Association of exogenous insulin or sulphonylurea treatment with an increased incidence of hepatoma in patients with hepatitis C virus infection

Dipeptidyl peptidase-4: A key player in chronic liver disease

Dipeptidyl peptidase-4 (DPP-4) is a membrane-associated peptidase, also known as CD26. DPP-4 has widespread organ distribution throughout the body and exerts pleiotropic effects via its peptidase activity. A representative target peptide is glucagon-like peptide-1, and inactivation of glucagon-like peptide-1 results in the development of glucose intolerance/diabetes mellitus and hepatic steatosis. In addition to its peptidase activity, DPP-4 is known to be associated with immune stimulation, binding to and degradation of extracellular matrix, resistance to anti-cancer agents, and lipid accumulation. The liver expresses DPP-4 to a high degree, and recent accumulating data suggest that DPP-4 is involved in the development of various chronic liver diseases such as hepatitis C virus infection, non-alcoholic fatty liver disease, and hepatocellular carcinoma. Furthermore, DPP-4 occurs in hepatic stem cells and plays a crucial role in hepatic regeneration. In this review, we described the tissue distribution and various biological effects of DPP-4. Then, we discussed the impact of DPP-4 in chronic liver disease and the possible therapeutic effects of a DPP-4 inhibitor.

Decreased expression of insulin and increased expression of pancreatic transcription factor PDX-1 in islets in patients with liver cirrhosis: a comparative investigation using human autopsy specimens

BACKGROUND

Glucose intolerance in patients with liver cirrhosis (LC), known as hepatogenous diabetes, is thought to be distinct from type 2 diabetes (T2DM) in some aspects. Hyperinsulinemia and/or insulin resistance in liver disease is associated with hepatocarcinogenesis, growth of hepatocellular carcinoma, and poor prognosis. However, the pathophysiological processes in islets that are responsible for hyperinsulinemia in LC are still not precisely known. Therefore, we investigated the histopathological differences in islets of Langerhans cells between LC and T2DM.

METHODS

A total of 35 human autopsy pancreatic tissue samples were used in this study (control, n = 18; T2DM, n = 6; LC, n = 11). The expression of insulin, glucagon, somatostatin, pancreatic duodenal homeobox-1 (PDX-1), proliferating cell nuclear antigen (PCNA), and Ki-67 was examined using immunohistochemistry and quantitated by image analysis.

RESULTS

Islet hypertrophy and a significant increase in PCNA-positive cells in islets were observed in the tissues from LC cases. The insulin-positive areas in islets were significantly decreased in LC cases compared with control and T2DM cases (P = 0.001, P = 0.035, respectively), whereas the PDX-1-positive area was significantly increased in LC cases (P = 0.001) compared with the control. Furthermore, disorganization of pancreatic endocrine cells and nucleocytoplasmic translocation of PDX-1 were both seen in the LC subjects.

CONCLUSIONS

In LC, islets undergo hypertrophy and exhibit paradoxical expression of insulin and PDX-1. In the subjects autopsied, insulin expression was decreased, whereas expression of the pancreatic transcription factor PDX-1 was increased in LC. These results point to important distinctions between LC and T2DM.

Hyperglycemia is a significant prognostic factor of hepatocellular carcinoma after curative therapy

AIM: To evaluate whether metabolic factors are related to distant recurrence of hepatocellular carcinoma (HCC) and survival after curative treatment.

METHODS: This retrospective study included 344 patients whose HCC was treated curatively by radiofrequency ablation (RFA) therapy. The mean age was 67.6 years and the mean observation period was 4.04 years. The etiological background of liver disease was hepatitis B virus infection in 30, hepatitis C virus infection in 278, excessive alcohol drinking in 9, and other in 27 patients. The Child-Pugh classification grade was A (n = 307) or B (n = 37). The number of HCC nodules was one in 260, two in 61, and three in 23 patients. For surveillance of HCC recurrence after curative therapy with RFA, patients were radiologically evaluated every 3 mo. Factors associated with distant recurrence of HCC or survival were studied.

RESULTS: Inadequate maintenance of blood glucose in diabetic patients was associated with higher incidence of distant recurrence. The 1-, 2-, and 3-year recurrence rates were significantly higher in diabetic patients with inadequate maintenance of blood glucose compared with the others: 50.6% vs 26.8%, 83.5% vs 54.4%, and 93.8% vs 73.0%, respectively (P = 0.0001). Inadequate maintenance of blood glucose was an independent predictor of distant recurrence [adjusted relative risk 1.97 (95%CI, 1.33-2.91), (P = 0.0007)] after adjustment for other risk factors, such as number of HCC nodules [2.03 (95%CI, 1.51-2.73), P < 0.0001] and initial level of serum alpha fetoprotein (AFP) [1.43 (95%CI, 1.04-1.97), P = 0.028]. Obesity was not an independent predictor of recurrence. The incidence of distant recurrence did not differ between diabetic patients with adequate maintenance of blood glucose and non-diabetic patients. Among 232 patients who had HCC recurrence, 138 had a second recurrence. The 1-, 2-, and 3-year rates of second recurrence were significantly higher in diabetic patients with inadequate maintenance of blood glucose than in the others: 9.0% vs 5.9%, 53.1% vs 24.3%, and 69.6% vs 42.3%, respectively (P = 0.0021). Inadequate maintenance of blood glucose in diabetic patients [1.99 (95%CI, 1.23-3.22), P = 0.0049] and presence of multiple HCC nodules [1.53 (95%CI, 1.06-2.22), P = 0.024] were again significantly associated with second HCC recurrence. Inadequate maintenance of blood glucose in diabetic patients was also a significant predictor of poor survival [2.77 (95%CI, 1.38-5.57), P = 0.0046] independent of excessive alcohol drinking [6.34 (95%CI, 1.35-29.7), P = 0.019], initial level of serum AFP [3.40 (95%CI, 1.88-6.18), P < 0.0001] and Child-Pugh classification grade B [2.24 (95%CI, 1.12-4.46), P = 0.022]. Comparing diabetic patients with inadequate maintenance of blood glucose vs the others, the 1-, 2-, and 3-year survival rates were significantly lower in diabetic patients with inadequate maintenance of blood glucose: 92% vs 99%, 85% vs 96%, and 70% vs 92%, respectively (P = 0.0003).

CONCLUSION: Inadequate maintenance of blood glucose in diabetic patients is a significant risk factor for recurrence of HCC and for poor survival after curative RFA therapy.

Metformin and reduced risk of hepatocellular carcinoma in diabetic patients: a meta-analysis

OBJECTIVES

Recent epidemiological studies suggest that metformin treatment may reduce the risks of cancer and overall cancer mortality among patients with diabetes mellitus (DM). However, data on hepatocellular carcinoma (HCC) are very limited and inconsistent. This meta-analysis was designed to pool data currently available to determine the association between metformin use and HCC among diabetic patients.

METHODS

The Medline and Embase databases were searched to identify the relevant studies between January 1966 and December 2011. The overall analysis was derived using a random-effects meta-analysis model (DerSimonian and Laird method). Subgroup analysis was performed to explore the source of heterogeneity and validate the results from overall analysis. The Newcastle-Ottawa Quality assessment scales were adopted for quality assessment; Begg's funnel plot and Egger's regression asymmetry test were used to detect the publication bias.

RESULTS

A total of seven studies were identified, including three cohort studies and four case-control studies. Based on the available data, the overall prevalence of HCC was 3.40% (562/16,549) in DM patients. The overall analysis showed a significantly reduced risk of HCC in metformin users versus nonusers in diabetic patients (relative risk (RR) 0.24, 95% confidence interval (CI) 0.13-0.46, p < 0.001). Fifteen subgroup analyses were performed, and most of them (12/15 = 80%) provided supporting evidence for the results of overall analysis. Begg's (Z = -0.15, p = 0.8819) and Egger's test (t = -0.79, p = 0.468) showed no significant risk of having a publication bias.

CONCLUSION

Metformin treatment was associated with reduced risk of HCC in diabetic patients. To clarify this relationship, more high-quality studies are required.

Chronic HCV infection was associated with severe insulin resistance and mild atherosclerosis: a population-based study in an HCV hyperendemic area

BACKGROUND

Hepatitis C virus (HCV) affects glucose and lipid metabolism in vitro; however, it is unclear whether HCV infection is associated with insulin resistance and atherosclerosis at the population level. We aimed to investigate this association in a Japanese cohort of the Seven Countries Study, and our investigation was conducted in Tanushimaru, an HCV hyperendemic area.

METHODS

A total of 1908 inhabitants of Tanushimaru were classified into 3 groups according to HCV infection status: those who were uninfected (n = 1780), those with transient infection (n = 88), and those with chronic infection (n = 40). Insulin resistance and atherosclerosis were evaluated by homeostasis model assessment for insulin resistance (HOMA-IR) and carotid intima-media thickness (IMT), respectively. Intergroup differences in variables were evaluated by age- and sex-matched multivariate regression analysis.

RESULTS

Significant intergroup differences were seen in fasting glucose and insulin levels. The HOMA-IR value was significantly higher in the group with chronic infection than the values in the uninfected and transiently infected groups (3.0 ± 0.39 vs. 1.3 ± 0.03 vs. 1.5 ± 0.14; P < 0.001). In contrast, low-density lipoprotein (LDL)-cholesterol and triglyceride levels were significantly lower in the group with chronic infection than the levels in the other groups. IMT was reduced in the group with chronic infection, with a significant intergroup difference (0.67 ± 0.02 vs. 0.71 ± 0.003 vs. 0.72 ± 0.01 mm; P = 0.003).

CONCLUSIONS

This population-based study in an HCV hyperendemic area revealed that chronic HCV infection was associated with severe insulin resistance and with mild atherosclerosis, suggesting a unique characteristic of HCV-related metabolic abnormality.

Type 2 diabetes, smoking, insulin use, and mortality from hepatocellular carcinoma: a 12-year follow-up of a national cohort in Taiwan

BACKGROUND

The effect of smoking and insulin use in the association between diabetes and hepatocellular carcinoma (HCC) is not known.

MATERIALS AND METHODS

Age-standardized HCC mortality trends during 1995-2006 in the general population were calculated. A total of 88,694 type 2 diabetic patients aged ≥25 years recruited in 1995-1998 were followed till 2006. Age- and sex-specific mortality rates and the mortality rate ratios (vs. the average mortality rates in the general population) were calculated. Risk factors were evaluated by Cox regression.

RESULTS

The age-standardized mortality trend slightly increased significantly in women but was steady in men. For diabetic patients aged ≥25 years, 830 men and 515 women died of HCC during 1995-2006. Mortality rate ratios (95 % confidence interval) were larger with the decreasing age: 7.36 (6.52, 8.31), 2.48 (2.22, 2.78), 1.79 (1.59, 2.02), and 1.87 (1.51, 2.32) for age 25-54, 55-64, 65-74, and ≥75 years for men, respectively, 10.12 (7.73, 13.25), 4.08 (3.57, 4.67), 2.45 (2.15, 2.78), and 1.71 (1.34, 2.19) for women. Age, male sex, lower BMI, smoking, and insulin use were associated with HCC mortality, but diabetes duration was not. Smoking and insulin use carried a significantly higher risk of 22-29 % and 37-58 %, respectively, without interaction. A dose-responsive pattern between the duration of insulin use and HCC mortality was noted, with a relative risk of 1.5-1.7 in those who used insulin for ≥10 years.

CONCLUSIONS

Diabetic patients have a higher risk of HCC mortality, which is more remarkable in the younger age. Smoking and insulin are potentially modifiable risk factors.

Diabetes, hepatitis virus infection and hepatocellular carcinoma: A case-control study in hepatitis endemic area

AIM

  In spite of numerous studies on the association between diabetes mellitus (DM) and hepatocellular carcinoma (HCC), the results are inconsistent and whether and how the effect of DM on the risk for HCC is modified or synergistically exerted by hepatitis virus infection are still unclear. We aimed to elucidate and quantify the effect modification and synergism between hepatitis B and C virus (HBV and HCV, respectively) and DM leading to the risk for HCC and also assess the independent contribution of DM to the risk for HCC at population level (population attributable fraction) in a high prevalence area of hepatitis virus infection.

METHODS

  A hospital-based case-control study was conducted from one medical center. Information on hepatitis B and C virus infection and DM status (defined by 8-h fasting blood glucose level ≥126 mg/dL, current use of oral hyperglycemic agent or insulin injection) was collected to assess interaction of hepatitis virus infection with DM on the risk for HCC.

RESULTS

  The association between DM and the risk for HCC was significant regardless of the presence of HBV infection, whereas a significant positive association was noted for HCV negativity. Synergistic interactions between DM and HBV infection were significant. In the absence of both hepatitis virus infections, the independent effect of DM accounted for 7.5% risk for HCC from the underlying population.

CONCLUSION

  The effect of DM on the risk for developing HCC is higher in HCV negative patients and synergistic with HBV infection. The independent effect of DM provides a new insight to the prevention of HCC other than virus-related mechanism.

Hepatitis C virus induced insulin resistance impairs response to anti viral therapy

Hepatitis C virus (HCV) infection is an important risk factor for insulin resistance (IR). The latter is the pathogenic foundation underlying metabolic syndrome, steatosis and cirrhosis, and possibly hepatocellular carcinoma (HCC). The interplay between genetic and environmental risk factors ultimately leads to the development of IR. Obesity is considered a major risk factor, with dysregulation of levels of secreted adipokines from distended adipose tissue playing a major role in IR. HCV-induced IR may be due to the HCV core protein inducing proteasomal degradation of insulin receptor substrates 1 and 2, blocking intracellular insulin signaling. The latter is mediated by increased levels of both tumour necrosis factor-α (TNF-α) and suppressor of cytokine signaling 3 (SOC-3). IR, through different mechanisms, plays a role in the development of steatosis and its progression to steatohepatitis, cirrhosis and even HCC. In addition, IR has a role in impairing TNF signaling cascade, which in turn blocks STAT-1 translocation and interferon stimulated genes production avoiding the antiviral effect of interferon.

Insulin resistance and metabolic hepatocarcinogenesis with parent-of-origin effects in A×B mice

Insulin resistance is a defining feature of metabolic syndrome and type 2 diabetes mellitus but also may occur independently of these conditions. Nonalcoholic fatty liver disease (NAFLD), the hepatic manifestation of these disorders, increases the risk of hepatocellular carcinoma (HCC). However, mechanisms linking hyperinsulinemia to NAFLD and HCC require clarification. We describe a novel model of primary insulin resistance and HCC with strong parent-of-origin effects. Male AB6F1 (A/JCr dam × C57BL/6 sire) but not B6AF1 (B6 dam × A/J sire) mice developed spontaneous insulin resistance, NAFLD, and HCC without obesity or diabetes. A survey of mitochondrial, imprinted, and sex-linked traits revealed modest associations with X-linked genes. However, a diet-induced obesity study, including B6.A chromosome substitution-strain (consomic) mice, showed no segregation by sex chromosome. Thus, parent-of-origin effects were specified within the autosomal genome. Next, we interrogated mechanisms of insulin-associated hepatocarcinogenesis. Steatotic hepatocytes exhibited adipogenic transition characterized by vacuolar metaplasia and up-regulation of vimentin, adipsin, fatty acid translocase (CD36), peroxisome proliferator-activated receptor-γ, and related products. This profile was largely recapitulated in insulin-supplemented primary mouse hepatocyte cultures. Importantly, pyruvate kinase M2, a fetal anabolic enzyme implicated in the Warburg effect, was activated by insulin in vivo and in vitro. Thus, our study reveals parent-of-origin effects in heritable insulin resistance, implicating adipogenic transition with acquired anabolic metabolism in the progression from NAFLD to HCC.

Current understanding of insulin resistance in hepatitis C

Important breakthroughs have been made in recent years into understanding the close interaction between hepatitis C virus (HCV) infection and glucose homeostasis. Both cross-sectional and longitudinal studies have demonstrated that infection with HCV is associated with an increased risk of developing insulin resistance and Type 2 diabetes. A direct effect of HCV on hepatocyte insulin signaling has been shown in experimental models. Some preliminary observations seem to suggest that indirect mechanisms involving extrahepatic organs might also play a role. The interaction between HCV and glucose metabolism has significant clinical consequences. Insulin resistance and Type 2 diabetes not only accelerate the histological and clinical progression of chronic hepatitis C, but also reduce the virological response to IFN-α-based therapy. Thus, understanding the mechanisms underlying HCV-associated glucose metabolism derangements is of paramount interest in order to improve the clinical management of chronic hepatitis C. This article will focus on the studies that consistently argue in favor of an interrelation between HCV and insulin resistance and will highlight the latest discoveries in this field.

Data mining reveals complex interactions of risk factors and clinical feature profiling associated with the staging of non-hepatitis B virus/non-hepatitis C virus-related hepatocellular carcinoma

AIM

  Non-hepatitis B virus/non-hepatitis C virus-related hepatocellular carcinoma (NBNC-HCC) is often detected at an advanced stage, and the pathology associated with the staging of NBNC-HCC remains unclear. Data mining is a set of statistical techniques which uncovers interactions and meaningful patterns of factors from a large data collection. The aims of this study were to reveal complex interactions of the risk factors and clinical feature profiling associated with the staging of NBNC-HCC using data mining techniques.

METHODS

  A database was created from 663 patients with NBNC-HCC at 20 institutions. The Milan criteria were used as staging of HCC. Complex associations of variables and clinical feature profiling with the Milan criteria were analyzed by graphical modeling and decision tree algorithm methods, respectively.

RESULTS

  Graphical modeling identified six factors independently associated with the Milan criteria: diagnostic year of HCC; diagnosis of liver cirrhosis; serum aspartate aminotransferase (AST); alanine aminotransferase (ALT); α-fetoprotein (AFP); and des-γ-carboxy prothrombin (DCP) levels. The decision trees were created with five variables to classify six groups of patients. Sixty-nine percent of the patients were within the Milan criteria, when patients showed an AFP level of 200 ng/mL or less, diagnosis of liver cirrhosis and an AST level of less than 93 IU/mL. On the other hand, 18% of the patients were within the Milan criteria, when patients showed an AFP level of more than 200 ng/mL and ALT level of 20 IU/mL or more.

CONCLUSION

  Data mining disclosed complex interactions of the risk factors and clinical feature profiling associated with the staging of NBNC-HCC.

Insulin resistance and chronic liver disease

Increased insulin resistance is frequently associated with chronic liver disease and is a pathophysiological feature of hepatogenous diabetes. Distinctive factors including hepatic parenchymal cell damage, portal-systemic shunting and hepatitis C virus are responsible for the development of hepatogenous insulin resistance/diabetes. Although it remains unclear whether insulin secretion from pancreatic beta cells is impaired as it is in type 2 diabetes, retinopathic and cardiovascular risk is low and major causes of death in cirrhotic patients with diabetes are liver failure, hepatocellular carcinoma and gastrointestinal hemorrhage. Hemoglobin A1c is an inaccurate marker for the assessment and management of hepatogenous diabetes. Moreover, exogenous insulin or sulfonylureas may be harmful because these agents may promote hepatocarcinogenesis. Thus, pathogenesis, cause of death, assessment and therapeutic strategy for hepatogenous insulin resistance/diabetes differ from those for lifestyle-related type 2 diabetes. In this article, we review features of insulin resistance in relationship to chronic liver disease. We also discuss the impact of anti-diabetic agents on interferon treatment and hepatocarcinogenesis.

The dissociation between the diabetes and both Child-Pugh score and in-hospital mortality in cirrhotic patients due to hepatitis B, hepatitis C, or alcoholic

BACKGROUND

Up to 30% of the cirrhotic patients may clinically be classified as having diabetes. The aims of this retrospective study were to evaluate the prevalence of diabetes, its association with the severity of cirrhosis, and subsequent implication on mortality in a broad population of cirrhotic patients in Taiwan.

METHODS

From January 2004 to October 2008, 4,127 cirrhotic patients were reviewed. The latest demographic data were gathered after the latest laboratory measurement in the outpatient or inpatient department. In all, 2,945 patients were included on the basis of the etiology of cirrhosis: hepatitis B, hepatitis C, hepatitis B, and hepatitis C co-infection, or alcoholics.

RESULTS

The observed cases of diabetes were significantly higher in cirrhotic patients than general population. Neither the Child-Pugh score (odds ratio = 0.99, p = 0.527) nor the model for end-stage liver disease score (MELD) (odds ratio = 1.00, p = 0.352) was associated with diabetes. The presence of diabetes was dissociated with renal function by means of serum creatinine (β = -0.01, p = 0.604) or estimated glomerular filtration rate (eGFR) (β = -0.02, p = 0.233), or in-hospital mortality (odds ratio = 1.08, p = 0.362).

CONCLUSION

The prevalence of diabetes was higher in cirrhotic patients in Taiwan. The prevalence of diabetes was dissociated with Child-Pugh or MELD score. The diagnosis of diabetes did not affect the renal function or in-hospital mortality in cirrhotic patients. Since the clinical outcomes of diabetes were different from cirrhotic patients to general population, it is unclear whether the treatment of diabetes and improved glycemic control will benefit cirrhotic patients.

Diabetes mellitus and hepatocellular carcinoma: Comparison of Chinese patients with and without HBV-related cirrhosis

AIM: To determine the role of diabetes mellitus (DM) and other associated factors in Chinese hepatocellular carcinoma (HCC) patients with cirrhosis, compared with those HCC patients without cirrhosis, in the single setting of hepatitis B virus (HBV) infection, after other known concomitant diseases were excluded.

METHODS: A total of 482 patients, treated at the China-Japan Friendship Hospital, Ministry of Health (Beijing, China), in the period January 2003 to June 2009, and with a hospital discharge diagnosis of HCC, were included. Demographic, clinical, laboratory, metabolic and instrumental features were analyzed.

RESULTS: Of the total, 310 patients were diagnosed with HBV infection and, following the inclusion and exclusion criteria, 224 were analyzed, including 122 patients (54.5%) with cirrhosis (the case group) and 102 patients without cirrhosis (the control group). Twenty-seven patients (12.1%) were diabetic, including 19 in the case group and 8 in the control group (19/122 = 15.6% vs 8/102 = 7.8%, P = 0.077). Thirty-one possible relevant parameters were compared by univariate analysis, and 9 variables were selected for multivariable analysis, including DM (P = 0.077), past history of HBV infection (P = 0.005), total bilirubin (P < 0.001), albumin level (P < 0.001), international normalized ratio (INR) (P < 0.001), alanine aminotransferase (P = 0.050), platelet (P < 0.001), total cholesterol (P = 0.047), and LDL cholesterol (P = 0.002) levels. Diabetes showed a statistical difference by multivariable analysis [odds ratio (OR) 4.88, 95% confidence interval (CI): 1.08-21.99, P = 0.039], although no significant difference was found in univariate analysis. In addition, three cirrhosis-related parameters remained statistically different, including INR (OR 117.14, 95% CI: 4.19-3272.28, P = 0.005), albumin (OR 0.89, 95% CI: 0.80-0.99, P = 0.027), and platelet count (OR 0.992, 95% CI: 0.987-0.999, P = 0.002).

CONCLUSION: Besides the three cirrhosis-related parameters, DM was found to be the sole independent factor associated with HCC in patients with HBV-related cirrhosis, compared with those without cirrhosis.

Importance of hepatitis C virus-associated insulin resistance: Therapeutic strategies for insulin sensitization

Insulin resistance is one of the pathological features in patients with hepatitis C virus (HCV) infection. Generally, persistence of insulin resistance leads to an increase in the risk of life-threatening complications such as cardiovascular diseases. However, these complications are not major causes of death in patients with HCV-associated insulin resistance. Indeed, insulin resistance plays a crucial role in the development of various complications and events associated with HCV infection. Mounting evidence indicates that HCV-associated insulin resistance may cause (1) hepatic steatosis; (2) resistance to anti-viral treatment; (3) hepatic fibrosis and esophageal varices; (4) hepatocarcinogenesis and proliferation of hepatocellular carcinoma; and (5) extrahepatic manifestations. Thus, HCV-associated insulin resistance is a therapeutic target at any stage of HCV infection. Although the risk of insulin resistance in HCV-infected patients has been documented, therapeutic guidelines for preventing the distinctive complications of HCV-associated insulin resistance have not yet been established. In addition, mechanisms for the development of HCV-associated insulin resistance differ from lifestyle-associated insulin resistance. In order to ameliorate HCV-associated insulin resistance and its complications, the efficacy of the following interventions is discussed: a late evening snack, coffee consumption, dietary iron restriction, phlebotomy, and zinc supplements. Little is known regarding the effect of anti-diabetic agents on HCV infection, however, a possible association between use of exogenous insulin or a sulfonylurea agent and the development of HCC has recently been reported. On the other hand, insulin-sensitizing agents are reported to improve sustained virologic response rates. In this review, we summarize distinctive complications of, and therapeutic strategies for, HCV-associated insulin resistance. Furthermore, we discuss supplementation with branched-chain amino acids as a unique insulin-sensitizing strategy for patients with HCV-associated insulin resistance.