• BMB Reports
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• 제42권2호
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• pp.119-124
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• 2009

PI(3,4,5)$P_3$ produced by the activated PI3-kinase is a key lipid second messenger in cell signaling downstream of insulin. Skeletal muscle and kidney-enriched inositol phosphatase (SKIP) identified as a 5'-inositol phosphatase that hydrolyzes PI(3,4,5) $P_3$ to PI(3,4)$P_2$, negatively regulates the insulin-induced glycogen synthesis in skeletal muscle. However the mechanism by which this occurs remains unclear. To elucidate the function of SKIP in glycogen synthesis, we employed RNAi techniques to knockdown the SKIP gene in differentiating C2C12 myoblasts. Insulininduced phosphorylation of Akt (protein kinase B) and GSK-3$\beta$ (Glycogen synthase kinase), subsequent dephosphorylation of glycogen synthase and glycogen synthesis were increased by inhibiting the expression of SKIP, whereas the insulin-induced glycogen synthesis was decreased by overexpression of WT-SKIP. Our results suggest that SKIP plays a negative regulatory role in Akt/ GSK-3$\beta$/GS (glycogen synthase) pathway leading to glycogen synthesis in myocytes.

• 한국균학회지
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• 제13권4호
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• pp.235-241
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• 1985

본 연구는, catabolic repression시킨 효모세포를 완전배지와 최소배지에서 derepression시켜, 배양시기 및 인산 첨가농도(free, limited, sufficient)에 따른 5종의 다당류 합성변화를 조사하였다. 그리고 다당류 합성과 무기폴리인산 축적량 및 인지질 합성 사이의 상관지수를 구하여 합성시 관련되는 유의한 정도를 검정하였다. 그 결과, 최소배지에서 catabolic derepression시킨 효모세포가, 완전배지에서 derepression시킨 세포에 비하여, glycogen의 합성이 발리 그리고 많이 일어났고, acid soluble glycogen type이 주된 함량을 나타내었으며, alkali soluble glycogen은 당이 많이 소모된 24시간 배양 후에 소량 나타났다. 무기인산 첨가정도에 따라 total glycogen합성이 일정한 비율로 빨리 그리고 높게 일어났다. Glucan의 합성에는 ALPase 중 ALPase "C"가 관련할 것으로 추정되었다. Mannan은 ezponential phase초기와 정체기때, acid soluble 분획은 정체기때 최대함량을 나타내었다. Mannan 합성과 poly-P "C"축적량 사이의 상관지수는 0.866, mannan합성과 인지질 사이의 상관지수는 0.726으로 나타나 매우 유의하였다.

• Toxicological Research
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• 제8권1호
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• pp.9-15
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• 1992

Hydroxybrazilin was examined for its effects on glycogen synthesis in primary cultured rat hepatocytes. At 10-6 M hydroxybrazilin, glycogen synthesis was increased in basal state, but not in insulin stimulated state. However, any signiFicant changes were nor observed at 10-5 M hydroxybrazilin in both states. The glycogen synthesis was rather suppressed at 10-5M hydroxybrazilin. It was also observed that hydroxybrazilin increased insulin sensitivity but not insulin responsiveness at 10-5M concentration. These results suggest that hydroxybrazilin might exert hypoglycemic action through its effects on insulin receptor and post receptor events.

• Journal of Yeungnam Medical Science
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• 제7권1호
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• pp.19-27
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• 1990

Slow twitch soleus와 fast twitch plantaris근의 운동, insulin, 전기자극에 대한 반응을 시험관 내에서 $^{14}C$-glucose를 이용한 glycogen합성능으로 비교하고 협력근 절제 4주후에 유도한 대상성비후근의 glycogen의 합성능을 같은 방법으로 평가하여 지속적인 과부하에 따른 각 근섬유의 반응을 비교하고자 한 본 연구의 결과를 요약하면 다음과 같다. 대조군의 soleus에서는 glycogen으로 incorporation되는 glucose양으로 볼때 운동에 의한 증가는 없었으나 insulin, 전기자극 등의 인자에 의해서는 증가하였으며 운동이 이들 인자들과 합쳐 졌을때는 이들의 작용을 증폭 시켰다. 그러나 plantaris에서는 운동과 전기자극을 합한 군과 모든자극을 함께 가한 군에서만 유의한 증가를 보여서 insulin이나 glucose대사의 관점에서 볼때 soleus가 훨씬 활동적임을 알 수 있었다. 협력근 절제로 인한 4주간의 과부하로 인한 비후군의 glycogen합성능은 soleus에서 대조군의 그것과 양상은 비슷하였으나 그 절대 량에서 크게 못미쳤으며 plantaris에서는 대조군과 매우 유사한 반응을 나타내었다. 이와같은 결과로 볼때 협력근 절제 4주후에 여러 효소의 활동도가 안정상태에 이른다는 여러 보고에 기초하면 지속적인 과부하에 대한 각 근섬유의 반응양상이 차이가 나서 fast twitch근의 근활동이 더 향상되는 것으로 사료된다.

• 운동영양학회지
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• 제24권2호
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• pp.1-5
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• 2020

[Purpose] Lactate has several beneficial roles as an energy resource and in metabolism. However, studies on the effects of oral administration of lactate on fat metabolism and glycogen synthesis are limited. Therefore, the purpose of the present study was to investigate how oral administration of lactate affects fat metabolism and glycogen synthesis factors at specific times (0, 30, 60, 120 min) after intake. [Methods] Male Sprague Dawley (SD) rats (n = 24) were divided into four groups as follows: the control group (0 min) was sacrificed immediately after oral lactate administration; the test groups were administered lactate (2 g/kg) and sacrificed after 30, 60, and 120 min. Skeletal muscle and liver mRNA expression of GLUT4, FAT/CD36, PDH, CS, PC and GYS2 was assessed using reverse transcription-polymerase chain reaction. [Results] GLUT4 and FAT/CD36 expression was significantly increased in skeletal muscle 120 min after lactate administration. PDH expression in skeletal muscle was altered at 30 and 120 min after lactate consumption, but was not significantly different compared to the control. CS, PC and GYS2 expression in liver was increased 60 min after lactate administration. [Conclusion] Our results indicate that exogenous lactate administration increases GLUT4 and FAT/CD36 expression in the muscle as well as glycogen synthase factors (PC, GYS2) in the liver after 60 min. Therefore, lactate supplementation may increase fat utilization as well as induce positive effects on glycogen synthesis in athletes.

• Preventive Nutrition and Food Science
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• 제22권3호
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• pp.172-183
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• 2017

Vitamin A and its metabolites modulate insulin resistance and regulate stearoyl-CoA desaturase 1 (SCD1), which are also known to affect insulin resistance. Here, we tested, whether vitamin A-mediated changes in insulin resistance markers are associated with SCD1 regulation or not. For this purpose, 30-week old male lean and glucose-intolerant obese rats of WNIN/GR-Ob strain were given either a stock or vitamin A-enriched diet, i.e. 2.6 mg or 129 mg vitamin A/kg diet, for 14 weeks. Compared to the stock diet, vitamin A-enriched diet feeding improved hyperglycemia and glucose-clearance rate in obese rats and no such changes were seen in lean rats receiving identical diets. These changes were corroborated with concomitant increase in circulatory insulin and glycogen levels of liver and muscle (whose insulin signaling pathway genes were up-regulated) in obese rats. Further, the observed increase in muscle glycogen content in these obese rats could be explained by increased levels of the active form of glycogen synthase, the key regulator of glycogen synthesis pathway, possibly inactivated through increased phosphorylation of its upstream inhibitor, glycogen synthase kinase. However, the unaltered hepatic SCD1 protein expression (despite decreased mRNA level) and increased muscle-SCD1 expression (both at gene and protein levels) suggest that vitamin A-mediated changes on glucose metabolism are not associated with SCD1 regulation. Chronic consumption of vitamin A-enriched diet improved hyperglycemia and glucose-intolerance, possibly, through the regulation of intracellular signaling and glycogen synthesis pathways of muscle and liver, but not associated with SCD1.

• Journal of Yeungnam Medical Science
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• 제5권2호
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• pp.79-86
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• 1988

Sprague-Dawley중 흰쥐에게 $^{14}C$-glucose가 들어있는 glucose용액을 경구 투여한 후 특성이 다른 골격근에서 투여 glucose가 glycogen으로 합성된 양과 운동부하가 이에 미치는 효과를 관찰한 본 연구 결과를 요약하면 다음과 같다. Glucose 경구투여 후 위장관에서의 흡수율은 운동부하군 및 대조군 모두 30분에 55% 정도였고 90분후에는 70% 가량이 흡수되었다. 투여 glucose로부터 유래된 골격근 glycogen 합성량은 양군 모두 SOL에서 가장 높았으며 WV가 가장 낮았다. 운동부하군이 대조군에 비하여 glycogen 합성량이 많았으며 특히 SOL, RV에서 현저히 높았다. 운동부하군에서 투여 glucose로부터 합성된 glycogen의 양이 90분후에는 SOL, RV 그리고 EDL에서는 대조군보다 월등히 많았으나 WV에서는 차이가 없었으며 30분경에는 SOL만이 유의하게 높았다. 투여 glucose에서 유래한 glycogen 합성속도는 운동부하군에서 WV를 제외한 모든 근육에서 초기 30분보다 후반 60분이 월동이 빨랐으나 SOL을 제외한 대조군과 WV는 처음 30분동안에 대부분의 glycogen이 합성되었다. 간장에서는 투여 glucose로부터 합성된 glycogen양은 양군 모두에서 초기 30분동안에는 합성량이 미미했으나 운동부하군의 90분동안에는 30분에 비하여 무려 20여배의 증가를 보였다.

• Journal of Ginseng Research
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• 제18권2호
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• pp.102-107
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• 1994

When at liver homogenates were incubated with 1mM $CCl_4$ for five min, glycogen level was decreased, while treatment with protein fraction $G_4$ increased the glycogen level. In addition $G_4$ inhibited the phosphorylation of 34 KD and 118 KD polypeptides induced by $CCl_4$. These protein were more strongly phosphorylated by $Ca^{2+}$/calmodulin-dependent kinase than by C-kinase. Since 34 KD polypeptide was solely phosphorylated by NaF (50mM), an inhibitor of both glycogen syntheses and phosphoprotein phosphates, it is inferred that 3 KD polypeptide is glycogen synthase-likd protein. Because glycogen synthesis is inhibited by phosphorylation of $Ca^{2+}$-dependent glycogen syntheses, it is suggested that $G_4$ increased liver glycogen level by inhibiting phosphorylation of 34 KD polypeptide which is thought to glycogen syntheses-like protein.

• Preventive Nutrition and Food Science
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• 제7권2호
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• pp.113-118
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• 2002

Alpha-lipoic acid is a known hypoglycemic agent that may be useful in the treatment of diabetes. The objective of this study was to investigate the fate of glucose in isolated muscles incubated with lipoic acid by determining its direct effects on specific metabolic and signaling pathways. Soleus muscles from healthy rats were incubated with lipoic acid in the absence or presence of insulin. Glucose transport, glycogen synthesis, glucose oxidation and lipid synthesis were determined and affects on major pathways associated with insulin signaling were evaluated. Glucose transport was not significantly altered by the addition of lipoic acid to the incubation medium. However, lipoic acid decreased glycogen synthesis in comparison to controls. Glucose oxidation was moderately increased while de-novo lipid synthesis from glucose was inhibited. Wortmannin repressed insulin stimulation of glucose incorporation into glycogen, an effect that was augmented by the combined treatment of wortmannin and lipoic acid. Basal and insulin-stimulated serine phosphorylation of Akt was not changed by the addition of lipoic acid to the incubation medium. These data show that in this in vitro model, lipoic acid did not significantly affect glucose uptake but dramatically modified pathways of glucose metabolism within muscle tissue.

• Annals of Clinical Neurophysiology
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• 제16권2호
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• pp.81-85
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• 2014

Primary metabolic myopathy as a type of congenital myopathies was first described by McArdle in 1951. Glycogen storage disease is a disease caused by genetic mutations involved in glycogen synthesis, glycogenolysis or glycolysis. Several types of glycogen storage disease are known to cause metabolic myopathies. We report a case of adult onset metabolic myopathy with glycogen storage.