Hepatic Glucose Concentrations Research Articles

Evaluation of Hepatic Glucose and Palmitic Acid Metabolism in Rodents on High‐Fat Diet Using Deuterium Metabolic Imaging

BackgroundOne of the main features of several metabolic disorders is dysregulation of hepatic glucose and lipid metabolism. Deuterium metabolic imaging (DMI) allows for assessing the uptake and breakdown of 2H‐labeled substrates, giving specific insight into nutrient processing in healthy and diseased organs. Thus, DMI could be a useful approach for analyzing the differences in liver metabolism of healthy and diseased subjects to gain a deeper understanding of the alterations related to metabolic disorders.PurposeEvaluating the feasibility of DMI as a tool for the assessment of metabolic differences in rodents with healthy and fatty livers (FLs).Study TypeAnimal Model.Population18 male Sprague Dawley rats on standard (SD, n = 9, healthy) and high‐fat diet (HFD, n = 9, FL disease).Field Strength/SequencePhase‐encoded 1D pulse‐acquire sequence and anatomy co‐registered phase‐encoded 3D pulse‐acquire chemical shift imaging for 2H at 9.4T.AssessmentLocalized and nonlocalized liver spectroscopy was applied at eight time points over 104 minutes post injection. The obtained spectra were preprocessed and quantified using jMRUI (v7.0) and the resulting amplitudes translated to absolute concentration (mM) according to the 2H natural abundance water peak.Statistical TestsTwo‐way repeated measures ANOVA were employed to assess between‐group differences, with statistical significance at P < 0.05.ResultsDMI measurements demonstrated no significant difference (P = 0.98) in the uptake of [6,6′‐2H2]glucose between healthy and impaired animals (AUCSD = 1966.0 ± 151.5 mM ‐ minutes vs. AUCHFD = 2027.0 ± 167.6 mM·minutes). In the diseased group, the intrahepatic uptake of palmitic acid d‐31 was higher (AUCHFD = 57.4 ± 17.0 mM·minutes, AUCSD = 33.3 ± 10.5 mM·minutes), but without statistical significance owing to substantial in‐group variation (P = 0.73).Data ConclusionDMI revealed higher concentrations of palmitic acid in rats with FL disease and no difference in hepatic glucose concentration between healthy and impaired animals. Thus, DMI appears to be a useful tool for evaluating metabolism in rodents with FL disease.Level of Evidence2Technical EfficacyStage 3.

In vivo anti-diabetic activity, physicochemical and sensory properties of Kunu enriched with African walnut

This study aimed at determining the anti-diabetic, physicochemical and sensory characteristics of African walnut enriched- kunu beverage in streptozotocin (STZ)-induced diabetic Wistar rats. The physicochemical, sensory and anti-diabetic properties of the four formulated samples viz: NWJ (90% kunu + 10% raw walnut juice); BWJ (90% kunu + 10% boiled walnut juice); RWJ (90% kunu + 10% roasted walnut juice) and ZWJ (kunu 100%) were evaluated using standard methods. The boiling and roasting of the walnut juice affected the TTA and brix of the enriched kunu but all have similar pH around 5. The significant (p < 0.05) increase in insulin, glycogen concentrations, hexokinase and glucose 6-phosphate dehydrogenase activities were observed in the STZ-induced rats after treatment with the enriched kunu. However, the decrease in hepatic glucose concentration and fructose-1,6-bisphosphatase activities in the treated rats, signified a significant (p < 0.05) lowering of the fasting blood glucose level (from 30 to 10 mmol/l) when compared with the untreated rats. Besides, the boiling process of the BWJ sample gave it a significantly (p < 0.05) higher overall acceptability when compared to the RWJ, NWJ and ZWJ samples. The study established the antidiabetic potentials and consumer acceptability of African walnut enriched kunu as potential functional food in diabetes management.

Justicia carnea extracts ameliorated hepatocellular damage in streptozotocin-induced type 1 diabetic male rats via decrease in oxidative stress, inflammation and increasing other risk markers

Introduction Diabetes mellitus is still a raging disease not fully subdued globally, especially in Africa. Our study aims to evaluate the anti-diabetic potentials of Justicia carnea extracts [crude (JCC), free (JFP) and bound phenol (JBP) fractions], in streptozotocin (STZ)-induced type-1 diabetes in male albino rats. Materials and Methods About thirty (30) animals were induced for type 1 diabetes with STZ; thereafter, treatment began for 14 days, after which the animals were euthanized, blood/serum was collected, the liver was removed and divided into two portions, for biochemical and histopathological analyses. Standard procedures were used to evaluate the liver biomarkers, like alanine transaminase (ALT), fructose-1,6-bisphosphatase, glucose-6- phosphatase, hexokinase activities, albumin, bilirubin, hepatic glucose concentrations; antioxidant status and pro- and anti-inflammatory cytokines were similarly assessed. Results These results revealed that the extracts ameliorated the harmful effects of STZ-induced diabetes in the liver by enhancing the activities of liver-based biomarkers, reducing the concentrations of pro-inflammatory cytokines and increasing the anti-inflammatory cytokine. Discussion The results agreed with previous research, and the free phenol fraction showed excellent results compared to others Conclusion These suggested that J. carnea could serve as an alternative remedy in ameliorating liver complications linked to oxidative damage and inflammation in STZ-induced type-1 diabetes.

Antidiabetic efficacies of methanolic and ethyl acetate extracts of Aristolochia ringens (Vahl) roots: in vivo comparative studies

Antidiabetic effects of methanol and ethyl acetate extracts of roots of Aristolochia ringens (Vahl) were comparatively assessed in streptozotocin (STZ)-induced rats. Pulverized root of A. ringens was soaked with methanol, filtered, and concentrated to dryness. The resulting residue was subsequently dissolved in ethyl acetate, filtered, and concentrated to dryness to obtain ethyl acetate extract. Methanol and ethyl acetate extracts of A. ringens root yielded 20.50 g (10.25%) and 16.4 g (8.2%) respectively. Both extracts (150 mg/kg bw) and metformin (14.2 mg/kg bw) used as reference were administered orally to STZ-induced diabetic rats for 7 days. Fasting blood glucose (FBG) level was monitored and percentage reduction in glycemia computed. Hepatic concentrations of glucose and glycogen as well as alpha amylase and glucose-6-phosphate dehydrogenase activities were also evaluated. FBG level persisted in animals that were diabetic but not treated (323.20 ± 1.01 mg/dL), whereas FBG levels in treated rats following administration of metformin, ethyl acetate, and methanol extracts for 7 days were 148.55 ± 1.62, 129.08 ± 2.52, and 181.21 ± 0.44 mg/dL, resulting in percentage reduction of 80.93%, 85.44%, and 69.10% in glycemia respectively. Ethyl acetate extracts from A. ringens root caused higher reduction in hepatic glucose concentration with concomitant increase in glycogen level when compared to the methanol extract. The root extracts also stimulated the activity of glucose-6-phosphate dehydrogenase while inhibiting the activity of α-amylase in the liver of the treated groups compared to the untreated groups. Findings from this study revealed that ethyl acetate extract of Aristolochia ringens displayed strong antidiabetic potential than the methanol extract of the same plant.

Alterations of the redox state, pentose pathway and glutathione metabolism in an acute porphyria model. Their impact on heme pathway

A classical acute porphyria model in rats consists of combined treatment with 2-allyl-2-isopropylacetamide (AIA) and 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC). The present work describes the effects of this treatment on the pentose phosphate (PP) pathway, glutahione metabolism and redox state and how they contribute to alter the glucose pool of hepatocytes and modulate porphyria, in Wistar rat livers. Our approach is based on the fact that glucose is a repressor of 5-aminolevulinic synthase (ALA-S), the rate-limiting enzyme of the heme pathway, and treatment with AIA/DCC causes oxidative stress. Different doses of the xenobiotcs were used. The results show that AIA (500 mg/kg body weight [BW])/DDC (50 mg/kg [BW]) treatment increased glutathione peroxidase (GPx) activity by 46%, decreased both glutathione reductase (GR) and glutathione S-transferase (GST) activity by 69% and 52%, respectively, and reduced by 51% reduced glutathione (GSH) and increased by 100% glutathione disulfide (GSSG) concentrations, therefore lowering by four-fold the GSH/GSSG ratio. The activity of glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme of PP-pathway, was increased by 129% as well as that of 6-phosphogluconate dehydrogenase. NADPH and the NADPH/NADP(+) ratio were increased by 14% and 28%, respectively. These effects could be attributed to the generation of reactive oxygen species (ROS) elicited by the porphyrinogenic treatment, shown by enhanced DNA damage and ROS production. G6PD stimulation would decrease hepatic glucose concentrations and consequently exacerbate the porphyria. A decrease in glucose could stimulate ALA-S and this would add to the effect of drug-induced heme depletion. Since the key role of GST is to inactivate toxic compounds, the drastic fall in its activity together with the accumulation of ALA would account for the symptoms of this hepatic disease model. The present findings show the high metabolic interplay between pathways and constitute a relevant contribution to achieve a better treatment of acute human porphyria.

A Cyclic Guanosine Monophosphate–Dependent Pathway Can Regulate Net Hepatic Glucose Uptake in Vivo

We previously showed that hepatic nitric oxide regulates net hepatic glucose uptake (NHGU), an effect that can be eliminated by inhibiting hepatic soluble guanylate cyclase (sGC), suggesting that the sGC pathway is involved in the regulation of NHGU. The aim of the current study was to determine whether hepatic cyclic guanosine monophosphate (cGMP) reduces NHGU. Studies were performed on conscious dogs with transhepatic catheters. A hyperglycemic-hyperinsulinemic clamp was established in the presence of portal vein glucose infusion. 8-Br-cGMP (50 µg/kg/min) was delivered intraportally, and either the glucose load to the liver (CGMP/GLC; n = 5) or the glucose concentration entering the liver (CGMP/GCC; n = 5) was clamped at 2× basal. In the control group, saline was given intraportally (SAL; n = 10), and the hepatic glucose concentration and load were doubled. 8-Br-cGMP increased portal blood flow, necessitating the two approaches to glucose clamping in the cGMP groups. NHGU (mg/kg/min) was 5.8 ± 0.5, 2.7 ± 0.5, and 4.8 ± 0.3, whereas the fractional extraction of glucose was 11.0 ± 1, 5.5 ± 1, and 8.5 ± 1% during the last hour of the study in SAL, CGMP/GLC, and CGMP/GCC, respectively. The reduction of NHGU in response to 8-Br-cGMP was associated with increased AMP-activated protein kinase phosphorylation. These data indicate that changes in liver cGMP can regulate NHGU under postprandial conditions.

Chinese Prescription Kangen-karyu Ameliorates the Development of Diabetic Hepatic Damages via Regulating Oxidative Stress and Inflammation in the Liver of db/db Mice

The prevention and treatment of diabetic complications are considered to be the most important for the general care of diabetic patients. We have been conducting pre-clinical animal experiments related to diabetes using kangen-karyu, a Chinese prescription, to examine its therapeutic potential. In the present study, we further studied the anti-diabetic mechanism of kangen-karyu, especially on the regulation of hyperglycemia-induced hepatic oxidative stress and inflammation in db/db mice. Kangen-karyu (100 or 200 mg/kg body weight/day, per os (p.o.) was administered every day for 18 weeks to db/db mice, and its effect was compared with vehicle-treated db/db and m/m mice. The administration of kangen-karyu decreased the elevated serum and hepatic glucose concentration in db/db mice. The elevated expressions of p22(phox) and Nox-4 proteins (reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits) were significantly decreased after kangen-karyu treatments. The oxidative stress-related markers in hepatic tissue (reactive oxygen species, reduced glutathione/oxidized glutathione ratio, and thiobarbituric acid-reactive substance) were also significantly ameliorated by the kangen-karyu treatments. The db/db mice exhibited the up-regulation of nuclear factor-κBp65, cyclooxygenase-2, and inducible nitric oxide synthase levels in the liver; however, kangen-karyu treatment significantly reduced those expressions. Taking these into consideration, our findings support the therapeutic evidence for kangen-karyu ameliorating the development of diabetic hepatic damages via regulating oxidative stress and inflammation.

Liver Glycogen Synthase, Phosphorylase, and the Glycogen Concentration in Rats Given a Glucose Load Orally: A 24-Hour Study

Fasted rats were given 4 g/kg glucose orally. Synthase R (active forms), total synthase, and phosphorylase a activities, and hepatic glycogen, glucose B-phosphate (glucose-6-P), uridine diphosphoglucose (UDP-glucose), glucose, and plasma glucose concentrations were determined over the subsequent 24 h. The resulting glycogen concentration changes could be divided into three distinct phases. A glycogen synthetic phase (between 0 and 4 h), a stability phase (between 4 and 12 h), and a degradation phase (between 12 and 24 h). Synthase R activity increased rapidly and reached a maximum at 20 min. With the onset of glycogen synthesis it gradually decreased below the control values, reaching a nadir by 4 h. During the glycogen stability phase it gradually increased again up to the control value. It then remained stable during the subsequent glycogen degradation phase. Phosphorylase a activity did not change throughout the entire 24-h period. Glucose-6-P concentration increased almost twofold at 20 min. It then decreased but was above the control values at the 24th h. The plasma and hepatic glucose concentrations increased as expected after the glucose load. They then decreased but remained above the control value at all subsequent time points. In summary, the synthase R, phosphorylase a activities, or changes in the known allosteric modifiers of these enzymes could not explain the changes in glycogen concentration. The reasons for these discrepancies remain to be determined.

Primacy of liver glucosensors in the sympathetic response to progressive hypoglycemia.

The impact of hepatic glucose concentration on the sympathetic response to progressive hypoglycemia was examined in chronically cannulated conscious male dogs (n = 6). Graded hypoglycemia was induced via peripheral insulin infusion (30 pmol.kg-1.min-1) with either peripheral (PER) or portal (POR) glucose infusion. Over the 260-min experimental period, arterial glycemia was adjusted from 5.2 +/- 0.1 to 2.5 +/- 0.1 mM in decrements of approximately 0.5 mM every 40 min. Arterial glycemias were not significantly different between PER and POR at any measured level. However, hepatic glycemia was significantly elevated at all times during POR (8.4 +/- 0.8 to 3.4 +/- 0.2 mM) when compared to PER (5.2 +/- 0.2 to 2.5 +/- 0.1 mM). Plasma epinephrine values were significantly greater during PER vs. POR at all arterial glycemias below 4.0 mM. At the lowest level of arterial glycemia studied (2.5 +/- 0.2 mM) the epinephrine response above basal was 3-fold greater for PER (8.7 +/- 1.7 nM) when compared to POR (2.6 +/- 0.6 nM) (P < 0.01). Plasma norepinephrine results were similar for the two protocols, with PER demonstrating a 3-fold greater response above basal when compared to POR at 2.5 mM arterial glycemia (P < 0.05). While the sympathetic response was markedly different between protocols when expressed as a function of arterial glycemia, when expressed as a function of hepatic glycemia this discrepancy was largely eliminated. This latter observation supports the liver as the primary locus for glycemic detection relevant to the sympathoadrenal response when hypoglycemia develops slowly--i.e., over a period of 2-3 h. A comparison of the current findings with our previous observations suggests that the hepatic glucosensors may play a greater role in hypoglycemic counterregulation as the rate of fall in glycemia is less.

Importance of Hepatic Glucoreceptors in Sympathoadrenal Response to Hypoglycemia

To ascertain whether hepatic glucoreceptors are important to hypoglycemic counterregulation, a localized euglycemic clamp was employed across the liver during general hypoglycemia. Dogs were infused peripherally with insulin (18-21 pmol.kg-1.min-1) for 150 min to induce systemic hypoglycemia. During the liver-clamp (LC) protocol, glucose was infused via the portal vein to maintain euglycemia at the liver. In control experiments, i.e., matched infusion (MI), glucose was infused peripherally at a rate determined to yield similar arterial glycemia levels in the two protocols. Arterial glucose concentrations were not different between protocols during the final hour of insulin infusion (3.26 +/- 0.21 and 3.25 +/- 0.21 mM during LC and MI, respectively; P = 0.91). Calculated hepatic glucose concentrations during the same period were significantly higher for LC (5.22 +/- 0.23 mM) than for MI (3.25 +/- 0.21 mM). During MI, both epinephrine and norepinephrine rose significantly from basal values of 562 +/- 87 pM and 1.21 +/- 0.19 nM to plateaus of 3691 +/- 1097 pM (P = 0.0001) and 2.38 +/- 0.35 nM (P = 0.0002), respectively. However, during LC, the elevation in epinephrine was suppressed by 42 +/- 8% (P = 0.015) relative to MI. Six of seven animals demonstrated a suppression in the norepinephrine response, averaging 32 +/- 13% (NS, P = 0.068). The glucagon response to hypoglycemia was unaffected by the level of hepatic glycemia. Hepatic hypoglycemia is essential to produce the full sympathoadrenal response to insulin-induced hypoglycemia.

Relationship of hepatic glucose uptake to intrahepatic glucose concentration in fasted rats after glucose load.

Glucose concentration gradients across the liver and hepatic blood flow were measured to characterize the relationship of hepatic glucose uptake to hepatic glucose concentration for 240 min after administration of a large oral glucose load to fasted rats. Extraction of glucose occurred only transiently, from 20 to 80 min after glucose administration. The liver changed from net glucose output to net glucose removal only when the intracellular hepatic glucose concentration exceeded 12.5 mumol/ml water. Even when arteriovenous glucose concentrations gradients were compatible with net direct hepatic uptake of glucose, the hepatic glucose concentration always exceeded the inflow glucose concentration. These data indicate that direct glucose uptake occurred against a concentration gradient when the liver is considered as a whole. The hepatic intracellular-to-extracellular glucose concentration gradient changed very little, suggesting that this is not being regulated by glucose, insulin, or other effectors. The mechanism by which the hepatic glucose concentration and net hepatic glucose uptake versus output are coordinated is unknown. The rate of glycogen synthesis was linear for 120 min after administration of the glucose load. This occurred in the presence of direct uptake of glucose early in the time course and later in the presence of net glucose output by the liver. Net direct uptake of glucose by the liver could account for, at most, 37-55% of the glycogen formed. Fractional extraction of both lactate and alanine decreased after glucose was given, but net hepatic uptake of these metabolites could account for 33-49 and 7-10%, respectively, of the glycogen formed, depending on plasma versus blood water flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of hormone and glucose administration on hepatic glucose and glycogen metabolism in vivo. A 13C NMR study.

Effects of peripheral venous injection of glucagon and insulin on [1-13C]glucose incorporation into hepatic glycogen of rats were studied by 13C NMR in vivo. Each animal was given a continuous somatostatin infusion and a 100-mg intravenous injection of [1-13C] glucose in NMR experiments or unlabeled glucose in parallel experiments for determination of serum glucose. Insulin administration caused serum glucose to fall below basal levels and accelerated the loss of hepatic [1-13C]glucose; these effects were counteracted by the addition of glucagon. Glucagon administration alone did not affect serum glucose or hepatic [1-13C] glucose but caused the loss of [1-13C]glucose from glycogen and inhibited [1-13C]glucose incorporation into glycogen. Insulin did not alter [1-13C]glucose incorporation into glycogen when given alone or in combination with glucagon. The data are consistent with a model in which liver glycogen synthesis increases linearly with hepatic glucose concentration above a threshold glucose concentration. Insulin did not alter the rate constant or the threshold for synthesis.

1164 EFFECT OF EXTENDED MATERNAL STARVATION ON THE INTRAHEPATIC REGULATION OF METABOLISM IN NEWBORN DOGS

Hepatic metabolic intermediates from fasted newborn pups of 6 control and eight 5-day starved pregnant mothers (MCS) were studied between 0 and 24 hrs of age. In the MCS fetus, glycogen concentrations were significantly reduced (416vs526 μ mol/g)+ and uridinediphosphate glucose levels increased (0.196vs0.135) suggesting diminished fetal glycogen synthesis. After birth glycogen levels diminished at the same rate in the 2 groups being 197 and 304 at 24 hrs. Hepatic glucose concentrations were reduced in the MCS pups at 3 hrs (2.90vs5.97) reaching control levels at 6 and 9 hrs, again declining at 24 hrs (3.09vs5.29). Glucose-6-phosphate and fructose-6-phosphate concentrations after MCS were low in the fetus and throughout the 24 hrs. Tricarboxylic acid cycle (TCA) intermediates tended to be low after 6 hrs in the MCS group; α-ketoglutarate levels being significantly reduced at 6 and 9 hrs, malate at 9 and 24 hrs, and citrate at 24 hrs. After birth, MCS resulted in significant lowering of hepatic ATP levels while energy charge was low only at 6 and 9 hrs. In addition the cytoplasmic NAD/NADH ratio was significantly more oxidized at 3 hrs in the MCS pups. Intrahepatic ammonia concentrations were significantly elevated at 0,6,9 and 24 hrs. CONCLUSION: Extended MCS results in 1)reduced fetal glycogen synthesis or augmented fetal glycogenolysis and 2)diminished hepatic energy production after birth in spite of enhanced net hepatic glycolytic flux as a result of phosphofructokinase activation by low levels of ATP, citrate and NADH. *Deceased +Mean