Splanchnic and peripheral glucose metabolism in cirrhosis

Glucose turnover at whole-body and skeletal muscle level in response to parenteral nutrition in male patients with alcoholic liver cirrhosis

BACKGROUND & AIMS

Cirrhosis is associated with insulin resistance and impaired glucose tolerance, which may be caused by impairments at different tissue levels (liver, skeletal muscle, and/or beta cell).

METHODS

Here, glucose kinetics at whole-body and skeletal muscle level in patients with cirrhosis (Child-Pugh A and B) were studied during parenteral nutrition using the isotope dilution technique and arteriovenous balance approach across the leg. As opposed to the euglycemic hyperinsulinemic clamp or glucose tolerance tests applied in previous studies, this approach provides a nutrient composition more similar to a normal meal while circumventing any possible portal-systemic shunting, impaired hepatic uptake and incretin effect.

RESULTS

We confirmed the presence of hepatic and peripheral insulin resistance in our patient population. Endogenous glucose production was less suppressed in response to parenteral nutrition. However, glucose uptake in skeletal muscle was increased.

CONCLUSION

Our results suggests that in our study participants with cirrhosis, the hepatic and peripheral insulin resistance is compensated for by increased insulin secretion and thus, increased glucose uptake in muscle. Hereby, glucose homeostasis is maintained.

Lack of the Lysosomal Membrane Protein, GLMP, in Mice Results in Metabolic Dysregulation in Liver

Ablation of glycosylated lysosomal membrane protein (GLMP, formerly known as NCU-G1) has been shown to cause chronic liver injury which progresses into liver fibrosis in mice. Both lysosomal dysfunction and chronic liver injury can cause metabolic dysregulation. Glmp^gt/gt mice (formerly known as Ncu-g1^gt/gtmice) were studied between 3 weeks and 9 months of age. Body weight gain and feed efficiency of Glmp^gt/gt mice were comparable to wild type siblings, only at the age of 9 months the Glmp^gt/gt siblings had significantly reduced body weight. Reduced size of epididymal fat pads was accompanied by hepatosplenomegaly in Glmp^gt/gt mice. Blood analysis revealed reduced levels of blood glucose, circulating triacylglycerol and non-esterified fatty acids in Glmp^gt/gt mice. Increased flux of glucose, increased de novo lipogenesis and lipid accumulation were detected in Glmp^gt/gt primary hepatocytes, as well as elevated triacylglycerol levels in Glmp^gt/gt liver homogenates, compared to hepatocytes and liver from wild type mice. Gene expression analysis showed an increased expression of genes involved in fatty acid uptake and lipogenesis in Glmp^gt/gt liver compared to wild type. Our findings are in agreement with the metabolic alterations observed in other mouse models lacking lysosomal proteins, and with alterations characteristic for advanced chronic liver injury.

Activity of glycogen synthase and glycogen phosphorylase in normal and cirrhotic rat liver during glycogen synthesis from glucose or fructose

Cirrhotic patients often demonstrate glucose intolerance, one of the possible causes being a decreased glycogen-synthesizing capacity of the liver. At the same time, information about the rates of glycogen synthesis in the cirrhotic liver is scanty and contradictory. We studied the dynamics of glycogen accumulation and the activity of glycogen synthase (GS) and glycogen phosphorylase (GP) in the course of 120min after per os administration of glucose or fructose to fasted rats with CCl4-cirrhosis or fasted normal rats. Blood serum and liver pieces were sampled for examinations. In the normal rat liver administration of glucose/fructose initiated a fast accumulation of glycogen, while in the cirrhotic liver glycogen was accumulated with a 20min delay and at a lower rate. In the normal liver GS activity rose sharply and GPa activity dropped in the beginning of glycogen synthesis, but 60min later a high synthesis rate was sustained at the background of a high GS and GPa activity. Contrariwise, in the cirrhotic liver glycogen was accumulated at the background of a decreased GS activity and a low GPa activity. Refeeding with fructose resulted in a faster increase in the GS activity in both the normal and the cirrhotic liver than refeeding with glucose. To conclude, the rate of glycogen synthesis in the cirrhotic liver is lower than in the normal one, the difference being probably associated with a low GS activity.

CPAP treatment does not affect glucose-insulin metabolism in sleep apneic patients

Objective: We investigated glucose metabolism and insulin resistance in non-obese and moderately overweight sleep apnea patients, as well as their response to nasal CPAP treatment.Methods: A group of subjects with glucose intolerance was screened for sleep disordered breathing by clinical interview and ambulatory recordings. Ten subjects were found to have untreated sleep apnea and were asked to participate in further investigation. This included nocturnal polysomnography, oral glucose tolerance test and indirect calorimetry. Subjects then had calibration of nasal CPAP with polysomnography. Two months after start of treatment, all subjects were restudied as at baseline. In parallel, six obstructive sleep apnea syndrome (OSAS) subjects, diagnosed through the sleep clinic, were matched for gender, age and oxygen desaturation index with the other group, and had a euglycemic hyperinsulinemic clamp at baseline and after 2 months of nasal CPAP.Results: The first ten patients showed no change in total glucose oxidation, glucose oxidation by weight or by fat free mass, or insulin energetic expenditure, despite nocturnal usage of nasal CPAP. Similarly, when comparing baseline to the treatment at 2 months, the six OSAS patients had no change in mean glycemia, insulin, C peptide and hemoglobin (Hgb) A1C measurements. No difference in the amount of glucose infused during the duration of the clamp was noted either.Conclusion: Our data do not support the existence of a significant relationship between glucose and insulin metabolism and obstructive sleep apnea. Obesity, when present, is the important variable.

Impaired splanchnic and peripheral glucose uptake in liver cirrhosis

BACKGROUND/AIM

Patients with liver cirrhosis are insulin-resistant and frequently glucose-intolerant. Although peripheral glucose uptake has been shown to be impaired in liver cirrhosis, little is known about the significance of splanchnic (hepatic) glucose uptake after oral glucose load.

METHODS/RESULTS

We performed an oral glucose tolerance test and euglycemic hyperinsulinemic clamp with oral glucose load for eight patients with liver cirrhosis and eight patients with chronic active hepatitis. The patients with liver cirrhosis had higher plasma glucose levels 2 h after glucose load than those with chronic active hepatitis (228+/-22 mg/dl vs. 102+/-9 mg/dl, p<0.01). Using the euglycemic hyperinsulinemic clamp with oral glucose load, we simultaneously measured peripheral and splanchnic glucose uptake. Peripheral glucose uptake in liver cirrhosis was 6.1+/-0.7 mg x kg(-1) x min(-1), which was lower than that in healthy volunteers (10.5+/-0.9 mg x kg(-1) x min(-1), p<0.05) and in chronic active hepatitis (8.4+/-0.3 mg x kg(-1) x min(-1), p<0.05). Furthermore, splanchnic glucose uptake in liver cirrhosis was much lower (20.1+/-3.4%) than in healthy volunteers (36.0+/-4.0%, p<0.05) and in chronic active hepatitis (37.2+/-3.1%, p<0.05).

CONCLUSION

These results suggest that glucose intolerance in patients with liver cirrhosis is caused by a defect of the glucose uptake of both splanchnic and peripheral tissues.

Contributions of net hepatic glycogenolysis and gluconeogenesis to glucose production in cirrhosis

Net hepatic glycogenolysis and gluconeogenesis were examined in normal (n = 4) and cirrhotic (n = 8) subjects using two independent methods [13C nuclear magnetic resonance spectroscopy (NMR) and a 2H2O method]. Rates of net hepatic glycogenolysis were calculated by the change in hepatic glycogen content before ( approximately 11:00 PM) and after ( approximately 7:00 AM) an overnight fast using 13C NMR and magnetic resonance imaging. Gluconeogenesis was calculated as the difference between the rates of glucose production determined with an infusion of [6,6-2H2]glucose and net hepatic glycogenolysis. In addition, the contribution of gluconeogenesis to glucose production was determined by the 2H enrichment in C-5/C-2 of blood glucose after intake of 2H2O (5 ml/kg body water). Plasma levels of total and free insulin-like growth factor I (IGF-I) and IGF-I binding proteins-1 and -3 were significantly decreased in the cirrhotic subjects (P < 0.01 vs. controls). Postprandial hepatic glycogen concentrations were 34% lower in the cirrhotic subjects (P = 0.007). Rates of glucose production were similar between the cirrhotic and healthy subjects [9.0 +/- 0.9 and 10.0 +/- 0.8 micromol. kg body wt-1. min-1, respectively]. Net hepatic glycogenolysis was 3.5-fold lower in the cirrhotic subjects (P = 0.01) and accounted for only 13 +/- 6% of glucose production compared with 40 +/- 10% (P = 0.03) in the control subjects. Gluconeogenesis was markedly increased in the cirrhotic subjects and accounted for 87 +/- 6% of glucose production vs. controls: 60 +/- 10% (P = 0.03). Gluconeogenesis in the cirrhotic subjects, as determined from the 2H enrichment in glucose C-5/C-2, was also increased and accounted for 68 +/- 3% of glucose production compared with 54 +/- 2% (P = 0.02) in the control subjects. In conclusion, cirrhotic subjects have increased rates of gluconeogenesis and decreased rates of net hepatic glycogenolysis compared with control subjects. These alterations are likely important contributing factors to their altered carbohydrate metabolism.

Hepatic energy and substrate metabolism: a possible metabolic basis for early nutritional support in cirrhotic patients

In the liver, the in vivo assessment of metabolic functions is limited by methodologic problems. The present evidence suggests that the liver contributes to 20-30% of whole body energy expenditure. Hepatic fuel selection can change considerably under different circumstances. During tissue catabolism (i.e., depletion of glycogen stores, increased lipid oxidation), the "hepatic respiratory quotient (RQ)" is lower than whole body RQ, suggesting that hepatic catabolism exceeds whole body catabolism. By contrast, the hepatic RQ may exceed whole body RQ during tissue anabolism (i.e., after full repletion of hepatic glycogen stores and significant lipogenesis). In cirrhosis, both the hepatic RQ and the whole body RQ are markedly reduced. When compared with the whole body level, the cirrhosis-induced decrease in the hepatic RQ is more pronounced. Given that liver catabolism exceeds (or possibly precedes) whole body catabolism, early nutritional support is mandatory in cirrhotic patients. The assessment of hepatic, in addition to whole body, energy metabolism may provide a basis for future recommendations of more specific nutritional support in patients with liver diseases.

Impaired nonoxidative glucose metabolism in patients with liver cirrhosis: effects of two insulin doses

Glucose intolerance is encountered in the majority of cirrhotic patients. This alteration has been attributed to a defective insulin-mediated glucose uptake in peripheral tissue, where nonoxidative glucose disposal seems to be chiefly impaired. To further investigate insulin action under euglycemic conditions, we studied how physiological (100 microU/mL) and pharmacological (1,000 microU/mL) plasma insulin concentrations affect whole-body insulin-mediated glucose uptake, as well as oxidative and nonoxidative glucose disposal, in cirrhotic patients and controls. To this aim, a sequential two-step insulin euglycemic clamp combined with indirect calorimetry was performed in eight cirrhotic patients and six control subjects. During the first step of the clamp, total glucose uptake was reduced by 40% in cirrhotic patients versus controls (4.42 +/- 1.39 v 7.63 +/- 1.60 mg/kg/min, P = .002). By increasing insulin to pharmacological levels, glucose disposal increased in both groups. However, the maximum rate of glucose metabolism achieved in cirrhotic patients was lower than in controls at all times (10.29 +/- 2.04 v 12.82 +/- 0.51 mg/kg/min, P = .012). Glucose oxidation was lower in cirrhotics in the basal state, but similar in both groups during insulin/glucose infusion. On the other hand, the reduced nonoxidative glucose disposal observed in cirrhotic patients was not normalized even by increasing insulin to pharmacological levels. In conclusion, in liver cirrhosis a reduced insulin sensitivity is associated with a reduced insulin responsiveness that is mainly caused by defective nonoxidative glucose disposal.