In this study, red pitaya juice was used as an intervention in order to investigate the ability of the fruit juice to reverse the abnormalities in body composition, metabolic, liver, kidneys and heart function in high carbohydrate, high-fat diet induced obese rats as a model of metabolic syndrome. Previous research confirmed that rats fed with high carbohydrate and high fat diet for 8 weeks produced abdominal obesity, impaired glucose tolerance, hypertension, dyslipidemia, inflammation, endothelial dysfunction, cardiac fibrosis together with increased stiffness of the heart [17, 18]. All these changes closely mimic the human metabolic syndrome.
Results revealed that red pitaya supplementation increased food intake only in corn starch diet-fed control rats while no changes were observed in red pitaya juice supplementation for high carbohydrate, high-fat diet-induced obese rats and the corn starch diet fed control rats. In other words, the intervention does not affect satiety of obese rats as the quantity of food taken was shown to be regulated by the factors involved in satiety perception . There was report suggesting that the food intake was influenced by the sensitivity of the rats to the palatability of the food in the diet . Therefore, it was proposed that the lean control rats in the present study were more sensitive to the palatability of red pitaya juice as compared to high carbohydrate, high-fat diet-induced obese rats. Food rich in sugar and fat is an example of palatable foods that inhibit the satiety signals and up regulate hunger sensation . Despite of that, energy intake was increased significantly for red pitaya supplemented rats suggested that red pitaya contains higher amount of energy-supplying macronutrients. Red pitaya added up to the total energy content of the diet, leading to progressive increment in body weight, and total body fat throughout the intervention period. A growing body evidences showed that eating fruits can reduce energy density and reduce energy density is associated with lower energy intake and decrease body weight . Furthermore, Flood-Obbagy and Rolls  indicated that consumption of fruits before meal can increase satiety and reduce energy intake but the effects are different for different forms of fruits. Whole fruit is related to more chewing while fruit juices do not require chewing at all. The amount of chewing is then linked to cephalic-phase responses that control the food intake [26, 27]. This may explain the reduce risk of type 2 diabetes mellitus following consumption of specific whole fruits particularly grapes, apples, bananas, and blueberries in prospective longitudinal cohort study among women and men from Nurses’ Health study and Health Professionals Health Study respectively .
It is fascinating to address the suppression effects of red pitaya on body fat for HRP rats. As the diet was continue for 8 weeks, supplementation of red pitaya did not result in further weight gain for obese rats. A current review on regulation of body fat mass in obesity indicated that body resisted fat loss once obesity is established  probably through adaptive mechanism of increasing metabolic rate. Contradictory, total body fat mass in corn starch fed rats were significantly elevated when supplemented with red pitaya. It could be the normal physiological responses upon increasing energy intake in red pitaya supplemented rats. In conjunction with that abdominal circumference were increased in CRP and HRP rats. A possible explanation for this might be that the increase in fat mass in red pitaya fed rats was deposited in abdominal region, hence it can be detrimental to their health. It was expected to see no changes in lean mass for red pitaya supplemented rats as lean mass is a metabolically active tissues required for maintaining basic cell function, thus was not affected by treatment.
Liver and kidneys from H fed rats had higher wet weights as compared to C fed rats as observed in previous study  while no changes in wet weight of spleen and hearts. Likewise, a recent study presented liver abnormalities comprises of higher liver weight, increases in alanine transaminase (ALT) and aspartate transaminase (AST) and the occurrence of inflammatory infiltrates in rats while renal abnormalities were evidenced from the increased in weight, fat accumulation, and glomerular sclerosis with consumption of high fat diet . A probably explanation for this defects is through the deposition of lipid in the liver upon fructose exposure which in turn conquer most of the hepatocytes volume and upset the liver structure and function . Besides, some glucose transporter like GLUT2 may be involved in the transport of fructose to the kidney . Besides, red pitaya-fed rats showed a trend of reduction in stiffness of the heart. Previous studies reported that diastolic stiffness, cardiac fibrosis, and elevated superoxide production were directly associated with each other . Therefore, it could be that the accumulation of interstitial cardiac collagen was reduced  following red pitaya supplementation, hence showed the trend of ameliorating cardiac stiffness.
To have better insight of liver function, the enzymes activities were measured. The collective measurement of alkaline phosphatase (ALP), alanine transaminase (ALT) and aspartate transaminase (AST) reflects the severity of liver damage. ALP is induction enzyme that is mainly found in the cell membrane of the liver and the elevation of this enzyme indicates primary hepatic disease like cholestatic liver disease. Although the increase in ALP can be result from extra-hepatic sources like bone marrow and skeletal muscle, the effects was minimal. Whilst, both ALT and AST are leakage enzymes, and their elevation indicate significant hepatocellular damage. The possible causes may vary including toxicity, inflammation, hypoxia and tissue trauma . However, AST is also found in heart, kidneys, brain, and skeletal muscle and had been used as a nonspecific marker for myocardiac infarction . Results revealed that red pitaya juice treatment significantly reduced ALP and ALT but caused significant increment in AST. Therefore, the present results suggest that red pitaya juice ameliorated liver damage due to high carbohydrate, high fat feeding. The reduction of liver enzymes after the intervention probably indicated the decrease in deposition of fat and the degree of necrosis in liver cells . In contrast, the elevated level of AST could be due to myocardial damage as the heart muscle is rich in aminotransferase enzymes especially AST. The decrease in ALT has been shown to have protective effects from death diabetes and Ischemic heart disease in adults from National Health and Nutrition Examination Survey (NHANES) III . On the other hand, the increased in ALT has been associated with systemic and hepatic insulin resistance, along with increase in the secretion of insulin and reduces insulin clearance from the liver . Hence, the present study showed that red pitaya juice is an important mediator for attenuation of liver injury. Histopathological evidence of liver and heart section after supplementation with 5% red pitaya juice revealed mild improvement in hepatic vacuolation and no inflammation was seen during microscopic examination. Also, the collagen deposition was reduced in left ventricle of the heart. This results was in line with the reduce ALP and ALT enzymes indicative of improvement in liver injury as well as consistent with a slightly reduction in diastolic stiffness. Previous report indicated that intervention with 5% purple carrot juice was also able to reverse the structural damage in the liver caused by high fat feeding by showing minimal signs of microvesicular steatosis .