Liver glycogen-induced enhancements in hypoglycemic counterregulation require neuroglucopenia.

Iatrogenic hypoglycemia is a prominent barrier to achieving optimal glycemic control in patients with diabetes, in part due to dampened counterregulatory hormone responses. It has been demonstrated that elevated liver glycogen content can enhance these hormonal responses through signaling to the brain via afferent nerves, but the role that hypoglycemia in the brain plays in this liver glycogen effect remains unclear. During the first 4hrs of each study, the liver glycogen content of dogs was increased by using an intraportal infusion of fructose to stimulate hepatic glucose uptake (HG; n=13), or glycogen was maintained near fasting levels with a saline infusion (NG; n=6). After a 2hr control period, during which the fructose/saline infusion was discontinued, insulin was infused intravenously for an additional 2hrs to bring about systemic hypoglycemia in all animals, whereas brain euglycemia was maintained in a subset of the HG group by infusing glucose bilaterally into the carotid and vertebral arteries (HG-HeadEu; n=7). Liver glycogen content was markedly elevated in the two HG groups (43±4, 73±3 and 75±7 mg/g in NG, HG and HG-HeadEu, respectively). During the hypoglycemic period, arterial plasma glucose levels were indistinguishable between groups (53±2, 52±1 and 51±1 mg/dL, respectively), but jugular vein glucose levels were kept euglycemic (88±5 mg/dL) only in the HG-HeadEu group. Glucagon and epinephrine responses to hypoglycemia were higher in HG compared to NG, whereas despite the increase in liver glycogen, neither increased above basal in HG-HeadEu. These data demonstrate that the enhanced counterregulatory hormone secretion that accompanies increased liver glycogen content requires hypoglycemia in the brain.

The Role of Hormones in the Regulation of Glycogen Metabolism in the Clawed Toad Xenopus Laevis (Daudin)

The hormonal regulation of amphibian glycogen metabolism was studied in Xenopus laevis as a typical member of the anurans (tailless amphibians).The main focus of this study was given to the effects of various hormones on the glycogen/glucose balance in adult toads. We determined biochemically the liver and muscle glycogen contents as well as the blood glucose and lipid levels for a number of hormones and also diabetes inducing substances. Additionally, we examined ultrastructure changes in hepatocytes induced by the various treatments, and also investigated the activity of carbohydrate-relevant enzymes by histochemistry. With one exception, the liver glycogen content of Xenopus remained basically unchanged by the treatments or was even slightly enhanced. Only human chorionic gonadotropin, through which the vitellogenic response is triggered, prompts a significant decrease of liver glycogen in females. Under the same conditions the male liver glycogen content remained stable. Muscle glycogen contents were not affected by any of the treatments. Blood glucose and lipid levels on the other hand were elevated considerably in both sexes after application of either epinephrine or cortisol. The ultrastructural examination revealed a proliferation of Rough Endoplasmic Reticulum (RER) in hepatocytes from epinephrine treated toads of both sexes as well as from HCG treated females. By histochemistry, we detected an elevated glucose-6-phosphatase activity in the hepatocytes from toads treated with either epinephrine or cortisol. These treatments also led to enhanced glycogen phosphorylase activity in males, and to a slightly elevated glyceraldehyde-3-phosphate dehydrogenase activity in females. Our results show that the hepatic glycogen is extremely stable in adult Xenopus. Only vitellogenesis causes a marked utilization of glycogen. Since the blood glucose levels are elevated in epinephrine or cortisol treated toads without the liver glycogen being affected, we conclude that either protein and/or lipid metabolism are involved in carbohydrate metabolism in Xenopus laevis.

Effects of Sideritis scardica Extract on Glucose Tolerance, Triglyceride Levels and Markers of Oxidative Stress in Ovariectomized Rats

Menopause is characterized by deep metabolic disturbances, including decreased insulin sensitivity, adiposity, and changes in lipid profiles. Estrogen replacement therapy can partially reverse these changes, and while it is safe in most healthy postmenopausal women, there are still existing concerns regarding an increased risk for breast and endometrial cancer as well as a risk for cardiovascular and thromboembolic disease. Therefore, certain natural compounds with positive metabolic effects may be considered as a possible alternative or adjunctive treatment in patients not willing to take estrogens or patients with contraindications for estrogens. The aim of this study was to investigate the influence of Sideritis scardica (mountain tea) extract on metabolic disturbances induced by ovariectomy in rats. The study included 24 rats divided into three groups: ovariectomized rats treated with 200 mg/kg S. scardica extract for 24 weeks (n = 8), ovariectomized non-treated (n = 8), and Sham-operated (n = 8) rats. Food intake, weight gain, body composition, fasting glucose levels, response to oral glucose challenge, liver glycogen content, catalase activity, thiol groups, and malondialdehyde concentrations as well as AMP-activated protein kinase activity in liver cells were studied. Ovariectomized rats treated with S. scardica extract had lower blood triglycerides, reduced fasting glucose levels, as well lower glucose peaks after oral glucose challenge, increased liver glycogen content, and significantly higher catalase activity and thiol group concentration than non-treated ovariectomized rats. The ability of S. scardica extract to attenuate metabolic disturbances associated with ovariectomy was associated with the activation of AMP-activated protein kinase in liver cells.

The effect of peptide tyrosine tyrosine (PYY3–36), a selective Y2 receptor agonist on streptozotocin-induced diabetes in albino rats

Objective. The aim of the present study was to assess the effect of the PYY3–36, as a potential therapy for the type 2 diabetes mellitus (T2DM), induced by high fat diet (HFD) and an intraperitoneal (i.p.) administration of streptozotocin (STZ) in albino rats.Methods. Forty adult male albino Wistar rats were divided into: 1) control group (C, in which the rats were fed with a standard diet and received vehicle; 2) diabetic group (D, in which T2DM was induced by feeding the rats with HFD for four weeks followed by a single i.p. injection of 35 mg/kg STZ, this group was also allowed to have HFD till the end of the study; and 3) D+PYY3–36 group (in which the diabetic rats were treated with 50 µg/kg i.p. PYY3–36 twice a day for one week). Food intake, water intake, body weight (b.w.), visceral fat weight (VFW), liver glycogen content, serum levels of glucose, insulin, and interleukin-6 (IL-6), were measured. Homeostatic-model assessment of insulin resistance (HOMA-IR) was estimated. The gene expression of the hypothalamic neuropeptide Y (NPY) and visceral nuclear factor kappa B (NF-κB) were assessed by a reverse transcription polymerase chain reaction (RT-PCR).Results. The PYY3–36 administration to the diabetic group of rats significantly increased the serum insulin levels and liver glycogen content, decreased the body weight, VFW, food intake, water intake, serum levels of the glucose, IL-6, and HOMA-IR. It also decreased the expression of both the hypothalamic NPY and the visceral fat NF-κB.Conclusion. With respect to the fact of improved insulin release and enhanced insulin sensitivity (an effect that may be mediated via suppressing accumulation of visceral fat and inflammatory markers), in the rats treated with PYY3–36, the PYY3–36 might be considered for the future as a promising therapeutic tool in T2DM.

Biochemical study of striped catfish Pangasianodon hypophthalmus broodstock induced by PMSG hormone + anti‒dopamine and turmeric addition

<p align="center"><strong>ABSTRACT</strong></p><p align="center"><strong> </strong></p><p>This study aimed to evaluate biochemical changes (cholesterol, triglyceride, HDL, LDL, glucose, and plasma protein) on striped catfish <em>Pangasianodon hypophthalmus </em>broodstock induced with PMSG hormone and turmeric addition. An observation was also done to blood glycogen content. The striped catfish broodstock was fed on commercial feed without any addition (control) and with turmeric addition (HKu). In control treatment, there was a decreasing on cholesterol, meanwhile, the triglyceride (TG) value was increased. The HDL concentration was decreased in 2^nd sampling and increased in 4^th sampling. In 1^st until 4^th sampling, glucose was quite stable, while LDL was on extremely low concentration. In HKu treatment, the cholesterol value was higher than the control treatment. The TG concentration also higher than control in 3^rd sampling and decreased in 4^th sampling. The HDL concentration was increased and higher than the control treatment, while LDL concentration was lower. The liver glycogen content on the control and HKu treatment were 0.015 (mg/100 mL) and 0.181 (mg/100 mL) respectively; while in the flesh of the control and HKu treatment were 0.76 (mg/100 mL) and 1.19 (mg/100 mL) respectively; and in the gonad of control and HKu treatment were 0.10 (mg/100 mL) and 0.70 (mg/100 mL) respectively. It was shown that the glycogen content in the liver, flesh, and gonad on experimental fish was higher than control treatment.</p><p> </p><p>Keywords : biochemistry, hormone, turmeric, channel catfish, reproduction</p><p> </p><p> </p><p align="center"><strong>ABSTRAK</strong></p><p align="center"><strong> </strong></p><p>Penelitian ini bertujuan untuk mengkaji perubahan biokimia (kolesterol, trigliserida, HDL, LDL, glukosa dan protein plasma) induk ikan patin <em>Pangasianodon hypophthalmus </em>yang diberi perlakuan hormon PMSG dan kunyit (HKu). Pengamatan juga dilakukan terhadap glikogen dalam darah induk patin. Induk ikan patin diberi pakan tanpa penambahan kunyit (kontrol) dan pakan yang diberi HKu. Hasil penelitian pada kontrol menunjukkan adanya penurunan kolesterol, sedangkan pada TG mengalami peningkatan. HDL menurun pada sampling ke‒2 dan meningkat pada sampling ke‒4. Sementara itu, pada LDL rendah sekali dan pada glukosa terlihat stabil dari sampling ke‒1 sampai ke‒4. Pada perlakuan HKu terlihat bahwa pada kolesterol menghasilkan nilai lebih tinggi dibanding kontrol. Pada TG terlihat juga nilai lebih tinggi dibanding kontrol pada sampling ke‒3 dan menurun pada sampling ke‒4. Konsentrasi HDL meningkat dan lebih tinggi dibanding kontrol, sedangkan nilai LDL lebih rendah. Data yang diperoleh pada kadar glikogen hati perlakuan kontrol adalah 0,015 (mg/100 mL) dan HKu 0,181 (mg/100 mL); sedangkan pada daging kontrol sebesar 0,76 (mg/100 mL) dan HKu 1,19 (mg/100 mL); serta gonad kontrol 0,10 (mg/100 mL) dan HKu 0,70 (mg/100 mL). Hal ini menunjukkan kadar glikogen pada hati, daging, dan gonad ikan yang diberi perlakuan bernilai lebih tinggi dibanding kontrol. </p><p> </p><p>Kata kunci : biokimia, hormon, kunyit, ikan patin, reproduksi</p><p> </p><p> </p>

Sucrose ingestion after exhaustive exercise accelerates liver, but not muscle glycogen repletion compared with glucose ingestion in trained athletes

The purpose of this study was to assess the effects of sucrose vs. glucose ingestion on postexercise liver and muscle glycogen repletion. Fifteen well-trained male cyclists completed two test days. Each test day started with glycogen-depleting exercise, followed by 5 h of recovery, during which subjects ingested 1.5 g·kg−1·h−1 sucrose or glucose. Blood was sampled frequently and 13C magnetic resonance spectroscopy and imaging were employed 0, 120, and 300 min postexercise to determine liver and muscle glycogen concentrations and liver volume. Results were as follows: Postexercise muscle glycogen concentrations increased significantly from 85 ± 27 (SD) vs. 86 ± 35 mmol/l to 140 ± 23 vs. 136 ± 26 mmol/l following sucrose and glucose ingestion, respectively (no differences between treatments: P = 0.673). Postexercise liver glycogen concentrations increased significantly from 183 ± 47 vs. 167 ± 65 mmol/l to 280 ± 72 vs. 234 ± 81 mmol/l following sucrose and glucose ingestion, respectively (time × treatment, P = 0.051). Liver volume increased significantly over the 300-min period after sucrose ingestion only (time × treatment, P = 0.001). As a result, total liver glycogen content increased during postexercise recovery to a greater extent in the sucrose treatment (from 53.6 ± 16.2 to 86.8 ± 29.0 g) compared with the glucose treatment (49.3 ± 25.5 to 65.7 ± 27.1 g; time × treatment, P < 0.001), equating to a 3.4 g/h (95% confidence interval: 1.6-5.1 g/h) greater repletion rate with sucrose vs. glucose ingestion. In conclusion, sucrose ingestion (1.5 g·kg−1·h−1) further accelerates postexercise liver, but not muscle glycogen repletion compared with glucose ingestion in trained athletes.