Diabetes and cirrhosis: Current concepts on diagnosis and management

Type 2 diabetes mellitus is often associated with cirrhosis as comorbidities, acute illness, medications, and other conditions profoundly alter glucose metabolism. Both conditions are closely related in NAFLD, the leading cause of chronic liver disease, and given its rising burden worldwide, management of type 2 diabetes mellitus in cirrhosis will be an increasingly common dilemma. Having diabetes increases cirrhosis-related complications, including HCC as well as overall mortality. In the absence of effective treatments for cirrhosis, patients with type 2 diabetes mellitus should be systematically screened as early as possible for NAFLD-related fibrosis/cirrhosis using noninvasive tools, starting with a FIB-4 index followed by transient elastography, if available. In people with cirrhosis, an early diagnosis of diabetes is critical for an optimal management strategy (ie, nutritional goals, and glycemic targets). Diagnosis of diabetes may be missed if based on A1C in patients with cirrhosis and impaired liver function (Child-Pugh B-C) as anemia may turn the test unreliable. Clinicians must also become aware of their high risk of hypoglycemia, especially in decompensated cirrhosis where insulin is the only therapy. Care should be within multidisciplinary teams (nutritionists, obesity management teams, endocrinologists, hepatologists, and others) and take advantage of novel glucose-monitoring devices. Clinicians should become familiar with the safety and efficacy of diabetes medications for patients with advanced fibrosis and compensated cirrhosis. Management is conditioned by whether the patient has either compensated or decompensated cirrhosis. This review gives an update on the complex relationship between cirrhosis and type 2 diabetes mellitus, with a focus on its diagnosis and treatment, and highlights knowledge gaps and future directions.

Nadolol reduces insulin sensitivity in liver cirrhosis: a randomized double-blind crossover trial

BACKGROUND

Liver cirrhosis is frequently complicated by portal hypertension leading to increased mortality from variceal bleeding and hepatic decompensation. Noncardioselective β-blockers not only reduce portal hypertension and prevent variceal bleeding in cirrhosis but also impair glucose tolerance and insulin sensitivity in other settings. This study aimed to determine whether nonselective β-blockade with nadolol impairs glucose metabolism in liver cirrhosis.

METHODS

A randomized, double-blind, placebo-controlled crossover trial of nadolol in cirrhotic patients examined insulin sensitivity, disposition index, and glucose tolerance. Stable cirrhotic patients of mixed etiology underwent an intravenous glucose tolerance test and hyperinsulinemic-euglycemic clamp for the measurement of insulin secretion and insulin sensitivity (n = 16) and a 75-g oral glucose tolerance test (n = 17). These measurements were conducted twice (after 3 months of treatment with nadolol or placebo and, after a 1-month washout period, after 3 months on the alternative treatment). Total body fat and plasma catecholamines were measured at the end of each 3-month treatment.

RESULTS

Compared with placebo, nadolol treatment reduced insulin sensitivity (79.7 ± 10.1 vs 99.6 ± 10.3 μL/kg fat-free mass·min^-1 ·(mU/L)^-1 , P = .005). Insulin secretion was unchanged (P = .24), yielding a lower disposition index with nadolol (6083 ± 2007 vs 8692 ± 2036, P = .050). There was no change in total body fat or plasma catecholamines. A 2-hour plasma glucose concentration from the oral glucose tolerance test was higher on nadolol than placebo (10.8 ± 0.9 vs 9.9 ± 0.9 mmol/L, P = .035).

CONCLUSIONS

Nadolol significantly worsened insulin sensitivity, glycemia, and disposition index in patients with liver cirrhosis. These findings may have significant clinical implications because cirrhosis is already associated with an increased prevalence of diabetes.

Nutrition in alcoholic liver disease

The liver plays an important role in the metabolism, synthesis, storage, and absorption of nutrients. Patients with cirrhosis are prone to nutritional deficiencies and malnutrition, with a higher prevalence among patients with decompensated disease. Mechanisms of nutritional deficiencies in patients with liver disease are not completely understood and probably multifactorial. Malnutrition among patients with cirrhosis or alcoholic liver disease correlates with poor quality of life, increased risk of infections, frequent hospitalizations, complications, mortality, poor graft and patient survival after liver transplantation, and economic burden. Physicians, including gastroenterologists and hepatologists, should be conversant with assessment and management of malnutrition and nutritional supplementation.

Fed-state clamp stimulates cellular mechanisms of muscle protein anabolism and modulates glucose disposal in normal men

Since maximum anabolism occurs postprandially, we developed a simulated fed state with clamped hyperinsulinemia, physiological hyperglycemia, and hyperaminoacidemia (Hyper-3) and explored muscle cellular mechanisms. Whole body [1-(13)C]leucine and [3-(3)H]glucose kinetics in healthy men were compared between hyperinsulinemic, euglycemic, isoaminoacidemic (Hyper-1, n = 10) and Hyper-3 (n = 9) clamps. In Hyper-3 vs. Hyper-1, nonoxidative leucine R(d) [rate of disappearance (synthesis)] was stimulated more (45 +/- 4 vs. 24 +/- 4 micromol/min, P < 0.01) and endogenous R(a) [rate of appearance (breakdown)] was inhibited similarly; hence net balance increased more (86 +/- 6 vs. 49 +/- 2 micromol/min, P < 0.001). Glucose R(d) was similar; thus Hyper-3 metabolic clearance rate (331 +/- 23 vs. 557 +/- 41 ml/min, P < 0.0005) and R(d)/insulin (M, 0.65 +/- 0.10 vs. 1.25 +/- 0.10 mg.min(-1).pmol(-1).l, P < 0.001) were less, despite higher insulin (798 +/- 74 vs. 450 +/- 24 pmol/l, P < 0.005). In vastus lateralis muscle biopsies, phosphorylation of Akt (P = 0.025), mammalian target of rapamycin (mTOR), ribosomal protein S6 kinase (p70(S6K1); P = 0.008), S6 (P = 0.049), and 4E-binding protein 1 (4E-BP1; P = 0.001) increased. With decreased eukaryotic initiation factor-4E (eIF4E).4E-BP1 complex (P = 0.01), these are consistent with increased mTOR complex 1 (mTORC1) signaling and translation initiation of protein synthesis. Although mRNA expression of ubiquitin, MAFbx 1, and MuRF-1 was unchanged, total ubiquitinated proteins decreased 20% (P < 0.01), consistent with proteolysis suppression. The Hyper-3 clamp increases whole body protein synthesis, net anabolism, and muscle protein translation initiation pathways and decreases protein ubiquitination. The main contribution of hyperaminoacidemia is stimulation of synthesis rather than inhibition of proteolysis, and it attenuates the expected increment of glucose disposal.

Mild-to-moderate chronic cholestatic liver disease increases leucine oxidation in children

Malnutrition is prevalent in children with chronic cholestatic liver disease. Using the noninvasive indicator amino acid oxidation (IAAO) technique, we recently determined that mild-to-moderate chronic cholestatic (MCC) liver disease increases the need for branched-chain amino acids (BCAA) in children. To examine the underlying mechanisms responsible for this increased need for BCAA in liver disease, we measured L-[1-(13C)]-leucine oxidation in the postabsorptive and fed states in 10 children with MCC liver disease (8.8 +/- 3.5 y) and in 11 healthy children (9.4 +/- 2.2 y). The oxidation of L-[1-(13C)]-leucine to 13CO2 [F13CO2 in micromol/(kg.h)] was determined after a primed, continuous oral administration of the tracer. Total BCAA in diet was provided at 300 mg/(kg.d) to ensure that leucine oxidation was measured when leucine intake was in excess of requirements. In the postabsorptive state, the rate of release of 13CO2 from 13C-leucine oxidation (F13CO2) and whole-body leucine oxidation were significantly higher in children with MCC liver disease (P < 0.05). However, F13CO2 and whole-body leucine oxidation did not differ in the fed state. We conclude that the increased need for dietary BCAA in MCC liver disease is mediated in part by increased leucine oxidation in the postabsorptive state.

The hyperinsulinemic amino acid clamp increases whole-body protein synthesis in young subjects

We propose that hyperinsulinemia stimulates protein synthesis when postabsorptive plasma amino acid (AA) concentrations are maintained. During a euglycemic hyperinsulinemic clamp, many AA, notably the branched-chain amino acids (BCAA), decline markedly. Therefore, we tested whether individual plasma AA could be maintained within the range of postabsorptive concentrations to assess the effects of insulin, infused at 40 mU/m(2) x min on whole-body protein and glucose metabolism, using [1-(13)C]-leucine and [3-(3)H]-glucose methodology. Validation studies of background [(13)C] enrichment and breath (13)CO(2) recovery factors were performed in a subset of 6 subjects. In 10 healthy, young men, infusion rates of an AA solution were based on fluorometric determinations of total BCAA every 5 minutes. All 21 plasma AA remained in the target range; 15, including the BCAA, alanine, and glycine were within 13% of baseline, and only 6 (Thr, His, Arg, Asn, Cit, Tyr) varied more (18% to 42%). Notably, both leucine flux and nonoxidative leucine R(d) (protein synthesis) increased with insulin (2.36 +/- 0.06 to 2.81 +/- 0.10 and 1.79 +/- 0.05 to 2.18 +/- 0.10 micromol/kg fat-free mass (FFM) x min, respectively; P <.0005) while leucine oxidation only tended to increase (P =.05) and endogenous leucine R(a) (protein breakdown) decreased by 18% (2.36 +/- 0.06 to 1.94 +/- 0.09 micromol/kg FFM x min; P <.0005), resulting in a marked elevation of net protein synthesis (-0.57 +/- 0.02 to 0.24 +/- 0.02 micromol/kg FFM x min; P <.0000001). Thus, in vivo protein anabolism was induced when maintaining postabsorptive plasma amino acid concentrations during hyperinsulinemia through a suppression of whole-body protein breakdown, no significant change in oxidation and an elevation of synthesis compared with postabsorptive conditions.

Protein metabolism in liver cirrhosis: from albumin to muscle myofibrils

PURPOSE OF REVIEW

Liver cirrhosis in the advanced state is characterized by protein wasting, as indicated by the loss of muscle mass, hypoalbuminemia, and an abnormal amino acid profile. The protein wasting condition cirrhosis is associated with a poor prognosis and reduced survival. Poor nutrition, metabolic and hormonal abnormalities, and other disease-associated alterations may all concur to protein wasting. An understanding of the causes and mechanisms leading to protein wasting in cirrhosis may help in the development of nutritional interventions and new therapies.

RECENT FINDINGS

Albumin and muscle protein turnover in cirrhotic patients have been studied in vivo with the aid of isotope dilution techniques or organ catheterization. Albumin synthesis appears to parallel liver function, i.e. the more compromised is the liver, the less is the albumin production rate. Meal-induced albumin synthesis is impaired even in compensated cirrhotic patients. Skeletal muscle protein synthesis is diminished in cirrhosis, and total muscle protein breakdown also appears to be increased, thus explaining the reduced muscle mass. Either hormone or substrate resistance, or newly involved substances (cytokines, insulin-like growth factor 1, leptin) may play a role in the reduced synthesis of both albumin and muscle proteins in liver cirrhosis.

SUMMARY

Abnormalities of both albumin and muscle protein turnover have been demonstrated in liver cirrhotic patients. The possible role of the multiple hormonal and metabolic abnormalities of this disease, as well that of cytokines and other recently discovered substances, need to be investigated further.

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.

Alcoholic myopathy: biochemical mechanisms

Between one- and two-thirds of all alcohol abusers have impairment of muscle function that may be accompanied by biochemical lesions and/or the presence of a defined myopathy characterised by selective atrophy of Type II fibres. Perturbations in protein metabolism are central to the effects on muscle and account for the reductions in muscle mass and fibre diameter. Ethanol abuse is also associated with abnormalities in carbohydrate (as well as lipid) metabolism in skeletal muscle. Ethanol-mediated insulin resistance is allied with the inhibitory effects of ethanol on insulin-stimulated carbohydrate metabolism. It acutely impairs insulin-stimulated glucose and lipid metabolism, although it is not known whether it has an analogous effect on insulin-stimulated protein synthesis. In alcoholic cirrhosis, insulin resistance occurs with respect to carbohydrate metabolism, although the actions of insulin to suppress protein degradation and stimulate amino acid uptake are unimpaired. In acute alcohol-dosing studies defective rates of protein synthesis occur, particularly in Type II fibre-predominant muscles. The relative amounts of mRNA-encoding contractile proteins do not appear to be adversely affected by chronic alcohol feeding, although subtle changes in muscle protein isoforms may occur. There are also rapid and sustained reductions in total (largely ribosomal) RNA in chronic studies. Loss of RNA appears to be related to increases in the activities of specific muscle RNases in these long-term studies. However, in acute dosing studies (less than 1 day), the reductions in muscle protein synthesis are not due to overt loss of total RNA. These data implicate a role for translational modifications in the initial stages of the myopathy, although changes in transcription and/or protein degradation may also be superimposed. These events have important implications for whole-body metabolism.

Insulin resistance in non-alcoholic steatohepatitis

BACKGROUND

Non-alcoholic steatohepatitis is a chronic liver disease that is capable of progressing to end-stage liver disease, but generally has a benign course. Obesity, non-insulin-dependent diabetes mellitus and hyperlipidaemia are the most common associations of the disease.

AIMS

To investigate the insulin resistance in patients with non-alcoholic steatohepatitis who have no other causes of insulin resistance such as obesity, diabetes mellitus, and hyperlipidaemia.

PATIENTS

Thirteen patients (7 male, 6 female) with non-alcoholic steatohepatitis and 12 (6 male, 6 female) healthy volunteers.

METHODS

All patients and healthy volunteers were submitted to biochemical tests and hyperinsulinaemic euglycaemic insulin clamp technique.

RESULTS

Basal insulin levels and C-peptide levels were significantly higher in non-alcoholic steatohepatitis group than in controls (p<0.001 and p<0.001, respectively). Hyperinsulinaemic euglycaemic insulin clamp technique revealed lower glucose utilization in the non-alcoholic steatohepatitis group and the difference was statistically significant (p<0.001).

CONCLUSIONS

Our study revealed marked hyperinsulinaemia and insulin resistance in patients with non-alcoholic steatohepatitis. Hyperinsulinaemia and insulin resistance may contribute to pathogenesis of nonalcoholic steatohepatitis.

A balanced 5:1 carbohydrate:protein diet: a new method for supplementing protein to patients with chronic liver disease

BACKGROUND AND AIMS

Protein malnutrition in patients with chronic liver disease contributes to bone and muscle weakness and compromises immune function and survival. In contrast, high-protein diets may induce or exacerbate hepatic encephalopathy. The aim of the present study was to test whether increased amounts of protein, balanced by dietary carbohydrate in a 1:5 ratio, may be given to chronic liver disease patients in order to minimize postprandial increases in plasma amino acid (AA) concentrations.

METHODS

Eight patients with chronic liver disease were studied. Each received, in a randomized order, three different diets of 2510 kJ of either high protein (37:50:28, carbohydrate:protein:fat), high carbohydrate (126:10:6) or a balanced 5:1 carbohydrate:protein diet (105:21:11). All patients were followed for plasma AA, glucose and insulin levels, as well as for cognitive and behavioral changes.

RESULTS

Following the high protein diet, AA concentrations were significantly increased. In contrast, after the balanced diet, AA levels were practically constant enabled. All diets was well tolerated and no cognitive or behavioral changes appeared.

CONCLUSION

The administration of a balanced 5:1 carbohydrate:protein diet may enable patients with chronic liver disease to tolerate increased amounts of dietary protein, without altering plasma amino acid concentrations.

Abnormalities in branched-chain amino acid metabolism in cirrhosis: influence of hormonal and nutritional factors and directions for future research

Plasma branched-chain amino acid (BCAA) levels are decreased in patients with liver cirrhosis, owing to an increase in BCAA tissue uptake and/or catabolism and a decrease in BCAA production from proteins. Non-specific factors such as malnutrition worsen this picture. Studies of BCAA fluxes and protein turnover in cirrhotic patients have given conflicting results due to patient heterogeneity, differences in method and bias in the expression of results. In well compensated cirrhosis, muscle wasting is moderate and probably due more to decreased protein synthesis than to increased protein catabolism. Hyperinsulinemia has been suggested as the main cause of decreased BCAA levels, by increasing BCAA uptake in muscle and additionally in adipose tissue. However, as depletion of fat stores is frequent in cirrhosis, this effect is certainly quantitatively weak. Also, there is no correlation between state of hyperinsulinemia and decrease in BCAA levels. An effect of cytokines (IL1 and TNF) on muscle BCAA catabolism is a possibility. Until recently, the contribution of the liver to abnormal BCAA metabolism has been underestimated. In cirrhotic liver an increase in liver transamination of branched-chain keto acids (BCKAs) has been suggested and may result from inhibition of liver BCKA dehydrogenase. A modification of protein turnover in cirrhotic liver must be also considered. Lastly, the contribution of non-hepatocyte liver cells, which are activated in cirrhosis, remains to be assessed.

Defective nonoxidative leucine degradation and endogenous leucine flux in cirrhosis during an amino acid infusion

The metabolic fate of leucine's first and second carbon may be different depending on the tissue in which leucine is metabolized, as well as the prevailing hormonal milieu of that tissue. However, previous studies of leucine kinetics in humans have used only leucine labeled (as tracer) at the first carbon position. Because cirrhosis is associated with factors (such as insulin resistance and altered fuel substrate utilization) that may influence how leucine is degraded, the kinetics of leucine's first and second carbon using a simultaneous infusion of [1-14C] leucine and [2-13C] leucine were studied in the postabsorptive state and during an amino acid infusion in 6 stable cirrhotic patients and 6 matched controls. The data were normalized for different body compartments that were quantified from the dilution of H2 [180] and bromide. The body cell mass, but not body weight or fat-free body mass, was decreased in cirrhosis (P < .001). In response to the amino acid infusion, total leucine appearance from proteolysis and leucine's incorporation into protein increased significantly in both groups, but were higher in cirrhotic patients. Endogenous protein breakdown decreased in normals but remained unchanged in cirrhosis. These alterations in leucine metabolism became more prominent when data were expressed based on the body cell mass rather than on body weight. The oxidation of leucine's first carbon (C1) was decreased in cirrhosis, but the oxidation of leucine's second carbon (C2) did not differ between groups during both the postabsorptive period and the amino acid infusion, while nonoxidative leucine degradation [the difference between the oxidation of leucine's (C1) and (C2)] was also decreased in cirrhosis. In addition, there was a positive correlation between nonoxidative leucine degradation (which represents leucine incorporation into fat), and the respiratory quotient obtained from indirect calorimetry (r = .87; P < .001). These data suggest that the extent of leucine carbon oxidation is dependent on whether fat or carbohydrate is the prevailing fuel substrate. In addition, cirrhotic patients have decreased nonoxidative leucine degradation and are unable to suppress endogenous protein breakdown normally in response to amino acid administration. These abnormalities may contribute to the diminished fat stores and body cell mass commonly observed in cirrhosis.

Protein metabolism and liver disease

In health, the liver orchestrates the metabolism of proteins and amino acids. When the liver is diseased, the regulation of protein metabolism is frequently disturbed. The manifestations of disturbed protein metabolism in liver disease are varied and change with disease aetiology and severity. The hallmarks of protein and amino acid metabolism in liver disease are lowered concentrations of circulating branched-chain and increased concentrations of circulating aromatic amino acids with concomitantly altered amino acid kinetics. The changes in amino acid kinetics in liver disease are characterized by increased endogenous leucine flux, an indicator of protein breakdown, and leucine oxidation in the post-absorptive state (when calculated using a reciprocal-pool model and normalized for body cell mass). In addition, the increase in whole-body protein synthesis in response to an amino acid infusion may be attenuated in patients with cirrhosis. These changes are often accompanied by clinically apparent muscle wasting, manifest as protein-calorie malnutrition, and associated low levels of hepatically synthesized plasma proteins. While the pathogenesis of these changes in protein and amino acid metabolism has not been elucidated, altered levels of circulating hormones, known to affect protein metabolism, are probably important. Lowered levels of micronutrients and trace metals and elevated levels of cytokines may also play a role.

Protein turnover in abstinent and non-abstinent patients with alcoholic cirrhosis

OBJECTIVE

This study was designed to measure the effect of chronic alcohol intake on leucine turnover in outpatients with stable alcoholic liver cirrhosis.

METHODS

Protein turnover rate was measured using L [1-14C] leucine in ten outpatients with proven alcoholic cirrhosis and in five healthy controls. After the performance of the turnover, the patients were divided in two groups depending on the evidence of alcohol ingestion in the previous month.

RESULTS

Non-abstinent patients had a significantly higher leucine flux and non-oxidative disposal (73.8 +/- 25.4 and 65.9 +/- 21.6) than abstinent cirrhotic patients (48.9 +/- 9.5 and 43.7 +/- 9.0) and normal controls 37.3 +/- 8.9 and 31.1 +/- 7.6 mumol/m2/min (p < 0.01). Leucine oxidation and serum leucine levels were similar in the three groups.

CONCLUSION

Alcohol intake in alcoholic cirrhotic patients has a catabolic effect that could be associated with the nutritional imbalances observed in alcoholic liver disease.

Fasting and postprandial phenylalanine and leucine kinetics in liver cirrhosis

To investigate body protein turnover and the pathogenesis of increased concentration of plasma phenylalanine in liver cirrhosis, we have studied phenylalanine and leucine kinetics in cirrhotic (diabetic and nondiabetic) patients, and in normal subjects, both in the postabsorptive state and during a mixed meal, using combined intravenous and oral isotope infusions. Postabsorptive phenylalanine concentration and whole body rate of appearance (Ra) were approximately 40% greater (P < 0.05) in patients than in controls. Leucine concentrations were comparable, but intracellular leucine Ra was also increased (P < 0.05), suggesting increased whole body protein breakdown. Postprandial phenylalanine Ra was also greater (P < 0.05) in the patients. This difference was due to a diminished fractional splanchnic uptake of the dietary phenylalanine (approximately 40% lower in the cirrhotics vs. controls, P < or = 0.05). Postprandial leucine Ra was also increased in the patients, but splanchnic uptake of dietary leucine was normal. Thus both increased body protein breakdown and decreased splanchnic extraction of dietary phenylalanine can account for the increased phenylalanine concentrations in liver cirrhosis.

Insulin action on protein metabolism

On the basis of the preceding observations, the following sequence of events can be postulated during insulin deficiency or excess. The main feature of insulin deficiency is the disruption of protein balance in muscle that rapidly leads to emaciation and wasting. Muscle protein degradation is greatly enhanced while increased amino acid availability maintains protein synthesis. In splanchnic tissues, both degradation and synthesis are increased but with an altered pattern, so that the levels of some proteins are increased (e.g. proteins of the acute-phase response), while those of others are decreased (e.g. albumin). As a result, intracellular protein content in liver is maintained but secretion of plasma proteins is abnormal. In healthy subjects, an acute increase in insulin concentration, as occurs after a meal, leads to a rapid suppression of protein breakdown in the splanchnic area. If hyperinsulinaemia is not supported by an exogenous amino acid supply, as might occur during a protein-free meal or experimentally during euglycaemic hyperinsulinaemic clamping, the plasma as well as muscle free amino acid concentration drops, owing to reduced splanchnic release. With reduced amino acid availability, insulin is not anabolic in muscle. If amino acid concentrations are maintained at normal or high levels, e.g. following a mixed meal, a net protein deposition in muscle may occur, primarily because of a stimulation of synthesis and possibly owing to inhibition of breakdown.

Leucine and phenylalanine kinetics in compensated liver cirrhosis: effects of insulin

BACKGROUND

The pathogenesis of the altered ratio of branched-chain amino acid to aromatic amino acid concentration in liver cirrhosis is poorly known. We explored the possible link between altered amino acid concentrations and kinetics in cirrhosis.

METHODS

Post-absorptive leucine and phenylalanine rates of appearance (Ra) and their response to insulin were studied in patients with compensated, nondiabetic cirrhosis and in controls.

RESULTS

In the cirrhotics, concentration of postabsorptive phenylalanine was greater and that of alpha-ketoisocaproate lower than in controls, whereas concentration of leucine was comparable. Leucine Ra was lower, phenylalanine Ra was greater, and the ratio of leucine Ra to phenylalanine Ra was markedly decreased (P < 0.001) in patients vs. controls (2.40 +/- 0.23 vs. 3.67 +/- 0.19, respectively). During an euglycemic-hyperinsulinemic clamp, glucose disposal was reduced and leucine Ra was suppressed more profoundly in cirrhotics than in controls, whereas suppression of phenylalanine Ra was comparable.

CONCLUSIONS

In compensated liver cirrhosis, postabsorptive phenylalanine Ra is increased with respect to leucine Ra, suggesting the existence either of altered amino acid pools and/or transport or of abnormally sequenced proteins and/or peptides. Insulin resistance is restricted to glucose, but not to amino acid metabolism.

Controlled trial on nutrition supplementation in outpatients with symptomatic alcoholic cirrhosis

A controlled trial on nutrition supplementation in ambulatory patients with decompensated alcoholic liver disease was carried out during 1 year. Fifty-one patients were studied; 26 were assigned to an experimental group receiving a daily supplement of 1000 kcal and 34 g of proteins given as a casein-based enteral nutrition product and 25 to a control group receiving one placebo capsule. Patients were examined in a special clinic once a month or more if required. Sixty-eight percent of patients admitted to alcohol ingestion or had alcohol in urine samples on at least one occasion. Dietary recalls showed a significantly higher protein and caloric intake in case patients subjects (p < .0001). Nine patients died during the study, three case patients and six control patients (p = NS). The frequency of hospitalizations was significantly less in the experimental group. This difference was attributed to a reduction in severe infections. Mid-arm circumference, serum albumin concentration, and hand grip strength improved earlier in case patients, although both groups had a significant improvement in these parameters. Bilirubin and aspartate aminotransferase decreased and prothrombin time increased significantly in both groups during the study period, without differences between groups. It is concluded that nutrition support decreases nutrition-associated complications in patients with alcoholic liver disease.

Insulin sensitivity, insulin secretion and glucose effectiveness in diabetic and non-diabetic cirrhotic patients

In cirrhotic patients with normal fasting glucose levels both insulin insensitivity and a blunted early insulin response to oral glucose are important determinants of the degree of intolerance to oral glucose. It is not known whether the ability of hyperglycaemia per se to enhance glucose disposal (glucose effectiveness) is also impaired. It is also unclear whether overt diabetes is due to: (1) more marked insulin insensitivity; (2) impaired insulin secretion; (3) reduced glucose effectiveness; or (4) a combination of these mechanisms. We used the "minimal model" to analyse the results of a 3-h intravenous glucose tolerance test to assess glucose effectiveness, insulin sensitivity and insulin responses in 12 non-diabetic cirrhotic patients, 8 diabetic cirrhotic patients and 10 normal control subjects. Fasting blood glucose levels were 4.8 +/- 0.2, 7.5 +/- 0.6 and 4.7 +/- 0.1 mmol/l, respectively. Fasting insulin and C-peptide levels were higher in both cirrhotic patient groups compared with control subjects. The glucose clearance between 6 and 19 min after i.v. glucose was lower in both cirrhotic groups (non-diabetic, 1.56 +/- 0.14, diabetic, 0.76 +/- 0.06, control subjects, 2.49 +/- 0.16 min-1%, both p < 0.001 vs control subjects). Serum insulin peaked at 3 and 23 min in the non-diabetic cirrhotic patients and control subjects; both peaks were higher in the non-diabetic cirrhotic patients and showed a delayed return to basal levels.(ABSTRACT TRUNCATED AT 250 WORDS)