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← Theoretical 2

Q84 — Dietary Fat, Sucrose and Cardiac Hypertrophy in Hypertensive Rats

Theoretical 2 Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Cardiovascular Physiology

Males from inbred lines of rats with spontaneous hypertension (SHR) and normal blood pressure (WKY) were separated into 5 groups and received different diets for 10 weeks. The first group of each line received standard food (SF), groups 2, 3, 4 received SF + a different fatty acid, group 5 received SF+sucrose. In groups 2–5, the added component comprised 11% of the energy value of the SF.

Line Diet Change in body mass (%) Systolic pressure, 0 week (mmHg) Systolic pressure, 10 weeks (mmHg)
WKY SF+trans-fat 14.7 ± 1.3 122.2 ± 0.6 123.1 ± 0.6
WKY SF+sucrose 14.9 ± 2.4 123.2 ± 2.0 123.6 ± 2.2
SHR SF 14.2 ± 2.0 121.3 ± 2.1 121.9 ± 1.6
SHR SF+butter 18.7 ± 1.3 122.1 ± 0.9 125.6 ± 1.3
SHR SF+trans-fat 10.1 ± 0.3 200.1 ± 1.8 199.9 ± 0.8
SHR SF+sucrose 20.6 ± 3.3** 189.3 ± 3.6 190.1 ± 3.9

Table 1. Measurements of body mass and blood pressure of the caudal artery were measured at the start and end of the experiments (selected rows; some SF/palm-oil rows in the original are not fully legible in the source scan).

Bar chart of heart-mass-to-body-mass ratio, panel A for WKY rats and panel B for SHR rats, across Control, Butter, Palm oil, Trans-fat, and Sucrose diet groups. WKY palm oil and trans-fat groups show a significant decrease relative to control; SHR butter and trans-fat groups show a significant increase relative to control. Figure 1. Ratio of the heart mass to total body mass in different dietary regimes. A – WKY group, B – SHR group. * p<0.05, ** p<0.01.

Using the information and the data in the table and figure above, determine which of the statements are true or which are false.

A. WKY rats receiving SF+palm oil had increased body mass, higher systolic blood pressure and hypertrophy of the cardiac muscle over that in the control.
B. In SHR rats receiving SF+butter, increased body mass could contribute to the hypertrophy of the cardiac muscle
C. In SHR rats, heightened systolic pressure was observed only when trans-fats and sucrose were prevalent in diet
D. The high content of trans-fats and easily digested carbohydrates in the diet of WKY rats contributed to higher body mass and increased systolic blood pressure
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Question reproduced from IBO 2022, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)