Twenty-eight adult patients with biopsy-proven NASH were enrolled in the study and 26 completed the 48 weeks of therapy and underwent follow-up metabolic testing, imaging and repeat liver biopsy. The two drop-outs included a 26-year-old woman who stopped therapy after 12 weeks because she had moved and her employment did not allow time for travel for outpatient visits and a 53-year-old woman who stopped therapy after 24 weeks because of desire to pursue other treatments. These patients were not included in further analyses.
The 26 patients included 13 women and the average age was 44 years. All patients were either overweight (31%) or obese (69%) (). Although no patient was being treated for diabetes at the time of enrolment, seven patients (27%) fulfilled the criteria for having diabetes and another eight (31%) had impaired glucose tolerance. Average serum ALT levels were 70 U/L (normal = 6–41 U/L) and AST 47 U/L (normal 9–34 U/L). On the day metformin was started, five patients had normal ALT and seven had normal AST levels. All patients had NASH on liver biopsy and NASH activity index scores ranged from 4 to 10 (median = 8). All but 4 patients had some degree of fibrosis and one had cirrhosis on pre-treatment liver biopsy.
Metformin treatment was well tolerated. No serious adverse events occurred and no patient stopped therapy because of side effects. The most common side effect was mild and intermittent diarrhoea with variable amounts of abdominal bloating and discomfort that affected most patients to some degree during the first few weeks of treatment. However, diarrhoea and intestinal upset resolved despite continuation of full doses of therapy in all except two patients who underwent dose reduction at 12 and 16 weeks; one being maintained on 1500 mg and one on 1000 mg daily. No patient developed hypoglycaemia, evidence of lactic acidosis, congestive heart failure or renal dysfunction.
Overall, average serum ALT and AST levels improved minimally during the study and the differences between mean baseline and end-of-treatment aminotransferase values were not statistically significant (). Changes in aminotransferase levels appeared to be dichotomous, in that ALT levels fell into the normal range in nine patients and AST levels in six patients by the end of treatment, but changed minimally overall. ALT levels remained in the normal range in four of the five patients who had normal values at the start of therapy so that the proportion of patients with normal ALT levels was significantly higher at the end of treatment (50% vs. 19%; Fisher’s exact test: P = 0.04). Other biochemical test results did not change appreciably including serum bilirubin, albumin, prothrombin time and cholesterol or triglyceride levels. There were mild increases in mean HDL cholesterol levels. Blood counts, including haematocrit, total white blood cell count and platelet count did not change (data not shown).
Biochemical data at baseline and after 48 weeks of metformin
Twenty-six patients underwent follow-up liver biopsy after 48 weeks of metformin treatment (). All features of the NASH activity index improved somewhat, the changes being the greatest for cellular injury and less for parenchymal inflammation and steatosis. Mallory bodies were less evident in follow-up liver biopsies. The average NASH activity index improved significantly, falling from 8.2 to 5.9 (P < 0.001). The primary outcome (a three-point improvement in NASH activity index with improvements in at least two components of the score and no worsening of fibrosis or increase in Mallory bodies) was achieved by eight patients (31%), all of whom also had improvements in serum aminotransferase elevations. Among the 26 patients, 20 showed improvement (nine had a threepoint or greater, 11 a one- to two-point improvement), five had no change and one had a two-point increase in the NASH activity index.
Histological data at baseline and after 48 weeks of metformin
In contrast to activity scores, liver fibrosis scores decreased minimally and not significantly after 48 weeks of therapy (mean NASH fibrosis scores 1.7 initially vs. 1.5 at end of treatment). Overall, eight patients had a one or more point improvement in fibrosis scores, 14 had no change and four had worsening of one or two points.
Patients on metformin often lost weight and the average weight loss during the 48 weeks of treatment was 6 kg (change in weight range: +1.3 to −18.9 kg; ). The weight loss was maximal during the first 6 months, but continued throughout the treatment period (). Weight loss, similar to the histological and biochemical improvements, appeared to be dichotomous: 18 patients (69%) lost at least 2 kg and five (19%) lost more than 10 kg of weight. In the remaining eight patients, average weight did not change. There was a strong positive correlation between weight change and changes in serum aminotransferase levels (for ALT: r = 0.52, P = 0.005; for AST, r = 0.50, P = 0.009) and between weight loss and decreases in NASH activity index scores (r = 0.76, P < .0001).
Anthropometric data at baseline and after 48 weeks of metformin
Changes in body weight in 26 patients treated with metformin for 48 weeks.
There was a slight average decrease in waist circumference, but a similar decrease in hip circumference, so that the average waist/hip ratio did not change (). Whole body composition by DEXA showed that the weight loss was because of decreases in both lean body and fat mass so that the per cent body fat decreased minimally (34.3–33.2%). The liver fat as assessed by MRI also decreased minimally from 14.9% to 13.0% (P = 0.50) without a significant change in total liver volume. Total abdominal fat did not change; however, visceral fat decreased (200–170 cm2), while subcutaneous fat increased (254–290 cm2) as estimated by cross sectional CT.
Changes in measures of insulin sensitivity
Improvements in fasting blood glucose, insulin, C-peptide and free fatty acid levels occurred during metformin treatment, but most of the changes did not reach statistical significance (). Impaired glucose tolerance was present in eight and diabetes in seven patients before therapy, this distribution shifting to 13 with impaired glucose tolerance and three with diabetes at the end of therapy. Fasting blood glucose and insulin results showed significant improvements in HOMA by 44% (P = 0.04). HOMA values improved in all except four patients and improved more in patients with a histological response. FSIGT results (in 21 patients who were tested before and after treatment) showed no significant change in acute insulin response to glucose (AIRG), insulin sensitivity index (SI), glucose effectiveness (SG) or glucose disposition index (DI).
Insulin sensitivity at baseline and after 40 weeks of metformin
Differences between responders and nonresponders
Eight patients (31%) met the histological criteria of response and the remaining 18 were classified as nonresponders, although many of them had some degree of histological improvement (). At baseline, responders had a lower average BMI than nonresponders, but this difference was not statistically significant. None of the patients with baseline BMI of 40 or more achieved a histological response on treatment. There was no significant difference between responders and nonresponders at baseline with regard to other features such as average age, ALT, AST, HOMA, NASH activity index and fibrosis scores.
Comparison of histological responders and nonresponders to metformin therapy
On therapy, responders were more likely to lose weight. Furthermore, there was a trend for decreases in ALT and AST being greater among the responders than nonresponders (). However, the histological responders and nonresponders did not different with regard to improvements in HOMA, decreases in hepatic fat or hepatic volume (by MRI) or changes in total, visceral and subcutaneous fat.
Changes in weight over the 48 weeks of therapy in relationship to response are shown in . After 48 weeks of metformin treatment, the average weight change was −10.5 kg in responders vs. −4.0 kg in nonresponders (P = 0.02). All histological responders lost more than 5 kg during therapy (range 5.7–18.7 kg) and three responders were no longer overweight (BMI <25) at the end of 48 weeks of treatment.
Figure 2 Changes in average weight in eight responders and 18 nonresponders to a 48-week course of metformin. The diamonds represent the mean weights of the eight responders and the squares, the mean weights of the 18 nonresponders during therapy and then again (more ...)
also shows the changes in weight during follow-up to at least 24 weeks after treatment which was available on 24 patients, five of whom (one responder and four nonresponders) had diabetes and asked to remain on metformin. During follow-up, the average body weight increased in both responders and nonresponders. Indeed, all except two patients gained at least one kilogram in weight, the average weight gain being 4.1 kg. The two exceptions to the weight gain comprised one patient with diabetes on metformin (−0.1 kg weight change) and another patient who attributed her weight loss (−5.7 kg) to severe situational depression.
Responders were also more likely to have improvements in serum ALT levels during therapy than nonresponders; the average levels in responders decreasing to within the normal range by the end of therapy (). At the end of treatment, ALT levels were normal in all except one responder (whose ALT level was 59 U/L). When metformin was stopped, however, serum ALT levels tended to rise towards baseline.
Figure 3 Changes in mean serum alanine aminotransferase (ALT) in eight responders and 18 nonresponders during a 48-week course of metformin. Squares represent the mean values of the 18 nonresponders, the diamonds, the mean values for the eight responders. While (more ...)
Finally, HOMA values improved markedly during the first 8 weeks of starting metformin, improving more among responders than among nonresponders; thereafter, HOMA values remained constant, although decreased slightly among responders (). By 48 weeks, HOMA values in responders ranged from 1.2 to 3.1 (mean = 1.9) and were normal (<2.5) in six of the eight; in contrast, in nonresponders, HOMA values ranged between 1.1 and 17.4 (mean = 5.5) and were normal in only four of 18. With stopping therapy, HOMA values began to rise towards baseline levels among both responders and nonresponders.
Figure 4 Changes in average homeostasis model assessment (HOMA) values in eight responders and 18 nonresponders to a 48-week course of metformin. The diamonds represent the mean HOMA values of the eight responders and the squares, those of the 18 nonresponders (more ...)
Analysis by degree of improvement in NASH activity index showed a close association of improved histology with weight loss during treatment, which was the strongest when expressed as per cent weight loss (r = 0.79, P < 0.00001) (). Improvements in NASH activity index scores also correlated with the degree of improvement in serum ALT levels (r = 0.6, P < 0.01), but not with improvement in HOMA values expressed as either absolute or per cent change (r = 0.26, P = 0.18).
Figure 5 Correlation between per cent change in body weight and change in NASH activity index after 48 weeks of metformin. The eight squares represent responders and the 18 circles represent nonresponders. There was a positive significant correlation between decrease (more ...)