高血壓:腹部脂肪比總脂肪量更危險


  【24drs.com】根據線上發表於9月1日美國心臟學院期刊的一篇文章,腹部脂肪比體脂肪更容易引起高血壓。
  
  德州大學西南醫學中心的Alvin Chandra醫師等人,分析了「達拉斯心臟研究」這項研究的903名參與者的資料,這些研究對象皆完成第二階段研究且平均被追蹤7年。
  
  原始研究世代共有2,716名參與者(年齡18-65歲[中位數40歲],57%是婦女、60%非白人,身體質量指數[BMI]中位數27.5 kg/m2),在2000-2002年完成第一階段研究;研究者排除原本即有高血壓(≧140 mm Hg/≧90 mm Hg)、有服用降血壓藥物、血壓讀數偏高的研究對象。
  
  由受訓過的研究員為這些研究對象量取多次血壓值,進行核磁共振掃描,使用雙X光吸光測定法測量下半身體脂肪組成,進行靜脈血液樣本的生化分析。
  
  納入的903人中,230人(26%)在中位數7年後發生高血壓,這些人年紀偏長、糖尿病盛行率較高、大部份是黑人、研究開始時的血壓值比較高,BMI、內臟脂肪組織(VAT)和皮下脂肪組織(SAT)也都比較高(所有的P < .01)。
  
  有發生高血壓者,在研究開始時的BMI值高於那些沒有發生高血壓者(29.9 kg/m2 vs 26.9 kg/m2;P < .0001),不過,兩組的平均區間體重增加幾乎相同。
  
  研究者使用多變項風險回歸模式計算發現,BMI和發生高血壓顯著相關(P < .0001)。然後,當研究者把VAT和SAT納入變項時,發現VAT值較高是與發生高血壓獨立相關的唯一脂肪參數(相對風險[RR]為1.22;95%信心區間[CI]為1.07-1.39;P = .004),研究者發現,年齡、性別、種族之關聯性皆無差異。
  
  校正發炎標記之後,前述關聯依舊顯著。
  
  研究者寫道,這些研究結果證明,內臟脂肪在這關聯性上比體脂肪更重要。這些結果看來,VAT是BMI和心血管疾病關聯的重要關鍵,VAT和造成發生高血壓與胰島素阻抗有關。
  
  不過,研究者指出,還不清楚特定機轉,無法從這個觀察研究提出因果關係。
  
  研究者結論指出,這些資料得自多種族、隨機組成之世代,結果顯示肥胖和發生高血壓有關,特別是內臟脂肪,腹膜後脂肪的關聯最強。這和越來越多認為與VAT有關而非體脂肪之研究論點一致,各種的心血管風險因素最後促成不良的臨床事件。
  
  紐約市Icahn醫學院的Lawrence R. Krakoff醫師在編輯評論中寫道, 腹膜後脂肪作為未來發生高血壓的預測因子可能很重要,需要以更大型的流行病學調查、採用簡單方便的特定測量方式測得這個特定脂肪,特別是資源有限時。「達拉斯心臟研究」這項研究提供了具有良好特徵的前瞻型資料庫,其後續分析或許可以有助於揭露這類方法。
  
  資料來源:http://www.24drs.com/professional/list/content.asp?x_idno=7113&x_classno=0&x_chkdelpoint=Y
  

Hypertension: Abdominal Fat May Be More Risky Than Total Fat

By Larry Hand
Medscape Medical News

Fat around the abdomen may be more of a cause of hypertension than overall body fat, according to an article published online September 1 and in the September 9 issue of the Journal of the American College of Cardiology.

Alvin Chandra, MD, from the University of Texas Southwestern Medical Center in Dallas, and colleagues analyzed the records of 903 participants in the Dallas Heart Study who completed the second study phase and were followed for a mean of 7 years.

The researchers drew the study population from an original cohort of 2716 participants (aged 18 to 65 years [median, 40 years old], 57% women, 60% nonwhite, with a median body mass index [BMI] of 27.5 kg/m2) who completed phase 1 of the study during 2000 to 2002. They excluded participants who had baseline hypertension (?140 mm Hg/?90 mm Hg), participants who were taking antihypertensive medications, and participants with elevated blood pressure readings.

Trained professionals took multiple blood pressure measurements, scanned participants with magnetic resonance imaging, used dual X-ray absorptiometry to measure lower body fat composition, and conducted biomarker analysis of venous blood samples.

Of the 903 participants, 230 (26%) had developed hypertension after a median of 7 years. Those participants were older, had higher prevalence of diabetes, were more commonly black, and had higher blood pressure at baseline, as well as higher measures of BMI, visceral adipose tissue (VAT), and subcutaneous adipose tissue (SAT) (all P < .01).

Baseline BMI was higher among the participants who developed hypertension than among those who did not (29.9 kg/m2 vs 26.9 kg/m2; P < .0001). However, the median interval weight increase was almost the same between groups.

Yes, but...

Using multivariable risk regression models, the researchers calculated that BMI was significantly associated with the development of hypertension (P < .0001). Then, when they added in VAT and SAT as variables, they found that higher VAT remained as the only fat parameter independently associated with developing hypertension (relative risk [RR], 1.22; 95% confidence interval [CI], 1.07-1.39; P = .004). They observed no differences in the association among sex, age, or race variables.

The association remained significant after further adjustments for inflammatory biomarkers.

The results suggest "that visceral adipose, rather than total adiposity, is more important in this relationship," the researchers write.

"These results suggest that VAT may be the important link between BMI and cardiovascular disease, and that VAT may be acting in part by promoting the development of hypertension and insulin resistance."

However, the researchers note that the specific mechanism remains unknown, and they cannot draw a causal relationship from an observational study.

They conclude, "These data from a multiethnic, probability-based cohort demonstrate that the association between obesity and the development of hypertension is specifically accounted for by visceral adiposity. The strongest associations were observed with retroperitoneal fat. These data are consistent with a growing body of literature implicating VAT, rather than generalized adiposity, in the aggregation of cardiovascular risk factors that eventually drive adverse clinical events."

In an accompanying editorial comment, Lawrence R. Krakoff, MD, from the Icahn School of Medicine and Mount Sinai in New York City, writes, "The possible importance of retroperitoneal adiposity as a predictor of future hypertension implies the need for simple and practical methods to measure this particular fat depot in larger epidemiological surveys, especially when resources are limited. Further analysis of such a well-characterized prospective database provided by the Dallas Heart Study may unmask such methods."

Four coauthors have reported various relationships with several pharmaceutical companies; none of the other coauthors has reported any relevant financial interests.

J Am Coll Cardiol. 2014;64:997-1004.

    
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