Journal Club 亀田メディカルセンター 糖尿病内分泌内科 Diabetes and Endocrine Department, Kameda Medical Center 松田 昌文 Matsuda, Masafumi 2006 年 8 月 3 日 8:20-8:50 B 棟８階 カンファレンス室

Abstract

Microparticles : endothelial cell-derived submicroscopic membranous vesicles procoaculant properties inflammatory process Endothelial Dysfunction Background Obesity : health problem : cardiovascular risk diabetes, dyslipidemia, hypertension, prothrombotic state

Hypothesis a) Circulating endothelial and platelet microparticles in obese women are increased. b) One of the measure of obesity (body mass index, waist-to-hip ratio, waist or hip circumference) has the strongest relation with circulating microparticles. c) There is a relation between circulating microparticles and endothelial-dependent vasodilation. Thus the circulating microparticles, which reflect a certain part of obesity, indicate endothelial dysfunction.

BMI ≧ 30 Study Subjects Women

FLOW-MEDIATED DILATATION

Microparticles Microparticles were identified by their characteristic forward and side scatter, and their ability to bind cell-specific monoclonal antibodies Endothelial microparticles (EMP) were defined as CD31+/CD42b- particles, while platelet microparticles (PMP) were defined as CD31+/CD42b+ particles. The rationale of 2-color method (CD31 and CD42b) was that significant CD31 occurs on both EMP and PMP, whereas CD42b is restricted to platelets, allowing discrimination between them.

BMI did not correlate with either EMP (r=0.02, p=0.9) or PMP (r=- 0.07, p=0.645), while WHR showed significant correlation with both microparticles (r=0.699, P<0.001; r=0.373, P=0.016, respectively). However, neither waist nor hip in isolation correlated with EMP (r=0.143, r=0.59; r=-0.276, r=0.2, respectively) or PMP (r=0.28, p=0.2; r=-0.15, p=0.78, respectively). Age, blood pressure, glucose and lipid (cholesterol, triglycerides, HDL-cholesterol) parameters did not correlate with circulating levels of both EMP and PMP. HOMA correlated with EMP (r=0.34, P=0.04) and FMD (r=-0.29, p=0.045), while CRP correlated with EMP only (r=0.29, p=0.043). Women with high levels of circulating microparticles displayed an impairment of FMD, demonstrating a significant correlation of EMP and PMP with endothelium-dependent vasodilation in the brachial artery. Additional predictors of FMD in this population of obese women were WHR, age, HOMA, and the HDL-cholesterol level. Multivariate analysis correcting for age, anthropometric indices, lipid parameters, HOMA, and PMP identified EMP as the only independent predictor for an impaired endothelial-dependent vasodilation. RESULTS SUMMARY

Our findings show that endothelial microparticles are elevated in women with visceral obesity and independently involved in the pathogenesis of endothelial dysfunction. Whether assessment of circulating endothelial micropartcicles may be a novel marker for risk stratification, a useful tool for monitoring efficacious antiatherogenic strategies, or a target for novel therapeutic options remain to be defined in future investigations. CONCLUSION

Leptin → Lean : stop appetite, increase energy exp. (increased sympathetic NS) Insulin → Lean Increase POMC/CART decrease NPY/AgRP MC4Receptors  MSH IRS

Hypothesis PIP 3 signal in POMC cells is important for the control of energy balance.

Leptin → Lean : stop appetite, increase energy exp. (increased sympathetic NS) Insulin → Lean Increase POMC/CART decrease NPY/AgRP MC4Receptors  MSH IRS X

X Cre POMC lox Pten  -galactosidase

IRS X Cre POMC lox Pten  -galactosidase

IRS X OBESITY:hyperphagia ???

IRS X OBESITY:hyperphagia X tolubtamide X

(A) To visualize Cre-mediated recombination, immunohistochemistry for  -gal was performed in hypothalamic tissues of double- heterozygous reporter mice (PomcCre- RosaArte1). Blue (DAPI), DNA; green,  -gal. (B) Western blot analysis of Pten and insulin receptor b (IR-b) subunit in hypothalamus, brain, liver, pancreas, white adipose tissue (WAT), and skeletal muscle of control (CO) and PPKO mice. NO CHANGE Figure 1

(C) PIP3 formation in hypothalamic neurons of control and PPKO mice. Double immunohistochemistry of ARC neurons of COArte1 and PPKOArte1 reporter mice was performed in mice fasted overnight, which were injected intravenously with either saline or insulin and sacrificed 10 and 20 minutes after insulin stimulation. Arrows indicate 1 POMC and 1 non-POMC neuron in each panel. (D) Quantification of PIP3 levels in control and PPKO POMC neurons in the basal (fasted) state. Values are mean ± SEM of sections obtained from 3 control and 3 PPKO mice. A total of 808 POMC neurons were analyzed. At left are examples of different magnitudes of PIP3 immunoreactivity (arrowheads) as described in Methods. Blue (DAPI), DNA; red, b-gal (POMC neurons); green, PIP3. Stained more!

NO POMC In adrenal gland Unaltered histomorphology

Male PPKO

Female PPKO

NO CHANGE should cause anorexic effect!

Leptin → Lean : stop appetite, increase energy exp. (increased sympathetic NS) Insulin → Lean Increase POMC/CART decrease NPY/AgRP MC4Receptors  MSH IRS

2mg/kg twice/day ND-fed male ND-fed female stat3 responding!

IRS X Cre POMC lox Pten LacZ/EGFP

same

PI3K inhibitor Reverses the enhanced K ATP currents

in vivo again

Pharmacology in control

In conclusion, whatever the extent to which individual hormones contribute to PI3K activation, our data clearly demonstrate that precise control of PIP 3 formation and K ATP channel activity in POMC neurons is crucial for the maintenance of energy homeostasis. Further exploration of this pathway, which acts independently of that leading to Stat3 phosphorylation, may help to define novel approaches to treatment of obesity and diabetes. CONCLUSION

Figure 1

Figure 2