Degradation Of Liver Glycogen Research Articles

Golden pompano (Trachinotus blochii) adapts to acute hypoxic stress by altering the preferred mode of energy metabolism

The golden pompano (Trachinotus blochii) is becoming increasingly popular among consumers for its delicate meat and high nutritional value. High farming density, eutrophication, and high-temperature conditions increase the probability of hypoxia and thus hypoxic stress, which poses a major challenge for the future development of golden pompano aquaculture. Here, we simulated severe hypoxic stress to distinguish hypoxia-tolerant and hypoxia-sensitive individuals from hundreds of fish. We then used next-generation sequencing to analyze the mRNA expression profiles of the brains and livers under hypoxia to identify the causes of differences in hypoxia tolerance among different groups. The pathways involved in highly expressed genes in the brain were mainly related to signal transduction, endocrine function, and environmental information processing, while the pathways involved in highly expressed genes in the liver were mainly related to metabolism. Under hypoxic conditions, the degradation of liver glycogen in the hypoxia-tolerant group was inhibited under hypoxia. However, in the hypoxia-intolerant group, glycogen decomposition is not inhibited, glucose consumption increases, and there is no tendency to convert to lipid metabolism, leading to metabolic disorders. In the process of adapting to hypoxia, fish first use anaerobic glycolysis to compensate for the lack of energy due to hypoxia. However, as the stress persists, glycolysis is inhibited, and lipid metabolism becomes the preferred mode of energy metabolism; specifically, acetyl-CoA may be produced through lipid metabolism in the hypoxia-tolerant group and then participate in the tricarboxylic acid cycle to provide energy. Death in the hypoxia-intolerant group may stem from the metabolic disorder of glucose and lipid homeostasis. Although additional research is needed to confirm these possibilities, our findings suggest that converting the preferred way of energy metabolism to lipid metabolism may be a way for fish to adapt to acute hypoxic stress.

Hydrolyzed peptides from purple perilla (Perilla frutescens L. Britt.) seeds improve muscle synthesis and exercise performance in mice.

The purple perilla (Perilla frutescens L. Britt.) seed peptides (PPSP) were obtained and their improvement of muscle synthesis and exercise performance was investigated in this work. Results showed that the weight-average molecular weight of the PPSP was 869 Dalton. The PPSP were rich in branched-chain amino acids (18.82g/100g) and anti-fatigue amino acids, including glutamate (Glu), aspartic acid (Asp), and arginine (Arg). After the administration of PPSP at 1.2gkg-1 day-1 for 4weeks, the muscle coefficient and muscle fiber thickness in mice displayed a distinct (p<.05) increase via the upregulation of myogenic differentiation (MyoD) and myogenin (MyoG). The improved muscle strength and exercise tolerance were also observed. Simultaneously, the levels of the biochemical blood markers associated with fatigue and the glycogen degradation in liver and muscle were significantly (p<.05) suppressed. These results suggested that PPSP could effectively promote muscle synthesis and ameliorate exercise fatigue. PRACTICAL APPLICATIONS: Purple perilla is an annual herbal plant and widely grown in Asian countries as an important crop and food. It is believed that the protein content of purple perilla seeds can reach 23.7%, and the protein is rich in essential amino acids. However, the information about the beneficial effects of their proteins or peptides on muscle synthesis and anti-exercise fatigue were still limited. The present results discovered that the PPSP can effectively promote the growth of muscle tissue and improve exercise tolerance. It is indicated that PPSP may have a potential application value in partly or completely replacing animal proteins such as whey protein.

Metformin and Berberine suppress glycogenolysis by inhibiting glycogen phosphorylase and stabilizing the molecular structure of glycogen in db/db mice

Glycogen is a branched glucose polymer involved in sustaining blood glucose homeostasis. Liver glycogen comprises α particles (up to 300 nm in diameter) made of joined β particles (∼20 nm in diameter). Glycogen α particles in a mouse model for diabetes are molecularly fragile, breaking down into smaller β particles more readily than in healthy mice. Glycogen phosphorylase (GP), a rate-limiting enzyme in glycogen degradation, is overexpressed in diabetic mice. This study shows that Metformin and Berberine, two common drugs, two common drugs used to treat diabetes, are able to revert the liver glycogen of diabetic mice to the stable structure seen in non-diabetic mice. It is also shown that these drugs reduce the GP level via the cAMP/PKA signaling pathway in diabetic livers and decrease the affinity of GP with the glycogen of db/db mice. These effects of these drugs may slow down the degradation of liver glycogen and improve glucose homeostasis.

ACSL1 multi‐tissue knockout mice are resistant to diet‐and age‐induced obesity and insulin resistance

Long chain acyl‐CoA synthetase 1 (ACSL1) is the major activator of long‐chain fatty acids in heart and adipose tissue. In order to understand the functional role of ACSL1, we studied mice with a temporally‐induced knockout of ACSL1 in multiple tissues (Acsl1T−/−), including heart, skeletal muscle, kidney, and white adipose. Compared to littermate controls (tamoxifen‐injected ACSL1flox/flox), lack of ACSL1 caused 80–90% lower oxidation of palmitate in heart and adipose. Compared to controls, hearts that lacked ACSL1 took up 75% less [1‐14C]bromopalmitate and 10‐fold more 2‐[14C]deoxyglucose. Compared to controls, chow‐fed Acsl1T−/− mice had higher rates of glycogen degradation in liver and heart. When fed a high fat diet (HFD; 45% of kcal from lard and soybean oil), ACSL1T−/− male mice failed to become obese. HFD‐fed ACSL1T−/− and control mice had similar food intake, respiratory quotients and heat production, but ACSL1T−/− mice were significantly more active at night. HFD‐fed control mice had abnormal glucose and insulin tolerance tests, whereas HFD‐fed ACSL1T−/− mice maintained normal whole‐body insulin sensitivity. With aging, 14‐month old chow‐fed ACSL1T−/− female mice also had a lower fat mass and better glucose tolerance than controls. Thus, ACSL1T−/− mice were protected from HFD‐and age‐induced obesity and insulin resistance.

The regulation of glycogen metabolism in mouse liver

The enzymes involved in the synthesis and the degradation of liver glycogen were studies in two inbred strains of mice in an attempt to assess the mechanisms that regulate glycogen concentration. Glycogen content was greater initially, and increased more rapidly, in fasted mice of the C57BL/FnLn strain than the I/FnLn strain following injections of glucose or of glucose plus insulin. These strain differences in glycogen content were correlated with a greater activity of, and more rapid increases in, the glucose 6-phosphate-independent form of glycogen transferase. The conversion in vitro of the glucose 6-phosphate-dependent form to the independent form was also more rapid in C57-strain mice. Under all experimental conditions, the total activity of glycogen transferase was the same. The activity of glucose-6-phosphate was consistent with the strain differences in glycogen content and was greater in I-strain mice. Here the content of glucose 6-phosphate was also consistently less. The regulatory role of glycogen phosphorylase was difficult to evaluate. In fasted mice of the C57 strain, the activities of glycogen phosphorylase and its converting enzymes, phophorylase kinase and phosphorylase phosphatase, were greater than in I-strain mice. Glucose administration reduced the activities of all three enzymes in C57-strain mice but had no effect on the enzymes in I-strain mice.

The effect of cortisol on synthesis and degradation of liver glycogen

1. The incorporation of 14C from [ 14C 6]glucose, [2- 14c]pyruvate and [2- 14C]glycine into liver glycogen together with the randomization of 14C from [6- 14C]glucose in glucose and the distribution of [ 14C 6]glucose in glycogen have been investiaged in cortisol treated and control rats. The results show: 2. 1. 14c from blood glucose is incorporated into liver glycogen of fasting cortisol-treated animals to a large extent only after degradation to a C 3 unit, and resynthesis to glucose. 3. 2. The synthesis of glucose from its degradation products and from amino acids and the incorporation of this glucose are enhanced after cortisol treatment. 4. 3. The decorporation of 14C from glycogen after injection of [ 14C]pyruvate is delayed in cortisol treated rats. 5. 4. The renewal rate of the terminal glucose in the glycosidic chains of the glycogen is slower in corticol-treated rats. These results indicate that besides an enhanced glyconeogenesis and glycogen synthesis an impairment of glycogen degradation causes the high liver glycogen content in cortisol-treated rats.

Distribution of C4, Administered as CaC4O3, in Rat Liver Glycogen and Blood Glucose and Lactate.

SummaryExperiments are reported in which it was found; that CaC'4O3 implanted intraperitoneally in rats produced a qualitatively similar isotope distribution pattern in the liver glycogen, and blood glucose and lactate. This result suggests that in isotope feeding experiments, analysis of the blood glucose and lactate may yield information comparable to that obtained by the degradation of liver glycogen. Additional experiments to put this question to a more critical test are in progress.