Insulin glargine maintains equivalent glycemic control and better lipometabolic control than NPH insulin in type 1 diabetes patients who missed a meal.

Our goal was to investigate blood glucose and lipometabolism control in type 1 diabetes patients who missed breakfast and the accompanying insulin injection of NPH insulin (NPH) or insulin glargine (glargine) as part of a basal-bolus regimen. This was a multi-center, open-label, controlled study in adults (> or =18 years) with HbA (1c)< or =11.5% on insulin therapy with NPH as basal insulin. Patients were randomized to receive prandial insulin plus either bedtime glargine (n=28) or NPH (n=32). Insulin was titrated to target fasting blood glucose levels 80-130 mg/dl at 06:00-07:00. Patients had no intake of insulin or food between 22:00 and 12:00 the next day. The change in blood glucose levels (07:00-11:00) was similar (27.5 mg/dl vs. 35.4 mg/dl), but the mean blood glucose level was higher with glargine vs. NPH at 22:00 (158.2 mg/dl vs. 130.2 mg/dl). During the period without insulin or food intake, blood glucose decreased with glargine (-25.8 mg/dl) and increased with NPH (+9.1 mg/dl; p=0.0284). Nonesterified fatty acid (07:00 and 09:00-12:00) and beta-hydroxybutyrate (07:00 and 10:00-12:00) levels were lower with glargine vs. NPH (both p<0.05). For patients who miss a morning meal, glargine is associated with maintained glycemic and lipometabolic control compared with NPH insulin.     

Omitting Late-Night Eating May Cause Hypoglycemia in “Well Controlled” Basal Insulin-Treated Type 2 Diabetes

ObjectiveTo assess hypoglycemia caused by eating the last meal of the day earlier or its omission in “well controlled” type 2 diabetes mellitus patients treated with once-nightly basal insulin.MethodsPreviously basal insulin-titrated subjects (n = 20) (fasting plasma glucose, FPG, < 110 mg/dL and no self-reported hypoglycemia) underwent continuous glucose monitoring (CGM) during 3 consecutive eating conditions of 3 days each; (1) usual eating, (2) the last meal restricted to 18:00, and (3) 1 sequential meal omitted/day thereby creating a fasting day after transposing the 4-hour period after a meal with that when the meal was omitted. One 24-hour (00:00 to 00:00) period within each eating condition was selected for comparison.ResultsThe mean duration in all hypoglycemic ranges doubled (P = .0584 or greater) when the last meal was omitted or eaten at 18:09 ± 0:39 instead of 19:43 ± 1:01, the usual time for the subjects’ undisturbed eating. The mean duration of hypoglycemia was greatest between 00:00 to 06:00 compared to the 3 other 6-hour periods of the day.ConclusionsIncreased hypoglycemia occurs when the subject’s last meal is eaten earlier or omitted and may not be recognized because it occurs predominately during sleep. When titrating basal insulin from the morning FPG, considerations should be given to the effect of the last meal of the day and possible hypoglycemia between 00:00 and 06:00 to avoid excessive basal insulin treatment. (Endocr Pract. 2015;21:280-285)     

Plasma variation of atrial natriuretic peptide in central hypervolemia (diurnal or nocturnal) induced by antiorthostatic decubitus at -6 degrees

Plasma levels of ANP were measured during a 4 hrs head-down tilt at -6 degrees in 5 healthy male volunteers (aged 20-22 M.2). The experiments took place from 8 to 14 hrs, (day), and from 22 to 7 hrs (night). The control period was 1 hr. in a seated position (8 to 9 hrs. for day and 22 to 23 hrs. for night). Blood samples were collected at 9 and 23 hrs. and every 20 min. during the first hours, and every hours thereafter. Electroencephalograms were continuously recorded during night. Our results showed a similar increase in ANP during both experimental conditions. During night there was no correlations between ANP and sleep stages. Finally the differences observed in renal responsiveness to central volume expansion during day or night could not be explained by a difference in renin, aldosterone, vasopressin (previously demonstrated in several studies) or ANP secretion.     

Diurnal changes in blood metabolites and their relation to plasma growth hormone and time of feeding in mithun heifers (Bos frontalis)

The aim of the present study was to investigate what, if any, diurnal changes occur in blood metabolites in relation to plasma growth hormone (GH) and feeding time among mithun (Bos frontalis), a semi-wild ruminant. Blood samples were collected at hourly intervals during a 24 h span from 6 mithun heifers (averaging 2.5 yr of age and averaging 230 kg in weight) that were fed twice a day at 11:00 and 16:00 h. Samples were assayed for plasma GH and blood metabolites, non-esterified fatty acids (NEFA), glucose, and alpha-amino nitrogen. The total sampling period was divided into a 1) postprandial (after meal) period (period I: 11:00 to 21:00 h) and 2) interprandial period (period II: 22:00 to 10:00 h) and also into night (20:00 to 05:00 h) and day (06:00 to 10:00 h) periods for statistical analysis. Plasma glucose and alpha-amino nitrogen levels increased (p<0.01), and plasma NEFA and GH decreased (p<0.01) after each meal. No diurnal rhythmicity was detected in plasma glucose or alpha-amino nitrogen levels. Interestingly, plasma NEFA and GH levels were higher (p<0.01) during the interprandial (period II) and night periods, indicating an energy deficit that occurred progressively during the interprandial period of nocturnal feed deprivation. In twice-daily-fed mithuns we conclude that: 1) plasma metabolites and GH exhibited a definite pattern of change with time of feeding; 2) concentrations of plasma NEFA were higher nocturnally due to an energy deficit and that GH levels were higher during the interprandial period after the second meal; 3) the interprandial period after the second feeding may be considered to constitute a short-term food deprivation; 4) the longer interprandial period of 19 h in this study between the second and subsequent morning meal may be changed into equally divided feedings to minimize the short-term energy deficit; and 5) blood sampling for blood metabolites in mithuns should be conducted at a fixed time of day with special emphasis on time of feeding.     

Postprandial metabolic profiles following meals and snacks eaten during simulated night and day shift work

Shift workers are known to have an increased risk of developing cardiovascular disease (CVD) compared with day workers. An important factor contributing to this increased risk could be the increased incidence of postprandial metabolic risk factors for CVD among shift workers, as a consequence of the maladaptation of endogenous circadian rhythms to abrupt changes in shift times. We have previously shown that both simulated and real shift workers showed relatively impaired glucose and lipid tolerance if a single test meal was consumed between 00:00-02:00 h (night shift) compared with 12:00-14:00 h (day shift). The objective of the present study was to extend these observations to compare the cumulative metabolic effect of consecutive snacks/meals, as might normally be consumed throughout a period of night or day shift work. In a randomized crossover study, eight healthy nonobese men (20-33 yrs, BMI 20-25kg/m2) consumed a combination of two meals and a snack on two occasions following a standardized prestudy meal, simulating night and day shift working (total energy 2500 kcal: 40% fat, 50% carbohydrate, 10% protein). Meals were consumed at 01:00/ 13:00 h and 07:00/19:00h, and the snack at 04:00/16:00 h. Blood was taken after an overnight fast, and for 8 h following the first meal on each occasion, for the measurement of glucose, insulin, triacylglycerol (TAG), and nonesterified fatty acids (NEFA). RM-ANOVA (factors time and shift) showed a significant effect of shift for plasma TAG, with higher levels on simulated night compared to day shift (p < 0.05). There was a trend toward an effect of shift for plasma glucose, with higher plasma glucose at night (p = 0.08), and there was a time-shift interaction for plasma insulin levels (p < 0.01). NEFA levels were unaffected by shift. Inspection of the area under the plasma response curve (AUC) following each meal and snack revealed that the differences in lipid tolerance occurred throughout the study, with greatest differences occurring following the mid-shift snack. In contrast, glucose tolerance was relatively impaired following the first night-time meal, with no differences observed following the second meal. Plasma insulin levels were significantly lower following the first meal (p < 0.05), but significantly higher following the second meal (p < 0.01) on the simulated night shift. These findings confirm our previous observations of raised postprandial TAG and glucose at night, and show that sequential meal ingestion has a more pronounced effect on subsequent lipid than carbohydrate tolerance.     

Adipokine levels are altered by shiftwork: a preliminary study

Shiftwork is often associated with metabolic diseases, and in the past few years, several cytokines have been postulated to contribute to various diseases, including insulin resistance. The aim of this study was to compare the concentrations of adiponectin, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in samples of young adult men exposed to a fixed (i) night shift (n = 9), working from 22:00 to 06:00 h; (ii) early morning shift (n = 6), working from 06:00 to 14:00 h; and (iii) day shift (n = 7), working from 08:00 to 17:00 h. The fixed night-shift and early-morning-shift samples were considered collectively as a shiftworker group given their work times. Blood samples were collected during the regular working day at 4-h intervals over the course of 24 h, thus totaling six samples. Morphological and physical activity parameters did not differ between the three groups. Total energy intake was lowest on the early morning shifts (p 相似文献   

Postprandial Metabolic Profiles Following Meals and Snacks Eaten during Simulated Night and Day Shift Work

Shift workers are known to have an increased risk of developing cardiovascular disease (CVD) compared with day workers. An important factor contributing to this increased risk could be the increased incidence of postprandial metabolic risk factors for CVD among shift workers, as a consequence of the maladaptation of endogenous circadian rhythms to abrupt changes in shift times. We have previously shown that both simulated and real shift workers showed relatively impaired glucose and lipid tolerance if a single test meal was consumed between 00:00–02:00 h (night shift) compared with 12:00–14:00 h (day shift). The objective of the present study was to extend these observations to compare the cumulative metabolic effect of consecutive snacks/meals, as might normally be consumed throughout a period of night or day shift work. In a randomized crossover study, eight healthy nonobese men (20–33 yrs, BMI 20–25 kg/m²) consumed a combination of two meals and a snack on two occasions following a standardized prestudy meal, simulating night and day shift working (total energy 2500 kcal: 40% fat, 50% carbohydrate, 10% protein). Meals were consumed at 01:00/13:00 h and 07:00/19:00 h, and the snack at 04:00/16:00 h. Blood was taken after an overnight fast, and for 8 h following the first meal on each occasion, for the measurement of glucose, insulin, triacylglycerol (TAG), and nonesterified fatty acids (NEFA). RM-ANOVA (factors time and shift) showed a significant effect of shift for plasma TAG, with higher levels on simulated night compared to day shift (p < 0.05). There was a trend toward an effect of shift for plasma glucose, with higher plasma glucose at night (p = 0.08), and there was a time-shift interaction for plasma insulin levels (p < 0.01). NEFA levels were unaffected by shift. Inspection of the area under the plasma response curve (AUC) following each meal and snack revealed that the differences in lipid tolerance occurred throughout the study, with greatest differences occurring following the mid-shift snack. In contrast, glucose tolerance was relatively impaired following the first night-time meal, with no differences observed following the second meal. Plasma insulin levels were significantly lower following the first meal (p < 0.05), but significantly higher following the second meal (p < 0.01) on the simulated night shift. These findings confirm our previous observations of raised postprandial TAG and glucose at night, and show that sequential meal ingestion has a more pronounced effect on subsequent lipid than carbohydrate tolerance.     

Diurnal Changes in Blood Metabolites and Their Relation to Plasma Growth Hormone and Time of Feeding in Mithun Heifers (Bos frontalis)

The aim of the present study was to investigate what, if any, diurnal changes occur in blood metabolites in relation to plasma growth hormone (GH) and feeding time among mithun (Bos frontalis), a semi‐wild ruminant. Blood samples were collected at hourly intervals during a 24 h span from 6 mithun heifers (averaging 2.5 yr of age and averaging 230 kg in weight) that were fed twice a day at 11:00 and 16:00 h. Samples were assayed for plasma GH and blood metabolites, non‐esterified fatty acids (NEFA), glucose, and alpha‐amino nitrogen. The total sampling period was divided into a 1) postprandial (after meal) period (period I: 11:00 to 21:00 h) and 2) interprandial period (period II: 22:00 to 10:00 h) and also into night (20:00 to 05:00 h) and day (06:00 to 10:00 h) periods for statistical analysis. Plasma glucose and alpha‐amino nitrogen levels increased (p<0.01), and plasma NEFA and GH decreased (p<0.01) after each meal. No diurnal rhythmicity was detected in plasma glucose or alpha‐amino nitrogen levels. Interestingly, plasma NEFA and GH levels were higher (p<0.01) during the interprandial (period II) and night periods, indicating an energy deficit that occurred progressively during the interprandial period of nocturnal feed deprivation. In twice‐daily‐fed mithuns we conclude that: 1) plasma metabolites and GH exhibited a definite pattern of change with time of feeding; 2) concentrations of plasma NEFA were higher nocturnally due to an energy deficit and that GH levels were higher during the interprandial period after the second meal; 3) the interprandial period after the second feeding may be considered to constitute a short‐term food deprivation; 4) the longer interprandial period of 19 h in this study between the second and subsequent morning meal may be changed into equally divided feedings to minimize the short‐term energy deficit; and 5) blood sampling for blood metabolites in mithuns should be conducted at a fixed time of day with special emphasis on time of feeding.     

Insulin receptor changes in type 2 diabetes after short term insulin treatment

We have studied erythrocyte insulin receptor changes before and after 8 days of continuous subcutaneous insulin infusion by a pump in 11 uncontrolled obese non-insulin-dependent diabetics (type 2), diet and drug resistant for at least three months previously. All the patients were hospitalized. On day 1 of the study, their oral hypoglycemic agents were stopped and hypocaloric diet (1000 Kcal/day) was maintained (strictly reinforced). This period of reinforced treatment was not accompanied by correction of hyperglycemia. On day 9 patients were placed for 12 hours on artificial pancreas in order to bring their fasting blood glucose levels down to normal values. Then they were submitted to a continuous subcutaneous insulin infusion (CSII) for the following 8 days. There was a significant decrease in mean fasting plasma glucose (P less than 0.001) and a rise in insulin (P less than 0.05) levels after insulin treatment. Mean specific insulin binding was also significantly increased (P less than 0.01). The increase in binding (with insulin therapy) correlated with the fall in fasting hyperglycemia (r = 0.786, P less than 0.01). In addition, the increase in binding correlated negatively with changes in fasting plasma insulin levels (r = -0.867, P less than 0.01), under treatment, on one hand and with the dose of exogenous insulin administered (r = -0.681, P less than 0.05) on the other hand. There was no correlation between binding and fasting plasma insulin levels (before and after insulin therapy), or between diabetes duration and any of the previous parameters.(ABSTRACT TRUNCATED AT 250 WORDS)     

Naphthol-yellow-S protein content of individual rat hepatocytes as related to food intake and short-term starvation

With regard to the protein content, as analysed cytophotometrically, of hepatocytes from rats kept under a 12L 12D photoperiod (photophase 7:00-19:00), the following facts have been established: 1) Hepatocytes of different classes of ploidy all demonstrate, more or less equally, daily variations in protein content and also its reduction after 24-h fasting. 2) With computer analysis of data obtained at eight time points during a period of 24 h, a sinusoidal curve of the protein content of individual mononuclear tetraploid hepatocytes throughout the day could be demonstrated with a maximum at 6:20 and a minimum at 18:20. 3) Animals, fed with meals via a dispensing machine from 23:00 to 24:00 only, show a similar sinusoidal curve but with higher amplitude, and a virtually identical mean value as those fed ad libitum. The maximum was found at 10:40, revealing a time lag of 12 h after food intake, the minimum at 22:40. 4) Trained animals deprived of food during the standardized feeding time revealed a moderate reduction of their hepatocyte protein content in the first 6 h, then a 6-h period with a steep fall followed by a slower reduction. After 24 h, the mean hepatocyte protein mass had decreased to 72% of that at the commencement of fasting at 23:00.     

The 24-h pattern of human prolactin in serum.

Radioimmunoassay determinations of serum prolactin every 2 hrs in twelve healthy subjects (six women and six men), aged between 22 and 34, reveal that several episodes of hormone secretion occur over a 24-h period. The two episodes displaying significant oscillations have 24-h and 8-h periods, with maxima occurring respectively at 04(30) and at 07(00), 15(00) and 23(00). Accordingly, the highest prolactin levels in serum occur during the night, but oscillations are present throughout the day. The observation schedule adopted leads us to conclude that the main secretory rhythm is synchronized with sleep. The 8-h periods seem to be rather dependent on the course of time.     

Adipokine Levels Are Altered by Shiftwork: A Preliminary Study

Shiftwork is often associated with metabolic diseases, and in the past few years, several cytokines have been postulated to contribute to various diseases, including insulin resistance. The aim of this study was to compare the concentrations of adiponectin, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in samples of young adult men exposed to a fixed (i) night shift (n?=?9), working from 22:00 to 06:00?h; (ii) early morning shift (n?=?6), working from 06:00 to 14:00?h; and (iii) day shift (n?=?7), working from 08:00 to 17:00?h. The fixed night-shift and early-morning-shift samples were considered collectively as a shiftworker group given their work times. Blood samples were collected during the regular working day at 4-h intervals over the course of 24?h, thus totaling six samples. Morphological and physical activity parameters did not differ between the three groups. Total energy intake was lowest on the early morning shifts (p?<?.03). Both shiftworker groups ingested a significantly higher percentage of fat (p?<?.003) and a lower percentage of carbohydrate (p?<?.0005) than the day group. The early morning group had a lower mean 24-h level of adiponectin than the other two groups (p?=?.016), and both the early morning and night groups exhibited higher mean 24-h levels of TNF-α than the day group (p?=?.0001). The 24-h mean levels of IL-6 did not differ significantly between the groups (p?=?.147). None of the groups exhibited a significant circadian effect on adiponectin (p?=?.829), TNF-α (p?=?.779), or IL-6 (p?=?.979) levels. These results indicate that individuals who are enrolled in shiftwork are susceptible to alterations in the secretion of cytokines that are involved in insulin resistance and cardiovascular disease, both of which are known to affect this population. (Author correspondence: tmello@demello.net.br)     

圈养白头叶猴春季昼夜活动节律

2008 年3 ～5 月,采用瞬时扫描法,对上海动物园5 只白头叶猴的行为进行24 h 昼夜连续观察。结果表明:春季圈养白头叶猴一天的活动起于06∶ 00 左右,结束于18∶ 00 或18∶ 30。白天白头叶猴的主要行为为休息、取食和移动,平均频次依次是13.79 次、4.75 次和2.18 次。夜间的主要行为为休息、移动和抓挠,平均频次依次是22.13 次、0.43 次和0.26 次。不同个体昼夜活动节律差异很大。其中,移动、理毛、玩耍和其它行为的差异显著。夜间无理毛和玩耍行为,移动行为在夜间21∶ 00, 00 ∶ 30, 03∶00 和04∶ 30 出现高峰。在22∶ 30, 01∶ 00, 02∶ 00, 03∶ 30, 04∶ 30 和05∶30 则出现抓挠高峰。这预示白头叶猴夜间休息时处于一个“轻睡眠”状态。同时,雌雄白头叶猴昼夜移动行为差异显著。     

A compromise phase position for permanent night shift workers: circadian phase after two night shifts with scheduled sleep and light/dark exposure

Night shift work is associated with a myriad of health and safety risks. Phase-shifting the circadian clock such that it is more aligned with night work and day sleep is one way to attenuate these risks. However, workers will not be satisfied with complete adaptation to night work if it leaves them misaligned during days off. Therefore, the goal of this set of studies is to produce a compromise phase position in which individuals working night shifts delay their circadian clocks to a position that is more compatible with nighttime work and daytime sleep yet is not incompatible with late nighttime sleep on days off. This is the first in the set of studies describing the magnitude of circadian phase delays that occurs on progressively later days within a series of night shifts interspersed with days off. The series will be ended on various days in order to take a "snapshot" of circadian phase. In this set of studies, subjects sleep from 23:00 to 7:00 h for three weeks. Following this baseline period, there is a series of night shifts (23:00 to 07:00 h) and days off. Experimental subjects receive five 15 min intermittent bright light pulses (approximately 3500 lux; approximately 1100 microW/cm2) once per hour during the night shifts, wear sunglasses that attenuate all visible wavelengths--especially short wavelengths ("blue-blockers")--while traveling home after the shifts, and sleep in the dark (08:30-15:30 h) after each night shift. Control subjects remain in typical dim room light (<50 lux) throughout the night shift, wear sunglasses that do not attenuate as much light, and sleep whenever they want after the night shifts. Circadian phase is determined from the circadian rhythm of melatonin collected during a dim light phase assessment at the beginning and end of each study. The sleepiest time of day, approximated by the body temperature minimum (Tmin), is estimated by adding 7 h to the dim light melatonin onset. In this first study, circadian phase was measured after two night shifts and day sleep periods. The Tmin of the experimental subjects (n=11) was 04:24+/-0.8 h (mean+/-SD) at baseline and 7:36+/-1.4 h after the night shifts. Thus, after two night shifts, the Tmin had not yet delayed into the daytime sleep period, which began at 08:30 h. The Tmin of the control subjects (n=12) was 04:00+/-1.2 h at baseline and drifted to 4:36+/-1.4 h after the night shifts. Thus, two night shifts with a practical pattern of intermittent bright light, the wearing of sunglasses on the way home from night shifts, and a regular sleep period early in the daytime, phase delayed the circadian clock toward the desired compromise phase position for permanent night shift workers. Additional night shifts with bright light pulses and daytime sleep in the dark are expected to displace the sleepiest time of day into the daytime sleep period, improving both nighttime alertness and daytime sleep but not precluding adequate sleep on days off.     

Diurnal variations of plasma lipoproteins and liver lipids in rats fed starch sucrose or fat

The incidence of the dietary source of energy on lipid transport and accumulation was investigated over a full nycthemeral cycle in adapted rats fed ad libitum. Starch, sucrose and lard were compared. Lipoprotein composition of the plasma, liver and plasma lipids and insulinemia were analyzed every 3 hours over 24 hours. The pattern of VLDL concentration was dependent on the nature of the energetic substrate. Feeding starch resulted in a remarkable stability of lipoproteins, liver and plasma lipids, despite clearcut diurnal variations in plasma non esterified fatty acids, insulinemia and liver glycogen. In sucrose-fed rats VLDL rose to a sharp maximum in the post prandial period (9-12:00) and were totally cleared by 18:00. In fat-fed rats, HDL were elevated during the night, suggesting a possible stimulation of their synthesis by dietary fat in the intestine. LDL were constantly elevated with peak values at 21:00 while VLDL were very low, even at night, despite elevated levels of non-esterified fatty acids. It is concluded that, in animals adapted to a high fat-diet, a high level of circulating non esterified fatty acids is not sufficient to promote the synthesis of VLDL. The main regulating factor appears to be the intensity of hepatic lipogenesis which is stimulated by sucrose and inhibited by lard. No correlation was found between variations in plasma VLDL and insulinemia.     

Timing of food intake during simulated night shift impacts glucose metabolism: A controlled study

Eating during the night may increase the risk for obesity and type 2 diabetes in shift workers. This study examined the impact of either eating or not eating a meal at night on glucose metabolism. Participants underwent four nights of simulated night work (SW1–4, 16:00–10:00 h, <50 lux) with a daytime sleep opportunity each day (10:00–16:00 h, <3 lux). Healthy males were assigned to an eating at night (NE; n = 4, meals; 07:00, 19:00 and 01:30 h) or not eating at night (NEN; n = 7, meals; 07:00 h, 09:30, 16:10 and 19:00 h) condition. Meal tolerance tests were conducted post breakfast on pre-night shift (PRE), SW4 and following return to day shift (RTDS), and glucose and insulin area under the curve (AUC) were calculated. Mixed-effects ANOVAs were used with fixed effects of condition and day, and their interactions, and a random effect of subject identifier on the intercept. Fasting glucose and insulin were not altered by day or condition. There were significant effects of day and condition × day (both p < 0.001) for glucose AUC, with increased glucose AUC observed solely in the NE condition from PRE to SW4 (p = 0.05) and PRE to RTDS (p < 0.001). There was also a significant effect of day (p = 0.007) but not condition × day (p = 0.825) for insulin AUC, with increased insulin from PRE to RTDS in both eating at night (p = 0.040) and not eating at night (p = 0.006) conditions. Results in this small, healthy sample suggest that not eating at night may limit the metabolic consequences of simulated night work. Further study is needed to explore whether matching food intake to the biological clock could reduce the burden of type 2 diabetes in shift workers.     

A week of simulated night work delays salivary melatonin onset

In most studies, the magnitude and rate of adaptation to various night work schedules is assessed using core body temperature as the marker of circadian phase. The aim of the current study was to assess adaptation to a simulated night work schedule using salivary dim light melatonin onset (DLMO) as an alternative circadian phase marker. It was hypothesised that the night work schedule would result in a phase delay, manifest in relatively later DLMO, but that this delay would be somewhat inhibited by exposure to natural light. Participants worked seven consecutive simulated 8-hour night shifts (23:00-07:00 h). By night 7, there was a mean cumulative phase delay of 5.5 hours, equivalent to an average delay of 0.8 hours per day. This indicates that partial circadian adaptation occurred in response to the simulated night work schedule. The radioimmunoassay used in the current study provides a sensitive assessment of melatonin concentration in saliva that can be used to determine DLMO, and thus provides an alternative phase marker to core body temperature, at least in laboratory studies.     

PARADOXICAL POST-EXERCISE RESPONSES OF ACYLATED GHRELIN AND LEPTIN DURING A SIMULATED NIGHT SHIFT

Approximately 10% of employees undertake night work, which is a significant predictor of weight gain, possibly because responses to activity and eating are altered at night. It is known that the appetite-related hormone, acylated ghrelin, is suppressed after an acute bout of exercise during the day, but no researcher has explored whether evening exercise alters acylated ghrelin and other appetite-related outcomes during a subsequent night shift. Six healthy men (mean?±?SD: age 30?±?8 yrs, body mass index 23.1?±?1.1?kg/m²) completed two crossover trials (control and exercise) in random order. Participants fasted from 10:00?h, consumed a test meal at 18:00?h, and then cycled at 50% peak oxygen uptake or rested between 19:00–20:00?h. Participants then completed light activities during a simulated night shift which ended at 05:00?h. Two small isocaloric meals were consumed at 22:00 and 02:00?h. Venous blood samples were drawn via cannulation at 1?h intervals between 19:00–05:00?h for the determination of acylated ghrelin, leptin, insulin, glucose, triglyceride, and non-esterified fatty acids concentrations. Perceived hunger and wrist actimetry were also recorded. During the simulated night shift, mean?±?SD acylated ghrelin concentration was 86.5?±?40.8 pg/ml following exercise compared with 71.7?±?37.7 pg/ml without prior exercise (p?=?0.015). Throughout the night shift, leptin concentration was 263?±?242 pg/ml following exercise compared with 187?±?221 pg/ml without prior exercise (p?=?0.017). Mean levels of insulin, triglyceride, non-esterified fatty acids, and wrist actimetry level were also higher during the night shift that followed exercise (p?<?0.05). These data indicate that prior exercise increases acylated ghrelin and leptin concentrations during a subsequent simulated night shift. These findings differ from the known effects of exercise on acylated ghrelin and leptin during the day, and therefore have implications for energy balance during night work. (Author correspondence: c.j.morris@2006.ljmu.ac.uk).     

Variations in diurnal and nocturnal waking state in air traffic controllers

Physiological variables of 22 air traffic controllers (ATCs), mean age 32, were continuously telemetrically recorded from 08:00 to 17:30 and on the following day from 19:00 to either 00:00 or 0.3:00. EEG (alpha and theta indices, slow delta waves), EOG (palpebral blinks), EMG (from the neck muscles) and EKG (HR) were recorded. Comparison between day and night shows an increase at night of HR and slow waves, particularly after midnight. These results were compared with similar ones obtained from two other populations of the same age having very different professional activities (university personnel and factory workers). The EEG indices and HR are higher in ATCs. The work load imposed by the need in air traffic control to maintain a high level of vigilance, especially difficult after midnight, is in great part responsible for the high values of physiological parameters observed in this study.     

Differences in sleep, light, and circadian phase in offshore 18:00-06:00 h and 19:00-07:00 h shift workers

Complaints concerning sleep are high among those who work night shifts; this is in part due to the disturbed relationship between circadian phase and the timing of the sleep-wake cycle. Shift schedule, light exposure, and age are all known to affect adaptation to the night shift. This study investigated circadian phase, sleep, and light exposure in subjects working 18:00-06:00 h and 19:00-07:00 h schedules during summer (May-August). Ten men, aged 46+/-10 yrs (mean+/-SD), worked the 19:00-07:00 h shift schedule for two or three weeks offshore (58 degrees N). Seven men, mean age 41+/-12 yrs, worked the 18:00-06:00 h shift schedule for two weeks offshore (61 degrees N). Circadian phase was assessed by calculating the peak (acrophase) of the 6-sulphatoxymelatonin rhythm measured by radioimmunoassay of sequential urine samples collected for 72 h at the end of the night shift. Objective sleep and light exposure were assessed by actigraphy and subjective sleep diaries. Subjects working 18:00-06:00 h had a 6-sulphatoxymelatonin acrophase of 11.7+/-0.77 h (mean+/-SEM, decimal hours), whereas it was significantly later, 14.6+/-0.55 h (p=0.01), for adapted subjects working 19:00-07:00 h. Two subjects did not adapt to the 19:00-07:00 h night shift (6-sulphatoxymelatonin acrophases being 4.3+/-0.22 and 5.3+/-0.29 h). Actigraphy analysis of sleep duration showed significant differences (p=0.03), with a mean sleep duration for those working 19:00-07:00 h of 5.71+/-0.31 h compared to those working 18:00-06:00 h whose mean sleep duration was 6.64+/-0.33 h. There was a trend to higher morning light exposure (p=0.07) in the 19:00-07:00 h group. Circadian phase was later (delayed on average by 3 h) and objective sleep was shorter with the 19:00-07:00 h than the 18:00-06:00 h shift schedule. In these offshore conditions in summer, the earlier shift start and end time appears to favor daytime sleep.