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Articles by I Tabas
Total Records ( 2 ) for I Tabas
  S Li , Y Sun , C. P Liang , E. B Thorp , S Han , A. W Jehle , V Saraswathi , B Pridgen , J. E Kanter , R Li , C. L Welch , A. H Hasty , K. E Bornfeldt , J. L Breslow , I Tabas and A. R. Tall

Rationale: The complications of atherosclerosis are a major cause of death and disability in type 2 diabetes. Defective clearance of apoptotic cells by macrophages (efferocytosis) is thought to lead to increased necrotic core formation and inflammation in atherosclerotic lesions.

Objective: To determine whether there is defective efferocytosis in a mouse model of obesity and atherosclerosis.

Methods and Results: We quantified efferocytosis in peritoneal macrophages and in atherosclerotic lesions of obese ob/ob or ob/ob;Ldlr–/– mice and littermate controls. Peritoneal macrophages from ob/ob and ob/ob;Ldlr–/– mice showed impaired efferocytosis, reflecting defective phosphatidylinositol 3-kinase activation during uptake of apoptotic cells. Membrane lipid composition of ob/ob and ob/ob;Ldlr–/– macrophages showed an increased content of saturated fatty acids (FAs) and decreased -3 FAs (eicosapentaenoic acid and docosahexaenoic acid) compared to controls. A similar defect in efferocytosis was induced by treating control macrophages with saturated free FA/BSA complexes, whereas the defect in ob/ob macrophages was reversed by treatment with eicosapentaenoic acid/BSA or by feeding ob/ob mice a fish oil diet rich in -3 FAs. There was also defective macrophage efferocytosis in atherosclerotic lesions of ob/ob;Ldlr–/– mice and this was reversed by a fish oil–rich diet.

Conclusions: The findings suggest that in obesity and type 2 diabetes elevated levels of saturated FAs and/or decreased levels of -3 FAs contribute to decreased macrophage efferocytosis. Beneficial effects of fish oil diets in atherosclerotic cardiovascular disease may involve improvements in macrophage function related to reversal of defective efferocytosis and could be particularly important in type 2 diabetes and obesity.

  I Tabas , A Tall and D. Accili

Abstract: Atherothrombotic vascular disease is the major cause of death and disability in obese and diabetic subjects with insulin resistance. Although increased systemic risk factors in the setting of insulin resistance contribute to this problem, it is likely exacerbated by direct effects of insulin resistance on the arterial wall cells that participate in atherosclerosis. A critical process in the progression of subclinical atherosclerotic lesions to clinically relevant lesions is necrotic breakdown of plaques. Plaque necrosis, which is particularly prominent in the lesions of diabetics, is caused by the combination of macrophage apoptosis and defective phagocytic clearance, or efferocytosis, of the apoptotic macrophages. One cause of macrophage apoptosis in advanced plaques is activation of a proapoptotic branch of the unfolded protein response, which is an endoplasmic reticulum stress pathway. Macrophages have a functional insulin receptor signaling pathway, and downregulation of this pathway in the setting insulin resistance enhances unfolded protein response–induced apoptosis. Moreover, other aspects of the obesity/insulin-resistance syndrome may adversely affect efferocytosis. These processes may therefore provide an important mechanistic link among insulin resistance, plaque necrosis, and atherothrombotic vascular disease and suggest novel therapeutic approaches to this expanding health problem.

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