Functional coupling of angiotensin II type 1 receptor with insulin resistance of energy substrate uptakes in immortalized cardiomyocytes (HL-1 cells)

Department of Preclinical and Clinical Pharmacology, University of Florence, Florence, Italy.
British Journal of Pharmacology (Impact Factor: 4.84). 04/2008; 153(5):907-14. DOI: 10.1038/sj.bjp.0707563
Source: PubMed


Increased angiotensin II levels and insulin resistance coexist at the early stages of cardiomyopathies. To determine whether angiotensin II increases insulin resistance in cardiomyocytes, we studied the effect of angiotensin II on basal and insulin-stimulated transport rate of energy substrates in immortalized cardiomyocytes (HL-1 cells).
Glucose and palmitic acid uptakes were measured using [(3)H]2-deoxy-D-glucose and [(14)C]palmitic acid, respectively, in cells exposed or not exposed to angiotensin II (100 nM), angiotensin II plus irbesartan or PD123319, type 1 and 2 receptor antagonists, or PD98059, an inhibitor of ERK1/2 activation. Cell viability, DNA, protein synthesis and surface area were evaluated by the MTT test, [(3)H]thymydine, [(3)H]leucine and morphometric analysis, respectively. Type 1 receptor levels were measured by western blot analysis.
Basal uptakes of glucose and palmitic acid by HL-1 cells (0.37+/-0.07 and 7.31+/-0.22 pmol per 10(4)cells per min, respectively) were both stimulated by 100 nM insulin (+91 and +64%, respectively). Cells exposed to angiotensin II remained viable and did not show signs of hypertrophy. In these conditions, the basal palmitic acid uptake of the cells increased (11.41+/-0.46 pmol per 10(4) cells per min) and insulin failed to stimulate the uptake of glucose and fatty acids. Changes in the rate of uptake of energy substrates were prevented or significantly reduced by irbesartan or PD98059.
Angiotensin II is a candidate for increasing insulin resistance in cardiomyocytes. Our results suggest a further mechanism for the cardiovascular protection offered by the angiotensin II type 1 receptor blockers.

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Available from: Chiara Nediani, Feb 06, 2014
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    • "Ang II inhibited INS-induced glucose uptake in vascular smooth muscle cells in an ERK1/2-dependent manner, and increased Ser307 phosphorylation of IRS-1 was also inhibited by MEK inhibitor PD98059 [123]. Ang II causes INS resistance in cardiomyocytes which is sensitive to ERK1/2 inhibition [124]. In this regard, the role of mir-212 is noteworthy. "
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    ABSTRACT: Cardiac insulin resistance is a metabolic and functional disorder that is often associated with obesity and/or the cardiorenal metabolic syndrome (CRS), and this disorder may be accentuated by chronic alcohol consumption. In conditions of over-nutrition, increased insulin (INS) and angiotensin II (Ang II) activate mammalian target for rapamycin (mTOR)/p70 S6 kinase (S6K1) signaling, whereas chronic alcohol consumption inhibits mTOR/S6K1 activation in cardiac tissue. Although excessive activation of mTOR/S6K1 induces cardiac INS resistance via serine phosphorylation of INS receptor substrates (IRS-1/2), it also renders cardioprotection via increased Ang II receptor 2 (AT2R) upregulation and adaptive hypertrophy. In the INS-resistant and hyperinsulinemic Zucker obese (ZO) rat, a rodent model for CRS, activation of mTOR/S6K1signaling in cardiac tissue is regulated by protective feed-back mechanisms involving mTOR↔AT2R signaling loop and profile changes of microRNA that target S6K1. Such regulation may play a role in attenuating progressive heart failure. Conversely, alcohol-mediated inhibition of mTOR/S6K1, down-regulation of INS receptor and growth-inhibitory mir-200 family, and upregulation of mir-212 that promotes fetal gene program may exacerbate CRS-related cardiomyopathy.
    Experimental Diabetes Research 01/2012; 2012(1687-5214):654904. DOI:10.1155/2012/654904 · 4.33 Impact Factor
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    • "Potential link of ERK1/2 with oxidative stress and insulin resistance in cardiomyocytes has been documented (19). Accordingly, we examined the effect of chronic treatment of H2O2 on ERK1/2 phosphorylation in HL-1 with and without insulin stimulation. "
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