Skeletal and cardiac myopathy in HIV-1 transgenic rats.
The mechanism by which human immunodeficiency virus (HIV)-1 infection in humans leads to the erosion of lean body mass is poorly defined. Therefore, the purpose of the present study was to determine whether transgenic (Tg) rats that constitutively overexpress HIV-1 viral proteins exhibit muscle wasting and to elucidate putative mechanisms. Over 7 mo, Tg rats gained less body weight than pair-fed controls exclusively as a result of a proportional reduction in lean, not fat, mass. Fast- and slow-twitch muscle atrophy in Tg rats did not result from a reduction in the in vivo-determined rate of protein synthesis. In contrast, urinary excretion of 3-methylhistidine, as well as the content of atrogin-1 and the 14-kDa actin fragment, was elevated in gastrocnemius of Tg rats, suggesting increased muscle proteolysis. Similarly, Tg rats had reduced cardiac mass, which was independent of a change in protein synthesis. This decreased cardiac mass was associated with a reduction in stroke volume, but cardiac output was maintained by a compensatory increase in heart rate. The HIV-induced muscle atrophy was associated with increased whole body energy expenditure, which was not due to an elevated body temperature or secondary bacterial infection. Furthermore, the atrophic response could not be attributed to the development of insulin resistance, decreased levels of circulating amino acids, or increased tissue cytokines. However, skeletal muscle and, to a lesser extent, circulating insulin-like growth factor I was reduced in Tg rats. Although hepatic injury was implicated by increased plasma levels of aspartate and alanine aminotransferases, hepatic protein synthesis was not different between control and Tg rats. Hence, HIV-1 Tg rats develop atrophy of cardiac and skeletal muscle, the latter of which results primarily from an increased protein degradation and may be related to the marked reduction in muscle insulin-like growth factor I.
Pruznak
Anne M
AM
Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
Hong-Brown
Ly
L
Lantry
Rachel
R
She
Pengxiang
P
Frost
Robert A
RA
Vary
Thomas C
TC
Lang
Charles H
CH
D000596:Amino Acids / Q000097:blood; D000818:Animals; D030801:Animals, Genetically Modified; D001284:Atrophy / Q000473:pathology; D015152:Blotting, Northern; D001823:Body Composition / Q000502:physiology; D001831:Body Temperature / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D002153:Calorimetry, Indirect; D016207:Cytokines / Q000378:metabolism; D004734:Energy Metabolism / Q000502:physiology; D019247:HIV Wasting Syndrome / Q000235:genetics* / Q000473:pathology*; D015497:HIV-1 / Q000235:genetics*; D054298:Human Immunodeficiency Virus Proteins / Q000096:biosynthesis / Q000235:genetics; D007328:Insulin / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D007668:Kidney / Q000503:physiopathology; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis; D018482:Muscle, Skeletal / Q000473:pathology*; D009135:Muscular Diseases / Q000235:genetics* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000473:pathology*; D023282:Nuclease Protection Assays; D009929:Organ Size / Q000502:physiology; D051381:Rats; D011916:Rats, Inbred F344
D000596:Amino Acids; D016207:Cytokines; D054298:Human Immunodeficiency Virus Proteins; D007328:Insulin; D009124:Muscle Proteins; D007334:Insulin-Like Growth Factor I