Modelling seasonal and geographical n-3 polyunsaturated fatty acid contents in marine fish from the Northeast Atlantic Ocean.

Demand for n-3 polyunsaturated fatty acids (n-3 PUFAs) exceeds supply. Large-scale studies on effects of season and geography of n-3 PUFAs in marine fish from the Northeast Atlantic Ocean (NEAO) may be used to optimize utilization and improve nutrition security. Using a sinusoid model, seasonal cycles of n-3 PUFAs were determined and found to be species-specific and clearly pronounced for the pelagic zooplankton feeding species. The Greenland halibut showed very little seasonal variation. The n-3 PUFA content in North Sea autumn-spawning (NSAS) herring peaked in summer, while Norwegian spring-spawning (NSS) herring and mackerel had their peak in autumn. A time shift of peaks in n-3 PUFAs between the two herring stocks was detected, likely due to different spawning strategies in addition to a delay of n-3 PUFAs flux in the northern regions of the NEAO. This study demonstrates that consideration of nutrient contents, such as n-3 PUFAs, when organizing and structuring fishery approaches may improve overall nutritional yield. Based on total annual Norwegian fish landings and seasonal variation in n-3 PUFA contents, n-3 PUFAs yield could theoretically be increased from 13.79 kilo ton per year from the current fishing tactics, to 15.54 if the pelagic species were only caught during the time of their seasonal n-3 PUFA peaks. Pelagic fish is a good source for dietary n-3 PUFAs, but harvest timing will also influence n-3 PUFAs intake by human consumers. One portion of fatty fish harvested during winter/spring may not meet the weekly intake reference nutritional guidelines for n-3 PUFAs. Marine n-3 PUFAs yields also varied geographically and decreased southwards, with the lowest values in Skagerrak. This study can serve as a model to understand patterns of reproductive cycles and geographical distribution of n-3 PUFAs in fatty fish from the NEAO and the novel approach may be useful to support sustainable, seasonal fishing programmes for optimization of n-3 PUFAs yields.

Changes in Plasma Pyruvate and TCA Cycle Metabolites upon Increased Hepatic Fatty Acid Oxidation and Ketogenesis in Male Wistar Rats.

Altered hepatic mitochondrial fatty acid ß-oxidation and associated tricarboxylic acid (TCA) cycle activity contributes to lifestyle-related diseases, and circulating biomarkers reflecting these changes could have disease prognostic value. This study aimed to determine hepatic and systemic changes in TCA-cycle-related metabolites upon the selective pharmacologic enhancement of mitochondrial fatty acid ß-oxidation in the liver, and to elucidate the mechanisms and potential markers of hepatic mitochondrial activity. Male Wistar rats were treated with 3-thia fatty acids (e.g., tetradecylthioacetic acid (TTA)), which target mitochondrial biogenesis, mitochondrial fatty acid ß-oxidation, and ketogenesis predominantly in the liver. Hepatic and plasma concentrations of TCA cycle intermediates and anaplerotic substrates (LC-MS/MS), plasma ketones (colorimetric assay), and acylcarnitines (HPLC-MS/MS), along with associated TCA-cycle-related gene expression (qPCR) and enzyme activities, were determined. TTA-induced hepatic fatty acid ß-oxidation resulted in an increased ratio of plasma ketone bodies/nonesterified fatty acid (NEFA), lower plasma malonyl-CoA levels, and a higher ratio of plasma acetylcarnitine/palmitoylcarnitine (C2/C16). These changes were associated with decreased hepatic and increased plasma pyruvate concentrations, and increased plasma concentrations of succinate, malate, and 2-hydroxyglutarate. Expression of several genes encoding TCA cycle enzymes and the malate-oxoglutarate carrier (Slc25a11), glutamate dehydrogenase (Gdh), and malic enzyme (Mdh1 and Mdh2) were significantly increased. In conclusion, the induction of hepatic mitochondrial fatty acid ß-oxidation by 3-thia fatty acids lowered hepatic pyruvate while increasing plasma pyruvate, as well as succinate, malate, and 2-hydroxyglutarate.

Dietary Selenomethionine Reduce Mercury Tissue Levels and Modulate Methylmercury Induced Proteomic and Transcriptomic Alterations in Hippocampi of Adolescent BALB/c Mice.

Methylmercury (MeHg) is a well-known environmental contaminant, particularly harmful to the developing brain. The main human dietary exposure to MeHg occurs through seafood consumption. However, seafood also contains several nutrients, including selenium, which has been shown to interact with MeHg and potentially ameliorate its toxicity. The aim of this study was to investigate the combined effects of selenium (as selenomethionine; SeMet) and MeHg on mercury accumulation in tissues and the effects concomitant dietary exposure of these compounds exert on the hippocampal proteome and transcriptome in mice. Adolescent male BALB/c mice were exposed to SeMet and two different doses of MeHg through their diet for 11 weeks. Organs, including the brain, were sampled for mercury analyses. Hippocampi were collected and analyzed using proteomics and transcriptomics followed by multi-omics bioinformatics data analysis. The dietary presence of SeMet reduced the amount of mercury in several organs, including the brain. Proteomic and RNA-seq analyses showed that both protein and RNA expression patterns were inversely regulated in mice receiving SeMet together with MeHg compared to MeHg alone. Several pathways, proteins and RNA transcripts involved in conditions such as immune responses and inflammation, oxidative stress, cell plasticity and Alzheimer's disease were affected inversely by SeMet and MeHg, indicating that SeMet can ameliorate several toxic effects of MeHg in mice.

Transplantation of microbiota from drug-free patients with schizophrenia causes schizophrenia-like abnormal behaviors and dysregulated kynurenine metabolism in mice.

Accumulating evidence suggests that gut microbiota plays a role in the pathogenesis of schizophrenia via the microbiota-gut-brain axis. This study sought to investigate whether transplantation of fecal microbiota from drug-free patients with schizophrenia into specific pathogen-free mice could cause schizophrenia-like behavioral abnormalities. The results revealed that transplantation of fecal microbiota from schizophrenic patients into antibiotic-treated mice caused behavioral abnormalities such as psychomotor hyperactivity, impaired learning and memory in the recipient animals. These mice also showed elevation of the kynurenine-kynurenic acid pathway of tryptophan degradation in both periphery and brain, as well as increased basal extracellular dopamine in prefrontal cortex and 5-hydroxytryptamine in hippocampus, compared with their counterparts receiving feces from healthy controls. Furthermore, colonic luminal filtrates from the mice transplanted with patients' fecal microbiota increased both kynurenic acid synthesis and kynurenine aminotransferase II activity in cultured hepatocytes and forebrain cortical slices. Sixty species of donor-derived bacteria showed significant difference between the mice colonized with the patients' and the controls' fecal microbiota, highlighting 78 differentially enriched functional modules including tryptophan biosynthesis function. In conclusion, our study suggests that the abnormalities in the composition of gut microbiota contribute to the pathogenesis of schizophrenia partially through the manipulation of tryptophan-kynurenine metabolism.

Lean-seafood intake increases urinary iodine concentrations and plasma selenium levels: a randomized controlled trial with crossover design.

PURPOSE: Iodine deficiency due to insufficient nutritional intake is a public health challenge in several European countries, including Norway. Lean-seafood has a high iodine and arsenic (As) content and is a good source of selenium (Se). Evidence of a direct effect of increased intake of lean-seafood on iodine status is limited. The main aims were to determine the iodine status at baseline and to investigate possible dietary effects on urinary iodine concentration (UIC) after intervention with lean-seafood versus non-seafood. Plasma Se, and plasma and urinary As concentrations were also measured. METHODS: A randomized controlled crossover study comprising two 4 weeks experimental periods with two balanced diets varied in main proteins (60% of total dietary proteins) of lean-seafood and non-seafood, separated by a 5 week washout period. RESULTS: Twenty participants (7 males, 13 females) were included and the mean ± SD age was 50.6 ± 15.3 years for all participants. Fasting UIC was median (25th, 75th percentile) 70 (38, 110) and 79 (49, 94) µg/L in the lean-seafood and non-seafood intervention at baseline, respectively. UIC increased after 4 weeks of the lean-seafood intervention to 135 (110, 278) µg/L, but not after the non-seafood intervention [58 (33, 91) µg/L] (P diet-effect < 0.001). Fasting plasma Se increased in the lean-seafood intervention and decreased in the non-seafood intervention (P diet-effect = 0.001). Fasting urinary and plasma As increased in the lean-seafood intervention and was unchanged in the non-seafood intervention (P diet-effect < 0.001). CONCLUSION: The participant's UIC was below the recommended median (100 µg/L) at baseline, but increased sufficiently after a 4 week intervention with lean-seafood.

One-Year Treatment with Olanzapine Depot in Female Rats: Metabolic Effects.

BACKGROUND: Antipsychotic drugs can negatively affect the metabolic status of patients, with olanzapine as one of the most potent drugs. While patients are often medicated for long time periods, experiments in rats typically run for 1 to 12 weeks, showing olanzapine-related weight gain and increased plasma lipid levels, with transcriptional upregulation of lipogenic genes in liver and adipose tissue. It remains unknown whether metabolic status will deteriorate with time. METHODS: To examine long-term metabolic effects, we administered intramuscular long-acting injections of olanzapine (100 mg/kg BW) or control substance to female rats for up to 13 months. RESULTS: Exposure to olanzapine long-acting injections led to rapid weight gain, which was sustained throughout the experiment. At 1, 6, and 13 months, plasma lipid levels were measured in separate cohorts of rats, displaying no increase. Hepatic transcription of lipid-related genes was transiently upregulated at 1 month. Glucose and insulin tolerance tests indicated insulin resistance in olanzapine-treated rats after 12 months. CONCLUSION: Our data show that the continuous increase in body weight in response to long-term olanzapine exposure was accompanied by surprisingly few concomitant changes in plasma lipids and lipogenic gene expression, suggesting that adaptive mechanisms are involved to reduce long-term metabolic adverse effects of this antipsychotic agent in rats.

Seafood intake and the development of obesity, insulin resistance and type 2 diabetes.

We provide an overview of studies on seafood intake in relation to obesity, insulin resistance and type 2 diabetes. Overweight and obesity development is for most individuals the result of years of positive energy balance. Evidence from intervention trials and animal studies suggests that frequent intake of lean seafood, as compared with intake of terrestrial meats, reduces energy intake by 4-9 %, sufficient to prevent a positive energy balance and obesity. At equal energy intake, lean seafood reduces fasting and postprandial risk markers of insulin resistance, and improves insulin sensitivity in insulin-resistant adults. Energy restriction combined with intake of lean and fatty seafood seems to increase weight loss. Marine n-3 PUFA are probably of importance through n-3 PUFA-derived lipid mediators such as endocannabinoids and oxylipins, but other constituents of seafood such as the fish protein per se, trace elements or vitamins also seem to play a largely neglected role. A high intake of fatty seafood increases circulating levels of the insulin-sensitising hormone adiponectin. As compared with a high meat intake, high intake of seafood has been reported to reduce plasma levels of the hepatic acute-phase protein C-reactive protein level in some, but not all studies. More studies are needed to confirm the dietary effects on energy intake, obesity and insulin resistance. Future studies should be designed to elucidate the potential contribution of trace elements, vitamins and undesirables present in seafood, and we argue that stratification into responders and non-responders in randomised controlled trials may improve the understanding of health effects from intake of seafood.

Meals based on cod or veal in combination with high or low glycemic index carbohydrates did not affect diet-induced thermogenesis, appetite sensations, or subsequent energy intake differently.

The objective of this study was to investigate the acute effects of meals containing protein from either cod or veal in combination with high or low glycemic index (GI) carbohydrates, on diet-induced thermogenesis (DIT) (primary endpoint), appetite, energy intake (EI), as well as postpranidal ghrelin, glucose, and insulin responses. Twenty-three overweight men and women (mean ±â€¯SD age: 30.0 ±â€¯7.6 y, BMI: 27.2 ±â€¯1.4 kg/m2) consumed 4 test meals: cod with mashed potatoes (high GI carbohydrate), cod with wholegrain pasta (low GI carbohydrate), veal with mashed potatoes, and veal with wholegrain pasta (∼2010 kJ, ∼25.5 E% protein, ∼41.0 E% carbohydrate, ∼33.5 E% fat). Energy expenditure was measured at baseline and six times postprandially, each lasting 25 min. Additionally, appetite sensations were measured every half hour. Arterialized venous blood samples were drawn every 20 min until an ad libitum buffet-style lunch was served 3.5 h later. DIT did not differ between test meals (P > 0.05), and there were no differences in appetite sensations or ad libitum EI (all, P > 0.05). Meal-time interactions were found for glucose and insulin (P = 0.04 and P < 0.001). Pairwise comparisons revealed that glucose and insulin peaks were higher after the meals with high GI carbohydrates. No differences were found between meals with cod or veal in combination with carbohydrates with low or high GI on DIT, appetite sensations, or EI in overweight men and women. However, as expected meals with high GI carbohydrates resulted in higher glucose and insulin responses compared to meals with low GI carbohydrates regardless of protein source.

Metagenomic analysis of faecal microbiome as a tool towards targeted non-invasive biomarkers for colorectal cancer.

OBJECTIVE: To evaluate the potential for diagnosing colorectal cancer (CRC) from faecal metagenomes. DESIGN: We performed metagenome-wide association studies on faecal samples from 74 patients with CRC and 54 controls from China, and validated the results in 16 patients and 24 controls from Denmark. We further validated the biomarkers in two published cohorts from France and Austria. Finally, we employed targeted quantitative PCR (qPCR) assays to evaluate diagnostic potential of selected biomarkers in an independent Chinese cohort of 47 patients and 109 controls. RESULTS: Besides confirming known associations of Fusobacterium nucleatum and Peptostreptococcus stomatis with CRC, we found significant associations with several species, including Parvimonas micra and Solobacterium moorei. We identified 20 microbial gene markers that differentiated CRC and control microbiomes, and validated 4 markers in the Danish cohort. In the French and Austrian cohorts, these four genes distinguished CRC metagenomes from controls with areas under the receiver-operating curve (AUC) of 0.72 and 0.77, respectively. qPCR measurements of two of these genes accurately classified patients with CRC in the independent Chinese cohort with AUC=0.84 and OR of 23. These genes were enriched in early-stage (I-II) patient microbiomes, highlighting the potential for using faecal metagenomic biomarkers for early diagnosis of CRC. CONCLUSIONS: We present the first metagenomic profiling study of CRC faecal microbiomes to discover and validate microbial biomarkers in ethnically different cohorts, and to independently validate selected biomarkers using an affordable clinically relevant technology. Our study thus takes a step further towards affordable non-invasive early diagnostic biomarkers for CRC from faecal samples.

Lower levels of Persistent Organic Pollutants, metals and the marine omega 3-fatty acid DHA in farmed compared to wild Atlantic salmon (Salmo salar).

Contaminants and fatty acid levels in farmed- versus wild Atlantic salmon have been a hot topic of debate in terms of food safety. The present study determined dioxins (polychlorinated dibenzo-p-dioxin and dibenzofuran), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides (OCPs), metals and fatty acids in wild and farmed Atlantic salmon. Contaminant levels of dioxins, PCBs, OCPs (DDT, dieldrin, lindane, chlordane, Mirex, and toxaphene), and mercury were higher in wild salmon than in farmed salmon, as were the concentrations of the essential elements selenium, copper, zinc and iron, and the marine omega-3 fatty acid docosahexaenoic acid (DHA). PBDE, endosulfan, pentachlorobenzene, hexachlorobenzene, cadmium and lead levels were low and comparable in both wild and farmed fish, and there was no significant difference in the marine omega-3 fatty acid eicosapentaenoic acid (EPA) concentration. The total fat content was significantly higher in farmed than wild salmon due to a higher content of both saturated and monounsaturated fatty acids, as well as a higher content of omega-6 fatty acids. The omega-3 to omega-6 fatty acid ratio was considerably lower in farmed than wild salmon due to the high level of omega-6 fatty acids. Contaminant concentrations in Atlantic salmon were well below maximum levels applicable in the European Union. Atlantic salmon, both farmed and wild, is a good source of EPA and DHA with a 200g portion per week contributing 3.2g or 2.8g respectively, being almost twice the intake considered adequate for adults by the European Food Safety Authority (i.e. 250mg/day or 1.75g/week).

p53 regulates expression of uncoupling protein 1 through binding and repression of PPARγ coactivator-1α.

The tumor suppressor p53 (TRP53 in mice) is known for its involvement in carcinogenesis, but work during recent years has underscored the importance of p53 in the regulation of whole body metabolism. A general notion is that p53 is necessary for efficient oxidative metabolism. The importance of UCP1-dependent uncoupled respiration and increased oxidation of glucose and fatty acids in brown or brown-like adipocytes, termed brite or beige, in relation to energy balance and homeostasis has been highlighted recently. UCP1-dependent uncoupled respiration in classic interscapular brown adipose tissue is central to cold-induced thermogenesis, whereas brite/beige adipocytes are of special importance in relation to diet-induced thermogenesis, where the importance of UCP1 is only clearly manifested in mice kept at thermoneutrality. We challenged wild-type and TRP53-deficient mice by high-fat feeding under thermoneutral conditions. Interestingly, mice lacking TRP53 gained less weight compared with their wild-type counterparts. This was related to an increased expression of Ucp1 and other PPARGC1a and PPARGC1b target genes but not Ppargc1a or Ppargc1b in inguinal white adipose tissue of mice lacking TRP53. We show that TRP53, independently of its ability to bind DNA, inhibits the activity of PPARGC1a and PPARGC1b. Collectively, our data show that TRP53 has the ability to regulate the thermogenic capacity of adipocytes through modulation of PPARGC1 activity.

Effect of a long-term high-protein diet on survival, obesity development, and gut microbiota in mice.

Female C57BL/6J mice were fed a regular low-fat diet or high-fat diets combined with either high or low protein-to-sucrose ratios during their entire lifespan to examine the long-term effects on obesity development, gut microbiota, and survival. Intake of a high-fat diet with a low protein/sucrose ratio precipitated obesity and reduced survival relative to mice fed a low-fat diet. By contrast, intake of a high-fat diet with a high protein/sucrose ratio attenuated lifelong weight gain and adipose tissue expansion, and survival was not significantly altered relative to low-fat-fed mice. Our findings support the notion that reduced survival in response to high-fat/high-sucrose feeding is linked to obesity development. Digital gene expression analyses, further validated by qPCR, demonstrated that the protein/sucrose ratio modulated global gene expression over time in liver and adipose tissue, affecting pathways related to metabolism and inflammation. Analysis of fecal bacterial DNA using the Mouse Intestinal Tract Chip revealed significant changes in the composition of the gut microbiota in relation to host age and dietary fat content, but not the protein/sucrose ratio. Accordingly, dietary fat rather than the protein/sucrose ratio or adiposity is a major driver shaping the gut microbiota, whereas the effect of a high-fat diet on survival is dependent on the protein/sucrose ratio.

Lean Seafood Intake Reduces Postprandial C-peptide and Lactate Concentrations in Healthy Adults in a Randomized Controlled Trial with a Crossover Design.

BACKGROUND: Recently we showed that lean seafood consumption reduced circulating triacylglycerol (TG) and VLDL concentrations and prevented an elevated total-to-HDL-cholesterol ratio relative to intake of a nonseafood diet. OBJECTIVE: We aimed to elucidate whether diet-induced altered carbohydrate metabolism could be a contributing factor to the previously observed different lipoprotein patterns. METHODS: This was a secondary outcome and explorative randomized controlled trial with a crossover design in 20 healthy adults (7 men and 13 women) that were 50.6 ± 3.4 (mean ± SEM) y old, weighed 75.7 ± 2.5 kg, and had a body mass index (BMI, in kg/m(2)) of 25.6 ± 0.7. After a 3-wk run-in period and separated by a 5-wk wash-out period, the participants consumed 2 balanced diets [in percentage of energy (energy%); 29% fat, 52% carbohydrates, 19% protein] for 4 wk. The diets varied in the main protein sources; 60 energy% of total protein was from either lean seafood or nonseafood sources. On the first and last day of each diet period, fasting and postprandial blood samples were collected before and after consumption of test meals (in energy%; 28% fat, 52% carbohydrates, 20% protein) with cod or lean beef. RESULTS: The diets did not alter serum insulin and glucose concentrations. However, relative to the nonseafood diet period, the lean seafood diet period reduced postprandial C-peptide (P = 0.04) and lactate (P = 0.012) concentrations and fasting and postprandial TG/HDL-cholesterol ratios (P = 0.002). Hence, different postprandial lactate levels occurred at equal glucose concentrations. CONCLUSIONS: Even though the diets did not alter serum insulin and glucose concentrations, intake of the lean seafood compared with the nonseafood diet reduced postprandial concentrations of C-peptide and lactate and the TG/HDL-cholesterol ratio in healthy adults in a manner that may affect the long-term development of insulin resistance, type 2 diabetes, and cardiovascular disease. This trial was registered at www.clinicaltrials.gov as NCT01708681.

FFAR4 (GPR120) Signaling Is Not Required for Anti-Inflammatory and Insulin-Sensitizing Effects of Omega-3 Fatty Acids.

Free fatty acid receptor-4 (FFAR4), also known as GPR120, has been reported to mediate the beneficial effects of omega-3 polyunsaturated fatty acids (ω3-PUFAs) by inducing an anti-inflammatory immune response. Thus, activation of FFAR4 has been reported to ameliorate chronic low-grade inflammation and insulin resistance accompanying obesity. However, conflicting reports on the role of FFAR4 in mediating the effects of ω3-PUFAs are emerging, suggesting that FFAR4 may not be the sole effector. Hence analyses of the importance of this receptor in relation to other signaling pathways and prominent effects of ω3-PUFAs remain to be elucidated. In the present study, we used Ffar4 knockouts (KO) and heterozygous (HET) mice fed either low fat, low sucrose reference diet; high fat, high sucrose ω3-PUFA; or high fat, high sucrose ω6-PUFA diet for 36 weeks. We demonstrate that both KO and HET mice fed ω3-PUFAs were protected against obesity, hepatic triacylglycerol accumulation, and whole-body insulin resistance. Moreover, ω3-PUFA fed mice had increased circulating protein levels of the anti-inflammatory adipokine, adiponectin, decreased fasting insulin levels, and decreased mRNA expression of several proinflammatory molecules within visceral adipose tissue. In conclusion, we find that FFAR4 signaling is not required for the reported anti-inflammatory and insulin-sensitizing effects mediated by ω3-PUFAs.

Indomethacin treatment prevents high fat diet-induced obesity and insulin resistance but not glucose intolerance in C57BL/6J mice.

Chronic low grade inflammation is closely linked to obesity-associated insulin resistance. To examine how administration of the anti-inflammatory compound indomethacin, a general cyclooxygenase inhibitor, affected obesity development and insulin sensitivity, we fed obesity-prone male C57BL/6J mice a high fat/high sucrose (HF/HS) diet or a regular diet supplemented or not with indomethacin (±INDO) for 7 weeks. Development of obesity, insulin resistance, and glucose intolerance was monitored, and the effect of indomethacin on glucose-stimulated insulin secretion (GSIS) was measured in vivo and in vitro using MIN6 ß-cells. We found that supplementation with indomethacin prevented HF/HS-induced obesity and diet-induced changes in systemic insulin sensitivity. Thus, HF/HS+INDO-fed mice remained insulin-sensitive. However, mice fed HF/HS+INDO exhibited pronounced glucose intolerance. Hepatic glucose output was significantly increased. Indomethacin had no effect on adipose tissue mass, glucose tolerance, or GSIS when included in a regular diet. Indomethacin administration to obese mice did not reduce adipose tissue mass, and the compensatory increase in GSIS observed in obese mice was not affected by treatment with indomethacin. We demonstrate that indomethacin did not inhibit GSIS per se, but activation of GPR40 in the presence of indomethacin inhibited glucose-dependent insulin secretion in MIN6 cells. We conclude that constitutive high hepatic glucose output combined with impaired GSIS in response to activation of GPR40-dependent signaling in the HF/HS+INDO-fed mice contributed to the impaired glucose clearance during a glucose challenge and that the resulting lower levels of plasma insulin prevented the obesogenic action of the HF/HS diet.

Proteomic analysis of cAMP-mediated signaling during differentiation of 3 T3-L1 preadipocytes.

Initiation of adipocyte differentiation is promoted by the synergistic action of insulin/insulin-like growth factor, glucocorticoids, and agents activating cAMP-dependent signaling. The action of cAMP is mediated via PKA and Epac, where at least part of the PKA function relates to strong repression of Rho kinase activity, whereas Epac counteracts the reduction in insulin/insulin-like growth factor signaling associated with complete repression of Rho kinase activity. However, detailed knowledge of the Epac-dependent branch and the interplay with PKA is still limited. In the present study, we present a comprehensive evaluation of Epac-mediated processes and their interplay with PKA during the initiation of 3 T3-L1 preadipocyte differentiation using a combination of proteomics, molecular approaches, and bioinformatics. Proteomic analyses revealed 7 proteins specifically regulated in response to Epac activation, 4 in response to PKA activation, and 11 in response to the combined activation of Epac and PKA during the initial phase of differentiation. Network analyses indicated that the identified proteins are involved in pathways of importance for glucose metabolism, inositol metabolism, and calcium-dependent signaling thereby adding a novel facet to our understanding of cAMP-mediated potentiation of adipocyte differentiation.

Transcriptome profiling of brown adipose tissue during cold exposure reveals extensive regulation of glucose metabolism.

We applied digital gene expression profiling to determine the transcriptome of brown and white adipose tissues (BAT and WAT, respectively) during cold exposure. Male C57BL/6J mice were exposed to cold for 2 or 4 days. A notable induction of genes related to glucose uptake, glycolysis, glycogen metabolism, and the pentose phosphate pathway was observed in BAT from cold-exposed animals. In addition, glycerol-3-phosphate dehydrogenase 1 expression was induced in BAT from cold-challenged mice, suggesting increased synthesis of glycerol from glucose. Similarly, expression of lactate dehydrogenases was induced by cold in BAT. Pyruvate dehydrogenase kinase 2 (Pdk2) and Pdk4 were expressed at significantly higher levels in BAT than in WAT, and Pdk2 was induced in BAT by cold. Of notice, only a subset of the changes detected in BAT was observed in WAT. Based on changes in gene expression during cold exposure, we propose a model for the intermediary glucose metabolism in activated BAT: 1) fluxes through glycolysis and the pentose phosphate pathway are induced, the latter providing reducing equivalents for de novo fatty acid synthesis; 2) glycerol synthesis from glucose is increased, facilitating triacylglycerol synthesis/fatty acid re-esterification; 3) glycogen turnover and lactate production are increased; and 4) entry of glucose carbon into the tricarboxylic acid cycle is restricted by PDK2 and PDK4. In summary, our results demonstrate extensive and diverse gene expression changes related to glucose handling in activated BAT.

Dietary n-6 PUFA, carbohydrate:protein ratio and change in body weight and waist circumference: a follow-up study.

OBJECTIVE: To investigate the association between the intake of n-6 PUFA and subsequent change in body weight and waist circumference at different levels of the carbohydrate:protein ratio. DESIGN: Follow-up study with anthropometric measurements at recruitment and on average 5·3 years later. Dietary intake was determined at recruitment by using an FFQ that was designed for the study and validated. We applied linear regression models with 5-year change in weight or waist circumference as outcome and including a two-way interaction term between n-6 PUFA and carbohydrate intakes, lower-order terms, protein intake, long-chain n-3 PUFA intake and other potential confounders. Due to adjustment for intake of protein, levels of carbohydrate indirectly reflect levels of the carbohydrate:protein ratio. SETTING: Diet, Cancer and Health follow-up study, Denmark. SUBJECTS: Women and men (n 29 152) aged 55 years. RESULTS: For a high intake of n-6 PUFA (6·9 % of energy) v. a low intake of n-6 PUFA (3·4 % of energy), the difference in 5-year weight change was -189·7 g (95 % CI -636·8, 257·4 g) at a low carbohydrate:protein ratio and -86·7 g (95 % CI -502·9, 329·6 g) at a high carbohydrate:protein ratio; the differences in 5-year waist circumference change were 0·26 cm (95 % CI -0·47, 0·98 cm) and -0·52 cm (95 % CI -1·19, 0·15 cm), respectively. Inclusion of the dietary glycaemic index did not change the results. CONCLUSIONS: No consistent associations between the intake of n-6 PUFA and change in body weight or waist circumference at different levels of the carbohydrate:protein ratio were observed.

PPARγ ligand production is tightly linked to clonal expansion during initiation of adipocyte differentiation.

Adipocyte differentiation is orchestrated by the ligand-activated nuclear receptor PPARγ. Endogenous ligands comprise oxidized derivatives of arachidonic acid and structurally similar PUFAs. Although expression of PPARγ peaks in mature adipocytes, ligands are produced primarily at the onset of differentiation. Concomitant with agonist production, murine fibroblasts undergo two rounds of mitosis referred to as mitotic clonal expansion. Here we show that mouse embryonic fibroblasts deficient in either of two cell cycle inhibitors, the transcription factor p53 or its target gene encoding the cyclin-dependent kinase inhibitor p21, exhibit increased adipogenic potential. The antiadipogenic effect of p53 relied on its transcriptional activity and p21 expression but was circumvented by administration of an exogenous PPARγ agonist suggesting a linkage between cell cycling and PPARγ ligand production. Indeed, cell cycle inhibitory compounds decreased PPARγ ligand production in differentiating 3T3-L1 preadipocytes. Furthermore, these inhibitors abolished the release of arachidonic acid induced by the hormonal cocktail initiating adipogenesis. Collectively, our results suggest that murine fibroblasts require clonal expansion for PPARγ ligand production at the onset of adipocyte differentiation.

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 (1)H 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.