Activation of mitochondrial-driven apoptosis in skeletal muscle cells is not mediated by reactive oxygen species production.

While the acquisition of apoptosis resistance is part of the differentiation program of skeletal muscle cells, differentiated muscle cells can undergo apoptosis in response to physiological or pathological stimuli. The generation of reactive oxygen species by mitochondria plays a major role in the control of apoptosis in many cell types. Indeed their involvement in controlling apoptosis in differentiated muscle cells, or in generating resistance to apoptosis remains unknown.

In vitro cytotoxicity and mitochondrial toxicity of tenofovir alone and in combination with other antiretrovirals in human renal proximal tubule cells.

We assessed the in vitro toxicity of tenofovir (TFV) and compared it with those of zidovudine (AZT), didanosine (ddI), ritonavir (RTV), and lopinavir (LPV) alone and in combination in human renal proximal tubule epithelial cells (RPTECs). The cells were treated with various concentrations and combinations of the tested antiretrovirals for up to 22 days, and cytotoxicity was determined. In addition, we assessed the levels of mitochondrial DNA (mtDNA) and cytochrome oxidase II (COII) mRNA in RPTECs treated with reverse transcriptase inhibitors.

Developmental and tissue-specific involvement of peroxisome proliferator-activated receptor-alpha in the control of mouse uncoupling protein-3 gene expression.

Uncoupling protein-3 (UCP3) is a member of the mitochondrial carrier family expressed preferentially in skeletal muscle and heart. It appears to be involved in metabolic handling of fatty acids in a way that minimizes excessive production of reactive oxygen species. Fatty acids are powerful regulators of UCP3 gene transcription.

Altered expression of master regulatory genes of adipogenesis in lipomas from patients bearing tRNA(Lys) point mutations in mitochondrial DNA.

The mechanisms underlying the appearance of lipomas in patients bearing mutations in the tRNA(Lys) gene of mitochondrial DNA are unknown. We investigated changes in gene expression patterns in lipomas from three patients bearing A8344G or G8363A tRNA(Lys) gene mutations. Uncoupling protein-1 mRNA was detected in the lipomas, in contrast with undetectable expression in normal adipose tissue.

Thiazolidinediones and rexinoids induce peroxisome proliferator-activated receptor-coactivator (PGC)-1alpha gene transcription: an autoregulatory loop controls PGC-1alpha expression in adipocytes via peroxisome proliferator-activated receptor-gamma coactivation.

Thiazolidinediones (TZDs) are insulin-sensitizing drugs currently used to treat type 2 diabetes. They are activators of peroxisome proliferator-activated receptor (PPAR)-gamma, and adipose tissue constitutes a major site for their biological effects. PPAR coactivator (PGC)-1alpha is a transcriptional coactivator of PPARgamma and other transcription factors.

In vivo effects of highly active antiretroviral therapies containing the protease inhibitor nelfinavir on mitochondrially driven apoptosis.

Background: In vitro studies have reported controversial effects of protease inhibitors (PIs) on mitochondrially driven apoptosis. Additionally, since PIs in the clinical setting are almost always given in combination with nucleoside analogues, which may have negative effects on mitochondrial DNA (mtDNA), the impact of PI-containing highly active antiretroviral therapy (HAART) on apoptosis and mtDNA content is unclear.

Patients And Methods: A cross-sectional study was performed including 20 HIV-negative (HIV-) patients, 16 HIV-positive, antiretroviral-naive (HIV+) patients and 17 HIV-positive patients receiving the PI nelfinavir (NFV) plus zidovudine and lamivudine (AZT+3TC) or didanosine and stavudine (ddl+d4T)--collectively known as HIV+PI--as first-line antiretroviral treatment for at least 12 months.

Reverse transcriptase inhibitors alter uncoupling protein-1 and mitochondrial biogenesis in brown adipocytes.

Objective: Human adipose depots contain remnant brown adipocytes interspersed among white adipocytes, and disturbances of brown with respect to white adipocyte biology have been implicated in highly active antiretroviral therapy (HAART)-induced lipomatosis. Brown adipocytes express the uncoupling protein-1 (UCP1) and contain a large number of mitochondria, potential targets of HAART toxicity. The aim of this study was to evaluate the effects of reverse transcriptase inhibitors (RTIs) on primary brown adipocytes differentiated in culture.

Defective thermoregulation, impaired lipid metabolism, but preserved adrenergic induction of gene expression in brown fat of mice lacking C/EBPbeta.

C/EBPbeta (CCAAT/enhancer-binding protein beta) is a transcriptional regulator of the UCP1 (uncoupling protein-1) gene, the specific marker gene of brown adipocytes that is responsible for their thermogenic capacity. To investigate the role of C/EBPbeta in brown fat, we studied the C/EBPbeta-null mice. When placed in the cold, C/EBPbeta(-/-) mice did not maintain body temperature.

Lithium inhibits brown adipocyte differentiation.

Lithium impairs the appearance of the characteristic morphology of brown adipocytes and downregulates the expression of marker genes of brown adipocyte differentiation. These effects are dose-dependent and are more pronounced when exposure of preadipocytes to lithium is initiated at early stages of differentiation. Although lithium reduces the expression of genes common to both white and brown adipocytes [fatty acid binding protein aP2 (aP2/FABP) or peroxisome proliferating activated receptor gamma], genes expressed differentially in brown adipocytes, i.

Lipodystrophy associated with highly active anti-retroviral therapy for HIV infection: the adipocyte as a target of anti-retroviral-induced mitochondrial toxicity.

The lipodystrophy syndrome and associated metabolic alterations are the most prevalent adverse effects in HIV-infected patients taking highly active anti-retroviral therapy (HAART). This syndrome involves profound disturbances in adipose tissue. The toxic effect of nucleoside reverse transcriptase inhibitors on mitochondrial function is a major contributor to the lipodystrophy syndrome.

Thyroid hormones directly activate the expression of the human and mouse uncoupling protein-3 genes through a thyroid response element in the proximal promoter region.

The transcription of the human UCP3 (uncoupling protein-3) gene in skeletal muscle is tightly regulated by metabolic signals related to fatty acid availability. However, changes in thyroid status also modulate UCP3 gene expression, albeit by unknown mechanisms. We created transgenic mice bearing the entire human UCP3 gene to investigate the effect of thyroid hormones on human UCP3 gene expression.

Uncoupling protein-3 sensitizes cells to mitochondrial-dependent stimulus of apoptosis.

The mitochondrial uncoupling protein-3 is a member of the mitochondrial carrier protein family. As a homologue of the thermogenic brown fat uncoupling protein-1, it possesses a mitochondrial uncoupling activity and thus can influence cell energy metabolism but its exact biological function remains unclear. In the present study, uncoupling protein-3 was expressed in 293 cells using the tetracycline-inducible system and its impact on cell bioenergetics and responsiveness to the apoptotic stimulus was determined.

The developmental regulation of peroxisome proliferator-activated receptor-gamma coactivator-1alpha expression in the liver is partially dissociated from the control of gluconeogenesis and lipid catabolism.

The developmental regulation of peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha) gene expression was studied in mice and compared with that of marker genes of liver energy metabolism. The PGC-1alpha gene was highly expressed in fetal liver compared with that in adults and remained high in neonatal liver. The regulation of PGC-1alpha gene expression during the fetal and early neonatal periods was dissociated from that of gluconeogenic genes, i.

Retinoids and retinoid receptors in the control of energy balance: novel pharmacological strategies in obesity and diabetes.

Obesity and type II diabetes are closely related metabolic diseases with an increasing incidence worldwide. No clear-cut pharmacological treatment for these complex metabolic disturbances is available despite current efforts. New directions and perspectives for the pharmacological or nutritional treatment of these diseases should be defined.

Functional relationship between MyoD and peroxisome proliferator-activated receptor-dependent regulatory pathways in the control of the human uncoupling protein-3 gene transcription.

Uncoupling protein-3 (UCP3) gene is a member of the mitochondrial carrier superfamily preferentially expressed in skeletal muscle and up-regulated by fatty acids. Peroxisome proliferator-activated receptor (PPAR)alpha and PPARdelta (also known as PPARbeta) mediate human UCP3 gene regulation by fatty acids through a direct-repeat (DR-1) element in the promoter. DR-1 mutation renders UCP3 promoter unresponsive to PPAR ligand in vitro and consistently blocks gene induction by fatty acids in vivo.

Mitochondrial biogenesis in brown adipose tissue is associated with differential expression of transcription regulatory factors.

The differentiation of brown adipocytes during late fetal development or in cell culture is associated with enhanced mitochondrial biogenesis and increased gene expression for components of the respiratory chain/oxidative phosphorylation system. We have shown that this is due to a rise in mitochondrial DNA abundance and the corresponding increase in mitochondrial genome transcripts and gene products, as well as to the coordinate induction of nuclear-encoded genes for mitochondrial proteins. We studied how the expression of key components of the transcriptional regulation of mitochondrial biogenesis is regulated during this process.

The chlorophyll-derived metabolite phytanic acid induces white adipocyte differentiation.

Phytanic acid is a derivative of the phytol side-chain of chlorophyll. It appears in humans following the ingestion of fat-containing foods and is present in human blood at a low micromolar concentration. It may activate retinoid X receptors (RXR) or peroxisome proliferator-activated receptor (PPAR) alpha in vitro.

Phytanic acid, but not pristanic acid, mediates the positive effects of phytol derivatives on brown adipocyte differentiation.

The phytol derivatives phytanic acid and pristanic acid may activate nuclear hormone receptors and influence gene expression and cell differentiation. Phytanic acid induces brown adipocyte differentiation. It was determined that brown fat and brown adipocytes are sites of high gene expression of phytanoyl-CoA hydroxylase, the enzyme required for initiation of peroxisomal alpha-oxidation of phytanic acid.

Epitope mapping of mitochondrial adenine nucleotide translocase-1 in idiopathic dilated cardiomyopathy.

Mitochondrial adenine nucleotide translocase (ANT) is a specific target for the autoantibody response in idiopathic dilated cardiomyopathy (IDCM). We have undertaken an epitope analysis of ANT in IDCM by immunoblot with recombinant GST-ANT fusion proteins and with cellulose-bound decapeptides of human ANT1. Forty-five patients with IDCM, 17 patients with ischemic left ventricle dysfunction (LVD) and 20 controls were analyzed for circulating antibodies against ANT (AAb-ANT).

Mitochondrial biogenesis and thyroid status maturation in brown fat require CCAAT/enhancer-binding protein alpha.

Brown fat differentiation in mice is fully achieved in fetuses at term and entails the acquisition of not only adipogenic but also thermogenic and oxidative mitochondrial capacities. The present study of the mice homozygous for a deletion in the gene for CCAAT/enhancer-binding protein alpha (C/EBPalpha-null mice) demonstrates that C/EBPalpha is essential for all of these processes. Developing brown fat from C/EBPalpha-null mice showed a lack of uncoupling protein-1 expression, impaired adipogenesis, and reduced size and number of mitochondria per cell when compared with wild-type mice.

Phytanic acid, a novel activator of uncoupling protein-1 gene transcription and brown adipocyte differentiation.

Phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) is a phytol-derived branched-chain fatty acid present in dietary products. Phytanic acid increased uncoupling protein-1 (UCP1) mRNA expression in brown adipocytes differentiated in culture. Phytanic acid induced the expression of the UCP1 gene promoter, which was enhanced by co-transfection with a retinoid X receptor (RXR) expression vector but not with other expression vectors driving peroxisome proliferator-activated receptor (PPAR)alpha, PPARgamma or a form of RXR devoid of ligand-dependent sensitivity.

Overexpression of UCP3 in cultured human muscle lowers mitochondrial membrane potential, raises ATP/ADP ratio, and favors fatty acid vs. glucose oxidation.

The skeletal muscle mitochondrial uncoupling protein-3 (UCP3) promotes substrate oxidation, but direct evidence for its metabolic role is lacking. Here, we show that UCP3 overexpression in cultured human muscle cells decreased mitochondrial membrane potential (DYm). Despite this, the ATP content was not significantly decreased compared with control cells, whereas ADP content was reduced and thus the ATP/ADP ratio raised.

Gene expression of leptin and uncoupling proteins: molecular end-points of fetal development.

Uncoupling proteins (UCPs) are considered to be major determinants of energy expenditure in mammals. During development in rodents, the expression of the UCP genes occurs sequentially. UCP2 mRNA is expressed long before birth.

Differential regulation of expression of genes encoding uncoupling proteins 2 and 3 in brown adipose tissue during lactation in mice.

Thermogenic activity in brown adipose tissue (BAT) decreases during lactation; the down-regulation of the gene encoding uncoupling protein 1 (UCP1) is involved in this process. Our studies show that UCP2 mRNA expression does not change during the breeding cycle in mice. In contrast, UCP3 mRNA is down-regulated in lactation but it recovers after weaning, in parallel with UCP1 mRNA.