Admiraal W M, Verberne H J, Karamat F A, Soeters M R, Hoekstra J B L, Holleman F
Department of Internal Medicine F4-215, Academic Medical Center, PO Box 22660, 1100DD, Amsterdam, the Netherlands,
Diabetologia. 2013 Oct;56(10):2231-7. doi: 10.1007/s00125-013-2938-5. Epub 2013 Jun 25.
AIMS/HYPOTHESIS: South Asians have a disproportionately high risk of developing abdominal obesity, insulin resistance and type 2 diabetes. Brown adipose tissue (BAT) has been identified as a possible target to fight obesity and protect against metabolic disturbance. We explored whether lower BAT activity in South Asians compared with Europids may contribute to the high risk of metabolic disturbance.
We studied 20 healthy men (ten Europids/ten South Asians, BMI 19-25 kg/m(2), age 18-32 years). Following 2 h of cold exposure (16-18°C) after an overnight fast, (18)F-fluorodeoxyglucose ((18)F-FDG) positron-emission tomography-computed tomography (CT) and (123)I-metaiodobenzylguanidine ((123)I-MIBG) single-photon emission computed tomography-CT were performed to visualise metabolic BAT activity and sympathetic stimulation of BAT. Metabolic BAT activity was defined as maximal standardised uptake value (SUV(max)) of (18)F-FDG, and sympathetic stimulation of BAT as semiquantitative uptake value (SQUV) of (123)I-MIBG. We performed hyperinsulinaemic-euglycaemic clamps to assess insulin sensitivity. Spearman's correlations for SUV(max) of (18)F-FDG and both SQUV of (123)I-MIBG and insulin sensitivity were determined.
The median (interquartile range) SUV(max) of (18)F-FDG in South Asians (7.5 [2.2-10.6] g/ml) was not different from the median SUV(max) obtained in Europids (4.5 [2.2-8.4] g/ml; p = 0.59). There was no correlation between BAT activity and insulin sensitivity. Correlations between SQUV of (123)I-MIBG and SUV(max) of (18)F-FDG were positive, both in the total population (ρ = 0.80, p < 0.001) and after stratification by ethnicity (Europids, ρ = 0.65, p = 0.04; South Asians, ρ = 0.83, p = 0.01).
CONCLUSIONS/INTERPRETATION: This is the first study to prospectively investigate ethnic differences in metabolic BAT activity during cold exposure. We did not find differences in BAT activity between South Asians and Europids. Therefore, it seems unlikely that BAT plays an important role in the development of unfavourable metabolic profiles in South Asians.
目的/假设：南亚人患腹部肥胖、胰岛素抵抗和2型糖尿病的风险极高。棕色脂肪组织（BAT）已被确定为对抗肥胖和预防代谢紊乱的一个可能靶点。我们探究了与欧洲裔相比，南亚人较低的BAT活性是否可能导致其代谢紊乱风险较高。
我们研究了20名健康男性（10名欧洲裔/10名南亚裔，体重指数19 - 25kg/m²，年龄18 - 32岁）。在空腹过夜后进行2小时冷暴露（16 - 18°C），之后进行¹⁸F - 氟脱氧葡萄糖（¹⁸F - FDG）正电子发射断层扫描 - 计算机断层扫描（CT）以及¹²³I - 间碘苄胍（¹²³I - MIBG）单光子发射计算机断层扫描 - CT，以观察代谢性BAT活性和BAT的交感神经刺激情况。代谢性BAT活性定义为¹⁸F - FDG的最大标准化摄取值（SUV(max)），BAT的交感神经刺激定义为¹²³I - MIBG的半定量摄取值（SQUV）。我们进行了高胰岛素 - 正常血糖钳夹试验以评估胰岛素敏感性。确定了¹⁸F - FDG的SUV(max)与¹²³I - MIBG的SQUV以及胰岛素敏感性之间的Spearman相关性。
南亚人¹⁸F - FDG的SUV(max)中位数（四分位间距）为7.5[2.2 - 10.6]g/ml，与欧洲裔获得的SUV(max)中位数（4.5[2.2 - 8.4]g/ml；p = 0.59）无差异。BAT活性与胰岛素敏感性之间无相关性。¹²³I - MIBG的SQUV与¹⁸F - FDG的SUV(max)之间的相关性在总体人群中为正（ρ = 0.80，p < 0.001），按种族分层后（欧洲裔，ρ = 0.65，p = 0.04；南亚裔，ρ = 0.83，p = 0.01）也为正。
结论/解读：这是第一项前瞻性研究冷暴露期间代谢性BAT活性种族差异的研究。我们未发现南亚人和欧洲裔之间BAT活性存在差异。因此，BAT似乎不太可能在南亚人不良代谢状况的发展中起重要作用。
