Mainly from cell culture studies, a series of genes that have been suggested to be characteristic of different types of adipocytes have been identified. Here we have examined gene expression patterns in nine defined adipose depots: interscapular BAT, cervical BAT, axillary BAT, mediastinic BAT, cardiac WAT, inguinal WAT, retroperitoneal WAT, mesenteric WAT, and epididymal WAT. We found that each depot displayed a distinct gene expression fingerprint but that three major types of depots were identifiable: the brown, the brite, and the white. Although differences in gene expression pattern were generally quantitative, some gene markers showed, even in vivo, remarkable depot specificities: Zic1 for the classical BAT depots, Hoxc9 for the brite depots, Hoxc8 for the brite and white in contrast to the brown, and Tcf21 for the white depots. The effect of physiologically induced recruitment of thermogenic function (cold acclimation) on the expression pattern of the genes was quantified; in general, the depot pattern dominated over the recruitment effects. The significance of the gene expression patterns for classifying the depots and for understanding the developmental background of the depots is discussed, as are the possible regulatory functions of the genes.

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The absorption kinetics of NPH (isophane) insulin injected subcutaneously into the abdominal wall and subcutaneously (SC) and intramuscularly (IM) into the thigh was studied in 11 Type 1 diabetic patients. The thickness of the subcutaneous adipose tissue layer was measured by ultrasound. NPH (isophane) insulin injected IM into the thigh was absorbed faster than NPH insulin injected SC into the thigh (T50%, IM 8.0 +/- 0.6 h and SC 10.3 +/- 0.7 h, p less than 0.05). No difference in T50% values was found for injection into the abdominal wall (9.7 +/- 1.2h) compared with the thigh. The mean absorption rate from 1.5 to 13.5 h after injection was higher after injection IM into the thigh (6.4 +/- 0.3% of initial dose injected absorbed per h) than after SC injection into the thigh (5.2 +/- 0.3% h-1) and SC into the abdominal wall (5.1 +/- 0.3% h-1) (p less than 0.01). The most constant absorption rate was obtained after SC injection into the thigh (within-study day CV of the mean absorption rate 19.9 +/- 3.2% vs 34.4 +/- 3.2% after IM injection into the thigh and 27.1 +/- 4.9% after SC injection into the abdominal wall (p less than 0.02]. The study provides further evidence that the subcutaneous tissue of the thigh is the preferred injection site for NPH insulin.