Time course of skeletal muscle repair and gene expression following acute hind limb ischemia in mice.

DNA microarrays were used to measure the time course of gene expression during skeletal muscle damage and regeneration in mice following femoral artery ligation (FAL). We found 1,289 known sequences were differentially expressed between the FAL and control groups. Gene expression peaked on day 3, and the functional cluster "inflammation" contained the greatest number of genes. Muscle function was depressed for 3 days postligation, but returned to normal by day 7. Decreased muscle function was accompanied by reduced expression of genes involved in mitochondrial energy production, muscle contraction, and calcium handling. The induction of MyoD on day 1 denoted the beginning of muscle regeneration and was followed by the reemergence of the embryonic forms of muscle contractile proteins, which peaked at day 7. Transcriptional analysis indicated that the ischemic skeletal muscle may transition through a functional adaptation stage with recovery of contractile force prior to full regeneration. Several members of the insulin-like growth factor axis were coordinately induced in a time frame consistent with their playing a role in the regenerative process.

Transgenic mice expressing human fibroblast growth factor-19 display increased metabolic rate and decreased adiposity.

The fibroblast growth factors (FGFs), and the corresponding receptors, are implicated in more than just the regulation of epithelial cell proliferation and differentiation. Specifically, FGF23 is a regulator of serum inorganic phosphate levels, and mice deficient in FGF receptor-4 have altered cholesterol metabolism. The recently described FGF19 is unusual in that it is nonmitogenic and appears to interact only with FGF receptor-4. Here, we report that FGF19 transgenic mice had a significant and specific reduction in fat mass that resulted from an increase in energy expenditure. Further, the FGF19 transgenic mice did not become obese or diabetic on a high fat diet. The FGF19 transgenic mice had increased brown adipose tissue mass and decreased liver expression of acetyl coenzyme A carboxylase 2, providing two mechanisms by which FGF19 may increase energy expenditure. Consistent with the reduction in expression of acetyl CoA carboxylase 2, liver triglyceride levels were reduced.

Stanniocalcin 1 alters muscle and bone structure and function in transgenic mice.

Fish stanniocalcin (STC) inhibits uptake of calcium and stimulates phosphate reabsorption. To determine the role of the highly homologous mammalian protein, STC-1, we created and characterized transgenic mice that express STC-1 under control of a muscle-specific promoter. STC-1 transgenic mice were smaller than wild-type littermates and had normal growth plate cartilage morphology but increased cartilage matrix synthesis. In STC-1 mice, the rate of bone formation, but not bone mineralization, was decreased. Increased cortical bone thickness and changes in trabeculae number, density, and thickness in STC-1 mice indicated a concomitant suppression of osteoclast activity, which was supported by microcomputed tomography analyses and histochemistry. Skeletal muscles were disproportionately small and showed altered function and response to injury in STC-1 mice. Electron microscopy indicated that muscle mitochondria were dramatically enlarged in STC-1 mice. These changes in STC-1 mice could not be explained by deficits in blood vessel formation, as vascularity in organs and skeletal tissues was increased as was induction of vascularity in response to femoral artery ligation. Our results indicate that STC-1 can affect calcium homeostasis, bone and muscle mass and structure, and angiogenesis through effects on osteoblasts, osteoclasts, myoblasts/myocytes, and endothelial cells.

Lipoprotein subclass profiles of hyperlipidemic diabetic mice measured by nuclear magnetic resonance spectroscopy.

Dyslipidemia accelerates vascular complications of diabetes. Nuclear magnetic resonance (NMR) analysis of lipoprotein subclasses is used to evaluate a mouse model of human familial hypercholesterolemia +/- streptozotocin (STZ)-induced diabetes. A double knockout (DKO) mouse (low-density lipoprotein receptor [LDLr] -/-; apolipoprotein B [apoB] mRNA editing catalytic polypeptide-1 [Apobec1] -/-) was studied. Wild-type (WT) and DKO mice received sham or STZ injections at age 7 weeks, yielding control (WT-C, DKO-C) and diabetic (WT-D, DKO-D) groups. Fasting serum was collected when the mice were killed (age 40 weeks) for Cholestech analysis (Cholestech Corp, Hayward, CA) and NMR lipoprotein subclass profile. By Cholestech, fasting triglyceride and total cholesterol increased in DKO-C versus WT-C. Diabetes further increased total cholesterol in DKO. High-density lipoprotein cholesterol (HDL-C) was similar among all groups. NMR revealed that LDL in all groups was present in a subclass the size of large human LDL and was increased 48-fold in DKO-C versus WT-C animals, but was unaffected by diabetes. HDL was found in a subclass equivalent to large human HDL, and was similar among groups. In conclusion, NMR analysis reveals lipoprotein subclass distributions and the effects of genetic modification and diabetes in mice, but lack of particles the size of human small LDL and small HDL may limit the relevance of the present animal model to human disease.

Nephropathy in a hypercholesterolemic mouse model with streptozotocin-induced diabetes.

BACKGROUND/AIMS: The contribution of preexisting hypercholesterolemia to diabetic nephropathy remains unclear. We assessed the impact of hypercholesterolemia on diabetic nephropathy using a double knockout (DKO) mouse, null for the low-density lipoprotein receptor (LDLRNDASH;/NDASH;) and the apoB mRNA editing catalytic polypeptide 1 (APOBEC1NDASH;/NDASH;). METHODS: Wild-type (WT) and DKO mice received sham or streptozotocin injections at age 7 weeks, yielding control (WT-C, DKO-C) and diabetic (WT-D, DKO-D) groups. At sacrifice (age 40 weeks), albuminuria was determined by ELISA, and kidney sections were examined by light and electron microscopy. RESULTS: Albuminuria increased in diabetic mice (WT-D: 82.4 +/- 37.2 microg/18 h; DKO-D: 58.0 +/- 45.7 microg/18 h) versusnondiabetic controls (WT-C: 10.2 +/- 7.2 microg/18 h; DKO-C: 8.6 +/- 5.3 microg/18 h) (p LT; 0.0001), but was unaffected by hypercholesterolemia. Light microscopy of kidney sections demonstrated increased collagen levels in glomeruli in WT-D mice, but not in DKO-D mice or either control group. Electron microscopy showed a thickened glomerular basement membrane in WT-D mice only. The proximal tubular basement membrane thickness was increased in both diabetic groups versusnondiabetic controls (p LT; 0.01); in WT-D mice this was attributable to collagen accumulation, but in DKO-D mice it was mainly caused by lipid vacuoles. CONCLUSIONS: In this animal model, preexisting hypercholesterolemia did not exacerbate either glomerular lesions of diabetes (collagen accumulation, basement membrane thickening) or albuminuria, but appeared to mitigate these effects. Furthermore, the combination of hypercholesterolemia and diabetes resulted in a significant lipid accumulation in the tubular basement membrane.