Mediating effects of physical activity and obesity on the relationship between the triglyceride-glucose index and metabolic syndrome in Korean children : a cross-sectional study

다국어 초록 (Multilingual Abstract)

This purpose of the study was to examine whether physical activity (PA) and central obesity mediate the association between insulin resistance (IR), assessed using the triglyceride–glucose (TyG) index, and physical fitness (PF) in Korean children, and further evaluated the diagnostic performance of the TyG index for identifying metabolic syndrome (MetS). A total of 526 children aged 7–12 years were included. PA was classified into low-, moderate-, and vigorous-intensity PA (LPA, MPA, and VPA), while central obesity was assessed using waist-to-hip ratio (WHR). PF was evaluated using a composite score derived from endurance, muscular strength, power, and flexibility. MetS was defined using a continuous MetS risk score, with the highest quartile indicating MetS presence. Parallel mediation analyses were conducted using the PROCESS macro with adjustment for age, sex, and Tanner stage, and receiver operating characteristic (ROC) curve analyses were performed to compare the diagnostic performance of the TyG index with homeostasis model assessment of insulin resistance (HOMA-IR) and percent body fat (PBF). Higher TyG index levels were associated with greater adiposity, higher IR, lower VPA, and poorer PF. In mediation analyses, WHR and VPA demonstrated significant indirect associations between the TyG index and PF, whereas LPA and MPA did not. These mediating associations remained significant when LPA and MPA were excluded from the model, while the direct association between the TyG index and PF was not significant when mediators were included. ROC curve analysis showed that the TyG index demonstrated good diagnostic performance for identifying MetS, comparable to or exceeding that of HOMA-IR and PBF. These findings suggest that 1) the association between TyG index and PF are partially mediated by both central obesity and VPA and 2) the TyG index may serve as a biomarker for detecting MetS risk in pediatric populations.

국문 초록 (Abstract)

본 연구의 목적은 한국 아동을 대상으로 중성지방–포도당 지수(triglyceride–glucose index, TyG 지수)로 평가한 인슐린 저항성과 체력의 연관성에서 신체활동과 중심비만이 매개 역할을 하는지를 규명하고, 동시에 대사증후군판별에 대한 TyG 지수의 진단 성능을 평가하는 데 있다. 본 연구에는 7–12세 아동 526명이 포함되었다. 신체활동은 저강도, 중강도, 고강도 신체활동으로 분류하였으며, 중심비만은 허리엉덩이둘레비를 이용하여 평가하였다. 체력은 심폐지구력, 근력, 순발력, 유연성으로 구성된 종합 체력 점수로 평가하였다. 대사증후군은 연속형 대사증후군 위험 점수를 사용하여 정의하였으며, 상위 사분위수에 해당하는 경우를 대사증후군 존재로 분류하였다. 매개효과 분석은 연령, 성별, Tanner 단계로 보정한 후 PROCESS macro를 이용한 병렬 매개분석을 통해 수행하였고, 수신자조작특성 (receiver operating characteristic, ROC) 곡선 분석을 통해 TyG 지수의 대사증후군 진단 성능을 homeostasis model assessment of insulin resistance(HOMA-IR) 및 체지방률과 비교하였다. TyG 지수가 높을수록 비만도와 인슐린 저항성은 증가하였고, 고강도 신체활동과 체력 수준은 낮았다. 매개분석 결과, 허리엉덩이둘레비와 고강도 신체활동은 TyG 지수와 체력 간의 연관성에서 유의한 간접 연관성을 보였으나, 저강도와 중강도 신체활동은 유의한 매개 효과를 나타내지 않았다. 또한 저강도와 중당도를 제외한 모델에서도 이러한 매개 연관성은 유지되었으며, 매개변수를 포함한 경우 TyG 지수와 체력 간의 직접 연관성은 유의하지 않았다. ROC 곡선 분석 결과, TyG 지수는 대사증후군 판별에 있어 HOMA-IR 및 체지방률과 비교하여 유사하거나 더 우수한 진단 성능을 보였다. 이러한 결과는 중심비만과 고강도 신체활동이 TyG 지수로 정의된 인슐린 저항성과 체력 간의 연관성에서 중요한 매개 역할을 함을 시사하며, TyG 지수가 소아 인구집단에서 대사 위험을 평가하는 실용적인 지표로 활용될 수 있음을 제시한다.

목차 (Table of Contents)

• Ⅰ. INTRODUCTION 1
• 1. Significance of the Study 1
• 2. Purpose of the Study 3
• 3. Hypotheses 3
• Ⅱ. REVIEW OF LITERATURE 4
• 1. Definition and Prevalence of Insulin Resistance 4
• 2. Development of Insulin Resistance 4
• 3. Biomarkers of Insulin Resistance 8
• 4. Definition and Prevalence of Metabolic Syndrome 9
• 5. Metabolic Syndrome and Insulin Resistance 10
• 6. Physical Activity and Insulin Resistance 11
• 7. Physical Fitness and Metabolic Syndrome 12
• 8. Physical Activity Intensity, Obesity, and Metabolic Syndrome 14
• 9. Limitations of Previous Studies and Research Gap 15
• Ⅲ. METHODS 17
• 1. Study Participants 17
• 2. Measurement of Anthropometrics and Body Composition 17
• 3. Definition of Metabolic Syndrome 18
• 4. Measurement of Physical Activity and Physical Fitness 19
• 5. Statistical Analyses 20
• Ⅳ. RESULTS 22
• 1. Participant Characteristics 22
• 2. Relationships between Metabolic Syndrome and Measured Parameters 25
• 3. Relationships between the TyG Index and Measured Parameters 28
• 4. Bivariate Correlations Between the TyG Index and Body Fatness, Physical Activity, and Physical Fitness 33
• 5. Mediation Analysis 33
• 6. Receiver Operating Characteristic Curve Analysis 36
• Ⅴ. DISCUSSION 38
• 1. Vigorous Physical Activity and Waist-to-Hip Ratio Partially Mediates the Relationship Between the TyG Index and Physical Fitness 38
• 2. TyG Index Can Accurately Detect the Presence of MetS 39
• 3. Breaking the Vicious Circle: How to Increase High Intensity Activity in Metabolically Risky Children 40
• Ⅵ. CONCLUSION 43
• Ⅶ. REFERENCES 44
• Ⅷ. 논문요약 59