Metabolic effects of liver transplantation in cirrhotic patients

The Sympathetic-Immune Milieu in Metabolic Health and Diseases: Insights from Pancreas, Liver, Intestine, and Adipose Tissues

Sympathetic innervation plays a crucial role in maintaining energy balance and contributes to metabolic pathophysiology. Recent evidence has begun to uncover the innervation landscape of sympathetic projections and sheds light on their important functions in metabolic activities. Additionally, the immune system has long been studied for its essential roles in metabolic health and diseases. In this review, the aim is to provide an overview of the current research progress on the sympathetic regulation of key metabolic organs, including the pancreas, liver, intestine, and adipose tissues. In particular, efforts are made to highlight the critical roles of the peripheral nervous system and its potential interplay with immune components. Overall, it is hoped to underscore the importance of studying metabolic organs from a comprehensive and interconnected perspective, which will provide valuable insights into the complex mechanisms underlying metabolic regulation and may lead to novel therapeutic strategies for metabolic diseases.

Branched Chain Amino Acids are associated with Metabolic Complications in Liver Transplant Recipients

BACKGROUND

Obesity, dyslipidemia and type 2 diabetes (T2D) contribute substantially to increased cardiovascular morbidity and mortality in patients after orthotopic liver transplantation (OLTx). Elevated plasma branched chain amino acids (BCAA) are linked to metabolic disturbances and cardiovascular disease (CVD) risk profiles in several non-OLTx populations.

METHODS

Cross-sectional analysis of liver transplant recipients from TransplantLines, a single-center biobank and cohort study. BCAA plasma levels were measured by means of nuclear-magnetic resonance spectroscopy. CVD and cardiometabolic factors were collected by using data from electronic patient records. Associations were determined between BCAA plasma levels and T2D, Metabolic Syndrome (MetS), CVD as well as mTOR inhibition in liver transplant recipients.

RESULTS

336 Patients were divided into sex-stratified tertiles of total BCAA. MetS (P<0.001) and T2D (P=0.002) were significantly more frequent in subjects in the highest BCAA tertile. In logistic regression analyses, the multivariable adjusted odds ratio (OR) per 1 standard deviation increase in BCAA was 1.68 (95%CI: 1.18-2.20, P=0.003) for MetS and 1.60 (95%CI: 1.14-2.23, P=0.006) for T2D. Use of Sirolimus (mTOR inhibitor) was significantly associated with higher BCAA plasma levels, independent of age, sex, time after OLTx, MetS and other immunosuppressive medication (adjusted P=0.002).

CONCLUSION

Elevated BCAA plasma levels are associated with T2D, MetS and use of Sirolimus in liver transplant recipients. BCAA plasma levels may represent a valuable biomarker for cardiometabolic complications after OLTx.

Brain insulin signalling in metabolic homeostasis and disease

Insulin signalling in the central nervous system regulates energy homeostasis by controlling metabolism in several organs and by coordinating organ crosstalk. Studies performed in rodents, non-human primates and humans over more than five decades using intracerebroventricular, direct hypothalamic or intranasal application of insulin provide evidence that brain insulin action might reduce food intake and, more importantly, regulates energy homeostasis by orchestrating nutrient partitioning. This Review discusses the metabolic pathways that are under the control of brain insulin action and explains how brain insulin resistance contributes to metabolic disease in obesity, the metabolic syndrome and type 2 diabetes mellitus.

Safety of surgical denervation of the common hepatic artery in insulin-resistant dogs

The objective of this study was to assess the safety of surgical common hepatic artery denervation (CHADN). This procedure has previously been shown to improve glucose tolerance in dogs fed a high-fat high-fructose (HFHF) diet. We assessed the hypoglycemic response of dogs by infusing insulin at a constant rate (1.5 mU/kg/min) for 3 h and monitoring glucose and the counterregulatory hormones (glucagon, catecholamine, and cortisol). After an initial hypoglycemic study, the dogs were randomly assigned to a SHAM surgery (n = 4) or hepatic sympathetic denervation (CHADN, n = 5) and three follow-up studies were performed every month up to 3 months after the surgery. The level of norepinephrine (NE) in the liver and the pancreas was significantly reduced in the CHADN dogs, showing a decrease in sympathetic tone to the splanchnic organs. There was no evidence of any defect of the response to hypoglycemia after the CHADN surgery. Indeed, the extent of hypoglycemia was similar in the SHAM and CHADN groups (~45 mg/dl) for the same amount of circulating insulin (~50 µU/ml) regardless of time or surgery. Moreover the responses of the counterregulatory hormones were similar in extent and pattern during the 3 h of hypoglycemic challenge. Circulating lactate, glycerol, free fatty acids, and beta-hydroxybutyrate were also unaffected by CHADN during fasting conditions or during the hypoglycemia. There were no other notable surgery-induced changes over time in nutrients, minerals, and hormones clinically measured in the dogs nor in the blood pressure and heart rate of the animals. The data suggest that the ablation of the sympathetic nerve connected to the splanchnic bed is not required for a normal counterregulatory response to insulin-induced hypoglycemia and that CHADN could be a safe new therapeutic intervention to improve glycemic control in individuals with metabolic syndrome or type 2 diabetes.

Cu isotopic signature in blood serum of liver transplant patients: a follow-up study

End-stage liver disease (ESLD) is life-threatening and liver transplantation (LTx) is the definitive treatment with good outcomes. Given the essential role of hepatocytes in Cu homeostasis, the potential of the serum Cu isotopic composition for monitoring a patient’s condition post-LTx was evaluated. For this purpose, high-precision Cu isotopic analysis of blood serum of ESLD patients pre- and post-LTx was accomplished via multi-collector ICP-mass spectrometry (MC-ICP-MS). The Cu isotopic composition of the ESLD patients was fractionated in favour of the lighter isotope (by about −0.50‰). Post-LTx, a generalized normalization of the Cu isotopic composition was observed for the patients with normal liver function, while it remained light when this condition was not reached. A strong decrease in the δ⁶⁵Cu value a longer term post-LTx seems to indicate the recurrence of liver failure or cancer. The observed trend in favour of the heavier Cu isotopic composition post-LTx seems to be related with the restored biosynthetic capacity of the liver, the restored hepatic metabolism and/or the restored biliary secretion pathways. Thus, Cu isotopic analysis could be a valuable tool for the follow-up of liver transplant patients and for establishing the potential recurrence of liver failure.

Management of immunosuppressant agents following liver transplantation: Less is more

Immunosuppression in organ transplantation was revolutionary for its time, but technological and population changes cast new light on its use. First, metabolic syndrome (MS) is increasing as a public health issue, concomitantly increasing as an issue for post-orthotopic liver transplantation patients; yet the medications regularly used for immunosuppression contribute to dysfunctional metabolism. Current mainstay immunosuppression involves the use of calcineurin inhibitors; these are potent, but nonspecifically disrupt intracellular signaling in such a way as to exacerbate the impact of MS on the liver. Second, the impacts of acute cellular rejection and malignancy are reviewed in terms of their severity and possible interactions with immunosuppressive medications. Finally, immunosuppressive agents must be considered in terms of new developments in hepatitis C virus treatment, which undercut what used to be inevitable viral recurrence. Overall, while traditional immunosuppressive agents remain the most used, the specific side-effect profiles of all immunosuppressants must be weighed in light of the individual patient.

Risk of de novo post-transplant type 2 diabetes in patients undergoing liver transplant for non-alcoholic steatohepatitis

Background

Non-alcoholic steatohepatitis (NASH) is often seen together with components of metabolic syndrome. The aim of this study was to assess the risk of de novo post-transplant type 2 diabetes (DM) in liver transplant recipients with NASH.

Methods

All adult patients from the Scientific Registry of Transplant Recipients (2003–2012) transplanted for NASH or cryptogenic cirrhosis (the NASH cohort) without pre-transplant DM were included in this retrospective cross-sectional study.

Results

Total 2,916 NASH subjects and 14,268 controls with non-HCV related cirrhosis or hepatocellular carcinoma were included. Patients with NASH were, on average, 6 years older, more likely female and overweight/obese. By 5 years post-transplant, 39.8 % NASH vs. 27.0 % controls developed at least one onset of de novo DM; this was observed starting 6 months post-transplant: 22.9 % vs. 16.7 % (relative risk 1.38). Later in follow-up, the relative risk of de novo DM was also higher in NASH: 1.46 by 3 years, 1.47 by 5 years (all p < 0.0001). After exclusion of DM that resolved after the first year, long-term DM remained higher in the NASH cohort: 7.6 % vs. 4.3 %, p < 0.0001. In multivariate analysis, after adjustment for confounders including the use of immunosuppressants, having NASH was independently associated with development of de novo post-transplant DM: adjusted hazard ratio (95 % CI) = 1.29 (1.18–1.42), p < 0.0001.

Conclusions

Liver transplant recipients with NASH have a higher risk of de novo post-transplant DM. This suggests the presence of an underlying metabolic disorder beyond fatty liver that may be causative for both NASH and type 2 diabetes.

Alterations in carbohydrate metabolism in cirrhotic patients before and after liver transplant

AIM

The main objective of this study is to demonstrate whether carbohydrate metabolism alterations identified in patients with advanced cirrhosis show any improvement after liver transplant.

METHODS

The study included 86 patients who underwent liver transplant between March 2010 and February 2011. An oral glucose tolerance test was performed before the liver transplant, and 6 and 12 months after. Beta cell function and insulin resistance were also calculated, applying formulae that use basal plasma glycaemia and insulin, and plasma glycaemia and insulin during an oral glucose tolerance test. Risk factors for pre- and post-transplant diabetes were also studied. The diagnosis of diabetes was based on an OGTT.

RESULTS

The proportion of patients with diabetes before transplant, and at month 6 and 12 after transplant were 70.9%, 48.8% and 39.2%, respectively. Compared to baseline, at month 6 the odds ratio of having diabetes was 0.39 (IC 95% [0.21, 0.73]) and at month 12 it was 0.26 (IC 95% [0.14, 0.50]). The composite insulin sensitivity index values at 6 and 12 months were 1.72 units higher (IC 95% [0.84, 2.58]) and 1.58 units higher (IC 95% [0.68, 2.44)] than baseline. A statistically significant association was found between high MELD values and high body mass index, and risk of pre-transplant diabetes (p=0.001 and p=0.033, respectively). Cirrhosis aetiology did not influence the risk of diabetes.

CONCLUSIONS

In this study, we were able to ascertain that alterations in carbohydrate metabolism typical of advanced cirrhosis improve after liver transplant. This improvement is mainly due to an improvement in insulin resistance.

Liver transplantation for nonalcoholic fatty liver disease: New challenges and new opportunities

Nonalcoholic fatty liver disease (NAFLD) is becoming rapidly one of the most common indications for orthotopic liver transplantation in the world. Development of graft steatosis is a significant problem during the post-transplant course, which may happen as a recurrence of pre-existing disease or de novo NAFLD. There are different risk factors that might play a role in development of graft steatosis including post-transplant metabolic syndrome, immune-suppressive medications, genetics and others. There are few studies that assessed the effects of NAFLD on graft and patient survival; most of them were limited by the duration of follow up or by the number of patients. With this review article we will try to shed light on post-liver transplantation NAFLD, significance of the disease, how it develops, risk factors, clinical course and treatment options.

Evolving aspects of liver transplantation for nonalcoholic steatohepatitis

PURPOSE OF REVIEW

Nonalcoholic steatohepatitis (NASH), obesity, and the metabolic syndrome are highly prevalent. NASH, a rare indication for liver transplantation in the early 1990s, is now the third most common indication. This review considers key aspects of the liver transplantation for NASH.

RECENT FINDINGS

NASH is one consequence of obesity, almost always occurring in the context of metabolic syndrome and oxidative stress. Recurrence of NASH can be severe. The components of metabolic syndrome are often exacerbated following liver transplantation by factors such as immunosuppression, and are important predictors of patient morbidity and mortality. Many aspects of the metabolic syndrome are modifiable. The roles bariatric surgery, nutritional and pharmacotherapy of NASH, and the impact of established and new immunosuppressive agents have recently evolved.

SUMMARY

A nuanced approach is needed in management of obesity, metabolic syndrome, and immunosuppression in liver transplant recipients.

Interaction between the central and peripheral effects of insulin in controlling hepatic glucose metabolism in the conscious dog

The importance of hypothalamic insulin action to the regulation of hepatic glucose metabolism in the presence of a normal liver/brain insulin ratio (3:1) is unknown. Thus, we assessed the role of central insulin action in the response of the liver to normal physiologic hyperinsulinemia over 4 h. Using a pancreatic clamp, hepatic portal vein insulin delivery was increased three- or eightfold in the conscious dog. Insulin action was studied in the presence or absence of intracerebroventricularly mediated blockade of hypothalamic insulin action. Euglycemia was maintained, and glucagon was clamped at basal. Both the molecular and metabolic aspects of insulin action were assessed. Blockade of hypothalamic insulin signaling did not alter the insulin-mediated suppression of hepatic gluconeogenic gene transcription but blunted the induction of glucokinase gene transcription and completely blocked the inhibition of glycogen synthase kinase-3β gene transcription. Thus, central and peripheral insulin action combined to control some, but not other, hepatic enzyme programs. Nevertheless, inhibition of hypothalamic insulin action did not alter the effects of the hormone on hepatic glucose flux (production or uptake). These data indicate that brain insulin action is not a determinant of the rapid (<4 h) inhibition of hepatic glucose metabolism caused by normal physiologic hyperinsulinemia in this large animal model.

Evidence against a physiologic role for acute changes in CNS insulin action in the rapid regulation of hepatic glucose production

This Perspective will discuss the physiologic relevance of data that suggest CNS insulin action is required for the rapid suppression of hepatic glucose production. It will also review data from experiments on the conscious dog, which show that although the canine brain can sense insulin and, thereby, regulate hepatic glucoregulatory enzyme expression, CNS insulin action is not essential for the rapid suppression of glucose production caused by the hormone. Insulin's direct hepatic effects are dominant, thus it appears that insulin's central effects are redundant in the acute regulation of hepatic glucose metabolism.

Liver denervation increases the levels of serum triglyceride and cholesterol via increases in the rate of VLDL secretion

BACKGROUND

Intra-hepatic metabolism of lipids is subject to hormonal, metabolic and neural regulation, but little is known about the latter. Catecholamines stimulate the output of glucose and inhibit the release of very low density lipoproteins (VLDL) from the liver.

OBJECTIVES

To investigate the effects and involved mechanism of liver denervation on the levels of serum and liver lipids.

METHODS

Two groups of male rats were taken as control and cases and the liver was denerved chemically by 90% phenol in the case group. On the fourth day of the operation, blood samples were taken and the liver homogenized for lipid and glycogen analyses. Cholesterol, triglyceride, HDLc and glucose were measured enzymatically. Total phospholipids were analyzed by the measuring of liberated inorganic phosphate in organic phase. Glycogen was extracted by ethanol and analyzed by phenol/sulphuric acid reagent. In a separate experiment, the rate of triglyceride secretion was measured in vivo by using tyloxapol and compared in two groups.

RESULTS

The serum concentrations of triglyceride (73.7 ± 6.3 vs. 45.8 ± 1.6 mg/dL, P ≤ 0.003) and cholesterol (87.7 ± 3.7 vs. 67.4 ± 2.2mg/dL, P ≤ 0.001) were significantly higher in the denerved compared with the control group. The serum glucose showed a significant decrease (170.5 ± 5.4 vs. 140.6 ± 10.7 mg/dL, P ≤ 0.04) in the denerved group while HDLc had no significant difference between the two groups. Denerved rats compared to the control rats had the higher levels of hepatic glycogen (201.1 ± 20.6 vs. 100.7 ± 19.9 mg/g liver, P ≤ 0.02). The contents of liver triglyceride, cholesterol and total phospholipids did not differ significantly between two groups. The mean rate of triglyceride secretion from the liver increased in the denerved group (276.1 ± 16.1 vs. 230.6 ± 7.7 mg/dL.h, P ≤ 0.03).

CONCLUSIONS

Liver denervation increases the levels of serum triglyceride and cholesterol via increases in the rate of VLDL secretion. Liver innervation plays a role on the regulation of metabolism of lipids and carbohydrates.

The role of the autonomic nervous liver innervation in the control of energy metabolism

Despite a longstanding research interest ever since the early work by Claude Bernard, the functional significance of autonomic liver innervation, either sympathetic or parasympathetic, is still ill defined. This scarcity of information not only holds for the brain control of hepatic metabolism, but also for the metabolic sensing function of the liver and the way in which this metabolic information from the liver affects the brain. Clinical information from the bedside suggests that successful human liver transplantation (implying a complete autonomic liver denervation) causes no life threatening metabolic derangements, at least in the absence of severe metabolic challenges such as hypoglycemia. However, from the benchside, data are accumulating that interference with the neuronal brain-liver connection does cause pronounced changes in liver metabolism. This review provides an extensive overview on how metabolic information is sensed by the liver, and how this information is processed via neuronal pathways to the brain. With this information the brain controls liver metabolism and that of other organs and tissues. We will pay special attention to the hypothalamic pathways involved in these liver-brain-liver circuits. At this stage, we still do not know the final destination and processing of the metabolic information that is transferred from the liver to the brain. On the other hand, in recent years, there has been a considerable increase in the understanding which brain areas are involved in the control of liver metabolism via its autonomic innervation. However, in view of the ever rising prevalence of type 2 diabetes, this potentially highly relevant knowledge is still by far too limited. Thus the autonomic innervation of the liver and its role in the control of metabolism needs our continued and devoted attention.

Extracellular amino acid levels in the human liver during transplantation: a microdialysis study from donor to recipient

Using microdialysis, we have monitored extracellular levels of amino acids and related amines in the human liver at three stages of the transplantation procedure: donor retrieval, back table preparation and during 48 h post-implantation. By comparing the ratio of mean levels at the donor and back table stages, with the ratio between early (2-6 h) and late (43-48 h) post-reperfusion, these amines were classified into one of three groups. In one group, back table levels were markedly higher than during the donor stage, with levels declining over time post-reperfusion. A second group had much lower levels in the back table than during the donor phase, and post-reperfusion levels were either stable or increased over time. Concentrations of amino acids in the final group remained relatively constant at all stages. This study illustrates the value of microdialysis in providing organ-specific metabolic data that may indicate specific mechanisms of poor graft function.

Effect of orthotopic liver transplantation (OLT) on branched-chain amino acid requirement

Little is known regarding the impact of liver transplantation on amino acid requirements in children. Since plasma levels of the branched-chain amino acids (BCAA) are decreased in the presence of normal levels of the aromatic amino acids after liver transplantation, normalization of hepatic function may not fully correct changes in BCAA metabolism that occur in the pretransplant period. The goal of the present study was to determine total BCAA requirements of children following liver transplantation. The requirement of total BCAA was determined using indicator amino acid oxidation (IAAO) in five clinically stable children (5.7 +/- 3.5 y, mean +/- SD) 1-8 y post liver transplantation. Children received in random order 6 graded intakes of total BCAA. Individual BCAA in the test diet were provided in the same proportions as present in egg protein to minimize the potential interactive effects of individual BCAA on assessment of requirement. Total BCAA requirement was determined by measuring the oxidation of L-[1-13C] phenylalanine to 13CO2 [F13CO2 in micromol/kg/h], after a primed, continuous infusion of the tracer and using a two-phase linear regression crossover regression analysis. The estimated average requirement and the upper limit of the 95% CI for total BCAA in children who have undergone liver transplantation were 172 and 206 mg/kg/d), respectively. Total BCAA requirement in children who have undergone orthotopic liver transplantation (OLT) remain increased in the post-liver transplant period when compared with healthy school aged children, but is decreased when compared with children with mild-moderate chronic cholestatic (MCC) liver disease.

Major influence of liver function itself but not of immunosuppression determines glucose tolerance after living-donor liver transplantation

Controversial data exists concerning the impact of immunosuppressive therapy on the development of post-transplantation diabetes mellitus (PTDM). Therefore, we investigated glucose metabolism in healthy donors and in recipients of living-donor liver transplants (LD-LTX, n=18) without pre-existing diabetes mellitus before, on day 10, month 6, and month 12 after intervention. The computer-assisted analysis of glucose, insulin, and C-peptide profiles obtained from frequently sampled intravenous glucose tolerance tests allows to achieve an integrated view of factors controlling glucose tolerance, i.e., insulin sensitivity (SI), first and second phase insulin secretion (phi1 and phi2). SI of donors declined by day 10 after operation (SI 2.65 +/- 0.41 vs. 4.90 +/- 0.50 10(-4) minute(-1) microU ml(-1), P < 0.01) but returned to values as before after 6 months. Phi1 did not change. Phi(2), however, significantly increased by day 10 (8.57 +/- 0.82 10(9) minute(-1) to 13.77 +/- 1.53 10(9) minute(-1), P < 0.01) but was in the same range as before after 6 months. In parallel to donors SI of recipients progressively increased after LD-LTX. Phi1 did not alter in recipients. Phi2 continuously decreased and was not different from donors by month 12. The extent of liver injury assessed by liver enzyme concentrations and liver function represented by cholinesterase activity, albumin, and INR were closely related with changes of SI in donors and recipients during the first year after intervention. In conclusion, the extent of liver damage plays a predominant role in regulating glucose tolerance. No impact of immunosuppressive therapy on SI, phi1 and phi2 was detected.

Glucose and lipid metabolism after liver transplantation in inbred rats: consequences of hepatic denervation

The liver plays a central role in glucose and lipid homeostasis. Because liver transplantation severs the hepatic nerves which influence this function, we hypothesized that insulin resistance and hyperlipidemia develop after liver transplantation, thus increasing the atherosclerotic risk. Therefore, we studied inbred rats 8 months after orthotopic liver transplantation (Tx, n = 39) or laparotomy (sham, n = 37) by either oral glucose tolerance test (Tx, n = 13; sham, n = 8), meal tolerance test (Tx, n = 9; sham, n = 13), or euglycemic hyperinsulinemic clamp with tritiated glucose infusion (Tx, n = 17; sham, n = 16). We found that liver transplantation significantly increased basal hepatic glucose production (HGP) in the clamp study by 20% (37.3 +/- 2.2 vs 31.0 +/- 2.1 micromol kg -1 .min -1 , P < .05) and fasting plasma low-density lipoprotein (LDL) cholesterol by 36% (0.79 +/- 0.06 vs 0.58 +/- 0.05 mmol/L, P < .05). However, it did not affect HGP, total glucose uptake, metabolic clearance rate of insulin, and suppression of plasma nonesterified fatty acids, which were all normal in response to rising plasma insulin concentrations in the dose-response clamp studies. The oral glucose tolerance test and meal tolerance test also showed normal glucose and nonesterified fatty acids homeostasis with adequate pancreatic insulin secretion and hepatic insulin clearance after liver transplantation. The only consequences of liver transplantation are increased basal HGP and plasma LDL cholesterol, which may be caused by persistent vagal denervation of the liver. Although insulin resistance is absent, elevated plasma LDL cholesterol increases the atherosclerotic risk.

Branched-chain amino acid supplementation in patients with liver diseases

Because of their peculiar role in whole-body nitrogen metabolism and the competitive action on amino acid transport across the blood-brain barrier, branched-chain amino acids (BCAAs) have been extensively used in subjects with liver disease to preserve or to restore muscle mass and to improve hepatic encephalopathy. There are no data regarding safe limits of BCAA administration; the results appear to be better when BCAA-enriched formulas or BCAA-supplemented diets are preferred to pure BCAA formulas. Improved nitrogen retention might ameliorate the nutritional status, a prognostic index of long-term survival in cirrhosis and of short-term survival in patients undergoing surgical procedures. The effects on nutrition and ultimately on prognosis of patients with advanced cirrhosis were confirmed in a large multicenter, long-term trial where oral BCAA supplements were compared with equicaloric or equinitrogenous-equicaloric supplements (maltodextrin or lactoalbumin). Similarly, BCAA treatment improved the prognosis of patients with hepatocellular carcinoma, treated by surgical resection or chemoembolization, and of liver transplant patients. The mechanism(s) for the beneficial effects of BCAAs might be mediated by their stimulating activity on hepatocyte growth factor, favoring liver regeneration. The debate regarding the potential effectiveness of BCAAs dates back to the early 1980s. The number of patients who cannot tolerate dietary proteins in amounts sufficient to meet the higher catabolism of advanced liver disease is probably low, but BCAAs remain the sole treatment of proved efficacy in this specific setting.

Update on branched-chain amino acid supplementation in liver diseases

PURPOSE OF REVIEW

Branched-chain amino acids (BCAAs) have a peculiar role in whole-body nitrogen metabolism. BCAAs are a substrate for protein synthesis, and have been used to conserve or restore muscle mass in advanced liver disease. In addition, the competitive action of BCAAs on amino acid transport across the blood-brain barrier may improve hepatic encephalopathy.

RECENT FINDINGS

The effects of branched-chain amino acids on nutrition and ultimately on prognosis of patients with advanced cirrhosis have been confirmed in a large multicenter, long-term trial. Similarly, BCAA treatment improved the prognosis of patients with hepatocellular carcinoma, treated by chemoembolization. The mechanism for the beneficial effects of BCAA is likely to depend on the stimulating activity of BCAA on hepatocyte growth factor, favoring liver regeneration.

SUMMARY

After an experience of 25 years with branched-chain amino acids, new data supports their beneficial effect in liver diseases. Although the number of patients who cannot tolerate dietary proteins in amounts sufficient to meet their increased catabolism is probably low, in this specific setting BCAAs remain the sole treatment of proved efficacy.

Transplanted liver: consequences of denervation for liver functions

Following liver transplantation, all hepatic nerves are transected; thus, liver allografts are completely isolated from neural control of their hosts. Despite this absolute denervation, liver allograft function does not appear to be significantly impaired after successful transplantation. In experimental animal models, hepatic denervation has no major effects on bile acid production and biotransformation, while it increases blood pressure and salt retention; decreases the number of hepatic progenitor cells, cholangiocyte proliferation, and liver regeneration; and influences the hepatic microcirculation, diet behavior, and glycemic control. In humans, hepatic denervation after liver transplantation has no major deleterious effects on bile secretion, liver regeneration, and hepatic blood flow. Insulin resistance and postprandial hyperglycemia, changes in ingestion behavior, and reduced stimulation of hepatic progenitor cells in the canals of Hering are the major side effects of absent liver innervation. Despite these abnormalities, patients can lead a new life with improved quality of life.

Alterations in glucose metabolism associated with liver cirrhosis persist in the clinically stable long-term course after liver transplantation

With increasing long-term survival rates after orthotopic liver transplantation (OLT), metabolic alterations complicating the clinical course, such as diabetes mellitus (DM), become increasingly important. Liver cirrhosis is associated with severe alterations in glucose metabolism. However, it is currently unclear whether these changes are reversed by successful OLT. We therefore characterized glucose metabolism in patients with liver cirrhosis and normal fasting glucose levels before OLT (cir), in the clinically stable long-term course after OLT (OLT), and control subjects (con) using oral glucose tolerance tests (cir = 100, OLT = 62, con = 32), euglycemic-hyperinsulinemic clamps (cir = 10, OLT = 27, con = 14), and positron emission tomography (PET) scan analysis with 18F-fluorodeoxyglucose (FDG) as a tracer (cir = 7, OLT = 7, con = 5). Fasting insulin and C-peptide levels were significantly elevated in patients with liver cirrhosis compared with both control subjects (P <.001) and patients after OLT (P <.001). After OLT, insulin was normalized, whereas C-peptide remained elevated (P < 0.01). In the patients with liver cirrhosis, 27% had a normal glucose tolerance, 38% had an impaired glucose tolerance (IGT), and 35% were diabetic. After OLT, 34% had a normal glucose tolerance, 29% an IGT, and 37% were diabetic. Comparison of the same patients before and after OLT demonstrated that IGT or diabetes before OLT was the major risk factor for these conditions after OLT, which was independent of either immunosuppression (cyclosporine vs FK506) or low-dose prednisolone. Total glucose uptake was reduced in patients with liver cirrhosis to less than half the values in control subjects (21.2 +/- 2.8 vs 43.7 +/- 2.4 micromol/kg/minute, respectively, P <.001), whereas patients after OLT showed intermediate values (35.7 +/- 1.4 micromol/kg/minute, P < 0.05 vs con, P < 0.01 vs cir). This difference was caused by a reduction in nonoxidative glucose metabolism in patients with liver cirrhosis compared with control subjects (7.4 +/- 1.9 vs 28.7 +/- 1.8 micromol/kg/minute, respectively, P <.01) and patients after OLT (20.1 +/- 1.4 micromol/kg/minute, P < 0.05 vs con and OLT). In the PET study, skeletal muscle glucose uptake was significantly reduced in patients with liver cirrhosis compared with control subjects (3.5 +/- 0.4 vs 11.8 +/- 2.5 micromol/100g/minute, respectively, P <.05). After OLT, muscle glucose uptake improved compared with patients with liver cirrhosis (5.9 +/- 1.0 micromol/100g/minute, P <.05) but remained significantly lower than in control subjects (P <.05). In conclusion, these results demonstrate that preexisting IGT or diabetes are the major risk factors for IGT and diabetes after OLT. This finding was independent of the immunosuppressive medication. The peripheral insulin resistance in cirrhosis is characterized by a decrease in nonoxidative glucose disposal that is improved, but not normalized, after OLT.

Nonhepatic glucose production in humans

Extrahepatic glucose release was evaluated during the anhepatic phase of liver transplantation in 14 recipients for localized hepatocarcinoma with mild or absent cirrhosis, who received a bolus of [6,6-2H2]glucose and l-[3-13C]alanine or l-[1,2-13C2]glutamine to measure glucose kinetics and to prove whether gluconeogenesis occurred from alanine and glutamine. Twelve were studied again 7 mo thereafter along with seven healthy subjects. At the beginning of the anhepatic phase, plasma glucose was increased and then declined by 15%/h. The right kidney released glucose, with an arteriovenous gradient of -3.7 mg/dl. Arterial and portal glucose concentrations were similar. The glucose clearance was 25% reduced, but glucose uptake was similar to that of the control groups. Glucose production was 9.5 +/- 0.9 micromol.kg-1. min-1, 30% less than in controls. Glucose became enriched with 13C from alanine and especially glutamine, proving the extrahepatic gluconeogenesis. The gluconeogenic precursors alanine, glutamine, lactate, pyruvate, and glycerol, insulin, and the counterregulatory hormones epinephrine, cortisol, growth hormone, and glucagon were increased severalfold. Extrahepatic organs synthesize glucose at a rate similar to that of postabsorptive healthy subjects when hepatic production is absent, and gluconeogenic precursors and counterregulatory hormones are markedly increased. The kidney is the main, but possibly not the unique, source of extrahepatic glucose production.

Assessment of insulin sensitivity based on a fasting blood sample in men with liver cirrhosis before and after liver transplantation

BACKGROUND

Insulin resistance is a key factor in the pathogenesis of hepatogenous diabetes and influences the prognosis of chronic liver diseases. In vivo assessment of insulin resistance in humans is expensive; therefore, surrogate indices based on a fasting plasma glucose and insulin concentrations (HOMA-IS, QUICKI) were proposed. This study aimed to test whether these simple indices are reliable measures of insulin sensitivity in patients with liver cirrhosis before and after liver transplantation (LTx).

METHODS

HOMA-IS and QUICKI were compared with insulin sensitivity as assessed with the gold standard technique (insulin clamp) in 20 patients with liver cirrhosis, in 36 patients after LTx, and in 25 matched healthy subjects (predominantly men). To test whether these indices may be applied also in prospective studies, 10 patients with liver cirrhosis were studied longitudinally before and 2 years after LTx.

RESULTS

Both HOMA-IS and QUICKI were associated with insulin sensitivity in patients with liver cirrhosis (r=0.63, P=0.005 and r=0.60, P=0.009) and in LTx patients (r=0.41, P=0.02 and r=0.46, P=0.05). Both were able to detect the improvement of insulin sensitivity after LTx in the patients studied prospectively.

CONCLUSIONS

HOMA-IS and QUICKI are simple reliable tools to assess insulin sensitivity in clinical and epidemiologic investigations of chronic liver disease before and after LTx.

Resting energy expenditure in diabetic and nondiabetic patients with liver cirrhosis: relation with insulin sensitivity and effect of liver transplantation and immunosuppressive therapy

BACKGROUND

Hypermetabolism, insulin resistance, and diabetes are common in patients with liver cirrhosis.

OBJECTIVE

We assessed whether diabetes and insulin resistance influence postabsorptive energy homeostasis in these patients and whether liver transplantation (LTx) and immunosuppressive drugs affect these relations.

DESIGN

Twenty-six patients with liver cirrhosis (16 with and 10 without diabetes) were studied with an insulin clamp and indirect calorimetry. Eleven of these subjects were studied 9 mo after LTx to longitudinally assess its effects. To cross-sectionally explore a longer follow-up period, we studied 65 patients 6, 14, and 32 mo after LTx. Seven patients with chronic uveitis (receiving immunosuppressive therapy) and 20 healthy subjects served as control subjects.

RESULTS

Diabetic and nondiabetic patients with cirrhosis had insulin resistance (S(I(clamp)); P < 0.03) and higher measured resting energy expenditure (REE) as a percentage of predicted REE than did healthy subjects (107.6 +/- 1.8% compared with 97.4 +/- 2.3%; P < 0.03), and these 2 alterations were associated (R(2) = 0.119, P = 0.0002). The longitudinal study showed an improvement in the 2 variables after LTx, but full restoration was not achieved. The cross-sectional analysis confirmed this observation in patients studied 6 mo (n = 28) after LTx. In patients studied 14 (n = 21) and 32 mo (n = 16) after LTx, S(I(clamp)) and measured REE as a percentage of predicted REE were not significantly different from those in control subjects.

CONCLUSIONS

In patients with liver cirrhosis, higher-than-normal postabsorptive REE was associated with insulin resistance regardless of diabetes. This abnormality persisted in patients studied 6-9 mo after LTx but improved simultaneously with the improvement in insulin sensitivity thereafter.

Amino acid kinetics during the anhepatic phase of liver transplantation

Alanine and glutamine are interorgan nitrogen/carbon carriers for ureagenesis and gluconeogenesis, which are mainly but not necessarily only hepatic. The liver is central to alanine and glutamine metabolism, but most organs can produce and use them. We studied amino acid kinetics after liver removal to depict initial events of liver failure and to provide a model to study extrahepatic gluconeogenesis and nitrogen disposal in humans. We measured amino acid kinetics with [5,5,5-(2)H(3)]leucine and [3-(13)C]alanine or [1,2-(13)C(2)]glutamine tracers in 21 subjects during and after the anhepatic phase of liver transplantation: 12 were at 7 months posttransplantation, and 7 were healthy control subjects. Anhepatic leucine kinetics, including proteolysis, was unchanged. Alanine plasma and whole-body contents increased 3x and 2x, with a halved metabolic clearance and a doubled production, 2% greater than disposal. Free whole-body glutamine decreased 25% but increased 50% in plasma. Glutamine clearance was halved, and the production decreased by 25%, still 2% greater than disposal. Liver replacement decreased alanine and glutamine concentrations, leaving leucine unchanged. Liver removal caused doubled alanine fluxes, minor changes in glutamine, and no changes in leucine. The initial events after liver removal are an accumulation of three-carbon compounds, an acceleration of alanine turnover, and limited nitrogen storage in alanine and glutamine.

Plasma amino acids in cirrhosis and after liver transplantation: influence of liver function, hepatic hemodynamics and circulating hormones

Liver cirrhosis is characterized by substantial changes in amino acid (AA) metabolism, resulting in a deranged plasma AA profile. To investigate the effect of liver transplantation (OLT), we studied arterial AA profiles in 52 patients with advanced cirrhosis, 16 stable patients over 6 months after OLT and 48 controls. Changes in AA levels were correlated with portal pressure (hepatic venous pressure gradient), functional hepatic blood flow (indocyanine green extraction) and circulating hormone levels (catecholamines, insulin, C-peptide). Fourteen of 18 measured AA were significantly altered in cirrhosis and 11 of 18 remained abnormal after OLT compared with controls. Aromatic AA (AAA) and methionine were elevated in cirrhosis (p < 0.001 each), increasing with disease stage, and normalized after OLT. Branched chain AA (BCAA) levels were decreased in cirrhosis (p < 0.001) and were unrelated to disease stage. After OLT, BCAA levels remained subnormal (p < 0.01), although higher than in cirrhosis (p < 0.001). AAA levels increased with decreasing functional hepatic blood flow (r = -0.67; p < 0.001) and increasing portal pressure (r = 0.59; p < 0.001). BCAA levels decreased with increasing catecholamine (r = - 0.54, p < 0.001) and insulin levels (r = - 0.40, p = 0.001). We conclude that despite normal liver function, AA metabolism is only partially normalized after OLT. AAA levels mainly determined by hepatic metabolic function and functional liver blood flow return to normal, while BCAA levels remain subnormal, indicating persistent changes in muscular AA metabolism after OLT.

Metabolic effects of restoring partial beta-cell function after islet allotransplantation in type 1 diabetic patients

Successful intraportal islet transplantation normalizes glucose metabolism in diabetic humans. To date, full function is not routinely achieved after islet transplantation in humans, with most grafts being characterized by only partial function. Moreover, the duration of full function is variable and cannot be sufficiently predicted with available methods. In contrast, most grafts retain partial function for a long time. We hypothesized that partial function can restore normal protein and lipid metabolism in diabetic individuals. We studied 45 diabetic patients after islet transplantation. Labeled glucose and leucine were infused to assess whole-body glucose and protein turnover in 1) 6 type 1 diabetic patients with full function after intraportal islet transplantation (FF group; C-peptide > 0.6 nmol/l; daily insulin dosage 0.03 +/- 0.02 U x kg(-1) body wt x day(-1); fasting plasma glucose < 7.7 mmol/l; HbA1c < or = 6.5%), 2) 17 patients with partial function (PF group; C-peptide > 0.16 nmol/l; insulin dosage < 0.4 U x kg(-1) body wt x day(-1)), 3) 9 patients with no function (NF group; C-peptide < 0.16 nmol/l; insulin dosage > 0.4 U x kg(-1) body wt x day(-1)), and 4) 6 patients with chronic uveitis as control subjects (CU group). Hepatic albumin synthesis was assessed in an additional five PF and five healthy volunteers by means of a primed-continuous infusion of [3,3,3-2H3]leucine. The insulin requirement was 97% lower than pretransplant levels for the FF group and 57% lower than pretransplant levels for the PF group. In the basal state, the PF group had a plasma glucose concentration slightly higher than that of the FF (P = 0.249) and CU groups (P = 0.08), but was improved with respect to the NF group (P < 0.01). Plasma leucine (101.1 +/- 5.9 micromol/l) and branched-chain amino acids (337.6 +/- 16.6 micromol/l) were similar in the PF, FF, and CU groups, and significantly lower than in the NF group (P < 0.01). During insulin infusion, the metabolic clearance rate of glucose was defective in the NF group versus in the other groups (P < 0.01). Both the basal and insulin-stimulated proteolytic and proteosynthetic rates were comparable in the PF, FF, and CU groups, but significantly higher in the NF group (P = 0.05). In addition, the PF group had a normal hepatic albumin synthesis. Plasma free fatty acid concentrations in the PF and FF groups were similar to those of the CU group, but the NF group showed a reduced insulin-dependent suppression during the clamp. We concluded that the restoration of approximately 60% of endogenous insulin secretion is capable of normalizing the alterations of protein and lipid metabolism in type 1 diabetic kidney recipients, notwithstanding chronic immunosuppressive therapy. The results of the present study indicate that "success" of islet transplantation may be best defined by a number of metabolic criteria, not just glucose concentration/metabolism alone.

Suspected necrolytic migratory erythema associated with chronic hepatopathy in a cat

A cat presenting with generalised hypotrichosis and crusts on the feet and tail was found to have an unusual chronic hepatopathy. There was also evidence of a chronic small intestinal disease which went undiagnosed. Necrolytic migratory erythema was suspected based on clinical findings and dermatohistopathology, and an association with the chronic hepatopathy was suggested. This is the first report of such an association in a cat. Serum zinc, amino acids and essential fatty acids were analysed, and medical treatment was given with equivocal efficacy.

Persistence of anomalies in the growth hormone-releasing hormone-stimulated growth hormone response in diabetic-uremic patients after combined kidney-pancreas transplantation

Increased circulating growth hormone (GH) levels and aberrant response to different stimuli characterize both type 1 diabetes mellitus and chronic uremia and are associated with severe retinal, kidney and heart complications. Combined kidney and pancreas transplantation is a therapy that restores the endogenous, closed-loop, insulin secretion in diabetes and cure uremia. To evaluate if combined transplantation can restore a normal secretion and response of GH to growth hormone releasing hormone (GH-RH), we studied four groups of subjects: (1) seven type 1 diabetic patients with end-stage renal failure who had received pancreas and kidney transplantation (KPTx); (2) six diabetic uremic subjects, candidates for combined transplantation (IDDUP); (3) nine patients with chronic uveitis on immunosuppressive therapy comparable to pancreas recipients, six of whom treated only with prednisone (UVEST), while three (4) were treated with both prednisone and cyclosporin (UVESTCY). All subjects underwent a GH-RH test (50 microg intravenously, i.v., at 13:00 h). Serum insulin levels were significantly higher in IDDUP compared to UVEST (P=0.05) both at baseline and post GH-RH stimulus, while were similar to KPTx (P=0.2) and UVESTCY (P=0.7). In contrast, plasma free fatty acids were similar in all groups. In IDDUP baseline plasma glycerol was higher than in KPTx (P=0.04) and UVEST (P=0.02) and similar to UVESTCY (P=0.36); glycerol concentration did not change after GH-RH (P=0.08). Before and after GH-RH, serum GH levels tended to be higher in IDDUP (P=0.5) and KPTx (P=0.2) compared to UVEST and UVESTCY. Our results indicate that: 1) kidney-pancreas transplantation does not normalize the GH response to GH-RH; 2) GH abnormalities are not due either to the chronic immunosuppressive therapy or to the insulin effect on GH release; 3) GH abnormalities are probably secondary to functional and/or organic complications of the hypothalamus and/or pituitary as a sequela of diabetes mellitus.

Evidence for impaired glucose effectiveness in cirrhotic patients after liver transplantation

To evaluate the impact of acute and chronic liver disease and single immunosuppression (cyclosporine A [CSA] or FK506) on insulin sensitivity and glucose effectiveness in liver-grafted patients, we performed a frequently sampled intravenous glucose tolerance test (FSIGTT) in nondiabetic patients after orthotopic liver transplantation (OLT) with acute liver failure ([ALF] group, n = 9, with CSA therapy), in patients after OLT with chronic liver disease (CSA group, n = 8; FK506 group, n = 8), and in 9 healthy control subjects. Insulin sensitivity and glucose effectiveness were determined by analyzing glucose and insulin data from the FSIGTT with Bergman's minimal model technique for glucose. The intravenous glucose tolerance index ([KG] ie, the slope of the regression of the logarithm of blood glucose concentration) was not different between the ALF group (2.17 +/- 0.16 min(-1)) and controls (2.29 +/- 0.13 min(-1)), but was lower (P < .05) in both groups with chronic liver disease (CSA group, 1.46 +/- 0.1; FK506 group, 1.61 +/- 0.11 min(-1)) compared with the ALF group (P < .05). A positive relation for the KG and glucose effectiveness was found in all liver-grafted patients and controls. Insulin sensitivity was not different between all liver-grafted patients and controls. The body mass index (BMI) was the overall determinant of insulin sensitivity in all groups. Single immunosuppressive therapy does not impair insulin sensitivity in liver-grafted patients. The lower glucose effectiveness in liver-grafted patients with chronic liver disease but not in patients after ALF points to a defect in the regulation of glucose-mediated glucose uptake in peripheral tissue.

Contribution of reduced insulin sensitivity and secretion to the pathogenesis of hepatogenous diabetes: effect of liver transplantation

Diabetes mellitus frequently complicates cirrhosis but the pathogenic mechanisms are unknown. To assess the contribution of reduced insulin action and secretion, 24 cirrhotic-diabetic patients waiting for liver transplant because of an unresectable hepatocarcinoma underwent an oral glucose tolerance test (OGTT) to assess the beta-cell function and an insulin clamp combined with [3-(3)H]glucose infusion to measure whole body glucose metabolism before and 2 years after the transplant. Seven cirrhotic nondiabetic patients, 11 patients with chronic uveitis on similar immunosuppressive therapy, and 7 healthy subjects served as control groups. Cirrhotic patients showed a profound insulin resistance, and diabetics in addition also showed increased endogenous glucose production (P <.05) and insulin deficiency during the OGTT (P <.05). Liver transplantation normalized endogenous glucose production and insulin sensitivity but failed to cure diabetes in 8 of the 24 patients because a markedly low insulin response during the OGTT. Age, body mass index, family history of diabetes, immunosuppressive drugs, and pathogenesis of cirrhosis did not predict in whom liver transplant was going to cure diabetes. On the contrary, a reduced secretory response characterized the patients in whom the transplant would not be curative. In summary, insulin resistance was a primary event complicating cirrhosis but additional beta-cell secretory defects were crucial for development of diabetes. Liver transplantation, lessening insulin resistance, cured hepatogenous diabetes in 67% of cirrhotic-diabetic patients; nevertheless 33% were still diabetics because the persistence of a reduced beta-cell function, which makes these patients eventually eligible for combined islet transplantation.

The effects of maintenance doses of FK506 versus cyclosporin A on glucose and lipid metabolism after orthotopic liver transplantation

BACKGROUND

Posttransplant diabetes mellitus (PTDM) has gained widespread attention due to the micro and macro-vascular complications that increase the morbidity and mortality of patients receiving solid organs. The higher incidence of PTDM has been mainly attributed to the immunosuppressive therapy. Therefore, this study compares the metabolic side effects of low dose maintenance therapy of FK-506 and Cyclosporin A (CsA) in 14 patients 1 year after orthotopic liver transplant and analyzes possible factors that contribute to the development of PTDM.

METHODS

Two groups (n=7) differing in their immunosuppressive regimen (FK506 or CsA) were matched to eight control subjects and compared to each other. The effects of in vivo insulin action were assessed by means of the euglycemic hyperinsulinemic clamp technique. Arginine stimulation tests at normo- (5.5 mM) and hyperglycemic (15 mM) levels were performed and the acute insulin, C-peptide, and glucagon response (2-5 min) to arginine were determined.

RESULTS

Insulin sensitivity (total glucose disposal) was statistically lower in patients treated with FK-506 and CsA (5.05+/-0.47 and 5.05+/-0.42 mg/kg/min) as compared to controls (6.62+/-0.38 mg/kg/min) (P<0.02), with a significantly higher nonoxidative glucose disposal for the control group (P<0.01), and lower free fatty acid levels (P<0.05). Absolute values for acute insulin response were higher but not significantly different for the transplanted groups. The lower percentage of increase of insulin release after arginine stimulation observed in the FK-506 and CsA groups as compared with controls (754%+/-100, 644%+/-102 vs. 1191%+/-174) (P<0.03 and 0.02, respectively), suggests a reduced beta cell secretory reserve in both treated groups. Also, the acute glucagon response to arginine during hyperglycemia declined less in the FK-506 (28%) and CsA groups (29%) compared with controls (48%) (P<0.05) indicating a defect in the pancreatic beta cell-alpha cell axis.

CONCLUSIONS

There are no major metabolic differences on low maintenance doses between FK-506 and CsA. Both immunosuppressant agents contribute to the development of PTDM at different levels.

Regulation of glucose homeostasis in humans with denervated livers

The liver plays a major role in regulating glucose metabolism, and since its function is influenced by sympathetic/ parasympathetic innervation, we used liver graft as a model of denervation to study the role of CNS in modulating hepatic glucose metabolism in humans. 22 liver transplant subjects were randomly studied by means of the hyperglycemic/ hyperinsulinemic (study 1), hyperglycemic/isoinsulinemic (study 2), euglycemic/hyperinsulinemic (study 3) as well as insulin-induced hypoglycemic (study 4) clamp, combined with bolus-continuous infusion of [3-3H]glucose and indirect calorimetry to determine the effect of different glycemic/insulinemic levels on endogenous glucose production and on peripheral glucose uptake. In addition, postabsorptive glucose homeostasis was cross-sectionally related to the transplant age (range = 40 d-35 mo) in 4 subgroups of patients 2, 6, 15, and 28 mo after transplantation. 22 subjects with chronic uveitis (CU) undergoing a similar immunosuppressive therapy and 35 normal healthy subjects served as controls. The results showed that successful transplantation was associated with fasting glucose concentration and endogenous glucose production in the lower physiological range within a few weeks after transplantation, and this pattern was maintained throughout the 28-mo follow-up period. Fasting glucose (4. 55+/-0.06 vs. 4.75+/-0.06 mM; P = 0.038) and endogenous glucose production (11.3+/-0.4 vs. 12.9+/-0.5 micromol/[kg.min]; P = 0.029) were lower when compared to CU and normal patients. At different combinations of glycemic/insulinemic levels, liver transplant (LTx) patients showed a comparable inhibition of endogenous glucose production. In contrast, in hypoglycemia, after a temporary fall endogenous glucose production rose to values comparable to those of the basal condition in CU and normal subjects (83+/-5 and 92+/-5% of basal), but it did not in LTx subjects (66+/-7%; P < 0.05 vs. CU and normal subjects). Fasting insulin and C-peptide levels were increased up to 6 mo after transplantation, indicating insulin resistance partially induced by prednisone. In addition, greater C-peptide but similar insulin levels during the hyperglycemic clamp (study 1) suggested an increased hepatic insulin clearance in LTx as compared to normal subjects. Fasting glucagon concentration was higher 6 mo after transplantation and thereafter. During euglycemia/hyperinsulinemia (study 3), the insulin-induced glucagon suppression detectable in CU and normal subjects was lacking in LTx subjects; furthermore, the counterregulatory response during hypoglycemia was blunted. In summary, liver transplant subjects have normal postabsorptive glucose metabolism, and glucose and insulin challenge elicit normal response at both hepatic and peripheral sites. Nevertheless, (a) minimal alteration of endogenous glucose production, (b) increased concentration of insulin and glucagon, and (c) defective counterregulation during hypoglycemia may reflect an alteration of the liver-CNS-islet circuit which is due to denervation of the transplanted graft.