👤 Christine Wanke

Plasmalemma vesicle-associated protein (PLVAP) is the main component of endothelial diaphragms in fenestrae, caveolae, and transendothelial channels. PLVAP is expressed in the adult kidney glomerulus upon injury. Glomerular endothelial injury is associated with progressive loss of kidney function in diabetic kidney disease (DKD). This study aimed to investigate whether PLVAP could serve as a marker for glomerular endothelial damage in DKD. Glomerular PLVAP expression was analyzed in different mouse models of DKD and their respective healthy control animals using automatic digital quantification of histological whole kidney sections. Transgenic mice expressing a dominant-negative GIP receptor (GIPR Show less

Cardiovascular disease (CVD) risk with low high-density lipoprotein cholesterol (HDL-C) and high triglycerides is common in the general population in India. As nevirapine (NVP)-based antiretroviral therapy (ART) tends to increase HDL-C, gene polymorphisms associated with HDL-C metabolism in HIV-infected adults on stable NVP-based ART were studied. A cross-sectional study was conducted between January 2013 and July 2014 among adults receiving NVP-based ART for 12-15 months. Blood lipids were estimated and gene polymorphisms in apolipoprotein C3 (APOC3), cholesteryl ester transfer protein (CETP) and lipoprotein lipase (LPL) genes were analyzed by real-time polymerase chain reaction. Framingham's 10-yr CVD risk score was estimated. Logistic regression was done to show factors related to low HDL-C levels. Of the 300 patients included (mean age: 38.6±8.7 yr; mean CD4 count 449±210 cell/μl), total cholesterol (TC) >200 mg/dl was observed in 116 (39%) patients. Thirty nine per cent males and 47 per cent females had HDL-C levels below normal while 32 per cent males and 37 per cent females had TC/HDL ratio of 4.5 and 4.0, respectively. Body mass index [adjusted odds ratio (aOR)=1.70, 95% confidence interval (CI) 1.01-2.84, P=0.04] and viral load (aOR=3.39, 95% CI: 1.52-7.52, P=0.003) were negatively associated with serum HDL-C levels. The 10-yr risk score of developing CVD was 11-20 per cent in 3 per cent patients. Allelic variants of APOC3 showed a trend towards low HDL-C. High-risk lipid profiles for atherosclerosis and cardiovascular disease were common among HIV-infected individuals, even after 12 months of NVP-based ART. Targeted interventions to address these factors should be recommended in the national ART programmes. Show less

The glucagon-like peptide-1 receptor (GLP1R) agonist liraglutide improves glycemic control and reduces body weight of adult type 2 diabetic patients. However, efficacy and safety of liraglutide in adolescents has not been systematically investigated. Furthermore, possible pro-proliferative effects of GLP1R agonists on the endocrine and exocrine pancreas need to be further evaluated. We studied effects of liraglutide in adolescent pigs expressing a dominant-negative glucose-dependent insulinotropic polypeptide receptor (GIPR(dn)) in the beta-cells, leading to a pre-diabetic condition including disturbed glucose tolerance, reduced insulin secretion and progressive reduction of functional beta-cell mass. Two-month-old GIPR(dn) transgenic pigs were treated daily with liraglutide (0.6-1.2 mg per day) or placebo for 90 days. Glucose homeostasis was evaluated prior to and at the end of the treatment period by performing mixed meal and intravenous glucose tolerance tests (MMGTT and IVGTT). Finally animals were subjected to necropsy and quantitative-stereological analyses were performed for evaluation of alpha- and beta-cell mass, beta-cell proliferation as well as acinus-cell proliferation. MMGTT at the end of the study revealed 23% smaller area under the curve (AUC) for glucose, a 36% smaller AUC insulin, and improved insulin sensitivity, while IVGTT showed a 15% smaller AUC glucose but unchanged AUC insulin in liraglutide- vs. placebo-treated animals. Liraglutide led to marked reductions in body weight gain (-31%) and food intake (-30%) compared to placebo treatment, associated with reduced phosphorylation of insulin receptor beta (INSRB)/insulin-like growth factor-1 receptor beta (IGF1RB) and protein kinase B (AKT) in skeletal muscle. Absolute alpha- and beta-cell mass was reduced in liraglutide-treated animals, but alpha- and beta-cell mass-to-body weight ratios were unchanged. Liraglutide neither stimulated beta-cell proliferation in the endocrine pancreas nor acinus-cell proliferation in the exocrine pancreas, excluding both beneficial and detrimental effects on the pig pancreas. Although plasma liraglutide levels of adolescent transgenic pigs treated in our study were higher compared to human trials, pro-proliferative effects on the endocrine or exocrine pancreas or other liraglutide-related side-effects were not observed. Show less

The aim of this study was to examine postnatal islet and beta-cell expansion in healthy female control mice and its disturbances in diabetic GIPR(dn) transgenic mice, which exhibit an early reduction of beta-cell mass. Pancreata of female control and GIPR(dn) transgenic mice, aged 10, 45, 90 and 180 days were examined, using state-of-the-art quantitative-stereological methods. Total islet and beta-cell volumes, as well as their absolute numbers increased significantly until 90 days in control mice, and remained stable thereafter. The mean islet volumes of controls also increased slightly but significantly between 10 and 45 days of age, and then remained stable until 180 days. The total volume of isolated beta-cells, an indicator of islet neogenesis, and the number of proliferating (BrdU-positive) islet cells were highest in 10-day-old controls and declined significantly between 10 and 45 days. In GIPR(dn) transgenic mice, the numbers of islets and beta-cells were significantly reduced from 10 days of age onwards vs. controls, and no postnatal expansion of total islet and beta-cell volumes occurred due to a reduction in islet neogenesis whereas early islet-cell proliferation and apoptosis were unchanged as compared to control mice. Insulin secretion in response to pharmacological doses of GIP was preserved in GIPR(dn) transgenic mice, and serum insulin to pancreatic insulin content in response to GLP-1 and arginine was significantly higher in GIPR(dn) transgenic mice vs. controls. We could show that the increase in islet number is mainly responsible for expansion of islet and beta-cell mass in healthy control mice. GIPR(dn) transgenic mice show a disturbed expansion of the endocrine pancreas, due to perturbed islet neogenesis. Show less

Early stages of various entities of progressive kidney diseases are commonly characterized by development of glomerular hypertrophy and albuminuria. The purpose of the present study was to identify protein biomarker candidates for these glomerular alterations. Quantitative differences in the glomerular proteomes of two unrelated murine nephropathy models in the defined stage of glomerular hypertrophy at onset of albuminuria were identified by 2-D DIGE and MALDI-TOF/TOF analysis. Investigated mouse models were (I): transgenic (tg) mice expressing a dominant negative glucose-dependent insulinotropic polypeptide receptor (GIPR(dn) ), a model of diabetes mellitus associated nephropathy and (II): growth hormone (GH)-tg mice, an established model of progressive glomerulosclerosis. In GIPR(dn) -tg mice, nine differentially abundant glomerular proteins were unambiguously identified, and eight in GH-tg mice (each versus controls). Four proteins (Annexin A4, Dihydropyrimidinase-related protein 2, Myosin regulatory light chain 2, Tropomyosin 1) displayed a congeneric differential glomerular abundance in both models, thus representing a common differential protein expression profile of glomerular hypertrophy at onset of albuminuria. The glomerular presence of these proteins was also detected in specimen of human focal and segmental glomerulosclerosis and diabetic nephropathy. Our findings suggest a pathogenetic relevance of the identified proteins in early stages of chronic kidney diseases and their potential use as diagnostic markers. Show less

The insulinotropic action of the incretin glucose-dependent insulinotropic polypeptide (GIP) is impaired in type 2 diabetes, while the effect of glucagon-like peptide-1 (GLP-1) is preserved. To evaluate the role of impaired GIP function in glucose homeostasis and development of the endocrine pancreas in a large animal model, we generated transgenic pigs expressing a dominant-negative GIP receptor (GIPR(dn)) in pancreatic islets. GIPR(dn) transgenic pigs were generated using lentiviral transgenesis. Metabolic tests and quantitative stereological analyses of the different endocrine islet cell populations were performed, and beta-cell proliferation and apoptosis were quantified to characterize this novel animal model. Eleven-week-old GIPR(dn) transgenic pigs exhibited significantly reduced oral glucose tolerance due to delayed insulin secretion, whereas intravenous glucose tolerance and pancreatic beta-cell mass were not different from controls. The insulinotropic effect of GIP was significantly reduced, whereas insulin secretion in response to the GLP-1 receptor agonist exendin-4 was enhanced in GIPR(dn) transgenic versus control pigs. With increasing age, glucose control deteriorated in GIPR(dn) transgenic pigs, as shown by reduced oral and intravenous glucose tolerance due to impaired insulin secretion. Importantly, beta-cell proliferation was reduced by 60% in 11-week-old GIPR(dn) transgenic pigs, leading to a reduction of beta-cell mass by 35% and 58% in 5-month-old and 1- to 1.4-year-old transgenic pigs compared with age-matched controls, respectively. The first large animal model with impaired incretin function demonstrates an essential role of GIP for insulin secretion, proliferation of beta-cells, and physiological expansion of beta-cell mass. Show less

Diabetic nephropathy is the leading cause of end-stage renal disease and the largest contributor to the total cost of diabetes care. Rodent models are excellent tools to gain more insight into the pathogenesis of diabetic nephropathy. In the present study, we characterize the age-related sequence of diabetes-associated kidney lesions in GIPR(dn) transgenic mice, a novel mouse model of early-onset diabetes mellitus. Clinical-chemical analyses as well as qualitative and quantitative morphological analyses of the kidneys of GIPR(dn) transgenic animals and nontransgenic littermate controls were performed at 3, 8, 20, and 28 wk of age. Early renal changes of transgenic mice consisted of podocyte hypertrophy, reduced numerical volume density of podocytes in glomeruli, and homogenous thickening of the glomerular basement membrane, followed by renal and glomerular hypertrophy as well as mesangial expansion and matrix accumulation. At 28 wk of age, glomerular damage was most prominent, including advanced glomerulosclerosis, tubulointerstitial lesions, and proteinuria. Real-time PCR demonstrated increased glomerular expression of Col4a1, Fn1, and Tgfb1. Immunohistochemistry revealed increased mesangial deposition of collagen type IV, fibronectin, and laminin. The present study shows that GIPR(dn) transgenic mice exhibit renal changes that closely resemble diabetes-associated kidney alterations in humans. Data particularly from male transgenic mice indicate that podocyte hypertrophy is directly linked to hyperglycemia, without the influence of mechanical stress. GIPR(dn) transgenic mice are considered an excellent new tool to study the mechanisms involved in onset and progression of diabetic nephropathy. Show less

Transgenic mice overexpressing a dominant negative glucose-dependent insulinotropic polypeptide receptor (GIPR(dn)) have recently been shown to develop diabetes mellitus due to disturbed postnatal development of the endocrine pancreas. In this study, the effects of feeding a high fibre/low calorie diet on the diabetic phenotype of GIPR(dn) transgenic mice were examined. Transgenic and control animals received either a conventional breeding diet (BD) or a high fibre diet (HF). Both fasting and postprandial blood glucose levels and HbA1C levels were largely elevated in transgenic mice vs. controls (p<0.05), irrespective of the diet fed. Food and water intake and the daily urine volume of GIPR(dn) transgenic mice were higher than that of control mice (p<0.05). Transgenic animals receiving the HF diet showed significantly lower blood glucose and HbA1C levels as well as less food and water intake than transgenic mice fed BD. The 365-day survival of transgenic mice was significantly lower than that of control mice. Transgenic animals fed the HF diet lived significantly longer than their counterparts receiving BD. GIPR(dn) transgenic mice develop a severe diabetic phenotype which can be ameliorated by a HF diet, thereby resembling some aspects of the pathophysiology of human type 2 diabetes mellitus. Show less

The expression of a dominant negative glucose-dependent insulinotropic polypeptide receptor (GIPRdn) under the control of the rat pro-insulin gene promoter induces severe diabetes mellitus in transgenic mice. This study aims to gain further insight into the effect of the expression of a dominant negative GIPR on glucose homeostasis and postnatal development of the endocrine pancreas. The diabetic phenotype of GIPRdn transgenic animals was first observed between 14 and 21 days of age (urine glucose>1000 mg/dl). After onset of diabetes, serum glucose was significantly higher and insulin values were significantly lower in GIPRdn transgenic mice vs. non-transgenic littermate controls. Morphometric studies of pancreatic islets and their endocrine cell types were carried out at 10, 30 and 90 days of age. The total islet and total beta-cell volume of transgenic mice was severely reduced as compared to control mice, irrespective of the age at sampling (p<0.05). The total volume of isolated insulin positive cells that were not contained within established islets was significantly reduced in transgenic mice, indicating disturbed islet neogenesis. These findings demonstrate in vivo evidence that intact signaling of G-protein coupled receptors is involved in postnatal islet and beta-cell development and neogenesis of the pancreatic islets. Show less

Saccharomyces cerevisiae must reach a carbon source-modulated critical cell size, protein content per cell at the onset of DNA replication (Ps), in order to enter S phase. Cells grown in glucose are larger than cells grown in ethanol. Here, we show that an increased level of the cyclin-dependent inhibitor Far1 increases cell size, whereas far1 Delta cells start bud emergence and DNA replication at a smaller size than wild type. Cln3 Delta, far1 Delta, and strains overexpressing Far1 do not delay budding during an ethanol glucose shift-up as wild type does. Together, these findings indicate that Cln3 has to overcome Far1 to trigger Cln-Cdc28 activation, which then turns on SBF- and MBF-dependent transcription. We show that a second threshold is required together with the Cln3/Far1 threshold for carbon source modulation of Ps. A new molecular network accounting for the setting of Ps is proposed. Show less