The physiological effects of deleting the mouse SLC30A8 gene encoding zinc transporter-8 are influenced by gender and genetic background.

The SLC30A8 gene encodes the islet-specific transporter ZnT-8, which is hypothesized to provide zinc for insulin-crystal formation. A polymorphic variant in SLC30A8 is associated with altered susceptibility to type 2 diabetes. Several groups have examined the effect of global Slc30a8 gene deletion but the results have been highly variable, perhaps due to the mixed 129SvEv/C57BL/6J genetic background of the mice studied. We therefore sought to remove the conflicting effect of 129SvEv-specific modifier genes.The impact of Slc30a8 deletion was examined in the context of the pure C57BL/6J genetic background.Male C57BL/6J Slc30a8 knockout (KO) mice had normal fasting insulin levels and no change in glucose-stimulated insulin secretion (GSIS) from isolated islets in marked contrast to the ∼50% and ∼35% decrease, respectively, in both parameters observed in male mixed genetic background Slc30a8 KO mice. This observation suggests that 129SvEv-specific modifier genes modulate the impact of Slc30a8 deletion. In contrast, female C57BL/6J Slc30a8 KO mice had reduced (∼20%) fasting insulin levels, though this was not associated with a change in fasting blood glucose (FBG), or GSIS from isolated islets. This observation indicates that gender also modulates the impact of Slc30a8 deletion, though the physiological explanation as to why impaired insulin secretion is not accompanied by elevated FBG is unclear. Neither male nor female C57BL/6J Slc30a8 KO mice showed impaired glucose tolerance.Our data suggest that, despite a marked reduction in islet zinc content, the absence of ZnT-8 does not have a substantial impact on mouse physiology

Requirement for Class II Phosphoinositide 3-Kinase C2α in Maintenance of Glomerular Structure and Function▿

An early lesion in many kidney diseases is damage to podocytes, which are critical components of the glomerular filtration barrier. A number of proteins are essential for podocyte filtration function, but the signaling events contributing to development of nephrotic syndrome are not well defined. Here we show that class II phosphoinositide 3-kinase C2α (PI3KC2α) is expressed in podocytes and plays a critical role in maintaining normal renal homeostasis. PI3KC2α-deficient mice developed chronic renal failure and exhibited a range of kidney lesions, including glomerular crescent formation and renal tubule defects in early disease, which progressed to diffuse mesangial sclerosis, with reduced podocytes, widespread effacement of foot processes, and modest proteinuria. These findings were associated with altered expression of nephrin, synaptopodin, WT-1, and desmin, indicating that PI3KC2α deficiency specifically impacts podocyte morphology and function. Deposition of glomerular IgA was observed in knockout mice; importantly, however, the development of severe glomerulonephropathy preceded IgA production, indicating that nephropathy was not directly IgA mediated. PI3KC2α deficiency did not affect immune responses, and bone marrow transplantation studies also indicated that the glomerulonephropathy was not the direct consequence of an immune-mediated disease. Thus, PI3KC2α is critical for maintenance of normal glomerular structure and function by supporting normal podocyte function

Prolonging the circulatory retention of SPIONs using dextran sulfate : in vivo tracking achieved by functionalisation with near-infrared dyes

<p>Intraperitoneal (Panels <b>A</b> and <b>C</b>) and oral (Panel <b>B</b>) glucose tolerance tests were performed on 6 hr fasted conscious C57BL/6J WT (closed symbols) and <i>Slc30a8</i> KO (open symbols) male mice as described in Materials and Methods. The IPGTT results in Panel <b>A</b> show the mean glucose concentrations ± S.E.M. in WT (n = 11; mean age ∼20 weeks) and <i>Slc30a8</i> KO (n = 9; mean age ∼20 weeks) animals. The OGTT results in Panel <b>B</b> show the mean glucose concentrations ± S.E.M. in WT (n = 16; mean age ∼22 weeks) and <i>Slc30a8</i> KO (n = 9; mean age ∼22 weeks) animals. The IPGTT results in Panel <b>C</b> show the mean glucose concentrations ± S.E.M. in WT (n = 17; mean age ∼4 weeks) and <i>Slc30a8</i> KO (n = 19; mean age ∼4 weeks) animals. *p<0.05 <i>versus</i> WT.</p

Biochemical characterization of C57BL/6J <i>Slc30a8</i> KO mice.

<p><b>Panel A:</b> Immunohistochemical staining of wild type and <i>Slc30a8</i> KO mouse pancreas with antisera raised to insulin, glucagon, and ZnT-8 was performed as described in Materials and Methods. Representative pictures are shown. WT, wild type; KO, knockout. <b>Panel B:</b> Zinc content in isolated islets was determined as described in Material and Methods. Results represent the mean ± S.E.M. (n = 3 independent islet preparations for each genotype with each islet preparation assayed in quintuplicate). *p<0.05 <i>versus</i> WT.</p

Analysis of insulin content and glucose-stimulated insulin secretion in male C57BL/6J <i>Slc30a8</i> KO mouse islets <i>in situ</i>.

<p>Islets were isolated from male C57BL/6J WT and <i>Slc30a8</i> KO mice and then insulin content (<b>Panel A</b>) and glucose-stimulated insulin secretion (<b>Panel B</b>) were assayed as described in Materials and Methods. Results show the mean data ± S.E.M. from 3 islet preparations isolated from ∼18 week old male mice. *p<0.05 <i>versus</i> 5 mM glucose.</p

Normalized expression of selected <i>SLC30</i> genes by quantitative RT-PCR in 9–23 week old human fetal pancreas and adult human islets.

<p>Data in triplicate (mean ± S.E.M.) is normalized to endogenous <i>GAPDH</i> and quantified and expressed relative to 9 week old fetal samples. <i>SLC30A2</i> expression was detectable in the fetal pancreas from 19 weeks. *p<0.05 from 9 weeks for <i>SLC30A8</i> (black bars).</p

Phenotypic characterization of fasted C57BL/6J <i>Slc30a8</i> KO mice.

<p>Length: *F WT vs. F KO, p<0.01; Cholesterol: *M WT vs. M Het p<0.01; Insulin: *F WT vs. F Het, p<0.001; **F WT vs. F KO, p<0.05; Proinsulin: *M WT vs. KO, p<0.05.</p><p>At 16 weeks of age mice were fasted for 5 hours and then weighed. One hour later mice were anesthetized, their length was measured and blood isolated. Blood glucose and plasma cholesterol, triacylglycerol, glycerol, insulin and glucagon levels were determined as described in Materials and Methods. Results represent mean data ± S.E.M. obtained from the indicated number of animals in parentheses.</p