Optimization and scale-up of oligonucleotide synthesis in packed bed reactors using computational fluid dynamics modeling

A computational fluid dynamics (CFD) model for the analysis of oligonucleotide synthesis in packed bed reactors was developed and used to optimize the scale up of the process. The model includes reaction kinetics data obtained under well defined conditions comparable to the situation in the packed bed. The model was validated in terms of flow conditions and reaction kinetics by comparison with experimental data. Experimental validation and the following model parameter studies by simulation were performed on the basis of a column with 0.3 g oligonucleotide capacity. The scale-up studies based on CFD modelling were calculated on a 440 g scale (oligonucleotide capacity).

Subcutaneous adipose tissue zinc-α2-glycoprotein is associated with adipose tissue and whole-body insulin sensitivity

OBJECTIVE

To examine the regulatory aspects of zinc-α2-glycoprotein (ZAG) association with obesity-related insulin resistance.

METHODS

ZAG mRNA and protein were analyzed in subcutaneous adipose tissue (AT) and circulation of lean, obese, prediabetic, and type 2 diabetic men; both subcutaneous and visceral AT were explored in lean and extremely obese. Clinical and ex vivo findings were corroborated by results of in vitro ZAG silencing experiment.

RESULTS

Subcutaneous AT ZAG was reduced in obesity, with a trend to further decrease with prediabetes and type 2 diabetes. ZAG was 3.3-fold higher in subcutaneous than in visceral AT of lean individuals. All differences were lost in extreme obesity. Obesity-associated changes in AT were not paralleled by alterations of circulating ZAG. Subcutaneous AT ZAG correlated with adiposity, adipocyte hypertrophy, whole-body and AT insulin sensitivity, mitochondrial content, expression of GLUT4, PGC1α, and adiponectin. Subcutaneous AT ZAG and adipocyte size were the only predictors of insulin sensitivity, independent on age and BMI. Silencing ZAG resulted in reduced adiponectin, IRS1, GLUT4, and PGC1α gene expression in primary human adipocytes.

CONCLUSIONS

ZAG in subcutaneous, but not in visceral AT, was markedly reduced in obesity. Clinical, cellular, and molecular evidence indicate that ZAG plays an important role in modulating whole-body and AT insulin sensitivity.

Exercise-mimicking treatment fails to increase Fndc5 mRNA & irisin secretion in primary human myotubes

Irisin, myokine secreted by skeletal muscle, was suggested to mediate some of exercise health benefits via "browning" of white adipose tissue. However, mounting evidence contradicts the regulatory role of exercise for muscle irisin production/secretion in humans. Thus, we explored the direct effect of exercise-mimicking treatment on irisin in human primary muscle cells in vitro. Human primary muscle cell cultures were established from lean, obese prediabetic and type-2-diabetic individuals. Complex metabolic phenotyping included assessment of insulin sensitivity (euglycemic hyperinsulinemic clamp) and adiposity content&distribution (MRI&MRS). In vitro exercise-mimicking treatment (forskolin+ionomycin) was delivered in 1-h pulse/day during differentiation. Fndc5 mRNA (qRT-PCR) and secreted irisin (ELISA) were determined in cells and media. Exercise-mimicking treatment more than doubled Pgc1α mRNA in differentiated muscle cells. Nevertheless, Fndc5 mRNA was reduced by 18% and irisin in media by 20%. Moreover, Fncd5 mRNA was increased in myotubes derived from individuals with type-2-diabetes, independent on exercise-mimicking treatment. Fndc5 mRNA in cells was positively related to fasting glycemia (p=0.0001) and negatively to whole-body insulin sensitivity (p<0.05). Collectively, our data do not support the role of exercise-related signaling pathways in irisin regulation in human skeletal muscle and confirm our previous observations on increased Fndc5 expression in muscle cells from individuals with type-2-diabetes.

The origin and definition of brite versus white and classical brown adipocytes

White adipose tissue stores energy while brown adipose tissue contributes to body temperature maintenance through non-shivering thermogenesis. In addition, brite (brown-in-white) adipocytes resembling classical brown adipocytes within predominantly white adipose tissue can be found in response to cold adaptation or other stimuli. Even though our understanding of brite adipocyte formation has increased substantially in the last few years, it is still unclear how brite and classical brown adipocytes are formed in vivo. In this review, we outline and discuss the current understanding of brite adipocyte nomenclature, developmental origin and possible mechanisms of their recruitment. We reason that future work in the field will bridge in vivo tracing studies and primary cell characterization with molecular mechanistic data from in vitro approaches to devise new means to increase energy expenditure.

Effects of obesity, diabetes and exercise on Fndc5 gene expression and irisin release in human skeletal muscle and adipose tissue: in vivo and in vitro studies

Irisin was identified as a myokine secreted by contracting skeletal muscle, possibly mediating some exercise health benefits via 'browning' of white adipose tissue. However, a controversy exists concerning irisin origin, regulation and function in humans. Thus, we have explored Fndc5 gene and irisin protein in two clinical studies: (i) a cross-sectional study (effects of type 2 diabetes (T2D) in drug-naive men) and (ii) an intervention study (exercise effects in sedentary, overweight/obese individuals). Glucose tolerance and insulin sensitivity were assessed. Maximal aerobic capacity and muscle strength were measured before and after training. Body composition (magnetic resonance imaging), muscle and liver fat content (1H-magnetic resonance spectroscopy (MRS)) and in vivo muscle metabolism (32P-MRS) were determined. Skeletal muscle and subcutaneous abdominal adipose tissue samples were taken in the fasted state and during euglycaemic hyperinsulinaemia (adipose tissue) and before/after exercise training (muscle). We found that muscle Fndc5 mRNA was increased in prediabetes but not T2D. Fndc5 in adipose tissue and irisin in plasma were reduced in T2D by 40% and 50%, respectively. In contrast, T2D-derived myotubes expressed/secreted the highest levels of Fndc5/irisin. Neither hyperinsulinaemia (adipose tissue/plasma) nor exercise (muscle/plasma) affected Fndc5/irisin in vivo. Circulating irisin was positively associated with muscle mass, strength and metabolism and negatively with fasting glycaemia. Glucose and palmitate decreased Fndc5 mRNA in myotubes in vitro. We conclude that distinct patterns of Fndc5/irisin in muscle, adipose tissue and circulation, and concordant in vivo down-regulation in T2D, indicate that irisin might distinguish metabolic health and disease. Moreover, Fndc5/irisin was discordantly regulated in diabetic muscle and myotubes in vitro, suggesting that whole body factors, such as glucose and fatty acids, might be important for irisin regulation. Exercise did not affect Fndc5/irisin. However, irisin was positively linked to muscle mass, strength and metabolism, pointing to common regulatory factors and/or the potential for irisin to modify muscle phenotype.

Malfunctioning of adipocytes in obesity is linked to quantitative surfaceome changes

Increased triglyceride accumulation in adipocytes caused by a misbalance between energy intake and energy consumption, results in increased adipocyte size, excess adipose tissue, increased body weight and ultimately, obesity. It is well established that enlarged adipocytes exhibit malfunctions that contribute to whole body insulin resistance, a key factor for the development of type 2 diabetes. However, the underlying molecular cause for dysfunctional adipocyte behavior and signaling is poorly understood. Since the adipocyte cell surface proteome, or surfaceome, represents the cellular signaling gateway to the microenvironment, we studied the contribution of this subproteome to adipocyte malfunctions in obesity. By using the chemoproteomic Cell Surface Capture (CSC) technology, we established surfaceome maps of primary adipocytes derived from different mouse models for metabolic disorders. Relative quantitative comparison between these surfaceome maps revealed a set of cell surface glycoproteins with modulated location-specific abundance levels. RNAi mediated targeting of a subset of the detected obesity modulated cell surface glycoproteins in an in vitro model system provided functional evidence for their role in adiponectin secretion and the lipolytic activity of adipocytes. Thus, we conclude that the identified cell surface glycoproteins which exhibit obesity induced abundance changes and impact adipocyte function at the same time contribute to adipocyte malfunction in obesity. The regulation of their concerted activities could improve adipocyte function in obesity.

Longitudinal evaluation of hepatic lipid deposition and composition in ob/ob and ob/+ control mice

Obesity is associated with insulin resistance (IR) and hepatosteatosis. Understanding the link between IR and hepatosteatosis could be relevant to chronic clinical outcomes. The objective of this study was to quantitatively assess lipid deposition (fractional lipid mass, fLM) and composition (fraction of polyunsaturated lipids, fPUL and mean chain length, MCL) in livers of ob/ob mice, a genetic model of obesity and mild diabetes, and ob/+ heterozygous control animals in a noninvasive manner using (1) H-MRS at 9.4T. For accurate quantification, intensity values were corrected for differences in T2 values while T1 effects were considered minimal due to the long TR values used. Values of fLM, fPUL and MCL were derived from T2 -corrected signal intensities of lipids and water resonance. Hepatic lipid signals were compared with fasted plasma insulin, glucose and lipid levels. Statistically significant correlations between fPUL and fasting plasma insulin/glucose levels were found in adolescent ob/ob mice. A similar correlation was found between fLM and fasting plasma insulin levels; however, the correlation between fLM and fasting plasma glucose levels was less obvious in adolescent ob/ob mice. These correlations were lost in adult ob/ob mice. The study showed that in adolescent ob/ob mice, there was an obvious link between lipid deposition/composition in the liver and plasma insulin/glucose levels. This correlation was lost in adult animals, probably due to the limited lipid storage capacity of the liver.

Genetic modulation of the serotonergic pathway: influence on weight reduction and weight maintenance

The serotonergic pathway plays a major role in the development of obesity. Its activity can be modulated by the 5-HT transporter-linked polymorphic region in the SLC6A4 gene and the upstream variable number of tandem repeats polymorphism in the MAOA gene. We studied whether these genetic modulations have an influence on weight reduction and weight maintenance in a one-year weight reduction program (OPTIFAST®52). The polymorphisms were genotyped by PCR in a sample of 135 female and 67 male subjects with severe obesity (44 ± 13 years, 122.3 ± 22.2 kg, BMI: 41.7 ± 6.7 kg/m2). The program leads to a total weight loss of 19.9 ± 9.8 kg (16.9 ± 8.3 %) in women and 27.4 ± 13.6 kg (20.4 ± 9.9 %) in men. Anthropometric measurements and blood levels were determined at the start of the program (T0), after the weight reduction phase (T1) and after the subsequent weight maintenance phase at the end of the program (T2). Each polymorphism alone did not significantly influence weight loss or weight maintenance neither in men nor in women. However, women carrying both risk genotypes (SS and 3/3) displayed a lower total weight loss during the program (p = 0.05). This effect derived mainly from difficulties in the weight maintenance phase (p = 0.11), while the weight reduction phase was not affected (p = 0.61). No influence was found in men (p = 0.93). Modulation of the serotonergic pathway by carrying both risk alleles seems to influence success of weight loss programs in women with severe obesity due to problems in stabilizing body weight after weight reduction.

Transcriptional cofactor TBLR1 controls lipid mobilization in white adipose tissue

Lipid mobilization (lipolysis) in white adipose tissue (WAT) critically controls lipid turnover and adiposity in humans. While the acute regulation of lipolysis has been studied in detail, the transcriptional determinants of WAT lipolytic activity remain still largely unexplored. Here we show that the genetic inactivation of transcriptional cofactor transducin beta-like-related 1(TBLR1) blunts the lipolytic response of white adipocytes through the impairment of cAMP-dependent signal transduction. Indeed, mice lacking TBLR1 in adipocytes are defective in fasting-induced lipid mobilization and, when placed on a high-fat-diet, show aggravated adiposity, glucose intolerance, and insulin resistance. TBLR1 levels are found to increase under lipolytic conditions in WAT of both human patients and mice, correlating with serum free fatty acids (FFAs). As a critical regulator of WAT cAMP signaling and lipid mobilization, proper activity of TBLR1 in adipocytes might thus represent a critical molecular checkpoint for the prevention of metabolic dysfunction in subjects with obesity-related disorders.

Transcriptional regulation of adipocyte formation by the liver receptor homologue 1 (Lrh1)-Small hetero-dimerization partner (Shp) network

Altered adipose tissue formation is a well-known effectors of obesity and T2D. Here, we describe the role of Lrh1 and its co-repressor Shp in the control of adipocyte formation. Expression of Lrh1 in the pre-adipocyte containing SVF is induced in obese mice models and humans while Shp expression is reduced. We demonstrate, that Lrh1 is an inhibitor of adipogenesis while Shp acts functions as an activator through repression of Lrh1 activity. This regulation is at least in part modulated by estradiol conversion through the regulation of Cyp19a1 gene expression. In vivo, loss of Lrh1 leads to induced adipogenesis, while loss of Shp causes uncontrolled activation of Lrh1 and reduced adipogenesis. As Shp expression has been linked to the development of obesity and metabolic disorders, it is possible that alterations of the Shp/Lrh1 network lead to changes in adipocyte formation, which might contribute to the development of obesity associated T2D.

Bone morphogenic proteins signaling in adipogenesis and energy homeostasis

A great deal is known about the molecular mechanisms regulating terminal differentiation of pre-adipocytes into mature adipocytes. In contrast, the knowledge about pathways that trigger commitment of mesenchymal stem cells into the adipocyte lineage is fragmented. In recent years, the role of members of the bone morphogenic protein family in regulating the early steps of adipogenesis has been the focus of research. Findings based on these studies have also highlighted an unexpected role for some bone morphogenic protein in energy homeostasis via regulation of adipocyte development and function. This review summarizes the knowledge about bone morphogenic proteins and their role in adipocyte commitment and regulation of whole body energy homeostasis. This article is part of a Special Issue entitled Brown and White Fat: From Signaling to Disease.

Effectiveness of a low-calorie weight loss program in moderately and severely obese patients

AIMS

To compare effectiveness of a 1-year weight loss program in moderately and severely obese patients.

METHODS

The study sample included 311 obese patients participating in a weight loss program, which comprised a 12-week weight reduction phase (low-calorie formula diet) and a 40-week weight maintenance phase. Body weight and glucose and lipid values were determined at the beginning of the program as well as after the weight reduction and the weight maintenance phase. Participants were analyzed according to their BMI class at baseline (30-34.9 kg/m²; 35-39.9 kg/m²; 40-44.9 kg/m²; 45-49.9 kg/m²; ≥50 kg/m²). Furthermore, moderately obese patients (BMI < 40 kg/m²) were compared to severely obese participants (BMI ≥ 40 kg/m²).

RESULTS

Out of 311 participants, 217 individuals completed the program. Their mean baseline BMI was 41.8 ± 0.5 kg/m². Average weight loss was 17.9 ± 0.6%, resulting in a BMI of 34.3 ± 0.4 kg/m² after 1 year (p < 0.001). Overall weight loss was not significantly different in moderately and severely obese participants. Yet, severely obese participants achieved greater weight loss during the weight maintenance phase than moderately obese participants (-3.1 ± 0.7% vs. -1.2 ± 0.6%; p = 0.04). Improvements in lipid profiles and glucose metabolism were found throughout all BMI classes.

CONCLUSION

1-year weight loss intervention improves body weight as well as lipid and glucose metabolism not only in moderately, but also in severely obese individuals.

Maternal high-fat diet in mice programs emotional behavior in adulthood

The maternal environment has a significant role in the normal development of the fetus and may have long-term impact on brain development including critical central pathways such as the gamma-aminobutyric acid (GABA), serotonergic and the neurotrophin systems. For example, maternal malnutrition plays an important role in programming many aspects of physiology and behavior including predisposition to mental-health related disorders such as anxiety. Here we investigated the effects of maternal high-fat diet or control diet for nine weeks (prior to gestation, gestation and lactation) on the adult offspring with respect to anxiety related behaviors as well as exploration and conditioned fear response. We found that offspring born to high-fat diet mothers showed increased anxiety-like behaviors, but intact conditioned fear response and exploratory behavior. In addition, brain-derived neurotrophic factor (BDNF) was significantly increased in the dorsal hippocampus, while GABA(A) alpha2 receptor subunit and 5-hydroxytryptamine 1A (5-HT1A) receptor showed increased levels in the ventral hippocampus. In summary, these findings suggest that maternal high-fat diet consumption during critical periods in the development of the fetus, might increase the risk of abnormal behaviors in adulthood related to anxiety.

Regulation of adipocyte formation by GLP-1/GLP-1R signaling

Increased nutrient intake leads to excessive adipose tissue accumulation, obesity, and the development of associated metabolic disorders. How the intestine signals to adipose tissue to adapt to increased nutrient intake, however, is still not completely understood. We show here, that the gut peptide GLP-1 or its long-lasting analog liraglutide, function as intestinally derived signals to induce adipocyte formation, both in vitro and in vivo. GLP-1 and liraglutide activate the GLP-1R, thereby promoting pre-adipocyte proliferation and inhibition of apoptosis. This is achieved at least partly through activation of ERK, PKC, and AKT signaling pathways. In contrast, loss of GLP-1R expression causes reduction in adipogenesis, through induction of apoptosis in pre-adipocytes, by inhibition of the above mentioned pathways. Because GLP-1 and liraglutide are used for the treatment of type 2 diabetes, these findings implicate GLP-1 as a regulator of adipogenesis, which could be an alternate pathway leading to improved lipid homeostasis and controlled downstream insulin signaling.

Adipogenesis and insulin sensitivity in obesity are regulated by retinoid-related orphan receptor gamma

Obesity is a well-known risk factor for the development of secondary complications such as type 2 diabetes. However, only a part of the obese population develops secondary metabolic disorders. Here, we identify the transcription factor retinoid-related orphan receptor gamma (RORγ) as a negative regulator of adipocyte differentiation through expression of its newly identified target gene matrix metalloproteinase 3. In vivo differentiation of adipocyte progenitor cells from Rorγ-deficient mice is enhanced and obese Rorγ^−/− mice show decreased adipocyte sizes. These small adipocytes are highly insulin sensitive, leading to an improved control of circulating free fatty acids. Ultimately, Rorγ^−/− mice are protected from hyperglycemia and insulin resistance in the state of obesity. In adipose stromal-vascular fraction from obese human subjects, Rorγ expression is correlated with adipocyte size and negatively correlated with adipogenesis and insulin sensitivity. Taken together, our findings identify RORγ as a factor, which controls adipogenesis as well as adipocyte size and modulates insulin sensitivity in obesity. RORγ might therefore serve as a novel pharmaceutical target to treat obesity-associated insulin resistance.

Tissue inhibitor of matrix metalloproteinase 1 (TIMP1) controls adipogenesis in obesity in mice and in humans

AIMS/HYPOTHESIS

Extracellular matrix reorganisation is a crucial step of adipocyte differentiation and is controlled by the matrix metalloproteinase-tissue inhibitor of matrix metalloproteinase (TIMP) enzyme system. We therefore sought to define the role of TIMP1 in adipogenesis and to elucidate whether upregulation of TIMP1 in obesity has direct effects on adipocyte formation.

METHODS

TIMP1 protein levels and mRNA were measured in lean and obese mice with a focus on levels in adipose tissue. We also analysed the effect of recombinant murine TIMP1 on adipogenesis, adipocyte size and metabolic control in vitro and in vivo.

RESULTS

TIMP1 levels were increased in the serum and adipose tissue of obese mouse models. Recombinant murine TIMP1 inhibited adipocyte differentiation in 3T3-L1 as well as in subcutaneous primary pre-adipocytes. Conversely, neutralising TIMP1 with a specific antibody enhanced adipocyte differentiation. In vivo, injection of recombinant TIMP1 in mice challenged with a high-fat diet led to enlarged adipocytes. TIMP1-treated mice developed an impaired metabolic profile with increased circulating NEFA levels, hepatic triacylglycerol accumulation and accelerated insulin resistance. Altered glucose clearance in TIMP1-injected mice was due to changes in adipose tissue glucose uptake, whereas muscle glucose clearance remained unaffected.

CONCLUSIONS/INTERPRETATION

TIMP1 is a negative regulator of adipogenesis. In vivo, TIMP1 leads to enlarged adipocytes in the state of overnutrition. This might contribute to the detrimental metabolic consequences seen in TIMP1-injected mice, such as systemic fatty acid overload, hepatic lipid accumulation and insulin resistance.

Weight loss improves endothelial function independently of ADMA reduction in severe obesity

This prospective study was performed in order to establish whether improvement of endothelial function after weight reduction can be explained by a decrease of elevated asymmetric dimethyl arginine (ADMA), an inhibitor of endogenous NO-synthase (eNOS). Therefore, 21 obese subjects (BMI: 41.1±6.4 kg/m(2)) were studied at baseline and after 12 weeks of weight reduction with a very low calorie diet. Biochemical and clinical parameters of endothelial function were assessed before and after weight loss. Biochemical parameters were determined by measurement of ADMA and soluble intercellular adhesion molecule (sICAM). Clinical parameters were assessed by pulse wave analysis (PWA). Weight intervention resulted in a 21.4±6.8 kg reduction of body weight from 119.7±12.8 kg at study start to 98.3±11.6 kg at study end (p<0.001). Accordingly, biochemical markers improved under weight reduction (ADMA from 0.47±0.07 mmol/l to 0.42±0.08 mmol/l; p=0.002; ICAM from 276±42 ng/ml to 236±29 ng/ml; p<0.001). Further, clinical parameters of functional endothelial function improved with an increase of deltaRI after salbutamol inhalation from -1% before to -9% after weight reduction (p=0.02). Interestingly, improvement of endothelial function correlated with improved HOMA index only (r=-0.60, p=0.04) but not with reduced ADMA levels, improved hypertension or reduced body weight. In conclusion, weight reduction with a very low calorie diet improves endothelial function measured by pulse wave velocity. The missing correlation with ADMA suggests possible further mechanisms underlying this observed effect, for example, improvement of insulin resistance.