Therapeutic Advances in GastroenterologyOriginal Research
The effect of metformin and standard
therapy versus standard therapy alone
in nondiabetic patients with insulin
resistance and nonalcoholic steatohepatitis
(NASH): a pilot trial
William W. Shields, K.E. Thompson, G.A. Grice, S.A. Harrison and W.J. Coyle
Abstract: Nonalcoholic steatohepatitis (NASH) is increasing in prevalence and is related to
underlying insulin resistance. The aim of this study was to assess the efficacy of metformin
on the characteristic histopathologic lesions of NASH. This was a 12-month prospective,
randomized, placebo-controlled trial comparing diet and exercise alone to diet, exercise
and metformin in nondiabetic patients with insulin resistance and NASH. Patients were
randomized to either group A or B. Group A received placebo, dietary counseling, recom-
mendations for weight loss and exercise four times per week. Group B received long-acting
metformin 500mg daily (titrated to 1000mg daily) plus dietary counseling, recommendations
for weight loss and exercise four times per week. Histopathology was assessed at 12 months
and biopsies were scored by two pathologists who were blinded to all data. Twenty-three
subjects were screened and 19 were randomized to either group A (n¼10) or group B (n¼9).
Seven of the 10 subjects in group A completed the study including repeat liver biopsy while all
patients in group B completed the study. Body mass index improved in both groups decreasing
by 1.7kg/m2in group A and 0.9kg/m2in group B (not significant, control versus treatment).
Homeostasis model assessment of insulin resistance scores improved in both groups
decreasing by 1.14 in group A and 1.58 in group B (not significant, control versus treatment).
No significant difference in histopathology was seen between groups on follow-up liver
biopsy. Metformin appeared to have little effect in improvement in liver function tests or
liver histology in nondiabetic patients with insulin resistance and NASH. Decrease in BMI
through diet and exercise significantly improved HOMA-IR scores, serum
aminotransferases and liver histology.
Keywords: NASH, insulin resistance, metformin, histopathology
Nonalcoholic fatty liver disease (NAFLD) is an
increasingly recognized condition of excess fat
deposition within the liver [Angulo, 2002].
NAFLD includes a spectrum of liver pathology
ranging from bland hepatic steatosis to steato-
inflammatory and fibrosing condition of the
liver thought to be an intermediate stage of
NAFLD that may progress to end-stage liver dis-
ease, liver-related death and hepatocellular carci-
noma [Sanyal, 2003; Bugianesi et al. 2002;
McCullough, 2002]. The pathologic criteria are
now well established and the diagnosis can only
be made once the absence or limited use of
alcohol is confirmed. The estimated prevalence
of NAFLD may be as high as one third in the
general population [Browning et al. 2004].
Bland hepatic steatosis seems to have a relatively
Therapeutic Advances in
(2009) 2(3) 157–163
? The Author(s), 2009.
Reprints and permissions:
William W. Shields
Medical Center San Diego,
San Diego, CA, USA
Department of Pathology,
Naval Medical Center
San Diego, San Diego, CA,
Hepatology, Brooke Army
Medical Center, Fort Sam
Houston, TX, USA
Hepatology, Scripps Clinic
Torrey Pines, LaJolla, CA,
benign clinical course whereas up to 20% of
[McCullough, 2002]. The metabolic syndrome,
characterized by increased waist circumference,
hypertriglyceridemia, reduced high density lipo-
protein (HDL) levels, elevated blood pressure,
and/or fasting hyperglycemia, is a strong risk
factor for NAFLD and insulin resistance plays a
pivotal role in the pathophysiology of the disease
[Hamaguchi et al. 2005; Choudhury et al. 2004].
The optimal therapy for NAFLD has not been
established. Current recommendations are for
moderate weight loss in order to decrease insulin
include avoiding offending agents such as alcohol
and controlling associated medical disorders such
as diabetes mellitus and hyperlipidemia [Reid,
2006]. Pharmacotherapy focusing on improving
or reversing insulin resistance is a target of
research. Metformin received approval by the
FDA for clinical use in the United States in
1995 and revolutionized the treatment of dia-
betes mellitus type 2 and insulin resistance.
Rather than increase insulin levels it works to
improve insulin sensitivity and therefore decrease
insulin requirements [Bailey and Turner, 1996].
Previous studies of metformin have shown bio-
chemical improvement in NAFLD patients and
suggest histologic improvement [Loomba et al.
2009; Buglianesi et al. 2005; Uygun et al. 2004;
Coyle and Delaney, 1999], but have been limited
to uncontrolled trials. We hypothesized that 12
months of metformin therapy would improve
liver histology compared to diet and exercise in
nondiabetic, insulin-resistant patients with biopsy
Materials and methods
The study subjects were obtained as consecutive
patients referred to the adult gastroenterology
clinic at the Naval Medical Center, San Diego
with a histologic diagnosis of NASH defined by
the presence of cytologic ballooning and inflam-
mation in addition to steatosis. Study subjects
must have had a liver biopsy within 18 months
of enrollment to be eligible for the study. Subjects
were included if they had biopsy-confirmed
NASH and one of the following: a body mass
index (BMI) 427kg/m2; a fasting blood sugar
between 110 and 125mg/dl; a diagnosis of poly-
Additional inclusion criteria included age greater
than 17 years, geographic stability for 1 year from
study inclusion and an unremarkable serologic
evaluation for chronic liver diseases including
viral hepatitis studies, autoimmune studies, anti-
mitochondrial antibodies, iron indices and, when
deemed appropriate, alpha-1 antitrypsin studies
and ceruloplasmin levels. Patients were excluded
if they had known diabetes mellitus (type 1 or 2),
a fasting blood sugar4125mg/dl, prior history of
alcoholic liver disease, any other known chronic
liver disease, renal insufficiency (defined in this
study as a serum creatinine 41.2), a known
allergic reaction to metformin, prior use of an
insulin-sensitizing agent such as metformin or a
thiazolidinedione, gastric bypass within 2 years,
untreated thyroid disease, coagulopathy, chronic
thrombocytopenia, or significant alcohol use
80g/week during the 2 years prior to study enroll-
ment. All subjects signed an informed consent
for participation in the study. The study was
approved byour Department
Investigation and Institutional Review Board.
Subjects who met eligibility requirements were
randomized to group A or B by the pharmacy
using a computer-generated program. Patients
randomized to group A (control group) received
placebo. Group B (treatment group) received
long-acting metformin 500mg daily. In addition,
both groups were referred to a dietician for coun-
seling regarding a DASH (Dietary Approaches to
Stop Hypertension) diet emphasizing fruit, vege-
tables and lowering saturated fat and cholesterol.
Both groups were also advised to attempt to com-
plete 30 minutes of aerobic exercise four times
per week. Study participants were seen 2 weeks
after enrollment and at 6-week intervals there-
after where BMI was measured and compliance
with exercise regimen was assessed. At the
3-month follow-up visit, if serum aminotrans-
ferases did not show improvement then the
placebo or metformin dose was doubled (to a
maximum dose of metformin of 1000mg/d).
The treatment period was 12 months in duration
and repeat liver biopsy was performed after com-
pletion of the therapy.
All subjects had a complete clinical, anthropo-
metric and laboratory evaluation at the time of
enrollment. The clinical data included age, race,
sex, blood pressure, height, weight and BMI.
Therapeutic Advances in Gastroenterology 2 (3)
Baseline laboratory measurements included fast-
ing insulin and glucose measurement, fasting lipid
profile with total cholesterol, triglycerides and
HDL levels and liver enzymes including alanine
aminotransferase (ALT), aspartate aminotrans-
ferase (AST) and alkaline phosphatase. A home-
ostasis model assessment of insulin resistance
(or HOMA-IR) score was calculated using the
formula: fasting insulin (mIU/ml) ? fasting glu-
cose (mg/dl)/405 [Matthews et al. 1985]. A liver
study and repeated in 12 months at study conclu-
sion. All biopsies were evaluated separately in a
blinded fashion by two study pathologists who
scored the histology using the scoring system pro-
posed by Brunt et al.  (Box 1). At study
conclusion, scores were assessed. Scores differing
by 1 or less between the two pathologists were
averaged. Scores differing by more than 1 were
than re-evaluated by both pathologists and a
final score was given. In addition, all biopsies
were given a NAFLD activity score as proposed
by Kleiner et al. .
The primary objective of this pilot study was
improvement in histopathology in metformin-
Secondary endpoints included overall improve-
ment in BMI, HOMA-IR and serum amino-
The scores were compared across study arms at
entry and at end of study using a Wilcoxon
signed-rank test. The scores were compared
between the two study groups using the two-
sample Wilcoxon rank-sum test. The analysis
was carried out on an intention-to-treat basis.
A p value of 50.05 was considered significant.
All data in the text and tables are given as
means ? standard deviation.
Twenty-three consecutive patients were assessed
and fulfilled entry criteria for eligibility in the
study. Four patients declined to participate.
Nineteen patients were randomly assigned to
either group A (n¼10) or group B (n¼9). All
patients in group B completed the study includ-
ing repeat liver biopsy at 12 months. All liver
biopsies were deemed adequate for interpreta-
tion. Three patients in group A did not complete
the study (two were lost to follow up and
study). Their data are included in the final inten-
tion-to-treat analysis. Four of nine patients in
group B (treatment group) were titrated up to
metformin 1000mg/day. Figure 1 illustrates the
The baseline clinical and demographic data from
the two groups are shown in Table 1. The two
groups were similar regarding their laboratory
and anthropometric data. The treatment group
was older and predominantly male. The majority
of patients in both groups were Caucasian, obese
(BMI430) and had laboratory evidence of insu-
lin resistance and hyperlipidemia. Most showed
mild abnormalities in ALT and AST.
BMI improved in both treatment arms. In group
A, the BMI decreased by 1.7kg/m2whereas in
group B the BMI decreased by 0.9kg/m2. The
difference between control group and treatment
group was not significant (p¼0.514). In all study
Box 1. Nonalcoholic steatohepatitis histopathologic
scoring system [Brunt et al. 1999].
Steatosis (% of hepatocytes in specimen):
2-up to 33%
Hepatocellular Ballooning and Disarry:
1-minimal, focally involving
2-mild, obvious ballooning
3-marked, obvious ballooning and disarry
Intra-acinar (lobular) inflammation (inflammatory
foci per 20x):
Portal Tract Inflammation:
1-zone 3 perisinusoidal/pericellular fibrosis
2-zone 3 perisinusoidal/pericellular fibrosis with
3-zone 3 perisinusoidal/pericellular fibrosis with
periportal fibrosis with bridging
WW Shields, KE Thompson et al.
subjects, the BMI decreased by 1.3kg/m2.
This was significant (p¼0.007) and is illustrated
in Figure 2.
Insulin resistance was improved in all study sub-
jects. HOMA-IR decreased by 1.14 in group A
and by 1.58 in group B. There was no significant
difference between the two groups (p¼0.886).
Overall, HOMA-IR decreased by 1.18. This
was significant (p¼0.002) and is illustrated in
Liver enzymes improved in both treatment
groups (Figures 4 and 5). ALT levels decreased
by 40.7IU/l in group A, 21.5IU/l in group B and
31.6IU/l overall. ASTlevelsdecreased by
20.1IU/l in group A, 5.7IU/l in group B and
13.2IU/l overall. The differences between the
two groups were not significant for ALT, AST
or alkaline phosphatase. The overall improve-
ments were significant for ALT (p¼0.014) and
AST (p¼0.04) and approached significance with
alkaline phosphatase (p¼0.056).
Histologic outcomes are shown in Table 2. There
between the two groups in regards to overall
NAFLD activity score (NAS), individual compo-
nents of NAS or fibrosis. There was, however, a
significant improvement in steatosis and NAS
across all study subjects (p¼0.021).
Insulin resistance and the metabolic syndrome
play a central role in the pathogenesis of
NAFLD and NASH [Choudhury, 2004]. At pre-
sent, the standard of care is aimed at weight loss
through aerobic exercise and dietary changes.
However, large, randomized controlled trials
evaluating the efficacy of weight loss on histo-
pathology in NASH are lacking [Clark, 2006].
Subsequently, multiple pharmacotherapies have
been investigated with variable results including
lipid lowering agents [Gomez-Dominguez et al.
2006; Basaranoglu et al. 1998], vitamin E
[Sanyal et al. 2004], pentoxifylline [Adams et al.
2004] and ursodeoxycholic acid [Lindor et al.
2004]. Small randomized, controlled trials have
suggested a benefit using the thiazolidinedione,
pioglitazone. Belfort et al.  demonstrated
both metabolic and histologic improvement in
Assessed for eligibility
Declined to participate
Allocated to control group
Allocated to treatment
Lost to follow-up (n=2)
Discontinued intervention (n=1)
Figure 1. Study flow.
Table 1. Baseline clinical and demographic data.
Fasting Insulin (mIU/mL)
Total Cholestero (mg/dl)
Alk Phos (IU/L)
Therapeutic Advances in Gastroenterology 2 (3)
55 patients with NASH treated for 6 months with
pioglitazone [Belfort et al. 2006]. This has been
supported by a more recent study of pioglitazone
in 74 NASH patients treated for 1 year with pio-
glitazone [Aithal et al. 2008]. However, this type
of insulin sensitizer is associated with side effects
such as weight gain and increased fracture risk
that raise questions as to the utility of using this
drug long term. Furthermore, not every NASH
patient appears to have a favorable histopatholo-
gic response. Therefore, it would seem appropri-
ate to assess the utility of other medications that
improve insulin sensitivity such as metformin.
Metformin is indicated for the treatment of dia-
betes mellitus and as such would be considered a
candidate drug to treat NASH given the under-
lying association. Improvement in insulin sensi-
tivity is thought to occur via upregulation of
AMP-activated protein kinase (AMPK), an inte-
gral component of glucose and lipid metabolism
that results in decreased hepatic glucose and
triacylglycerol production as well as increased
peripheral glucose utilization
muscle. A recent Cochrane Review suggested a
favorable response with metformin in two small,
randomized trials in improving aminotrans-
ferases [Angelico et al. 2007]. Data is limited
with regards to changes in histology and trials
Group AGroup BOverall
Figure 3. Insulin resistance (HOMA-IR) between
groups at baseline (blue bars) and end of treatment
Figure 4. Alanine aminotransferase between groups
at baseline (blue bars) and end of treatment (red
Group AGroup B Overall
groups at baseline (blue bars) and end of treatment
5. Aspartateaminotransferase between
Group A Group BOverall
Figure 2. Body mass index (kg/m2) between study
treatment (red bars).
WW Shields, KE Thompson et al.
reviewing metformin lack double-blinding con-
trols and/or control biopsy data. Our study is
double blinded, placebo-controlled trial of 12
months of therapy with metformin in the treat-
ment of NASH in nondiabetic patients with
primary histologic endpoints. There was no sig-
nificant difference between patients treated with
metformin compared to those randomized to
placebo with regards to changes in serum amino-
All patients met with a dietician and were given
instructions for a DASH diet. In addition, they
were asked to comply with an aerobic exercise
regimen of 30 minutes at least four times a
week. Lifestyle modifications have been the stan-
dard of care in the treatment of NAFLD despite
limited supportive data. Our patients signifi-
cantly improved their BMI throughout the
12-month study. This improvement in BMI was
associated with an improvement in insulin resis-
tance as HOMA-IR scores were significantly
lower at the end of the study in both groups.
In addition, there was significant improvement
in serum aminotransferase levels and more
importantly in liver histology with a significant
improvement in steatosis and NAFLD activity
scores. There were also trends toward signifi-
cance in improvement in ballooning degeneration
and overall inflammatory grade. Our study pro-
vides needed support for continued recommen-
dations of lifestyle modifications in the treatment
of NAFLD. Furthermore, our study demon-
strates that liver histology can improve with
weight loss and exercise alone.
Our study has a number of limitations. First, as a
pilot study, it is limited by a small sample size
increasing the risk of type II error associated
with the statistical results. Second, the potential
benefit may be masked by a relatively low dose of
metformin (maximum 1000mg/d). It is impor-
tant to note, however, that our study specifically
excluded patients with a diagnosis of diabetes
mellitus type 2. Finally, although our study has
histologic endpoints at 12 months, the benefits of
inflammation improvement and potential fibrosis
reversal may require longer-term histologic data.
Clearly, in the field of NASH large-scale trials
Metformin appears to have little effect compared
with placebo in improving liver chemistries or
liver histology in nondiabetic, insulin-resistant
patients with NASH. Weight loss utilizing the
DASH diet and regular aerobic exercise signifi-
cantly improves insulin resistance, serum amino-
transferases and liver histology in NASH.
Conflict of interest statement
The opinion or assertions contained herein are
the private views of the authors and are not to
be construed as official or reflecting the view of
the Department of the Army, Navy or the
Department of Defense.
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