(n-3) fatty acids and cardiovascular health: are effects of EPA and DHA shared or complementary?

Considerable research supports cardiovascular benefits of consuming omega-3 PUFA, also known as (n-3) PUFA, from fish or fish oil. Whether individual long-chain (n-3) PUFA have shared or complementary effects is not well established. We reviewed evidence for dietary and endogenous sources and cardiovascular effects on biologic pathways, physiologic risk factors, and clinical endpoints of EPA [20:5(n-3)], docosapentaenoic acid [DPA, 22:5(n-3)], and DHA [22:6(n-3)]. DHA requires direct dietary consumption, with little synthesis from or retroconversion to DPA or EPA. Whereas EPA is also largely derived from direct consumption, EPA can also be synthesized in small amounts from plant (n-3) precursors, especially stearidonic acid. In contrast, DPA appears principally derived from endogenous elongation from EPA, and DPA can also undergo retroconversion back to EPA. In experimental and animal models, both EPA and DHA modulate several relevant biologic pathways, with evidence for some differential benefits. In humans, both fatty acids lower TG levels and, based on more limited studies, favorably affect cardiac diastolic filling, arterial compliance, and some metrics of inflammation and oxidative stress. All three (n-3) PUFA reduce ex vivo platelet aggregation and DHA also modestly increases LDL and HDL particle size; the clinical relevance of such findings is uncertain. Combined EPA+DHA or DPA+DHA levels are associated with lower risk of fatal cardiac events and DHA with lower risk of atrial fibrillation, suggesting direct or indirect benefits of DHA for cardiac arrhythmias (although not excluding similar benefits of EPA or DPA). Conversely, EPA and DPA, but not DHA, are associated with lower risk of nonfatal cardiovascular endpoints in some studies, and purified EPA reduced risk of nonfatal coronary syndromes in one large clinical trial. Overall, for many cardiovascular pathways and outcomes, identified studies of individual (n-3) PUFA were relatively limited, especially for DPA. Nonetheless, the present evidence suggests that EPA and DHA have both shared and complementary benefits. Based on current evidence, increasing consumption of either would be advantageous compared to little or no consumption. Focusing on their combined consumption remains most prudent given the potential for complementary effects and the existing more robust literature on cardiovascular benefits of their combined consumption as fish or fish oil for cardiovascular benefits.     

The Laurence-Moon-Bardet-Biedl syndrome: unresponsiveness to the action of testosterone, a possible mechanism.

The pathogenesis of hypogonadism and hypogenitalism was investigated in a male patient with the complete form of the Laurence-Moon-Bardet-Biedl syndrome. Synthetic gonadotropin-releasing hormone induced an increase in serum luteinizing hormone levels from 16.5 mIU/ml to 19.3 mIU/ml and in follicle-stimulating hormone levels from 18.5 mIU/ml to 25.9 mIU/ml. Serum testosterone levels were normal and did not rise after stimulation with human chorionic gonadotropin. The administration of thyrotropin-releasing hormone resulted in an increase in serum thyrotropin levels from 9.0 microU/ml to 12.0 microU/ml. Serum testoterone/estradiol-binding globulin, adrenocorticotropic hormone, and T3 resin uptake were normal. Serum cortisol showed a normal diurnal variation. The sex chromatin test was negative and the karyotupe revealed a 46,XY chromosome pattern. On biopsy, the left testis lacked germinal cells and the right testis showed spermatogenic arrest. Signs of hypogonadism and hypogenitalism persisted after 11 months of testosterone treatment. In this patient the target-organ unresponsiveness resulted in hypogenitalism and hypogonadism.     

The development of myocardial insulin resistance in conscious dogs with advanced dilated cardiomyopathy

BACKGROUND: The failing heart demonstrates a preference for glucose as its metabolic substrate. Advanced, severe DCM is characterized by depletion of adenosine triphosphate (ATP) stores, which may be a consequence of impaired insulin mediated glucose uptake and oxidation at a time when the myocardium prefers glucose as its substrate. We examined the time course and magnitude of myocardial insulin resistance during the evolution of dilated cardiomyopathy. METHODS AND RESULTS: Thirty-four conscious, chronically instrumented dogs were studied at four stages during the evolution of dilated cardiomyopathy (DCM) induced by rapid RV pacing [control, early, late and advanced severe]. Transmyocardial glucose, lactate, and non-esterified fatty acid (NEFA) concentrations were measured in the fasting state. The cellular insulin signaling cascade and ATP levels were measured on myocardial samples. NEFA and insulin concentrations increased early and progressively in DCM in association with increased norepinephrine concentrations and progressive hemodynamic impairment. In advanced DCM but not earlier stages, myocardial ATP levels were decreased by 34%. There was decreased myocardial glucose uptake evident under both basal (-29 +/- 5%) and insulin stimulated (-32 +/- 4%) conditions in advanced, severe DCM, associated with a 31% reduction in GLUT-4 translocation. Importantly, there were no alterations in proximal steps in insulin signaling, but significant reductions in serine (Ser473) phosphorylation of Akt-1. CONCLUSIONS: Advanced, severe DCM is associated with the development of myocardial insulin resistance. There is impaired myocardial glucose uptake and altered myocardial insulin signaling, involving decreased Ser 473 phosphorylation of Akt-1. Myocardial insulin resistance in advanced, severe DCM was also associated with reduced myocardial ATP levels.     

Human hypertrophic scar‐like nude mouse model: Characterization of the molecular and cellular biology of the scar process

Hypertrophic scar (HTS) following thermal injury and other forms of trauma is a dermal fibroproliferative disorder that leads to considerable morbidity. Because of the lack of an ideal animal model, research is difficult. We have established an HTS model that involves transplanting human split‐thickness skin graft (STSG) or full‐thickness skin graft (FTSG) onto the backs of nude mice. The animals developed raised, firm, and reddish scars 2 months following transplantation. Histology and micromeasurement indicate raised, thickened engrafted skin with STSG and FTSG. In contrast, thickening was not observed with full‐thickness rat skin grafts used as controls. Masson's trichrome staining demonstrates increased accumulations of collagen fibrils in the dermis in both scars grafted with STSG and FTSG. Staining cells with toludine blue and an antibody for F4/80 showed an increase in the infiltration of mast cells and macrophages. Quantification of fibrocytes reveals increased fibrocytes. Moreover, STSG grafted skin had significantly more macrophages, mast cells, and fibrocytes than FTSG. Real‐time polymerase chain reaction analysis showed significantly elevated mRNA levels for type I collagen, transforming growth factor‐β, connective tissue growth factor and heat shock protein 47 in both types of engrafted skin. These data demonstrate that human skin grafted onto nude mice develops red raised and thickened scars having intrinsic properties that closely resemble HTS formation as seen in humans. Interestingly, STSG developed more scar than FTSG. Furthermore, inflammatory cells and bone marrow‐derived fibrocytes may play a critical role in HTS development in this animal model.     

Systematic review and meta-analysis of methotrexate use and risk of cardiovascular disease

Inflammation predicts risk for cardiovascular disease (CVD) events, but the relation of drugs that directly target inflammation with CVD risk is not established. Methotrexate is a disease-modifying antirheumatic drug broadly used for the treatment of chronic inflammatory disorders. A systematic review and meta-analysis of evidence of relations of methotrexate with CVD occurrence were performed. Cohorts, case-control studies, and randomized trials were included if they reported associations between methotrexate and CVD risk. Inclusions and exclusions were independently adjudicated, and all data were extracted in duplicate. Pooled effects were calculated using inverse variance-weighted meta-analysis. Of 694 identified publications, 10 observational studies in which methotrexate was administered in patients with rheumatoid arthritis, psoriasis, or polyarthritis met the inclusion criteria. Methotrexate was associated with a 21% lower risk for total CVD (n = 10 studies, 95% confidence interval [CI] 0.73 to 0.87, p <0.001) and an 18% lower risk for myocardial infarction (n = 5, 95% CI 0.71 to 0.96, p = 0.01), without evidence for statistical between-study heterogeneity (p = 0.30 and p = 0.33, respectively). Among prespecified sources of heterogeneity explored, stronger associations were observed in studies that adjusted for underlying disease severity (relative risk 0.64, 95% CI 0.43 to 0.96, p <0.01) and for other concomitant medication (relative risk 0.73, 95% CI 0.63 to 0.84, p <0.001). Publication bias was potentially evident (funnel plot, Begg's test, p = 0.06); excluding studies with extreme risk estimates did not, however, alter results (relative risk 0.81, 95% CI 0.74 to 0.89). In conclusion, methotrexate use is associated with a lower risk for CVD in patients with chronic inflammation. These findings suggest that a direct treatment of inflammation may reduce CVD risk.