Adrian Heald

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.

Close relation of fasting insulin-like growth factor binding protein-1 (IGFBP-1) with glucose tolerance and cardiovascular risk in two populations.

Aims/hypothesis. Insulin resistance/hyperinsulinaemia is implicated in the development of cardiovascular disease and diabetes but its role and causal pathways are not clear. We tested the hypothesis that the insulin-like growth factor system is independently associated with cardiovascular risk within susceptible populations based on previous reports of the links between low circulating insulin-like growth factor binding protein-1 concentrations and increased macrovascular disease in Type II (non-insulin-dependent) diabetes mellitus. Methods. In a population-based study 272 subjects (142 subjects of European and 130 Pakistani of origin) underwent a 75 g oral glucose tolerance test and standardised anthropometry. Fasting concentrations of insulin-like growth factor binding protein-1 (IGFBP-1), insulin-like growth factor-I (IGF-I), insulin-like growth factor-II (IGF-II), intact insulin and lipids were measured and were related to 2-h glucose tolerance test status. Insulin sensitivity was calculated using the homeostasis model assessment (HOMA). Results. Insulin-like growth factor binding protein-1 was significantly lower in subjects with impaired glucose tolerance when compared with normal glucose tolerance in both ethnic groups (Europeans F = 6.7, p = 0.002 and Pakistanis F = 4.4, p = 0.01). Multiple linear regression modelling showed that insulin-like growth factor binding protein-1 was independently associated with 2-h glucose (β = 0.16, p = 0.009) and logistic regression indicated a 40 % reduction in risk of impaired glucose tolerance for every 2.7 ng/ml increase in the insulin-like growth factor binding protein-1 concentration [odds ratio 0.6 (CI = 0.49–0.71), p = 0.001)]. In addition, insulin-like growth factor binding protein-1 was significantly correlated negatively with several established cardiovascular factors, and positively with insulin sensitivity. Conclusion/interpretation. Insulin-like growth factor binding protein-1 is closely related to risk factors for diabetes and cardiovascular disease in people of European and Pakistani origin. It has potential use as a marker of (hepatic) insulin resistance in clinical intervention studies and further implicates the insulin-like growth factor system in the development of macrovascular disease. [Diabetologia (2001) 44: 333–339]

Long‐term negative impact on quality of life in patients with successfully treated Cushing's disease

objective  A cohort of pituitary tumour patients, who had undergone definitive treatment within a 15‐year period at a single neuroscience centre, were investigated as to whether there were differences in psychological well‐being and psychosocial functioning, dependent on endocrine pathology and treatment variables.

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.

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.

The influence of dietary intake on the insulin-like growth factor (IGF) system across three ethnic groups: a population-based study.

OBJECTIVE The insulin-like growth factor (IGF) system has been implicated in the aetiopathogenesis of cancer, cardiovascular disease and diabetes. Since dietary factors and ethnicity are considered contributory to the development of these diseases, we examined the IGF system in relation to nutritional intake by ethnic group. DESIGN, SUBJECTS AND SETTING Dietary intake in 257 subjects of White European, African-Caribbean and Pakistani ethnic origin living in Manchester, UK was assessed using ethnic-group-specific food-frequency questionnaires to assess habitual nutrient intake over the previous 12 months. Fasting IGF-I, IGF-II and IGF-binding protein-1 (IGFBP-1) concentrations were determined and their relationship to specific dietary constituents was analysed. RESULTS Analysis by quintiles of nutrient intake showed a significant increase in circulating IGF-I concentration with increasing dietary fat intake (F for trend=3.9, ), saturated fat intake and for protein intake There was also a significant increase in IGF-II by quintiles of dietary protein intake There was a trend for increasing IGF-I with increasing energy intake. The relationships between circulating concentration of IGFBP-1, an acute regulator of IGF action, and fat/protein intake were opposite to those for IGF-I and IGF-II. Multiple linear regression modelling showed that people of Pakistani origin and older subjects had lower levels of IGF-I (Pakistani origin vs. others, ) (age, for both). There was an independent inverse relationship between IGF-I and dietary carbohydrate intake CONCLUSIONS This study provides evidence for a dietary contribution to regulation of the IGF system, although the effects of ethnicity on circulating IGF levels remain dominant. We propose that the IGF systems influences on cancer risk in specific ethnic groups are potentially modifiable by dietary intervention.

Physical health in schizophrenia: a challenge for antipsychotic therapy

In the management of schizophrenia, mental health outcomes are the principal focus of treatment. The objective is to control the psychotic symptoms while minimising negative features of the illness, to achieve an overall improvement in the societal functioning of patients. Physical health is also important because if it is compromised, many of the benefits of improved mental health will be offset. Compared with the general population, schizophrenia patients are at increased risk of weight gain, abdominal obesity, diabetes, metabolic syndrome, and cardiovascular disease. These physical health problems can contribute to the decreased quality of life, lowered self-esteem and reduced life expectancy commonly reported in schizophrenia. For these reasons there is a pressing need to improve both the monitoring and the management of physical health in patients with schizophrenia as a part of their overall care. A consensus for metabolic monitoring of patients receiving treatment with antipsychotic drugs is available. However, the practicing clinician requires guidance about management of physical health in routine clinical practice. This should include recommendations for measurements that have strong predictive value about physical health risks yet are easy to make, and about the use of medications that have the least effect on physical health parameters. This article will review the gravity of the physical health risks facing schizophrenia patients.

Most commercial insulin assays fail to detect recombinant insulin analogues

Insulin assays are utilized in various clinical scenarios, including the assessment of insulin therapy compliance or of suspected insulin overdose. In an interpretative exercise carried out by UK National External Quality Assessment Service (NEQAS), serum sent to the participating laboratories was spiked with 30 pmol/L of the short-acting insulin analogue Human Actrapid. Only two out of 24 participant laboratories had sufficient assay cross-reactivity with Actrapid to interpret the results as suggestive of insulin administration. The development of specific insulin assays has led to deterioration in the ability to detect non-compliance or overdose with recombinant insulin treatment. Clinicians should be aware of this significant limitation, which could lead to misdiagnosis.

Serum testosterone, testosterone replacement therapy and all-cause mortality in men with type 2 diabetes: retrospective consideration of the impact of PDE5 inhibitors and statins

Low testosterone levels occur in over 40% of men with type 2 diabetes mellitus (T2DM) and have been associated with increased mortality. Testosterone replacement together with statins and phosphodiesterase 5 inhibitors (PDE5I) are widely used in men with T2DM.