Metabolic Response of Diabetic Patients with Obesity and No Obesity during Bruce Treadmill Test ()
1. Introduction
In recent years, Western lifestyle diseases, such as diabetes mellitus, arterial hypertension, obesity, cardiovascular diseases, etc. have been made epidemic in our country like others. These diseases, to great extent, are due to food overconsumption, poor body training and unhealthy diets [1] [2] [3] [4]. Epidemiological and clinical studies in Greece (ATTICA study) [5] [6] [7] show that the frequency of the diseases, depending on the social and economic conditions, the age and the lifestyle of the population like similar studies in other countries.
In Europe, there are 48 million people with diabetes (7.8% of the population) while, in relative studies predicting that by the end of 2025, the percentage will increase to 20% and the disease will be offended increasingly young and obese individuals. These statistics concern Greece also, which holds one of the first places, in the frequency of obese children [6].
Today obesity is considered a “disease” and a health problem, because it is associated with serious diseases like diabetes and cardiovascular diseases, and is one of the risk factors of metabolic syndrome. Obesity is not combined only with the quantity and the poor quality of food, but more often is combined with a sedentary lifestyle and non-fitness. Genetic factors are responsible for the obesity and diabetes but these diseases would not have occurred if there was not a corresponding morbidly environment. It is known from international studies that even small changes in daily lifestyle (for instance improving the quality and reducing the amount of food and introducing physical activity in the daily program) contribute to the reduction of hyperglycemia, hypertension and BMI [1] [2] [3].
The latest WHO recommendations (2020) in all age groups of healthy subjects and individuals with chronic diseases (overweight, obesity, diabetes, hypertension, atherosclerotic, cardiovascular disease, cancer) report that the physical exercise must be at least 75 - 150 minutes of vigorous-intensity aerobic physical activity; or an equivalent combination of moderate- and vigorous intensity activity throughout the week for substantial health benefits. As part of their weekly physical activity, older adults with these chronic conditions should do varied multicomponent physical activity that emphasizes functional balance and strength training at moderate or greater intensity on 3 or more days a week, to enhance functional capacity and prevent falls [8]. Brisk walking seems to be the preferred aerobic exercise as improves the metabolic biomarkers (4). The same is happening with Yoga exercise where metabolic biomarkers and oxidative stress biomarkers are improved too [9].
Based on all mentioned before and because of diabetes, obesity and hypertension are major public health problems in our country, we studied the changes caused by physical exercise on biochemical and hormonal parameters in diabetic, obese and hypertensive patients. In spite of measuring metabolic biomarkers during certain training sport periods, we measured metabolic biomarkers at a given time and intensity exercise done during the stressing test by BRUCE [10].
2. Materials and Methods
The study took place in the Fatigue Laboratory of Cardiological Clinic of General Hospital of Zakynthos island. 59 patients participated, 39 men (66.1%) and 20 women (33.9%). Their age varied between 33 to 80 years old. We separated them in four groups according to their Body Mass Index (BMI) and if they suffered from type 2 diabetes mellitus (DM2) or not (Tables 1-3).
Among the 59 participants of our study 23 were diabetics with DM2 while the rest of them (36 persons) were non-diabetics. The average age of diabetics was 62 ± 9 years old, while the age of non-diabetics was 56 ± 12 years old. The two groups (DM2 vs non DM2) hadn’t statistical important differences between their age (p = 0.060) and BMI (p = 0.293). On the contrary the participants with DM2
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Table 1. The four patient’s groups of our study.
1Persons with glucose levels > 115 mg/dL, 2Persons with BMI > 27.
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Table 2. The group’s values of age and BMI.
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Table 3. The group’s values of age and BMI.
suffered more often from hypertension than of non DM2 participants with statistical significance (p = 0.002).
The BRUCE tests were done according to the international guidelines. Their duration (5 to 15 minutes) and their stress adjusted to each patient’s age and physical condition. All blood determinations were done 30 minutes before the Bruce test and just after the end of it. The blood tests included glucose, urea, creatinine, potassium, sodium, cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, CRP, CK, CK-MB, LDH, CRP, TSH, FT3, FT4, T3, T4 C-peptide, insulin, growth hormone, cortisol and renin/aldosterone. All individuals had CRP values as negative.
The concentrations of the results are presented as: mean value ± standard deviation (Tables 4-6). We converted almost all units to SI (moles) in order our
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Table 4. Comparisons of Diabetics according to BMI (Diabetic normal body weight persons [group A] vs Diabetic overweight persons [group B]). The table includes number of participants (N), average, standard deviation and the level of significance (P [Wilcoxon signed test]) of several laboratory tests before and after BRUCE test.
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Table 5. Comparisons of Non-Diabetics according to BMI (Non-Diabetic normal body weight persons [group D] vs Non-Diabetic overweight persons [group C]). The table includes number of participants (N), average, standard deviation and the level of significance (P [Wilcoxon signed test]) of several laboratory tests before and after BRUCE test.
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Table 6. Comparisons of hypertensive vs non-hypertensive persons. The table includes number of participants (N), average, standard deviation and the level of significance (P [Wilcoxon signed test]) of several laboratory tests before and after BRUCE test.
results to be compared to other studies. All statistical tests were done by Wilcoxon signed test since all statistical distributions were no normal. The statistical package was SPSS v.28 (academic license).
3. Results
The results of the study were collected in three tables represented five different comparisons or our groups according to BMI, the presence DM2 and High Pressure.
Some of the participants suffered from arterial hypertension (50% of the diabetics and 15% of the non-diabetics). This finding led us to study if our test’s results differed between hypertensive and non-hypertensive persons (Table 6).
The muscular work of Bruce treadmill had negative correlation with age and no correlation with other physical conditions of the participant like hypertension. dyslipidemia and coronary disease. The negative correlation of the muscular work with the age complies with previous studies which proved that the maximum aerobic capacity (VO2max) decreases every new decade with an accelerated rate [10]. The participants with prolong endurance times in Bruce test (t > 10 min) were 33 - 54 years’ old. These persons either they were working in agricultural industry or other high demanding muscular jobs either they were persons with daily exercise programs. All these had the highest capacity of aerobic work and the better performance in Bruce test.
4. Conclusions
Carbohydrates. The levels of glucose decreased in all participants’ groups (statistical significance p < 0.01). The decrease is due to glucose overconsumption from the working muscles. It is known that the muscles’ reliance on the glucose is parallel to the decrease of glycogen’s reserves and to the intensity of the muscular effort [11].
Insulin/C-peptide. The levels of insulin and C-peptide are supposed to be increased as a feedback to the decrease of glucose. This happened in groups A, C and D (insulin) and in group B (C-peptide). Their differences, before and after Bruce test, were not statistical important.
Lipids. Lipids and LDL-cholesterol are supposed to be decreased after extensive exercise. Triglycerides and HDL had a statistical important reduction (P < 0.05), on the contrary, to the total cholesterol and LDL-cholesterol which change was not statistically important.
Thyroid hormones. Despite the physical condition of the participants (DM2, obesity, arterial hypertension) the level of TSH decreased after Bruce test. The overweight participants had a larger reduction of TSH than the normal weight persons. In order to find out the reasons for the TSH decrease, we studied the correlation between the TSH levels and age, TSH and BMI, TSH and duration of Bruce test and TSH of diabetics versus the TSH of non-diabetics. The correlation between BMI and TSH in diabetics before and after the Bruce test had statistical significance (r = 0.518, p < 0.05). The participants with DM2 increased the levels of renin and aldosterone after the completion of the muscular work. Both increases have statistical significance (p < 0.05). After the end of muscular activity, the levels of growth hormone increased too. These differences between diabetics and non-diabetics were statistically important (p < 0.05) only for the non-obese persons. The reason for TSH change is probably its feedback mechanism. Since the production of TRH hormone is decreasing during the exercise and the changes for thyroid metabolism during the stress [12] [13]. Furthermore, the results of this study confirmed the theory about the involution of the thyroid gland in body exercise effects.
Cortisol. Cortisol is supposed to be increased because of the stress and the anxiety of the patients during the Bruce test [14] [15] [16]. This didn’t happen in our experiment. Cortisol levels have a wide biological variation, a larger number of participants would probably provide more understanding results.
Growth hormone. Growth hormone increased in all groups (A, B, C and D) after Bruce tests. The differences were statistical important between non-obese persons. According to bibliography growth hormone increases during exercise since it stimulates fuel metabolism and decreases lipids [17]. Obesity blocks the normal growth hormone’s stimulation during exercise [17] [18]. This proved in our study too.
Renin/aldosterone. Renin and aldosterone are supposed to be increased during the muscular work which activates the hormone mechanism of renin/ angiotensin/aldosterone which tends to restore the blood pressure and increase the concentration of renin and aldosterone [19]. In our study, that proved true only between the diabetics. In diabetics, the increased levels of renin/aldosterone Diabetics increased values after Bruce tests had statistical importance (p < 0.05). Non-Diabetics without obesity had lower levels of aldosterone (P < 0.05) but their levels of renin increased like diabetics (P < 0.05).
Urine protein. The levels of urine microalbumin, before and after Bruce test, increased in all groups of our study. Among the diabetics with BMI < 27 and the non-diabetics with BMI > 27 the increase was statistically important (p < 0.05). The diabetics with BMI > 27 had already higher values of urine microalbumin than the non-diabetics, before the test, which become even higher after the test. Initially, these persons had small amounts of protein in urine strip, but these protein levels increased during the muscular work. We observed also that hypertensive persons had increased levels of microalbumin after the Bruce test. In one case, the increased values of microalbumin had a relation to chronic renal failure. Urinalysis revealed that some persons had “trace” levels of urine protein after the Bruce test. Persons with low values of urine microalbumin before the test and high values (>30 mg/L) after the test had also a hypertensive response to Bruce test [20] [21] [22].
5. Discussion
Nowadays, physical exercise is considered part of treatment protocol for diabetes mellitus, arterial hypertension and obesity. The triptych: consulting, diet (under specialists’ supervision) and exercise, is capable to decrease the risk of DM2 in 60% of non-diabetics with impaired glucose tolerance [9] [11]. Additionally, the medium level physical exercise improves significantly the glycemic tests’ results in persons with DM2 as diabetics who follow an aerobic exercise program of medium intensity have decreased death rates [23]. An obesity therapeutic program should include physical exercise besides the decrease of received calories. This combination would have more possibilities of success compared to programs that ignore the physical exercise [24] [25].
Body exercise influences the levels of blood substances. This influence depends on exercise’s intensity, duration, participation of particular muscles, kind of exercise (continuous or not), environmental conditions (temperature, moisture, etc.) and the dietary preparation of the person [26] [27]. This study attempted to prove that physical exercise, even with short duration like that of Bruce test, has beneficial results in persons with DM2, obesity and arterial hypertension, as well as in normal persons. These beneficial results can be summarized as follows: decrease of glucose, triglycerides and TSH, increase of HDL-cholesterol. These parameters are considered the target of every therapeutical intervention in patients with DM2, obesity and/or arterial hypertension.
Furthermore, persons with mild to medium primary hypertension, the body exercise decreases systolic and diastolic hypertension [28]. It is well known that in general population the ratio of hypertension in diabetics is twice more than in normal persons. This difference is due to the insulin resistance of the patients with DM2 [29]. Specifically, the percentage of hypertensive patients with DM2 patients varies between 30% - 50%, while the percentage of hypertensive patients with impaired glucose tolerance (IGT) varies between 20% - 40% [11] [29]. During Bruce test the produced muscular work is too high and the organism loses its ability to produce energy only from glucose’s metabolism. So, the organism covers the needs of muscular cells’ energy from the metabolism of carbohydrates and fats [30]. During the first stages of muscular work the muscle’s glycogen and blood glucose are rapidly consumed and as the muscular exercise is continuing and the perfusion of the muscles is increasing, glycogen and glucose are replaced by other sources of energy like the free fatty acids, which is the basic source at this stage [31].
On the contrary to the reduction of glucose, there was no statistical significance in the reduction of cholesterol and LDL-cholesterol. Probably this is due to the short time interval of the muscles’ work. It is proved that the prolonged muscles’ work decreases more effectively the levels of total cholesterol and LDL-cholesterol [32].
The extremely high levels of urine microalbumin, after Bruce test, are due to the increase of arterial pressure because of the stress. The increase of urine microalbumin is related to diabetic nephropathy [20] and hypertension (systolic arterial pressure and 24h variation of systolic and diastolic arterial pressure) [21] [22]. Both are considered early signs of kidney disease.