes.

AGER1 regulates endothelial cell NADPH oxidase-dependent oxidant stress via PKC-δ: implications for vascular disease

Advanced glycated end-product receptor 1 (AGER1) protects against vascular disease promoted by oxidants, such as advanced glycated end products (AGEs), via inhibition of reactive oxygen species (ROS). However, the specific AGEs, sources, and pathways involved remain undefined. The mechanism of cellular NADPH oxidase (NOX)-dependent ROS generation by defined AGEs, N(epsilon)-carboxymethyl-lysine- and methylglyoxal (MG)-modified BSA, was assessed in AGER1 overexpressing (AGER1(+) EC) or knockdown (sh-mRNA-AGER1(+) EC) human aortic endothelial (EC) and ECV304 cells, and aortic segments from old (18 mo) C57BL6-F(2) mice, propagated on low-AGE diet (LAGE), or LAGE supplemented with MG (LAGE+MG). Wild-type EC and sh-mRNA-AGER1(+) EC, but not AGER1(+) EC, had high NOX p47(phox) and gp91(phox) activity, superoxide anions, and NF-kappaB p65 nuclear translocation in response to MG and N(epsilon)-carboxymethyl-lysine. These events involved epidermal growth factor receptor-dependent PKC-delta redox-sensitive Tyr-311 and Tyr-332 phosphorylation and were suppressed in AGER1(+) ECs and enhanced in sh-mRNA-AGER1(+) ECs. Aortic ROS, PKC-delta Tyr-311, and Tyr-332 phosphorylation, NOX expression, and nuclear p65 in older LAGE+MG mice were significantly increased above that in age-matched LAGE mice, which had higher levels of AGER1. In conclusion, circulating AGEs induce NADPH-dependent ROS generation in vascular aging in both in vitro and in vivo models. Furthermore, AGER1 provides protection against AGE-induced ROS generation via NADPH.

Overexpression of Human Insulin-Like Growth Factor Binding Protein-1 in the Mouse Leads to Nephron Deficit

IGFs and their binding proteins are important regulators of fetal development. We have previously reported that overexpression of the human IGF binding protein-1 in mice is associated with glomerulosclerosis. The aim of this study was to investigate whether, in that model, decreased bioavailability of IGFs also affected nephrogenesis. When the mothers expressed human IGF binding protein-1, pups were growth retarded and had a reduced number of nephrons. Even nontransgenic pups born to heterozygous mothers had a nephron reduction, indicating that renal hypoplasia was secondary to fetal growth retardation. When the transgene was expressed only in the fetus, pups had a normal birth weight and the kidney was normal at birth, as indicated by histologic studies. However, a significant reduction in the nephron number was observed at 3 mo of age. Because nephrogenesis continues for a few days after birth in the mouse, this indicated that human IGF binding protein-1 overexpression altered postnatal nephrogenesis. In addition, exogenously added IGF-II, but not IGF-I, was effective in stimulating in vitro nephrogenesis. Together these elements suggest that reduced amounts of circulating IGFs, presumably IGF-II, impair kidney development.

Pentosan polysulfate treatment reduces cyclosporine-induced nephropathy in salt-depleted rats.

BACKGROUNDnLong-term cyclosporine (CsA) treatment leads to a decreased glomerular filtration rate, hyalinosis of afferent arterioles, and striped cortical tubulo-interstitial fibrosis. We showed previously that pentosan polysulfate (SP54) prevented the development of microvascular and interstitial lesions in mouse models of progressive glomerulosclerosis. In this study, we examined the effect of pentosan polysulfate on the development of CsA nephropathy.nnnMETHODSnPair-fed Sprague-Dawley rats were fed a low-sodium (0.03%) diet and received CsA (15 mg/kg, subcutaneously, in olive oil)/5% glucose, pentosan polysulfate (10 mg/kg, subcutaneously in 5% glucose) plus CsA, olive oil/pentosan polysulfate, or olive oil/5% glucose for 30 days. Creatinine clearance (CrCl) was determined at three time points. Afferent arteriolar lesions, glomerular volume, and tubulo-interstitial lesions were quantitated. RNA was extracted from cortex.nnnRESULTSnSevere lesions were found in the CsA group. A reduction in the number of affected arterioles (32%) and the degree of chronic tubulo-interstitial lesions (44%) was found in pentosan polysulfate/CsA-treated rats. A 20% decrease in glomerular volume was found in CsA rats, but not in pentosan polysulfate/CsA-treated rats. Pentosan polysulfate treatment did not prevent the CsA-induced decrease in CrCl (approximately 30%) at 4 weeks. CsA did not affect cortical endothelial or neuronal nitric-oxide synthase or mRNA levels, but there was small increase in neuronal nitric-oxide synthase mRNA levels in the pentosan polysulfate/CsA-treated group.nnnCONCLUSIONSnPentosan polysulfate reduced structural renal lesions in CsA-treated, salt-depleted Sprague-Dawley rats.

Glomerular Lesions in Malignancies

Glomerular lesions have been recognized in nearly all forms of malignant diseases. The incidence within each category of malignancy varies substantially but in most series represents less than 2% of the population. While there is a considerable variety of glomerular lesions, a number of general statements may be made. In Hodgkins disease and other lymphomas, the most common lesion is minimal lesion nephrotic syndrome, reflecting possibly an anomaly of T cell function. Amyloidosis which used to be the commonest lesion has nearly disappeared. On the other hand, in patients with chronic lymphocytic leukemia a large proportion of glomerular lesions fall into the category of proliferative glomerulonephritis. In carcinoma the vast majority of glomerular lesions with proteinuria or the nephrotic syndrome are due to membranous glomerulonephritis. This suggests either a local alteration of fixed glomerular antigens, or localization of tumor antigens planted in the glomeruli leading to the formation of local immunocomplexes. Amyloid AA is still frequent in carcinoma and complicates as much as 3% of renal adenocarcinomas.

The Aging Kidney Phenotype and Systemically Derived Stem Cells

The desire to extend lifespan and health has occupied the scientific and lay communities during most of recorded history. This quest includes the search for some magical elixir: Ponce de Leon vainly sought the legendary Fountain of Youth in Florida, and charlatans continue to sell potions that