Nonalcoholic fatty liver disease has been considered the hepatic manifestation of
obesity. It is unclear whether supplementation with
green tea extract rich in
epigallocatechin-3-gallate (EGCG) influences the activity of mitochondrial respiratory chain complexes and
insulin resistance in the liver. EGCG regulated hepatic mitochondrial respiratory chain complexes and was capable of improving lipid metabolism, attenuating
insulin resistance in obese mice. Mice were divided into four groups: control diet+water (CW) or EGCG (CE) and hyperlipidic diet+water (HFW) or EGCG (HFE). All animals received water and diets ad libitum for 16 weeks. Placebo groups received water (0.1 ml/day) and EGCG groups (0.1 ml EGCG and 50 mg/kg/day) by gavage.
Cytokines concentrations were obtained by ELISA,
protein expression through Western blotting and mitochondrial complex enzymatic activity by colorimetric assay of substrate degradation. HFW increased
body weight gain, adiposity index, retroperitoneal and mesenteric adipose tissue relative weight, serum
glucose,
insulin and Homeostasis Model Assessment of Basal
Insulin Resistance (HOMA-IR);
glucose intolerance was observed in oral
glucose tolerance test (OGTT) as well as ectopic fat liver deposition. HFE group decreased
body weight gain, retroperitoneal and mesenteric adipose tissue relative weight, HOMA-IR,
insulin levels and liver fat accumulation; increased complexes II-III and IV and
malate dehydrogenase activities and improvement in
glucose uptake in OGTT and
insulin sensitivity by increased
protein expression of total AKT, IRĪ± and IRS1. We did not find alterations in inflammatory parameters analyzed. EGCG was able to prevent
obesity stimulating the mitochondrial complex chain, increasing energy expenditure, particularly from the oxidation of
lipid substrates, thereby contributing to the prevention of hepatic steatosis and improved
insulin sensitivity.