作者：Marlene Busko
出處：WebMD醫學新聞
September 11, 2008 —一項使用正子攝影（PET）的研究證實，健康人腦部血清素運輸子蛋白的濃度，在秋天與冬天，顯著地比春天與夏天高。
第一作者蒙大拿多倫多大學的Nicole Praschak-Rieder醫師寫道，血清素運輸子蛋白的密度變異是個過去尚未描述過的機轉，且這具有解釋季節性情感性異常（SAD）的潛力；SAD是一種在某些易感受個體、規律地發生的憂鬱事件。
來自多倫多大學的資深作者Jeffery H. Meyer醫師向Medscape精神學表示，未來，我們可能可以改變來自於季節的環境因素，以降低憂鬱事件的發生率。
他指出，就像我們現在有對預防心臟疾病的生活型態建議，在未來，我們可能有預防重鬱症的生活型態建議。
這項研究發表於9月號的一般精神學誌。
【打敗SAD】
Meyer醫師表示，研究指出大約有1至2%的多倫多居民以及居住在類似緯度的居民，有SAD的問題，且盛行率在緯度更高的地區預計將會更高。
研究者表示，在晴朗、夏天時感到比較快樂與更有精神，而在陰暗、冬天的時候感到比較悲觀與無精打采，這被認為與腦中血清素濃度變化有關，但是其機轉仍然需要釐清。
在這項研究中，研究者目的在檢驗血清素運輸蛋白濃度，這個蛋白將血清素自腦中細胞外空間移除，以這個運輸蛋白的濃度研究是否有季節的效應。他們假設血清素運輸蛋白密度有季節變異效應，且這會對應到每日日光平均時間。
研究者以與血清素運輸蛋白結合的高度選擇性放射線標記進行PET掃描。在這些掃描中，高濃度血清素運輸蛋白密度（高血清素運輸蛋白電壓）對照到細胞外空間的低血清素濃度，而血清素在細胞外空間發生作用。
【可修飾的危險因子】
這項研究收納了88位居住在多倫多的居民，其中有41位女性47位男性，平均年齡為33歲（從20到51歲），這些病患在不同研究中被收納為健康受試者。
總共38位受試者在秋天與冬天接受PET掃描（9月23日到3月20日），而另外50位受試者在春天與夏天接受掃描（3月21日到9月22日）。研究者使用30年氣象曆來決定一年中每天的日光平均時間。
男性與女性，於秋天與冬天接受PET掃描的，相較於在春天與夏天接受PET掃描的，其血清素運輸蛋白結合電壓值在所有腦部區域顯著較高（P=.01~.001）。
所有腦部區域的血清素運輸蛋白結合電壓較高與陽光較少有關（P=.05~<.001）。
Meyer醫師表示，然而，我們不能改變我們的基因，且很難避免壓力，季節性環境因素對於重鬱事件的重要性，是這具有可以修飾的潛力。
他附帶表示，為了要治療SAD，選擇性血清素再回收抑制劑抗憂鬱藥物，這可以阻斷80%血清素運輸蛋白位置，也是有幫助的，而光照療法可能是有效的，如果每天的暴露時間夠長的話。
該團隊正在研究光照療法與其他環境因子是如何影響血清素運輸蛋白，以發現預防這項疾病的最佳環境。
研究作者表示無相關資金上的往來。
PET Helps Elucidate Mechanism Behind Seasonal Mood Changes
By Marlene Busko
Medscape Medical News
September 11, 2008 — A study using positron-emission tomography (PET) has shown that levels of serotonin transporter protein in the brains of healthy individuals were significantly higher in the fall and winter than in the spring and summer.
This seasonal variation of serotonin transporter density is "a previously undescribed mechanism" that has the potential to explain seasonal affective disorder (SAD), the researchers, with first author Nicole Praschak-Rieder, MD, from the University of Toronto, in Ontario, write. SAD is the regular occurrence of depressive episodes in the fall and winter in some vulnerable individuals,
"In future, we might be able to change environmental effects from seasons, to lower the risk for depressive episodes," senior author and lead investigator Jeffrey H. Meyer, MD, from the University of Toronto, told Medscape Psychiatry.
"Just as now we have lifestyle recommendations to prevent heart disease, in the future, we may have lifestyle recommendations to prevent major depressive disorder," he said.
The study is published in the September issue of the Archives of General Psychiatry.
Beating SAD
Studies have reported that about 1% to 2% of people living in Toronto and places at a similar latitude experience SAD, and the prevalence in more northern latitudes is thought to be even higher, Dr. Meyer said.
Feeling happier and more energetic on sunny, summer days and feeling less optimistic and less energetic on dark, winter days is believed to be related to changes in brain levels of serotonin, but the mechanism remains to be elucidated, the researchers write.
In this study, the researchers aimed to examine the levels of serotonin transporter protein, which clears serotonin away from extracellular spaces in the brain, to see whether there was a seasonal effect. They hypothesized that there is a seasonal variation in serotonin transporter density and that this would correspond to changes in average daily hours of sunshine.
The investigators performed PET scans using a highly selective radiolabel that binds to serotonin transporter. In these scans, high levels of serotonin transporter density (high serotonin transporter binding potential) correspond to low levels of serotonin in the extracellular spaces where it exerts its effect.
Modifiable Risk Factors
The study subjects included 88 individuals living in Toronto — 41 women and 47 men with a mean age of 33 years (range, 20 – 51 years) — who were enrolled in various studies as healthy controls.
A total of 38 of the participants had PET scans done in the fall and winter (September 23 to March 20) and 50 had scans done in the spring and summer (March 21 to September 22). The investigators used 30-year meteorologic data to determine the average hours of sunshine for each day of the year.
Among both men and women, serotonin transporter binding potential values were significantly higher in all investigated brain regions in individuals who had PET scans done in the fall and winter vs those who had scans done in the spring and summer (P = .01 – .001).
Higher values of serotonin transporter binding potential in all brain regions correlated with days that were less sunny (P =. 05 to <.001).
"Whereas we can’t change our genes and it is difficult to avoid stress, the importance of [seasonal environmental factors] in the likelihood of major depressive episodes is that it has the potential to be more readily modifiable," said Dr. Meyer.
To treat SAD, selective-serotonin-reuptake-inhibitor antidepressants, which block 80% of serotonin transporter sites, are often helpful, and light therapy treatment is probably helpful if the daily exposure is long enough, he added.
The group is continuing investigate how light exposure and other environmental factors influence serotonin transporter to find the optimal environment to prevent illness.
The study authors report no financial disclosures.
Arch Gen Psychiatry 2008; 65: 1072-1078. Abstract
[ 本帖最後由 goodcat1111 於 2008-9-21 22:34 編輯 ] |
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