Besides their role in intestinal resorption of lipids, bile acids are regarded as endocrine and metabolic signaling molecules. The detailed profile of bile acid species in peripheral blood after an oral lipid tolerance test (OLTT) is unknown. We quantified the regulation of 18 bile acids after OLTT in healthy individuals. 100 volunteers were characterized by anthropometric and laboratory parameters and underwent OLTT. Venous blood was drawn in the fasted state (0 h) and at 2h, 4h, and 6 h after OLTT. Serum concentrations of 18 bile acids were measured by LC-MS/MS. All of the 6 taurine-conjugated bile acids (TUDCA, THDCA, TCA, TCDCA, TDCA, TLCA) and all of the 6 glycine-conjugated bile acids (GUDCA, GHDCA, GCA, GCDCA, GDCA, GLCA) rose significantly at 2h and remained elevated during OLTT. Of the primary bile acids, CA remained unchanged, whereas CDCA significantly decreased at 4h. Of the secondary bile acids, DCA, UDCA and HDCA were not altered, whereas LCA decreased. There was a significant positive correlation between the intestinal feed-back regulator of bile acid synthesis FGF-19 and bile acids. This correlation seems to depend on all of the six taurine-conjugated bile acids and on GCA, GDCA, and GCDCA. Females and users of hormonal contraception displayed higher levels of taurine-conjugated bile acids. The novelty of the study is based on the identification of single bile acids during OLTT. LC-MS/MS-based quantification of bile acids in serum provides a reliable tool for future investigation of endocrine and metabolic effects of bile acids.

Meteorin-like protein (Metrnl) is an adipo-myokine with pleiotropic effects in adipose tissue (AT). Its systemic regulation in obesity and under weight loss is unclear. Circulating Metrnl concentrations were analyzed by ELISA in severely obese patients undergoing bariatric surgery (BS) or low calorie diet (LCD). Metrnl mRNA expression was analyzed in human and murine tissues and cell lines by quantitative real-time PCR. About 312 morbidly obese individuals underwent BS (n = 181; BMI 53.4 + 6.8 kg/m²) or LCD (n = 131; BMI 43.5 + 6.7 kg/m²). Serum samples were obtained at baseline and 3, 6, and 12 months after intervention. AT specimen from subcutaneous and visceral adipose tissue were resected during BS. Serum Metrnl levels were lower in type 2 diabetic patients and negatively correlated with HbA1c. In BS and LCD patients, Metrnl concentrations significantly increased after 3 months and returned to baseline levels after 12 months. There was no gender-specific effect. Metrnl mRNA expression did not differ between visceral and subcutaneous AT in n = 130 patients. In contrast, Metrnl gene expression in mice was highest in intra-abdominal AT followed by subcutaneous, peri-renal, and brown AT. In the murine 3T3-L1 cell line, Metrnl expression was high in pre-adipocytes and mature adipocytes with a transient downregulation during adipocyte differentiation. Metrnl expression remained unaffected upon treatment with glucose, insulin, fatty acids, bile acids, and incretins. Polyunsaturated omega-3 and omega-6 fatty acids downregulated Metrnl expression. Systemic Metrnl is transiently upregulated during massive weight loss and gene expression in adipocytes is differentially regulated.

Adipocytes express various pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) and actively participate in anti-bacterial and anti-viral host defence. Obesity is associated with adipose tissue PRR expression. The potential role of Toll-like receptor 9 (TLR9) in adipocytes has not yet been investigated. Here, we evaluated TLR9 expression during adipocyte differentiation (AD) of 3T3-L1 adipocytes, in primary murine adipocytes and in different murine and human adipose tissue depots by real-time PCR, immunocytochemistry and immunohistochemistry. TLR9 expression was inhibited using specific siRNA-mediated knockdown, and TLR9 signaling was induced using specific class A, B and C agonistic CpG-oligodeoxynucleotide (ODN) treatment vs ODN controls in 3T3-L1 adipocytes and in primary murine adipocytes from Tlr9^wt/wt vs Tlr9^−/− mice. We found that TLR9 gene expression is induced during AD and that TLR9 protein is expressed in murine gonadal and human visceral adipocytes. AD depends on intact TLR9 expression. Tlr9^−/− mice demonstrate significantly reduced adiponectin serum levels, while siRNA-mediated TLR9 knockdown led to reduced adiponectin mRNA expression in adipocytes. TLR9 ligands (CpG-ODNs) inhibit pro-inflammatory resistin secretion in mature 3T3-L1 adipocytes. Tlr9^−/− as compared to Tlr9^wt/wt adipocytes exhibit increased resistin and MCP1 secretion and reduced adiponectin secretion into cell culture supernatants, while TLR9 ligands (ODNs) show differential effects in Tlr9^−/− vs Tlr9^wt/wt primary murine adipocytes. TLR9 expression is significantly increased in visceral compared to subcutaneous adipose tissue depots in non-diabetic obese patients and correlates with systemic resistin levels in a compartment-specific manner. Thus, adipocytic TLR9 is a putative, new protective factor during (obesity-associated) adipose tissue inflammation.

Context: Regulation of FGF-19 and FGF-21 by oral uptake of lipids and carbohydrates in healthy individuals is poorly characterized. Objective: We investigated the regulation of FGF-19 and FGF-21 in 2 large cohorts of healthy volunteers during oral lipid tolerance test (OLTT; n=100) and oral glucose tolerance test (OGTT; n=100). Design and setting: 100 volunteers underwent OLTT and OGTT in an outpatient setting. Venous blood was drawn at 0 h (fasting) and at 2, 4, and 6 h in OLTT or 1 and 2 h in OGTT. In order to dissect carbohydrate-induced from lipid-induced effects, a special OLTT solution was applied. Subjects were characterized by anthropometric and laboratory parameters. Serum concentrations of FGF-19 and FGF-21 were measured by enzyme-linked immunosorbent assay (ELISA). Results: Mean FGF-19 levels ranged between 12 and 544 pg/ml with a fasting mean value of 105±81 pg/ml and 118±86 pg/ml in OLTT and OGTT. Mean FGF-21 levels ranged between 4 and 1 393 pg/ml with a fasting mean value of 160±204 pg/ml and 235±288 pg/ml in OLTT and OGTT. There was a significant, positive correlation between FGF-19 and FGF-21 in OLTT (p<0.001, r=0.5) and in OGTT (p=0.011, r=0.4). FGF-21 levels were positively correlated with waist circumference and waist hip-ratio in both cohorts. OGTT had no effect on FGF-19 and FGF-21. In contrast, FGF-19 levels were significantly induced and FGF-21 levels were significantly reduced during OLTT. Conclusions: OLTT is a physiological inductor of FGF-19 and a repressor of FGF-21 in healthy adults. There is a significant and positive correlation between FGF-19 and FGF-21. Dietary lipids specifically and differentially regulate FGF-19 and FGF-21 whereas dietary carbohydrates have no effect. The present data provide the clinical basis for the postulated negative feedback loop between dietary lipids and postprandial inhibition of hepatic lipogenesis.

Therapy-refractory persistent hypoparathyroidism after extensive neck surgery is a rare but severe complication. Parathyroid allotransplantation may represent a definitive treatment option. A 32-year old female was referred to our hospital with intractable persistent hypocalcemia after neck surgery for papillary thyroid cancer. Despite optimal medical treatment including calcium and vitamin D supplementation and even hormonal replacement therapy hypocalcemic symptoms failed to improve. The quality of life was considered very low. In light of the unsuccessful medical therapy and the young age of the patient parathyroid allotransplantation seemed an attractive treatment option to restore normal calcium homeostasis despite of the need for immunosuppressive therapy after the procedure. Therefore, we performed living-donor allotransplantation of two healthy parathyroid glands to the recipient’s left forearm. The surgical intervention was successful. Neither the donor nor the recipient showed any complications. In the postoperative course clinical symptoms of hypocalcemia significantly improved whereas serum calcium and parathyroid hormone (PTH) levels progressively increased into the normal range. Former intense replacement therapy could be discontinued completely in a stepwise fashion. To date, nearly three years after transplantation, the patient remains asymptomatic with normal serum levels of calcium and PTH. Successful living-donor parathyroid allotransplantation for postsurgical hypoparathyroidism represents an innovative therapeutic strategy that could provide the definitive treatment in those patients in which the disease is therapy-refractory. The procedure can be justified even in nontransplant recipients. Retrieval of parathyroid glands from healthy donors is feasible and safe.