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It has been speculated that the effect of taurine on glucose homeostasis could
involve a lipid lowering effect (El Mesallamy et al.
2010
) and/or enhancement of
insulin signaling (Nandhini et al.
2005
) . However, the mechanism(s) by which taurine
affects glucose homeostasis is largely unknown and no long-term studies of this
effect have been performed. Thus, we performed a long-term study in fructose-fed
Wistar rats examining fasting glucose and lipid parameters as well as glucose tolerance
with or without taurine supplementation.
5.2
Methods
5.2.1
Animals, Study Design, and Diet
All experimental procedures complied with guidelines laid down by The Danish
Animal Experiments Inspectorate and by the local animal facility at the University of
Copenhagen, Denmark. Male Wistar Hannover GALAS (HanTac:WH) rats (Taconic,
Ejby, Denmark) were fed ad libitum, housed two rats per cage, and kept at a 12-h
light/dark cycle. Animals as well as food and water intake were measured biweekly.
Twenty-four 5-week-old rats were fed four different diet regimes for 26 weeks.
The rats were divided randomly into four groups of six, ensuring a similar start
weight of each group, and fed a control diet or a high-fructose diet with 10% (w/v)
fructose (Sigma-Aldrich, St. Louis, MO, USA) in the drinking water either with or
without 2% (w/v) taurine supplementation. The carbohydrate control diet contained
68% energy from glucose (corn starch or maltodextrin), 21% casein, and 12% corn
oil (Research Diets, New Brunswick, NJ, USA). The fructose-rich diet contained
50% energy from fructose, 18% energy from glucose (corn starch or maltodextrin),
21% casein, and 12% energy from corn oil (Research Diets). As the animals receiv-
ing the fructose diet also obtained fructose from the drinking water, approximately
62% of their energy intake was derived from fructose (data not shown).
Fructose and taurine were supplemented in drinking water by dissolving fructose
and/or taurine directly in the water used in the animal facility. The taurine used for
supplementation was of the chemically synthesized variety (Sigma-Aldrich).
An Echo MRI 4-in-1 for Small Animals (EchoMRI, Houston, TX, USA) was
used to monitor total body fat mass of unanesthetized animals. Values are averages
of duplicate measurements.
5.2.2
Oral Glucose Tolerance Test
Animals were fasted for 16-18 h before an oral glucose tolerance test (OGTT) was
carried out. The required amount of glucose (2 g per kg) was given as a solution
(45% w/v) by gavage. Blood glucose levels were determined before glucose
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