Spanheimer R, Zlatev T, Umpierrez G, DiGirolamo M
Department of Medicine, University of Iowa School of Medicine, Iowa City 52246.
J Nutr. 1991 Apr;121(4):518-24. doi: 10.1093/jn/121.4.518.
Malnutrition is associated with defects in connective tissue metabolism such as altered growth and wound healing. Because collagen is the major protein in most tissues, we determined the threshold for induction of altered collagen production by partial food restriction in rats. Groups of animals were fasted 2 or 4 d or were fed 20-100% of a predetermined food intake for 4 to 8 d. Collagen and noncollagen protein production in articular cartilage were determined using purified collagenase digestion of collagen labeled for 2 h in vitro with [3H]proline. Significant decreases in collagen (P less than 0.01) were seen in rats after 4 d of 40% (weight-losing rats) or after 8 days of 80% (weight-gaining rats) ad libitum intake. Collagen production decreased with both duration and degree of food deprivation; after 8 d of 20% intake, collagen was less than 10% that of controls fed ad libitum (P less than 0.001). In contrast, noncollagen protein production was significantly decreased only after 4 or 8 d of less than 40% intake (weight-losing rats). Maximum suppression of noncollagen protein was to approximately 65% of levels in controls fed ad libitum (P less than 0.01) and was not further reduced in fasted rats. Insulin-like growth factor-I levels were significantly decreased with duration and severity of diet in parallel with changes in collagen. The degree and sensitivity of altered collagen production to small changes in food intake suggest close regulation of this peptide and a potential role for decreased collagen synthesis in connective tissues during mild states of undernutrition.
营养不良与结缔组织代谢缺陷有关，如生长改变和伤口愈合异常。由于胶原蛋白是大多数组织中的主要蛋白质，我们确定了大鼠部分食物限制诱导胶原蛋白产生改变的阈值。将动物分组，禁食2天或4天，或给予预定食物摄入量的20%-100%，持续4至8天。使用纯化的胶原酶消化在体外用[3H]脯氨酸标记2小时的胶原蛋白，测定关节软骨中胶原蛋白和非胶原蛋白的产生。在40%摄入量（体重减轻的大鼠）4天后或80%摄入量（体重增加的大鼠）8天后，大鼠的胶原蛋白显著减少（P<0.01）。胶原蛋白的产生随食物剥夺的持续时间和程度而降低；在20%摄入量8天后，胶原蛋白不到自由进食对照组的10%（P<0.001）。相比之下，只有在摄入量低于40%（体重减轻的大鼠）4天或8天后，非胶原蛋白的产生才显著降低。非胶原蛋白的最大抑制约为自由进食对照组水平的65%（P<0.01），禁食大鼠中未进一步降低。胰岛素样生长因子-I水平随饮食的持续时间和严重程度显著降低，与胶原蛋白的变化平行。胶原蛋白产生对食物摄入量微小变化的改变程度和敏感性表明该肽受到密切调节，并且在轻度营养不良状态下结缔组织中胶原蛋白合成减少可能起作用。
