Aims/hypothesis Pentamethylquercetin (PMQ) has recently been shown to have glucose-lowering properties. Here, we aimed to characterise the effectiveness and underlying mechanisms of PMQ for ameliorating metabolic disorders in vivo and vitro. Methods We generated a mouse model of obesity by neonatal administration of monosodium glutamate (MSG) and used it to assess the properties of PMQ as a treatment for metabolic disorders. We also investigated the possible underlying mechanisms of PMQ in the prevention of metabolic disorders. Results Compared with normal mice, MSG mice had metabolic disorders, including central obesity, hyperinsulinaemia, insulin resistance, hyperglycaemia, hyperlipidaemia, decreased phosphorylation of AMP-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC), and downregulated levels of GLUT4 in gastrocnemius muscles. In MSG mice, PMQ treatment (5, 10, 20 mg/kg daily) reduced body weight gain, waist circumference, adipose tissue mass, serum glucose, triacylglycerol and total cholesterol, while improving insulin resistance, activating AMPK and increasing ACC phosphorylation and GLUT4 abundance. In C2C12 myotubes, PMQ (10 μmol/l) increased glucose consumption by ∼65%. PMQ treatment (1-10 μmol/l) also activated AMPK, increased ACC phosphorylation and GLUT4 abundance, and upregulated the expression of some key genes involved in fatty acid oxidation. Conclusions/interpretation These findings suggest that PMQ can ameliorate metabolic disorders at least in part via stimulation of AMPK activity.

The identification of the differential expression of genes in the ovaries of egg-laying and prelaying Zi geese is required to improve the laying performance of the geese. In the present study, suppression subtractive hybridization and reverse dot-blot were employed to identify such genes, using the ovary as a model. Furthermore, expression profiling of estrogen receptor 1, estrogen receptor 2, follicle stimulating hormone receptor, prolactin receptor, ferritin H chain, and ovary differentially expressed unknown gene 08 in ovaries from geese was performed by quantitative real-time PCR. Total RNA from the ovaries of laying and prelaying Zi geese was pooled and the mRNA was isolated. The cDNA that was reverse-transcribed from the ovarian mRNA of the prelaying geese was subtracted from the cDNA isolated from the laying geese. Four hundred sixty-five clones containing putative differentially expressed gene fragments were further identified by reverse dot-blot. Ninety-seven clones were subjected to sequencing and further analysis. Sequence analysis showed that the expression of 18 known (including a mitochondrial gene) and 8 unknown gene fragments was higher in the ovaries of laying geese compared with prelaying geese. Seventeen of the known genes encode proteins that belong to groups involved with binding, catalytic activity, enzyme regulatory activity, signal transducer activity, structural molecule, and transporter activity. The results of the quantitative real-time PCR showed that the expression of estrogen receptor 1, estrogen receptor 2, follicle stimulating hormone receptor, prolactin receptor, ferritin H chain, and ovary differentially expressed unknown gene 08 was higher in the ovaries of the laying geese than in those of the prelaying geese (P<0.05). These differentially expressed genes may be relevant to the progression of prelaying geese to the egg-laying stage. Further study is required to elucidate the molecular mechanism that controls egg-laying in geese, to improve the productivity of laying geese.

Primary bovine mammary epithelial cells (BMEC) were cultured in media containing varying concentrations of glucose, to determine the effects of glucose availability on glucose transport and its mechanism in bovine mammary gland. The BMEC incubated with 10 and 20 mM glucose had twofold greater glucose uptake than that with 2.5 mM glucose (P , 0.05). Increased glucose availability enhanced the cell proliferation (P , 0.05). As the glucose uptake is mediated by facilitative glucose transporters (GLUTs), the expression of GLUT mRNA was investigated. Compared with the control (2.5 mM), 5 and 10 mM glucose did not influence the abundance of GLUT1 mRNA (P , 0.05), whereas 20 mM glucose decreased the GLUT1 mRNA expression in the BMEC (P , 0.05). The expression of GLUT8 mRNA was not affected by any concentration of glucose (P . 0.05). As GLUTs are coupled with hexokinases (HKs) in regulating glucose uptake, the expression of HKs and their activities were also studied. The HK activity was greater in 5, 10 and 20 mM glucose than that in 2.5 mM glucose (P , 0.05). The expression of HK2 mRNA rather than HK1 mRNA was detected in the BMEC; however, the abundance of HK2 mRNA was not elevated by any concentrations of glucose compared with control (P . 0.05). Furthermore, addition of 3-bromopyruvate (30, 50 or 70 mM), an inhibitor of HK2, resulted in the decrease of glucose uptake and cell proliferation at both 2.5 and 10 mM glucose (P , 0.05). Therefore, the glucose concentrations may affect glucose uptake partly by altering the activity of HKs, and HK2 may play an important role in the regulation of glucose uptake in the BMEC.

This study was conducted to investigate the effects of phenylalanine (Phe) and threonine (Thr) oligopeptides on αs1 casein gene expression and milk protein synthesis in bovine mammary epithelial cells. Primary mammary epithelial cells were obtained from Holstein dairy cows and incubated in Dulbecco's modified Eagle's medium-F12 medium (DMEM/F12) containing lactogenic hormones (prolactin and glucocorticoids). Free Phe (117 μg/ml) was substituted partly with peptide-bound Phe (phenylalanylphenylalanine, phenylalanyl threonine, threonyl-phenylalanyl-phenylalanine) in the experimental media. After incubation with experimental medium, cells were collected for gene expression analysis and medium was collected for milk protein or amino acid determination. The results showed that peptide-bound Phe at 10% (11.7 μg/ml) significantly enhanced αs1 casein gene expression and milk protein synthesis as compared with equivalent amount of free Phe. When 10% Phe was replaced by phenylalanylphenylalanine, the disappearance of most essential amino acids increased significantly, and gene expression of peptide transporter 2 and some amino acid transporters was significantly enhanced. These results indicate that the Phe and Thr oligopeptides are important for milk protein synthesis, and peptide-bound amino acids could be utilised more efficiently in milk protein synthesis than the equivalent amount of free amino acids.

This study was conducted to investigate the expression of oligopeptide transporter 2 (PepT2) and its potential function in bovine mammary gland. First, the PepT2 mRNA and protein were determined in cultured mammary epithelial cells. Then the effects of lactogenic hormones (prolactin, hydrocortisone or insulin) and substrate (threonyl-phenylalanyl-phenylalanine) on PepT2 were investigated. The PepT2 mRNA and protein were successfully detected in bovine mammary epithelial cells. PepT2 gene expression was enhanced by the addition of 50, 500 and 5000 ng/ml prolactin, 10 and 100 ng/ml hydrocortisone, and 50, 500, 5000 and 50,000 ng/ml insulin. PepT2 mRNA abundance was increased when 5, 10 and 15% of threonyl-phenylalanyl-phenylalanine was included. Responses of PepT2 to lactogenic hormones and oligopeptide inferred that it may play an important role in bovine mammary gland.