Total parenteral nutrition entrains the central and peripheral circadian clocks

Expression of circadian regulatory genes is dysregulated by increased cytokine production in mice subjected to concomitant intestinal injury and parenteral nutrition

BACKGROUND

We have developed a mouse model of Parenteral Nutrition Associated Cholestasis (PNAC) in which combining intestinal inflammation and PN infusion results in cholestasis, hepatic macrophage activation, and transcriptional suppression of bile acid and sterol signaling and transport. In the liver, the master circadian gene regulators Bmal/Arntl and Clock drive circadian modulation of hepatic functions, including bile acid synthesis. Once activated, Bmal and Clock are downregulated by several transcription factors including Reverbα (Nr1d1), Dbp (Dbp), Dec1/2 (Bhlhe40/41), Cry1/2 (Cry1/2) and Per1/2 (Per1/2). The aim of this study was to examine the effects of PN on expression of hepatic circadian rhythm (CR) regulatory genes in mice.

METHODS

WT, IL1KO or TNFRKO mice were exposed to dextran sulfate sodium (DSS) for 4 days followed by soy-oil lipid emulsion-based PN infusion through a central venous catheter for 14 days (DSS-PN) and the expression of key CR regulatory transcription factors evaluated. Animals were NPO on a 14 hr light-dark cycle and were administered PN continuously over 24 hrs. Mice were sacrificed, and hepatic tissue obtained at 9-10AM (Zeitgeber Z+3/Z+4 hrs). PNAC was defined by increased serum aspartate aminotransferase, alanine aminotransferase, total bile acids, and total bilirubin and the effect of i.p. injection of recombinant IL-1β (200ng/mouse) or TNFα (200ng/mouse) on CR expression was examined after 4 hrs.

RESULTS

In the PNAC model, DSS-PN increased serum biomarkers of hepatic injury (ALT, AST, serum bile acids) which was suppressed in both DSS-PN IL1KO and DSS-PN TNFRKO mice. In WT DSS-PN, mRNA expression of Arntl and Dec1 was suppressed corresponding to increased Nr1d1, Per2, Dbp and Dec2. These effects were ameliorated in both DSS-PN IL1KO and DSS-PN TNFRKO groups. Western analysis of the circadian transcription factor network revealed in WT mice DSS-PN significantly suppressed Reverbα, Bmal, Dbp, Per2 and Mtnr1b. With the exception of Dbp, DSS-PN mediated suppression was ameliorated by both IL1KO and TNFRKO. Intraperitoneal injection of IL-1β or TNFα into WT mice increased serum AST and ALT and suppressed mRNA expression of Nr1d1, Arntl and Clock and increased Dbp and Per2.

CONCLUSIONS

Altered expression of CR-dependent regulatory genes during PNAC accompanies cholestasis and is, in part, due to increased cytokine (IL-1β and TNFα) production. Evaluation of the effects of modulating CR in PNAC thus deserves further investigation.

Metabolomics Pilot Study Identifies Desynchronization of 24-H Rhythms and Distinct Intra-patient Variability Patterns in Critical Illness: A Preliminary Report

Background: Synchronized circadian rhythms play a key role in coordinating physiologic health. Desynchronized circadian rhythms may predispose individuals to disease or be indicative of underlying disease. Intensive care unit (ICU) patients likely experience desynchronized circadian rhythms due to disruptive environmental conditions in the ICU and underlying pathophysiology. This observational pilot study was undertaken to determine if 24-h rhythms are altered in ICU patients relative to healthy controls by profiling 24-h rhythms in vital signs and plasma metabolites.

Methods: We monitored daily rhythms in 5 healthy controls and 5 ICU patients for 24 h. Heart rate and blood pressure were measured every 30 min, temperature was measured every hour, and blood was sampled for mass spectrometry-based plasma metabolomics every 4 h. Bedside sound levels were measured every minute. Twenty-four hours rhythms were evaluated in vitals and putatively identified plasma metabolites individually and in each group using the cosinor method.

Results: ICU patient rooms were significantly louder than healthy controls' rooms and average noise levels were above EPA recommendations. Healthy controls generally had significant 24-h rhythms individually and as a group. While a few ICU patients had significant 24-h rhythms in isolated variables, no significant rhythms were identified in ICU patients as a group, except in cortisol. This indicates a lack of coherence in phases and amplitudes among ICU patients. Finally, principal component analysis of metabolic profiles showed surprising patterns in plasma sample clustering. Each ICU patient's samples were clearly discernable in individual clusters, separate from a single cluster of healthy controls.

Conclusions: In this pilot study, ICU patients' 24-h rhythms show significant desynchronization compared to healthy controls. Clustering of plasma metabolic profiles suggests that metabolomics could be used to track individual patients' clinical courses longitudinally. Our results show global disordering of metabolism and the circadian system in ICU patients which should be characterized further in order to determine implications for patient care.

Per2Gene Expressions in the Suprachiasmatic Nucleus and Liver Differentially Respond to Nutrition Factors in Rats

BACKGROUND

We previously reported that parenteral nutrition (PN) altered the circadian rhythm of clock gene expression in the suprachiasmatic nucleus (SCN) and liver of rats. The present study was designed to investigate what factor(s) in the PN solution causes the alteration.

METHODS

Male Wistar rats, kept under light and dark conditions, were divided into 4 groups after cannulation. The sham operation group received saline solution from 8 am to 8 pm at the rate of 36 mL/kg/12 hours. The glucose, amino acid, and saline groups received a glucose solution (20% wt/vol glucose, 261 kcal/kg/d, Na(+) 50 meq/L and Cl(-) 50 meq/L), an amino acid solution (4.3% wt/vol 1.78 gN/kg/d, Na +50 meq/L and Cl(-) 50 meq/L) and a saline solution from 8 am to 8 pm at a rate of 240 mL/kg/12 hours, respectively. Rats were killed every 4 hours (9 am = Zeitgeber Time (ZT) 02, 1 pm = ZT06, 5 pm = ZT10, 9 pm = ZT14, 1 am = ZT18, 5 am = ZT22, n = 3 at each point), and brain and liver samples were removed. rPer2 expression in the SCN and liver was analyzed by in situ hybridization and Northern blotting, respectively.

RESULTS

Compared with the sham-operation rats, the peak time of rPer2 expression in the SCN was significantly affected by glucose, amino acid, and saline solutions. Among them, glucose-group rats showed the rPer2 expression most similar to that of diurnal PN. On the other hand, the rPer2 expression in the liver was shifted in the glucose and amino-acid-solution groups. The pattern of rPer2 expressions in the amino acid group was most similar to that of the diurnal PN group.

CONCLUSIONS

These results indicate that the most potent entrainer for the SCN clock is glucose, whereas that for the liver is amino acid.

Continuous enteral and parenteral feeding each reduces heart rate variability but differentially influences monocyte gene expression in humans

Enteral (EN) or parenteral (PN) nutrition is used to support critically ill patients until oral feeding resumes. Enteral nutrition is assumed preferable to PN, but the differential influence on immune function is not well defined. Autonomic nervous activity is known to influence innate immune responses, and we hypothesized that EN and PN could influence both autonomic signaling and gene activation in peripheral blood monocytes (PBMs). Ten subjects (aged 18-36 years) received continuous EN or PN for 72 h. Peripheral blood monocytes were isolated from whole blood before and after continuous feeding and were analyzed for gene expression using a microarray platform. Gene expression after feeding was compared from baseline and between groups. To measure autonomic outflow, subjects also underwent heart rate variability (HRV) monitoring during feeding. Time and frequency domain HRV data were compared between groups and five orally fed subjects for changes from baseline and changes over time. During continuous EN and PN, subjects exhibited declines in both time and frequency domain HRV parameters compared with baseline and with PO subjects, indicating a loss of vagal/parasympathetic tone. However, PN feeding had a much greater influence on PBM gene expression compared with baseline than EN, including genes important to innate immunity. Continuous EN and PN are both associated with decreasing vagal tone over time, yet contribute differently to PBM gene expression, in humans. These preliminary findings support assumptions that PN imposes a systemic inflammatory risk but also imply that continuous feeding, independent of route, may impart additional risk through different mechanisms.

The role of the circadian clock system in nutrition and metabolism

Mammals have an endogenous timing system in the suprachiasmatic nuclei (SCN) of the hypothalamic region of the brain. This internal clock system is composed of an intracellular feedback loop that drives the expression of molecular components and their constitutive protein products to oscillate over a period of about 24 h (hence the term 'circadian'). These circadian oscillations bring about rhythmic changes in downstream molecular pathways and physiological processes such as those involved in nutrition and metabolism. It is now emerging that the molecular components of the clock system are also found within the cells of peripheral tissues, including the gastrointestinal tract, liver and pancreas. The present review examines their role in regulating nutritional and metabolic processes. In turn, metabolic status and feeding cycles are able to feed back onto the circadian clock in the SCN and in peripheral tissues. This feedback mechanism maintains the integrity and temporal coordination between various components of the circadian clock system. Thus, alterations in environmental cues could disrupt normal clock function, which may have profound effects on the health and well-being of an individual.

Feeding cues and injected nutrients induce acute expression of multiple clock genes in the mouse liver

The circadian clock is closely associated with energy metabolism. The liver clock can rapidly adapt to a new feeding cycle within a few days, whereas the lung clock is gradually entrained over one week. However, the mechanism underlying tissue-specific clock resetting is not fully understood. To characterize the rapid response to feeding cues in the liver clock, we examined the effects of a single time-delayed feeding on circadian rhythms in the liver and lungs of Per2::Luc reporter knockin mice. After adapting to a night-time restricted feeding schedule, the mice were fed according to a 4, 8, or 13 h delayed schedule on the last day. The phase of the liver clock was delayed in all groups with delayed feeding, whereas the lung clock remained unaffected. We then examined the acute response of clock and metabolism-related genes in the liver using focused DNA-microarrays. Clock mutant mice were bred under constant light to attenuate the endogenous circadian rhythm, and gene expression profiles were determined during 24 h of fasting followed by 8 h of feeding. Per2 and Dec1 were significantly increased within 1 h of feeding. Real-time RT-PCR analysis revealed a similarly acute response in hepatic clock gene expression caused by feeding wild type mice after an overnight fast. In addition to Per2 and Dec1, the expression of Per1 increased, and that of Rev-erbα decreased in the liver within 1 h of feeding after fasting, whereas none of these clock genes were affected in the lung. Moreover, an intraperitoneal injection of glucose combined with amino acids, but not either alone, reproduced a similar hepatic response. Our findings show that multiple clock genes respond to nutritional cues within 1 h in the liver but not in the lung.

Role of clock genes in gastrointestinal motility

Biological rhythms coordinate the timing of our internal bodily functions. Colonic motility follows a rhythm as well: most people will have a bowel movement in the morning and rarely during the night. Recent work provides a potential mechanism for this observation: the mouse colon possesses a functional circadian clock as well as a subset of rhythmically expressed genes that may directly impact on colonic motility. Furthermore, measures of colonic motility such as the colonic tissue contractile response to acetylcholine, stool output, and intracolonic pressure changes vary as a function of the time of day, but these variations are attenuated in mice with disrupted clock function. These laboratory findings are supported by clinical observations. Gastrointestinal symptoms such as diarrhea or constipation are prevalent among shift workers and time-zone travelers, both of which are conditions associated with disruptions in biological rhythms. This review will discuss new insights into the role of clock genes in colonic motility and their potential clinical relevance.

Injection of LPS causes transient suppression of biological clock genes in rats

BACKGROUND

The biological clock regulates circadian rhythm and is important for sustaining homeostasis. Here we examined the response of biological clock genes to systemic inflammatory stimulation.

MATERIALS AND METHODS

At 08:00 h (= Zeitgeber time [ZT] 01), male Wistar rats (7-wk-old) maintained on a 12:12 h light:dark cycle (light on 07:00-19:00 h) received intravenous injection of 1 mg/kg lipopolysaccharide (LPS group) or 0.3 mL saline (control group). They were then sacrificed every 4 h (09:00 h = ZT 02, 13:00 h = ZT 06, 17:00 h = ZT 10, 21:00 h = ZT 14, 01:00 h = ZT 18, 05:00 h = ZT 22) over a 2-d period, and blood, brain, and liver samples were obtained for analysis (n = 4 at each time for each group). The expression levels of clock gene, rPer2, and those of clock controlled gene, rDBP, were quantified in the suprachiasmatic nucleus by in situ hybridization, while those of rPer1, rPer2, rDBP, rPPARA, and rFKBP51 in the liver were determined by quantitative RT-PCR.

RESULTS

In the suprachiasmatic nucleus of control rats, rPer2 and rDBP mRNA expression levels showed robust circadian patterns with peak levels at ZT 06 and ZT 10, respectively. LPS significantly suppressed both genes on day 1 but recovery was noted on day 2. Similarly, LPS significantly suppressed rPer1, rPer2, rDBP, rPPARA, and rFKBP51 mRNA expression levels in the liver on day 1 but recovery was noted on day 2, whereas a robust circadian pattern was noted in the control group.

CONCLUSION

Our results indicate that LPS causes transient suppression of the biological clock genes and suggest that the biological clock plays an important role in the response to systemic inflammatory stimulation.

Clock gene expression in the murine gastrointestinal tract: endogenous rhythmicity and effects of a feeding regimen

BACKGROUND & AIMS

Based on observations that the gastrointestinal tract is subject to various 24-hour rhythmic processes, it is conceivable that some of these rhythms are under circadian clock gene control. We hypothesized that clock genes are present in the gastrointestinal tract and that they are part of a functional molecular clock that coordinates rhythmic physiologic functions.

METHODS

The effects of timed feeding and vagotomy on temporal clock gene expression (clock, bmal1, per1-3, cry1-2) in the gastrointestinal tract and suprachiasmatic nucleus (bmal, per2) of C57BL/6J mice were examined using real-time polymerase chain reaction and Western blotting (BMAL, PER2). Colonic clock gene localization was examined using immunohistochemistry (BMAL, PER1-2).

RESULTS

Clock immunoreactivity was observed in the myenteric plexus and epithelial crypt cells. Clock genes were expressed rhythmically throughout the gastrointestinal tract. Timed feeding shifted clock gene expression at the RNA and protein level but did not shift clock gene expression in the central clock. Vagotomy did not alter gastric clock gene expression compared with sham-treated controls.

CONCLUSIONS

The murine gastrointestinal tract contains functional clock genes, which are molecular core components of the circadian clock. Daytime feeding in nocturnal rodents is a strong synchronizer of gastrointestinal clock genes. This synchronization occurs independently of the central clock. Gastric clock gene expression is not mediated through the vagal nerve. The presence of clock genes in the myenteric plexus and epithelial cells suggests a role for clock genes in circadian coordination of gastrointestinal functions such as motility, cell proliferation, and migration.

The relationship between nutrition and circadian rhythms in mammals

The master clock located in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus regulates circadian rhythms in mammals. The clock is an intracellular, transcriptional mechanism sharing the same molecular components in SCN neurons and in peripheral cells, such as the liver, intestine, and retina. The circadian clock controls food processing and energy homeostasis by regulating the expression and/or activity of enzymes involved in cholesterol, amino acid, lipid, glycogen, and glucose metabolism. In addition, many hormones involved in metabolism, such as insulin, glucagon, adiponectin, corticosterone, leptin, and ghrelin, exhibit circadian oscillation. Furthermore, disruption of circadian rhythms is involved in the development of cancer, metabolic syndrome, and obesity. Metabolism and food intake also feed back to influence the biological clock. Calorie restriction (CR) entrains the SCN clock, whereas timed meals entrain peripheral oscillators. Furthermore, the cellular redox state, dictated by food metabolism, and several nutrients, such as glucose, ethanol, adenosine, caffeine, thiamine, and retinoic acid, can phase-shift circadian rhythms. In conclusion, there is a large body of evidence that links feeding regimens, food components, and the biological clock.

Altered expression profiles of clock genes hPer1 and hPer2 in peripheral blood mononuclear cells of cancer patients undergoing surgery

Patients undergoing surgery often develop symptoms of circadian rhythm disorders such as insomnia or delirium. However, the effect of surgery on the biological clock remains unknown. The present study examines the expression of clock genes in peripheral blood mononuclear cells (PBMCs) and measures plasma hormone concentrations in patients with esophageal cancer and early gastric cancer who underwent surgery. Six blood samples per day were collected from 9 patients with esophageal cancer before and after esophagectomy and from 9 patients with early gastric cancer before and after laparoscopy-assisted distal gastrectomy (LADG). The expression profiles of hPer1 and hPer2 mRNAs in PBMCs were determined by real-time RT-PCR. Plasma melatonin and cortisol concentrations were measured by radioimmunoassay. Plasma melatonin levels decreased in both groups throughout the day and plasma cortisol levels changed after surgery. The acrophase of clock gene expression was altered after surgery as follows: hPer1, from 6:19+/-1:50 to 13:59+/-0:59 (p=0.0003) and from 7:47+/-1:27 to 12:33+/-1:30 (p=0.0043) and hPer2, from 5:01+/-2:59 to 19:30+/-2:15 (p<0.0001) and from 6:49+/-1:59 to 13:39+/-3:06 (p=0.0171) in patients with esophageal and early gastric cancer, respectively. The post-operative phase change of hPer2 was more prominent after esophagectomy than after LADG. Our results suggest that surgical stress affects the peripheral clock as well as endogenous hormones in humans.

Skipping breakfast: gender effects on resting heart rate measures in preadolescents

The cardiovascular response in children to morning nutrition has received little attention, and associated gender-related effects are virtually uninvestigated. This study evaluated resting heart-rate (HR) and heart-rate variability (HRV) in preadolescents after overnight fasting and again after eating a standardized breakfast or continuing to fast. HR increased slightly after eating and decreased significantly with continued fasting. These effects were present for both sexes. Relative to children who ate, those who continued fasting showed increases in HRV-particularly for inter-beat-interval and low frequency component (LF: 0.04-0.15 Hz) measures. Analyses revealed significant increases across variability measures for fasting children, but a selective LF decrease in those who were fed-an effect most prominent in females. Otherwise, males and females showed similar treatment-related changes in HRV. While within-gender comparisons showed similar results for HR, i.e., faster HR in fed compared with fasting males and females, respectively, fasting females-but not males-showed significantly greater increases in variability relative to their fed counterparts. Together, these findings suggest that extended overnight fasting initiates an increase in parasympathetic activity that attenuates the expected increase in cardiovascular output following a mid-morning meal. Observed gender differences were related to greater parasympathetic activity in males and to the apparent emphasis on parasympathetic regulation of LF variability. The implications of these findings for health concerns, the nature of responses to physiological and cognitive stressors, and how such differences may influence performance variables-particularly early in development when cardiovascular responses to these stressors may be more sensitive to nutritional factors-are discussed.

Total parenteral nutrition using continuous intravenous infusion via the posterior vena cava in rats

This study was conducted to evaluate the feasibility of total parenteral nutrition (TPN) in rats using continuous intravenous infusion (tail cuff method) via the posterior vena cava. A catheter was inserted into the posterior vena cava from the femoral vein of 10 females (Experiment 1) and 16 females (Experiment 2). The depth of the inserted catheter from the femoral vein was set at 4.5 cm for Experiment 1 and was set at 6 cm for Experiment 2. The test animals were divided into two groups in each experiment: a 5% D-Mannitol (MAN) group and a TPN group. In Experiment 1, TPN rats showed macroscopic lesions (edema in peritoneum, increased collateral vasculature, induration in perivenous tissue, and thrombus) at the tip of the catheter. The diameter of the posterior vena cava (2.86 +/- 0.16 mm, mean +/- S.D.) was significantly greater than that of the anterior vena cava (2.45 +/- 0.22 mm) in 10 rats of Experiment 1. In Experiment 2, TPN rats showed no abnormalities at necropsy. Our findings suggest that TPN administered via the posterior vena cava in Sprague-Dawley rats requires the catheter to be inserted to a depth of 6 cm from the femoral vein. We hypothesize that this is because it is inserted to the level of the renal vein branch where the diameter of the posterior vena cava may be greatest.

CONTRIBUTION OF INTESTINAL CALCIUM ABSORPTION TO 1,25-DIHYDROXYVITAMIN D3-INDUCED CALCIUM ACTION IN THE TOTAL PARENTERAL NUTRITION RAT

To investigate the contribution of intestinal calcium (Ca) absorption to 1,25-dihydroxyvitamin D(3) (1,25(OH) (2)D(3))-induced Ca action, we assessed parameters related to Ca metabolism after a single dosing of 1,25(OH)(2)D (3) in the total parenteral nutrition (TPN) solution or 5% D-mannitol (MAN) solution treatment with rats. Animals were divided into 6 groups (vehicle, 100 microg/kg p.o. and 25 microg/kg i.v.; n=8) in Experiment 1 and 8 groups (vehicle, 1, 10 and 100 microg/kg p.o.; n=6) in Experiment 2 at TPN or MAN solution treatment. In both experiments, the parameters related to Ca metabolisms, urinary Ca and urinary deoxypyridinoline on 0-24 hr or serum Ca, osteocalcin and parathyroid hormone at 24 hr were measured after 1,25(OH)(2)D (3) dosing. 1,25(OH)(2)D(3)-related increased urinary Ca or serum Ca were observed in both experiments. Decrease rates in change of urinary Ca in TPN solution treatment rats were 36.3% (100 microg/kg p.o.) or 47.1% (25 microg/kg i.v.) of MAN solution treatment rats in Experiment 1, and 29.0% (1 microg/kg), 56.2% (10 microg/kg) or 35.3% (100 microg/kg) of MAN solution treatment rats in Experiment 2. Decrease rates in change of serum Ca at 72 hr in TPN solution treatment rats were 57.3% (100 microg/kg p.o.) or 44.5% (25 microg/kg i.v.) of MAN solution treatment rats in Experiment 1, and were 57.0% (100 microg/kg) of MAN solution treatment rats in Experiment 2. There were no differences in the change of serum Ca in the 1,25(OH)(2)D(3) 1 or 10-microg/kg group in Experiment 2. Our results suggest that differences in urinary Ca or serum Ca between MAN solution treatment rats and TPN solution treatment rats express the contribution of intestinal Ca absorption to 1,25(OH)(2)D(3)-induced Ca action in the conditions of the study.

The suprachiasmatic nucleus controls the daily variation of plasma glucose via the autonomic output to the liver: are the clock genes involved?

In order to drive tissue-specific rhythmic outputs, the master clock, located in the suprachiasmatic nucleus (SCN), is thought to reset peripheral oscillators via either chemical and hormonal cues or neural connections. Recently, the daily rhythm of plasma glucose (characterized by a peak before the onset of the activity period) has been shown to be directly driven by the SCN, independently of the SCN control of rhythmic feeding behaviour. Indeed, the daily variation in glucose was not impaired unless the scheduled feeding regimen (six-meal schedule) was associated with an SCN lesion. Here we show that the rhythmicity of both clock-gene mRNA expression in the liver and plasma glucose is not abolished under such a regular feeding schedule. Because the onset of the activity period and hyperglycemia are correlated with an increased sympathetic tonus, we investigated whether this autonomic branch is involved in the SCN control of plasma glucose rhythm and liver rhythmicity. Interestingly, hepatic sympathectomy combined with a six-meal feeding schedule resulted in a disruption of the plasma glucose rhythmicity without affecting the daily variation in clock-gene mRNA expression in the liver. Taking all these data together, we conclude that (i) the SCN needs the sympathetic pathway to the liver to generate the 24-h rhythm in plasma glucose concentrations, (ii) rhythmic clock-gene expression in the liver is not dependent on the sympathetic liver innervation and (iii) clock-gene rhythmicity in liver cells is not sufficient for sustaining a circadian rhythm in plasma glucose concentrations.