Neonatal exendin-4 prevents the development of diabetes in the intrauterine growth retarded rat

Uteroplacental insufficiency resulting in fetal growth retardation is a common complication of pregnancy and a significant cause of perinatal morbidity and mortality. Epidemiological studies show an increased incidence of type 2 diabetes in humans who were growth retarded at birth. The mechanisms by which an abnormal intrauterine milieu leads to the development of diabetes in adulthood are not known. Therefore, a rat model of uteroplacental insufficiency was developed; intrauterine growth-retarded (IUGR) rats develop diabetes with a phenotype similar to that observed in the human with type 2 diabetes. We show here that administration of a pancreatic beta-cell trophic factor, exendin-4 (Ex-4), during the prediabetic neonatal period dramatically prevents the development of diabetes in this model. This occurs because neonatal Ex-4 prevents the progressive reduction in insulin-producing beta-cell mass that is observed in IUGR rats over time. Expression of PDX, a critical regulator of pancreas development and islet differentiation, is restored to normal levels, and islet beta-cell proliferation rates are normalized by the neonatal Ex-4 treatment. These results indicate that exposure to Ex-4 in the newborn period reverses the adverse consequences of fetal programming and prevents the development of diabetes in adulthood.

Novel mutation in the TOR1A (DYT1) gene in atypical early onset dystonia and polymorphisms in dystonia and early onset parkinsonism

Dystonia is a movement disorder involving sustained muscle contractions and abnormal posturing with a strong hereditary predisposition and without a distinct neuropathology. In this study the TOR1A (DYT1) gene was screened for mutations in cases of early onset dystonia and early onset parkinsonism (EOP), which frequently presents with dystonic symptoms. In a screen of 40 patients, we identified three variations, none of which occurred in EOP patients. Two infrequent intronic single base pair (bp) changes of unknown consequences were found in a dystonia patient and the mother of an EOP patient. An 18-bp deletion (Phe323_Tyr328del) in the TOR1A gene was found in a patient with early onset dystonia and myoclonic features. This deletion would remove 6 amino acids close to the carboxy terminus, including a putative phosphorylation site of torsinA. This 18-bp deletion is the first additional mutation, beyond the GAG-deletion (Glu302/303del), to be found in the TOR1A gene, and is associated with a distinct type of early onset dystonia.

Rapid-onset dystonia-parkinsonism in a second family

Rapid-onset dystonia-parkinsonism (RDP), first described in a large Midwestern family, is now reported in a second, apparently unrelated, family in which four individuals have this same syndrome. All four developed sudden onset of dysarthria, dysphagia, severe dystonic spasms, bradykinesia, and postural instability over less than 1 hour to a few days. Three of the four had stable limb dystonia for several years preceding the onset of combined dystonia-parkinsonism. Treatment with levodopa/carbidopa provided little benefit. We propose diagnostic criteria for RDP and further define the spectrum of this unusual disease.

Pharmacological Correction of Trafficking Defects in ATP-sensitive Potassium Channels Caused by Sulfonylurea Receptor 1 Mutations

ATP-sensitive potassium (K_ATP) channels play a key role in mediating glucose-stimulated insulin secretion by coupling metabolic signals to β-cell membrane potential. Loss of K_ATP channel function due to mutations in ABCC8 or KCNJ11, genes encoding the sulfonylurea receptor 1 (SUR1) or the inwardly rectifying potassium channel Kir6.2, respectively, results in congenital hyperinsulinism. Many SUR1 mutations prevent trafficking of channel proteins from the endoplasmic reticulum to the cell surface. Channel inhibitors, including sulfonylureas and carbamazepine, have been shown to correct channel trafficking defects. In the present study, we identified 13 novel SUR1 mutations that cause channel trafficking defects, the majority of which are amenable to pharmacological rescue by glibenclamide and carbamazepine. By contrast, none of the mutant channels were rescued by K_ATP channel openers. Cross-linking experiments showed that K_ATP channel inhibitors promoted interactions between the N terminus of Kir6.2 and SUR1, whereas channel openers did not, suggesting the inhibitors enhance intersubunit interactions to overcome channel biogenesis and trafficking defects. Functional studies of rescued mutant channels indicate that most mutants rescued to the cell surface exhibited WT-like sensitivity to ATP, MgADP, and diazoxide. In intact cells, recovery of channel function upon trafficking rescue by reversible sulfonylureas or carbamazepine was facilitated by the K_ATP channel opener diazoxide. Our study expands the list of K_ATP channel trafficking mutations whose function can be recovered by pharmacological ligands and provides further insight into the structural mechanism by which channel inhibitors correct channel biogenesis and trafficking defects.

Simultaneous expression of early and late histone messenger RNAs in individual cells during development of the sea urchin embryo

The transition from early (E) to late (L) histone gene expression in developing sea urchin (Strongylocentrotus purpuratus) embryos was examined for H2B, H3, and H4 mRNAs by in situ hybridization of class-specific probes. Hybridization patterns indicate that the shift from E to L mRNAs occurs gradually and simultaneously in all blastomeres. Thus, during the transition the ratio of L to E mRNAs is similar in most cells. This suggests that no sudden changes in histone composition occur in individual cells which might be related to alterations in gene expression associated with differentiation of cell lineages. Around the midpoint of the transition, clusters of cells progressively appear which contain little, if any, E or L histone mRNA. This modulation of expression is coordinated for the three late genes examined because most individual cells contain either high or low levels of all three mRNAs. At blastula stage these clusters of unlabeled cells appear to be randomly distributed throughout the embryo. Subsequently the unlabeled regions expand and are found predominantly in aboral ectoderm as these cells cease to divide. Thus, the L/E histone mRNA ratio is not differentially regulated in diverse cell lineages, and the major differences in total histone mRNA content among individual cells may be related to cell cycle and/or the cessation of division.

Hormonal basis of variation in oestrous cyclicity in selected strains of mice

Reproductive hormone secretion and ovarian LH receptor content were studied during the oestrous cycle of mice that differed in fertility after genetic selection. Strain variation in the secretory pattern of progesterone was observed along with differences in the timing and magnitude of prolactin release. Scatchard analysis showed similar affinities of the LH receptor for hCG in strains with increased or decreased reproductive performance, with a single order of binding sites during both pro-oestrus and dioestrus. The number of unoccupied LH receptors during pro-oestrus was greatest in mice with increased reproductive performance. These results provide evidence that trait selection can change gonadotrophin receptor concentration and the dynamics of hormone secretion during the oestrous cycle of the mouse.

Pheromonal regulation of the mouse estrous cycle by a heterogenotypic male

The role of male pheromones in estrous cyclicity was studied in mice selected for different reproductive traits. When females are exposed to males of their own strain, estrous cycles are highly regular in females selected for increased embryo survival (line E). In contrast, cycle regularity is reduced by exposure of line E females to males from a strain characterized by irregular estrous cycles (line CN-). To investigate the inhibition of estrous cyclicity and the role of androgen in this phenomenon, line E females were housed in the olfactory presence of E males and later rehoused with one of the following: intact or castrated males of line E (homogenotypic condition) or line CN-heterogenotypic condition) or castrated CN- males provided with testosterone replacement. A final exposure to homogenotypic (line E) males was provided. Estrous cyclicity was decreased when line E females were rehoused with intact or castrated CN- males. Metestrus was prolonged by intact CN- males, whereas diestrus was prolonged in the presence of castrated CN- males. Androgen treatment did not enable castrated CN- males to prolong metestrus. These results demonstrate that: 1) heterogenotypic pheromones inhibit estrous cyclicity in line E; and 2) the inhibitory influence of line CN- males on line E estrous cyclicity is mediated by factors in addition to or other than testosterone.

Contraceptive use in women with inherited metabolic disorders: a retrospective study and literature review

BACKGROUND

Reproductive planning is an emerging concern for women with inherited metabolic disease (IMD). Anticipatory guidance on contraception is necessary to prevent unintended pregnancies in this population. Few resources exist to aid informed decision-making on contraceptive choice. A retrospective case-control study was performed to examine trends in reproductive planning for adolescent and adult women seen at the Children's Hospital of Philadelphia (CHOP). Literature review on contraception and IMD was performed to assess global use.

RESULTS

In a cohort of 221 reproductive-aged female IMD patients, 29.4% reported routine contraceptive use. Anticipatory guidance on contraception was provided by metabolic physicians to 36.8% of patients during the study period. Contraception discussion was more likely to occur in women older than 21 years, who lived independently and were followed by gynecology. Women who received contraception counseling from their metabolic physician were 40-fold more likely to use regular contraception. Use of combined hormonal contraceptives was most commonly reported, but contraception choice varied by age and IMD.

CONCLUSION

Metabolic physicians are ideally suited to provide guidance on contraception to women with IMD. Reproductive planning should be addressed routinely using shared decision-making. Contraceptives should be selected for their efficacy, effects on metabolism, and likelihood of patient adherence.