Phosphoenolpyruvate Carboxykinase mRNA Research Articles

Dietary Bile Acid Supplementation Could Regulate the Glucose, Lipid Metabolism, and Microbiota of Common Carp (Cyprinus carpio L.) Fed with a High-Lipid Diet.

This study sought to examine the role of bile acids in the regulation of glucose and lipid metabolism, intestinal flora, and growth in high-fat diet-fed common carp (Cyprinus carpio L.). Fish (6.34 ± 0.07 g) were fed for 56 days with three different diets, the control diet (CO, 5.4% lipid), high-fat diet (HF, 11% lipid), and high-fat diet with 60 mg/kg bile acids (BAs, 11% lipid). The results showed that high-fat diets resulted in poor growth performance and increased triglyceride (TG) in serum and the liver. The addition of bile acids significantly alleviated the adverse effects of a high-fat diet. The mRNA expression results indicated that bile acids may improve lipid metabolism through the enhancement of the peroxisome proliferator-activated receptor (PPARa). The expression of gluconeogenesis-related phosphoenolpyruvate carboxykinase (PEPCK) mRNA was inhibited, while fibroblast growth factor 19 (FGF19) was significantly higher. Bile acids reshaped the intestinal microflora community, with the level of Bacteroidetes increasing. The correlation analysis indicated that Patescibacteria, Dependentiae, Myxococcota, and Planctomycetota in the gut are associated with genes involved in glucose and lipid metabolism. These results indicated that bile acids could ameliorate the negative effects of high-fat diets on common carp.

Urtica dioica (Gazaneh) distillate restores glucose metabolism in diabetic rats.

Diabetes has become an important health problem in the world. Natural agents, with antidiabetic property, are potential candidates for improving diabetes. Urtica Dioica Distillate (UDD) or Araghe Gazaneh is widely used for the treatment of diabetes as per traditional medicine. Despite the tremendous use of UDD as an antidiabetic compound in folk medicine, the antidiabetic effects of UDD has been neglected by medical scientists. In this study, we aimed to evaluate the effects of UDD on the glucose metabolism in diabetic rats. A total of 24 male rats were divided equally into four groups, two treatment and two control groups, each containing normal or Streptozotocin (STZ)-induced diabetic rats. During 4 weeks, control and treatment rats received water or UDD, respectively. Fasting blood sugar (FBS), HbA1c, serum creatinine, blood urea nitrogen, and specific activities of hepatic enzymes including glucokinase (GK), hexokinase (HK), glucose-6-phosphate dehydrogenase (G6PD), and muscle glucose transporter type 4 (GLUT4) and liver phosphoenolpyruvate carboxykinase (PEPCK) mRNA levels were measured. FBS and HbA1c increased in diabetic groups. Treatment with UDD significantly lowered FBS and prevented weight loss. Decreased FBS level was associated with higher activity levels of GK and HK in UDD-treated diabetic rats. G6PD-specific activity decreased in diabetic control rats compared to nondiabetic ones, but UDD treatment improved it to the normal levels. A significant decrease in the expression level of GLUT4 was observed in diabetic control rats compared to nondiabetic ones, but UDD increased it to the normal levels. These findings suggest that UDD might exert therapeutic effects against diabetes by improving glucose metabolism and can be used as an alternative or complementary medicine for the treatment of diabetic patients.

Alterations of the expression levels of glucose, inflammation, and iron metabolism related miRNAs and their target genes in the hypothalamus of STZ-induced rat diabetes model

BackgroundThe hypothalamus of the central nervous system is implicated in the development of diabetes due to its glucose-sensing function. Dysregulation of the hypothalamic glucose-sensing neurons leads to abnormal glucose metabolism. It has been described that fractalkine (FKN) is involved in the development of hypothalamic inflammation, which may be one of the underlying causes of a diabetic condition. Moreover, iron may play a role in the pathogenesis of diabetes via the regulation of hepcidin, the iron regulatory hormone synthesis. MicroRNAs (miRNAs) are short non-coding molecules working as key regulators of gene expression, usually by inhibiting translation. Hypothalamic miRNAs are supposed to have a role in the control of energy balance by acting as regulators of hypothalamic glucose metabolism via influencing translation.MethodsUsing a miRNA array, we analysed the expression of diabetes, inflammation, and iron metabolism related miRNAs in the hypothalamus of a streptozotocin-induced rat type 1 diabetes model. Determination of the effect of miRNAs altered by STZ treatment on the target genes was carried out at protein level.ResultsWe found 18 miRNAs with altered expression levels in the hypothalamus of the STZ-treated animals, which act as the regulators of mRNAs involved in glucose metabolism, pro-inflammatory cytokine synthesis, and iron homeostasis suggesting a link between these processes in diabetes. The alterations in the expression level of these miRNAs could modify hypothalamic glucose sensing, tolerance, uptake, and phosphorylation by affecting the stability of hexokinase-2, insulin receptor, leptin receptor, glucokinase, GLUT4, insulin-like growth factor receptor 1, and phosphoenolpyruvate carboxykinase mRNA molecules. Additional miRNAs were found to be altered resulting in the elevation of FKN protein. The miRNA, mRNA, and protein analyses of the diabetic hypothalamus revealed that the iron import, export, and iron storage were all influenced by miRNAs suggesting the disturbance of hypothalamic iron homeostasis.ConclusionIt can be supposed that glucose metabolism, inflammation, and iron homeostasis of the hypothalamus are linked via the altered expression of common miRNAs as well as the increased expression of FKN, which contribute to the imbalance of energy homeostasis, the synthesis of pro-inflammatory cytokines, and the iron accumulation of the hypothalamus. The results raise the possibility that FKN could be a potential target of new therapies targeting both inflammation and iron disturbances in diabetic conditions.Graphical

Targeting IRE1α and PERK in the endoplasmic reticulum stress pathway attenuates fatty acid-induced insulin resistance in bovine hepatocytes

Endoplasmic reticulum (ER) stress can be induced by various stimuli and triggers the unfolded protein response to activate intracellular signaling pathways that are mediated by 3 ER-resident sensors: inositol requiring protein-1α (IRE1α), PKR-like ER kinase (PERK), and activating transcription factor-6 (ATF6). In nonruminants, ER stress plays a critical role in hepatic insulin resistance. However, whether ER stress plays a role in nonesterified fatty acid (NEFA)-induced hepatic insulin resistance in dairy cows is still unknown. Experiments were conducted using primary bovine hepatocytes isolated from 5 healthy calves (body weight: 30-40 kg; 1 d old). First, hepatocytes were treated with NEFA (1.2 mM) for 0.5, 1, 2, 3, 5, 7, 9, or 12 h. Treatment with NEFA elevated abundance of phosphorylated IRE1α and PERK, and cleavage of ATF6, along with the ER stress-associated genes XBP1, ATF4, and DNAJC3, resulting in both linear and quadratic effects. Furthermore, ER Tracker red staining and transmission electron microscopy results indicated that ER was dilated and degranulated in response to NEFA treatment, suggesting that ER stress was induced by NEFA treatment in bovine hepatocytes. Second, to assess the effect of ER stress on NEFA-induced insulin resistance, hepatocytes were treated with different concentrations of NEFA (0, 0.6, 1.2, or 2.4 mM) for 5 h with or without tauroursodeoxycholic acid (TUDCA, a canonical inhibitor of ER stress). Here, NEFA induced insulin resistance by increasing the abundance of insulin receptor substrate-1 (IRS1) phosphorylation at the inhibitory residue Ser 307 (S307) and decreasing the abundance of phosphorylated protein kinase B (AKT) and glycogen synthase kinase-3β (GSK3β) in a dose-dependent manner. This was accompanied by upregulation of an abundance of gluconeogenic genes [phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6-Pase)]. These detrimental effects of NEFA on insulin signaling could be reversed with TUDCA treatment, indicating a mechanistic link between ER stress and NEFA-induced insulin resistance. In a third experiment, pGPU6/GFP/Neo vectors containing short hairpin RNA targeting IRE1α were used to silence IRE1α transcription, and GSK2656157 (PERK phosphorylation inhibitor) and 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF; an inhibitor of ATF6) were used to block PERK and ATF6 branches, respectively. Notably, the silencing of the IRE1α branch improved NEFA-induced insulin resistance by decreasing phosphorylation of IRS1 (S307) and increasing phosphorylation of AKT and GSK3β, and reducing PEPCK and G6-Pase mRNA abundance, which was likely dependent on IRE1α kinase activity. Similarly, blockage of the PERK branch increased phosphorylation of AKT and GSK3β, and reduced PEPCK and G6-Pase mRNA abundance, but had no effect on phosphorylation of IRS1 (S307). However, results showed that inhibition of the ATF6 branch had no effects on phosphorylation of IRS1, AKT, and GSK3β, and instead found increasing PEPCK and G6-Pase mRNA abundance. Taken together, data in the present study found that impeding IRE1α and PERK signaling might aid in relieving hepatic insulin resistance. However, the more detailed mechanisms of how IRE1α and PERK signaling contribute to hepatic insulin resistance in dairy cows remain to be determined.

Reduced insulin signaling and high glucagon in early insulin resistance impaired fast-fed regulation of renal gluconeogenesis via insulin receptor substrate.

Gluconeogenesis is one of the key processes through which the kidney contributes to glucose homeostasis. Urinary exosomes (uE) have been used to study renal gene regulation noninvasively in humans and rodents. Recently, we demonstrated fast-fed regulation of phosphoenolpyruvate carboxykinase (PEPCK), the rate-limiting enzyme for gluconeogenesis, in human uE. The regulation was impaired in subjects with early insulin resistance. Here, we studied primary human proximal tubule cells (hPT) and human uE to elucidate a potential link between insulin resistance and fast-fed regulation of renal PEPCK. We demonstrate that fasted hPTs had higher PEPCK and insulin receptor substrate-2 (IRS2) mRNA and protein levels, relative to fed cells. The fast-fed regulation was, however, attenuated in insulin receptor knockdown (IRKO) hPTs. The IRKO was confirmed by the blunted insulin-induced response on PEPCK, PGC1α, p-IR, and p-AKT expression in IRKO cells. Exosomes secreted by the wild-type or IRKO hPT showed similar regulation to the respective hPT. Similarly, in human uE, the relative abundance of IRS-2 mRNA (to IRS1) was higher in the fasted state relative to the fed condition. However, the fast-fed difference was absent in subjects with early insulin resistance. These subjects had higher circulating glucagon levels relative to subjects with optimal insulin sensitivity. Furthermore, in hPT cells, glucagon significantly induced PEPCK and IRS2 gene, and gluconeogenesis. IR knockdown in hPT cells further increased the gene expression levels. Together the data suggest that reduced insulin sensitivity and high glucagon in early insulin resistance may impair renal gluconeogenesis via IRS2 regulation.

Cyclocarya paliurus triterpenoids suppress hepatic gluconeogenesis via AMPK-mediated cAMP/PKA/CREB pathway

BackgroundAbnormal enhancement of hepatic gluconeogenesis is a vital mechanism of the pathogenesis of Type 2 diabetes mellitus (T2DM); thus, its suppression may present an efficient therapeutic strategy for T2DM. Cyclocarya paliurus (CP), a plant species native to China, has been reported to have anti-hyperglycemia activity. Our previous studies have revealed that Cyclocarya paliurus triterpenic acids (CPT) exert the favorable glucose-lowering activity, but the regulatory effect of CPT on hepatic gluconeogenesis is still unclarified. PurposeThis study aimed to investigate the potential role and mechanism of CPT in gluconeogenesis. Study designIn this study, the ameliorative effect and underlying mechanism of CPT on gluconeogenesis were investigated: high-fat diet and streptozotocin-induced T2DM mice and glucagon-challenged mouse primary hepatocytes. MethodsT2DM model mice with or without oral administration of CPT for 4 weeks were monitored for body weight, glucose and lipid metabolism. Hematoxylin and eosin staining was used to observe liver lipid deposition. Real-time PCR assays were performed to examine the mRNA expression of glucose-6-phosphate (G6Pase), and phosphoenolpyruvate carboxykinase (PEPCK), two key enzymes involved in liver gluconeogenesis. Western blotting was used to determine AMP-dependent protein kinase (AMPK) expression and induction of the glucagon signaling pathway. The possible mechanism of CPT on liver gluconeogenesis was further explored in glucagon-induced mouse primary hepatocytes. ResultsIn vivo and in vitro experiments revealed that CPT treatment significantly reduced fasting blood glucose, total cholesterol and triglyceride levels, and improved insulin resistance. Furthermore, CPT could obviously decreased the mRNA and protein expression of G6Pase and PEPCK, the cyclic AMP content, the phosphorylation level of protein kinase A and cyclic AMP response element-binding protein. But CPT promoted the phosphorylation of AMP-dependent protein kinase (AMPK) and activation of phosphodiesterase 4B. Mechanistically, intervention with Compound C (an AMPK inhibitor) partially blocked the suppressive effect of CPT on hepatic gluconeogenesis. ConclusionThese findings suggested that CPT may inhibit hepatic gluconeogenesis against T2DM by activating AMPK.

Renal gluconeogenesis induction by glucagon and insulin receptor deletion in humans

Gluconeogenesis is one of the key processes through which the kidney contributes to glucose homeostasis. Recently, we provided evidence to suggest that early insulin resistance may impair fast‐fed regulation of Phosphoenolpyruvate Carboxykinase (PEPCK), rate‐limiting enzyme for gluconeogenesis in humans. To confirm this and to elucidate a link between insulin resistance and fast‐fed regulation of PEPCK in the kidneys, we studied primary proximal tubule cells (hPT) and urinary extracellular vesicles (uEVs) from humans. We demonstrate that fasted hPTs had higher PEPCK and insulin receptor substrate‐2 (IRS2) mRNA levels than fed cells. The fast‐fed regulation was, however, attenuated in insulin receptor knockdown hPTs (IRKO). The insulin receptor knockdown was confirmed by a blunted insulin‐induced suppression in PEPCK and PGC1α mRNA and p‐IR and p‐AKT protein expression in IRKO cells. Exosomes secreted by the wild‐type or IRKO hPT showed similar regulation as observed in the respective hPT. Similarly, in human uE, the relative abundance of IRS‐2 mRNA (to IRS1) was higher in the fasted state relative to the fed condition. However, the fast‐fed difference was absent in subjects with early insulin resistance. These subjects had higher circulating glucagon levels relative to subjects with optimal insulin sensitivity. Furthermore, in hPT cells, glucagon significantly induced PEPCK mRNA, IRS2 mRNA, and gluconeogenesis. Insulin receptor deletion further increased their levels. Together the data suggest that reduced insulin sensitivity and high glucagon in early insulin resistance may impair renal gluconeogenesis via IRS2 regulation. Funding from ICMR‐CARE and SGPGI intramural to ST and CSIR to RS.

Posttranscriptional regulation of glutamate dehydrogenase 2 and phosphoenolpyruvate carboxykinase in Komagataella phaffii.

The yeast Komagataella phaffii (a.k.a. Pichia pastoris) harbours a unique glutamate utilization pathway in which the cytosolic enzymes glutamate dehydrogenase 2 (GDH2), aspartate aminotransferase 2 (AAT2) and phosphoenolpyruvate carboxykinase (PEPCK) catalyze the sequential conversion of glutamate to α-ketoglutarate, oxaloacetate and phosphoenolpyruvate respectively. GDH2 and PEPCK are essential for glutamate catabolism. Their synthesis is induced by autophagy during carbon starvation and are essential for cell survival. Here, we demonstrate that GDH2 and PEPCK reciprocally regulate each other's protein levels during glutamate catabolism such that GDH2 is downregulated in Δpepck and PEPCK is downregulated in Δgdh2. We further demonstrate that sequential conversion of glutamate to α-ketoglutarate and oxaloacetate by GDH2 and AAT2, respectively, is essential for PEPCK synthesis in cells metabolizing glutamate. Our studies indicate that translation of GDH2 mRNA is induced by glutamate while oxaloacetate derived from glutamate is likely to be the inducer of PEPCK mRNA translation during glutamate catabolism. Thus, GDH2- and PEPCK-catalyzed reactions are essential for ATP generation and gluconeogenesis respectively during carbon starvation and glutamate catabolism in K. phaffii. We conclude that K. phaffii harbours a unique translational regulatory circuit in which substrates of GDH2 and PEPCK act as inducers of their synthesis, a phenomenon not reported in any yeast species.

Carbon starvation-induced synthesis of GDH2 and PEPCK is essential for the survival of Pichia pastoris

The industrial yeast Pichia pastoris can utilize amino acids as the sole source of carbon. It possesses a post-transcriptional regulatory circuit that governs the synthesis of cytosolic glutamate dehydrogenase 2 (GDH2) and phosphoenolpyruvate carboxykinase (PEPCK), key enzymes of amino acid catabolism. Here, we demonstrate that the post-transcriptional regulatory circuit is activated during carbon starvation resulting in the translation of GDH2 and PEPCK mRNAs. GDH2 and PEPCK synthesis is abrogated in Δatg1 indicating a key role for autophagy or an autophagy-related process. Finally, carbon-starved Δgdh2 and Δpepck exhibit poor survival. This study demonstrates a key role for amino acid catabolism during carbon starvation, a phenomenon hitherto unreported in other yeast species.

Interactions of dietary carbohydrate and vitamin D3 on growth performance, insulin signaling pathway and glucose metabolism in juvenile abalone Haliotis discus hannai

A 115-day feeding trial was conducted to investigate the effect of dietary carbohydrate and vitamin D3 levels, and their interactions on growth performance, body composition, insulin signaling pathway and glucose metabolism in juvenile abalone Haliotis discus hannai (initial body weight: 2.06 ± 0.01 g). Nine experimental diets in a 3 × 3 two-factor design were formulated with different carbohydrate levels (27.5%, 32% and 36.5%) and vitamin D3 levels (0, 1000 IU/kg and 5000 IU/kg). Results showed that the highest specific growth rate (SGR) of abalone was observed in the treatment with 36.5% of dietary carbohydrate and 1000 IU/kg of vitamin D3. The serum glucose, body crude lipid and muscle glycogen contents of abalone significantly increased with increasing dietary carbohydrate levels (P < 0.05). Diet with 1000 IU/kg of vitamin D3 significantly reduced the serum glucose and body crude lipid content (P < 0.05). Significant interactions between dietary carbohydrate and vitamin D3 were observed in SGR and crude lipid content (P < 0.05). Diet with 36.5% carbohydrate up-regulated the expression of pyruvate kinase, glucose-6-phosphate dehydrogenase (G6PDH), insulin receptor (IR), insulin receptor substrate (IRS), protein kinase B (Akt), glycogen synthase and glycogen phosphorylase (PYG), whereas decreased the phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6P) and glycogen synthesis kinase-3β. Diet with 1000 IU/kg of vitamin D3 significantly up-regulated the hexokinase, IR, IRS, Akt and glucose transporter 1 mRNA levels, whereas decreased the G6PDH (P < 0.05). The interaction between dietary carbohydrate and vitamin D3 were significant on PEPCK, G6P, G6PDH and PYG mRNA levels (P < 0.05). In conclusion, dietary carbohydrates and vitamin D3 could affect glucose metabolism by regulating glycolysis, gluconeogenesis and pentose phosphate pathway in abalone. Besides, they triggered the insulin signaling pathway, and further influence glucose transport and glycogen synthesis, which could promote the utilization of carbohydrate in abalone.

Phosphoenolpyruvate Carboxykinase (PCK) in the Brain Gluconeogenic Pathway Contributes to Oxidative and Lactic Injury After Stroke.

To demonstrate the role of the rate-limiting and ATP-dependent gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PCK) in oxidative and lactic stress and the effect of phenothiazine on PCK after stroke, a total of 168 adult male Sprague Dawley rats (3months old, 280-300g) underwent 2-h intraluminal middle cerebral artery occlusion (MCAO) and reperfusion for 6, 24, 48h, or 7days. Phenothiazine (chlorpromazine and promethazine (C+P)) (8mg/kg) and 3-mercaptopicolinic acid (3-MPA, a PCK inhibitor, 100μM) were administered at reperfusion onset. The effects of phosphoenolpyruvate, 3-MPA, or PCK knockdown were studied in neuronal cultures subjected to oxygen/glucose deprivation. Reactive oxygen species, lactate, phosphoenolpyruvate (PEP; a gluconeogenic product), mRNA, and protein of total PCK, PCK-1, and PCK-2 increased after MCAO and oxygen-glucose deprivation (OGD). Oxaloacetate (a gluconeogenic substrate) decreased, while PEP and glucose were increased, suggesting reactive gluconeogenesis. These changes were attenuated by phenothiazine, 3-MPA, or PCK shRNA. PCK-1 and -2 existed primarily in neurons, while the effects of ischemic stroke on the PCK expression were seen predominately in astrocytes. Thus, phenothiazine reduced infarction and oxidative/lactic stress by inhibiting PCKs, leading to functional recovery.

Resveratrol attenuates dapagliflozin-induced renal gluconeogenesis via activating the PI3K/Akt pathway and suppressing the FoxO1 pathway in type 2 diabetes.

Dapagliflozin alleviates hyperglycemia by increasing glycosuria, but it induces renal gluconeogenesis, thus neutralizing its efficacy. Resveratrol (Rsv), a natural polyphenolic chemical, improves insulin sensitivity in type 2 diabetes (T2D). Here, we investigated the regulatory effects and underlying mechanisms of Rsv on dapagliflozin-induced renal gluconeogenesis. Male ob/ob mice were given the vehicle (HF), dapagliflozin (1 mg kg-1), Rsv (10 mg kg-1), or dapagliflozin and Rsv combination for 10 weeks. Glucose metabolism was evaluated by glucose and pyruvate tolerance tests. HK-2 cells (human renal proximal tubule cells) were treated with dapagliflozin (1 μmol L-1) for 2 h and further incubated with Rsv (10 μmol L-1) for 12 h. The effects of Rsv on gluconeogenesis and insulin signaling were assessed. Dapagliflozin treatment increased glucose production in HK-2 cells and lowered blood glucose and induced gluconeogenesis in ob/ob mice. After Rsv treatment, the enhanced glucose production and gluconeogenesis were alleviated. The upregulated mRNA and protein expression of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) and the activation of the forkhead transcription factor O1 (FoxO1) protein in the dapagliflozin group were attenuated by Rsv administration. Rsv also improved renal insulin signaling by increasing PI3K and Akt phosphorylation. The PI3K inhibitor LY294002 dramatically decreased the p-Akt expression and activated FoxO1 by dephosphorylation, thus diminishing the inhibitory effects of Rsv on dapagliflozin-induced PEPCK and G6Pase expression. The data showed the mechanisms of Rsv in attenuating dapagliflozin-induced renal gluconeogenesis via activating the PI3K/Akt pathway and further suppressing FoxO1 activation, suggesting a potential intervention to achieve better glucose-lowering effects for SGLT2 inhibitors in T2D therapy.

Melatonin stimulates transcription of the rat phosphoenolpyruvate carboxykinase gene in hepatic cells.

Melatonin plays physiological roles in various critical processes, including circadian rhythms, oxidative stress defenses, anti-inflammation responses, and immunity; however, the current understanding of the role of melatonin in hepatic glucose metabolism is limited. In this study, we examined whether melatonin affects gene expression of the key gluconeogenic enzyme, phosphoenolpyruvate carboxykinase (PEPCK). We found that melatonin treatment increased PEPCK mRNA levels in rat highly differentiated hepatoma (H4IIE) cells and primary cultured hepatocytes. In addition, we found that melatonin induction was synergistically enhanced by dexamethasone, whereas it was dominantly inhibited by insulin. We also report that the effect of melatonin was blocked by inhibitors of mitogen-activated protein kinase/extracellular signal-regulated protein kinase (MAPK/ERK), RNA polymerase II, and protein synthesis. Furthermore, the phosphorylated (active) forms of ERK1 and ERK2 (ERK1/2) increased 15min after melatonin treatment. We performed luciferase reporter assays to show that melatonin specifically stimulated promoter activity of the PEPCK gene. Additional reporter analysis using 5'-deleted constructs revealed that the regulatory regions responsive to melatonin mapped to two nucleotide regions, one between -467 and -398 nucleotides and the other between -128 and +69 nucleotides, of the rat PEPCK gene. Thus, we conclude that melatonin induces PEPCK gene expression via the ERK1/2 pathway at the transcriptional level, and that induction requires denovo protein synthesis.

Culture salinity alters dietary protein requirement, whole body composition and nutrients metabolism related genes expression in juvenile Genetically Improved Farmed Tilapia (GIFT) (Oreochromis niloticus)

An 8-week experimental trial was designed to explore the effects of dietary protein level (DPL) and salinity on the growth performance and physiological parameters of genetically improved farmed tilapia (GIFT) juveniles (Oreochromis niloticus). Six diets were formulated with different dietary protein levels (18.20%, 24.32%, 30.60%, 36.42%, 43.27% and 49.49%) and two salinity levels (0and 8‰) in a 6 × 2 factorial design. 720GIFT juveniles (initial weight 3.25 g) were distributed into 36 plastic tanks (180 L) and fed each of the diets four times daily to satiation. The results suggested that the growth performance was increased significantly with increasing DPLs up to a certain level (36.42%) in freshwater and brackish water. The whole-body lipid content of the fish decreased significantly with increasing salinity, while the protein content increased (P < 0.05). However, the protein content increased significantly and the lipid, moisture and ash contents were not significantly affected by the increase in DPL. With the increasing DPL at two salinities, the expression levels of hepatic insulin-like growth factor-1 increased significantly, reaching a maximum at 36.42% DPL. With the increasing DPL at the two salinity levels, the expression level of oligopeptide transporter 2 mRNA significantly decreased (P < 0.05). The target of rapamycin, 4E binding protein 1, ribosomal protein S6 and oligopeptide transporter 1β mRNA levels were not significantly affected by the DPL, but they increased significantly with an increase in salinity (P < 0.05). Regarding glucolipid metabolism, glycogen synthase, glucokinase and glucose transporter 2 mRNA levels decreased with an increase in DPL (P < 0.05). The fatty acid synthase and glucokinase mRNA levels decreased with an increase in salinity, while glycogen synthase and glucose transporter 2 mRNA levels increased (P < 0.05). The phosphoenolpyruvate carboxykinase mRNA level was not significantly affected by the DPL, but it increased with increasing salinity (P < 0.05). For the feed conversion ratio and weight gain rate, the broken-line model analysis showed that the optimal protein requirements at 8‰ salinity were higher than those at 0‰ salinity and the protein requirement were 37.70%, 37.86% (8‰) and 33.70%, 38.21% (0‰), respectively. GIFT juveniles exhibited improved glycogen synthesis at 8‰ salinity and fat deposition at 0‰ salinity.

Berberine reduces gut-vascular barrier permeability via modulation of ApoM/S1P pathway in a model of polymicrobial sepsis

AimsThe hyperpermeability of gut-vascular barrier (GVB) plays a role in gut-derived sepsis. The goal of this study was to evaluate if berberine might improve hepatic apolipoprotein M (ApoM) generation and raise plasma ApoM level to protect the compromised GVB. Materials and methodsThe compromised GVB was induced by sepsis. Hepatic ApoM mRNA and phosphoenolpyruvate carboxykinase (PEPCK) mRNA and plasma ApoM level were assayed by qRT-PCR and ELISA, respectively. The permeability of intestinal capillary in vivo and of rat intestinal microvascular endothelial cells (RIMECs) in vitro was assayed by FITC-dextran. The blood glucose was detected by a glucometer. Plasma insulin, TNF-α and IL-1β were assayed by ELISA. The plasmalemma vesicle-associated protein-1 (PV1), β-catenin and occludin in RIMECs were assayed by Western blot. Key findingsSepsis decreased hepatic ApoM mRNA and plasma ApoM level, but raised hepatic PEPCK mRNA and plasma glucose, insulin, TNF-α, and IL-1β levels. The increased vascular endothelial permeability was abrogated by recombinant rat ApoM in vivo or ApoM-bound S1P in vitro. ApoM-bound S1P decreased PV1 but increased occludin and β-catenin expression in LPS-treated RIMECs. Berberine in a dose-dependent manner raised hepatic ApoM mRNA and plasma ApoM level, but decreased septic hyperglycemia, insulin resistance and plasma TNF-α and IL-1β levels. Berberine reduced sepsis-induced PEPCK and TLR4 mRNA overexpression in the liver. SignificanceThis study demonstrated berberine inhibited TLR4-mediated hyperglycemia, insulin resistance and proinflammatory molecule production, thereby increasing ApoM gene expression and plasma ApoM. Berberine protected the damaged GVB via modulation of ApoM/S1P pathway.

Pretreatment with saturated and unsaturated fatty acids regulates fatty acid oxidation in Madin-Darby bovine kidney cells

Metabolic fates of fatty acids in tissue may be influenced by extracellular concentration and profile of fatty acids. Previous work has demonstrated the ability of C18:3n-3 cis to ameliorate the effects of C16:0- or C18:0-induced depression of pyruvate carboxylase (PC) mRNA expression. Pyruvate carboxylase catalyzes oxaloacetate synthesis and connects gluconeogenesis from lactate and fatty acid metabolism. Our objective was to determine the effects of co-presence of saturated and unsaturated fatty acids on cellular partitioning of [1-14C]C16:0 metabolism to CO2 or acid-soluble products (ASP) in Madin-Darby bovine kidney cells and the role of PC in this relationship. We hypothesized that the ratio of saturated to unsaturated fatty acid pretreatments regulates [1-14C]C16:0 partitioning to CO2 or ASP. Cells were exposed for 21 h to either individual fatty acids, C16:0, C18:0, C18:1n-9 cis, or C18:3n-3 cis, or to fatty acid combinations in 10:90, 25:75, 50:50, 75:25, or 90:10 ratios for 3 combinations: C16:0/C18:3n-3 cis, C18:0/C18:3n-3 cis, or C18:1n-9 cis/C18:3n-3 cis. Total fatty acid concentration was 1.0 mM during the 21-h pretreatment phase. Following the 21-h incubation phase with fatty acid combinations, cells were incubated in the presence of 1.0 mM [1-14C]C16:0 for 3 h to determine the rate of metabolism to CO2 and ASP collection (per µg DNA-1·h-1). Pretreatment with either C16:0 or C18:0 alone significantly depressed subsequent oxidation of [1-14C]C16:0 to ASP by 62.7 and 41.2%, respectively, compared with C18:3n-3 cis pretreatment. Similar patterns were observed for [1-14C]C16:0 oxidation to CO2. Expression of PC mRNA was significantly decreased with exposure to either C16:0 or C18:0 compared with expression after exposure to either C18:3n-3 cis or control 1% BSA in Dulbecco's modified Eagle's medium. Expression of cytosolic phosphoenolpyruvate carboxykinase (PCK1) mRNA followed a similar pattern. Fatty acid treatments containing C18:1n-9 cis did not alter PC or PCK1 expression from control or C18:3n-3 cis results. Pearson coefficient correlations were determined for PC mRNA expression and rate of [1-14C]C16:0 metabolism to CO2 or ASP, including ketones, and for PCK1 mRNA expression and rate of [1-14C]C16:0 metabolism to CO2 or ASP. Production of CO2 from [1-14C]C16:0 was positively correlated (r = 0.63) with PC expression, whereas ASP production from [1-14C]C16:0 only tended to positively correlate (r = 0.51) with PC mRNA expression. Production of CO2 or ASP from [1-14C]C16:0 were both positively correlated (r = 0.80 and r = 0.69, respectively) with PCK1 expression. Results show a regulation of ketone production by Madin-Darby bovine kidney cells in response to saturated and unsaturated fatty acid pretreatments.

Myricitrin Ameliorates Hyperglycemia, Glucose Intolerance, Hepatic Steatosis, and Inflammation in High-Fat Diet/Streptozotocin-Induced Diabetic Mice.

To test the hypothesis that myricitrin (MYR) improves type 2 diabetes, we examined the effect of MYR on hyperglycemia, glucose intolerance, hepatic steatosis, and inflammation in high-fat diet (HFD) and streptozotocin (STZ)-induced type 2 diabetic mice. Male C57BL/6J mice were randomly divided into three groups: non-diabetic, diabetic control, and MYR (0.005%, w/w)-supplemented diabetic groups. Diabetes was induced by HFD and STZ, and MYR was administered orally for 5 weeks. Myricitrin exerted no significant effects on food intake, body weight, fat weight, or plasma lipids levels. However, MYR significantly decreased fasting blood glucose levels, improved glucose intolerance, and increased pancreatic β-cell mass compared to the diabetic control group. Myricitrin administration also markedly increased glucokinase mRNA expression and activity as well as lowered glucose-6-phosphatase and phosphoenolpyruvate carboxykinase mRNA expression and activity in the liver. In addition, liver weight, hepatic triglyceride content, and lipid droplet accumulation were markedly decreased following MYR administration. These changes were seemingly attributable to the suppression of the hepatic lipogenic enzymes—fatty acid synthase and phosphatidate phosphohydrolase. Myricitrin also significantly lowered plasma MCP-1 and TNF-α levels and the mRNA expression of hepatic pro-inflammatory genes. These results suggest that MYR has anti-diabetic potential.

Kampo medicines, Rokumigan, Hachimijiogan, and Goshajinkigan, significantly inhibit glucagon-induced CREB activation

The pathophysiology of type 2 diabetes mellitus (T2DM) is characterized by not only insulin resistance, but also the abnormal regulation of glucagon secretion, suggesting that antagonizing the glucagon-induced signaling pathway has therapeutic potential in the treatment of T2DM. Although various Kampo medicines (traditional herbal medicines) are often utilized to ameliorate the symptoms of T2DM, their effects on glucagon signaling have not yet been clarified. In the present study, we examined the effects of nine types of representative Kampo formulations prescribed for T2DM on glucagon-induced CREB activation in HEK293T cells stably expressing glucagon receptor (Gcgr) and a hepatic cell line HepG2. Among these Kampo medicines, Rokumigan, Hachimijiogan, and Goshajinkigan significantly suppressed the glucagon-induced transactivation of the cAMP-responsive element (CRE)-binding protein (CREB) by inhibiting its interaction with CREB-binding protein (CBP), which led to a reduction in the expression of phosphoenolpyruvate carboxykinase (PEPCK) mRNA. Furthermore, among the crude drugs commonly contained in these three Kampo medicines, Rehmannia Root (Jio), Moutan Bark (Botampi), and Cornus Fruit (Shanzhuyu) exerted inhibitory effects on glucagon-induced CREB activation. Collectively, the present results provide a novel mechanism, the inhibition of glucagon signaling, by which Rokumigan, Hachimijiogan, and Goshajinkigan improve the symptoms of T2DM.

Reactive oxygen species-dependent regulation of pyruvate dehydrogenase kinase-4 in white adipose tissue.

Reactive oxygen species (ROS) are important signaling molecules mediating the exercise-induced adaptations in skeletal muscle. Acute exercise also drives the expression of genes involved in reesterification and glyceroneogenesis in white adipose tissue (WAT), but whether ROS play any role in this effect has not been explored. We speculated that exercise-induced ROS would regulate acute exercise-induced responses in WAT. To address this question, we utilized various models to alter redox signaling in WAT. We examined basal and exercise-induced gene expression in a genetically modified mouse model of reduced mitochondrial ROS emission [mitochondrial catalase overexpression (MCAT)]. Additionally, H2O2, various antioxidants, and the β3-adrenergic receptor agonist CL316243 were used to assess gene expression in white adipose tissue culture. MCAT mice have reduced ROS emission from WAT, enlarged WAT depots and adipocytes, and greater pyruvate dehydrogenase kinase-4 (Pdk4) gene expression. In WAT culture, H2O2 reduced glyceroneogenic gene expression. In wild-type mice, acute exercise induced dramatic but transient increases in Pdk4 and phosphoenolpyruvate carboxykinase (Pck1) mRNA in both subcutaneous inguinal WAT and epididymal WAT depots, which was almost completely absent in MCAT mice. Furthermore, the induction of Pdk4 and Pck1 in WAT culture by CL316243 was markedly reduced in the presence of antioxidants N-acetyl-cysteine or vitamin E. Genetic and nutritional approaches that attenuate redox signaling prevent exercise- and β-agonist-induced gene expression within WAT. Combined, these data suggest that ROS represent important mediators of gene expression within WAT.

Oral Phenelzine Treatment Mitigates Metabolic Disturbances in Mice Fed a High-Fat Diet.

Novel mechanisms and health benefits have been recently suggested for the antidepressant drug phenelzine (PHE), known as a nonselective monoamine oxidase inhibitor. They include an antilipogenic action that could have an impact on excessive fat accumulation and obesity-related metabolic alterations. We evaluated the metabolic effects of an oral PHE treatment on mice fed a high-fat diet (HFD). Eleven-week-old male C57BL/6 mice were fed a HFD and either a 0.028% PHE solution (HFD + PHE) or water to drink for 11 weeks. PHE attenuated the increase in body weight and adiposity without affecting food consumption. Energy efficiency was lower in HFD + PHE mice. Lipid content was reduced in subcutaneous fat pads, liver, and skeletal muscle. In white adipose tissue (WAT), PHE reduced sterol regulatory element-binding protein-1c and phosphoenolpyruvate carboxykinase mRNA levels, inhibited amine-induced lipogenesis, and did not increase lipolysis. Moreover, HFD + PHE mice presented diminished levels of hydrogen peroxide release in subcutaneous WAT and reduced expression of leukocyte transmigration markers and proinflammatory cytokines in visceral WAT and liver. PHE reduced the circulating levels of glycerol, triacylglycerols, high-density lipoprotein cholesterol, and insulin. Insulin resistance was reduced, without affecting glucose levels and glucose tolerance. In contrast, PHE increased rectal temperature and slightly increased energy expenditure. The mitigation of HFD-induced metabolic disturbances points toward a promising role for PHE in obesity treatment and encourages further research on its mechanisms of action. SIGNIFICANCE STATEMENT: Phenelzine reduces body fat, markers of oxidative stress, inflammation, and insulin resistance in high-fat diet mice. Semicarbazide-sensitive amine oxidase, monoamine oxidase, phosphoenolpyruvate carboxykinase, and sterol regulatory element-binding protein-1c are involved in the metabolic effects of phenelzine. Phenelzine could be potentially used for the treatment of obesity-related complications.