coq7/clk-1 regulates mitochondrial respiration and the generation of reactive oxygen species via coenzyme Q

Coenzyme Q homeostasis in aging: Response to non-genetic interventions

Coenzyme Q (CoQ) is a key component for many essential metabolic and antioxidant activities in cells in mitochondria and cell membranes. Mitochondrial dysfunction is one of the hallmarks of aging and age-related diseases. Deprivation of CoQ during aging can be the cause or the consequence of this mitochondrial dysfunction. In any case, it seems clear that aging-associated CoQ deprivation accelerates mitochondrial dysfunction in these diseases. Non-genetic prolongevity interventions, including CoQ dietary supplementation, can increase CoQ levels in mitochondria and cell membranes improving mitochondrial activity and delaying cell and tissue deterioration by oxidative damage. In this review, we discuss the importance of CoQ deprivation in aging and age-related diseases and the effect of prolongevity interventions on CoQ levels and synthesis and CoQ-dependent antioxidant activities.

Elevated mitochondrial DNA copy number found in ubiquinone-deficient clk-1 mutants is not rescued by ubiquinone precursor 2-4-dihydroxybenzoate

Inside mitochondria reside semi-autonomous genomes, called mtDNA. mtDNA is multi-copy per cell and mtDNA copy number can vary from hundreds to thousands of copies per cell. The variability of mtDNA copy number between tissues, combined with the lack of variability of copy number within a tissue, suggest a homeostatic copy number regulation mechanism. Mutations in the gene encoding the Caenorhabditis elegans hydroxylase, CLK-1, result in elevated mtDNA. CLK-1's canonical role in ubiquinone biosynthesis results in clk-1 mutants lacking ubiquinone. Importantly, clk-1 mutants also exhibit slowed biological timing phenotypes (pharyngeal pumping, defecation, development) and an activated stress response (UPR^mt). These biological timing and stress phenotypes have been attributed to ubiquinone deficiency; however, it is unknown whether the mtDNA phenotype is also due to ubiquinone deficiency. To test this, in animals carrying the uncharacterized clk-1 (ok1247) mutant allele, we supplemented with an exogenous ubiquinone precursor 2-4-dihydroxybenzoate (DHB), which has previously been shown to restore ubiquinone biosynthesis. We measured phenotypes as a function of DHB across a log-scale range. Unlike the biological timing and stress phenotypes, the elevated mtDNA phenotype was not rescued. Since CLK-1's canonical role is in ubiquinone biosynthesis and DHB does not rescue mtDNA copy number, we infer CLK-1 has an additional function in homeostatic mtDNA copy number regulation.

Velvet antler methanol extracts (MEs) protects against oxidative stress in Caenorhabditis elegans by SKN-1

Velvet antler is one of the most important animal medicines or functional foods widely used in East Asia for many centuries, which has several biological activities including anti-ageing and health promotion. To date, the mechanism underlying these effects of velvet antler is widely studied by its protein or polypeptide components. Few studies have been reported for the function of the other components in velvet antler. Herein, C. elegans is used as the model animal to dissect how none protein components of velvet antler affect in vivo oxidative stress. Methanol extracts (MEs) from velvet antler which has few protein components extends the maximum lifespan of C. elegans compared to the control under oxidative stress, while water extracts (WEs) which is protein-rich component has no apparent function. The activity of MEs is mediated by clk-1 signaling pathway, but not via daf-2, eat-2 or glp-1 pathway. Further investigations show MEs decrease endogenous ROS by promoting SKN-1 nuclei translocation, subsequently up-regulating the expression of its target genes gst-4, gst-7 and gst-10 in C. elegans. In all, MEs, the none protein components of velvet antler, protects against oxidative stress in C. elegans, which indicates it might be a product with potential of being a curative medicine.

Metabolic Biomarkers in Nematode C. elegans During Aging

Changes in energy metabolism occur not only in diseases such as cancer but also in the normal development and aging processes of various organisms. These metabolic changes result to lead to imbalances in energy metabolism related to cellular and tissue homeostasis. In the model organism C. elegans, which is used to study aging, an imbalance in age-related energy metabolism exists between mitochondrial oxidative phosphorylation and aerobic glycolysis. Cellular lactate and pyruvate are key intermediates in intracellular energy metabolic pathways and can indicate age-related imbalances in energy metabolism. Thus, the cellular lactate/pyruvate ratio can be monitored as a biomarker during aging. Moreover, recent studies have proposed a candidate novel biomarker for aging and age-related declines in the nematode C. elegans.

Regulation of Age-related Decline by Transcription Factors and Their Crosstalk with the Epigenome

Aging is a complex phenomenon, where damage accumulation, increasing deregulation of biological pathways, and loss of cellular homeostasis lead to the decline of organismal functions over time. Interestingly, aging is not entirely a stochastic process and progressing at a constant rate, but it is subject to extensive regulation, in the hands of an elaborate and highly interconnected signaling network. This network can integrate a variety of aging-regulatory stimuli, i.e. fertility, nutrient availability, or diverse stresses, and relay them via signaling cascades into gene regulatory events - mostly of genes that confer stress resistance and thus help protect from damage accumulation and homeostasis loss. Transcription factors have long been perceived as the pivotal nodes in this network. Yet, it is well known that the epigenome substantially influences eukaryotic gene regulation, too. A growing body of work has recently underscored the importance of the epigenome also during aging, where it not only undergoes drastic age-dependent changes but also actively influences the aging process. In this review, we introduce the major signaling pathways that regulate age-related decline and discuss the synergy between transcriptional regulation and the epigenetic landscape.

Extended lifespan, reduced body size and leg skeletal muscle mass, and decreased mitochondrial function in clk-1 transgenic mice

Mutational inactivation of clk-1, which encodes an enzyme necessary for the biosynthesis of coenzyme Q (CoQ), extends the lifespan of Caenorhabditis elegans. However, whether mammalian clk-1 regulates the lifespan of mice is not known because clk-1-deficiencies are embryonic lethal. Here, we investigated the lifespan of clk-1 transgenic mice (Tg96/I), which were rescued from embryonic lethality via the transgenic expression of mouse clk-1. Tg96/I mice lived longer and had smaller bodies than wild-type mice, but Tg96/I mice had CoQ levels equivalent to wild-type mice. The small-sized Tg96/I mice exhibited reduced whole-body oxygen consumption (VO2) during the dark period, and lean leg skeletal muscles with reduced mitochondrial VO2 and ATP content compared with wild-type mice. These findings indicate a close relationship between lifespan extension and decreased mitochondrial function, which was induced by the transgenic expression of clk-1, in leg skeletal muscles that exhibit high metabolic activity.

The biochemistry and cell biology of aging: metabolic regulation through mitochondrial signaling

Cellular and organ metabolism affects organismal lifespan. Aging is characterized by increased risks for metabolic disorders, with age-associated degenerative diseases exhibiting varying degrees of mitochondrial dysfunction. The traditional view of the role of mitochondria generated reactive oxygen species (ROS) in cellular aging, assumed to be causative and simply detrimental for a long time now, is in need of reassessment. While there is little doubt that high levels of ROS are detrimental, mounting evidence points toward a lifespan extension effect exerted by mild to moderate ROS elevation. Dietary caloric restriction, inhibition of insulin-like growth factor-I signaling, and inhibition of the nutrient-sensing mechanistic target of rapamycin are robust longevity-promoting interventions. All of these appear to elicit mitochondrial retrograde signaling processes (defined as signaling from the mitochondria to the rest of the cell, for example, the mitochondrial unfolded protein response, or UPR(mt)). The effects of mitochondrial retrograde signaling may even spread to other cells/tissues in a noncell autonomous manner by yet unidentified signaling mediators. Multiple recent publications support the notion that an evolutionarily conserved, mitochondria-initiated signaling is central to the genetic and epigenetic regulation of cellular aging and organismal lifespan.

Exogenous administration of coenzyme Q10 restores mitochondrial oxygen consumption in the aged mouse brain

The level of coenzyme Q (CoQ) has been shown to decrease in an age-dependent manner in several types of animals. However, whether CoQ-dependent mitochondrial function decreases with aging remains unclear. In this study, we found that mitochondrial complexes I and II exhibited significantly reduced oxygen consumption in the brains of aged male mice relative to young male mice, although this decrease in oxygen consumption was not accompanied by a change in the CoQ9 or CoQ10 content. Nevertheless, the administration of exogenous CoQ10 significantly increased the content of CoQ10 and CoQ9 in the brain mitochondria of aged male mice and restored complex I- and II-mediated oxygen consumption to levels comparable to those observed in young mice. These results indicate that mitochondrial oxygen consumption in the brain decreases in aged male mice. Furthermore, these results suggest that exogenous CoQ10 restores mitochondrial oxygen use to levels equivalent to those observed in young mice.

Phenelzine mitochondrial functional preservation and neuroprotection after traumatic brain injury related to scavenging of the lipid peroxidation-derived aldehyde 4-hydroxy-2-nonenal

Phenelzine (PZ) is a scavenger of the lipid peroxidation (LP)-derived reactive aldehyde 4-hydroxynonenal (4-HNE) due to its hydrazine functional group, which can covalently react with 4-HNE. In this study, we first examined the ability of PZ to prevent the respiratory depressant effects of 4-HNE on normal isolated brain cortical mitochondria. Second, in rats subjected to controlled cortical impact traumatic brain injury (CCI-TBI), we evaluated PZ (10 mg/kg subcutaneously at 15 minutes after CCI-TBI) to attenuate 3-hour post-TBI mitochondrial respiratory dysfunction, and in separate animals, to improve cortical tissue sparing at 14 days. While 4-HNE exposure inhibited mitochondrial complex I and II respiration in a concentration-dependent manner, pretreatment with equimolar concentrations of PZ antagonized these effects. Western blot analysis demonstrated a PZ decrease in 4-HNE in mitochondrial proteins. Mitochondria isolated from peri-contusional brain tissue of CCI-TBI rats treated with vehicle at 15 minutes after injury showed a 37% decrease in the respiratory control ratio (RCR) relative to noninjured mitochondria. In PZ-treated rats, RCR suppression was prevented (P<0.05 versus vehicle). In another cohort, PZ administration increased spared cortical tissue from 86% to 97% (P<0.03). These results suggest that PZ's neuroprotective effect is due to mitochondrial protection by scavenging of LP-derived 4-HNE.

Tissue-specific oxidative stress and loss of mitochondria in CoQ-deficient Pdss2 mutant mice

Primary human CoQ(10) deficiencies are clinically heterogeneous diseases caused by mutations in PDSS2 and other genes required for CoQ(10) biosynthesis. Our in vitro studies of PDSS2 mutant fibroblasts, with <20% CoQ(10) of control cells, revealed reduced activity of CoQ(10)-dependent complex II+III and ATP synthesis, without amplification of reactive oxygen species (ROS), markers of oxidative damage, or antioxidant defenses. In contrast, COQ2 and ADCK3 mutant fibroblasts, with 30-50% CoQ(10) of controls, showed milder bioenergetic defects but significantly increased ROS and oxidation of lipids and proteins. We hypothesized that absence of oxidative stress markers and cell death in PDSS2 mutant fibroblasts were due to the extreme severity of CoQ(10) deficiency. Here, we have investigated in vivo effects of Pdss2 deficiency in affected and unaffected organs of CBA/Pdss2(kd/kd) mice at presymptomatic, phenotypic-onset, and end-stages of the disease. Although Pdss2 mutant mice manifest widespread CoQ(9) deficiency and mitochondrial respiratory chain abnormalities, only affected organs show increased ROS production, oxidative stress, mitochondrial DNA depletion, and reduced citrate synthase activity, an index of mitochondrial mass. Our data indicate that kidney-specific loss of mitochondria triggered by oxidative stress may be the cause of renal failure in Pdss2(kd/kd) mice.

Effects of inhibiting CoQ10 biosynthesis with 4-nitrobenzoate in human fibroblasts

Coenzyme Q₁₀ (CoQ₁₀) is a potent lipophilic antioxidant in cell membranes and a carrier of electrons in the mitochondrial respiratory chain. We previously characterized the effects of varying severities of CoQ₁₀ deficiency on ROS production and mitochondrial bioenergetics in cells harboring genetic defects of CoQ₁₀ biosynthesis. We observed a unimodal distribution of ROS production with CoQ₁₀ deficiency: cells with <20% of CoQ₁₀ and 50–70% of CoQ₁₀ did not generate excess ROS while cells with 30–45% of CoQ₁₀ showed increased ROS production and lipid peroxidation. Because our previous studies were limited to a small number of mutant cell lines with heterogeneous molecular defects, here, we treated 5 control and 2 mildly CoQ₁₀ deficient fibroblasts with varying doses of 4-nitrobenzoate (4-NB), an analog of 4-hydroxybenzoate (4-HB) and inhibitor of 4-para-hydroxybenzoate:polyprenyl transferase (COQ2) to induce a range of CoQ₁₀ deficiencies. Our results support the concept that the degree of CoQ₁₀ deficiency in cells dictates the extent of ATP synthesis defects and ROS production and that 40–50% residual CoQ₁₀ produces maximal oxidative stress and cell death.

Calorie restriction modifies ubiquinone and COQ transcript levels in mouse tissues

We studied ubiquinone (Q), Q homologue ratio, and steady-state levels of mCOQ transcripts in tissues from mice fed ad libitum or under calorie restriction. Maximum ubiquinone levels on a protein basis were found in kidney and heart, followed by liver, brain, and skeletal muscle. Liver and skeletal muscle showed the highest Q(9)/Q(10) ratios with significant interindividual variability. Heart, kidney, and particularly brain exhibited lower Q(9)/Q(10) ratios and interindividual variability. In skeletal muscle and heart, the most abundant mCOQ transcript was mCOQ7, followed by mCOQ8, mCOQ2, mPDSS2, mPDSS1, and mCOQ3. In nonmuscular tissues (liver, kidney, and brain) the most abundant mCOQ transcript was mCOQ2, followed by mCOQ7, mCOQ8, mPDSS1, mPDSS2, and mCOQ3. Calorie restriction increased both ubiquinone homologues and mPDSS2 mRNA in skeletal muscle, but mCOQ7 was decreased. In contrast, Q(9) and most mCOQ transcripts were decreased in heart. Calorie restriction also modified the Q(9)/Q(10) ratio, which was increased in kidney and decreased in heart without alterations in mPDSS1 or mPDSS2 transcripts. We demonstrate for the first time that unique patterns of mCOQ transcripts exist in muscular and nonmuscular tissues and that Q and COQ genes are targets of calorie restriction in a tissue-specific way.

Reactive metabolites and AGE/RAGE-mediated cellular dysfunction affect the aging process: a mini-review

Aging is a dynamic process in which its rate and subsequent longevity of an organism are dependent upon the balance between the reactive intermediates of normal cellular metabolism and the ability of the body to reduce these by-products through a multifaceted antioxidant defence system. Every disturbance of this balance constitutes a clear and present danger to the macromolecular integrity of the body. When defence mechanisms become diminished or impaired, the resulting imbalance results in accumulation of endogenous agents, such as reactive oxygen and carbonyl species, and a state of increased cellular stress, which can accelerate the rate of aging. Glycation is the non-enzymatic glycosylation of proteins, nucleotides and lipids by saccharide derivatives. Glucose and other reducing sugars are important glycating agents, but the most reactive physiological relevant glycating agents, are the dicarbonyls, in particular methylglyoxal. Endogenously formed dicarbonyl compounds can react with proteins to form advanced glycation endproducts (AGEs). Experimental models have recently provided evidence that reduced detoxification of AGE precursors by the glyoxalase system, engagement of the cellular receptor RAGE and RAGE-dependent sustained activation of the pro-inflammatory transcription factor nuclear factor κB might significantly contribute to the rate of aging and the onset of age-related neurodegenerative, musculoskeletal and vascular diseases.

Multiple measures of functionality exhibit progressive decline in a parallel, stochastic fashion in Drosophila Sod2 null mutants

Oxidative damage has been proposed as an important factor in the progression of pathological and non-pathological age-related functional declines. Here, we examine functional deterioration in short-lived flies mutant for the mitochondrial antioxidant Manganese Superoxide Dismutase (Sod2). We find that the decline of several functional measures of aging occurs, in an accelerated fashion, in Sod2 mutants. Olfactory behavior, locomotor ability and cardiac performance were all seen to decline rapidly in Sod2 mutants. On average, functional declines in Sod2 mutants occur in a pattern similar to that seen in late-life Drosophila with a normal complement of Sod2. In longitudinal experiments, however, we find that functional failures occur in every possible sequence in Sod2 mutants. Significantly, failure of these functional measures is not irreversible, as spontaneous functional recovery was sometimes observed. These findings support a model where ROS-related damage strikes at multiple organ systems in parallel, rather than a "chain of dominos" model, in which primary organ failure contributes to the deterioration of further organ systems.

Cognitive performance and age-related changes in the hippocampal proteome

Declining cognitive performance is associated with increasing age, even in the absence of overt pathological processes. We and others have reported that declining cognitive performance is associated with age-related changes in brain glucose utilization, long-term potentiation and paired-pulse facilitation, protein expression, neurotransmitter levels, and trophic factors. However, it is unclear whether these changes are causes or symptoms of the underlying alterations in dendritic and synaptic morphology that occur with age. In this study, we examined the hippocampal proteome for age- and cognition-associated changes in behaviorally stratified young and old rats, using two-dimensional in-gel electrophoresis and MS/MS. Comparison of old cognitively intact with old cognitively impaired animals revealed additional changes that would not have been detected otherwise. Interestingly, not all age-related changes in protein expression were associated with cognitive decline, and distinct differences in protein expression were found when comparing old cognitively intact with old cognitively impaired rats. A large number of protein changes with age were related to the glycolysis/gluconeogenesis pathway. In total, the proteomic changes suggest that age-related alterations act synergistically with other perturbations to result in cognitive decline. This study also demonstrates the importance of examining behaviorally-defined animals in proteomic studies, as comparison of young to old animals regardless of behavioral performance would have failed to detect many cognitive impairment-specific protein expression changes evident when behavioral stratification data were used.

How to live long and prosper: autophagy, mitochondria, and aging

Autophagy is a process of cellular self-degradation in which portions of the cytoplasm are sequestered within cytosolic double-membrane vesicles and delivered to the lysosome/vacuole. This process occurs in all eukaryotic cells and is partly a stress response; autophagy is induced during starvation and hypoxia. However, autophagy also plays a role during development and is associated with a range of diseases. Accumulating data also suggest the involvement of autophagy in aging. For example, the role of various hormones and nutrient sensing pathways in life span extension may involve autophagy. Similarly, autophagy is the primary mechanism for removing damaged organelles, such as mitochondria, which may have a direct impact on aging. Here, we review the role of autophagy, with an emphasis on the signaling pathways that are involved in regulation, and the consequences of autophagy induction with regard to aging.

Effect of thyroid hormone on mitochondrial properties and oxidative stress in cells from patients with mtDNA defects

Mitochondrial (mt)DNA mutations contribute to various disease states characterized by low ATP production. In contrast, thyroid hormone [3,3',5-triiodothyronine (T(3))] induces mitochondrial biogenesis and enhances ATP generation within cells. To evaluate the role of T(3)-mediated mitochondrial biogenesis in patients with mtDNA mutations, three fibroblast cell lines with mtDNA mutations were evaluated, including two patients with Leigh's syndrome and one with hypertrophic cardiomyopathy. Compared with control cells, patient fibroblasts displayed similar levels of mitochondrial mass, peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha), mitochondrial transcription factor A (Tfam), and uncoupling protein 2 (UCP2) protein expression. However, patient cells exhibited a 1.6-fold elevation in ROS production, a 1.7-fold elevation in cytoplasmic Ca2+ levels, a 1.2-fold elevation in mitochondrial membrane potential, and 30% less complex V activity compared with control cells. Patient cells also displayed 20-25% reductions in both cytochrome c oxidase (COX) activity and MnSOD protein levels compared with control cells. After T(3) treatment of patient cells, ROS production was decreased by 40%, cytoplasmic Ca2+ was reduced by 20%, COX activity was increased by 1.3-fold, and ATP levels were elevated by 1.6-fold, despite the absence of a change in mitochondrial mass. There were no significant alterations in the protein expression of PGC-1alpha, Tfam, or UCP2 in either T(3)-treated patient or control cells. However, T(3) restored the mitochondrial membrane potential, complex V activity, and levels of MnSOD to normal values in patient cells and elevated MnSOD levels by 21% in control cells. These results suggest that T(3) acts to reduce cellular oxidative stress, which may help attenuate ROS-mediated damage, along with improving mitochondrial function and energy status in cells with mtDNA defects.

Maternal cocaine administration in mice alters DNA methylation and gene expression in hippocampal neurons of neonatal and prepubertal offspring

Previous studies documented significant behavioral changes in the offspring of cocaine-exposed mothers. We now explore the hypothesis that maternal cocaine exposure could alter the fetal epigenetic machinery sufficiently to cause lasting neurochemical and functional changes in the offspring. Pregnant CD1 mice were administered either saline or 20 mg/kg cocaine twice daily on gestational days 8–19. Male pups from each of ten litters of the cocaine and control groups were analyzed at 3 (P3) or 30 (P30) days postnatum. Global DNA methylation, methylated DNA immunoprecipitation followed by CGI² microarray profiling and bisulfite sequencing, as well as quantitative real-time RT-PCR gene expression analysis, were evaluated in hippocampal pyramidal neurons excised by laser capture microdissection. Following maternal cocaine exposure, global DNA methylation was significantly decreased at P3 and increased at P30. Among the 492 CGIs whose methylation was significantly altered by cocaine at P3, 34% were hypermethylated while 66% were hypomethylated. Several of these CGIs contained promoter regions for genes implicated in crucial cellular functions. Endogenous expression of selected genes linked to the abnormally methylated CGIs was correspondingly decreased or increased by as much as 4–19-fold. By P30, some of the cocaine-associated effects at P3 endured, reversed to opposite directions, or disappeared. Further, additional sets of abnormally methylated targets emerged at P30 that were not observed at P3. Taken together, these observations indicate that maternal cocaine exposure during the second and third trimesters of gestation could produce potentially profound structural and functional modifications in the epigenomic programs of neonatal and prepubertal mice.

Glyoxalase-1 prevents mitochondrial protein modification and enhances lifespan in Caenorhabditis elegans

Studies of mutations affecting lifespan in Caenorhabditis elegans show that mitochondrial generation of reactive oxygen species (ROS) plays a major causative role in organismal aging. Here, we describe a novel mechanism for regulating mitochondrial ROS production and lifespan in C. elegans: progressive mitochondrial protein modification by the glycolysis-derived dicarbonyl metabolite methylglyoxal (MG). We demonstrate that the activity of glyoxalase-1, an enzyme detoxifying MG, is markedly reduced with age despite unchanged levels of glyoxalase-1 mRNA. The decrease in enzymatic activity promotes accumulation of MG-derived adducts and oxidative stress markers, which cause further inhibition of glyoxalase-1 expression. Over-expression of the C. elegans glyoxalase-1 orthologue CeGly decreases MG modifications of mitochondrial proteins and mitochondrial ROS production, and prolongs C. elegans lifespan. In contrast, knock-down of CeGly increases MG modifications of mitochondrial proteins and mitochondrial ROS production, and decreases C. elegans lifespan.

Oxidative stress causes heart failure with impaired mitochondrial respiration

Elderly people insidiously manifest the symptoms of heart failure, such as dyspnea and/or physical disabilities in an age-dependent manner. Although previous studies suggested that oxidative stress plays a pathological role in the development of heart failure, no direct evidence has been documented so far. In order to investigate the pathological significance of oxidative stress in the heart, we generated heart/muscle-specific manganese superoxide dismutase-deficient mice. The mutant mice developed progressive congestive heart failure with specific molecular defects in mitochondrial respiration. In this paper, we showed for the first time that the oxidative stress caused specific morphological changes of mitochondria, excess formation of superoxide (O(2)(*)(-)), reduction of ATP, and transcriptional alterations of genes associated with heart failure in respect to cardiac contractility. Accordingly, administration of a superoxide dismutase mimetic significantly ameliorated the symptoms. These results implied that O(2)(*)(-) generated in mitochondria played a pivotal role in the development and progression of heart failure. We here present a bona fide model for human cardiac failure with oxidative stress valuable for therapeutic interventions.

Genetic and molecular characterization of CLK-1/mCLK1, a conserved determinant of the rate of aging

The clk-1 gene of the nematode Caenorhabditis elegans encodes an evolutionarily conserved enzyme that is necessary for ubiquinone biosynthesis. Loss-of-function mutations in clk-1, as well as in its mouse orthologue mclk1, increase lifespan in both organisms. In nematodes, clk-1 extends lifespan by a mechanism that is distinct from the insulin signaling-like pathway but might have similarities to calorie restriction. The evolutionary conservation of the effect of clk-1/mclk1 on lifespan suggests that the gene affects a fundamental mechanism of aging. The clk-1/mclk1 system could allow for the understanding of this mechanism by combining genetic and molecular investigations in worms with studies in mice, where age-dependent disease processes relevant to human health can be modeled.

Fenofibrate activates the biochemical pathways and the de novo expression of genes related to lipid handling and uncoupling protein-3 functions in liver of normal rats

Fibrates (anti-hyperlipidemic agents) enhance the mRNA expression of uncoupling protein 2 (UCP2) in the liver and that of uncoupling protein 3 (UCP3) in skeletal muscle in standard-diet-fed rats and induce a de novo expression of UCP3 (mRNA and protein) in the liver of high-fat-fed rats. Here, we report that in the liver of normal rats, fenofibrate induces a de novo expression of UCP3 and a 6-fold increase in UCP2 mRNA, whereas UCP2 protein was not detectable. Indeed, we evidenced an ORF in UCP2 exon 2 potentially able to inhibit the expression of the protein. Fenofibrate increases the expression and activity of hepatic enzymes and cofactors involved in lipid handling and UCP3 activity and, as is the case for UCP3, induces other muscle-specific genes (e.g., Carnitine palmitoyl transferase 1b and Ubiquinone biosynthesis protein COQ7 homolog). In addition, we demonstrated that in mitochondria from fenofibrate-treated rats a palmitoyl-carnitine-induced GDP-sensitive uncoupling takes place, involving UCP3 rather than other uncouplers (i.e., UCP2 and Adenine Nucleotide Translocase). Thus, the liver of fenofibrate-treated standard-diet- fed rat is a useful model for investigations of the biochemical functions of UCP3 and allowed us to demonstrate that fenofibrate programs a gene-expression pattern able to modulate lipid handling and UCP3 activation.

Coq3 and Coq4 define a polypeptide complex in yeast mitochondria for the biosynthesis of coenzyme Q

Coenzyme Q (Q) is a redox active lipid essential for aerobic respiration in eukaryotes. In Saccharomyces cerevisiae at least eight mitochondrial polypeptides, designated Coq1-Coq8, are required for Q biosynthesis. Here we present physical evidence for a coenzyme Q-biosynthetic polypeptide complex in isolated mitochondria. Separation of digitonin-solubilized mitochondrial extracts in one- and two-dimensional Blue Native PAGE analyses shows that Coq3 and Coq4 polypeptides co-migrate as high molecular mass complexes. Similarly, gel filtration chromatography shows that Coq1p, Coq3p, Coq4p, Coq5p, and Coq6p elute in fractions higher than expected for their respective subunit molecular masses. Coq3p, Coq4p, and Coq6p coelute with an apparent molecular mass exceeding 700 kDa. Coq3 O-methyltransferase activity, a surrogate for Q biosynthesis and complex activity, also elutes at this high molecular mass. We have determined the quinone content in lipid extracts of gel filtration fractions by liquid chromatography-tandem mass spectrometry and find that demethoxy-Q(6) is enriched in fractions with Coq3p. Co-precipitation of biotinylated-Coq3 and Coq4 polypeptide from digitonin-solubilized mitochondrial extracts shows their physical association. This study identifies Coq3p and Coq4p as defining members of a Q-biosynthetic Coq polypeptide complex.