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The tissue-specific response to rumen-protected conjugated linoleic acid supply (rpCLA) of liver, two muscles, and three adipose tissues of heavy lambs was studied. Twenty-four lambs, 8 months old, divided into 4 groups of 6, were fed at libitum on a ration supplemented without or with a mixture of rpCLA. Silica and hydrogenated soybean oil was the rpCLA coating matrix. The lambs were slaughtered at 11 months of age. Tissues were collected and analyzed for their FA profiles. The dietary rpCLA supplement had no influence on carcass fatness nor on the fat content of the liver and tissues and had little influence on the FA profiles of these tissues. In the adipose tissues, rpCLA increased the proportions of saturated FAs, 18:0 and 18:2t10c12, and decreased the proportions of monounsaturated FAs in the adipose tissues. In muscles, the effects were the opposite. The results suggest that Δ9 desaturase activity is inhibited by the rpCLA mixture in adipose tissues to a greater extent than in the other tissues.

Objective: Perturbations in hepatic lipid and very-low-density lipoprotein (VLDL) metabolism are involved in the pathogenesis of obesity and hepatic insulin resistance. The objective of this study is to delineate the mechanism of subdiaphragmatic vagotomy in preventing obesity, hyperlipidemia, and insulin resistance., Approach and Results: By subjecting the complete subdiaphragmatic vagotomized mice to various nutritional conditions and investigating hepatic de novo lipogenesis pathway, we found that complete disruption of subdiaphragmatic vagal signaling resulted in a significant decrease of circulating VLDL-triglyceride compared with the mice obtained sham procedure. Vagotomy further prevented overproduction of VLDL-triglyceride induced by an acute fat load and a high-fat diet-induced obesity, hyperlipidemia, hepatic steatosis, and glucose intolerance. Mechanistic studies revealed that plasma glucagon-like peptide-1 was significantly raised in the vagotomized mice, which was associated with significant reductions in mRNA and protein expression of SREBP-1c (sterol regulatory element-binding protein 1c), SCD-1 (stearoyl-CoA desaturase-1), and FASN (fatty acid synthase), as well as enhanced hepatic insulin sensitivity. In vitro, treating mouse primary hepatocytes with a glucagon-like peptide-1 receptor agonist, exendin-4, for 48 hours inhibited free fatty acid, palmitic acid treatment induced de novo lipid synthesis, and VLDL secretion from hepatocytes., Conclusions: Elevation of glucagon-like peptide-1 in vagotomized mice may prevent VLDL overproduction and insulin resistance induced by high-fat diet. These novel findings, for the first time, delineate an intrinsic gut-liver regulatory circuit that is mediated by glucagon-like peptide-1 in regulating hepatic energy metabolism., (© 2017 American Heart Association, Inc.)

As a key insulin target tissue for maintaining systemic glucose homeostasis, the liver plays important roles in improving obesity-associated insulin intolerance via selective cannabinoid CB 1 receptor antagonism/inverse agonism. However, it is unclear whether this receptor inverse agonism affects hepatic glucose metabolism. MJ08 is a novel cannabinoid CB 1 receptor antagonist/inverse agonist that has superior inverse agonism over the well-known antagonist/inverse agonist, SR141716 (rimonabant). MJ08 remarkably elevates fasting blood glucose independent of inhibition of insulin release in mice. In the current study, MJ08 was used to investigate the mechanism by which liver cannabinoid CB 1 receptor inverse activation regulates hepatic glucose metabolism. MJ08 stimulated hepatic glucose production (HGP) in a dose-dependent manner and promoted gluconeogenic gene expression in perfused rat liver. SR141716 exhibited similar but weaker effects. The cannabinoid CB 1 receptor agonist (WIN 55,212-2), Gs protein-cyclic AMP (cAMP)-dependent pathway inhibitors (NF449 and H89), β-adrenoceptor antagonist (propranolol), and peripheral sympathetic inhibitor (reserpine) could antagonize MJ08-induced HGP. Furthermore, MJ08 and SR141716 induced monoamine neurotransmitter (noradrenaline) release and increased cAMP content significantly in perfused liver, although only a slight increase was observed in primary cultured hepatocytes. These results indicate that local liver cannabinoid CB 1 receptor inverse agonism via hepatic sympathetic innervation is responsible for the HGP induced by MJ08. Thus, high inverse agonistic activity could increase fasting blood glucose levels and should be avoided in the development of peripheral cannabinoid CB 1 receptor-targeted weight-loss drugs., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Sodium-glucose cotransporter 2 (SGLT2) inhibitors have both anti-diabetic and anti-obesity effects. However, the precise mechanism of the anti-obesity effect remains unclear. We previously demonstrated that the glycogen depletion signal triggers lipolysis in adipose tissue via liver-brain-adipose neurocircuitry. In this study, therefore, we investigated whether the anti-obesity mechanism of SGLT2 inhibitor is mediated by this mechanism. Diet-induced obese mice were subjected to hepatic vagotomy (HVx) or sham operation and loaded with high fat diet containing 0.015% tofogliflozin (TOFO), a highly selective SGLT2 inhibitor, for 3 weeks. TOFO-treated mice showed a decrease in fat mass and the effect of TOFO was attenuated in HVx group. Although both HVx and sham mice showed a similar level of reduction in hepatic glycogen by TOFO treatment, HVx mice exhibited an attenuated response in protein phosphorylation by protein kinase A (PKA) in white adipose tissue compared with the sham group. As PKA pathway is known to act as an effector of the liver-brain-adipose axis and activate triglyceride lipases in adipocytes, these results indicated that SGLT2 inhibition triggered glycogen depletion signal and actuated liver-brain-adipose axis, resulting in PKA activation in adipocytes. Taken together, it was concluded that the effect of SGLT2 inhibition on weight loss is in part mediated via the liver-brain-adipose neurocircuitry., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Nonalcoholic fatty liver disease ranges from simple steatosis to nonalcoholic steatohepatitis (NASH). Kupffer cells play a central role in promoting hepatic inflammation, which leads to the development of NASH. We investigated the anti-inflammatory effect of hepatic vagus-mediated stimulation of the α7 nicotinic acetylcholine receptor (α7nAChR) on Kupffer cells in NASH pathogenesis., Methods: Wild-type (WT) mice undergoing hepatic vagotomy (HV) were fed a methionine- and choline-deficient (MCD) diet for 1 week. α7nAChR knockout (α7KO) chimeric mice were generated by transplanting α7KO bone marrow cells into irradiated and Kupffer cell-deleted WT recipients. Kupffer cells were isolated from WT mice and treated with α7nAChR agonist under stimulation by lipopolysaccharide and/or palmitic acid., Results: HV aggravated MCD diet-induced NASH in both steatosis and inflammation. The hepatic inflammatory response, including the upregulation of tumor necrosis factor alpha (TNFα), interleukin (IL)-12, and monocyte chemoattractant protein 1 (MCP-1), was accelerated in HV mice, accompanied by the downregulation of PPARα pathway genes. Kupffer cells were highly activated via the phosphorylation and nuclear translocation of nuclear factor-kappa B (NF-κB) in MCD diet-fed HV mice. The α7nAchR agonist suppressed the inflammatory response of primary Kupffer cells induced by lipopolysaccharide and palmitic acid by attenuating the NF-κB cascade. α7KO chimeric mice fed an MCD diet for 1 week developed advanced NASH with highly activated Kupffer cells. The hepatic expression of TNFα, IL-12, and MCP-1 was upregulated in α7KO chimeric mice, accompanied by abnormal lipid metabolism., Conclusions: Hepatic vagus activity regulates the inflammatory response of Kupffer cells via α7nAChR in NASH development.

Objectives: Acute peripheral infection is associated with central and peripheral inflammation, increased oxidative stress, and adaptive sickness behaviors. Sulforaphane (SFN) activates the transcription factor nuclear factor E2-related factor 2 (Nrf2), which upregulates antioxidant genes and lowers inflammation. The objectives of this study were to examine the effects of SFN on proinflammatory markers and Nrf2 target genes in hippocampus and liver of mice challenged with lipopolysaccharide (LPS), and to evaluate sickness response following the LPS immune challenge., Methods: Adult Balb/c mice received SFN (50 mg/kg, i.p.) for 3 days before being injected i.p. with LPS (1 µg) to mimic an acute peripheral infection. Sickness behaviors were measured at baseline and 6 hours after LPS. Expression of proinflammatory mediators and antioxidant genes were analyzed in hippocampus and liver 6 hours after LPS., Results: SFN elevated Nrf2 target genes and reduced expression of proinflammatory mediators in hippocampus and liver, but did not improve LPS-induced sickness response., Discussion: The nutritional bioactive SFN displays potent anti-inflammatory properties against LPS-induced inflammation in vitro, but has not been previously assessed in vivo during peripheral infection as a potential treatment for sickness behavior. These data indicate that SFN has anti-inflammatory effects in both brain and periphery, but that longer exposure to SFN may be necessary to reduce sickness behavior.

Background: Interruption of sympathetic innervation to the liver and visceral adipose tissue (VAT) in animal models has been reported to reduce VAT lipolysis and hepatic secretion of very low density lipoprotein (VLDL) and concentrations of triglyceride-rich lipoprotein particles. Whether functional impairment of sympathetic nervous system (SNS) innervation to tissues of the abdominal cavity reduce circulating concentrations of triglyceride (TG) and VLDL particles (VLDL-P) was tested in men with spinal cord injury (SCI)., Methods: One hundred-three non-ambulatory men with SCI [55 subjects with neurologic injury at or proximal to the 4th thoracic vertebrae (↑T4); 48 subjects with SCI at or distal to the 5th thoracic vertebrae (↓T5)] and 53 able-bodied (AB) subjects were studied. Fasting blood samples were obtained for determination of TG, VLDL-P concentration by NMR spectroscopy, serum glucose by autoanalyzer, and plasma insulin by radioimmunoassay. VAT volume was determined by dual energy x-ray absorptiometry imaging with calculation by a validated proprietary software package., Results: Significant group main effects for TG and VLDL-P were present; post-hoc tests revealed that serum TG concentrations were significantly higher in ↓T5 group compared to AB and ↑T4 groups [150±9 vs. 101±8 (p<0.01) and 112±8 mg/dl (p<0.05), respectively]. VLDL-P concentration was significantly elevated in ↓T5 group compared to AB and ↑T4 groups [74±4 vs. 58±4 (p<0.05) and 55±4 μmol/l (p<0.05)]. VAT volume was significantly higher in both SCI groups than in the AB group, and HOMA-IR was higher and approached significance in the SCI groups compared to the AB group. A linear relationship between triglyceride rich lipoproteins (i.e., TG or Large VLDL-P) and VAT volume or HOMA-IR was significant only in the ↓T5 group., Conclusions: Despite a similar VAT volume and insulin resistance in both SCI groups, the ↓T5 group had significantly higher serum TG and VLDL-P values than that observed in the ↑T4 and the AB control groups. Thus, level of injury is an important determinate of the concentration of circulating triglyceride rich lipoproteins, which may play a role in the genesis of cardiometabolic dysfunction.

Background/aims: Hepatic innervation in liver diseases is not fully understood. We here evaluated S100B expression as a marker of hepatic nerves in patients with various chronic liver diseases, topographically and semi-quantitatively., Methods: Liver specimens were obtained from 70 subjects (three controls, and 32 chronic hepatitis B, 14 chronic hepatitis C, 14 liver cirrhosis, and seven hepatocellular carcinoma patients). The hepatic nerve density was calculated based on immunohistochemical staining of S100B protein in the portal tracts and hepatic lobules. S100B mRNA levels were semi-quantitatively assessed as the S100B /glyceraldehyde 3-phosphate dehydrogenase ( GAPDH ) mRNA ratio., Results: The densities of the hepatic nerves in portal tracts of chronic liver diseases were not significantly different from those of normal controls but the hepatic nerve densities in lobular areas of liver cirrhosis were significantly decreased ( p = 0.025). Compared to the control, the S100B / GAPDH mRNA ratio was significantly decreased in chronic liver diseases ( p = 0.006) and most decreased in chronic hepatitis C patients ( p = 0.023). In chronic liver diseases, The S100B / GAPDH mRNA ratio tended to decrease as the fibrosis score > 0 ( p = 0.453) but the overall correlation between the S100B / GAPDH mRNA ratio and fibrosis score was not statistically significant ( r = 0.061, p = 0.657)., Conclusions: Hepatic innervation is decreased in cirrhotic regenerating nodules compared to the control group and seems to decrease in early stages of fibrosis progression. Further studies are needed to clarify the association between changes of hepatic innervation and chronic liver disease progression.

Purpose of Review: Hepatic lipid and lipoprotein metabolism is an important determinant of fasting dyslipidemia and the development of fatty liver disease. Although endocrine factors like insulin have known effects on hepatic lipid homeostasis, emerging evidence also supports a regulatory role for the central nervous system (CNS) and neuronal networks. This review summarizes evidence implicating a bidirectional liver-brain axis in maintaining metabolic lipid homeostasis, and discusses clinical implications in insulin-resistant states., Recent Findings: The liver utilizes sympathetic and parasympathetic afferent and efferent fibers to communicate with key regulatory centers in the brain including the hypothalamus. Hypothalamic anorexigenic and orexigenic peptides signal to the liver via neuronal networks to modulate lipid content and VLDL production. In addition, peripheral hormones such as insulin, leptin, and glucagon-like-peptide-1 exert control over hepatic lipid by acting directly within the CNS or via peripheral nerves. Central regulation of lipid metabolism in other organs including white and brown adipose tissue may also contribute to hepatic lipid content indirectly via free fatty acid release and changes in lipoprotein clearance., Summary: The CNS communicates with the liver in a bidirectional manner to regulate hepatic lipid metabolism and lipoprotein production. Impairments in these pathways may contribute to dyslipidemia and hepatic steatosis in insulin-resistant states.

Objective(s): Although accumulating evidence has shown that the autonomic nervous system is involved in liver pathology, its role in regulating cancer development remains unclear. The purpose of this study was to elucidate its detailed mechanisms., Methods: A mouse model of liver metastasis of colorectal cancer was used. To elucidate the potential mechanisms involved, we examined the effect of selective hepatic vagotomy on the survival rate and liver-to-body weight. We further evaluated the possible involvement of the hepatic sympathetic nerve fibers in this model., Results: The mortality rate and the liver-to-body weight ratio after cancer inoculation were significantly higher in the vagotomized mice than in the sham-operated mice. The vagotomized mice exhibited a transient decrease in hepatic norepinephrine levels following cancer inoculation. Interestingly, the vagotomy-induced exacerbation of liver metastasis was attenuated by supplementary norepinephrine or phenylephrine, a selective α1-adrenoceptor agonist, but not by clonidine, a selective α2-adrenoceptor agonist., Conclusion: Collectively, these results suggest that the hepatic vagus nerve may play a protective role against liver metastasis. Hepatic sympathetic nerves may also be involved as a protective efferent loop, possibly acting through the α1-adrenoceptor., (© 2018 S. Karger AG, Basel.)

The IL-33/ST2 axis plays a protective role in T-cell-mediated hepatitis, but little is known about the functional impact of endogenous IL-33 on liver immunopathology. We used IL-33-deficient mice to investigate the functional effect of endogenous IL-33 in concanavalin A (Con A)-hepatitis. IL-33(-/-) mice displayed more severe Con A liver injury than wild-type (WT) mice, consistent with a hepatoprotective effect of IL-33. The more severe hepatic injury in IL-33(-/-) mice was associated with significantly higher levels of TNF-α and IL-1β and a larger number of NK cells infiltrating the liver. The expression of Th2 cytokines (IL-4, IL-10) and IL-17 was not significantly varied between WT and IL-33(-/-) mice following Con A-hepatitis. The percentage of CD25(+) NK cells was significantly higher in the livers of IL-33(-/-) mice than in WT mice in association with upregulated expression of CXCR3 in the liver. Regulatory T cells (Treg cells) strongly infiltrated the liver in both WT and IL-33(-/-) mice, but Con A treatment increased their membrane expression of ST2 and CD25 only in WT mice. In vitro, IL-33 had a significant survival effect, increasing the total number of splenocytes, including B cells, CD4(+) and CD8(+) T cells, and the frequency of ST2(+) Treg cells. In conclusion, IL-33 acts as a potent immune modulator protecting the liver through activation of ST2(+) Treg cells and control of NK cells., (Copyright © 2016 the American Physiological Society.)

A pandemic of diabetes and obesity has been developing worldwide in close association with excessive nutrient intake and a sedentary lifestyle. Variations in the protein content of the diet have a direct impact on glucose homeostasis because amino acids (AAs) are powerful modulators of insulin action. In this work we review our recent findings on how elevations in the concentration of the circulating AAs leucine and proline activate a metabolic mechanism located in the mediobasal hypothalamus of the brain that sends a signal to the liver via the vagus nerve, which curtails glucose output. This neurogenic signal is strictly dependent on the metabolism of leucine and proline to acetyl-coenzyme A (CoA) and the subsequent production of malonyl-CoA; the signal also requires functional neuronal ATP-sensitive potassium channels. The liver then responds by lowering the rate of gluconeogenesis and glycogenolysis, ultimately leading to a net decrease in glucose production and in concentrations of circulating glucose. Furthermore, we review here how our work with proline suggests a new role of astrocytes in the central regulation of glycemia. Last, we outline how factors such as the consumption of fat-rich diets can interfere with glucoregulatory mechanisms and, in the long term, may contribute to the development of hyperglycemia, a hallmark of type 2 diabetes., (© 2016 American Society for Nutrition.)

During insulin-resistant states such as type II diabetes mellitus (T2DM), insulin fails to suppress hepatic glucose production (HGP) yet promotes lipid synthesis. This metabolic state has been termed "selective insulin resistance" to indicate a defect in one arm of the insulin-signaling cascade, potentially downstream of Akt. Here we demonstrate that Akt-dependent activation of mTORC1 and inhibition of Foxo1 are required and sufficient for de novo lipogenesis, suggesting that hepatic insulin signaling is likely to be intact in insulin-resistant states. Moreover, cell-nonautonomous suppression of HGP by insulin depends on a reduction of adipocyte lipolysis and serum FFAs but is independent of vagal efferents or glucagon signaling. These data are consistent with a model in which, during T2DM, intact liver insulin signaling drives enhanced lipogenesis while excess circulating FFAs become a dominant inducer of nonsuppressible HGP., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Rising temperatures resulting from climate change will increase the incidence of heat stress, negatively impacting the labor force and food animal production. Heat stress elevates circulating β-OH butyrate, which induces vasodilation through GPR109a. Interestingly, both heat stress and intraperitoneal β-OH butyrate administration induce hypophagia. Thus, we aimed to investigate the role of β-OH butyrate in heat stress hypophagia in mice. We found that niacin, a β-OH butyrate mimetic that cannot be oxidized to generate ATP, also reduces food intake. Interestingly, the depression in food intake as a result of 8-h intraperitoneal niacin or 48-h heat exposure did not result from changes in hypothalamic expression of orexigenic or anorexigenic signals (AgRP, NPY, or POMC). Genetically eliminating GPR109a expression did not prevent the hypophagic response to heat exposure, intraperitoneal β-OH butyrate (5.7 mmol/kg), or niacin (0.8 mmol/kg). Hepatic vagotomy eliminated the hypophagic response to β-OH butyrate and niacin but did not affect the hypophagic response to heat exposure. We subsequently hypothesized that the hypophagic response to heat stress may depend on direct effects of β-OH butyrate at the central nervous system: β-OH butyrate induced hormonal changes (hyperinsulinemia, hypercorticosteronemia, and hyperleptinemia), or gene expression changes. To test these possibilities, we blocked expression of hepatic hydroxyl methyl glutaryl CoA synthase II (HMGCS2) to prevent hepatic β-OH butyrate synthesis. Mice that lack HMGCS2 maintain a hypophagic response to heat stress. Herein, we establish that the hypophagia of heat stress is independent of GPR109a, the hepatic vagus afferent nerve, and hepatic ketone body synthesis., (Copyright © 2016 the American Physiological Society.)

Olanzapine, an atypical antipsychotic, is widely prescribed for the treatment of schizophrenia and bipolar disorder despite causing undesirable metabolic side effects. A variety of mechanisms and brain sites have been proposed as contributors to the side effects; however, the role of the dorsal motor nucleus of the vagus nerve (DMV), which plays a crucial role in the regulation of subdiaphragmatic organs and thus governs energy and glucose homeostasis, is largely unknown. Identifying the effect of olanzapine on the excitability of DMV neurons in both sexes is thus crucial to understanding possible underlying mechanisms. Whole cell patch-clamp electrophysiological recordings were conducted in stomach- and liver-related DMV neurons identified with retrograde viral tracers and in random DMV neurons. The effect of olanzapine on the neuronal excitability of DMV neurons both in male and female mice was established. Our data demonstrate that olanzapine hyperpolarizes the DMV neurons in both sexes and this effect is reversible. The hyperpolarization is associated with decreased firing rate and input resistance. Olanzapine also decreases the excitability of a subset of stomach- and liver-related DMV neurons. Our study demonstrates that olanzapine has a powerful effect on DMV neurons in both sexes, indicating its ability to reduce vagal output to the subdiaphragmatic organs, which likely contributes to the metabolic side effects observed in both humans and experimental models. These findings suggest that the metabolic side effects of olanzapine may partially originate in the DMV., (Copyright © 2016 the American Physiological Society.)

Galanin-like peptide (GALP) is a neuropeptide involved in the regulation of feeding behavior and energy metabolism in mammals. While a weight loss effect of GALP has been reported, its effects on lipid metabolism have not been investigated. The aim of this study was to determine if GALP regulates lipid metabolism in liver and adipose tissue via an action on the sympathetic nervous system. The respiratory exchange ratio of mice administered GALP intracerebroventricularly was lower than that of saline-treated animals, and fatty acid oxidation-related gene mRNA levels were increased in the liver. Even though the respiratory exchange ratio was reduced by GALP, this change was not significant when mice were treated with the sympatholytic drug, guanethidine. Lipolysis-related gene mRNA levels were increased in the adipose tissue of GALP-treated mice compared with saline-treated animals. These results show that GALP stimulates fatty acid β-oxidation in liver and lipolysis in adipose tissue, and suggest that the anti-obesity effect of GALP may be due to anorexigenic actions and improvement of lipid metabolism in peripheral tissues via the sympathetic nervous system.

Nesfatin-1 acts on the hypothalamus and regulates the autonomic nervous system. However, the hypothalamic mechanisms of nesfatin-1 on the autonomic nervous system are not well understood. In this study, we found that intracerebroventricular (ICV) administration of nesfatin-1 increased the extracellular signal-regulated kinase (ERK) activity in rats. Furthermore, the activity of sympathetic nerves, in the kidneys, liver, and white adipose tissue (WAT), and blood pressure was stimulated by the ICV injection of nesfatin-1, and these effects were abolished owing to pharmacological inhibition of ERK. Renal sympathoexcitatory and hypertensive effects were also observed with nesfatin-1 microinjection into the paraventricular hypothalamic nucleus (PVN). Moreover, nesfatin-1 increased the number of phospho (p)-ERK1/2-positive neurons in the PVN and coexpression of the protein in neurons expressing corticotropin-releasing hormone (CRH). Pharmacological blockade of CRH signaling inhibited renal sympathetic and hypertensive responses to nesfatin-1. Finally, sympathetic stimulation of WAT and increased p-ERK1/2 levels in response to nesfatin-1 were preserved in obese animals such as rats that were fed a high-fat diet and leptin receptor-deficient Zucker fatty rats. These findings indicate that nesfatin-1 regulates the autonomic nervous system through ERK signaling in PVN-CRH neurons to maintain cardiovascular function and that the antiobesity effect of nesfatin-1 is mediated by hypothalamic ERK-dependent sympathoexcitation in obese animals., (© 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.)

Human and animal studies increasingly point toward a neural pathogenesis of the metabolic syndrome, involving hypothalamic and autonomic nervous system dysfunction. We hypothesized that increased very-low-density lipoprotein-triglyceride (VLDL-TG) secretion by the liver in a rat model for dyslipidemia, that is, the obese Zucker (fa/fa) rat, is due to relative hyperactivity of sympathetic, and/or hypoactivity of parasympathetic hepatic innervation. To test the involvement of the autonomic nervous system, we surgically denervated the sympathetic or parasympathetic hepatic nerve in obese Zucker rats. Our results show that cutting the sympathetic hepatic nerve lowers VLDL-TG secretion in obese rats, finally resulting in lower plasma TG concentrations after 6 weeks. In contrast, a parasympathetic denervation results in increased plasma total cholesterol concentrations. The effect of a sympathetic or parasympathetic denervation of the liver was independent of changes in humoral factors or changes in body weight or food intake. In conclusion, a sympathetic denervation improves the lipid profile in obese Zucker rats, whereas a parasympathetic denervation increases total cholesterol levels. We believe this is a novel treatment target, which should be further investigated.

The hepatic nervous system has a well-known impact on the regulation of liver function and organism homeostasis. The aim of this review is to summarize the new available data regarding the role of hepatic nerves. In the last decade, studies have shown that hepatic nerves exert subtle but significant modifications on the regulation of glucose and lipid metabolism, food intake, and liver regeneration. They also play a role in liver disease pathogenesis, and hepatic denervation has beneficial results to liver graft ischemia-reperfusion injury. Available data are still limited, and further research toward neural pathways involving the liver that can modify response to disease is required., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Background & Aims: Phosphatidylethanolamine N-methyltransferase (PEMT), a liver enriched enzyme, is responsible for approximately one third of hepatic phosphatidylcholine biosynthesis. When fed a high-fat diet (HFD), Pemt(-/-) mice are protected from HF-induced obesity; however, they develop steatohepatitis. The vagus nerve relays signals between liver and brain that regulate peripheral adiposity and pancreas function. Here we explore a possible role of the hepatic branch of the vagus nerve in the development of diet induced obesity and steatohepatitis in Pemt(-/-) mice., Methods: 8-week old Pemt(-/-) and Pemt(+/+) mice were subjected to hepatic vagotomy (HV) or capsaicin treatment, which selectively disrupts afferent nerves, and were compared to sham-operated or vehicle-treatment, respectively. After surgery, mice were fed a HFD for 10 weeks., Results: HV abolished the protection against the HFD-induced obesity and glucose intolerance in Pemt(-/-) mice. HV normalized phospholipid content and prevented steatohepatitis in Pemt(-/-) mice. Moreover, HV increased the hepatic anti-inflammatory cytokine interleukin-10, reduced chemokine monocyte chemotactic protein-1 and the ER stress marker C/EBP homologous protein. Furthermore, HV normalized the expression of mitochondrial electron transport chain proteins and of proteins involved in fatty acid synthesis, acetyl-CoA carboxylase and fatty acid synthase in Pemt(-/-) mice. However, disruption of the hepatic afferent vagus nerve by capsaicin failed to reverse either the protection against the HFD-induced obesity or the development of HF-induced steatohepatitis in Pemt(-/-) mice., Conclusions: Neuronal signals via the hepatic vagus nerve contribute to the development of steatohepatitis and protection against obesity in HFD fed Pemt(-/-) mice., (Copyright © 2014 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

The aim of the study was to investigate nerve fibers (NF) in human fetal livers. An immunohistochemical study was performed. NF were classified into portal tract innervation (PoI) and parenchymal innervation (PaI). The hilum area showed many Pol NF at 7 GW, and NF increased with gestational week (GW). Direct innervations to biliary epithelium were recognized. In large portal tracts, a few NCAM-positive mesenchymal cells were seen at 8 GW and many mesenchymal cells were noted around 12 GW. Apparent NF emerged around 15 GW, and NF increased with GW. Many NF plexuses were seen in 30-40 GW. In small portal tracts, no NF were seen in 7-10 GW. A few NCAM-positive mesenchymal cells emerged in 11 GW, and they increased thereafter. Apparent NF were seen around 20 GW and NF increased with GW. At term (40 GW), PoI NF were still immature. Ductal plate (DP) was positive for NCAM, NSE, chromogranin and synaptophysin, and direct innervations to DP were seen. The direct innervations to developing bile ducts and peribiliary glands were also seen. PaI NF were first seen at 21 GW and was consistent until 40 GW in which a few NF were seen in PaI. These observations suggest that PoI NF arise from committed portal mesenchyme. PaI NF are very immature at 40 GW. There are direct innervations to bile ducts, peribiliary glands, portal veins, hepatic arteries, and DP.

Leptin action in the brain has emerged as an important regulator of liver function independently from its effects on food intake and body weight. The autonomic nervous system plays a key role in the regulation of physiological processes by leptin. Here, we used direct recording of nerve activity from sympathetic or vagal nerves subserving the liver to investigate how brain action of leptin controls hepatic autonomic nerve activity. Intracerebroventricular (ICV) administration of leptin activated hepatic sympathetic traffic in rats and mice in dose- and receptor-dependent manners. The hepatic sympatho-excitatory effects of leptin were also observed when leptin was microinjected directly into the arcuate nucleus (ARC), but not into the ventromedial hypothalamus (VMH). Moreover, using pharmacological and genetic approaches, we show that leptin-induced increase in hepatic sympathetic outflow depends on PI3K but not AMP-activated protein kinase (AMPK), STAT3, or ERK1/2. Interestingly, ICV leptin also increased hepatic vagal nerve activity in rats. We show that this response is reproduced by intra-ARC, but not intra-VMH, leptin administration and requires PI3K and AMPK. We conclude that central leptin signaling conveys the information to the liver through the sympathetic and parasympathetic branches of the autonomic nervous system. Our data also provide important insight into the molecular events underlying leptin's control of hepatic autonomic nerve activity by implicating PI3K and AMPK pathways., (Copyright © 2015 the authors 0270-6474/15/350474-11$15.00/0.)

The brain emerges as a regulator of hepatic triglyceride-rich very-low-density lipoproteins (VLDL-TG). The neurocircuitry involved as well as the ability of fatty acids to trigger a neuronal network to regulate VLDL-TG remain unknown. Here we demonstrate that infusion of oleic acid into the mediobasal hypothalamus (MBH) activates a MBH PKC-δ→KATP-channel signalling axis to suppress VLDL-TG secretion in rats. Both NMDA receptor-mediated transmissions in the dorsal vagal complex (DVC) and hepatic innervation are required for lowering VLDL-TG, illustrating a MBH-DVC-hepatic vagal neurocircuitry that mediates MBH fatty acid sensing. High-fat diet (HFD)-feeding elevates plasma TG and VLDL-TG secretion and abolishes MBH oleic acid sensing to lower VLDL-TG. Importantly, HFD-induced dysregulation is restored with direct activation of either MBH PKC-δ or KATP-channels via the hepatic vagus. Thus, targeting a fatty acid sensing-dependent hypothalamic-DVC neurocircuitry may have therapeutic potential to lower hepatic VLDL-TG and restore lipid homeostasis in obesity and diabetes.

Glucose produced by the liver is a major energy source for the brain. Considering its critical dependence on glucose, it seems only natural that the brain is capable of monitoring and controlling glucose homeostasis. In addition to neuroendocrine pathways, the brain uses the autonomic nervous system to communicate with peripheral organs. Within the brain, the hypothalamus is the key region to integrate signals on energy status, including signals from lipid, glucose, and hormone sensing cells, with afferent neural signals from the internal and external milieu. In turn, the hypothalamus regulates metabolism in peripheral organs, including the liver, not only via the anterior pituitary gland but also via multiple neuropeptidergic pathways in the hypothalamus that have been identified as regulators of hepatic glucose metabolism. These pathways comprise preautonomic neurons projecting to nuclei in the brain stem and spinal cord, which relay signals from the hypothalamus to the liver via the autonomic nervous system. The neuroendocrine and neuronal outputs of the hypothalamus are not separate entities. They appear to act as a single integrated regulatory system, far more subtle, and complex than when each is viewed in isolation. Consequently, hypothalamic regulation should be viewed as a summation of both neuroendocrine and neural influences. As a result, our endocrine-based understanding of diseases such as diabetes and obesity should be expanded by integration of neural inputs into our concept of the pathophysiological process., (© 2014 American Physiological Society.)

Rationale: Dopamine β-hydroxylase (DBH) catalyzes the conversion of dopamine to norepinephrine in the central nervous system and peripherally. DBH variants are associated with large changes in circulating DBH and implicated in multiple disorders; yet causal relationships and tissue-specific effects remain unresolved., Objective: To characterize regulatory variants in DBH, effect on mRNA expression, and role in modulating sympathetic tone and disease risk., Methods and Results: Analysis of DBH mRNA in human tissues confirmed high expression in the locus coeruleus and adrenal gland, but also in sympathetically innervated organs (liver>lung>heart). Allele-specific mRNA assays revealed pronounced allelic expression differences in the liver (2- to 11-fold) attributable to promoter rs1611115 and exon 2 rs1108580, but only small differences in locus coeruleus and adrenals. These alleles were also associated with significantly reduced mRNA expression in liver and lung. Although DBH protein is expressed in other sympathetically innervated organs, mRNA levels were too low for analysis. In mice, hepatic Dbh mRNA levels correlated with cardiovascular risk phenotypes. The minor alleles of rs1611115 and rs1108580 were associated with sympathetic phenotypes, including angina pectoris. Testing combined effects of these variants suggested protection against myocardial infarction in 3 separate clinical cohorts., Conclusions: We demonstrate profound effects of DBH variants on expression in 2 sympathetically innervated organs, liver and lung, but not in adrenals and brain. Preliminary results demonstrate an association of these variants with clinical phenotypes responsive to peripheral sympathetic tone. We hypothesize that in addition to endocrine effects via circulating DBH and norepinephrine, the variants act in sympathetically innervated target organs., (© 2014 American Heart Association, Inc.)

During fasting, profound changes in the regulation of the hypothalamus-pituitary-thyroid axis occur in order to save energy and limit catabolism. In this setting, serum T3 and T4 are decreased without an appropriate TSH and TRH response reflecting central down-regulation of the hypothalamus-pituitary-thyroid axis. Hepatic thyroid hormone (TH) metabolism is also affected by fasting, because type 3 deiodinase (D3) is increased, which is mediated by serum leptin concentrations. A recent study showed that fasting-induced changes in liver TH sulfotransferases (Sults) and uridine 5'-diphospho-glucuronosyltransferase (Ugts) depend on a functional melanocortin system in the hypothalamus. However, the pathways connecting the hypothalamus and the liver that induce these changes are currently unknown. In the present study, we investigated in rats whether the fasting-induced changes in hepatic TH metabolism are regulated by the autonomic nervous system. We selectively cut either the sympathetic or the parasympathetic input to the liver. Serum and liver TH concentrations, deiodinase expression, and activity and Sult and Ugt expression were measured in rats that had been fasted for 36 hours or were fed ad libitum. Fasting decreased serum T3 and T4 concentrations, whereas intrahepatic TH concentrations remained unchanged. D3 expression and activity increased, as was the expression of constitutive androstane receptor, Sult1b1, and Ugt1a1, whereas liver D1 was unaffected. Neither sympathetic nor parasympathetic denervation affected the fasting-induced alterations. We conclude that fasting-induced changes in liver TH metabolism are not regulated via the hepatic autonomic input in a major way and more likely reflect a direct effect of humoral factors on the hepatocyte.

Background: We examined the intrinsic hepatic innervation after partial hepatectomy (PH) in rats and the presence and pattern of neural sprouting in regenerating liver., Methods: Male Wistar rats (age 9-13 weeks-w, weight 204-356 g), were submitted to two-thirds PH. Rats were sacrificed at postoperative days (d) 1, 3, 5, 7, at 2 and 4 w, and at 3 and 6 months (m) (6-7 animals/group, control group n = 4). Immunohistochemistry for the pan-neural marker protein gene product 9.5 (PGP9.5) and growth-associated protein 43 (GAP-43), a marker of regenerating nerve axons, was performed on tissue sections from the R1 lobe of the regenerating liver. Portal tracts (PTs) with immunoreactive fibers were counted in each section and computer-assisted morphometric analysis (Image Pro Plus) was used to measure nerve fiber density (number of immuno-positive nerve fibers/mm2 (40x))., Results: Immunoreactivity for PGP9.5 was positive in all groups. The number of PGP9.5 (+) nerve fibers decreased from 0.32 +/- 0.12 (control group) to 0.18 +/- 0.09 (1d post-PH group), and gradually increased reaching pre-PH levels at 6 m (0.3 +/- 0.01). In contrast, immunoreactivity for GAP-43 was observed at 5d post-PH, and GAP-43 (+) PTs percentage increased thereafter with a peak at 3 m post-PH. GAP-43 (+) nerve fiber density increased gradually from 5d (0.05 +/- 0.06) with a peak at 3 m post-PH (0.21 +/- 0.027). At 6 m post-PH, immunoreactivity for GAP-43 was not detectable., Conclusions: Following PH in rats: 1) nerve fiber density in portal tracts decreases temporarily, and 2) neural sprouting in the regenerating liver lobes starts at 5d, reaches peak levels at 3 m and disappears at 6 m post-PH, indicating that the increase in hepatic mass after PH provides an adequate stimulus for the sprouting process.

Objectives: The purpose of this study is to investigate the impact of the hepatic branch of the vagus and Roux-en-Y gastric bypass (RYGB) on the level of fasting and postprandial serum glucagon-like peptide-1 (GLP-1) in type 2 diabetic mellitus rats., Methods: Randomized block design, factorial experiment. Forty-five type 2 diabetic rats were divided into four groups: sham operation (S, n = 10) and sham operation with the hepatic branch of the vagotomy (SV, n = 11), Roux-en-Y gastric bypass (RYGB, n = 12) and RYGB without preservation of the vagus (RYGBV, n = 12). Levels of fasting and postprandial serum GLP-1 30 min after 50 % glucose solution (2 g/kg) by gavage were determined before surgery and postoperatively at 1, 4, and 8 weeks. Interactions between RYGB and the common hepatic branch were also assessed., Results: Roux-en-Y gastric bypass surgery significantly increased the concentration of postprandial serum GLP-1 and maintained it at a higher level (P < 0.05). Preservation of vagus hepatic branch only increased the concentration of postprandial serum GLP-1 at the initial stage (P < 0.05), which gradually weakened over time (P > 0.05). Both RYGB and vagotomy of the hepatic branch had no influence on fasting serum GLP-1 (P > 0.05)., Conclusions: During RYGB surgery for the long-term treatment of T2DM, preservation of the hepatic branch of the vagus might have no impact on serum GLP-1 level.

Background: The impact of the hepatic branch of the vagus and Roux-en-Y gastric bypass (RYGB) on the hypoglycemic effect and glucagon-like peptide-1 (GLP-1) in rats with type 2 diabetes mellitus (T2DM) was investigated, and interactions were preliminarily analyzed., Methods: A total of 45 rats with T2DM were divided into four groups: sham operation (S, n = 10), sham operation with the hepatic branch of the vagus resected (SV, n = 11), RYGB (n = 12), and RYGB without preservation of the vagus (RYGBV, n = 12). Body mass, fasting blood glucose (FBG), fasting serum insulin, and concentrations of fasting serum GLP-1 were examined in the first, second, fourth, and eighth week before and after surgery. The effects of RYGB and the hepatic branch of the vagus on GLP-1 levels in the eighth postoperative week were also analyzed., Results: RYGB caused a significant reduction in the weight of rats with T2DM (P < 0.05), improved the levels of serum GLP-1 and insulin (P < 0.05), and decreased FBG level (P < 0.05). Retention of the hepatic branch of the vagus maintained weight reduction for a longer period (P < 0.05) and increased the levels of serum GLP-1 and insulin (P < 0.05), but had no impact on FBG level (P > 0.05)., Conclusions: RYGB had better therapeutic efficacy in rats with T2DM. Care should be taken during RYGB surgery to preserve the hepatic branch of the vagus., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Dysregulation of hepatic glucose uptake (HGU) and inability of insulin to suppress hepatic glucose production (HGP) contribute to hyperglycaemia in patients with type 2 diabetes (T2D). Growing evidence suggests that insulin can inhibit HGP not only through a direct effect on the liver but also through a mechanism involving the brain. Yet, the notion that insulin action in the brain plays a physiological role in the control of HGP continues to be controversial. Although studies in dogs suggest that the direct hepatic effect of insulin is sufficient to explain day-to-day control of HGP, a surprising outcome has been revealed by recent studies in mice, investigating whether the direct hepatic action of insulin is necessary for normal HGP: when the hepatic insulin signalling pathway was genetically disrupted, HGP was maintained normally even in the absence of direct input from insulin. Here, we present evidence that points to a potentially important role of the brain in the physiological control of both HGU and HGP in response to input from insulin as well as other hormones and nutrients., (© 2014 John Wiley & Sons Ltd.)

It has been demonstrated that intraoperative radiotherapy is a therapeutic option for patients suffering from perihilar cholangiocarcinoma. Aim of our study was to investigate vascular and nerve damages after irradiation of the liver hilum in a pig model. Twenty-four pigs underwent central bile duct resection followed by biliodigestive anastomosis. Nine pigs underwent this surgical procedure alone (group 1). Ten pigs were treated with additional intraoperative radiation therapy (IORT) of 20Gy to the liver hilum (group 2). And five pigs received operation and IORT with 40Gy to the area of anastomosis (group 3). Six weeks after operation and treatment the animals were sacrificed and histopathological examination was performed. Histology showed no vascular or nerve damage in non-irradiated perihilar tissue. Significant changes of nerve structures occurred, as well as vascular damage in large and even more in small hilar arteries in the irradiated neighboring liver tissue. In detail for small hilar arteries: intima proliferation (p ≤ .0001), endothelial swelling (p ≤ .0001), fibrinoid arterial wall necrosis (p ≤ .0001), and arterial thrombosis (p = .0079) were detected. Venous vessels did not show significant dose dependant cell damage. Overall, 20Gy as a single dose application during operation showed similar damage to vessels and nerves compared to 40Gy. A radiation dosage of 20Gy seems to be sufficient to induce necrosis due to vascular and nerve damage in potential malignant liver tissue with acceptable damage to surrounding tissue. Perineural invaded tumor cells might be diminished due to IORT.

Orexin-A (a neuropeptide in the hypothalamus) plays an important role in many physiological functions, including the regulation of glucose metabolism. We have previously found that the development of post-ischemic glucose intolerance is one of the triggers of ischemic neuronal damage, which is suppressed by hypothalamic orexin-A. Other reports have shown that the communication system between brain and peripheral tissues through the autonomic nervous system (sympathetic, parasympathetic and vagus nerve) is important for maintaining glucose and energy metabolism. The aim of this study was to determine the involvement of the hepatic vagus nerve on hypothalamic orexin-A-mediated suppression of post-ischemic glucose intolerance development and ischemic neuronal damage. Male ddY mice were subjected to middle cerebral artery occlusion (MCAO) for 2 h. Intrahypothalamic orexin-A (5 pmol/mouse) administration significantly suppressed the development of post-ischemic glucose intolerance and neuronal damage on day 1 and 3, respectively after MCAO. MCAO-induced decrease of hepatic insulin receptors and increase of hepatic gluconeogenic enzymes on day 1 after was reversed to control levels by orexin-A. This effect was reversed by intramedullary administration of the orexin-1 receptor antagonist, SB334867, or hepatic vagotomy. In the medulla oblongata, orexin-A induced the co-localization of cholin acetyltransferase (cholinergic neuronal marker used for the vagus nerve) with orexin-1 receptor and c-Fos (activated neural cells marker). These results suggest that the hepatic branch vagus nerve projecting from the medulla oblongata plays an important role in the recovery of post-ischemic glucose intolerance and mediates a neuroprotective effect by hypothalamic orexin-A.

Brown adipose tissue (BAT) burns calories to produce heat, and is thus relevant to energy balance. Interscapular BAT (IBAT) of donor mice was transplanted into recipient mice (transBATation). To test whether transBATation counteracts high-fat diet (HFD)-induced obesity, some sham-operated and recipient mice were fed a HFD (HFD-sham, HFD-trans) while others remained on a standard chow (chow-sham, chow-trans). HFD-trans mice had lower body weight and fat and greater energy expenditure, but similar caloric intake compared with HFD-sham mice. We hypothesized that HFD-trans mice had elevated sympathetic activity compared with HFD-sham mice, contributing to increased energy expenditure and fuel mobilization. This was supported by findings that HFD-trans mice had greater energy expenditure during a norepinephrine challenge test and higher core temperatures after cold exposure than did HFD-sham mice, implicating enhanced whole-body metabolic response and elevated sympathetic activity. Additionally, transBATation selectively increased sympathetic drive to some, but not all, white adipose tissue depots and skeletal muscles, as well as the endogenous IBAT, heart, and liver. Collectively, transBATation confers resistance to HFD-induced obesity via increase in whole-body sympathetic activity, and differential activation of sympathetic drive to some of the tissues involved in energy expenditure and fuel mobilization., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Background: In human beings or animals, ischemia/reperfusion (I/R) injury of the liver may occur in many clinical conditions, such as circulating shock, liver transplantation and surgery and several other pathological conditions. I/R injury has a complex pathophysiology resulting from a number of contributing factors. Therefore, it is difficult to achieve effective treatment or protection by individually targeting the mediators. This study aimed at studying the effects of local somatothermal stimulation preconditioning on the right Qimen (LR14) on hepatic I/R injury in rats., Methods: Eighteen male Sprague-Dawley rats were randomly divided into three groups. The rats were preconditioned with thermal tolerance study, which included one dose of local somatothermal stimulation (LSTS) on right Qimen (LR14) at an interval of 12 h, followed by hepatic ischemia for 60 min and then reperfusion for 60 min. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) have been used to assess the liver functions, and liver tissues were taken for the measurements such as malondialdehyde (MDA), glutathione (GSH), catalase (CAT), superoxidase dismutase (SOD), and myeloperoxidase (MPO)., Results: The results show that the plasma ALT and AST activities were higher in the I/R group than in the control group. In addition, the plasma ALT and AST activities decreased in the groups that received LSTS. The hepatic SOD levels reduced significantly by I/R injury. Moreover, the hepatic MPO activity significantly increased by I/R injury while it decreased in the groups given LSTS., Conclusions: Our findings show that LSTS provides a protective effects on the liver from the I/R injury. Therefore, LSTS might offer an easy and inexpensive intervention for patients who have suffered from I/R of the liver especially in the process of hepatotomy and hepatic transplantation.

We previously reported that glucagon-like peptide-1 (GLP-1) appearance in the portal vein facilitates hepatic vagal afferent activity, and this further augments reflexively the pancreatic vagal efferents in anesthetized rats, suggesting a neuroincretin effect of GLP-1. To determine whether the GLP-1-induced vagal pathways lead to a neuronal-mediated component (NMC) of insulin secretion, we infused GLP-1 at a physiological or pharmacological dose (1 or 3 pmol·kg(-1)·min(-1), respectively) into the portal vein in conscious rats with selective hepatic vagotomy (Vagox) or sham operation (Sham). The experiments consisted of two sequential 10-min intraportal infusions (P1 and P2): glucose at a physiological rate (56 μmol·kg(-1)·min(-1)) in P1 and the glucose plus GLP-1 or vehicle in P2. Under arterial isoglycemia across the groups, the physiological GLP-1 infusion in Sham augmented promptly and markedly arterial insulin levels, approximately twofold the levels in glucose alone infusion (P < 0.005), and insulin levels in Vagox diminished apparently (P < 0.05). Almost 60% of the GLP-1-induced insulin secretion (AUC) in Sham met the NMC, i.e., difference between insulin secretion in Sham and Vagox, (AUC 976 ± 65 vs. 393 ± 94 pmol·min/l, respectively, P < 0.005). Intraportal pharmacological GLP-1 infusion further augmented insulin secretion in both groups, but the NMC remained in 46% (NS; Sham vs. Vagox). In contrast, "isoglycemic" intravenous GLP-1 infusion (3 pmol·kg(-1)·min(-1)) evoked an equal insulin secretion in both groups. Thus, the present results indicate that GLP-1 appearing in the portal vein evokes a powerful neuronal-mediated insulinotropic effect, suggesting the neuroincretin effect.

The impact of denervation and delymphatization (DD) on liver tissue remains a topic of major interest in liver transplantation, as the organ or its part continues to function well. Various chemical and/or surgical interventions have been developed to achieve in situ liver denervation and delymphatization, but it is evident that DD can be achieved only through "ectomia", ie, complete isolation of the organ from adjacent and connected structures. This Study describes a liver DD model based on a technique of autotransplantation (replantation), maximally preventing ischemia in the transplanted (replanted) graft and dyscirculatory complications in the recipient. Experiments were performed on eight male mongrel dogs. Venous reservoir and roller pumps were used in a forced nontraditional bypass scheme. Autotransplantation was performed by step-by-step dissection of the suprahepatic, infrahepatic, and portal structures, leading to DD, with subsequent recovery of the blood vessel and bile duct. DD was achieved successfully with stable hemodynamic parameters during all surgery periods. All animals survived. This model of liver autotransplantation lead to DD of the organ. It was characterized by hemodynamic stability of the liver as well as of the whole body at every stage of the surgery, proffering liver DD for experimental studies., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Aim: To investigate the expression of dipeptidyl peptidase (DPP) 8 and DPP9 in lymphocytes and various models of liver fibrosis., Methods: DPP8 and DPP9 expression were measured in mouse splenic CD4⁺ T-cells, CD8⁺ T-cells and B-cells (B220⁺), human lymphoma cell lines and mouse splenocytes stimulated with pokeweed mitogen (PWM) or lipopolysaccharide (LPS), and in dithiothreitol (DTT) and mitomycin-C treated Raji cells. DPP8 and DPP9 expression were measured in epidermal growth factor (EGF) treated Huh7 hepatoma cells, in fibrotic liver samples from mice treated with carbon tetrachloride (CCl₄) and from multidrug resistance gene 2 (Mdr2/Abcb4) gene knockout (gko) mice with biliary fibrosis, and in human end stage primary biliary cirrhosis (PBC)., Results: All three lymphocyte subsets expressed DPP8 and DPP9 mRNA. DPP8 and DPP9 expression were upregulated in both PWM and LPS stimulated mouse splenocytes and in both Jurkat T- and Raji B-cell lines. DPP8 and DPP9 were downregulated in DTT treated and upregulated in mitomycin-C treated Raji cells. DPP9-transfected Raji cells exhibited more annexin V⁺ cells and associated apoptosis. DPP8 and DPP9 mRNA were upregulated in CCl₄ induced fibrotic livers but not in the lymphocytes isolated from such livers, while DPP9 was upregulated in EGF stimulated Huh7 cells. In contrast, intrahepatic DPP8 and DPP9 mRNA expression levels were low in the Mdr2 gko mouse and in human PBC compared to non-diseased livers., Conclusion: These expression patterns point to biological roles for DPP8 and DPP9 in lymphocyte activation and apoptosis and in hepatocytes during liver disease pathogenesis.

The liver is a key organ in controlling glucose and lipid metabolism during feeding and fasting. In addition to hormones and nutrients, inputs from the autonomic nervous system are also involved in fine-tuning hepatic metabolic regulation. Previously, we have shown in rats that during fasting an intact sympathetic innervation of the liver is essential to maintain the secretion of triglycerides by the liver. In the current study, we hypothesized that in the postprandial condition the parasympathetic input to the liver inhibits hepatic VLDL-TG secretion. To test our hypothesis, we determined the effect of selective surgical hepatic denervations on triglyceride metabolism after a meal in male Wistar rats. We report that postprandial plasma triglyceride concentrations were significantly elevated in parasympathetically denervated rats compared with control rats (P = 0.008), and VLDL-TG production tended to be increased (P = 0.066). Sympathetically denervated rats also showed a small rise in postprandial triglyceride concentrations (P = 0.045). On the other hand, in rats fed on a six-meals-a-day schedule for several weeks, a parasympathetic denervation resulted in >70% higher plasma triglycerides during the day (P = 0.001), whereas a sympathetic denervation had no effect. Our results show that abolishing the parasympathetic input to the liver results in increased plasma triglyceride levels during postprandial conditions.

The liver has a nervous system containing both afferent and efferent neurons that are involved in a number of processes. The afferent arm includes the sensation of lipids, glucose, and metabolites (after eating and drinking) and triggers the nervous system to make appropriate physiological changes. The efferent arm is essential for metabolic regulation, modulation of fibrosis and biliary function and the control of a number of other processes. Experimental models have helped us to establish how: (i) the liver is innervated by the autonomic nervous system; and (ii) the cell types that are involved in these processes. Thus, the liver acts as both a sensor and effector that is influenced by neurological signals and ablation. Understanding these processes hold significant implications in disease processes such as diabetes and obesity, which are influenced by appetite and hormonal signals.

Long-term reduced hypothalamic estrogen signaling leads to increased food intake and decreased locomotor activity and energy expenditure, and ultimately results in obesity and insulin resistance. In the current study, we aimed to determine the acute obesity-independent effects of hypothalamic estrogen signaling on glucose metabolism. We studied endogenous glucose production (EGP) and insulin sensitivity during selective modulation of systemic or intrahypothalamic estradiol (E2) signaling in rats 1 week after ovariectomy (OVX). OVX caused a 17% decrease in plasma glucose, which was completely restored by systemic E2. Likewise, the administration of E2 by microdialysis, either in the hypothalamic paraventricular nucleus (PVN) or in the ventromedial nucleus (VMH), restored plasma glucose. The infusion of an E2 antagonist via reverse microdialysis into the PVN or VMH attenuated the effect of systemic E2 on plasma glucose. Furthermore, E2 administration in the VMH, but not in the PVN, increased EGP and induced hepatic insulin resistance. E2 administration in both the PVN and the VMH resulted in peripheral insulin resistance. Finally, sympathetic, but not parasympathetic, hepatic denervation blunted the effect of E2 in the VMH on both EGP and hepatic insulin sensitivity. In conclusion, intrahypothalamic estrogen regulates peripheral and hepatic insulin sensitivity via sympathetic signaling to the liver.

During fasting, animals maintain their energy balance by shifting their energy source from carbohydrates to triglycerides. However, the trigger for this switch has not yet been entirely elucidated. Here we show that a selective hepatic vagotomy slows the speed of fat consumption by attenuating sympathetic nerve-mediated lipolysis in adipose tissue. Hepatic glycogen pre-loading by the adenoviral overexpression of glycogen synthase or the transcription factor TFE3 abolished this liver-brain-adipose axis activation. Moreover, the blockade of glycogenolysis [corrected] through the knockdown of the glycogen phosphorylase gene and the resulting elevation in the glycogen content abolished the lipolytic signal from the liver, indicating that glycogen is the key to triggering this neurocircuitry. These results demonstrate that liver glycogen shortage activates a liver-brain-adipose neural axis that has an important role in switching the fuel source from glycogen to triglycerides under prolonged fasting conditions.

The liver plays an important role in maintaining glucose homeostasis in the body. In the prandial state, some of the glucose which is absorbed by the gastrointestinal tract is converted into glycogen and stored in the liver. In contrast, the liver produces glucose by glycogenolysis and gluconeogenesis while fasting. Thus, the liver contributes to maintaining blood glucose level within normoglycemic range. Glycogenesis and glycogenolysis are regulated by various mechanisms including hormones, the sympathetic and parasympathetic nervous systems and the hepatic glucose content. In this study, we examined a rat model in which the celiac superior mesenteric ganglion (CSMG) was resected. We attempted to elucidate how the celiac sympathetic nervous system is involved in regulating glucose homeostasis by assessing the effects of CSMG resection on glucose excursion during an oral glucose tolerance test, and by examining hepatic glycogen content and hepatic glycogen phosphorylase (GP) activity. On the oral glucose tolerance test, CSMG-resected rats demonstrated improved glucose tolerance and significantly increased GP activity compared with sham-operated rats, whereas there were no significant differences in insulin, glucagon or catecholamine levels between the 2 groups. These results suggest that the celiac sympathetic nervous system is involved in regulating the rate of glycogen consumption through GP activity. In conclusion, the examined rat model showed that the celiac sympathetic nervous system regulates hepatic glucose metabolism in conjunction with vagal nerve innervations and is a critical component in the maintenance of blood glucose homeostasis.

Insulinoma-associated protein (IA)-2 and IA-2β are transmembrane proteins involved in neurotransmitter secretion. Mice with targeted disruption of both IA-2 and IA-2β (double-knockout, or DKO mice) have numerous endocrine and physiological disruptions, including disruption of circadian and diurnal rhythms. In the present study, we have assessed the impact of disruption of IA-2 and IA-2β on molecular rhythms in the brain and peripheral oscillators. We used in situ hybridization to assess molecular rhythms in the hypothalamic suprachiasmatic nuclei (SCN) of wild-type (WT) and DKO mice. The results indicate significant disruption of molecular rhythmicity in the SCN, which serves as the central pacemaker regulating circadian behavior. We also used quantitative PCR to assess gene expression rhythms in peripheral tissues of DKO, single-knockout, and WT mice. The results indicate significant attenuation of gene expression rhythms in several peripheral tissues of DKO mice but not in either single knockout. To distinguish whether this reduction in rhythmicity reflects defective oscillatory function in peripheral tissues or lack of entrainment of peripheral tissues, animals were injected with dexamethasone daily for 15 days, and then molecular rhythms were assessed throughout the day after discontinuation of injections. Dexamethasone injections improved gene expression rhythms in liver and heart of DKO mice. These results are consistent with the hypothesis that peripheral tissues of DKO mice have a functioning circadian clockwork, but rhythmicity is greatly reduced in the absence of robust, rhythmic physiological signals originating from the SCN. Thus, IA-2 and IA-2β play an important role in the regulation of circadian rhythms, likely through their participation in neurochemical communication among SCN neurons.

Background: Hepatic blood flow is known to decrease during pneumoperitoneum. Studies have shown that such changes affect kidney urinary output through the sympathetic pathway known as the hepatorenal reflex. This study investigated the potential role of the hepatorenal reflex in pneumoperitoneum-induced oliguria. The authors hypothesized that oliguria detectable during pneumoperitoneum is caused by activation of the hepatorenal reflex., Methods: Denervation of the sympathetic nervous structure was performed in 15 rats by applying 1 ml of 90 % aqueous phenol solution circumferentially to the portal vein and vena cava area at their entrance to the liver. The same was applied to only the peritoneum in 15 nondenervated rats. After 2 weeks, the rats were divided into three subgroups (5 rats per subgroup) that were exposed respectively to carbon dioxide-induced pneumoperitoneum at 0, 10, and 15 mmHg for 2 h. Statistical analysis was performed using Student's t test and analyses of variance., Results: Denervation did not affect the preinsufflation parameters. The denervated and the nondenervated 0-mmHg subgroups presented with similar parameters. The postinsufflation mean urine output was significantly lower in the nondenervated than in the denervated 10- and 15-mmHg subgroups (p = 0.0097). The denervated rats had a final creatinine clearance 29 % lower than the preinsufflation value (p = 0.83), whereas the nondenervated animals presented a 79 % drop in creatinine clearance (p = 0.02)., Conclusion: The study findings indicate that the hepatorenal reflex plays an important role in the pathophysiology of oliguria that occurs during pneumoperitoneum in the rat.

The hypothalamic suprachiasmatic nucleus (SCN) is an essential component of the circadian timing system, and an important determinant of neuroendocrine and metabolic regulation. Recent data indicate a modulatory role for the immune system on the circadian timing system. The authors investigated how the circadian timing system affects the hypothalamo-pituitary-adrenal (HPA) axis and glucose regulatory responses evoked by an immune challenge induced by lipopolysaccharide (LPS). LPS-induced increases in corticosterone were minimal during the trough of the daily corticosterone rhythm; in contrast, LPS effects on glucose, glucagon, and insulin did not vary across time-of-day. Complete ablation of the SCN resulted in increased corticosterone responses but did not affect LPS-induced hyperglycemia. The paraventricular nucleus (PVN) of the hypothalamus is an important neuroendocrine and autonomic output pathway for hypothalamic information, as well as one of the main target areas of the SCN. Silencing the neuronal activity in the PVN did not affect the LPS-induced corticosterone surge and only slightly delayed the LPS-induced plasma glucose and glucagon responses. Finally, surgical interruption of the neuronal connection between hypothalamus and liver did not affect the corticosterone response but slightly delayed the LPS-induced glucose response. Together, these data support the previously proposed circadian modulation of LPS-induced neuroendocrine responses, but they are at variance with the suggested major role for the hypothalamic pacemaker on the autonomic output of the hypothalamus, as reflected by the effects of LPS on glucose homeostasis. The latter effects are more likely due to direct interactions of LPS with peripheral tissues, such as the liver.

Background/aims: All autonomic hepatic nerves are transected following liver transplantation. Recent studies have shown the relationship between an inhibition of autonomic nerves and the accumulation of hepatic progenitor cells (HPC). This study aims to elucidate the influence of hepatic denervation on the accumulation of HPC in the process of liver regeneration., Methodology: Male Sprague-Dawley rats underwent hepatic denervation. Immediately after either denervation (DN group, n=30) or a sham operation (control group, n=30), a two-thirds hepatectomy was performed, and these were sacrificed chronologically. An immunohistochemical analysis of HPC was performed with a mouse monoclonal OV6 type antibody., Results: The liver per body weight ratio gradually increased in both groups. On postoperative day (POD) 7, the DN group showed a significantly higher ratio. The HPC expression gradually increased in both groups. The maximal HPC number was observed on POD 7 in the DN group and on POD 3 in the control group. Although there was no significant difference in the HPC numbers between the DN and control group until POD 3, the number of HPC were significantly higher in livers of the denervated rats than in those of the sham operated rats between POD 5 and 14., Conclusions: The hepatic autonomic nerves were thus suggested to play an important role in the accumulation of HPC during liver regeneration in rats.

Excessive secretion of triglyceride-rich very low-density lipoproteins (VLDL-TG) contributes to diabetic dyslipidemia. Earlier studies have indicated a possible role for the hypothalamus and autonomic nervous system in the regulation of VLDL-TG. In the current study, we investigated whether the autonomic nervous system and hypothalamic neuropeptide Y (NPY) release during fasting regulates hepatic VLDL-TG secretion. We report that, in fasted rats, an intact hypothalamic arcuate nucleus and hepatic sympathetic innervation are necessary to maintain VLDL-TG secretion. Furthermore, the hepatic sympathetic innervation is necessary to mediate the stimulatory effect of intracerebroventricular administration of NPY on VLDL-TG secretion. Since the intracerebroventricular administration of NPY increases VLDL-TG secretion by the liver without affecting lipolysis, its effect on lipid metabolism appears to be selective to the liver. Together, our findings indicate that the increased release of NPY during fasting stimulates the sympathetic nervous system to maintain VLDL-TG secretion at a postprandial level.

Background & Aims: The duodenum senses nutrients to maintain energy and glucose homeostasis, but little is known about the signaling and neuronal mechanisms involved. We tested whether duodenal activation of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase A (PKA) is sufficient and necessary for cholecystokinin (CCK) signaling to trigger vagal afferent firing and regulate glucose production., Methods: In rats, we selectively activated duodenal PKA and evaluated changes in glucose kinetics during the pancreatic (basal insulin) pancreatic clamps and vagal afferent firing. The requirement of duodenal PKA signaling in glucose regulation was evaluated by inhibiting duodenal activation of PKA in the presence of infusion of the intraduodenal PKA agonist (Sp-cAMPS) or CCK1 receptor agonist (CCK-8). We also assessed the involvement of a neuronal network and the metabolic impact of duodenal PKA activation in rats placed on high-fat diets., Results: Intraduodenal infusion of Sp-cAMPS activated duodenal PKA and lowered glucose production, in association with increased vagal afferent firing in control rats. The metabolic and neuronal effects of duodenal Sp-cAMPS were negated by coinfusion with either the PKA inhibitor H89 or Rp-CAMPS. The metabolic effect was also negated by coinfusion with tetracaine, molecular and pharmacologic inhibition of NR1-containing N-methyl-d-aspartate (NMDA) receptors within the dorsal vagal complex, or hepatic vagotomy in rats. Inhibition of duodenal PKA blocked the ability of duodenal CCK-8 to reduce glucose production in control rats, whereas duodenal Sp-cAMPS bypassed duodenal CCK resistance and activated duodenal PKA and lowered glucose production in rats on high-fat diets., Conclusions: We identified a neural glucoregulatory function of duodenal PKA signaling., (Copyright © 2012 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Glucagon-like peptide-1 (GLP-1) stimulates insulin secretion and suppresses food intake. Recent studies indicate that the hepatic vagal afferent nerve is involved in this response. Dipeptidyl peptidase-IV (DPP-IV) inhibitor extends the half-life of endogenous GLP-1 by preventing its degradation. This study aimed to determine whether DPP-IV inhibitor-induced elevation of portal GLP-1 levels affect insulin secretion and feeding behavior via the vagal afferent nerve and hypothalamus. The effect of DPP-IV inhibitor infusion into the portal vein or peritoneum on portal and peripheral GLP-1 levels, food intake, and plasma insulin and glucose was examined in sham-operated and vagotomized male Sprague-Dawley rats. Analyses of neuronal histamine turnover and immunohistochemistry were used to identify the CNS pathway that mediated the response. Intraportal administration of the DPP-IV inhibitor significantly increased portal (but not peripheral) GLP-1 levels, increased insulin levels, and decreased glucose levels. The DPP-IV inhibitor suppressed 1- and 12- but not 24-h cumulative food intake. Intraportal infusion of the DPP-IV inhibitor increased hypothalamic neuronal histamine turnover and increased c-fos expression in several areas of the brain. These responses were blocked by vagotomy. Our results indicate that DPP-IV inhibitor-induced changes in portal but not systemic GLP-1 levels affect insulin secretion and food intake. Furthermore, our findings suggest that a neuronal pathway that includes the hepatic vagal afferent nerve and hypothalamic neuronal histamine plays an important role in the pharmacological actions of DPP-IV inhibitor., (© 2011 The Authors. Journal of Neurochemistry © 2011 International Society for Neurochemistry.)