Val109Asp Polymorphism of the Omentin-1 Gene and Incidence of Knee Osteoarthritis in a Chinese Han Population: A Correlation Analysis

Figures & data

Table 1 Selected Characteristics of the Patients with KOA and Controls [($\overline{\text{x}}\pm \text{s}$), M (25%,75%), n (%)]

Characteristics	KOA (n=383)	NC (n=460)	p-value
Age (year)	51.3±12.1	50.6±11.5	0.312
Gender
Male	167	192	0.683
Female	216	268
KOA symptoms duration (months)	42.5 (18, 68.3)	–
KOA location (%)
Unilateral cases	68 (17.8)	–
Bilateral cases	315 (82.2)	–
Smokers (%)
Current-	101 (26.4)	126 (27.4)	0.701
Ex-	27 (7.1)	29 (6.3)	0.658
Alcohol (%)	78 (20.4)	91 (19.8)	0.664
Physical exercise (%)
Never	162 (42.4)	180 (39.1)	0.481
Occasional	105 (27.5)	113 (24.6)	0.372
Regular	115 (30.1)	167 (36.3)	0.296
NSAIDs (%)	136 (35.5)	4 (0.1)	<0.001
SBP (mmHg)	128±11	127±10	0.587
DBP (mmHg)	82±10	80±9	0.321
BMI (kg/m^2)	24.34±3.44	23.87±3.03	0.384
WHR	0.87±0.07	0.86±0.06	0.595
FPG (mmol/L)	5.45±0.31	4.97±0.21	0.202
TCH (mmol/L)	4.69±0.69	4.67±0.75	0.503
TG (mmol/L)	1.57±0.32	1.51±0.29	0.492
K-L grade
1	45 (11.7)	–
2	114 (29.8)	–
3	142 (37.1)	–
4	82 (21.4)	–
Plasma IL-1β (pg/mL)	0.7 (0.5, 1.4)	0.6 (0.3. 0.9)	0.285
Plasma IL-6 (pg/mL)	20.3 (15.3, 26.8)	15.2 (8.5, 21.1)	0.078
Serum CRP (mg/L)	11.5 (8.9,17.7)	6.2 (4.2,10.8)	0.036
Plasma omentin-1 (ng/L)	10.8 (7.2,18.3)	19.2 (10.8, 28.7)	0.028

Notes: Data are presented mean±standard deviations or numbers (%) or median with interquartile range (IQR); Differences between two groups analyzed using the independent sample t-test to analyze the normally distributed continuous variables, using the non-parametric test to analyze the abnormally distributed continuous variables. And using x² test to analyze the count data.

Abbreviations: KOA, knee osteoarthritis; NC, normal control; NSAID, non-steroid anti-inflammatory drug; SBP, systolic blood pressure; DBP, diastolic blood pressure; BMI, body mass index; WHR, weight hip ratio; FPG, fasting plasma glucose; TCH, total cholesterol; TG, triglyceride; KL, Kellgren-Lawrence; IL, interleukin; CRP, C-reaction protein.

Table 2 Logistc Regression Analysis of Association Between Omentin-1 Gene Val109Asp Polymorphism and Risk of KOA [n (%)]

Variables	KOA (n =383)	NC (n =460)	Unadjusted Odds Ratios (95% CI)	p-value	Adjusted Odds Ratios (95% CI)	p-value^a
Genotypes
Asp/Asp	226 (59.0)	282 (61.3)	1.000 (Reference)	–	1.000 (Reference)	–
Val/Asp	112 (29.2)	142 (30.9)	1.095 (0.841–4.825)	0.317	1.104 (0.789–5.274)	0.361
Val/Val	45 (11.8)	36 (7.9)	1.531 (0.698–3.915)	0.196	1.614 (0.705–4.926)	0.123
Alleles
Asp	564 (73.6)	706 (76.7)	1.000 (Reference)	–	–	–
Val	202 (26.4)	214 (23.3)	1.136 (0.695–6.124)	0.282	–	–

Note: ^aAdjusted for age, gender, BMI, WHR, TCH, TG, lifestyle characteristics.

Abbreviations: KOA, knee osteoarthritis; NC, normal control; BMI, body mass index; WHR, weight hip ratio; TCH, total cholesterol; TG, triglyceride.

Figure 1 Agarose gel electrophoresis for PCR products of different genotypes of the omentin-1 gene (334 bp). Val/Asp: Lane 1, 3–6, 9, 12, 13, 16; Val/Val: Lane 10, 11; Asp/Asp: Lane 2, 7, 8, 14, 15.

Figure 2 DNA sequence of omentin-1 gene region showing omentin-1 polymorphism in humans. DNA sequencing of the representative samples showing three genotypes (A/A, A/T and T/T) in omentin-1 gene for Val109Asp polymorphism. Among them, A/A genotype (1) is Val/Val genotype, A/T genotype (2) is Val/Asp genotype, T/T genotype (3) is Asp/Asp genotype. In the chromatogram Blue, Black, Green and Red peaks show C, G, A and T nucleotides respectively. The highlighted region in the chromatogram represents the site for Val109Asp polymorphism. Sample 1: GCAGCAAAGCAGA/ACTACCC. Sample 2: GCAGCAAAGCAGT/ACTACCC. Sample 3: GCAGCAAAGCAGT/TCTACCC.

Table 3 Multivariable Linear Regression Analysis of Association Between Omentin-1 Gene Val109Asp Polymorphism and Risk of KOA Stratified by BMI

Genotypes	BMI (kg/m^2)	KOA (n=383)	NC (n=460)	Unadjusted Odds Ratios (95% CI)	p-value	Adjusted Odds Ratios (95% CI)	p-value^a
Asp/Asp	<25	71	137	1.000 (Reference)	–	1.000 (Reference)	–
Val/Asp+Val/Val	<25	35	108	1.146 (0.502–3.972)	0.698	1.125 (0.496–4.183)	0.711
Asp/Asp	≥25	175	125	2.952 (1.264–6.104)	0.029	2.564 (1.085–5.317)	0.033
Val/Asp+Val/Val	≥25	102	90	1.583 (1.097–7.314)	0.037	1.416 (1.018–7.072)	0.042

Note: ^aAdjusted for age, gender, BMI, WHR, TCH, TG, lifestyle characteristics.

Abbreviations: KOA, knee osteoarthritis; NC, normal control; BMI, body mass index; WHR, weight hip ratio; TCH, total cholesterol; TG, triglyceride.

Table 4 Multivariable Linear Regression Analysis of Association Between Omentin-1 Gene Val109Asp Polymorphism and Risk of KOA Stratified by Age

Genotypes	Age (Year)	KOA (n=383)	NC (n=460)	Unadjusted Odds Ratios (95% CI)	p-value	Adjusted Odds Ratios (95% CI)	p-value^a
Asp/Asp	<55	52	153	1.000 (Reference)	-	1.000 (Reference)	-
Val/Asp+Val/Val	<55	49	89	1.089 (0.683–2.529)	0.326	1.117 (0.582–3.361)	0.338
Asp/Asp	≥55	194	109	1.291 (1.754–8.562)	0.042	1.283(1.492–9.186)	0.046
Val/Asp+Val/Val	≥55	88	109	1.862 (1.132–7.297)	0.029	1.735 (1.107–8.681)	0.038

Note: ^aAdjusted for age, gender, BMI, WHR, TCH, TG, lifestyle characteristics.

Abbreviations: KOA, knee osteoarthritis; NC, normal control; BMI, body mass index; WHR, weight hip ratio; TCH, total cholesterol; TG, triglyceride.

Table 5 Comparison of Clinical Parameters of Different Genotypes in KOA Patients and Controls [($\overline{\text{x}}\pm \text{s}$), M (25%,75%), n (%)]

Variables/Group	Genotypes			p-value	Intergroup Comparisons (p-value)
	Val/Val	Val/Asp	Asp/Asp
Age (year)					a	b	c
KOA	51.3±11.8	51.1±12.4	50.7±12.8	0.832	0.794	0.801	0.838
NC	50.6±10.9	50.8±12.1	49.9±11.2	0.801	0.812	0.748	0.783
Gender (Male/Female), n (%)
KOA	14/18	44/61	109/137	0.423	0.397	0.402	0.426
NC	24/31	59/80	109/157	0.395	0.402	0.328	0.371
SBP (mmHg)
KOA	128±11	129±11	128±10	0.794	0.763	0.692	0.801
NC	127±10	128±10	127±11	0.807	0.793	0.717	0.812
DBP (mmHg)
KOA	82±10	82±10	83±11	0.771	0.807	0.735	0.729
NC	81±9	80±8	80±9	0.792	0.774	0.825	0.716
Body mass index (kg/m^2)
KOA	23.98±3.82	24.18±3.42	24.47±3.38	0.524	0.387	0.641	0.402
NC	24.15±3.24	23.95±3.15	24.22±3.29	0.498	0.506	0.411	0.528
Waist hip ratio
KOA	0.87±0.07	0.87±0.08	0.88±0.07	0.763	0.812	0.794	0.705
NC	0.86±0.07	0.86±0.07	0.87±0.06	0.797	0.824	0.756	0.785
FPG (mmol/L)
KOA	5.54±0.29	5.51±0.28	5.52±0.31	0.811	0.834	0.805	0.793
NC	4.97±0.19	5.11±0.21	4.98±0.23	0.705	0.724	0.695	0.701
Total cholesterol (mmol/L)
KOA	4.67±0.67	4.68±0.71	4.72±0.64	0.684	0.598	0.612	0.675
NC	4.64±0.75	4.66±0.72	4.68±0.78	0.725	0.734	0.687	0.761
Triglyceride (mmol/L)
KOA	1.56±0.29	1.62±0.33	1.56±0.31	0.637	0.607	0.598	0.642
NC	1.52±0.31	1.49±0.28	1.53±0.29	0.504	0.461	0.487	0.526
Omentin-1 (ng/L)
KOA	9.7 (7.2, 11.3)	11.5 (8.8, 14.9)	13.1 (9.8, 18.3)	0.041	0.101	0.097	0.027
NC	18.7 (16.2, 20.3)	20.7 (16.8, 24.5)	22.1 (15.1, 28.7)	0.108	0.124	0.098	0.083
IL-1β (pg/mL)
KOA	1.1 (0.8, 1.5)	0.9 (0.7, 1.3)	0.8 (0.6, 1.2)	0.187	0.161	0.212	0.155
NC	0.5 (0.3, 0.8)	0.6 (0.4, 0.9)	0.5 (0.3, 0.8)	0.412	0.394	0.402	0.525
IL-6 (pg/mL)
KOA	23.1 (18.3, 26.5)	20.6 (19.8, 27.1)	18.2 (15.8, 23.4)	0.097	0.143	0.107	0.075
NC	17.9 (12.5, 21.7)	15.3 (10.8, 19.2)	13.6 (8.5, 17.5)	0.086	0.073	0.176	0.085
CRP (mg/L)
KOA	15.3 (11.4,18.1)	13.7 (10.4,16.3)	11.3 (8.7,15.1)	0.105	0.127	0.261	0.097
NC	6.8 (4.9, 9.8)	5.7 (3.1, 10.1)	4.9 (2.9, 7.8)	0.113	0.149	0.202	0.084
K-L grade (1/2), n (%)	3/5	12/30	30/79	0.245	0.285	0.213	0.197
K-L grade (3/4), n (%)	14/10	39/24	89/48	0.198	0.204	0.172	0.189
K-L grade (3+4/1+2), n (%)
KOA	24/8	63/42	137/109	0.046	0.087	0.112	0.039
NC	–	–	–	–	–	–	–

Notes: Data are presented mean ± standard deviations or numbers (%) or median with IQR; Differences among three groups analyzed using one-way ANOVA to analyze the normally distributed continuous variables, and LSD t- test for further pairwise comparison. Whereas, for non-normal data, Wilcoxon test was used for comparison among three groups, Mann Whitney U-test was used for further pairwise comparison. And using χ² test to analyze the count data. Intergroup comparisons: a (Val/Val vs Val/Asp), b (Val/Asp vs Asp/Asp), c (Val/Val vs Asp/Asp).

Abbreviations: KOA, knee osteoarthritis; NC, normal control; SBP, systolic blood pressure; DBP, diastolic blood pressure; IL, interleukin; CRP, C-reaction protein; K–L, Kellgren–Lawrence.

Table 6 Comparison of the Levels of Synovial Fluid Omentin-1, IL-1β, IL-6 and CRP Among Different Genotypes in KOA Patients [M (25%,75%)]

Variables	n	Val/Val	Val/Asp	Asp/Asp	P-value	Intergroup Comparisons (P-value)
						a	b	c
Omentin-1 (ng/L)	186	2.5 (1.8, 3.9)	4.1 (2.8, 6.2)	6.2 (3.9, 7.3)	0.029	0.098	0.134	0.016
IL-1β (pg/mL)	186	6.3 (3.9, 8.7)	4.4 (2.5, 6.6)	2.6 (1.2, 5.1)	0.023	0.114	0.087	0.017
IL-6 (pg/mL)	186	49.5 (31.7, 65.2)	36.5 (22.9, 53.9)	30.8 (18.1, 46.2)	0.043	0.085	0.114	0.024
CRP (mg/L)	186	42.3 (27.1, 69.3)	36.2 (29.7, 52.6)	27.5 (17.4, 42.1)	0.041	0.105	0.072	0.033

Notes: Data are presented median with IQR; Wilcoxon test was used for comparison among three groups, Mann Whitney U-test was used for further pairwise comparison. Intergroup comparisons: a (Val/Val vs Val/Asp), b (Val/Asp vs Asp/Asp), c (Val/Val vs Asp/Asp).

Abbreviations: KOA, knee osteoarthritis; IL, interleukin; CRP, C-reaction protein.

Table 7 Comparison of the Expressions of IL-1 β, IL-6, MMP-13, Collagen-I and Collagen-III in Articular Cartilage of Knee Joint Among Different Genotypes in KOA Patients [M (25%,75%)]

Variables	n	Val/Val	Val/ Asp	Asp/Asp	P-value	Intergroup Comparisons (P-value)
						a	b	c
IL-1β (pg/mL)	78	15.2 (7.9, 22.1)	12.7 (8.4, 19.2)	9.6 (4.2, 12.4)	0.033	0.102	0.098	0.027
IL-6 (pg/mL)	78	61.4 (28.8, 91.3)	53.8 (23.6, 75.9)	41.6 (22.7, 65.6)	0.042	0.086	0.152	0.036
MMP-13 (pg/mL)	78	118.3 (27.7, 55.2)	92.8 (48.3, 134.6)	78.1 (31.6, 103.4)	0.039	0.075	0.119	0.032
Collagen-II (μg/mL)	78	61.9 (28.7, 107.1)	80.5 (39.3, 123.7)	101.9 (56.8, 212.1)	0.031	0.143	0.096	0.025

Notes: Data are presented median with IQR; Wilcoxon test was used for comparison among three groups, Mann Whitney U-test was used for further pairwise comparison. Intergroup comparisons: a (Val/Val vs Val/Asp), b (Val/Asp vs Asp/Asp), c (Val/Val vs Asp/Asp).

Abbreviations: KOA, knee osteoarthritis; IL, interleukin; MMP, Metalloproteinase.