1. Battle of the Macronutrients:
Exploring the Physiological Impacts of High Fructose and High Fat Diets.
L.N. Woodie & S.N. Blythe
Biology Department, Washington and Lee University, Lexington, Virginia, USA
We conducted a pilot study to see if there would be differences in a set shifting task due to high fat diet exposure. We wanted to see if male Sprauge-Dawley rats were capable of performing an attentional shift before we began our primary project. Since our task will only involve a one-dimension shift we show that the rats can perform this task and that *****there is a diet difference at the one-dimension shift point in the task***** The task used a two-dimension shift near the end where there wasn’t a statistically significant interaction between diet and performance on the task.
4 ½ weeks blood test
10 weeks on diet
Week 10 final glucose test, blood draw, begin to restrict food after blood draw to be at 85% bw
Week 11 attention task, kept food restricted
Week 12 continued attention task, food restricted, wrapped up study
Purpose
To elucidate differences in the physiology and behavior of rats fed a high fat or high fructose diet.
Background
The Western-Style diet is composed primarily of high fructose and high fat foods. 2
This diet is hypothesized to play an important role in the development of obesity and insulin resistance.3
Impaired insulin signaling has been suggested to negatively impact physiological and cognitive function.1
Processing of fat and fructose occur differently, so there may be diverse effects observed in animals only fed one or the other.
1. Rats Fed a High Fat Diet Develop Visceral Adiposity.
3. A High Fructose Diet Impairs Cognitive Flexibility. a) b) c) *
Preliminary Morris Water Maze a a d) c) b) a) b
There was no significant difference among the groups in the preliminary Morris Water Maze probe for total distance (a), target quadrant entries (b), annulus crossings (c), and time spent in target quadrant (d).
Rats fed a high-fat diet had a significantly heavier body mass (a), and consumed more kilocalories (c) than animals fed a high fructose or control diet by the end of the study. The high fat and high fructose fed rats had fat pad weight per 100 grams of body weight that was significantly different from the control.
Reverse Morris Water Maze d) c) b) a) * 1 2 8 7 6 5 4 3 9
(Weeks)
Animal Arrival
Start Diets
Diet Exposure Continues
Experimental Timeline and Methods
Rats fed a diet high in fructose traveled significantly less total distance (t=0.03, p<0.05) (a) ,and entered the target quadrant significantly less (t=0.02, p<0.05) (b) than the high fat fed animals. There was no significant difference between the diet groups for annulus crossings (c), or time spent in target quadrant (d).
Rats fed a high fructose diet had significantly higher levels of fasting insulin (p=0.029) (a), and serum triglycerides (p=0.000) (d) than the animals fed a high fat or control diet. There was no significant difference among the groups for fasting blood glucose (b), QUICKI number (c), liver lipids (e), or serum TNF-α.
2. High Fructose Fed Rats have Elevated Serum Insulin and Triglycerides.
Blood Glucose Test
Sacrifice f) e) d) c) b) a) *
Morris Water Maze
kcal: 3.1 kcal/g
% Fat: 5.80%
% Carbohydrate: 44.30%
Control Diet
High Fat Diet
kcal: 5.24 kcal/g
% Fat: 60%
% Carbohydrate: 20% as corn starch
High Fructose Diet
kcal: 3.84 kcal/g
% Fat: 10%
% Carbohydrate: 55% as fructose
Conclusions
Rats fed experimental diets developed distinctly different physiological and behavioral symptoms of metabolic syndrome.
A high fat diet induces visceral obesity in conjunction with increased kcal intake.
A diet high in fructose causes elevated serum insulin and triglycerides.
Performance in the reverse MWM was impacted by the high fructose diet suggestive of impaired working memory.
These results show that separate components of the Western-style diet may play considerably different roles in physiology and behavior.
Tissue Collection
Brain Punches
Abdominal and Gonadal Fat Pads
Livers
Blood
References:
1. McNay, E.C., Recknagel, A.K. (2011) Reprint of: ‘Brain insulin signaling: A key
component of cognitive processes and potential basis for cognitive impairment in type 2 diabetes.’ Neurobiology of Learning and Memory 96:
2. Ross, A.P., Bartness, T.J., Mielke, J.G., Parent, M.B. (2009) A high fructose diet
impairs spatial memory in rats. Neurobiology of Learning and Memory 92:
3. Stanhope, K.L., Havel, P.J. (2008) Endocrine and metabolic effects of consuming beverages sweetened with fructose, glucose, sucrose, or high-fructose corn syrup. American Society for Clinical Nutrition 88: 1733S-1737S.
Acknowledgments
I would like to thank my thesis committee: Dr. Sarah Blythe, Dr. Helen I’Anson and Dr. Robert Humston, the kind, patient and wonderful members of the Blythe lab and the rest of the W&L Biology Dept. for their support.