Ostarine does not enhance the metabolic effect of exercise in obese rats.

Overweight and obesity are associated with severe metabolic disorders and an increased risk of cardiovascular diseases. It is a known fact that physical activity has a positive effect on metabolic parameters, and also reduces the risk of diseases such as diabetes. Some products can enhance the rate of lipolysis and help in improving fat loss. One of these are selective androgen receptor modulators (SARMs) which act as anabolic agents and are also believed to aid in fat-burning. In this study, we investigated whether 30 days of ostarine administration could potentially improve metabolic parameters using the rat model of obesity combined with exercise. We assessed the levels of biochemical and hormonal parameters in serum samples as well as insulin sensitivity indices of tissues. There were significant changes in the metabolic parameters with exercise. However, we did not find any additive effects of ostarine and exercise on most of the parameters tested. Similar results were obtained from the analysis of gene expression and the concentration of leptin and adiponectin. Our results indicated that ostarine had a lowering effect on cholesterol concentration in the serum (P<0.05). Moreover, when combining ostarine and exercise, additive changes were only observed in the levels of total and HDL cholesterol. No significant change was observed in the metabolic parameters of obese rats with the use of ostarine at the dose of 0.4 mg/kg body weight. Since ostarine is known to enhance performance, further research on its effects is needed.

Obesity is associated with increased level of kisspeptin in mothers' blood and umbilical cord blood - a pilot study.

OBJECTIVE: Kisspeptin (KP) is a major regulator of reproductive functions. It has also been shown to be involved in the metabolic changes associated with obesity. According to the well-established concept of prenatal programming, environmental factors can influence physiological and behavioral systems at the early stages of development. Thus, we hypothesized that in pregnant women, obesity can be associated with alterations in the levels of KP. We also assumed that the observed changes in obese mothers' blood (MB) would be reflected in the umbilical cord blood (CB). MATERIALS AND METHODS: We collected MB and CB from obese and nonobese women and analyzed the differences in metabolic and hormonal profiles, including KP concentration, using commercially available assays. RESULTS: We found that the level of KP was increased in the MB and CB of obese patients compared to nonobese subjects (p<0.05). A strong correlation was observed between the concentration of KP in MB and CB (r=0.8343; p<0.01). Moreover, we detected that the differences in the adipokine profile observed in the MB were not reflected in CB. CONCLUSIONS: Our results indicate that blood KP concentration can serve as a valuable marker in pregnant women. However, further studies are needed to understand the alterations of this peptide in obese pregnant woman and their potential effects on offspring.

Effect of ostarine (enobosarm/GTX024), a selective androgen receptor modulator, on adipocyte metabolism in Wistar rats.

Synthetic ligands of androgen receptor (AR) are a standard in the treatment of androgen deficiency. One of the effects of androgen deficiency is the disturbance in the homeostasis of lipid metabolism. Till date, there are no effective compounds developed to treat androgen deficiency without having any side effects. Nonsteroidal selective androgen receptor modulators (SARMs) are a promising solution for various clinical indications. In this study, we investigated the effect of ostarine (enobosarm), a nonsteroidal SARM, on the rat adipocyte metabolism using in vitro techniques. Isolated rat adipocytes were incubated in the presence of different concentrations of ostarine. Control incubation with testosterone as the natural ligand for AR was performed. AR inhibitors were used to investigate the genomic activity of ostarine. Changes in the intensity of lipolysis, lipogenesis, and the secretion of leptin and adiponectin were measured. Moreover, the gene expression of leptin and adiponectin was assessed. For the first time, we have shown that ostarine has a significant effect on the intensity of lipid metabolism. Ostarine downregulates the expression of leptin and adiponectin mRNAs, as well as decreases their release from rat adipocytes. According to our results, ostarine acts via AR with a similar effect as testosterone in the regulation of lipid metabolism and endocrine function of mature rat adipocytes in vitro. Our results indicate the need for further studies on the effects of SARM on the whole organism.

Orexin A but not orexin B regulates lipid metabolism and leptin secretion in isolated porcine adipocytes.

It is well known that orexins are involved in the metabolism and endocrine function of rodent adipocytes, but there are no data on other animal species, including pigs. Therefore, in this study, we tested the hypothesis that orexin A (OxA) and orexin B (OxB) modulate the metabolism and endocrine functions of isolated porcine adipocytes and adipose tissue explants. Moreover, we characterized the possible mechanism of OxA action in porcine adipocytes. According to the results, both orexin receptor 1 and orexin receptor 2 were expressed in the porcine adipose tissue. We found that OxA suppressed the release of glycerol from porcine adipocytes both in the absence (basal lipolysis; P < 0.05) and in the presence (stimulated lipolysis; P < 0.05) of isoproterenol. Orexin A increased basal and insulin-stimulated glucose uptake (P < 0.05), as well as it enhanced the rate of glucose incorporation into lipids with insulin (stimulated lipogenesis; P < 0.01) or without insulin (basal; P < 0.05). We have also shown that OxA stimulated the mRNA expression of glucose transporter 4 (P < 0.05) and its translocation into the plasma membrane (P < 0.01). Moreover, OxA upregulated the mRNA expression of leptin in isolated porcine adipocytes (P < 0.05) and increased the secretion of leptin (P < 0.05). We have also demonstrated one of the possible mechanisms of OxA action in adipocytes. In the presence of extracellular-signal-regulated kinase 1 and 2 (ERK1/2) inhibitor, the effect of OxA was not detectable in porcine adipocytes, which indicates that this peptide increased cell viability via ERK1/2 pathway (P < 0.05). However, OxB did not show any effect on the metabolism and endocrine functions of porcine adipocytes. In summary, we have shown for the first time that OxA has a significant impact on the intensity of lipolysis, glucose uptake, lipogenesis, as well as on the expression and secretion of leptin. Therefore, we conclude that OxA but not OxB regulates lipid metabolism in porcine adipose tissue and that this regulation is partly mediated via ERK1/2 pathway. The action of orexins should be further explored to better understand their role in the regulation of adiposity in pigs.

Serum levels of spexin and kisspeptin negatively correlate with obesity and insulin resistance in women.

Spexin (SPX) and kisspeptin (KISS) are novel peptides relevant in the context of regulation of metabolism, food intake, puberty and reproduction. Here, we studied changes of serum SPX and KISS levels in female non-obese volunteers (BMI<25 kg/m(2)) and obese patients (BMI>35 kg/m(2)). Correlations between SPX or KISS with BMI, McAuley index, QUICKI, HOMA IR, serum levels of insulin, glucagon, leptin, adiponectin, orexin-A, obestatin, ghrelin and GLP-1 were assessed. Obese patients had lower SPX and KISS levels as compared to non-obese volunteers (SPX: 4.48+/-0.19 ng/ml vs. 6.63+/-0.29 ng/ml; p<0.001, KISS: 1.357+/-0.15 nmol/l vs. 2.165+/-0.174 nmol/l; p<0.01). SPX negatively correlated with BMI, HOMA-IR, insulin, glucagon, active ghrelin and leptin. Positive correlations were found between SPX and QUICKI index, McAuley index, serum levels of obestatin, GLP-1 and adiponectin and orexin-A Serum KISS negatively correlated with BMI, HOMA-IR, serum levels of insulin, glucagon, active ghrelin and leptin. KISS positively correlated with QUICKI index, McAuley index and adiponectin. In summary, SPX and KISS show negative correlations with obesity, insulin resistance indices, and hormones known to affect insulin sensitivity in females. Both, SPX and KISS could be therefore relevant in the pathophysiology of obesity and insulin resistance.

Chronic orexin-A (hypocretin-1) treatment of type 2 diabetic rats improves glucose control and beta-cell functions.

Orexin regulates food intake and energy expenditure. Here, we test the ability of orexin-A (OXA, hypocretin-1) at improving metabolic control in type 2 diabetic animals and elaborate potential mechanisms of action. Rats with experimentally induced type 2 diabetes by a combination of streptozotocin injection and high-fat diet feeding were chronically infused with OXA. In vitro experiments were conducted on isolated pancreatic islets, primary adipocytes and insulin secreting INS-1E cells. OXA improved glucose control, enhanced insulin sensitivity and attenuated pancreatic ß-cell loss in type 2 diabetic rats. Ex vivo, apoptotic death of pancreatic islets isolated from OXA-treated type 2 diabetic animals as well as the impairment of glucose-stimulated insulin secretion were attenuated, as compared to islets derived from vehicle-treated rats. OXA reduced plasma tumor necrosis factor-α (TNF-α) and non-esterified fatty acids (NEFA) levels in type 2 diabetic rats. OXA decreased palmitate- and TNF-α-induced apoptosis of INS-1E cells. OXA improves glucose control by enhancing insulin sensitivity and protecting ß-cells from apoptotic cell death in type 2 diabetic animals.

Effects of Orchidectomy and Testosterone Replacement on Numbers of Kisspeptin-, Neurokinin B-, and Dynorphin A-Immunoreactive Neurones in the Arcuate Nucleus of the Hypothalamus in Obese and Diabetic Rats.

Neurones expressing kisspeptin, neurokinin B and dynorphin A, located in the arcuate nucleus of the hypothalamus (ARC), are important regulators of reproduction. Their functions depend on metabolic and hormonal status. We hypothesised that male rats with high-fat diet-induced obesity (DIO) and/or streptozotocin-induced diabetes mellitus type 1 (DM1) and type 2 (DM2) will have alterations in numbers of immunoreactive (-IR) cells: kisspeptin-IR and/or neurokinin B-IR and dynorphin A-IR neurones in the ARC in the sham condition. In addition, orchidectomy alone (ORX) and with testosterone treatment (ORX+T) will unmask possible deficits in the response of these neurones in DIO, and/or DM1 and DM2 rats. Rats were assigned to four groups: a control (C) and one diabetic group (DM1) were fed a regular chow diet, whereas the obese group (DIO) and the other diabetic group (DM2) were fed a high-fat diet. To induce diabetes, streptozotocin was injected. After 6 weeks, each group was divided into three subgroups: ORX, ORX+T and sham. After another 2 weeks, metabolic and hormonal profiles were assessed and immunocytochemistry was performed. We found that: (1) under sham conditions: (i) DM1 and DM2 animals had higher numbers of kisspeptin-IR cells than controls and (ii) DM2 rats had increased numbers of neurokinin B-IR and dynorphin A-IR cells compared to C animals; (2) ORX and ORX+T treatments unmasked deficits of the studied neurones in DM1 and DM2 but not in DIO animals; and (3) DIO, DM1 and DM2 rats had altered metabolic and hormonal profiles, in particular decreased levels of testosterone. We concluded that alterations in numbers of kisspeptin-IR and neurokinin B-IR neurones in the ARC and their response to ORX and ORX+T may account for disruptions of metabolic and reproductive functions in diabetic but not in obese rats.

Effects of high-fat diet-induced obesity and diabetes on Kiss1 and GPR54 expression in the hypothalamic-pituitary-gonadal (HPG) axis and peripheral organs (fat, pancreas and liver) in male rats.

Recent data indicates that kisspeptin, encoded by the KISS1 gene, could play a role in transducing metabolic information into the hypothalamic-pituitary-gonadal (HPG) axis, the mechanism that controls reproductive functions. Numerous studies have shown that in a state of negative energy balance, the hypothalamic kisspeptin system is impaired. However, data concerning positive energy balance (e.g. diabetes and obesity) and the role of kisspeptin in the peripheral tissues is scant. We hypothesized that: 1) in diet-induced obese (DIO) male rats and/or rats with diabetes type 1 (DM1) and type 2 (DM2), altered reproductive functions are related to an imbalance in Kiss1 and GPR54 mRNA in the HPG axis; and 2) in DIO and/or DM1 and/or DM2 rats, Kiss1 and GPR 54 expression are altered in the peripheral tissues involved in metabolic functions (fat, pancreas and liver). Animals were fed a high-fat or control diets and STZ (streptozotocin - toxin, which destroys the pancreas) was injected in high or low doses to induce diabetes type 1 (DM1) or diabetes type 2 (DM2), respectively. RT-PCR and Western blot techniques were used to assess the expression of Kiss1 and GRP54 in tissues. At the level of mRNA, we found that diabetic but not obese rats have alterations in Kiss1 and/or GPR54 mRNA levels in the HPG axis as well as in peripheral tissues involved in metabolic functions (fat, pancreas and liver). The most severe changes were seen in DM1 rats. However, in the case of protein levels in the peripheral tissues (fat, pancreas and liver), changes in Kiss1/GPR54 expression were noticed in DIO, DM1 and DM2 animals and were tissue-specific. Our data support the hypothesis that alterations in Kiss1/GPR54 balance may account for both reproductive and metabolic abnormalities reported in obese and diabetic rats.

TRPV6 channel modulates proliferation of insulin secreting INS-1E beta cell line.

Transient receptor potential channel vanilloid type 6 (TRPV6) is a non-selective cation channel with high permeability for Ca²âº ions. So far, the role of TRPV6 in pancreatic beta cells is unknown. In the present study, we characterized the role of TRPV6 in controlling calcium signaling, cell proliferation as well as insulin expression, and secretion in experimental INS-1E beta cell model. TRPV6 protein production was downregulated using siRNA by approx. 70%, as detected by Western blot. Intracellular free Ca²âº ([Ca²âº]i) was measured by fluorescence Ca²âº imaging using fura-2. Calcineurin/NFAT signaling was analyzed using a NFAT reporter assay as well as a calcineurin activity assay. TRPV6 downregulation resulted in impaired cellular calcium influx. Its downregulation also reduced cell proliferation and decreased insulin mRNA expression. These changes were companied by the inhibition of the calcineurin/NFAT signaling. In contrast, insulin exocytosis was not affected by TRPV6 downregulation. In conclusion, this study demonstrates for the first time the expression of TRPV6 in INS-1E cells and rat pancreatic beta cells and describes its role in modulating calcium signaling, beta cell proliferation and insulin mRNA expression. In contrast, TRPV6 fails to influence insulin secretion.

In ovo injection of prebiotics and synbiotics affects the digestive potency of the pancreas in growing chickens.

The purpose of the study was to examine the effect of 2 prebiotics and 2 synbiotics on the digestive potency of pancreas in 1-, 3-, 7-, 14-, 21-, and 34-day-old cockerels. Prebiotics (inulin and Bi²tos) and synbiotics (inulin + Lactococcus lactis subsp. lactis and Bi²tos + Lactococcus lactis subsp. cremoris) were injected in ovo into the air cell on the 12th d embryonic development. Their application increased the activity of amylase, lipase, and trypsin in the pancreas. The most pronounced changes were observed at the end of the investigated rearing period (d 34). The strongest stimulative effects on amylase were shown by both synbiotics, on lipase synbiotic Bi²tos + Lactococcus lactis subsp. cremoris, and on trypsin all the used prebiotics and synbiotics. Simultaneously, neither the absolute nor the relative mass of the pancreas in comparison to control group were changed. Also, the injected in ovo compounds did not cause a deterioration in the posthatching condition of the chicken liver, as determined by measurement of the activity of marker enzymes in the blood (alanine aminotransferase and aspartate aminotransferase). Treatment with the prebiotics and synbiotics did not change the feed conversion ratio but Bi²tos (galacto-oligosaccharide) and inulin (fructan) + Lactococcus lactis subsp. lactis significantly increased final BW.

Resistin - from gene expression to development of diabetes.

Adipocyte-originated hormonal factors, playing a role of signaling particles, are widely engaged in energy control, feeding behavior and general glucose or lipid metabolism. One of them – resistin – has been suspected to initiate or develop insulin resistance and diabetes. From the moment of discovery of resistin, during last 13 years, numerous investigations put some light on a potential role of this hormone in mammals. In this review knowledge on resistin, including its structure, physiological role related to obesity and diabetes, as well as, gene sequence and phenotypic effects of the identified polymorphisms in human and domestic mammals is discussed.

Obestatin inhibits lipogenesis and glucose uptake in isolated primary rat adipocytes.

Ghrelin and obestatin are encoded by the preproghrelin gene and originate from post-translational processing of the preproghrelin peptide. Obestatin is mainly present in the stomach, but its action is focused on appetite inhibition in opposition to ghrelin function. Recently, it has been presented that obestatin may regulate adipocyte metabolism and influence fat content. However, obestatin action is still poorly understood. Therefore, we aimed to investigate obestatin function on adipocyte metabolism in the rat. We studied changes in the mRNA expression of active and inactive isoforms of obestatin receptors. In addition, we analyzed influence of obestatin on lipogenesis, lipolysis and glucose transport in isolated adipocytes. Moreover, we also performed analysis of obestatin action on lipolysis in differentiated rat preadipocytes with silenced obestatin receptor. We found significantly higher expression of the obestatin receptor Gpr39-1a active form at an mRNA level following adipocytes incubation with obestatin. We did not observe expression changes in the inactive form of obestatin receptor Gpr39-1b. Additionally, we found significant changes in Gpr39-1a expression following obestatin receptor silencing in cells incubated with obestatin in comparison to control. Obestatin inhibited both, basal and insulin-stimulated lipogenesis and glucose transport in adipocytes. Furthermore, obestatin potentiated adrenalin-stimulated lipolysis. We also found reduced glycerol release following obestatin incubation in adipocytes with silenced Gpr39 gene. Our results indicate that obestatin acts via the GPR39 receptor in isolated adipocytes, and that through this mechanism obestatin influences lipid accumulation, glucose uptake and lipolysis.

Orexin A stimulates glucose uptake, lipid accumulation and adiponectin secretion from 3T3-L1 adipocytes and isolated primary rat adipocytes.

AIMS/HYPOTHESIS: Orexin A (OXA) modulates body weight, food intake and energy expenditure. In vitro, OXA increases PPARγ (also known as PPARG) expression and inhibits lipolysis, suggesting direct regulation of lipid metabolism. Here, we characterise the metabolic effects and mechanisms of OXA action in adipocytes. METHODS: Isolated rat adipocytes and differentiated murine 3T3-L1 adipocytes were exposed to OXA in the presence or absence of phosphoinositide 3-kinase (PI3K) inhibitors. Pparγ expression was silenced using small interfering RNA. Glucose uptake, GLUT4 translocation, phosphatidylinositol (3,4,5)-trisphosphate production, lipogenesis, lipolysis, and adiponectin secretion were measured. Adiponectin plasma levels were determined in rats treated with OXA for 4 weeks. RESULTS: OXA PI3K-dependently stimulated active glucose uptake by translocating the glucose transporter GLUT4 from cytoplasm into the plasma membrane. OXA increased cellular triacylglycerol content via PI3K. Cellular triacylglycerol accumulation resulted from increased lipogenesis as well as from a decrease of lipolysis. Adiponectin levels in chow- and high-fat diet-fed rats treated chronically with OXA were increased. OXA stimulated adiponectin expression and secretion in adipocytes. Both pharmacological blockade of peroxisome proliferator-activated receptor γ (PPARγ) activity or silencing Pparγ expression prevented OXA from stimulating triacylglycerol accumulation and adiponectin production. CONCLUSIONS/INTERPRETATION: Our study demonstrates that OXA stimulates glucose uptake in adipocytes and that the evolved energy is stored as lipids. OXA increases lipogenesis, inhibits lipolysis and stimulates the secretion of adiponectin. These effects are conferred via PI3K and PPARγ2. Overall, OXA's effects on lipids and adiponectin secretion resemble that of insulin sensitisers, suggesting a potential relevance of this peptide in metabolic disorders.