Role of High-Fat Diet and Cocoa Bean Extract on Adipose Tissue and Liver Morphology

Abstract

Background: Excessive intake of fat is a risk factor for obesity and results in remodeling and dysfunction of adipose tissue with subsequent damage to the liver, pancreas, skeletal muscles, and blood vessels. In spite of several public health initiatives, high-fat diet-associated complications continue to be an important source of morbidity and mortality across the globe. Over time, obesity and adipose tissue dysfunction develop with subsequent deposition of fat droplets into the liver cells (liver steatosis). This obesity-associated remodeling of the adipose tissue and the liver cells generate a systemic pro-inflammatory state mediated by the production of adipokines such as TNF-α, IL-1β and IL-6 which leads to insulin resistance and ultimately contribute to the development of cardiovascular diseases and type 2 diabetes. Cocoa polyphenols have the capacity to restore changes in adipocytes and hepatocytes and improve blood glucose and insulin sensitivity. Aim: To investigate the role of high-fat diet on inflammation and morphology of adipose tissue and liver cells and whether regular intake of natural cocoa can minimize the effects. Methodology: Twenty-four (24) male Sprague Dawley rats were randomly assigned into four (4) groups of six (6) animals. Group 1 (control) was the untreated group and was given standard rat chow and tap water. Group 2 was treated with standard rat chow and natural cocoa drink. Group 3 was treated with high-fat diet (40% fat) and tap water. Group 4 was treated with high-fat diet (40% fat) and natural cocoa drink. The experimental period for the treatment was nine (9) weeks. The weight of the animals as well as fasting blood glucose (FBG) were monitored weekly. Blood samples were taken via cardiac puncture before and after the main study, for determination of inflammatory marker, tumor necrosis factor-alpha (TNF-α). The adipose tissue (epididymal, intestinal and mesenteric) and the liver were harvested at the end of the treatment for micro architecture examination and morphometric analysis by stereological methods Results: High-fat diet resulted in significant increase in weight at the end of 9 weeks, whereas natural cocoa intake reduced this effect (p = 0.0167). The epididymal, intestinal and mesenteric adipocyte sizes increased significantly in HFD only group with average sizes 71.06μm, 56.36μm and 56.17μm respectively compared to all the other groups. Adipocyte size however, was significantly reduced in HFD fed rats treated with cocoa with average epididymal size (60.63μm), intestinal (49.07μm) and mesenteric (48.20μm). The volume density of fat droplets in the hepatocytes was significantly high in rats fed HFD only (4.15 x 102 μm3) when compared to control and other groups with p=0.0011. Meanwhile rats treated with HFD and cocoa showed significantly lower fat infiltration (0.8 x 102 μm3) in the hepatocytes. Blood glucose levels increased significantly in high-fat diet only group but were significantly lower in the cocoa fed groups. Conclusion: Regular High-fat diet intake resulted in increased weight gain, increased adipocyte size, fat infiltration of hepatocytes as well as increased blood glucose levels but natural cocoa intake minimized these effects.