Expanded Porphyrin Contraction: From [22]Triphyrin(6.6.0) to [22]Triphyrin(6.5.0).

An expanded triphyrin containing a bipyrrole moiety and annulene links, namely tetraphenyl-[22]triphyrin(6.5.0), 2, has been synthesized. The synthesis proceeded by a postsynthetic transformation of tetraphenyl-[22]triphyrin(6.6.0), 1, in a metal-free unexpected and unprecedented ring contraction during column chromatography on alumina. The observed transformation, located at the hydrocarbon chain linking the pyrrole units, formally corresponds to a subtraction of one carbon atom from an annulene circuit. In contrast to the flexible substrate 1, the product 2 is conformationally rigid, and capable of chloride anion binding in its protonated form.

Maternal taurine supplementation in rats partially prevents the adverse effects of early-life protein deprivation on ß-cell function and insulin sensitivity.

Dietary protein restriction during pregnancy and lactation in rats impairs ß-cell function and mass in neonates and leads to glucose intolerance in adult offspring. Maternal taurine (Tau) supplementation during pregnancy in rats restores ß-cell function and mass in neonates, but its long-term effects are unclear. The prevention of postnatal catch-up growth has been suggested to improve glucose tolerance in adult offspring of low-protein (LP)-fed mothers. The objective of this study was to examine the relative contribution of ß-cell dysfunction and insulin resistance to impaired glucose tolerance in 130-day-old rat offspring of LP-fed mothers and the effects of maternal Tau supplementation on ß-cell function and insulin resistance in these offspring. Pregnant rats were fed i) control, ii) LP, and iii) LP+Tau diets during gestation and lactation. Offspring were given a control diet following weaning. A fourth group consisting of offspring of LP-fed mothers, maintained on a LP diet following weaning, was also studied (LP-all life). Insulin sensitivity in the offspring of LP-fed mothers was reduced in females but not in males. In both genders, LP exposure decreased ß-cell function. Tau supplementation improved insulin sensitivity in females and ß-cell function in males. The LP-all life diet improved ß-cell function in males. We conclude that i) maternal Tau supplementation has persistent effects on improving glucose metabolism (ß-cell function and insulin sensitivity) in adult rat offspring of LP-fed mothers and ii) increasing the amount of protein in the diet of offspring adapted to a LP diet after weaning may impair glucose metabolism (ß-cell function) in a gender-specific manner.

Exposure of the pregnant rat to low protein diet causes impaired glucose homeostasis in the young adult offspring by different mechanisms in males and females.

The understanding of the mechanisms by which gender dimorphisms are involved in the modulation of insulin sensitivity and glucose tolerance can be crucial to unravel the development of type 2 diabetes. Rats treated with a low protein diet (LP, 8% protein content) during pregnancy and lactation have a reduced beta-cell mass at birth and a reduced insulin secretion at weaning. In this study we examined the effect of LP diet on glucose homeostasis from birth to adulthood when offspring previously exposed to LP were subsequently switched to control diet (C, 20% protein content) at weaning. The LP group had a reduced body weight after weaning compared to the C-fed rats, although their food intake was not significantly different. Furthermore, LP males had a significant increase in visceral adiposity relative to their body weight (P < 0.05). Intraperitoneal glucose tolerance test (IGTT) showed that glucose clearance was unchanged until 130 days of age when LP-fed females showed elevated blood glucose compared to C, despite similar plasma insulin levels. Females also demonstrated a significant reduction in mean pancreatic islet number, individual islet size and beta cell mass. However, no differences in IGTT or islet morphometry were observed in LP males, although basal insulin levels were twofold higher. Akt phosphorylation in response to insulin was reduced in adipose and skeletal muscle of adult rats following exposure to LP diet in early life when compared to control-fed animals, but this was only apparent in males. Plasma testosterone levels were also reduced in males at 130 days age. These data suggest that the development of impaired glucose homeostasis in offspring of LP-fed rats is likely to occur by different mechanisms in males and females.

Malignant transformation of a solitary fibrous tumor of the liver and intractable hypoglycemia.

Sarcomas of the liver are rare. We report a case of intractable hypoglycemia secondary to a solitary fibrous tumor that underwent malignant transformation into a fibrosarcoma. A 70-year-old man presented with a hepatic mass and tumor-associated hypoglycemia which was resistant to medical management. Blood tests were remarkable only for elevated serum insulin-like growth factor (IGF)-2. The hypoglycemia resolved following resection of a solitary fibrous tumor surrounded by a high-grade fibrosarcoma. Real time reverse transcriptase polymerase chain reaction (RT-PCR) measured elevated levels of IGF2 mRNA in both the solitary fibrous tumor and the fibrosarcoma. Immunoblotting demonstrated a series of bands in the size range of pro-IGF2. Unfortunately, disseminated metastases developed 1 year later, concurrent with a recurrence of hypoglycemia, marked again by elevation of serum IGF2. Solitary fibrous tumors of the liver have a real risk of malignant transformation. The severity of the tumor-associated hypoglycemia may parallel the tumor burden and activity. The syndrome is the systemic effect of IGF2 secreted by the tumor. Surgery can treat the hypoglycemia syndrome and the underlying malignancy.

Altered pancreatic morphology in the offspring of pregnant rats given reduced dietary protein is time and gender specific.

Restriction of dietary protein during gestation and lactation in the rat results in a reduction in beta cell mass, insulin content and release in the offspring, and glucose intolerance when the offspring reach adulthood. The present study was designed to identify if a particular developmental window existed during prenatal development when endocrine pancreatic development was most susceptible to nutritional insult. Pregnant rats received a low-protein (8%, LP), but isocalorific diet from conception to parturition, during the first 2 weeks of gestation (LP (1-2)), the second week only (LP (2)), or the third week (LP (3)). At other times, they received a 20% protein (C) diet, while control animals received this diet continuously. When the offspring were examined at 130 days age, animals that had received LP diet had a significantly impaired glucose tolerance compared with control-fed animals. Pancreatic morphology was examined in the offspring on postnatal days 1 and 21. The LP diet resulted in a significant decrease in the numbers of large (more than 10 000 microm(2)) and medium (between 5000 and 10 000 microm(2)) sized islets present at postnatal day 1 for all LP treatments. Consequently, mean islet area and the mean number of beta cells were reduced. The impact of LP diet was most pronounced in LP (2) for females and in LP (3) for males, and this was greater than for continuous LP exposure. Insulin and Glut-2 mRNA expression were impacted negatively by LP in early and late gestation, but increased following administration in mid-gestation. Total pancreatic insulin content was not altered by LP treatment. Pdx-1, a transcription factor associated with both beta cell development and insulin gene transcription, was decreased in female offspring following LP (1-2) and LP (3), but not in males. Pancreatic expression of nestin mRNA, and the abundance of nestin-immunoreactive cells within islets, was decreased by all LP treatments. By postnatal day 21, the mean islet area and number of beta cells had largely recovered. However, insulin and Glut-2 mRNAs were elevated in offspring exposed to LP diet, particularly in females. The studies show that LP dietary insult in early, middle, or late gestation, all result in a relative deficiency of beta cells following birth, due to a failure to develop larger islets, but that females were particularly susceptible in mid-gestation and males in late gestation.

Ontogeny of regeneration of beta-cells in the neonatal rat after treatment with streptozotocin.

We induced partial beta-cell loss within the pancreas of neonatal rats using streptozotocin (STZ) to better characterize the mechanisms leading to beta-cell regeneration postnatally. Rats were administered either STZ (70 mg/kg) or buffer alone on postnatal d 4, and the endocrine pancreas was examined between 4 and 40 d later. STZ-treated rats showed an approximately 60% loss of existing beta-cells and a moderate hyperglycemia (<15 mm glucose), with levels returning to near-control values after 20 d. Within preexisting islets, there was increased cell proliferation in both insulin- and glucagon-positive cells at 8 d as well as alpha-cell hyperplasia. These were associated with increased pancreatic content and circulating levels of glucagon. Pancreatic levels of glucagon-like polypeptide-1 (GLP-1) were increased 8 d after STZ compared with control values, and the GLP-1/glucagon ratio changed in favor of GLP-1. Administration of a GLP-1 receptor antagonist, GLP-1-(9-39), resulted in decreased recovery of beta-cells after STZ and worse glucose tolerance. Atypical glucagon-positive cells were found within islets that colocalized pancreatic duodenal homeobox-1 or glucose transporter-2. Pancreatic levels of insulin mRNA did not return to control values until 40 d after STZ. Insulin-positive cells were found after 8 d that colocalized glucagon and GLP-1. The model shows that the pancreas of the young rat can rapidly regenerate a loss of beta-cells, and this is associated with hyperplasia of alpha-cells with an altered phenotype of increased GLP-1 synthesis. The target cells of GLP-1 probably include immature beta-cells that coexpress proglucagon.

Adipose tissue gene expression profiling reveals distinct molecular pathways that define visceral adiposity in offspring of maternal protein-restricted rats.

There is increasing evidence that poor early growth confers an increased risk of type 2 diabetes, hypertension, and other features of the metabolic syndrome in later life. We hypothesized that this may result from poor nutrition during early life exerting permanent effects on the structure and function of key metabolic organ systems. To study the long-term impact of early-life undernutrition on susceptibility to visceral adiposity, we used a rat model of maternal protein restriction (MPR) in which dams were fed a low-protein diet (containing 8% instead of 20% protein in control diet) throughout pregnancy and lactation. MPR offspring were born smaller than controls (offspring of dams on control diet) and in adulthood developed visceral adiposity. We compared the pattern of gene expression in visceral adipose tissue (VAT) between MPR offspring and controls with Affymetrix rat expression arrays. Of the total number of genes and expressed sequence tags analyzed (15,923 probe sets), 9,790 (61.5%) were expressed in VAT. We identified 650 transcripts as differentially expressed > or =1.5-fold in the VAT of MPR offspring. Gene ontology analysis revealed a global upregulation of genes involved in carbohydrate, lipid, and protein metabolism. A number of genes involved in adipocyte differentiation, angiogenesis, and extracellular matrix remodeling were also upregulated. However, in marked contrast to other rodent models of obesity, the expression of a large number of genes associated with inflammation was reduced in this rat model. Thus visceral adiposity in this early-life programmed rat model is marked by dynamic changes in the transcriptional profile of VAT. Our data provide new insights into the molecular mechanisms that underlie the early-life programming of visceral adiposity.

Burkholderia cepacia complex isolates survive intracellularly without replication within acidic vacuoles of Acanthamoeba polyphaga.

We have previously demonstrated that isolates of the Burkholderia cepacia complex can survive intracellularly in murine macrophages and in free-living Acanthamoeba. In this work, we show that the clinical isolates B. vietnamiensis strain CEP040 and B. cenocepacia H111 survived but did not replicate within vacuoles of A. polyphaga. B. cepacia-containing vacuoles accumulated the fluid phase marker Lysosensor Blue and displayed strong blue fluorescence, indicating that they had low pH. In contrast, the majority of intracellular bacteria within amoebae treated with the V-ATPse inhibitor bafilomycin A1 localized in vacuoles that did not fluoresce with Lysosensor Blue. Experiments using bacteria fluorescently labelled with chloromethylfluorescein diacetate demonstrated that intracellular bacteria remained viable for at least 24 h. In contrast, Escherichia coli did not survive within amoebae after 2 h post infection. Furthermore, intracellular B. vietnamiensis CEP040 retained green fluorescent protein within the bacterial cytoplasm, while this protein rapidly escaped from the cytosol of phagocytized heat-killed bacteria into the vacuolar lumen. Transmission electron microscopy analysis confirmed that intracellular Burkholderia cells were structurally intact. In addition, both Legionella pneumophila- and B. vietnamiensis-containing vacuoles did not accumulate cationized ferritin, a compound that localizes within the lysosome. Thus, our observations support the notion that B. cepacia complex isolates can use amoebae as a reservoir in the environment by surviving without intracellular replication within an acidic vacuole that is distinct from the lysosomal compartment.

Bone marrow-derived stem cells initiate pancreatic regeneration.

We show that transplantation of adult bone marrow-derived cells expressing c-kit reduces hyperglycemia in mice with streptozotocin-induced pancreatic damage. Although quantitative analysis of the pancreas revealed a low frequency of donor insulin-positive cells, these cells were not present at the onset of blood glucose reduction. Instead, the majority of transplanted cells were localized to ductal and islet structures, and their presence was accompanied by a proliferation of recipient pancreatic cells that resulted in insulin production. The capacity of transplanted bone marrow-derived stem cells to initiate endogenous pancreatic tissue regeneration represents a previously unrecognized means by which these cells can contribute to the restoration of organ function.

Quantitation of polyamines in hypothalamus and pituitary of female and male developing rats.

The quantitation of four polyamines in hypothalamus and pituitary is studied in male and female developing rats using an improved high-performance liquid chromatography method. In the hypothalamus, putrescine (PUT) reaches the highest concentration (nmol/mg protein) on day 6. It shows the lowest value in comparison with any other polyamine. Spermidine (SPD) is high during the first postnatal days. Spermine (SPM) fluctuates, and agmatine (AGM) is highest during the first week. SPD, SPM and AGM are lower in females. In the pituitary, PUT, SPD and AGM are high during the first week. SPM remains constant and it is higher in males. AGM is higher in males only on day 1. PUT shows the lowest concentration of all. Concentrations of PUT, SPD and SPM are higher in the pituitary; AGM is higher in the hypothalamus. alpha-Difluoromethylornithine (a specific and irreversible inhibitor of ornithine decarboxylase) decreases PUT and SPD, increased SPM and AGM remain unchanged in the hypothalamus and pituitary. Thus, each polyamine has its own pattern in hypothalamus and in pituitary during development in males and females; these changes could be related to the hypothalamic control of pituitary secretion of hormones related to reproduction in mammals.

Effects of polyamines on the release of gonadotropin-releasing hormone and gonadotropins in developing female rats.

Polyamines, putrescine (PUT), spermidine (SPD), spermine (SPM), and agmatine (AGM), are polycationic amines related to multiple cell functions found in high concentrations during the development of hypothalamus and pituitary. In previous works, we demonstrated that alpha-difluoromethylornithine (DFMO), an inhibitor of polyamines biosynthesis, induced a delay in puberty of female rats, accompanied by high, sustained follicle-stimulating hormone (FSH) levels during the infantile period. Also, DFMO treatment induced changes in polyamine concentration both in hypothalamus and pituitary of rats, mainly a decrease of PUT and SPD, an increase in SPM, and no change in AGM. In the present work, we investigated the direct effects of polyamines on the secretion of hypothalamic GnRH and pituitary gonadotropins in 6- and 15-day-old female rats. In 6-day-old animals, in vitro incubations with PUT, SPD, and AGM of hypothalami or anterior pituitaries were able to inhibit GnRH, FSH, and leutinizing hormone (LH) secretion, respectively. SPM showed a nonspecific transient inhibitory effect on FSH. When challenged with either high K(+) (hypothami) or GnRH (pituitaries), the tissues incubated in the presence of polyamines showed no differences when compared with their controls. No effects of polyamines in 15-day-old rats in either tissue were observed. Pituitary cell cultures of 6-day-old animals incubated with DFMO for 4 days showed a significant increase in FSH, but not in LH. We conclude that high PUT, SPD, and AGM levels during the first 10 days of life are important for the development of the hypothalamic-hypophyseal unit, probably related to an inhibitory effect on GnRH and gonadotropins. Therefore, polyamine participation, especially PUT and SPD, is of importance in the regulation of GnRH and gonadotropin secretion in the neonatal and infantile periods, critical stages in the establishment of sexual differentiation.