Resveratrol improves cardiac function and exercise performance in MI-induced heart failure through the inhibition of cardiotoxic HETE metabolites.

Numerous epidemiological studies have demonstrated that approximately 40% of myocardial infarctions (MI) are associated with heart failure (HF). Resveratrol, a naturally occurring polyphenol, has been shown to be beneficial in the treatment of MI-induced HF in rodent models. However, the mechanism responsible for the effects of resveratrol are poorly understood. Interestingly, resveratrol is known to inhibit cytochrome P450 1B1 (CYP1B1) which is involved in the formation of cardiotoxic hydroxyeicosatetraenoic acid (HETE) metabolites. Therefore, we investigated whether resveratrol could improve MI-induced cardiac remodeling and HF in rats through the inhibition of CYP1B1 and its metabolites. To do this, rats were subjected to either sham surgery or a surgery to ligate the left anterior descending artery to induce a MI and subsequent HF. Three weeks post-surgery, rats with established HF were treated with control diet or administered a diet containing low dose of resveratrol. Our results showed that low dose resveratrol treatment significantly improves % ejection fraction in MI rats and reduces MI-induced left ventricular and atrial remodeling. Furthermore, non-cardiac symptoms of HF such as reduced physical activity improved with low dose resveratrol treatment. Mechanistically, low dose resveratrol treatment of rats with established HF restored levels of fatty acid oxidation and significantly improved cardiac energy metabolism as well as significantly inhibited CYP1B1 and cardiotoxic HETE metabolites induced in MI rats. Overall, the present work provides evidence that low dose resveratrol reduces the severity of MI-induced HF, at least in part, through the inhibition of CYP1B1 and cardiotoxic HETE metabolites.

Fecal transplant from resveratrol-fed donors improves glycaemia and cardiovascular features of the metabolic syndrome in mice.

Oral administration of resveratrol attenuates several symptoms associated with the metabolic syndrome, such as impaired glucose homeostasis and hypertension. Recent work has shown that resveratrol can improve glucose homeostasis in obesity via changes in the gut microbiota. Studies involving fecal microbiome transplants (FMTs) suggest that either live gut microbiota or bacterial-derived metabolites from resveratrol ingestion are responsible for producing the observed benefits in recipients. Herein, we show that obese mice receiving FMTs from healthy resveratrol-fed mice have improved glucose homeostasis within 11 days of the first transplant, and that resveratrol-FMTs is more efficacious than oral supplementation of resveratrol for the same duration. The effects of FMTs from resveratrol-fed mice are also associated with decreased inflammation in the colon of obese recipient mice. Furthermore, we show that sterile fecal filtrates from resveratrol-fed mice are sufficient to improve glucose homeostasis in obese mice, demonstrating that nonliving bacterial, metabolites, or other components within the feces of resveratrol-fed mice are sufficient to reduce intestinal inflammation. These postbiotics may be an integral mechanism by which resveratrol improves hyperglycemia in obesity. Resveratrol-FMTs also reduced the systolic blood pressure of hypertensive mice within 2 wk of the first transplant, indicating that the beneficial effects of resveratrol-FMTs may also assist with improving cardiovascular conditions associated with the metabolic syndrome.

Co-administration of resveratrol with doxorubicin in young mice attenuates detrimental late-occurring cardiovascular changes.

Aims: Doxorubicin (DOX) is among the most effective chemotherapies used in paediatric cancer patients. However, the clinical utility of DOX is offset by its well-known cardiotoxicity, which often does not appear until later in life. Since hypertension significantly increases the risk of late-onset heart failure in childhood cancer survivors, we investigated whether juvenile DOX exposure impairs the ability to adapt to angiotensin II (Ang II)-induced hypertension later in life and tested a treatment that could prevent this. Methods and results: Five-week-old male mice were administered a low dose of DOX (4 mg/kg) or saline once a week for 3 weeks and then allowed to recover for 5 weeks. Following the 5-week recovery period, mice were infused with Ang II or saline for 2 weeks. In another cohort, mice were fed chow containing 0.4% resveratrol 1 week before, during, and 1 week after the DOX administrations. One week after the last DOX administration, p38 mitogen-activated protein kinase (MAPK) was activated in hearts of DOX-treated mice demonstrating molecular signs of cardiac stress; yet, there was no change in cardiac function between groups. However, DOX-treated mice failed to develop compensatory cardiac hypertrophy in response to Ang II-induced hypertension later in life. Of importance, mice receiving DOX with resveratrol co-administration displayed normalization in p38 MAPK activation in the heart and a restored capacity for cardiac hypertrophy in response to Ang II-induced hypertension. Conclusion: We have developed a juvenile mouse model of DOX-induced cardiotoxicity that displays no immediate overt physiological dysfunction; but, leads to an impaired ability of the heart to adapt to hypertension later in life. We also show that co-administration of resveratrol during DOX treatment was sufficient to normalize molecular markers of cardiotoxicity and restore the ability of the heart to undergo adaptive remodelling in response to hypertension later in life.

A novel complex I inhibitor protects against hypertension-induced left ventricular hypertrophy.

Since left ventricular hypertrophy (LVH) increases the susceptibility for the development of other cardiac conditions, pharmacotherapy that mitigates pathological cardiac remodeling may prove to be beneficial in patients with LVH. Previous work has shown that the activation of the energy-sensing kinase AMP-activated protein kinase (AMPK) can inhibit some of the molecular mechanisms that are involved in LVH. Of interest, metformin activates AMPK through its inhibition of mitochondrial complex I in the electron transport chain and can prevent LVH induced by pressure overload. However, metformin has additional cellular effects unrelated to AMPK activation, raising questions about whether mitochondrial complex I inhibition is sufficient to reduce LVH. Herein, we characterize the cardiac effects of a novel compound (R118), which is a more potent complex I inhibitor than metformin and is thus used at a much lower concentration. We show that R118 activates AMPK in the cardiomyocyte, inhibits multiple signaling pathways involved in LVH, and prevents Gq protein-coupled receptor agonist-induced prohypertrophic signaling. We also show that in vivo administration of R118 prevents LVH in a mouse model of hypertension, suggesting that R118 can directly modulate the response of the cardiomyocyte to stress. Of importance, we also show that while R118 treatment prevents adaptive remodelling in response to elevated afterload, it does so without compromising systolic function, improves myocardial energetics, and prevents a decline in diastolic function in hypertensive mice. Taken together, our data suggest that inhibition of mitochondrial complex I may be worthy of future investigation for the treatment of LVH.NEW & NOTEWORTHY Inhibition of mitochondrial complex I by R118 reduces left ventricular hypertrophy (LVH) and improves myocardial energetics as well as diastolic function without compromising systolic function. Together, these effects demonstrate the therapeutic potential of complex I inhibitors in the treatment of LVH, even in the presence of persistent hypertension.

Improved Glucose Homeostasis in Obese Mice Treated With Resveratrol Is Associated With Alterations in the Gut Microbiome.

Oral administration of resveratrol is able to improve glucose homeostasis in obese individuals. Herein we show that resveratrol ingestion produces taxonomic and predicted functional changes in the gut microbiome of obese mice. In particular, changes in the gut microbiome were characterized by a decreased relative abundance of Turicibacteraceae, Moryella, Lachnospiraceae, and Akkermansia and an increased relative abundance of Bacteroides and Parabacteroides Moreover, fecal transplantation from healthy resveratrol-fed donor mice is sufficient to improve glucose homeostasis in obese mice, suggesting that the resveratrol-mediated changes in the gut microbiome may play an important role in the mechanism of action of resveratrol.

Chronic insulin infusion induces reversible glucose intolerance in lean rats yet ameliorates glucose intolerance in obese rats.

BACKGROUND: Although insulin resistance (IR) is a key factor in the pathogenesis of type 2 diabetes (T2D), the precise role of insulin in the development of IR remains unclear. Therefore, we investigated whether chronic basal insulin infusion is causative in the development of glucose intolerance. METHODS: Normoglycemic lean rats surgically instrumented with i.v. catheters were infused with insulin (3mU/kg/min) or physiological saline for 6weeks. At infusion-end, plasma insulin levels along with glucose tolerance were assessed. RESULTS: Six weeks of insulin infusion induced glucose intolerance and impaired insulin response in healthy rats. Interestingly, the effects of chronic insulin infusion were completely normalized following 24h withdrawal of exogenous insulin and plasma insulin response to glucose challenge was enhanced, suggesting improved insulin secretory capacity. As a result of this finding, we assessed whether the effects of insulin therapy followed by a washout could ameliorate established glucose intolerance in obese rats. Obese rats were similarly instrumented and infused with insulin or physiological saline for 7days followed by 24h washout. Seven day-insulin therapy in obese rats significantly improved glucose tolerance, which was attributed to improved insulin secretory capacity and improved insulin signaling in liver and skeletal muscle. CONCLUSION: Moderate infusion of insulin alone is sufficient to cause glucose intolerance and impair endogenous insulin secretory capacity, whereas short-term, intensive insulin therapy followed by insulin removal effectively improves glucose tolerance, insulin response and peripheral insulin sensitivity in obese rats. GENERAL SIGNIFICANCE: New insight into the link between insulin and glucose intolerance may optimize T2D management.

Resveratrol prevents pathological but not physiological cardiac hypertrophy.

UNLABELLED: The mechanisms responsible for how resveratrol inhibits pathological left ventricular hypertrophy (LVH) but not physiological LVH have not been elucidated. Herein, we show that in rat cardiomyocytes, lower concentrations of resveratrol (0.1 and 1 µM) are efficient at selectively inhibiting important regulators involved in pathological LVH (such as nuclear factor of activated T cells (NFAT)) while not affecting pathways involved in physiological LVH (Akt and p70S6 kinase (p70S6K)). These differential responses are also observed in both mouse and rat models of in vivo physiological and pathological LVH. Interestingly, in all of the experiments involving a low concentration of resveratrol (1 µM), the observed effects on Akt, p70S6K, and NFAT were independent from AMP-activated protein kinase (AMPK) activation while these effects at higher concentrations of resveratrol (50 µM) were potentiated by AMPK activation. In summary, we show that resveratrol can concentration/dose selectively inhibit various pro-hypertrophic signaling pathways and that resveratrol has differential effects on the modification of these signaling cascades in response to pathological stimuli versus physiological stimuli. This has important clinical implications as our findings support the concept that resveratrol may be useful in the selective treatment of pathological LVH. KEY MESSAGE: Resveratrol differentially regulates pathological and physiological cardiac hypertrophy. Resveratrol dose selectively inhibits pathological cardiac signaling pathways. Resveratrol inhibits NFAT-dependent transcription. At low concentrations, effects of resveratrol are AMPK-independent. Resveratrol may be used to selectively treat pathological cardiac hypertrophy.

Increased CD36 expression in middle-aged mice contributes to obesity-related cardiac hypertrophy in the absence of cardiac dysfunction.

As aging is a significant risk factor for the development of left ventricular hypertrophy and cardiovascular disease, we hypothesized that hearts from middle-aged mice may be more sensitive to the effects of a high fat (HF) diet than hearts from young mice. To investigate this, young (10-12 week old) and middle-aged (40-44 week old) male mice were fed a low fat (LF) or HF diet (10 or 60 kcal% fat, respectively) for 12 weeks. Following this 12-week period, we show that CD36 protein expression was not changed in hearts from young mice yet was increased 1.5-fold in the middle-aged HF group compared with LF-fed age-matched counterparts. Correlated with increased CD36 expression, middle-aged mice displayed a greater degree of cardiac hypertrophy compared with young mice when fed a HF diet, and this was observed in the absence of cardiac dysfunction. Furthermore, middle-aged CD36 knockout mice were protected against HF diet-induced cardiac hypertrophy, supporting a link between CD36 and cardiac hypertrophy. To further explore potential mechanisms that may explain why middle-aged mice are more susceptible to HF diet-induced cardiac hypertrophy, we investigated mediators of cardiac growth. We show that myocardial ceramide levels were significantly increased in middle-aged mice fed a HF diet compared with LF-fed controls, which was also correlated with inhibition of AMP-activated protein kinase (AMPK). Consistent with AMPK being a negative regulator of cardiac hypertrophy, decreased AMPK activity also resulted in the activation of the mTOR/p70S6K pathway, which is known to enhance protein synthesis associated with cardiac hypertrophy. Together, these data suggest that increased myocardial CD36 expression in hearts from middle-aged mice may contribute to HF diet-induced cardiac hypertrophy and that this may be mediated by elevated ceramide levels signaling through AMPK. Overall, we suggest that inhibition of CD36-mediated fatty acid uptake may prevent obesity-related cardiomyopathies in the middle-aged population.

Improved cardiac metabolism and activation of the RISK pathway contributes to improved post-ischemic recovery in calorie restricted mice.

Recent evidence has suggested that activation of AMP-activated protein kinase (AMPK) induced by short-term caloric restriction (CR) protects against myocardial ischemia-reperfusion (I/R) injury. Because AMPK plays a central role in regulating energy metabolism, we investigated whether alterations in cardiac energy metabolism contribute to the cardioprotective effects induced by CR. Hearts from control or short-term CR mice were subjected to ex vivo I/R and metabolism, as well as post-ischemic functional recovery was measured. Even in the presence of elevated levels of fatty acids, CR significantly improved recovery of cardiac function following ischemia. While rates of fatty acid oxidation or glycolysis from exogenous glucose were similar between groups, improved functional recovery post-ischemia in CR hearts was associated with high rates of glucose oxidation during reperfusion compared to controls. Consistent with CR improving energy supply, hearts from CR mice had increased ATP levels, as well as lower AMPK activity at the end of reperfusion compared to controls. Furthermore, in agreement with the emerging concept that CR is a non-conventional form of pre-conditioning, we observed a significant increase in phosphorylation of Akt and Erk1/2 at the end of reperfusion. These data also suggest that activation of the reperfusion salvage kinase (RISK) pathway also contributes to the beneficial effects of CR in reducing post-ischemia contractile dysfunction. These findings also suggest that short-term CR improves post-ischemic recovery by promoting glucose oxidation, and activating the RISK pathway. As such, pre-operative CR may be a clinically relevant strategy for increasing ischemic tolerance of the heart.

Resveratrol inhibits cardiac hypertrophy via AMP-activated protein kinase and Akt.

Whereas studies involving animal models of cardiovascular disease demonstrated that resveratrol is able to inhibit hypertrophic growth, the mechanisms involved have not been elucidated. Because studies in cells other than cardiomyocytes revealed that AMP-activated protein kinase (AMPK) and Akt are affected by resveratrol, we hypothesized that resveratrol prevents cardiac myocyte hypertrophy via these two kinase systems. Herein, we demonstrate that resveratrol reduces phenylephrine-induced protein synthesis and cell growth in rat cardiac myocytes via alterations of intracellular pathways involved in controlling protein synthesis (p70S6 kinase and eukaryotic elongation factor-2). Additionally, we demonstrate that resveratrol negatively regulates the calcineurin-nuclear factor of activated T cells pathway thus modifying a critical component of the transcriptional mechanism involved in pathological cardiac hypertrophy. Our data also indicate that these effects of resveratrol are mediated via AMPK activation and Akt inhibition, and in the case of AMPK, is dependent on the presence of the AMPK kinase, LKB1. Taken together, our data suggest that resveratrol exerts anti-hypertrophic effects by activating AMPK via LKB1 and inhibiting Akt, thus suppressing protein synthesis and gene transcription.

Increased hepatic CD36 expression contributes to dyslipidemia associated with diet-induced obesity.

OBJECTIVE: The etiology of type 2 diabetes often involves diet-induced obesity (DIO), which is associated with elevated plasma fatty acids and lipoprotein associated triglycerides. Since aberrant hepatic fatty acid uptake may contribute to this, we investigated whether increased expression of a fatty acid transport protein (CD36) in the liver during DIO contributes to the dyslipidemia that precedes development of type 2 diabetes. RESEARCH DESIGN AND METHODS: We determined the effect DIO has on hepatic CD36 protein expression and the functional consequence of this in terms of hepatic triglyceride storage and secretion. In addition, in vivo adenoviral gene delivery of CD36 to the livers of lean mice was performed to determine if increased hepatic CD36 protein was sufficient to alter hepatic fatty acid uptake and triglyceride storage and secretion. RESULTS: During DIO, CD36 protein levels in the liver are significantly elevated, and these elevated levels correlate with increased hepatic triglyceride storage and secretion. These alterations in liver lipid storage and secretion were also observed upon forced expression of hepatic CD36 in the absence of DIO and were accompanied with a marked rise in hepatic fatty acid uptake in vivo, demonstrating that increased CD36 expression is sufficient to recapitulate the aberrant liver lipid handling observed in DIO. CONCLUSIONS: Increased expression of hepatic CD36 protein in response to DIO is sufficient to exacerbate hepatic triglyceride storage and secretion. As these CD36-mediated effects contribute to the dyslipidemia that often precedes the development of type 2 diabetes, increased hepatic CD36 expression likely plays a causative role in the pathogenesis of type 2 diabetes.

Expression of an active LKB1 complex in cardiac myocytes results in decreased protein synthesis associated with phenylephrine-induced hypertrophy.

AMP-activated protein kinase (AMPK) is a major metabolic regulator in the cardiac myocyte. Recently, LKB1 was identified as a kinase that regulates AMPK. Using immunoblot analysis, we confirmed high expression of LKB1 in isolated rat cardiac myocytes but show that, under basal conditions, LKB1 is primarily localized to the nucleus, where it is inactive. We examined the role of LKB1 in cardiac myocytes, using adenoviruses that express LKB1, and its binding partners Ste20-related adaptor protein (STRADalpha) and MO25alpha. Infection of neonatal rat cardiac myocytes with all three adenoviruses substantially increased LKB1/STRADalpha/MO25alpha expression, LKB1 activity, and AMPKalpha phosphorylation at its activating phosphorylation site (threonine-172). Since activation of AMPK can inhibit hypertrophic growth and since LKB1 is upstream of AMPK, we hypothesized that expression of an active LKB1 complex would also inhibit protein synthesis associated with hypertrophic growth. Expression of the LKB1/STRADalpha/MO25alpha complex in neonatal rat cardiac myocytes inhibited the increase in protein synthesis observed in cells treated with phenylephrine (measured via [(3)H]phenylalanine incorporation). This was associated with a decreased phosphorylation of p70S6 kinase and its substrate S6 ribosomal protein, key regulators of protein synthesis. In addition, we show that the pathological cardiac hypertrophy in transgenic mice with cardiac-specific expression of activated calcineurin is associated with a significant decrease in LKB1 expression. Together, our data show that increased LKB1 activity in the cardiac myocyte can decrease hypertrophy-induced protein synthesis and suggest that LKB1 activation may be a method for the prevention of pathological cardiac hypertrophy.

Activation of cardiac AMP-activated protein kinase by LKB1 expression or chemical hypoxia is blunted by increased Akt activity.

AMP-activated protein kinase (AMPK) plays a major role in the regulation of cardiac energy substrate utilization and can be negatively regulated by Akt activation in the heart. It has recently been shown that Akt directly phosphorylates AMPKalpha(1)/alpha(2) on Ser(485/491) in vitro and prevents the AMPK kinase (AMPKK) LKB1 from phosphorylating AMPKalpha at its primary activation site, Thr(172) (S Horman, D Vertommen, R Heath, D Neumann, V Mouton, A Woods, U Schlattner, T Wallimann, D Carling, L Hue, and MH Rider. J Biol Chem 281: 5335-5340, 2006). To determine whether this is also the case in the cardiac myocyte, neonatal rat cardiac myocytes (NRCM) were infected with a recombinant adenovirus expressing a constitutively active mutant of Akt1 (myrAkt1) and then with or without adenoviruses expressing the active LKB1 complex. Expression of myrAkt1 blunted LKB1-induced phosphorylation of AMPKalpha at Thr(172), which resulted in a dramatic decrease in phosphorylation of AMPK's target, acetyl CoA-carboxylase. This decrease in AMPK activity was associated with prior Akt1-dependent phosphorylation of AMPKalpha(1)/alpha(2) at Ser(485/491). To investigate whether Akt1 activation was also able to prevent other AMPKKs from phosphorylating AMPKalpha, we subjected NRCM to chemical hypoxia and noted a marked increase in phosphorylation of AMPKalpha at Thr(172), despite no change in LKB1 activity. NRCM expressing myrAkt1 demonstrated increased phosphorylation of AMPKalpha(1)/alpha(2) at Ser(485/491) and a complete inhibition of chemical hypoxia-induced phosphorylation of AMPKalpha at Thr(172). Taken together, our data show that activation of Akt1 is able to prevent activation of cardiac AMPK by LKB1 and at least one other AMPKK, likely by prior phosphorylation of AMPKalpha(1)/alpha(2) at Ser(485/491).

Activation of AMP-activated protein kinase inhibits protein synthesis associated with hypertrophy in the cardiac myocyte.

A necessary mediator of cardiac myocyte enlargement is protein synthesis, which is controlled at the levels of both translation initiation and elongation. Eukaryotic elongation factor-2 (eEF2) mediates the translocation step of peptide-chain elongation and is inhibited through phosphorylation by eEF2 kinase. In addition, p70S6 kinase can regulate protein synthesis by phosphorylating eEF2 kinase or via phosphorylation of ribosomal protein S6. We have recently shown that eEF2 kinase is also controlled by phosphorylation by AMP-activated protein kinase (AMPK), a key regulator of cellular energy homeostasis. Moreover, the mammalian target of rapamycin has also been shown to be inhibited, indirectly, by AMPK, thus leading to the inhibition of p70S6 kinase. Although AMPK activation has been shown to modulate protein synthesis, it is unknown whether AMPK could also be a regulator of cardiac hypertrophic growth. Therefore, we investigated the role of AMPK activation in regulating protein synthesis during both phenylephrine- and Akt-induced cardiac hypertrophy. Metformin and 5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside were used to activate AMPK in neonatal rat cardiac myocytes. Activation of AMPK significantly decreased protein synthesis induced by phenylephrine treatment or by expression of constitutively active Akt. Activation of AMPK also resulted in decreased p70S6 kinase phosphorylation and increased phosphorylation of eEF2, suggesting that inhibition of protein synthesis involves the eEF2 kinase/eEF2 axis and/or the p70S6 kinase pathway. Together, our data suggest that the inhibition of protein synthesis by pharmacological activation of AMPK may be a key regulatory mechanism by which hypertrophic growth can be controlled.

Akt activity negatively regulates phosphorylation of AMP-activated protein kinase in the heart.

In the heart, insulin stimulates a variety of kinase cascades and controls glucose utilization. Because insulin is able to activate Akt and inactivate AMP-activated protein kinase (AMPK) in the heart, we hypothesized that Akt can regulate the activity of AMPK. To address the potential existence of this novel signaling pathway, we used a number of experimental protocols to activate Akt in cardiac myocytes and monitored the activation status of AMPK. Mouse hearts perfused in the presence of insulin demonstrated accelerated glycolysis and glucose oxidation rates as compared with non-insulin-perfused hearts. In addition, insulin caused an increase in Akt phosphorylation and a decrease in AMPK phosphorylation at its major regulatory site (threonine 172 of the alpha catalytic subunit). Transgenic mice overexpressing a constitutively active mutant form of Akt1 displayed decreased phosphorylation of cardiac alpha-AMPK. Isolated neonatal cardiac myocytes infected with an adenovirus expressing constitutively active mutant forms of either Akt1 or Akt2 also suppressed AMPK phosphorylation. However, Akt-dependent depression of alpha-AMPK phosphorylation could be overcome in the presence of the AMPK activator, metformin, suggesting that an override mechanism exists that can restore AMPK activity. Taken together, this study suggests that there is cross-talk between the AMPK and Akt pathways and that Akt activation can lead to decreased AMPK activity. In addition, our data suggest that the ability of insulin to inhibit AMPK may be controlled via an Akt-mediated mechanism.

Phosphorylation of cardiac protein kinase B is regulated by palmitate.

In this study isolated perfused working rat hearts were used to investigate the role of palmitate-regulated protein kinase B (PKB) phosphorylation on glucose metabolism. Rat hearts were perfused aerobically in working mode with 11 mM glucose and either 100 microU/ml insulin or 100 microU/ml insulin and 1.2 mM palmitate. PKB activity and phosphorylation state were reduced in the presence of 1.2 mM palmitate, which correlates with a decrease in glycolysis (47%), glucose oxidation (84%), and glucose uptake (43%). In contrast to skeletal muscle, neither p38 nor ERK underwent changes in their phosphorylation states in response to insulin or insulin and palmitate. Moreover, pharmacological restoration of glucose oxidation rates in hearts perfused with 1.2 mM palmitate demonstrated no increase in PKB phosphorylation state. In cultured mouse cardiac muscle HL-1 cells, insulin markedly increased PKB phosphorylation, which was blunted by pre- and cotreatment with 1.2 mM palmitate. However, neither palmitate nor C(2)-ceramide treatment of insulin-stimulated cells was able to accelerate PKB dephosphorylation beyond that observed following the removal of insulin alone. Taken together, these experiments show the control of PKB phosphorylation by palmitate is independent of ceramide and suggest that this signaling event may be an important regulator of myocardial glucose uptake and oxidation.