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Purpose As internet dividends are gradually disappearing, loyalty programs have become the panacea for monetizing traffic, attracting new customers and retaining existing customers. Improving their effectiveness has thus become key to enterprises’ market competitiveness. However, member customers’ hedonic adaptation to this relationship strategy undermines its effectiveness. Based on the hedonic adaptation theory, this study aims to analyze the process of member customers' hedonic adaptation to preferential treatment in loyalty programs and explore the boundary conditions of alleviating this effect. Design/methodology/approach This study surveyed 271 member customers in China and tested the hypothesized relationships using structural equation modeling and multigroup analysis. Findings Preferential treatment suffers from hedonic adaptation to member customer engagement and customer gratitude, and customer tenure is a key condition for these effects. Customer gratitude is an intermediary mechanism that explains the hedonic adaptation effect of preferential treatment to member customers engagement. In addition, the structural characteristics of loyalty programs form the boundary condition that alleviates hedonic adaptation. The authors found that high-tier and -payment strategies are more likely to mitigate hedonic adaptation of preferential treatment to customer gratitude. Originality/value This study elucidates the factors that influence the effectiveness of preferential treatment and provides constructive insights into customer relationship management and for improving enterprise performance.

Mitochondrial reactive oxygen species (mROS) are central to physiology. While excess mROS production has been associated with several disease states, its precise sources, regulation, and mechanism of generationin vivoremain unknown, limiting translational efforts. Here we show that in obesity, hepatic ubiquinone (Q) synthesis is impaired, which raises the QH2/Q ratio, driving excessive mROS production via reverse electron transport (RET) from site IQin complex I. Using multiple complementary genetic and pharmacological modelsin vivowe demonstrated that RET is critical for metabolic health. In patients with steatosis, the hepatic Q biosynthetic program is also suppressed, and the QH2/Q ratio positively correlates with disease severity. Our data identify a highly selective mechanism for pathological mROS production in obesity, which can be targeted to protect metabolic homeostasis.

Drawing on organizational learning theory and literature on guanxi, this study examines how and why ambidextrous learning balance influences firm innovation capability in Chinese business circles. We propose a U-shaped relation between ambidextrous learning balance and firm innovation capability which is mediated by guanxi inertia and knowledge inertia in different ways. Specifically, ambidextrous learning balance has an inverted U-shaped impact on guanxi inertia and further influences firm innovation capability. Whereas, ambidextrous learning balance has a linear positive influence on innovation capability through a decreased level of knowledge inertia. Based on survey data collected from, The results obtained from a sample of 197 Chinese channel enterprises using SEMs analysis provide strong support for our hypotheses. In addition, the findings based on firms with unbalanced ambidextrous learning indicate that as opposed to exploratory learning, higher level of exploitative learning leads to an increase in guanxi inertia and a decrease in knowledge inertia. These conclusions reveal how ambidextrous learning balance influence innovation capability for a firm with inherent learning preference which is not discussed by the extant research. At the same time, this study fills the gap of ambidextrous learning balance by considering the influence of culture. Our work also informs foreign practitioners of the optimal ways of learning for innovation in China.

Activation of fatty acid oxidation is a promising therapy for NAFLD. Lowering acetyl-CoA carboxylase (ACC) activity depletes malonyl-CoA, activates CPT1, and increases mitochondrial fatty acid delivery. ACC1/2 liver double KO mice (LDKO) are protected from hepatic steatosis and have elevated ketogenesis in the prandial state. However, fasted LDKO mice exhibit an unexpected inhibition of ketogenesis, indicated by lower blood ketones and reduced in vivo ketone turnover of [3,4-13C2]acetoacetate and [U-13C4]β-hydroxybutyrate. Despite impaired fasting ketogenesis in vivo, perfused livers isolated from fasted mice and starved primary hepatocytes had normal or elevated ketone production, suggesting that a substrate-mediated mechanism inhibits ketosis in vivo. There were no differences in plasma NEFAs, but hepatic lactate was elevated during fasting in LDKO mice. The increase in lactate was sufficient to suppress ketone production in isolated perfused liver. An in vivo [U-13C3]lactate/pyruvate challenge was more rapidly diluted in fasted LKDO mice, indicating that alternative endogenous sources of pyruvate were available. Indeed, essential amino acids were elevated in fasted LDKO liver, but not plasma, suggestive of hepatic proteolysis as a source of amino acids. Liver size was 20% larger in LDKO mice, independent of glycogen storage or triglyceride content, but was consistent with increased insulin action and activation of Nrf2 which have been linked to hepatomegaly. Autophagy during fasting was normal or increased, suggesting that hepatomegaly supplies excess amino acids in the fasted state. Injection of exogenous alanine or glutamine in fasted WT mice recapitulated the fasted LDKO phenotype by increasing plasma glucose and lactate and decreasing ketone concentrations. Thus, hepatic growth is increased in the absence of malonyl-CoA synthesis, which provides a surplus of amino acids, anaplerotic maintenance of the TCA cycle and lower ketogenesis during fasting. Disclosure S.Deja: None. S.C.Burgess: n/a. J.A.Fletcher: None. B.Kucejova: None. M.N.Mizerska: None. X.Fu: None. C.Kim: None. J.Browning: None. J.Young: Consultant; Pfizer Inc., Research Support; Merck & Co., Inc., Stock/Shareholder; Metalytics, Inc. J.D.Horton: Board Member; Draupnir Bio, Consultant; Eli Lilly and Company, ESPERION Therapeutics, Inc., Gilead Sciences, Inc., Janssen Pharmaceuticals, Inc., Pfizer Inc., Regeneron Pharmaceuticals Inc. Funding National Institutes of Health (R01DK078184, P41EB015908)

Redox balance is critical for numerous cellular functions, including substrate oxidation, biosynthesis, and antioxidant defenses. Redox homeostasis is dysregulated in many metabolic diseases, including obesity and Type 2 diabetes. In addition to its role in replenishing TCA cycle intermediates, we previously showed that pyruvate carboxylase (PC) -mediated anaplerosis is necessary to regulate redox state, including the NADPH/NADP+ ratio and antioxidant capacity in liver, though the mechanism is unclear. We hypothesized that PC elicits effects on redox by modifying ratios of metabolites involved in redox mediated exchange reactions. Malic enzyme-1 (Me1) catalyzes the reversible, NADPH dependent, decarboxylation of malate to pyruvate. This enzyme plays a vital role in recycling malate and providing NADPH during lipogenesis. We show here that Me1 mediates redox by sensing TCA cycle function through the mass action of malate and pyruvate. We tested the role of Me1, as a sensor of anaplerosis in the TCA cycle and regulator of redox, using acute Me1 knockdown (Me1KD) in liver-specific PC knockout (LPCKO) mice. Stable isotope tracers were used to examine anaplerosis, gluconeogenesis, and pyruvate cycling fluxes, and targeted metabolomics were used to evaluate tissue energy status and redox. Anaplerosis, pyruvate cycling, and gluconeogenesis were lower in the absence of liver PC but were unaffected by Me1KD. Loss of PC decreased the malate/pyruvate ratio, congruent with impaired conversion of pyruvate to TCA cycle intermediates, which resulted in a concomitant decrease in the NADPH/NADP+ ratio. Acute removal of Me1 in LPCKO mice normalized NADPH/NADP+ and restored the malate/pyruvate ratio. Additionally, mitochondrial NAD+/NADH and FAD+/FADH redox states were more oxidized in LPCKO liver and were normalized by loss of Me1. Thus, despite not altering the aforementioned fluxes, Me1 transmits redox state in response to TCA cycle function by sensing alterations in the malate/pyruvate ratio. Disclosure M.R.Inigo: None. J.A.Fletcher: None. B.Kucejova: None. G.Sharma: None. S.Deja: None. X.Fu: None. S.C.Burgess: n/a. Funding Robert A. Welch Foundation Grant (I-1804)

Exercise is an important lifestyle intervention for the prevention and treatment of NAFLD. Importantly, exercise can reduce hepatic steatosis independent of changes in body mass, which may stem from increased oxidative demand in liver during exercise. Increased hepatic gluconeogenesis (GNG) and tricarboxylic acid (TCA) cycle flux have been observed during exercise in rodents, but it is unclear whether this adaptation is chronically maintained outside of the exercise window. Liver metabolism is also altered by nutritional status. Fasting promotes hepatic fat oxidation, ketogenesis and GNG, while feeding promotes glycogen storage and fat synthesis. Hence, fasting and exercise may have a positive interaction, whereas exogenous nutrient intake or glucose infusion is known to reduce the induction of GNG during exercise. Here, we tested whether nutritional status impacts exercise induced hepatic metabolic adaptations. Sprague-Dawley rats were kept sedentary or provided voluntary wheel running (VWR) for 4 weeks in the presence or absence of food restriction during the dark phase when rats spontaneously run. Experiments were conducted one day following the last exercise bout. Hepatic metabolic flux was examined by in vivo stable isotope infusions of [U-13C3]propionate, [3,4-13C2]glucose and 2H2O in rats using mass spectrometry and computational analysis. Chronic VWR in the fed state had no effect on basal hepatic fluxes outside of the exercise window. However, exercise during food restriction chronically induced a 2-fold induction of TCA cycle turnover, increase in GNG from glycerol and lowered ketogenesis outside of the exercise window. Thus, VWR during food restriction triggered an increase in hepatic energy demand that was sustained for at least 24 hours, while the effects of exercise in the fed state dissipated by 24 hours. These data suggest that acute nutritional state may be an important factor in the long-term programming of liver metabolism by exercise. Disclosure S.Deja: None. B.Kucejova: None. A.Maurer: None. M.N.Mizerska: None. X.Fu: None. J.P.Thyfault: None. S.C.Burgess: n/a. Funding National Institutes of Health (R01DK121497, R01DK078184, P41EB015908)

Background and purpose Overexpression or aberrant activation of the T-lymphokine-activated killer cell-originated protein kinase (TOPK) promotes gene expression and growth of solid tumours, implying that TOPK would be a rational target in developing novel anticancer drugs. Acetylshikonin, a diterpenoid compound isolated from Lithospermum erythrorhizon root, exerts a range of biological activities. Here we have investigated whether acetylshikonin, by acting as an inhibitor of TOPK, can attenuate the proliferation of colorectal cancer cells and the growth of patient-derived tumours, in vitro and in vivo. Experimental approach Targets of acetylshikonin, were identified using kinase profiling analysis, kinetic/binding assay, and computational docking analysis and knock-down techniques. Effects of acetylshikonin on colorectal cancer growth and the underlying mechanisms were evaluated in cell proliferation assays, propidium iodide and annexin-V staining analyses and western blots. Patient-derived tumour xenografts in mice (PDX) and immunohistochemistry were used to assess anti-tumour effects of acetylshikonin. Key results Acetylshikonin directly inhibited TOPK activity, interacting with the ATP-binding pocket of TOPK. Acetylshikonin suppressed cell proliferation by inducing cell cycle arrest at the G1 phase, stimulated apoptosis, and increased the expression of apoptotic biomarkers in colorectal cancer cell lines. Mechanistically, acetylshikonin diminished the phosphorylation and activation of TOPK signalling. Furthermore, acetylshikonin decreased the volume of PDX tumours and reduced the expression of TOPK signalling pathway in xenograft tumours. Conclusion and implications Acetylshikonin suppressed growth of colorectal cancer cells by attenuating TOPK signalling. Targeted inhibition of TOPK by acetylshikonin might be a promising new approach to the treatment of colorectal cancer.

[Image: see text] Intracellular nucleotides and acyl-CoAs are metabolites that are central to the regulation of energy metabolism. They set the cellular energy charge and redox state, act as allosteric regulators, modulate signaling and transcription factors, and thermodynamically activate substrates for oxidation or biosynthesis. Unfortunately, no method exists to simultaneously quantify these biomolecules in tissue extracts. A simple method was developed using ion-pairing reversed-phase high-performance liquid chromatography–electrospray-ionization tandem mass spectrometry (HPLC-ESI-MS/MS) to simultaneously quantify adenine nucleotides (AMP, ADP, and ATP), pyridine dinucleotides (NAD(+) and NADH), and short-chain acyl-CoAs (acetyl, malonyl, succinyl, and propionyl). Quantitative analysis of these molecules in mouse liver was achieved using stable-isotope-labeled internal standards. The method was extensively validated by determining the linearity, accuracy, repeatability, and assay stability. Biological responsiveness was confirmed in assays of liver tissue with variable durations of ischemia, which had substantial effects on tissue energy charge and redox state. We conclude that the method provides a simple, fast, and reliable approach to the simultaneous analysis of nucleotides and short-chain acyl-CoAs.

Ketogenesis occurs in liver mitochondria where acetyl-CoA molecules, derived from lipid oxidation, are condensed into acetoacetate (AcAc) and reduced to β-hydroxybutyrate (BHB). During carbohydrate scarcity, these two ketones are released into circulation at high rates and used as oxidative fuels in peripheral tissues. Despite their physiological relevance and emerging roles in a variety of diseases, endogenous ketone production is rarely measured in vivo using tracer approaches. Accurate determination of this flux requires a two-pool model, simultaneous BHB and AcAc tracers, and special consideration for the stability of the AcAc tracer and analyte. We describe the implementation of a two-pool model using a metabolic flux analysis (MFA) approach that simultaneously regresses liquid chromatography-tandem mass spectrometry (LC-MS/MS) ketone isotopologues and tracer infusion rates. Additionally, 1H NMR real-time reaction monitoring was used to evaluate AcAc tracer and analyte stability during infusion and sample analysis, which were critical for accurate flux calculations. The approach quantifies AcAc and BHB pool sizes and their rates of appearance, disposal, and exchange. Regression analysis provides confidence intervals and detects potential errors in experimental data. Complications for the physiological interpretation of individual ketone fluxes are discussed.

Carbohydrates and lipids are primary energy sources in mammals; thus, their oxidation and synthesis are carefully controlled. The tricarboxylic acid (TCA) cycle is necessary to oxidize these substrates, and in liver it also supports their synthesis. However, its role in regulating these processes, particularly de novo lipogenesis (DNL) is underappreciated. We report that activation of hepatic gluconeogenesis (GNG) is required to trigger the canonical lipid and carbohydrate response to fasting in mice. Phosphoenolpyruvate carboxykinase (PEPCK) catalyzes cataplerotic flux from the TCA cycle and is required for GNG from lactate, pyruvate and amino acids. Knockdown (KD) or knockout (KO) of PEPCK caused the massive accumulation of TCA cycle intermediates and KO mice developed fatty liver after an overnight fast. Lipidomic profiling of liver suggested increased lipid desaturation and elongation with loss of PEPCK. 2H NMR analysis of liver lipids following 2H2O administration demonstrated elevated fasting DNL in KO mice, which was similar to fed WT mice. In addition, fasting ketogenesis, estimated by infusions of [U-13C]BHB and [3,4-13C]AcAc, was decreased in KO mice. Despite an impaired fasting response, the expression of genes related to control of fat oxidation and DNL were not decreased, suggesting that loss of regulation was mediated by a metabolic mechanism. Inhibition of GNG produced a reduced mitochondrial redox state which limited oxidative pathways and decreased acetyl-CoA concentration. Inhibition of GNG also decreased fasting ATP requirements, resulting in a high energy charge which suppressed activation of AMPK, its canonical suppression of acetyl-CoA carboxylase and caused increased malonyl-CoA during fasting. Hence, PEPCK mediated cataplerosis and GNG during fasting is not only an important source of glucose, it is also necessary to shift cellular redox and energetics to states necessary to suppress lipogenesis and maintain ketogenesis during fasting. Disclosure S. Deja: None. J. Duarte: None. J.A. Fletcher: None. B. Kucejova: None. X. Fu: None. G. Vale: None. J. Young: Board Member; Self; Metalytics. Consultant; Self; Pfizer Inc. J. Browning: None. S.C. Burgess: None. Funding National Institutes of Health (R01DK078184, P41EB015908); Robert A. Welch Foundation (I-1804)

Liver triglyceride accumulation associated with insulin resistance is partially mediated by elevated de novo lipogenesis (DNL); thus, limiting this pathway is a promising therapeutic strategy for NAFLD. Targeted suppression of acetyl-CoA carboxylase (ACC) activity depletes malonyl-CoA resulting in lower DNL and a simultaneous increase in fat oxidation due to activation of CPT-1. Recently developed ACC1/2 liver specific double KO mice (LDKO) are protected from hepatic steatosis and closely recapitulate pharmacological inhibition of ACC1/2 in humans with NAFLD. However, hepatic ACC inhibition causes surprising elevations in circulating triglyceride and glucose concentrations. LDKO mice had worsened glucose tolerance, which was most consequential during a HFD and especially prominent during fasting. Glucose labeling from 2H2O and [U-13C3] lactate was higher in LDKO hepatocytes, an effect that was dependent on the availability of long chain fatty acids, suggesting that loss of malonyl-CoA and activation of CPT-1 promote gluconeogenesis (GNG). Ketogenesis was increased in LDKO hepatocytes and showed limited response to insulin. Acetyl-CoA was elevated in the fed state, as previously reported, but was normal during fasting when hyperglycemia was most prominent. LDKO mice exhibited massive accumulation of liver citrate and a high fasted hepatic energy charge, which are both known to activate GNG. Hence, despite improved hepatic lipid profile and insulin sensitivity, LDKO liver activates GNG. The resulting hyperinsulinemia partially ameliorates the glycemia phenotype, but may also induce hepatomegaly through canonical signaling pathways and effects on energy status. Thus, activation of fat oxidation in liver lowers lipid accumulation, but has downstream metabolic effects on energetically dependent pathways, such as GNG, that may promote elevated glucose levels in contexts of reduced insulin action, such as fasting and diet induced obesity. Disclosure S. Deja: None. J.A. Fletcher: None. B. Kucejova: None. X. Fu: None. C. Kim: None. J. Browning: None. J.D. Horton: Board Member; Self; Pfizer Inc. Consultant; Self; Gilead Sciences, Inc., Janssen Pharmaceuticals, Inc., Merck & Co., Inc. Stock/Shareholder; Self; Catabasis Pharmaceuticals. Other Relationship; Self; Regeneron Pharmaceuticals, Sanofi. S.C. Burgess: None. Funding National Institutes of Health (R01DK078184, P41EB015908); Robert A. Welch Foundation (I-1804)

Hepatic lipid synthesis and Vldl production plays a major role in whole body lipid homeostasis. Insulin imposed regulation of liver metabolism is in large part executed on a transcriptional level. Several published studies focused on the effect of hepatic insulin resistance and the role of mTORC1 in liver lipid metabolism, sometimes with conflicting results. Here we used mouse genetic models with short-term liver specific removal of the insulin receptor (complete signaling pathway inactivation), Tsc1 (mTORC1 activation), Raptor (mTORC1 inactivation), Pten (simultaneous mTORC1 and Akt activation), and Raptor Pten (simultaneous mTORC1 inactivation and Akt activation) to precisely dissect the role of insulin signaling in the regulation of lipid metabolism. In vivo 2H2O administration, 1H and 2H NMR analyses revealed hepatic de novo fatty acid (FA) and triglyceride (TG) synthesis, export, as well as FA profiles both in liver and plasma. By direct examination of in vivo hepatic de novo lipogenesis (DNL), the direction and magnitude of changes observed in lipogenic gene expression did not correlate well with differences observed in DNL flux. For example, PtenLKO mice had a 3-fold increase in DNL flux with little effect on lipogenic gene expression. Our results suggest that in some contexts other factors, possibly including metabolite availability, TCA cycle metabolism, redox state or energy charge impose stronger control over DNL than regulation of gene expression. We also show that triglyceride synthesis and incorporation of de novo synthesized FA into triglycerides is regulated by mTORC1. While mTORC1 positively regulates export of newly synthesized TG it has a negative effect on export of de novo produced FA. Disclosure B. Kucejova: None. S. Deja: None. J. Duarte: None. X. Fu: None. S.C. Burgess: None. Funding National Institutes of Health (R01DK078184)

Elevated hepatic de novo lipogenesis (DNL) is a key characteristic of patients with Nonalcoholic Fatty Liver Disease (NAFLD). Liver pyruvate carboxylase (PC) may be critical for DNL since PC replenishes oxaloacetate that is converted to citrate as source for acetyl-CoA during DNL. PC may also play a role in triglyceride (TG) synthesis by replenishing oxaloacetate that is used for glyceroneogenesis. Thus, PC is considered a lipogenic enzyme, though most evidence has been derived from non-liver cell culture models and indirect measures in livers of animal models. Liver-specific PC knockout mice (LPCKO) have lower circulating TG on a high fat diet, but fasting liver TG was not improved. To determine whether liver-specific PC is required for DNL and glyceroneogenesis, we examined LPCKO mice using a 1H/2H NMR approach to directly measure flux through DNL and TG-glycerol synthesis. PCf/f and LPCKO mice were exposed to either standard chow or a high sucrose diet (HSD) for 10 days. Ad libitum fed PCf/f and LPCKO mice were then administered D2O overnight. Liver lipids were extracted, and positional isotopomer analysis by 1H/2H NMR was used to determine DNL and TG-glycerol synthesis fluxes. DNL flux was not significantly different between PCf/f and LPCKO mice under standard chow conditions and only tended to be moderately lower in LPCKO mice after a short-term HSD treatment. TG-glycerol synthesis was also similar between PCf/f and LPCKO, regardless of diet. Surprisingly, liver triglyceride levels were modestly higher in standard chow fed LPCKO than PCf/f mice, and no significant differences were found between HSD-fed PCf/f and LPCKO mice. Our initial findings suggest that PC is not required for DNL and TG-glycerol synthesis during the fed state and therefore indicate that alternative pathways may exist to supply of cytosolic acetyl-CoA for lipid synthesis. Disclosure M.R. Inigo: None. S. Deja: None. B. Kucejova: None. J.A. Fletcher: None. X. Fu: None. S.C. Burgess: None. Funding Robert A. Welch Foundation (I-1804)

Genetic variants that increase the risk of fatty liver disease and cirrhosis have recently been identified in the proximity of membrane-bound O-acyltransferase domain-containing 7 (MBOAT7). To elucidate the link between these variants and fatty liver disease, we characterized Mboat7 liver-specific KO mice (Mboat7 LSKO). Chow-fed Mboat7 LSKO mice developed fatty livers and associated liver injury. Lipidomic analysis of liver using MS revealed a pronounced reduction in 20-carbon PUFA content in phosphatidylinositols (PIs) but not in other phospholipids. The change in fatty acid composition of PIs in these mice was associated with a marked increase in de novo lipogenesis because of activation of SREBP-1c, a transcription factor that coordinates the activation of genes encoding enzymes in the fatty acid biosynthesis pathway. Hepatic removal of both SREBP cleavage-activating protein (Scap) and Mboat7 normalized hepatic triglycerides relative to Scap-only hepatic KO, showing that increased SREBP-1c processing is required for Mboat7-induced steatosis. This study reveals a clear relationship between PI fatty acid composition and regulation of hepatic fat synthesis and delineates the mechanism by which mutations in MBOAT7 cause hepatic steatosis., Graphical abstract

E-referral incentive programs are key instruments to carry out relationship marketing on social platforms. This study explores the effect of e-referral incentive programs on customer loyalty and it...

Key points Low intrinsic aerobic capacity is associated with increased all-cause and liver-related mortality in humans. Low intrinsic aerobic capacity in the low capacity runner (LCR) rat increases susceptibility to acute and chronic high-fat/high-sucrose diet-induced steatosis, without observed increases in liver inflammation. Addition of excess cholesterol to a high-fat/high-sucrose diet produced greater steatosis in LCR and high capacity runner (HCR) rats. However, the LCR rat demonstrated greater susceptibility to increased liver inflammatory and apoptotic markers compared to the HCR rat. The progressive non-alcoholic fatty liver disease observed in the LCR rats following western diet feeding was associated with further declines in liver fatty acid oxidation and mitochondrial respiratory capacity compared to HCR rats. Abstract Low aerobic capacity increases risk for non-alcoholic fatty liver disease and liver-related disease mortality, but mechanisms mediating these effects remain unknown. We recently reported that rats bred for low aerobic capacity (low capacity runner; LCR) displayed susceptibility to high fat diet-induced steatosis in association with reduced hepatic mitochondrial fatty acid oxidation (FAO) and respiratory capacity compared to high aerobic capacity (high capacity runner; HCR) rats. Here we tested the impact of aerobic capacity on susceptibility for progressive liver disease following a 16-week 'western diet' (WD) high in fat (45% kcal), cholesterol (1% w/w) and sucrose (15% kcal). Unlike previously with a diet high in fat and sucrose alone, the inclusion of cholesterol in the WD induced hepatomegaly and steatosis in both HCR and LCR rats, while producing greater cholesterol ester accumulation in LCR compared to HCR rats. Importantly, WD-fed low-fitness LCR rats displayed greater inflammatory cell infiltration, serum alanine transaminase, expression of hepatic inflammatory markers (F4/80, MCP-1, TLR4, TLR2 and IL-1β) and effector caspase (caspase 3 and 7) activation compared to HCR rats. Further, LCR rats had greater WD-induced decreases in complete FAO and mitochondrial respiratory capacity. Intrinsic aerobic capacity had no impact on WD-induced hepatic steatosis; however, rats bred for low aerobic capacity developed greater hepatic inflammation, which was associated with reduced hepatic mitochondrial FAO and respiratory capacity and increased accumulation of cholesterol esters. These results confirm epidemiological reports that aerobic capacity impacts progression of liver disease and suggest that these effects are mediated through alterations in hepatic mitochondrial function.

The heart oxidizes fatty acids, carbohydrates, and ketone bodies inside the tricarboxylic acid (TCA) cycle to generate the reducing equivalents needed for ATP production. Competition between these substrates makes it difficult to estimate the extent of pyruvate oxidation. Previously, hyperpolarized pyruvate detected propionate-mediated activation of carbohydrate oxidation, even in the presence of acetate. In this report, the optimal concentration of propionate for the activation of glucose oxidation was measured in mouse hearts perfused in Langendorff mode. This study was performed with a more physiologically relevant perfusate than the previous work. Increasing concentrations of propionate did not cause adverse effects on myocardial metabolism, as evidenced by unchanged O2consumption, TCA cycle flux, and developed pressures. Propionate at 1 mM was sufficient to achieve significant increases in pyruvate dehydrogenase flux (3×), and anaplerosis (6×), as measured by isotopomer analysis. These results further demonstrate the potential of propionate as an aid for the correct estimation of total carbohydrate oxidative capacity in the heart. However, liquid chromotography/mass spectroscopy-based metabolomics detected large changes (~30-fold) in malate and fumarate pool sizes. This observation leads to a key observation regarding mass balance in the TCA cycle; flux through a portion of the cycle can be drastically elevated without changing the O2consumption.

Computational models based on the metabolism of stable isotope tracers can yield valuable insight into the metabolic basis of disease. The complexity of these models is limited by the number of tracers and the ability to characterize tracer labeling in downstream metabolites. NMR spectroscopy is ideal for multiple tracer experiments since it precisely detects the position of tracer nuclei in molecules, but it lacks sensitivity for detecting low-concentration metabolites. GC-MS detects stable isotope mass enrichment in low-concentration metabolites, but lacks nuclei and positional specificity. We performed liver perfusions and in vivo infusions of (2)H and (13)C tracers, yielding complex glucose isotopomers that were assigned by NMR and fit to a newly developed metabolic model. Fluxes regressed from (2)H and (13)C NMR positional isotopomer enrichments served to validate GC-MS-based flux estimates obtained from the same experimental samples. NMR-derived fluxes were largely recapitulated by modeling the mass isotopomer distributions of six glucose fragment ions measured by GC-MS. Modest differences related to limited fragmentation coverage of glucose C1–C3 were identified, but fluxes such as gluconeogenesis, glycogenolysis, cataplerosis and TCA cycle flux were tightly correlated between the methods. Most importantly, modeling of GC-MS data could assign fluxes in primary mouse hepatocytes, an experiment that is impractical with (2)H or (13)C NMR.

Mesenchymal stem cells (MSCs) are multilineage cells with the ability to self-renew and differentiate into a variety of cell types, which play key roles in tissue healing and regenerative medicine. Bone marrow-derived mesenchymal stem cells (BMSCs) are the most frequently used stem cells in cell therapy and tissue engineering. However, it is prerequisite for BMSCs to mobilize from bone marrow and migrate into injured tissues during the healing process, through peripheral circulation. The migration of BMSCs is regulated by mechanical and chemical factors in this trafficking process. In this paper, we review the effects of several main regulatory factors on BMSC migration and its underlying mechanism; discuss two critical roles of BMSCs—namely, directed differentiation and the paracrine function—in tissue repair; and provide insight into the relationship between BMSC migration and tissue repair, which may provide a better guide for clinical applications in tissue repair through the efficient regulation of BMSC migration.

Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent, and potentially morbid, disease that affects one-third of the US population. Normal liver safely accommodates lipid excess during fasting or carbohydrate restriction by increasing their oxidation to acetyl-CoA and ketones, yet lipid excess during NAFLD leads to hyperglycemia and, in some, steatohepatitis. To examine potential mechanisms, we studied flux through pathways of hepatic oxidative metabolism and gluconeogenesis using 5 simultaneous stable isotope tracers in ketotic (24-hour-fasted) individuals with a wide range of hepatic triglyceride content levels (0%–52%). Ketogenesis was progressively impaired as hepatic steatosis and glycemia worsened. Conversely, the alternative pathway for acetyl-CoA metabolism, oxidation in the tricarboxylic acid (TCA) cycle, was upregulated in NAFLD as ketone production diminished and positively correlated with rates of gluconeogenesis and plasma glucose concentrations. Increased respiration and energy generation that occurred in liver when β-oxidation and TCA cycle activity were coupled may explain these findings, inasmuch as calculated hepatic oxygen consumption was higher during fatty liver and highly correlated with gluconeogenesis. These findings demonstrate that increased glucose production and hyperglycemia in NAFLD is a consequence not of acetyl-CoA production per se, but rather of how acetyl-CoA is further metabolized in liver.

Rats selectively bred for high capacity running (HCR) or low capacity running (LCR) display divergence for intrinsic aerobic capacity and hepatic mitochondrial oxidative capacity, both factors associated with susceptibility for nonalcoholic fatty liver disease. Here, we tested if HCR and LCR rats display differences in susceptibility for hepatic steatosis after 16 wk of high-fat diets (HFD) with either 45% or 60% of kcals from fat. HCR rats were protected against HFD-induced hepatic steatosis, whereas only the 60% HFD induced steatosis in LCR rats, as marked by a doubling of liver triglycerides. Hepatic complete fatty acid oxidation (FAO) and mitochondrial respiratory capacity were all lower in LCR compared with HCR rats. LCR rats also displayed lower hepatic complete and incomplete FAO in the presence of etomoxir, suggesting a reduced role for noncarnitine palmitoyltransferase-1-mediated lipid catabolism in LCR versus HCR rats. Hepatic complete FAO and mitochondrial respiration were largely unaffected by either chronic HFD; however, 60% HFD feeding markedly reduced 2-pyruvate oxidation, a marker of tricarboxylic acid (TCA) cycle flux, and mitochondrial complete FAO only in LCR rats. LCR rats displayed lower levels of hepatic long-chain acylcarnitines than HCR rats but maintained similar levels of hepatic acetyl-carnitine levels, further supporting lower rates of β-oxidation, and TCA cycle flux in LCR than HCR rats. Finally, only LCR rats displayed early reductions in TCA cycle genes after the acute initiation of a HFD. In conclusion, intrinsically high aerobic capacity confers protection against HFD-induced hepatic steatosis through elevated hepatic mitochondrial oxidative capacity.

This paper deals with the problem of the robustly absolute stability for neutral-type Lur'e systems with mixed time-varying delay. By combining the piecewise analysis theory with the reciprocally convex method and Wirtinger-based inequality technology, some new delay-dependent stability criteria are proposed via a modified Lyapunov-Krasovskii functional LKF approach. The stability conditions can be solved by using standard linear matrix inequality LMI convex optimization solvers. The criteria are less conservative than some previous ones. Three numerical examples are presented to show the effectiveness of the proposed approach.

SummaryDysregulated mitochondrial metabolism during hepatic insulin resistance may contribute to pathophysiologies ranging from elevated glucose production to hepatocellular oxidative stress and inflammation. Given that obesity impairs insulin action but paradoxically activates mTORC1, we tested whether insulin action and mammalian target of rapamycin complex 1 (mTORC1) contribute to altered in vivo hepatic mitochondrial metabolism. Loss of hepatic insulin action for 2 weeks caused increased gluconeogenesis, mitochondrial anaplerosis, tricarboxylic acid (TCA) cycle oxidation, and ketogenesis. However, activation of mTORC1, induced by the loss of hepatic Tsc1, suppressed these fluxes. Only glycogen synthesis was impaired by both loss of insulin receptor and mTORC1 activation. Mice with a double knockout of the insulin receptor and Tsc1 had larger livers, hyperglycemia, severely impaired glycogen storage, and suppressed ketogenesis, as compared to those with loss of the liver insulin receptor alone. Thus, activation of hepatic mTORC1 opposes the catabolic effects of impaired insulin action under some nutritional states.

This paper is concerned with the robust stability for neutral-type Lur’e system with mixed time-varying delays. By combining the delay-fraction theory with the reciprocally convex method andWirtinger-based inequality technology, some new delay-derivative-dependent stability criteria are derived via a modified Lyapunov-Krasovskii functional (LKF) approach. The criteria are less conservative than some previous ones.