Obesity-related insulin resistance may be caused by adipokines such as IL-6, which is known to be elevated with the insulin resistance syndrome. A previous study reported that IL-6 knockout mice (IL-6−/−) developed maturity onset obesity, with disturbed carbohydrate and lipid metabolism, and increased leptin levels. Because IL-6 is associated with insulin resistance, one might have expected IL-6−/− mice to be more insulin sensitive. We examined body weights of growing and older IL-6−/− mice and found them to be similar to wild-type (IL-6+/+) mice. Dual-energy X-ray absorptiometry analysis at 3 and 14 mo revealed no differences in body composition. There were no differences in fasting blood insulin and glucose or in triglycerides. To further characterize these mice, we fed 11-mo-old IL-6−/− and IL-6+/+ mice a high- (HF)- or low-fat diet for 14 wk, followed by insulin (ITT) and glucose tolerance tests (GTT). An ITT showed insulin resistance in the HF animals but no difference due to genotype. In the GTT, IL-6−/− mice demonstrated elevated postinjection glucose levels by 60% compared with IL-6+/+ but only in the HF group. Although IL-6−/− mice gained weight and white adipose tissue (WAT) with the HF diet, they gained less weight than the IL-6+/+ mice. Total lipoprotein lipase activity in WAT, muscle, and postheparin plasma was unchanged in the IL-6 −/− mice compared with IL-6+/+ mice. There were no differences in plasma leptin or TNF-α due to genotype. Plasma adiponectin was ∼53% higher (71.7 ± 14.1 μg/ml) in IL-6−/− mice than in IL-6+/+ mice but only in the HF group. Thus these data show that IL-6−/− mice do not demonstrate obesity, fasting hyperglycemia, or abnormal lipid metabolism, although HF IL-6−/− mice demonstrate elevated glucose after a GTT.

To establish genetic tools for conditional gene deletion in mouse neurons, we generated two independent neuron-specific enolase (Nse)-cre transgenic lines. The transgenic line termed Nse-cre(CK1) showed cre activity in most neuronal regions in the nervous system, while the Nse-cre(CK2) line exhibited a unique cre activity that has not been reported in other cre transgenic lines. Nse-cre(CK2) cre activity was detectable from embryogenesis and mostly restricted to neuronal regions. In postnatal brain, the Nse-cre(CK2) line exhibited cre activity limited to differentiated neurons in the cerebral cortex and hippocampus. Cre activity was assayed in several internal organs and sporadic activity was limited to the kidney and testis. We conclude that these cre lines will be useful for studying loss of gene function in specific neuronal populations.

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Mitoxantrone has been approved by the FDA for the treatment of multiple sclerosis (MS). However, the mechanisms by which mitoxantrone modulates MS are largely unknown. Activated astrocytes produce nitric oxide (NO), TNF-α, and IL-1β, molecules which can be toxic to central nervous system (CNS) cells including oligodendrocytes, thus potentially contributing to the pathology associated with MS. MCP-1 is a chemokine believed to modulate the migration of monocytes to inflammatory lesions present in the CNS of MS patients. IL-12 and IL-23 have been demonstrated to play critical roles in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of MS, by contributing to the development of CD4+ T cell lineages termed Th1 and Th17, respectively. The current study demonstrates that mitoxantrone inhibits lipopolysachharide (LPS) induction of NO, TNF-α, IL-1β, and MCP-1 production by primary astrocytes. Mitoxantrone also inhibited IL-12 and IL-23 production by these cells. Furthermore, mitoxantrone suppressed the expression of C-reactive protein (CRP). Finally, we demonstrate that mitoxantrone suppressed LPS induction of NF-κB DNA-binding activity, suggesting a novel mechanism by which mitoxantrone suppresses the expression of proinflammatory molecules. Collectively, these studies demonstrate that mitoxantrone represses astrocyte production of potentially cytotoxic molecules, as well as molecules capable of altering T-cell phenotype. These in vitro studies suggest mechanisms by which mitoxantrone may modulate inflammatory diseases including MS.

Lipoprotein lipase (LPL) is a key enzyme in lipoprotein and adipocyte metabolism. Defects in LPL can lead to hypertriglyceridemia and the subsequent development of atherosclerosis. The mechanisms of regulation of this enzyme are complex and may occur at multiple levels of gene expression. Because the 3 -untranslated region (UTR) is involved in LPL translational regulation, transgenic mice were generated with adipose tissue expression of an LPL construct either with or without the proximal 3 -UTR and driven by the aP2 promoter. Both transgenic mouse colonies were viable and expressed the transgene, resulting in a 2-fold increase in LPL activity in white adipose tissue. Neither mouse colony exhibited any obvious phenotype in terms of body weight, plasma lipids, glucose, and non-esterified fatty acid levels. In the mice expressing hLPL with an intact 3 -UTR, hLPL mRNA expression approximately paralleled hLPL activity. However in the mice without the proximal 3 -UTR, hLPL mRNA was low in the setting of large amounts of hLPL protein and LPL activity. In previous studies, the 3 -UTR of LPL was critical for the inhibitory effects of constitutively expressed hormones, such as thyroid hormone and catecholamines. Therefore, these data suggest that the absence of the 3 -UTR results in a translationally unrepressed LPL, resulting in a moderate overexpression of adipose LPL activity.Lipoprotein lipase (LPL) 1 is a central enzyme in lipid metabolism. The enzyme is synthesized and secreted by adipocytes and muscle cells, and transported to the capillary endothelium, where hydrolysis of the triglyceride core of circulating VLDL and chylomicrons takes place. Although the changes in LPL activity with different physiologic states have been well described (1), the mechanism of LPL regulation is complex and occurs at levels of transcription (2-6), translation (7-11), and post-translational processing (12-15) in response to both cell type and regulatory factors. Previous studies have demonstrated translational regulation of LPL. In response to glucose (7), thyroid hormone (8), and catecholamines (9), there were significant changes in LPL protein synthesis, with no changes in adipocyte LPL mRNA levels. In addition, the decrease in LPL activity in both diabetic patients, and rats is due predominantly to decreased LPL translation (10, 16).LPL is an important marker of adipocyte differentiation, and LPL expression increases in parallel with cellular triglyceride accumulation in preadipocytes (17, 18). Although adipose tissue can synthesize non-esterified fatty acids (NEFA) de novo, NEFA for lipid storage are preferentially obtained from LPLmediated hydrolysis of plasma lipoproteins (19). Hence, LPL has been called "the gatekeeper of the adipocyte" (20), and has been implicated in the development of obesity.Based on LPL's putative role as an adipocyte "gatekeeper," one might expect that transgenic mice would become obese if LPL were overexpressed in adipose tissue, and lean if LPL were overexpressed in muscle. Several recent studies have ...