Is the morning peak of acute myocardial infarction's onset due to sleep-related breathing disorders? A prospective study

Many studies have shown that the risk of experiencing a myocardial infarction (MI) is increased during the first hours of the morning. Sleep apnea syndrome (SAS) is associated with an enhanced adrenergic activity, prolonged a few hours after awakening. We aimed at assessing whether sleep breathing disorders could be a culprit for the morning excess rate of MI. We studied 40 middle-aged men admitted for an acute MI. An overnight polysomnographic study was performed 37.4 +/- 9.4 days after the MI. The prevalence of SAS was high (30%). The prevalence of SAS was significantly higher in patients with the MI onset during the morning. The circadian pattern was significantly different in patients with or without SAS: those with SAS presented an important peak of MI onset during the period between 06.00 and 11.59 h. None of them had their MI during the period between 24.00 and 05.59 h. This different nyctohemeral pattern underlines the potential role of sleep breathing disorders as a trigger of MI.     

Are the insulin-like growth factors relevant to cancer?

Recognition of molecular pathways relevant to cancer biology have led to advances in prevention and treatment. Numerous laboratory and clinical investigations have implicated the insulin-like growth factors (IGFs) in tumourigenesis. In this review, the evidence for the involvement of IGFs in cancer is discussed. While these data are persuasive, it is clear that additional methods to regulate IGF action in cancer patients are needed to substantiate the role of this growth factor family in cancer biology.     

Arterial hypertension and thyroid disorders: what is important to know in clinical practice?

This review describes the pathogenic mechanisms of blood pressure (BP) regulation and long-term control in thyroid disorders. Variations from the euthyroid status affect virtually all physiological systems but the effects on the cardiovascular system are particularly pronounced. Thyroid disorders induce several hemodynamic changes leading to elevated BP as a consequence of their interaction with endothelial function, vascular reactivity, renal hemodynamic and renin-angiotensin system. However, in thyroid disorders, the regulation of BP and the development and maintenance of variable forms of arterial hypertension (HT) are different. Hyperthyroidism results in an increased endothelium-dependent responsiveness secondary to the shear stress induced by the hyperdynamic circulation, and contributes to reduce vascular resistance. Conversely, hypothyroidism is accompanied by a marked decrease in sensitivity to sympathetic agonists with an increase of peripheral vascular resistance and arterial stiffness. Furthermore in animal models, hypothyroidism reduces the endothelium-dependent and nitric oxide-dependent vasodilatation. HT due to thyroid disorders is usually reversible with achievement of euthyroidism, but in some cases pharmacological treatment for BP control is required. In hyperthyroidism, β-blockers are the first-choice treatment to control BP but when they are contraindicated or not tolerated, ACE-inhibitors or calcium-channel blockers (CCB) are recommended. Hypothyroidism is a typical low rennin HT form showing a better antihypertensive response to CCB and diuretics; indeed in hypothyroidism a low-sodium diet seems further to improve BP control. Randomized clinical trials to compare the efficacy on BP control of the antihypertensive treatment in thyroid disorders are needed.     

Is hypertension related to the number of nephrons?

The kidney has a key role in blood pressure control, and an abnormal regulation of sodium balance is involved in essential hypertension. It has been suggested that a reduced nephron number at birth could be one possible mechanism. Indeed various strains of hypertensive animals exhibit a reduced nephron number. In human beings, two autopsy studies have clearly shown a lower (about 50%) nephron number in hypertensive subjects. The glomeruli are also enlarged, indicating hyperfiltration. This could be the cause of both high blood pressure and later nephrosclerosis. A low number of nephrons is part of the perinatal programming which occurs together with fetal growth retardation, and this has been reproduced experimentally. There is a negative correlation between birth weight and glomerular number. Such a situation is associated with a largely increased risk of cardiovascular complications in adulthood.     

Are genetic variants of the methyl group metabolism enzymes risk factors predisposing to obesity?

Obesity, due to the combination of inherited genes and environmental factors, is continually increasing. We evaluated the relationship between polymorphisms of methylene-tetrahydrofolate reductase (MTHFR C677T and A1298C), methionine synthase (MTR A2756G), methionine synthase reductase (MTRR A66G), betaine:homocysteine methyltransferase (BHMT G742A) and cystathionine beta-synthase (CBS 68-bp ins) genes and the risk of obesity. We studied these polymorphic variants in 54 normal and 82 obese subjects [body mass index (BMI)=22.4+/-1.8, 34.1+/-7.1; ages 35.2+/-10.7, 43.3+/-10.6 respectively]. Levels of total plasma homocysteine (t-Hcy), folates, and vitamins B6 and B12 were not significantly different, while leptin concentration was significantly higher (p=0.005) in the obese patients compared to the lean controls. The frequency of only (a) MTHFR (AC), (b) MTR (AG), and (c) MTRR (AG) heterozygous genotypes was statistically different in the obese compared to the control group (p=0.03, p=0.007, and p=0.01). Single (a), (b), and (c) heterozygous genotypes had a significant risk of developing obesity [p=0.02, 0.01, and 0.03; odds ratio (OR)=2.5, 3.0, and 2.4; 95% confidence interval (CI)=1.2-5.3, 1.3-7.1, and 1.2-5.1 respectively] and the risk remarkably increased for combined genotypes a+b, a+c, b+c, and a+b+c (p=0.002, 0.002, 0.016, 0.006; OR=7.7, 5.4, 5.8, 15.4; 95% CI=1.9-30.4, 1.7-16.8, 1.4-23.2, 1.6- 152.3). These findings suggest that in obese subjects, Hcy cycle efficiency is impaired by MTHFR, MTR, and MTRR inability to supply methyl-group donors, providing evidence that MTHFR, MTR, and MTRR gene polymorphisms are genetic risk factors for obesity.     

Moving beyond guidelines: Are report cards the answer to high rates of uncontrolled hypertension?

Hypertension control rates remain alarmingly low worldwide despite the extensive evidence for decreased rates of cardiovascular, cerebrovascular, and renal events in response to blood pressure (BP) lowering to recommended targets. Several classes of antihypertensive drugs are available, which in combination can produce major decreases in BP, with minimal side effects. Moreover, most patients only have mild hypertension and, in general, can be controlled to < 140/90 mm Hg by proper combinations of two antihypertensive drugs. Although patient-related factors clearly contribute to poor control of hypertension, physician-related factors, particularly “passive” therapeutic inertia, are as responsible if not more so. Recent studies clearly indicate that monitoring performance of individual physicians and providing feedback on the care delivered by them can move treatment of hypertension to BP control rates in the 60% to 70% range. If health care organizations would implement this approach, enormous benefits could be expected for the prevention of cardiovascular and cerebrovascular disease.     

Genetics and essential hypertension: candidate genes or screening of the whole genome?

Essential hypertension is a major cardiovascular risk factor in the industrialised countries. Its hereditary nature has been well established in many familial studies: about 30% of blood pressure variance is thought to be genetically determined. However, the identification of the culprit genes has met with many difficulties: the multitude of genes, the effect of which is difficult to appreciate, the many possible genetic polymorphisms of each gene studied, the very important role of environmental factors (diet, physical activity, etc...) on the blood pressure itself or on the effect of the genes which control the blood pressure. With the exception of some rare caricatural forms of mendelian transmitted hypertension, the search for genes has focused on large case control studies and/or studies of siblings with hypertension. Two main approaches are used with these collections of subjects. The first consists of analysing so-called "candidate" genes which code for proteins whose function is known and which may influence the blood pressure. In the last ten years, many candidate genes have been assessed with often controversial results. The second approach is to carry out, with no a priori, a complete screen of the genome. These more recent studies have also provided contradictory results. To date, the results illustrate the difficulty of genetic analysis of a complex trait and the necessity of more integrated approaches: analysis of combination of polymorphisms, analysis of a phenotype under standardised environmental conditions, analysis of gene-environment interactions.     

Review: Insulin and endothelin: an interplay contributing to hypertension development?

CONTEXT: The aim of this article was to review the existing data on the interactions among insulin, insulin resistance, and endothelin and how those contribute to the development of hypertension in insulin-resistant states. EVIDENCE ACQUISITION: A literature search of MEDLINE database was performed to identify English-language articles published during the last 20 yr. Search terms used were endothelin, insulin, insulin resistance, and hyperinsulinemia in combination with blood pressure and hypertension. Reference lists of retrieved articles were also evaluated for relevant information. EVIDENCE SYNTHESIS: Several mechanisms connect insulin resistance and compensatory hyperinsulinemia with blood pressure elevation in the context of the metabolic syndrome, i.e. sodium retention, sympathetic activation, and impairment of endothelial nitric oxide production. Accumulating evidence suggests that activation of the endothelin system seems to be another important, yet less discussed, mechanism. In vitro studies have shown that insulin stimulates both endothelin-1 production and action on the vascular wall. In vivo, high levels of insulin result in increase in circulating endothelin-1 in healthy individuals, and this effect is also seen in insulin-resistant subjects, a relationship not observed with nitric oxide production. Moreover, endothelin receptor antagonism effectively reduces blood pressure in animal models of insulin resistance and hypertension. On the other hand, elevation of endothelin-1 levels can further increase insulin resistance, forming possibly a deleterious circle. CONCLUSIONS: Endothelin-1 may play a crucial role in the pathogenesis of hypertension in insulin-resistant states. Future research should examine the potential of endothelin receptor antagonism to help blood pressure control in patients with insulin resistance.     

Are metabolic factors still important in the era of direct antiviral agents in patients with chronic hepatitis C?

The high rate of sustained viral response(SVR)to boceprevir or telaprevir-based triple therapy in hepatitis C(HCV)-related,non-cirrhotic na ve patients or relapsers to previous antiviral treatment leads clinicians to believe that the impact of metabolic host factors on SVR is minimal when triple therapy is used,unlike what is observed with the peginterferon and ribavirin schedules.This concept is strongly expressed by some opinion leaders on the basis of the data derived from subanalyses of registrative trials as well as from a post-hoc analysis of the phaseⅡC208 clinical trial.The perception of unrestrainable therapeutic success with the use of newer,more powerful antivirals is now reinforced by the brilliant results obtained with sofosbuvir,an HCV NS5B polymerase inhibitor,as well as by the data from the phaseⅡandⅢstudies on the various combinations of second-generation NS3/4A inhibitors and NS5A and/or NS5B inhibitors.However,a great deal of concern has emerged from the real world scenario in which patients are often older and have more comorbidities than patients in theworld of trials.Furthermore,many of them have advanced fibrosis and previous failure with peginterferon and ribavirin treatment.Some data from the recent literature suggest that the host metabolic factors may play a minor but non-negligible role in these difficult-to-treat patients,an issue that will hopefully be investigated in further studies.This editorial aims to provide a detailed analysis of the role that host metabolic factors played in the past and what role they may play in the era of direct antiviral agents.     

Are environmental factors important in primary systemic vasculitis? A case-control study

OBJECTIVE: To investigate the association between primary systemic vasculitis (PSV) and environmental risk factors. METHODS: Seventy-five PSV cases and 273 controls (220 nonvasculitis, 19 secondary vasculitis, and 34 asthma controls) were interviewed using a structured questionnaire. Factors investigated were social class, occupational and residential history, smoking, pets, allergies, vaccinations, medications, hepatitis, tuberculosis, and farm exposure in the year before symptom onset (index year). The Standard Occupational Classification 2000 and job-exposure matrices were used to assess occupational silica, solvent, and metal exposure. Stepwise multiple logistic regression was used to calculate the odds ratio (OR) and 95% confidence interval (95% CI) adjusted for potential confounders. Total PSV, subgroups (47 Wegener's granulomatosis [WG], 12 microscopic polyangiitis, 16 Churg-Strauss syndrome [CSS]), and antineutrophil cytoplasmic antibody (ANCA)-positive cases were compared with control groups. RESULTS: Farming in the index year was significantly associated with PSV (OR 2.3 [95% CI 1.2-4.6]), with WG (2.7 [1.2-5.8]), with MPA (6.3 [1.9-21.6]), and with perinuclear ANCA (pANCA) (4.3 [1.5-12.7]). Farming during working lifetime was associated with PSV (2.2 [1.2-3.8]) and with WG (2.7 [1.3-5.7]). Significant associations were found for high occupational silica exposure in the index year (with PSV 3.0 [1.0-8.4], with CSS 5.6 [1.3-23.5], and with ANCA 4.9 [1.3-18.6]), high occupational solvent exposure in the index year (with PSV 3.4 [0.9-12.5], with WG 4.8 [1.2-19.8], and with classic ANCA [cANCA] 3.9 [1.6-9.5]), high occupational solvent exposure during working lifetime (with PSV 2.7 [1.1-6.6], with WG 3.4 [1.3-8.9], and with cANCA 3.3 [1.0-10.8]), drug allergy (with PSV 3.6 [1.8-7.0], with WG 4.0 [1.8-8.7], and with cANCA 4.7 [1.9-11.7]), and allergy overall (with PSV 2.2 [1.2-3.9], with WG 2.7 [1.4-5.7]). No other significant associations were found. CONCLUSION: A significant association between farming and PSV has been identified for the first time. Results also support previously reported associations with silica, solvents, and allergy.