Actions of insulin on the mammalian heart: metabolism, pathology and biochemical mechanisms

Brownsey, Roger W.; Boone, Adrienne N.; Allard, Michael F.

doi:10.1016/s0008-6363(97)00051-5

Cited by 115 publications

(78 citation statements)

References 257 publications

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“…992 ± 160 µg). These data are consistent with the observations that several proteins are downregulated in diabetic hearts (19). When RNA samples were electrophoresed using formamide/formaldehyde agarose gels, two distinct bands representing 28S and 18S ribosomal RNA were observed (data not shown).…”

Section: Induction Of Experimental Stz-induced Diabetessupporting

confidence: 91%

The Effect of Diabetes on Expression of β1-,β2-, and β3-Adrenoreceptors in Rat Hearts

et al. 2001

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Diabetic hearts exhibit decreased responsiveness to stimulation by ␤-adrenoreceptor (␤-AR) agonists. This decrease in activity may be due to changes in expression and/or signaling of ␤-AR. Recently we showed that right atrial strips from 14-week streptozotocin (STZ)-induced diabetic rat hearts exhibit decreased responsiveness to ␤ 1 -AR agonist stimulation, but not to ␤ 2 -AR agonist. In the present study, we investigated the effects of long-term diabetes on the expression of cardiac ␤ 1 -, ␤ 2 -, and ␤ 3 -ARs and looked at whether these changes could be restored with insulin treatment. Using reverse transcription-polymerase chain reaction (RT-PCR), PAGE, and Western blot analysis, we found that ␤ 1 -AR mRNA and protein levels decreased by 34.9 ± 5.8 and 44.4 ± 5.8%, respectively, in 14 week-STZtreated diabetic rat hearts when compared with agematched controls. On the other hand, mRNA levels encoding ␤ 2 -and ␤ 3 -ARs increased by 72.5 ± 16.6 and 97.3 ± 26.1%, respectively. Although the latter translated into a proportional increase in ␤ 3 -AR protein levels (100.0 ± 17.0%), ␤ 2 -AR protein levels decreased to 82.6 ± 1.1% of control. Insulin treatment for 2 weeks, after 12 weeks of untreated diabetes, partially restored ␤ 1 -AR mRNA and protein levels to 60.1 ± 8.4 and 83.2 ± 5.0%, respectively, of control. Although insulin treatment minimally attenuated the rise in mRNA levels encoding ␤ 2 -and ␤ 3 -ARs, the steady-state levels of these proteins returned to near control values. These data suggest that the decreased responsiveness of diabetic hearts to stimulation of ␤-AR agonists may be due to a decrease in ␤ 1 -AR and an increase ␤ 3 -AR expression. Diabetes 50: [455][456][457][458][459][460][461] 2001

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Section: Induction Of Experimental Stz-induced Diabetessupporting

confidence: 91%

The Effect of Diabetes on Expression of β1-,β2-, and β3-Adrenoreceptors in Rat Hearts

et al. 2001

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“…Like insulin, these factors also modulate gene expression via signaling through the MAPK pathway. 32,35 Our characterization of the muscarinic signaling system in atrial cardiomyocytes could explain certain clinical features seen in obese patients with hyperinsulinemia, such as hypertension, tachycardia or increased risk of sudden cardiac death. Previous clinical studies have found that a lower parasympathetic function was associated with increasing body fat, 11,36,37 and that parasympathetic withdrawal in obese patients was correlated with hyperinsulinemia.…”

Section: Discussionmentioning

confidence: 99%

“…35 Insulin also has a cardioprotective effect through the activation of antiapoptotic pathways 39 and its ability to limit oxidative stress, 40 thus leading to the consideration of insulin as a protective hormone for cardiomyocytes. Our study suggests that this concept of insulin should be taken with caution in the setting of obesity, since insulin-induced downregulation of M 2 R activity may alter the autonomic control of the heart.…”

Section: Discussionmentioning

confidence: 99%

Insulin downregulates M2-muscarinic receptors in adult rat atrial cardiomyocytes: a link between obesity and cardiovascular complications

et al. 2004

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OBJECTIVE:To determine whether decreased cardiac parasympathetic activity observed in obesity is due to insulin-induced alterations in cardiac M 2 -muscarinic receptors and/or adenylyl cyclase activity. DESIGN AND METHODS: After incubation with increasing concentrations of insulin, adult rat atrial cardiomyocytes were assayed for M 2 -muscarinic receptor binding density and affinity, and for M 2 R mRNA expression using RT-PCR analysis. Forskolinstimulated adenylyl cyclase activity and its inhibition by carbachol were also assayed, as was endothelial nitric oxide synthase mRNA expression. The effects of insulin on M 2 -muscarinic receptor density and mRNA expression levels were analyzed using the insulin signaling inhibitors rapamycin, wortmanin and PD 098059. RESULTS: Insulin induces a concentration-and time-dependent decrease in expression of the M 2 R mRNA, and in [ 3 H]Nmethylscopolamine binding by the receptor. These effects on the M 2 R mRNA levels and on [ 3 H]N-methylscopolamine binding were prevented by PD 98059, but not by wortmanin or rapamycin. Basal and forskolin-induced cAMP production did not differ, but the inhibition of forskolin-simulated enzyme activity by carbachol was blunted by insulin. No change in the mRNA levels for endothelial nitric oxide synthase was observed. CONCLUSION: In rat atrial cardiomyocytes, insulin markedly alters both the M 2 -muscarinc receptor density, and its mRNA expression through transcriptional regulation and adenylyl cyclase activity. These data suggest that the obesity-associated decrease in cardiac parasympathetic tone may be related to hyperinsulinemia, which could directly contribute to cardiovascular morbidity in obese patients.

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“…Although it used insulin (50 µU/ml) and high glucose (22 mM) to stimulate glucose utilization [26], they were used only during cell isolation (~70 min) at physiological levels [27]. This is in contrast to the other methods that use "KB" medium [10,11] or BDM [12,13], both of which are not natural to the cells and have been reported to affect their normal physiology.…”

Section: Comparison With Other Heart Cell Isolation Techniquesmentioning

confidence: 99%

A Simple Technique for Isolating Healthy Heart Cells from Mouse Models

Shioya

2007

J. Physiol. Sci

128

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Single heart cells of mouse models provide powerful tools for heart research. However, their isolation is not easy, and it imposes a significant bottleneck on their use in cellular studies of the heart. Aiming to overcome this problem, this report introduces a novel technique that reproducibly isolates healthy heart cells from mouse models. Using simple devices that ensure easy handling and the rapid aortic cannulation of a small mouse heart, cell isolation was done under physiological conditions without using the "KB" medium or 2,3-butanedione monoxime (BDM). The isolated cells consistently had a healthy appearance and a high viability of 75 ± 5% (mean ± SD) in Tyrode solution containing 1.8 mM Ca 2+ . After 8 h of storage at 37°C, they still had a viability of 45 ± 12%. The cells showed normal contraction properties when field-stimulated, and they generated normal action potentials and membrane currents under the whole-cell clamp condition. The β-adrenergic signal transduction of the cells was also normal when it was examined with the isoproterenol enhancement of the L-type Ca 2+ current.Key words: mouse, cardiac myocyte, contraction, action potential, ionic current.Single heart cells of mouse models provide powerful tools for heart research. In these cells, one can take advantage of the versatility of recent genetic engineering technology [1] and also of the accuracy of single-cell measurement techniques such as patch-clamp and Ca 2+ imaging. So far, molecular mechanisms of fundamental heart functions, such as excitation-contraction coupling, action potential shaping, and β-adrenergic signaling, have been successfully unveiled by using single heart cells of mouse models [2][3][4][5][6][7]. Moreover, these cells also provide a convenient platform for analyzing pathogenic mechanisms and the pathophysiology of hereditary heart diseases in molecular detail [8,9].For such single-cell studies, healthy heart cells are absolutely necessary; however, their isolation from mouse models is not easy. Surgery and aortic cannulation of a small mouse heart are hard to do and require a long time, and during that time, the heart suffers from complete ischemia. Consequently, the cells isolated from these hearts show various signs of ischemic damages, such as bizarre appearance, low viability levels, and abnormalities in their excitation and contraction properties. Cells of these kinds are hard to use for the experiment, and the data they provide are often difficult to interpret. This issue imposes a significant bottleneck on the use of mouse heart cells and is especially problematic in genetically engineered mouse models that are usually available only in limited amounts.To solve this problem, two major work-arounds have been devised and used for heart cell isolation from mouse models. One is to incubate the cells in high-K + , Ca 2+ -free "KB" medium at 4°C [10,11], and the other is to administer 10-20 mM 2,3-butanedione monoxime (BDM) in the media for cell isolation and storage [12,13]. Both workarounds proved to be...

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Actions of insulin on the mammalian heart: metabolism, pathology and biochemical mechanisms

Cited by 115 publications

References 257 publications

The Effect of Diabetes on Expression of β1-,β2-, and β3-Adrenoreceptors in Rat Hearts

The Effect of Diabetes on Expression of β1-,β2-, and β3-Adrenoreceptors in Rat Hearts

Insulin downregulates M2-muscarinic receptors in adult rat atrial cardiomyocytes: a link between obesity and cardiovascular complications

A Simple Technique for Isolating Healthy Heart Cells from Mouse Models

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