GK Expression Research Articles

Glycerol Kinase Drives Hepatic de novo Lipogenesis and Triglyceride Synthesis in Nonalcoholic Fatty Liver by Activating SREBP-1c Transcription, Upregulating DGAT1/2 Expression, and Promoting Glycerol Metabolism.

Glycerol kinase (GK) participates in triglyceride (TG) synthesis by catalyzing glycerol metabolism. Whether GK contributes to nonalcoholic fatty liver (NAFL) is unclear. The expression of hepatic Gk is found to be increased in diet-induced and genetic mouse models of NAFL and is positively associated with hepatic SREBP-1c expression and TG levels. Cholesterol and fatty acids stimulate GK expression in hepatocytes. In HFD-induced NAFL mice, knockdown of hepatic Gk decreases expression of SREBP-1c and its target lipogenic genes as well as DGAT1/2, increases serum glycerol levels, decreases serum TG levels, and attenuates hepatic TG accumulation. Overexpression of GK in hepatocytes in mice or in culture produces opposite results. Mechanistic studies reveal that GK stimulates SREBP-1c transcription directly by binding to its gene promoter and indirectly by binding to SREBP-1c protein, thereby increasing lipogenic gene expression and de novo lipogenesis. Studies with truncated GK and mutant GKs indicate that GK induces SREBP-1c transcription independently of its enzyme activity. GK contributes to lipid homeostasis under physiological conditions by catalyzing glycerol metabolism rather than by regulating SREBP-1c transcription. Collectively, these results demonstrate that increased hepatic GK promotes de novo lipogenesis and TG synthesis in NAFL by stimulating SREBP-1c transcription and DGAT1/2 expression and catalyzing glycerol metabolism.

γ-aminobutyric acid improves the growth performance, food intake and glucose homeostasis of Micropterus salmoides fed high-carbohydrate diets

This study aimed to assess the function of γ-aminobutyric acid (GABA) on growth performance, food intake and glucose homeostasis of Micropterus salmoides fed carbohydrate (CHO)-enriched diets. The intracerebroventricular glucose + GABA co-injected fish had higher cumulative food intake, and expression of orexigenic genes (ghrelin and neuropeptide y (npy)) in the brain than those of the single glucose-injected group. In the feeding trial, M. salmoides (10.35 ± 0.05 g) were fed four feeds containing a control feed (10 % CHO, C) and three GABA contents [0 (HC), 50 (HC-G1), and 100 (HC-G2) mg kg−1, respectively] of high-CHO feed (20 % CHO) for 12 weeks. High CHO prominently (P < 0.05) decreased WGR, SGR, FI, p-Ampk protein content, and expression of ghrelin, npy, fbpase, pparα, cpt1α and aco1 compared with the control group, but the opposite was true for plasma glucose and triglyceride levels, tissue glycogen and lipid contents, and expression of proopiomelanocortin, leptin a, gk, pk, gs, chrebp, srebp1, fas and acc1. HC-G2 diets prominently (P < 0.05) up-regulated WGR, SGR, FI, p-Ampk protein content, and expression of ghrelin, npy, gk, pk, chrebp, srebp1, fas and acc1 compared with the HC group. Also, HC-G2 diets increased glucose tolerance of M. salmoides fed high-CHO diets after glucose loading. Overall, GABA improved the growth performance, food intake and glucose homeostasis of high-CHO-fed fish by the increase of appetite, glycolysis, glycogenesis and lipolysis, as well as the inhibition of gluconeogenesis and lipid synthesis.

Spirulina versus metformin for controlling some insulin signaling pathway genes in induced polycystic ovary syndrome rat model

Polycystic ovary syndrome (PCOS) is a prevalent endocrinologic and gynecologic disorder that affects women of reproductive age; besides, insulin resistance (IR) occurs in 50–70 % of PCOS cases. Metformin (Met) is commonly prescribed for IR management; however, it does not affect IR with some gastrointestinal symptoms. Spirulina platensis (SP) is a blue-green alga that may increase insulin sensitivity. Therefore, our study aims to evaluate SP as an alternative treatment to Met for improving glucose homeostasis by assessing the expression of 11 crucial genes involved in the insulin signaling pathway. After induction of the PCOS model using dehydroepiandrosterone (DHEA) (60 mg/kg bwt) for 30 consecutive days, rats were allocated into six groups. Relative liver weight, glutamic pyruvic transaminase (GPT) serum levels, glutamic-oxaloacetic transaminase (GOT), and insulin were determined. Furthermore, the gene expression of Ins1, Irs1, Pik3ca, Prkcz, Foxo1, Srebf1, Ppargc1a, Pklr, Gk, G6pc, and Pepck in the rat's liver tissue was determined using qRT-PCR. Treatment of the PCOS control group with Met or SP revealed a decrease in all these parameters compared with the PCOS model. Additionally, we found a statistically significant difference in the expression of both the Gk and Prkcz genes. To summarize our study results, SP or Met supplementation to PCOS rats had almost the same effect on assessed relative liver weight, GOT, GPT, and insulin levels compared with PCOS control rats. If further studies confirm and detect more impact of SP on IR in PCOS, SP could be used instead of Met since the latter causes many side effects.

Adaptation of Chinese perch (Siniperca chuatsi) to different levels of dietary carbohydrates

The objective of the study was to investigate the effects of dietary carbohydrate on growth performance, feed utilization, proximate compositions, and hepatic glucolipid metabolism in Chinese perch. Triplicate groups of Chinese perch (29.51 ± 0.24 g) were fed five isonitrogenous and isolipidic diets containing graded levels of carbohydrate (2.4%, 9.7%, 16.5%, 23.9%, and 30.1%) for 8 weeks. The results based on second-order polynomial regression analysis of specific growth rate (SGR) proved that Chinese perch obtained the best growth performance at the 10.93% dietary carbohydrate level. Compared to 2.4%-carbohydrate group, 9.7%-carbohydrate group exhibited the increase in daily weight gain (DWG) and protein retention ratio (PER) and the decrease in feed conversion efficiency (FCR). Moreover, 9.7%-carbohydrate group showed the increase in the mRNA levels of pfk and cs involved in aerobic oxidation pathway, the content of liver glycogen increased significantly, and no change in glucose level. Above results suggested that a part of carbohydrates may be converted into energy for growth by aerobic oxidation pathway, or converted into glycogen for storage to maintain glucose homeostasis in Chinese perch fed with moderate-carbohydrate diet. Differently, 23.9%-carbohydrate and 30.1%-carbohydrate groups showed the decrease in DWG and PER, and the increase in FCR, compared to 2.4%-carbohydrate group. Additionally, 23.9%-carbohydrate and 30.1%-carbohydrate group presented the increase in the mRNA levels of g6pca and pc involved in gluconeogenesis, which caused the increase in plasma glucose level. However, other plasma indices related to TG-metabolite and its transport (total cholesterol, and low-density lipoprotein) did not show difference, which combined with elevated fatty acid synthesis-related gene accα mRNA level resulted in excessive liver lipid deposition. Above results indicated that unregulated gluconeogenesis and invalid outward transportation of liver TG-rich metabolites may account for the glucose intolerance of Chinese perch fed with carbohydrate-rich diet. Furthermore, compared to the results from the 4th week, the expression of gk, pfk, pc, cs, and accα genes significantly increased in the 30.1%-carbohydrate group at the 8th week. Both liver and muscle exhibited a significant elevation in crude fat content, while Daily DWG experienced a noticeable decrease. These results indicated that the glucose metabolism and growth of Chinese perch in the high-carbohydrate group are influenced by the interaction of feeding duration and carbohydrate levels. And within a certain time frame, Chinese perch can tolerate a diet rich in carbohydrates.

Identification of Isthmin-1 in common carp (Cyprinus carpio L.) and the effects on glucose metabolism in vivo and in vitro.

Isthmin-1 (Ism1) plays roles in glucose uptake in mammals as an adipokine. To investigate its role in the glucose metabolism of common carp (Cyprinus carpio. L), the Ism1 sequence was cloned, and its expression and distribution in tissues were detected. In addition, we prepared and purified the recombinant Ism1 protein using the E. coli expression system and assessed changes in the expression of key genes related to glucose metabolism through both in vivo injection experiments and primary hepatocyte experiments in vitro. The results revealed that the open reading frame of Ism1 was 1377 bp long, encoding 458 amino acids. Similarity analysis indicated that Ism1 exhibited a close evolutionary relationship with goldfish (Carassius auratus), sharing 98.35% amino acid similarity. Ism1 was expressed in all tissues of common carp, with the highest level observed in the heart, followed by the gill, head kidney, and hepatopancreas. Distinct patterns of Ism1 expression were identified during the oral glucose tolerance test and long-term high-carbohydrate and high-fat diet feeding experiments. In vivo studies demonstrated that the serum glucose concentration was reduced on treatment with Ism1, accompanied by a significant upregulation of mRNA levels for gk, hk, and pfk genes in hepatopancreas; conversely pepck and g6pase mRNA levels were significantly downregulated in the hepatopancreas under these conditions as well. Furthermore, our primary hepatocyte experiment confirmed that Ism1 could inhibit pepck and g6pase mRNA expression, while promoting gk, hk, and pfk mRNA expression levels. In conclusion, Ism1, in common carp, could participate in the glucose metabolism, which provides essential information for future studies on the function of Ism1.

Bone Allograft Acid Lysates Change the Genetic Signature of Gingival Fibroblasts.

Bone allografts are widely used as osteoconductive support to guide bone regrowth. Bone allografts are more than a scaffold for the immigrating cells as they maintain some bioactivity of the original bone matrix. Yet, it remains unclear how immigrating cells respond to bone allografts. To this end, we have evaluated the response of mesenchymal cells exposed to acid lysates of bone allografts (ALBA). RNAseq revealed that ALBA has a strong impact on the genetic signature of gingival fibroblasts, indicated by the increased expression of IL11, AREG, C11orf96, STC1, and GK-as confirmed by RT-PCR, and for IL11 and STC1 by immunoassays. Considering that transforming growth factor-β (TGF-β) is stored in the bone matrix and may have caused the expression changes, we performed a proteomics analysis, TGF-β immunoassay, and smad2/3 nuclear translocation. ALBA neither showed detectable TGF-β nor was the lysate able to induce smad2/3 translocation. Nevertheless, the TGF-β receptor type I kinase inhibitor SB431542 significantly decreased the expression of IL11, AREG, and C11orf96, suggesting that other agonists than TGF-β are responsible for the robust cell response. The findings suggest that IL11, AREG, and C11orf96 expression in mesenchymal cells can serve as a bioassay reflecting the bioactivity of the bone allografts.

BAAE-AgNPs Improve Symptoms of Diabetes in STZ-induced Diabetic Rats.

Nanoparticles can be employed to improve the therapeutic activity of natural products. Type 2 diabetes mellitus is a serious health condition that has spread like a "modern pandemic" worldwide. In the present study, we developed silver nanoparticles, AgNPs, with an aqueous extract from Balanites aegyptiaca to investigate their antioxidant and anti-inflammatory activity in STZ-induced diabetic rats. Aqueous extracts of Balanites aegyptiaca seeds (BAAE) were used in the synthesis of BAAE-AgNPs, which were characterized using FTIR and TEM. Different doses of BAAE-AgNP (1/50 LD50; 29.4 mg/kg b.w. and 1/20 LD50:73.5 mg/kg b.w.) were administered to STZ-induced diabetic rats to evaluate their potential antidiabetic activity. FTIR spectral data indicated the presence of flavonoids and polyphenols in BAAE-AgNPs. The size of the BAAE-AgNPs, determined by TEM examination, was 49.33 ± 7.59 nm, with a zeta potential of +25.37. BAAE-AgNPs were characterized by an LD50 value of 1470 mg/kg b.w. In diabetic rats, the daily oral administration of both doses of BAAE-AgNPs (29.4 and 73.5 mg/kg b.w.) for 12 weeks resulted in a significant improvement in body weight, insulin homeostasis, HbA1c, HDL-C, MDA, and pancreatic SOD, CAT, and GSH. They reduced plasma glucose, cholesterol, and triglycerides. This treatment also resulted in a significant decrease in pancreatic IL-6, P53, and TNF-α in diabetic rats. Furthermore, BAAE-AgNPs down-regulated pancreatic TGF-β1 and Akt gene expression in diabetic rats and resulted in a significant decrease in the regulation of hepatic GLUT-2, as well as an increase in the regulation of hepatic GK and pancreatic B-cl2 gene expression. The histopathological results obtained indicated that BAAE-AgNPs improved pancreatic tissue metabolism by enhancing antioxidant enzymes, suppressing inflammatory cytokines, and scavenging free radicals. The findings implied that similar to the glibenclamide-treated groups, in the BAAE-AgNPs treated group, the compromised antioxidant status normalized in STZ-induced diabetes. By scavenging free radicals, BAAE-AgNPs protected against lipid peroxidation while reducing the risk of complications from diabetes. Compared to the daily dose of 29.4 mg, the impact was more prominent at 73.5 mg.

Sodium chloride alleviates oxidative stress and physiological responses induced by extreme winter cold in genetically improved farmed tilapia (GIFT; Oreochromis niloticus)

A 6-week trial was designed to investigate the effects of dietary sodium chloride supplementation on physiological, metabolic, and molecular stress response parameters. The findings showed that (1) there were no significant differences between sodium chloride supplementation groups (0.05S, 0.1S, and 0.15S) and the control group (P > 0.05), except for the 0.2S diet, which showed better final body weight, weight gain rate, specific growth rate, and feed conversion ratio than the control group (P < 0.05). (2) The hypothermic stress experiment results showed that the survival rates in the 0.1S and 0.15S diets were significantly higher than the control group (P < 0.05). (3) Transcription results showed that these enriched pathways in the gill were mainly energy metabolism and apoptosis pathways, while the major enrichment pathways in the liver were mainly amino acid metabolism and carbohydrate metabolism. (4) The plasma parameter results showed, compared to the control group, the 0.15S diet significantly increased the plasma GLU, TG contents, and Na+ and K+ concentrations and decreased the plasma ALT activity (P < 0.05). In addition, the 0.1S diet increased the plasma ALB content and Cl− concentration (P < 0.05). The gill Na+/K+-ATPase activity decreased markedly when the fish were fed the 0.1S and 0.15S diets (P < 0.05). The antioxidant enzyme activity results showed that the 0.1S and 0.15S diets significantly increased the T-SOD activities (P < 0.05). Gene expression results showed that compared to the control group, the 0.1S and 0.15S diets up-regulated the expression of gys, hsp70, mlcp, mlc, myosin, tnt mRNA, and down-regulated the akt, gk, and erk mRNA expression. Based on the regression analysis, the optimum dietary sodium chloride levels range from 0.10 % to 0.13 % of the diet, which could facilitate energy regulation, improve the immune response, and ultimately strengthen the cold resistance of GIFT.

Red and golden tomato administration improves fat diet-induced hepatic steatosis in rats by modulating HNF4α, Lepr, and GK expression.

Nonalcoholic fatty liver disease (NAFLD), characterized by lipid accumulation within hepatocytes exceeding 5% of liver weight, is strongly related to metabolic disorders, obesity, and diabetes and represents a health emergency worldwide. There is no standard therapy available for NAFLD. Lifestyle intervention, including phytonutrient intake, is key in preventing NAFLD development and progression. We used a rat model of NAFLD to evaluate the effect of dietary supplementation with red tomato (RT) and golden tomato (GT)-a patented mix of fruit with varying degrees of ripeness and particularly rich in naringenin and chlorogenic acid-after steatosis development. We assessed the effects on body weight, metabolic profile, and hepatic steatosis. We found a correlation between the amelioration of all the parameters and the liver gene expression. Our results showed that, together with the reversion of steatosis, the consumption of RT and GT can cause a significant reduction in triglycerides, low-density lipoprotein-cholesterol, fasting glucose, and homeostasis model assessment index. Meanwhile, we observed an increase in high-density lipoprotein-cholesterol according to the amelioration of the general lipidic profile. Regarding hepatic gene expression, we found the upregulation of Gk and Hnf4α involved in metabolic homeostasis, Lepr involved in adipokine signaling, and Il6 and Tnf involved in inflammatory response. Taken together, our results suggest that dietary intake of red and golden tomatoes, as a nutraceutical approach, has potential in preventing and therapeutics of NAFLD.

Expression and characterisation of human glycerol kinase: the role of solubilising agents and molecular chaperones.

Glycerol kinase (GK; EC 2.7.1.30) facilitates the entry of glycerol into pathways of glucose and triglyceride metabolism and may play a potential role in Type 2 diabetes mellitus (T2DM). However, the detailed regulatory mechanisms and structure of the human GK are unknown. The human GK gene was cloned into the pET-24a(+) vector and over-expressed in Escherichia coli BL21 (DE3). Since the protein was expressed as inclusion bodies (IBs), various culture parameters and solubilising agents were used but they did not produce bioactive His-GK; however, co-expression of His-GK with molecular chaperones, specifically pKJE7, achieved expression of bioactive His-GK. The overexpressed bioactive His-GK was purified using coloumn chromatography and characterised using enzyme kinetics. The overexpressed bioactive His-GK was purified apparently to homogeneity (∼295-fold) and characterised. The native His-GK was a dimer with a monomeric molecular weight of ∼55 kDa. Optimal enzyme activity was observed in TEA buffer (50 mM) at 7.5 pH. K+ (40 mM) and Mg2+ (2.0 mM) emerged as prefered metal ions for His-GK activity with specific activity 0.780 U/mg protein. The purified His-GK obeyed standard Michaelis-Menten kinetics with Km value of 5.022 µM (R2=0.927) for its substrate glycerol; whereas, that for ATP and PEP was 0.767 mM (R2=0.928) and 0.223 mM (R2=0.967), respectively. Other optimal parameters for the substrate and co-factors were also determined. The present study demonstrates that co-expression of molecular chaperones assists with the expression of bioactive human GK for its characterisation.

Differential regulatory effects of dietary lipid level on growth, antioxidant capacity and expression of genes involved in lipid and glucose metabolism of juvenile mud crab Scylla paramamosain

Three isonitrogenous diets (41% crude protein) with 4.87%, 10.75% and 16.10% lipid were designed to evaluate the effects of dietary lipid levels growth, antioxidant capacity, expression levels of genes related to lipid and glucose metabolism of juvenile Scylla paramamosain. Each diet was fed to four replicates of 32 crabs with initial weight 5.10 ± 0.05 g for 6 weeks. The results indicated that crabs fed diet with 10.75% lipid exhibited significantly higher percent weight gain (PWG) and specific growth rate (SGR) than those fed diet with 4.87% lipid (P < 0.05), and crabs fed diets with 10.75% and 16.10% lipid had significantly higher protein efficiency ratio (PER) and feed efficiency (FE) than those fed diet with 4.87% lipid (P < 0.05). Crabs fed diet with 4.87% lipid had the lowest concentrations of lipid and glycogen in muscle, lipid content in hepatopancreas and hemolymph glucose among all treatments (P < 0.05). The concentrations of free fatty acid (FFA), triglyceride (TG), total cholesterol (TCHO) and pyruvate in hemolymph and hepatopancreas increased significantly with the dietary lipid levels increasing from 4.87% to 16.10% (P < 0.05), while the concentration of crustacean insulin-like (INS) in hemolymph and crustacean hyperglycemic hormone (CHH) in hepatopancreas significantly decreased with the increase of dietary lipid levels (P < 0.05). In the hepatopancreas, The Oil Red-positive area significantly increased with increase of dietary lipid levels (P < 0.05). Crabs fed diet with 16.10% lipid showed the lowest concentration of glutathione peroxidase (GSH-Px) (P < 0.05). On the contrary, the highest concentration of malondialdehyde (MDA) was observed at crabs fed diet with 16.10% lipid (P < 0.05). Crabs fed diets with 10.75% and 16.10% lipid down-regulated expression of genes related to long-chain-PUFA biosynthesis and lipid synthesis in hepatopancreas than those fed diet with 4.87% lipid (P < 0.05). The mRNA level of cpt1 significantly up-regulated with the increase of dietary lipid levels, while the mRNA expression level cpt2, acox1 and fabp4 in hepatopancreas significantly down-regulated in crabs fed diets with 10.75% and 16.10% lipid (P < 0.05). The expression of gk and pfk in crabs fed diet with 16.10% lipid significantly down-regulated than those in other groups (P < 0.05). The expressions level of genes related to gluconeogenesis significantly down-regulated in crabs fed diets with 10.75% and 16.10% lipid (P < 0.05). The lowest mRNA expression of glucose transporter 4 (glut4) was occurred in crabs fed diet with 16.10% lipid (P < 0.05). Overall, the results of present study demonstrated that the dietary 10.75% lipid can improve the growth and feed utilization for juvenile mud crab, in addition, dietary lipid can affect the antioxidant capacity, lipid metabolism, glucose metabolism and insulin signaling pathway, dietary excessive lipid resulted in lipid deposition of hepatopancreas for juvenile mud crab.

The potent contraceptive gestodene exerts insulinotropic effects through its a-ring reduced metabolites with intrinsic estrogen-like activity in pancreatic β-cells.

The contraceptive gestodene is a potent synthetic progestin used in several low-dose contraceptive formulations. Clinical studies reported a relationship between long-term use of combined oral contraceptives containing gestodene (GDN) and profound alterations in glucose metabolism in women. The observation that contraceptive synthetic progestins exert hormone-like effects other than their progestational activities, prompted us to investigate whether GDN may induce estrogen-like effects, even though GDN does not interact with estrogen receptors. The aim of this study was to investigate whether GDN affect pancreatic β-cell activity, directly or through its conversion to other bioactive metabolites. The effects of GDN and its two derivatives 3β,5α-tetrahydro-GDN and 3α,5α-tetrahydro-GDN on insulin 2 (Ins II) and glucokinase (Gk) expression and glucose-stimulated insulin secretion were determined in pancreatic islets from female rats. Gestodene did exert significant effects on islet β-cells activity. The most striking finding was that 3β,5α-tetrahydro-GDN and 3α,5α-tetrahydro-GDN had greater stimulatory effects on Ins II and Gk expression than that observed with GDN, consistent with their effects on glucose-stimulated insulin secretion. The effects on gene expression induced by GDN-derivatives were abolished by ICI 182,780 and MPP. In addition, the presence of inhibitors of androgen and progestin-metabolizing enzymes eliminated gene expression induced by GDN. These results indicated that GDN is metabolized to A-ring reduced metabolites with estrogen-like activities and through this mechanism, GDN may affect β-cell activity. Altogether, the data suggest that 19-nortestosterone-derived contraceptives such as GDN, possess insulinotropic effects through their conversion into metabolites with intrinsic estrogen-like activity in pancreatic β-cells.

Berberrubine, a Main Metabolite of Berberine, Alleviates Non-Alcoholic Fatty Liver Disease via Modulating Glucose and Lipid Metabolism and Restoring Gut Microbiota.

Non-alcoholic fatty liver disease (NAFLD) is a major public health problem in many countries. Berberine (BBR) is an effective therapeutic agent in alleviating NAFLD. Berberrubine (BRB) is one of the main active metabolites of BBR, which shows significant anti-obesity and antihypoglycemic effects. However, whether BRB is responsible for the in vivo therapeutic effect and the underlying mechanism of BRB on NAFLD have not been elucidated. In this study, the ability of BRB to ameliorate NAFLD, together with its molecular mechanism, was investigated. The results showed that BRB treatments could significantly improve hepatic steatosis and insulin resistance in high-fat diet (HFD)–fed mice and oleic acid (OA)–treated HepG2 cells. Meanwhile, BBR and BRB treatment similarly prevented lipid accumulation by regulating the protein expression of ATGL, GK, PPARα, CPT-1, ACC1, FAS, and CD36. In addition, compared with BBR, BRB could maintain glucose homeostasis via GLUT2, GSK3β, and G6Pase in HFD-fed mice. Furthermore, the components of the gut microbiota in mice were analyzed by 16S rRNA gene sequencing. BBR and BRB treatment could greatly modify the structure and composition of gut microbiota. At the genus level, BBR and BRB treatment decreased Lactobacillus and Romboutsia, while BBR increased beneficial bacteria, such as Akkermansia and Bacteroides, and BRB increased beneficial bacteria, such as Ileibacterium and Mucispirillum. Altogether, both BRB and BBR were active in alleviating NAFLD in vivo and BRB might be used as a functional material to treat NAFLD clinically.

Polysaccharide from Hovenia dulcis (Guaizao) improves pancreatic injury and regulates liver glycometabolism to alleviate STZ-induced type 1 diabetes mellitus in rats

Hovenia dulcis is a traditional medicinal and edible plant and has a major geographical presence in China. In this study, a polysaccharide purified from H. dulcis (HDPs-2A) was found to ameliorate type 1 diabetes mellitus (T1DM) in streptozotocin-induced diabetic rat. HDPs-2A treatment resulted in significantly lower fasting blood glucose levels, but higher body weight, plasma insulin, and liver glycogen levels. Moreover, HDPs-2A improved dyslipidemia, pancreatic oxidative stress, and reduced serum pro-inflammatory factors. In addition, HDPs-2A up-regulated PDX-1, activated and up-regulated IRS2 expression, and regulated apoptosis and regeneration of islet β cells to recover islet β-cell function injury in TIDM rats. HDPs-2A also up-regulated the expression of pancreatic GK and GLUT2 to improve insulin secretion ability of islet β-cells, ultimately improving the glucose metabolism disorder of T1DM rats. Moreover, HDPs-2A significantly up-regulated the expression of GK and down-regulated the expression of G6Pase in liver to improve liver glycogen synthesis, inhibit liver gluconiogenesis, and improve liver glucose metabolism disorder of T1DM rats. In summary, the hypoglycemic mechanisms of HDPs-2A may include regulating the regeneration and apoptosis of islet β-cells and activating liver glycometabolism-related signaling pathways in T1DM rats.

Irisin Regulates Hepatic Glucose Metabolism via AMPK and PI3K/Akt Activation

Irisin plays a crucial role in the glucose metabolism of mammals and fish. However, the mechanism by which irisin regulates hepatic glucose metabolism is not entirely known. To clarify irisin’s function and underlying mechanisms in common carp glucose metabolism, the FNDC5 expression patterns were detected after insulin/glucagon injection, long-term high-glucose, and high-fat diet feeding. In vivo, the activity of PFK and the synthesis of liver glycogen were significantly increased, while the enzyme activity of PEPCK was reduced after intraperitoneal injection with irisin. In contrast, irisin siRNA attenuated the brain and liver FNDC5a and FNDC5b expression, and the serum glucose was increased. Glut2, gs, hk, and pfk were considerably downregulated in the brain and liver, while pygl, pepck, and g6pase were remarkably upregulated after siRNA treatment. In vitro, irisin activates the phosphorylation level of AMPK and PI3K/Akt in primary hepatocytes. Compound C and wortmannin inhibit AMPK and PI3K/Akt, reversing irisin-induced expression of g6pase, fbpase, pepck, gk, gs, pfk, hk, and gsk3b. At the same time, compound C attenuated irisin-induced expression of pi3k and akt. Our research reveals the mechanisms of irisinA and irisinB as glucose metabolism regulators in teleost for the first time.

Genistein Alleviates High-Fat Diet-Induced Obesity by Inhibiting the Process of Gluconeogenesis in Mice.

Genistein is an isoflavone phytoestrogen that has been shown to improve obesity; however, the underlying molecular mechanisms involved therein have not been clearly elucidated. In this study, we administered genistein to high-fat diet-induced obese mice to investigate its effect on hepatic gluconeogenesis. The results showed that genistein treatment significantly inhibited body weight gain, hyperglycemia, and adipose and hepatic lipid deposition in high-fat diet-induced obese mice. Glucose tolerance test (GTT), insulin tolerance test (ITT) and pyruvate tolerance test (PTT) showed that genistein treatment significantly inhibited gluconeogenesis and improved insulin resistance in obese mice. In addition, this study also found that genistein could promote the expression of miR-451 in vitro and in vivo, and the dual-luciferase reporter system showed that G6pc (glucose-6-phosphatase) may be a target gene of miR-451. Both genistein treatment and in vivo injection of miR-451 agomir significantly inhibited gluconeogenesis and inhibited the expression of G6pc and Gk (glycerol kinase, a known target gene of miR-451). In conclusion, genistein may inhibit gluconeogenesis in obese mice by regulating the expression of Gk and G6pc through miR-451. These results may provide insights into the functions of miR-451 and food-derived phytoestrogens in ameliorating and preventing gluconeogenesis-related diseases.

Dietary protein/carbohydrate ratio and feeding frequency affect feed utilization, intermediary metabolism, and economic efficiency of gilthead seabream (Sparus aurata) juveniles

To evaluate the effects of dietary protein/carbohydrate (P/CHO) ratio and feeding frequency (FF) on growth, intermediary metabolism, and economic efficiency of gilthead seabream (Sparus aurata) juveniles, two practical isolipidic (17%) diets were formulated to include high protein (50%)/ low starch (10%) (diet P50/CHO10) or low protein (40%)/ high starch (20%) (diet P40/CHO20). Triplicate groups of fish with 9.1 ± 0.01 g were fed for 60 days with these diets until visual satiation at three FF: one (9:00), two (9:00 and 17:00), or three (9:00, 13:00, and 17:00) meals per day. Dietary P/CHO ratios did not affect growth performance while feeding 2 or 3 meals per day improved fish growth. Fish fed diet P40/CHO20 had increased feed intake (FI), protein efficiency ratio (PER), and nitrogen retention (NR), and lower feed efficiency (FE), nitrogen intake (NI), and economic conversion ratio (ECR). Feeding 2 or 3 meals per day increased FI, NI, ECR, and economic profit index, and decreased FE, PER, and NR. Fish fed diet P40/CHO20 presented increased hepatic lipid and glycogen content, hepatocyte area covered by lipid vacuoles, and glucokinase (gk) gene expression, and decreased glutamate dehydrogenase expression. Fish fed 3 meals per day had decreased plasma triglycerides and total protein levels, while fish fed 2 or 3 meals per day presented decreased hepatic growth hormone receptor-i (ghr-i), gk, and fatty acid synthase gene expression. Interaction between P/CHO ratio and FF was only observed in plasmatic glucose, cholesterol, and total lipids levels, and insulin-like growth factor-1, and ghr-ii gene expression. Overall, glycogenesis, glycolysis, and economic efficiency seemed to be increased while the amino acid catabolism was reduced in fish fed the P40/CHO20 diet. Higher FF increased growth and economic efficiency, and reduced glycolysis and lipogenesis pathways. In conclusion, a diet with P40/CHO20 ratio fed twice a day appears to be the most adequate strategy regarding feed utilization and economic efficiency for gilthead seabream juveniles in order to achieve optimum sustainable aquaculture.

Molecular cloning, tissue distribution and functional characterization of glucose-dependent insulinotropic peptide (GIP) gene in Ctenopharyngodon idella

As the incretin hormone, Glucose-dependent insulinotropic peptide (GIP) plays an important role in lipid metabolism, glucose uptake, and bone metabolism in mammals. To evaluate the roles of GIP in the teleost, the gip gene was isolated from the foregut of grass carp by RT-PCR. The ORF of grass carp gip was 327 bp and encodes 108 amino acids. And the mature peptide of grass carp was 31 amino acids. The tissue distribution results showed that gip mRNA was highly expressed in the gut, and was also at high levels in the spleen and brain region. In the oral glucose tolerance test (OGTT), the gip expression was significantly increased in foregut by glucose treatment for 1 and 3 h. The primary hepatocytes and intraperitoneal injection studies showed that the glut2, g6pase, pepck, acc1, fas, hsl, lpl expression were increased and the gk and cpt1 expression were decreased by GIP treatment. And the expression of pi3k, akt and pka were also increased by GIP treatment. In the primary hepatocytes, the effects of GIP on g6pase, glut2, lpl and cpt1 expression were relieved by Wortmannin (PI3K inhibitor), and the effects of GIP on pepck, gk and hsl expression were alleviated by H89•2HCl (PKA inhibitor). And glucose and triglyceride (TG) contents are promoted in primary hepatocytes by GIP treatment. In the intraperitoneal injection experiment, the serum glucose, total cholesterol (T-CHO) and low-density lipoprotein cholesterol (LDL-C) contents were reduced, and serum TG and high-density lipoprotein cholesterol (HDL-C) contents were elevated after GIP injection. Our studies for the first time unveil the potential role of GIP as a regulatory factor of glucose and lipid metabolism in teleost.

The effects of dietary Lactococcus spp. on growth performance, glucose absorption and metabolism of common carp, Cyprinus carpio L.

Based on beneficial effects of Lactococcus spp. and their extracellular polysaccharides on common carp (Cyprinus carpio L.) in previous studies, the main purpose of this paper was to investigate the functions of single or multi-strains of Lactococcus spp. on the growth performance, glucose absorption and metabolism of common carp. The results showed that when the fish consumed diets containing single (Lactococcus lactis Q-8, L. lactis Q-9, L. lactis Z-2) or multi-strains of Lactococcus spp. (5 × 108 CFU g−1 of feed) for 60 days, the final weight, weight gain (WG), specific growth rate (SGR) and condition factor (CF) had significantly (P < .05) increased, especially in the multi-strains addition groups. While the feed conversion ratio (FCR) of all Lactococcus spp. addition groups was significantly lower than that in the control group (P < .05). Viscera-somatic index (VSI) and survival rate in each experimental group was no significant difference during the feeding period (P > .05). For the glucose absorption, Lactococcus spp. addition groups significantly increased the blood glucose concentration and up-regulated the expression of Sglt1 and Gult2 in intestine compared with the control group (P < .05). In addition, the contents of hepatopancreas glycogen were also significantly increased in the Lactococcus spp. addition groups (P < .05). For the glucose metabolism in hepatopancreatic, the Lactococcus spp. addition groups significantly decreased the expression of GK and PK in glycolysis (P < .05), while increased the G6Pase and PEPCK expression in gluconeogenesis (P < .05). Furthermore, with the prolongation of feeding time, the synergistic effects on the expression levels of absorption and metabolism related genes, and the glycogen content were better in the multi-strains addition groups. Overall, these results suggested that the Lactococcus spp. improved the growth performance, and exerted glucose absorption and metabolism effects in common carp, which provide a theoretical basis for the rational use of potential probiotics and carbohydrate in aquaculture.

Glycerol suppresses glucose consumption in trypanosomes through metabolic contest.

Microorganisms must make the right choice for nutrient consumption to adapt to their changing environment. As a consequence, bacteria and yeasts have developed regulatory mechanisms involving nutrient sensing and signaling, known as "catabolite repression," allowing redirection of cell metabolism to maximize the consumption of an energy-efficient carbon source. Here, we report a new mechanism named "metabolic contest" for regulating the use of carbon sources without nutrient sensing and signaling. Trypanosoma brucei is a unicellular eukaryote transmitted by tsetse flies and causing human African trypanosomiasis, or sleeping sickness. We showed that, in contrast to most microorganisms, the insect stages of this parasite developed a preference for glycerol over glucose, with glucose consumption beginning after the depletion of glycerol present in the medium. This "metabolic contest" depends on the combination of 3 conditions: (i) the sequestration of both metabolic pathways in the same subcellular compartment, here in the peroxisomal-related organelles named glycosomes; (ii) the competition for the same substrate, here ATP, with the first enzymatic step of the glycerol and glucose metabolic pathways both being ATP-dependent (glycerol kinase and hexokinase, respectively); and (iii) an unbalanced activity between the competing enzymes, here the glycerol kinase activity being approximately 80-fold higher than the hexokinase activity. As predicted by our model, an approximately 50-fold down-regulation of the GK expression abolished the preference for glycerol over glucose, with glucose and glycerol being metabolized concomitantly. In theory, a metabolic contest could be found in any organism provided that the 3 conditions listed above are met.