Franz-Volhard Clinical Research Center at the Experimental and Clinical Research Center, University Hospital Charite Campus Buch and HELIOS Klinikum-Berlin, 13125 Berlin, Germany.
J Clin Endocrinol Metab. 2010 Apr;95(4):1634-43. doi: 10.1210/jc.2009-1293. Epub 2010 Feb 3.
Type 2 familial partial lipodystrophy (FPLD) is an autosomal-dominant lamin A/C-related disease associated with exercise intolerance, muscular pain, and insulin resistance. The symptoms may all be explained by defective metabolism; however, metabolism at the tissue level has not been investigated.
We hypothesized that in FPLD, insulin resistance and impaired aerobic exercise capacity are explained by a common underlying mechanism, presumably a muscular metabolic defect.
Carbohydrate and lipid metabolism was studied on 10 FPLD patients, one patient with limb-girdle muscular dystrophy (LGMD1B, a different lamin A/C disease), and 10 healthy control subjects before and during an oral glucose tolerance test by indirect calorimetry and im microdialysis. Muscle biopsies were taken for in vitro studies.
We observed marked increased skeletal muscle fatty acid beta-oxidation rate in vitro and in vivo, even after glucose ingestion in FPLD patients. However, fatty acid oxidation was largely incomplete and accompanied by increased ketogenesis. The lipid oxidation abnormality was associated with impaired glucose disposition through reduction in glucose oxidation, rather than decreased cellular glucose uptake. A microarray showed down-regulation of complex I respiratory chain, glycolysis, and nuclear transport genes. Although not overtly insulin resistant, the LGMD1B patient showed similar metabolic derangements as the FPLD patients.
Our study suggests imbalance between lipid oxidation and oxidative glucose metabolism in FPLD and LGMD1B patients. The observation suggests an intrinsic defect in skeletal muscle metabolism due to lamin A/C dysfunction. The metabolic FPLD phenotype likely results from this intrinsic defect combined with lipodystrophic "lipid pressure" due to decreased adipose tissue lipid storage capacity.
2 型家族性部分脂肪营养不良（FPLD）是一种常染色体显性遗传的核纤层蛋白 A/C 相关疾病，与运动不耐受、肌肉疼痛和胰岛素抵抗有关。这些症状都可以用代谢缺陷来解释；然而，组织水平的代谢尚未得到研究。
我们假设在 FPLD 中，胰岛素抵抗和有氧运动能力受损是由一个共同的潜在机制解释的，推测是肌肉代谢缺陷。
通过间接热量测定法和 im 微透析法，在口服葡萄糖耐量试验前后，我们研究了 10 例 FPLD 患者、1 例肢带型肌营养不良症 1B 型（一种不同的核纤层蛋白 A/C 疾病）患者和 10 例健康对照者的碳水化合物和脂质代谢。采集肌肉活检标本进行体外研究。
我们观察到 FPLD 患者即使在葡萄糖摄入后，体外和体内骨骼肌脂肪酸β氧化率显著增加。然而，脂肪酸氧化很大程度上是不完全的，并伴有酮体生成增加。脂质氧化异常与葡萄糖氧化减少有关，而不是细胞葡萄糖摄取减少，导致葡萄糖处置受损。微阵列显示，复合物 I 呼吸链、糖酵解和核转运基因下调。尽管 LGMD1B 患者没有明显的胰岛素抵抗，但表现出与 FPLD 患者相似的代谢紊乱。
我们的研究表明，FPLD 和 LGMD1B 患者的脂质氧化和氧化葡萄糖代谢之间存在不平衡。这一观察结果表明，由于核纤层蛋白 A/C 功能障碍，骨骼肌代谢存在内在缺陷。代谢型 FPLD 表型可能是由于这种内在缺陷与由于脂肪组织脂质储存能力降低而导致的脂肪营养不良“脂质压力”相结合所致。
