C. Isherwood

Meal Timing Regulates the Human Circadian System

Summary Circadian rhythms, metabolism, and nutrition are intimately linked [1, 2], although effects of meal timing on the human circadian system are poorly understood. We investigated the effect of a 5-hr delay in meals on markers of the human master clock and multiple peripheral circadian rhythms. Ten healthy young men undertook a 13-day laboratory protocol. Three meals (breakfast, lunch, dinner) were given at 5-hr intervals, beginning either 0.5 (early) or 5.5 (late) hr after wake. Participants were acclimated to early meals and then switched to late meals for 6 days. After each meal schedule, participants’ circadian rhythms were measured in a 37-hr constant routine that removes sleep and environmental rhythms while replacing meals with hourly isocaloric snacks. Meal timing did not alter actigraphic sleep parameters before circadian rhythm measurement. In constant routines, meal timing did not affect rhythms of subjective hunger and sleepiness, master clock markers (plasma melatonin and cortisol), plasma triglycerides, or clock gene expression in whole blood. Following late meals, however, plasma glucose rhythms were delayed by 5.69 ± 1.29 hr (p < 0.001), and average glucose concentration decreased by 0.27 ± 0.05 mM (p < 0.001). In adipose tissue, PER2 mRNA rhythms were delayed by 0.97 ± 0.29 hr (p < 0.01), indicating that human molecular clocks may be regulated by feeding time and could underpin plasma glucose changes. Timed meals therefore play a role in synchronizing peripheral circadian rhythms in humans and may have particular relevance for patients with circadian rhythm disorders, shift workers, and transmeridian travelers.

The influence of alcohol consumed with a meal on endothelial function in healthy individuals

BACKGROUND Alcohol and polyphenols in wine and fruit juices have been strongly implicated in the favourable effects on of these beverages on vascular function. Despite a wealth of information on the metabolic and vascular effects of alcohol and polyphenols, the combined influences of these substances on vascular function, especially when consumed with food, is poorly understood. A study was designed to determine the effects of a phenolic-rich grape juice, with or without alcohol, on vascular endothelial function in the postprandial state. METHODS Ten subjects consumed a standard meal with a test drink on three separate occasions. On each occasion, the test drink accompanying the meal was either red grape juice, red grape juice plus alcohol (12% v/v), or water. Endothelial function was measured by flow mediated dilatation (FMD) prior to then 30 and 60 minutes after consuming the meal. Blood samples were taken for the determination of plasma glucose, triacylglycerol (TAG) and non esterified fatty acids (NEFA) at regular intervals. RESULTS There was a significant effect of the three treatments (P = 0.0026) and time (P = 0.021) on percentage FMD. The meals with the grape juice and grape juice plus alcohol produced similar FMD responses but were both significantly greater than the meal with water. The concentration of plasma glucose, TAG and NEFA were similar after each treatment. CONCLUSION Alcohol had no effect on vascular function in the early postprandial phase. These findings provide new evidence to support the potential benefit of non-alcoholic components within alcoholic beverages on vascular function in the fed state.

Twenty-four-hour rhythmicity of circulating metabolites: effect of body mass and type 2 diabetes

Metabolic profiling of individuals with type 2 diabetes mellitus (T2DM) has previously been limited to single‐time‐point samples, ignoring time‐of‐day variation. Here, we tested our hypothesis that body mass and T2DM affect daily rhythmicity and concentrations of circulating metabolites across a 24‐h day in 3 age‐matched, male groups—lean, overweight/obese (OW/OB), and OW/OB with T2DM—in controlled laboratory conditions, which were not confounded by large meals. By using targeted liquid chromatography/mass spectrometry metabolomics, we quantified 130 plasma metabolites every 2 h over 24 h, and we show that average metabolite concentrations were significantly altered by increased body mass (90 of 130) and T2DM (56 of 130). Thirty‐eight percent of metabolites exhibited daily rhythms in at least 1 study group, and where a metabolite was rhythmic in >1 group, its peak time was comparable. The optimal time of day was assessed to provide discriminating biomarkers. This differed between metabolite classes and study groups—for example, phospholipids showed maximal difference at 5:00 am (lean vs. OW/OB) and at 5:00 pm (OW/OB vs. T2DM). Metabolites that were identified with both robust 24‐h rhythms and significant concentration differences between study groups emphasize the importance of controlling the time of day for diagnosis and biomarker discovery, offering a significant improvement over current single sampling.—Isherwood, C.M., Van der Veen, D.R., Johnston, J.D., Skene, D. J. Twenty‐four‐hour rhythmicity of circulating metabolites: effect of body mass and type 2 diabetes. FASEB J. 31, 5557‐5567 (2017). www.fasebj.org

Relationship between Human Pupillary Light Reflex and Circadian System Status

Intrinsically photosensitive retinal ganglion cells (ipRGCs), whose photopigment melanopsin has a peak of sensitivity in the short wavelength range of the spectrum, constitute a common light input pathway to the olivary pretectal nucleus (OPN), the pupillary light reflex (PLR) regulatory centre, and to the suprachiasmatic nuclei (SCN), the major pacemaker of the circadian system. Thus, evaluating PLR under short wavelength light (λmax ≤ 500 nm) and creating an integrated PLR parameter, as a possible tool to indirectly assess the status of the circadian system, becomes of interest. Nine monochromatic, photon-matched light stimuli (300 s), in 10 nm increments from λmax 420 to 500 nm were administered to 15 healthy young participants (8 females), analyzing: i) the PLR; ii) wrist temperature (WT) and motor activity rhythms (WA), iii) light exposure (L) pattern and iv) diurnal preference (Horne-Östberg), sleep quality (Pittsburgh) and daytime sleepiness (Epworth). Linear correlations between the different PLR parameters and circadian status index obtained from WT, WA and L recordings and scores from questionnaires were calculated. In summary, we found markers of robust circadian rhythms, namely high stability, reduced fragmentation, high amplitude, phase advance and low internal desynchronization, were correlated with a reduced PLR to 460–490 nm wavelengths. Integrated circadian (CSI) and PLR (cp-PLR) parameters are proposed, that also showed an inverse correlation. These results demonstrate, for the first time, the existence of a close relationship between the circadian system robustness and the pupillary reflex response, two non-visual functions primarily under melanopsin-ipRGC input.

Does alcohol consumed with a meal affect vascular function

Numerous studies in the literature report effects of alcohol and polyphenols on vascular function. However, interpretation of these effects has been confounded by the limitation of study designs and the composition of the food and drinks consumed. It has been reported that de-alcoholised red wine improves vascular function, although red wine has no such effect. The aim of the present study was to determine whether it is alcohol or other components of polyphenol-containing drinks that influence vascular function. Six healthy subjects (three females and three males; age 22.7 (SE 5.2) years, BMI 22.3 (SE 1.94; range 19.4–25.3) kg/m) were recruited. Written consent was obtained before the start of the study and ethical permission was obtained from the University of Surrey Ethics Committee (EC/2993/1211/SBMS). They consumed a standard meal on three separate occasions. The meal consisted of lasagne and chocolate cake, with a total energy intake of 3402 kJ (813 kcal; % energy intake: 47.3 from fat, 16.7 from protein, 37 from carbohydrate). On each occasion subjects consumed a different drink (175 ml) with their meal: red-grape juice plus water (A); red-grape juice plus vodka (12% (v/v) alcohol; B); water (C). The drinks and food were consumed at the same time of day (13.00 hours) in a randomised order to remove any order effects. Vascular function was assessed by flow-mediated dilatation (FMD) using ultrasound (Acuson Aspen; CVS, Aliso Viejo, CA, USA) and measurements of the branchial artery were obtained using branchial image software (Medical Imaging Applications, LLC). Baseline FMD responses were recorded before the start of each study and further readings were taken 30 and 60 min after consuming the meal. Capillary blood samples were taken for the measurement of glucose, TAG and NEFA. The Figure shows the percentage FMD responses to all three meals. Repeated-measures ANOVA showed a significant effect of the treatments (meal + drinks; P= 0.008). While there was no independent effect of time (P= 0.079), there was a significant interaction between treatment and time (P= 0.012). There was no significant difference in percentage FMD or other variables at baseline. There were also no significant differences in plasma glucose, TAG and NEFA, either within treatments or between treatments.

Impact of liver fat on the differential partitioning of hepatic triacylglycerol into VLDL subclasses on high and low sugar diets

Dietary sugars are linked to the development of non-alcoholic fatty liver disease (NAFLD) and dyslipidaemia, but it is unknown if NAFLD itself influences the effects of sugars on plasma lipoproteins. To study this further, men with NAFLD (n = 11) and low liver fat ‘controls’ (n = 14) were fed two iso-energetic diets, high or low in sugars (26% or 6% total energy) for 12 weeks, in a randomised, cross-over design. Fasting plasma lipid and lipoprotein kinetics were measured after each diet by stable isotope trace-labelling. There were significant differences in the production and catabolic rates of VLDL subclasses between men with NAFLD and controls, in response to the high and low sugar diets. Men with NAFLD had higher plasma concentrations of VLDL1-triacylglycerol (TAG) after the high (P<0.02) and low sugar (P<0.0002) diets, a lower VLDL1-TAG fractional catabolic rate after the high sugar diet (P<0.01), and a higher VLDL1-TAG production rate after the low sugar diet (P<0.01), relative to controls. An effect of the high sugar diet, was to channel hepatic TAG into a higher production of VLDL1-TAG (P<0.02) in the controls, but in contrast, a higher production of VLDL2-TAG (P<0.05) in NAFLD. These dietary effects on VLDL subclass kinetics could be explained, in part, by differences in the contribution of fatty acids from intra-hepatic stores, and de novo lipogenesis. The present study provides new evidence that liver fat accumulation leads to a differential partitioning of hepatic TAG into large and small VLDL subclasses, in response to high and low intakes of sugars.

The effect of obesity and type 2 diabetes (T2DM) on human metabolite rhythms

Obesity and type 2 diabetes (T2DM) have been associated with increased circulating concentrations of acylcarnitines and branched chain amino acids (BCAA) (isoleucine, leucine, and valine) in single time point studies. Investigating 24 h daily rhythms (peak time and amplitude) of these metabolites in obesity and T2DM would help direct future study into any circadian clock-related mechanisms behind these changes. The hypothesis that weight and/or T2DM affect the concentration and rhythmicity of acylcarnitines and BCAA across a 24 h day was tested. In a controlled laboratory study, hourly milkshakes (06:30–21:30 h) were given to 8 lean (L), 10 overweight (OW) and 7 OW with T2DM men, aged 45–65 years, lying semi-recumbent and awake between 06:30–22:30 h (light period) and asleep between 22:30– 06:30 h (dark period). Plasma samples (2 h across 24 h) were analysed using quantitative targeted LC/MS metabolomics (Biocrates, Austria). Two-way ANOVA identified significant group differences with increased 24 h concentrations in propionylcarnitine (C3) (L vs OW and L vs T2DM, p < 0·001), butyrylcarnitine (C4) (L vs OW and L vs T2DM, p < 0·001) and valerylcarnitine (C5) (L vs OW, p < 0·001) in OW and T2DM compared to the L group. C3 and C4 displayed significant 24 h rhythms in all groups (Fig. 1). C5 lost its rhythm in OW and T2DM. Weight and T2DM increased the 24 h concentrations of isoleucine (L vs OW, p = 0·009; L vs T2DM, p < 0·001), leucine (L vs OW, p = 0·035; L vs T2DM, p = 0·010) and valine (L vs T2DM, p < 0·001) in the OW and T2DM groups compared to the L group. Isoleucine and valine displayed significant daily rhythms in the L and OW groups only (Fig. 1), with no significant daily rhythm for leucine in any group.

NAFLD exacerbates the effect of dietary sugar on liver fat and development of an atherogenic lipoprotein phenotype

word count: 258 Word count: 3,844 Address for correspondence: Professor Margot Umpleby, Diabetes and Metabolic Medicine, The Leggett Building, University of Surrey, Daphne Jackson Rd, Manor Park, Guildford GU2 7WG, UK Phone: +44(0) 1483 688579 Fax: +44 (0) 1483 688501 E-mail: m.umpleby@surrey.ac.uk

Individuals with moderately raised liver fat show a greater increase in liver fat in response to a high sugar diet

Liver fat has been associated with the development of cardio-metabolic risk, and linked to a high intake of dietary sugars. To investigate these associations further, we examined the effects of two, 12 week diets, high and low in sugars, on the percentage of liver fat, and the influence of the initial percentage of liver fat. The dietary intervention used a randomised, cross-over design, and was conducted in a free-living setting with men (aged 40–65, n = 17) at increased cardio-metabolic risk according to the previously described ‘RISCK’ Study protocol. Percentage liver fat was measured before and after each diet by magnetic resonance spectroscopy. The high and low sugar diets, that delivered 27% and 9% energy as sugar, with starch to sugar ratios of 1:1 and 3:1, were accompanied by a consistent increase and decrease in liver fat, respectively. These changes resulted in a significant difference in the percentage of liver fat between the two diets (post-diet medians: 7.3% versus 2.2%, p<0.05). Individuals with a moderate increase in their percentage of liver fat at baseline (>4.2%), showed a significantly greater increase in liver fat after the high sugar diet relative to the low sugar diet.

The effect of prawn consumption on lipoprotein subclasses in healthy males

, there is no speciÞc evidenceto refute the link between prawn consumption, LDL-cholesterol and CHD risk. The aim of the present study was to assess the effects ofcold-water prawns on lipoproteins, in particular small, dense LDL (sdLDL), VLDL and HDL, in a randomly-controlled dietary inter-vention trial in healthy male volunteers. Prawns (200g) contain dietary cholesterol equivalent to a large egg yolk and approximately 1glong-chain n-3 fatty acids EPA and DHA, a level that has been shown to favourably insuence serum lipids.Healthy male volunteers, ( n 18; 20Ð65 years) were recruited from existing subject databases held at the University of Surrey. Allsubjects were normolipidaemic (total cholesterol < 6.5m