Absence of Diabetes and Pancreatic Exocrine Dysfunction in a Transgenic Model of Carboxyl-Ester Lipase-MODY (Maturity-Onset Diabetes of the Young)

Background

CEL-MODY is a monogenic form of diabetes with exocrine pancreatic insufficiency caused by mutations in CARBOXYL-ESTER LIPASE (CEL). The pathogenic processes underlying CEL-MODY are poorly understood, and the global knockout mouse model of the CEL gene (CELKO) did not recapitulate the disease. We therefore aimed to create and phenotype a mouse model specifically over-expressing mutated CEL in the pancreas.

Methods

We established a monotransgenic floxed (flanking LOX sequences) mouse line carrying the human CEL mutation c.1686delT and crossed it with an elastase-Cre mouse to derive a bitransgenic mouse line with pancreas-specific over-expression of CEL carrying this disease-associated mutation (TgCEL). Following confirmation of murine pancreatic expression of the human transgene by real-time quantitative PCR, we phenotyped the mouse model fed a normal chow and compared it with mice fed a 60% high fat diet (HFD) as well as the effects of short-term and long-term cerulein exposure.

Results

Pancreatic exocrine function was normal in TgCEL mice on normal chow as assessed by serum lipid and lipid-soluble vitamin levels, fecal elastase and fecal fat absorption, and the normoglycemic mice exhibited normal pancreatic morphology. On 60% HFD, the mice gained weight to the same extent as controls, had normal pancreatic exocrine function and comparable glucose tolerance even after resuming normal diet and follow up up to 22 months of age. The cerulein-exposed TgCEL mice gained weight and remained glucose tolerant, and there were no detectable mutation-specific differences in serum amylase, islet hormones or the extent of pancreatic tissue inflammation.

Conclusions

In this murine model of human CEL-MODY diabetes, we did not detect mutation-specific endocrine or exocrine pancreatic phenotypes, in response to altered diets or exposure to cerulein.     

Biotechnological production of l(+)-lactic acid from wood hydrolyzate by batch fermentation of Enterococcus faecalis

The inhibition of lactic acid fermentation by wood hydrolyzate was decreased (approx. 20%) by adaptation of Enterococcus faecalis RKY1 to wood hydrolyzate-based medium whereby lactic acid productivity and cell growth were enhanced by 0.5 g l(-1) h(-1) and 2.1 g l(-1), respectively. When the diluted or concentrated wood hydrolyzate (equivalent to 25-100 g glucose l(-1)) was supplemented with 15 g yeast extract l(-1), 24-93 g lactic acid l(-1) was produced at a rate between 1.7 g l(-1) h(-1) and 3.2 g l(-1) h(-1).     

Synergism between curdlan and GM-CSF confers a strong inflammatory signature to dendritic cells

A simultaneous engagement of different pathogen recognition receptors provides a tailor-made adaptive immunity for an efficient defense against distinct pathogens. For example, cross-talk of TLR and C-type lectin signaling effectively shapes distinct gene expression patterns by integrating the signals at the level of NF-κB. In this study, we extend this principle to a strong synergism between the dectin-1 agonist curdlan and an inflammatory growth factor, GM-CSF. Both together act in synergy in inducing a strong inflammatory signature that converts immature dendritic cells (DCs) to potent effector DCs. A variety of cytokines (IL-1β, IL-6, TNF-α, IL-2, and IL-12p70), costimulatory molecules (CD80, CD86, CD40, and CD70), chemokines (CXCL1, CXCL2, CXCL3, CCL12, CCL17), as well as receptors and molecules involved in fugal recognition and immunity such as Mincle, dectin-1, dectin-2, and pentraxin 3 are strongly upregulated in DC treated simultaneously with curdlan and GM-CSF. The synergistic effect of both stimuli resulted in strong IκBα phosphorylation, its rapid degradation, and enhanced nuclear translocation of all NF-κB subunits. We further identified MAPK ERK as one possible integration site of both signals, because its phosphorylation was clearly augmented when curdlan was coapplied with GM-CSF. Our data demonstrate that the immunomodulatory activity of curdlan requires an additional signal provided by GM-CSF to successfully initiate a robust β-glucan-specific cytokine and chemokine response. The integration of both signals clearly prime and tailor a more effective innate and adaptive response against invading microbes and fungi.     

CASVM: web server for SVM-based prediction of caspase substrates cleavage sites

Caspases belong to a unique class of cysteine proteases which function as critical effectors of apoptosis, inflammation and other important cellular processes. Caspases cleave substrates at specific tetrapeptide sites after a highly conserved aspartic acid residue. Prediction of such cleavage sites will complement structural and functional studies on substrates cleavage as well as discovery of new substrates. We have recently developed a support vector machines (SVM) method to address this issue. Our algorithm achieved an accuracy ranging from 81.25 to 97.92%, making it one of the best methods currently available. CASVM is the web server implementation of our SVM algorithms, written in Perl and hosted on a Linux platform. The server can be used for predicting non-canonical caspase substrate cleavage sites. We have also included a relational database containing experimentally verified caspase substrates retrievable using accession IDs, keywords or sequence similarity. AVAILABILITY: http://www.casbase.org/casvm/index.html     

Effects of acutely inhibiting PI3K isoforms and mTOR on regulation of glucose metabolism in vivo

In in vitro studies class-I PI3Ks (phosphoinositide 3-kinases), class-II PI3Ks and mTOR (mammalian target of rapamycin) have all been described as having roles in the regulation of glucose metabolism. The relative role each plays in the normal signalling processes regulating glucose metabolism in vivo is less clear. Knockout and knockin mouse models have provided some evidence that the class-I PI3K isoforms p110α, p110β, and to a lesser extent p110γ, are necessary for processes regulating glucose metabolism and appetite. However, in these models the PI3K activity is chronically reduced. Therefore we analysed the effects of acutely inhibiting PI3K isoforms alone, or PI3K and mTOR, on glucose metabolism and food intake. In the present study impairments in glucose tolerance, insulin tolerance and increased hepatic glucose output were observed in mice treated with the pan-PI3K/mTOR inhibitors PI-103 and NVP-BEZ235. The finding that ZSTK474 has similar effects indicates that these effects are due to inhibition of PI3K rather than mTOR. The p110α-selective inhibitors PIK75 and A66 also induced these phenotypes, but inhibitors of p110β, p110δ or p110γ induced only minor effects. These drugs caused no significant effects on BMR (basal metabolic rate), O2 consumption or water intake, but BEZ235, PI-103 and PIK75 did cause a small reduction in food consumption. Surprisingly, pan-PI3K inhibitors or p110α inhibitors caused reductions in animal movement, although the cause of this is not clear. Taken together these studies provide pharmacological evidence to support a pre-eminent role for the p110α isoform of PI3K in pathways acutely regulating glucose metabolism.     

Large increase in Leuconostoc citreum KM20 dextransucrase activity achieved by changing the strain/inducer combination in an E. coli expression system

A recombinant putative dextransucrase (DexT) was produced from Leuconostoc citreum KM20 as a 160 kDa protein, but its productivity was very low (264 U/l). For optimization, we examined enzyme activity in 7 Escherichia coli strains with inducer molecules such as lactose or IPTG. E. coli BL21-CodonPlus(DE3)-RIL exhibited the highest enzyme activity with lactose. Finally, DexT activity was remarkably increased by 12-fold under the optimized culture conditions of a cell density to start induction (OD???) of 0.95, a lactose concentration of 7.5 mM, and an induction temperature of 17 degrees C. These results may effectively apply to the heterologous expression of other large DexT genes.