Effects of age, diet and obesity on insulin secretion from isolated perfused rat pancreas: Response to glucose, arginine and glucagon-like peptide 1 (7-37)

The insulin secretory responses to glucose, arginine and glucagon-like peptide (GLP)-1-(7- 37 have been evaluated from the isolated perfused pancreas of rats with either acquired or genetic obesity, ie, a) fed ad libitum 14-mo old Sprague-Dawley rats as compared to age-matched animals subjected to two types of dietary restriction (every-other-day feeding, EOD, and 40% restriction? 40% DR), and b) 2.5-mo old genetically obese fa/fa rats as compared to the lean counterpart, In mature fed ad libitum rats, the glucose-stimulated insulin release from the perfused pancreas was increased 5-fold by addition of 0.1 nM GLP-1 (7-37), a subsequent challenge with high glucose resulted in an improvement of the first phase of insulin release, In 40% DR rats, a similar pattern of secretion was observed, with the difference of a lower response to arginine than in fed ad libitum animals, In EOD rats, the overall secretory performance of the perfused pancreas was approximately 50% lower than in the fed ad libitum group but probably adequate to the reduced weight of the animals, In genetically obese young rats, both the response to GLP-1 (7-37) anti the total insulin secretion were higher than in the lean controls. Interestingly, the maximal insulin outputs from the perfused pancreases were observed in both the groups of overweight animals, In conclusion no impairment in the secretory responsiveness of beta-cells occurs in obese animals, Conversely, at least within the age limits of the present study, the endocrine pancreas develops a compensatory ability to match the augmented insulin demand due to the over-weight. In the light of the observed great sensitivity of the isolated perfused pancreas to GLP-1 (7-37), changes in the responsiveness of beta-cells to incretins might be involved in the modulation of the endocrine pancreatic function of obese rats

MILK PRODUCTION IN COMMERCIAL CATTLE DAIRY FARMS IN KOSOVA

A study research was carried out in comercial dairy farms in Kosovo with the aim to contribute to the understanding of the situation of milk production and factors affecting milk productivity. Seventeen dairy cattle farms were selected for the study. The fresh milk samples were collected and record analyses were done according to the International Committee for Animal Recording using the A4 standard method, and were carried out from August 2007 till September 2008. Meanwhile, 4694 milk samples from 461 individual cows were collected. Depending on the cow breed, daily milk yield was very different (P < 0.0001) ranging from 18.92 0.22 to 12.34 0.53. Effect of the farm and lactation number was also very significant (P < 0.0001), showing that there are huge managment variation from farm to farm (for about 14.87 kg/day) and during different lactations (16.910.26 to 18.430.24 kg/day). According to this study, although in generaly milk yield was very much constant, in some months of year cows in Kosovo tend to produce more milk. Huge differences (about 29.06%) were noticed also within the same breed comparing the current production in Kosovo and from cow breed origine in Austria. It was concluded that low milk yield was achieved for all breeds compared to their genetic potential. Furthermore, according to current dairy farm management condition in Kosovo, more favorable breeds tend to be dual purpose breeds compare to more milk specialized ones

MILK PRODUCTION IN COMMERCIAL CATTLE DAIRY FARMS IN KOSOVA

A study research was carried out in comercial dairy farms in Kosovo with the aim to contribute to the understanding of the situation of milk production and factors affecting milk productivity. Seventeen dairy cattle farms were selected for the study. The fresh milk samples were collected and record analyses were done according to the International Committee for Animal Recording using the A4 standard method, and were carried out from August 2007 till September 2008. Meanwhile, 4694 milk samples from 461 individual cows were collected. Depending on the cow breed, daily milk yield was very different (P < 0.0001) ranging from 18.92 0.22 to 12.34 0.53. Effect of the farm and lactation number was also very significant (P < 0.0001), showing that there are huge managment variation from farm to farm (for about 14.87 kg/day) and during different lactations (16.910.26 to 18.430.24 kg/day). According to this study, although in generaly milk yield was very much constant, in some months of year cows in Kosovo tend to produce more milk. Huge differences (about 29.06%) were noticed also within the same breed comparing the current production in Kosovo and from cow breed origine in Austria. It was concluded that low milk yield was achieved for all breeds compared to their genetic potential. Furthermore, according to current dairy farm management condition in Kosovo, more favorable breeds tend to be dual purpose breeds compare to more milk specialized ones

Increasing uncoupling protein-2 in pancreatic beta cells does not alter glucose-induced insulin secretion but decreases production of reactive oxygen species

Aims/hypothesis: Levels of uncoupling protein-2 (UCP2) are regulated in the pancreatic beta cells and an increase in the protein level has been associated with mitochondrial uncoupling and alteration in glucose-stimulated insulin secretion. However, it is not clear whether an increase in uncoupling protein-2 per se induces mitochondrial uncoupling and affects ATP generation and insulin secretion. Materials and methods: Transgenic mice with beta cell-specific overexpression of the human UCP2 gene and INS-1 cells with doxycycline-inducible overproduction of the protein were generated and the consequences of increased levels of UCP2 on glucose-induced insulin secretion and on parameters reflecting mitochondrial uncoupling were determined. Results: In transgenic mice, an increase in beta cell UCP2 protein concentration did not significantly modify plasma glucose and insulin levels. Glucose-induced insulin secretion and elevation in the ATP/ADP ratio were unaltered by an increase in UCP2 level. In INS-1 cells, a similar increase in UCP2 level did not modify glucose-induced insulin secretion, cytosolic ATP and ATP/ADP ratio, or glucose oxidation. Increased levels of UCP2 did not modify the mitochondrial membrane potential and oxygen consumption. Increased UCP2 levels decreased cytokine-induced production of reactive oxygen species. Conclusion/interpretation: The results obtained in transgenic mice and in the beta cell line do not support the hypothesis that an increase in UCP2 protein per se uncouples the mitochondria and decreases glucose-induced insulin secretion. In contrast, the observation that increased UCP2 levels decrease cytokine-induced production of reactive oxygen species indicates a potential protective effect of the protein on beta cells, as observed in other cell type

Defining the identity and the niches of epithelial stem cells with highly pleiotropic multilineage potency in the human thymus

Thymus is necessary for lifelong immunological tolerance and immunity. It displays a distinctive epithelial complexity and undergoes age-dependent atrophy. Nonetheless, it also retains regenerative capacity, which, if harnessed appropriately, might permit rejuvenation of adaptive immunity. By characterizing cortical and medullary compartments in the human thymus at single-cell resolution, in this study we have defined specific epithelial populations, including those that share properties with bona fide stem cells (SCs) of lifelong regenerating epidermis. Thymic epithelial SCs display a distinctive transcriptional profile and phenotypic traits, including pleiotropic multilineage potency, to give rise to several cell types that were not previously considered to have shared origin. Using here identified SC markers, we have defined their cortical and medullary niches and shown that, in vitro, the cells display long-term clonal expansion and self-organizing capacity. These data substantively broaden our knowledge of SC biology and set a stage for tackling thymic atrophy and related disorders

Reconstitution of a functional human thymus by postnatal stromal progenitor cells and natural whole-organ scaffolds.

The thymus is a primary lymphoid organ, essential for T cell maturation and selection. There has been long-standing interest in processes underpinning thymus generation and the potential to manipulate it clinically, because alterations of thymus development or function can result in severe immunodeficiency and autoimmunity. Here, we identify epithelial-mesenchymal hybrid cells, capable of long-term expansion in vitro, and able to reconstitute an anatomic phenocopy of the native thymus, when combined with thymic interstitial cells and a natural decellularised extracellular matrix (ECM) obtained by whole thymus perfusion. This anatomical human thymus reconstruction is functional, as judged by its capacity to support mature T cell development in vivo after transplantation into humanised immunodeficient mice. These findings establish a basis for dissecting the cellular and molecular crosstalk between stroma, ECM and thymocytes, and offer practical prospects for treating congenital and acquired immunological diseases

In Vivo Conditional Pax4 Overexpression in Mature Islet β-Cells Prevents Stress-Induced Hyperglycemia in Mice

OBJECTIVE To establish the role of the transcription factor Pax4 in pancreatic islet expansion and survival in response to physiological stress and its impact on glucose metabolism, we generated transgenic mice conditionally and selectively overexpressing Pax4 or a diabetes-linked mutant variant (Pax4R129 W) in β-cells. RESEARCH DESIGN AND METHODS Glucose homeostasis and β-cell death and proliferation were assessed in Pax4- or Pax4R129 W-overexpressing transgenic animals challenged with or without streptozotocin. Isolated transgenic islets were also exposed to cytokines, and apoptosis was evaluated by DNA fragmentation or cytochrome C release. The expression profiles of proliferation and apoptotic genes and β-cell markers were studied by immunohistochemistry and quantitative RT-PCR. RESULTS Pax4 but not Pax4R129 W protected animals against streptozotocin-induced hyperglycemia and isolated islets from cytokine-mediated β-cell apoptosis. Cytochrome C release was abrogated in Pax4 islets treated with cytokines. Interleukin-1β transcript levels were suppressed in Pax4 islets, whereas they were increased along with NOS2 in Pax4R129 W islets. Bcl-2, Cdk4, and c-myc expression levels were increased in Pax4 islets while MafA, insulin, and GLUT2 transcript levels were suppressed in both animal models. Long-term Pax4 expression promoted proliferation of a Pdx1-positive cell subpopulation while impeding insulin secretion. Suppression of Pax4 rescued this defect with a concomitant increase in pancreatic insulin content. CONCLUSIONS Pax4 protects adult islets from stress-induced apoptosis by suppressing selective nuclear factor-κB target genes while increasing Bcl-2 levels. Furthermore, it promotes dedifferentiation and proliferation of β-cells through MafA repression, with a concomitant increase in Cdk4 and c-myc expression

Activity of the insulo-acinar axis in the isolated perfused rat pancreas

The object of the present investigation was to determine whether insulin secreted by the endocrine pancreas and carried in the insulo-acinar portal system has a direct effect on pancreatic enzyme secretion. For this purpose, the isolated rat pancreas was perfused in a nonrecirculating system. The perfusate contained 3 mM glucose, and either caerulein or vasoactive intestinal polypeptide was used to stimulate exocrine secretion. The amount of insulin reaching the exocrine pancreas was reduced by two different experimental procedures. In the first, use was made of streptozotocin-diabetic rats treated with insulin in vivo. Treatment was such that the contents of amylase and lipase, vastly altered in the untreated diabetic state, were normalized before the perfusion studies. In the second procedure, insulin reaching the exocrine pancreas was reduced by antiinsulin serum in the perfusate. In these procedures, the reduced insulin bioavailability was associated with a reduction in caerulein- and vasoactive intestinal polypeptide-stimulated enzyme release, which was shown as a reduction of maximum responsiveness to caerulein without alteration of sensitivity. By contrast, in dispersed pancreatic acini where the insulo-acinar axis was completely disrupted, amylase secretion from diabetic and nondiabetic tissue was identical over a wide range of caerulein concentrations, showing that the secretory defect seen in the perfusion studies was not inherent to the exocrine tissue. The results show that basal insulin secretion has a direct effect on pancreatic enzyme output and that the insulo-acinar axis may play an important role in the regulation of acinar cell function.link_to_subscribed_fulltex

Biologic activity and pharmacokinetics of biosynthetic human insulin in the rat

The biologic potency (plasma glucose depression) of pancreatic human insulin was compared with that of biosynthetic human insulin (BHI), manufactured by recombinant DNA techniques in bacteria, following intravenous injection in rats. The specific activity of the pancreatic human insulin was 32 U/mg, while that for BHI was 27 U/mg. These values were not significantly difference, but were higher than the value for pancreatic pork insulin (25 U/mg). The pharmacokinetics of i.v. injected A14-mono-125I-insulin (pork) were found to be similar to those observed for semisynthetic [3H]insulin (pork), the respective metabolic clearance rates (MCR) being 20.8 +/- 0.8 ml/min/kg (N = 4) and 23.6 +/- 1 ml/min/kg (N = 5) (P greater than 0.1). The MCR for A14-mono-125I-BHI was 24.6 +/- 2.2 ml/min/kg (N = 4), which was significantly higher (P less than 0.025) than the value for A14-mono-125I-pork insulin. BHI is thus no less active than pork insulin in rats and possibly somewhat more active. The small difference in activity may be due to increased affinity for rat insulin receptors, resulting in a more rapid MCR for BHI. In addition, the A14-monoiodinated insulin tracer used in these studies is indistinguishable from semisynthetic [3H]insulin in terms of its rate of clearance, indicating that the insulin molecule has not suffered any iodination damage and is thus a valid tracer for metabolic and receptor studies