No abstract

Apolipoprotein E (apoE) is highly expressed in adipose tissue and adipocytes in which its expression is regulated by peroxisome proliferator-activated receptor (PPAR)-␥ agonists and tumor necrosis factor-␣. There is, however, no information regarding a role for endogenous apoE in differentiated adipocyte function. In this report, we define a novel role for apoE in modulating adipocyte lipid metabolism. ApoE ؊/؊ mice have less body fat and smaller adipocytes compared with wild-type controls. Freshly isolated adipose tissue from apoE ؊/؊ mice contains lower levels of triglyceride and free fatty acid, and these differences are maintained in cultured adipocytes derived from preadipocytes. Adenoviral expression of apoE in apoE ؊/؊ -cultured adipocytes increases triglyceride and fatty acid content. During incubation with apoE-containing triglyceride-rich lipoproteins, apoE ؊/؊ adipose tissue accumulates less triglyceride than wild type. The absence of apoE expression in primary cultured adipocytes also leads to changes in the expression of genes involved in the metabolism/turnover of fatty acids and the triglyceride droplet. Markers of adipocyte differentiation were lower in freshly isolated and cultured apoE ؊/؊ adipocytes. Importantly, PPAR-␥-mediated changes in lipid content and gene expression are markedly altered in cultured apoE ؊/؊ adipocytes. These results establish a novel role for endogenous apoE in adipocyte lipid metabolism and have implications for constructing an integrated model of adipocyte physiology in health and disease. Diabetes 55:3394 -3402, 2006 O besity and its consequent insulin resistance are major health problems in the U.S., imparting significant risk for diabetes and cardiovascular disease (1-4). The prevalence of obesity is predicted to substantially increase over the next several decades, and there is a need to better understand adipocyte and adipose tissue physiology. In the past several years, it has become apparent that adipocytes and adipose tissue actively modulate systemic substrate availability and produce a number of protein factors with endocrine, paracrine, and autocrine regulatory activity (5,6). Apolipoprotein E (apoE), which was first described as a product of hepatocytes and a surface component of lipoproteins, e.g., in humans, chylomicrons, VLDL, remnant lipoproteins, and HDL, has been shown to be highly expressed in adipocytes and adipose tissue (7). Interestingly, apoE has been shown to be highly expressed in a number of cell types that experience high lipid flux (8 -15). The physiologic role of apoE expression in other cell types has been intensively studied and characterized (8 -15). In macrophages and steroidogenic cells, for example, endogenous apoE expression plays an important role in cellular lipid balance. Adipocytes and adipose tissue, like macrophages and steroidogenic cells, also experience large lipid fluxes integral to their differentiated function, yet there is no information regarding a potential physiologic role of apoE expressed in the adipocyte. Our lab...

The generation of deep-ultraviolet (UV) coherent light from nonlinear optical (NLO) materials [1][2][3][4] as one of the most promising resource, has become a topic of intensive study because of its important applications in a broad range of fields, such as semiconductor photolithography, laser micromachining, photochemical synthesis, and material processing. They are able to shorten the wavelength of light by a factor of two (or doubling the frequency), based on the process of second-harmonic generation (SHG), which occurs only when a centrosymmetric symmetry operation is absent in a crystal. However, for a noncentrosymmetric (NCS) crystal to be used as a nonlinear optical material the essential crystal property requirements are that the crystals possess a large NLO response, wide transparent window, suitable birefringence for phase-matching, good mechanical strength, and chemical stability. [4,5] After continuous efforts over several decades, many NCS compounds were obtained by incorporating functional borate structure units, such as B 3 O 6 and B 3 O 7 . b-BaB 2 O 4 (BBO) [6] and LiB 3 O 5 (LBO) [7] are the most advanced NLO materials, which have widely been used as optoelectronic devices. However, to date, KBe 2 BO 3 F 2 (KBBF) [8,9] is the only material that can generate coherent light wavelengths below 200 nm by direct SHG, which makes KBBF a research hotspot. Unfortunately, the KBBF crystal is very difficult to grow in thickness owing to the growth habit of the layer, which severely limits the coherent light output power. Thus, finding the optimal composition that is facile to synthesize, yields large single crystals, and simultaneously satisfies the NLO requirements has attracted considerable attention. [10,11] The presence of large NLO coefficients in a structure is usually in contradiction with wide band gaps in one compound. For instance, the structural units in the known compounds are second-order Jahn-Teller (SOJT) polar dis- [17] which combine with diverse other functional building units to produce materials with large NLO coefficients, for example, Cd 4 BiO-(BO 3 ) 3 (6 KDP), [18] Pb 2 B 5 O 9 I (13.5 KDP), [19] and Ba 23 Ga 8 Sb 2 S 38 (22 AgGaS 2 ).[20] However, the structural units produce an unwanted effect-the UV absorption edge shifts toward the red region, making them less suitable for the deep-UV applications. It is necessary to create the subtle balance of above-mentioned conflicting factors so as to search for the new deep-UV NLO crystals with excellent comprehensive performances.To circumvent the wide absorption window requirement, basic structural units having excitation energies near the UV region are necessary. Such units are BO 3 , BO 4 , SiO 4 , and PO 4 . [6,7,21] A compound Rb 2 Be 2 Si 2 O 7 [22] was ever expected to be a substitution for KBBF owing to its similar structure characteristics with KBBF and without the layer habit. But, the weak SHG response of Rb 2 Be 2 Si 2 O 7 makes the substitution end in naught. However, the borosilicate may be a potential candidate for a deep-...

No abstract