CORRELATION OF SERUM URIC ACID LEVELS TO THE PREVALENCE AND
SEVERITY OF NON ALCOHOLIC FATTY LIVER DISEASE: A CROSS SECTIONAL
STUDY IN SOUTH INDIAN MALES
Dr.T.P. Antony, Dr. Iwin David, Dr. Alex Thomas, Dr. Sojan George K, Dr. Robert Ambookan, Dr. Sachin Menon
Department of Internal Medicine, Amala Institute of Medical Sciences,
Amala Nagar, Trichur District, Kerala, India.
__________________________________________________________________________________
ABSTRACT:
BACK GROUND: Increased uric acid is associated with the metabolic syndrome and insulin
resistance. Non-alcoholic fatty liver disease (NAFLD) is the commonest manifestation of insulin
resistance. Very few studies compare the association between serum uric acid levels and NAFLD.
OBJECTIVES: To assess the co-relation of serum uric acid levels with the prevalence and severity of
NAFLD in apparently healthy south Indian males.
METHODS: Among the individuals attending the master health check up program at a
tertiary care centre in central Kerala, 216 apparently healthy male subjects without other
risk factors were enrolled in the study. Serum uric acid levels were measured in a 12 hour
fasting venous sample, along with fasting blood sugar, lipid profile, liver function tests,
calcium, phosphate, urea and creatinine. Serum uric acid levels were categorized into the
following quartiles: < 3.0, 3.1-5.0, 5.0-6.5 and > 6.5 mg/dL. Hepatic steatosis was diagnosed
and graded based on abdominal ultrasonographic findings by hyperechogenicity of liver in
comparison to kidney, difference of echogenicity between the liver and diaphragm, and
visibility of vascular structures. The data was analysed using the Chi square test and logistic
regression analysis.
RESULTS: Of the 216 subjects included in the study, the prevalence of NAFLD was found to
be 54.17%. Among these 85.47% had grade 1 and 14.53% had grade 2 hepatic steatosis. The
prevalence of NAFLD in the various quartiles were 20% (0 - 3.0), 31.3% (3.1 - 5.0), 50% (5.1 6.5) and 92.5% (6.5 - 10) which was statistically significant (p<0.005). The proportion of
patients with higher grades of steatosis was more in the higher quartiles. Grade 2 NAFLD
was seen only among those with serum uric acid levels > 5mg/dl, of which 70.60% had uric
acid levels > 6.5 mg/dL. Among those with grade 1 steatosis, 79% of subjects had uric acid
levels above 5mg/dl with 37% having levels >6.5 mg/dL.
CONCLUSION: Serum uric acid levels were found to have a positive correlation with the
prevalence and severity of non alcoholic fatty liver disease even within the physiological
limits.
KEYWORDS: NAFLD; Uric acid
1 .INTRODUCTION:
Non alcoholic fatty liver disease (NAFLD) comprises a spectrum of hepatic pathologies that
resemble alcoholic liver disease in subjects without excessive alcohol consumption1. The spectrum of
NAFLD includes simple hepatic steatosis, which over time can progress to NASH, with the
subsequent development of fibrosis and cirrhosis. It is now known that many patients with hitherto
identified “cryptogenic” cirrhosis in fact have liver disease on the basis of NASH, with the resolution
of the steatosis once patients become catabolic due to cirrhosis. Increasingly, patients are being
identified with cryptogenic cirrhosis who have most likely had NASH for decades. These patients can
develop liver failure and require liver transplantation, and some patients can progress to the
development of hepatocellular cancer2.Uric acid is an independent risk factor for various metabolic
abnormalities, most notably the metabolic syndrome 3 , 4 which has insulin resistance as the basic
underlying defect. Hyperuricemia often precedes the development of hyperinsulinemia 5, 6, obesity7,
and diabetes 8, 9 in the metabolic syndrome. It has been hypothesized that uric acid can play a role in
the development of non-alcoholic fatty liver disease. 10,11. In our study we examined the correlation
between the levels of serum uric acid and fatty liver grades detected sonologicaly , which was a
practical and reliable method for detecting fatty liver12,13 in an asymptomatic population.
2. METHODS:
2.1 STUDY SUBJECTS: After getting institutional ethics committee approval and detailed
informed consent, a total of 590 patients of age between 15 and 60 yrs attending the
master health check up clinic in a tertiary centre in central Kerala between 1.2.10 and
31.7.10 were interviewed. Since gender related differences play a major role in the
incidence of NAFLD, only male subjects were included in the study. Subjects with history of
excessive alcohol intake (> 140 gms/week); past history of liver diseases, cholecystectomy,
gout, malignancies or other systemic illness; positive viral hepatitis serology; serum
creatinine > 2 mg/dL and those who have taken hepatotoxic medications in the last 3 yrs
were excluded from the study. The exclusion procedure involved surveys on alcohol intake,
self reported past medical history and laboratory tests. Alcohol intake was assessed through
two open questions (1) How often did you have a drink containing alcohol per week in the
past 6 months? (2) How many glasses did you have on a typical day when you were drinking
in the past 6 months? For the 2nd question one glass of alcoholic beverage was calculated
based on the type of beverage consumed (beer - 4%, wine - 12% and foreign liquor - 40 %).
From the answers to the above questions subjects were excluded after calculating their
daily alcohol intake. After exclusions, of the total 590 patients, 216 apparently healthy south
Indian males were included in the study.
2.2 MEASUREMENTS:
Because liver biopsy in apparently healthy subjects is not ethical and the sample size was large, a
diagnosis of fatty liver was based on abdominal ultrasonography. Liver with any degree of hepatic
steatosis was considered fatty in the present study. Hhepatic steatosis was diagnosed by abdominal
B mode ultrasonography using a GE Voluson 730 pro 3.5-5 Mega Hertz curvilinear transducer carried
out by a single experienced radiologist who did not have access to the subjects clinical or lab results.
Hepatic steatosis was assessed semi quantitatively, and graded on the basis of abnormally intense,
high level echoes arising from the hepatic parenchyma, liver-kidney differences in echo amplitude,
echo penetration into the deep portion of the liver and clarity of the liver blood vessel structure 15, 16.
Images were captured in a standard fashion with the patient in the supine position with the right
arm raised above the head. An ultrasonographic diagnosis of fatty liver was defined as the presence
of a diffuse increase of fine echoes in the liver parenchyma compared with the kidney or spleen
parenchyma. Based on the observed findings they were divided into 3 grades of fatty infiltration 14.
Grade 1  slight diffuse increase in fine echoes in the hepatic parenchyma with normal visualization
of the diaphragm and intra hepatic vessel borders.
Grade 2 moderate diffuse increase in fine echoes in the hepatic parenchyma with slightly impaired
visualization of the intra hepatic vessels and diaphragm.
Grade 3 marked increase in fine echoes in the hepatic parenchyma with poor or no visualization of
the intra hepatic vessels borders posterior portion of right lobe of liver and diaphragm
After a 12 hour overnight fast, blood samples were collected from all subjects from the ante
cubital vein. Fasting blood sugar (FBS), total cholesterol, triglycerides, low-density lipoprotein(LDL)
and high-density lipoprotein (HDL) cholesterol, phosphate, calcium, albumin, bilirubin, aspartate
aminotransferase (AST), Alanine aminotransferase (ALT), urea, serum creatinine and uric acid were
measured by enzymatic methods using the dry chemistry method with the Johnson & Johnson Vitros
5,1 FS automated chemistry analyzer. The following criteria were used to define normal levels of the
components assessed: FBS < 100mg/dl, PO4 < 4.5mg/dl, calcium < 10.2mg/dl, albumin < 5 g/dl
,bilirubin < 1mg/dl ,SGOT < 35 u/l ,SGPT < 35 u/l ,ALP < 128 u/l ,Total cholesterol < 200mg/dl
,triglycerides < 150mg/dl ,HDL < 60mg/dl ,LDL < 180mg/dl ,Urea < 40mg/dl and creatinine <
1.1mg/dl. Normal uric acid levels were reported as 3 – 6.5 mg/dl. For the purpose of research,
patients were divided on the basis of their uric acid levels into various quartiles (<3), (3-5), (5-6.5)
and (>6.5).
2.3 STATISTICAL ANALYSIS:
The distribution of hepatic steatosis and hyperuricemia were compared using a chi-square
test. Logistic regression analysis was used to analyse the independent relationships of fatty
liver and the measured variables. Statistical significance was indicated at p value < 0.05. All
statistical analyses were performed using SPSS software version 10.0 KO.
VARIABLES
MEAN + STANDARD ERROR
SIGNIFICANCE(P)
FBS
100.94+2.10
0.001*
PHOSPHATE
3.89+0.03
0.781
CALCIUM
9.33+0.02
0.176
ALBUMIN
4.39+0.02
0.122
TOTAL BILIRUBIN
0.61+0.02
0.841
SGOT
37.20+1.07
0.137
SGPT
51.11+2.33
0.067
ALP
79.13+1.41
0.565
TOTAL CHOLESTEROL
201.42+2.61
0.005*
TRIGLYCERIDES
145.60+5.51
0.355
HDL
44.32+0.72
0.120
LDL
129.91+2.50
0.051
24.71+0.51
0.240
CREATININE
0.93+0.01
0.082
URIC ACID
5.63+0.08
0.001*
UREA
* P<0.05
3. RESULTS:
The mean age of our patients was 48 .5 +/- 8 yrs. The mean BMI of our patients 25.2
kg/ m2 . Of the 216 subjects included in the study, the prevalence of NAFLD was found to be
54.17%. Among these 85.47% had grade 1 and 14.53% had grade 2 hepatic steatosis. Among
the various parameters assessed, serum uric acid levels, fasting blood sugar and total
cholesterol levels were found to have an association with the presence of hepatic steatosis
which was statistically significant (p value < 0.05). The prevalence of NAFLD in the various
quartiles were 20% (0 - 3.0), 31.3% (3.1 - 5.0), 50% (5.1 - 6.5) and 92.5% (6.5 - 10). The
difference was statistically significant (p<0.005). The prevalence of hepatic steatosis was
greatest (92.5%) in subjects whose uric acid levels were above the upper limit of normal
range (> 6.5 mg/dl). Among those with uric acid levels above 5mg/dl, the prevalence of
steatosis was 50%. The prevalence of steatosis was 31.3 % and 20 % in the lower quartiles
(3.1 – 5.0 mg/dl and 0 – 3.0 mg/dl respectively).
In patients with uric acid levels of 0 - 3.0mg/dl, 80% had no steatosis while 20 % had
grade 1 NAFLD. In those with uric acid levels 3.1 - 5.0 mg/dl, 31.2% had grade 1 NAFLD.
50.0% of patients with uric acid levels in the 3rd quartile (5.1 - 6.5 mg/dl) had steatosis with
44.75 having grade 1 and 5.3 % grade 2 NAFLD. In the last quartile (6.5 – 10 mg/dl) 7.5had
no steatosis, 69.8 5 had grade 1 NAFLD and 22.7 % had grade 2 NAFLD. Grade 2 NAFLD was
seen only among those with serum uric acid levels > 5mg/dl, of which 70.60% had uric acid
levels > 6.5 mg/dL. Among those with grade 1 steatosis, 79% of subjects had uric acid levels
above 5mg/dl with 37% having levels >6.5 mg/dL.
80
70
FATTY LIVER
60
50
GRADE 0
40
GRADE 1
30
GRADE 2
20
10
0
<3
3.1-5
5.1-6.5
>6.5
URIC ACID LEVELS
Fig 1. Correlation of NAFLD in various uric acid quartiles
Fig 2: Proportion of NAFLD in various quartiles of Uric acid
FATTY LIVER
URIC ACID
0
1
2
TOTAL
0-3
4
1
0
5
Row %
80
20
0
100
3.1-5
44
20
0
64
Row %
68.8
31.3
0
100
5.1-6.5
47
42
5
94
Row %
50
44.7
5.3
100
6.5-10
4
37
12
53
Row %
7.5
69.8
22.6
100
TOTAL
99
100
17
216
Row %
45.8
46.3
7.9
100
4. DISCUSSION:
NAFLD is now recognized worldwide as an important cause of chronic liver disease.
The prevalence of NAFLD in this study was 54.17 %. This is more than the prevalence
reported in various other studies in the male population. The difference can be explained
because of the higher BMI of our patients and the study population being not fully
representative of the general population. Further population based studies will be required
to estimate the exact prevalence of NAFLD in central Kerala.
In logistic regression analysis, we observed a significant and independent
relationship between uric acid levels and the presence of hepatic steatosis. Our results are
in agreement with previous studies. Serum uric acid was independently associated with
biopsy-proven hepatic steatosis in a study of 1915 Chinese patients aged 12–80 years with
chronic hepatitis B infection17. Li et al.18 also reported similar results in a study of 8925
(6802 men) apparently healthy Chinese. The HERAS study by Yong Jae Li et al reported
similar results in a prospective study conducted in 3768 Koreans19. However to prove a role
in causation further elaborate studies are required.
This study also reveals a correlation between the severity of non alcoholic fatty liver
disease and uric acid levels even within the normal range. Moreover grades above grade 1
were always associated with uric acid levels above 5mg/dl. These findings are in
concordance with our understanding regarding the association between serum uric acid
concentrations and insulin resistance. Thus, the significant association between serum uric
acid and NAFLD suggest that insulin resistance is a possible mechanism linking uric acid with
NAFLD. Despite the significant relationship between uric acid and NAFLD in the present
study, it cannot be concluded whether serum uric acid concentration is a risk factor actively
involved in the development of NAFLD. Because this study is of cross-sectional design,
causal relationship cannot be determined, warranting prospective studies.
Our study has several limitations. First, because study subjects were volunteers
visiting master health checkup clinic in a single centre and belonged to an affluent, healthier
group compared to community-based cohorts, the study population may not be
representative of the general population. Therefore, this study may have been affected
by selection bias. Second, only males were included in the study. Different factors could
influence the prevalence of NAFLD in females hence the data cannot be generalized to the
whole population. Third, the effect of other potential confounding variables on uric acid
concentration, e.g., diet pattern, a history of medications with hyperuricemic activity was
not considered. Fourth, central obesity is more likely to be associated with metabolic
syndrome and NAFLD. However waist circumference was not measured in this study. Finally,
although liver biopsy is the gold standard for the diagnosis of fatty liver, it was not
performed in the present study. However, liver biopsy is an invasive and impractical
procedure in the standard clinical setting. Ultrasonography is a non-invasive and widely
available method for qualitative assessment of fatty infiltration. Thus, ultrasonography is
the preferred modality for mass screening for hepatic steatosis and has reasonable
sensitivity (up to 94%) and specificity (up to 84%) 20.
CONFLICTS OF INTEREST: None.
ACKNOWLEDGMENT:
To Mrs. Jini M.B. our statistician.
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