Association between DNA methylation of the KITLG gene and cortisol levels under stress: a replication study

Figures & data

Figure 1. Distribution of KITLG methylation levels at each of the seven CpG units (a) raw methylation data; (b) log transformed methylation data which gives a better indication of the distribution of the data.

Table 1. Participant characteristics (n = 142).

Characteristic	Value
Age, mean (SD)	69.7 (3.1)
Females, %	48.6
<12 years of education (%)	55.6
Clinical depression^a, %	15.5
Cardiovascular ischemic pathologies^b, %	9.0
Cognitive impairment (MMSE^c<26), %	4.2
The Childhood Adversity Questionnaire^d, %:
Death of a parent	20.3
Physical and/or sexual abuse	14.8
Number of adverse events^e, %:
0 events	8.54
1–2 events	35.51
3 or 4 events	30.25
5 or more events	25.7
Cortisol Levels, mean (SD)^f
Morning cortisol, basal (ng/dl)	5.53 (0.57)*
Morning cortisol, stress (ng/dl)	5.65 (0.54)
Evening cortisol, basal (ng/dl)	3.49 (0.86)*
Evening cortisol, stress (ng/dl)	3.55 (0.77)
Diurnal cortisol, basal (AUC)^g	63.19 (7.41)*
Diurnal cortisol, stress (AUC)^g	64.40 (6.88)

^aA Mini-International Neuropsychiatric Interview (MINI, French version 5.00) (Sheehan et al., 1998) diagnosis of major depressive disorder according to DSM-IV criteria, and/or high levels of depressive symptomatology according to the Centre for Epidemiological Studies Depression Scale (CES-D), with a score ≥16 (Radloff, 1977).

^bHistory of cardiovascular ischemic pathologies (angina pectoris, myocardial infarction, stroke, cardiovascular surgery, arteritis).

^cMMSE: Mini–mental state examination.

^dFrom a total of n = 128.

^eFrom a list of 25-items, including physical, sexual and verbal abuse (Ritchie et al., 2009).

^fLn of cortisol concentration (expressed as ng/dl).

^gAUC was standardized and calculated using the extrapolated values from the equation of the regression line of the three cortisol values measured between 08 h and 22 h (Chaudieu et al., 2008).

* Significant correlation with stress-induced cortisol (p < .01).

Figure 2. Scatterplot indicating the association between KITLG DNA methylation at unit CpG 2.3 and stress reactivity cortisol levels (a) morning cortisol; (b) diurnal cortisol levels (AUC).

Table 2. Linear regression models for the association between KITLG DNA methylation (%) and cortisol levels under stress.

	Model 1^a			Model 2^b			Model 3^b
Cortisol levels under stress	ß (SE)	p	t	ß (SE)	p	t	ß (SE)	p	t
Morning cortisol
CpG 2.3 methylation	−1.85 (0.67)	.007	−2.77	−1.88 (0.67)	.006	−2.80	−1.64 (0.68)	.01	−2.42
Age	–	–	–	0.003 (0.02)	.85	0.19	0.0002 (0.02)	.99	0.01
Sex	–	–	–	−0.097 (0.10)	.33	−0.99	−0.15 (0.10)	.14	−1.48
Depression	–	–	–	–	–	–	0.24 (0.14)	.09	1.72
Evening cortisol
CpG 2.3 methylation	−0.93 (1.03)	.37	−0.90	−0.93 (1.04)	.38	−0.89	−0.600 (1.06)	.57	−0.57
Age	–	–	–	0.003 (0.03)	.03	0.10	−0.001 (0.03)	.03	−0.05
Sex	–	–	–	0.006 (0.15)	.15	0.04	−0.068 (0.16)	.16	−0.42
Depression	–	–	–	–	–	–	0.328 (0.22)	.22	1.50
AUC
CpG 2.3 methylation	−19.43 (8.87)	.03	0.031	−19.63 (8.95)	.03	−2.19	−15.67 (8.99)	.09	−1.74
Age	–	–	–	0.04 (0.23)	.85	0.18	−0.008 (0.23)	.97	−0.03
Sex	–	–	–	−0.64 (1.32)	.63	−0.48	−1.54 (1.36)	.26	−1.13
Depression	–	–	–	–	–	–	3.98 (1.86)	.04	2.14

ß: the beta coefficient from the linear regression model; SE: standard error

^aUnivariate model.

^bModel adjusted for age, sex and clinical depression.

Table 3. The association between childhood stressful events and KITLG DNA methylation.

	Death of a parent (yes vs. no)			Physical or sexual abuse (yes vs. no)
KITLG DNA methylation (%)	Mean difference (SE)	p	t	Mean difference (SE)	p	t
CpG 1	−0.05 (0.13)	.70	−0.38	−0.16 (0.13)	.22	−1.24
CpG 2.3	0.24 (0.16)	.13	1.52	0.25 (0.16)	.12	1.59
CpG 4	−0.006 (0.11)	.96	−0.05	0.11 (0.10)	.26	1.13
CpG 5	−0.10 (0.09)	.27	−1.12	0.01 (0.07)	.90	0.13
CpG 6.7.8	−0.10 ( 0.08)	.22	−1.24	−0.02 (0.09)	.82	−0.22
CpG 9	0.05 (0.12)	.68	0.41	−0.05 (0.11)	.67	−0.43
CpG 22	−0.12 (0.12)	.32	−1.00	0.02 (0.10)	.86	0.18

SE: standard error.

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Data availability

The datasets analyzed during this study are available from the corresponding author on reasonable request.