• Journal of Life Science
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• v.29 no.9
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• pp.964-971
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• 2019

Hepatic lipid accumulation and insulin resistance increases in patients with non-alcoholic fatty liver disease. Piperine is a major compound found in black pepper (Piper nigrum) and long pepper (P. longum). Piperine has been used in fine chemical for its anti-cancer, anti-obesity, anti-diabetic, anti-inflammatory and anti-oxidant properties. However, the signaling-based mechanism of piperine and its role as an inhibitor of lipogenesis and insulin resistance in human hepatocyte cells remains ill-defined. In the present study, we explored the effects of piperine on lipid accumulation and insulin resistance, and explored the potential underlying molecular mechanisms in palmitate-treated HepG2 cells. Piperine treatment resulted in a significant reduction of triglyceride content. Furthermore, piperine treatment decreased palmitate-treated intracellular lipid deposition by inhibiting the lipogenic target genes, sterol-regulatory-element-binding protein 1c (SREBP-1c) and fatty acid synthase (FAS); whereas the expression of carnitine palmitoyl transferase (CPT-1) and phosphorylation of acetyl coenzyme A carboxylase (ACC) gene involved in fatty acid oxidation was increased. Moreover, piperine also inhibited the phosphorylation of insulin receptor substrate (IRS)-1 (Ser307). Piperine treatment modulated palmitate-treated lipid accumulation and insulin resistance in HepG2 cells with concomitant reduction of lipogenic target genes, such as SREBP-1 and FAS, and induction of CPT-1-ACC and phosphorylation of IRS-1 (Tyr632)-Akt pathways. Therefore, piperine represents a promising treatment for the prevention of lipid accumulation and insulin resistance.

• BMB Reports
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• v.54 no.6
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• pp.323-328
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• 2021

Periodontal diseases have been reported to have a multidirectional association with metabolic disorders. We sought to investigate the correlation between periodontitis and diabetes or fatty liver disease using HFD-fed obese mice inoculated with P. gingivalis. Body weight, alveolar bone loss, serological biochemistry, and glucose level were determined to evaluate the pathophysiology of periodontitis and diabetes. For the evaluation of fatty liver disease, hepatic nonalcoholic steatohepatitis (NASH) was assessed by scoring steatosis, inflammation, hepatocyte ballooning and the crucial signaling pathways involved in liver metabolism were analyzed. The C-reactive protein (CRP) level and NASH score in P. gingivalis-infected obese mice were significantly elevated. Particularly, the extensive lobular inflammation was observed in the liver of obese mice infected with P. gingivalis. Moreover, the expression of metabolic regulatory factors, including peroxisome proliferator-activated receptor γ (Pparγ) and the fatty acid transporter Cd36, was up-regulated in the liver of P. gingivalis-infected obese mice. However, inoculation of P. gingivalis had no significant influence on glucose homeostasis, insulin resistance, and hepatic mTOR/AMPK signaling. In conclusion, our results indicate that P. gingivalis can induce the progression of fatty liver disease in HFD-fed mice through the upregulation of CD36-PPARγ axis.

• Journal of Ginseng Research
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• v.35 no.3
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• pp.308-314
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• 2011

In the present study, we investigate anti-diabetic effect of pectinase-processed ginseng radix (GINST) in high fat diet-fed ICR mice. The ICR mice were divided into three groups: regular diet group, high fat diet control group (HFD), and GINSTtreated group. To induce hyperglycemia, mice were fed a high fat diet for 10 weeks, and mice were administered with 300 mg/kg of GINST once a day for 5 weeks. Oral glucose tolerance test revealed that GINST improved glucose tolerance after glucose challenge. Compared to the HFD control group, fasting blood glucose and insulin levels were decreased by 57.8% (p<0.05) and 30.9% (p<0.01) in GINST-treated group, respectively. With decreased plasma glucose and insulin levels, the insulin resistance index of the GINST-treated group was reduced by 68.1% (p<0.01) compared to the HFD control group. Pancreas of GINST-treated mice preserved a morphological integrity of islets and consequently having more insulin contents. In addition, GINST up-regulated the levels of phosphorylated AMP-activated protein kinase (AMPK) and its target molecule, glucose transporter 4 (GLUT4) protein expression in the skeletal muscle. Our results suggest that GINST ameliorates a hyperglycemia through activation of AMPK/GLUT4 signaling pathway, and has a therapeutic potential for type 2 diabetes.

• The Korea Journal of Herbology
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• v.30 no.2
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• pp.11-18
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• 2015

Objectives : Polygoni Multiflori Radix (Jeokhasuo in Korean) is a Oriental traditional herbs widely used in East Asian countries. Overconsumption of fructose results in hypertension, dyslipidemia, obesity and impaired glucose tolerance which have documented as a risk of cardiovascular diseases. This experimental study was designed to investigate the beneficial effects of an ethanol extract from Polygoni Multiflori Radix (PMR) in high-fructose (HF) diet-induced metabolic syndrome rat model. Methods : Sprague-Dawley (SD) rats were divided into three groups; Control group, receiving regular diet and tap water, HF group, and HF + PMR group both receiving supplemented with 65% fructose (n=10), respectively. The HF + PMR group initially received HF diet with PMR (100 mg/kg/day) for 8 weeks. Results : PMR significantly prevented the metabolic disturbances such as hyperlipidemia, hypertension and impaired glucose tolerance. Chronic treatment with PMR significantly decreased body weight, fat weight and adipocyte size, suggesting a role of anti-obesity effect. PMR led to improve the hyperlipidemia through the increase in HDL cholesterol level as well as the decrease in triglyceride and LDL cholesterol level. In addition, PMR suppressed adhesion molecules and endothelin-1 (ET-1) expression in aorta resulting in the decrease of hypertension. In muscle tissue, PMR significantly recovered the HF-induced insulin resistance through increase of insulin receptor substrate-1 (IRS-1), p-$AMPK{\alpha}1/2$, and p-Akt expression. PMR improved HF-induced metabolic disorders and its action was caused by energy metabolism-mediated insulin signaling activation. Conclusions : These results demonstrate that PMR may be a beneficial therapeutic for metabolic syndrome through the improvement of hyperlipidemia, obesity, insulin resistance and hypertension.

• 한국체육학회지인문사회과학편
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• v.54 no.2
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• pp.431-439
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• 2015

The purpose of this study was to investigate the effects of resistance exercise training and high-protein diet on anabolic factors and insulin resistance of skeletal muscle in sarcopenic obese rats. 50wks of male Sprague-Dawley rats were randomly assigned for 4 groups(Chow, HP, Ex, HPEx) after 6 weeks of high-rat diet induced obesity period. The 8-week of ladder climbing exercise significantly reduced body fat and insulin resistance, significantly increased mTOR activity. However hind limb muscles weight were not changed. When treat with exercise and high-protein diet, body fat and insulin resistance did not improve, but rather the effect of exercise training appeared to be inhibited. Therefore high protein diet for improving the sarcopenic obesity may be need more study about the amount and composition of protein.

• The Korean Journal of Physiology and Pharmacology
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• v.20 no.6
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• pp.649-655
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• 2016

TonEBP belongs to the Rel family of transcription factors and plays important roles in inflammation as well as kidney homeostasis. Recent studies suggest that TonEBP expression is also involved in differentiation of several cell types such as myocytes, chondrocytes, and osteocytes. In this study, we investigated the roles of TonEBP during adipocyte differentiation in 3T3-L1 cells. TonEBP mRNA and protein expression was dramatically reduced during adipocyte differentiation. Sustained expression of TonEBP using an adenovirus suppressed the formation of lipid droplets as well as the expression of FABP4, a marker of differentiated adipocytes. TonEBP also inhibited the expression of $PPAR{\gamma}$, a known master regulator of adipocytes. RNAi-mediated knock down of TonEBP promoted adipocyte differentiation. However, overexpression of TonEBP did not affect adipogenesis after the initiation of differentiation. Furthermore, TonEBP expression suppressed mitotic clonal expansion and insulin signaling, which are required early for adipocyte differentiation of 3T3-L1 cells. These results suggest that TonEBP may be an important regulatory factor in the early phase of adipocyte differentiation.

• Journal of Nutrition and Health
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• v.55 no.1
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• pp.70-84
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• 2022

Purpose: Skeletal muscles display significant heterogeneity in metabolic responses, owing to the composition of metabolically distinct fiber types. Recently, numerous studies have reported that in skeletal muscles, suppression of genes related to fatty acid channeling alters the triacylglycerol (TAG) synthesis and switches the energy substrates. However, such responses may differ, depending on the type of muscle fiber. Hence, we conducted in vitro and animal studies to compare the metabolic responses of different types of skeletal muscle fibers to the deficiency of fatty acyl-CoA synthetase (Acsl)6, one of the main fatty acid-activating enzymes. Methods: Differentiated skeletal myotubes were transfected with selected Acsl6 short interfering RNA (siRNA), and C57BL/6J mice were subjected to siRNA to induce Acsl6 deficiency. TAG accumulation and expression levels of insulin signaling proteins in response to acute glucose supplementation were measured in immortalized cell-based skeletal myotubes, oxidative muscles (OM), and glycolytic muscles (GM) derived from the animals. Results: Under conditions of high glucose supplementation, suppression of the Acsl6 gene resulted in decreased TAG and glycogen synthesis in the C2C12 skeletal myotubes. The expression of Glut4, a glucose transporter, was similarly downregulated. In the animal study, the level of TAG accumulation in OM was higher than levels determined in GM. However, a similar decrease in TAG accumulation was obtained in the two muscle types in response to Acsl6 suppression. Moreover, Acsl6 suppression enhanced the phosphorylation of insulin signaling proteins (Foxo-1, mTORc-1) only in GM, while no such changes were observed in OM. In addition, the induction ratio of phosphorylated proteins in response to glucose or Acsl6 suppression was significantly higher in GM than in OM. Conclusion: The results of this study demonstrate that Acsl6 differentially regulates the energy metabolism of skeletal muscles in response to glucose supplementation, thereby indicating that the fiber type or fiber composition of mixed muscles may skew the results of metabolic studies.

• Journal of Physiology & Pathology in Korean Medicine
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• v.28 no.5
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• pp.486-493
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• 2014

Adipocytes are endocrine cells that release bioactive mediators called adipokines. In condition of obesity characterized by low-grade chronic inflammation, adipocytes release inflammatory adipokines, which is related to insulin resistance. Bojungchiseub-tang (BJCST) has been used in symptoms and signs of edema, dampness-phlegm, kidney failure, and so on in Korean medicine. BJCST is also expected to have anti-obesity activities. In the present study, we examined whether BJCST modulate the production of inflammatory adipokines and the activations of the mitogen-activated protein kinases (MAPK) signaling pathway related to induce adipocyte inflammation to elucidate the effects and its mechanism of BJCST on lowering the content of inflammatory adipokines in 3T3-L1 adipocytes. As a result, BJCST suppressed the production of proinflammatory cytokines, tumor necrosis factor (TNF) $-{\alpha}$, interleukin (IL) $-1{\beta}$, IL-6, interferon (IFN) -${\gamma}$, granulocyte-macrophage colony-stimulating factor (GM-CSF), monocyte chemoattractant protein-1 (MCP-1), and the production of other inflammatory mediators, prostaglandin $E_2(PGE_2)$ and nitric oxide(NO)viadownregulationofcyclooxygenase-2(COX-2)andinducible NO synthase (iNOS) gene expressions. In addition, BJCST decreased the phosphorylation of MAPK that promotes the production of inflammatory adipokines in 3T3-L1 mature adipocytes. In conclusion, BJCST could regulate the production of inflammatory adipokines and MAPK signaling pathway related to induction of adipose inflammation.

• Asian-Australasian Journal of Animal Sciences
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• v.20 no.7
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• pp.1030-1038
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• 2007

Results on localization of growth hormone receptor (GHR), interaction of growth hormone (GH) with receptor in buffalo adipose tissue and identification of activated signaling molecules in the action of GH are presented. Bovine GH (bGH) was labeled with fluorescein or biotin. Fluorescein-labelled bGH was used for localization of GHRs in buffalo adipocytes. The receptors were present on the cell surface. The affinity of binding of GH to its receptor was determined by designing an experiment in which buffalo adipose tissue explants, biotinylated GH and streptavidin-peroxidase conjugate were employed. The affinity constant was calculated to be $2{\times}10^8M^{-1}$. The receptor density on adipose tissue was found to be 1 femto mole per mg of tissue. Signalling molecules generated in the action of GH were tentatively identified by employing Western blot and enhanced chemiluminescence techniques using anti-phosphotyrosine antibody. Based on molecular weights of proteins reactive to anti-phosphotyrosine antibody, three signaling molecules viz. insulin receptor substrate, Janus activated kinase (Jak) and mitogen activated protein were tentatively identified. These signaling molecules appeared in a time (incubation time of explants with growth hormone) dependent way. The activation of Jak2 was confirmed by employing anti-Jak2 antibody in a Western blot. The activation of Jak2 occurred during 5 min incubation of buffalo adipose tissue explants with GH and incubation for an additional period, viz. 30 min. or 60 min., resulted in a drastic reduction in activation. The results suggest that Jak2 activation is an early event in the action of GH in buffalo adipose tissue.

• The Korean Journal of Physiology and Pharmacology
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• v.24 no.5
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• pp.423-431
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• 2020

This study aimed to evaluate the effect of curcumin on brain hypoxic-ischemic (HI) damage in neonatal rats and whether the phosphoinositide 3-kinase (PI3K)/Akt/vascular endothelial growth factor (VEGF) signaling pathway is involved. Brain HI damage models were established in neonatal rats, which received the following treatments: curcumin by intraperitoneal injection before injury, insulin-like growth factor 1 (IGF-1) by subcutaneous injection after injury, and VEGF by intracerebroventricular injection after injury. This was followed by neurological evaluation, hemodynamic measurements, histopathological assessment, TUNEL assay, flow cytometry, and western blotting to assess the expression of p-PI3K, PI3K, p-Akt, Akt, and VEGF. Compared with rats that underwent sham operation, rats with brain HI damage showed remarkably increased neurological deficits, reduced right blood flow volume, elevated blood viscosity and haematocrit, and aggravated cell damage and apoptosis; these injuries were significantly improved by curcumin pretreatment. Meanwhile, brain HI damage induced the overexpression of p-PI3K, p-Akt, and VEGF, while curcumin pretreatment inhibited the expression of these proteins. In addition, IGF-1 treatment rescued the curcumin-induced down-regulated expression of p-PI3K, p-Akt, and VEGF, and VEGF overexpression counteracted the inhibitory effect of curcumin on brain HI damage. Overall, pretreatment with curcumin protected against brain HI damage by targeting VEGF via the PI3K/Akt signaling pathway in neonatal rats.