Participants will be recruited in and near the vicinity of Maastricht by advertising on local
billboards, in local newspapers, public spaces, contacting previous participants who gave
consent to be contacted again, and on the internet. Those who express interest will be
invited for a screening. Upon arrival at the research facility, participant will sign an
informed consent form (see chapter 11.2 for complete procedure). Subsequently, measurements
of height, weight and blood pressure will be performed. The blood pressure measurement will
be performed 3 times to obtain an average blood pressure value (to avoid measuring a peak or
dip in the pressure). Furthermore, a 10-lead electrocardiogram (ECG) will be recorded and the
subjects will fill out a medical history (see document F1.1). Following this, a two-hour oral
glucose tolerance test (OGTT) will be performed to assess glucose tolerance (applies only for
potential pre-diabetic subjects). Fasting blood sample (19 mL in total) from the T2DM
patients will be obtain via venepuncture and no OGTT will be performed. After inclusion in
the study, participants will undergo two study periods (period 1 and period 2) of eight days.
During each period, participants will visit the research facilities three times.
Sample size:
The primary aim of this study is to determine if acute cold-induced shivering will decrease
the area under the curve (AUC) for 24-hour glucose of individuals with a different degree of
metabolic impairment, including pre-diabetic participants and patients with T2DM. Thus, the
study will be powered accordingly to allow for detecting the expected minimal effect in both
groups. It is expected to see a clinically meaningful decrease in AUC for 24-hour glucose of
at least 15% in the pre-diabetic participants. Based on literature, investigators anticipate
a more pronounced (20%) effect in 24-hour AUC for glucose in T2DM patients. To ensure that
both groups are powered appropriately, the sample size calculation of the T2DM patients will
be followed and 12 participants will be included in each group. When a drop-out rate of 20%
is considered, investigators anticipate that up to 15 participants will need to be included
in each group to reach this sample size. From experience with similar studies it is estimated
that there will be a screening failure of 50% and 70% for the T2DM and pre-diabetes groups,
respectively. Therefore, it is expected that researchers will need to screen 30 and 50
individuals, respectively, from each study population.
Use of co-interventions: to minimise the variability in blood glucose induced by diet, all
participants will be asked to consume standardised meals during the two study periods.
Additionally, subjects will be asked to avoid strenuous physical activity (e.g. walking long
distances, stair climbing for >10 minutes or cycling for >30 min, hiking) or structured
exercise during the study periods to minimize exercise induced variability in blood glucose.
In addition, participants are asked to withstand from alcohol and caffeine-containing drinks
24 hours before and after cold exposure. Participants will be instructed to keep their normal
sleeping pattern throughout the entire study. During wash-out participants are advised to
maintain their normal dietary habits and activity pattern.
Measurements:
Participants will be equipped with a continuous glucose monitor (CGM) to continuously measure
blood glucose during each study period. Participants will be asked to wear a FreeStyle Libre
Pro iQ (Abbott) glucose monitor, which is a system able to measure reliable blood glucose
levels over a longer period; it is a standard technique in daily diabetes practice. To
determine physical activity levels throughout both study periods, participants will be asked
to wear an activPAL activity monitor (PAL Technologies Ltd). Respiratory gas exchange will be
measured using an open-air circuit respirometry with an automated ventilated hood system
(Omnical, Maastricht Instruments, Maastricht University, Maastricht, The Netherlands). The O2
(oxygen) consumption and CO2 (carbondioxide) production will be measured, from which energy
expenditure and substrate oxidation can be calculated. Core temperature will be measured
during the two cold exposure interventions with a telemetric pill (BodyCap, France) that will
be swallowed in the evening before each cold exposure day. During the two cold exposure days
(visit 2 and 5) surface electromyography (EMG) sensors (Trigno wireless system, Delsys Inc.,
USA) will be attached to the surface of 6 muscles (upper trapezius fibres, latissimus dorsi,
pectoralis major, vastus lateralis, vastus medialis, rectus femoris) to determine skeletal
muscle electrical activity. Prior to the start of the cold exposure intervention during visit
2 and 5 a catheter will be inserted in the antecubital vein of the participant to repeatedly
draw blood during the intervention. Blood samples will be collected in the appropriate tubes
and immediately centrifuged at high speed and plasma will be immediately frozen in liquid
nitrogen and stored at -80 ̊C for later analysis. Blood will be analyzed for: glucose,
insulin, cholesterol, triglycerides, free fatty acids and other relevant metabolic health
markers. Subjects will be provided with standardised meals for both study periods (same
period as the CGM measurements are performed). The total daily caloric intake will be
determined by multiplying the basal metabolic rate (BMR) of the subject by a PAL value, where
the BMR will be estimates using the Harris-Benedict formula. Since our participants are
sedentary by study design, a PAL value of 1.5 for participants aged <50 years and 1.4 for
subject aged 50-75 will be used, as done in a previous study within the same research group
(NL78281.068.21). The caloric distribution throughout the day and the macronutrient
composition of the meals will maximally reflect the habitual diet of the Dutch population. As
such, the breakfast, lunch and dinner will account for ~20-25%, ~20-25% and ~40-45% of the
total caloric intake, respectively, and snacks will account for up to 10%.
Statistical analysis:
For all study parameters data will be reported as minimum, maximum, mean ± SD and/or ± SEM,
or as median and range in case of a highly skewed distribution. All primary, secondary, and
explorative study parameters are numerical values or an average of numerical values of a
defined time period. Statistical analyses will be performed using the statistical computer
program SPSS version 26.0. P-values of ≤ 0.05 (two-sided testing) will be considered
statistically significant. Missing values will not be replaced. If a missing value occurs for
a specific parameter, the subject in question will not contribute to the analysis of that
parameter and therefore no intention-to-treat procedure will be followed but a per protocol
analysis. Only participants who fully complied with the study protocol and fulfilled the
entire study will be included in the analysis of the outcome parameters. Paired sample t-test
analysis will be conducted to investigate the effects of shivering on the primary outcome
(24-hour AUC for glucose measured before vs. after acute shivering) in the two study groups.
The secondary outcome (24-hour AUC for glucose in response to acute mild vs. moderate
shivering) will be investigated using a linear mixed model with treatment (shivering
intensity) and time as fixed factors.
Safety reporting:
In accordance to section 10, subsection 4, of the WMO, the sponsor will suspend the study if
there is sufficient ground that continuation of the study will jeopardise subject health or
safety. The sponsor will notify the accredited METC (Medical Ethics Commitee) without undue
delay of a temporary halt including the reason for such an action. The study will be
suspended pending a further positive decision by the accredited METC. The investigator will
take care that all subjects are kept informed.
Adverse events are defined as any undesirable experience occurring to a subject during the
study, whether or not considered related to the cold exposure intervention/trial procedure.
All adverse events reported spontaneously by the subject or observed by the investigator or
his staff will be recorded.
The investigator will report all (Serious Adverse Events) SAEs to the sponsor without undue
delay after obtaining knowledge of the events.
The sponsor will report the SAEs through the web portal ToetsingOnline to the accredited METC
that approved the protocol, within 7 days of first knowledge for SAEs that result in death or
are life threatening followed by a period of maximum of 8 days to complete the initial
preliminary report. All other SAEs will be reported within a period of maximum 15 days after
the sponsor has first knowledge of the serious adverse events.
Data monitoring:
The study will be monitored by the Clinical Trails Centre Maastricht (CTCM). The study is
classified as a clinical trial with negligible. In accordance with this risk classification,
in total, three monitor visits will be performed: initial, interim and close out visit.
During these visits source data verification (including electronic case report forms, medical
records, etc.) and overall quality assurance will be performed by the accredited monitor.
The sponsor/investigator will submit a summary of the progress of the trial to the accredited
METC once a year. Information will be provided on the date of inclusion of the first subject,
numbers of subjects included and numbers of subjects that have completed the trial, serious
adverse events/ serious adverse reactions, other problems, and amendments.
The investigator/sponsor will notify the accredited METC of the end of the study within a
period of 8 weeks. The end of the study is defined as the last patient's last visit. The
sponsor will notify the METC immediately of a temporary halt of the study, including the
reason of such an action.
Handling and storage of data and documents:
At the start of the study, participants will be assigned a study code (SHVR + number of
inclusion) that will not change during the study. The code will consist of the study acronym
and a number in sequential order of screening; i.e. SHVR001, SHVR002, SHVR003, etc. This code
will be followed with the period, P1 or P2. This code is linked with the name, address, date
of birth, and telephone number of the participant in a password protected file. For all
purposes, this code will be used for participant identification. Only the responsible
principal investigator (Joris Hoeks) and the researcher conducting this study (Dzhansel
Hashim) can access this file. The privacy of the participants who take part in the study will
be protected. This means that the study code will not contain the participants' initials or
birth date as explained above. In case data, documents or samples will be analyzed outside
the scope of this proposed study, the participants will be asked for permission but only if
the participant provided permission to be approached for follow-up research on the informed
consent. Data files containing personal information of participants are stored separately and
password protected. All human material, research data and documents will be stored for 15
years.
Ethical consideration:
This study will be conducted according to the principles of the Declaration of Helsinki (64th
WMA General Assembly, Fortaleza, Brazil, October 2013) and in accordance with the Medical
Research Involving Human Subjects Act (WMO) and other guidelines, regulations and Acts.