Circadian rhythms and medical diseases: does it matter when drugs are taken?

The polymorphism of ARNTL2 (BMAL2) gene rs2306074 C>T is associated with susceptibility of Alzheimer disease in Chinese population

In the present study, we investigated whether polymorphism of ARNTL2 (BMAL2) gene rs2306074 T/C was associated with susceptibility of Alzheimer disease (AD) in Chinese population. A case-control method was employed in this study. 296 unrelated AD patients and 423 control subjects were recruited in current study. The prevalence of C carriers in BMAL2 gene rs2306074 T/C in AD patients was significantly higher than that of control subjects in both the whole sample and APOE ε 4 non-carriers (in the whole sample: χ (2) = 5.938, P = 0.012; in APOE ε 4 non-carriers: χ (2) = 9.048, P < 0.0001). In addition, both in the whole sample and APOE ε 4 non-carriers, prevalence of CC genotypes in BMAL2 gene rs2306074 of AD patients was also significantly higher than that in controls (in the whole sample: χ (2) = 5.126, P = 0.018; in APOE ε 4 non-carriers: χ (2) = 7.389, P = 0.023). However, there was no significant difference of prevalence of C carriers and CC genotypes in BMAL2 gene rs2306074 T/C between AD patients and control subjects among APOE ε 4 carriers (C carriers: χ (2) = 0.020, P = 0.900; CC genotypes: χ (2) = 0.017, P = 0.946). C carriers in BMAL2 gene rs2306074 T/C are associated with a high susceptibility of AD among APOE ε 4 non-carriers but not among APOE ε 4 carriers in Chinese population.

Circadian rhythms in anesthesia and critical care medicine: potential importance of circadian disruptions

The rotation of the earth and associated alternating cycles of light and dark--the basis of our circadian rhythms--are fundamental to human biology and culture. However, it was not until 1971 that researchers first began to describe the molecular mechanisms for the circadian system. During the past few years, groundbreaking research has revealed a multitude of circadian genes affecting a variety of clinical diseases, including diabetes, obesity, sepsis, cardiac ischemia, and sudden cardiac death. Anesthesiologists, in the operating room and intensive care units, manage these diseases on a daily basis as they significantly affect patient outcomes. Intriguingly, sedatives, anesthetics, and the intensive care unit environment have all been shown to disrupt the circadian system in patients. In the current review, we will discuss how newly acquired knowledge of circadian rhythms could lead to changes in clinical practice and new therapeutic concepts.

Negative impact of physician prescribed drug dosing schedule requirements on patient adherence to cardiovascular drugs

PURPOSE

The aim of this study was to determine whether dosing schedule requirements impair overall cardiovascular drug adherence.

METHODS

A cohort study was performed with hospitalized patients at high risk of cardiovascular disease between April and September 2011. Patients were asked whether the prescribed time for taking their statin and antiplatelet drugs created any inconvenience in their daily routine and, if so, were asked to describe the reasons. Patient adherence to treatment was assessed using the Morisky Medication Adherence Scale (MMAS-8). A cohort of physicians was separately studied between June and September 2011. Physicians were interviewed to determine their dosing schedule preference when prescribing statin and anti-platelet drugs, and the rationale for choosing a specific dosing schedule.

RESULTS

In the study, 103 patients and 59 physicians were included. Statins were most frequently prescribed in the evening (90%). Thienopyridines were prescribed both at lunch time (41%) and in the morning (35%). Aspirin was most frequently (65.3%) prescribed at lunch time. In total, 24.3% of patients reported being inconvenienced by their drug dosing schedule, and these subjects were less adherent to their drug regimen than those who did not report inconvenience (46.2% versus 16.7%, p = 0.014). Our results also demonstrate that there is no pharmacologic rationale for prescribing a particular drug dosing schedule for statin or anti-platelet drugs.

CONCLUSIONS

Physicians should assess patient convenience, when prescribing medication, to optimize treatment adherence.

In silico analysis of cell cycle synchronisation effects in radiotherapy of tumour spheroids

Tumour cells show a varying susceptibility to radiation damage as a function of the current cell cycle phase. While this sensitivity is averaged out in an unperturbed tumour due to unsynchronised cell cycle progression, external stimuli such as radiation or drug doses can induce a resynchronisation of the cell cycle and consequently induce a collective development of radiosensitivity in tumours. Although this effect has been regularly described in experiments it is currently not exploited in clinical practice and thus a large potential for optimisation is missed. We present an agent-based model for three-dimensional tumour spheroid growth which has been combined with an irradiation damage and kinetics model. We predict the dynamic response of the overall tumour radiosensitivity to delivered radiation doses and describe corresponding time windows of increased or decreased radiation sensitivity. The degree of cell cycle resynchronisation in response to radiation delivery was identified as a main determinant of the transient periods of low and high radiosensitivity enhancement. A range of selected clinical fractionation schemes is examined and new triggered schedules are tested which aim to maximise the effect of the radiation-induced sensitivity enhancement. We find that the cell cycle resynchronisation can yield a strong increase in therapy effectiveness, if employed correctly. While the individual timing of sensitive periods will depend on the exact cell and radiation types, enhancement is a universal effect which is present in every tumour and accordingly should be the target of experimental investigation. Experimental observables which can be assessed non-invasively and with high spatio-temporal resolution have to be connected to the radiosensitivity enhancement in order to allow for a possible tumour-specific design of highly efficient treatment schedules based on induced cell cycle synchronisation.

The sensitivity of a cell to a dose of radiation is largely affected by its current position within the cell cycle. While under normal circumstances progression through the cell cycle will be asynchronous in a tumour mass, external influences such as chemo- or radiotherapy can induce a synchronisation. Such a common progression of the inner clock of the cancer cells results in the critical dependence on the effectiveness of any drug or radiation dose on a suitable timing for its administration. We analyse the exact evolution of the radiosensitivity of a sample tumour spheroid in a computer model, which enables us to predict time windows of decreased or increased radiosensitivity. Fractionated radiotherapy schedules can be tailored in order to avoid periods of high resistance and exploit the induced radiosensitivity for an increase in therapy efficiency. We show that the cell cycle effects can drastically alter the outcome of fractionated irradiation schedules in a spheroid cell system. By using the correct observables and continuous monitoring, the cell cycle sensitivity effects have the potential to be integrated into treatment planing of the future and thus to be employed for a better outcome in clinical cancer therapies.