comparative histological, immunohistochemical, and biochemical study of the effect of green tea extracts or chromium picolinate administration on the white visceral adipose tissue and liver in albino rats fed on high-fat diet

ABSTRACT

Obesity has become a major health problem, as a growing proportion of the population worldwide is overweight. The coincidence of obesity, insulin resistance, hypertension, dyslipidemia, and hepatic steatosis is commonly referred to as the 'metabolic syndrome'. The investigation of the antiobesity properties of food components is a popular field of research and one of these natural agents of interest is green tea extract [GTE]. Nevertheless, chromium picolinate [CP] is also postulated to have an effect on the body fat composition. The present study aimed to assess the changes in the visceral white adipose tissue and the liver of adult male albino rats that are fed on high-fat diet [HFD] following administration of GTE or CP supplements histologically, immunohistochemically, and biochemically. A total of 60 adult male albino rats [120-150g] were randomly assigned into four groups. Group I [the control group] included 30 rats and were subdivided into three equal subgroups [Ia, Ib, Ic]; all were fed on standard rat chow. Groups Ib and Ic were given GTE and CP, respectively, orally through an orogastric tube. Group II included 10 rats that were allowed a free access to HFD. Group III [the GTE and HFD group] included 10 rats that received GTE orally [200 mg/kg body weight/day] in conjunction with HFD. Group IV [the CP and HFD group] included 10 rats that received CP orally [80 micro g/kg body weight/day] in conjunction with HFD. The experiment continued for 3 months. Perinephric white adipose tissue [PWAT] and liver specimens were dissected from all rats at the end of the experiment for histological and immunohistochemical examination. Blood samples were taken for estimation of fasting blood glucose [FBG] and fasting blood insulin [FBI] levels. Histologically, groups Ib and Ic revealed almost the control pattern of the liver and PWAT similar to group Ia. Group II showed focal areas of cellular infiltration and congestion of the blood vessels of the liver sections. Most hepatocytes appeared swollen with cytoplasmic vacuolation. PWAT revealed a marked increase in the amount and size of the adipocytes. Groups III and IV revealed almost the control pattern of the liver except for few areas of cellular infiltrations in group IV. Groups III and IV showed a marked decrease in the amount of PWAT, which was more remarkable in group IV. Decrease in the size of many adipocytes was more manifested in group IV. Immunohistochemically, increased expression of insulin receptors in the adipocytes of PWAT and to a lesser extent in the hepatocytes of group III was noticed. Group IV showed more noticeable increased expression of insulin receptors compared with group III. Biochemically, FBI in the obesity group was higher as compared with the control group. Groups III and IV revealed a significant decrease in the FBI level. Fasting blood glucose level showed significant increase in group II only. Supplementation with either GTE or CP may be useful as antiobesity agents and can be used to prevent the impact of obesity on the liver and to improve insulin resistance