Study of life style habits on risk of type 2 diabetes.

BACKGROUND: Diabetes mellitus has become one of the great epidemics of our time. AIM: Characterized by derangement of carbohydrate, protein and fat metabolism. Diabetic patients may have some other habits like drinking, smoking, lack of physical activity. In the present study, we have tried to study the effect of all these habits on lipid profile and antioxidative enzymes, i.e., catalase and superoxide dismutase.
MATERIALS AND METHODS: Different kits and standard biochemical methods were used to estimate all these parameters.
RESULTS: Diabetics as well as diabetic individuals who were engaged in drinking, smoking and regular physical exercise showed a significant rise in glucose levels compared to normal subjects. Similarly, cholesterol, triglyceride and high-density lipoprotein cholesterol levels and activity of catalase were found to be increased in all diabetic subjects, but that of superoxide dismutase decreased as compared to normal subjects. In all cases, exercise has a beneficial effect. Furthermore, females were more prone to destructive effects of diabetes than males.
CONCLUSION: We can conclude that smoking and drinking by diabetic subjects further deteriorates the effects of diabetes, while regular physical exercise has beneficial effects.

INTRODUCTION

Diabetes mellitus is a metabolic disorder characterized by hyperglycemia and is one of the leading causes of death. Non-insulin dependent diabetes mellitus is partially of genetic etiology,[1] but it also strongly influenced by environmental factors, and life-style of the patients. Oxidative stress and overproduction of reactive oxygen species (ROS), which occur during diabetes, play important roles in cardiovascular morbidity and mortality.[2] All cells utilize molecular oxygen for metabolic purposes and are at the risk of being damaged by oxygen-derived free radicals and lipid peroxidation products. Complementary antioxidants provide defense against this oxidative injury. The antioxidant defense mechanisms range from low molecular-weight compounds (glutathione, tocopherols, selenium, and vitamin E) to complex enzymatic systems (superoxide dismutase, glutathione peroxidase and catalase). A disturbance of the cellular pro-oxidant/antioxidant balance in favor of the former may denote an oxidative stress.[3]

Diabetes is a complex disease where the carbohydrate and fat metabolism is impaired.[4] It is well known that diabetes is associated with an increased incidence of macrovascular complications, including coronary artery disease (CAD), and cerebrovascular and peripheral disease.[5] The elevated triglyceride (TG) levels may be caused by medical conditions such as diabetes, hypothyroidism, kidney disease, or liver disease. Dietary causes of elevated TG levels may include obesity and high intakes of fat, alcohol, and concentrated sweets. Several studies have indicated the high prevalence of hyperlipidemia, which may have harmful effect on the diabetic patients and, therefore, there is a need of monitoring serum lipid concentration in diabetic patients. Therefore, assessment of various lipid fractions in cases of diabetes mellitus may be of some help in the prognosis of patients and in preventing the possibilities of complication or secondary disorders.

Factors such as age, sex and certain aspects of life-style, including diet, level of physical activity, and level of diabetes control also affect lipid profile.[6] People who have type 2 diabetes tend to have high levels of triglycerides and low levels of high-density lipoprotein (HDL) and similar low-density lipoprotein (LDL) levels than people who do not have diabetes. Both sexes show an increase in lipoprotein levels as they age.

There are independent risks of diabetes with smoking and alcohol consumption. Epidemiological studies of alcohol intake and risk of type 2 diabetes have pronounced conflicting results.[7] Several studies have indicated that moderate drinkers had the lowest risk for diabetes, and non-drinkers and heavy drinkers had a higher risk. Excessive alcohol intake may contribute to excess intake and obesity, induction of pancreatitis, disturbance of carbohydrate metabolism, and impairment of liver function.[8] Smoking has also been identified as a risk factor for resistance, which can lead to diabetics.[9]

The importance of sedentary life-style as a risk factor for diabetes and of the protective effects of physical activity in the maintenance of diabetes has also been studied. Regular physical exercise enhances the antioxidant defense system and protects against exercise induced free radical damage.[10] On the other hand, intense exercise in untrained individuals overwhelms defenses resulting in increased free radical damage. Thus, the “weekend warrior” who is predominantly sedentary during the week but engages in vigorous bouts of exercise during the weekend may be doing more harm than good.[11]

MATERIALS AND METHODS

This retrospective study was conducted on subjects with/without type 2 diabetes mellitus. The patients (150) were matched for age, gender, glucose levels, and diabetes duration with 30 patients in each group. Patient selection was made during the period of 3 months. The subjects with blood glucose levels ≤110 mg/dl and who were neither on any medication nor having any other disease were taken as healthy controls. Type 2 diabetes mellitus was considered to be present if the fasting blood glucose was ≥126 mg/dl and the patient was using glucose lowering medication.

Subjects with any other disease, including diabetic complications and also those under antioxidant medication or lipid lowering drugs were excluded from the study. The diabetics were allowed their regular life styles.

All procedures followed were approved by the institutional ethical committee and were carried according to the Helsinki Declaration of 1975, as revised in 2000 and with the written consent and adequate understanding by all the volunteers after explaining the nature and purpose of the study. The fasting blood samples were procured from the known normal healthy (non-diabetic control) and diabetic subjects from the diabetic clinic.

All the investigations were performed in the serum of diabetic and control subjects. Following groups were made based on the life-style of diabetic subjects with the help of the questionnaire provided to them: Control; diabetes alone; diabetics involved in smoking; diabetics engaged in drinking; and diabetics doing exercise.

Blood samples procured were allowed to stand at room temperature for 30 min, centrifuged at 1500 rpm (revolutions per minute) and serum was separated carefully from the pellets.

Biochemical estimations

Cholesterol, triglyceride, and HDL-cholesterol (HDL-C) were estimated using the kits obtained from Reckon Diagnostics Pvt. Ltd. Baroda, India. The chemicals used in other parameters were obtained from Sisco Research Laboratories (SRL) Pvt. Ltd., Mumbai.

Glucose was estimated by the method of Trinder et al.[12] Triglyceride was estimated by the method of Cole et al.[13] Cholesterol was estimated by the method of Allain et al.[14] HDL-C was estimated by the method of Tietz et al.[15] Catalase was estimated in the kinetic mode at 240 nm in double beam ultraviolet spectrophotometer (Shimadzu) by the method of Luck.[16] The activity of superoxide dismutase was estimated according to the method of Kono.[17]

Statistical analysis

The comparison between control and various groups was done using ANOVA. P value <0.05 was considered significant.

RESULTS

Glucose levels were found to be elevated significantly in all the groups as compared to normal subjects. However, the increase in glucose levels was less pronounced in case of exercising diabetic subjects [Table 1]. When the glucose levels of males and females were compared, females were found to have much higher glucose levels (P < 0.05) than males [Table 2]. Cholesterol levels were found to be raised in all the groups, but this increase was significant (P < 0.001) only in the diabetic subjects and in the diabetics who were also engaged in drinking (P < 0.05) as compared to the normal ones. However, in all these cases, the cholesterol levels were found to be in the normal range. Similar trend was noticed in the levels of triglycerides and LDL-cholesterol (LDL-C) in all the groups [Table 3].

Table 1

Glucose values in different diabetic groups

Table 2

Effect of gender on glucose levels in diabetic subjects

Table 3

Effect of drinking, smoking and exercise on serum lipid profile in diabetic subjects

However, HDL-C levels were found to be decreased significantly in all the groups when compared to the normal individuals. When the lipid profile of the male and female diabetic subjects were compared, it was again noticed that females were more prone to the damage due to diabetes than the male subjects [Table 4].

Table 4

Effect of gender on lipid profile in diabetic subjects

Activity of catalase was found to have significantly increased in the diabetic patients (P < 0.01), in the diabetic subjects doing exercise (P < 0.001) and diabetics on drinking (P < 0.01) as compared to the healthy subjects. On the other hand, in the diabetics who are smoking also, the activity of catalase was found to be decreased, in comparison with the normal individuals [Table 5].

Table 5

Effect of drinking, smoking and exercise on the activity of catalase and superoxide dismutase in the serum of diabetic subjects

The activity of superoxide dismutase was found to be increased in patients with exercise but decreased in all other groups. However, the decrease was found to be significant (P < 0.01) only in case of diabetes with smoking patients [Table 5]. Females were found to have high catalase and superoxide dismutase activity than in the males, but this rise was not statistically significant in both cases [Table 6].

Table 6

Effect of gender on the activity of catalase and superoxide dismutase in the serum of diabetic subjects

DISCUSSION

It is a well-established fact that diabetes is a risk factor for cardiovascular disease.[5] Cardiovascular complications are the leading cause of morbidity associated with diabetes. Since diabetes mellitus has been associated with lipid abnormalities,[4] it has been customary to utilize the measurement of blood glucose, triglycerides, total cholesterol, HDL-C and LDL-C in profiling the risk of diabetes. Impairment of insulin secretion leads to an excessive and prolonged rise in glucose concentration. As observed in our study, diabetic smokers also had higher blood-glucose levels as compared to the normal individuals which may be because smoking has been known to stimulate the release of the counter regulatory hormones and consequently, cause temporal elevation in blood-glucose levels.[18] Alcohol intake by diabetic individuals also showed a significant elevation in the blood-glucose levels in their serum, and this rise was even more than that observed in case of only diabetic individuals as compared to the normal ones. However, contradictory studies also showed that there is no dose–response relation between alcohol intake and glucose levels.[19] Glucose levels were also found to be elevated in the exercising diabetic persons, but this increase was less prominent than was observed in other groups. This shows that regular physical activity can prevent or postpone the onset of type 2 diabetes. It was also confirmed in the present study that females are more prone to developing diabetes than the males.

There is growing evidence that excess generation of highly reactive free radicals, largely due to hyperglycemia, causes oxidative stress, which further exacerbates the development and progression of diabetes and its complications. Present study indicated a significant increase in the levels of cholesterol, triglycerides, and LDL cholesterol and a significant decrease in HDL-C in the diabetic individuals as compared to the normal ones but these raised levels were again found to be in the normal range. This may be due to the restriction in their dietary habits, i.e., their dietary habits may be adequate to maintain normal lipid levels. However, contradictory reports are also available, which show abnormalities of serum lipids in untreated and treated diabetics by Indian and Foreign workers.[20] Further it was observed that the serum lipids in diabetic patients, including total cholesterol, was significantly higher in females than in males. Even the triglycerides and LDL-C were also found to be significantly higher in both sexes. Several studies also showed that the men showed higher serum triglycerides, lower HDL-C than did women.[21] In the present study, smokers had higher levels of serum total cholesterol and LDL-C and lower levels of HDL-C than non-smokers as was reported by other studies also.[22] Thus, it is speculated that insulin resistance in the subjects. This might be attributable to increased effects of smoking on other physiological factors, such as body-fat distribution, in younger people. Prevention of smoking in early life might be an important aspect of prevention of non-insulin dependent diabetes mellitus, as well as of cardiovascular disease. Exercising diabetics showed almost normal levels of all the lipids as was found in the normal individuals. While comparing the lipid levels of males and females, it was found that females are more prone, i.e., females have higher levels than males, thus indicating that diabetes increases the risk of developing heart disease more in women than in male.[23]

Hyperglycemia also results in increased production of the ROS within numerous biochemical pathways that can lead to an increase in antioxidative enzymes. This state of excess generation of free radicals, observed both in type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes causes oxidative stress. This oxidative stress exuberates the development and progress of diabetes and its complications. Recently, a hypothesis was proposed that suggested that all the above processes involved in the elevation of oxidative stress are a consequence of superoxide by mitochondrial respiratory chain during hyperglycemia. In the present study, significantly higher activity of the antioxidant enzymes, i.e., catalase[24] and decrease in the activity of superoxide dismutase were found in diabetic patients as compared to the normal individuals who were taken as control. Superoxide dismutase activity is undoubtedly important to the regulation of oxidative stress in diabetes. However, there is a variation as to the status of this enzyme in the diabetic state. Some studies have reported decreased superoxide dismutase activity,[25] while others have shown increases or no change in the enzyme activity.[26]

This finding suggests that both walking and more physical activity are associated with reductions in risk of diabetes[5] and activity may slow the initiation and progression of type 2 diabetes and its cardiovascular sequelae via favorable effects on body weight, insulin sensitivity, glycemic control, blood pressure, lipid profile, endothelial function, and inflammatory defense systems. However, more studies are needed to determine the intensity, frequency, and duration of exercise that is more effective in prevention of diabetes. Thus, although our observational study falls short in unraveling cause–effect relationships, but it is tempting to speculate that for adequate treatment of diabetes, increased emphasis on antioxidative enzymes and lipid profile, either pharmacologically or through life-style modifications, may constitute a valuable means to attenuate diabetes risk in apparently healthy population.