Gluconeogenic enzyme PCK1 supports S-adenosylmethionine biosynthesis and promotes H3K9me3 modification to suppress hepatocellular carcinoma progression.

Deciphering the crosstalk between metabolic reprogramming and epigenetic regulation is a promising strategy for cancer therapy. In this study, we discovered that the gluconeogenic enzyme PCK1 fueled the generation of S-adenosylmethionine (SAM) through the serine synthesis pathway. The methyltransferase SUV39H1 catalyzed SAM, which served as a methyl donor to support H3K9me3 modification, leading to the suppression of the oncogene S100A11. Mechanistically, PCK1 deficiency-induced oncogenic activation of S100A11 was due to its interaction with AKT1, which upregulated PI3K/AKT signaling. Intriguingly, the progression of hepatocellular carcinoma (HCC) driven by PCK1 deficiency was suppressed by SAM supplement or S100A11 KO in vivo and in vitro. These findings reveal the availability of the key metabolite SAM as a bridge connecting the gluconeogenic enzyme PCK1 and H3K9 trimethylation in attenuating HCC progression, thus suggesting a potential therapeutic strategy against HCC.

Growth hormone promotes hepatic gluconeogenesis by enhancing BTG2-YY1 signaling pathway.

Growth hormone (GH) is one of the critical factors in maintaining glucose metabolism. B-cell translocation gene 2 (BTG2) and yin yang 1 (YY1) are key regulators of diverse metabolic processes. In this study, we investigated the link between GH and BTG2-YY1 signaling pathway in glucose metabolism. GH treatment elevated the expression of hepatic Btg2 and Yy1 in primary mouse hepatocytes and mouse livers. Glucose production in primary mouse hepatocytes and serum blood glucose levels were increased during GH exposure. Overexpression of hepatic Btg2 and Yy1 induced key gluconeogenic enzymes phosphoenolpyruvate carboxykinase 1 (PCK1) and glucose-6 phosphatase (G6PC) as well as glucose production in primary mouse hepatocytes, whereas this phenomenon was markedly diminished by knockdown of Btg2 and Yy1. Here, we identified the YY1-binding site on the Pck1 and G6pc gene promoters using reporter assays and point mutation analysis. The regulation of hepatic gluconeogenic genes induced by GH treatment was clearly linked with YY1 recruitment on gluconeogenic gene promoters. Overall, this study demonstrates that BTG2 and YY1 are novel regulators of GH-dependent regulation of hepatic gluconeogenic genes and glucose production. BTG2 and YY1 may be crucial therapeutic targets to intervene in metabolic dysfunction in response to the GH-dependent signaling pathway.

Crocins from Crocus sativus L. in the Management of Hyperglycemia. In Vivo Evidence from Zebrafish.

Diabetes mellitus is a disease characterized by persistent high blood glucose levels and accompanied by impaired metabolic pathways. In this study, we used zebrafish to investigate the effect of crocins isolated from Crocus sativus L., on the control of glucose levels and pancreatic ß-cells. Embryos were exposed to an aqueous solution of crocins and whole embryo glucose levels were measured at 48 h post-treatment. We showed that the application of crocins reduces zebrafish embryo glucose levels and enhances insulin expression. We also examined whether crocins are implicated in the metabolic pathway of gluconeogenesis. We showed that following a single application of crocins and glucose level reduction, the expression of phosphoenolpyruvate carboxykinase1 (pck1), a key gene involved in glucose metabolism, is increased. We propose a putative role for the crocins in glucose metabolism and insulin management.

Effect of feeding type 2 diabetes mellitus rats with synbiotic yogurt sweetened with monk fruit extract on serum lipid levels and hepatic AMPK (5' adenosine monophosphate-activated protein kinase) signaling pathway.

Monk fruit extract (MFE) is a natural sweetener that has been used as an ingredient of food and pharmaceutical products. The effects of feeding synbiotic yogurt fortified with MFE to rats with type 2 diabetes induced by high-fat diet and streptozotocin on serum lipid levels and hepatic AMPK signaling pathway were evaluated. Results showed that oral administration of the synbiotic yogurt fortified with MFE could improve serum lipid levels, respiratory exchange rate, and heat level in type 2 diabetic rats. Transcriptome analysis showed that synbiotic yogurt fortified with MFE may affect the expression of genes involved in binding, catalytic activity, and transporter activity. The Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that these differentially expressed genes were related to AMPK signaling pathway, linoleic acid metabolism, and α-linolenic acid metabolism. Western blotting confirmed that synbiotic yogurt fortified with MFE could activate AMPK signaling and improve the protein level of the hepatic gluconeogenic enzyme G6Pase in diabetic rats. The results indicated that MFE could be a novel sweetener for functional yogurt and related products.

Impact of adrenomedullin blockage on lipid metabolism in female mice exposed to high-fat diet.

PURPOSE: Adrenomedullin (ADM) levels are elevated in gestational and type 2 diabetic patients. ADM also stimulates lipolysis in vitro. Disturbed lipid metabolism has been implicated in the pathogenesis of diabetes. Here, we explore whether blockade of ADM is beneficial for metabolic homeostasis in a diabetic mouse model. METHODS: C57BL/6J female mice were placed on either a control or a high fat high sucrose (HFHS) diet for 8 weeks. At week 4, osmotic mini-pumps were implanted for constant infusion of either saline or ADM antagonist, ADM22-52. Glucose tolerance tests were performed prior to infusion and 4 weeks after infusion began. Animals were then sacrificed and visceral adipose tissue collected for further analysis. RESULTS: Mice fed HFHS displayed glucose intolerance, increased mRNA expressions in VAT for Adm and its receptor components, Crlr. HFHS fed mice also had increased basal and isoprenaline-induced glycerol release by VAT explants. ADM22-52 did not significantly affect glucose intolerance. ADM22-52 did suppress basal and isoprenaline-induced glycerol release by VAT explants. This alteration was associated with enhanced mRNA expression of insulin signaling factors Insr and Glut4, and adipogenic factor Pck1. CONCLUSIONS: HFHS diet induces glucose intolerance and enhances ADM and its receptor expressions in VAT in female mice. ADM22-52 treatment did not affect glucose intolerance in HFHS mice, but reduced both basal and isoprenaline-induced lipolysis, which is associated with enhanced expression of genes involved in adipogenesis. These results warrant further research on the effects of ADM blockade in improving lipid homeostasis in diabetic patients.

PROTECTIVE EFFECT OF CAMEL MILK AS ANTI-DIABETIC SUPPLEMENT: BIOCHEMICAL, MOLECULAR AND IMMUNOHISTOCHEMICAL STUDY.

BACKGROUND: Diabetes is a serious disease affects human health. Diabetes in advanced stages is accompanied by general weakness and alteration in fats and carbohydrates metabolism. Recently there are some scientific trends about the usage of camel milk (CM) in the treatment of diabetes and its associated alterations. CM contains vital active particles with insulin like action that cure diabetes and its complications but how these effects occur, still unclear. MATERIALS AND METHODS: Seventy-five adult male rats of the albino type divided into five equal groups. Group 1 served as a negative control (C). Group 2 was supplemented with camel milk (CM). Diabetes was induced in the remaining groups (3, 4 and 5). Group 3 served as positive diabetic control (D). Group 4 served as diabetic and administered metformin (D+MET). Group 5 served as diabetes and supplemented with camel milk (D+CM). Camel milk was supplemented for two consecutive months. Serum glucose, leptin, insulin, liver, kidney, antioxidants, MDA and lipid profiles were assayed. Tissues from liver and adipose tissues were examined using RT-PCR analysis for the changes in mRNA expression of genes of carbohydrates and lipid metabolism. Pancreas and liver were used for immunohistochemical examination using specific antibodies. RESULTS: Camel milk supplementation ameliorated serum biochemical measurements that altered after diabetes induction. CM supplementation up-regulated mRNA expression of IRS-2, PK, and FASN genes, while down-regulated the expression of CPT-1 to control mRNA expression level. CM did not affect the expression of PEPCK gene. On the other hand, metformin failed to reduce the expression of CPT-1 compared to camel milk administered rats. Immunohistochemical findings revealed that CM administration restored the immunostaining reactivity of insulin and GLUT-4 in the pancreas of diabetic rats. CONCLUSION: CM administration is of medical importance and helps physicians in the treatment of diabetes mellitus.

The odd-carbon medium-chain fatty triglyceride triheptanoin does not reduce hepatic steatosis.

BACKGROUND & AIMS: Non-alcoholic fatty-liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome. Previously, we showed that a high-protein diet minimized diet-induced development of fatty liver and even reversed pre-existing steatosis. A high-protein diet leads to amino-acid catabolism, which in turn causes anaplerosis of the tricarboxylic-acid (TCA) cycle. Therefore, we hypothesized that anaplerosis of the TCA cycle could be responsible for the high-protein diet-induced improvement of NAFLD by channeling amino acids into the TCA cycle. Next we considered that an efficient anaplerotic agent, the odd-carbon medium-chain triglyceride triheptanoin (TH), might have similar beneficial effects. METHODS: C57BL/6J mice were fed low-fat (8en%) or high-fat (42en%) oleate-containing diets with or without 15en% TH for 3 weeks. RESULTS: TH treatment enhanced the hepatic capacity for fatty-acid oxidation by a selective increase in hepatic Ppara, Acox, and Cd36 expression, and a decline in plasma acetyl-carnitines. It also induced pyruvate cycling through an increased hepatic PCK1 protein concentration and it increased thermogenesis reflected by an increased Ucp2 mRNA content. TH, however, did not reduce hepatic lipid content. CONCLUSION: The comparison of the present effects of dietary triheptanoin with a previous study by our group on protein supplementation shows that the beneficial effects of the high-protein diet are not mimicked by TH. This argues against anaplerosis as the sole explanatory mechanism for the anti-steatotic effect of a high-protein diet.

Two Alkaloids from Bulbs of Lycoris sanguinea MAXIM. Suppress PEPCK Expression by Inhibiting the Phosphorylation of CREB.

In the fasting state, gluconeogenesis is upregulated by glucagon. Glucagon stimulates cyclic adenosine monophosphate production, which induces the expression of key enzymes for gluconeogenesis, such as cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C), which are involved in gluconeogenesis through the protein kinase A/cAMP response element-binding protein (CREB) pathway. Using a luciferase reporter gene assay, a methanol extract of the bulbs of Lycoris sanguinea MAXIM. var. kiushiana Makino was found to suppress cAMP-enhanced PEPCK-C promoter activity. In addition, two alkaloids, lycoricidine and lycoricidinol, in the extract were identified as active constituents. In forskolin-stimulated human hepatoma cells, these alkaloids suppressed the expression of a reporter gene under the control of cAMP response element and also prevented increases in the endogenous levels of phosphorylated CREB and PEPCK mRNA expression. These results suggest that lycoricidine and lycoricidinol suppress PEPCK-C expression by inhibiting the phosphorylation of CREB and may thus have the potential to prevent excessive gluconeogenesis in type 2 diabetes. Copyright © 2016 John Wiley & Sons, Ltd.

Gentiopicroside and sweroside from Veratrilla baillonii Franch. induce phosphorylation of Akt and suppress Pck1 expression in hepatoma cells.

The use of phytochemicals and herbal medicines has accompanied human history. Advances in modern biomedical sciences have allowed us to investigate the functional mechanisms of herbal medicines and phytochemicals. Veratrilla baillonii Franch. has long been used as a medicinal herb in southwestern China. Here, we analyzed the effects of an ethanol extract from V. baillonii (VBFE) on the expression levels of the cytosolic form of the phosphoenolpyruvate carboxykinase gene (Pck1) mRNA and components of the insulin signalling cascade in HL1C hepatoma cells. Compared with the insulin control, VBFE treatment inhibited the expression of Pck1 mRNA in a dose-dependent manner. This was associated with the phosphorylation of Akt and Erk1/2 in a time-dependent manner. Further analysis of the purified components of VBFE indicated that gentiopicroside and sweroside from VBFE, alone and in combination, suppressed Pck1 expression and induced Akt and Erk1/2 phosphorylation. In conclusion, gentiopicroside and sweroside suppress Pck1 expression and induce phosphorylation of components in the insulin signalling cascade. This is the first study to demonstrate that gentiopicroside and sweroside show insulin-mimicking effects on the regulation of Pck1 expression. Further studies are warranted to explore the potential of gentiopicroside and sweroside in the control of blood glucose in animals.

Immunometabolic Status during the Peripartum Period Is Enhanced with Supplemental Zn, Mn, and Cu from Amino Acid Complexes and Co from Co Glucoheptonate.

The peripartum (or transition) period is the most-critical phase in the productive life of lactating dairy cows and optimal supply of trace minerals through more bioavailable forms could minimize the negative effects associated with this phase. Twenty Holstein cows received a common prepartal diet and postpartal diet. Both diets were partially supplemented with an inorganic (INO) mix of Zn, Mn, and Cu to supply 35, 45, and 6 ppm, respectively, of the diet dry matter (DM). Cows were assigned to treatments in a randomized completed block design, receiving an daily oral bolus with INO or organic trace minerals (AAC) Zn, Mn, Cu, and Co to achieve 75, 65, 11, and 1 ppm supplemental, respectively, in the diet DM. Liver tissue and blood samples were collected throughout the experiment. The lower glutamic-oxaloacetic transaminase concentration after 15 days in milk in AAC cows indicate lower hepatic cell damage. The concentration of cholesterol and albumin increased, while IL-6 decreased over time in AAC cows compared with INO indicating a lower degree of inflammation and better liver function. Although the acute-phase protein ceruloplasmin tended to be lower in AAC cows and corresponded with the reduction in the inflammatory status, the tendency for greater serum amyloid A concentration in AAC indicated an inconsistent response on acute-phase proteins. Oxygen radical absorbance capacity increased over time in AAC cows. Furthermore, the concentrations of nitric oxide, nitrite, nitrate, and the ferric reducing ability of plasma decreased with AAC indicating a lower oxidative stress status. The expression of IL10 and ALB in liver tissue was greater overall in AAC cows reinforcing the anti-inflammatory response detected in plasma. The greater overall expression of PCK1 in AAC cows indicated a greater gluconeogenic capacity, and partly explained the greater milk production response over time. Overall, feeding organic trace minerals as complexed with amino acids during the transition period improved liver function and decreased inflammation and oxidative stress.

Combretum lanceolatum flowers ethanol extract inhibits hepatic gluconeogenesis: an in vivo mechanism study.

Context Ethnopharmacological studies have demonstrated that plants of the Combretum genus presented antidiabetic activity, including Combretum lanceolatum Pohl ex Eichler (Combretaceae). Objective This study investigated the hepatic mechanisms of action of C. lanceolatum flowers ethanol extract (ClEtOH) related to its antihyperglycaemic effect in streptozotocin-diabetic rats. Materials and methods Male Wistar rats were divided into normal (N) and diabetic control (DC) rats treated with vehicle (water); diabetic rats treated with 500 mg/kg metformin (DMet) or 500 mg/kg ClEtOH (DT500). After 21 d of treatment, hepatic glucose and urea production were investigated through in situ perfused liver with l-glutamine. Changes in the phosphoenolpyruvate carboxykinase (PEPCK) levels and in the activation of adenosine monophosphate-activated protein kinase (AMPK) and insulin-signalling intermediates were also investigated. Results Similar to DMet, DT500 rats showed a reduction in the rates of hepatic production of glucose (46%) and urea (22%) in comparison with DC. This reduction was accompanied by a reduction in the PEPCK levels in liver of DT500 (28%) and DMet (43%) when compared with DC. AMPK phosphorylation levels were higher in the liver of DT500 (17%) and DMet (16%) rats. The basal AKT phosphorylation levels were increased in liver of DT500 rats, without differences in the insulin-stimulated AKT phosphorylation and in the insulin receptor levels between DC and DT500 rats. Discussion and conclusion The antidiabetic activity of ClEtOH can be attributed, at least in part, to inhibition of hepatic gluconeogenesis, probably due to the activation of both AMPK and AKT effectors and reduction in the PEPCK levels.

Dietary carbohydrate and lipid source affect cholesterol metabolism of European sea bass (Dicentrarchus labrax) juveniles.

Plant feedstuffs (PF) are rich in carbohydrates, which may interact with lipid metabolism. Thus, when considering dietary replacement of fishery by-products with PF, knowledge is needed on how dietary lipid source (LS) and carbohydrates affect lipid metabolism and other metabolic pathways. For that purpose, a 73-d growth trial was performed with European sea bass juveniles (IBW 74 g) fed four diets differing in LS (fish oil (FO) or a blend of vegetable oils (VO)) and carbohydrate content (0 % (CH-) or 20 % (CH+) gelatinised starch). At the end of the trial no differences among diets were observed on growth and feed utilisation. Protein efficiency ratio was, however, higher in the CH+ groups. Muscle and liver fatty acid profiles reflected the dietary LS. Dietary carbohydrate promoted higher plasma cholesterol and phospholipids (PL), whole-body and hepatic (mainly 16 : 0) lipids and increased muscular and hepatic glycogen. Except for PL, which were higher in the FO groups, no major alterations between FO and VO groups were observed on plasma metabolites (glucose, TAG, cholesterol, PL), liver and muscle glycogen, and lipid and cholesterol contents. Activities of glucose-6-phosphate dehydrogenase and malic enzyme - lipogenesis-related enzymes - increased with carbohydrate intake. Hepatic expression of genes involved in cholesterol metabolism was up-regulated with carbohydrate (HMGCR and CYP3A27) and VO (HMGCR and CYP51A1) intake. No dietary regulation of long-chain PUFA biosynthesis at the transcriptional level was observed. Overall, very few interactions between dietary carbohydrates and LS were observed. However, important insights on the direct relation between dietary carbohydrate and the cholesterol biosynthetic pathway in European sea bass were demonstrated.

Effect of sorghum grain supplementation on glucose metabolism in cattle and sheep fed temperate pasture.

The aim of this work was to evaluate the effect of sorghum grain supplementation on plasma glucose, insulin and glucagon concentrations, and hepatic mRNA concentrations of insulin receptor (INSR), pyruvate carboxylase (PC), and phosphoenolpyruvate carboxykinase (PCK1) mRNA and their association with nutrient intake, digestion and rumen volatile fatty acids (VFA) in cattle and sheep fed a fresh temperate pasture. Twelve Hereford × Aberdeen Angus heifers and 12 Corriedale × Milchschaf wethers in positive energy balance were assigned within each species to one of two treatments (n = 6 per treatment within specie): non-supplemented or supplemented with sorghum grain at 15 g/kg of their body weight (BW). Supplemented cattle had greater plasma glucose concentrations, decreased plasma glucagon concentrations and tended to have greater plasma insulin and insulin-to-glucagon ratio than non-supplemented ones. Hepatic expression of INSR and PC mRNA did not differ between treatments but PCK1 mRNA was less in supplemented than non-supplemented cattle. Supplemented sheep tended to have greater plasma glucagon concentrations than non-supplemented ones. Plasma glucose, insulin, insulin-to-glucagon ratio, and hepatic expression of INSR and PC mRNA did not differ between treatments, but PCK1 mRNA was less in supplemented than non-supplemented sheep. The inclusion of sorghum grain in the diet decreased PCK1 mRNA but did not affect PC mRNA in both species; these effects were associated with changes in glucose and endocrine profiles in cattle but not in sheep. Results would suggest that sorghum grain supplementation of animals in positive energy balance (cattle and sheep) fed a fresh temperate pasture would modify hepatic metabolism to prioritize the use of propionate as a gluconeogenic precursor.

Changes in glucose metabolism and reversion of genes expression in the liver of insulin-resistant rats exposed to malathion. The protective effects of N-acetylcysteine.

Organophosphorus pesticides are known to disturb glucose homeostasis and increase incidence of metabolic disorders and diabetes via insulin resistance. The current study investigates the influence of malathion on insulin signaling pathways and the protective effects of N-acetylcysteine (NAC). Malathion (200 mg/kg) and NAC (2 g/l) were administered orally to rats, during 28 consecutive days. Malathion increases plasma glucose, plasma insulin and glycated hemoglobin levels. Further, we observed an increase of insulin resistance biomarkers and a decrease of insulin sensitivity indices. The GP, GSK3ß and PEPCK mRNA expressions were amplified by malathion while, the expression of glucokinase gene is down-regulated. On the basis of biochemical and molecular findings, it is concluded that malathion impairs glucose homeostasis through insulin resistance and insulin signaling pathways disruptions in a way to result in a reduced function of insulin into hepatocytes. Otherwise, when malathion-treated rats were compared to NAC supplemented rats, fasting glucose and insulin levels, as well as insulin resistance indices were reduced. Furthermore, NAC restored liver GP and PEPCK expression. N-acetylcysteine showed therapeutic effects against malathion-induced insulin signaling pathways disruption in liver. These data support the concept that antioxidant therapies attenuate insulin resistance and ameliorate insulin sensitivity.

The caffeoylquinic acid-rich Pandanus tectorius fruit extract increases insulin sensitivity and regulates hepatic glucose and lipid metabolism in diabetic db/db mice.

Caffeoylquinic acids (CQAs) are widely distributed in various foods. While some CQAs have been shown to possess antihyperglycemic activities, whether it is beneficial for diabetes patients to ingest CQA-rich foods has still to be known. In this work, the antihyperglycemic and antihyperlipidemic effects of CQA-rich Pandanus tectorius fruit extract (PTF) was investigated in diabetic db/db mice. Treatment with PTF (200 mg/kg) significantly decreased body weight and fasting glucose level, alleviated hyperinsulinism and hyperlipidemia and declined glucose area under the curve in oral glucose tolerance test and insulin tolerance test. The elevated levels of serum proinflammatory cytokines and islet hypertrophy in db/db mice were remarkably attenuated by PTF treatment. Biochemical analysis showed that administration of PTF significantly stimulated the phosphorylation of AMP-activated protein kinase (AMPK) and Akt substract of 160 kDa (AS160), and enhanced the expression and translocation of glucose transporter type 4 (GLUT4) in skeletal muscles. It also increased the activity of hexokinase, decreased the expression of glucose 6-phosphatase and phosphoenolpyruvate carboxykinase and switched the transcription of several key lipid metabolic genes in the liver, which, in turn, improved hepatic glucose and lipid profiles as determined by nuclear magnetic resonance-based metabolomics. Overall, the CQA-rich PTF is beneficial for the treatment of diabetes. It may alleviate hyperglycemia and dyslipidemia via activation of AMPK-AS160-GLUT4 pathway in skeletal muscles and inhibition of gluconeogenesis and lipogenesis in the liver.

Hypothalamic nesfatin-1/NUCB2 knockdown augments hepatic gluconeogenesis that is correlated with inhibition of mTOR-STAT3 signaling pathway in rats.

Nesfatin-1, an 82-amino acid neuropeptide, has recently been characterized as a potent metabolic regulator. However, the metabolic mechanisms and signaling steps directly associated with the action of nesfatin-1 have not been well delineated. We established a loss-of-function model of hypothalamic nesfatin-1/NUCB2 signaling in rats through an adenoviral-mediated RNA interference. With this model, we found that inhibition of central nesfatin-1/NUCB2 activity markedly increased food intake and hepatic glucose flux and decreased glucose uptake in peripheral tissue in rats fed either a normal chow diet (NCD) or a high-fat diet (HFD). The change of hepatic glucose fluxes in the hypothalamic nesfatin-1/NUCB2 knockdown rats was accompanied by increased hepatic levels of glucose-6-phosphatase and PEPCK and decreased insulin receptor, insulin receptor substrate 1, and AKT kinase phosphorylation. Furthermore, knockdown of hypothalamic nesfatin-1 led to decreased phosphorylation of mammalian target of rapamycin (mTOR) and signal transducer and activator of transcription 3 (STAT3) and the subsequent suppressor of cytokine signaling 3 levels. These results demonstrate that hypothalamic nesfatin-1/NUCB2 plays an important role in glucose homeostasis and hepatic insulin sensitivity, which is, at least in part, associated with the activation of the mTOR-STAT3 signaling pathway.

Antihyperglycemic action of rhodiola-aqeous extract in type1-like diabetic rats.

BACKGROUND: Rhodiola rosea (Rhodiola) is a plant in the Crassulaceae family that grows in cold regions of the world. It is mainly used in clinics as an adaptogen. Recently, it has been mentioned that Rhodiola increases plasma ß-endorphin to lower blood pressure. Thus, the present study aims to investigate the antidiabetic action of Rhodiola in relation to opioids in streptozotocin-induced diabetic rats (STZ-diabetic rats). METHODS: In the present study, the plasma glucose was analyzed with glucose oxidase method, and the determination of plasma ß-endorphin was carried out using a commercially available enzyme-linked immunosorbent assay. The adrenalectomy of STZ-diabetic rats was used to evaluate the role of ß-endorphin. In addition, quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blotting analysis were performed to investigate mRNA and protein expressions. RESULTS: Rhodiola-water extract dose-dependently lowered the plasma glucose in STZ-diabetic rats and this action was reversed by blockade of opioid µ-receptors using cyprodime. An increase of plasma ß-endorphin by rhodiola-water extract was also observed in same manner. The plasma glucose lowering action of rhodiola-water extract was attenuated in bilateral adrenalectomized rats. In addition, continuous administration of rhodiola-water extract for 3 days in STZ-diabetic rats resulted in an increased expression of glucose transporter subtype 4 (GLUT 4) in skeletal muscle and a marked reduction of phosphoenolpyruvate carboxykinase (PEPCK) expression in liver. These effects were also reversed by blockade of opioid µ-receptors. CONCLUSIONS: Taken together, rhodiola-water extract improves hyperglycemia via an increase of ß-endorphin secretion from adrenal gland to activate opioid µ-receptors in STZ-diabetic rats.

Hypothalamic AMPK activation blocks lipopolysaccharide inhibition of glucose production in mice liver.

Endotoxic hypoglycaemia has an important role in the survival rates of septic patients. Previous studies have demonstrated that hypothalamic AMP-activated protein kinase (hyp-AMPK) activity is sufficient to modulate glucose homeostasis. However, the role of hyp-AMPK in hypoglycaemia associated with endotoxemia is unknown. The aims of this study were to examine hyp-AMPK dephosphorylation in lipopolysaccharide (LPS)-treated mice and to determine whether pharmacological hyp-AMPK activation could reduce the effects of endotoxemia on blood glucose levels. LPS-treated mice showed reduced food intake, diminished basal glycemia, increased serum TNF-α and IL-1ß levels and increased hypothalamic p-TAK and TLR4/MyD88 association. These effects were accompanied by hyp-AMPK/ACC dephosphorylation. LPS-treated mice also showed diminished liver expression of PEPCK/G6Pase, reduction in p-FOXO1, p-AMPK, p-STAT3 and p-JNK level and glucose production. Pharmacological hyp-AMPK activation blocked the effects of LPS on the hyp-AMPK phosphorylation, liver PEPCK expression and glucose production. Furthermore, the effects of LPS were TLR4-dependent because hyp-AMPK phosphorylation, liver PEPCK expression and fasting glycemia were not affected in TLR4-mutant mice. These results suggest that hyp-AMPK activity may be an important pharmacological target to control glucose homeostasis during endotoxemia.

Hypoglycemic action of borapetoside A from the plant Tinospora crispa in mice.

AIM: This study explores the hypoglycemic effects of borapetoside A, the most active principle among three major diterpenoids (borapetosides A, B, and C) isolated from ethanol extract of Tinospora crispa vines. METHODS: We employed mouse mitogenic C2C12 and hepatocellular carcinoma Hep3B cells in this study. Furthermore, the mice were divided into three groups, including streptozotocin-induced type 1 diabetes mellitus, diet-induced type 2 diabetes mellitus, and normal control. The mice in each group were treated with assigned vehicle control, borapetoside A, or other active agents. RESULTS: Borapetoside A was shown to increase the glycogen content and decrease the plasma glucose concentration in a concentration or dose-dependent manner in vitro and in vivo. The hypoglycemic effects in the normal mice and the mice with type 2 diabetes mellitus were associated with the increases of the plasma insulin levels; whereas, the insulin levels remained unchanged in the mice with type 1 diabetes mellitus. Borapetoside A not only attenuated the elevation of plasma glucose induced by an intraperitoneal glucose tolerance test, but also increased the glycogen synthesis of IL-6 treated C2C12 cells. Moreover, the elevated protein expression levels of phosphoenolpyruvate carboxykinase were reversed after borapetoside A treatment twice a day for 7 days. CONCLUSIONS: The hypoglycemic effects of borapetoside A were mediated through both the insulin-dependent and the insulin-independent pathways. Furthermore, borapetoside A was shown to increase the glucose utilization in peripheral tissues, to reduce the hepatic gluconeogenesis, and to activate the insulin signaling pathway; they thereby contributed to the lowering of the plasma glucose. Comparison of the structures of three borapetosides suggests clearly that the C-8 stereochemistry plays a key role in hypoglycemic effect since the active borapetoside A and C possess 8R-chirality but the inactive borapetoside B possess 8S-chirality. The location of glycoside at C-3 for borapetoside A but C-6 for borapetoside C and the formation of lactone between C-4 and C-6 for borapetoside A, could account for the different potency in hypoglycemic action for these two compounds.

PKCθ over expression in the central nucleus of the amygdala or hypothalamus has differential effects on energy balance and peripheral glucose homeostasis.

The increase in PKCθ expression in the amygdala of rats fed high fat diet (HFD) has been related to the loss of the anorectic response to insulin injections into the central nucleus of the amygdala (CeA) in these animals. PKCθ overexpression in the CeA increases food intake, body weight and body fat and inhibits insulin stimulation of Akt signaling. To study the effects of bilateral overexpression of PKCθ in the CeA of rats on peripheral metabolism, rats were injected into the CeA or 3rd ventricle with a lentiviral (LV)-PKCθ construct or LV-Green fluorescent protein (GFP) construct as a control and fed either LFD or HFD. Insulin and glucose tolerance tests were undertaken and hepatic AMPK activation, Pepck, Srebp1c gene expression and lipid levels assayed. CeA LV-PKCθ injected rats increased food intake, body weight and body fat and increased hepatic, but not serum, triglyceride levels compared to control rats that received a CeA-LV-GFP construct. Hepatic AMP-kinase activity was reduced but expression of Pepck increased while serum insulin decreased, glucose tolerance improved and the hypoglycemic response to insulin was enhanced in CeA LV-PKCθ injected rats. In contrast, rats that received LV-PKCθ injections into the 3rd Ventricle did not show any changes in food intake or body weight although serum, but not hepatic, triglyceride levels were increased and glucose tolerance was impaired. The data suggest that activation of PKCθ in the CeA and hypothalamus have different effects on energy balance and peripheral metabolism and that insulin signaling in the amygdala regulates peripheral metabolism.