J. Martin Gibson

Circulating concentrations of insulin-like growth factor-I and development of glucose intolerance: A prospective observational study

BACKGROUND Results of experimental and clinical studies suggest that insulin-like growth factor-I (IGF-I) and IGF binding protein-1 (IGFBP-1) could be important determinants of glucose homoeostasis. However, experimental models might also reflect compensatory and adaptive metabolic processes. We therefore prospectively examined the associations between circulating concentrations of IGF-I and IGFBP-1 and development of glucose tolerance. METHODS Participants in this cohort study were a random sample of 615 normoglycaemic men and women aged 45-65 years. Participants underwent oral glucose tolerance testing based on WHO definitions and criteria in 1990-92 and 1994-96. At the baseline visit, we measured serum concentrations of IGF-I and IGFBP-1, and assessed the relation between these peptides and subsequent glucose intolerance. FINDINGS At 4.5 years of follow-up, 51 (8%) of 615 participants developed impaired glucose tolerance or type-2 diabetes. After adjustment for correlates of IGF-I and risk factors for glucose intolerance, the odds ratio for risk of impaired glucose tolerance or type-2 diabetes for participants with IGF-I concentrations above the median (> or = 152 microg/L) compared with those with concentrations below the median (<152 microg/L) was 0.50 (0.26-0.95). Consistent with this finding, IGF-I also showed a significant inverse association with subsequent 2-h glucose concentrations, which was independent of correlates of IGF-I and risk factors for glucose tolerance (p for linear trend=0.026). We also found that this inverse association was independently modified by IGFBP-1 (p for interaction=0.011). INTERPRETATION These data show that circulating IGF-I and its interaction with IGFBP-1 could be important determinants of glucose homoeostasis and provide further evidence for the possible protective role of IGF-I against development of glucose intolerance.

Type 2 Diabetes Whole-Genome Association Study in Four Populations: The DiaGen Consortium

Type 2 diabetes (T2D) is a common, polygenic chronic disease with high heritability. The purpose of this whole-genome association study was to discover novel T2D-associated genes. We genotyped 500 familial cases and 497 controls with >300,000 HapMap-derived tagging single-nucleotide-polymorphism (SNP) markers. When a stringent statistical correction for multiple testing was used, the only significant SNP was at TCF7L2, which has already been discovered and confirmed as a T2D-susceptibility gene. For a replication study, we selected 10 SNPs in six chromosomal regions with the strongest association (singly or as part of a haplotype) for retesting in an independent case-control set including 2,573 T2D cases and 2,776 controls. The most significant replicated result was found at the AHI1-LOC441171 gene region.

C-reactive protein and the insulin-like growth factor (IGF)-system in relation to risk of cardiovascular disease in different ethnic groups

Inflammatory processes, marked in part by the acute phase reactant C-reactive protein (CRP) and insulin resistance are implicated in atherogenesis. Low insulin-like growth factor-I (IGF-I) and IGF binding protein-1 (IGFBP-1) concentrations are closely associated with insulin resistance. We examined CRP in ethnic groups with differing risk for cardiovascular disease and type 2 diabetes and its relationship with insulin sensitivity (Homeostasis model assessment (HOMA)-S) and the IGF system. European (n=155), Pakistani (n=108) and African-Caribbean (African Caribbean) (n=177) origin participants were randomly sampled from population registers. All underwent basic anthropometry, glucose tolerance testing and measurement of insulin sensitivity, CRP and other metabolic variables. CRP was significantly lower in African Caribbean men and women than in other ethnic groups. Across all groups CRP correlated negatively with (HOMA-S) (rho=-0.29, P<0.001). Regression analysis which included ethnicity and body mass index (BMI) showed that low HOMA-S (beta=-0.17, P<0.001) and low IGFBP-1 (beta=-0.14, P<0.001) were independently and inversely associated with CRP, but the effect was modified by obesity. In obese subjects insulin sensitivity was not associated with CRP. However, for the whole population, a 2.7 mg/l increase in CRP was associated with a 50% (95% confidence interval (CI) 10-210%) greater risk of WHO defined metabolic syndrome, independent of IGF-I (odds ratio (OR) 0.46 (95% CI 0.22-0.96)), IGFBP-1 (OR 0.58 (0.44-0.76)), female sex (OR 0.43 (0.22-0.84)), NEFA (OR 1.06 (1.03-1.09)) and Pakistani ethnicity. High CRP (as a measure of chronic subclinical inflammation), low IGF-I and low IGFBP-1 are independently associated with the presence of the metabolic syndrome and with insulin resistance. In obese subjects insulin sensitivity is not associated with changes in CRP whilst in non-obese subjects CRP independently contributes to variation in HOMA-S.

Effectiveness of Fluticasone Furoate–Vilanterol for COPD in Clinical Practice

BACKGROUND Evidence for the management of chronic obstructive pulmonary disease (COPD) comes from closely monitored efficacy trials involving groups of patients who were selected on the basis of restricted entry criteria. There is a need for randomized trials to be conducted in conditions that are closer to usual clinical practice. METHODS In a controlled effectiveness trial conducted in 75 general practices, we randomly assigned 2799 patients with COPD to a once-daily inhaled combination of fluticasone furoate at a dose of 100 μg and vilanterol at a dose of 25 μg (the fluticasone furoate-vilanterol group) or to usual care (the usual-care group). The primary outcome was the rate of moderate or severe exacerbations among patients who had had an exacerbation within 1 year before the trial. Secondary outcomes were the rates of primary care contact (contact with a general practitioner, nurse, or other health care professional) and secondary care contact (inpatient admission, outpatient visit with a specialist, or visit to the emergency department), modification of the initial trial treatment for COPD, and the rate of exacerbations among patients who had had an exacerbation within 3 years before the trial, as assessed in a time-to-event analysis. RESULTS The rate of moderate or severe exacerbations was significantly lower, by 8.4% (95% confidence interval, 1.1 to 15.2), with fluticasone furoate-vilanterol therapy than with usual care (P=0.02). There was no significant difference in the annual rate of COPD-related contacts to primary or secondary care. There were no significant between-group differences in the rates of the first moderate or severe exacerbation and the first severe exacerbation in the time-to-event analyses. There were no excess serious adverse events of pneumonia in the fluticasone furoate-vilanterol group. The numbers of other serious adverse events were similar in the two groups. CONCLUSIONS In patients with COPD and a history of exacerbations, a once-daily treatment regimen of combined fluticasone furoate and vilanterol was associated with a lower rate of exacerbations than usual care, without a greater risk of serious adverse events. (Funded by GlaxoSmithKline; Salford Lung Study ClinicalTrials.gov number, NCT01551758 .).

Significant ethnic variation in total and free testosterone concentration

objective Measurement of serum testosterone is an integral part of the assessment of men presenting to endocrine clinics. Little is known about the variation of total bound or bioavailable testosterone by ethnic group. The principal determinant of testosterone bioavailability is SHBG, which itself is a marker for insulin sensitivity. Our aim was to examine variations in testosterone and SHBG levels across three ethnic groups in relation to ethnic differences in insulin sensitivity.

Association between insulin-like growth factor-I: insulin-like growth factor-binding protein-1 ratio and metabolic and anthropometric factors in men and women.

Several prospective observational studies have suggested that elevated circulating IGF-I levels are associated with an increased risk of cancer. These observations may provide a potential mechanism through which previously identified metabolic and anthropometric factors, such as obesity and elevated insulin and glucose levels, may operate. We therefore examined metabolic and anthropometric influences on circulating levels of insulin-like growth factor-I (IGF-I), insulin-like growth factor-binding protein-1 (IGFBP-1), and the IGF-I:IGFBP-1 ratio in a middle-aged population of 349 men and 492 women. IGF-I showed only modest inverse associations with indices of adiposity. However, we found that low IGFBP-I levels and an increased IGF-I:IGFBP-1 ratio were strongly associated with increased levels of insulin and glucose in men and women. Body mass index was also positively related to the IGF-I:IGFBP-1 ratio in men (P < 0.001) and women (P < 0.001), independent of metabolic correlates of IGFBP-1 and IGF-I. Similarly, waist:hip ratio and waist circumference were also associated with an increased IGF-I:IGFBP-1 ratio and low circulating IGFBP-1 levels. These findings suggest that individuals with greater fat mass and upper body obesity may have elevated levels of bioavailable or free IGF-I, which could, in part, mediate the reported associations among metabolic and anthropometric factors and cancer risk.

Impaired Glucose Tolerance and Insulin Resistance in Heart Failure: Underrecognized and Undertreated?

BACKGROUND A link between diabetes mellitus (DM) and heart failure (HF) has been well-recognized for more than a century. HF is also closely linked to abnormal glucose regulation (AGR) and insulin resistance (IR) in patients without DM and, similarly, these conditions commonly coexist. In epidemiological studies, each condition appears to predict the other. The prevalence of AGR/IR in HF patients without DM is significantly underrecognized and, as yet, the optimal method for screening for these abnormalities in the outpatient setting is unclear. METHODS AND RESULTS The purpose of this review is to overview the prevalence and prognostic impact of AGR and IR in HF patients without DM and discuss potential pathophysiological pathways that link these conditions with HF. The severity of glucose intolerance in patients with HF correlates with functional and clinical severity of HF and is an independent predictor of an adverse outcome. It is thought that changes in cardiac metabolism, including a switch from glucose metabolism toward fatty acid metabolism, may in part contribute to the pathophysiological processes associated with HF patients with AGR/IR. CONCLUSIONS We discuss how pharmacological targeting of metabolic pathways in the myocardium of these patients with HF may represent novel therapeutic strategies in these at-risk patients.

Statins are detrimental to human placental development and function; use of statins during early pregnancy is inadvisable.

The rapid rise in obesity, metabolic syndrome and type 2 diabetes is one of the major healthcare problems of the Western world. Affected individuals are often treated with statins (HMG CoA reductase inhibitors) to reduce circulating cholesterol levels and the risk of developing cardiovascular disease [1]; given the evolving demographic profile of these conditions, such drugs are increasingly prescribed to women of reproductive age. Cholesterol is essential for normal foetal development and therefore the use of lipid-lowering drugs, including statins, is contraindicated during pregnancy. However, a recent study suggests that the detrimental effects of statins may be restricted to the more lipophilic compounds as there have been no reports of foetal congenital abnormalities in association with the relatively hydrophilic statins, for example pravastatin [2]. The actions of statins are not limited to modulation of cholesterol levels, as inhibition of HMG CoA reductase also interferes with the production of dolichol and isoprenoids; dolichol is involved in the N-linked glycosylation of membrane-targeted glycoproteins, whereas isoprenoids are necessary for the optimal function of numerous intracellular signalling molecules. Previous studies indicate that the insulin-like growth factor (IGF) system – a key system in the control of foetal growth – is particularly sensitive to such modulation by statins [3]. IGFs mediate their effect on foetal growth, at least in part, by promoting normal placental development; thus maternal IGF can enhance the growth, survival and differentiation of the placental trophoblast cell layer [4], which is responsible for maintaining the nutrient/waste exchange barrier between mother and foetus. We therefore investigated if statins affect IGF action in the human placenta, using pravastatin as an example of a hydrophilic statin that is potentially compatible with use in pregnancy and the potent lipohilic compound, cerivastatin, which is no longer clinically available but is known to abrogate IGF effects in other cell models. We have used an explant model of early pregnancy placental villous tissue that can be maintained in a viable state for several days [4], representing a much more physiologically relevant system for toxicology studies than cell culture. In particular, cell proliferation is maintained, the vectorial relationship between maternal and foetal blood compartments is preserved and test compounds may be supplied to the maternal surface of the placenta to faithfully recapitulate in vivo exposure. As expected,

Association of elevated insulin-like growth factor binding protein-1 with insulin resistance in hyperthyroidism

Insulin‐like growth factor binding‐protein‐1 (IGFBP‐1) has a role in glucose homeostasis and is present at high concentrations in hyperthyroidism. We have investigated the relationship between IGFBP‐1 concentration and glucose homeostasis in hyperthyroidism.

Economic Analysis of a Telemedicine Intervention to Improve Glycemic Control in Patients with Diabetes Mellitus Illustration of a Novel Analytic Method

Background and objectiveAn economic analysis of telemedicine support to improve glycemic control in patients with type 2 diabetes mellitus, illustrating the use of an analytic framework that efficiently combines telemedicine program findings with published estimates of treatment cost effectiveness.MethodThe Pro-Active Call Centre Treatment Support (PACCTS) trial compared tailored, protocol-driven call-center support with usual care as methods to manage glycemic control in 591 patients with diabetes in Salford, UK. Economic analysis of the trial describes the cost of delivering telemedicine support and level of improved glycemic control achieved in patients. These findings are linked to current best evidence for the long-term cost effectiveness of treatment to help inform whether the provision of call-center support to improve glycemic control should become routine health policy.ResultsUnder trial conditions, the cost effectiveness of the PACCTS intervention was estimated to be £43 400/ quality-adjusted life-year (QALY) [2003 costings]. Under routine-use call-center conditions (a full caseload of patients with moderate to poor glycemic control) cost effectiveness was estimated to be lower at £33 700/QALY. Set against a threshold of £30 000/QALY, Monte Carlo simulation suggests the probability of PACCTS being cost-effective in routine use is 29%.DiscussionDespite being received well by patients and healthcare professionals alike, telemedicine support solely to achieve improved glycemic control in patients with type 2 diabetes was found to be borderline cost effective. Major uncertainties that could change this result include the underlying cost effectiveness of improved glycemic control, which is currently imprecisely known. Research is ongoing in patients with type 2 diabetes to extend call-center support to improve blood pressure and lipid management, where if similar improvements are obtained, the call center should prove highly cost effective. The novel analytic approach illustrated provides a clear framework for thinking about the design and analysis of behavioral change policies for healthcare.