Acute effects of pioglitazone on glucose metabolism in perfused rat liver

Pioglitazone, a thiazolidinedone derivative, decreases insulin resistance and improves hyperglycemia in insulin-resistant obese and/or diabetic animals. However, the mechanisms by which hyperglycemia is improved are not well defined. We investigated the effects of pioglitazone on hepatic glucose metabolism using a perfused rat liver model. Perfusion with the buffer containing 1 – 10 μm pioglitazone for 20 min dose-dependently increased the hepatic fructose 2,6-bisphosphate content, a potent activator of 6-phosphofructo 1-kinase. The furctose 2,6-bisphosphate level after 20 min perfusion with 10 μm pioglitazone was 64.9± 14.5 pmol/mg ⋅ protein, significantly higher than the control (48.3±10.9 pmol/mg ⋅ protein). When the liver from a starved for 48 h rat was perfused with the buffer containing 2 mm lactate but no glucose, glucose was generated from lactate via the gluconeogenic pathway and flowed into the effluent perfusate at a constant rate of 31±0.6 μmol/g ⋅ liver/h. The addition of 10 μm pioglitazone decreased the glucose output rate to 19.3±3.8 μmol/g ⋅ liver/h. Dose-dependent inhibition of glucose output by pioglitazone was observed in the 1 – 10 μm dose range. These results indicate that pioglitazone may not only stimulate glycolysis but also inhibit gluconeogenesis in the liver. These acute and insulin-independent effects on hepatic glucose metabolism may partly account for the diverse anti-diabetic effects of pioglitazone. Received:13 May 1996 / Accepted in revised form: 14 April 1997     

Galactose and glucose metabolism in the isolated perfused suckling and adult rat liver

The development of the technique for the perfusion of the immature liver has enabled us to characterize metabolic differences in carbohydrate metabolism in the suckling versus adult rat livers. Livers of fasted suckling and adult rats were perfused with 4 mM galactose or 4 mM glucose. Galactose uptake was the same for both age groups during the first 35 min. The adult liver maintained the initial rate of uptake after this period while the immature liver began to take up galactose more rapidly. By the end of the experimental period, on a weight basis, uptake by the young liver was three times that of the adult. Analysis of the livers at the end of the 90 min perfusion showed hepatic galactose concentrations to be one-half of circulating media levels.Glucose output was observed in each group during perfusion with either galactose or glucose. In the immature liver, galactose perfusion stimulated more glucose output than did the glucose perfusion. In the adult, however, both sugars resulted in the same levels of glucose output. Galactose perfusion resulted in glucose levels in young liver being higher than the media; while in the adult, the level was lower than the media.Galactose perfused livers of the suckling and adult contained significantly more uridine-5′-diphosphogalactose than the glucose perfused livers of each age.     

The effects of glucagon and TH-glucagon on steroid metabolism in isolated rat hepatocytes

Glucagon decreases the activity of steroid-metabolising enzymes in isolated rat liver cells at physiological concentrations. Higher concentrations are less effective. TH-glucagon (1-N-alpha-trinitrophenylhistidine-12-homoarginine-glucagon) also reduces enzyme activity but does not lose activity at higher concentrations. The effects of the two hormones mimic closely their reported effects on phosphatidylinositol-4,5-bisphosphate breakdown. It is, thus, likely that the effect of glucagon on steroid metabolism is mediated via breakdown of this phospholipid. The calcium ionophore, A23187, had no effect on steroid metabolism whereas the phorbol ester 4 beta-phorbol-12-myristate-13-acetate (PMA) mimicked the effect of glucagon, showing that activation of protein kinase C but not Ca2+ mobilization may be involved in glucagon's action on hepatic steroid metabolism.     

Enhanced galactose metabolism in isolated perfused livers of folate-treated suckling rats

Folic acid (1 mg/day) was administered intraperitoneally to seven-day-old suckling rats for a period of seven days. Livers of folate-treated animals took up galactose rapidly during the first 35 minutes of perfusion, whereas uptake was delayed in the controls (sham-injected and untreated). More glucose was released by all groups when galactose was perfused than when other substrates were used. With each hexose tested, livers of the folate group consistently released less glucose but more lactate than the controls. The specific activity of galactose-1-phosphate uridyltransferase was elevated in livers of the folate group compared to the controls perfused with either galactose or glucose. A similar finding was made for ATP levels in perfused livers of this group. The differences in transferase and ATP levels in perfused livers of folate-treated over the control groups may explain the enhanced galactose uptake pattern.     

Effects of galanin on hormone secretion from the in situ perfused rat pancreas and on glucose production in rat hepatocytes in vitro

Galanin is a novel peptide, widely distributed throughout the central and peripheral nervous system, including nerve endings surrounding the pancreatic islets. In dogs, galanin infusion has been reported to induce hyperglycemia along with a reduction of circulating insulin. In this work, we have studied the effect of galanin (a 200 ng bolus followed by constant infusion at a concentration of 16.8 ng/ml for 22-24 min) on insulin, glucagon, and somatostatin secretion in the perfused rat pancreas. In addition, we have investigated the effect of galanin (10 and 100 nM) on glycogenolysis and gluconeogenesis in isolated rat hepatocytes. In the rat pancreas, galanin infusion marked inhibited unstimulated insulin release as well as the insulin responses to glucose (11 mM), tolbutamide (100 mg/liter) and arginine (5 mM). Galanin failed to alter the glucagon and somatostatin responses to glucose, tolbutamide, and arginine. In isolated rat hepatocytes, galanin did not influence glycogenolysis or glucagon phosphorylase a activity. Gluconeogenesis and the hepatocyte concentration of fructose 2,6-bisphosphate were also unaffected by galanin. In conclusion: in the perfused rat pancreas, galanin inhibited insulin secretion without modifying glucagon and somatostatin output, thus pointing to a direct effect of galanin on the B cell; and in rat hepatocytes, galanin did not affect glycogenolysis or gluconeogenesis; hence, the reported hyperglycemia induced by exogenous galanin does not seem to be accounted for by a direct effect of this peptide on hepatic glucose production.     

Interaction of sympathomimetics and insulin with hepatic glucose production by isolated perfused rat livers: effects of continuous versus pulsatile infusion

To elucidate the efficacy of continuous vs. intermittent exposure to epinephrine, phenylephrine, and insulin, hepatic glucose production was monitored in isolated perfused rat livers (means +/- SE, n = 6 each). To this end livers of fed rats were perfused with 5 mM glucose Krebs-Ringer buffer in a nonrecirculating system. Using this model it was shown that intermittent exposure (3 min on/off period, dose reduction -50%) to epinephrine (0.4 microM, alpha + beta-agonist) and phenylephrine (5 microM, alpha-agonist) elicited an almost identical rise in hepatic glucose production [epinephrine: 0.72 +/- 0.08 mmol/(86 min X 100 g BW); phenylephrine: 0.68 +/- 0.07 mmol/(86 min X 100 g BW) as their continuous administration (epinephrine: 0.78 +/- 0.06 mmol/(86 min X 100 g BW); phenylephrine: 0.74 +/- 0.09 mmol/(86 min X 100 g BW)]. Inhibition by insulin (100 mU/liter) given either continuously or intermittently (3 min on/off intervals; dose reduction -50%) was equipotent for epinephrine- and phenylephrine-stimulated hepatic glucose production. When the off period was doubled to 6 min, thereby reducing the total insulin dose to 33%, no significant suppression of epinephrine- and phenylephrine-stimulated hepatic glucose production was observed. From this we conclude that 1) the effect on hepatic glucose production of pulsatile (3 min on/off, dose reduction 50%) and continuous administration is equipotent for the respective action of epinephrine, phenylephrine as well as of insulin; and 2) insulin is more effective (P less than 0.02) in inhibiting hepatic glucose production stimulated by an alpha-agonist (phenylephrine; 5.0 microM) than in counteracting alpha + beta-agonist action (epinephrine; 0.4 microM). The characteristics of hepatic glucose release as stimulated by alpha- and/or beta-adrenergic agonists and its inhibition by continuously or intermittently infused insulin were simulated and described by a computer model. Thereby, no qualitative difference could be demonstrated in alpha- vs. beta-adrenergic agonists action on stimulated hepatic glucose production.     

Regulation of glucose synthesis in hormone-sensitive isolated rat hepatocytes

A simplified procedure was developed for isolation of intact, hormone-sensitive liver cells in a high and reproducible yield. These cells produce glucose from various precursors at rates comparable to those achieved in isolated perfused liver. Glucagon enhanced glucose synthesis from pyruvate, dihydroxyacetone, fructose, or xylitol more effectively at low than at high substrate concentration. At high pyruvate concentrations (>2 mM), glucagon or adenosine 3':5'-cyclic monophosphate (0.1 mM) exerts a curious inhibition of gluconeogenesis that can be reverted to stimulation on addition of ethanol. It is suggested that glucagon and cyclic AMP inhibit pyruvate dehydrogenase and thus limit the supply of reducing equivalents needed for glucose formation. Supporting evidence for hormonal control of pyruvate dehydrogenase in isolated liver cells is provided by the fact that glucagon decreases and insulin increases decarboxylation of [1-(14)C]pyruvate. Calcium salts (1.3 mM) enhance glucose formation from pyruvate but greatly enhance the inhibition exerted by the divalent cationophore, A23187. Inhibition by glucagon of glucose synthesis from pyruvate is additive with the effects of A23187 + Ca(++). However, with dihydroxyacetone as substrate, glucagon partially reverses the inhibition exerted by A23187 + Ca(++). The results are consistent with glucagon effecting an inhibition of pyruvate dehydrogenase and a stimulation of hexosediphosphatase activities.     

Glycyrrhizinate reduces portal hypertension in isolated perfused rat livers with chronic hepatitis

AIM:To investigate the effects of diammonium glycyrrhizinate(Gly)on portal hypertension(PHT)in isolated portal perfused rat liver(IPPRL)with carbon tetrachloride(CCl4)-induced chronic hepatitis.METHODS:PHT model was replicated with CCl4 in rats for 84 d.Model was identified by measuring the ascetic amounts,hepatic function,portal pressure in vivo,splenic index,and pathological alterations.Inducible nitric oxide synthase(iNOS)in liver was assessed by immunohistochemistry.IPPRLs were performed at d0,d28,d56,and d84.After phenylephrine-induced constriction,Gly was geometrically used to reduce PHT.Gly action was expressed as median effective concentration(EC50)and area under the curve(AUC).Underlying mechanism was exploited by linear correlation between AUC values of Gly and existed iNOS in portal triads.RESULTS:PHT model was confirmed with ascites,splenomegaly,serum biomarkers of hepatic injury,and elevated portal pressure.Pathological findings had shown normal hepatic structure at d0,degenerations at d28,fibrosis at d56,cirrhosis at d84in PHT rats.Pseudo lobule ratios decreased and collagen ratios increased progressively along with PHT development.Gly does dose-dependently reduce PHT in IPPRLs with CCl4-induced chronic hepatitis.Gly potencies were increased gradually along with PHT development,characterized with its EC50at 2.80×10-10,3.03×10-11,3.77×10-11and 4.65×10-11mol/L at d0,d28,d56and d84,respectively.Existed iNOS was located at hepatocyte at d0,stellate cells at d28,stellate cells and macrophages at d56,and macrophages in portal triads at d84.Macrophages infiltrated more into portal triads and expressed more iNOS along with PHT development.AUC values of Gly were positively correlated with existed iNOS levels in portal triads.CONCLUSION:Gly reduces indirectly PHT in IPPRL with CCl4-induced chronic hepatitis.The underlying mechanisms may relate to rescue NO bioavailability from macrophage-derived peroxynitrite in portal triads.     

Effects of inhibin on activin A-Induced glucose metabolism in rat hepatocytes

This study was conducted to investigate the effects of inhibin on hepatic glucose metabolism. We have previously reported that activin A induced a dose-dependent glycogenolytic action on hepatocytes, and that 10⁻⁹ M activin A induced a maximum glycogenolytic effect. Inhibin itself induced no increase or decrease in glucose output at any dose tested. At a concentration of 10⁻¹⁰ M, inhibin was seen to inhibit 10⁻⁹ M activin A-induced glucose output by 30% as compared to the control. In contrast to its inhibitory effect on the action of activin A, 10⁻¹⁰ M and higher concentrations of inhibin did not inhibit angiotensin II-or vasopressin-induced glycogenolysis. We further investigated the mechanism of the inhibitory effect of inhibin on activin A-induced glycogenolysis, and found that 10⁻¹⁰ M inhibin did inhibit the increase in cytoplasmic-free calcium concentration that was seen with 10⁻⁹ M activin A. We also investigated the effects of inhibin on the activin A-induced production of inositol trisphosphates, and the results showed that 10⁻¹⁰ M inhibin inhibited the activin A-induced production of inositol trisphosphates by 30% compared to the control. Furthermore, it was demonstrated that inhibin did not affect the binding of activin A to isolated hepatocytes. These data demonstrated that inhibin inhibited the activin A-induced glycogenolysis by inhibiting the increases of inositol trisphosphates and cytoplasmic free calcium concentrations.     

Acute effects of decreased glutamine supply on protein and amino acid metabolism in hepatic tissue: a study using isolated perfused rat liver

Glutamine deficiency, a common finding in severe illness, has a negative influence on immune status, protein metabolism, and disease outcome. In several studies, a close relationship between glutamine, branched-chain amino acid (BCAA), and protein metabolism was demonstrated. The aim of the present study was to investigate the effect of glutamine deficiency on amino acid and protein metabolism in hepatic tissue using a model of isolated perfused rat liver (IPRL). Parameters of protein metabolism and amino acid metabolism were measured using both recirculation and single pass technique with L-[1-(14)C]leucine and [1-(14)C]ketoisocaproate (KIC) as a tracer. Glutamine concentration in perfusion solution was 0.5 mmol/L in control and 0 mmol/L in the glutamine-deficient group. The net release of glutamine (about 11 micromol/g/h) and higher net uptake of most of the amino acids was observed in the glutamine-deficient group. There was an insignificant effect of lack of glutamine on hepatic protein synthesis, proteolysis, and the release of urea. However, significantly lower release of proteins by the liver perfused with glutamine-deficient solution was observed. The lack of glutamine in perfusion solution caused a significant decrease in leucine oxidation (6.66 +/- 1.04 v 13.67 +/- 2.38, micromol/g dry liver/h, P <.05) and an increase in KIC oxidation (163.7 +/- 16.5 v 92.0 +/- 12.9 micromL/g dry liver/h, P <.05). We conclude that decreased delivery of glutamine to hepatic tissue activates glutamine synthesis, decreases resynthesis of essential BCAA from branched-chain keto acids (BCKA), increases catabolism of BCKA, and has an insignificant effect on protein turnover in hepatic tissue.     

Interactions of propionate and carnitine metabolism in isolated rat hepatocytes

Accumulation of propionate and its metabolic products propionyl-CoA and methylmalonyl CoA results in disruption of normal hepatic metabolism. Carnitine can partially restore normal cellular function in the presence of propionate. This beneficial effect of carnitine has been hypothesized to result from removal of propionyl groups in the form of propionylcarnitine. The present study was designed to elucidate the kinetics of propionylcarnitine formation in isolated rat hepatocytes, and the consequences of propionylcarnitine formation on propionate and carnitine metabolism. 14C-Propionate was converted to CO2, glucose, and propionylcarnitine in the hepatocyte system. Rates of CO2 production plateaued at propionate concentrations above 0.5 to 1.0 mmol/L, while in contrast, rates of glucose production declined as the propionate concentration was increased from 1.0 to 10.0 mmol/L. Increasing concentrations of carnitine up to 10.0 mmol/L resulted in increased production of propionylcarnitine. Despite formation of propionylcarnitine, propionate conversion to CO2 and glucose was unaffected by addition of carnitine. Thus, 10 mmol/L carnitine was able to increase total propionate metabolism (conversion to CO2, glucose and propionylcarnitine) by 40%. Hepatocyte metabolism of propionate was associated with a decrease in carnitine concentration and an increase in short chain acylcarnitines. This decrease in carnitine concentration was also seen in the presence of 150 mumol/L added carnitine, and was greater with propionate as a substrate as compared to butyrate. High performance liquid chromatography was used to permit specific quantification of propionylcarnitine. This technique confirmed that in the presence of propionate, propionylcarnitine was the major acylcarnitine generated and was responsible for the depletion of free carnitine from the system.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation and biochemical analysis of vesicles from taurohyodeoxycholic acid-infused isolated perfused rat livers

AIM:To isolate biliary lipid-carrying vesicles from isolated perfused rat livers after taurohyodeoxycholic acid(THDC)infusion.Biliary lipid vesicles have been implicated in hepatic disease and THDC was used since it increases biliary phospholipid secretion.METHODS:Rat livers were isolated and perfused via the hepatic portal vein with THDC dissolved in Krebs Ringer Bicarbonate solution,pH 7.4,containing 1 mmol/L CaCl2,5 mmol/L glucose,a physiological amino acid mixture,1%bovine serum albumin and 20%(v/v)washed human erythrocytes at a rate of 2000 nmol/min for 2h.The livers were then removed,homogenized and subjected to centrifugation,and the microsomal fraction was obtained and further centrifuged at 350000 g for 90 min to obtain subcellular fractions.These were analyzed for total phospholipid,cholesterol,protein and alkaline phosphodiesterase I(PDE).RESULTS:No significant changes were observed in the total phospholipid,cholesterol and protein contents of the gradient fractions obtained from the microsomal preparation.However,the majority of the gradient fractions(ρ=1.05-1.07 g/mL andρ=1.95-1.23 g/mL)obtained from THDC-infused livers had significantly higher PDE activity compared to the control livers.The low density gradient fraction(ρ=1.05-1.07 g/mL)which was envisaged to contain the putative vesicle population isolated from THDC-perfused livers had relatively small amounts of phospholipids and protein when compared to the relevant control fractions;however,they displayed an increase in cholesterol and PDE activity.The phospholipids were also isolated by thin layer chromatography and subjected to fractionation by high performance liquid chromatography;however,no differences were observed in the pattern of the fatty acid composition of the phospholipids isolated from THDC and control perfused livers.The density gradient fractions(ρ=1.10-1.23 g/mL)displayed an increase in all the parameters measured from both control and THDCinfused livers.CONCLUSION:No significant changes in biliary lipids were observed in t     

Acute and chronic effects of hyperglycaemia on glucose metabolism

Summary In normal man, several hormonal and metabolic adjustments allow the maintenance of the blood glucose concentration within narrow limits. Hyperglycaemia participates in this regulation via stimulation of glucose disposal and inhibition of glucose production. The effects are mediated, in addition to changes in insulin and glucagon secretion, by the mass-action effect of glucose. In both Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) diabetic patients, hyperglycaemia, by mass-action abnormally elevates the basal glucose utilization rate but compensates for reduced postprandial insulin-stimulated glucose disposal. When exposed to chronic hyperglycaemia, the body tissues seem to protect themselves, at least partly, against excessive glucose utilization. These protective mechanisms include both a reduction in insulin stimulated glucose disposal and insulin secretion. Chronic hyperglycaemia may also reduce non-insulin-dependent glucose utilization, at least in rats. In Type 1 diabetic patients with normal peripheral insulin concentrations, chronic hyperglycaemia per se could be a major cause of insulin resistance. In Type 2 diabetic patients, insulin resistance is often already present before the development of overt fasting hyperglycaemia. At the diabetic stage, hyperglycaemia could, however, maintain a self-perpetuating cycle, where the deleterious effects of high glucose concentrations on insulin action and secretion cause further deterioration of glycaemic control. The biochemical basis for hyperglycaemia-induced insulin resistance is still far from clear, but could involve changes in the glucose transporter number and gene expression.     

Uptake and metabolism of endothelin in the isolated perfused rat lung

The uptake and metabolism of endothelin was studied in the isolated perfused rat lung. 125I-Labeled endothelin (4 x 10(-12) M) was rapidly removed from the lung perfusate. More than 90% of the label was removed by 5 min, and only 4-5% remained in the perfusate after 30 min. In the presence of 10(-9) or 5 x 10(-9) M unlabeled endothelin added 6 min before 125I-labeled endothelin, the radiolabel was more slowly removed, so that after 30 min 19 or 73% of the label, respectively, remained in the perfusate. Although a high level of unlabeled endothelin in the perfusate reduced the uptake of 125I-labeled endothelin, it did not displace radiolabel previously taken up by the lung. Analysis of radiolabel composition showed that endothelin metabolism was less than 15% in both the lung and the perfusate after 30 min of lung perfusion. Autoradiography of the lung indicated that the radiolabel was located primarily within the alveolar wall. These results suggest that circulating endothelin is readily but finitely taken up in the pulmonary microvasculature where it is avidly bound but slowly metabolized.     

Vanadate inhibits glucose output from isolated perfused rat liver

Previous studies have demonstrated that vanadate ions mimic many of the actions of insulin in in vitro systems. Also, vanadate administered to diabetic hyperglycemic rats lowers their blood glucose levels to normal values. In this study we demonstrate that vanadate inhibits glucose output in the isolated perfused rat liver. Glucose production was suppressed maximally (about 50% to 60%), on addition of extremely low vanadate ion concentrations (0.5 to 1 mumol/L). This concentration is about two log units lower than the vanadate ion concentrations that are required to activate hexose uptake and glucose metabolism in vitro and is within the range of endogenous intracellular vanadium concentration. Insulin had little or no effect in inhibiting hepatic glucose output in this experimental system. The effect of vanadate ions is rapid in onset and is not accompanied by any signs of liver toxicity as assessed by various criteria. In conclusion, the study indicates that (a) vanadate ions inhibits hepatic glucose output, maximally and at extremely low, nontoxic concentrations (ID50 = 0.7 +/- 0.1 mumol/L). (b) The modulation action of the ion is fast and probably occurs at point(s) distal to the insulin receptor itself. (c) The liver participates in the process of maintaining euglycemia in diabetic rats receiving optimal doses of vanadate orally.     

Stimulation of glucose production by activin-A in isolated rat hepatocytes

The effect of activin-A on glycogenolysis was studied in isolated rat hepatocytes. Activin-A stimulated glucose output in hepatocytes in a dose-dependent manner. The maximal effect of the glycogenolytic action of activin-A, which was about 50% of the glucagon action, was obtained at 10(-9) M. When 10(-9) M activin-A and 5 x 10(-9) M glucagon were added simultaneously, the actions of these two agents were additive. In contrast, there was no additivity when 10(-9) M activin-A and 10(-8) M angiotensin-II were added. Activin-A did not increase cAMP at any doses tested, but induced a rapid increase in cytoplasmic free calcium concentration. Activin-A increased the cytoplasmic free calcium concentration even in the presence of 1 microM extracellular calcium, suggesting that activin-A caused calcium release from an intracellular calcium pool(s). The internal calcium pool affected by activin-A appeared to be the same as that affected by either angiotensin-II or vasopressin. When [3H] inositol-labeled hepatocytes were incubated with activin-A, radioactivity in the inositol trisphosphate fraction was rapidly increased. These results indicate that activin-A acts on rat hepatocytes and stimulates glycogenolysis by activating the calcium messenger system.     

Interactive effects of catecholamines and hypercapnia on glucose production in isolated trout hepatocytes

In response to added catecholamines, isolated trout (Salmo gairdneri) hepatocytes substantially increase the output of glucose into the surrounding medium. This effect is due to activation of glycogen breakdown concomitant with increases in gluconeogenesis and cell respiration. Each metabolic parameter is activated to a similar extent. In hormone-treated and untreated cells, glycogenolysis accounts for more than 97% of glucose production. Activation of glycogen phosphorylase is implicated in the degradation of cell glycogen, while increased flux through the gluconeogenic pathway from lactate is associated with inactivation of pyruvate kinase, possibly through enzyme phosphorylation as indicated by the activity ratio measured at low and saturating concentrations of phosphoenolpyruvate. From studies with specific adrenergic agonists and antagonists, we conclude that stimulation of glycogenolysis and gluconeogenesis in trout hepatocytes is consistent with a beta-adrenergic effect. Results are inconclusive with respect to catecholamine-mediated activation of cell respiration. None of the monitored cell acid-base variables (pH, PCO2, [HCO3-]) are implicated in the catecholamine-dependent changes in metabolic output of hepatocytes. Imposed hypercapnic conditions (increased medium PCO2 and decreased medium pH), which cause changes in cell acid-base parameters, result in a depression of lactate oxidation and gluconeogenesis, while the rate of glycogenolysis is not affected. In addition, the total amounts of glycogen phosphorylase and pyruvate kinase assayable are negatively affected by hypercapnic treatment of hepatocytes. Under hypercapnic conditions, cells are highly responsive to adrenergic agonists. It appears that--especially in the long term--the catecholamine-dependent activation of gluconeogenesis may compensate for the acid-base-dependent shortfall in glucose output by the liver.