Thiazolidinediones (TZDs) act through peroxisome proliferator activated receptor (PPAR) γ to increase insulin sensitivity in type 2 diabetes (T2DM), but deleterious effects of these ligands mean that selective modulators with improved clinical profiles are needed. We obtained a crystal structure of PPARγ ligand binding domain (LBD) and found that the ligand binding pocket (LBP) is occupied by bacterial medium chain fatty acids (MCFAs). We verified that MCFAs (C8–C10) bind the PPARγ LBD in vitro and showed that they are low-potency partial agonists that display assay-specific actions relative to TZDs; they act as very weak partial agonists in transfections with PPARγ LBD, stronger partial agonists with full length PPARγ and exhibit full blockade of PPARγ phosphorylation by cyclin-dependent kinase 5 (cdk5), linked to reversal of adipose tissue insulin resistance. MCFAs that bind PPARγ also antagonize TZD-dependent adipogenesis in vitro. X-ray structure B-factor analysis and molecular dynamics (MD) simulations suggest that MCFAs weakly stabilize C-terminal activation helix (H) 12 relative to TZDs and this effect is highly dependent on chain length. By contrast, MCFAs preferentially stabilize the H2-H3/β-sheet region and the helix (H) 11-H12 loop relative to TZDs and we propose that MCFA assay-specific actions are linked to their unique binding mode and suggest that it may be possible to identify selective PPARγ modulators with useful clinical profiles among natural products.

Background: PPARγ agonists improve insulin sensitivity but also evoke weight gain.Results: GQ-16 is a PPARγ partial agonist that blocks receptor phosphorylation by Cdk5 and improves insulin sensitivity in diabetic mice in the absence of weight gain.Conclusion: The unique binding mode of GQ-16 appears to be responsible for the compound's advantageous pharmacological profile.Significance: Similar compounds could have promise as anti-diabetic therapeutics.

Brown-like adipocytes exist in several adipose depots including white (WAT) as well as brown (BAT). Activation of these UCP1 cells is a potential therapeutic strategy to combat obesity. Studies have shown that posttranslational modifications of PPARγ regulate select adipocyte programs. Deacetylation of K268 and K293 in the ligand-binding domain of PPARγ by Sirt1 induces browning of WAT. Phosphorylation of S273 of PPARγ by CDK5 or ERK stimulates a diabetogenic program of gene expression in WAT. Here, we report that roscovitine, a CDK inhibitor, prevents S273 phosphorylation and promotes formation of UCP1 (brite) adipocytes in WAT. It also enhances energy expenditure as well as prevents diet-induced obesity and insulin resistance. Analysis of fluorescence-activated cell-sorted UCP1 adipocytes shows that the mRNA signature of brite adipocytes is distinct from beige adipocytes, which arise through catecholamine signaling. These results suggest that brown-like adipocytes in WAT may arise from multiple origins.

Lot 89SF has been the reference standard serum pool used in pneumococcal enzyme-linked immunosorbent assays (ELISAs) since 1990. In 2005, it was estimated that there remained between 2 and 5 years' supply of lot 89SF. Since lot 89SF was the reference standard used in the evaluation of the seven-valent pneumococcal conjugate vaccine Prevnar (PCV7), the link to clinical efficacy would be severed if stocks became completely depleted. Furthermore, demonstration of immune responses comparable to those elicited by PCV7 is a licensure approach used for new pneumococcal conjugate vaccines, so a replacement reference standard was required. A total of 278 volunteers were immunized with the 23-valent unconjugated polysaccharide vaccine Pneumovax II, and a unit of blood was obtained twice within 120 days following immunization. Plasma was prepared, pooled, and confirmed to be free from hepatitis B virus (HBV), hepatitis C virus (HCV), and HIV. The pooled serum was poured at 6 ml per vial into 15,333 vials and lyophilized. Immunological bridging of 007sp to 89SF was used to establish equivalent reference values for 13 pneumococcal capsular serotypes (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F) by five independent laboratories. Antibody concentrations in 007sp were established relative to the lot 89SF reference preparation using the WHO reference ELISA. Subsequently, 12 existing WHO calibration sera had concentrations reassigned for 13 pneumococcal serotypes using new serum 007sp as the reference, and these were compared to concentrations relative to the original reference serum. Agreement was excellent for the 12 WHO calibration sera. The 007sp preparation has replaced 89SF as the pneumococcal reference standard. Sufficient quantity of this new preparation is available such that, with judicious use, it should be available for at least 25 years.Streptococcus pneumoniae human reference serum lot 89SF has been used as a standard serum in enzyme-linked immunosorbent assay (ELISA) designed to measure IgGspecific antibody for individual pneumococcal capsular polysaccharides since 1990. This standard serum greatly facilitated the standardization of ELISA methodologies during a critical period when the first polysaccharide-conjugate vaccines were being evaluated for licensure. Lot 89SF consists of pooled, defibrinated plasma collected in the late 1980s from 17 individuals vaccinated with a 23-valent pneumococcal polysaccharide vaccine (Pnu-imune; Lederle), a 4-valent meningococcal polysaccharide vaccine (Menomune; Connaught), and Haemophilus influenzae type b conjugate vaccine (ProHibit; Connaught). The final volume of this collection was approximately 10 liters (3 ml/vial). Serotypespecific weight-based values for IgG, IgA, and IgM were derived for serotypes 1,3,4,5, 6B, 7F, 9V, 14, 18C, 19F, and 23F for lot 89SF by Quateart et al. (5). Assignments for the additional serotypes in the 23-valent pneumococcal polysaccharide vaccine were subsequently bridged from the assignments for the original 11 serotypes (6). The lot 89...

Summary The functional conversion of white adipose tissue (WAT) into a tissue with brown adipose tissue (BAT)-like activity, often referred to a ‘browning’, represents an intriguing strategy to combat obesity and metabolic disease. We demonstrate that thyroid hormone receptor (TR) activation by a synthetic agonist markedly induces a program of adaptive thermogenesis in subcutaneous WAT that coincides with a restoration of cold tolerance to cold-intolerant mice. Distinct from most other browning agents, pharmacological TR activation dissociates the browning of WAT from activation of classical BAT. TR agonism also induces the browning of white adipocytes in vitro, indicating that TR mediated browning is cell autonomous. These data establish TR agonists as a class of browning agents, implicate the TRs in the browning of WAT, and suggest a profound pharmacological potential of this action.