Overexpression of lipoprotein lipase in transgenic rabbits leads to increased small dense LDL in plasma and promotes atherosclerosis

Lipoprotein lipase (LPL) is a key enzyme in the hydrolysis of triglyceride-rich lipoproteins. Previous studies using transgenic mice and rabbits have demonstrated that high level of LPL activity in adipose and skeletal muscle protects against diet-induced hypercholesterolemia and subsequently prevents aortic atherosclerosis. However, it is unknown, per se, whether increased LPL activity itself is antiatherogenic, or whether the antiatherogenic effect of LPL is dependent upon the LPL lipid-lowering effect. To address this issue, we fed LPL transgenic and littermate rabbits diets containing different amounts of cholesterol (0.3-0.6%) adjusted to maintain their plasma cholesterol concentrations at similarly high levels for 16 weeks. We analyzed their lipoprotein profiles and compared their susceptibility to atherosclerosis. The results showed that the overexpression of LPL in transgenic rabbits reduced remnant lipoproteins (beta-VLDL, d<1.006 g/ml) but concomitantly led to a significant increase of the large (d=1.02-1.04 g/ml) and small LDLs (d=1.04-1.06 g/ml) compared to the amounts in control rabbits. Furthermore, we found that with equally high hypercholesterolemia, transgenic rabbits developed 1.8-fold more extensive aortic atherosclerosis than control rabbits. To examine the hypothesis that altered lipoprotein profiles may be responsible for the enhanced atherosclerosis in transgenic rabbits, we studied the atherogenic properties of apoB-containing lipoproteins in vitro. These studies revealed that small-sized LDLs of transgenic rabbits were more susceptible to copper-induced oxidation and had higher affinity to biglycan than large remnant lipoproteins. We conclude, therefore, that LPL exerts a dual function in terms of its atherogenicity, namely antiatherogenicity, through enhancing receptor-mediated remnant lipoprotein catabolism and proatherogenicity via the generation of a large amount of small-sized LDLs. At an equal atherogenic-cholesterol level, small and dense LDLs are more atherogenic than large remnant lipoproteins.     

A case of sarcomatoid carcinoma of the thymus

A 57-year-old woman presented with a 10×10 cm anterior mediations mass. The tumor had Invaded the pericardium, both lungs and the left brachiocephallc vein, and was treated by partial resection and postoperative radiation therapy. Pathological examination of the tumor revealed squamous cell carcinoma with a spindle cell sarcomatous component. Immunohistochemically, keratin and epithelial membrane antlgen were posltive In both the spindle cell sarcomatous areas and the squamous cell carcinomatous area and thus, a diagnosis of thymic carcinoma of sarcomatoid type was made. The patient died of recurrent disease 1 year after surgery. This case is the seventh reported In the English literature Because of the poor outcome, adjuvant therapy is recommended.     

Anti-thrombotic effects and bleeding risk of AJvW-2, a monoclonal antibody against human von Willebrand factor

1. A murine anti-human vWF monoclonal antibody, AJvW-2, was developed that inhibited the interaction between platelet glycoprotein Ib (GPIb) and von Willebrand factor (vWF) during the ristocetin- (IC₅₀=0.7±0.1 μg ml⁻¹) and botrocetin- (IC₅₀=1.8±0.3 μg ml⁻¹) induced aggregation of human platelets.
2. AJvW-2 inhibited the high shear stress (10.8 N m⁻²) induced aggregation of human platelets dose-dependently with an IC₅₀=2.4±0.3 μg ml⁻¹, but had no effect on low shear stress induced platelet aggregation (1.2 N m⁻²) up to 100 μg ml⁻¹.
3. AJvW-2 also inhibited the high shear stress (5.0 N m⁻²) induced adhesion of human platelets to collagen I with the same efficacy (IC₅₀=2.4±0.3 μg ml⁻¹), but had no effect at low shear conditions (1.5 N m⁻²).
4. AJvW-2 inhibited the botrocetin-induced aggregation of platelets from guinea-pig, rat, rabbit, dog and pig at the same concentration range as human platelets; it likewise also inhibited the high shear stress induced aggregation and adhesion to collagen I of guinea-pig platelets.
5. AJvW-2 prevented arterial thrombus formation in guinea-pigs at a dose of 100 μg kg⁻¹ without prolonging the template bleeding time, whereas the GPIIb/IIIa antagonist lamifiban mediated inhibition of thrombosis at 1000 μg kg⁻¹ was accompanied by a significant prolongation of the bleeding time.
6. These results suggest that AJvW-2 is a potent inhibitor of the GPIb-vWF interaction and a potential novel antithrombotic agent with lower bleeding risk than GPIIb/IIIa antagonists.

     

Pathophysiogical role of leptin in lifestyle-related diseases. Studies with transgenic skinny mice overexpressing leptin

Leptin is a major adipocyte-derived hormone that is involved in the regulation of food intake and energy expenditure. Plasma leptin concentrations are elevated in obese subjects, suggesting its pathophysiological role in obesity-related lifestyle-related diseases. We have recently succeeded in the generation of transgenic skinny mice overexpressing leptin. They exhibit increased glucose metabolism and insulin sensitivity accompanied by a significant increase in insulin signaling for glucose utilization in the skeletal muscle and liver. They also show blood pressure elevation through the sympathetic activation. Introduction of the lethal yellow agouti (A(y)) allele into transgenic skinny mice results in late-onset obesity and diabetes with blood pressure elevation similar to those found in nontransgenic agouti mice (A(y)/+ mice). After caloric restriction, blood pressure elevation is reversed but insulin resistance still remains in A(y)/+ mice in parallel with a reduction of plasma leptin concentrations. By contrast, blood pressure elevation is sustained but insulin resistance is reversed in transgenic mice overexpressing leptin with the A(y) allele (Tg/+:A(y)/+ mice), which remain hyperleptinemic. Collectively, our data suggest the pathophysiologic and therapeutic implication of leptin in obesity-related insulin resistance and hypertension.     

Safety measures for gastrointestinal endoscopy in patients receiving antithrombotic therapy

Aim: Owing to carelessness of endoscopists, invasive procedures, such as biopsy, are sometimes carried out inadvertently in patients receiving antithrombotic therapy. The aim of the present study was to retrospectively evaluate the actual status of such careless mistakes and the efficacy of new safety measures. Methods: A questionnaire survey was conducted in 34 endoscopists at Toranomon Hospital about experiences of careless mistakes and experiences of anxiety before and after the procedure. ‘Anxiety before procedure’ was defined as the experience of discontinuing a given procedure because endoscopists remembered that the patient was receiving antithrombotic therapy, and ‘anxiety after procedure’ was defined as the experience of feeling anxious about the status of medication after the invasive procedure. A new measure was introduced at Health Management Center in August 2009. In this measure, endoscopists directly interview each patient about the status of medication just before examination, and attach forceps valves of one of two colors depending on the status of medication. A blue forceps valve is attached for patients undergoing antithrombotic therapy, and a conventional black forceps valve is attached for patients not undergoing antithrombotic therapy. Six months after introduction, a questionnaire survey was conducted in 10 endoscopists in this center. Results: Approximately half of endoscopists (18/34) experienced such careless mistakes. ‘Anxiety’ had been experienced by approximately 80%. After introduction, there was no report of careless mistakes and frequency of ‘anxiety’ evaluated by visual analog scale score decreased significantly. Conclusion: This new safety measure is expected to facilitate safer gastrointestinal endoscopy in patients receiving antithrombotic therapy.     

Distinctive evaluation of nonmucinous and mucinous subtypes of bronchioloalveolar carcinomas in EGFR and K-ras gene-mutation analyses for Japanese lung adenocarcinomas: confirmation of the correlations with histologic subtypes and gene mutations

Although adenocarcinomas of the lung are associated with epidermal growth factor receptor (EGFR) gene mutations and sensitivity to EGFR tyrosine kinase inhibitors, it remains unclear whether bronchioloalveolar carcinoma (BAC) components and/or subtypes affect these associations. We aimed to clarify correlations between EGFR gene mutations and BAC components and to establish the histologic features as reliable predictors for the mutations. We examined 141 non-small cell lung cancers (NSCLCs), including 118 adenocarcinomas, for mutations in exons 19 and 21 of the EGFR gene together with mutations in codon 12 of the K-ras gene using loop-hybrid mobility shift assays, a highly sensitive polymerase chain reaction-based method. Adenocarcinomas were subdivided into subtypes with a nonmucinous or mucinous BAC component and those without BAC components. In NSCLCs, EGFR mutations were detected in 75 cases (53.2%) and were significantly associated with adenocarcinoma, female sex, and never smoking. Among adenocarcinomas, nonmucinous and mucinous BAC components were significantly associated with EGFR and K-ras gene mutations, respectively. Because EGFR mutations were detected even in most pure nonmucinous BACs, ie, lung adenocarcinoma in situ, EGFR mutation is considered a critical event in the pathogenesis of nonmucinous BAC tumors.