BACKGROUND: Human adenovirus-36 (Ad-36) increases adiposity and paradoxically lowers serum cholesterol and triglycerides in chickens, mice, and non-human primates. The role of Ad-36 in human obesity is unknown. OBJECTIVES: To determine the prevalence of Ad-36 antibodies in obese and nonobese humans. To evaluate the association of Ad-36 antibodies with body mass index (BMI) and serum lipids. DESIGN: Cohort study. Volunteers from obesity treatment programs, communities, and a research study. SUBJECTS: Obese and nonobese volunteers at the University of Wisconsin, Madison, WI, and the Bowen Center, Naples, Florida. Obese and thin volunteer research subjects and 89 twin pairs at Columbia University, New York. INTERVENTIONS: Study 1: 502 subjects; serum neutralization assay for antibodies to Ad-2, Ad-31, Ad-36, and Ad-37; serum cholesterol and triglycerides assays. Study 2: BMI and %body fat in 28 twin pairs discordant for Ad-36 antibodies. MAIN OUTCOME MEASURES: Presence of antibodies to adenoviruses, BMI, serum cholesterol and triglycerides levels. RESULTS: Significant (Po0.001) association of obesity and positive Ad-36 antibody status, independent of age, sex, and collection site. Ad-36 antibodies in 30% of obese, 11% of nonobese. Lower serum cholesterol and triglycerides (Po0.003) in Ad-36 antibody-positive vs -negative subjects. Twin pairs: antibody-positive twins had higher BMIs (24.575.2 vs 23.174.5 kg/m 2 , Po0.03) and %body fat (29.679.5% vs 27.579.9%, Po0.04). No association of Ad-2, Ad-31, or Ad-37 antibodies with BMI or serum lipids. CONCLUSIONS: Ad-36 is associated with increased body weight and lower serum lipids in humans. Prospective studies are indicated to determine if Ad-36 plays a role in the etiology of human obesity.

Methods GPI-LpL construct.A PCR-based strategy was used to ligate the DNA sequence encoding the last 37 amino acids of membrane decay accelerating factor (DAF) (9, 10) containing the GPI-anchoring sequence to a human LpL (hLpL) minigene (11) (see Figure 1a). This strategy required the elimination of the LpL termination codon

C]TG, we observed that hearts also internalize intact core lipid. Inhibition of lipoprotein lipase (LPL) with tetrahydrolipstatin or dissociation of LPL from the heart with heparin reduced cardiac uptake of TG by 82 and 64%, respectively (P Ͻ 0.01). Palmitate uptake by the heart was not changed by either treatment. Uptake of TG was 88% less in hearts from LPL knockout mice that were rescued via LPL expression in the liver. Our data suggest that the heart is especially effective in removal of circulating TG and core lipids and that this is due to LPL hydrolysis and not its bridging function. fatty acids; lipoprotein lipase; triglycerides; lipid emulsion; very low-density lipoprotein; heart; myocyte FATTY ACIDS (FA) are an important fuel source for heart and skeletal muscle, providing over 70% of the energy needs for cardiac function (2,5,33). FA are delivered to cardiac myocytes in three ways. 1) FA are derived from the hydrolysis of triglyceride (TG) stored in adipose tissue via hormone-sensitive lipase and circulate complexed with albumin. 2) FA are produced from intracellular hydrolysis of TG in the core of internalized lipoproteins. 3) FA are also generated in the local capillary bed by lipoprotein lipase (LPL)-mediated hydrolysis of TG in circulating chylomicrons and very low-density lipoproteins (VLDL). Despite the fact that the molar concentration of FA in lipoprotein TG is an order of magnitude greater than that of albumin FA, it is widely believed that albumin-FA is the primary source of energy for the heart (21). However, cardiac muscle is the tissue with the greatest expression of LPL (9). Moreover, expression of LPL solely in the heart is adequate to maintain normal levels of plasma TG (19). Thus it is likely that hearts are continuously generating a large amount of FA from TG lipolysis.A number of early studies that measured FA delivery to muscle (11,14) were limited in their scope, measuring only the contribution of albumin-bound FA delivery to muscle without considering additional pathways. More recently, FA metabolism in isolated perfused working hearts has been studied and FA oxidation quantified (3,11,14,24,34). Comparison data on FA delivery to the heart under conditions that mimic those in vivo are limited. The contribution of lipoprotein-TG to heart energy production, especially in the postprandial period when the heart is bathed in dietary TG, is uncertain.This study had two objectives. The first was to compare the heart uptake of FA bound to albumin and FA derived from the hydrolysis of TG-rich lipoproteins with that of other tissues. Kinetic studies were performed in mice to assess two or more pathways of FA delivery concurrently. This allowed us to assess, in vivo, FA delivery to the heart in the context of whole body metabolism. Intralipid emulsion particles, which are similar in size and TG content to chylomicrons (17), and VLDL were utilized to determine lipoprotein particle FA delivery. In addition, palmitate complexed to bovine serum albumin (BSA) was used to assess free FA delivery ...

Long-chain fatty acids (FAs) are the predominant energy substrate utilized by the adult heart. The heart can utilize unesterified FA bound to albumin or FA obtained from lipolysis of lipoprotein-bound triglyceride (TG). We used heart-specific lipoprotein lipase knock-out mice (hLpL0) to test whether these two sources of FA are interchangeable and necessary for optimal heart function. Hearts unable to obtain FA from lipoprotein TG were able to compensate by increasing glucose uptake, glycolysis, and glucose oxidation. HLpL0 hearts had decreased expression of pyruvate dehydrogenase kinase 4 and increased cardiomyocyte expression of glucose transporter 4. Conversely, FA oxidation rates were reduced in isolated perfused hLpL0 hearts. Following abdominal aortic constriction expression levels of genes regulating FA and glucose metabolism were acutely up-regulated in control and hLpL0 mice, yet all hLpL0 mice died within 48 h of abdominal aortic constriction. Older hLpL0 mice developed cardiac dysfunction characterized by decreased fractional shortening and interstitial and perivascular fibrosis. HLpL0 hearts had increased expression of several genes associated with transforming growth factor-␤ signaling. Thus, long term reduction of lipoprotein FA uptake is associated with impaired cardiac function despite a compensatory increase in glucose utilization.Normal cardiac muscle function requires adequate delivery of oxygen and energy substrates for the production of ATP. In the adult heart, fatty acid (FA) 4 oxidation accounts for 60 -70% of oxygen consumption, with the balance provided by glucose and lactate (1-3). However, during conditions such as ischemia (4, 5) and hypertrophy (4 -6) the heart becomes more dependent on glucose. This initial adaptive response is beneficial in that it maintains ATP levels (7, 8) in the face of diminished mitochondrial oxidative phosphorylation. High rates of FA oxidation inhibit glucose oxidation and impair the recovery of mechanical function during reperfusion of ischemic hearts (9), whereas partial inhibition of FA oxidation during acute ischemia increases glucose oxidation and improves contractile power and efficiency (10 -12). Several pharmacological agents have been developed, including dichloroacetate and ranolazine, which increase glucose oxidation in isolated hearts subjected to ischemia (4, 12). Furthermore, trimetazine, an inhibitor of long-chain 3-ketoacyl-coenzyme A thiolase (the final enzyme in the ␤-oxidation pathway), is cardioprotective in several models of ischemia (13). However, the long term effects of reduced FA oxidation on cardiac energetics and function are unknown.All tissues have several routes through which they may acquire FAs. The heart avidly utilizes FA associated with albumin, and this can be demonstrated both in vivo and in perfused hearts. However, esterified FAs contained in lipoproteins are the major source of cardiac FA (14). These two sources of FA can compete for uptake in perfused hearts (15); this is not surprising, because conversion of TG to ...

Fatty acids are the primary energy source for the heart. The heart acquires fatty acids associated with albumin or derived from lipoprotein lipase (LpL)-mediated hydrolysis of lipoprotein triglyceride (TG). We generated heart-specific LpL knock-out mice (hLpL0) to determine whether cardiac LpL modulates the actions of peroxisome proliferator-activated receptors and affects whole body lipid metabolism. Male hLpL0 mice had significantly elevated plasma TG levels and decreased clearance of postprandial lipids despite normal postheparin plasma LpL activity. Very large density lipoprotein-TG uptake was decreased by 72% in hLpL0 hearts. However, heart uptake of albumin-bound free fatty acids was not altered. Northern blot analysis revealed a decrease in the expression of peroxisome proliferatoractivated receptor ␣-response genes involved in fatty acid ␤-oxidation. Surprisingly, the expression of glucose transporters 1 and 4 and insulin receptor substrate 2 was increased and that of pyruvate dehydrogenase kinase 4 and insulin receptor substrate 1 was reduced. Basal glucose uptake was increased markedly in hLpL0 hearts. Thus, the loss of LpL in the heart leads to defective plasma metabolism of TG. Moreover, fatty acids derived from lipoprotein TG and not just albumin-associated fatty acids are important for cardiac lipid metabolism and gene regulation.The heart, unlike most skeletal muscles, is constantly undergoing contraction and relaxation, events that require a large amount of energy. Under normal conditions, the heart derives ϳ70% of its energy from the oxidation of long-chain fatty acids (FA) 1 and the remainder comes from glucose and lactate metabolism (1, 2). However, a number of conditions including fasting, aerobic exercise, and diabetes increase the contribution of FA to ATP production by the heart (3). FA are supplied to the heart from the hydrolysis of triglyceride (TG)-rich lipoproteins via lipoprotein lipase (LpL) (4) and via uptake of albuminbound FA derived from adipose TG stores. The relative importance of these two pathways for cardiac metabolism and regulation of FA-responsive genes is unknown. LpL controls FA uptake through the hydrolysis of TG in chylomicrons and very large density lipoproteins (VLDL) (5). Although most lipolysis of plasma TG is thought to occur in skeletal muscle and adipose, several lines of evidence suggest that cardiac muscle is an important site of regulation of plasma TG levels (4, 6). Cardiac muscle is the tissue with the greatest expression of LpL on a per gram basis (7). Moreover, mice expressing LpL only in the heart are able to maintain normal lipid levels (4, 6).We used the Cre-loxP recombination system to generate mice with a cardiac-specific ablation of the LpL gene to elucidate the role of cardiac LpL in heart and plasma lipoprotein metabolism and gene expression. This allowed us to investigate the role of LpL in the heart without directly altering LpL function and activity in skeletal muscle or adipose tissue. Our data show that the loss of LpL in the heart leads ...

Methods GPI-LpL construct.A PCR-based strategy was used to ligate the DNA sequence encoding the last 37 amino acids of membrane decay accelerating factor (DAF) (9, 10) containing the GPI-anchoring sequence to a human LpL (hLpL) minigene (11) (see Figure 1a). This strategy required the elimination of the LpL termination codon

14 C]palmitate uptake and confirmed that Intralipid inhibition requires local LpL. Our data demonstrate that reduced FA uptake and oxidation occur before mechanical dysfunction in hLpL GPI lipotoxicity. This physiology is reproduced with perfusion of hearts with TG-containing particles. Together, the results demonstrate that cardiac uptake of TG-derived FA reduces utilization of albumin-FA. lipotoxicity; triglyceride; fatty acid metabolism; lipoprotein lipase LONG-CHAIN FATTY ACIDS (FA) comprise the main fuel source for the heart and meet up to 70 -80% of cardiac energy needs (1, 18). FA may be supplied to the heart in three ways (2). First, triglycerides (TG) in adipose tissue may be hydrolyzed by hormone-sensitive lipase into FA. These FA circulate as a complex with albumin. Second, myocytes can take up whole lipoprotein particles containing core TG, which can be hydrolyzed intracellularly to yield FA. Finally, local lipolysis of circulating lipoproteins [chylomicrons and very-low-density lipoproteins (VLDL)] by lipoprotein lipase (LpL) within surrounding capillary beds generates free FA (FFA) (9).The heart normally metabolizes FA immediately; it has little capacity for storage (18). However, excess cardiac lipid is thought to cause cardiomyopathy in human conditions such as inborn errors of metabolism, diabetes, and obesity (4, 8, 13). Animal models of lipotoxic cardiomyopathy have been created that reproduce the abnormalities seen when the heart's ability to oxidize FA is exceeded (5).Our 14 C]palmitate with or without VLDL or Intralipid; Intralipid is a surrogate for TG-rich lipoproteins. Finally, we assessed the role of LpL in the metabolism of Intralipid using two compounds, heparin and poloxamer 407 (P407; a novel lipase inhibitor). Our data show that hearts from both hLpL GPI and wild-type mice perfused with TG-rich particles have reduced FFA uptake and oxidation. Therefore, hearts use TGderived FA as an alternative fuel and, in some situations, as the primary source of FA. MATERIALS AND METHODSAnimals. All experiments were conducted using male C57BL/6 mice that were 2-3 mo old and weighed 20 -30 g. Animals were housed in a room undergoing a 12:12-h light-dark cycle and were provided access to standard chow and water ad libitum.A number of experiments were performed in transgenic mice overexpressing a cardiomyocyte-anchored form of LpL. These mice, termed hLpL GPI , are described in a previous publication (19). hLpL GPI mice develop a lipotoxic cardiomyopathy with age. They have normal circulating levels of lipoproteins and FFA.Isolated heart preparations. For metabolic studies, an isovolumic isolated Langendorff heart preparation was used, as reported previously (11). Mice were anesthetized with a mixture of ketamine (80 mg/kg) and xylazine (10 mg/kg) via intraperitoneal injection. Anticoagulation was not performed, because heparin displaces LpL from its binding site. After deep anesthesia was achieved, a thoracotomy was performed and the heart rapidly excised. Hearts were perfused with modified Krebs-...

hLpLGPI transgenic mice that overexpress human lipoprotein lipase (hLpL) with a glycosylphosphatidylinositol anchor on cardiomyocytes develop lipotoxic cardiomyopathy associated with increased cardiac uptake of plasma lipids. We hypothesized that peroxisome proliferator-activated receptor (PPAR)␣, PPAR␥, or a PPAR␣/␥ agonist would alter cardiac function by modulating lipid uptake by the heart. hLpL GPI mice were administered rosiglitazone (10 mg/kg/day), fenofibrate (100 mg/ kg/day), or DRF2655, an alkoxy propanoic acid analog (10 mg/kg/day), for 16 days. Rosiglitazone reduced plasma triglyceride (TG) from 107.63 Ϯ 6.98 to 77.61 Ϯ 3.98 mg/dl, whereas fenofibrate had no effect. DRF2655 reduced TG to 33.17 Ϯ 4.12 mg/dl. Rosiglitazone and DRF2655 decreased heart TG and total cholesterol; fenofibrate had no effect. Molecular markers for cardiac dysfunction, atrial natriuretic factor, brain natriuretic peptide, and tumor necrosis factor-␣ were decreased with rosiglitazone and increased with fenofibrate. Echocardiographic measurements showed reduced fractional shortening and increased left ventricular systolic dimension with fenofibrate. No changes in these parameters were observed with rosiglitazone or DRF2655 treatment. Muscle-specific carnitine palmitoyltransferase-1 and fatty acid transporter protein-1 gene expression were increased with fenofibrate and DRF2655 treatment; no change in expression of these genes was noted with rosiglitazone treatment. Rosiglitazone and DRF2655 reduced TG uptake by the heart, and fenofibrate treatment increased fatty acid uptake. Thus, in a lipotoxic cardiomyopathy mouse model, a PPAR␥ agonist reduced cardiac lipid and markers of cardiomyopathy, whereas an agonist of PPAR␣ did not improve cardiac lipids and worsened heart function. These changes were paralleled by alterations in heart lipid uptake. Overall, PPAR activators exhibit differential effects in this model of lipotoxic dilated cardiomyopathy.