Longer genotypically-estimated leukocyte telomere length is associated with increased adult glioma risk

Telomere maintenance has emerged as an important molecular feature with impacts on adult glioma susceptibility and prognosis. Whether longer or shorter leukocyte telomere length (LTL) is associated with glioma risk remains elusive and is often confounded by the effects of age and patient treatment. We sought to determine if genotypically-estimated LTL is associated with glioma risk and if inherited single nucleotide polymorphisms (SNPs) that are associated with LTL are glioma risk factors. Using a Mendelian randomization approach, we assessed differences in genotypically-estimated relative LTL in two independent glioma case-control datasets from the UCSF Adult Glioma Study (652 patients and 3735 controls) and The Cancer Genome Atlas (478 non-overlapping patients and 2559 controls). LTL estimates were based on a weighted linear combination of subject genotype at eight SNPs, previously associated with LTL in the ENGAGE Consortium Telomere Project. Mean estimated LTL was 31bp (5.7%) longer in glioma patients than controls in discovery analyses (P = 7.82×10-8) and 27bp (5.0%) longer in glioma patients than controls in replication analyses (1.48×10-3). Glioma risk increased monotonically with each increasing septile of LTL (O.R.=1.12; P = 3.83×10-12). Four LTL-associated SNPs were significantly associated with glioma risk in pooled analyses, including those in the telomerase component genes TERC (O.R.=1.14; 95% C.I.=1.03-1.28) and TERT (O.R.=1.39; 95% C.I.=1.27-1.52), and those in the CST complex genes OBFC1 (O.R.=1.18; 95% C.I.=1.05-1.33) and CTC1 (O.R.=1.14; 95% C.I.=1.02-1.28). Future work is needed to characterize the role of the CST complex in gliomagenesis and further elucidate the complex balance between ageing, telomere length, and molecular carcinogenesis.     

Macro creatine kinase type 1 with electrophoretic mobility identical to that of the MB isoenzyme

We describe the case of an elderly woman whose symptoms and electrocardiographic pattern initially suggested acute myocardial infarction. The value for total serum creatine kinase (EC 2.7.3.2; CK) was 737 U/L (reference interval: 22-269 U/L), and electrophoresis for CK isoenzymes demonstrated two bands, the more anodal migrating to the CK-MB region and the second migrating between the CK-MB and CK-MM regions. The above-normal total CK and electrophoretic pattern persisted during her 11-day hospital course. The QuiCK-MB (International Immunoassay Labs.) and Tandem-E CK-MB (Hybritech) immunoassays, however, showed CK-MB mass measurements within the normal range. In further investigation with a mixture of patient's serum and human-serum-based control containing all CK isoenzymes, the electrophoretic mobility of only CK-BB was altered, proving that the patient had antibody to the B unit of CK in her serum. Immunofixation revealed the more anodal band to be a CK-IgA lambda complex, and the more cathodal band, a CK-IgG kappa complex. Mixing the patient's serum with polyclonal antibody specific for CK-B slowed the electrophoretic mobility of only the more anodal band. Polyclonal antibody specific for CK-M had no effect on either band. Evidently, this patient had two different types of macro CK type 1, both containing CK-BB. We conclude that macro CK type 1 can mimic CK-MB and be a source of confusion.     

DURATION-1: Exenatide Once Weekly Produces Sustained Glycemic Control and Weight Loss Over 52 Weeks

OBJECTIVE

In the Diabetes Therapy Utilization: Researching Changes in A1C, Weight and Other Factors Through Intervention with Exenatide Once Weekly (DURATION-1) study, the safety and efficacy of 30 weeks of treatment with the glucagon-like peptide-1 receptor agonist exenatide once weekly (exenatide QW; 2 mg) was compared with exenatide BID in 295 patients with type 2 diabetes. We now report the safety and efficacy of exenatide QW in 1) patients who continued treatment for an additional 22 weeks (52 weeks total) and 2) patients who switched from exenatide BID to exenatide QW after 30 weeks.

RESEARCH DESIGN AND METHODS

In this randomized, multicenter, comparator-controlled, open-label trial, 258 patients entered the 22-week open-ended assessment phase (n = 128 QW-only; n = 130 BID→QW). A1C, fasting plasma glucose (FPG), body weight, blood pressure, fasting lipids, safety, and tolerability were assessed.

RESULTS

Patients continuing exenatide QW maintained A1C improvements through 52 weeks (least squares mean −2.0% [95% CI −2.1 to −1.8%]). Patients switching from exenatide BID to exenatide QW achieved further A1C improvements; both groups exhibited the same A1C reduction and mean A1C (6.6%) at week 52. At week 52, 71 and 54% of all patients achieved A1C <7.0% and ≤6.5%, respectively. In both treatment arms, FPG was reduced by >40 mg/dl, and body weight was reduced by >4 kg after 52 weeks. Nausea occurred less frequently in this assessment period and was predominantly mild. No major hypoglycemia was observed.

CONCLUSION

Exenatide QW elicited sustained improvements in glycemic control and body weight through 52 weeks of treatment. Patients switching to exenatide QW experienced further improvements in A1C and FPG, with sustained weight loss.Type 2 diabetes is a complex and increasingly prevalent disease associated with interrelated comorbidities, including obesity, dyslipidemia, and hypertension. The importance of treating not only hyperglycemia, but also the associated comorbidities, is recognized as necessary to reduce the risk of complications, particularly cardiovascular disease (1). Lifestyle modification can improve glycemic control as well as body weight, blood pressure, and lipid profiles; however, behavioral modifications are inherently difficult, and most patients eventually require multiple medications (2–6). Although several classes of antihyperglycemic medications are currently indicated for the treatment of type 2 diabetes, most of them do not improve the comorbidities and several are associated with weight gain.Exenatide, a glucagon-like peptide-1 receptor (GLP-1R) agonist, improves glycemic control in patients with type 2 diabetes through multiple mechanisms of action: increased glucose-dependent insulin secretion, attenuated postprandial glucagon secretion, slowed gastric emptying, and increased satiety (7,8). The twice-daily formulation of exenatide (exenatide BID) improves both fasting and postprandial glucose control, resulting in A1C reductions of roughly 0.8–1.0% in placebo-controlled trials (9–12) and 1.0–1.4% in open-label trials (13–15). These improvements in glucose control were maintained in patients completing 3 years of treatment (−1.0%) (16). Exenatide therapy is also associated with weight loss and improvement in cardiovascular risk factors, including blood pressure and serum lipid profiles (16). Furthermore, the glucose-dependent mechanisms of action of exenatide minimize the risk of hypoglycemia. GLP-1R agonists have recently been added to the American Diabetes Association and European Association for the Study of Diabetes consensus algorithm for the treatment of type 2 diabetes as an option after the addition of metformin in patients in whom body weight and hypoglycemia risk are concerns (1).Exenatide BID is administered within the 60-min period before the morning and evening meals and primarily exerts its pharmacodynamic effects on glucose concentrations during the postprandial period. A long-acting once-weekly formulation of exenatide (exenatide QW) has been developed. Weekly administration of 2 mg exenatide QW results in therapeutic plasma exenatide concentrations within 2 weeks and steady-state plasma exenatide concentrations within the therapeutic target range 6–7 weeks after initiation of therapy (17,18).The Diabetes Therapy Utilization: Researching Changes in A1C, Weight and Other Factors Through Intervention with Exenatide Once Weekly (DURATION-1) trial was designed as a two-stage protocol. We previously reported the first stage, a randomized open-label comparison of exenatide QW to exenatide BID in patients with type 2 diabetes over 30 weeks (17). Both therapies improved glycemic control, and the improvement in A1C observed with exenatide QW treatment was significantly greater than that observed with exenatide BID (−1.9 vs. −1.5%, respectively). Similar improvements in body weight, blood pressure, and fasting lipids were demonstrated with both forms of exenatide therapy. We now describe 52-week results from the second phase of the DURATION-1 trial which examined the safety and efficacy of 1) switching from exenatide BID to exenatide QW after 30 weeks of treatment and 2) continuing exenatide QW treatment for an additional 22 weeks (52 weeks total).     

Carbon dioxide contributes to the beneficial effect of pressurization in a portable hyperbaric chamber at high altitude

Regional cerebral oxygenation (rSO2) and peripheral oxygen saturation (SpO2) have been studied in subjects inside a portable hyperbaric chamber at altitude during pressurization. The effects of the accumulation of carbon dioxide within the chamber on rSO2 and SpO2 have also been investigated. Three studies of cerebral regional oxygenation were undertaken, using near-IR spectroscopy, in subjects who had ascended to 3475 m in the Alps, 4680 m in the Andes or 5005 m in the Himalayas. At 3475 m and 5005 m the effects of the removal of inspired carbon dioxide by a soda lime scavenger were also studied. On pressurization of the chamber to 19.95 kPa, inspired carbon dioxide rose within the chamber from 0.03% (0.06 kPa) ambient to over 1% (1.3 kPa). At 5005 m, SpO2 rose from a baseline of 79.5% (S.D. 4.5%) to 95.9% (2.0%) (P<0.0001), and cerebral rSO2 rose from 64.6% (3.4%) to 69.4% (3.6%) (P<0.0001). The introduction of a soda lime CO2 scavenger into the breathing circuit resulted in a drop in SpO2 from 95.9% (2.03%) to 93.6% (2.07%) (P<0.001) and a fall in rSO2 from 69.4% (3.64%) to 68.5% (3.5%) (P<0.01). Chamber pressure was maintained throughout at 19.95 kPa. Similar changes were seen at the other altitudes. Cerebral rSO2 increased rapidly following pressurization at all three altitudes. Scavenging of inspired carbon dioxide was associated with a significant fall in cerebral rSO2 and SpO2, and we estimate that the contribution of carbon dioxide may account for up to one-third of the beneficial effect of the portable hyperbaric chamber.