Novel biomarkers in patients with uncontrolled hypertension with and without kidney damage

Figures & data

Figure 1. Illustration depicting potential biomarkers associated with endothelial and kidney cell pathology, inflammation, and fibrosis in the context of hypertension and hypertension mediated organ damage.

Table 1. Panel of plasma biomarkers included in this study.

Name	Family	Biological processes
IL-1RA	Cytokine-Interleukin	Inhibits and modulates interleukin 1 related immune and inflammatory responses. IL-1RA concentration is considered to indicate immune activation, rather than a net anti-inflammatory state.
IL-18	Cytokine-Interleukin	A pro-inflammatory cytokine cleaved into its active form by NLR family pyrin domain containing 3 inflammasome (NLRP3) upon sensing damage or pathogenic signals.
TNF	TNF superfamily	The TNF-activated nuclear factor kappa B (NF-κB) pathway is a master regulator of the inflammatory response involving upregulation of NLRP3 inflammasome, pro-IL-1β and pro-IL-18 gene expression.
MCP-1	Cytokine-Chemokine	The NLRP3 inflammasome with secretion of IL-1ß synergises with angiotensin-II to promote NF-kB activation and a proinflammatory response characterised by increased MCP-1 production. MCP-1 is a chemotactic protein for monocytes and macrophages, implicated in tissue repair and fibrosis.
OPN	Cytokine-non-structural extracellular matrix protein	Pro-inflammatory stimuli and activation of the NLRP3 inflammasome leads to increased tissue levels of osteopontin. Osteopontin is expressed in activated macrophages, T cells, smooth muscle, endothelial and epithelial cells and regulates cell adhesion, migration, proliferation and promotes macrophage and T cell infiltration.
RANTES	Cytokine-Chemokine	RANTES is produced by several cells implicated in the development of hypertension, including vascular endothelium, smooth muscle, perivascular adipocytes and renal epithelial cells. RANTES is a chemotactic molecule for monocytes and T cells.
vWF-A2	Glycoprotein involved in both haemostasis and thrombosis	An endothelial ligand for platelet glycoproteins and a suggested marker for endothelial injury and activation. Plasma levels of vWF-A2 shows the amount of protein, but not its functional status.
Uromodulin (Tamm–Horsfall protein)	Glycoprotein produced by tubular cells of the thick ascending limb and the early distal tubule.	Uromodulin is released into the blood as monomers and urine where it polymerises. Reduced plasma concentrations of uromodulin are found in persons with interstitial fibrosis or tubular atrophy. Despite being highly prognostic for kidney failure, early tubulointerstitial injury and fibrosis are challenging to detect using standard clinical measures.
NGAL	Lipocalin family	NGAL is consistently expressed at low levels in various cell types, detectable in the systemic circulation of healthy individuals. Following kidney injury, upregulation in the thick ascending limb, distal tubule and collecting duct increases urinary and plasma NGAL levels. Plasma NGAL may serve as a marker for tubular damage in hypertension, potentially playing a pivotal role in kidney interstitial fibrosis.

Table 2. Characteristics of healthy controls and patients with hypertension (n = 215)

Characteristic	Healthy controls (n = 39)		Patients with hypertension (n = 176)		Patients with hypertension (n = 176)
					Controlled hypertension (n = 55)		Uncontrolled hypertension without kidney HMOD (n = 59)		Uncontrolled hypertension with kidney HMOD (n = 62)
Female sex, n (%)	20	(51)	79	(45)	27	(49)	28	(47)	24	(39)
Age, years	55.6	(9.4)	61.1^a	(11.1)	58.4	(10.4)	59.9	(10.8)	64.7^b,c	(11.2)
Cardiovascular disease, n (%)	0	0	39^a	(22)	7	(13)	11	(19)	21^b	(34)
Active smoker, n (%)	5	(13)	28	(16)	9	(16)	9	(15)	10	(16)
Office systolic blood pressure, mmHg	123	(12)	152^a	(20)	132	(11)	161^b	(16)	161^b	(18)
Office diastolic blood pressure, mmHg	76	(9)	87^a	(13)	81	(9)	92^b	(13)	88^b	(13)
Ambulatory systolic blood pressure, 24 h mean, mmHg	–	–	–	–	120	(9)	149^b	(9)	148^b	(10)
Ambulatory diastolic blood pressure, 24 h mean, mmHg	–	–	–	–	74	(6)	85^b	(9)	81^b	(9)
Ambulatory systolic blood pressure, daytime mean, mmHg	–	–	–	–	125	(9)	154^b	(10)	152^b	(10)
Ambulatory diastolic blood pressure, daytime mean, mmHg	–	–	–	–	78	(6)	89^b	(9)	85^b,c	(10)
Ambulatory systolic blood pressure, night-time mean, mmHg	–	–	–	–	108	(12)	133^b	(13)	139^b,c	(14)
Ambulatory diastolic blood pressure, night-time mean, mmHg	–	–	–	–	64	(7)	72^b	(10)	74^b	(10)
Number of antihypertensive agents per day, n	0	NA	3^a	(2–4)	3	(2–3)	3	(2–3)	4^b,c	(3–4)
Adherence to all self-reported antihypertensive agents, n					44	(80.0)	37	(62.7)	50^c	(80.6)
BMI, kg/m^2	25.8	(2.9)	30.1^a	(5.5)	27.9	(4.1)	29.9^b	(5.8)	32.1^b,c	(5.5)
Cholesterol, mmol/L	–	–	–	–	5.0	(1.1)	4.9	(1.1)	4.9	(1.2)
HDL cholesterol, mmol/L	–	–	–	–	1.6	(0.5)	1.5	(0.5)	1.4^b	(0.4)
LDL cholesterol, mmol/L	–	–	–	–	3.1	(1.0)	3.1	(1.0)	3.1	(1.1)
Triglycerides, mmol/L	–	–	–	–	1.5	(0.9)	1.6	(0.8)	2.0^b,c	(1.0)
Lipid-lowering treatment, n (%)	4	(10)	89^a	(51)	27	(49)	23	(39)	39^c	(63)
Diabetes, n (%)	0	NA	49^a	(28)	6	(11)	9	(15)	33^b,c	(53)
HbA1c, mmol/mol	34	(33–36)	38^a	(35–43)	38	(35–39)	37	(34–41)	43^b,c	(38–53)
Serum creatinine (µmol/L)	74.0	(11.7)	79.9^a	(24.4)	75.7	(15.0)	70.7	(13.8)	92.6^b,c	(32.6)
eGFR (mL/min/1.73 m^2)	89.5	(12.6)	82.4^a	(18.5)	86.8	(15.1)	88.2^b	(10.5)	72.8^b,c	(23.1)
ACR, mg/mmol	0.2	(0.2–0.4)	1.3^a	(0.6–5.7)	0.5	(0.3–1.1)	0.9^b	(0.5–1.4)	15.1^b,c	(5.5–43.0)

Data are mean (SD), median (IQR) or number (%) as appropriate. Uncontrolled hypertension was defined as systolic daytime ambulatory blood pressure ≥135 mmHg, and kidney HMOD as ACR > 3.0 mg/mmol or eGFR < 60 mL/min/1.73 m².

^a Significant differences between healthy controls and hypertensive patients.

^b Significant differences between the group with controlled hypertension compared to uncontrolled hypertension without and with kidney HMOD.

^c Significant differences between the group with uncontrolled hypertension without kidney HMOD compared to uncontrolled hypertension with kidney HMOD.

Adherence to all self-reported antihypertensive agents: A pharmacologist evaluated the serum concentration analyses and found the patient adherent to all self-reported antihypertensive agents. Cardiovascular disease: Prior myocardial infarction, angina, stroke or peripheral artery disease. Diabetes: Self-reported, or HbA1C ≥ 48 mmol/mol, or use of antidiabetic agents. eGFR: Glomerular filtration rate, calculated using the 2009 creatinine-based CKD-EPI equation; HMOD: hypertension-mediated organ damage; NA: not applicable; ACR: urine albumin to creatinine ratio

Table 3. Levels of biomarkers between healthy controls and hypertensive patients (n = 215).

Biomarker	Healthy controls (n = 39)		Hypertensive patients (n = 176)		p Value
IL-1 RA (ng/mL)	0.32	(0.28–0.39)	0.42	(0.31–0.64)	0.002
IL-18 (ng/mL)	0.10	(0.07–0.16)	0.12	(0.09–0.17)	0.13
TNF (pg/mL)	4.17	(3.54–5.50)	4.6	(3.7–6.0)	0.20
MCP-1 (ng/mL)	0.11	(0.09–0.14)	0.12	(0.10–0.15)	0.18
OPN (ng/mL)	41.7	(28.5–50.5)	36.6	(27.1–49.9)	0.23
RANTES (ng/mL)	14.5	(4.8–32.2)	8.5	(3.9–19.0)	0.12
vWF-A2 (ng/mL)	0.81	(0.54–0.95)	0.83	(0.59–1.11)	0.60
NGAL (ng/mL)	104	(92–115)	113	(93–144)	0.020
Uromodulin (ng/mL)	475	(370–593)	369	(239–506)	<0.001

Median levels (IQR) of plasma biomarkers.

Independent-samples Mann–Whitney U Test.

IL-1RA: interleukin 1 receptor antagonist; IL-18: interleukin-18; TNF: tumour necrosis factor; MCP-1: monocyte chemoattractant protein-1; OPN: osteopontin; RANTES: regulated upon activation normal T-cell expressed and secreted; vWF-A2: von Willebrand factor A2; NGAL: neutrophil gelatinase-associated lipocalin; uromodulin: Tamm–Horsfall protein

Table 4. The trend in biomarker medians in relation to all study groups (n = 215).

Biomarkers	Healthy controls (Median (IQR) (n = 39)	Controlled hypertension (Median (IQR) (n = 55)	Uncontrolled hypertension without kidney HMOD (Median (IQR) (n = 59)	Uncontrolled hypertension with kidney HMOD (Median (IQR) (n = 62)	Non-parametric correlation coefficient	p Value
IL-1 RA (ng/mL)	0.32 (0.28–0.39)	0.39 (0.29–0.56)	0.37 (0.26–0.57)	0.51 (0.36–0.74)	0.20	<0.001
IL-18 (ng/mL)	0.10 (0.07–0.16)	0.12 (0.09–0.15)	0.11 (0.08–0.14)	0.15 (0.11–0.19)	0.15	0.003
TNF (pg/mL)	4.17 (3.54–5.50)	4.18 (3.60–4.79)	4.30 (3.23–5.50)	5.86 (4.71–7.84)	0.25	<0.001
MCP-1 (ng/mL)	0.11 (0.09–0.14)	0.11 (0.09–0.13)	0.12 (0.10–0.16)	0.13 (0.11–0.17)	0.17	0.001
OPN (ng/mL)	41.7 (28.5–50.5)	33.6 (22.4–38.2)	38.0 (27.6–50.7)	41.5 (31.4–54.7)	0.09	0.09
RANTES (ng/mL)	14.5 (4.8–32.2)	9.31 (5.42–19.56)	8.80 (4.17–21.45)	7.08 (3.43–17.57)	−0.10	0.049
vWF-A2 (ng/mL)	0.81 (0.54–0.95)	0.78 (0.55–0.99)	0.68 (0.47–0.97)	0.95 (0.71–1.29)	0.12	0.025
NGAL (ng/mL)	104 (92–115)	101 (90–136)	106 (87–128)	138 (109–195)	0.25	<0.001
Uromodulin (ng/mL)	475 (370–593)	400 (272–538)	467 (342–529)	248 (178–396)	−0.27	<0.001

Kendall’s rank correlation (Kendall’s tau) for a monotonic tendency in biomarker medians across study groups.

Uncontrolled hypertension was defined as systolic daytime ambulatory blood pressure ≥135 m mHg, and kidney HMOD as ACR > 3.0 mg/mmol or eGFR < 60 mL/min/1.73 m².

HMOD: hypertension-mediated organ damage; ACR: urinary albumin to creatinine ratio; eGFR: glomerular filtration rate calculated using the creatinine-based CKD-EPI equation; IL-1RA: interleukin 1 receptor antagonist; IL-18: interleukin-18; TNF: tumour necrosis factor; MCP-1: monocyte chemoattractant protein-1; RANTES: regulated upon activation normal T-cell expressed and secreted; OPN: osteopontin; vWF-A2: von Willebrand factor A2; NGAL: neutrophil gelatinase-associated lipocalin; uromodulin: Tamm–Horsfall protein

Figure 2. Multinomial logistic regression among patients with hypertension, controlled hypertension as reference category (n = 176).

Figure 3. Binary logistic regression among patients with uncontrolled hypertension, uncontrolled hypertension without kidney HMOD as reference category (n = 121).