基斯‧奧爾康 / 2024 年 6 月 17 日 / 愛滋病地圖

一項針對感染愛滋病毒的義大利男性的研究發現，大約十分之一的 50 歲以下男性患有肌肉萎縮和腹部肥胖，骨礦物質密度低也很常見。

這項發表在《內分泌學調查雜誌》的研究也發現，低肌肉質量和低骨礦物質密度與性荷爾蒙睪固酮和雌二醇水平低有關。

該研究旨在調查感染愛滋病毒的年輕男性性荷爾蒙與身體組成之間的關係。儘管早期診斷和治療，但肌肉質量低下或肌肉減少症在愛滋病毒感染者中仍然很常見。感染愛滋病毒的年輕男性可能比未感染愛滋病毒的人更早出現肌肉損失。 在一般人群中，肌肉減少症在 60 歲以上的人群中更為常見。

肌肉組織的損失會導致執行日常任務的力量喪失、耐力喪失、平衡能力差和行走速度減慢。

肌肉流失最常見的原因是缺乏身體活動、肥胖、慢性健康問題（如腎臟病和糖尿病）以及性荷爾蒙水平低。

HIV感染者睪固酮水平低對肌肉損失的影響程度尚不清楚，性荷爾蒙水平與骨礦物質密度之間的關係也不確定。

摩德納和博洛尼亞大學的研究人員想了解性荷爾蒙水平是否與年輕愛滋病毒感染者的低肌肉質量有關，以及低肌肉質量和高身體脂肪含量的愛滋病毒感染者男性的比例。隨著年齡的增長，這群人可能特別容易跌倒、虛弱和有代謝問題，包括糖尿病和心血管疾病。

他們對 307 名 50 歲以下的愛滋病毒男性患者進行了一項橫斷面研究，這些男性在摩德納愛滋病毒代謝診所接受追蹤。參與者的平均年齡為 47 歲，感染愛滋病毒的平均時間為 16 年。

該研究評估了身體組成、骨礦物質密度、荷爾蒙和代謝測量。

身體組成分析使用兩種測量尺度來評估肌少症（肌肉質量減少）：

• 四肢瘦體質量指數 (ALMI)，計算瘦體重除以身高平方

• 四肢去脂體重/體重(ALM/W)，即去脂體重除以總體重。歐洲專家小組建議將此作為診斷肌少性肥胖的首選方法。

使用 ALMI 發現 34% 的人患有肌少症，而使用 ALM/W 則發現 14% 的人患有肌少症。經 ALMI 診斷出患有肌少症的男性體重指數 (BMI) 較低，除腰椎測量點外的所有部位的骨礦物質密度均顯著降低。然而，經 ALM/W 診斷出患有肌少症的男性的體重指數 (BMI) 高於未患有肌少症的男性，且骨礦物質密度與其他族群沒有差異。

透過這兩種測量診斷的肌少症與較低的遊離睪固酮和總睪固酮有關。在經 ALMI 診斷為肌少症的患者中，雌二醇對應睪固酮的比值顯著降低。

儘管兩種測量方法確定的肌肉減少症盛行率存在差異，但肌肉減少症肥胖（肌肉質量低的肥胖）的盛行率幾乎相同（ALMI 為 11%，ALM/W 為 12%）。本研究中的肥胖被定義為體重指數低於 30 的人其體脂百分比高於 26%（歸類為「隱性」肥胖），或體脂百分比高於 26%且體重指數為30 或以上的人（「明顯」肥胖）。在這個世代中，23% 的參與者患有隱性肥胖，而 3% 的參與者患有明顯肥胖。

經多變量分析發現，當透過 ALMI 測量肌少症時，肌少症肥胖與低雌二醇 (estradiol <18pg/ml)、自 HIV 診斷後的時間和低遊離睪固酮相關。

研究人員表示，本研究中觀察到的低肌肉質量和低骨礦物質密度模式與跌倒、骨折和虛弱有關。他們補充說，肌肉減少性肥胖與一般人群死亡或嚴重疾病的風險增加有關。

他們指出：「骨骼和肌肉不僅在解剖學上緊密相互作用，而且在化學和代謝上也緊密相互作用」。

然而，研究結果顯示，睪固酮補充劑可能無法解決骨肌減少症。該世代中患有肌少症的男性中雌二醇 (estradiol) 對應睪固酮的比值較低，顯示雌激素 (oestrogen) 水平較低，研究人員表示，需要更多的研究來調查雌激素在多大程度上可以預防愛滋病毒男性的肌少症。

「這項研究首先強調並證實了性類固醇、雌激素而不是雄激素在骨骼、肌肉和脂肪組織之間嚴格相互聯繫中的核心作用…這些發現重新重申[……]性荷爾蒙深入參與關聯骨骼、脂肪和骨骼肌的惡性循環，」研究人員說。

對於任何經歷肌肉流失的人的建議是，確保他們的健康飲食含有足夠的蛋白質（每餐 25-30 克）。定期的阻力運動可以逆轉肌肉流失並在以後的生活中保持肌肉。

參考文獻：De Vicentis S et al. 「感染愛滋病毒的年輕男性肌肉減少性肥胖和骨質密度降低；身體組成和性類固醇相互作用」。 《內分泌學調查雜誌》，2024 年 4 月 20 日線上發表。

Muscle loss combined with excess fat frequently seen in Italian men with HIV

Keith Alcorn / 17 June 2024 / aidsmap

Muscle wasting coupled with abdominal obesity was present in around one in ten men under 50, with low bone mineral density also being common, a study of Italian men living with HIV has found.

The study, published in the Journal of Endocrinological Investigation, also found that low muscle mass and low bone mineral density were associated with low levels of the sex hormones testosterone and estradiol.

The research was carried out to investigate the relationship between sex hormones and body composition in younger men with HIV. Low muscle mass, or sarcopenia, remains common in men with HIV despite earlier diagnosis and treatment. In younger men with HIV, muscle loss may appear earlier than in people without HIV.  In the general population, sarcopenia is more common in people over 60 years old.

Loss of muscle tissue leads to loss of strength for carrying out everyday tasks, loss of stamina, poor balance and slowed walking.

The most common causes of muscle loss are physical inactivity, obesity, chronic health conditions such as kidney disease and diabetes, and low sex hormone levels.

The extent to which muscle loss is influenced by low levels of testosterone in men with HIV is unclear, and the relationship between sex hormone levels and bone mineral density is uncertain too.

Researchers at universities in Modena and Bologna wanted to understand whether sex hormone levels are associated with low muscle mass in younger men with HIV, and the proportions of men with HIV with both low muscle mass and high body fat content. This group may be especially vulnerable to falls, frailty and metabolic problems including diabetes and cardiovascular disease as they grow older.

They carried out a cross-sectional study of 307 men with HIV under the age of 50 who were under follow-up at the Modena HIV Metabolic Clinic. Participants had a median age of 47 years and had been living with HIV for a median of 16 years.

The study assessed body composition, bone mineral density, hormones and metabolic measurements.

The analysis of body composition used two scales of measurement to assess sarcopenia (reduced muscle mass):

• Appendicular lean mass index (ALMI), which calculates lean body mass divided by height squared
• Appendicular lean mass/body weight (ALM/W), which divides lean body mass by total body weight. This has been recommended by a European expert panel as the preferred means of diagnosing sarcopenic obesity.

Using ALMI, 34% were found to have sarcopenia, while using ALM/W showed that 14% had sarcopenia. Men with sarcopenia diagnosed by ALMI had lower body mass index and significantly lower bone mineral density at all sites apart from the lumbar measurement point. However, men with sarcopenia diagnosed by ALM/W had higher body mass index than those without sarcopenia and showed no difference with the rest of the cohort in bone mineral density.

Sarcopenia diagnosed by both measurements was associated with lower free testosterone and total testosterone. In those diagnosed with sarcopenia by ALMI, the ratio of estradiol to testosterone was significantly lower.

Despite the differences in the prevalence of sarcopenia identified by the two methods of measurement, the prevalence of sarcopenic obesity – obesity with low muscle mass – was almost the same (11% for ALMI and 12% ALM/W respectively). Obesity in this study was defined as either a body fat percentage above 26% in a person with a body mass index below 30 (classified as ‘hidden’ obesity), or a body fat percentage above 26% in a person with a body mass index of 30 or above (‘overt’ obesity) . In this cohort, 23% of participants had hidden obesity, while 3% had overt obesity.

A multivariate analysis found that sarcopenic obesity was associated with low estradiol (<18pg/ml), time since HIV diagnosis and low free testosterone, when sarcopenia was measured by ALMI.

The study investigators say that the pattern of low muscle mass and low bone mineral density observed in this study is associated with falls, fractures and frailty. They add that sarcopenic obesity is associated with an increased risk of death or serious illness in the general population.

“Bone and muscle closely interact with each other not only anatomically, but also chemically and metabolically,” they note.

However, the study findings show that testosterone supplements may not resolve osteosarcopenia. The low ratio of estradiol to testosterone in men with sarcopenia in this cohort indicates low oestrogen levels and the study investigators say that more research is needed to investigate the extent to which oestrogen protects against sarcopenia in men with HIV.

“This study first highlights and then confirms the central role of sex steroids, estrogens rather than androgens, in the strict interconnection between bone, muscle and adipose tissue […] These findings reiterate […] the deep involvement of sex hormones in the vicious circle connecting bone, fat, and skeletal muscle,” say the study investigators.

The advice for anyone experiencing muscle loss is to ensure they have a healthy diet containing adequate amounts of protein (25-30 grams per meal). Regular resistance exercise can reverse muscle loss and maintain muscle in later life.

References De Vicentis S et al. Sarcopenic obesity and reduced BMD in young men living with HIV; body composition and sex steroids interplay. Journal of Endocrinological Investigation, published online 20 April 2024