Hepatic Energy Research Articles

Maternal Exercise Mediates Hepatic Metabolic Programming via Activation of AMPK-PGC1α Axis in the Offspring of Obese Mothers.

Maternal obesity is associated with an increased risk of hepatic metabolic dysfunction for both mother and offspring and targeted interventions to address this growing metabolic disease burden are urgently needed. This study investigates whether maternal exercise (ME) could reverse the detrimental effects of hepatic metabolic dysfunction in obese dams and their offspring while focusing on the AMP-activated protein kinase (AMPK), representing a key regulator of hepatic metabolism. In a mouse model of maternal western-style-diet (WSD)-induced obesity, we established an exercise intervention of voluntary wheel-running before and during pregnancy and analyzed its effects on hepatic energy metabolism during developmental organ programming. ME prevented WSD-induced hepatic steatosis in obese dams by alterations of key hepatic metabolic processes, including activation of hepatic ß-oxidation and inhibition of lipogenesis following increased AMPK and peroxisome-proliferator-activated-receptor-γ-coactivator-1α (PGC-1α)-signaling. Offspring of exercised dams exhibited a comparable hepatic metabolic signature to their mothers with increased AMPK-PGC1α-activity and beneficial changes in hepatic lipid metabolism and were protected from WSD-induced adipose tissue accumulation and hepatic steatosis in later life. In conclusion, this study demonstrates that ME provides a promising strategy to improve the metabolic health of both obese mothers and their offspring and highlights AMPK as a potential metabolic target for therapeutic interventions.

Hepatic Dysregulation of Bile Acid Homeostasis in Hyperandrogenemic Female Mouse Model of Polycystic Ovary Syndrome

Introduction and Purpose: Polycystic Ovary Syndrome (PCOS) is recognized as the most common endocrine disorder in women of reproductive age. Notably, PCOS women with hyperandrogenism have a pronounced increased risk for cardio-metabolic comorbidities compared with healthy individuals. Bile acids are endocrine signaling molecules that modulate hepatic lipid, glucose, and energy metabolism by aiding in absorption of lipids. Alteration of bile acid homeostasis affects overall metabolic homeostasis and contributes to pathogenesis of an array of metabolic diseases, although the molecular mechanisms of this have not been studied in PCOS. Methods: Four-week old C57BL/6N female mice were implanted subcutaneously with dihydrotestosterone (DHT, 8.0 mg) or vehicle silastic tubes (n=8/grp). Weekly body weight, food intake, and body composition was assessed. Fasting serum was obtained and the oral glucose tolerance test (OGTT) was performed in the last week of treatment. Animals were euthanized on treatment day 90 and livers were harvested. Expression levels of mRNA were assessed using RT-qPCR. Results: DHT treated females had significantly higher liver mass (1,387 ± 51 vs 1,197 ± 29 g, p<0.05), increased lean mass (21.25 ± 0.27 vs 19.58 ± 0.23 g, p<0.05) and increased fat mass (4.83 ± 0.47 vs 3.59 ± 0.36 g, p<0.05) compared to the vehicle counterparts. These hyperandrogenemic females additionally showed altered glucose homeostasis, having increased fasting glucose (201.10 ± 11.11 vs 152.80 ± 9.23 mg/dL, p<0.05) and an increased area under the curve (209.2± 11.0 vs 160.8± 3.5 mg.min/dL, p<0.05) following OGTT. Hepatic expression of both classic (Cyp8b1, 1.4 ± 0.1-fold, p<0.05) and alternative (Cyp7b1, 2.0 ± 0.3-fold, p<0.05) bile acid synthesis cytochrome P450 enzyme genes were significantly upregulated in DHT treated animals. Additionally, expression of sulfotransferase Sult2a2 was completely abolished in DHT treated animals compared with vehicle animals, indicating the possibility of androgen regulation of the sulfonation of bile acids marked for elimination. Liver expression of both the bile acid receptor G-protein coupled bile acid receptor 1 and the androgen receptor were both significantly downregulated (Gpbar1: 0.68 ± 0.08-fold, AR: 0.46 ± 0.04-fold, p<0.05) in DHT treated animals. Conclusions: Bile acid synthesis, transport, and elimination are tightly controlled processes in the liver to maintain a constant bile acid pool and limit reabsorption. Together, our results highlight the potential role of androgens in DHT-treated female mice in the dysregulation of bile acid homeostasis and its potential contribution to influence metabolic dysfunction. (Supported by NIH grants NIGMS P20GM-121334 to LLYC and DGR, and NIH NIDDK R21DK-113500 to DGR and the Mississippi Center of Excellence in Perinatal Research.)

The photosensitiser azure A disrupts mitochondrial bioenergetics through intrinsic and photodynamic effects

Azure A (AA) is a cationic molecule of the class of phenothiazines that has been applied in vitro as a photosensitising agent in photodynamic antimicrobial chemotherapy. It is a di-demethylated analogue of methylene blue (MB), which has been demonstrated to be intrinsically and photodynamically highly active on mitochondrial bioenergetics. However, as far as we know, there are no studies about the photodynamic effects of AA on mammalian mitochondria. Therefore, this investigation aimed to characterise the intrinsic and photodynamic acute effects of AA (0.540 μM) on isolated rat liver mitochondria, isolated hepatocytes, and isolated perfused rat liver. The effects of AA were assessed by evaluating several parameters of mitochondrial bioenergetics, oxidative stress, cell viability, and hepatic energy metabolism. The photodynamic effects of AA were assessed under simulated hypoxic conditions, a suitable way for mimicking the microenvironment of hypoxic solid tumour cells. AA interacted with the mitochondria and, upon photostimulation (10 min of light exposure), produced toxic amounts of reactive oxygen species (ROS), which damaged the organelle, as demonstrated by the high levels of lipid peroxidation and protein carbonylation. The photostimulated AA also depleted the GSH pool, which could compromise the mitochondrial antioxidant defence. Bioenergetically, AA photoinactivated the complexes I, II, and IV of the mitochondrial respiratory chain and the F1FO–ATP synthase complex, sharply inhibiting the oxidative phosphorylation. Upon photostimulation (10 min of light exposure), AA reduced the efficiency of mitochondrial energy transduction and oxidatively damaged lipids in isolated hepatocytes but did not decrease the viability of cells. Despite the useful photobiological properties, AA presented noticeable dark toxicity on mitochondrial bioenergetics, functioning predominantly as an uncoupler of oxidative phosphorylation. This harmful effect of AA was evidenced in isolated hepatocytes, in which AA diminished the cellular ATP content. In this case, the cells exhibited signs of cell viability reduction in the presence of high AA concentrations, but only after a long time of incubation (at least 90 min). The impairments on mitochondrial bioenergetics were also clearly manifested in intact perfused rat liver, in which AA diminished the cellular ATP content and stimulated the oxygen uptake. Consequently, gluconeogenesis and ureogenesis were strongly inhibited, whereas glycogenolysis and glycolysis were stimulated. AA also promoted the release of cytosolic and mitochondrial enzymes into the perfusate concomitantly with inhibition of oxygen consumption. In general, the intrinsic and photodynamic effects of AA were similar to those of MB, but AA caused some distinct effects such as the photoinactivation of the complex IV of the mitochondrial respiratory chain and a diminution of the ATP levels in the liver. It is evident that AA has the potential to be used in mitochondria-targeted photodynamic therapy, even under low oxygen concentrations. However, the fact that AA directly disrupts mitochondrial bioenergetics and affects several hepatic pathways that are linked to ATP metabolism, along with its ability to perturb cellular membranes and its little potential to reduce cell viability, could result in significant adverse effects especially in long-term treatments.

TREM2 sustains macrophage-hepatocyte metabolic coordination in nonalcoholic fatty liver disease and sepsis

Sepsis is a leading cause of death in critical illness, and its pathophysiology varies depending on preexisting medical conditions. Here we identified nonalcoholic fatty liver disease (NAFLD) as an independent risk factor for sepsis in a large clinical cohort and showed a link between mortality in NAFLD-associated sepsis and hepatic mitochondrial and energetic metabolism dysfunction. Using in vivo and in vitro models of liver lipid overload, we discovered a metabolic coordination between hepatocyte mitochondria and liver macrophages that express triggering receptor expressed on myeloid cells-2 (TREM2). Trem2-deficient macrophages released exosomes that impaired hepatocytic mitochondrial structure and energy supply because of their high content of miR-106b-5p, which blocks Mitofusin 2 (Mfn2). In a mouse model of NAFLD-associated sepsis, TREM2 deficiency accelerated the initial progression of NAFLD and subsequent susceptibility to sepsis. Conversely, overexpression of TREM2 in liver macrophages improved hepatic energy supply and sepsis outcome. This study demonstrates that NAFLD is a risk factor for sepsis, providing a basis for precision treatment, and identifies hepatocyte-macrophage metabolic coordination and TREM2 as potential targets for future clinical trials.

Regulation of hepatic circadian metabolism by the E3 ubiquitin ligase HRD1-controlled CREBH/PPARα transcriptional program

ObjectiveThe endoplasmic reticulum (ER)-resident E3 ligase HRD1 and its co-activator Sel1L are major components of ER-associated degradation (ERAD) machinery. Here, we investigated the molecular mechanism and functional significance underlying the circadian regulation of HRD1/Sel1L-mediated protein degradation program in hepatic energy metabolism. MethodsGenetically engineered animal models as well as gain- and loss-of-function studies were employed to address the circadian regulatory mechanism and functional significance. Gene expression, transcriptional activation, protein–protein interaction, and animal metabolic phenotyping analyses were performed to dissect the molecular network and metabolic pathways. ResultsHepatic HRD1 and Sel1L expression exhibits circadian rhythmicity that is controlled by the ER-tethered transcriptional activator CREBH, the nuclear receptor peroxisome proliferator-activated receptor α (PPARα), and the core clock oscillator BMAL1 in mouse livers. HRD1/Sel1L mediates polyubiquitination and degradation of the CREBH protein across the circadian cycle to modulate rhythmic expression of the genes encoding the rate-limiting enzymes or regulators in fatty acid (FA) oxidation, triglyceride (TG) lipolysis, lipophagy, and gluconeogenesis. HRD1 liver-specific knockout (LKO) mice displayed increased expression of the genes involved in lipid and glucose metabolism and impaired circadian profiles of circulating TG, FA, and glucose due to overproduction of CREBH. The circadian metabolic activities of HRD1 LKO mice were inversely correlated with those of CREBH KO mice. Suppressing CREBH overproduction in the livers of HRD1 LKO mice restored the diurnal levels of circulating TG and FA of HRD1 LKO mice. ConclusionOur work revealed a key circadian-regulated molecular network through which the E3 ubiquitin ligase HRD1 and its co-activator Sel1L regulate hepatic circadian metabolism.

PPARs in liver physiology

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors and transcriptional modulators with crucial functions in hepatic and whole-body energy homeostasis. Besides their well-documented roles in lipid and glucose metabolism, emerging evidence also implicate PPARs in the control of other processes such as inflammatory responses. Recent technological advances, such as single-cell RNA sequencing, have allowed to unravel an unexpected complexity in the regulation of PPAR expression, activity and downstream signaling. Here we provide an overview of the latest advances in the study of PPARs in liver physiology, with a specific focus on formerly neglected aspects of PPAR regulation, such as tissular zonation, cellular heterogeneity, circadian rhythms, sexual dimorphism and species-specific features.

Nicotinamide supplementation during postpartum and peripartum modulates hepatic energy and lipid metabolism, oxidative status, and metabolomics profile, as well as lipids in the adipose tissue of goats

Dairy ruminants are often in negative energy balance, primarily in the postpartum period, resulting in many metabolic disorders and economic losses. Improving energy efficiency during the peripartum period is urgently important. It has been previously highlighted that nicotinamide (NAM) supplementation during the peripartum period could benefit energy balance, while the underlying metabolic alterations and differences between postpartum NAM supplementation and peripartum NAM supplementation have not been extensively studied. This study attempted to elucidate the effects of NAM supplementation during the postpartum and peripartum periods on rumen fermentation, liver mitochondrial respiratory chain status, lipid metabolism, oxidative status, and liver metabolite profile of does. Fifteen multiparous does with similarity were paired and allocated to 3 groups (n = 5): control (C, no NAM supplementation), postpartum supplementation (P, NAM supplemented from d 1 to 28 after kidding), and entire-peripartum supplementation (EP, NAM supplemented from d -2 1 to 28 around kidding). Does were drenched with NAM at 5 g/d and subsequently slaughtered on d 28. The ruminal proportion of acetic acid tended to decrease, and propionic acid and valeric acid were increased in P and EP. The does in P and EP had a decreased acetic acid to propionic acid ratio. Does in EP had higher liver mitochondrial respiratory chain complexes. The activity of liver complex Ⅱ was elevated in P and EP, and NAM supplementation tended to increase ATP production. Liver metabolomics and tissue biochemical analyses demonstrated that TG synthesis was decreased in abdominal adipose tissue by NAM supplementation. In the liver, the decomposition and synthesis of TG were both promoted, and amino acid metabolism was enriched by NAM supplementation. Moreover, the oxidative status of the blood and liver was improved by NAM supplementation, and NAM supplementation during the postpartum period was more effective but did not appear to be sufficient to cope with the metabolites of oxidative phosphorylation. Overall, these data suggested that NAM supplementation during postpartum and entire peripartum periods favored the rumen fermentation pattern to propionic acid-type and improved liver energy efficiency with benefited lipid metabolism. Supplementing NAM starting in the prepartum period is necessary for better oxidative status and energy metabolism in the peripartum period.

The Postnatal Offspring of Finasteride-Treated Male Rats Shows Hyperglycaemia, Elevated Hepatic Glycogen Storage and Altered GLUT2, IR, and AR Expression in the Liver

Background: A growing body of data indicates that the physiology of the liver is sex-hormone dependent, with some types of liver failure occurring more frequently in males, and some in females. In males, in physiological conditions, testosterone acts via androgen receptors (AR) to increase insulin receptor (IR) expression and glycogen synthesis, and to decrease glucose uptake controlled by liver-specific glucose transporter 2 (GLUT-2). Our previous study indicated that this mechanism may be impaired by finasteride, a popular drug used in urology and dermatology, inhibiting 5α-reductase 2, which converts testosterone (T) into dihydrotestosterone (DHT). Our research has also shown that the offspring of rats exposed to finasteride have an altered T–DHT ratio and show changes in their testes and epididymides. Therefore, the goal of this study was to assess whether the administration of finasteride had an trans-generational effect on (i) GLUT-2 dependent accumulation of glycogen in the liver, (ii) IR and AR expression in the hepatocytes of male rat offspring, (iii) a relation between serum T and DHT levels and the expression of GLUT2, IR, and AR mRNAs, (iv) a serum glucose level and it correlation with GLUT-2 mRNA. Methods: The study was conducted on the liver (an androgen-dependent organ) from 7, 14, 21, 28, and 90-day old Wistar male rats (F1:Fin) born by females fertilized by finasteride-treated rats. The control group was the offspring (F1:Control) of untreated Wistar parents. In the histological sections of liver the Periodic Acid Schiff (PAS) staining (to visualize glycogen) and IHC (to detect GLUT-2, IR, and AR) were performed. The liver homogenates were used in qRT-PCR to assess GLUT2, IR, and AR mRNA expression. The percentage of PAS-positive glycogen areas were correlated with the immunoexpression of GLUT-2, serum levels of T and DHT were correlated with GLUT-2, IR, and AR transcript levels, and serum glucose concentration was correlated with the age of animals and with the GLUT-2 mRNA by Spearman’s rank correlation coefficients. Results: In each age group of F1:Fin rats, the accumulation of glycogen was elevated but did not correlate with changes in GLUT-2 expression. The levels of GLUT-2, IR, and AR transcripts and their immunoreactivity statistically significantly decreased in F1:Fin animals. In F1:Fin rats the serum levels of T and DHT negatively correlated with androgen receptor mRNA. The animals from F1:Fin group have statistically elevated level of glucose. Additionally, in adult F1:Fin rats, steatosis was observed in the liver (see Appendix A). Conclusions: It seems that treating male adult rats with finasteride causes changes in the carbohydrate metabolism in the liver of their offspring. This can lead to improper hepatic energy homeostasis or even hyperglycaemia, insulin resistance, as well as some symptoms of metabolic syndrome and liver steatosis.

LncRNA in hepatic glucose and lipid metabolism: a review

In recent years, long non-coding RNA (lncRNA) has been proved to be involved in the regulation of biological processes at various levels, attracting research interests in life science. LncRNA possesses the unique capability and exert discrete effects on transcription, translation and post-translational modification of the target genes through interacting with DNA, RNA and protein. Current studies have revealed that lncRNA plays an important role in hepatic metabolism via diverse pathways. This review focuses on the function of lncRNA and its relationship with hepatic energy metabolism and the correlated diseases, to elucidate the underlying mechanisms and prospects of lncRNA researches.

Cadmium induced skeletal underdevelopment, liver cell apoptosis and hepatic energy metabolism disorder in Bufo gargarizans larvae by disrupting thyroid hormone signaling

Cadmium (Cd) is hazardous to human health and it is also highly detrimental to amphibian life. In this study, Bufo gargarizans larvae were exposed to environmentally relevant Cd concentrations of 5, 100 and 200 μg L−1 from Gosner stage (Gs) 26 to Gs 42 of metamorphic climax about 6 weeks. The results showed thyroid structural injuries and thyroid signaling disruption were induced by high Cd exposure (100 and 200 μg L−1). Moreover, tadpole skeleton including whole body, vertebrata, forelimb and hindlimb was developmentally delayed by high Cd exposure through downregulating the mRNA expressions of genes involved with skeletal ossification and growth pathway. Moreover, liver histopathological injuries were caused by high Cd exposure featured by hepatocytes malformation, nuclear degeneration and increasing melanomacrophage centers. Meanwhile, liver apoptosis rate showed on the rise in a dose-dependent way and Cd stimulated liver apoptosis by upregulating mRNA expressions of genes related to extrinsic and intrinsic apoptosis pathways. Furthermore, high Cd caused hepatic glucometabolism disorder by decreasing the genetic expressions associated with glycolysis and mitochondrial oxidative phosphorylation. In addition, liver lipid metabolism was disrupted by high Cd exposure through downregulating mRNA levels of genes related to fatty oxidation and upregulating mRNA levels of genes related to fatty acid synthesis. We suggested that Cd did great harm to tadpole health by disturbing thyroid function, skeletal growth, liver cell apoptosis signaling and hepatic energy metabolism pathway.

Increasing hepatic glycogen moderates the diabetic phenotype in insulin-deficient Akita mice

Hepatic glycogen metabolism is impaired in diabetes. We previously demonstrated that strategies to increase liver glycogen content in a high-fat-diet mouse model of obesity and insulin resistance led to a reduction in food intake and ameliorated obesity and glucose tolerance. These effects were accompanied by a decrease in insulin levels, but whether this decrease contributed to the phenotype observed in this animal was unclear. Here we sought to evaluate this aspect directly, by examining the long-term effects of increasing liver glycogen in an animal model of insulin-deficient and monogenic diabetes, namely the Akita mouse, which is characterized by reduced insulin production. We crossed Akita mice with animals overexpressing protein targeting to glycogen (PTG) in the liver to generate Akita mice with increased liver glycogen content (Akita-PTGOE). Akita-PTGOE animals showed lower glycemia, lower food intake, and decreased water consumption and urine output compared with Akita mice. Furthermore, Akita-PTGOE mice showed a restoration of the hepatic energy state and a normalization of gluconeogenesis and glycolysis back to nondiabetic levels. Moreover, hepatic lipogenesis, which is reduced in Akita mice, was reverted in Akita-PTGOE animals. These results demonstrate that strategies to increase liver glycogen content lead to the long-term reduction of the diabetic phenotype, independently of circulating insulin.

Dietary Beta-Hydroxy Beta-Methyl Butyrate Supplementation Alleviates Liver Injury in Lipopolysaccharide-Challenged Piglets.

The current study was performed to investigate whether dietary β-hydroxy-β-methylbutyrate (HMB) could regulate liver injury in a lipopolysaccharide- (LPS-) challenged piglet model and to determine the mechanisms involved. Thirty piglets (21 ± 2 days old, 5.86 ± 0.18 kg body weight) were randomly divided into the control (a basal diet, saline injection), LPS (a basal diet), or LPS+HMB (a basal diet + 0.60% HMB-Ca) group. After 15 d of treatment with LPS and/or HMB, blood and liver samples were obtained. The results showed that in LPS-injected piglets, HMB supplementation ameliorated liver histomorphological abnormalities induced by LPS challenge. Compared to the control group, the activities of serum aspartate aminotransferase and alkaline phosphatase were increased in the LPS-injected piglets (P < 0.05). The LPS challenge also downregulated the mRNA expression of L-PFK, ACO, L-CPT-1, ICDH β, and AMPKα1/2 and upregulated the mRNA expression of PCNA, caspase 3, TNF-α, TLR4, MyD88, NOD1, and NF-κB p65 (P < 0.05). However, these adverse effects of the LPS challenge were reversed by HMB supplementation (P < 0.05). These results indicate that HMB may exert protective effects against LPS-induced liver injury, and the underlying mechanisms might involve the improvement of hepatic energy metabolism via regulating AMPK signaling pathway and the reduction of liver inflammation via modulating TLR4 and NOD signaling pathways.

Defective FXR-SHP Regulation in Obesity Aberrantly Increases miR-802 Expression, Promoting Insulin Resistance and Fatty Liver.

Aberrantly elevated expression in obesity of microRNAs (miRNAs), including the miRNA miR-802, contributes to obesity-associated metabolic complications, but the mechanisms underlying the elevated expression are unclear. Farnesoid X receptor (FXR), a key regulator of hepatic energy metabolism, has potential for treatment of obesity-related diseases. We examined whether a nuclear receptor cascade involving FXR and FXR-induced small heterodimer partner (SHP) regulates expression of miR-802 to maintain glucose and lipid homeostasis. Hepatic miR-802 levels are increased in FXR-knockout (KO) or SHP-KO mice and are decreased by activation of FXR in a SHP-dependent manner. Mechanistically, transactivation of miR-802 by aromatic hydrocarbon receptor (AHR) is inhibited by SHP. In obese mice, activation of FXR by obeticholic acid treatment reduced miR-802 levels and improved insulin resistance and hepatosteatosis, but these beneficial effects were largely abolished by overexpression of miR-802. In patients with nonalcoholic fatty liver disease (NAFLD) and in obese mice, occupancy of SHP is reduced and that of AHR is modestly increased at the miR-802 promoter, consistent with elevated hepatic miR-802 expression. These results demonstrate that normal inhibition of miR-802 by FXR-SHP is defective in obesity, resulting in increased miR-802 levels, insulin resistance, and fatty liver. This FXR-SHP-miR-802 pathway may present novel targets for treating type 2 diabetes and NAFLD.

Gluconeogenesis, But Not Glycogenolysis, Contributes to the Increase in Endogenous Glucose Production by SGLT-2 Inhibition.

Recent studies indicate that sodium-glucose cotransporter 2 (SGLT-2) inhibition increases endogenous glucose production (EGP), potentially counteracting the glucose-lowering potency, and stimulates lipid oxidation and lipolysis. However, the acute effects of SGLT-2 inhibition on hepatic glycogen, lipid, and energy metabolism have not yet been analyzed. We therefore investigated the impact of a single dose of dapagliflozin (D) or placebo (P) on hepatic glycogenolysis, hepatocellular lipid (HCL) content and mitochondrial activity (kATP). Ten healthy volunteers (control [CON]: age 30 ± 3 years, BMI 24 ± 1 kg/m2, HbA1c 5.2 ± 0.1%) and six patients with type 2 diabetes mellitus (T2DM: age 63 ± 4 years, BMI 28 ± 1.5 kg/m2, HbA1c 6.1 ± 0.5%) were investigated on two study days (CON-P vs. CON-D and T2DM-P vs. T2DM-D). 1H/13C/31P MRS was performed before, 90-180 min (MR1), and 300-390 min (MR2) after administration of 10 mg dapagliflozin or placebo. EGP was assessed by tracer dilution techniques. Compared with CON-P, EGP was higher in CON-D (10.0 ± 0.3 vs. 12.4 ± 0.5 μmol kg-1 min-1; P < 0.05) and comparable in T2DM-D and T2DM-P (10.1 ± 0.7 vs. 10.4 ± 0.5 μmol kg-1 min-1; P = not significant [n.s.]). A strong correlation of EGP with glucosuria was observed (r = 0.732; P < 0.01). The insulin-to-glucagon ratio was lower after dapagliflozin in CON-D and T2DM-D compared with baseline (P < 0.05). Glycogenolysis did not differ between CON-P and CON-D (-3.28 ± 0.49 vs. -2.53 ± 0.56 μmol kg-1 min-1; P = n.s.) or T2DM-P and T2DM-D (-0.74 ± 0.23 vs. -1.21 ± 0.33 μmol kg-1 min-1; P = n.s.), whereas gluconeogenesis was higher after dapagliflozin in CON-P compared with CON-D (6.7 ± 0.6 vs. 9.9 ± 0.6 μmol kg-1 min-1; P < 0.01) but not in T2DM. No significant changes in HCL and kATP were observed. The rise in EGP after SGLT-2 inhibition is due to increased gluconeogenesis, but not glycogenolysis. Changes in glucagon and the insulin-to-glucagon ratio are not associated with an increased hepatic glycogen breakdown. HCL and kATP are not significantly affected by a single dose of dapagliflozin.

Early changes in hepatic energy metabolism and lipid content in recent-onset type 1 and 2 diabetes mellitus

Non-alcoholic fatty liver disease (NAFLD) is associated with abnormal mitochondrial capacity. While oxidative capacity can be increased in steatosis, hepatic ATP decreases in long-standing diabetes. However, longitudinal studies on diabetes-related NAFLD and its relationship to hepatic energy metabolism are lacking. This prospective study comprised volunteers with type 1 (T1DM, n= 30) and type 2 (T2DM, n= 37) diabetes. At diagnosis and 5 years later, we used 1H/31P magnetic resonance spectroscopy to measure hepatocellular lipid (HCL), γATP and inorganic phosphate (Pi) concentrations, and to assess adipose tissue volumes. Insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamps. At diagnosis, individuals with T2DM had higher HCL and adipose tissue volumes, but lower whole-body insulin sensitivity than those with T1DM, despite comparable glycemic control. NAFLD was present in 38% of individuals with T2DM and 7% with T1DM. After 5 years, visceral adipose tissue only increased in individuals with T2DM, while HCL almost doubled in this group (p <0.001), resulting in a 70% prevalence of NAFLD (independent of diabetes treatment). Changes in HCL correlated with adipose tissue volume and insulin resistance (r= 0.50 and r= 0.44, both p <0.05). Pi decreased by 17% and 10% in individuals with T2DM and T1DM (p <0.05), respectively. In T1DM, HCL did not change, whereas γATP decreased by 10% and correlated negatively with glycated hemoglobin (r= -0.56, p <0.05). The rapid increase in HCL during the early course of T2DM likely results from enlarging adipose tissue volume and insulin resistance in response to impaired hepatic mitochondrial adaptation. The decrease of phosphorus metabolites in T1DM may be due to pharmacological insulin supply. Previous studies suggested that the impaired function of mitochondria, the power plants of cells, can promote fatty liver and type 2 diabetes mellitus. This study now shows that during the first 5 years of type 2 diabetes the increase in body fat content rapidly leads to a doubling of liver fat content, whereas the energy metabolism of the patients' livers progressively declines. These data suggest that fat tissue mass and liver mitochondria have an important role in the development of fatty liver disease in humans with diabetes. NCT01055093.

Hepatic and muscular mitochondrial dysfunction and energy metabolism disturbances in a murine colon ward cancer and chemotherapy model

Hepatic and muscular mitochondrial dysfunction and energy metabolism disturbances in a murine colon ward cancer and chemotherapy model

Palmitate and pyruvate carbon flux in response to choline and methionine in bovine neonatal hepatocytes

Choline and methionine may serve unique functions to alter hepatic energy metabolism. Our objective was to trace carbon flux through pathways of oxidation and glucose metabolism in bovine hepatocytes exposed to increasing concentrations of choline chloride (CC) and d,l-methionine (DLM). Primary hepatocytes were isolated from 4 Holstein calves and maintained for 24 h before treatment with CC (0, 10, 100, 1000 μmol/L) and DLM (0, 100, 300 μmol/L) in a factorial design. After 21 h, [1-14C]C16:0 or [2-14C]pyruvate was added to measure complete and incomplete oxidation, and cellular glycogen. Reactive oxygen species (ROS), cellular triglyceride (TG), and glucose and ß-hydroxybutyrate (BHB) export were quantified. Exported very-low density lipoprotein particles were isolated for untargeted lipidomics and to quantify TG. Interactions between CC and DLM, and contrasts for CC (0 vs. [10, 100, 1000 μmol/L] and linear and quadratic contrast 10, 100, 1000 μmol/L) and DLM (0 vs. [100, 300 μmol/L] and 100 vs. 300 μmol/L) were evaluated. Presence of CC increased complete oxidation of [1-14C]C16:0 and decreased BHB export. Glucose export was decreased, but cellular glycogen was increased by the presence of CC and increasing CC. Presence of CC decreased ROS and marginally decreased cellular TG. No interactions between CC and DLM were detected for these outcomes. These data suggest a hepato-protective role for CC to limit ROS and cellular TG accumulation, and to alter hepatic energy metabolism to support complete oxidation of FA and glycogen storage regardless of Met supply.

Specific ablation of the NCoR corepressor δ splice variant reveals alternative RNA splicing as a key regulator of hepatic metabolism.

The NCoR corepressor plays critical roles in mediating transcriptional repression by both nuclear receptors and non-receptor transcription factors. Alternative mRNA splicing of NCoR produces a series of variants with differing molecular and biological properties. The NCoRω splice-variant inhibits adipogenesis whereas the NCoRδ splice-variant promotes it, and mice bearing a splice-specific knockout of NCoRω display enhanced hepatic steatosis and overall weight gain on a high fat diet as well as a greatly increased resistance to diet-induced glucose intolerance. We report here that the reciprocal NCoRδ splice-specific knock-out mice display the contrary phenotypes of reduced hepatic steatosis and reduced weight gain relative to the NCoRω-/- mice. The NCoRδ-/- mice also fail to demonstrate the strong resistance to diet-induced glucose intolerance exhibited by the NCoRω-/- animals. The NCoR δ and ω variants possess both unique and shared transcriptional targets, with expression of certain hepatic genes affected in opposite directions in the two mutants, others altered in one but not the other genotype, and yet others changed in parallel in both NCoRδ-/- and NCoRω-/- animals versus WT. Gene set expression analysis (GSEA) identified a series of lipid, carbohydrate, and amino acid metabolic pathways that are likely to contribute to their distinct steatosis and glucose tolerance phenotypes. We conclude that alternative-splicing of the NCoR corepressor plays a key role in the regulation of hepatic energy storage and utilization, with the NCoRδ and NCoRω variants exerting both opposing and shared functions in many aspects of this phenomenon and in the organism as a whole.

The effects of açaí oil addition in tilapia diets on performance, hepatic energy metabolism enzymes and antioxidant responses

The aim of the present study was to determine whether açai oil (Euterpe oleraceae) addition in the diets of juvenile Nile tilapia (Oreochromis niloticus) in biofloc system would stimulate hepatic energy metabolism and antioxidant responses. Treatments are as follows: T0 (6%-soybean oil), T1 (1%-AÇAI; 5%-SOY), T3 (3% AÇAI; 3%-SOY) and T6 (6%-AÇAI). In the liver, reactive oxygen species levels were significantly lower in T1, T3 and T6 than in T0, lipid peroxidation levels were significantly lower in T3 and T6, and nitric oxide levels were significantly lower in the T6 than in T0. Glutathione peroxidase activity was significantly higher in the T3 and T6 than in T0, while superoxide dismutase activity and total antioxidant capacity levels were significantly higher in the T6 than in T0. Adenylate kinase activity was significantly lower in the T6 than in T0. These results suggest that the açai oil addition in Nile tilapia diets stimulated antioxidant responses.

In vivo absolute quantification of hepatic γ-ATP concentration in mice using 31 P MRS at 11.7 T.

Measurement of ATP concentrations and synthesis in humans indicated abnormal hepatic energy metabolism in obesity, non-alcoholic fatty liver disease (NAFLD) and Type 2 diabetes. Further mechanistic studies on energy metabolism require the detailed phenotyping of specific mouse models. Thus, this study aimed to establish and evaluate a robust and fast single voxel 31 P MRS method to quantify hepatic γ-ATP concentrations at 11.7 T in three mouse models with different insulin sensitivities and liver fat contents (72-week-old C57BL/6 control mice, 72-week-old insulin resistant sterol regulatory-element binding protein-1c overexpressing (SREBP-1c+ ) mice and 10-12-week-old prediabetic non-obese diabetic (NOD) mice). Absolute quantification was performed by employing an external reference and a matching replacement ATP phantom with 3D image selected in vivo spectroscopy 31 P MRS. This single voxel 31 P MRS method non-invasively quantified hepatic γ-ATP within 17 min and the repeatability tests provided a coefficient of variation of 7.8 ± 1.1%. The mean hepatic γ-ATP concentrations were markedly lower in SREBP-1c+ mice (1.14 ± 0.10 mM) than in C57BL/6 mice (2.15 ± 0.13 mM; p < 0.0002) and NOD mice (1.78 ± 0.13 mM; p < 0.006, one-way ANOVA test). In conclusion, this method allows us to rapidly and precisely measure hepatic γ-ATP concentrations, and thereby to non-invasively detect abnormal hepatic energy metabolism in mice with different degrees of insulin resistance and NAFLD. Thus, this 31 P MRS will also be useful for future mechanistic as well as therapeutic translational studies in other murine models.