老年衰弱症及代謝症候群與老化生物標記相關性研究

Frailty, Metabolic Syndrome and Aging Biomarkers in the Elderly

高東煒(Tung-Wei Kao)

指導教授 ： 楊偉勛

國立臺灣大學/醫學院/臨床醫學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.00665

摘要

研究背景
Fried 於2001年提出衰弱症的操作性定義。過去的研究，多著墨於臨床症狀之表現與系統性共病症及後續生活品質、機構入住率、罹病率、死亡率之關係，偏向流行病學之領域。在生物指標方面，部分研究發現衰弱症與發炎指標如interleukin-6 (IL-6), C-reactive protein (CRP)存在正相關，至於衰弱症在分子生物學的研究則相當少見。1998年世界衛生組織統一定義「代謝症候群」。此症候群已知跟許多疾病相關，而老年人又常合併許多慢性疾病。老化在代謝症候群中扮演著重要的角色。面臨高齡化社會之衝擊，台灣之研究仍屬不足。本研究試圖了解社區老年人衰弱症及代謝症候群之流行病學情況及可能相關之生物標記，包含白血球端粒長度，p16 mRNA表現量，血液中myostatin，follistatin濃度之相關性。

研究設計與方法
此為橫斷性，觀察性之研究。以65歲(含)以上的社區老人為研究對象，以結構式問卷收集人口學資料、生活型態、健康狀況、身體活動程度等，並收集血液檢體 20毫升。萃取白血球DNA，以qPCR方式分析其端粒長度；另萃取 RNA，翻成cDNA，以p16為引子，做qPCR，測出p16 mRNA表現量。另取個案之血清，以ELISA kit 測量其myostatin，follistatin 濃度。

結果
共有165位個案。其中男性75位(45.5%)，女性90位(54.5%)，平均年齡為75.8±7.7。衰弱症共有16位，佔9.7%。代謝症候群43位，比例約26.1%。依衰弱症多寡分成五組，其中部分慢性疾病、血色素濃度、p16mRNA表現量等，在五組間具有顯著差異。但端粒長度、血清follistatin, myostatin濃度等，則無組別間顯著差異。依代謝症候群多寡分成六組，只有白血球數量在組間具有顯著差異(p<0.001)。依代謝症候群之有無分組，兩組之間在中風病史、p16mRNA 表現量則具有顯著差異(p=0.003); 但在白血球數量部份則未具有顯著差異(p=0.218)。
衰弱數量多寡與年紀、部分慢性疾病、p16mRNA 表現量呈現正相關(p=0.025); 與血色素呈現負相關(p=0.01)。代謝症候群的多寡與中風、白血球數量、p16mRNA 表現量呈現正相關。利用線性迴歸分析衰弱多寡與變項間的相關性，其中年紀、中風、失智篩檢分數越高、p16mRNA 表現量越多的受試者有較多機會出現衰弱症; 而與血色素呈現負相關(β coefficient= -0.175, p=0.038)。利用邏吉斯迴歸分析衰弱症有無與各變項之相關性，則皆呈現無顯著差異。
以線性迴歸模型分析代謝症候群多寡與各變項之間的相關性，中風病史、白血球數量呈現正相關。利用邏吉斯迴歸模型分析代謝症候群的有無與各變項之間的相關性，白血球數量高、有中風病史者，其代謝症候群的機會也較高。

討論
本次研究中，出現衰弱症者佔9.7%，略高於國外；若以衰弱症的多寡來看，由於部分組別受試者較少、樣本數不均，因此並未觀察到各組間隨著衰弱程度的增加其慢性疾病的比例也隨之增加的現象。但若以有無衰弱做分組，則衰弱症的這組，其部分慢性病比例皆較無衰弱症這組多，失智篩檢分數亦較高。台灣研究之衰弱症盛行率相差甚多，本研究雖為單一醫學中心老年人口，但測量工具依Fried的定義操作，涵蓋客觀的握力與行走速度等項目。
若依衰弱症的多寡加以分組，慢性疾病在組間具有顯著差異，可見老年衰弱症涵蓋的範圍包括生理、心理、社會各面向。若將個案分成有無衰弱症兩組時，則血色素濃度及p16mRNA 表現量部分，就不具顯著差異。由此觀察到衰弱症的切點不同時，組間各變項的差異就出現變化。在代謝症候群的分析中也觀察到同樣的情況。
在衰弱症多寡相關性分析部份，年紀、慢性疾病、p16mRNA 表現量呈現正相關；血色素則呈現負相關。在代謝症候群多寡的相關性分析部份，其中僅與中風病史、白血球數量及p16mRNA 表現量呈現正相關。或許可推測在代謝症候群的臨床表癥背後，代表著生理上呈現著發炎與老化兩種現象。
利用線性迴歸分析衰弱症與各變項之間的相關性，其中部分變項呈現正相關，而與血色素呈現負相關。但利用邏吉斯迴歸分析則未觀察到具有顯著差異，或許是由於衰弱症的受試者樣本數不足的關係，也或許是因為切點的不同，造成統計上不同的結果。利用線性迴歸及邏吉斯迴歸模型分析代謝症候群與各變項之間的相關性，其中中風病史、白血球數量，與代謝症候群呈現正相關。足見白血球數量的多寡，在代謝症候群的相關性分析上具有顯著的意義。
本研究為結合客觀測量工具與生物標記分析的研究，或許由於樣本數不足的關係，致使研究結果並無預期的成果。由於衰弱症目前的操作仍依照Fried的定義，屬於臨床症狀的診斷集合，包含生理、心理、社會各面向的問題都有可能造成衰弱症，針對此概念性的議題，要試圖以單一個生物標記去解釋相關性，或許較為困難；相對於衰弱症，代謝症候群是相對比較有確切客觀指標的集合，背後代表的疾病也相對明確，所以與發炎相關的生物標記就比較能夠觀察到其與代謝症候群的相關性。

結論
本次研究台灣北部社區老年人，出現衰弱症者佔9.7% ; 代謝症候群的比例約26.1%。衰弱症的數量多寡與年紀、中風病史、失智程度、p16mRNA 表現量呈現正相關，與血色素呈現負相關。但若區分衰弱症有無做分析時，則未觀察到具有顯著相關性。代謝症候群數量多寡與代謝症候群之有無皆與中風病史、白血球數量呈現正相關。

關鍵字

衰弱症 ； 代謝症候群 ； 老化生物標記

並列摘要

Introduction
Studies on frailty attract more and more attentions in the field of geriatric medicine. Fried (2001) tried to set up the operational definition on frailty as having 3 or more of the following conditions: unintended weight loss, exhaustion, weakness,low walk speed and low activity. Current clinical researches on frailty are nearly based on this definition.
Previous studies tend to focus on epidemiological analyses, the relationships of frailty and life quality, rate of institutionalization, morbidity and mortality. On biomarkers analyses, some studies indicate frailty is associated with C-reactive protein (CRP) and interleukin-6 (IL-6). However, researches of molecular biology on frailty are relatively sparse.
Metabolic syndrome is defined as having 3 or more of the following conditions: central obesity, hypertension, hyperglycemia, hypertriglyceridemia, low level of high-density lipoprotein. It is related to multiple chronic diseases. Aging maybe plays an important role on metabolic syndrome.
Researches between frailty, metabolic syndrome and related biomarkers in Taiwanese population are relatively scarce. We try to design a research to observe the
epidemiologic distributions on frailty and metabolic syndrome and their correlations to aging biomarkers from community- dwelling old adults in the north of Taiwan.

Materials and methods
This is a cross-sectional, observational study. Old adults with ages 65 and above who lived in the community were recruited. Basic demography, health condition,
physical activities were reviewed by structured questionnaire, 20ml peripheral blood was collected. Extract DNA from white blood cell, using quantitative polymerase chain reaction (qPCR) measure the telomere length. Extract RNA, reverse to cDNA, using p16 as a probe to perform qPCR to measure p16 mRNA expression level. Serum myostatin and follistatin level were also measured by ELISA kit.

Results
165 old adults were recruited. 75 were men(45.5%), 90 were women(54.5%); age was 75.8±7.7 on average. 6 men (8.0%) and 10 women (11.1%) were frail. Prevalence of frailty was 9.7%. 17 men (22.6%) and 26 women (28.8%) had metabolic syndrome. Prevalence of metabolic syndrome was 26.1%.
Chronic diseases, hemoglobin, p16mRNA expression levels were significant different between categories of frailty numbers. White blood cell (WBC) counts was significant different between categories of numbers of metabolic syndrome ( p<0.001). Telomere length, serum level of follistatin and myostation revealed no significant difference between categories of frailty and metabolic syndrome analyses.
Numbers of frailty was positive correlated to p16mRNA expression levels (p=0.025), but negative correlated to hemoglobin (p=0.01). This findings also revealed on linear regression model analyses.
Numbers of metabolic syndrome was positive correlated to WBC counts, p16mRNA expression levels. However, on linear regression model, p16mRNA expression levels was not associated to numbers of metabolic syndrome. The significant difference also diminished on logistic regression model analyses. Only WBC counts was positively correlated to numbers of metabolic syndrome. On logistic regression model, higher levels of WBC counts increased risk to metabolic syndrome (OR=1.59, 95% confidence interval=1.14-2.22, p=0.006).

Discussion
The prevalence of frailty in this study was higher than it was in the U.S. Although this is a single center study, we used objective tools to measure grip strength and walking speed to fit Fried’s definition avoiding subject measurements in previous researches in Taiwan.
Chronic diseases including bio-psycho-social aspects between each categories were significant differences on frailty analyses. It was supported that not only physical but mental condition will contribute to the severity of frailty. Some variables were associated with numbers of frailty, but this association was not sustained on frailty versus non-fraitly analyses. The same condition was found on metabolic syndrome analyses. It was suspected that different cutpoint on frailty and metabolic syndrome definition had different results.
This study try to link objective physical activity measurement and potential aging biomarkers; however, maybe the sample sizes were limited, the results were not significant. Since the definition of frailty was focused on clinical observation including bio-psycho-social aspects; it was difficult to use a single biomarker to explain the whole picture. Comparing to frailty, metabolic syndrome was a cluster of objective measurement regarding definite low-grade inflammatory disease, the biomarker of inflammation such as WBC counts was supposed to be higher in the populations with metabolic syndrome.

Conclusion
In this study, the prevalence of frailty and metabolic syndrome was 9.7% and 26.1% respectively. Numbers of frailty was positive correlated to age, stroke histoy, cognitive impairment, p16mRNA expression levels; but negative correlated to hemoglobin. The significant correlation was not existed on frailty versus non-frailty analyses. Metabolic syndrome was positive correlated to stroke history and WBC counts.

並列關鍵字

frailty ； metabolic syndrome ； telomere length ； p16mRNA ； aging biomarkers

參考文獻

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