The effect of dairy products on liver fat and metabolic risk markers in males with abdominal obesity - a four-arm randomized controlled trial

BACKGROUND & AIMS

In recent years, epidemiological studies have reported links between the consumption of fermented dairy products, such as yogurt, and health; however, evidence from human intervention trials is scarce and inconsistent. We aimed to investigate the effect of consumption of four different types of dairy products (two fermented and two non-fermented) on liver fat (primary outcome) and metabolic risk markers in males with abdominal obesity.

METHODS

In this parallel randomized controlled trial with four arms, 100 males aged 30-70 years, with body mass index 28.0-45.0 kg/m2, and waist circumference ≥102 cm underwent a 16-weeks intervention where they were instructed to consume 400 g/day of either milk, yogurt, heat-treated yogurt, or acidified milk as part of their habitual diet. Liver fat was measured by magnetic resonance imaging.

RESULTS

In the complete case analyses (n = 80), no effects of the intervention or differences between groups were detected in anthropometry or body composition including liver fat. Moreover, no effects were detected in inflammatory markers. Main effects of time were detected in blood pressure (decrease; P < 0.001), insulin (decrease; P < 0.001), C-peptide (decrease; P = 0.040), homeostatic model assessment for insulin resistance (decrease; P < 0.001), total cholesterol (decrease; P = 0.016), low-density lipoprotein (decrease; P = 0.033), high-density lipoprotein (decrease; P = 0.006), and alanine transaminase (decrease; P = 0.019). Interactions between group and time failed to reach significance.

CONCLUSIONS

In conclusion, findings from our study do not confirm that fermented yogurt products are superior in reducing liver fat or improving metabolic risk markers compared to non-fermented milk products. In fact, all intervention products (both fermented yogurt products and non-fermented milk products) did not affect liver fat and caused largely similar modest favorable changes in some metabolic risk markers. The study was registered at www.

CLINICALTRIALS

gov (# NCT04755530).

Administration of whey protein complexed vitamin D3 to vitamin D3-deficient growing Sprague-Dawley rats

Vitamin D deficiency is a global health issue with consequences for bone health. Complexation of vitamin D₃ with specific whey proteins might increase the bioavailability and enhance the effect of dietary supplementation on health outcomes. The current rat study was set up to investigate if complexation of vitamin D₃ with whey protein isolate (WPI) or β-lactoglobulin (B-LG) increases bioavailability of the vitamin and how it impacts markers of bone turnover and bone structure. For 8 weeks, growing male Sprague Dawley rats (n = 48) were fed a vitamin D-deficient diet and during the final 4 weeks gavage dosing of vitamin D₃ either alone (VitD) or complexed with WPI (VitD + WPI) or β-LG (VitD + B-LG) was administered. A placebo treatment (placebo) was also included. After sacrifice, samples of bone were collected and analyzed using biomechanical testing and μCT scanning. The concentrations of vitamin D₃, vitamin D₃ metabolites and bone markers (P1NP and CTX) were measured in serum. The results showed that VitD + B-LG appeared to induce lower levels of 25-hydroxy vitamin D₃ in serum compared to VitD alone. Markers of bone turnover were generally higher in the VitD group compared to placebo and the VitD + WPI and VitD + B-LG treatments. No effects of treatments on bone strength or bone microstructure were detected. In conclusion, whey protein complexation of vitamin D₃ supplements appeared to have no beneficial effects on circulating vitamin D₃ metabolites but this did not impose changes in bone strength or trabecular bone microstructure.

Matrix structure of dairy products results in different postprandial lipid responses: a randomized crossover trial

BACKGROUND

The dairy matrix may influence digestion and absorption of lipids and thereby risk of cardiovascular diseases (CVDs). However, few postprandial studies have compared dairy products that differed only in terms of their matrix.

OBJECTIVES

We aimed to investigate acute 8-h postprandial lipid, glycemic, and appetite responses after intake of isoenergetic dairy meals with different matrixes, but similar nutritional composition.

METHODS

Twenty-five normal-weight men (18-40 y old) were enrolled in a randomized controlled crossover trial. On 4 test days, a meal with 1 of 4 dairy products was served: cheddar cheese (Cheese), homogenized Cheese (Hom. Cheese), micellar casein isolate (MCI) with cream (MCI Drink), and a gel produced from the MCI Drink by addition of Glucono Delta-Lactone (MCI Gel). The fat- and protein-matched dairy products differed in terms of their casein network, fat droplet size, and/or texture. Blood biochemistry and appetite responses were collected.

RESULTS

Eighteen participants completed the trial. Postprandial triglycerides (TGs) (primary outcome) increased by (mean ± SEM) 0.24 ± 0.07 and 0.19 ± 0.07 mmol/L after MCI Gel compared with Cheese and Hom. Cheese, respectively (both P ≤ 0.05). Likewise, MCI Gel increased TG incremental AUC compared with Cheese and Hom. Cheese (both P < 0.05), and peak compared with Cheese (P < 0.05). ApoB-48 (primary outcome) was unaffected by dairy matrix. For free fatty acids (FFAs), glucose, and insulin, time × meal interactions were observed (all P < 0.001). During the first 2 h, FFAs were lower for Cheese than for MCI products, whereas the opposite was observed for glucose and insulin.

CONCLUSIONS

Postprandial TG but not apoB-48 response was higher after MCI Gel, indicating that the type of casein network influences lipid responses. This suggests that the dairy matrix may also affect risk factors for CVDs. Reducing fat droplet size (i.e., Hom. Cheese) did not affect blood biochemistry.This trial was registered at clinicaltrials.gov as NCT03656367.

Influence of type of dairy matrix micro- and macrostructure on in vitro lipid digestion

Recent research indicates that the food matrix can influence digestion kinetics and uptake of nutrients, thus affecting human health. The aim of this study was to obtain knowledge on how variations in microstructure and texture of foods represented by four dairy products; (i) cheddar cheese, (ii) a homogenized cheddar cheese, (iii) a micellar casein and cream drink or (iv) a micellar casein and cream gel, all of identical nutrient ratios of protein : fat and calcium : fat, affect the in vitro digestibility kinetics of lipids. Rheology of the four dairy structures was measured at 10 °C and 37 °C before digestion, and during the gastric phase of in vitro digestion. During digestion cheddar cheese was most resistant to enzymatic and mechanical disintegration, followed by homogenized cheese, while both the drink and gel had low resistance and dissolved in the gastric juice. Particle size, fat droplet size and microstructure were assessed by light scattering and confocal microscopy during digestion. Significantly larger fat droplets were observed during digestion of the cheddar cheese sample. The release of free fatty acids during the initial intestinal digestion showed cheddar cheese to provide a significantly lower release than homogenized cheese, whereas the drink and gel both had significantly higher free fatty acid release. The results suggest that the cheese matrix resistance to degradation and its large fat droplets were responsible for a slower fat digestion.

Lactose and Bovine Milk Oligosaccharides Synergistically Stimulate B. longum subsp. longum Growth in a Simplified Model of the Infant Gut Microbiome

Increasing awareness of the importance of a healthy Bifidobacterium-rich microbiome has led to a need for more knowledge on how different prebiotic carbohydrates specifically impact the infant microbiome, especially as a community instead of single bacterial targets. In this study, we combined proton nuclear magnetic resonance (¹H NMR) metabolomics and molecular biology methods for quantification of bacteria to compare the prebiotic effect of bovine milk oligosaccharides (BMO) and synthetic galacto oligosaccharides (GOS) using mono- and cocultures of eight major bacteria related to a healthy infant microbiome. The results revealed that BMO treatments supported growth of Bifidobacterium longum subsp. longum and Parabacteroides distasonis, while at the same time growth of Clostridium perfringens and Escherichia coli was inhibited. In addition, there was a synergistic effect of combining lactose and BMO in regards to reducing C. perfringens, maintaining stable numbers of P. distasonis and simultaneously increasing numbers of the beneficial B. longum subsp. longum. These results indicate that the oligosaccharide composition plays a vital role in shaping the developing microbiota.

Salmon in Combination with High Glycemic Index Carbohydrates Increases Diet-Induced Thermogenesis Compared with Salmon with Low Glycemic Index Carbohydrates⁻An Acute Randomized Cross-Over Meal Test Study

The study investigated the acute effects of meals containing either salmon or veal in combination with carbohydrates with high or low glycemic index (GI) on diet-induced thermogenesis (DIT) (primary endpoint), appetite sensations, and energy intake (EI). Twenty-five overweight men and women ingested four iso-caloric test meals: salmon with mashed potatoes (high GI) (SM), salmon with wholegrain pasta (low GI) (SP), veal with mashed potatoes (VM) and veal with wholegrain pasta (VP). Energy expenditure was measured in the fasting state and six times postprandially for 25 min with 5-min breaks between each measurement. Appetite sensations were measured every 30 min. Blood samples, from arterialized venous blood, were drawn every 20 min until an ad libitum buffet-style lunch was served 3.5 h later. DIT was 40% higher after the SM meal compared to the SP meal (p = 0.002). Prospective food consumption was lower after the SM meal compared with the VP meal (p = 0.01). There were no differences in satiety, hunger, fullness, or ad libitum EI between the test meals (all p > 0.05). In conclusion, salmon with high GI carbohydrates increased DIT compared to salmon with low GI carbohydrates. This indicates that DIT is sensitive to the GI of the carbohydrates after intake of salmon but not veal.

Quantification of Human Milk Phospholipids: the Effect of Gestational and Lactational Age on Phospholipid Composition

Human milk (HM) provides infants with macro- and micronutrients needed for growth and development. Milk phospholipids are important sources of bioactive components, such as long-chain polyunsaturated fatty acids (LC-PUFA) and choline, crucial for neural and visual development. Milk from mothers who have delivered prematurely (<37 weeks) might not meet the nutritional requirements for optimal development and growth. Using liquid chromatography tandem-mass spectrometry, 31 phospholipid (PL) species were quantified for colostrum (<5 days postpartum), transitional (≥5 days and ≤2 weeks) and mature milk (>2 weeks and ≤15 weeks) samples from mothers who had delivered preterm (n = 57) and term infants (n = 22), respectively. Both gestational age and age postpartum affected the PL composition of HM. Significantly higher concentrations (p < 0.05) of phosphatidylcholine (PC), sphingomyelin (SM) and total PL were found in preterm milk throughout lactation, as well as significantly higher concentrations (p < 0.002) of several phosphatidylethanolamine (PE), PC and SM species. Multivariate analysis revealed that PLs containing LC-PUFA contributed highly to the differences in the PL composition of preterm and term colostrum. Differences related to gestation decreased as the milk matured. Thus, gestational age may impact the PL content of colostrum, however this effect of gestation might subside in mature milk.

Metabolomics and bacterial diversity of packaged yellowfin tuna (Thunnus albacares) and salmon (Salmo salar) show fish species-specific spoilage development during chilled storage

Microbial (colony counts, 16S rRNA gene amplification), chemical (pH, ¹H NMR spectroscopy) and sensory changes in raw Atlantic Salmon (Salmo salar) and tuna (Thunnus albacares) fillets stored under vacuum at 3 °C were evaluated over a period of 12 days. Both species of fish are globally important and among the ten most consumed fishes in the world. Although the sensory analyses showed a decrease in the quality of both fish species, only the salmon fillets were considered spoiled at the end of the storage period. In salmon, trimethylamine was the main spoilage product and bacterial colony counts reached an average of 7.3 log10 cfu/g. The concentration of glucose decreased and the concentration of organic acids increased during storage revealing glucose fermentation. Photobacterium was the dominating genus in the salmon studied. In the tuna studied, the bacterial colony counts reached only an average of 4.6 log10 cfu/g. The dominating bacteria in tuna were Pseudomonas spp. Glucose levels did not decrease, suggesting that amino acids and lactate most likely acted as carbon sources for bacteria in tuna. In conclusion, the study revealed that salmon was clearly a more perishable fish than tuna.

The effect of casein, hydrolyzed casein, and whey proteins on urinary and postprandial plasma metabolites in overweight and moderately obese human subjects

BACKGROUND

Casein and whey proteins differ in amino acid composition and absorption rate; however, the absorption rate of casein can be increased to mimic that of whey proteins by exogenous hydrolysis. In view of these compositional differences, we studied the metabolic responses to intake of casein, hydrolyzed casein, and whey proteins in overweight and moderately obese men and women by investigating select urinary and blood plasma metabolites.

RESULTS

A total of 21 urinary and 23 plasma metabolites were identified by nuclear magnetic resonance spectroscopy. The postprandial plasma metabolites revealed a significant diet-time interaction for isoleucine (P = 0.001) and tyrosine (P = 0.001). The level of isoleucine and tyrosine peaked 90 min postprandially with a 1.4-fold difference following intake of whey proteins compared with either casein or hydrolyzed casein. A 1.2-fold higher urinary level of lactate was observed after intake of whey proteins compared with intake of intact casein (P < 0.01).

CONCLUSION

The plasma metabolites revealed different amino acid profiles reflecting the amino acid composition of casein and whey proteins. Furthermore, the results support that casein hydrolysates neither affect the postprandial amino acid absorption rate nor the amino acid level compared with that of intact casein. The urinary lactate increases following whey protein intake might indicate a higher metabolism of glucogenic amino acids. © 2018 Society of Chemical Industry.

The Effect of Gestational and Lactational Age on the Human Milk Metabolome

Human milk is the ideal nutrition source for healthy infants during the first six months of life and a detailed characterisation of the composition of milk from mothers that deliver prematurely (<37 weeks gestation), and of how human milk changes during lactation, would benefit our understanding of the nutritional requirements of premature infants. Individual milk samples from mothers delivering prematurely and at term were collected. The human milk metabolome, established by nuclear magnetic resonance (NMR) spectroscopy, was influenced by gestational and lactation age. Metabolite profiling identified that levels of valine, leucine, betaine, and creatinine were increased in colostrum from term mothers compared with mature milk, while those of glutamate, caprylate, and caprate were increased in mature term milk compared with colostrum. Levels of oligosaccharides, citrate, and creatinine were increased in pre-term colostrum, while those of caprylate, caprate, valine, leucine, glutamate, and pantothenate increased with time postpartum. There were differences between pre-term and full-term milk in the levels of carnitine, caprylate, caprate, pantothenate, urea, lactose, oligosaccharides, citrate, phosphocholine, choline, and formate. These findings suggest that the metabolome of pre-term milk changes within 5–7 weeks postpartum to resemble that of term milk, independent of time of gestation at pre-mature delivery.

Metabolomics investigation to shed light on cheese as a possible piece in the French paradox puzzle

An NMR-based metabolomics approach was used to investigate the differentiation between subjects consuming cheese or milk and to elucidate the potential link to an effect on blood cholesterol level. Fifteen healthy young men participated in a full crossover study during which they consumed three isocaloric diets with similar fat contents that were either (i) high in milk, (ii) high in cheese with equal amounts of dairy calcium, or (iii) a control diet for 14 days. Urine and feces samples were collected and analyzed by NMR-based metabolomics. Cheese and milk consumption decreased urinary choline and TMAO levels and increased fecal excretion of acetate, propionate, and lipid. Compared with milk intake, cheese consumption significantly reduced urinary citrate, creatine, and creatinine levels and significantly increased the microbiota-related metabolites butyrate, hippurate, and malonate. Correlation analyses indicated that microbial and lipid metabolism could be involved in the dairy-induced effects on blood cholesterol level.

Intake of hydrolyzed casein is associated with reduced body fat accretion and enhanced phase II metabolism in obesity prone C57BL/6J mice

The amount and form of dietary casein have been shown to affect energy metabolism and lipid accumulation in mice, but the underlying mechanisms are not fully understood. We investigated 48 hrs urinary metabolome, hepatic lipid composition and gene expression in male C57BL/6J mice fed Western diets with 16 or 32 energy% protein in the form of extensively hydrolyzed or intact casein. LC-MS based metabolomics revealed a very strong impact of casein form on the urinary metabolome. Evaluation of the discriminatory metabolites using tandem mass spectrometry indicated that intake of extensively hydrolyzed casein modulated Phase II metabolism associated with an elevated urinary excretion of glucuronic acid- and sulphate conjugated molecules, whereas glycine conjugated molecules were more abundant in urine from mice fed the intact casein diets. Despite the differences in the urinary metabolome, we observed no differences in hepatic expression of genes involved in Phase II metabolism, but it was observed that expression of Abcc3 encoding ATP binding cassette c3 (transporter of glucuronic acid conjugates) was increased in livers of mice fed hydrolyzed casein. As glucuronic acid is derived from glucose and sulphate is derived from cysteine, our metabolomic data provided evidence for changes in carbohydrate and amino acid metabolism and we propose that this modulation of metabolism was associated with the reduced glucose and lipid levels observed in mice fed the extensively hydrolyzed casein diets.

Chemical and proteolysis-derived changes during long-term storage of lactose-hydrolyzed ultrahigh-temperature (UHT) milk

Proteolytic activity in milk may release bitter-tasting peptides and generate free amino terminals that react with carbohydrates, which initiate Maillard reaction. Ultrahigh temperature (UHT) heat treatment inactivates the majority of proteolytic enzymes in milk. In lactose-hydrolyzed milk a β-galactosidase preparation is applied to the milk after heat treatment, which has proteolytic side activities that may induce quality deterioration of long-term-stored milk. In the present study proteolysis, glycation, and volatile compound formation were investigated in conventional (100% lactose), filtered (60% lactose), and lactose-hydrolyzed (<1% lactose) UHT milk using reverse phase high-pressure liquid chromatography-mass spectrometry, proton nuclear magnetic resonance, and gas chromatography-mass spectrometry. Proteolysis was observed in all milk types. However, the degree of proteolysis was significantly higher in the lactose-hydrolyzed milk compared to the conventional and filtered milk. The proteins most prone to proteolysis were β-CN and αs1-CN, which were clearly hydrolyzed after approximately 90 days of storage in the lactose-hydrolyzed milk.

Lactose-hydrolyzed milk is more prone to chemical changes during storage than conventional ultra-high-temperature (UHT) milk

The enzymatic hydrolysis of lactose to glucose and galactose gives rise to reactions that change the chemistry and quality of ambient-stored lactose-hydrolyzed ultra-high-temperature (UHT) milk. The aim of the present study was to investigate and compare chemical changes in lactose-hydrolyzed and conventional UHT milk during a 9 month ambient storage period. Several complementary analyses of volatiles, free amino acids, acetate, furosine, and level of free amino terminals were concluded. The analyses revealed an increased level of free amino acids and an increased formation rate of specific compounds such as furosine and 2-methylbutanal in lactose-hydrolyzed UHT milk compared to conventional UHT milk during storage. These observations indicate more favorable conditions for Maillard and subsequent reactions in lactose-hydrolyzed milk compared to conventional UHT milk stored at ambient temperature. Furthermore, it is postulated that proteolytic activity from the lactase-enzyme preparation may be responsible for the observed higher levels of free amino acids in lactose-hydrolyzed UHT milk.

Urinary loss of tricarboxylic acid cycle intermediates as revealed by metabolomics studies: an underlying mechanism to reduce lipid accretion by whey protein ingestion?

Whey protein intake is associated with the modulation of energy metabolism and altered body composition both in human subjects and in animals, but the underlying mechanisms are not yet elucidated. We fed obesity-prone C57BL/6J mice high-fat diets with either casein (HF casein) or whey (HF whey) for 6 weeks. At equal energy intake and apparent fat and nitrogen digestibility, mice fed HF whey stored less energy as lipids, evident both as lower white adipose tissue mass and as reduced liver lipids, compared with HF-casein-fed mice. Explorative analyses of 48 h urine, both by ¹H NMR and LC–MS metabolomic platforms, demonstrated higher urinary excretion of tricarboxylic acid (TCA) cycle intermediates citric acid and succinic acid (identified by both platforms), and cis-aconitic acid and isocitric acid (identified by LC–MS platform) in the HF whey, relative to in the HF-casein-fed mice. Targeted LC–MS analyses revealed higher citric acid and cis-aconitic acid concentrations in fed state plasma, but not in liver of HF-whey-fed mice. We propose that enhanced urinary loss of TCA cycle metabolites drain available substrates for anabolic processes, such as lipogenesis, thereby leading to reduced lipid accretion in HF-whey-fed compared to HF-casein-fed mice.

High-throughput FTIR spectroscopy of intact HepG2 cells reveals additive and non-additive effects of individual fatty acids when given as mixtures

In the present study we investigated the ability of high-throughput FTIR spectroscopy in combination with multivariate data analysis to reveal if any combinatory effects of fatty acids in mixture are present in liver HepG2 cell cultures after three days of exposure. For this investigation we used an experimental mixture design containing three different octadecenoic acids (oleic acid: C18:1 cis- 9, elaidic acid: C18:1 trans- 9 and vaccenic acid: C18:1 trans- 11) of a total concentration of 100 μM. The results obtained revealed both additive and non-additive effects of individual fatty acids when combined in mixtures. Furthermore, we demonstrate by use of scanning electron microscopy that cells are preserved as intact structures ensuring that FTIR measurements are obtained on whole cell keeping cell compounds in their natural surroundings during measurements.

Relationship between RN(-) genotype and drip loss in meat from Danish pigs

The presence of the RN(-)-gene determined in 72 halothane negative Danish pigs, either by a direct genotyping or the glycolytic potential of the meat, in relation to drip loss, was investigated. The drip loss in the M. longissimus dorsi from RN-carriers (n=26), as determined by genotyping was 9.9% compared to 8.6% in non-carriers (n=46) (P=0.07). When a glycolytic potential of >230 μmol lactate/g meat was used to differentiate between carriers and non carriers of the RN(-)-gene, the drip loss in carriers was 10.6% (n=17) compared to 8.7% in non-carriers (n=55) (P<0.01). These results suggest that the presence of the RN(-)-gene in Danish slaughter pigs only partially explains the large variation in drip loss observed in Danish pork.

Metabolomics reveals drastic compositional changes during overwintering of Jerusalem artichoke (Helianthus tuberosus L.) tubers

Metabolic changes were investigated in overwintering Jerusalem artichoke (Helianthus tuberosus L.) tubers using proton nuclear magnetic resonance ((1)H NMR) metabolomics. Three varieties were studied; as a result of overwintering, the amount of inulin was found to decrease in Jerusalem artichoke tubers. This was mainly due to its conversion to sucrose and, at the same time, formation of inulin with a lower degree of polymerization. Major effects on the concentration of citric acid, malic acid, γ-aminobutyric acid (GABA), and adenosine were also found. Intriguingly, malic acid concentration increased and citric acid concentration decreased. These changes, together with an increase in sucrose and GABA concentrations, were ascribed to mobilization of nutrients prior to sprouting, suggesting that malic acid and GABA serve as carbon and nitrogen sources during sprouting of Jerusalem artichokes.

Natural variability in bovine milk oligosaccharides from Danish Jersey and Holstein-Friesian breeds

Free oligosaccharides are key components of human milk and play multiple roles in the health of the neonate, by stimulating growth of selected beneficial bacteria in the gut, participating in development of the brain, and exerting antipathogenic activity. However, the concentration of oligosaccharides is low in mature bovine milk, normally used for infant formula, compared with both human colostrum and mature human milk. Characterization of bovine milk oligosaccharides in different breeds is crucial for the identification of viable sources for oligosaccharide purification. An improved source of oligosaccharides can lead to infant formula with improved oligosaccharide functionality. In the present study we have analyzed milk oligosaccharides by high-performance liquid chromatography chip quadrupole time-of-flight mass spectrometry and performed a detailed data analysis using both univariate and multivariate methods. Both statistical tools revealed several differences in oligosaccharide profiles between milk samples from the two Danish breeds, Jersey and Holstein-Friesians. Jersey milk contained higher relative amounts of both sialylated and the more complex neutral fucosylated oligosaccharides, while the Holstein-Friesian milk had higher abundance of smaller and simpler neutral oligosaccharides. The statistical analyses revealed that Jersey milk contains levels of fucosylated oligosaccharides significantly higher than that of Holstein-Friesian milk. Jersey milk also possesses oligosaccharides with a higher degree of complexity and functional residues (fucose and sialic acid), suggesting it may therefore offer advantages in term of a wider array of bioactivities.

Assessment of meat quality by NMR--an investigation of pork products originating from different breeds

In the present study, meat obtained from uncommon and novel pig crossings between the rare Iberian and Mangalitza pigs and the more frequent Duroc and Landrace/Yorkshire pigs was characterized by time-domain proton NMR relaxometry and high-resolution proton NMR spectroscopy to elucidate the potential of NMR to assess the meat quality of new-introduced pig breeds. Multivariate data analysis of proton NMR T(2) relaxation curves obtained on fresh meat samples revealed differences in the T(2) relaxation pattern of the different breeds included in the study. Comparison of NMR T(2) relaxation data with gravimetric determination of water-holding capacity (WHC) indicated that this should be ascribed to differences in the WHC of the different meats, and that NMR T(2) relaxation in accordance with previous studies provides unique information about WHC, which may be ascribed to the fact that NMR T(2) relaxation reflects information about intrinsic meat structure. High-resolution proton NMR spectroscopy of freeze exudate and meat extracts also revealed differences in the metabolite profile of the meat between the different breeds studied. The effects of breed on the amount of lactate in the freeze exudate were observed, which could be linked to WHC of the meat. In conclusion, the different NMR techniques applied could provide complementary information about biophysical and biochemical factors of importance for meat quality assessment.

Quality of sour cherry juice of different clones and cultivars (Prunus cerasus L.) determined by a combined sensory and NMR spectroscopic approach

Juice was manufactured from seven different sour cherry clones/cultivars and evaluated by quantitative descriptive sensory analysis and (1)H NMR spectroscopy. The sensory evaluation showed a large variation in several sensory attributes between the sour cherry clones/cultivars, which could be divided into two groups on the basis of both the sensory data and the NMR spectroscopic data. These groups were closely related to the genetic background of the clones. Kelleris clones were distinctly different from Stevnsberry and Fanal clones. Hence, (1)H NMR spectroscopic data seem to correlate with sensory quality of different sour cherry clones. In addition, malic acid was the most important metabolite for modeling the two highly correlated sensory attributes sweetness and sourness, whereas the glucose content had a slight effect and the fructose content had no impact on sweetness/sourness. Other metabolites (ethyl acetate, asparagine, ethanol) could be correlated with sensory attributes; however, a direct causal connection could not be established.

Molecular water motions of skim milk powder solutions during acidification studied by 17O and 1H nuclear magnetic resonance and rheology

The molecular motion of water was studied in glucono-δ-lactone-acidified skim milk powder (SMP) solutions with various pH values and dry matter contents. NMR relaxometry measurements revealed that lowering the pH in SMP solutions affected 17O and 1H T2 relaxation rates almost identically. Consequently, the present study indicates that the proteins present in the samples do not affect the 1H relaxation behavior markedly, even at relatively high SMP concentrations (15-25%). Comparison of rheological measurements and NMR measurements suggested that the collapse of κ-casein during acidification could contribute to the initial decrease in 17O and 1H relaxation rate in the pH range between 6.6 and 5.5 for 15% SMP and in the pH range between 6.6 and 5.9 for 25% SMP. However, below pH 5.5 the viscosity and 17O and 1H NMR relaxation rates did not correlate, revealing that the aggregation of casein micelles, which increases viscosity below pH 5.5, does not involve major repartitioning of water.

Metabolomic phenotyping of a cloned pig model

BACKGROUND

Pigs are widely used as models for human physiological changes in intervention studies, because of the close resemblance between human and porcine physiology and the high degree of experimental control when using an animal model. Cloned animals have, in principle, identical genotypes and possibly also phenotypes and this offer an extra level of experimental control which could possibly make them a desirable tool for intervention studies. Therefore, in the present study, we address how phenotype and phenotypic variation is affected by cloning, through comparison of cloned pigs and normal outbred pigs.

RESULTS

The metabolic phenotype of cloned pigs (n = 5) was for the first time elucidated by nuclear magnetic resonance (NMR)-based metabolomic analysis of multiple bio-fluids including plasma, bile and urine. The metabolic phenotype of the cloned pigs was compared with normal outbred pigs (n = 6) by multivariate data analysis, which revealed differences in the metabolic phenotypes. Plasma lactate was higher for cloned vs control pigs, while multiple metabolites were altered in the bile. However a lower inter-individual variability for cloned pigs compared with control pigs could not be established.

CONCLUSIONS

From the present study we conclude that cloned and normal outbred pigs are phenotypically different. However, it cannot be concluded that the use of cloned animals will reduce the inter-individual variation in intervention studies, though this is based on a limited number of animals.

Nutritional regulation of bile acid metabolism is associated with improved pathological characteristics of the metabolic syndrome

Bile acids (BAs) are powerful regulators of metabolism, and mice treated orally with cholic acid are protected from diet-induced obesity, hepatic lipid accumulation, and increased plasma triacylglycerol (TAG) and glucose levels. Here, we show that plasma BA concentration in rats was elevated by exchanging the dietary protein source from casein to salmon protein hydrolysate (SPH). Importantly, the SPH-treated rats were resistant to diet-induced obesity. SPH-treated rats had reduced fed state plasma glucose and TAG levels and lower TAG in liver. The elevated plasma BA concentration was associated with induction of genes involved in energy metabolism and uncoupling, Dio2, Pgc-1α, and Ucp1, in interscapular brown adipose tissue. Interestingly, the same transcriptional pattern was found in white adipose tissue depots of both abdominal and subcutaneous origin. Accordingly, rats fed SPH-based diet exhibited increased whole body energy expenditure and heat dissipation. In skeletal muscle, expressions of the peroxisome proliferator-activated receptor β/δ target genes (Cpt-1b, Angptl4, Adrp, and Ucp3) were induced. Pharmacological removal of BAs by inclusion of 0.5 weight % cholestyramine to the high fat SPH diet attenuated the reduction in abdominal obesity, the reduction in liver TAG, and the decrease in nonfasted plasma TAG and glucose levels. Induction of Ucp3 gene expression in muscle by SPH treatment was completely abolished by cholestyramine inclusion. Taken together, our data provide evidence that bile acid metabolism can be modulated by diet and that such modulation may prevent/ameliorate the characteristic features of the metabolic syndrome.

Metabolic profiling of heat or anoxic stress in mouse C2C12 myotubes using multinuclear magnetic resonance spectroscopy

In the present study, the metabolic effects of heat and anoxic stress in myotubes from the mouse cell line C2C12 were investigated by using a combination of (13)C, (1)H, and (31)P nuclear magnetic resonance (NMR) spectroscopy and enrichment with [(13)C]-glucose. Both the (13)C and the (1)H NMR spectra showed reduced levels of the amino acids alanine, glutamate, and aspartate after heat or anoxic stress. The decreases were smallest at 42 degrees C, larger at 45 degrees C, and most pronounced after anoxic conditions. In addition, in both the (1)H and the (31)P NMR spectra, decreases in the high-energy phosphate compounds adenosine triphosphate and phosphocreatine with increasing severity of stress were identified. At anoxic conditions, an increase in (13)C-labeled lactate and appearance of glycerol-3-phosphate were observed. Accumulation of lactate and glycerol-3-phosphate is in agreement with a shift to anaerobic metabolism due to inhibition of the aerobic pathway in the mitochondria. Conversely, lower levels of unlabeled ((12)C) lactate were apparent at increasing severity of stress, which indicate that lactate is released from the myotubes to the medium. In conclusion, the metabolites identified in the present study may be useful markers for identifying severity of stress in muscles.

NMR-based metabonomic investigation of heat stress in myotubes reveals a time-dependent change in the metabolites

NMR-based metabonomics was applied to elucidate the time-dependent stress responses in mouse myotubes after heat exposure of either 42 or 45 degrees C for 1 h. Principal component analysis (PCA) revealed that the gradual time-dependent changes in metabolites contributing to the clustering and separation of the control samples from the different time points after heat stress primarily are in the metabolites glucose, leucine, lysine, phenylalanine, creatine, glutamine, and acetate. In addition, PC scores revealed a maximum change in metabolite composition 4 h after the stress exposure; thereafter, samples returned toward control samples, however, without reaching the control samples even 10 h after stress. The results also indicate that the myotubes efficiently regulate the pH level by release of lactate to the culture medium at a heat stress level of 42 degrees C, which is a temperature level reached in muscles of pigs during exposure to slaughter stress.

Oxidative stress-induced metabolic changes in mouse C2C12 myotubes studied with high-resolution 13C, 1H, and 31P NMR spectroscopy

In this study, stress in relation to slaughter was investigated in a model system by the use of (13)C, (1)H, and (31)P nuclear magnetic resonance (NMR) spectroscopy for elucidating changes in the metabolites in C2C12 myotubes exposed to H(2)O(2)-induced stress. Oxidative stress resulted in lower levels of several metabolites, mainly amino acids; however, higher levels of alanine were apparent in the (13)C spectra after incubation with [(13)C(1)]glucose. In the (13)C spectra [(13)C(3)]lactate tended to increase after exposure to increasing concentrations of H(2)O(2); conversely, a tendency to lower levels of the unlabeled ((12)C) lactate were identified in the (1)H spectra after stress exposure. These data indicate an increase in de novo synthesis of alanine, concomitant with a release of lactate from the myotubes to the medium at oxidative stress conditions. The changes in the metabolite levels could possibly be useful as markers for meat quality traits.

Creatine-induced activation of antioxidative defence in myotube cultures revealed by explorative NMR-based metabonomics and proteomics

Background

Creatine is a key intermediate in energy metabolism and supplementation of creatine has been used for increasing muscle mass, strength and endurance. Creatine supplementation has also been reported to trigger the skeletal muscle expression of insulin like growth factor I, to increase the fat-free mass and improve cognition in elderly, and more explorative approaches like transcriptomics has revealed additional information. The aim of the present study was to reveal additional insight into the biochemical effects of creatine supplementation at the protein and metabolite level by integrating the explorative techniques, proteomics and NMR metabonomics, in a systems biology approach.

Methods

Differentiated mouse myotube cultures (C2C12) were exposed to 5 mM creatine monohydrate (CMH) for 24 hours. For proteomics studies, lysed myotubes were analyzed in single 2-DGE gels where the first dimension of protein separation was pI 5-8 and second dimension was a 12.5% Criterion gel. Differentially expressed protein spots of significance were excised from the gel, desalted and identified by peptide mass fingerprinting using MALDI-TOF MS. For NMR metabonomic studies, chloroform/methanol extractions of the myotubes were subjected to one-dimensional ¹H NMR spectroscopy and the intracellular oxidative status of myotubes was assessed by intracellular DCFH₂ oxidation after 24 h pre-incubation with CMH.

Results

The identified differentially expressed proteins included vimentin, malate dehydrogenase, peroxiredoxin, thioredoxin dependent peroxide reductase, and 75 kDa and 78 kDa glucose regulated protein precursors. After CMH exposure, up-regulated proteomic spots correlated positively with the NMR signals from creatine, while down-regulated proteomic spots were negatively correlated with these NMR signals. The identified differentially regulated proteins were related to energy metabolism, glucose regulated stress, cellular structure and the antioxidative defence system. The suggested improvement of the antioxidative defence was confirmed by a reduced intracellular DCFH₂ oxidation with increasing concentrations of CMH in the 24 h pre-incubation medium.

Conclusions

The explorative approach of this study combined with the determination of a decreased intracellular DCFH₂ oxidation revealed an additional stimulation of cellular antioxidative mechanisms when myotubes were exposed to CMH. This may contribute to an increased exercise performance mediated by increased ability to cope with training-induced increases in oxidative stress.

NMR and the water-holding issue of pork

Consumers' awareness of food quality has never been more pronounced. Meat forms a substantial part of the food consumption, and accordingly techniques to control the quality of meat are needed. In addition, a better understanding of how basic biochemical and biophysical factors influence the final meat quality is also required for optimization of the quality. Water-holding capacity (WHC) is a major quality attribute of fresh meat. However, the exact mechanisms determining the WHC of meat are not fully understood. Especially, characteristics about proposed water populations in the meat and how they are interrelated with drip loss need to be studied further. Moreover, the distribution and mobility of water in muscle during its conversion to meat and how they are affected by intrinsic and extrinsic factors are poorly elucidated. Nuclear magnetic resonance (NMR) has during recent years gained increasing use within different areas of muscle physiology and meat science. NMR (1)H relaxation methodologies enable detection of the mobility of protons in heterogeneous materials and thereby provide possibilities for a characterization of the properties of water. The objective of this presentation is to give an overview of the use of NMR relaxation measurements to characterize the proposed water populations in meat and investigate how the distribution and mobility of the water changes postmortem. In addition, applications of NMR spectroscopy in metabolic studies will be considered.

NMR-based metabonomic studies reveal changes in the biochemical profile of plasma and urine from pigs fed high-fibre rye bread

This study presents an NMR-based metabonomic approach to elucidate the overall endogenous biochemical effects of a wholegrain diet. Two diets with similar levels of dietary fibre and macronutrients, but with contrasting levels of wholegrain ingredients, were prepared from wholegrain rye (wholegrain diet (WGD)) and non-wholegrain wheat (non-wholegrain diet (NWD)) and fed to four pigs in a crossover design. Plasma samples were collected after 7 d on each diet, and 1H NMR spectra were acquired on these. Partial least squares regression discriminant analysis (PLSDA) on spectra obtained for plasma samples revealed that the spectral region at 3·25 parts per million dominates the differentiation between the two diets, as the WGD is associated with higher spectral intensity in this region. Spiking experiments and LC–MS analyses of the plasma verified that this spectral difference could be ascribed to a significantly higher content of betaine in WGD plasma samples compared with NWD samples. In an identical study with the same diets, urine samples were collected, and1H NMR spectra were acquired on these. PLS-DA on spectra obtained for urine samples revealed changes in the intensities of spectral regions, which could be ascribed to differences in the content of betaine and creatine/creatinine between the two diets, and LC–MS analyses verified a significantly lower content of creatinine in WGD urine samples compared with NWD urine samples. In conclusion, using an explorative approach, the present studies disclosed biochemical effects of a wholegrain diet on plasma betaine content and excretion of betaine and creatinine.

Metabolic Profiling of Liver from Hypercholesterolemic Pigs Fed Rye or Wheat Fiber and from Normal Pigs. High-Resolution Magic Angle Spinning1H NMR Spectroscopic Study

This study presents the first application of a high-resolution magic angle spinning 1H NMR approach to elucidate the metabolic effects of a hypercholesterolemic condition and two high-fiber diets based on rye and wheat bread, respectively, in intact pig liver biopsy samples. Standard 1D and spin-echo 1H spectra were acquired on a total of 20 biopsy samples, and 2D total correlation spectroscopy experiments were carried out on selected samples for assignment of the observed resonances. Principal component analyses and partial least-squares regression discriminant analysis revealed differences in the hepatic lipid content and choline-containing compounds between normal and hypercholesterolemic pigs. In addition, the results demonstrated that the liver metabolite profile of hypercholesterolemic pigs fed a high-fiber rye bread differed from that of pigs fed high-fiber wheat bread with respect to both the lipoprotein fractions and the choline-containing compounds. These findings suggest that earlier reports on high-fiber rye diet-induced effects on plasma HDL/LDL content partially can be ascribed to effects on liver cholesterol metabolism and that the hepatic phospholipase pathways of phosphatidylcholine breakdown are affected by the high-fiber rye diet.

Evaluation of cooling strategies for pumping of milk – Impact of fatty acid composition on free fatty acid levels

Cooling strategies for pumping of raw milk were evaluated. Milk was pumped for 450 s at 31 °C, or pumped after cooling to 4 °C and subsequently subjected to various incubation times. Two types of milk were used; i.e. milk from cows fed a diet high in saturated fat supplements resulting in significantly larger milk fat globules than the other type of milk which comes from cows fed a low-fat diet that stimulates high de novo fat synthesis. The content of liquid fat was determined by low-field 1H NMR, which showed that milk from cows given the saturated fat diet also contained less liquid fat at both 4 ° and 31 °C than the other type of milk. This can be ascribed to the differences in the fatty acid composition of the milk as a result of the fatty acid composition of the diets. After pumping of the milk at 31 °C, measurement of fat globule size distribution revealed a significant coalescence of milk fat globules in the milk obtained from the saturated fat diet due to pumping. Pumping at 4 °C or pumping the other type of milk did not result in coalescence of milk fat globules. Formation of free fatty acids increased significantly in both types of milk by pumping at 31 °C. Cooling the milk to 4 °C immediately before pumping inhibited an increased content of free fatty acids. However, when the milk was incubated at 4 °C for 60 min after cooling and then subjected to pumping, a significant increase in the formation of free fatty acids was observed in both types of milk. It is suggested that this increase in free fatty acids is caused by transition of polymorphic crystal forms or higher level of attached lipoprotein lipases to the milk fat globule before pumping.

Cooking effects on water distribution in potatoes using nuclear magnetic resonance relaxation

Continuous low-field (LF) (1)H NMR relaxometry was used to monitor the structural changes during cooking of potatoes with two different dry matter (DM) contents. A principal component analysis of the relaxation decay curves revealed major events related to water mobility during cooking, which occur at 53 and 60 degrees C for potatoes with medium and low DM contents, respectively. Exponential analysis of the relaxation decays reveals two major water populations in the potato: a slow-relaxing (assigned to water in cytoplasm and extracellular cavities) water component, T(22) ( approximately 350-550 ms), and a fast-relaxing component (primarily assigned to water associated with starch and cell walls), T(21) ( approximately 45-65 ms). Significant DM dependent shifts in both the T(21) and T(22) relaxation time constants were observed during cooking, indicating that starch gelatinizes between 53 and 70 degrees C with water exchanging with the hydroxyls of starch (transition in T(21)) and cells start to disrupt with an increase in diffusion volumes at approximately 60 degrees C (transition in T(22)). The study reveals that continuous LF NMR measurement is an excellent and highly sensitive method to study changes in water mobility and water populations during the cooking of potatoes.

Post mortem energy metabolism and pH development in porcine M. longissimus dorsi as affected by two different cooling regimes. A (31)P-NMR spectroscopic study

(31)P-NMR spectroscopy was carried out on M. longissimus dorsi samples chilled by two different cooling profiles corresponding to commercial batch and tunnel chilling. The half-life of post mortem phosphocreatine (PCr) degradation was found to be significantly less in muscle samples exposed to tunnel chilling (rapid) compared with muscle samples exposed to batch chilling (soft) conditions, while no difference in the post mortem ATP degradation was found. Moreover, the post mortem pH development in the muscle samples differed considerably between the two cooling regimes. A maximum difference of approx. 0.25 pH units between the two cooling profiles was observed around 150 min post mortem. Theoretical calculations of the registered pH difference between rapid and soft chilling of muscle samples revealed that the temperature effect on the buffer capacity of muscle is the major determining factor in the detected difference in intracellular pH between the two cooling profiles, while any contribution from a temperature-induced delayed progress in the lactate formation post mortem seems negligible. Moreover, calculations on the effect of the registered pH difference between rapid and soft chilling of muscle samples resemble a 2.5 times greater denaturation of myosin in samples which were chilled softly compared with samples chilled more rapidly. Finally, the relationship to the functionality of meats from soft and rapid chilled pork carcasses is discussed.

Immunophenotyping large B-cell lymphomas. Flow cytometric pitfalls and pathologic correlation

Large cell lymphomas often challenge the diagnostic flow cytometrist. The purposes of this study were to improve our protocols for diagnosing large cell lymphomas and to correlate flow cytometric (FC) data with demographic and histologic features. We identified 63 cases of large B-cell lymphoma between January 1, 1995, and July 30, 1999, and reviewed the diagnostic slides and FC light scatter and staining patterns. The 51 lymphomas with adequate material for systemic review fell into 2 light scatter patterns: "clear cut," with large abnormal cells (high forward scatter relative to normal lymphocytes), 17 cases (33%); and "complex," 34 cases (67%). Clear-cut cases were more mitotically active (average of 42 vs 25 per 10 high-power fields), with higher cellularity. Apoptosis, geographic necrosis, and sclerosis were present histologically in many cases, regardless of FC findings. We conclude that morphologic features of large cell lymphomas do not predict which cases will be difficult to diagnose by FC. Gating strategies can be critical to improve the diagnostic yield.

Origin of multiexponential T(2) relaxation in muscle myowater

To obtain a further understanding of the nature of the multiexponential T(2) relaxation seen in muscle tissue water (myowater), relaxation measurements were carried out on whole, minced, and homogenized pork of three different qualities with regard to water-holding capacity (normal, red soft exudative, and dark firm dry). Whole, minced, and homogenized pork all resulted in multiexponential T(2) relaxation (three components) independently of the quality, even though microscopic studies on homogenized meat revealed considerable disruption of the macroscopic structure. This states that the relaxation behavior in meat cannot be explained by intra-/extracellular compartmentalization of the water as suggested in earlier studies. Subsequent studies of T(2) relaxation in either whole meat, where the structure integrity was changed by the introduction of dimethyl sulfoxide (membrane disruption) or urea (protein denaturation), or minced meat with added NaCl (inter-/intraprotein interactions) lead to the suggestion that in whole meat (i) the fastest relaxation component reflects water tightly associated with macromolecules, (ii) the intermediate relaxation component reflects water located within highly organized protein structures, for example, water in tertiary and/or quaternary protein structures and spatials with high myofibrillar protein densities including actin and myosin filament structures, and (iii) the slowest relaxation component reflects the extra-myofibrillar water containing the sarcoplasmatic protein fraction. Finally, relaxation patterns in heat-set gels of superprecipitated actomyosin and bovine serum albumin similar to that identified in whole meat support the proposed nature of T(2) relaxation in muscle myowater.