Cell-specific insulin resistance: implications for atherosclerosis.

Insulin resistance is increasingly acknowledged as an independent risk factor for cardiovascular disease. Despite this, our understanding of the cellular and molecular mechanisms that might account for this relationship remain incompletely understood. A key challenge has been in distinguishing between a 'whole-body' milieu of inflammation and oxidative stress from the ramifications of cell-specific resistance to insulin. Transgenic models have now begun to explore the cellular influences of insulin resistance on vascular biology, with novel implications for atherosclerosis across a range of cells including endothelial cells, endothelial progenitor cells, vascular smooth muscle cells, macrophages and fibroblasts. Emerging data from these models have also begun to challenge conventional dogma. In particular, the findings across various cell types are disparate with some even implying a protective influence on vascular biology. We now review these data, highlighting recent advances in our understanding of cellular resistance to insulin as well as those areas where there remains a paucity of data.

Diabetes mellitus and the heart.

Diabetes mellitus is a risk factor for the development of coronary artery disease and chronic heart failure. When carefully screened for, diabetes or prediabetic disorders, are present in the majority of patients with clinically manifest ischaemic heart disease, and confer a major adverse impact upon morbidity and mortality. Important therapeutic modifications are required in the management of coronary artery disease and chronic heart failure associated with diabetes, and vice versa. However, despite optimal management, aided by recent landmark trials solely recruiting patients with diabetes, outcomes for patients with diabetes and heart disease remain poor. This review outlines the epidemiology, pathogenesis and management of diabetic heart disease, along with highlighting the many gaps in the evidence-base and suggesting future research priorities.

Cardiovascular mortality and morbidity following radical radiotherapy for lung cancer: Is cardiovascular death under-reported?

BACKGROUND: Lung cancer is the most common malignancy worldwide. Radical radiotherapy is an essential treatment in the management of early and locally advanced lung cancer. Cardiac events are known to occur following radical radiotherapy for lung cancer. This study examines the burden of cardiac events post radiotherapy, and estimates the accuracy of death certification in patients who received radical radiotherapy for lung cancer. METHODS: We conducted a retrospective observational cohort study for all patients receiving radical radiotherapy for non-small cell lung cancer (NSCLC) at a large cancer centre between 01/01/2010 to 31/12/2016. Baseline cardiovascular disease and cancer status and treatment data were collected, along with hospital admission data and documented cause of death from the national registry for a median follow-up period of 34 months. RESULTS: Of 1224 patients included in the analysis, 378 (30.9%) patients had cardiovascular disease at baseline, including 140 (11.4%) with prior myocardial infarction. In the 846 patients without known cardiovascular disease, 451 (53.3%) had a QRISK2 predicted 10-year cardiovascular risk >20% over 10 years. During follow-up, 215 hospitalisations occurred (Incidence rate 6.2 per hundred patient years) which were classified as primarily cardiac, and 622 patients died (18 per 100 patient-years). However, death certificates stated a primary cardiac cause of death in only 33 cases (5.3% of deaths). Notably, 29% of patients dying out of hospital and certified as cancer death did not have documented cancer relapse prior to death, and 61% had no community palliative care input prior to death, implying these events may have been sudden and unexpected. CONCLUSION: There is a high prevalence of baseline cardiovascular disease in people undergoing radiotherapy for NSCLC, accompanied by significant rates of post-radiotherapy cardiovascular hospitalisation. However, only a small proportion of deaths are attributed to cardiovascular disease, together with the large amount of sudden deaths observed, this suggests that cardiovascular death is greatly under-reported in official statistics.

Prospective development and validation of a model to predict heart failure hospitalisation.

OBJECTIVE: Acute heart failure syndrome (AHFS) is a major cause of hospitalisation and imparts a substantial burden on patients and healthcare systems. Tools to define risk of AHFS hospitalisation are lacking. METHODS: A prospective cohort study (n=628) of patients with stable chronic heart failure (CHF) secondary to left ventricular systolic dysfunction was used to derive an AHFS prediction model which was then assessed in a prospectively recruited validation cohort (n=462). RESULTS: Within the derivation cohort, 44 (7%) patients were hospitalised as a result of AHFS during 1 year of follow-up. Predictors of AHFS hospitalisation included furosemide equivalent dose, the presence of type 2 diabetes mellitus, AHFS hospitalisation within the previous year and pulmonary congestion on chest radiograph, all assessed at baseline. A multivariable model containing these four variables exhibited good calibration (Hosmer-Lemeshow p=0.38) and discrimination (C-statistic 0.77; 95% CI 0.71 to 0.84). Using a 2.5% risk cut-off for predicted AHFS, the model defined 38.5% of patients as low risk, with negative predictive value of 99.1%; this low risk cohort exhibited <1% excess all-cause mortality per annum when compared with contemporaneous actuarial data. Within the validation cohort, an identically applied model derived comparable performance parameters (C-statistic 0.81 (95% CI 0.74 to 0.87), Hosmer-Lemeshow p=0.15, negative predictive value 100%). CONCLUSIONS: A prospectively derived and validated model using simply obtained clinical data can identify patients with CHF at low risk of hospitalisation due to AHFS in the year following assessment. This may guide the design of future strategies allocating resources to the management of CHF.

Secondary prevention of cardiovascular disease in type 2 diabetes and prediabetes: a cardiologist's perspective.

Patients with type 2 diabetes mellitus (T2DM) and prediabetes have a substantially greater risk of developing cardiovascular (CV) disease than the general population. This increased risk of CV disease is due to a complex cluster of risk factors including insulin resistance, hyperglycaemia, diabetic dyslipidaemia, hypertension and systemic inflammation. As a result of this cluster of risk factors, life expectancy is reduced by up to 10 years upon diagnosis of T2DM, principally because of fatal CV events. Patients with T2DM are not only more likely to sustain a CV event, but also have a higher risk of a fatal outcome from this event. Therefore, whilst primary prevention is critical in determining the prognosis of patients newly diagnosed with T2DM, many will go on to suffer CV events and represent a high-risk group requiring intensive secondary prevention techniques. Recent data demonstrate that contemporary prevention therapies do not afford equal benefits to T2DM sufferers after acute myocardial infarction compared with their non-diabetic counterparts. This finding highlights the need for more effective secondary preventative strategies to prevent recurrent CV events in patients with T2DM and prediabetes. The cardiologist's role in the multidisciplinary management of T2DM is to improve patient outcomes by optimising use of evidence-based strategies for the prevention of recurrent CV events.

Increased expression of a novel c-abl-related RNA in K562 cells.

The c-abl locus is translocated from chromosome 9 to chromosome 22 in chronic myelogenous leukemia (CML), creating the Philadelphia chromosome (22q-, Ph1), one of the most consistent chromosomal abnormalities found in human hematologic malignancy. The K562 cell line is a human cell line originally derived from a patient with CML. We have isolated cloned human c-abl probes to analyze the organization and expression of abl genes in patients with CML and in K562 cells. With these probes, we confirm the amplification of abl genes in K562 cells. In addition, we demonstrate the presence of increased amounts of a novel RNA species hybridizing to a c-abl probe in K562 cells. This same large RNA species is present in addition to two normal transcripts in the leukemic cells of patients with CML. These results provide evidence that the c-abl locus is abnormally expressed in CML.

Trans acting regulation of beta globin gene expression in erythroleukemia (K562) cells.

K562 cells are induced by hemin to produce gamma and epsilon globin but not beta globin, although the beta globin gene is intact, and when isolated is expressed in a transient expression assay (1, 2). We have previously shown that an epsilon globin gene transferred into K562 cells is expressed and inducible (3). In this paper, we report the stable transfer of a sickle or betaS globin gene into K562 cells. Thirty-six different transformed lines were tested; 24 of 36 lines contained an intact betaS globin gene. However, using S1 nuclease, Dot blot, and Northern blotting analyses, none of these lines showed beta globin mRNA expression. These results indicate that trans acting factors are responsible for the lack of expression of the beta globin gene in K562 cells.

Exploration of requirements for peptide binding to HLA DRB1*0101 and DRB1*0401.

The individual amino acid contacts responsible for peptide binding to DRB1*0101 and/or DRB1*0401 were defined using a quantitative binding assay. The differential contribution of each amino acid in two well studied T cell determinants, HA307-319 and RMBP 90-102, was delineated by comparing the IC50 values of analogues of varying length. This analysis confirmed the importance of a hydrophobic amino acid located near the amino-terminus for binding to both alleles and revealed that the contribution of the carboxyl-terminal amino acids differed between DRB1*0101 and DRB1*0401. Taking advantage of previous experiments demonstrating that all of the residues could be replaced with alanine, with the exception of the key hydrophobic amino acid, simplified analogues composed of polyalanines were used to prove 1) optimal binding depended on the position of the hydrophobic side chain relative to the amino- and carboxyl-termini; 2) aromatic amino acids were superior to aliphatic side chains at this position; and 3) a significant amount of free energy of binding arises from hydrogen bonding between the class II binding site and the amide bonds of the ligand. The role of each carbonyl and amide nitrogen was measured by assaying analogues containing reduced peptide bonds or N-methyl amino acids. Serine, but not glycine, could be used as a framework amino acid for peptide ligands, indicating that the beneficial aspects of these simplified structures was the combination of retaining the correct orientation of the peptide bonds, the restriction of the conformational freedom by limiting the possible phi/psi angles of the peptide, and avoidance of deleterious side-chain contacts. Collectively, these data were consistent with the peptide binding in a nonrepeating conformation with the vast majority of the free energy of binding arising from hydrogen bonds with the peptide backbone and a single, key hydrophobic side chain interacting in a conserved pocket in both DRB1*0101 and DRB1*0401.

Differential glycosylation of interleukin 2, the molecular basis for the NOD Idd3 type 1 diabetes gene?

The insulin-dependent diabetes (Idd) gene, Idd3, has been localised to a 0.35 cM region of chromosome 3 containing the structural gene for the cytokine interleukin 2 (IL-2). While variation of the N-terminal amino acid sequence of IL-2 has been shown to correlate with Idd3 allelic variation, differences in induction of proliferation by IL-2 allotypes have not been detected. In the current study, we examined the electrophoretic migration of IL-2 allotypes and have found two distinct patterns, consistent with differences in glycosylation, that correlate with diabetes-resistance and susceptibility. These findings strongly suggest that IL-2 variants may be functionally distinct.

Tetrapeptide derived inhibitors of complexation of a class II MHC: the peptide backbone is not inviolate.

Major histocompatabilty (MHC) proteins rely heavily on peptide backbone recognition for ligation. Nonetheless, modifications to the polyamide backbone of a tetrapeptide ligand can be made without abrogating binding.