Cnidii Fructus: A traditional Chinese medicine herb and source of antiosteoporotic drugs.

BACKGROUND: Osteoporosis (OP) is a prevalent chronic metabolic bone disease for which limited countermeasures are available. Cnidii Fructus (CF), primarily derived from Cnidium monnieri (L.) Cusson., has been tested in clinical trials of traditional Chinese medicine for the management of OP. Accumulating preclinical studies indicate that CF may be used against OP. MATERIALS AND METHODS: Comprehensive documentation and analysis were conducted to retrieve CF studies related to its main phytochemical components as well as its pharmacokinetics, safety and pharmacological properties. We also retrieved information on the mode of action of CF and, in particular, preclinical and clinical studies related to bone remodeling. This search was performed from the inception of databases up to the end of 2022 and included PubMed, China National Knowledge Infrastructure, the National Science and Technology Library, the China Science and Technology Journal Database, Weipu, Wanfang, the Web of Science and the China National Patent Database. RESULTS: CF contains a wide range of natural active compounds, including osthole, bergapten, imperatorin and xanthotoxin, which may underlie its beneficial effects on improving bone metabolism and quality. CF action appears to be mediated via multiple processes, including the osteoprotegerin (OPG)/receptor activator of nuclear factor-κB ligand (RANKL)/receptor activator of nuclear factor-κB (RANK), Wnt/ß-catenin and bone morphogenetic protein (BMP)/Smad signaling pathways. CONCLUSION: CF and its ingredients may provide novel compounds for developing anti-OP drugs.

Silencing ANGPTL8 reduces mouse preadipocyte differentiation and insulin signaling.

ANGPTL8, expressed mainly in the liver and adipose tissue, regulates the activity of lipoprotein lipase (LPL) present in the extracellular space and triglyceride (TG) metabolism through its interaction with ANGPTL3 and ANGPTL4. Whether intracellular ANGPTL8 can also exert effects in tissues where it is expressed is uncertain. ANGPTL8 expression was low in preadipocytes and much increased during differentiation. To better understand the role of intracellular ANGPTL8 in adipocytes and assess whether it may play a role in adipocyte differentiation, we knocked down its expression in normal mouse subcutaneous preadipocytes. ANGPTL8 knockdown reduced adipocyte differentiation, cellular TG accumulation and also isoproterenol-stimulated lipolysis at day 7 of differentiation. RNA-Seq analysis of ANGPTL8 siRNA or control siRNA transfected SC preadipocytes on days 0, 2, 4 and 7 of differentiation showed that ANGPTL8 knockdown impeded the early (day 2) expression of adipogenic and insulin signaling genes, PPARγ, as well as genes related to extracellular matrix and NF-κB signaling. Insulin mediated Akt phosphorylation was reduced at an early stage during adipocyte differentiation. This study based on normal primary cells shows that ANGPTL8 has intracellular actions in addition to effects in the extracellular space, like modulating LPL activity. Preadipocyte ANGPTL8 expression modulates their differentiation possibly via changes in insulin signaling gene expression.

Glycerol 3-phosphate phosphatase/PGPH-2 counters metabolic stress and promotes healthy aging via a glycogen sensing-AMPK-HLH-30-autophagy axis in C. elegans.

Metabolic stress caused by excess nutrients accelerates aging. We recently demonstrated that the newly discovered enzyme glycerol-3-phosphate phosphatase (G3PP; gene Pgp), which operates an evolutionarily conserved glycerol shunt that hydrolyzes glucose-derived glycerol-3-phosphate to glycerol, counters metabolic stress and promotes healthy aging in C. elegans. However, the mechanism whereby G3PP activation extends healthspan and lifespan, particularly under glucotoxicity, remained unknown. Here, we show that the overexpression of the C. elegans G3PP homolog, PGPH-2, decreases fat levels and mimics, in part, the beneficial effects of calorie restriction, particularly in glucotoxicity conditions, without reducing food intake. PGPH-2 overexpression depletes glycogen stores activating AMP-activate protein kinase, which leads to the HLH-30 nuclear translocation and activation of autophagy, promoting healthy aging. Transcriptomics reveal an HLH-30-dependent longevity and catabolic gene expression signature with PGPH-2 overexpression. Thus, G3PP overexpression activates three key longevity factors, AMPK, the TFEB homolog HLH-30, and autophagy, and may be an attractive target for age-related metabolic disorders linked to excess nutrients.

A peripherally restricted cannabinoid-1 receptor inverse agonist promotes insulin secretion and protects from cytokine toxicity in human pancreatic islets.

The cannabinoid receptor CB1R is expressed in pancreatic ß-cells; CB1R increased activity is associated with diabetes, obesity, cardiovascular disorders as well as decreased insulin secretion and insulin resistance. CB1R was shown to signal through G-protein coupling as well as ß-arrestins in ß-cells. Peripherally restricted CB1R inverse agonists purportedly have beneficial effects on insulin secretion in ß-cells, without the unwanted effects in the central nervous system. Here we show that a peripherally restricted CB1R inverse agonist, MRI-1891, augments glucose stimulated insulin secretion in isolated human pancreatic islets and mouse islets. The insulin secretion enhancing effect of MRI-1891 is comparable to exendin-4, an analogue of the glucagon like peptide-1 (GLP1). Moreover, MRI-1891 treatment protects isolated human islet cells against cytokine-induced apoptosis, similar to exendin-4. Thus, MRI-1891, a new class of CB1R inverse agonist, may be considered a potential therapeutic for both type 1 and type 2 diabetes because of its ability to protect pancreatic ß-cells from cytokine toxicity and to promote insulin secretion.

Hepatic glycerol shunt and glycerol-3-phosphate phosphatase control liver metabolism and glucodetoxification under hyperglycemia.

OBJECTIVE: Glycerol-3-phosphate (Gro3P) phosphatase (G3PP) hydrolyzes Gro3P to glycerol that exits the cell, thereby operating a "glycerol shunt", a metabolic pathway that we identified recently in mammalian cells. We have investigated the role of G3PP and the glycerol shunt in the regulation of glucose metabolism and lipogenesis in mouse liver. METHODS: We generated hepatocyte-specific G3PP-KO mice (LKO), by injecting AAV8-TBG-iCre to male G3PPfl/fl mice. Controls received AAV8-TBG-eGFP. Both groups were fed chow diet for 10 weeks. Hyperglycemia (16-20 mM) was induced by glucose infusion for 55 h. Hepatocytes were isolated from normoglycemic mice for ex vivo studies and targeted metabolomics were measured in mice liver after glucose infusion. RESULTS: LKO mice showed no change in body weight, food intake, fed and fasted glycemia but had increased fed plasma triglycerides. Hepatic glucose production from glycerol was increased in fasted LKO mice. LKO mouse hepatocytes displayed reduced glycerol production, elevated triglyceride and lactate production at high glucose concentration. Hyperglycemia in LKO mice led to increased liver weight and accumulation of triglycerides, glycogen and cholesterol together with elevated levels of Gro3P, dihydroxyacetone phosphate, acetyl-CoA and some Krebs cycle intermediates in liver. Hyperglycemic LKO mouse liver showed elevated expression of proinflammatory cytokines and M1-macrophage markers accompanied by increased plasma triglycerides, LDL/VLDL, urea and uric acid and myocardial triglycerides. CONCLUSIONS: The glycerol shunt orchestrated by G3PP acts as a glucose excess detoxification pathway in hepatocytes by preventing metabolic disturbances that contribute to enhanced liver fat, glycogen storage, inflammation and lipid build-up in the heart. We propose G3PP as a novel therapeutic target for hepatic disorders linked to nutrient excess.

ß-cell deletion of the PKm1 and PKm2 isoforms of pyruvate kinase in mice reveals their essential role as nutrient sensors for the KATP channel.

Pyruvate kinase (PK) and the phosphoenolpyruvate (PEP) cycle play key roles in nutrient-stimulated KATP channel closure and insulin secretion. To identify the PK isoforms involved, we generated mice lacking ß-cell PKm1, PKm2, and mitochondrial PEP carboxykinase (PCK2) that generates mitochondrial PEP. Glucose metabolism was found to generate both glycolytic and mitochondrially derived PEP, which triggers KATP closure through local PKm1 and PKm2 signaling at the plasma membrane. Amino acids, which generate mitochondrial PEP without producing glycolytic fructose 1,6-bisphosphate to allosterically activate PKm2, signal through PKm1 to raise ATP/ADP, close KATP channels, and stimulate insulin secretion. Raising cytosolic ATP/ADP with amino acids is insufficient to close KATP channels in the absence of PK activity or PCK2, indicating that KATP channels are primarily regulated by PEP that provides ATP via plasma membrane-associated PK, rather than mitochondrially derived ATP. Following membrane depolarization, the PEP cycle is involved in an 'off-switch' that facilitates KATP channel reopening and Ca2+ extrusion, as shown by PK activation experiments and ß-cell PCK2 deletion, which prolongs Ca2+ oscillations and increases insulin secretion. In conclusion, the differential response of PKm1 and PKm2 to the glycolytic and mitochondrial sources of PEP influences the ß-cell nutrient response, and controls the oscillatory cycle regulating insulin secretion.

Metabolic cycles and signals for insulin secretion.

In this review, we focus on recent developments in our understanding of nutrient-induced insulin secretion that challenge a key aspect of the "canonical" model, in which an oxidative phosphorylation-driven rise in ATP production closes KATP channels. We discuss the importance of intrinsic ß cell metabolic oscillations; the phasic alignment of relevant metabolic cycles, shuttles, and shunts; and how their temporal and compartmental relationships align with the triggering phase or the secretory phase of pulsatile insulin secretion. Metabolic signaling components are assigned regulatory, effectory, and/or homeostatic roles vis-à-vis their contribution to glucose sensing, signal transmission, and resetting the system. Taken together, these functions provide a framework for understanding how allostery, anaplerosis, and oxidative metabolism are integrated into the oscillatory behavior of the secretory pathway. By incorporating these temporal as well as newly discovered spatial aspects of ß cell metabolism, we propose a much-refined MitoCat-MitoOx model of the signaling process for the field to evaluate.

Glycerol-3-phosphate phosphatase operates a glycerol shunt in pancreatic ß-cells that controls insulin secretion and metabolic stress.

OBJECTIVE: The recently identified glycerol-3-phosphate (Gro3P) phosphatase (G3PP) in mammalian cells, encoded by the PGP gene, was shown to regulate glucose, lipid and energy metabolism by hydrolyzing Gro3P and to control glucose-stimulated insulin secretion (GSIS) in ß-cells, in vitro. However, whether G3PP regulates ß-cell function and insulin secretion in vivo is not known. METHODS: We now examined the role of G3PP in the control of insulin secretion in vivo, ß-cell function and glucotoxicity in inducible ß-cell specific G3PP-KO (BKO) mice. Inducible BKO mice were generated by crossing floxed-G3PP mice with Mip-Cre-ERT (MCre) mice. All the in vivo studies were done using BKO and control mice fed normal diet and the ex vivo studies were done using pancreatic islets from these mice. RESULTS: BKO mice, compared to MCre controls, showed increased body weight, adiposity, fed insulinemia, enhanced in vivo GSIS, reduced plasma triglycerides and mild glucose intolerance. Isolated BKO mouse islets incubated at high (16.7 mM), but not at low or intermediate glucose (3 and 8 mM), showed elevated GSIS, Gro3P content as well as increased levels of metabolites and signaling coupling factors known to reflect ß-cell activation for insulin secretion. BKO islets also showed reduced glycerol release and increased O2 consumption and ATP production at high glucose only. BKO islets chronically exposed to elevated glucose levels showed increased apoptosis, reduced insulin content and decreased mRNA expression of ß-cell differentiation markers, Pdx-1, MafA and Ins-2. CONCLUSIONS: The results demonstrate that ß-cells are endowed with a "glycerol shunt", operated by G3PP that regulates ß-cell metabolism, signaling and insulin secretion in vivo, primarily at elevated glucose concentrations. We propose that the glycerol shunt plays a role in preventing insulin hypersecretion and excess body weight gain and contributes to ß-cell mass preservation in the face of hyperglycemia.

Phosphoglycolate phosphatase homologs act as glycerol-3-phosphate phosphatase to control stress and healthspan in C. elegans.

Metabolic stress due to nutrient excess and lipid accumulation is at the root of many age-associated disorders and the identification of therapeutic targets that mimic the beneficial effects of calorie restriction has clinical importance. Here, using C. elegans as a model organism, we study the roles of a recently discovered enzyme at the heart of metabolism in mammalian cells, glycerol-3-phosphate phosphatase (G3PP) (gene name Pgp) that hydrolyzes glucose-derived glycerol-3-phosphate to glycerol. We identify three Pgp homologues in C. elegans (pgph) and demonstrate in vivo that their protein products have G3PP activity, essential for glycerol synthesis. We demonstrate that PGPH/G3PP regulates the adaptation to various stresses, in particular hyperosmolarity and glucotoxicity. Enhanced G3PP activity reduces fat accumulation, promotes healthy aging and acts as a calorie restriction mimetic at normal food intake without altering fertility. Thus, PGP/G3PP can be considered as a target for age-related metabolic disorders.

BaZiBuShen alleviates cognitive deficits and regulates Sirt6/NRF2/HO-1 and Sirt6/P53-PGC-1α-TERT signaling pathways in aging mice.

ETHNOPHARMACOLOGICAL RELEVANCE: BaZiBuShen formula (BZBS) is clinically used to counteract mental fatigue and to retard the aging process. Brain aging echoes in major risks of human sufferings and has become one of the main challenges to our societies and the health-care systems. AIM OF THE STUDY: To investigate the effect and mode of action of BZBS on aging-associated cognitive impairments. MATERIALS AND METHODS: BZBS was orally administered to D-galactose and NaNO2-induced aging mice. Premature senescence was assessed using the Morris water maze, step-down type passive avoidance, and pole-climbing tests. Telomere length was examined by qPCR analysis. Telomerase activity was assessed using PCR ELISA assay. Mitochondrial complex IV activity was examined by biochemical test. The levels of redox and immune status were determined by ELISA or biochemical assay. The expressions of sirtuin 6 (Sirt6), peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), P53, telomerase reverse transcriptase (TERT), heme oxygenase-1 (HO-1), phospho(p)-nuclear factor erythroid-2 related factor 2 (NRF2), caspase-3, Bcl-2 associated x (Bax), and B-cell lymphoma-2 (Bcl-2) in the cerebral cortex were examined by Western blot and/or immunohistochemical staining. RESULTS: BZBS intervention ameliorated reduced brain performances in aging mice, including memory, cognitive, and motor functions. In addition, BZBS administration to aging mice preserved redox homeostasis, attenuated immunosenescence, and maintained telomerase activity and telomere length. Moreover, BZBS treatment were associated with a declines in P53, caspase-3, Bax expressions and an increase in Sirt6, p-HO-1, p-NRF2, PGC-1α, and Bcl-2 expressions in the brains of this rapid aging mouse. CONCLUSIONS: BZBS attenuates premature senescence possibly via the preservation of redox homeostasis and telomere integrity, and inhibition of apoptosis in rapid aging mouse. The mechanism governing the alterations may be associated with through the activation of Sirt6/NRF2/HO-1 and Sirt6/P53-PGC-1α-TERT signaling pathways. The results suggest that BZBS may provide a novel strategy for confronting aging and age-associated diseases.

Dietary citrate acutely induces insulin resistance and markers of liver inflammation in mice.

Citrate is widely used as a food additive being part of virtually all processed foods. Although considered inert by most of the regulatory agencies in the world, plasma citrate has been proposed to play immunometabolic functions in multiple tissues through altering a plethora of cellular pathways. Here, we used a short-term alimentary intervention (24 hours) with standard chow supplemented with citrate in amount corresponding to that found in processed foods to evaluate its effects on glucose homeostasis and liver physiology in C57BL/6J mice. Animals supplemented with dietary citrate showed glucose intolerance and insulin resistance as revealed by glucose and insulin tolerance tests. Moreover, animals supplemented with citrate in their food displayed fed and fasted hyperinsulinemia and enhanced insulin secretion during an oral glucose tolerance test. Citrate treatment also amplified glucose-induced insulin secretion in vitro in INS1-E cells. Citrate supplemented animals had increased liver PKCα activity and altered phosphorylation at serine or threonine residues of components of insulin signaling including IRS-1, Akt, GSK-3 and FoxO1. Furthermore, citrate supplementation enhanced the hepatic expression of lipogenic genes suggesting increased de novo lipogenesis, a finding that was reproduced after citrate treatment of hepatic FAO cells. Finally, liver inflammation markers were higher in citrate supplemented animals. Overall, the results demonstrate that dietary citrate supplementation in mice causes hyperinsulinemia and insulin resistance both in vivo and in vitro, and therefore call for a note of caution on the use of citrate as a food additive given its potential role in metabolic dysregulation.

New Mammalian Glycerol-3-Phosphate Phosphatase: Role in ß-Cell, Liver and Adipocyte Metabolism.

Cardiometabolic diseases, including type 2 diabetes, obesity and non-alcoholic fatty liver disease, have enormous impact on modern societies worldwide. Excess nutritional burden and nutri-stress together with sedentary lifestyles lead to these diseases. Deranged glucose, fat, and energy metabolism is at the center of nutri-stress, and glycolysis-derived glycerol-3-phosphate (Gro3P) is at the crossroads of these metabolic pathways. Cellular levels of Gro3P can be controlled by its synthesis, utilization or hydrolysis. The belief that mammalian cells do not possess an enzyme that hydrolyzes Gro3P, as in lower organisms and plants, is challenged by our recent work showing the presence of a Gro3P phosphatase (G3PP) in mammalian cells. A previously described phosphoglycolate phosphatase (PGP) in mammalian cells, with no established physiological function, has been shown to actually function as G3PP, under physiological conditions, particularly at elevated glucose levels. In the present review, we summarize evidence that supports the view that G3PP plays an important role in the regulation of gluconeogenesis and fat storage in hepatocytes, glucose stimulated insulin secretion and nutri-stress in ß-cells, and lipogenesis in adipocytes. We provide a balanced perspective on the pathophysiological significance of G3PP in mammals with specific reference to cardiometabolic diseases.

Substantial PCSK9 inactivation in ß-cells does not modify glucose homeostasis or insulin secretion in mice.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays an important role in cholesterol homeostasis by promoting the degradation of the LDL receptor (LDLR). PCSK9 loss-of-function mutations are associated with increased fasting plasma glucose levels and slightly elevated risk of type 2-diabetes. Considering the known detrimental effects of cholesterol accumulation in ß-cell, and the widespread use of PCSK9 inhibitors to treat hypercholesterolemia, it is important to gain insight into the role of pancreatic PCSK9 in glucose homeostasis and ß-cell function. We generated the first ß-cell-specific KO of PCSK9 (ßKO). PCSK9 mRNA and protein expression were reduced by 48% and 78% in ßKO islets, respectively, indicating that ß-cells constitute a major site of PCSK9 expression. In islets, loss of ß-cell PCSK9 resulted in unchanged LDLR protein levels, but reduced LDLR mRNA, indicating that cholesterol internalization is enhanced and that ß-cell PCSK9 promotes LDLR degradation. In contrast, whole body PCSK9 KO mice exhibited 2-fold higher LDLR protein levels in islets and a stable expression of cholesterogenic genes. Whole body KO and ßKO mice presented normal glucose tolerance, insulin release in response to glucose load and insulin sensitivity. Ex vivo glucose-stimulated insulin secretion in presence or absence of fatty acids was similar in WT and KO islets. Like KO mice, individuals carrying loss-of-function PCSK9 variants may be protected from cholesterol-induced toxicity due to reduced circulating cholesterol levels. Using both whole body KO or ßKO models, our data demonstrate that PCSK9 deletion in mouse does not have any toxic effect on ß-cell function and glucose homeostasis.

Elevated Expression of Glycerol-3-Phosphate Phosphatase as a Biomarker of Poor Prognosis and Aggressive Prostate Cancer.

The limitations of the biomarker prostate-specific antigen (PSA) necessitate the pursuit of biomarkers capable of better identifying high-risk prostate cancer (PC) patients in order to improve their therapeutic management and outcomes. Aggressive prostate tumors characteristically exhibit high rates of glycolysis and lipogenesis. Glycerol 3-phosphate phosphatase (G3PP), also known as phosphoglycolate phosphatase (PGP), is a recently identified mammalian enzyme, shown to play a role in the regulation of glucose metabolism, lipogenesis, lipolysis, and cellular nutrient-excess detoxification. We hypothesized that G3PP may relieve metabolic stress in cancer cells and assessed the association of its expression with PC patient prognosis. Using immunohistochemical staining, we assessed the epithelial expression of G3PP in two different radical prostatectomy (RP) cohorts with a total of 1797 patients, for whom information on biochemical recurrence (BCR), metastasis, and mortality was available. The association between biomarker expression, biochemical recurrence (BCR), bone metastasis, and prostate cancer-specific survival was established using log-rank and multivariable Cox regression analyses. High expression of G3PP in PC epithelial cells is associated with an increased risk of BCR, bone metastasis, and PC-specific mortality. Multivariate analysis revealed high G3PP expression in tumors as an independent predictor of BCR and bone metastasis development. High G3PP expression in tumors from patients eligible for prostatectomies is a new and independent prognostic biomarker of poor prognosis and aggressive PC for recurrence, bone metastasis, and mortality.

Neutral sphingomyelinase-2 and cardiometabolic diseases.

Sphingolipids, in particular ceramides, play vital role in pathophysiological processes linked to metabolic syndrome, with implications in the development of insulin resistance, pancreatic ß-cell dysfunction, type 2 diabetes, atherosclerosis, inflammation, nonalcoholic steatohepatitis, and cancer. Ceramides are produced by the hydrolysis of sphingomyelin, catalyzed by different sphingomyelinases, including neutral sphingomyelinase 2 (nSMase2), whose dysregulation appears to underlie many of the inflammation-related pathologies. In this review, we discuss the current knowledge on the biochemistry of nSMase2 and ceramide production and its regulation by inflammatory cytokines, with particular reference to cardiometabolic diseases. nSMase2 contribution to pathogenic processes appears to involve cyclical feed-forward interaction with proinflammatory cytokines, such as TNF-α and IL-1ß, which activate nSMase2 and the production of ceramides, that in turn triggers the synthesis and release of inflammatory cytokines. We elaborate these pathogenic interactions at the molecular level and discuss the potential therapeutic benefits of inhibiting nSMase2 against inflammation-driven cardiometabolic diseases.

BaZiBuShen alleviates altered testicular morphology and spermatogenesis and modulates Sirt6/P53 and Sirt6/NF-κB pathways in aging mice induced by D-galactose and NaNO2.

ETHNOPHARMACOLOGICAL RELEVANCE: Sperm infertility and testicular atrophy are symptoms associated with aging. BaZiBuShen formula (BZBS), a patented Chinese herbal prescription composed of Semen Cuscutae, Fructus Lycii, Epimedii Folium, Fructus Schisandrae Sphenantherae, Fructus Cnidii, Fructus Rosae Laevigatae, Semen Allii Tuberosi., Radix Morindae Officinalis, Herba Cistanches, Fructus Rubi, Radix Rehmanniae Recens, Radix Cyathulae, Radix Ginseng, Cervi Cornu Pantotrichum, Hippocampus, and Fuctus Toosendan, has been used as a kidney-tonifying and anti-aging drug as well as for the treatment of impotence and male infertility in traditional Chinese medicine. AIM OF THE STUDY: We aimed at investigating whether BZBS preserves sperm and testes morphology in aging mice, and to explore the underlying mechanisms. MATERIALS AND METHODS: BZBS was orally administered to aging mice induced by D-galactose (D-gal) and NaNO2 for 65 days. Sperm quality and testes pathophysiological alterations were examined by a Semen Analysis System, hematoxylin-eosin staining, transmission electron microscopy, and mitochondrial complex IV activity. In addition, serum levels of total antioxidant capacity (TAC), malondialdehyde (MDA), 8-hydroxy-desoxyguanosine (8-OH-dG), reduced glutathione (GSH), oxidized glutathione disulfide (GSSG), testosterone (T), follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2) and tumor necrosis factor-α (TNF-α) were determined by ELISA. The expressions of P450 aromatase (CYP19), sirtuin 6 (Sirt6), P53, inducible nitric oxide synthase (iNOS), nuclear factor-kappa B (NF-κB)-p65, and phospho-NF-κB-p65 (NF-κB-pp65) in the testes were examined by western blot and/or immunohistochemical staining. RESULTS: Sustained exposure to D-gal/NaNO2 caused a deterioration of sperm quality and testes morphology in this rapid aging mouse model. BZBS treatment curtailed these alterations. These beneficial effects were associated with increased serum levels of TAC, GSH/GSSG, T, E2, and FSH, and decreased levels of MDA, TNF-α, and 8-OH-dG. BZBS treatment also downregulated the expressions of P53, iNOS, and NF-κB-pp65, as well as upregulated the expressions of Sirt6 and CYP19 in aging testes. CONCLUSIONS: BZBS preserves testicular morphology and spermatogenesis possibly via inhibition of oxidative stress and the modulation of the Sirt6/P53 and Sirt6/NF-κB signaling pathways. The results shed light on the beneficial effect of BZBS on sperm quality and fertility in aging males.

Blocking mitochondrial pyruvate import in brown adipocytes induces energy wasting via lipid cycling.

Combined fatty acid esterification and lipolysis, termed lipid cycling, is an ATP-consuming process that contributes to energy expenditure. Therefore, interventions that stimulate energy expenditure through lipid cycling are of great interest. Here we find that pharmacological and genetic inhibition of the mitochondrial pyruvate carrier (MPC) in brown adipocytes activates lipid cycling and energy expenditure, even in the absence of adrenergic stimulation. We show that the resulting increase in ATP demand elevates mitochondrial respiration coupled to ATP synthesis and fueled by lipid oxidation. We identify that glutamine consumption and the Malate-Aspartate Shuttle are required for the increase in Energy Expenditure induced by MPC inhibition in Brown Adipocytes (MAShEEBA). We thus demonstrate that energy expenditure through enhanced lipid cycling can be activated in brown adipocytes by decreasing mitochondrial pyruvate availability. We present a new mechanism to increase energy expenditure and fat oxidation in brown adipocytes, which does not require adrenergic stimulation of mitochondrial uncoupling.

Adipose ABHD6 regulates tolerance to cold and thermogenic programs.

Enhanced energy expenditure in brown (BAT) and white adipose tissues (WAT) can be therapeutic against metabolic diseases. We examined the thermogenic role of adipose α/ß-hydrolase domain 6 (ABHD6), which hydrolyzes monoacylglycerol (MAG), by employing adipose-specific ABHD6-KO mice. Control and KO mice showed similar phenotypes at room temperature and thermoneutral conditions. However, KO mice were resistant to hypothermia, which can be accounted for by the simultaneously increased lipolysis and lipogenesis of the thermogenic glycerolipid/free fatty acid (GL/FFA) cycle in visceral fat, despite unaltered uncoupling protein 1 expression. Upon cold stress, nuclear 2-MAG levels increased in visceral WAT of the KO mice. Evidence is provided that 2-MAG causes activation of PPARα in white adipocytes, leading to elevated expression and activity of GL/FFA cycle enzymes. In the ABHD6-ablated BAT, glucose and oxidative metabolism were elevated upon cold induction, without changes in GL/FFA cycle and lipid turnover. Moreover, response to in vivo ß3-adrenergic stimulation was comparable between KO and control mice. Our data reveal a MAG/PPARα/GL/FFA cycling metabolic signaling network in visceral adipose tissue, which contributes to cold tolerance, and that adipose ABHD6 is a negative modulator of adaptive thermogenesis.

The multi-faces of Angptl8 in health and disease: Novel functions beyond lipoprotein lipase modulation.

Angiopoietin-like protein (ANGPTL) family members, mainly ANGPTL3, ANGPTL4 and ANGPTL8, are physiological inhibitors of lipoprotein lipase (LPL), and play a critical role in lipoprotein and triglyceride metabolism in response to nutritional cues. ANGPTL8 has been described by different names in various studies and has been ascribed various functions at the systemic and cellular levels. Circulating ANGPTL8 originates mainly from the liver and to a smaller extent from adipose tissues. In the blood, ANGPTL8 forms a complex with ANGPTL3 or ANGPTL4 to inhibit LPL in fed or fasted conditions, respectively. Evidence is emerging for additional intracellular and receptor-mediated functions of ANGPTL8, with implications in NFκB mediated inflammation, autophagy, adipogenesis, intra-cellular lipolysis and regulation of circadian clock. Elevated levels of plasma ANGPTL8 are associated with metabolic syndrome, type 2 diabetes, atherosclerosis, hypertension and NAFLD/NASH, even though the precise relationship is not known. Whether ANGPTL8 has direct pathogenic role in these diseases, remains to be explored. In this review, we develop a balanced view on the proposed association of this protein in the regulation of several pathophysiological processes. We also discuss the well-established functions of ANGPTL8 in lipoprotein metabolism in conjunction with the emerging novel extracellular and intracellular roles of ANGPTL8 and the implicated metabolic and signalling pathways. Understanding the diverse functions of ANGPTL8 in various tissues and metabolic states should unveil new opportunities of therapeutic intervention for cardiometabolic disorders.

Nutrient-Induced Metabolic Stress, Adaptation, Detoxification, and Toxicity in the Pancreatic ß-Cell.

Paraphrasing the Swiss physician and father of toxicology Paracelsus (1493-1541) on chemical agents used as therapeutics, "the dose makes the poison," it is now realized that this aptly applies to the calorigenic nutrients. The case here is the pancreatic islet ß-cell presented with excessive levels of nutrients such as glucose, lipids, and amino acids. The short-term effects these nutrients exert on the ß-cell are enhanced insulin biosynthesis and secretion and changes in glucose sensitivity. However, chronic fuel surfeit triggers additional compensatory and adaptive mechanisms by ß-cells to cope with the increased insulin demand or to protect itself. When these mechanisms fail, toxicity due to the nutrient surplus ensues, leading to ß-cell dysfunction, dedifferentiation, and apoptosis. The terms glucotoxicity, lipotoxicity, and glucolipotoxicity have been widely used, but there is some confusion as to what they mean precisely and which is most appropriate for a given situation. Here we address the gluco-, lipo-, and glucolipo-toxicities in ß-cells by assessing the evidence both for and against each of them. We also discuss potential mechanisms and defend the view that many of the identified "toxic" effects of nutrient excess, which may also include amino acids, are in fact beneficial adaptive processes. In addition, candidate fuel-excess detoxification pathways are evaluated. Finally, we propose that a more general term should be used for the in vivo situation of overweight-associated type 2 diabetes reflecting both the adaptive and toxic processes to mixed calorigenic nutrients excess: "nutrient-induced metabolic stress" or, in brief, "nutri-stress."