Dietary Fiber/Carnitine, Diacylglycerol, and Low Glycemic Index Starch Effects on Obesity and Triglyceride Rich Lipoprotein Metabolsim in Dogs
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Obesity is the most common clinical disorder and is associated with various medical conditions in dogs. Appropriate dietary management potentially provides weight loss in a safe, healthy, and efficacious manner. In order to elucidate whether dietary fiber, carnitine, diacylglycerol (DAG), and low glycemic index (LGI) act on such dietary components, a series of studies was conducted: 1) the combination of dietary fiber/carnitine effect on short term (3 and 7 h) satiety and long term (6 weeks) canine weight loss, 2) the combination of dietary LGI/high glycemic index (HGI) starches and DAG/triacylglycerol (TAG) effect during a 9 week canine weight loss period, and 3) the DAG effect on triglyceride rich lipoprotein (TRL) metabolism isolated from canine plasma 3-4 h postprandially. The combination of dietary fiber/carnitine supplementation decreased both food and energy intake at 3 h post-feeding, suggesting that this combination diet provided 3 h post-meal satiety. This combination supplement also increased postprandial plasma B- hydroxybutyrate (BHB) at d 42 and body fat and weight loss at d 42 from baseline. This combination supplement did not alter plasma vitamin A distributions or concentrations although it contained high vitamin A as B-carotene. In the second study, the LGI diets resulted in a more pronounced body weight loss than the HGI diets due to lower diet digestibilities. These data are consistent with LGI diets decreasing metabolizable energy and consequently consuming less energy compared to the HGI diets. The DAG diets lowered postprandial plasma TAG at weeks 1 and 8 in and increased plasma BHB at week 8, suggesting an increase in fat oxidation. The combination of DAG/LGI decreased postprandial total cholesterol at week 8. Lipoprotein concentrations were not altered by diet types. Fasting lipoprotein lipase (LPL) and hepatic lipase (HL) activities were not affected by diets. In the final study, DAG ingestion decreased TRL and plasma TAG concentrations vs. TAG ingestion. The DAG enriched meal increased non-esterified fatty acid, monoacylglycerol, and 1,3-DAG and decreased TAG in TRLs which may be attributed to larger TRL particle size compared to the TAG meal. Consequently, the DAG derived TRLs showed increased affinity of core TAG for LPL and HL in vitro. Moreover, the intravenous injection of the DAG derived canine TRLs into mice underwent more rapid blood clearance associated with the greater hepatic uptake compared to the TAG derived TRL injection. In conclusion, the combination of dietary fiber/carnitine and DAG/LGI preferably reduced body weight and stimulated fat oxidation, which promotes overall weight loss. The postprandial plasma TAG lowering effect of DAG is the result, at least partially, from the efficient clearance of TRLs from blood circulation and their ability to act as a more efficient substrate for plasma lipolytic enzymes.