Secretion of glucagon, GLP-1 and GIP may be affected by circadian rhythm in healthy males.

BACKGROUND: Glucagon is secreted from pancreatic alpha cells in response to low blood glucose and increases hepatic glucose production. Furthermore, glucagon enhances hepatic protein and lipid metabolism during a mixed meal. Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are secreted from gut endocrine cells during meals and control glucose homeostasis by potentiating insulin secretion and inhibiting food intake. Both glucose homeostasis and food intake have been reported to be affected by circadian rhythms and vice versa. In this study, we investigated whether the secretion of glucagon, GLP-1 and GIP was affected by circadian rhythms. METHODS: A total of 24 healthy men with regular sleep schedules were examined for 24 h at the hospital ward with 15 h of wakefulness and 9 h of sleep. Food intake was standardized, and blood samples were obtained every third hour. Plasma concentrations of glucagon, GLP-1 and GIP were measured, and data were analyzed by rhythmometric statistical methods. Available data on plasma glucose and plasma C-peptide were also included. RESULTS: Plasma concentrations of glucagon, GLP-1, GIP, C-peptide and glucose fluctuated with a diurnal 24-h rhythm, with the highest levels during the day and the lowest levels during the night: glucagon (p < 0.0001, peak time 18:26 h), GLP-1 (p < 0.0001, peak time 17:28 h), GIP (p < 0.0001, peak time 18:01 h), C-peptide (p < 0.0001, peak time 17.59 h), and glucose (p < 0.0001, peak time 23:26 h). As expected, we found significant correlations between plasma concentrations of C-peptide and GLP-1 and GIP but did not find correlations between glucose concentrations and concentrations of glucagon, GLP-1 and GIP. CONCLUSIONS: Our results demonstrate that under meal conditions that are similar to that of many free-living individuals, plasma concentrations of glucagon, GLP-1 and GIP were observed to be higher during daytime and evening than overnight. These findings underpin disturbed circadian rhythm as a potential risk factor for diabetes and obesity. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT06166368. Registered 12 December 2023.

Association of ferritin and transferrin saturation with all-cause mortality, and the effect of concurrent inflammation: a danish cohort study.

The association between ferritin and transferrin saturation (TS), respectively, and all-cause mortality is unclear. Furthermore, the influence of concurrent inflammation has not been sufficiently elucidated. We investigated these associations and the effect of concurrently elevated C-reactive protein (CRP), and accordingly report the levels associated with lowest all-cause mortality for females and males with and without inflammation.Blood test results from 161,921 individuals were included. Statistical analyses were performed in sex-stratified subpopulations, with ferritin or TS level as continuous exposure variables, and were adjusted for age, co-morbidity and inflammation status using CRP. An interaction was used to investigate whether the effect of ferritin or TS on all-cause mortality was modified by inflammation status (CRP ≥ 10 mg/L or CRP < 10 mg/L). Low and high ferritin and TS levels were respectively associated with increased all-cause mortality in females and in males. These associations persisted with concurrent CRP ≥ 10 mg/L. The ferritin level associated with lowest mortality was 60 µg/L for females and 125 µg/L for males with CRP < 10 mg/L. It was 52 µg/L for females and 118 µg/L for males with CRP ≥ 10 mg/L. The TS level associated with lowest mortality was 33.9% for females and 32.3% for males with CRP < 10 mg/L. It was 28.7% for females and 30.6% for males with CRP ≥ 10 mg/L.Our findings can nuance clinical interpretation and further aid in defining recommended ranges for ferritin and TS.

Pneumatic tube validation: Reducing the need for donor samples by integrating a vial-embedded data logger.

BACKGROUND: The most common way to validate a pneumatic tube system is to compare pneumatic tube system-transported blood samples to blood samples carried by hand. The importance of measuring the forces inside the pneumatic tube system has also been emphasized. The aim of this study was to define a validation protocol using a mini data logger (VitalVial, Motryx Inc., Canada) to reduce the need for donor samples in pneumatic tube system validation. METHODS: As an indicator of the total vibration, the blood samples are exposed to under pneumatic tube system transportation; the area under the curve was determined by a VitalVial for all hospital Tempus600 lines using a five-day validation protocol. Only the three lines with the highest area under the curves were clinically validated by analysing potassium, lactate dehydrogenase and aspartate aminotransferase. A month after pneumatic tube system commissioning, a follow-up on laboratory data was performed. RESULTS: Mean area under the curve of the six lines ranged between 347 and 581. The variability of the area under the curve was between 1.51 and 11.55%. In the laboratory data follow-up, an increase in lactate dehydrogenase haemolysis was seen from the three lines with the highest area under the curve and the emergency department, which was not detected in the clinical validation. When the Tempus600 system was in commission, a higher mean area under the curve was measured. CONCLUSION: A three-day validation protocol using VitalVials is enough to determine the stability of a Tempus600 system and can greatly reduce the need for donor samples. When in commission, the stability of the pneumatic tube system should be verified and lactate dehydrogenase haemolysis should be routinely checked.

Circadian variations in plasma concentrations of cholecystokinin and gastrin in man.

Cholecystokinin (CCK) is a gut hormone which regulates gallbladder contraction and pancreatic enzyme secretion. In addition, CCK is also a major intestinal satiety signal. The knowledge about CCK in circulation, however, has been limited by difficulties in accurate measurement of the concentrations in plasma. Thus, CCK circulates in low concentrations and furthermore, it is structurally homologous to the antral hormone, gastrin, which circulates in higher concentrations. Therefore, most antibodies raised against CCK cross-react in immunoassays with gastrin. However, using highly sensitive and entirely specific in-house radioimmunoassays, which meet these challenges, we have now measured the daily concentration-variations of CCK and gastrin in plasma from young healthy men (n = 24). Plasma was sampled every third hour from each person during 24 h. The results show that the gastrointestinal secretion of both CCK and gastrin in man display significant circadian variations.

Evaluation of Serum Insulin-like Factor 3 Quantification by LC-MS/MS as a Biomarker of Leydig Cell Function.

BACKGROUND: The peptide hormone insulin-like factor 3 (INSL3) is a marker for Leydig cell function and the clinical use of serum INSL3 measurements has been suggested by several groups. AIM: (1) To establish a reference range for liquid chromatography-tandem mass spectrometry (LC-MS/MS) of serum INSL3 in healthy boys and men; and (2) to compare the associations of serum INSL3 and testosterone (T) to pubertal stage, lifestyle factors, diurnal variation, body composition, and human chorionic gonadotropin (hCG) stimulation. RESULTS: In a reference range based on LC-MS/MS analysis of serum from 1073 boys and men, INSL3 increased from levels close to the detection limit (0.03 µg/L) in prepubertal boys to a maximum mean level of 1.3 µg/L (95% CI, 0.9-2.7) in young men (19-40 years of age) and decreased slightly in older men (0.1 µg/L per decade). Serum T, but not INSL3, was associated with body mass index or body fat percentage and with alcohol consumption. Smoking was positively associated with serum T, but negatively associated with INSL3. There were significant diurnal variations in both INSL3 and T in men (P < 0.001), but serum INSL3 varied substantially less, compared with serum T (± 11% vs ± 26%). Mean serum INSL3 increased after hCG stimulation, but less than T (+ 17% vs + 53%). In both healthy men and in patients suspected of testicular failure, baseline serum INSL3 was more closely associated to the hCG-induced increase in serum T than baseline T itself. CONCLUSION: Measurement of serum INSL3 by LC-MS/MS has promise as a marker of testicular disorders.

Diurnal Variation of Markers for Cholesterol Synthesis, Cholesterol Absorption, and Bile Acid Synthesis: A Systematic Review and the Bispebjerg Study of Diurnal Variations.

Human studies have shown diurnal rhythms of cholesterol and bile acid synthesis, but a better understanding of the role of the circadian system in cholesterol homeostasis is needed for the development of targeted interventions to improve metabolic health. Therefore, we performed a systematic literature search on the diurnal rhythms of cholesterol synthesis and absorption markers and of bile acid synthesis markers. We also examined the diurnal rhythms of the cholesterol synthesis markers lathosterol and desmosterol, and of the cholesterol absorption markers cholestanol, campesterol, and sitosterol in serum samples from the Bispebjerg study. These samples were collected every three hours over a 24-hour period in healthy males (n = 24) who consumed low-fat meals. The systematic search identified sixteen papers that had examined the diurnal rhythms of the cholesterol synthesis markers lathosterol (n = 3), mevalonate (n = 9), squalene (n = 2), or the bile acid synthesis marker 7α-hydroxy-4-cholesten-3-one (C4) (n = 4). Results showed that lathosterol, mevalonate, and squalene had a diurnal rhythm with nocturnal peaks, while C4 had a diurnal rhythm with daytime peaks. Furthermore, cosinor analyses of the serum samples showed a significant diurnal rhythm for lathosterol (cosinor p < 0.001), but not for desmosterol, campesterol, sitosterol, and cholestanol (cosinor p > 0.05). In conclusion, cholesterol synthesis and bile acid synthesis have a diurnal rhythm, though no evidence for a diurnal rhythm of cholesterol absorption was found under highly standardised conditions. More work is needed to further explore the influence of external factors on the diurnal rhythms regulating cholesterol homeostasis.

The Effects of Naturalistic Light on Diurnal Plasma Melatonin and Serum Cortisol Levels in Stroke Patients during Admission for Rehabilitation: A Randomized Controlled Trial.

Background: Stroke patients admitted for rehabilitation often lack sufficient daytime blue light exposure due to the absence of natural light and are often exposed to light at unnatural time points. We hypothesized that artificial light imitating daylight, termed naturalistic light, would stabilize the circadian rhythm of plasma melatonin and serum cortisol levels among long-term hospitalized stroke patients. Methods: A quasi-randomized controlled trial. Stroke patients in need of rehabilitation were randomized between May 1, 2014, and June 1, 2015 to either a rehabilitation unit equipped entirely with always on naturalistic lighting (IU), or to a rehabilitation unit with standard indoor lighting (CU). At both inclusion and discharge after a hospital stay of at least 2 weeks, plasma melatonin and serum cortisol levels were measured every 4 hours over a 24-hour period. Circadian rhythm was estimated using cosinor analysis, and variance between time-points. Results: A total of 43 were able to participate in the blood collection. Normal diurnal rhythm of melatonin was disrupted at both inclusion and discharge. In the IU group, melatonin plasma levels were increased at discharge compared to inclusion (n = 23; median diff, 2.9; IQR: -1.0 to 9.9, p = 0.030) and rhythmicity evolved (n = 23; p = 0.007). In the CU group, melatonin plasma levels were similar between discharge and inclusion and no rhythmicity evolved. Overall, both patient groups showed normal cortisol diurnal rhythms at both inclusion and discharge. Conclusions: This study is the first to demonstrate elevated melatonin plasma levels and evolved rhythmicity due to stimulation with naturalistic light.

[Diagnostic measurements and diurnal rhythms].

Like the behaviour and physiology of the organism, biochemical parameters are subjected to diurnal variations through the daily 24-h light and dark cycle. Since blood sampling is carried out at all hours of the day and night, repeated blood testing from a patient throughout the day can be biased by diurnal variations, especially in parameters with high-amplitude 24-h rhythms. Concentration changes in biochemical parameters have thus to be interpreted in view of the 24-h rhythm, as only few recommendations regarding the optimal time of venipunctures and time-specific reference intervals exist.

Diurnal changes of biochemical metabolic markers in healthy young males - the Bispebjerg study of diurnal variations.

BACKGROUND: To examine whether time of the day has an effect on the circulating levels of metabolism parameters. METHODS: Venous blood samples were obtained under standardized conditions from 24 healthy young men every third hour through 24 hours. The metabolic markers and melatonin were examined at each time-point and data were analyzed by rhythmometric statistical methods. RESULTS: The normal 24-h rhythms of the participants were confirmed by significant oscillation of melatonin (p < 0.0001). Cosinor analysis revealed significant diurnal 24-h rhythms of five of the seven examined markers: Total cholesterol (p = 0.01, amplitude (amp) = 0.18 mmol/L) peaking in the early afternoon, Glucose (p < 0.0001, amp = 0.35 mmol/L) peaking around midnight, C-peptide (p < 0.001, amp = 360 pmol/L), triglyceride (p < 0.0001, amp = 0.37 mmol/L) peaking in the afternoon and low-density lipoprotein cholesterol (p = 0.003, amp = 0.16 mmol/L) peaking in the morning. C-peptide, triglyceride, and glucose had the highest 24-h oscillations in proportion to the reference ranges of the parameters for healthy young men. Glycated haemoglobin (HbA1c) (p = 0.07, amp = 0.57 mmol/L) and high-density lipoprotein (p = 0.09, amp = 0.06 mmol/L) did not show significant oscillations. CONCLUSIONS: When diagnosing and monitoring metabolic disorders compensation for the 24-h variation of the biochemical metabolic markers is needed especially C-peptide, triglyceride and glucose. Furthermore, the stable HbA1c level through 24 h makes it an accurate diagnostic test for diabetes mellitus.

Diurnal variation of von Willebrand factor in plasma: the Bispebjerg study of diurnal variations.

BACKGROUND: Quantitation of von Willebrand factor (VWF) in plasma is a central element in assessing von Willebrand disease (VWD). VWF activity is known to vary, which has partly been ascribed to biological and preanalytical variation. However, a possible diurnal expression of VWF has not been thoroughly tested. OBJECTIVES: We examined whether VWF antigen and VWF activity in plasma display a diurnal profile in healthy young males, and whether such variation is related to changes in release or elimination. METHODS: Plasma from 20 healthy young males was collected at 9 time-points over 24 h (15 h of light and 9 h of darkness); the plasma concentration of melatonin was used as an internal control to confirm the normal 24-h rhythms of the individual participants. RESULTS: The data, analyzed by rhythmometric statistics, revealed a significant variation (P = 0.02) and total amplitude of 22.6% in VWF antigen concentrations over the 24-h period. A pronounced variation in VWF activity was also observed, although not significant according to the 24-h statistical model. To examine whether the diurnal pattern was related to changes in elimination or secretion, the ratio between (i) coagulation factor VIII and VWF and (ii) VWF propeptide and VWF was determined. Taken together, the data suggest changes in release and not in clearance. CONCLUSIONS: Diurnal variation in von Willebrand antigen and activity in plasma represents an important aspect of the biological variation. Standardized time-of-day plasma sampling for quantitation of VWF in VWD patients seems warranted.

Rhythmic 24-hour variations of frequently used clinical biochemical parameters in healthy young males--the Bispebjerg study of diurnal variations.

PURPOSE: To evaluate the influence of time of day on the circulating concentrations of 14 frequently used clinical biochemical parameters in the Bispebjerg study of diurnal variations. MATERIALS AND METHODS: Venous blood samples were obtained under controlled environmental, activities and food conditions from 24 healthy young men every third hour through 24 hours, nine time points in total. At each time point, the parameters' concentrations were measured. The data were analyzed by rhythmometric statistical methods and in addition the biological variations were calculated. RESULTS: Significant oscillation of melatonin with an amplitude (amp) of 19.84 pg/ml and a peak at 03:34 h confirmed the normal 24-hour rhythms of the participants. Potassium (p < 0.0001, amp = 0.18 mmol/L), sodium (p < 0.0001, amp = 1.10 mmol/L) creatine kinase (p = 0.01, amp = 17.18 U/L), bilirubin (p < 0.0001, amp = 2.36 µmol/L) and aspartate aminotransferase (p < 0.0001, amp = 1.66 U/L) oscillated with gradually falling mean concentrations through the day to nadir around midnight. Urea nitrogen (p = 0.01, amp = 0.22 mmol/L) oscillated with gradually increasing mean concentrations through the day peaking around midnight. Lactate dehydrogenase (p < 0.0001, amp = 9.76 U/L) oscillated with gradually increasing concentrations through the early day peaking in the afternoon. Uric acid (p = 0.03, amp = 0.013 mmol/L) oscillated with gradually increasing concentrations through the night peaking in the morning. Potassium and sodium had the highest 24-hour oscillations in proportion to the reference intervals of the parameters for healthy young men. CONCLUSIONS: In the clinical setting, diurnal variations of clinical biochemical parameters commonly used through the day and night must be considered when concentration changes in the parameters are evaluated especially potassium and sodium.

Diurnal variation of hematology parameters in healthy young males: the Bispebjerg study of diurnal variations.

PURPOSE: To evaluate the influence of time of day on the circulating concentrations of 21 hematology parameters. MATERIALS AND METHODS: Venous blood samples were obtained under standardized circumstances from 24 healthy young men every third hour through 24 hours, nine time points in total. At each time point, the level of melatonin, iron, transferrin, transferrin saturation, ferritin, cobalamin, folate, red blood cells and white blood cells was measured. The data were analysed by rhythmometric statistical methods. The biological variations were calculated. RESULTS: Significant oscillation of melatonin (p < 0.0001) with an amplitude (amp) of 19.84 pg/ml and a peak level at 03:34 h confirmed the normal 24-hour rhythms of the participants. Erythrocytes (p < 0.0001, amp = 0.15 × 10(12)/L), hemoglobin (p < 0.0001, amp = 0.29 mmol/L), hematocrit (p < 0.0001, amp = 0.01), iron (p < 0.0001, amp = 4.00µmol/L), transferrin (p = 0.03, amp = 1.41µmol/L), transferrin saturation (p < 0.0001, amp = 6.37%) and folate (p < 0.0001, amp = 1.55nmol/L) oscillated significantly, with gradually falling mean levels through the day to nadir around midnight. Leukocyte count (p < 0.0001, amp = 0.78 × 10(9)/L), neutrophils (p = 0.001, 0.31 × 10(9)/L), eosinophils (p < 0.0001, amp = 0.04 × 10(9)/L), monocytes (p = 0.0009, amp = 0.06 × 10(9)/L), lymphocytes (p < 0.0001, amp = 0.49 × 10(9)/L) oscillated significantly with gradually increasing mean levels through the day peaking at midnight. Iron, leukocytes and hemoglobin had the highest 24 hour oscillations in proportion to the reference intervals of the parameters for healthy young men. CONCLUSIONS: Biochemical screenings are biased by diurnal variations, which must be considered when blood concentrations of these parameters are interpreted in the clinical setting.

Biological variation of free ß chorionic gonadotropin and pregnancy-associated plasma protein A in first trimester pregnancies.

BACKGROUND: Trisomy 21 risk estimation in first trimester pregnancies can be performed by a combined test based on ultrasound measurement of fetal nuchal translucency thickness and maternal plasma concentrations of free ß human chorionic gonadotropin (hCGß) and pregnancy-associated plasma protein A (PAPP-A). However, little knowledge exists regarding the biological variation of hCGß and PAPP-A when the time interval between sampling increases. METHODS: We estimated these variations from double measurements of hCGß and PAPP-A in first trimester pregnancies in 167 women. Data were divided into three groups based on the number of days between sampling. The correlation coefficients and biological variation were estimated for each group. RESULTS: The correlation coefficient between the first and second samples was 0.841 for hCGß, and 0.706 for PAPP-A. The ranges for biological variation were 11.9%-48.5% for hCGß and 31.6%-63.3% for PAPP-A, increasing with time between sampling. The average overall biological variation for hCGß was 29%, and 49.7% for PAPP-A. CONCLUSIONS: We found high biological variation for plasma concentrations of hCGß and PAPP-A, increasing with longer time intervals between sampling. From our data that showed high correlation of hCGß and PAPP-A in the first and second sample, we found no reason to recommend retesting. However, new studies should clarify whether PAPP-A should be collected early, and hCGß late, in the first trimester of pregnancy.