Visceral adipose tissue (VAT) is an important risk factor for obesityrelated metabolic disorders. Therefore, a reduction in VAT has become a key goal in obesity management. However, VAT is correlated with intrahepatic triglyceride (IHTG) content, so it is possible that IHTG, not VAT, is a better marker of metabolic disease. We determined the independent association of IHTG and VAT to metabolic function, by evaluating groups of obese subjects, who differed in IHTG content (high or normal) but matched on VAT volume or differed in VAT volume (high or low) but matched on IHTG content. Stable isotope tracer techniques and the euglycemic-hyperinsulinemic clamp procedure were used to assess insulin sensitivity and very-lowdensity lipoprotein-triglyceride (VLDL-TG) secretion rate. Tissue biopsies were obtained to evaluate cellular factors involved in ectopic triglyceride accumulation. Hepatic, adipose tissue and muscle insulin sensitivity were 41, 13, and 36% lower (P < 0.01), whereas VLDLtriglyceride secretion rate was almost double (P < 0.001), in subjects with higher than normal IHTG content, matched on VAT. No differences in insulin sensitivity or VLDL-TG secretion were observed between subjects with different VAT volumes, matched on IHTG content. Adipose tissue CD36 expression was lower (P < 0.05), whereas skeletal muscle CD36 expression was higher (P < 0.05), in subjects with higher than normal IHTG. These data demonstrate that IHTG, not VAT, is a better marker of the metabolic derangements associated with obesity. Furthermore, alterations in tissue fatty acid transport could be involved in the pathogenesis of ectopic triglyceride accumulation by redirecting plasma fatty acid uptake from adipose tissue toward other tissues.abdominal fat ͉ insulin resistance ͉ NAFLD ͉ steatosis ͉ VLDL V isceral adipose tissue (VAT) is an important and independent predictor of metabolic risk factors for coronary heart disease, particularly diabetes and dyslipidemia (1, 2). Moreover, data from metabolic studies conducted on human subjects (3, 4) indicate that an increase in VAT is associated with impaired glucose tolerance, insulin resistance, and increased very-low-density lipoproteintriglyceride (VLDL-TG) secretion. These observations and the unique anatomical location of visceral fat, which releases free fatty acids (FFA) and adipokines into the portal vein for direct transport to the liver, have led to the concept that VAT is responsible for many of the metabolic abnormalities associated with abdominal obesity (5, 6). Therefore, a reduction in visceral fat has become a key therapeutic goal in the management of obesity (6, 7).Although VAT is associated with metabolic disease, a causal link between VAT and metabolic dysfunction has not been demonstrated in humans. Recently, it has become clear that VAT correlates directly with intrahepatic triglyceride (IHTG) content (8-10), and an increase in IHTG is associated with the same metabolic abnormalities linked to an increase in VAT (9-12). Therefore, it is possible that VAT itself is n...

Protein restricted, high carbohydrate diets improve metabolic health in rodents, yet the precise dietary components that are responsible for these effects have not been identified. Further, the applicability of these studies to humans is unclear. Here, we demonstrate in a randomized controlled trial that a moderately protein restricted (PR) diet also improves markers of metabolic health in humans. Intriguingly, we find that feeding mice a diet specifically reduced in branched chain amino acids (BCAAs) is sufficient to improve glucose tolerance and body composition equivalently to a PR diet, via metabolically distinct pathways. Our results highlight a critical role for dietary quality at the level of amino acids in the maintenance of metabolic health, and suggest that diets specifically reduced in BCAAs, or pharmacological interventions in this pathway, may offer a translatable way to achieve many of the metabolic benefits of a PR diet.

OBJECTIVEInsulin resistance is commonly associated with obesity. Studies conducted in obese mouse models found that endoplasmic reticulum (ER) stress contributes to insulin resistance, and treatment with tauroursodeoxycholic acid (TUDCA), a bile acid derivative that acts as a chemical chaperone to enhance protein folding and ameliorate ER stress, increases insulin sensitivity. The purpose of this study was to determine the effect of TUDCA therapy on multiorgan insulin action and metabolic factors associated with insulin resistance in obese men and women.RESEARCH DESIGN AND METHODSTwenty obese subjects ([means ± SD] aged 48 ± 11 years, BMI 37 ± 4 kg/m2) were randomized to 4 weeks of treatment with TUDCA (1,750 mg/day) or placebo. A two-stage hyperinsulinemic-euglycemic clamp procedure in conjunction with stable isotopically labeled tracer infusions and muscle and adipose tissue biopsies were used to evaluate in vivo insulin sensitivity, cellular factors involved in insulin signaling, and cellular markers of ER stress.RESULTSHepatic and muscle insulin sensitivity increased by ∼30% (P < 0.05) after treatment with TUDCA but did not change after placebo therapy. In addition, therapy with TUDCA, but not placebo, increased muscle insulin signaling (phosphorylated insulin receptor substrateTyr and AktSer473 levels) (P < 0.05). Markers of ER stress in muscle or adipose tissue did not change after treatment with either TUDCA or placebo.CONCLUSIONSThese data demonstrate that TUDCA might be an effective pharmacological approach for treating insulin resistance. Additional studies are needed to evaluate the target cells and mechanisms responsible for this effect.

BACKGROUND & AIMS An increased number of macrophages in adipose tissue is associated with insulin resistance and metabolic dysfunction in obese people. However, little is known about other immune cells in adipose tissue from obese people, and whether they contribute to insulin resistance. We investigated the characteristics of T cells in adipose tissue from metabolically abnormal insulin-resistant obese (MAO) subjects, metabolically normal insulin-sensitive obese (MNO) subjects, and lean subjects. Insulin sensitivity was determined by using the hyperinsulinemic euglycemic clamp procedure. METHODS We assessed plasma cytokine concentrations and subcutaneous adipose tissue CD4+ T-cell populations in 9 lean, 12 MNO, and 13 MAO subjects. Skeletal muscle and liver samples were collected from 19 additional obese patients undergoing bariatric surgery to determine the presence of selected cytokine receptors. RESULTS Adipose tissue from MAO subjects had 3- to 10-fold increases in numbers of CD4+ T cells that produce interleukin (IL)-22 and IL-17 (a T-helper [Th] 17 and Th22 phenotype) compared with MNO and lean subjects. MAO subjects also had increased plasma concentrations of IL-22 and IL-6. Receptors for IL-17 and IL-22 were expressed in human liver and skeletal muscle samples. IL-17 and IL-22 inhibited uptake of glucose in skeletal muscle isolated from rats and reduced insulin sensitivity in cultured human hepatocytes. CONCLUSIONS Adipose tissue from MAO individuals contains increased numbers of Th17 and Th22 cells, which produce cytokines that cause metabolic dysfunction in liver and muscle in vitro. Additional studies are needed to determine whether these alterations in adipose tissue T cells contribute to the pathogenesis of insulin resistance in obese people.

Objective. To determine concentrations of crosslinked C-telopeptide fragments of type II collagen (CTX-II) in synovial fluid (SF) from patients with joint injury, osteoarthritis (OA), or other knee arthritides.Methods. Two study groups were used: a crosssectional group, which included healthy-knee volunteers (reference group [REF]) and patients with pseudogout (PPA), an anterior cruciate ligament tear with or without a meniscus tear (INJ), or primary knee OA (POA); and a longitudinal group, which included patients with arthroscopic cartilage changes or septic arthritis. CTX-II was quantified by competition enzyme-linked immunosorbent assay (ELISA) based on a monoclonal antibody that recognized the C-terminus of the peptide EKGPDP as a proteolytic neoepitope. Aggrecan fragments, matrix metalloproteinases 1 and 3, and tissue inhibitor of metalloproteinases 1 were determined by ELISAs.Results. Concentrations of CTX-II in SF were higher in patients with PPA, INJ, and POA than in the REF group (P < 0.001). After joint injury, mean levels of CTX-II in SF were increased above REF levels at all time intervals (P < 0.001), and were highest within hours after trauma. In those in the longitudinal study group with joint cartilage damage, variation coefficients for CTX-II were 81% (between patients) and 64% (within patient), monitored over 1 year. In a patient with septic arthritis, SF CTX-II increased at the onset of symptoms, and peaked 30-fold higher than the baseline. Concentrations of all biomarkers decreased with successful treatment.Conclusion. This is the first report to describe the release into SF of soluble molecular fragments specific for the degradation of mature, crosslinked, type II collagen (CII) in human OA and joint injury. The results provide strong evidence that the integrity of the CII network of cartilage is compromised soon after joint injury and in arthritis. This early degradation of CII may represent an important treatment target.Osteoarthritis (OA) and joint injury are characterized by remodeling and degradation of cartilage, bone, and other joint tissues. The normally very slow turnover rate of cartilage matrix (1) is increased, as observed by several techniques in both animal OA models and human OA. Phasic changes in both synthesis and degradation of collagen and other matrix molecules (2-6) are associated with altered tissue structure and material properties (7-9).Increased joint tissue turnover after injury and in OA can be detected by a release of molecules and molecular fragments into synovial fluid (SF), blood, and urine. For example, the stimulated synthesis of type II collagen (CII) results in higher levels of CII C-propeptide in SF (10,11). Stimulated aggrecan synthesis results in more aggrecan fragments carrying the 846 epitope (12). Higher synovial concentrations of matrix metalloproteinases (MMPs), such as MMP-1 and MMP-3, and proteinase activity after joint injury and in OA are consistent with the observed expression of these