Research Proposal: The Effect of Leucine Supplementation on Diabetic Athletes' Performance

Research Proposal: The Effect of Leucine Supplementation on Diabetic Athletes’
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Research Proposal: The Effect of Leucine Supplementation on
Diabetic Athletes’ Performance
Chadsley Wessinger
12/26/14

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Abstract
Objective: To determine the efficacy of luecine supplementation in combination with
standard diabetic care compared to standard diabetic care alone, on improving athletic
performance in diabetic athletes. Methods: 30 male diabetic athletes aged 18-35 will
participate in resistance exercise while supplemented with either leucine or a placebo
over the span of 12-weeks. A pre-test will establish a baseline while a post-test will
determine how effective the supplementation was. Anticipated Results: Luecine
supplementation will aid in improving the diabetic athletes’ performance. Implications:
Diabetic athletes will have a new option to supplement their diet to allow for great
glycemic control as well as increased athletic performance. Anticipated Conclusions:
There still needs to be more research done on this topic because much of the research has
been done on mice and rats or on non-diabetic humans.

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Introduction
Purpose: The aim of this study will be to determine the effect of leucine supplementation
on diabetic athletes’ performance. 30 male diabetic athletes aged 18-35 will participate in
resistance exercise over the span of 12-weeks. There will be a pre-test to set a baseline
and a post-test to measure the difference in performance.
Problem: Diabetic athletes may have a difficult time balancing training, nutrition, and
stress. So a supplement that could help them manage that would be a welcome option.
Much of the luecine research done to date has been on rodents or non-diabetic athletes;
there has been a limited amount done on diabetic athletes.
Prevalence and Incidence: In 2012 29.1 million or 9.3% of Americans had diabetes and
of those 29.1 million, 8.1 million were undiagnosed (1)
Significance of Research: If the leucine supplement is found to significantly improve the
performance of diabetic athletes, it will be in higher demand. These athletes will now
possess another option to help them participate in their sport.
Implications to Field of Nutrition: Commercially, more supplements will be produced
because of the increased demand. Additionally, more research will be done to ensure the
results are valid.
Background
Diabetic athletes, their family, and their medical care team must endure many problems
every day. As athletes they must invest much of their time to training, nutrition, and
dealing with the stress of competition. As diabetics they must be aware of adverse
physiological outcomes that may accompany being an athlete. Hypoglycemia or
ketoacidosis and microvascular and macrovascular disease are some of the potential

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conditions (2). These conditions are very serious, which is why the diabetic athlete
should be aware of their metabolic needs and what they can do to supplement them.
The American Diabetes Association (ADA) defines diabetes into two broad
terms: type 1 diabetes (T1D) and type 2 diabetes (T2D). T1D results in immune system-
mediated destruction of pancreatic β-cells (the cells responsible for release of insulin);
this results in the failure to produce insulin, leading to chronic hyperglycemia. T2D is a
result of insulin insensitivity among peripheral tissues, leading to the eventual lack of
insulin secretion and hyperglycemia (2).
Participating in exercise is recommended for individuals with diabetes as a means
of long-term treatment of the disease. Due to impairment of glycemic control and the
variable energy demands exercise requires, diabetic athletes must work closely with their
coaches, trainers, and doctors to monitor glycemic control. These parties should consider
supplementation, along with standard diabetic care when determining an effective meal
plan for the athlete.
Amino acid (AA) supplementation, specifically leucine supplementation is an
interesting topic when it comes athletes in general. It is a branched chain amino acid
(BCAA) that is known to increase protein synthesis following exercise (3). An increase in
protein synthesis could lead to an increase in muscle mass, which could ultimately lead to
an increase in athletic performance. Not only will leucine supplementation enhance
protein synthesis, but also its presence in the plasma may be positively correlated with
insulin release. When insulin activity is heightened, muscular stores of glycogen will
increase (4). An increase of glycogen stores, will allow for faster recovery time, and
therefore leading to better performance.

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Luecine supplementation in diabetic athletes is an even more interesting topic. As
an insulin secretagogue, leucine increases the amount of insulin secreted from β cells. An
insulin secretagogue is a substance that promotes insulin secretion (2). While this would
have no effect on athletes with T1D, those with T2D could experience an increased
glycemic control due to increased insulin levels, leading to increased glucose uptake into
peripheral tissues. The increase in glycemic control may allow to the athlete to perform
better.
Luecine supplementation has been a widely researched topic using mice, rats,
athletes, and diabetics as subjects. Most of the research tends show leucine
supplementation is beneficial in the management of blood glucose levels and the increase
in protein synthesis. Both of which lead to higher athletic performance.
In rats that were fed a high-fat diet supplemented with leucine, they experienced
an increase expression of upcoupling protein-3, better sensitivity to insulin, more
efficient gluconeogensis, and preservation of their islets of Langerhans. Uncoupling
protein-3 is an enzyme involved in fatty-acid oxidation. Sensitivity to insulin will result
in a greater uptake of glucose by the muscle. Gluconeogenesis will provide glucose that
will eventually be transported to the muscle for energy. The islets of Langerhans contain
cells that secrete insulin. The combination of these factors resulted in protection of
insulin insensitivity and regulation of adiposity levels in rats (5). Additionally, a similar
study resulted in reduction in hyperocholesterolemia in mice when fed a high-fat diet
supplemented with luecine (6). Whey protein in addition with leucine supplementation
has been shown to also decrease insulin resistance and antioxidant stress without
changing the weight of nonobese rats (7).

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Another study, which observed the changes in glucose homeostasis in rats infused
with leucine. The study showed leucine infusions improved glucose homeostasis through
a biomechanical pathway (8). In a separate study, rats with induced muscle atrophy and
insulin resistance underwent luecine supplementation coupled with resistance exercise.
This study’s results differ from much of the other research; resistance exercise improved
insulin resistance in the presence of atrophy, but leucine actually made the condition
worse (9). Another opposing finding from a study done by Xiao et al. determined that
leucine deprivation actually improved insulin sensitivity (10).
It has been shown that luecine supplementation also improves protein nutritional
status. So in conditions of extreme weight-loss, luecine limits the amount of protein
waste (11). In a study done by Anthony et al. leucine supplementation was shown to
increase muscle protein synthesis by 53% in rats compared to the control (12). Also,
leucine as a secretagoue stimulates an increase of Ca2+ concentrations inside the fetal β
cell of a rat. Ca2+ is one of the key cellular components for muscle contraction (13).
The rodent studies for the most part conclude that leucine improves glycemic
control and enhances molecular functions in skeletal muscle. An increase in glycemic
control can raise the muscle’s store of glycogen, which can be hydrolyzed for energy use.
Enhanced molecular functions in skeletal muscle can lead to more efficient energy
utilization, leading to improved performance.
A human study observed the effects of increased AA plasma concentrations on
seven healthy male volunteers. Krebs et al. concluded that the AAs contribute to insulin
resistance in peripheral tissues (14). This conflicts with other studies like the one done by
Parket et al., which found that a high protein diet was successful in improving glycemic

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control (15). Other studies show that leucine-in addition to improving glycemic control-
also enhances muscle recovery post-exercise (16) as well as enhances athletic
performance during exercise (17).
Methods
Study Population
Inclusion Criteria: The study will include adult males aged 18-35, with type 1 or type 2
diabetes, which participate in recreational resistance exercise. The age range is narrow
enough to expect similar performance from the participants, but also broad enough to be
representative. Males are the gender of choice because a greater proportion of the male
population participates in recreational resistance exercise. Participation in resistance
exercise is required because that is how athletic performance will be measured and it is
easily quantified. Exclusion Criteria: Any individual that is not male, under the age of 18,
over the age of 35, does not have type 1 or type 2 diabetes, and who does not participate
in resistance exercise.
Sampling Method: Flyers will be placed around campus in places of high traffic-
especially the recreation centers-in hopes of finding volunteers. The flyers will contain
information regarding how to take part in the study. The respondents will be required to
fill out a simple yes/no style survey asking about their gender, age, whether or not they
have diabetes, and if they participate in resistance exercise and how often.
Study Group Assignment: The goal number of participants is 30 adult males that meet the
inclusion criteria. There will be two groups, the experimental group and the control
group. The experimental group will receive leucine supplementation following resistance
exercise while the control group will be given a placebo substance. The participants will

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be randomly assigned to either the experimental or control group. The investigators will
not be aware of which group is which, to eliminate potential bias.
Study Enrollment Procedures: Information on how to enroll in the study will be found on
the flyers placed around campus. It will instruct the participants to contact the
investigators and complete a survey to make sure they meet the inclusion criteria. Once it
is determined who fits the inclusion criteria, those individuals’ answers will be further
evaluated to determine the best fits for the study. The individuals selected as the best fits
will then be contacted and told of where to meet the investigators so they may go over
any liability documents. The potential participants will meet with the investigators to go
over all possible outcomes that may result from the study. Once the participants agree,
they will sign a document and become officially enrolled.
Study Design
The true experimental design will be used to determine whether leucine supplementation
administered post-workout enhances athletic performance during a 12-week span. The
participants will be randomly assigned to either the experimental group (luecine
supplementation) or the control group (placebo). Limitations will also be in place to
ensure the investigators do not know which group is which. The participants will be
randomized, observed during a pre-test, given the luecine supplementation for 12-weeks,
and observed during a post-test.
Study Procedure: On the first and last day of the study the participants will undergo three
resistance exercise tests in the form of a one-repetition maximum effort of each lift. The
lifts will include the bench press, leg press, and overhead press. After the first session of
maxes, the participants will be instructed to continue training with a workout program

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designed by the study team to eliminate as much variability as possible. They will also be
instructed to take the leucine supplement post-work out around the same time every day
for consistency amongst participants. After the 12-week period of training and
supplementation, they will be tested again to determine whether the supplement improved
their performance or not.
Data Collection: The data being collected will be the participants’ performance on the
one-repetition maximum effort on each of the three lifts. The first lift performed for all
participants will be the leg press, the next will be the bench press, and the last one
performed that day will be the overhead press. After a 12-week period, this process will
be repeated in the same order to determine whether leucine supplementation aided in
increasing their lifts.
Data Analysis: After the data has been collected it will then be analyzed to see if there
were any significant changes from pre-test to post-test. The mean result from each lift
from the first session will be compared with the mean result from each lift from the
second session. To determine the statistical difference between the two sessions the
standard deviation will be used.
Anticipated Outcomes: Based on the prior research it is anticipated that luecine
supplementation will improve athletic performance in diabetic athletes. Luecine is a
BCAA that is known for increasing glycemic control and protein synthesis (2, 3). If the
athlete is managing their diabetes properly in combination with luecine supplementation,
it is expected that their one-repetition maximum effort will increase for each of the three
lifts after a 12-week period.
Study Limitations

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Internal Threats: Poor conduction of research by the investigators such as bias, inaccurate
data collection, inaccurate data analysis, etc.; failure of participants to comply with the
procedure by refusing to follow the suggested training routine, taking disproportionate
servings of the supplement, not trying as hard they can during the pre or post-tests, etc.
Another limitation could be that some of the participants are beginners, so any results
they see in increased performance could be due to the fact that as beginners it is easier for
them to make progress. Also, more experienced participants may find it harder to make
significant results. Injury during training is also a major concern for the participants
during this study as well as harmful conditions that may occur due to their diabetes.
Plan to Reduce Threats: To ensure the research study is conducted with good technique to
avoid bias from the researchers there will be strict guidelines put in place. It will be
difficult to make sure the participants follow the procedure because the investigators will
not be able to monitor them at all times. They will however, stay in contact with them via
email to encourage them to stay consistent with their training and supplementation.
Participants will be instructed on proper training and supplementation methods to reduce
the chances of injury or medical complications.
Study Implications
Diabetic athletes have much on their plate because of training, nutrition, and stress from
the sport that they participate in. In addition to properly managing their condition with
coaches, trainers, and doctors they should seek out possible supplementation options that
will make it easier to manage these things. Luecine provides an interesting supplement
option for diabetic athletes. If it is found to improve their performance it will become a
more desirable supplement for diabetic athletes. Because of an increased demand for

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leucine the commercial nutrition industry will produce more luecine supplements in
hopes of attracting new customers.
Conclusion
In conclusion, diabetic athletes should seek out leucine supplementation as a way to
improve their athletic performance. The prior research shows it increases glycemic
control as well as protein synthesis. Both of which may lead to increased athletic
performance. With that said, there still needs to be more research done specifically on
diabetic athletes supplemented with leucine because right now most of the research is
targeting at either rodents or non-diabetic athletes.

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References: (put into proper format)
1. Statistics About Diabetes. (2012, January 1). Retrieved November 26, 2014, from
http://www.diabetes.org/diabetes-basics/statistics/The Daily Management of
Athletes with Diabetes
2. Stuart M. Phillips (2012). Dietary protein requirements and adaptive advantages
in athletes. British Journal of Nutrition, 108, pp S158-S167.
doi:10.1017/S0007114512002516.
3. Welikonich, M., Nagle, E., Goss, F., Robertson, R., & Crawford, K. (2010).
Effect Of Carbohydrate-Protein Supplementation On Resistance Exercise
Performance, Perceived Exertion, And Salivary Cortisol. Medicine &
Science in Sports & Exercise, 586-587.
4. Binder, E., Bermúdez-Silva, F., André, C., Elie, M., Romero-Zerbo, S., Leste-
Lasserre, T., ... Aguila, M. (2013). Leucine Supplementation Protects from Insulin
Resistance by Regulating Adiposity Levels. PLoS ONE, 8(9), 1-12.
5. Zhang, Y., Guo, K., LeBlanc, R., Loh, D., Schwartz, G., & Yu, Y. (2007).
Increasing Dietary Leucine Intake Reduces Diet-Induced Obesity And Improves
Glucose And Cholesterol Metabolism In Mice Via Multimechanisms. Diabetes,
56, 1647-1654.
6. Tong, X., Li, W., Xu, J., Han, S., & Qin, L. (2014). Effects of whey protein and
leucine supplementation on insulin resistance in non-obese insulin-resistant model
rats. Nutrition, 1076-1080.

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7. Su, Y., Lam, T., He, W., Pocai, A., Bryan, J., Aguilar-Bryan, L., & Gutierrez-
Juarez, R. (2011). Hypothalamic Leucine Metabolism Regulates Liver Glucose
Production. Diabetes, 61, 85-93.
8. Nicastro, H., Zanchi, N., Luz, C., Moraes, W., Ramona, P., Filho, M., ... Lancha,
A. (2011). Effects of leucine supplementation and resistance exercise on
dexamethasone-induced muscle atrophy and insulin resistance in rats. Nutrition,
28(4), 465-471.
9. Xiao, F., Huang, Z., Li, H., Yu, J., Wang, C., Chen, S., ... Guo, F. (2011). Leucine
Deprivation Increases Hepatic Insulin Sensitivity via GCN2/mTOR/S6K1 and
AMPK Pathways. Diabetes, 60, 746-756.
10. Pedroso, J., Nishimura, L., Matos-Neto, E., Donato, J., & Tirapegui, J. (2013).
Leucine improves protein nutritional status and regulates hepatic lipid metabolism
in calorie-restricted rats. Cell Biochemistry and Function, 32(4).
11. Anthony, J., Reiter, A., Anthony, T., Crozier, S., Lang, C., Maclean, D., ...
Jefferson, L. (2002). Orally Administered Leucine Enhances Protein Synthesis in
Skeletal Muscle of Diabetic Rats in the Absence of Increases in 4E-BP1 or S6K1
Phosphorylation. Diabetes, 51, 928-936.
12. Weinhaus, A., & Poronnik, P. (1995). 13. Insulin Secretagogues, But Not
Glucose, Stimulate an Increase in [Ca2 ]i in the Fetal Rat β-Cell. Diabetes, 44,
118-124.
13. Krebs, M., Krssak, M., Bernroider, E., Anderwald, C., Brehm, A., Meyerspeer,
M., ... Roden, M. (2002). Mechanism of Amino Acid-Induced Skeletal Muscle
Insulin Resistance in Humans. Diabetes, 51, 599-605.

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14. Parker, B., Noakes, M., Luscombe, N., & Clifton, P. (2002). Effect Of A High-
Protein, High-Monounsaturated Fat Weight Loss Diet On Glycemic Control And
Lipid Levels In Type 2 Diabetes. Diabetes Care, 25(3), 425-430.
15. Kirby, T., Triplett, N., Haines, T., Skinner, J., Fairbrother, K., & Mcbride, J.
(2011). Effect of leucine supplementation on indices of muscle damage following
drop jumps and resistance exercise. Amino Acids, 1987-1996.
16. Welikonich, M., Nagle, E., Goss, F., Robertson, R., & Crawford, K. (2010).
Effect Of Carbohydrate-Protein Supplementation On Resistance Exercise
Performance, Perceived Exertion, And Salivary Cortisol. Medicine &
Science in Sports & Exercise, 586-587.

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