cell metabolism

This paper provides information sources and ideas for challenge and adventure activities. Main information sources are listed: libraries, ERIC, and several publishers and programs. Some useful publications are described that provide activities and ideas related to outdoor education, environmental issues, games, special populations, educational theory and practice, corporate experiential learning, facilitation, and adventure. Specific annual workshops in outdoor recreation and leadership are listed, as well as adventure organizations that offer training opportunities. Four sets of group activities for challenge and adventure programs are described: the spider's web, 2B or Knot 2B (group problem solving with ropes and knots), raccoon circles (group challenges using 1-inch tubular climbing webbing), and the lycra tube (group activities using five yards of lycra sewn into a tube). (SV)

The liking and selective ingestion of palatable foods-including sweets-is biologically controlled, and dysfunction of this regulation may promote unhealthy eating, obesity, and disease. The hepatokine fibroblast growth factor 21 (FGF21) reduces sweet consumption in rodents and primates, whereas knockout of Fgf21 increases sugar consumption in mice. To investigate the relevance of these findings in humans, we genotyped variants in the FGF21 locus in participants from the Danish Inter99 cohort (n = 6,514) and examined their relationship with a detailed range of food and ingestive behaviors. This revealed statistically significant associations between FGF21 rs838133 and increased consumption of candy, as well as nominal associations with increased alcohol intake and daily smoking. Moreover, in a separate clinical study, plasma FGF21 levels increased acutely after oral sucrose ingestion and were elevated in fasted sweet-disliking individuals. These data suggest the liver may secrete hor...

This paper discusses the topic of evaluating systems for health and entertainment when specifically targeting the older adult population. Building upon and extending on two previous studies that used a well-known discount usability evaluation method, heuristic evaluation, as well as a list of heuristics specifically created to evaluate smartphone apps that keep older adults' needs and characteristics in mind, this paper presents the assessment of the previous aggregated list of heuristics by ten experts after using it. Results show that the list of heuristics used in our previous studies does receive a positive assessment by the ten evaluators in terms of their appropriateness, completeness, usefulness, and clarity. Moreover, this paper reinforces that despite being a conventional and mature method, heuristic evaluation does offers valuable feedback regarding user interface flaws.

Highlights d Fifty percent of detected metabolites oscillate in mouse liver d Eighteen metabolites cycle in both liver and in the cellautonomous U2 OS system d These oscillations in the U2 OS system are driven by core clock genes d Genetic perturbation of CRY1 decouples transcriptional and metabolite rhythms

Resveratrol induces mitochondrial biogenesis and protects against metabolic decline but whether SIRT1 mediates these benefits is the subject of debate. To circumvent the developmental defects of germ-line SIRT1 knockouts, we have developed the first inducible system that permits wholebody deletion of SIRT1 in adult mice. Mice treated with a moderate dose of resveratrol showed increased mitochondrial biogenesis and function, AMPK activation and increased NAD + levels in skeletal muscle, whereas SIRT1 knockouts displayed none of these benefits. A mouse overexpressing SIRT1 mimicked these effects. A high dose of resveratrol activated AMPK in a SIRT1-independent manner, demonstrating that resveratrol dosage is a critical factor. Importantly, at both doses of resveratrol no improvements in mitochondrial function were observed in animals lacking SIRT1. Together these data indicate that SIRT1 plays an essential role in the ability of

NAD(+) availability decreases with age and in certain disease conditions. Nicotinamide mononucleotide (NMN), a key NAD(+) intermediate, has been shown to enhance NAD(+) biosynthesis and ameliorate various pathologies in mouse disease models. In this study, we conducted a 12-month-long NMN administration to regular chow-fed wild-type C57BL/6N mice during their normal aging. Orally administered NMN was quickly utilized to synthesize NAD(+) in tissues. Remarkably, NMN effectively mitigates age-associated physiological decline in mice. Without any obvious toxicity or deleterious effects, NMN suppressed age-associated body weight gain, enhanced energy metabolism, promoted physical activity, improved insulin sensitivity and plasma lipid profile, and ameliorated eye function and other pathophysiologies. Consistent with these phenotypes, NMN prevented age-associated gene expression changes in key metabolic organs and enhanced mitochondrial oxidative metabolism and mitonuclear protein imbala...

Skeletal muscle must perform different kinds of work, and distinct fiber types have evolved to accommodate these. Previous work had shown that the transcriptional coactivator PGC-1a drives the formation of type I and IIA muscle fibers, which are ''slow-twitch'' and highly oxidative. We show here that transgenic expression of PGC-1b, a coactivator functionally similar to but distinct from PGC-1a, causes a marked induction of IIX fibers, which are oxidative but have ''fast-twitch'' biophysical properties. PGC-1b coactivates the MEF2 family of transcription factors to stimulate the type IIX myosin heavy chain (MHC) promoter. PGC-1b transgenic muscle fibers are rich in mitochondria and are highly oxidative, at least in part due to coactivation by PGC-1b of ERRa and PPARa. Consequently, these transgenic animals can run for longer and at higher work loads than wild-type animals. Together, these data indicate that PGC-1b drives the formation of highly oxidative fibers containing type IIX MHC.

This paper discusses the topic of evaluating systems for health and entertainment when specifically targeting the older adult population. Building upon and extending on two previous studies that used a well-known discount usability evaluation method, heuristic evaluation, as well as a list of heuristics specifically created to evaluate smartphone apps that keep older adults' needs and characteristics in mind, this paper presents the assessment of the previous aggregated list of heuristics by ten experts after using it. Results show that the list of heuristics used in our previous studies does receive a positive assessment by the ten evaluators in terms of their appropriateness, completeness, usefulness, and clarity. Moreover, this paper reinforces that despite being a conventional and mature method, heuristic evaluation does offers valuable feedback regarding user interface flaws.

Peripheral processes that mediate beneficial effects of exercise on the brain remain sparsely explored. Here, we show that a muscle secretory factor, cathepsin B (CTSB) protein, is important for the cognitive and neurogenic benefits of running. Proteomic analysis revealed elevated levels of CTSB in conditioned medium derived from skeletal muscle cell cultures treated with AMP-kinase agonist AICAR. Consistently, running increased CTSB levels in mouse gastrocnemius muscle and plasma. Furthermore, recombinant CTSB application enhanced expression of brain-derived neurotrophic factor (BDNF) and doublecortin (DCX) in adult hippocampal progenitor cells through a mechanism dependent on the multifunctional protein P11. In vivo, in CTSB knockout (KO) mice, running did not enhance adult hippocampal neurogenesis and spatial memory function. Interestingly, in Rhesus monkeys and humans, treadmill exercise elevated CTSB in plasma. In humans, changes in CTSB levels correlated with fitness and hippo...

Animals require an immediate response to oxygen availability to allow rapid shifts between oxidative and glycolytic metabolism. These metabolic shifts are highly regulated by the HIF transcription factor. The factor inhibiting HIF (FIH) is an asparaginyl hydroxylase that controls HIF transcriptional activity in an oxygen-dependent manner. We show here that FIH loss increases oxidative metabolism, while also increasing glycolytic capacity, and that this gives rise to an increase in oxygen consumption. We further show that the loss of FIH acts to accelerate the cellular metabolic response to hypoxia. Skeletal muscle expresses 50-fold higher levels of FIH than other tissues: we analyzed skeletal muscle FIH mutants and found a decreased metabolic efficiency, correlated with an increased oxidative rate and an increased rate of hypoxic response. We find that FIH, through its regulation of oxidation, acts in concert with the PHD/vHL pathway to accelerate HIF-mediated metabolic responses to...

The liver and intestine play crucial roles in maintaining bile acid homeostasis. Here, we demonstrate that fibroblast growth factor 15 (FGF15) signals from intestine to liver to repress the gene encoding cholesterol 7α-hydroxylase (CYP7A1), which catalyzes the first and rate-limiting step in the classical bile acid synthetic pathway. FGF15 expression is stimulated in the small intestine by the nuclear bile acid receptor FXR and represses Cyp7a1 in liver through a mechanism that involves FGF receptor 4 (FGFR4) and the orphan nuclear receptor SHP. Mice lacking FGF15 have increased hepatic CYP7A1 mRNA and protein levels and corresponding increases in CYP7A1 enzyme activity and fecal bile acid excretion. These studies define FGF15 and FGFR4 as components of a gut-liver signaling pathway that synergizes with SHP to regulate bile acid synthesis.

Bacterial biofilms in the colon alter the host tissue microenvironment. A role for biofilms in colon cancer metabolism has been suggested but to date has not been evaluated. Using metabolomics, we investigated the metabolic influence that microbial biofilms have on colon tissues and the related occurrence of cancer. Patient-matched colon cancers and histologically normal tissues,

Indirect evidence from human studies suggests that brown adipose tissue (BAT) thermogenesis is fueled predominantly by fatty acids hydrolyzed from intracellular triglycerides (TGs). However, no direct experimental evidence to support this assumption currently exists in humans. The aim of this study was to determine the role of intracellular TG in BAT thermogenesis, in cold-exposed men. Using positron emission tomography with (11)C-acetate and (18)F-fluorodeoxyglucose, we showed that oral nicotinic acid (NiAc) administration, an inhibitor of intracellular TG lipolysis, suppressed the cold-induced increase in BAT oxidative metabolism and glucose uptake, despite no difference in BAT blood flow. There was a commensurate increase in shivering intensity and shift toward a greater reliance on glycolytic muscle fibers without modifying total heat production. Together, these findings show that intracellular TG lipolysis is critical for BAT thermogenesis and provides experimental evidence for...

Caloric restriction (CR) extends lifespan and delays the onset of age-related disorders in diverse species. Metabolic regulatory pathways have been implicated in the mechanisms of CR, but the molecular details have not been elucidated. Here, we show that CR engages RNA processing of genes associated with a highly integrated reprogramming of hepatic metabolism. We conducted molecular profiling of liver biopsies collected from adult male rhesus monkeys (Macaca mulatta) at baseline and after 2 years on control or CR (30% restricted) diet. Quantitation of over 20,000 molecules from the hepatic transcriptome, proteome, and metabolome indicated that metabolism and RNA processing are major features of the response to CR. Predictive models identified lipid, branched-chain amino acid, and short-chain carbon metabolic pathways, with alternate transcript use for over half of the genes in the CR network. We conclude that RNA-based mechanisms are central to the CR response and integral in metabo...

The Cdk7/cyclin H/me ´nage-a `-trois 1 (MAT1) heterotrimer has proposed functions in transcription as the kinase component of basal transcription factor TFIIH and is activated in adult hearts by Gq-, calcineurin-, and biomechanical stress-dependent pathways for hypertrophic growth. Using cardiac-specific Cre, we have ablated MAT1 in myocardium. Despite reduced Cdk7 activity, MAT1-deficient hearts grew normally, but fatal heart failure ensued at 6-8 weeks. By microarray profiling, quantitative RT-PCR, and western blotting at 4 weeks, genes for energy metabolism were found to be suppressed selectively, including targets of peroxisome proliferator-activated receptor g coactivator 1 (PGC-1). Cardiac metabolic defects were substantiated in isolated perfused hearts and isolated mitochondria. In culture, deleting MAT1 with Cre disrupted PGC-1 function: PGC-1a failed to activate PGC-1-responsive promoters and nuclear receptors, GAL4-PGC-1a was functionally defective, and PGC-1b was likewise deficient. PGC-1 bound to both MAT1 and Cdk7 in coprecipitation assays. Thus, we demonstrate a requirement for MAT1 in the operation of PGC-1 coactivators that control cell metabolism.

Nitrate, an inorganic anion abundant in vegetables, is converted in vivo to bioactive nitrogen oxides including NO. We recently demonstrated that dietary nitrate reduces oxygen cost during physical exercise, but the mechanism remains unknown. In a double-blind crossover trial we studied the effects of a dietary intervention with inorganic nitrate on basal mitochondrial function and whole-body oxygen consumption in healthy volunteers. Skeletal muscle mitochondria harvested after nitrate supplementation displayed an improvement in oxidative phosphorylation efficiency (P/O ratio) and a decrease in state 4 respiration with and without atractyloside and respiration without adenylates. The improved mitochondrial P/O ratio correlated to the reduction in oxygen cost during exercise. Mechanistically, nitrate reduced the expression of ATP/ADP translocase, a protein involved in proton conductance. We conclude that dietary nitrate has profound effects on basal mitochondrial function. These findings may have implications for exercise physiology-and lifestyle-related disorders that involve dysfunctional mitochondria.

WNK1 and WNK4 mutations have been reported to cause pseudohypoaldosteronism type II (PHAII), an autosomal-dominant disorder characterized by hyperkalemia and hypertension. To elucidate the molecular pathophysiology of PHAII, we generated Wnk4 D561A/+ knockin mice presenting the phenotypes of PHAII. The knockin mice showed increased apical expression of phosphorylated Na-Cl cotransporter (NCC) in the distal convoluted tubules. Increased phosphorylation of the kinases OSR1 and SPAK was also observed in the knockin mice. Apical localization of the ROMK potassium channel and transepithelial Cl À permeability in the cortical collecting ducts were not affected in the knockin mice, whereas activity of epithelial Na + channels (ENaC) was increased. This increase, however, was not evident after hydrochlorothiazide treatment, suggesting that the regulation of ENaC was not a genetic but a secondary effect. Thus, the pathogenesis of PHAII caused by a missense mutation of WNK4 was identified to be increased function of NCC through activation of the OSR1/SPAK-NCC phosphorylation cascade.

The transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) regulates metabolic genes in skeletal muscle and contributes to the response of muscle to exercise. Muscle PGC-1α transgenic expression and exercise both increase the expression of thermogenic genes within white adipose. How the PGC-1α-mediated response to exercise in muscle conveys signals to other tissues remains incompletely defined. We employed a metabolomic approach to examine metabolites secreted from myocytes with forced expression of PGC-1α, and identified β-aminoisobutyric acid (BAIBA) as a small molecule myokine. BAIBA increases the expression of brown adipocyte-specific genes in white adipocytes and β-oxidation in hepatocytes both in vitro and in vivo through a PPARα-mediated mechanism, induces a brown adipose-like phenotype in human pluripotent stem cells, and improves glucose homeostasis in mice. In humans, plasma BAIBA concentrations are increased with exercise and ...

Since the presence of brown adipose tissue (BAT) was confirmed in adult humans, BAT has become a therapeutic target for obesity and insulin resistance. We examined whether human subcutaneous white adipose tissue (sWAT) can adopt a BAT-like phenotype using a clinical model of prolonged and severe adrenergic stress. sWAT samples were collected from severely burned and healthy individuals. A subset of burn victims were prospectively followed during their acute hospitalization. Browning of sWAT was determined by the presence of multilocular adipocytes, uncoupling protein 1 (UCP1), and increased mitochondrial density and respiratory capacity. Multilocular UCP1-positive adipocytes were found in sWAT samples from burn patients. UCP1 mRNA, mitochondrial density, and leak respiratory capacity in sWAT increased after burn trauma. Our data demonstrate that human sWAT can transform from an energy-storing to an energy-dissipating tissue, which opens new research avenues in our quest to prevent a...

The vagus nerve innervates visceral organs providing a link between key metabolic cues and the CNS. However, it is not clear whether vagal neurons can directly respond to changing lipid levels and whether altered ''lipid sensing'' by the vagus nerve regulates energy balance. In this study, we systematically profiled the expression of all known nuclear receptors in laser-captured nodose ganglion (NG) neurons. In particular, we found PPARg expression was reduced by high-fat-diet feeding. Deletion of PPARg in Phox2b neurons promoted HFD-induced thermogenesis that involved the reprograming of white adipocyte into a brown-like adipocyte cell fate. Finally, we showed that PPARg in NG neurons regulates genes necessary for lipid metabolism and those that are important for synaptic transmission. Collectively, our findings provide insights into how vagal afferents survey peripheral metabolic cues and suggest that the reduction of PPARg in NG neurons may serve as a protective mechanism against dietinduced weight gain.

Pathologic angiogenesis mediated by abnormally polarized macrophages plays a central role in common age-associated diseases such as atherosclerosis, cancer, and macular degeneration. Here we demonstrate that abnormal polarization in older macrophages is caused by programmatic changes that lead to reduced expression of ATP binding cassette transporter ABCA1. Downregulation of ABCA1 by microRNA-33 impairs the ability of macrophages to effectively efflux intracellular cholesterol, which in turn leads to higher levels of free cholesterol within senescent macrophages. Elevated intracellular lipid polarizes older macrophages to an abnormal, alternatively activated phenotype that promotes pathologic vascular proliferation. Mice deficient for Abca1, but not Abcg1, demonstrate an accelerated aging phenotype, whereas restoration of cholesterol efflux using LXR agonists or miR-33 inhibitors reverses it. Monocytes from older humans with age-related macular degeneration showed similar changes. These findings provide an avenue for therapeutic modulation of macrophage function in common age-related diseases. (F) Measurement of proliferation of HMVECs after incubation with DIO or control macrophages. (G and H) Representative illustration (G) and quantification of CNV (white circle) volume (H) demonstrated an inability of DIO macrophages to inhibit CNV as compared to controls. Values are expressed as mean + SE. Statistically significant difference, **p < 0.01, ***p < 0.001.

Glycogenin is considered essential for glycogen synthesis, as it acts as a primer for the initiation of the polysaccharide chain. Against expectations, glycogenin-deficient mice (Gyg KO) accumulate high amounts of glycogen in striated muscle. Furthermore, this glycogen contains no covalently bound protein, thereby demonstrating that a protein primer is not strictly necessary for the synthesis of the polysaccharide in vivo. Strikingly, in spite of the higher glycogen content, Gyg KO mice showed lower resting energy expenditure and less resistance than control animals when subjected to endurance exercise. These observations can be attributed to a switch of oxidative myofibers toward glycolytic metabolism. Mice overexpressing glycogen synthase in the muscle showed similar alterations, thus indicating that this switch is caused by the excess of glycogen. These results may explain the muscular defects of GSD XV patients, who lack glycogenin-1 and show high glycogen accumulation in muscle.

Endothelial dysfunction is a central hallmark of diabetes. The transcriptional coactivator PGC-1a is a powerful regulator of metabolism, but its role in endothelial cells remains poorly understood. We show here that endothelial PGC-1a expression is high in diabetic rodents and humans and that PGC-1a powerfully blocks endothelial migration in cell culture and vasculogenesis in vivo. Mechanistically, PGC-1a induces Notch signaling, blunts activation of Rac/Akt/eNOS signaling, and renders endothelial cells unresponsive to established angiogenic factors. Transgenic overexpression of PGC-1a in the endothelium mimics multiple diabetic phenotypes, including aberrant re-endothelialization after carotid injury, blunted wound healing, and reduced blood flow recovery after hindlimb ischemia. Conversely, deletion of endothelial PGC-1a rescues the blunted wound healing and recovery from hindlimb ischemia seen in type 1 and type 2 diabetes. Endothelial PGC-1a thus potently inhibits endothelial function and angiogenesis, and induction of endothelial PGC-1a contributes to multiple aspects of vascular dysfunction in diabetes.

The decline in early life mortality since the 1950s has resulted in dramatic demographic shift towards aged population. Aging manifests as a decline in health, multiple organ dysfunction and increased vulnerability to diseases, which degrades quality of life. A verity of genetic and pharmacological interventions, mostly from non-vertebrate models, have been identified that can enhance lifespan. Whether these interventions extend healthspan, the disease free and functional period of life, has only sometimes been tested and is often a matter of debate. Human aging indices have been developed to assess elements of functional decline with aging (e.g. sarcopenia, cognitive function). However, corresponding comprehensive indices in mice are seldom applied to aging studies. To probe the relationship between healthspan and lifespan extension in mammals, we performed a series of longitudinal, clinically-relevant healthspan measurements. Metabolism and aging are tightly connected and specific...

Highlights d CD38 levels increase in tissues with age and correlate with NAD decline d NAD and mitochondrial function are preserved in old CD38 knockout mice d CD38 metabolizes NMN in vivo and modulates the response to NAD-replacement therapy

Highlights d Mitochondrial dysfunction causes lysosomal storage disorder and sphingolipidosis d Respiration-impaired cells increase lysosomal compartment through TFEB d Mitochondrial control of lysosome function restrains inflammatory T cell responses d Restoration of NAD + levels improves lysosome function and inflammatory responses

Highlights d Mfn2 loss in neurons causes NMJ dysfunction and skeletal muscle atrophy d Mfn2 upregulation in neurons delays the disease onset in SOD1 G93A mice by 68 days d Mfn2 in neurons protects NMJs in ALS, during aging, and upon nerve injury d Mfn2 in neurons regulates axonal transport of calpastatin to protect NMJs

Brown adipose tissue (BAT) is an energy-dispensing thermogenic tissue that plays an important role in balancing energy metabolism. Lineage-tracing experiments indicate that brown adipocytes are derived from myogenic progenitors during embryonic development. However, adult skeletal muscle stem cells (satellite cells) have long been considered uniformly determined toward the myogenic lineage. Here, we report that adult satellite cells give rise to brown adipocytes and that microRNA-133 regulates the choice between myogenic and brown adipose determination by targeting the 3 0 UTR of Prdm16. Antagonism of microRNA-133 during muscle regeneration increases uncoupled respiration, glucose uptake, and thermogenesis in local treated muscle and augments whole-body energy expenditure, improves glucose tolerance, and impedes the development of diet-induced obesity. Finally, we demonstrate that miR-133 levels are downregulated in mice exposed to cold, resulting in de novo generation of satellite cell-derived brown adipocytes. Therefore, microRNA-133 represents an important therapeutic target for the treatment of obesity. Cell Metabolism MicroRNA-133 Regulates Brown Adipose Determination

Previous studies have suggested that insulin resistance develops secondary to diminished fat oxidation and resultant accumulation of cytosolic lipid molecules that impair insulin signaling. Contrary to this model, the present study used targeted metabolomics to find that obesity-related insulin resistance in skeletal muscle is characterized by excessive b-oxidation, impaired switching to carbohydrate substrate during the fasted-to-fed transition, and coincident depletion of organic acid intermediates of the tricarboxylic acid cycle. In cultured myotubes, lipid-induced insulin resistance was prevented by manipulations that restrict fatty acid uptake into mitochondria. These results were recapitulated in mice lacking malonyl-CoA decarboxylase (MCD), an enzyme that promotes mitochondrial b-oxidation by relieving malonyl-CoA-mediated inhibition of carnitine palmitoyltransferase 1. Thus, mcd À/À mice exhibit reduced rates of fat catabolism and resist diet-induced glucose intolerance despite high intramuscular levels of long-chain acyl-CoAs. These findings reveal a strong connection between skeletal muscle insulin resistance and lipid-induced mitochondrial stress.

Dysregulated mitophagy has been linked to Parkinson&#39;s disease (PD) due to the role of PTEN-induced kinase 1 (PINK1) in mediating depolarization-induced mitophagy in vitro. Elegant mouse reporters have revealed the pervasive nature of basal mitophagy in vivo, yet the role of PINK1 and tissue metabolic context remains unknown. Using mito-QC, we investigated the contribution of PINK1 to mitophagy in metabolically active tissues. We observed a high degree of mitophagy in neural cells, including PD-relevant mesencephalic dopaminergic neurons and microglia. In all tissues apart from pancreatic islets, loss of Pink1 did not influence basal mitophagy, despite disrupting depolarization-induced Parkin activation. Our findings provide the first in vivo evidence that PINK1 is detectable at basal levels and that basal mammalian mitophagy occurs independently of PINK1. This suggests multiple, yet-to-be-discovered pathways orchestrating mammalian mitochondrial integrity in a context-dependent ...

The triglycerides in chylomicrons are hydrolyzed by lipoprotein lipase (LpL) along the luminal surface of the capillaries. However, the endothelial cell molecule that facilitates chylomicron processing by LpL has not yet been defined. Here, we show that glycosylphosphatidylinositolanchored high density lipoprotein-binding protein 1 (GPIHBP1) plays a critical role in the lipolytic processing of chylomicrons. Gpihbp1-deficient mice exhibit a striking accumulation of chylomicrons in the plasma, even on a low-fat diet, resulting in milky plasma and plasma triglyceride levels as high as 5,000 mg/dl. Normally, Gpihbp1 is expressed highly in heart and adipose tissue, the same tissues that express high levels of LpL. In these tissues, GPIHBP1 is located on the luminal face of the capillary endothelium. Expression of GPIHBP1 in cultured cells confers the ability to bind both LpL and chylomicrons. These studies strongly suggest that GPIHBP1 is an important platform for the LpL-mediated processing of chylomicrons in capillaries.

Palmitic acid hydroxystearic acids (PAHSAs) are endogenous lipids with anti-diabetic and anti-inflammatory effects. PAHSA levels are reduced in serum and adipose tissue of insulin-resistant people and high-fat diet (HFD)-fed mice. Here, we investigated whether chronic PAHSA treatment enhances insulin sensitivity and which receptors mediate PAHSA effects. Chronic PAHSA administration in chow- and HFD-fed mice raises serum and tissue PAHSA levels ∼1.4- to 3-fold. This improves insulin sensitivity and glucose tolerance without altering body weight. PAHSA administration in chow-fed, but not HFD-fed, mice augments insulin and glucagon-like peptide (GLP-1) secretion. PAHSAs are selective agonists for GPR40, increasing Ca+2 flux, but not intracellular cyclic AMP. Blocking GPR40 reverses improvements in glucose tolerance and insulin sensitivity in PAHSA-treated chow- and HFD-fed mice and directly inhibits PAHSA augmentation of glucose-stimulated insulin secretion in human islets. In contras...

The evolutionarily conserved target of rapamycin (TOR) signaling controls growth, metabolism and aging. In the first robust demonstration of pharmacologically-induced life extension in a mammal, longevity was extended in mice treated with rapamycin, an inhibitor of mechanistic TOR (mTOR). However, detrimental metabolic effects of rapamycin treatment were also reported, presenting a paradox of improved survival despite metabolic impairment. How rapamycin extended lifespan in mice with such paradoxical effects was unclear. Here we show that detrimental effects of rapamycin treatment were only observed during the early stages of treatment. As the treatment continued for 20 weeks, these effects were reversed or diminished; the mice had better metabolic profiles, increased oxygen consumption and ketogenesis, and markedly enhanced insulin sensitivity. Thus, prolonged rapamycin treatment led to beneficial metabolic alterations, consistent with life extension previously observed. Our findings provide a likely explanation of the "rapamycin paradox" and support the potential causal importance of these metabolic alterations in longevity.

Inflammatory processes play an important role in the pathogenesis of vascular diseases, and insulin-resistant diabetes mellitus type 2 represents an important risk factor for the development of atherosclerosis. To directly address the role of insulin resistance in myeloid lineage cells in the development of atherosclerosis, we have created mice with myeloid lineagespecific inactivation of the insulin receptor gene. On an ApoE-deficient background, MphIRKO mice developed smaller atherosclerotic lesions. There was a dramatic decrease in LPS-stimulated IL-6 and IL-1b expression in the presence of macrophage autonomous insulin resistance. Consistently, while insulin-resistant IRS-2-deficient mice on an ApoEdeficient background display aggravated atherosclerosis, fetal liver cell transplantation of IRS-2 2/2 ApoE 2/2 cells ameliorated atherosclerosis in Apo-E-deficient mice. Thus, systemic versus myeloid cell-restricted insulin resistance has opposing effects on the development of atherosclerosis, providing direct evidence that myeloid lineage autonomous insulin signaling provides proinflammatory signals predisposing to the development of atherosclerosis.

Obesity and atherosclerosis-related diseases account for over one-third of deaths in the western world. Controlling these conditions remains a major challenge due to an incomplete understanding of the molecular pathways involved. Here, we show that Wip1 phosphatase, a known negative regulator of Atm-dependent signaling, plays a major role in controlling fat accumulation and atherosclerosis in mice; specifically, Wip1 deficiency prevents both conditions. In the course of atherosclerosis, deletion of Wip1 results in suppression of macrophage conversion into foam cells, thus preventing the formation of atherosclerotic plaques. This process appears to be independent of p53 but rely on a noncanonical Atm-mTOR signaling pathway and on selective autophagy in regulation of cholesterol efflux. We propose that the Wip1-dependent control of autophagy and cholesterol efflux may provide avenues for treating obesity and atherosclerosis.

Highlights d Expression of the gcat gene decreases over the lifespan in three different species d A gcat-rescue pathway leads to increased production of methylglyoxal (MGO) d Both gcat impairment and low-dose MGO promote C. elegans healthspan d Both interventions require similar stress-response and proteasome pathways SUMMARY Whether and how regulation of genes and pathways contributes to physiological aging is topic of intense scientific debate. By performing an RNA expression-based screen for genes downregulated during aging of three different species, we identified glycine-C-acetyltransferase (GCAT, EC 2.3.1.29). Impairing gcat expression promotes the lifespan of C. elegans by interfering with threonine catabolism to promote methylglyoxal (MGO; CAS 78-98-8) formation in an amine oxidase-dependent manner. MGO is a reactive dicarbonyl inducing diabetic complications in mammals by causing oxidative stress and damaging cellular components, including proteins. While high concentrations of MGO consistently exert toxicity in nematodes, we unexpectedly find that low-dose MGO promotes lifespan, resembling key mediators of gcat impairment. These were executed by the ubiquitinproteasome system, namely PBS-3 and RPN-6.1 subunits, regulated by the stress-responsive transcriptional regulators SKN-1/NRF2 and HSF-1. Taken together, GCAT acts as an evolutionary conserved aging-related gene by orchestrating an unexpected nonlinear impact of proteotoxic MGO on longevity.

Activation of energy expenditure in thermogenic fat is a promising strategy to improve metabolic health, yet the dynamic processes that evoke this response are poorly understood. Here we show that synthesis of the mitochondrial phospholipid cardiolipin is indispensable for stimulating and sustaining thermogenic fat function. Cardiolipin biosynthesis is robustly induced in brown and beige adipose upon cold exposure. Mimicking this response through overexpression of cardiolipin synthase (Crls1) enhances energy consumption in mouse and human adipocytes. Crls1 deficiency in thermogenic adipocytes diminishes inducible mitochondrial uncoupling and elicits a nuclear transcriptional response through endoplasmic reticulum stress-mediated retrograde communication. Cardiolipin depletion in brown and beige fat abolishes adipose thermogenesis and glucose uptake, which renders animals insulin resistant. We further identify a rare human CRLS1 variant associated with insulin resistance and show tha...

SIRT1 is a NAD + -dependent enzyme that affects metabolism by deacetylating key transcriptional regulators of energy expenditure. Here, we tested whether deletion of PARP-2, an alternative NAD +consuming enzyme, impacts on NAD + bioavailability and SIRT1 activity. Our results indicate that PARP-2 deficiency increases SIRT1 activity in cultured myotubes. However, this increase was not due to changes in NAD + levels, but to an increase in SIRT1 expression, as PARP-2 acts as a direct negative regulator of the SIRT1 promoter. PARP-2 deletion in mice increases SIRT1 levels, promotes energy expenditure, and increases mitochondrial content. Furthermore, PARP-2 À/À mice were protected against diet-induced obesity. Despite being insulin sensitized, PARP-2 À/À mice were glucose intolerant due to a defective pancreatic function. Hence, while inhibition of PARP activity promotes oxidative metabolism through SIRT1 activation, the use of PARP inhibitors for metabolic purposes will require further understanding of the specific functions of different PARP family members.

The Cdk7/cyclin H/me ´nage-a `-trois 1 (MAT1) heterotrimer has proposed functions in transcription as the kinase component of basal transcription factor TFIIH and is activated in adult hearts by Gq-, calcineurin-, and biomechanical stress-dependent pathways for hypertrophic growth. Using cardiac-specific Cre, we have ablated MAT1 in myocardium. Despite reduced Cdk7 activity, MAT1-deficient hearts grew normally, but fatal heart failure ensued at 6-8 weeks. By microarray profiling, quantitative RT-PCR, and western blotting at 4 weeks, genes for energy metabolism were found to be suppressed selectively, including targets of peroxisome proliferator-activated receptor g coactivator 1 (PGC-1). Cardiac metabolic defects were substantiated in isolated perfused hearts and isolated mitochondria. In culture, deleting MAT1 with Cre disrupted PGC-1 function: PGC-1a failed to activate PGC-1-responsive promoters and nuclear receptors, GAL4-PGC-1a was functionally defective, and PGC-1b was likewise deficient. PGC-1 bound to both MAT1 and Cdk7 in coprecipitation assays. Thus, we demonstrate a requirement for MAT1 in the operation of PGC-1 coactivators that control cell metabolism.

The AMP-activated protein kinase (AMPK) is a potential therapeutic target for metabolic diseases based on its reported actions in the liver and skeletal muscle. We evaluated two distinct direct activators of AMPK: a non-selective activator of all AMPK complexes, PF-739, and an activator selective for AMPK β1-containing complexes, PF-249. In cells and animals, both compounds were effective at activating AMPK in hepatocytes, but only PF-739 was capable of activating AMPK in skeletal muscle. In diabetic mice, PF-739, but not PF-249, caused a rapid lowering of plasma glucose levels that was diminished in the absence of skeletal muscle, but not liver, AMPK heterotrimers and was the result of an increase in systemic glucose disposal with no impact on hepatic glucose production. Studies of PF-739 in cynomolgus monkeys confirmed translation of the glucose lowering and established activation of AMPK in skeletal muscle as a potential therapeutic approach to treat diabetic patients.

Ferritin is a multisubunit protein that is responsible for storing and detoxifying cytosolic iron. Ferritin can be found in serum but is relatively iron poor. Serum ferritin occurs in iron overload disorders, in inflammation, and in the genetic disorder hyperferritinemia with cataracts. We show that ferritin secretion results when cellular ferritin synthesis occurs in the relative absence of free cytosolic iron. In yeast and mammalian cells, newly synthesized ferritin monomers can be translocated into the endoplasmic reticulum and transits through the secretory apparatus. Ferritin chains can be translocated into the endoplasmic reticulum in an in vitro translation and membrane insertion system. The insertion of ferritin monomers into the ER occurs under low-free-iron conditions, as iron will induce the assembly of ferritin. Secretion of ferritin chains provides a mechanism that limits ferritin nanocage assembly and ferritin-mediated iron sequestration in the absence of the translational inhibition of ferritin synthesis.

The redox cofactor nicotinamide adenine dinucleotide (NAD) plays a central role in metabolism and is a substrate for signaling enzymes including poly-ADP-ribose-polymerases (PARPs) and sirtuins. NAD concentration falls during aging, which has triggered intense interest in strategies to boost NAD levels. A limitation in understanding NAD metabolism has been reliance on concentration measurements. Here, we present isotope-tracer methods for NAD flux quantitation. In cell lines, NAD was made from nicotinamide and consumed largely by PARPs and sirtuins. In vivo, NAD was made from tryptophan selectively in the liver, which then excreted nicotinamide. NAD fluxes varied widely across tissues, with high flux in the small intestine and spleen and low flux in the skeletal muscle. Intravenous administration of nicotinamide riboside or mononucleotide delivered intact molecules to multiple tissues, but the same agents given orally were metabolized to nicotinamide in the liver. Thus, flux analysi...

Nuclear receptor signaling plays an important role in energy metabolism. In this study we demonstrate that the nuclear receptor corepressor RIP140 is a key regulator of metabolism in skeletal muscle. RIP140 is expressed in a fiber type-specific manner, and manipulation of its levels in null, heterozygous, and transgenic mice demonstrate that low levels promote while increased expression suppresses the formation of oxidative fibers. Expression profiling reveals global changes in the expression of genes implicated in both myofiber phenotype and metabolic functions. Genes involved in fatty-acid oxidation, oxidative phosphorylation, and mitochondrial biogenesis are upregulated in the absence of RIP140. Analysis of cultured myofibers demonstrates that the changes in expression are intrinsic to muscle cells and that nuclear receptor-regulated genes are direct targets for repression by RIP140. Therefore RIP140 is an important signaling factor in the regulation of skeletal muscle function and physiology.