OBJECTIVE-We sought to determine the role of adipocyte death in obesity-induced adipose tissue (AT) inflammation and obesity complications.RESEARCH DESIGN AND METHODS-Male C57BL/6 mice were fed a high-fat diet for 20 weeks to induce obesity. Every 4 weeks, insulin resistance was assessed by intraperitoneal insulin tolerance tests, and epididymal (eAT) and inguinal subcutaneous AT (iAT) and livers were harvested for histological, immunohistochemical, and gene expression analyses.RESULTS-Frequency of adipocyte death in eAT increased from Ͻ0.1% at baseline to 16% at week 12, coincident with increases in 1) depot weight; 2) AT macrophages (ATM⌽s) expressing F4/80 and CD11c; 3) mRNA for tumor necrosis factor (TNF)-␣, monocyte chemotactic protein (MCP)-1, and interleukin (IL)-10; and 4) insulin resistance. ATM⌽s in crown-like structures surrounding dead adipocytes expressed TNF-␣ and IL-6 proteins. Adipocyte number began to decline at week 12. At week 16, adipocyte death reached ϳ80%, coincident with maximal expression of CD11c and inflammatory genes, loss (40%) of eAT mass, widespread collagen deposition, and accelerated hepatic macrosteatosis. By week 20, adipocyte number was restored with small adipocytes, coincident with reduced adipocyte death (fourfold), CD11c and MCP-1 gene expression (twofold), and insulin resistance (35%). eAT weight did not increase at week 20 and was inversely correlated with liver weight after week 12 (r ϭ Ϫ0. 85, P Ͻ 0.001). In iAT, adipocyte death was first detected at week 12 and remained Յ3%.CONCLUSIONS-These results implicate depot-selective adipocyte death and M⌽-mediated AT remodeling in inflammatory and metabolic complications of murine obesity. Diabetes

Holstein cows (n = 30) entering second or greater lactation were fed fat supplements (90 g/d of fatty acids) consisting of Ca salts of either palm fatty acid distillate (control) or a mixture of palm fatty acid distillate and mixed isomers of conjugated linoleic acid (CLA, 30.4 g/ d) from 2 wk prepartum through 20 wk postpartum to determine whether CLA would inhibit milk fat synthesis during early lactation and, in turn, affect energy metabolism of dairy cows during the transition period and early lactation. Feeding CLA did not affect DMI or plasma concentrations of glucose, nonesterfied fatty acids, or beta-hydroxbutyrate during the prepartum period and did not affect postpartum DMI. Feeding CLA reduced milk fat content by 12.5% during early lactation; however, cows fed CLA tended to produce approximately 3 kg/d more milk during the first 20 wk of lactation. Feeding CLA tended to decrease the contribution of short- and medium-chain (C < or = 16) fatty acids to milk fat. Changes in milk yield, milk fat content, and milk fatty acid composition were not apparent until after the second week of lactation. Yield of 3.5% fat-corrected milk, milk protein content, milk protein composition, and calculated energy balance were not affected by treatment. Postpartum concentrations of glucose, nonesterfied fatty acids, and beta-hydroxbutyrate in plasma and hepatic content of glycogen and triglycerides were similar between treatments. These data imply that with CLA treatment in early lactation, dairy cows decreased milk fat synthesis and appeared to respond by partitioning more nutrients toward milk synthesis rather than improving net energy balance.

Phosphorylation of the lipid droplet-associated protein perilipin A (Peri A) mediates the actions of cyclic AMP-dependent protein kinase A (PKA) to stimulate triglyceride hydrolysis (lipolysis) in adipocytes. Studies addressing how Peri A PKA sites regulate adipocyte lipolysis have relied on non-adipocyte cell models, which express neither adipose triglyceride lipase (ATGL), the rate-limiting enzyme for triglyceride catabolism in mice, nor the "downstream" lipase, hormone-sensitive lipase (HSL). ATGL and HSL are robustly expressed by adipocytes that we generated from murine embryonic fibroblasts of perilipin knock-out mice. Adenoviral expression of Peri A PKA site mutants in these cells reveals that mutation of serine 517 alone is sufficient to abrogate 95% of PKA (forskolin)-stimulated fatty acid (FA) and glycerol release. Moreover, a "phosphomimetic" (aspartic acid) substitution at serine 517 enhances PKA-stimulated FA release over levels obtained with wild type Peri A. Studies with ATGL-and HSL-directed small hairpin RNAs demonstrate that 1) ATGL activity is required for all PKA-stimulated FA and glycerol release in murine embryonic fibroblast adipocytes and 2) all PKA-stimulated FA release in the absence of HSL activity requires serine 517 phosphorylation. These results provide the first demonstration that Peri A regulates ATGL-dependent lipolysis and identify serine 517 as the Peri A PKA site essential for this regulation. The contributions of other PKA sites to PKA-stimulated lipolysis are manifested only in the presence of phosphorylated or phosphomimetic serine 517.Thus, serine 517 is a novel "master regulator" of PKA-stimulated adipocyte lipolysis. Triglyceride (TAG)3 and other neutral lipids are stored in adipocyte lipid droplets (LDs) and, in response to energy demand, are hydrolyzed by lipases (lipolysis) to generate fatty acids (FAs) as fuel for peripheral tissues (1-5). Tight regulation of adipocyte lipolysis in response to the inhibitory actions of insulin and the stimulatory actions of lipolytic hormones such as catecholamines maintains whole body energy homeostasis and metabolic health (6 -8). Catecholamines bind to ␤-adrenergic receptors on adipocytes, resulting in up-regulation of adenyl cyclase, activation of cAMP-dependent protein kinase A (PKA), and increased lipolytic rate (9). The ability of PKA to stimulate adipocyte lipolysis is mediated in large part by the LD-associated phosphoprotein perilipin (Peri) (1, 10, 11). Peri A (the predominant perilipin isoform in adipocytes) is the most prevalent PKA substrate in adipocytes. In the absence of hormonal stimulation (i.e. basal state), Peri A functions to sequester lipases from stored neutral lipid, thereby maintaining a low rate of constitutive lipolysis. After phosphorylation by PKA, Peri A facilitates lipase accessibility to lipid stores, thereby promoting lipolysis (12)(13)(14)(15)(16)(17)(18)(19)(20). The mechanism(s) by which Peri A phosphorylation facilitates TAG/lipase interaction in adipocytes is not elucidated.Previous studies of Pe...

Adipose tissue (AT) inflammation promotes insulin resistance (IR) and other obesity complications. AT inflammation and IR are associated with oxidative stress, adipocyte death, and the scavenging of dead adipocytes by proinflammatory CD11c+ AT macrophages (ATMPhi). We tested the hypothesis that supplementation of an obesitogenic (high-fat) diet with whole blueberry (BB) powder protects against AT inflammation and IR. Male C57Bl/6j mice were maintained for 8 wk on 1 of 3 diets: low-fat (10% of energy) diet (LFD), high-fat (60% of energy) diet (HFD) or the HFD containing 4% (wt:wt) whole BB powder (1:1 Vaccinium ashei and V. corymbosum) (HFD+B). BB supplementation (2.7% of total energy) did not affect HFD-associated alterations in energy intake, metabolic rate, body weight, or adiposity. We observed an emerging pattern of gene expression in AT of HFD mice indicating a shift toward global upregulation of inflammatory genes (tumor necrosis factor-alpha, interleukin-6, monocyte chemoattractant protein 1, inducible nitric oxide synthase), increased M1-polarized ATMPhi (CD11c+), and increased oxidative stress (reduced glutathione peroxidase 3). This shift was attenuated or nonexistent in HFD+B-fed mice. Furthermore, mice fed the HFD+B were protected from IR and hyperglycemia coincident with reductions in adipocyte death. Salutary effects of BB on adipocyte physiology and ATMPhi gene expression may reflect the ability of BB anthocyanins to alter mitogen-activated protein kinase and nuclear factor-kappaB stress signaling pathways, which regulate cell fate and inflammatory genes. These results suggest that cytoprotective and antiinflammatory actions of dietary BB can provide metabolic benefits to combat obesity-associated pathology.