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Abstract

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Disclosure:
  8. References

J Clin Hypertens (Greenwich). 2010;12:741–745. ©2010 Wiley Periodicals, Inc.

This study was designed to evaluate the prevalence of the metabolic syndrome (MetS), impaired fasting blood glucose (IFG), insulin resistance (IR), hypertriglyceridemia (HTG), and low high-density lipoprotein cholesterol (HDL-C) in adult Uygur and Kazak populations. Questionnaires, blood pressure, anthropometric measurement, and fasting glucose were evaluated. The age-adjusted prevalence of MetS and IFG was 3.43- and 1.47-fold higher, respectively, in Uygurs compared with Kazaks. The prevalence of IR and HTG was 1.33- and 2.22-fold higher, respectively, in Uygurs compared with Kazaks. In addition, the prevalence of low HDL-C was 4.05-fold higher in Uygurs compared with Kazaks. These data depicted greater risk for cardiometabolic syndrome in Uygurs compared with Kazaks. In addition, all prevalence with the exception of low HDL-C was greater in men compared with women in both ethnic groups. For body mass index (BMI) <24, 24 to 28, and ≥28 kg/m2, the prevalence of MetS, HTG, and low HDL-C was higher in Uygurs than Kazaks at the same BMI level. For individuals with a BMI between 24 and 28, the prevalence of IR but not IFG was significantly greater in Uygurs than Kazaks. At BMI ≥28, neither IFG nor IR was overtly different between the two ethnic groups.

The metabolic syndrome (MetS) is a cluster of diseases in individuals with high risk for heart disease and diabetes. Based on the Third Report of the Adult Treatment Panel National Cholesterol Education Program (NCEP-ATPIII) guideline, diagnosis of MetS requires presence of 3 of the following 5 criteria: hypertriglyceridemia (HTG) (triglycerides [TGs] ≥1.7 mmol/L); low high-density lipoprotein cholesterol (HDL-C) (HDL-C <0.9 mmol/L for men, <1.0 mmol/L for women), central obesity (waist circumference ≥102 cm for men, ≥88 cm for women), hypertension (systolic blood pressure ≥130 or diastolic pressure ≥85 mm Hg), and fasting hyperglycemia (fasting glucose ≥5.6 mmol/L).1,2 In addition, a level of homeostasis model assessment of insulin resistance (HOMA-IR) 2.73 or higher was deemed as high prevalence of insulin resistance (IR).1 It has been established that individuals with impaired fasting blood glucose (IFG) and HTG are more prone to the onset and development of type 2 diabetes.3 Recent epidemiologic evidence has revealed a rather high prevalence of both diabetes and hypertension in the Xinjiang region of China, albeit with an overt difference in the incidence of the two comorbidities between the two ethnic minorities in the region, namely the Uygur and Kazak ethnic populations.4,5 The two ethnic groups display different living styles and dietary regimen, which may contribute to the disparity in the prevalence of diabetes and hypertension between the two groups. Uygurs usually manifest a higher incidence of type 2 diabetes despite a reasonable food menu. To explore the mechanism of action behind the discrepancy in diabetes and hypertension between the Uygur and Kazak ethnic populations, the present study was designed to evaluate the epidemics of MetS, IFG, IR, HTG, and low HDL-C in Uygur and Kazak populations from multiple counties of the Xinjiang region.

Methods

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Disclosure:
  8. References

A cross-sectional design and a 3-step stratified sampling method were employed. At the initial stage, the entire Xinjiang province was stratified into the northern and southern Xinjiang areas. Different counties of Uygur and Kazak residential areas were selected from northern and southern parts of Xinjiang. During the second stage of sampling, several townships or districts were selected from each of the counties and cities. At final stage, individuals were chosen from the selected townships or districts. A total of 1379 Uygur (631 men and 748 women) and 1123 Kazak (472 men and 651 women) individuals aged 30 to 70 years were recruited from southern and northern Xinjiang areas. A set of questionnaires, including demographic information, family history of hypertension, type 2 diabetes, cardiovascular diseases, and cancer, were collected from all participants. Information regarding lifestyle, exercise, smoking, and alcohol consumption was also recorded. After 10 to 12 hours of fasting, peripheral blood was taken and put into the given vacuum tube between 8 am and 10 am. Three independent measurements from blood pressure and anthropometric indices including height, weight, and waist circumference were obtained by trained and certified health professionals using standard protocols. Blood glucose was determined after overnight fasting using a modified hexokinase enzymatic method. Written informed consent was obtained from all participants prior to data collection and measurements. The NCEP-ATPIII guideline diagnosis criteria and International Diabetes Federation criteria2 were adopted to define MetS or its components. We confirmed that all applicable institutional and governmental regulations concerning the ethical use of human volunteers were in compliance for this study, which were approved by the ethical committee of Xinjiang Medical University. Data were presented at mean ± standard deviation. All statistical analyses were performed using SPSS software (version 15.0; SPSS, Chicago, IL). Independent t test was used for parametric data, and the chi-square test was used to compare the prevalence of a given disease. A P value <.05 was considered statistically significant.

Results

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Disclosure:
  8. References

Table I describes the general characteristics of participants from the Uygur and Kazak ethnic groups. Age, sex, and waist circumference were comparable in participants from the two ethnic groups. The Kazaks had greater body weight, body mass index (BMI), systolic blood pressure, diastolic blood pressure, and HDL-C levels compared with the Uygur group (P<.05). On the other hand, the Uygurs displayed higher levels of fasting blood glucose and TGs than the Kazaks (P<.05). Levels of total cholesterol and low density lipoprotein were similar between the two populations. The age-adjusted prevalence of MetS was 10.3% and 3.3% and the prevalence of IFG was 10.6% and 7.2% in Uygurs and Kazaks, respectively. The prevalence of IR was 42.6% and 31.9% in Uygurs and Kazaks, respectively. The prevalence of HTG was 53.6% and 24.1% in Uygurs and Kazaks, respectively. In addition, the prevalence of low HDL-C was 49.1% and 12.1% in Uygurs and Kazaks, respectively. These data suggest that the overall prevalence of diabetes and hypertension is higher in the Uygurs than the Kazaks (P<.05). With the exception of HDL-C, the prevalence of all other risk factors was overtly higher in men compared with women in both ethnicities (P<.05). Our data also suggest that the prevalence of MetS and IR rise with age in both ethnic groups although the prevalence declines after the age of 60. Interestingly, the prevalence of low HLD-C decreased with increased age in both ethnic groups (P<.05) (Table II).

Table I.   General Characteristics of the Participants
 UygurKazak
  1. Data were mean ± SD. n=1379 and n=1123 for Uygur and Kazak groups, respectively. aP<.05 vs the Uygur group.

Age, y52.0±12.249.3±12.3
Male, %46.441.6
Body weight, kg68.1±13.175.5±14.5a
Body mass index, kg/m226.2±4.529.1±5.0a
Waistline, cm97.8±12.194.0±9.7
Systolic blood pressure, mm Hg130.7±22.5138.3±26.3a
Diastolic blood pressure, mm Hg82.9±13.188.4±15.7a
Total cholesterol, mmol/L4.3±0.95.0±0.7
High-density lipoprotein cholesterol, mmol/L0.98±0.241.4±0.5a
Low-density lipoprotein cholesterol, mmol/L2.5±0.72.2±1.0
Triglycerides, mmol/L2.0±1.41.4±1.3a
Fasting blood glucose, mmol/L6.6±3.25.1±1.4a
Table II.   Prevalence of Risk Factors by Age
Age, yMetabolic SyndromeImpaired Fasting Blood GlucoseInsulin ResistanceHypertriglyceridemiaLow High-Density Lipoprotein Cholesterol
MaleFemaleTotalMaleFemaleTotalMaleFemaleTotalMaleFemaleTotalMaleFemaleTotal
Uygur
 30–39 5.0 5.15.0 18.08.113.137.035.436.269.030.349.952.056.654.3
 40–4910.78.89.76.16.96.545.040.642.859.547.953.740.553.547.0
 50–5918.015.716.97.19.48.356.452.054.260.761.461.041.746.644.2
 60–7015.913.414.813.2 14.413.740.245.542.649.257.452.940.255.547.1
Age-adjusted11.09.610.312.09.1 10.6 43.4 41.8 42.6 61.2 45.7 53.6 44.9 53.6 49.1
Kazak
 30–393.00.91.911.90.96.536.614.025.531.716.724.310.915.813.3
 40–494.82.23.612.11.87.143.522.333.234.719.627.48.122.315.0
 50–598.73.96.410.04.47.349.342.045.820.714.417.78.79.99.3
 60–702.14.53.24.114.49.019.648.533.429.919.725.05.29.17.0
Age-adjusted4.22.33.310.43.87.237.625.931.930.417.524.18.915.512.1

To better evaluate the effect of body mass configuration on MetS, IFG, and HDL-C in Uygur and Kazak populations, the prevalence of these risk factors were compared in 3 different BMI categories. For BMI levels <24, 24 to 28, and ≥28 kg/m2, the prevalence of MetS was 31.7%, 52.4%, and 64.3% for Uygurs and 12.3%, 30.9%, and 46.2% for Kazaks, respectively. The prevalence of IFG was 5.9%, 8.5%, and 11.1% for Uygurs and 0.5%, 4.2%, and 8.5% for Kazaks, respectively. The prevalence of IR was 33.9%, 46.8%, and 51.7% for Uygurs, and 5.7%, 22.1%, and 48.2% for Kazaks, respectively, for BMI levels of <24, 24 to 28, and ≥28 kg/m2. The prevalence of HTG was 44.2%, 57.7%, and 59.6% for Uygurs and 7.5%, 16.1%, and 26.1% for Kazaks, respectively, for the 3 BMI groups. Finally, the prevalence of low levels of HDL-C was 53.7%, 47.7% ,and 44.8% for Uygur, and 14.5%, 12.2%, and 12.4% for Kazaks, respectively, among the 3 BMI groups. For all BMI groups, the prevalence of MetS, HTG, and low HDL-C was all greater in Uygurs than Kazaks at the same BMI level (P<.05). At the BMI level of 24 to 28, the prevalence of IFG was not significantly different between the two ethnic groups, although the prevalence of IR was higher in Uygurs than Kazaks. When BMI rose to ≥28, neither IFG nor IR was significantly different between the two ethnic groups (Table III).

Table III.   Prevalence of Risk Factors at Different Body Mass Index Levels
Body Mass Index, kg/m2Metabolic SyndromeImpaired Fasting GlucoseInsulin ResistanceHypertriglyceridemiaLow High-Density Lipoprotein Cholesterol
MaleFemaleTotalMaleFemaleTotalMaleFemaleTotalMaleFemaleTotalMaleFemaleTotal
Uygur
 <24 28.8 34.1 31.7 4.37.55.933.632.533.944.743.944.245.160.953.7
 24–285252.752.48.98.18.550.343.146.858.956.457.7 46.248.747.4
 ≥2859.166.264.39.8 12 11.1 50.2 52.7 51.7 65.5 55.5 59.635.4 51.3 44.8
Kazak
 <247.615.712.300.90.57.610.115.75.19.27.515.313.814.5
 24–2821.838.530.98.114.228.117.122.120.612.516.16.217.112.2
 ≥2841.749.146.211.56.68.554.643.948.233.82126.17.515.612.4

Discussion

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Disclosure:
  8. References

The main finding from our study indicates that the overall prevalence of MetS, IFG, IR, HTG, and low HDL-C is greater in the Uygurs compared with Kazaks. Epidemiologic studies have revealed that Kazaks tend to consume more meat and fewer vegetables, whereas Uygurs prefer to consume more fruit and vegetables than meat products.5 Nonetheless, there is a higher prevalence of diabetes in Uygurs than Kazaks in the Xinjiang region of China. Data from our present study indicate that Uygurs display a greater prevalence of MetS, IFG, IR, HTG, and low HDL-C than the Kazaks, supporting the notion of a greater incidence of diabetes in the Xinjiang region.

An earlier report suggested that the Uygurs display a significantly greater waist-to-hip ratio than the Kazaks even at similar BMI levels.3 Our previous data revealed that waist circumference in the Uygur population is significantly greater than in the Kazak population at the similar BMI level,6 indicating a higher adiposity in Uygurs than Kazaks. Uygurs are known to bear more fat tissue in the abdominal region, namely central adiposity, and are more prone to type 2 diabetes and associated complications.4–6 Therefore, it is natural to speculate that the difference in waist circumference may serve as a crucial factor to predict the risk prevalence of overweight, obesity, and cardiovascular diseases between the two ethnic groups.7

Data from our study suggested that the Kazaks have lower TGs associated with normal total cholesterol levels compared with the Uygurs. Earlier studies indicate that Kazaks appear to consume more horse meat with a higher unsaturated-to-saturated fatty acid ratio,5 which may contribute to the normal TG and higher HDL-C levels. Nonetheless, the precise mechanism of action underscoring the ethnic variation in TG and HDL-C levels are not understood. HTG is a unique diagnostic marker for IR and other cardiovascular diseases.8 It was reported that IR is closely associated with impaired lipoprotein lipase activity in non-Hispanic and Mexican Americans.9,10 At present, little information is available for the expression and activity of TG clearing enzyme lipoprotein lipase9 between Uygurs and Kazaks. Conversely increased adipose deposition triggered by HTG may be responsible for the higher prevalence of IR, IFG, and MetS in the Uygurs as opposed to the Kazaks. Our observation revealed that the prevalence of IR is higher in Uygurs than in Kazaks among all age and BMI groups, in a manner similar to TG and IFG levels. In our study, IR was evaluated by HOMA, where HOMA levels ranging between 2.1 and 3.8 depict IR.11 The HOMA threshold of 2.73 employed in our study is well within this range. The Uygurs exhibited higher prevalence of IR, HTG, and low HDL-C compared with Kazaks. Recent evidence suggested that HDL-C may possess the ability to stimulate insulin release,12 which may contribute, at least in part, to higher IFG levels in Uygurs compared with the Kazaks at the same BMI level.

Limitations

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Disclosure:
  8. References

Similar to all other population studies, our present study has several limitations. First, our study investigated geographic region within a certain period, which may or may not best represent the overall status for both the ethnicity and the diseases of interest. Second, the Uygur ethnic population migrated centuries ago from the Europe regions, thus resembling the Europa Pamierya race. As a result, a good portion of Uygurs is leaning toward white or Caucasian ethnicity. Our study failed to dissect such racial backgrounds in the Uygur and Kazak ethnic groups. Further comprehensive epidemiologic studies such as disease-prone genetic profiles are warranted to better elucidate the risk factors and prevalence of type 2 diabetes and hypertension in the Uygur and Kazak populations.

Disclosure:

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Disclosure:
  8. References

This study was supported in part by the National Natural Science Foundation of China (Grant No.30960469) and the Scientific Research Innovation Award, Xinjiang Medical University, 2008 (Grant No.2008-13).

References

  1. Top of page
  2. Abstract
  3. Methods
  4. Results
  5. Discussion
  6. Limitations
  7. Disclosure:
  8. References
  • 1
    Sumner AE, Cowie CC. Ethnic differences in the ability of triglyceride levels to identify insulin resistance. Atherosclerosis. 2008;196:696703.
  • 2
    Diabetes Atlas. Updated guidelines for the definition, diagnosis and classification of diabetes. International Diabetes Federation. 19th World Diabetes Congress, Cape Town, South Africa; 2006.
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    Yan W, Yang X, Zheng Y, et al. The metabolic syndrome in Uygur and Kazak population. Diabetes Care. 2005;28:25542555.
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    Wu HY, Chen LL, Zheng J, et al. Simple anthropometric indices in relation to cardiovascular risk factors in Chinese type 2 diabetic patients. Chin J Physiol. 2007;3:135142.
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    Li LL, Zhang YM, Du JY, et al. Analysis of metabolic features and food composition related with pathogenesis of type 2 diabetes mellitus in population of Uigurs and Kazaks in Xinjiang. Chin J Endocrinol Metab. 2005;21:141142.
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    Tao YC, Mao XM, Xie ZJ, et al. The prevalence of type 2 diabetes and hypertension in Uygur and Kazak populations. Cardiovasc Toxicol. 2008;8:155159.
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    Huxley R, James WP. Ethnic comparisons of the cross-sectional relationships between measures of body size with diabetes and hypertension. Obes Rev. 2008;1:5361.
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    Eckel RH, Grundy SM, Zimmet PZ. The metabolic syndrome. Lancet. 2005;365:14151428.
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    Sumner AE. Ethnic differences in triglyceride levels and high-density lipoprotein lead to underdiagnosis of the metabolic syndrome in black children and adults. J Pediatr. 2009;155:S7.e7e11.
  • 10
    Goodarzi MO, Guo X, Taylor KD, et al. Lipoprotein lipase is a gene for insulin resistance in Mexican Americans. Diabetes. 2004;53:214220.
  • 11
    Monzillo LU, Hamby O. Evaluation of insulin sensitivity in clinical practice and in research settings. Nutr Rev. 2003;61:397412.
  • 12
    Keogh JB, Clifton P. The effect of meal replacements high in glycomacropeptide on weight loss and markers of cardiovascular disease risk. Am J Clin Nutr. 2008;87:16021605.