Klein D J, Brown D M, Oegema T R
Diabetes. 1986 Oct;35(10):1130-42. doi: 10.2337/diab.35.10.1130.
The metabolism of glomerular proteoglycans was studied in an effort to understand the mechanisms leading to reduction of glomerular basement membrane (GBM) heparan sulfate (heparan-SO4) proteoglycan in diabetes. Glomeruli were isolated from control and streptozocin-induced diabetic rats after exposure to [35S]sulfate. A pool of rapidly metabolized 35S-glycosaminoglycans (GAG), predominantly heparan-35SO4, was present in GBMs from controls but not diabetics, whereas intact isolated glomeruli from the two groups contained similar quantities of 35S-macromolecules after 4 and 16 h in vitro. Glomeruli from diabetics contained less 35S-proteoglycan than controls after 16 h in vivo. A more rapid disappearance of [35S]sulfate from serum and an increased inorganic sulfate concentration in diabetes may account for this difference. Glomeruli from diabetics contained more heparan-35SO4 and less dermatan-35SO4 proteoglycan than control glomeruli in vitro. Diabetic glomerular heparan-35SO4 proteoglycan and its GAG chains had hydrodynamic sizes similar to controls (Mr, 13 and 1.25 X 10(4), respectively). A heparin-releasable heparan-35SO4 proteoglycan detected in isolated control glomeruli by gel electrophoresis was present in chase medium of glomeruli from diabetics in the absence of heparin. Two dermatan-35SO4 proteoglycans were synthesized in vitro. One had size and charge properties similar to glomerular heparan-35SO4 proteoglycan. A second, larger dermatan-35SO4 proteoglycan accumulated in tissue over 16 h. It was partially excluded from Sepharose CL-6B columns and eluted from Sepharose CL-4B columns at Kav = 0.32. The hydrodynamic sizes of both tissue forms of dermatan-35SO4 proteoglycans were similar in diabetics and controls. Differences in the biochemical characteristics of the major de novo synthesized glomerular proteoglycan pools could not be invoked to explain altered metabolism of GBM heparan sulfate in diabetic animals. These changes may result from diminished affinity of heparan sulfate proteoglycan for extracellular matrix or cell surfaces and may account for altered glomerular ultrafiltration properties in diabetes mellitus.
为了了解糖尿病时导致肾小球基底膜（GBM）硫酸乙酰肝素蛋白聚糖减少的机制，对肾小球蛋白聚糖的代谢进行了研究。给对照大鼠和链脲佐菌素诱导的糖尿病大鼠注射[35S]硫酸盐后，分离肾小球。对照组GBM中存在大量快速代谢的35S-糖胺聚糖（GAG），主要是硫酸乙酰肝素35SO4，而糖尿病组则没有；体外培养4小时和16小时后，两组完整分离的肾小球中35S-大分子的含量相似。糖尿病大鼠的肾小球在体内16小时后所含的35S-蛋白聚糖比对照组少。糖尿病时血清中[35S]硫酸盐更快消失以及无机硫酸盐浓度升高可能解释了这种差异。体外实验中，糖尿病组肾小球所含的硫酸乙酰肝素35SO4蛋白聚糖比对照组多，而硫酸皮肤素35SO4蛋白聚糖比对照组少。糖尿病组肾小球硫酸乙酰肝素35SO4蛋白聚糖及其GAG链的流体力学大小与对照组相似（Mr分别为13和1.25×10(4)）。通过凝胶电泳在分离的对照肾小球中检测到的可被肝素释放的硫酸乙酰肝素35SO4蛋白聚糖，在无肝素的情况下存在于糖尿病组肾小球的追踪培养基中。体外合成了两种硫酸皮肤素35SO4蛋白聚糖。一种的大小和电荷性质与肾小球硫酸乙酰肝素35SO4蛋白聚糖相似。第二种更大的硫酸皮肤素35SO4蛋白聚糖在16小时内积聚在组织中。它部分被排除在Sepharose CL-6B柱之外，并在Kav = 0.32时从Sepharose CL-4B柱中洗脱出来。糖尿病组和对照组中硫酸皮肤素35SO4蛋白聚糖两种组织形式的流体力学大小相似。不能用主要新合成的肾小球蛋白聚糖池的生化特性差异来解释糖尿病动物GBM硫酸乙酰肝素代谢的改变。这些变化可能是由于硫酸乙酰肝素蛋白聚糖对细胞外基质或细胞表面的亲和力降低所致，可能解释了糖尿病时肾小球超滤特性的改变。
