Molecular evolution of Cypridina noctiluca secretory luciferase for production of spectrum-shifted luminescence-emitting mutants and their application in nuclear receptor-reporter assays

Luciferase is a popular enzyme used for biological analyses, such as reporter assays. In addition to a conventional reporter assay using a pair of firefly and Renilla luciferases, a simple multicolor reporter assay using multiple firefly or beetle luciferases emitting different color luminescence with a single substrate has been reported. Secretory luciferases have also been used for convenient sample preparation in reporter assays; however, reporter assay using secretory luciferase mutants that emit spectrum-shifted luminescence have not yet been reported. In this study, we generated blue- and red-shifted (-16 and 12 nm) luminescence-emitting Cypridina secretory luciferase (CLuc) mutants using multiple cycles of random and site-directed mutagenesis. Even for red-shifted CLuc mutant, which exhibited relatively low activity and stability, its enzymatic activity was sufficiently high for a luciferase assay (3.26 × 106 relative light unit/s), light emission was sufficiently prolonged (half-life is 3 min), and stability at 37°C was high. We independently determined the luminescence of these CLuc mutants using a luminometer with an optical filter. Finally, we replaced the commonly used reporters, firefly and Renilla luciferases used in a conventional nuclear receptor-reporter assay with these CLuc mutants and established a secretory luciferase-based single-substrate dual-color nuclear receptor-reporter assay.

Comprehensive analysis of PPARγ agonist activities of stereo-, regio-, and enantio-isomers of hydroxyoctadecadienoic acids

Hydroxyoctadecadienoic acids (HODEs) are produced by oxidation and reduction of linoleates. There are several regio- and stereo-isomers of HODE, and their concentrations in vivo are higher than those of other lipids. Although conformational isomers may have different biological activities, comparative analysis of intracellular function of HODE isomers has not yet been performed. We evaluated the transcriptional activity of peroxisome proliferator-activated receptor γ (PPARγ), a therapeutic target for diabetes, and analyzed PPARγ agonist activity of HODE isomers. The lowest scores for docking poses of 12 types of HODE isomers (9-, 10-, 12-, and 13-HODEs) were almost similar in docking simulation of HODEs into PPARγ ligand-binding domain (LBD). Direct binding of HODE isomers to PPARγ LBD was determined by water-ligand observed via gradient spectroscopy (WaterLOGSY) NMR experiments. In contrast, there were differences in PPARγ agonist activities among 9- and 13-HODE stereo-isomers and 12- and 13-HODE enantio-isomers in a dual-luciferase reporter assay. Interestingly, the activity of 9-HODEs was less than that of other regio-isomers, and 9-(E,E)-HODE tended to decrease PPARγ-target gene expression during the maturation of 3T3-L1 cells. In addition, 10- and 12-(Z,E)-HODEs, which we previously proposed as biomarkers for early-stage diabetes, exerted PPARγ agonist activity. These results indicate that all HODE isomers have PPARγ-binding affinity; however, they have different PPARγ agonist activity. Our findings may help to understand the biological function of lipid peroxidation products.

Differential effects of protein intake versus intake of a defined oligopeptide on FGF-21 in obese human subjects in vivo

BACKGROUND

FGF-21 is described as a powerful metabolic regulator with beneficial effects including glucose-lowering and improvement of insulin sensitivity without hypoglycaemia. On the other hand, FGF-21 is activated when muscle and other tissues are stressed by external effects or internal cellular pathogens that lead to shortcomings in metabolic balance. Previous results suggested that FGF-21 could be a promising target to develop future metabolic therapeutics.

PURPOSE

The present study was performed to gain deeper insight into the regulation of FGF-21 by protein metabolism in obese human subjects.

METHODS

FGF-21 serum concentrations were measured in a cohort of n = 246 obese humans ± type 2 diabetes mellitus (T2DM) (median age 53.0 [46.0; 60.0] years and BMI 40.43 [35.11; 47.24] kg/m²) and related to the nutritional protein intake. In addition, the effect of a novel oligopeptide purified from a β-casein hydrolysate on FGF-21 was examined in vitro in liver cells and in vivo in a human intervention study with the main focus on metabolic inflammation including 40 mainly obese subjects (mean age 41.08 ± 9.76 years, mean BMI 38.29 ± 9.4 kg/m²) in a randomized 20 weeks double-blind cross-over design.

MAIN FINDINGS

In the cohort analysis, FGF-21 serum concentrations were significant lower with higher protein intake in obese subjects without T2DM but not in obese subjects with T2DM. Furthermore, relative methionine intake was inversely related to FGF-21. While global protein intake in obesity was inversely associated with FGF-21, incubation of HepG2 cells with a β-casein oligopeptide increased FGF-21 expression in vitro. This stimulatory effect was also present in vivo, since in the clinical intervention study treatment of obese subjects with the β-casein oligopeptide for 8 weeks significantly increased FGF-21 serum levels from W0 = 23.86 pg/mL to W8 = 30.54 pg/mL (p < 0.001), while no increase was found for placebo.

CONCLUSION

While the total nutritional protein intake is inversely associated with FGF-21 serum levels, a purified and well characterised oligopeptide is able to induce FGF-21 serum levels in humans. These findings suggest a differential role of various components of protein metabolism on FGF-21, rather than this factor being solely a sensor of total nutritional protein intake.

Peroxisome proliferator-activated receptor α ligands and modulators from dietary compounds: Types, screening methods and functions

Peroxisome proliferator-activated receptor α (PPARα) plays a key role in lipid metabolism and glucose homeostasis and a crucial role in the prevention and treatment of metabolic diseases. Natural dietary compounds, including nutrients and phytochemicals, are PPARα ligands or modulators. High-throughput screening assays have been developed to screen for PPARα ligands and modulators in our diet. In the present review, we discuss recent advances in our knowledge of PPARα, including its structure, function, and ligand and modulator screening assays, and summarize the different types of dietary PPARα ligands and modulators.

Modulation of brown adipocyte activity by milk by-products: Stimulation of brown adipogenesis by buttermilk

Brown adipocytes dissipate chemical energy in the form of heat through the expression of mitochondrial uncoupling protein 1 (Ucp1); Ucp1 expression is further upregulated by the stimulation of β-adrenergic receptors in brown adipocytes. An increase in energy expenditure by activated brown adipocytes potentially contributes to the prevention of or therapeutics for obesity. The present study examined the effects of milk by-products, buttermilk and butter oil, on brown adipogenesis and the function of brown adipocytes. The treatment with buttermilk modulated brown adipogenesis, depending on the product tested; during brown adipogenesis, buttermilk 1 inhibited the differentiation of HB2 brown preadipocytes. In contrast, buttermilk 3 and 5 increased the expression of Ucp1 in the absence of isoproterenol (Iso), a β-adrenergic receptor agonist, suggesting the stimulation of brown adipogenesis. In addition, the Iso-induced expression of Ucp1 was enhanced by buttermilk 2 and 3. The treatment with buttermilk did not affect the basal or induced expression of Ucp1 by Iso in HB2 brown adipocytes, except for buttermilk 5, which increased the basal expression of Ucp1. Conversely, butter oil did not significantly affect the expression of Ucp1, irrespective of the cell phase of HB2 cells, ie, treatment during brown adipogenesis or of brown adipocytes. The results of the present study indicate that buttermilk is a regulator of brown adipogenesis and suggest its usefulness as a potential food material for antiobesity.

Dietary influences on tissue concentrations of phytanic acid and AMACR expression in the benign human prostate

BACKGROUND

Alpha-methylacyl-CoA racemase (AMACR) is an enzyme involved in fatty acid metabolism that is markedly over-expressed in virtually all prostate cancers (PCa), relative to benign tissue. One of AMACR's primary substrates, phytanic acid, is derived predominately from red meat and dairy product consumption. Epidemiological evidence suggests links between dairy/red meat intake, as well as phytanic acid levels, and elevated PCa risk. This study investigates the relationships among dietary intake, serum and tissue concentrations of phytanic acid, and AMACR expression (mRNA and protein) in the histologically benign human prostate.

METHODS

Men undergoing radical prostatectomy for the treatment of localized disease provided a food frequency questionnaire (n = 68), fasting blood (n = 35), benign fresh frozen prostate tissue (n = 26), and formalin-fixed paraffin-embedded (FFPE) sections (n = 67). Serum and tissue phytanic acid concentrations were obtained by gas chromatography-mass spectrometry. We extracted RNA from epithelial cells using laser capture microdissection and quantified mRNA expression of AMACR and other genes involved in the peroxisomal phytanic acid metabolism pathway via qRT-PCR. Immunohistochemistry for AMACR was performed on FFPE sections and subsequently quantified via digital image analysis. Associations between diet, serum, and tissue phytanic acid levels, as well as AMACR and other gene expression levels were assessed by partial Spearman correlation coefficients.

RESULTS

High-fat dairy intake was the strongest predictor of circulating phytanic acid concentrations (r = 0.35, P = 0.04). Tissue phytanic acid concentrations were not associated with any dietary sources and were only weakly correlated with serum levels (r = 0.29, P = 0.15). AMACR gene expression was not associated with serum phytanic acid (r = 0.13, P = 0.47), prostatic phytanic acid concentrations (r = 0.03, P = 0.88), or AMACR protein expression (r = -0.16, P = 0.20).

CONCLUSIONS

Our data underscore the complexity of the relationship between AMACR and its substrates and do not support the unifying hypothesis that excess levels of dietary phytanic acid are responsible for both the overexpression of AMACR in prostate cancer and the potential association between PCa risk and intake of dairy foods and red meat.

Long-term commercial cow's milk consumption and its effects on metabolic parameters associated with obesity in young mice

SCOPE

Research has demonstrated that consumption of milk promotes weight loss and satiety, however conflicting evidence also exists. Therefore, we tested the effect of long-term milk consumption on body weight and metabolic parameters.

METHODS AND RESULTS

Newly weaned mice received whole milk, low-fat milk, or water as control for 17 weeks and serum, liver, and white adipose tissue (WAT) were tested for parameters associated with obesity and diabetes. Our results show that low-fat milk leads to the same overall caloric intake and body weight as the control group. However, the whole-milk group consumed more calories and reached a higher body weight. In addition, in the low-fat milk group, cholesterol, HDL-cholesterol, triglycerides, leptin, ghrelin, insulin, corticosterone, and glucagon were not significantly different than the control group. In contrast, in the whole-milk group, cholesterol, HDL-cholesterol, triglycerides, and glucagon were high compared with the control group. Metabolism in both liver and WAT showed only slight differences between the milk groups. Whereas the whole-milk group showed reduced insulin signaling in WAT, the low-fat milk group exhibited increased insulin signaling.

CONCLUSION

Whole-milk consumption leads to increased body weight and caloric intake and reduced insulin signaling in WAT, as opposed to low-fat milk consumption.

Probiotic Dahi containing Lactobacillus acidophilus and Bifidobacterium bifidum alleviates age-inflicted oxidative stress and improves expression of biomarkers of ageing in mice

The potential benefiting effects of probiotic Dahi on age-inflicted accumulation of oxidation products, antioxidant enzymes and expression of biomarkers of ageing were evaluated in mice. Probiotic Dahi were prepared by co-culturing in buffalo milk (3% fat) Dahi bacteria (Lactococcus lactis ssp. cremoris NCDC-86 and Lactococcus lactis ssp. lactis biovar diacetylactis NCDC-60) along with selected strain of Lactobacillus acidophilus LaVK2 (La-Dahi) or combined L. acidophilus and Bifidobacterium bifidum BbVK3 (LaBb-Dahi). Four groups of 12 months old mice (6 each) were fed for 4 months supplements (5 g/day) of buffalo milk (3% fat), Dahi, La-Dahi and LaBb-Dahi, respectively, with basal diet. The activities of catalase (CAT) and glutathione peroxidase (GPx) declined and the contents of oxidation products, thiobarbituric acid reactive substances (TBARS) and protein carbonyls, increased in red blood corpuscles (RBCs), liver, kidney and heart tissues and superoxide dismutase (SOD) activity increased in RBCs and hepatic tissues during ageing of mice. Feeding ageing mice with La-Dahi or LaBb-Dahi increased CAT activity in all the four tissues, and GPx activity in RBCs and hepatic tissue, and a significant decline in TBARS in plasma, kidney and hepatic tissues and protein carbonyls in plasma. Feeding mice with probiotic Dahi also reversed age related decline in expression of biomarkers of ageing, peroxisome proliferators activated receptor-α, senescence marker protein-30 (SMP-30) and klotho in hepatic and kidney tissues. The present study suggests that probiotic Dahi containing selected strains of bacteria can be used as a potential nutraceutical intervention to combat oxidative stress and molecular alterations associated with ageing.

Peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta) acts as regulator of metabolism linked to multiple cellular functions

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors. They function as ligand activated transcription factors. They exist in three isoforms, PPARalpha, PPARbeta (formerly PPARdelta), and PPARgamma. For all PPARs lipids are endogenous ligands, linking them directly to metabolism. PPARs form heterodimers with retinoic X receptors, and, upon ligand binding, modulate gene expression of downstream target genes dependent on the presence of co-repressors or co-activators. This results in cell-type specific complex regulations of proliferation, differentiation and cell survival. Specific synthetic agonists for all PPARs are available. PPARalpha and PPARgamma agonists are already in clinical use for the treatment of hyperlipidemia and type 2 diabetes, respectively. More recently, PPARbeta activation came into focus as an interesting novel approach for the treatment of metabolic syndrome and associated cardiovascular diseases. Although the initial notion was that PPARbeta is expressed ubiquitously, more recently extensive investigations have been performed demonstrating high PPARbeta expression in a variety of tissues, e.g. skin, skeletal muscle, adipose tissue, inflammatory cells, heart, and various types of cancer. In addition, in vitro and in vivo studies using specific PPARbeta agonists, tissue-specific over-expression or knockout mouse models have demonstrated a variety of functions of PPARbeta in adipose tissue, muscle, skin, inflammation, and cancer. We will focus here on functions of PPARbeta in adipose tissue, skeletal muscle, heart, angiogenesis and cancer related to modifications in metabolism and the identified underlying molecular mechanisms.