3.1 Sirtuin3 rs28365927 together with gender and age were associated with a risk for NAFLD in the non-matched model
The clinical characteristics of the NAFLD and non-NAFLD patients are shown in Table 2. The NAFLD patients had a higher age, ratio of males to females, BMI, SBP, DBP, WC, HC values and serum levels of ALT, AST, fasting blood-glucose (FBG), low density lipoprotein cholesterin (LDL-c), triglyceride (TG) and total cholesterol (TC) than the non-NAFLD patients (all P < 0.05). In addition, serum levels of high density lipoprotein cholesterol (HDL-c), total protein (TP) and albumin in the NAFLD patients were significantly lower than in the non-NAFLD patients (P < 0.05). No significant differences in the other parameters were observed between the two groups of patients (all P > 0.05).
Table 2
Clinical Characteristics of Patients with NAFLD and Non-NAFLD in study populationa.
Characteristics | Non-NAFLD patients (n = 387) | NAFLD patients (n = 292) | P Value |
Age, y | 41.97 ± 12.17 | 48.89 ± 11.57 | 0.000 |
Gender,Male /Female | 134/251 | 177/114 | 0.000 |
ALT, U/L | 19.37 ± 14.17 | 33.24 ± 29.92 | 0.000 |
AST, U/L | 22.59 ± 9.59 | 29.24 ± 14.47 | 0.000 |
FBG, mmol/L | 5.11 ± 1.42 | 5.55 ± 1.63 | 0.000 |
LDL-C, mmol/L | 2.81 ± 0.80 | 3.12 ± 0.83 | 0.000 |
TG, mmol/L | 1.34 ± 0.92 | 2.51 ± 1.84 | 0.000 |
TC, mmol/L | 4.88 ± 0.97 | 5.14 ± 1.07 | 0.001 |
HDL-C, mmol/L | 1.58 ± 0.38 | 1.27 ± 0.33 | 0.000 |
BMI, kg/m2 | 22.13 ± 2.56 | 26.25 ± 2.55 | 0.000 |
SBP, mmHg | 116.01 ± 17.21 | 123.95 ± 19.82 | 0.000 |
DBP, mmHg | 73.43 ± 11.87 | 84.07 ± 15.61 | 0.000 |
WC, cm | 73.65 ± 8.12 | 85.40 ± 8.29 | 0.000 |
HC, cm | 89.62 ± 6.00 | 95.28 ± 6.68 | 0.000 |
TP,g/L | 73.75 ± 3.84 | 72.51 ± 4.93 | 0.000 |
Albumin,g/L | 45.97 ± 3.09 | 45.03 ± 4.54 | 0.003 |
Globulin,g/L | 27.73 ± 3.38 | 27.88 ± 5.76 | 0.667 |
A/G | 1.69 ± 0.24 | 1.67 ± 0.33 | 0.444 |
TBIL, umol/L | 12.87 ± 8.14 | 12.80 ± 6.35 | 0.915 |
DBIL, umol/L | 5.22 ± 2.30 | 5.47 ± 3.47 | 0.260 |
TBA,umol/L | 3.55 ± 7.09 | 4.49 ± 4.98 | 0.232 |
Abbreviations :BMI Body Mass Index,SBP systemic blood pressure,DBP diastolic blood pressure,WC Waist circumference,HP Hip circumference,TP Total Protein, A/G the ratio of albumin to globulin, TBIL total bilirubin, DBIL direct bilirubin,TBA total bile acid,ALT glutamic-pyruvic transaminase,AST glutamic oxalacetic transaminase, FBG fasting blood-glucose, LDL-C low density lipoprotein cholesterin, TG triglyceride, TC total cholesterol, HDL-C high density lipoprotein cholesterol,NAFLD nonalcoholic fatty liver disease. |
aValues are expressed as mean ± SD or counts and compared by Student’s t-test if the data is normally distributed, otherwise Mann-Whitney U test is used, except for gender that p value stands for statistical significance using Chi-square test. P-value༜0.05 considered as statistically significant (in bold). |
The allele and genotype distributions of the 17 SNPs in the NAFLD and non-NAFLD groups are shown in Table 1 and demonstrate that only the genotype distributions of Sirtuin3 rs28365927 showed significant differences between the two groups (P < 0.05).The genotype distributions of Sirtuin3 rs28365927 were in accordance with the HWE in both the NAFLD and non-NAFLD patients (all P > 0.05) (Table 1).
Based on an analysis using the four genetic models, which includes dominant, recessive, additive and genotypic models, the correlations between NAFLD susceptibility and the genotype distributions of Sirtuin3 rs28365927 were explored further (Table 4). In the unmatched population, the Sirtuin3 rs28365927 GA + AA genotype was a significant risk factor for the development of NAFLD (OR = 1.976, 95%CI: 1.088–3.588, P = 0.025, after adjusting for age, gender and BMI) in the dominant model. There were no significant correlations between Sirtuin3 rs28365927 and NAFLD risk in the recessive and additive models, but there was a significant association between Sirtuin3 rs28365927 and higher NAFLD risk in the genotypic model (OR = 1.600, 95%CI: 1.061–2.415, P = 0.025, after adjusting for age and gender, GA vs GG).
Table 4
Association of rs28365927 with NAFLD based on four genetic models in the Study populationa.
| Unadjusted | | | Adjusteda | | | Adjustedb | | |
OR (95% CI) | P Value | | OR(95% CI) | P Value | | OR(95% CI) | P Value | |
unmatched | | | | | | | | | |
GA + AA vs GG | 1.489(1.034–2.145) | 0.032 | | 1.532(1.026–2.287) | 0.037 | | 1.976(1.088–3.588) | 0.025 | |
AA vs GA + GG | 0.491(0.129–1.868) | 0.297 | | 0.486(0.109–2.163) | 0.343 | | 1.077(0.123–9.433) | 0.947 | |
A vs G | 1.286(0.925–1.786) | 0.135 | | 1.327(0.925–1.905) | 0.124 | | 1.555(0.909–2.661) | 0.107 | |
GG | 1 | 0.042 | | 1 | 0.052 | | 1 | 0.204 | |
GA | 1.552(1.066–2.260) | 0.022 | | 1.600(1.061–2.415) | 0.025 | | 1.744(0.946–3.215) | 0.075 | |
AA | 0.542(0.142–2.068) | 0.370 | | 0.541(0.121–2.417) | 0.421 | | 1.225(0.138–10.897) | 0.855 | |
matched | | | | | | | | | |
GA + AA vs GG | 1.662(1.054–2.619) | 0.029 | | 1.655(1.048–2.612) | 0.031 | | 1.838(1.011–3.341) | 0.046 | |
AA vs GA + GG | 1.005(0.201–5.034) | 0.995 | | 1.004(0.199–5.053) | 0.996 | | 1.820(0.241–13.761) | 0.562 | |
A vs G | 1.523(1.007–2.304) | 0.046 | | 1.516(1.001–2.295) | 0.049 | | 1.716(1.001–2.942) | 0.050 | |
GG | 1 | 0.082 | | 1 | 0.087 | | 1 | 0.135 | |
GA | 1.705(1.069–2.721) | 0.025 | | 1.697(1.062–2.712) | 0.027 | | 1.822(0.987–3.363) | 0.055 | |
AA | 1.127(0.224–5.662) | 0.885 | | 1.126(0.223–5.687) | 0.885 | | 2.084(0.273–15.935) | 0.479 | |
Abbreviations:OR, odds ratio; p-value༜0.05 considered as statistically significant (in bold);four logistic regression models (dominant:heterozygotes and variant homozygotes vs. wild homozygotes; recessive:variant homozygotes vs. wild homozygotes and heterozygotes; additive: variant allele vs. wild allele; genotypic: heterozygotes or variant homozygotes vs. wild homozygotes) were used to analyze the SNPs. |
aBinary logistic regression model was adjusted for age and gender. |
bBinary logistic regression model was adjusted for age,gender and body mass index. |
The above results indicate that age, gender and Sirtuin3 rs28365927 were all associated with NAFLD risk.
3.2 Sirtuin3 rs28365927 is an independent risk factor for NAFLD in matched populations
Next, we further verified the association between Sirtuin3 rs28365927 and the risk for NAFLD with age and sex matched between the two groups. There were significant differences in the allele distributions of Sirtuin3 rs28365927 between the NAFLD and non-NAFLD patients (P = 0.045), while the genotype distribution was not significantly different (P = 0.079) in the matched populations (Table 3). As shown in Table 4, in the matched populations, the Sirtuin3 rs28365927 GA + AA genotype was a significant risk factor for the development of NAFLD (OR = 1.662, 95%CI: 1.054–2.619, P = 0.029). After adjusting for age, gender and BMI, the risk of the Sirtuin3 rs28365927 GA + AA genotype was still marked (OR = 1.838, 95%CI: 1.011–3.341, P = 0.046) in the dominant model. There was no significant correlation between Sirtuin3 rs28365927 and NAFLD risk in the recessive model, but a significant association was found between Sirtuin3 rs28365927 and higher NAFLD risk in both the additive (OR = 1.716, 95%CI: 1.001–2.942, P = 0.050, after adjusting for age, gender and BMI) and genotypic models (OR = 1.697, 95%CI: 1.062–2.712, P = 0.027, after adjusting for age and gender, GA vs GG).
Table 3
Allele and genotype distribution of SIRT3 rs28365927 in NAFLD patients and Non-NALFD patients.
| Variant Allele(A) | Wild-type allele(G) | p-value | Homozygote genotype(AA) | Heterozygote genotype(AG) | Wild-type genotype(GG) | p-value for HWE test (NAFLD/Non-NAFLD) | p-value | Call rate(%) |
| NAFLD/Non -NAFLD(%) | NAFLD/Non -NAFLD(%) | | NAFLD/Non -NAFLD(%) | NAFLD/Non -NAFLD(%) | NAFLD/Non -NAFLD(%) | | |
unmatched | 14.3%/11.4% | 85.7%/88.6% | 0.127 | 1.1%/2.1% | 26.4%/18.7% | 72.5%/79.2% | 0.178/0.126 | 0.040 | 98% |
matched | 14.3%/9.9% | 85.7%/90.1% | 0.045 | 1.4%/1.4% | 25.8%/17.0% | 72.8%/81.7% | 0.428/0.503 | 0.079 | 98% |
P-value༜0.05 considered as statistically significant (in bold). |
These data indicate that Sirtuin3 rs28365927 is an independent risk factor for NAFLD that is not associated with age or gender. Individuals carrying an A allele may have significantly increased NAFLD susceptibility in matched populations.
3.3 Sirtuin3 rs28365927 affects the clinical parameters in NAFLD patients
To investigate the potential correlation, we compared the Sirtuin3 rs28365927 genotype with the clinical parameters of the NAFLD patients. As shown in Table 5 and Fig. 3, among the NAFLD patients, serum levels of TBIL, DBIL and ALT in rs28365927 A allele carriers (GA + AA) were 11.1%, 14.7% and 41.5% higher, respectively, than in non-carriers (GG) (P = 0.022, P = 0.021, P = 0.012, respectively). In a covariate adjusted linear regression analysis, as shown in Table 6 and Fig. 4, rs28365927 A carriers (AA + AG) were positively correlated with higher ALT among the NAFLD patients (P = 0.045).
Table 5
Clinical Characteristics of SIRT3 rs28365927 A Carriers(AA + AG) and Non-Carriers(GG) in the NAFLD Populationa.
Characteristic | | Carriers (n = 78) | Non-Carriers (n = 206) | P Value |
Age, y | | 49.38 ± 11.89 | 48.78 ± 11.47 | 0.834 |
Gender,Male /Female | | 48/30 | 123/82 | 0.813 |
BMI, kg/m2 | | 25.80 ± 2.78 | 26.40 ± 2.47 | 0.123 |
SBP, mmHg | | 121.72 ± 18.15 | 124.45 ± 20.35 | 0.322 |
DBP, mmHg | | 82.28 ± 14.85 | 84.73 ± 15.96 | 0.623 |
WC, cm | | 85.02 ± 8.70 | 85.64 ± 8.21 | 0.747 |
HP, cm | | 94.43 ± 6.29 | 95.65 ± 6.88 | 0.220 |
TP,g/L | | 72.48 ± 5.33 | 72.42 ± 4.81 | 0.434 |
Albumin,g/L | | 45.00 ± 4.49 | 45.00 ± 4.63 | 0.529 |
Globulin,g/L | | 27.54 ± 3.08 | 27.72 ± 5.34 | 0.636 |
A/G | | 1.70 ± 0.50 | 1.66 ± 0.25 | 0.765 |
TBIL, umol/L | | 13.74 ± 6.20 | 12.37 ± 6.40 | 0.022 |
DBIL, umol/L | | 6.01 ± 3.41 | 5.24 ± 3.52 | 0.021 |
TBA,umol/L | | 4.66 ± 5.13 | 4.45 ± 5.00 | 0.959 |
ALT, U/L | | 38.64 ± 43.94 | 27.31 ± 12.92 | 0.012 |
AST, U/L | | 30.82 ± 14.47 | 28.62 ± 14.66 | 0.250 |
FBG, mmol/L | | 5.54 ± 1.41 | 5.56 ± 1.74 | 0.389 |
LDL-C, mmol/L | | 3.04 ± 0.80 | 3.160.86 | 0.314 |
TG, mmol/L | | 2.17 ± 0.96 | 2.66 ± 2.10 | 0.318 |
TC, mmol/L | | 5.11 ± 0.89 | 5.17 ± 1.13 | 0.968 |
HDL-C, mmol/L | | 1.26 ± 0.30 | 1.26 ± 0.33 | 0.779 |
Abbreviations :BMI Body Mass Index,SBP systemic blood pressure,DBP diastolic blood pressure,WC Waist circumference,HP Hip circumference,TP Total Protein, A/G the ratio of albumin to globulin, TBIL total bilirubin, DBIL direct bilirubin,TBA total bile acid,ALT glutamic-pyruvic transaminase,AST glutamic oxalacetic transaminase, FBG fasting blood-glucose, LDL-C low density lipoprotein cholesterin, TG triglyceride, TC total cholesterol, HDL-C high density lipoprotein cholesterol,NAFLD nonalcoholic fatty liver disease. |
aValues are expressed as mean ± SD and compared by Student’s t-test if the data is normally distributed, otherwise Mann-Whitney U test is used, except for gender that p value stands for statistical significance using Chi-square test. P-value༜0.05 considered as statistically significant (in bold). |
Table 6
Significant associations between rs28365927 A Carriers(AA + AG) and Clinical Characteristics in a covariate adjusted linear regression analysis in the NAFLD Populationa.
Characteristic | | β-coefficient | STAT | P Value | |
BMI, kg/m2 | | -0.569 | -1.506 | 0.133 | |
SBP, mmHg | | -3.082 | -1.117 | 0.265 | |
DBP, mmHg | | -2.583 | -1.196 | 0.233 | |
WC, cm | | -0.440 | -0.373 | 0.709 | |
HP, cm | | -1.148 | -1.196 | 0.233 | |
TP,g/L | | 0.116 | 0.185 | 0.853 | |
Albumin,g/L | | 0.060 | 0.106 | 0.915 | |
Globulin,g/L | | -0.424 | -0.558 | 0.577 | |
A/G | | 0.039 | 0.897 | 0.370 | |
TBIL, umol/L | | 1.220 | 1.511 | 0.132 | |
DBIL, umol/L | | 0.703 | 1.542 | 0.124 | |
TBA,umol/L | | 0.154 | 0.156 | 0.876 | |
ALT, U/L | | 7.632 | 2.013 | 0.045 | |
AST, U/L | | 2.446 | 0.857 | 0.393 | |
FBG, mmol/L | | 0.025 | 0.130 | 0.897 | |
LDL-C, mmol/L | | -0.101 | -0.903 | 0.367 | |
TG, mmol/L | | -0.437 | -1.968 | 0.050 | |
TC, mmol/L | | -0.019 | -0.135 | 0.893 | |
HDL-C, mmol/L | | -0.003 | -0.080 | 0.936 | |
Abbreviations :BMI Body Mass Index,SBP systemic blood pressure,DBP diastolic blood pressure,WC Waist circumference,HP Hip circumference,TP Total Protein, A/G the ratio of albumin to globulin, TBIL total bilirubin, DBIL direct bilirubin,TBA total bile acid,ALT glutamic-pyruvic transaminase,AST glutamic oxalacetic transaminase, FBG fasting blood-glucose, LDL-C low density lipoprotein cholesterin, TG triglyceride, TC total cholesterol, HDL-C high density lipoprotein cholesterol,NAFLD nonalcoholic fatty liver disease. |
aβ-coefficient: estimated quantitative effect of rs28365927 A Carriers on a phenotype of NAFLD, STAT: T statistic, P: level of statistical significance of the covariate(age and gender) adjusted linear regression analysis. P-value༜0.05 considered as statistically significant (in bold). |