Fish Oil Accelerates Diet-Induced Entrainment of the Mouse Peripheral Clock via GPR120

Marine n-3 polyunsaturated fatty acids slow sleep impairment progression by regulating central circadian rhythms in type 2 diabetes

The role of marine n-3 polyunsaturated fatty acids (PUFAs) in promoting sleep has been proposed, yet their benefits for patients with type 2 diabetes (T2D) and the underlying molecular mechanisms remain poorly understood. In this study, we identify a significant association between habitual fish oil use and improved sleep quality in a cohort of 27,549 patients with T2D. A subsequent randomized controlled trial demonstrates that fish oil supplementation enhances sleep parameters in patients with T2D, accompanied by the upregulation of core circadian clock genes, including Clock, Bmal1, and Per2. In vitro, DHA and EPA restore the rhythmic oscillations of key clock genes in hypothalamic neurons disrupted by palmitic acid. Notably, n-3 PUFAs target RORα to regulate circadian clock oscillations and facilitate BMAL1 nuclear translocation. Collectively, our findings highlight the potential of marine n-3 PUFAs as a dietary intervention to improve sleep health in patients with T2D. This study was registered at ClinicalTrials.gov (NCT03708887).

Chrononutrition in Critical Illness

Circadian rhythms in humans are biological rhythms that regulate various physiological processes within a 24-hour time frame. Critical illness can disrupt the circadian rhythm, as can environmental and clinical factors, including altered light exposure, organ replacement therapies, disrupted sleep-wake cycles, noise, continuous enteral feeding, immobility, and therapeutic interventions. Nonpharmacological interventions, controlling the ICU environment, and pharmacological treatments are among the treatment strategies for circadian disruption. Nutrition establishes biological rhythms in metabolically active peripheral tissues and organs through appropriate synchronization with endocrine signals. Therefore, adhering to a feeding schedule based on the biological clock, a concept known as "chrononutrition," appears to be vitally important for regulating peripheral clocks. Chrononutritional approaches, such as intermittent enteral feeding that includes overnight fasting and consideration of macronutrient composition in enteral solutions, could potentially restore circadian health by resetting peripheral clocks. However, due to the lack of evidence, further studies on the effect of chrononutrition on clinical outcomes in critical illness are needed. The purpose of this review was to discuss the role of chrononutrition in regulating biological rhythms in critical illness, and its impact on clinical outcomes.

Dietary Intake of Chromista Oil Alters Hepatic Metabolomic Profile of Mice With Excess Fat Mass

Increasing dietary intake of fish oil is frequently recommended for decreasing the risk for cardiovascular diseases and improving metabolic health. We hypothesised that dietary intake of chromista oil (a marine food product and a rich source of long-chain n-3 polyunsaturated fatty acids) ameliorates metabolic impairments in mice with established excess adiposity. Three-to 4-week-old mice (male) were fed a control (n = 12) or a high-fat diet (HFD, n = 24) for 12 weeks to establish body fat mass. Then, mice on the HFD were assigned to 2 groups (n = 12 each) with 1 continuing being fed the HFD and the other fed the HFD with chromista oil for an additional 12 weeks. Intake of chromista oil did not affect body weight and body adiposity of the mice fed the HFD; mice fed the HFD had significantly more body weight and fat mass than control mice. The flattened daily oscillations of respiratory exchange ratio induced by the HFD were not changed by chromista oil intake. Intake of chromista oil significantly increased plasma concentration of insulin, the calculated value of HOMA-IR, and plasma concentration of adiponectin in the mice fed the HFD. However, blood glucose was unaffected by chromista oil. Transcription of genes encoding circadian rhythm and fatty acid metabolism of the 2 HFD-fed groups were similar. Untargeted metabolomic analysis showed that intake of chromista oil altered the hepatic metabolomic profile with substantial alterations in amino acid metabolism. Findings from this study indicate that dietary intake of chromista oil does not improve glucose homeostasis or alter the diminished metabolic flexibility in mice with excess adiposity induced by the HFD. argeted metabolomic analysis is warranted to investigate the effects of dietary chromista oil, as a source of n-3 poly unsaturated fatty acids, on metabolism in models of obesity.

Histology, fatty acid composition, antioxidant and glycolipid metabolism, and transcriptome analyses of the acute cold stress response in Phoxinus lagowskii

Water temperature is a crucial environmental factor that significantly affects the physiological and biochemical processes of fish. Due to the occurrence of cold events in aquaculture, it is imperative to investigate how fish respond to cold stress. This study aims to uncover the mechanisms responds to acute cold stress by conducting a comprehensive analysis of the histomorphology, glycolipid metabolic and antioxidant enzymes, fatty acid composition and transcriptome at three temperatures (16 °C, 10 °C and 4 °C) in Phoxinus lagowskii. Our results showed that cold stress not damaged muscle microstructure but caused autophagy (at 10 °C). In addition, serum glucose (Glu) and triglycerides (TG) increased during cold stress. The activities of reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), fructose phosphokinase (PFK), hexokinase (HK), pyruvate kinase (PK), and malondialdehyde (MDA) content in muscle were measured and analyzed. During cold stress, superoxide dismutase and catalase activities increased, reactive oxygen species content decreased. No significant difference in Glutathione peroxidase (GPx) activity, malondialdehyde and total cholesterol (T-CHO) contents among groups. Phosphokinase and pyruvate kinase activities decreased, and HK activity increased during cold stress. Our study resulted in the identification of a total of 25,400 genes, with 2524 genes showing differential expression across different temperature treatments. Furthermore, KEGG pathway indicated that some pathways upregulated during light cold stress (at 10 °C, including autophagy, and AMP-activated protein kinase (AMPK) signaling pathway. Additionally, circadian rhythm is among the most enriched pathways in genes up-regulated during severe cold stress (at 4 °C). Our findings offer valuable insights into how cold-water fish respond to cold stress.

Akkermansia muciniphila supplementation improves glucose tolerance in intestinal Ffar4 knockout mice during the daily light to dark transition

IMPORTANCE

Alterations in the intestinal environment are associated with various diseases, and FFAR4 is abundantly enriched in the intestine, where it has been shown to have the ability to regulate intestinal hormone secretion and intestinal microbiota; here, we confirmed previous reports. Meanwhile, we found that intestinal FFAR4 regulates glucagon-like peptide 1 secretion by decreasing Akkermansia muciniphila abundance and show that such change is associated with the level of glucose utilization at ZT12 in mice. Intestinal FFAR4 deficiency leads to severely impaired glucose tolerance at the ZT12 moment in mice, and Akkermansia muciniphila supplementation ameliorates the abnormal glucose utilization at the ZT12 moment caused by FFAR4 deficiency, which is very similar to the dawn phenomenon in diabetic patients. Collectively, our data suggest that intestinal Ffar4 deteriorates glucose tolerance at the daily light to dark transition by affecting Akkermansia muciniphila.

Euglena gracilis-derived β-glucan paramylon entrains the peripheral circadian clocks in mice

Paramylon, a β-1,3-glucan storage polysaccharide derived from Euglena gracilis, has various health benefits, such as anti-obesity effects and modulation of immune function. However, whether paramylon intake affects the circadian clock remains unknown. In this study, we examined the effect of paramylon intake on the circadian clock. The results showed that the paramylon intake regulated peripheral clocks in mice. Furthermore, cecal pH and short-chain fatty acid concentrations after paramylon intake were measured. The correlation between changes in the expression of clock-related genes and alterations in the intestinal environment was confirmed. In addition, peripheral clock entrainment by paramylon intake was not observed in antibiotic-treated mice whose gut microbiota was weakened. These findings suggest that the regulation of the circadian clock by paramylon intake was mediated by changes in gut microbiota. In addition, the entraining effect of paramylon intake was also confirmed in mice bred under conditions mimicking social jetlag, which implies that paramylon intake may contribute to recovery from social jetlag. Thus, the appropriate consumption of paramylon may have a beneficial effect on health from a chrono-nutritional perspective.

Polygalae Radix shortens the circadian period through activation of the CaMKII pathway

CONTEXT

The mammalian circadian clock system regulates physiological function. Crude drugs, containing Polygalae Radix, and Kampō, combining multiple crude drugs, have been used to treat various diseases, but few studies have focussed on the circadian clock.

OBJECTIVE

We examine effective crude drugs, which cover at least one or two of Kampō, for the shortening effects on period length of clock gene expression rhythm, and reveal the mechanism of shortening effects.

MATERIALS AND METHODS

We prepared 40 crude drugs. In the in vitro experiments, we used mouse embryonic fibroblasts from PERIOD2::LUCIFERASE knock-in mice (background; C57BL/6J mice) to evaluate the effect of crude drugs on the period length of core clock gene, Per2, expression rhythm by chronic treatment (six days) with distilled water or crude drugs (100 μg/mL). In the in vivo experiments, we evaluated the free-running period length of C57BL/6J mice fed AIN-93M or AIN-93M supplemented with 1% crude drug (6 weeks) that shortened the period length of the PERIOD2::LUCIFERASE expression rhythm in the in vitro experiments.

RESULTS

We found that Polygalae Radix (ED₅₀: 24.01 μg/mL) had the most shortened PERIOD2::LUCIFERASE rhythm period length in 40 crude drugs and that the CaMKII pathway was involved in this effect. Moreover, long-term feeding with AIN-93M+Polygalae Radix slightly shortened the free-running period of the mouse locomotor activity rhythm.

DISCUSSION AND CONCLUSIONS

Our results indicate that Polygalae Radix may be regarded as a new therapy for circadian rhythm disorder and that the CaMKII pathway may be regarded as a target pathway for circadian rhythm disorders.

Role of Omega-3 Fatty Acids as Non-Photic Zeitgebers and Circadian Clock Synchronizers

Omega-3 fatty acids (ω-3 FAs) are well-known for their actions on immune/inflammatory and neurological pathways, functions that are also under circadian clock regulation. The daily photoperiod represents the primary circadian synchronizer ('zeitgeber'), although diverse studies have pointed towards an influence of dietary FAs on the biological clock. A comprehensive literature review was conducted following predefined selection criteria with the aim of updating the evidence on the molecular mechanisms behind circadian rhythm regulation by ω-3 FAs. We collected preclinical and clinical studies, systematic reviews, and metanalyses focused on the effect of ω-3 FAs on circadian rhythms. Twenty animal (conducted on rodents and piglets) and human trials and one observational study providing evidence on the regulation of neurological, inflammatory/immune, metabolic, reproductive, cardiovascular, and biochemical processes by ω-3 FAs via clock genes were discussed. The evidence suggests that ω-3 FAs may serve as non-photic zeitgebers and prove therapeutically beneficial for circadian disruption-related pathologies. Future work should focus on the role of clock genes as a target for the therapeutic use of ω-3 FAs in inflammatory and neurological disorders, as well as on the bidirectional association between the molecular clock and ω-3 FAs.

Association of Japanese Breakfast Intake with Macro- and Micronutrients and Morning Chronotype

(1) Background: Dietary intake may have a remarkable effect on sleep because skipping breakfast and having a late dinner affects many sleep parameters. Breakfast is the most important meal of the day for children and adults to maintain morning chronotype. We examine whether breakfast style is associated with nutrient intake and sleep factors. (2) Methods: This cross-sectional analysis, with a large sample size of 2671 (766 men and 1805 women aged 20–60 years after data brush-up), was based on data obtained from an online survey. Correlation analysis was performed using Spearman’s rank correlation test. The Kruskal–Wallis’s test followed by post hoc Dunn’s multiple comparison test was used to evaluate the interaction between sleep factors and breakfast categories. Multiple regression analyses were performed to identify variables associated with multiple confounding factors. Dietary data were analyzed using approximately one-month average dietary records from the application. The basic characteristics of the participants (age, sex, and BMI) and other lifestyle-related factors (sleep and physical activity) were obtained accordingly. Sleep parameters including the timing of weekday sleep onset, weekday wake-up, weekend (free day) sleep onset, weekend wake-up, sleep, and midpoints of sleep phase were calculated for each participant. We categorized participants’ breakfast types into five groups: (1) Japanese meal, where breakfast may contain Japanese ingredients such as rice; (2) Western meal, where breakfast may contain bread; (3) alternating eating patterns of Japanese and Western meals; (4) cereals and supplements, where breakfast may contain cereals or supplements and energy bars; and (5) skipped breakfast (no breakfast). (3) Results: The midpoint values of the sleep phase on weekends adjusted for sleep debt on work days (MSFsc) related to chronotype were higher in women, suggesting that they may prefer eveningness. Participants with obesity, young age, and low physical activity preferred eveningness with longer sleep durations. Intake of Japanese-style breakfast was significantly associated with early wake-up time on both weekdays and weekends. Cereal-style breakfast intake was significantly associated with late wake-up on both weekdays and weekends. Intake of macronutrients such as protein, fat, carbohydrate, and sodium at breakfast time was positively and strongly associated with the intake of Japanese breakfast, whereas macronutrients were negatively associated with the intake of cereal breakfast. Among micronutrients, vitamin K was positively correlated with Japanese breakfast and negatively correlated with cereal breakfast; (4) Conclusions: Japanese-style breakfast is associated not only with morning preference but also with high intake of macro- and micronutrients.

In-Season Nutrition Strategies and Recovery Modalities to Enhance Recovery for Basketball Players: A Narrative Review

Basketball players face multiple challenges to in-season recovery. The purpose of this article is to review the literature on recovery modalities and nutritional strategies for basketball players and practical applications that can be incorporated throughout the season at various levels of competition. Sleep, protein, carbohydrate, and fluids should be the foundational components emphasized throughout the season for home and away games to promote recovery. Travel, whether by air or bus, poses nutritional and sleep challenges, therefore teams should be strategic about packing snacks and fluid options while on the road. Practitioners should also plan for meals at hotels and during air travel for their players. Basketball players should aim for a minimum of 8 h of sleep per night and be encouraged to get extra sleep during congested schedules since back-to back games, high workloads, and travel may negatively influence night-time sleep. Regular sleep monitoring, education, and feedback may aid in optimizing sleep in basketball players. In addition, incorporating consistent training times may be beneficial to reduce bed and wake time variability. Hydrotherapy, compression garments, and massage may also provide an effective recovery modality to incorporate post-competition. Future research, however, is warranted to understand the influence these modalities have on enhancing recovery in basketball players. Overall, a strategic well-rounded approach, encompassing both nutrition and recovery modality strategies, should be carefully considered and implemented with teams to support basketball players' recovery for training and competition throughout the season.

The Combined Effects of Magnesium Oxide and Inulin on Intestinal Microbiota and Cecal Short-Chain Fatty Acids

Constipation is a common condition that occurs in many people worldwide. While magnesium oxide (MgO) is often used as the first-line drug for chronic constipation in Japan, dietary fiber intake is also recommended. Dietary fiber is fermented by microbiota to produce short-chain fatty acids (SCFAs). SCFAs are involved in regulating systemic physiological functions and circadian rhythm. We examined the effect of combining MgO and the water-soluble dietary fiber, inulin, on cecal SCFA concentration and microbiota in mice. We also examined the MgO administration timing effect on cecal SCFAs. The cecal SCFA concentrations were measured by gas chromatography, and the microbiota was determined using next-generation sequencing. Inulin intake decreased cecal pH and increased cecal SCFA concentrations while combining MgO increased the cecal pH lowered by inulin and decreased the cecal SCFA concentrations elevated by inulin. When inulin and MgO were combined, significant changes in the microbiota composition were observed compared with inulin alone. The MgO effect on the cecal acetic acid concentration was less when administered at ZT12 than at ZT0. In conclusion, this study suggests that MgO affects cecal SCFA and microbiota during inulin feeding, and the effect on acetic acid concentration is time-dependent.

Modulation of cellular circadian clocks by triterpenoids

Many living organisms on earth have clock systems in their body. It has increasingly become clear that a disturbance in the internal clocks has negative effects on our body. Terpenes are organic compounds found in various plants that are reported to have several pharmacological actions. In this study, we focused on commercially available 27 triterpenoids and evaluated their influence on the circadian rhythm of human U2OS cells and mouse NIH3T3 cells. The expression level of Per2, one of the core clock genes, was measured using luminescent reporters over the time period of a few days. We found that 8 triterpenoids reset the phase of the circadian clocks. Representative compounds were corosolic acid, cucurbitacin B, and celastrol; similar effects were also confirmed with some structural analogues of cucurbitacin B and celastrol. These compounds shifted the phase bilaterally depending on the stimulus timing and also acted as synchronizers in desynchronized cells. The effective concentrations of cucurbitacin B and celastrol were less than 0.5 μM. In addition, cucurbitacin B and celastrol were also found to be effective in tissue explants in mice. Furthermore, celastrol dose-dependently shortened the period length of NIH3T3 cells. Some of these compounds are found in edible and medicinal plants and may help regulate our circadian clocks in everyday life.

Cacao polyphenols regulate the circadian clock gene expression and through glucagon-like peptide-1 secretion

Energy metabolism and circadian rhythms are closely related together, i.e., the timing of nutrient intake affects metabolism under the regulation of circadian rhythms. Previously, we have reported that cacao liquor procyanidin (CLPr) promotes energy metabolism, resulting in preventing obesity and hyperglycemia. However, it is not unclear whether CLPr regulates clock gene expression. In this study, we investigated whether the administration timing of CLPr affected clock gene expression and found that CLPr regulated the circadian clock gene expression through the glucagon-like peptide-1 (GLP-1) signaling pathway. CLPr administration at Zeitgeber time 3 increased the expression level of Per family and Dbp in the liver. At the same administration timing, CLPr increased GLP-1 and insulin concentration in the plasma and phosphorylation of AMPK in the liver. It was noteworthy that an antagonist for GLP-1 receptor Exendin (9-39) canceled CLPr-increased expression of Per family and Dbp and phosphorylation of AMPK in the liver, in addition to insulin secretion. These results strongly suggest that CLPr-induced GLP-1 regulates the changes in clock gene expression in the liver through increased insulin. Thus, CLPr is a possible functional food material for prevention and/or amelioration of metabolic disorders through preventing circadian disruption through GLP-1 and AMPK pathways.

Feeding Rhythms and the Circadian Regulation of Metabolism

The molecular circadian clock regulates metabolic processes within the cell, and the alignment of these clocks between tissues is essential for the maintenance of metabolic homeostasis. The possibility of misalignment arises from the differential responsiveness of tissues to the environmental cues that synchronize the clock (zeitgebers). Although light is the dominant environmental cue for the master clock of the suprachiasmatic nucleus, many other tissues are sensitive to feeding and fasting. When rhythms of feeding behavior are altered, for example by shift work or the constant availability of highly palatable foods, strong feedback is sent to the peripheral molecular clocks. Varying degrees of phase shift can cause the systemic misalignment of metabolic processes. Moreover, when there is a misalignment between the endogenous rhythms in physiology and environmental inputs, such as feeding during the inactive phase, the body's ability to maintain homeostasis is impaired. The loss of phase coordination between the organism and environment, as well as internal misalignment between tissues, can produce cardiometabolic disease as a consequence. The aim of this review is to synthesize the work on the mechanisms and metabolic effects of circadian misalignment. The timing of food intake is highlighted as a powerful environmental cue with the potential to destroy or restore the synchrony of circadian rhythms in metabolism.

DHA substitution overcomes high-fat diet-induced disturbance in the circadian rhythm of lipid metabolism

Disruptions to circadian rhythm have been associated with an increased risk of nonalcoholic fatty liver disease (NAFLD). DHA has been found to affect both circadian rhythm and lipid metabolism. In this study, the relationship between DHA substitution and improvements in lipid metabolism and circadian clock regulation was studied. Male C57BL/6 mice were fed a control, a high fat or a DHA substituted diet for 12 weeks. Biochemical analysis and H&E staining showed that the high-fat diet (HFD) could induce NAFLD, and DHA substitution (AOH) could attenuate NAFLD. The qPCR results showed that the expressions of core clock genes Clock and Bmal1 were significantly higher at zeitgeber (ZT) 0 (7:00 am) than those at ZT12 (7:00 pm) in the control group, while this difference in day and night disappeared in the HFD group, but was observed in the AOH group. Western blotting results indicated that the expressions of rhythm output molecules (RORα and REV-ERBα) and their downstream protein INSIG2 all showed the corresponding circadian changes. SREBP-regulated proteins were significantly increased in the HFD group at both ZT0 and ZT12, but decreased in the AOH group accompanied by the corresponding changes in the protein expressions of HMGCR, LXR, CYP7A1 and CYP27A1. Altogether, HFD can decrease or disrupt circadian rhythm fluctuation by up-regulating the expression of core circadian rhythm genes Clock and Bmal1 at ZT12, and induce metabolic abnormalities through the INSIG2-SREBP pathway regulated by RORα and REV-ERBα. DHA substitution seems to restore circadian rhythm similar to the normal circadian rhythm of "night-high, day-low" through the metabolic pathway regulated by rhythmic nuclear receptors, improving the lipid metabolism rhythm and reducing liver fat.

"Circadian misalignment and the gut microbiome. A bidirectional relationship triggering inflammation and metabolic disorders"- a literature review

Over the last decade, emerging studies have related the gut microbiome and gut dysbiosis to sleep and sleep disorders. For example, intermittent hypoxia associated with obstructive sleep apnea was shown to reproducibly alter the gut microbiome. Circadian rhythm disorders (CRD) (eg, shift work disorders, delayed sleep phase syndrome, and advanced sleep phase syndrome) constitute another group of conditions that might be influenced by gut dysbiosis. Indeed, both central and peripheral clocks can affect and be affected by gut microbiota and their metabolites. In addition, the tight rhythmic regulation of almost all metabolic pathways involved in the anabolism and catabolism of carbohydrates, protein, and lipids in addition to detoxification processes that take place in specific cells could be ultimately linked to changes in the microbiota. Since there are no studies to date examining the impact of gut dysbiosis on delayed sleep phase and advanced sleep phase syndrome, and considering the ever-increasing number of people engaging in shift work, more accurate and informed delineation of the association between gut dysbiosis and shift work can provide guidance and opportunities for new avenues of treating circadian rhythm disorders and preventing the metabolic complications of shiftwork via restoration of gut dysbiosis. In this review, the potential bidirectional relationships between gut dysbiosis and circadian rhythm misalignment, their impact on different metabolic pathways, and the potential development of metabolic and systemic disorders, especially in shift work models are critically assessed.

Circadian expression of Glycoprotein 2 (Gp2) gene is controlled by a molecular clock in mouse Peyer's patches

The expression levels of many cell-surface proteins vary with the time of day. Glycoprotein 2 (Gp2), specifically expressed on the apical surface of M cells in Peyer's patches, functions as a transcytotic receptor for mucosal antigens. We report that cAMP response element-binding protein (CREB) regulates the transcription of the Gp2 gene, thereby generating the circadian change in its expression in mouse Peyer's patches. The transcytotic receptor activity of Gp2 was increased during the dark phase when the Gp2 protein abundance increased. Rhythmic expression of clock gene mRNA was observed in mouse Peyer's patches, and expression levels of Gp2 mRNA also exhibited circadian oscillation, with peak levels during the early dark phase. The promoter region of the mouse Gp2 gene contains several cAMP response elements (CREs). Chromatin immunoprecipitation assays revealed that CREB bound to the CREs in the Gp2 gene in Peyer's patches. Forskolin, which promotes CREB phosphorylation, increased the transcription of the Gp2 gene in Peyer's patches. As phosphorylation of CREB protein was increased when Gp2 gene transcription was activated, CREB may regulate the rhythmic expression of Gp2 mRNA in Peyer's patches. These findings suggest that intestinal immunity is controlled by the circadian clock system.

The Timing Effects of Soy Protein Intake on Mice Gut Microbiota

Soy protein intake is known to cause microbiota changes. While there are some reports about the effect of soy protein intake on gut microbiota and lipid metabolism, effective timing of soy protein intake has not been investigated. In this study, we examined the effect of soy protein intake timing on microbiota. Mice were fed twice a day, in the morning and evening, to compare the effect of soy protein intake in the morning with that in the evening. Mice were divided into three groups: mice fed only casein protein, mice fed soy protein in the morning, and mice fed soy protein in the evening under high-fat diet conditions. They were kept under the experimental condition for two weeks and were sacrificed afterward. We measured cecal pH and collected cecal contents and feces. Short-chain fatty acids (SCFAs) from cecal contents were measured by gas chromatography. The microbiota was analyzed by sequencing 16S rRNA genes from feces. Soy protein intake whether in the morning or evening led to a greater microbiota diversity and a decrease in cecal pH resulting from SCFA production compared to casein intake. In addition, these effects were relatively stronger by morning soy protein intake. Therefore, soy protein intake in the morning may have relatively stronger effects on microbiota than that in the evening.

Day-Time Patterns of Carbohydrate Intake in Adults by Non-Parametric Multi-Level Latent Class Analysis-Results from the UK National Diet and Nutrition Survey (2008/09-2015/16)

This study aims at combining time and quantity of carbohydrate (CH) intake in the definition of eating patterns in UK adults and investigating the association of the derived patterns with type 2 diabetes (T2D). The National Diet and Nutrition Survey (NDNS) Rolling Program included 6155 adults in the UK. Time of the day was categorized into 7 pre-defined time slots: 6–9 am, 9–12 noon, 12–2 pm, 2–5 pm, 5–8 pm, 8–10 pm, and 10 pm–6 am. Responses for CH intake were categorized into: no energy intake, CH <50% or ≥50% of total energy. Non-parametric multilevel latent class analysis (MLCA) was applied to identify eating patterns of CH consumption across day-time, as a novel method accounting for the repeated measurements of intake over 3–4 days nested within individuals. Survey-designed multivariable regression was used to assess the associations of CH eating patterns with T2D. Three CH eating day patterns (low, high CH percentage and regular meal CH intake day) emerged from 24,483 observation days; based on which three classes of CH eaters were identified and characterized as: low (28.1%), moderate (28.8%) and high (43.1%) CH eaters. On average, low-CH eaters consumed the highest amount of total energy intake (7985.8 kJ) and had higher percentages of energy contributed by fat and alcohol, especially after 8 pm. Moderate-CH eaters consumed the lowest amount of total energy (7341.8 kJ) while they tended to have their meals later in the day. High-CH eaters consumed most of their carbohydrates and energy earlier in the day and within the time slots of 6–9 am, 12–2 p.m. and 5–8 pm, which correspond to traditional mealtimes. The high-CH eaters profile had the highest daily intake of CH and fiber and the lowest intake of protein and fat. Low-CH eaters had greater odds than high-CH eaters of having T2D in self-reported but not in previously undiagnosed diabetics. Further research using prospective longitudinal studies is warranted to ascertain the direction of causality in the association of CH patterns with type 2 diabetes.

Phase resetting of circadian peripheral clocks using human and rodent diets in mouse models of type 2 diabetes and chronic kidney disease

The expression rhythms of clock genes, such as Per1, Per2, Bmal1, and Rev-erb α, in mouse peripheral clocks, are entrained by a scheduled feeding paradigm. In terms of food composition, a carbohydrate-containing diet is reported to cause strong entrainment through insulin secretion. However, it is unknown whether human diets entrain peripheral circadian clocks. In this study, we used freeze-dried diets for type 2 diabetes (DB) and chronic kidney disease (CKD), as well as low-carbohydrate diets. After 24 h of fasting, PER2::LUC knock-in mice were given access to food for 2 days during inactive periods, and bioluminescence rhythm was then measured using an in vivo imaging system. AIN-93M, the control mouse diet with a protein:fat:carbohydrate (PFC) ratio of 14.7:9.5:75.8, caused a significant phase advance (7.3 h) in the liver clock compared with that in 24 h fasted mice, whereas human diets caused significant but smaller phase advances (4.7-6.2 h). Compared with healthy and high fat/sucrose-induced DB mice, adenine-induced CKD mice showed attenuation of a phase-advance with a normal diet. There were no significant differences in phase-advance values between human diets (normal, DB, and CKD). In addition, a normal-carbohydrate diet (PFC ratio of 20.3:23.3:56.4) and a low-carbohydrate diet (PFC ratio of 36.4:42.9:20.7) caused similar phase advances in peripheral clocks. The present results strongly suggest that scheduled feeding with human diets can cause phase advances in the peripheral clocks of not only healthy, but also DB and CKD mice. This discovery provides support to the food-induced entrainment of peripheral clocks in human clinical trials.

Circadian rhythms: a possible new player in non-alcoholic fatty liver disease pathophysiology

Over the last decades, a better knowledge of the molecular machinery supervising the regulation of circadian clocks has been achieved, and numerous findings have helped in unravelling the outstanding significance of the molecular clock for the proper regulation of our physiologic and metabolic homeostasis. Non-alcoholic fatty liver disease (NAFLD) is currently considered as one of the emerging liver pathologies in the Western countries due to the modification of eating habits and lifestyle. Although NAFLD is considered a pretty benign condition, it can progress towards non-alcoholic steatohepatitis (NASH) and eventually hepatocellular carcinoma (HCC). The pathogenic mechanisms involved in NAFLD development are complex, since this disease is a multifactorial condition. Major metabolic deregulations along with a genetic background are believed to take part in this process. In this light, the aim of this review is to give a comprehensive description of how our circadian machinery is regulated and to describe to what extent our internal clock is involved in the regulation of hormonal and metabolic homeostasis, and by extension in the development and progression of NAFLD/NASH and eventually in the onset of HCC.

Links between the circadian rhythm, obesity and the microbiome

Obesity is linked to a wide range of serious illnesses. In addition to the important impact on the health of the individual, obesity also has a substantial impact on the economy. Disruption of physiological day-night cycles could contribute to the increased incidence of obesity. According to the American National Sleep Federation, the percentage of the people who reported a sleep duration of six hours or less increased from 12 to 37 % over ten years. Insufficient sleep leads not only to an increase of the total calorie intake but changes the meal preference in favor of palatable foods and meals with high carbohydrate content. A decrease of leptin and increase of ghrelin levels caused by sleep deficiency can also play a role. In addition to the higher caloric intake, the timing of food consumption should be taken into account. The same meal eaten during the night versus the day is associated with increased postprandial glucose and triglyceride levels. The gut microbiome has also been recently understood as an endocrine system, with links between the gut microbiome and circadian rhythm changes possibly influencing increased obesity.

Selected In-Season Nutritional Strategies to Enhance Recovery for Team Sport Athletes: A Practical Overview

Team sport athletes face a variety of nutritional challenges related to recovery during the competitive season. The purpose of this article is to review nutrition strategies related to muscle regeneration, glycogen restoration, fatigue, physical and immune health, and preparation for subsequent training bouts and competitions. Given the limited opportunities to recover between training bouts and games throughout the competitive season, athletes must be deliberate in their recovery strategy. Foundational components of recovery related to protein, carbohydrates, and fluid have been extensively reviewed and accepted. Micronutrients and supplements that may be efficacious for promoting recovery include vitamin D, omega-3 polyunsaturated fatty acids, creatine, collagen/vitamin C, and antioxidants. Curcumin and bromelain may also provide a recovery benefit during the competitive season but future research is warranted prior to incorporating supplemental dosages into the athlete's diet. Air travel poses nutritional challenges related to nutrient timing and quality. Incorporating strategies to consume efficacious micronutrients and ingredients is necessary to support athlete recovery in season.

Flexible clock systems: adjusting the temporal programme

Under natural conditions, many aspects of the abiotic and biotic environment vary with time of day, season or even era, while these conditions are typically kept constant in laboratory settings. The timing information contained within the environment serves as critical timing cues for the internal biological timing system, but how this system drives daily rhythms in behaviour and physiology may also depend on the internal state of the animal. The disparity between timing of these cues in natural and laboratory conditions can result in substantial differences in the scheduling of behaviour and physiology under these conditions. In nature, temporal coordination of biological processes is critical to maximize fitness because they optimize the balance between reproduction, foraging and predation risk. Here we focus on the role of peripheral circadian clocks, and the rhythms that they drive, in enabling adaptive phenotypes. We discuss how reproduction, endocrine activity and metabolism interact with peripheral clocks, and outline the complex phenotypes arising from changes in this system. We conclude that peripheral timing is critical to adaptive plasticity of circadian organization in the field, and that we must abandon standard laboratory conditions to understand the mechanisms that underlie this plasticity which maximizes fitness under natural conditions.This article is part of the themed issue 'Wild clocks: integrating chronobiology and ecology to understand timekeeping in free-living animals'.

Entrainment of the mouse circadian clock: Effects of stress, exercise, and nutrition

The circadian clock system in mammals plays a fundamental role in maintaining homeostasis. Entrainment is an important characteristic of the internal clock, by which appropriate timing is maintained according to external daily stimuli, such as light, stress, exercise, and/or food. Disorganized entrainment or a misaligned clock time, such as jet lag, increases health disturbances. The central clock in the suprachiasmatic nuclei, located in the hypothalamus, receives information about arousal stimuli, such as physical stress or exercise, and changes the clock time by modifying neural activity or the expression of circadian clock genes. Although feeding stimuli cannot entrain the central clock in a normal light-dark cycle, the central clock can partially detect the metabolic status. Local clocks in the peripheral tissues, including liver and kidney, have a strong direct response to the external stimuli of stress, exercise, and/or food that is independent of the central clock. The mechanism underlying entrainment by stress/exercise is mediated by glucocorticoids, sympathetic nerves, oxidative stress, hypoxia, pH, cytokines, and temperature. Food/nutrition-induced entrainment is mediated by fasting-induced hormonal or metabolic changes and re-feeding-induced insulin or oxyntomodulin secretion. Chrono-nutrition is a clinical application based on chronobiology research. Future studies are required to elucidate the effects of eating and nutrient composition on the human circadian clock. Here, we focus on the central and peripheral clocks mostly in rodents' studies and review the findings of recent investigations of the effects of stress, exercise, and food on the entrainment system.

Glucagon and/or IGF-1 Production Regulates Resetting of the Liver Circadian Clock in Response to a Protein or Amino Acid-only Diet

The circadian system controls the behavior and multiple physiological functions. In mammals, the suprachiasmatic nucleus (SCN) acts as the master pacemaker and regulates the circadian clocks of peripheral tissues. The SCN receives information regarding the light-dark cycle and is thus synchronized to the external 24-hour environment. In contrast, peripheral clocks, such as the liver clock, receive information from the SCN and other factors; in particular, food intake which leads to insulin secretion induces strong entrainment of the liver clock. On the other hand, the liver clock of insulin-depleted mice treated with streptozotocin (STZ) has been shown to be entrained by scheduled feeding, suggesting that insulin is not necessary for entrainment of the liver clock by feeding. In this study, we aimed to elucidate additional mechanism on entraining liver clock by feeding a protein-only diet and/or amino-acid administration which does not increase insulin levels. We demonstrated that protein-only diet and cysteine administration elicit entrainment of the liver clock via glucagon secretion and/or insulin-like growth factors (IGF-1) production. Our findings suggest that glucagon and/or IGF-1 production are additional key factors in food-induced entrainment.

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Dietary protein or cysteine increase serum glucagon and hepatic IGF-1 levels, and entrain liver circadian rhythm.

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Increasing IGF-1 levels is an additional entrainment factor of liver circadian rhythm.

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Hepatic IGF-1 production is found to be a key factor in the entrainment of liver circadian rhythm in STZ-treated mice.

Disruption of the circadian rhythm leads to multiple disorders; thus the maintenance of circadian oscillation is necessary for maintaining normalized physiological functions. Postprandial insulin secretion is known as an entraining factor of peripheral circadian rhythm; however, this pathway is not appropriate for diabetes patients in whom insulin signaling is disrupted. Here we report that both dietary protein and cysteine alone entrain liver circadian rhythm by increasing glucagon and/or IGF-1 levels independently of insulin. Findings indicate an additional entrainment factor that can be applied to chronotherapy by controlling food content or by supplementation in peoples with diabetes, circadian rhythm disorders.

Gut Microbiota-Derived Short Chain Fatty Acids Induce Circadian Clock Entrainment in Mouse Peripheral Tissue

Microbiota-derived short-chain fatty acids (SCFAs) and organic acids produced by the fermentation of non-digestible fibre can communicate from the microbiome to host tissues and modulate homeostasis in mammals. The microbiome has circadian rhythmicity and helps the host circadian clock function. We investigated the effect of SCFA or fibre-containing diets on circadian clock phase adjustment in mouse peripheral tissues (liver, kidney, and submandibular gland). Initially, caecal SCFA concentrations, particularly acetate and butyrate, induced significant day-night differences at high concentrations during the active period, which were correlated with lower caecal pH. By monitoring luciferase activity correlated with the clock gene Period2 in vivo, we found that oral administration of mixed SCFA (acetate, butyrate, and propionate) and an organic acid (lactate), or single administration of each SCFA or lactate for three days, caused phase changes in the peripheral clocks with stimulation timing dependency. However, this effect was not detected in cultured fibroblasts or cultured liver slices with SCFA applied to the culture medium, suggesting SCFA-induced indirect modulation of circadian clocks in vivo. Finally, cellobiose-containing diets facilitated SCFA production and refeeding-induced peripheral clock entrainment. SCFA oral gavage and prebiotic supplementation can facilitate peripheral clock adjustment, suggesting prebiotics as novel therapeutic candidates for misalignment.

[Chrono-nutrition and n-3 polyunsaturated fatty acid]

Circadian clock system has been widely maintained in many spices from prokaryote to mammals. "Circadian" means "approximately day" in Latin, thus circadian rhythm means about 24 hour rhythms. The earth revolves once every 24 hours, and our circadian system has been developed for adjusting to this 24 hour cycles, to get sun light information for getting their foods or for alive in birds or mammals. We have two different circadian systems so-called main oscillator located in the suprachiasmatic nucleus (SCN) of the hypothalamus, and local oscillator located in the various peripheral organ tissues such as liver, kidney and skeletal muscle. The SCN is directly entrained by light-dark information through retinal-hypothalamic tract, and then organizes local clock in peripheral tissues via many pathways including neural and hormonal functions. On the other hand, peripheral local clocks are entrained by feeding, exercise and stress stimuli through several cell signaling. Foods (protein, carbohydrate, and lipid) are important regulator of circadian clocks in peripheral tissues. Thus, controlling the timing of food consumption and food composition, a concept known as chrononutrition, is one area of active research to aid recovery from many physiological dysfunctions. In this review, we focus on molecular mechanisms of entrainment and the relationships between circadian clock systems and n-3 polyunsaturated fatty acid. We concentrate on experimental data obtained from cells or animals and humans and discuss how these findings translate into clinical research, and we highlight the latest developments in chrononutritional studies.

FFA4/GPR120: Pharmacology and Therapeutic Opportunities

Free Fatty Acid receptor 4 (FFA4), also known as GPR120, is a G-protein-coupled receptor (GPCR) responsive to long-chain fatty acids that is attracting considerable attention as a potential novel therapeutic target for the treatment of type 2 diabetes mellitus (T2DM). Although no clinical studies have yet been initiated to assess efficacy in this indication, a significant number of primary publications and patents have highlighted the ability of agonists with potency at FFA4 to improve glucose disposition and enhance insulin sensitivity in animal models. However, the distribution pattern of the receptor suggests that targeting FFA4 may also be useful in other conditions, ranging from cancer to lung function. Here, we discuss and contextualise the basis for these ideas and the results to support these conclusions.

Substantial focus on the therapeutic potential of FFA4/GPR120 is currently directed towards type 2 diabetes.

Progress in the identification and characterisation of FFA4/GPR120 agonist ligands is apparent in both the primary scientific and patent literatures.

In models of glucose handling, FFA4/GPR120 agonists appear highly effective.

Recent indications provide support for consideration of FFA4/GPR120 ligands in areas of cancer treatment.

High levels of expression of FFA4/GPR120 in the lung suggest utility in analysis of the potential therapeutic roles of FFA4/GPR120 ligands in both acute and chronic airway inflammatory conditions.

Modulation of circadian clocks by nutrients and food factors

Daily activity rhythms that are dominated by internal clocks are called circadian rhythms. A central clock is located in the suprachiasmatic nucleus of the hypothalamus, and peripheral clocks are located in most mammalian peripheral cells. The central clock is entrained by light/dark cycles, whereas peripheral clocks are entrained by feeding cycles. The effects of nutrients on the central and peripheral clocks have been investigated during the past decade and much interaction between them has come to light. For example, a high-fat diet prolongs the period of circadian behavior, a ketogenic diet advances the onset of locomotor activity rhythms, and a high-salt diet advances the phase of peripheral molecular clocks. Moreover, some food factors such as caffeine, nobiletin, and resveratrol, alter molecular and/or behavioral circadian rhythms. Here, we review nutrients and food factors that modulate mammalian circadian clocks from the cellular to the behavioral level.

Age-related circadian disorganization caused by sympathetic dysfunction in peripheral clock regulation

The ability of the circadian clock to adapt to environmental changes is critical for maintaining homeostasis, preventing disease, and limiting the detrimental effects of aging. To date, little is known about age-related changes in the entrainment of peripheral clocks to external cues. We therefore evaluated the ability of the peripheral clocks of the kidney, liver, and submandibular gland to be entrained by external stimuli including light, food, stress, and exercise in young versus aged mice using in vivo bioluminescence monitoring. Despite a decline in locomotor activity, peripheral clocks in aged mice exhibited normal oscillation amplitudes under light–dark, constant darkness, and simulated jet lag conditions, with some abnormal phase alterations. However, age-related impairments were observed in peripheral clock entrainment to stress and exercise stimuli. Conversely, age-related enhancements were observed in peripheral clock entrainment to food stimuli and in the display of food anticipatory behaviors. Finally, we evaluated the hypothesis that deficits in sympathetic input from the central clock located in the suprachiasmatic nucleus of the hypothalamus were in part responsible for age-related differences in the entrainment. Aged animals showed an attenuated entrainment response to noradrenergic stimulation as well as decreased adrenergic receptor mRNA expression in target peripheral organs. Taken together, the present findings indicate that age-related circadian disorganization in entrainment to light, stress, and exercise is due to sympathetic dysfunctions in peripheral organs, while meal timing produces effective entrainment of aged peripheral circadian clocks.

l-Ornithine affects peripheral clock gene expression in mice

The peripheral circadian clock is entrained by factors in the external environment such as scheduled feeding, exercise, and mental and physical stresses. In addition, recent studies in mice demonstrated that some food components have the potential to control the peripheral circadian clock during scheduled feeding, although information about these components remains limited. l-Ornithine is a type of non-protein amino acid that is present in foods and has been reported to have various physiological functions. In human trials, for example, l-ornithine intake improved a subjective index of sleep quality. Here we demonstrate, using an in vivo monitoring system, that repeated oral administration of l-ornithine at an early inactive period in mice induced a phase advance in the rhythm of PER2 expression. By contrast, l-ornithine administration to mouse embryonic fibroblasts did not affect the expression of PER2, indicating that l-ornithine indirectly alters the phase of PER2. l-Ornithine also increased plasma levels of insulin, glucose and glucagon-like peptide-1 alongside mPer2 expression, suggesting that it exerts its effects probably via insulin secretion. Collectively, these findings demonstrate that l-ornithine affects peripheral clock gene expression and may expand the possibilities of L-ornithine as a health food.

Forced rather than voluntary exercise entrains peripheral clocks via a corticosterone/noradrenaline increase in PER2::LUC mice

Exercise during the inactive period can entrain locomotor activity and peripheral circadian clock rhythm in mice; however, mechanisms underlying this entrainment are yet to be elucidated. Here, we showed that the bioluminescence rhythm of peripheral clocks in PER2::LUC mice was strongly entrained by forced treadmill and forced wheel-running exercise rather than by voluntary wheel-running exercise at middle time during the inactivity period. Exercise-induced entrainment was accompanied by increased levels of serum corticosterone and norepinephrine in peripheral tissues, similar to the physical stress-induced response. Adrenalectomy with norepinephrine receptor blockers completely blocked the treadmill exercise-induced entrainment. The entrainment of the peripheral clock by exercise is independent of the suprachiasmatic nucleus clock, the main oscillator in mammals. The present results suggest that the response of forced exercise, but not voluntary exercise, may be similar to that of stress, and possesses the entrainment ability of peripheral clocks through the activation of the adrenal gland and the sympathetic nervous system.

Nutrition and the circadian system

The human circadian system anticipates and adapts to daily environmental changes to optimise behaviour according to time of day and temporally partitions incompatible physiological processes. At the helm of this system is a master clock in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus. The SCN are primarily synchronised to the 24-h day by the light/dark cycle; however, feeding/fasting cycles are the primary time cues for clocks in peripheral tissues. Aligning feeding/fasting cycles with clock-regulated metabolic changes optimises metabolism, and studies of other animals suggest that feeding at inappropriate times disrupts circadian system organisation, and thereby contributes to adverse metabolic consequences and chronic disease development. 'High-fat diets' (HFD) produce particularly deleterious effects on circadian system organisation in rodents by blunting feeding/fasting cycles. Time-of-day-restricted feeding, where food availability is restricted to a period of several hours, offsets many adverse consequences of HFD in these animals; however, further evidence is required to assess whether the same is true in humans. Several nutritional compounds have robust effects on the circadian system. Caffeine, for example, can speed synchronisation to new time zones after jetlag. An appreciation of the circadian system has many implications for nutritional science and may ultimately help reduce the burden of chronic diseases.

Circadian rhythms of liver physiology and disease: experimental and clinical evidence

The circadian clock system consists of a central clock located in the suprachiasmatic nucleus in the hypothalamus and peripheral clocks in peripheral tissues. Peripheral clocks in the liver have fundamental roles in maintaining liver homeostasis, including the regulation of energy metabolism and the expression of enzymes controlling the absorption and metabolism of xenobiotics. Over the past two decades, research has investigated the molecular mechanisms linking circadian clock genes with the regulation of hepatic physiological functions, using global clock-gene-knockout mice, or mice with liver-specific knockout of clock genes or clock-controlled genes. Clock dysfunction accelerates the development of liver diseases such as fatty liver diseases, cirrhosis, hepatitis and liver cancer, and these disorders also disrupt clock function. Food is an important regulator of circadian clocks in peripheral tissues. Thus, controlling the timing of food consumption and food composition, a concept known as chrononutrition, is one area of active research to aid recovery from many physiological dysfunctions. In this Review, we focus on the molecular mechanisms of hepatic circadian gene regulation and the relationships between hepatic circadian clock systems and liver physiology and disease. We concentrate on experimental data obtained from cell or mice and rat models and discuss how these findings translate into clinical research, and we highlight the latest developments in chrononutritional studies.

Interdependence of nutrient metabolism and the circadian clock system: Importance for metabolic health

BACKGROUND

While additional research is needed, a number of large epidemiological studies show an association between circadian disruption and metabolic disorders. Specifically, obesity, insulin resistance, cardiovascular disease, and other signs of metabolic syndrome all have been linked to circadian disruption in humans. Studies in other species support this association and generally reveal that feeding that is not in phase with the external light/dark cycle, as often occurs with night or rotating shift workers, is disadvantageous in terms of energy balance. As food is a strong driver of circadian rhythms in the periphery, understanding how nutrient metabolism drives clocks across the body is important for dissecting out why circadian misalignment may produce such metabolic effects. A number of circadian clock proteins as well as their accessory proteins (such as nuclear receptors) are highly sensitive to nutrient metabolism. Macronutrients and micronutrients can function as zeitgebers for the clock in a tissue-specific way and can thus impair synchrony between clocks across the body, or potentially restore synchrony in the case of circadian misalignment. Circadian nuclear receptors are particularly sensitive to nutrient metabolism and can alter tissue-specific rhythms in response to changes in the diet. Finally, SNPs in human clock genes appear to be correlated with diet-specific responses and along with chronotype eventually may provide valuable information from a clinical perspective on how to use diet and nutrition to treat metabolic disorders.

SCOPE OF REVIEW

This article presents a background of the circadian clock components and their interrelated metabolic and transcriptional feedback loops, followed by a review of some recent studies in humans and rodents that address the effects of nutrient metabolism on the circadian clock and vice versa. We focus on studies in which results suggest that nutrients provide an opportunity to restore or, alternatively, can destroy synchrony between peripheral clocks and the central pacemaker in the brain as well as between peripheral clocks themselves. In addition, we review several studies looking at clock gene SNPs in humans and the metabolic phenotypes or tendencies associated with particular clock gene mutations.

MAJOR CONCLUSIONS

Targeted use of specific nutrients based on chronotype has the potential for immense clinical utility in the future. Macronutrients and micronutrients have the ability to function as zeitgebers for the clock by activating or modulating specific clock proteins or accessory proteins (such as nuclear receptors). Circadian clock control by nutrients can be tissue-specific. With a better understanding of the mechanisms that support nutrient-induced circadian control in specific tissues, human chronotype and SNP information might eventually be used to tailor nutritional regimens for metabolic disease treatment and thus be an important part of personalized medicine's future.

Diet rich in Docosahexaenoic Acid/Eicosapentaenoic Acid robustly ameliorates hepatic steatosis and insulin resistance in seipin deficient lipodystrophy mice

BACKGROUND

N-3 polyunsaturated fatty acids (n-3 PUFAs), in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have been shown to effectively improve hepatic steatosis and insulin resistance caused by obesity. Lipodystrophy could also develop insulin resistance and hepatic steatosis. However, the effect of supplemental DHA/EPA to hepatic steatosis caused by lipodystrophy is unknown. In this study, we investigated whether a diet rich in n-3 PUFAs could ameliorate severe steatosis in lipoatrophic seipin gene knockout (SKO) mice.

METHODS

Eight-week-old C57BL/6 J WT and SKO mice were fed with normal chow diet (NC), or 2 % DHA/EPA (3:1) diet for 12 weeks. Total cholesterol (TC) and triglycerides (TG) in plasma and liver, plasma high density lipoprotein-cholesterol (HDL-C), glucose (Glu), insulin, leptin and adiponectin levels were measured. Gene regulations and protein levels were investigated using quantitative PCR and western blot in liver.

RESULTS

We found that the DHA/EPA diet protected against hepatic steatosis effectively in SKO mice morphologically. Hepatic TG content was decreased about 40 % (p < 0.05) in SKO mice fed with the DHA/EPA diet compared to chow fed SKO controls. Glucose and insulin tolerance were also improved significantly in SKO mice with DHA/EPA diet. In analyzing hepatic gene expression pattern it was found that TG synthesis related genes, such as carbohydrate response element binding protein (ChREBP), stearoyl-CoA desaturase 1 (SCD1) and fatty acid synthase (Fas) were upregulated in SKO mice compared to WT mice but were significantly decreased in SKO mice on DHA/EPA diet. Fatty acid β-oxidation related genes, on the other hand, such as peroxisome proliferator-activated receptor α (PPARα), carnitine palmitoyltransferase (CPT) and acyl-CoA oxidase 1 (ACOX1) were elevated in both WT and SKO groups on DHA/EPA diets. The protein levels of PPARα, SCD1, CPT1α, Insulin receptor substrate 1 (IRS1) and ratio of p-AKT to AKT showed the same tendency as the result of genes expressions.

CONCLUSIONS

The results suggest that n-3 PUFAs rich diet ameliorates lipodystrophy-induced hepatic steatosis through reducing TG synthesis, improving insulin resistance and enhancing β-oxidation in SKO mice.

Diet rich in Docosahexaenoic Acid/Eicosapentaenoic Acid robustly ameliorates hepatic steatosis and insulin resistance in seipin deficient lipodystrophy mice

BACKGROUND

N-3 polyunsaturated fatty acids (n-3 PUFAs), in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have been shown to effectively improve hepatic steatosis and insulin resistance caused by obesity. Lipodystrophy could also develop insulin resistance and hepatic steatosis. However, the effect of supplemental DHA/EPA to hepatic steatosis caused by lipodystrophy is unknown. In this study, we investigated whether a diet rich in n-3 PUFAs could ameliorate severe steatosis in lipoatrophic seipin gene knockout (SKO) mice.

METHODS

Eight-week-old C57BL/6 J WT and SKO mice were fed with normal chow diet (NC), or 2 % DHA/EPA (3:1) diet for 12 weeks. Total cholesterol (TC) and triglycerides (TG) in plasma and liver, plasma high density lipoprotein-cholesterol (HDL-C), glucose (Glu), insulin, leptin and adiponectin levels were measured. Gene regulations and protein levels were investigated using quantitative PCR and western blot in liver.

RESULTS

We found that the DHA/EPA diet protected against hepatic steatosis effectively in SKO mice morphologically. Hepatic TG content was decreased about 40 % (p < 0.05) in SKO mice fed with the DHA/EPA diet compared to chow fed SKO controls. Glucose and insulin tolerance were also improved significantly in SKO mice with DHA/EPA diet. In analyzing hepatic gene expression pattern it was found that TG synthesis related genes, such as carbohydrate response element binding protein (ChREBP), stearoyl-CoA desaturase 1 (SCD1) and fatty acid synthase (Fas) were upregulated in SKO mice compared to WT mice but were significantly decreased in SKO mice on DHA/EPA diet. Fatty acid β-oxidation related genes, on the other hand, such as peroxisome proliferator-activated receptor α (PPARα), carnitine palmitoyltransferase (CPT) and acyl-CoA oxidase 1 (ACOX1) were elevated in both WT and SKO groups on DHA/EPA diets. The protein levels of PPARα, SCD1, CPT1α, Insulin receptor substrate 1 (IRS1) and ratio of p-AKT to AKT showed the same tendency as the result of genes expressions.

CONCLUSIONS

The results suggest that n-3 PUFAs rich diet ameliorates lipodystrophy-induced hepatic steatosis through reducing TG synthesis, improving insulin resistance and enhancing β-oxidation in SKO mice.