Cross regulation of sirtuin 1, AMPK, and PPARγ in conjugated linoleic acid treated adipocytes

Trans 10, cis 12-conjugated linoleic acid in low concentration reduces while in high concentration enhances adipocyte metabolism but effectively improves hepatic steatosis of obese mice

Trans 10, cis 12-conjugated linoleic acid (t10c12-CLA)-producing mice were used to investigate the antiobesity of obese males. Compared to wild-type littermates, high concentration t10c12-CLA in biallelic Pai/Pai mice reduced fat by up-regulation lipid metabolism in white adipose tissue (WAT). In contrast, low concentration t10c12-CLA in monoallelic Pai/wt mice could not reduce fat for down-regulation lipid metabolism in WAT. Simultaneously, t10c12-CLA enhanced thermogenesis and beta-oxidation in brown adipose tissue, alleviated steatosis by declining lipid metabolism in the liver, and lowered circulating triglycerides. On the other hand, low concentration t10c12-CLA specifically resulted in decreased circulating fibroblast growth factor 21, elevated glucose and high-density lipoprotein, whereas high concentration t10c12-CLA specifically increased circulating and hepatic cholesterol levels via up-regulation of low-density lipoprotein receptor in the liver. In conclusion, high concentration t10c12-CLA enhances local lipid metabolism in WAT and leads to fat loss, whereas low concentration t10c12-CLA attenuates the enzymic activities in WAT and fails to reduce fat. T10c12-CLA can effectively and concentration independently improve steatosis by attenuating hepatic lipid metabolism. These results suggest that low concentration of t10c12-CLA is beneficial, but high concentration is unfavorable to obese male mammals.

Effect of anthocyanins on metabolic syndrome through interacting with gut microbiota

Metabolic syndrome, as a complex pathological condition, is caused by a series of pathogenic factors and has become a global public health challenge. Anthocyanins, a natural water-soluble flavonoid pigment, have attracted much attention due to their antioxidant, anti-inflammatory, and anticancer biological activities. After ingestion, a majority of anthocyanins is not directly absorbed but rather reaches the colon. Hence, the exertion of their biological benefits is closely intertwined with the role played by gut microbiota. In this review, we introduce the pathogenesis and intervention methods of metabolic syndrome, as well as the interaction between anthocyanins and gut microbiota. We also discuss the therapeutic potential of anthocyanins through gut microbiota in addressing a range of metabolic syndrome conditions, including obesity, type 2 diabetes mellitus, cardiovascular diseases, non-alcoholic fatty liver disease, inflammatory bowel disease, polycystic ovary syndrome, osteoporosis, and cancer.

Isobicyclogermacrenal ameliorates hippocampal ferroptosis involvement in neurochemical disruptions and neuroinflammation induced by sleep deprivation in rats

BACKGROUND

Sleep deprivation (SLD) is a widespread condition that disrupts physiological functions and may increase mortality risk. Valeriana officinalis, a traditional medicinal herb known for its sedative and hypnotic properties, contains isobicyclogermacrenal (IG), a newly isolated active compound. However, research on the therapeutic potential of IG for treating SLD remains limited.

METHODS

In this study, IG was extracted and characterized from Valeriana officinalis, and an SLD model was established in rats using p-chlorophenylalanine (PCPA). Behavioral tests and pathological studies were conducted to assess the effects of IG on SLD, and transcriptomic and metabolomic analyses were utilized to investigate its underlying mechanisms.

RESULTS

IG administration significantly improved the cognitive performance of SLD rats in behavioral tests and ameliorated histological injuries in the hippocampus and cerebral cortex. IG treatment increased the levels of brain-derived neurotrophic factor (BDNF) and neurotransmitters such as serotonin (5-HT) in SLD rats. Additionally, IG directly targets TFRC, thereby improving iron metabolism in the hippocampus. Comprehensive transcriptomic and metabolomic analyses revealed that the improvements from IG stemmed from the mitigation of abnormalities in iron metabolism, cholesterol metabolism, and glutathione metabolism, leading to reduced oxidative stress, ferroptosis, and neuroinflammation in the hippocampus caused by SLD.

CONCLUSIONS

Collectively, these findings suggest that IG has the potential to ameliorate neurological damage and cognitive impairment caused by SLD, offering a novel strategy for protection against the adverse effects of SLD.

Shiitake mushroom powder supplementation increase antioxidative activity in dogs

Introduction

The prevalence of age-related diseases, including obesity (a lipid metabolism disorder), increases with the increase in a dog's lifespan. Most of age-related diseases are associated with oxidative stress by excessive production of reactive oxygen species (ROS) from impaired mitochondrial functions. Safe and effective supplements with antioxidative and anti-inflammatory activities are required to prevent obesity and associated complications. Shiitake mushroom exhibit various functions including antioxidant activity. We investigated the effect of shiitake powder supplementation in healthy dogs.

Methods

Shiitake powder was supplemented at a dose of 800 mg/kg body weight/day for 4 weeks. The dose was set as 0.60-0.65 mg/kg/day of eritadenine, a hypocholesterolemic factor.

Results

The body weight and body condition score of the dogs did not change after shiitake supplementation. In contrast, plasma total cholesterol concentrations decreased and superoxide dismutase activity and leukocyte sirtuin1 mRNA expression increased significantly in the dogs that received the supplement.

Discussion

Oral administration of shiitake powder increased antioxidative activity. The supplement may be useful in ameliorating the signs of age-related diseases, including obesity, in dogs.

Integration of network pharmacology, transcriptomics and molecular docking reveals two novel hypoglycemic components in snow chrysanthemum

Our previous studies uncovered the glucose-lowering properties of snow chrysanthemum tea, however, the active ingredients and underlying mechanisms were yet to be uncovered. Flavonoids are the most active and abundant components in snow chrysanthemum tea. In this study, we treated leptin-deficient diabetic ob/ob or high-fat diet (HFD)-induced C57BL/6 J obese mice with or without total flavonoids of snow chrysanthemum (TFSC) for 14 weeks. Results indicated that TFSC ameliorated dyslipidemia and fatty liver, thereby reducing hyperlipidemia. Further mechanism experiments, including RNA-seq and experimental validation, revealed TFSC improved glycolipid metabolism primarily by activating the AMPK/Sirt1/PPARγ pathway. Additionally, by integrating UPLC, network pharmacology, transcriptomics, and experimental validation, we identified two novel hypoglycemic compounds, sulfuretin and leptosidin, in TFSC. Treatment with 12.5 μmol/L sulfuretin obviously stimulated cellular glucose consumption, and sulfuretin (3.125, 6.25 and 12.5 μmol/L) significantly mitigated glucose uptake damage and reliably facilitated glucose consumption in insulin-resistant HepG2 cells. Remarkably, sulfuretin interacted with the ligand-binding pocket of PPARγ via three hydrogen bond interactions with the residues LYS-367, GLN-286 and TYR-477. Furthermore, a concentration of 12.5 μmol/L sulfuretin effectively upregulated the expression of PPARγ, exhibiting a comparable potency to a renowned PPARγ agonist at 20 μmol/L. Taken together, our findings have identified two new hypoglycemic compounds and revealed their mechanisms, which significantly expands people's understanding of the active components in snow chrysanthemum that have hypoglycemic effects.

Pharmacological Approaches to Decelerate Aging: A Promising Path

Biological aging or senescence is a course in which cellular function decreases over a period of time and is a consequence of altered signaling mechanisms that are triggered in stressed cells leading to cell damage. Aging is among the principal risk factors for many chronic illnesses such as cancer, cardiovascular disorders, and neurodegenerative diseases. Taking this into account, targeting fundamental aging mechanisms therapeutically may effectively impact numerous chronic illnesses. Selecting ideal therapeutic options in order to hinder the process of aging and decelerate the progression of age-related diseases is valuable. Along therapeutic options, life style modifications may well render the process of aging. The process of aging is affected by alteration in many cellular and signaling pathways amid which mTOR, SIRT1, and AMPK pathways are the most emphasized. Herein, we have discussed the mechanisms of aging focusing mainly on the mentioned pathways as well as the role of inflammation and autophagy in aging. Moreover, drugs and natural products with antiaging properties are discussed in detail.

Sirtuin function and metabolism: Role in pancreas, liver, and adipose tissue and their crosstalk impacting bone homeostasis

Mammalian sirtuins (SIRT1-7) are members of the nicotine adenine dinucleotide (NAD+)-dependent family of enzymes critical for histone deacetylation and posttranslational modification of proteins. Sirtuin family members regulate a wide spectrum of biological processes and are best known for maintaining longevity. Sirtuins are well characterized in metabolic tissues such as the pancreas, liver and adipose tissue (AT). They are regulated by a diverse range of stimuli, including nutrients and metabolic changes within the organism. Indeed, nutrient-associated conditions, such as obesity and anorexia nervosa (AN), were found to be associated with bone fragility development in osteoporosis. Interestingly, it has also been demonstrated that sirtuins, more specifically SIRT1, can regulate bone activity. Various studies have demonstrated the importance of sirtuins in bone in the regulation of bone homeostasis and maintenance of the balance between bone resorption and bone formation. However, to understand the molecular mechanisms involved in the negative regulation of bone homeostasis during overnutrition (obesity) or undernutrition, it is crucial to examine a wider picture and to determine the pancreatic, liver and adipose tissue pathway crosstalk responsible for bone loss. Particularly, under AN conditions, sirtuin family members are highly expressed in metabolic tissue, but this phenomenon is reversed in bone, and severe bone loss has been observed in human subjects. AN-associated bone loss may be connected to SIRT1 deficiency; however, additional factors may interfere with bone homeostasis. Thus, in this review, we focus on sirtuin activity in the pancreas, liver and AT in cases of over- and undernutrition, especially the regulation of their secretome by sirtuins. Furthermore, we examine how the secretome of the pancreas, liver and AT affects bone homeostasis, focusing on undernutrition. This review aims to lead to a better understanding of the crosstalk between sirtuins, metabolic organs and bone. In long term prospective it should contribute to promote improvement of therapeutic strategies for the prevention of metabolic diseases and the development of osteoporosis.

A comprehensive insight into the potential effects of resveratrol supplementation on SIRT-1: A systematic review

BACKGROUND AND AIMS

Silent information regulator 1 (Sirt1) involved in histone stability, transcriptional activity, and translocation. This systematic review aimed to summarize the effects of Resveratrol on Sirt1 expression.

MATERIALS AND METHODS

Electronic databases including Scopus, Medline and web of knowledge were searched up to March 2020.

RESULTS

Out of 801 studies identified in our search finally 12 articles included. Totally six studies evaluated the effects of resveratrol on SIRT1 gene expression, and six articles investigate protein expression.

CONCLUSION

The results of the included studies showed that resveratrol supplementation had beneficial effects on protein and gene expression of SIRT1.

Activators of SIRT1 in the kidney and protective effects of SIRT1 during acute kidney injury (AKI) (effect of SIRT1 activators on acute kidney injury)

Acute kidney injury (AKI) is a complex disorder and a clinical condition characterized by acute reduction in renal function. If AKI is not treated, it can lead to chronic kidney disease, which is associated with a high risk of death. SIRT1 (silent information regulator 1) is an NAD-dependent deacetylase. This enzyme is responsible for the processes of DNA repair or recombination, chromosomal stability, and gene transcription. This enzyme also plays a protective role in many diseases, including AKI. In this study, we review the mechanisms that mediate the protective effects of SIRT1 on AKI, including SIRT1 activators.

The effect of trans-palmitoleic acid on cell viability and sirtuin 1 gene expression in hepatocytes and the activity of peroxisome-proliferator-activated receptor-alpha

Background:

Accumulation of fatty acids in liver causes lipotoxicity which is followed by nonalcoholic fatty liver disease. The association between intakes of trans-fatty acids with metabolic diseases is still controversial. Accordingly, the objective of this study was to investigate the in vitro effects of trans-palmitoleic acid (tPA) and palmitic acid (PA) on lipid accumulation in hepatocytes, focusing on the gene expression of sirtuin 1 (SIRT1) as well as the transcriptional activity of peroxisome proliferator-activated receptor alpha (PPARα).

Materials and Methods:

In this experimental study, hepatocellular carcinoma (HepG2) cells were cultured and treated with various concentrations of tPA and PA (C16:0). The accumulation of triglyceride in the cells was measured by enzymatic method. Gene expression was evaluated by real-time polymerase chain reaction. The activity of PPARα was assessed by luciferase reporter assay after transfection of human embryonic kidney 293T cells by a vector containing the PPAR response element.

Results:

While concentration >1 mM for PA and cis-PA (cPA) reduced the viability of hepatocytes, tPA revealed an opposite effect and increased cell survival. Lipid accumulation in HepG2 cells after treatment with tPA was significantly lower than that in cells treated with PA. In addition, tPA at physiological concentration had no effect on the expression of SIRT1 while at high concentration significantly augmented its expression. There was a modest increase in PPARα activity at low concentration of tPA.

Conclusion:

tPA causes less lipid accumulation in hepatocytes with no detrimental effect on cell viability and might be beneficial for liver cells by the activation of SIRT1 and induction of PPARα activity.

Critical Role for AMPK in Metabolic Disease-Induced Chronic Kidney Disease

Chronic kidney disease (CKD) is prevalent in 9.1% of the global population and is a significant public health problem associated with increased morbidity and mortality. CKD is associated with highly prevalent physiological and metabolic disturbances such as hypertension, obesity, insulin resistance, cardiovascular disease, and aging, which are also risk factors for CKD pathogenesis and progression. Podocytes and proximal tubular cells of the kidney strongly express AMP-activated protein kinase (AMPK). AMPK plays essential roles in glucose and lipid metabolism, cell survival, growth, and inflammation. Thus, metabolic disease-induced renal diseases like obesity-related and diabetic chronic kidney disease demonstrate dysregulated AMPK in the kidney. Activating AMPK ameliorates the pathological and phenotypical features of both diseases. As a metabolic sensor, AMPK regulates active tubular transport and helps renal cells to survive low energy states. AMPK also exerts a key role in mitochondrial homeostasis and is known to regulate autophagy in mammalian cells. While the nutrient-sensing role of AMPK is critical in determining the fate of renal cells, the role of AMPK in kidney autophagy and mitochondrial quality control leading to pathology in metabolic disease-related CKD is not very clear and needs further investigation. This review highlights the crucial role of AMPK in renal cell dysfunction associated with metabolic diseases and aims to expand therapeutic strategies by understanding the molecular and cellular processes underlying CKD.

Activation of Cannabinoid Receptors Attenuates Endothelin-1-Induced Mitochondrial Dysfunction in Rat Ventricular Myocytes

Supplemental Digital Content is Available in the Text.

Evidence suggests that the activation of the endocannabinoid system offers cardioprotection. Aberrant energy production by impaired mitochondria purportedly contributes to various aspects of cardiovascular disease. We investigated whether cannabinoid (CB) receptor activation would attenuate mitochondrial dysfunction induced by endothelin-1 (ET1). Acute exposure to ET1 (4 hours) in the presence of palmitate as primary energy substrate induced mitochondrial membrane depolarization and decreased mitochondrial bioenergetics and expression of genes related to fatty acid oxidation (ie, peroxisome proliferator–activated receptor-gamma coactivator-1α, a driver of mitochondrial biogenesis, and carnitine palmitoyltransferase-1β, facilitator of fatty acid uptake). A CB1/CB2 dual agonist with limited brain penetration, CB-13, corrected these parameters. AMP-activated protein kinase (AMPK), an important regulator of energy homeostasis, mediated the ability of CB-13 to rescue mitochondrial function. In fact, the ability of CB-13 to rescue fatty acid oxidation–related bioenergetics, as well as expression of proliferator-activated receptor-gamma coactivator-1α and carnitine palmitoyltransferase-1β, was abolished by pharmacological inhibition of AMPK using compound C and shRNA knockdown of AMPKα1/α2, respectively. Interventions that target CB/AMPK signaling might represent a novel therapeutic approach to address the multifactorial problem of cardiovascular disease.

Possible Adverse Effects of High-Dose Nicotinamide: Mechanisms and Safety Assessment

Nicotinamide (NAM) at doses far above those recommended for vitamins is suggested to be effective against a wide spectrum of diseases and conditions, including neurological dysfunctions, depression and other psychological disorders, and inflammatory diseases. Recent increases in public awareness on possible pro-longevity effects of nicotinamide adenine dinucleotide (NAD+) precursors have caused further growth of NAM consumption not only for clinical treatments, but also as a dietary supplement, raising concerns on the safety of its long-term use. However, possible adverse effects and their mechanisms are poorly understood. High-level NAM administration can exert negative effects through multiple routes. For example, NAM by itself inhibits poly(ADP-ribose) polymerases (PARPs), which protect genome integrity. Elevation of the NAD+ pool alters cellular energy metabolism. Meanwhile, high-level NAM alters cellular methyl metabolism and affects methylation of DNA and proteins, leading to changes in cellular transcriptome and proteome. Also, methyl metabolites of NAM, namely methylnicotinamide, are predicted to play roles in certain diseases and conditions. In this review, a collective literature search was performed to provide a comprehensive list of possible adverse effects of NAM and to provide understanding of their underlying mechanisms and assessment of the raised safety concerns. Our review assures safety in current usage level of NAM, but also finds potential risks for epigenetic alterations associated with chronic use of NAM at high doses. It also suggests directions of the future studies to ensure safer application of NAM.

Over-expression of miR-34c leads to early-life visceral fat accumulation and insulin resistance

Overweight children and adolescents are at high risk for adult and late life obesity. This report investigates some underlying mechanisms contributing to obesity during early life in an animal model. We generated a strain of transgenic mice, cU2, overexpressing human microRNA 34c, a microRNA functionally implicated in adipogenesis. Male and female cU2 mice exhibit significant weight gain, accompanied by marked increase in abdominal fat mass and metabolic abnormalities, including reduction of both glucose clearance rate and insulin sensitivity, as early as two months of age. Adipogenesis derailment at this early age is suggested by decreased expression of adiponectin, the fat mass and obesity-associated gene, and the adiponectin receptor R1, coupled with a reduction of the brown fat biomarker PAT2 and the adipogenesis inhibitor SIRT1. Notably, adiponectin is an important adipokine and an essential regulator of glucose and fatty acid homeostasis. cU2 mice may provide a crucial animal model for investigating the role of miR-34c in early onset insulin resistance and visceral fat mass increase, contributing to accelerated body weight gain and metabolic disorders. Intervention in this dysregulation may open a new preventive strategy to control early-life weight gain and abnormal insulin resistance, and thus prevalent adult and late life obesity.

PPAR-γ: Its ligand and its regulation by microRNAs

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear receptor superfamily. PPARs are categorized into three subtypes, PPARα, β/δ, and γ, encoded by different genes, expressed in diverse tissues and participate in various biological functions and can be activated by their metabolic derivatives in the body or dietary fatty acids. The PPAR-γ also takes parts in the regulation of energy balance, lipoprotein metabolism, insulin sensitivity, oxidative stress, and inflammatory signaling. It has been implicated in the pathology of numerous diseases including obesity, diabetes, atherosclerosis, and cancers. Among various cellular and molecular targets that are able to regulate PPAR-γ and its underlying pathways, microRNAs (miRNAs) appeared as important regulators. Given that the deregulation of these molecules via targeting PPAR-γ could affect initiation and progression of various diseases, identification of miRNAs that affects PPAR-γ could contribute to the better understanding of roles of PPAR-γ in various biological and pathological conditions. Here, we have summarized the function and various ligands of PPAR-γ and have highlighted various miRNAs involved in the regulation of PPAR-γ.

Self-regulation of the inflammatory response by peroxisome proliferator-activated receptors

The peroxisome proliferator-activated receptor (PPAR) family includes three transcription factors: PPARα, PPARβ/δ, and PPARγ. PPAR are nuclear receptors activated by oxidised and nitrated fatty acid derivatives as well as by cyclopentenone prostaglandins (PGA₂ and 15d-PGJ₂) during the inflammatory response. This results in the modulation of the pro-inflammatory response, preventing it from being excessively activated. Other activators of these receptors are nonsteroidal anti-inflammatory drug (NSAID) and fatty acids, especially polyunsaturated fatty acid (PUFA) (arachidonic acid, ALA, EPA, and DHA). The main function of PPAR during the inflammatory reaction is to promote the inactivation of NF-κB. Possible mechanisms of inactivation include direct binding and thus inactivation of p65 NF-κB or ubiquitination leading to proteolytic degradation of p65 NF-κB. PPAR also exert indirect effects on NF-κB. They promote the expression of antioxidant enzymes, such as catalase, superoxide dismutase, or heme oxygenase-1, resulting in a reduction in the concentration of reactive oxygen species (ROS), i.e., secondary transmitters in inflammatory reactions. PPAR also cause an increase in the expression of IκBα, SIRT1, and PTEN, which interferes with the activation and function of NF-κB in inflammatory reactions.

miR‑330‑5p inhibits H2O2‑induced adipogenic differentiation of MSCs by regulating RXRγ

The elucidation of the underlying molecular mechanism of H2O2‑induced adipocyte differentiation in mesenchymal stem cells (MSCs) is important for the development of treatments for metabolic diseases. The aim of the present study was to identify microRNA (miR)‑330‑5p, which targets retinoid X receptor γ (RXRγ) and to determine the function of H2O2‑induced adipogenic differentiation of MSCs. During differentiation of MSCs into adipocytes induced by H2O2, miR‑330‑5p expression was decreased with a concomitant increase in RXRγ expression. A luciferase assay with RXRγ 3'‑untranslated region (UTR) reporter plasmid, including the miR‑330‑5p‑binding sequences, identified that the introduction of miR‑330‑5p decreases luciferase activity. However, it did not affect the activity of mutated RXRγ 3'‑UTR reporter. Enforced expression of miR‑330‑5p significantly inhibited adipocyte differentiation by decreasing RXRγ mRNA and protein levels. In contrast, inhibition of the endogenous miR‑330‑5p promoted the formation of lipid droplets by rescuing RXRγ expression. Furthermore, the effects of inhibition of RXRγ were similar to those of overexpression of miR‑330‑5p on H2O2‑induced adipogenic differentiation from MSCs. miR‑330‑5p inhibits H2O2‑induced adipogenic differentiation of MSCs, and this is dependent on RXRγ. Taken together, the results of the present study revealed that miR‑330‑5p acts as a critical regulator of RXRγ, and is able to determinate the fate of MSCs to differentiate into adipocytes. This suggests that miR‑330‑5p and RXRγ may be target molecules for controlling metabolic diseases.

Sirt7 promotes adipogenesis in the mouse by inhibiting autocatalytic activation of Sirt1

Sirtuins (Sirt1-Sirt7) are NAD⁺-dependent protein deacetylases/ADP ribosyltransferases, which play decisive roles in chromatin silencing, cell cycle regulation, cellular differentiation, and metabolism. Different sirtuins control similar cellular processes, suggesting a coordinated mode of action but information about potential cross-regulatory interactions within the sirtuin family is still limited. Here, we demonstrate that Sirt1 requires autodeacetylation to efficiently deacetylate targets such as p53, H3K9, and H4K16. Sirt7 restricts Sirt1 activity by preventing Sirt1 autodeacetylation causing enhanced Sirt1 activity in Sirt7^-/- mice. Increased Sirt1 activity in Sirt7^-/- mice blocks PPARγ and adipocyte differentiation, thereby diminishing accumulation of white fat. Thus, reduction of Sirt1 activity restores adipogenesis in Sirt7^-/- adipocytes in vitro and in vivo. We disclosed a principle controlling Sirt1 activity and uncovered an unexpected complexity in the crosstalk between two different sirtuins. We propose that antagonistic interactions between Sirt1 and Sirt7 are pivotal in controlling the signaling network required for maintenance of adipose tissue.

Nicotinamide is an inhibitor of SIRT1 in vitro, but can be a stimulator in cells

Nicotinamide (NAM), a form of vitamin B3, plays essential roles in cell physiology through facilitating NAD+ redox homeostasis and providing NAD+ as a substrate to a class of enzymes that catalyze non-redox reactions. These non-redox enzymes include the sirtuin family proteins which deacetylate target proteins while cleaving NAD+ to yield NAM. Since the finding that NAM exerts feedback inhibition to the sirtuin reactions, NAM has been widely used as an inhibitor in the studies where SIRT1, a key member of sirtuins, may have a role in certain cell physiology. However, once administered to cells, NAM is rapidly converted to NAD+ and, therefore, the cellular concentration of NAM decreases rapidly while that of NAD+ increases. The result would be an inhibition of SIRT1 for a limited duration, followed by an increase in the activity. This possibility raises a concern on the validity of the interpretation of the results in the studies that use NAM as a SIRT1 inhibitor. To understand better the effects of cellular administration of NAM, we reviewed published literature in which treatment with NAM was used to inhibit SIRT1 and found that the expected inhibitory effect of NAM was either unreliable or muted in many cases. In addition, studies demonstrated NAM administration stimulates SIRT1 activity and improves the functions of cells and organs. To determine if NAM administration can generate conditions in cells and tissues that are stimulatory to SIRT1, the changes in the cellular levels of NAM and NAD+ reported in the literature were examined and the factors that are involved in the availability of NAD+ to SIRT1 were evaluated. We conclude that NAM treatment can hypothetically be stimulatory to SIRT1.

Lipid Accumulation in HepG2 Cells Is Attenuated by Strawberry Extract through AMPK Activation

Regulation of lipid metabolism is essential for treatment and prevention of several chronic diseases such as obesity, diabetes, and cardiovascular diseases, which are responsible for most deaths worldwide. It has been demonstrated that the AMP-activated protein kinase (AMPK) has a direct impact on lipid metabolism by modulating several downstream-signaling components. The main objective of the present work was to evaluate the in vitro effect of a methanolic strawberry extract on AMPK and its possible repercussion on lipid metabolism in human hepatocellular carcinoma cells (HepG2). For such purpose, the lipid profile and the expression of proteins metabolically related to AMPK were determined on cells lysates. The results demonstrated that strawberry methanolic extract decreased total cholesterol, low-density lipoprotein (LDL)-cholesterol, and triglycerides levels (up to 0.50-, 0.30-, and 0.40-fold, respectively) while it stimulated the p-AMPK/AMPK expression (up to 3.06-fold), compared to the control. AMPK stimulation led to the phosphorylation and consequent inactivation of acetyl coenzyme A carboxylase (ACC) and inhibition of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), the major regulators of fatty acids and cholesterol synthesis, respectively. Strawberry treatment also entailed a 4.34-, 2.37-, and 2.47-fold overexpression of LDL receptor, sirtuin 1 (Sirt1), and the peroxisome proliferator activated receptor gamma coactivator 1-alpha (PGC-1α), respectively, compared to control. The observed results were counteracted by treatment with compound C, an AMPK pharmacological inhibitor, confirming that multiple effects of strawberries on lipid metabolism are mediated by the activation of this protein.

Aging-Related Correlation between Serum Sirtuin 1 Activities and Basal Metabolic Rate in Women, but not in Men

Sirtuin (SIRT) is a main regulator of metabolism and lifespan, and its importance has been implicated in the prevention against aging-related diseases. The purpose of this study was to identify the pattern of serum SIRT1 activity according to age and sex, and to investigate how serum SIRT1 activity is correlated with other metabolic parameters in Korean adults. The Biobank of Jeju National University Hospital, a member of the Korea Biobank Network, provided serum samples from 250 healthy adults. Aging- and metabolism-related factors were analyzed in serum, and the data were compared by the stratification of age and sex. Basal metabolic rate (BMR) decreased with age and was significantly lower in men in their fifties and older and in women in their forties and older compared with twenties in men and women, respectively. SIRT1 activities were altered by age and sex. Especially, women in their thirties showed the highest SIRT1 activities. Correlation analysis displayed that SIRT1 activity is positively correlated with serum triglyceride (TG) in men, and with waist circumference, systolic blood pressure, diastolic blood pressure, and serum TG in women. And, SIRT1 activity was negatively correlated with aspartate aminotransferase/alanine aminotransferase ratio in women (r = −0.183, p = 0.039). Positive correlation was observed between SIRT1 activity and BMR in women (r = 0.222, p = 0.027), but not in men. Taken together, these findings suggest the possibility that serum SIRT1 activities may be utilized as a biomarker of aging. In addition, positive correlation between SIRT1 activity and BMR in women suggests that serum SIRT1 activity may reflect energy expenditure well in human.

The Gut Microbiota and their Metabolites: Potential Implications for the Host Epigenome

The gut microbiota represents a metabolically active biomass of up to 2 kg in adult humans. Microbiota-derived molecules significantly contribute to the host metabolism. Large amounts of bacterial metabolites are taken up by the host and are subsequently utilized by the human body. For instance, short chain fatty acids produced by the gut microbiota are a major energy source of humans.It is widely accepted that microbiota-derived metabolites are used as fuel for beta-oxidation (short chain fatty acids) and participate in many metabolic processes (vitamins, such as folic acid). Apart from these direct metabolic effects, it also becomes more and more evident that these metabolites can interact with the mammalian epigenetic machinery. By interacting with histones and DNA they may be able to manipulate the host's chromatin state and functionality and hence its physiology and health.In this chapter, we summarize the current knowledge on possible interactions of different bacterial metabolites with the mammalian epigenetic machinery, mostly based on in vitro data. We discuss the putative impact on chromatin marks, for example histone modifications and DNA methylation. Subsequently, we speculate about possible beneficial and adverse consequences for the epigenome, the physiology and health of the host, as well as plausible future applications of this knowledge for in vivo translation to support personal health.

Bovine (Bos taurus) Bone Marrow Mesenchymal Cell Differentiation to Adipogenic and Myogenic Lineages

PURPOSE

We evaluated the effect of peroxisome proliferator-activated receptor (PPAR) agonists on the differentiation and metabolic features of bovine bone marrow-derived mesenchymal cells induced to adipogenic or myogenic lineages.

METHODS

Cells isolated from 7-day-old calves were cultured in basal medium (BM). For adipogenic differentiation, cells were cultured for one passage in BM and then transferred to a medium supplemented with either rosiglitazone, telmisartan, sirtinol or conjugated c-9, t-11 linoleic acid; for myogenic differentiation, third-passage cells were added with either bezafibrate, telmisartan or sirtinol. The expression of PPARx03B3; (an adipogenic differentiation marker), myosin heavy chain (MyHC; a myogenic differentiation marker) and genes related to energy metabolism were measured by quantitative real-time PCR in a completely randomized design.

RESULTS

For adipogenic differentiation, 20 µM telmisartan showed the highest PPARx03B3; expression (15.58 ± 0.62-fold, p < 0.0001), and differences in the expression of energy metabolism-related genes were found for hexokinase II, phosphofructokinase, adipose triglyceride lipase, acetyl-CoA carboxylase α(ACACα) and fatty acid synthase (p < 0.001), but not for ACACβ (p = 0.4275). For myogenic differentiation, 200 µM bezafibrate showed the highest MyHC expression (73.98 ± 11.79-fold), and differences in the expression of all energy metabolism-related genes were found (p < 0.05).

CONCLUSIONS

Adipocyte and myocyte differentiation are enhanced with telmisartan and bezafibrate, respectively, and energy uptake, storage and mobilization are improved with both.

Maternal High-Fat Feeding Increases Placental Lipoprotein Lipase Activity by Reducing SIRT1 Expression in Mice

This study investigated how maternal overnutrition and obesity regulate expression and activation of proteins that facilitate lipid transport in the placenta. To create a maternal overnutrition and obesity model, primiparous C57BL/6 mice were fed a high-fat (HF) diet throughout gestation. Fetuses from HF-fed dams had significantly increased serum levels of free fatty acid and body fat. Despite no significant difference in placental weight, lipoprotein lipase (LPL) protein levels and activity were remarkably elevated in placentas from HF-fed dams. Increased triglyceride content and mRNA levels of CD36, VLDLr, FABP3, FABPpm, and GPAT2 and -3 were also found in placentas from HF-fed dams. Although both peroxisome proliferator-activated receptor-γ (PPARγ) and CCAAT/enhancer binding protein-α protein levels were significantly increased in placentas of the HF group, only PPARγ exhibited a stimulative effect on LPL expression in cultured JEG-3 human trophoblasts. Maternal HF feeding remarkably decreased SIRT1 expression in placentas. Through use of an SIRT1 activator and inhibitor and cultured trophoblasts, an inhibitory effect of SIRT1 on LPL expression was demonstrated. We also found that SIRT1 suppresses PPARγ expression in trophoblasts. Most importantly, inhibition of PPARγ abolished the SIRT1-mediated regulatory effect on LPL expression. Together, these results indicate that maternal overnutrition induces LPL expression in trophoblasts by reducing the inhibitory effect of SIRT1 on PPARγ.

Sphingolipids are required for efficient triacylglycerol loss in conjugated linoleic Acid treated adipocytes

Conjugated linoleic acid (CLA) reduces adiposity in human and mouse adipocytes. This outcome is achieved through a variety of biological responses including increased energy expenditure and fatty acid oxidation, increased inflammation, repression of fatty acid biosynthesis, attenuated glucose transport, and apoptosis. In the current study, profiling of 261 metabolites was conducted to gain new insights into the biological pathways responding to CLA in 3T3-L1 adipocytes. Sphinganine and sphingosine levels were observed to be highly elevated in CLA treated adipocytes. Exogenous chemicals that increased endogenous ceramide levels decreased lipid levels in adipocytes, and activated AMP-activated protein kinase (AMPK) as well as NF-κB, both of which are typically activated in CLA treated adipocytes. Concurrent inhibition of ceramide de novo biosynthesis and recycling from existing sphingolipid pools attenuated the lipid lowering effect normally associated with responses to CLA, implicating ceramides as an important component of the lipid lowering response in CLA treated adipocytes.

The role of reactive oxygen species in mesenchymal stem cell adipogenic and osteogenic differentiation: a review

Mesenchymal stromal cells (MSCs) are promising candidates for tissue engineering and regenerative medicine. The multipotent stem cell component of MSC isolates is able to differentiate into derivatives of the mesodermal lineage including adipocytes, osteocytes, chondrocytes, and myocytes. Many common pathways have been described in the regulation of adipogenesis and osteogenesis. However, stimulation of osteogenesis appears to suppress adipogenesis and vice-versa. Increasing evidence implicates a tight regulation of these processes by reactive oxygen species (ROS). ROS are short-lived oxygen-containing molecules that display high chemical reactivity toward DNA, RNA, proteins, and lipids. Mitochondrial complexes I and III, and the NADPH oxidase isoform NOX4 are major sources of ROS production during MSC differentiation. ROS are thought to interact with several pathways that affect the transcription machinery required for MSC differentiation including the Wnt, Hedgehog, and FOXO signaling cascades. On the other hand, elevated levels of ROS, defined as oxidative stress, lead to arrest of the MSC cell cycle and apoptosis. Tightly regulated levels of ROS are therefore critical for MSC terminal differentiation, although the precise sources, localization, levels and the exact species of ROS implicated remain to be determined. This review provides a detailed overview of the influence of ROS on adipogenic and osteogenic differentiation in MSCs.

Modulation of peroxisome proliferator-activated receptor gamma (PPAR γ) by conjugated fatty acid in obesity and inflammatory bowel disease

Conjugated fatty acids including conjugated linoleic acid (CLA) and conjugated linolenic acid (CLNA) have drawn significant attention for their variety of biologically beneficial effects. Evidence suggested that CLA and CLNA could play physiological roles by regulating the expression and activity of PPAR γ. This review summarizes the current understanding of evidence of the role of CLA (cis-9,trans-11 CLA and trans-10,cis-12 CLA) and CLNA (punicic acid and α-eleostearic acid) in modulating the expression or activity of PPAR γ that could in turn be employed as complementary treatment for obesity and inflammatory bowel disease.

Annotation of the Daphnia magna nuclear receptors: comparison to Daphnia pulex

Most nuclear receptors (NRs) are ligand-dependent transcription factors crucial in homeostatic physiological responses or environmental responses. We annotated the Daphnia magna NRs and compared them to Daphnia pulex and other species, primarily through phylogenetic analysis. Daphnia species contain 26 NRs spanning all seven gene subfamilies. Thirteen of the 26 receptors found in Daphnia species phylogenetically segregate into the NR1 subfamily, primarily involved in energy metabolism and resource allocation. Some of the Daphnia NRs, such as RXR, HR96, and E75 show strong conservation between D. magna and D. pulex. Other receptors, such as EcRb, THRL-11 and RARL-10 have diverged considerably and therefore may show different functions in the two species. Curiously, there is an inverse association between the number of NR splice variants and conservation of the LBD. Overall, D. pulex and D. magna possess the same NRs; however not all of the NRs demonstrate high conservation indicating the potential for a divergence of function.

Quercetin reduces obesity-associated ATM infiltration and inflammation in mice: a mechanism including AMPKα1/SIRT1

Adipose tissue macrophage (ATM) plays a central role in obesity-associated inflammation and insulin resistance. Quercetin, a dietary flavonoid, possesses anti-inflammation and anti-insulin resistance properties. However, it is unclear whether quercetin can alleviate high-fat diet (HFD)-induced ATM infiltration and inflammation in mice. In this study, 5-week-old C57BL/6 mice were fed low-fat diet, HFD, or HFD with 0.l% quercetin for 12 weeks, respectively. Dietary quercetin reduced HFD-induced body weight gain and improved insulin sensitivity and glucose intolerance in mice. Meanwhile, dietary quercetin enhanced glucose transporter 4 translocation and protein kinase B signal in epididymis adipose tissues (EATs), suggesting that it heightened glucose uptake in adipose tissues. Histological and real-time PCR analysis revealed that quercetin attenuated mast cell and macrophage infiltration into EATs in HFD-fed mice. Dietary quercetin also modified the phenotype ratio of M1/M2 macrophages, lowered the levels of proinflammatory cytokines, and enhanced adenosine monophosphate-activated protein kinase (AMPK) α1 phosphorylation and silent information regulator 1 (SIRT1) expression in EATs. Further, using AMPK activator 5-aminoimidazole-4-carboxamide-1-β4-ribofuranoside and inhibitor Compound C, we found that quercetin inhibited polarization and inflammation of mouse bone marrow-derived macrophages through an AMPKα1/SIRT1-mediated mechanism. In conclusion, dietary quercetin might suppress ATM infiltration and inflammation through the AMPKα1/SIRT1 pathway in HFD-fed mice.

Role of SIRT1 and AMPK in mesenchymal stem cells differentiation

The differentiation capabilities of mesenchymal stem cells (MSCs) compromise with age and with in vitro passages which could impair the efficacy of cell therapy and tissue engineering. However, how to maintain these capabilities is not fully understood. Calorie restriction (CR, decreasing caloric intake by 30-40%) could extend longevity and reduce aging-related diseases. Recent studies revealed that CR could influence the lineage determination of stem cells including MSCs. Two important mediators of CR might be silent mating type information regulation 2 homolog 1 (SIRT1), a NAD(+)-dependent deacetylase, and AMP-activated protein kinase (AMPK), an energy-sensing kinase. Evidences are mounting that both SIRT1 and AMPK play important roles in cell fate determination of MSCs. Herein, we intend to sum up our understanding about the role of SIRT1 and AMPK in osteogenic and adipogenic potential of MSCs. Metabolic process of MSCs differentiation and the putative interplay of SIRT1 and AMPK in this process was also discussed.

Rutaecarpine analogues reduce lipid accumulation in adipocytes via inhibiting adipogenesis/lipogenesis with AMPK activation and UPR suppression

Obesity is characterized by expansion of adipose tissue, which results from an increase in adipocyte number (adipogenesis) and adipocyte size (lipogenesis). A reversal of these processes has been suggested to be a potential antiobetic therapy. Rutaecarpine (Rut) and its novel analogues (R17 and R18) were identified to exert potent effect in reducing lipid accumulation during adipocyte differentiation in 3T3-L1 adipocytes with little cytotoxicity. All three compounds reduced lipid accumulation in a dose-dependent manner, while R17 and R18 exhibited much more potent inhibitory effects compared to that of Rut. Further studies showed that R17 suppressed both adipogenesis and lipogenesis during all stages of adipocyte differentiation as indicated by the reduced protein and mRNA levels of key regulators of adipogenesis/lipogenesis, including PPARγ, C/EBPα, SREBP-1c, ACC, FAS, and SCD-1. We next examined the effect of R17 on the UPR pathway and the results showed that the UPR markers (PERK, eIF2α, IRE1α, and spliced XBP1 mRNA) were all significantly reduced by R17. Further studies revealed that R17 persistently activated AMPK during differentiation, suggesting that the AMPK may be an upstream mechanism for the effect of R17 on adipogenesis and lipogenesis via the adipogenic/lipogenic markers and the UPR pathway. Finally, studies in fast/refeeding mice demonstrated that R17 administration was able to reduce epididymal fat mass and the levels of plasma TG and FFA in vivo. Our results suggest that rutaecarpine analogues may have therapeutic potential for obesity and related metabolic disorders. The mechanism involves the suppression of adipogenic/lipogenic proteins and the suppression of the UPR pathway possibly via the AMPK.