A High-Fat Diet and NAD+ Rescue Premature Aging in Cockayne Syndrome
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ABSTRACT: Cockayne syndrome (CS) is an accelerated aging disorder characterized by progressive neurodegeneration caused by mutations in the genes encoding the DNA repair proteins CSA or CSB. Csbm/m mice were given a high-fat, caloric-restricted or resveratrol-supplemented diet. The high-fat diet rescued the phenotype of Csbm/m mice at the metabolic, transcriptomic and behavioral levels. Additional analysis suggests that the premature aging seen in CS mice, nematodes and human cells results from aberrant PARP activation due to deficient DNA repair leading to decreased SIRT1 activity and mitochondrial dysfunction. Notably, β-hydroxybutyrate levels are increased by the high-fat diet; and β-hydroxybutyrate, PARP inhibition, or NAD+ supplementation can activate SIRT1 and rescue CS-associated phenotypes. Mechanistically, CSB is able to displace activated PARP1 from damaged DNA to limit its activity. This study connects two emerging longevity metabolites, β-hydroxybutyrate and NAD+, through the deacetylase SIRT1 and suggests possible interventions for CS.
Project description:Cockayne syndrome (CS) is an accelerated aging disorder characterized by progressive neurodegeneration caused by mutations in the genes encoding the DNA repair proteins CSA or CSB. Csbm/m mice were given a high-fat, caloric-restricted or resveratrol-supplemented diet. The high-fat diet rescued the phenotype of Csbm/m mice at the metabolic, transcriptomic and behavioral levels. Additional analysis suggests that the premature aging seen in CS mice, nematodes and human cells results from aberrant PARP activation due to deficient DNA repair leading to decreased SIRT1 activity and mitochondrial dysfunction. Notably, β-hydroxybutyrate levels are increased by the high-fat diet; and β-hydroxybutyrate, PARP inhibition, or NAD+ supplementation can activate SIRT1 and rescue CS-associated phenotypes. Mechanistically, CSB is able to displace activated PARP1 from damaged DNA to limit its activity. This study connects two emerging longevity metabolites, β-hydroxybutyrate and NAD+, through the deacetylase SIRT1 and suggests possible interventions for CS. 4-month-old mice, WT and Csbm/m on a C57BL/6 background, were fed a standard AIN-93G diet (SD; carbohydrate:protein:fat ratio of 64:19:17 percent of kcal) ad libitum or at 40% CR, a SD supplemented with 100 mg/kgchow resveratrol ad libitum, or a high-fat diet ad libitum consisting of AIN-93G with 60% of calories from fat, primarily hydrogenated coconut oil (HFD; carbohydrate:protein:fat ratio of 16:23:61). Each group was on the specified diet for 8 months, after which the mice were sacrificed and the cerebellum was removed. For nicotinamide treatments, 4- or 18-month-old WT and Csbm/m mice were given daily injections of nicotinamide riboside (NR) (500 mg/kg/d, ip) or saline for one week, after which the mice were sacrificed and the cerebellum was removed. RNA was extracted from the cerebellums of all mice using Trizol, and RNA quality and quantity were tested using an Agilent 2100 BioAnalyzer with RNA 6000 nano chips. RNA was labeled using the standard Illumina protocol for Illumina TotalPrep RNA Amplification Kit. Labeled RNA was hybridized to Illumina's Sentrix MouseRef-8 v2 Expression BeadChips (Illumina, San Diego, CA) overnight and washed, stained and scanned the next day.
Project description:Cockayne syndrome (CS) is an accelerated aging disorder, caused by mutations in the CSA or CSB genes. In CSB-deficient cells, poly (ADP ribose) polymerase (PARP) is persistently activated by unrepaired DNA damage and PARP consumes and depletes cellular nicotinamide adenine dinucleotide (NAD), which leads to mitochondrial dysfunction. Here, the distribution of poly (ADP ribose) (PAR) was determined in CSB-deficient cells using ADPr-ChAP (ADP ribose-chromatin affinity purification), and the results show striking enrichment of PAR at transcription start sites (TSS), depletion of heterochromatin, and downregulation of H3K9me3-specific methyltransferases SUV39H1 and SETDB1. Induced-expression of SETDB1 in CSB-deficient cells downregulated PAR and normalized mitochondrial function. The results suggest that defects in CSB are strongly associated with loss of heterochromatin, downregulation of SETDB1, increased PAR in highly-transcribed regions, and mitochondrial dysfunction.
Project description:The purpose of this study is to investigate the role of SIRT1 in high-fat diet-induced liver steatosis and insulin resistance. SIRT1 is a nuclear enzyme that could remove an acetyl-group from target proteins by using NAD as co-substrate. Homologs of this protein in yeast and the roundworm C. elegans are able to delay the aging process in response to nutrients. However, the molecular mechanism by which SIRT1 sense the environment to mediate this response are poorly understood. We have shown that when chronically fed with a 40%-fat diet, SIRT1 heterozygous animals gain significantly more weight compared to wild type littermates. They are also hyperinsulimia, more insulin-resistant, and accumulate more lipids in liver. Interestingly, these animals also show signs of premature aging, such as an early appearance of gray fur, defective motor activity, and decreased fertility. In this microarray study, we analyzed the gene expression profiles in the liver of WT low-fat diet, Het low-fat diet, WT high-fat diet, and Het high-fat diet using Agilent Whole Genome Mouse 4x44 multiplex format oligo arrays following the Agilent-1-color microarray-based gene expression analysis protocol. This microarray analysis concluded that SIRT1 Het mice reponsed to the high-fat diet differently from the WT control mice. Liver total RNAs from SIRT1 WT and Het mice that were fed with either a low-fat diet or a high-fat diet for 34 weeks were used for a microarray gene expression study. Three biological replicates for each group were used.
Project description:Cockayne syndrome (CS) is a rare premature aging disease, which in the majority of cases is caused by mutations of the genes encoding the CSA or CSB proteins. CS patients display cachectic dwarfism and severe neurological manifestations and die by 12 years of age on average. The CS proteins are involved in transcription and DNA repair, including a specialized form of DNA repair called transcription-coupled nucleotide excision repair (TC-NER). However, there is also evidence for mitochondrial dysfunction in CS, likely contributing to the severe premature aging phenotype of this disease. Our cross-species transciptomic analysis in CS postmortem brain tissue, CS mouse and C. elegans models showed that mitochondrial dysfunction is indeed a common feature in CS. Interestingly, the restoration of mitochondrial dysfunction through NAD+ supplementation significantly improved lifespan and healthspan in the C. elegans models of CS, highlighting mitochondrial dysfunction as a major driver of the aging features of CS. We proceeded to perform molecular studies on cerebellar samples obtained from CS patients. We found that these patients exhibited molecular signatures of dysfunctional mitochondrial dynamics that can be corrected with NAD+ supplementation in primary cells with depleted CSA or CSB. Our study provides support for the interconnection between two major aging theories, DNA damage and mitochondrial dysfunction. Together these two agents contribute to an accelerated aging program that can be averted by NAD+ supplementation.
Project description:Cockayne syndrome (CS) is a rare premature aging disease, which in the majority of cases is caused by mutations of the genes encoding the CSA or CSB proteins. CS patients display cachectic dwarfism and severe neurological manifestations and die by 12 years of age on average. The CS proteins are involved in transcription and DNA repair, including a specialized form of DNA repair called transcription-coupled nucleotide excision repair (TC-NER). However, there is also evidence for mitochondrial dysfunction in CS, likely contributing to the severe premature aging phenotype of this disease. Our cross-species transciptomic analysis in CS postmortem brain tissue, CS mouse and C. elegans models showed that mitochondrial dysfunction is indeed a common feature in CS. Interestingly, the restoration of mitochondrial dysfunction through NAD+ supplementation significantly improved lifespan and healthspan in the C. elegans models of CS, highlighting mitochondrial dysfunction as a major driver of the aging features of CS. We proceeded to perform molecular studies on cerebellar samples obtained from CS patients. We found that these patients exhibited molecular signatures of dysfunctional mitochondrial dynamics that can be corrected with NAD+ supplementation in primary cells with depleted CSA or CSB. Our study provides support for the interconnection between two major aging theories, DNA damage and mitochondrial dysfunction. Together these two agents contribute to an accelerated aging program that can be averted by NAD+ supplementation.
Project description:Type 2 diabetes (T2D) has become an epidemic in our modern lifestyle, likely due to calorie-rich diets overwhelming our adaptive metabolic pathways. One such pathway is mediated by nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in mammalian NAD+ biosynthesis, and the NAD+-dependent protein deacetylase SIRT1. Here we show that NAMPT-mediated NAD+ biosynthesis is severely compromised in metabolic organs by high-fat diet (HFD). Strikingly, nicotinamide mononucleotide (NMN), a product of the NAMPT reaction and a key NAD+ intermediate, ameliorates glucose intolerance by restoring NAD+ levels in HFD-induced T2D mice. NMN also enhances hepatic insulin sensitivity and restores gene expression related to oxidative stress, inflammatory response, and circadian rhythm, partly through SIRT1 activation. Furthermore, NAD+ and NAMPT levels show significant decreases in multiple organs during aging, and NMN improves glucose intolerance and lipid profiles in age-induced T2D mice. These findings provide critical insights into a novel intervention against diet- and age-induced T2D. 4 regular chow fed mice (RC1-4) vs 4 high-fat diet fed (HFD) (HFD1a-4a) mice were analyzed on one chip (Chip-A). 4 HFD mice (HFD1b-4b) vs 4 HFD-NMN treated mice (NMN1-4) were examined on the other chip (Chip-B).
Project description:The purpose of this study is to investigate the role of SIRT1 in high-fat diet-induced liver steatosis and insulin resistance. SIRT1 is a nuclear enzyme that could remove an acetyl-group from target proteins by using NAD as co-substrate. Homologs of this protein in yeast and the roundworm C. elegans are able to delay the aging process in response to nutrients. However, the molecular mechanism by which SIRT1 sense the environment to mediate this response are poorly understood. We have shown that when chronically fed with a 40%-fat diet, SIRT1 heterozygous animals gain significantly more weight compared to wild type littermates. They are also hyperinsulimia, more insulin-resistant, and accumulate more lipids in liver. Interestingly, these animals also show signs of premature aging, such as an early appearance of gray fur, defective motor activity, and decreased fertility. In this microarray study, we analyzed the gene expression profiles in the liver of WT low-fat diet, Het low-fat diet, WT high-fat diet, and Het high-fat diet using Agilent Whole Genome Mouse 4x44 multiplex format oligo arrays following the Agilent-1-color microarray-based gene expression analysis protocol. This microarray analysis concluded that SIRT1 Het mice reponsed to the high-fat diet differently from the WT control mice.
Project description:There is currently no established treatment for Cockayne syndrome, a disease characterized by progressive early onset neurodegeneration with features of premature aging and death in childhood. Here, we tested if acetyl-CoA precursors, citrate and beta-hydroxybutyrate, could reduce features of Cockayne syndrome. We identified the gene Helicase 89B (Hel89B) as a homologue of CSB in drosophila and found that the ketone beta-hydroxybutyrate rescued features of premature aging in Hel89B deficient flies. In mammals, loss of the citrate carrier Indy exacerbated the phenotype of Csbm/m mice, rescued by a ketogenic diet. The rescue effect appeared to be mediated through ketone stimulated histone acetylation and facilitation of transcriptional resolution of non-B DNA. Notably, this appears to be a common effect of a ketogenic diet.
Project description:Type 2 diabetes (T2D) has become an epidemic in our modern lifestyle, likely due to calorie-rich diets overwhelming our adaptive metabolic pathways. One such pathway is mediated by nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in mammalian NAD+ biosynthesis, and the NAD+-dependent protein deacetylase SIRT1. Here we show that NAMPT-mediated NAD+ biosynthesis is severely compromised in metabolic organs by high-fat diet (HFD). Strikingly, nicotinamide mononucleotide (NMN), a product of the NAMPT reaction and a key NAD+ intermediate, ameliorates glucose intolerance by restoring NAD+ levels in HFD-induced T2D mice. NMN also enhances hepatic insulin sensitivity and restores gene expression related to oxidative stress, inflammatory response, and circadian rhythm, partly through SIRT1 activation. Furthermore, NAD+ and NAMPT levels show significant decreases in multiple organs during aging, and NMN improves glucose intolerance and lipid profiles in age-induced T2D mice. These findings provide critical insights into a novel intervention against diet- and age-induced T2D.
Project description:Hepatic metabolic derangements are key components in the development of fatty liver, insulin resistance, and atherosclerosis. SIRT1, a NAD+-dependent protein deacetylase, is an important regulator of energy homeostasis in response to nutrient availability. Here we demonstrate that hepatic SIRT1 regulates fatty acid metabolism by positively regulating PPAR-alpha. Hepatocyte-specific deletion of SIRT1 impairs PPAR-alpha signaling and decreased fatty acid beta-oxidation in the liver. When challenged with a high-fat diet, liver-specific SIRT1 knockout mice develop hepatic steatosis, hepatic inflammation, and endoplasmic reticulum stress. Taken together, our data indicate that SIRT1 plays a vital role in the regulation of hepatic lipid homeostasis.