Use of twice-daily exenatide in Basal insulin-treated patients with type 2 diabetes: a randomized, controlled trial.

BACKGROUND: Insulin replacement in diabetes often requires prandial intervention to reach hemoglobin A1(c) (HbA1(c)) targets. OBJECTIVE: To test whether twice-daily exenatide injections reduce HbA1(c) levels more than placebo in people receiving insulin glargine. DESIGN: Parallel, randomized, placebo-controlled trial, blocked and stratified by HbA1(c) level at site, performed from October 2008 to January 2010. Participants, investigators, and personnel conducting the study were masked to treatment assignments. (ClinicalTrials.gov registration number: NCT00765817) SETTING: 59 centers in 5 countries. PATIENTS: Adults with type 2 diabetes and an HbA1(c) level of 7.1% to 10.5% who were receiving insulin glargine alone or in combination with metformin or pioglitazone (or both agents). INTERVENTION: Assignment by a centralized, computer-generated, random-sequence interactive voice-response system to exenatide, 10 µg twice daily, or placebo for 30 weeks. MEASUREMENTS: The primary outcome was change in HbA1(c) level. Secondary outcomes included the percentage of participants with HbA1(c) values of 7.0% or less and 6.5% or less, 7-point self-monitored glucose profiles, body weight, waist circumference, insulin dose, hypoglycemia, and adverse events. RESULTS: 112 of 138 exenatide recipients and 101 of 123 placebo recipients completed the study. The HbA1(c) level decreased by 1.74% with exenatide and 1.04% with placebo (between-group difference, -0.69% [95% CI, -0.93% to -0.46%]; P < 0.001). Weight decreased by 1.8 kg with exenatide and increased by 1.0 kg with placebo (between-group difference, -2.7 kg [CI, -3.7 to -1.7]). Average increases in insulin dosage with exenatide and placebo were 13 U/d and 20 U/d. The estimated rate of minor hypoglycemia was similar between groups. Thirteen exenatide recipients and 1 placebo recipient discontinued the study because of adverse events (P < 0.010); rates of nausea (41% vs. 8%), diarrhea (18% vs. 8%), vomiting (18% vs. 4%), headache (14% vs. 4%), and constipation (10% vs. 2%) were higher with exenatide than with placebo. LIMITATIONS: The study was of short duration. There were slight imbalances between groups at baseline in terms of sex, use of concomitant glucose-lowering medications, and HbA1(c) levels, and more exenatide recipients than placebo recipients withdrew because of adverse events. CONCLUSION: Adding twice-daily exenatide injections improved glycemic control without increased hypoglycemia or weight gain in participants with uncontrolled type 2 diabetes who were receiving insulin glargine treatment. Adverse events of exenatide included nausea, diarrhea, vomiting, headache, and constipation. PRIMARY FUNDING SOURCE: Alliance of Eli Lilly and Company and Amylin Pharmaceuticals.

Detecting differential expression of parental or progenitor alleles in genetic hybrids and allopolyploids.

Three assays useful for detecting specific RNA transcripts are primer extension, S1 nuclease protection, and reverse-transcription-cleaved amplified polymorphic sequence (RT-CAPS) analysis. All three of these techniques are used routinely for gene expression analyses and allow insights not possible by RNA blot (northern blot) hybridization. In this chapter, we describe how the primer extension, S1 nuclease protection, and RT-CAPS methods can be used to discriminate one or more parental or progenitor alleles in hybrids or allopolyploids. We discuss the rationale for using the different techniques and provide examples of the data generated.

Evidence for nucleolus organizer regions as the units of regulation in nucleolar dominance in Arabidopsis thaliana interecotype hybrids.

Nucleolar dominance describes the silencing of one parent's ribosomal RNA (rRNA) genes in a genetic hybrid. In Arabidopsis thaliana, rRNA genes are clustered in two nucleolus organizer regions, NOR2 and NOR4. In F(8) recombinant inbreds (RI) of the A. thaliana ecotypes Ler and Cvi, lines that display strong nucleolar dominance inherited a specific combination of NORs, Cvi NOR4 and Ler NOR2. These lines express almost all rRNA from Cvi NOR4. The reciprocal NOR genotype, Ler NOR4/Cvi NOR2, allowed for expression of rRNA genes from both NORs. Collectively, these data reveal that neither Cvi rRNA genes nor NOR4 are always dominant. Furthermore, strong nucleolar dominance does not occur in every RI line inheriting Cvi NOR4 and Ler NOR2, indicating stochastic effects or the involvement of other genes segregating in the RI mapping population. A partial explanation is provided by an unlinked locus, identified by QTL analysis, that displays an epistatic interaction with the NORs and affects the relative expression of NOR4 vs. NOR2. Collectively, the data indicate that nucleolar dominance is a complex trait in which NORs, rather than individual rRNA genes, are the likely units of regulation.

Effects of exenatide combined with lifestyle modification in patients with type 2 diabetes.

OBJECTIVE: To determine the effect of a lifestyle modification program plus exenatide versus lifestyle modification program plus placebo on weight loss in overweight or obese participants with type 2 diabetes treated with metformin and/or sulfonylurea. METHODS: In this 24-week, multicenter, randomized, double-blind, placebo-controlled study, 194 patients participated in a lifestyle modification program, consisting of goals of 600 kcal/day deficit and physical activity of at least 2.5 hours/week. Participants were randomized to 5 microg exenatide twice daily injection + lifestyle modification program (n = 96) or placebo + lifestyle modification program (n = 98), and after 4 weeks increased their exenatide dose to 10 microg twice daily or volume equivalent of placebo. RESULTS: Baseline characteristics: (mean +/- standard deviation) age, 54.8 +/- 9.5 years; weight, 95.5 +/- 16.0 kg; hemoglobin A(1c), 7.6 +/- 0.8%. At 24 weeks (least squares mean +/- standard error), treatments showed similar decreases in caloric intake (-378 +/- 58 vs -295 +/- 58 kcal/day, exenatide + lifestyle modification program vs placebo + lifestyle modification program, P = .27) and increases in exercise-derived energy expenditure. Exenatide + lifestyle modification program showed greater change in weight (-6.16 +/- 0.54 kg vs -3.97 +/- 0.52 kg, P = .003), hemoglobin A(1c) (-1.21 +/- 0.09% vs -0.73 +/- 0.09%, P <.0001), systolic (-9.44 +/- 1.40 vs -1.97 +/- 1.40 mm Hg, P <.001) and diastolic blood pressure (-2.22 +/- 1.00 vs 0.47 +/- 0.99 mm Hg, P = .04). Nausea was reported more for exenatide + lifestyle modification program than placebo + lifestyle modification program (44.8% vs 19.4%, respectively, P <.001), with no difference in withdrawal rates due to adverse events (4.2% vs 5.1%, respectively, P = 1.0) or rates of hypoglycemia. CONCLUSIONS: When combined with lifestyle modification, exenatide treatment led to significant weight loss, improved glycemic control, and decreased blood pressure compared with lifestyle modification alone in overweight or obese participants with type 2 diabetes on metformin and/or sulfonylurea treatment.

Effects of exenatide plus rosiglitazone on beta-cell function and insulin sensitivity in subjects with type 2 diabetes on metformin.

OBJECTIVE: Study the effects of exenatide (EXE) plus rosiglitazone (ROSI) on beta-cell function and insulin sensitivity using hyperglycemic and euglycemic insulin clamp techniques in participants with type 2 diabetes on metformin. RESEARCH DESIGN AND METHODS: In this 20-week, randomized, open-label, multicenter study, participants (mean age, 56 +/- 10 years; weight, 93 +/- 16 kg; A1C, 7.8 +/- 0.7%) continued their metformin regimen and received either EXE 10 microg b.i.d. (n = 45), ROSI 4 mg b.i.d. (n = 45), or EXE 10 microg b.i.d. + ROSI 4 mg b.i.d. (n = 47). Seventy-three participants underwent clamp procedures to quantitate insulin secretion and insulin sensitivity. RESULTS A1C declined in all groups (P < 0.05), but decreased most with EXE+ROSI (EXE+ROSI, -1.3 +/- 0.1%; ROSI, -1.0 +/- 0.1%, EXE, -0.9 +/- 0.1%; EXE+ROSI vs. EXE or ROSI, P < 0.05). ROSI resulted in weight gain, while EXE and EXE+ROSI resulted in weight loss (EXE, -2.8 +/- 0.5 kg; EXE+ROSI, -1.2 +/- 0.5 kg; ROSI, + 1.5 +/- 0.5 kg; P < 0.05 between and within all groups). At week 20, 1st and 2nd phase insulin secretion was significantly higher in EXE and EXE+ROSI versus ROSI (both P < 0.05). Insulin sensitivity (M value) was significantly higher in EXE+ROSI versus EXE (P = 0.014). CONCLUSIONS: Therapy with EXE+ROSI offset the weight gain observed with ROSI and elicited an additive effect on glycemic control with significant improvements in beta-cell function and insulin sensitivity.

Locus-specific ribosomal RNA gene silencing in nucleolar dominance.

The silencing of one parental set of rRNA genes in a genetic hybrid is an epigenetic phenomenon known as nucleolar dominance. We showed previously that silencing is restricted to the nucleolus organizer regions (NORs), the loci where rRNA genes are tandemly arrayed, and does not spread to or from neighboring protein-coding genes. One hypothesis is that nucleolar dominance is the net result of hundreds of silencing events acting one rRNA gene at a time. A prediction of this hypothesis is that rRNA gene silencing should occur independent of chromosomal location. An alternative hypothesis is that the regulatory unit in nucleolar dominance is the NOR, rather than each individual rRNA gene, in which case NOR localization may be essential for rRNA gene silencing. To test these alternative hypotheses, we examined the fates of rRNA transgenes integrated at ectopic locations. The transgenes were accurately transcribed in all independent transgenic Arabidopsis thaliana lines tested, indicating that NOR localization is not required for rRNA gene expression. Upon crossing the transgenic A. thaliana lines as ovule parents with A. lyrata to form F1 hybrids, a new system for the study of nucleolar dominance, the endogenous rRNA genes located within the A. thaliana NORs are silenced. However, rRNA transgenes escaped silencing in multiple independent hybrids. Collectively, our data suggest that rRNA gene activation can occur in a gene-autonomous fashion, independent of chromosomal location, whereas rRNA gene silencing in nucleolar dominance is locus-dependent.

Molecular genetic analysis of ICEF, an integrative conjugal element that is present as a repetitive sequence in the chromosome of Mycoplasma fermentans PG18.

Mycoplasma genomes contain compact gene sets that approach the minimal complement necessary for life and reflect multiple evolutionary instances of genomic reduction. Lateral gene transfer may play a critical role in shaping the mobile gene pool in these organisms, yet complex mobile elements have not been reported within this genus. We describe here a large ( approximately 23-kb) genetic element with unique features that is present in four copies in the Mycoplasma fermentans PG18 chromosome, accounting for approximately 8% of the genome. These novel elements, designated ICEF (integrative conjugal elements of M. fermentans), resemble conjugative, self-transmissible integrating elements (constins) in that circular, nonreplicative extrachromosomal forms occur in which the left and right termini of the integrated element are juxtaposed and separated by a coupling sequence derived from direct repeats flanking chromosomal copies of ICEF as a result of target site duplication. ICEF contain multiple similarly oriented open reading frames (ORFs), of which some have homology to products of known conjugation genes but others have no known counterparts. Surprisingly, unlike other constins, ICEF lack homologs of known integrases, transposases, or recombinases, suggesting that a novel enzyme may be employed for integration-excision. Skewed distribution and varied sites of chromosomal integration among M. fermentans isolates suggest a role for ICEF in promoting genomic and phenotypic variation in this species. Identification of homologs of terminal ICEF ORFs in two additional mycoplasma species indicates that ICEF is the prototype member of a family of ICE-related elements that may be widespread among pathogenic mycoplasmas infecting diverse vertebrate hosts.

Chromosomal locus rearrangements are a rapid response to formation of the allotetraploid Arabidopsis suecica genome.

Allopolyploidy is a significant evolutionary process, resulting in new species with diploid or greater chromosome complements derived from two or more progenitor species. We examined the chromosomal consequences of genomic merger in Arabidopsis suecica, the allotetraploid hybrid of Arabidopsis thaliana and Arabidopsis arenosa. Fluorescence in situ hybridization with centromere, nucleolus organizer region (NOR), and 5S rRNA gene probes reveals the expected numbers of progenitor chromosomes in natural A. suecica, but one pair of A. thaliana NORs and one pair of A. arenosa-derived 5S gene loci are missing. Similarly, in newly formed synthetic A. suecica-like allotetraploids, pairs of A. thaliana NORs are gained de novo, lost, and/or transposed to A. arenosa chromosomes, with genotypic differences apparent between F(3) siblings of the same F(2) parent and between independent lines. Likewise, pairs of A. arenosa 5S genes are lost and novel linkages between 5S loci and NORs arise in synthetic allotetraploids. By contrast, the expected numbers of A. arenosa-derived NORs and A. thaliana-derived 5S loci are found in both natural and synthetic A. suecica. Collectively, these observations suggest that some, but not all, loci are unstable in newly formed A. suecica allotetraploids and can participate in a variety of alternative rearrangements, some of which resemble chromosomal changes found in nature.