Impaired cardiac functional reserve in type 2 diabetic db/db mice is associated with metabolic, but not structural, remodelling.

Aim: To identify the initial alterations in myocardial tissue associated with the early signs of diabetic cardiac haemodynamic dysfunction, we monitored changes in cardiac function, structural remodelling and gene expression in hearts of type 2 diabetic db/db mice.

Methods: Cardiac dimensions and function were determined echocardiographically at 8, 12, 16 and 18 weeks of age. Left ventricular pressure characteristics were measured at 18 weeks under baseline conditions and upon dobutamine infusion.

Time related changes in calcium handling in the isolated ischemic and reperfused rat heart.

The main aim of this study was to assess the kinetics of intracellular free calcium (Ca(2+)i) handling by isolated rat hearts rendered ischemic for 30 min followed by 30 min of reperfusion analyzing the upstroke and downslope of the Ca(2+)i transient. Changes in mechanical performance and degradation of membrane phospholipids--estimated by tissue arachidonic acid content--were correlated with Ca(2+)i levels of the heart. The fluorescence ratio technique was applied to estimate Ca(2+)i.

Ketone bodies disturb fatty acid handling in isolated cardiomyocytes derived from control and diabetic rats.

According to the current paradigm, fatty acid (FA) utilization is increased in the diabetic heart. Since plasma levels of competing substrates such as ketone bodies are increased during diabetes, the effect of those substrates on cardiac FA handling was explored. Cardiomyocytes were isolated from control and streptozotocin-treated diabetic rats and incubated with normal (80 microM) and elevated (160 microM) palmitate concentrations in the absence or presence of ketone bodies, including acetoacetate (AcAc).

Protein acylation in the cardiac muscle like cell line, H9c2.

Besides serving as oxidisable substrates, fatty acids (FA) are involved in co- and post-translational modification of proteins (protein acylation). Despite the high rate of fatty acid utilisation in the heart, information on protein acylation in cardiac muscle is scarce. To explore this subject in more detail, we used the H9c2 cell line as an experimental model.

Increased muscle fatigability in GLUT-4-deficient mice.

GLUT-4 plays a predominant role in glucose uptake during muscle contraction. In the present study, we have investigated in mice whether disruption of the GLUT-4 gene affects isometric and shortening contractile performance of the dorsal flexor muscle complex in situ. Moreover, we have explored the hypothesis that lack of GLUT-4 enhances muscle fatigability.

Concomitant accumulation of intracellular free calcium and arachidonic acid in the ischemic-reperfused rat heart.

This study was designed to elucidate the relationship between enhanced cytoplasmic calcium levels (Ca2+i) and membrane phospholipid degradation, a key step in the loss of cellular integrity during cardiac ischemia/reperfusion-induced damage. Isolated rat hearts were subjected to 15 min ischemia followed by 30 min reperfusion. Ca2+i was estimated by the Indo-1 fluorescence ratio technique.

Chronic catecholamine depletion switches myocardium from carbohydrate to lipid utilisation.

Purpose: Chronic cardiac transplantation denervation (i.e., global sympathetic denervation with myocardial catecholamine depletion, plus parasympathetic denervation) is known to inhibit myocardial oxidation of glucose.

Ischemic-reperfused isolated working mouse hearts: membrane damage and type IIA phospholipase A2.

For the murine heart the relationships between ischemia-reperfusion-induced loss of cardiac function, enzyme release, high-energy phosphate (HEP), and membrane phospholipid metabolism are ill-defined. Accordingly, isolated ejecting murine hearts were subjected to varying periods of ischemia, whether or not followed by reperfusion. On reperfusion, hemodynamic function was almost completely restored after 10 min of ischemia [83 +/- 14% recovery of cardiac output (CO)], but was severely depressed after 15 and 20 min of ischemia (40 +/- 24 and 31 +/- 24% recovery of CO, respectively).

Heat pretreatment differentially affects cardiac fatty acid accumulation during ischemia and postischemic reperfusion.

We investigated whether the cardioprotection induced by heat stress (HS) pretreatment is associated with mitigation of phospholipid degradation during the ischemic and/or postischemic period. The hearts, isolated from control rats and from heat-pretreated rats (42 degrees C for 15 min) either 30 min (HS0.5-h) or 24 h (HS24-h) earlier, were subjected to 45 min of no-flow ischemia, followed by 45 min of reperfusion.

Protein acylation in normoxic and ischemic/reperfused cardiac tissue.

In addition to a prominent role in tissue energy conversion, fatty acids are involved in signal transduction and modulation of cellular protein localization and function. The latter is accomplished by acylation of specific cellular proteins. In the present study the amount of fatty acyl moieties covalently bound to cardiac proteins and the effect of myocardial ischemia and reperfusion on the degree and relative fatty acyl composition of cardiac proteins have been investigated in isolated rat hearts.

Muscular long-chain fatty acid content during graded exercise in humans.

We measured the content of long-chain fatty acids (LCFA) in biopsies obtained from the vastus lateralis muscle in humans at rest and after different exercise intensities. Nine volunteers exercised at 65% of maximal oxygen uptake (VO2 max) for 40 min and at 90% of VO2 max for another 15 min on a Krogh bicycle ergometer. LCFA measured in muscle tissue averaged 76 +/- 5 nmol/g wet wt at rest, decreased significantly after exercise at 65% VO2 max to 48 +/- 4 nmol/g wet wt, and increased to 68 +/- 5 nmol/g wet wt (P < 0.

Heat stress pretreatment mitigates postischemic arachidonic acid accumulation in rat heart.

Heat stress pretreatment of the heart is known to protect this organ against an ischemic/reperfusion insult 24 h later. Degradation of membrane phospholipids resulting in tissue accumulation of polyunsaturated fatty acids, such as arachidonic acid, is thought to play an important role in the multifactorial process of ischemia/reperfusion-induced damage. The present study was conducted to test the hypothesis that heat stress mitigates the postischemic accumulation of arachidonic acid in myocardial tissue, as a sign of enhanced membrane phospholipid degradation.

Saturated but not mono-unsaturated fatty acids induce apoptotic cell death in neonatal rat ventricular myocytes.

The energy need of cardiac muscle cells in vivo is largely covered by the oxidation of saturated and mono-unsaturated fatty acids (FA). However, in vitro studies have shown that the saturated FA C16:0 at physiological concentrations exerts detrimental effects on primary cultures of neonatal rat ventricular myocytes by, as yet, unknown mechanisms. To evaluate the noxious effects of FA in more detail, neonatal cardiomyocytes were exposed to saturated (C16:0; C18:0) or mono-unsaturated (C16:1; cis-C18:1; trans-C18:1) FA, or combinations thereof for up to 48 h.

Gradient of fatty acids from blood plasma to skeletal muscle in dogs.

In anesthetized dogs, the amount of fatty acyl moieties in the fatty acid, triacylglycerol, and phospholipid fractions of arterial blood and biceps femoris muscle has been determined to delineate the presence of a fatty acid gradient from blood to skeletal muscle tissue, if any. The content of fatty acids in biceps femoris muscle was found to be very low (approximately 0.1% of total amount of unesterified and esterified fatty acyl moieties in the tissue sample).

Assessment of fatty acids in cardiac tissue as 9-anthryldiazomethane esters by high-performance liquid chromatography.

A high-performance liquid chromatographic technique for the rapid assessment fatty acids in cardiac tissue is described. A level of 50.4 +/- 14.

Effects of nicotinic acid and mepacrine on fatty acid accumulation and myocardial damage during ischemia and reperfusion.

To assess the nature of ischemia- and reperfusion-induced lipid changes and their consequences for myocardial function and integrity, Krebs-Henseleit perfused, isolated, working rat hearts were treated with nicotinic acid or mepacrine, putative inhibitors of triacylglycerol and phospholipid hydrolysis, respectively. In non-treated hearts 60 min ischemia resulted in a marked rise in myocardial fatty acid (FA) content. The FA content sharply increased further during 30 min reperfusion.

Lipid alterations in isolated, working rat hearts during ischemia and reperfusion: its relation to myocardial damage.

Disturbances in lipid metabolism may play an important role in the onset of irreversible myocardial damage. To investigate the effect of ischemia and reperfusion on lipid homeostasis and to delineate its possible consequences for myocardial damage, Krebs-Henseleit-perfused, working rat hearts were subjected to various periods of no-flow ischemia (10 to 90 minutes) with or without 30 minutes of reperfusion. During ischemia, the rise in nonesterified fatty acids (NEFAs) was preceded by the accumulation of substantial amounts of glycerol, indicating the presence of an active triacylglycerol-NEFA cycle.

The content of non-esterified fatty acids in rat myocardial tissue. A comparison between the Dole and Folch extraction procedures.

Oliver and coworkers hypothesized that under certain circumstances NEFA (non-esterified fatty acids = FFA = free fatty acids) might be toxic for myocardial function. Unambiguous conclusions on the putative detrimental effect of intracellularly localized NEFA are hampered by contradictory values published for the NEFA content in normoxic myocardial tissue. From studies in which the assay procedures were carefully evaluated, one might conclude that the NEFA content in dog and rat myocardial tissue will not exceed 60 and 150 nmol/g wet weight, respectively.

Accumulation of nonesterified fatty acids in ischemic canine myocardium.

In ischemic myocardium the time course of nonesterified fatty acid (NEFA) accumulation was studied in relation to changes in regional metabolism and mechanics. In open-chest dogs a coronary artery was partially occluded for 120 min. In the ischemic myocardium no increase was observed in NEFA content within 10 min, whereas changes were found in regional shortening, high-energy phosphate content, and glucose arteriologcal venous difference.

Serum-myocardium gradients of non-esterified fatty acids in dog, rat and man.

In the three species under investigation (dog, rat and man) a gradient from serum to heart tissue for total non-esterified fatty acids was assessed. The ratios serum/left ventricular tissue in dogs, serum/right auricular appendage in dogs, serum/whole heart tissue in rats and serum/right auricular appendage in man were found to be 6.4, 2.

Uptake and tissue content of fatty acids in dog myocardium under normoxic and ischemic conditions.

The effect of ischemia on the myocardial content of nonesterified fatty acids (NEFA), triacylglycerol, cholesteryl esters, and phospholipids assayed with gas-liquid chromatography was studied in an open-chest dog preparation. Ischemia was induced by partial occlusion of the left interventricular coronary artery during 120 minutes (n = 20). Tissue content of the lipid classes was assessed in biopsies taken from ischemic and normoxic areas of the left ventricular free wall.

Assessment of fatty acids in dog left ventricular myocardium.

The concentration and composition of fatty acids in four lipid classes in biopsies of dog left ventricular myocardium were determined, using gas-liquid chromatography. When precautions were taken to minimize lipolysis during storage of the tissue and the homogenization process, the following results were obtained: 29 +/- 10 nmol non-esterified fatty acids, 2.98 +/- 2.