Effect of Taurine and Methionine on Sarcoplasmic Reticular Ca2+ Transport and Phospholipid Methyltransferase Activity

Punna, S.; Ballard, Cherry; Hamaguchi, Takashi; Azuma, Junichi; Schaffer, Stephen

doi:10.1097/00005344-199424020-00014

Cited by 4 publications

(6 citation statements)

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“…Besides its antioxidant properties, taurine has other effects that could influence insulin secretion. At high concentrations (Ͼ10-fold those used here), taurine can alter calcium flux (37) and interact with GABA receptors (35); however, whether this occurs in the ␤-cell is not known. At high concentrations, taurine can also close ATP-sensitive K ϩ channels in ␤-cells (36).…”

Section: Discussionmentioning

confidence: 87%

Free Fatty Acid–Induced Reduction in Glucose-Stimulated Insulin Secretion

et al. 2007

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OBJECTIVE-An important mechanism in the pathogenesis of type 2 diabetes in obese individuals is elevation of plasma free fatty acids (FFAs), which induce insulin resistance and chronically decrease ␤-cell function and mass. Our objective was to investigate the role of oxidative stress in FFA-induced decrease in ␤-cell function. RESEARCH DESIGN AND METHODS-We used an in vivo model of 48-h intravenous oleate infusion in Wistar rats followed by hyperglycemic clamps or islet secretion studies ex vivo and in vitro models of 48-h exposure to oleate in islets and MIN6 cells.RESULTS-Forty-eight-hour infusion of oleate decreased the insulin and C-peptide responses to a hyperglycemic clamp (P Ͻ 0.01), an effect prevented by coinfusion of the antioxidants N-acetylcysteine (NAC) and taurine. Similar to the findings in vivo, 48-h infusion of oleate decreased glucose-stimulated insulin secretion ex vivo (P Ͻ 0.01) and induced oxidative stress (P Ͻ 0.001) in isolated islets, effects prevented by coinfusion of the antioxidants NAC, taurine, or tempol (4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl). Forty-eight-hour infusion of olive oil induced oxidative stress (P Ͻ 0.001) and decreased the insulin response of isolated islets similar to oleate (P Ͻ 0.01). Islets exposed to oleate or palmitate and MIN6 cells exposed to oleate showed a decreased insulin response to high glucose and increased levels of oxidative stress (both P Ͻ 0.001), effects prevented by taurine. Real-time RT-PCR showed increased mRNA levels of antioxidant genes in MIN6 cells after oleate exposure, an effect partially prevented by taurine. T ype 2 diabetes is characterized by both insulin resistance and defective insulin secretion (1). Obesity is the major predisposing factor for type 2 diabetes and is associated with excessive release of fatty acids from the expanded adipose tissue mass, leading to elevated plasma free fatty acids (FFAs), which are known to induce insulin resistance (2,3). Acute FFA exposure stimulates insulin secretion (4), but studies in vitro and in situ have shown that prolonged FFA exposure decreases glucose-stimulated insulin secretion (GSIS) (5). The effect of prolonged FFA elevation on ␤-cell function in vivo has been more controversial, as absolute GSIS was found to be increased (6 -8), unchanged (9,10), or decreased (11-13) by FFA. However, in most of these studies ␤-cell function was inadequate to compensate for FFA-induced insulin resistance (9 -13), at least in predisposed individuals (14). Although the mechanisms behind FFA-induced decrease in ␤-cell function are unclear, one possibility points toward oxidative stress. Pancreatic ␤-cells have low antioxidant defenses (15) and are thus susceptible to reactive oxygen species (ROS)-induced decrease in function and viability (16,17). Oxidative stress has been implicated in the decrease in GSIS induced by prolonged exposure to glucose (18,19), which is in many respects similar to that induced by prolonged exposure to FFA (4,20). However, whether oxidative stress plays a role in FFA-...

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Section: Discussionmentioning

confidence: 87%

Free Fatty Acid–Induced Reduction in Glucose-Stimulated Insulin Secretion

et al. 2007

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“…Furthermore, several of the amino acids comprising this pool are important for normal cellular function. For example taurine deficiency is associated with development of cardiomyopathy, possibly by influencing cellular calcium homeostasis and membrane stabilisation (Huxtable 1992;Punna et al, 1994;Schaffer et al, 1994;Suleiman, 1994). Although the significance of the non-essential amino acid pool has been largely viewed in terms of protein breakdown and synthesis, individual amino acids contribute to a variety of other cellular activities.…”

Section: Introductionmentioning

confidence: 99%

Effect of regular training on the myocardial and plasma concentrations of taurine and?-amino acids in thoroughbred horses

King

1998

Amino Acids

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Exercise induces significant changes in the free intracellular amino acid pool in skeletal muscle but little is known of whether such changes also occur in cardiac muscle. In this study the effect of regular exercise on the size and the constituents of the free amino acid pool in the hearts and in the plasma of thoroughbred horses was investigated. The total free intracellular amino acid pool in the hearts of control horses was 30.9 +/- 1.2 mumol/g wet weight (n = 6). Glutamine but not taurine was present at the highest concentration (13.5 +/- 0.9 and 7.7 +/- 0.69 mumol/g wet weight for glutamine and taurine respectively). As for the rest of the amino acids in the pool, only glutamate and alanine were present at levels greater than 1 mumol/g wet weight (4.6 +/- 0.25 and 1.7 +/- 0.14 for glutamate and alanine respectively). The tissue to plasma ratio was highest for taurine at 155, followed by glutamate at 111, aspartate and glutamine at 37, alanine at 5.8 and ratios of less than 3 for the rest of the amino acids. The total free intracellular amino acid pool in the hearts of exercised horses was slightly but not significantly lower than control (28.1 +/- 1.1 mumol/g wet weight, n = 6). Regular exercise increased the intracellular concentration of threonine, valine, isoleucine, leucine and phenylalanine but was only significant (p < 0.05) for threonine. This work has documented the profile of taurine and protein amino acids in the heart and in the plasma of thoroughbred horses and showed that in contrast to skeletal muscle, heart muscle does not show major changes in amino acids during regular exercise.

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“…It has been well documented that there is an increase in the level of taurine in the diabetic heart [23,27]. Although the precise reasons for this increase have not been established, it may represent an attempt to offset the alterations in Ca 2+ handling that occur in the diabetic state.…”

Section: Discussionmentioning

confidence: 99%

“…The mechanisms underlying such actions of taurine are as yet unknown, however, changes in membrane phospholipid distribution could be involved [27]. Taurine has been shown to inhibit phospholipid N-methyltransferase, which catalyses the conversion of phosphatidylethanolamine to phosphatidylcholine [13,23]. The possibility exists, therefore, that taurine may alter the activity of transporters and proteins within the membranes of the cardiac myocyte through changes in membrane characteristics, although it is important to recognise that this remains speculative at the present time.…”

Section: Discussionmentioning

confidence: 99%

“…Significant increases in intracellular taurine content have been shown in both congestive heart failure and insulindependent diabetes mellitus, in which myocardial taurine levels are reported to be increased approximately twofold [23,27]. The diabetic heart is characterised by a depressed contractile reserve, slowed contraction and slowed relaxation [8] and there is now compelling evidence that these impaired contractile properties stem predominantly from disturbances in Ca 2+ handling [8,33].…”

Section: Introductionmentioning

confidence: 99%

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Acute effects of taurine on intracellular calcium in normal and diabetic cardiac myocytes

Holloway

Kotsanas

Wendt

1999

Pfl�gers Archiv European Journal of Physiology

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The present study investigated the acute effects of taurine on intracellular Ca2+ ([Ca2+]i) in normal and diabetic cardiac myocytes. [Ca2+]i was monitored using fura-2 in single myocytes isolated from control or streptozotocin-treated rats and paced at frequencies between 0.33 Hz and 2.0 Hz in the absence or presence of 20 mM taurine. Increasing stimulus frequency resulted in significant increases in resting and peak [Ca2+]i, and amplitude of the Ca2+ transient in both control and diabetic myocytes. The amplitude of the Ca2+ transient and the extent of its increase with increasing frequency was, however, significantly lower in the diabetic myocytes. Taurine significantly increased resting [Ca2+]i, peak [Ca2+]i, and the amplitude of the Ca2+ transient in both control and diabetic myocytes at all stimulus frequencies examined. The degree of potentiation of the Ca2+ transient decreased with increasing stimulus frequency in control cells but not in diabetic cells. In the absence of taurine the decay of the Ca2+ transient was significantly slower in diabetic than control myocytes. Taurine was without significant effect on the time course of the Ca2+ transient decay in control cells, however, in diabetic cells it significantly accelerated the rate of decay. The data demonstrate directly that taurine is able to increase [Ca2+]i and the amplitude of the Ca2+ transient in both normal and diabetic cardiac myocytes. In addition several of the effects of taurine appeared to be more pronounced in diabetic than control cells.

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Effect of Taurine and Methionine on Sarcoplasmic Reticular Ca2+ Transport and Phospholipid Methyltransferase Activity

Cited by 4 publications

References 0 publications

Free Fatty Acid–Induced Reduction in Glucose-Stimulated Insulin Secretion

Free Fatty Acid–Induced Reduction in Glucose-Stimulated Insulin Secretion

Effect of regular training on the myocardial and plasma concentrations of taurine and?-amino acids in thoroughbred horses

Acute effects of taurine on intracellular calcium in normal and diabetic cardiac myocytes

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