Improved Glucose Handling Research Articles

LPAAT3 incorporates docosahexaenoic acid into skeletal muscle cell membranes and is upregulated by PPARδ activation

Adaption of skeletal muscle to endurance exercise includes PPARδ- and AMP-activated protein kinase (AMPK)/PPARγ coactivator 1α-mediated transcriptional responses that result in increased oxidative capacity and conversion of glycolytic to more oxidative fiber types. These changes are associated with whole-body metabolic alterations including improved glucose handling and resistance to obesity. Increased DHA (22:6n-3) content in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) is also reported in endurance exercise-trained glycolytic muscle; however, the DHA-metabolizing enzymes involved and the biological significance of the enhanced DHA content are unknown. In the present study, we identified lysophosphatidic acid acyltransferase (LPAAT)3 as an enzyme that was upregulated in myoblasts during in vitro differentiation and selectively incorporated DHA into PC and PE. LPAAT3 expression was increased by pharmacological activators of PPARδ or AMPK, and combination treatment led to further increased LPAAT3 expression and enhanced incorporation of DHA into PC and PE. Our results indicate that LPAAT3 was upregulated by exercise-induced signaling pathways and suggest that LPAAT3 may also contribute to the enhanced phospholipid-DHA content of endurance-trained muscles. Identification of DHA-metabolizing enzymes in the skeletal muscle will help to elucidate broad metabolic effects of DHA.

Discovery of an Isothiazole-Based Phenylpropanoic Acid GPR120 Agonist as a Development Candidate for Type 2 Diabetes.

We have discovered a novel series of isothiazole-based phenylpropanoic acids as GPR120 agonists. Extensive structure-activity relationship studies led to the discovery of a potent GPR120 agonist 4x, which displayed good EC50 values in both calcium and β-arrestin assays. It also presented good pharmaceutical properties and a favorable PK profile. Moreover, it demonstrated in vivo antidiabetic activity in C57BL/6 DIO mice. Studies in WT and knockout DIO mice showed that it improved glucose handling during an OGTT via GPR120. Overall, 4x possessed promising antidiabetic effect and good safety profile to be a development candidate.

The cannabinoid ligand LH-21 reduces anxiety and improves glucose handling in diet-induced obese pre-diabetic mice

LH-21 is a triazol derivative that has been described as a low-permeant neutral CB1 antagonist, though its pharmacology is still unclear. It has been associated with anti-obesity actions in obese rats. However, its role in preventing type 2 diabetes (T2D) onset have not been studied yet. Given CB1 receptors remain as potential pharmacological targets to fight against obesity and T2D, we wanted to explore the metabolic impact of this compound in an animal model of obesity and pre-diabetes as well as the lack of relevant actions in related central processes such as anxiety. C57BL/6J mice were rendered obese and pre-diabetic by feeding a high-fat diet for 15 weeks and then treated with LH-21 or vehicle for two weeks. Food intake, body weight and glucose handling were assessed, together with other relevant parameters. Behavioural performance was evaluated by the open field test and the elevated plus maze. LH-21 did not affect food intake nor body weight but it improved glucose handling, displaying tissue-specific beneficial actions. Unexpectedly, LH-21 induced anxiolysis and reverted obesity-induced anxiety, apparently through GPR55 receptor. These results suggest that LH-21 can be a new candidate to fight against diabetes onset. Indeed, this compound shows potential in counteracting obesity-related anxiety.

Genetic Disruption of Adenosine Kinase in Mouse Pancreatic β-Cells Protects Against High-Fat Diet-Induced Glucose Intolerance.

Islet β-cells adapt to insulin resistance through increased insulin secretion and expansion. Type 2 diabetes typically occurs when prolonged insulin resistance exceeds the adaptive capacity of β-cells. Our prior screening efforts led to the discovery that adenosine kinase (ADK) inhibitors stimulate β-cell replication. Here, we evaluated whether ADK disruption in mouse β-cells affects β-cell mass and/or protects against high-fat diet (HFD)-induced glucose dysregulation. Mice targeted at the Adk locus were bred to Rip-Cre and Ins1-Cre/ERT1Lphi mice to enable constitutive (βADKO) and conditional (iβADKO) disruption of ADK expression in β-cells, respectively. Weight gain, glucose tolerance, insulin sensitivity, and glucose-stimulated insulin secretion (GSIS) were longitudinally monitored in normal chow (NC)-fed and HFD-fed mice. In addition, β-cell mass and replication were measured by immunofluorescence-based islet morphometry. NC-fed adult βADKO and iβADKO mice displayed glucose tolerance, insulin tolerance and β-cell mass comparable to control animals. By contrast, HFD-fed βADKO and iβADKO animals had improved glucose tolerance and increased in vivo GSIS. Improved glucose handling was associated with increased β-cell replication and mass. We conclude that ADK expression negatively regulates the adaptive β-cell response to HFD challenge. Therefore, modulation of ADK activity is a potential strategy for enhancing the adaptive β-cell response.

Unintended Consequences: Renal Denervation Attenuates Hypertension Development but Impairs Glucose Metabolism in Female Fawn‐Hooded Hypertensive Rats

For both men and women, hypertension (HTN) is the highest risk factor for cardiovascular disease and stroke – the two leading causes of morbidity and mortality throughout the world. Though HTN etiology remains debated, altered sympathetic nervous activity, particularly to the kidney (RSNA), is regarded as a primary contributor to the development and maintenance of HTN. Ablation of renal sympathetic nerves (RDNx) reportedly prevents and/or reverses several forms of experimental hypertension. Several off‐target improvements are also reported, such as glucose metabolism. However, an overwhelming majority of these experimental models and mechanisms focus only on responses in male subjects. Moreover, the sex differences in sympathetic control of blood pressure in hypertension remain poorly defined. In this study, we assessed the role of RDNx to prevent hypertension development and metabolic dysfunction in the Fawn‐Hooded Hypertensive (FHH) rat model. We hypothesized that RDNx would attenuate the development of HTN, and improve glucose handling in female and male rats. FHH rats (10 weeks old) underwent sham or bilateral RDNx surgeries (n=5/group). For the following six weeks, 24‐hour mean arterial pressure (MAP) was monitored by radiotelemetry. Glucose handling was assessed biweekly by glucose tolerance test (GTT). Cardiovascular data was averaged weekly, and analyzed by two‐way ANOVA with a Bonferroni post‐hoc test (α=.05). Data presented as mean ± SEM. Six weeks post‐treatment, RDNx attenuated the HTN in the females (p<.05) vs. sham controls (107±5 vs. 118±3). Interestingly, no difference in MAP between RDNx and sham males was observed (129±2 vs. 125±1mmHg). Regarding glucose metabolism, baseline fasting blood glucose (FBG) and glucose tolerance (GT) were similar between males and females prior to RDNx. After six weeks, FBG in female sham FHH (100.9±2.3mg/dL) was higher (p<.05) than male shams (89.2±2.7mg/dL). Likewise, GT was impaired in female rats compared to male shams. In contrast to our hypothesis, RDNx worsened the FBG (110±2.6mg/dL) and GT in female vs. female shams. No effect of time or RDNx on glucose handling was observed males. In summary, RDNx attenuated HTN development in female FHH rats; however, glucose metabolism was impaired by RDNx in females but not in males. These results suggest that sex may need to be considered in the use of RDNx to treat HTN. These findings are clinically important in that RDNx responses may be partially dependent on sex, and may result in negative outcomes such as impaired glucose metabolism in females. Further examination of sex differences in the responses to RDNx is underway.Support or Funding InformationNIH 5R01HL116476; NIH 2T32HL7741

The signalling mechanisms of a novel mitochondrial complex I inhibitor prevent lipid accumulation and attenuate TNF-α-induced insulin resistance in vitro

RTC-1 has recently been identified as a member of a new class of anti-diabetic compounds acting through the inhibition of complex I of the mitochondrial respiratory chain (NADH:ubiquinone oxidoreductase) to improve glucose handling and inhibit weight gain in mice fed a high-fat diet (HFD). The exact mechanism by which the reduced activity of NADH:ubiquinone oxidoreductase, in response to RTC-1, promotes these improved metabolic parameters remains to be established. Through extensive in vitro analysis, new molecular insights into these downstream signalling pathways have been obtained. RTC-1-induced inhibition of NADH:ubiquinone oxidoreductase was found to promote glucose uptake in C2C12 myotubes in vitro, through the activation of the Akt substrate of 160kDa (AS160), in response to the increased activity of Akt and AMP-activated protein kinase (AMPK). RTC-1-induced phosphorylation of the AMPK substrate, acetyl-CoA carboxylase (ACC) in vitro, was associated with a decrease in lipid accumulation in 3T3-L1 adipocytes and murine mesenchymal stromal cells (MSC). The novel compound also prevented tumour necrosis factor-alpha (TNF-α)-induced insulin resistance and demonstrated insulin sensitising effects in C2C12 myotubes. Taken together, these results present a systematic analysis of the signalling mechanisms responsible for the potent anti-diabetic and anti-obesogenic effects of this modulator of mitochondrial function, strengthening the potential use of such compounds for the treatment of type 2 diabetes mellitus (T2DM).

Abstract P638: Muscadine Grape Seed Extract Improves Glucose Handling in Female but not Male Hypertensive (mRen2)27 Rats

Muscadine grapes ( Vitis rotundifolia ) are enriched in polyphenols and other flavan-3-ols that may potentially convey cardiovascular benefit through the antioxidant properties of these compounds. In the current study, we established the effects of a muscadine grape extract (MGE, Piedmont Research and Development Corp.) on blood pressure and metabolic function in 20 week-old female and male hemizygous (mRen2)27 transgenic rats, an Ang II-AT 1 R-dependent model of hypertension. Littermates were treated with MGE (0.2 mg/mL) in the drinking water for 6 weeks (n = 7; male and n=5; female); controls were given water only (n = 7; male and n = 6; female). Intraperitoneal glucose tolerance test (IPGTT) assessed glucose metabolism and serum levels of glucose and insulin were also determined. There were no significant differences between the control and MGE-treated groups for either sex in systolic blood pressure (males: 168 ± 5 vs. 179 ± 4 mmHg; females: 183 ± 5 vs. 162 ± 11 mmHg) or body weight (males: 513 ± 12 vs. 508 ± 22 g; females: 297 ± 4 vs. 294 ± 89 g). The glucose response (area under the curve - AUC) in the female MGE-treated group was markedly lower compared to the untreated controls; however, MGE elicited no effect on the glucose AUC in males (see figure). Although MGE did not influence serum insulin AUC in males or females, the MGE-treated females exhibited a trend for a lower glucose-insulin index. We conclude that MGE intake improves glucose utilization in adult female hypertensive rats independent of changes in blood pressure or body weight. The mechanism(s) underlying the differential response to MGE between the female and male (mRen2)27 transgenic remain to be established

A novel thermoregulatory role for PDE10A in mouse and human adipocytes.

Phosphodiesterase type 10A (PDE10A) is highly enriched in striatum and is under evaluation as a drug target for several psychiatric/neurodegenerative diseases. Preclinical studies implicate PDE10A in the regulation of energy homeostasis, but the mechanisms remain unclear. By utilizing small‐animal PET/MRI and the novel radioligand [18F]‐AQ28A, we found marked levels of PDE10A in interscapular brown adipose tissue (BAT) of mice. Pharmacological inactivation of PDE10A with the highly selective inhibitor MP‐10 recruited BAT and potentiated thermogenesis in vivo. In diet‐induced obese mice, chronic administration of MP‐10 caused weight loss associated with increased energy expenditure, browning of white adipose tissue, and improved insulin sensitivity. Analysis of human PET data further revealed marked levels of PDE10A in the supraclavicular region where brown/beige adipocytes are clustered in adults. Finally, the inhibition of PDE10A with MP‐10 stimulated thermogenic gene expression in human brown adipocytes and induced browning of human white adipocytes. Collectively, our findings highlight a novel thermoregulatory role for PDE10A in mouse and human adipocytes and promote PDE10A inhibitors as promising candidates for the treatment of obesity and diabetes.

Abstract 213: Differential Effects of Nanoformulated Copper/zinc Superoxide Dismutase in Regulating Fasting Blood Glucose Levels in Mice Fed a Low versus High Fat Diet

We previously reported that nanoformulated copper/zinc superoxide dismutase (nanoSOD) ameliorates adipose tissue inflammation without altering systemic glucose homeostasis in a mouse model of diet-induced obesity. A recent report showed that mice lacking SOD1 exhibit insulin resistance only upon low fat (chow) but not high fat (HF)-diet feeding suggesting that the effect of nanoSOD in modulating systemic glucose levels may depend on the diet type. The objective of this study is to determine the effectiveness of nanoSOD in altering muscle gene expression and/or systemic glucose handling in mice fed a low versus high fat (HF) diet. Six-eight wk old wild type C57BL/6 mice were fed a low fat chow diet (CD) or a HF fat (45%) for 10 wk. The mice were injected with nanoSOD (1000 units/kg body wt.) once in two days for fifteen days. The fasting blood glucose level was significantly reduced in CD+NanoSOD-treated mice compared to CD control ( P <0.05) . Insulin tolerance test revealed that nanoSOD-treated mice showed improved glucose handling in response to insulin in CD but not in HF diet-fed mice. The muscle mRNA expression of LPL , a gene involved in fatty acid uptake, was significantly increased ( P <0.05) and ACOX-1 , a fatty acid oxidation gene, showed a trend towards an increase ( P <0.052) upon nanoSOD treatment in HF-diet fed mice. On the other hand, genes involved in fatty acid metabolism including ACOX1, CPT1a , and CPT2 were significantly down-regulated in CD+nanoSOD treated mice. Moreover, the expression of FASN ( P <0.05) and SREBP1 ( P <0.01), genes promoting fatty acid synthesis was significantly reduced in CD+nanoSOD treated mice. Further, the mRNA expression of PCX which promotes both gluconeogenesis and lipogenesis was significantly reduced ( P <0.01) in CD+nanoSOD treated mice. Taken together, our data show that nanoSOD exerts differential effects on the muscle expression of genes involved in fatty acid metabolism in low fat versus HF diet-fed conditions. Because fatty acid oversupply is a key mediator of muscle insulin resistance, a switch in nutrient supply favoring fatty acid oxidation during HF diet-feeding may have a role in mediating the differential influence of nanoSOD in modulating systemic glucose homeostasis in low versus HF diet-fed conditions.

Zinc supplementation for improving glucose handling in pre-diabetes: A double blind randomized placebo controlled pilot study

AimsThere are a number of studies showing that zinc supplementation may improve glucose handling in people with established diabetes. We sought to investigate whether this zinc-dependent improvement in glucose handling could potentially be harnessed to prevent the progression of pre-diabetes to diabetes. In this double-blind randomized placebo-controlled trial, we determined participants’ fasting blood glucose levels, (FBG) and Homeostasis Model Assessment (HOMA) parameters (beta cell function, insulin sensitivity and insulin resistance) at baseline and after 6 months of zinc supplementation. MethodsThe Bangladesh Institute of Health Sciences Hospital (BIHS) (Mirpur, Dhaka, Bangladesh) database was used to identify 224 patients with prediabetes, of whom 55 met the inclusion criteria and agreed to participate. The participants were randomized either to the intervention or control group using block randomization. The groups received either 30mg zinc sulphate dispersible tablet or placebo, once daily for six months. ResultsAfter six months, the intervention group significantly improved their FBG concentration compared to the placebo group (5.37±0.20mmol/L vs 5.69±0.26, p<0.001) as well as compared to their own baseline (5.37±0.20mmol/L vs 5.8±0.09, p<0.001). Beta cell function, insulin sensitivity and insulin resistance all showed a statistically significant improvement as well. ConclusionTo our knowledge this is the first trial to show an improvement in glucose handling using HOMA parameters in participants with prediabetes. Larger randomized controlled trials are warranted to confirm these findings and to explore clinical endpoints.

Novel mitochondrial complex I inhibitors restore glucose-handling abilities of high-fat fed mice.

Metformin is the main drug of choice for treating type 2 diabetes, yet the therapeutic regimens and side effects of the compound are all undesirable and can lead to reduced compliance. The aim of this study was to elucidate the mechanism of action of two novel compounds which improved glucose handling and weight gain in mice on a high-fat diet. Wildtype C57Bl/6 male mice were fed on a high-fat diet and treated with novel, anti-diabetic compounds. Both compounds restored the glucose handling ability of these mice. At a cellular level, these compounds achieve this by inhibiting complex I activity in mitochondria, leading to AMP-activated protein kinase activation and subsequent increased glucose uptake by the cells, as measured in the mouse C2C12 muscle cell line. Based on the inhibition of NADH dehydrogenase (IC50 27µmolL(-1)), one of these compounds is close to a thousand fold more potent than metformin. There are no indications of off target effects. The compounds have the potential to have a greater anti-diabetic effect at a lower dose than metformin and may represent a new anti-diabetic compound class. The mechanism of action appears not to be as an insulin sensitizer but rather as an insulin substitute.

Low-calcium diet prevents fructose-induced hyperinsulinemia and ameliorates the response to glucose load in rats.

BackgroundConsuming a fructose-rich diet leads to hyperinsulinemia, impaired glucose tolerance, and insulin resistance. In humans, the consumption of high levels of refined sugars often coincides with a diet containing suboptimal levels of calcium. Calcium and carbohydrate metabolism interact, so there is potential for fructose to have different health outcomes depending on whether the diet is calcium-rich or calcium-poor.MethodsWe evaluated the metabolic effects of feeding fructose to rats that were maintained on either a calcium-replete diet or a low-calcium diet. Growing male Sprague Dawley rats were fed diets based on the AIN-93G formulation, with the main source of carbohydrate derived either from a mixture of cornstarch and sucrose or from fructose. Half the rats given each carbohydrate source were fed calcium at recommended levels (125 mmol/kg Ca2+); the others were fed a diet low in calcium (25 mmol/kg Ca2+). At various times, glucose and insulin tolerance tests were conducted to assess glucose metabolism.ResultsRats fed low-calcium diet had lower fasting insulin levels irrespective of the carbohydrate source they ate. They had a normal glycemic response to a glucose load and did not develop hyperinsulinemia under conditions of fructose feeding. The drop in blood glucose levels in response to insulin injection was larger in rats fed low-calcium diet than in those fed calcium-replete diet.ConclusionsLow-calcium diet prevented fructose-induced hyperinsulinemia and improved glucose handling under conditions of fructose feeding. Potential mechanisms underlying these effects of the low-calcium diet remain to be determined, but possibilities include impairment of insulin release from the pancreas and improved peripheral insulin sensitivity.

Abstract P076: Suppressor of Cytokine Signaling 3 (SOCS3) in POMC Neurons and Its Role in Regulating Blood Pressure, Body Weight and Glucose in Obesity

Suppressor of cytokine signaling 3 (SOCS3), a negative regulator of leptin signaling, may be involved in development of obesity-induced leptin resistance. Although we previously showed that activation of proopiomelanocortin (POMC) neurons mediates the chronic effects of leptin on blood pressure (BP), the role of SOCS3 in modulating BP in obesity is still unclear. In this study, we investigated the role of SOCS3 specifically in POMC neurons in regulating body weight, glucose handling and BP in mice fed a normal or high fat (45%, HFD) chow. Male and female SOCS3flox/flox-POMC/cre mice in which SOCS3 was selectively deleted in POMC neurons and control SOCS3flox/flox mice were used. Food intake and body weight were measured from 8 to 16 weeks of age, and a glucose tolerance test (GTT) was performed at 20 wks of age. At 22 wks of age, mice were implanted with telemetry probe to measure BP and heart rate (HR) and fed a HFD for 6 weeks. Compared to control mice, both male and female SOCS3flox/flox-POMC/cre mice were lighter at 16 wks (29.1 ± 3.5 vs 31.9 ± 3.6 g in male and 21.5 ± 2.2 vs 26.1 ± 5.7 in female, n=9-11, p&lt;0.05) but food intake was similar in both groups. Only male SOCS3flox/flox-POMC/cre mice exhibited improved glucose handling (AUC: 1059 ± 52 vs 1283 ± 54 mg/dL x 120 min, n=7-10, p&lt;0.05 ) and no differences were observed in female mice. When fed normal chow, BP was similar in SOCS3flox/flox-POMC/cre and control mice (116 ± 7 vs 113 ± 5 mmHg) at 23 wks. After a HFD for 6 weeks, SOCS3flox/flox-POMC/cre mice had a greater BP increase compared to control mice (7.2 ± 1.9 vs 0.9 ± 1.8 mmHg, n=4-9, P&lt;0.05) but no significant differences were observed in food intake or body weight between two groups. These results suggest that SOCS3 deletion specifically in POMC neurons reduced body weight in male and female mice, and improved glucose handling only in male mice. HFD increased BP in SOCS3flox/flox-POMC/cre but not in control mice, suggesting that SOCS3 in POMC neurons may modulate BP response to HFD.

The effect of hyperinsulinaemic-euglycaemic clamp and exercise on bone remodeling markers in obese men.

Bone remodelling markers (BRMs) are suppressed following a glucose load and during glucose infusion. As exercise increases indices of bone health and improves glucose handling, we hypothesised that, at rest, hyperinsulinaemic-euglycaemic clamp will suppress BRMs in obese men and that exercise prior to the clamp will prevent this suppression. Eleven obese nondiabetic men (age 58.1±2.2 years, body mass index=33.1±1.4 kg m(-2) mean±s.e.m.) had a hyperinsulinaemic-euglycaemic clamp (HEC) at rest (Control) and 60 min post exercise (four bouts × 4 min cycling at 95% of hazard ratiopeak). Blood samples were analysed for serum insulin, glucose, bone formation markers, total osteocalcin (tOC) and procollagen type 1 N-terminal propeptide (P1NP), and the bone resorption marker, β-isomerised C-terminal telopeptides (β-CTx). In the control trial (no exercise), tOC, P1NP and β-CTx decreased with HEC by >10% compared with baseline (P<0.05). Fasting serum glucose, but not insulin, tended to correlate negatively with the BRMs (β range -0.57 to -0.66, p range 0.051-0.087). β-CTx, but not OC or P1NP, increased within 60 min post exercise (∼16%, P<0.01). During the post-exercise HEC, the glucose infusion rate was ∼30% higher compared with the no exercise trial. Despite this, BRMs were only suppressed to a similar extent as in the control session (10%). HEC suppressed BRMs in obese men. Exercise did not prevent this suppression of BRMs by HEC but improved glucose handling during the trial. It remains to be tested whether an exercise intervention of longer duration may be able to prevent the effect of HEC on bone remodelling.

Dietary restriction in moderately obese rats improves body size and glucose handling without the renal and hepatic alterations observed with a high-protein diet.

Obesity is increasing worldwide, and high-protein (HP) diets are widely used for weight loss. However, the overall safety of HP diets is not well established in obese individuals, who make up a significant proportion of the population. To evaluate the health effects of an HP diet in obesity, obesity-prone (OP) Sprague-Dawley rats were given high-fat diets for 12 weeks to induce obesity. Following this, for 8 more weeks, these rats were given either a normal-protein (NP) (15% of energy) or an HP (35% of energy) diet ad libitum, or the NP diet at a restricted level to achieve body weights similar to those of the HP group (pair-weighted (PW) group). Obesity-resistant (OR) control rats were also given the NP diet throughout the feeding period. The HP-OP group had higher food intake but lower body weight, improved glucose handling, and lowered serum haptoglobin compared with the NP-OP group. These benefits were also observed in PW-OP rats. In addition, PW-OP rats had less fat accumulation when compared with NP-OP rats, and an improved Lee index, lower liver size, and lower serum alanine aminotransferase when compared with HP-OP rats. On the other hand, kidney size, proteinuria, and serum homocysteine were increased in HP-OP rats compared with NP-OP rats, whereas PW-OP rats did not experience these effects. These results indicate that in obese rats, more benefits are obtained via dietary restriction with an NP diet and without some of the potentially detrimental effects of an HP diet.

Oral administration of osteocalcin improves glucose utilization by stimulating glucagon-like peptide-1 secretion

Uncarboxylated osteocalcin (GluOC), a bone-derived hormone, regulates energy metabolism by stimulating insulin secretion and pancreatic β-cell proliferation. We previously showed that the effect of GluOC on insulin secretion is mediated largely by glucagon-like peptide-1 (GLP-1) secreted from the intestine in response to GluOC exposure. We have now examined the effect of oral administration of GluOC on glucose utilization as well as the fate of such administered GluOC in mice. Long-term intermittent or daily oral administration of GluOC reduced the fasting blood glucose level and improved glucose tolerance in mice without affecting insulin sensitivity. It also increased the fasting serum insulin concentration as well as the β-cell area in the pancreas. A small proportion of orally administered GluOC reached the small intestine and remained there for at least 24h. GluOC also entered the general circulation, and the serum GLP-1 concentration was increased in association with the presence of GluOC in the intestine and systemic circulation. The putative GluOC receptor, GPRC6A was detected in intestinal cells, and was colocalized with GLP-1 in some of these cells. Our results suggest that orally administered GluOC improved glucose handling likely by acting from both the intestinal lumen and the general circulation, with this effect being mediated in part by stimulation of GLP-1 secretion. Oral administration of GluOC warrants further study as a safe and convenient option for the treatment or prevention of metabolic disorders.

Adipose invariant natural killer T cells

Adipose tissue is a dynamic organ that makes up a substantial proportion of the body; in severe obesity it can account for 50% of body mass. Details of the unique immune system resident in human and murine adipose tissue are only recently emerging, and so it has remained a largely unexplored and unappreciated immune site until now. Adipose tissue harbours a unique collection of immune cells, which often display unusual functions compared with their counterparts elsewhere in the body. These resident immune cells are key to maintaining tissue and immune homeostasis, yet in obesity their chronic aberrant stimulation can contribute to the inflammation and pathogenesis associated with obesity. Anti-inflammatory adipose-resident lymphocytes are often depleted in obesity, whereas pro-inflammatory immune cells accumulate, leading to an overall inflammatory state, which is a key step in the development of obesity-induced metabolic disease. A good example is invariant natural killer T (iNKT) cells, which make up a large proportion of lymphocytes in human and murine adipose tissue. Here, they are unusually poised to produce anti-inflammatory or regulatory cytokines, however in obesity, iNKT cells are greatly reduced. As iNKT cells are potent transactivaors of other immune cells, and can act as a bridge between innate and adaptive immunity, their loss in obesity represents the loss of a major regulatory population. Restoring iNKT cells, or activating them in obese mice leads to improved glucose handling, insulin sensitivity, and even weight loss, and hence represents an exciting therapeutic avenue to be explored for restoring homeostasis in obese adipose tissue.

Modulation of de novo purine biosynthesis leads to activation of AMPK and results in improved glucose handling and insulin sensitivity.

BackgroundAMP activated protein kinase (AMPK) regulates key metabolic reactions and plays a major role in glucose homeostasis. Activating the AMPK is considered as one of the potential therapeutic strategies in treating type-2 diabetes. However, targeting AMPK by small molecule mediated approach can be challenging owing to diverse isoforms of the enzyme and their varied combination in different tissues. In the current study we employ a novel strategy of achieving AMPK activation through increasing the levels of cellular AMP (an allosteric activator of AMPK) levels by activating the enzyme involved in AMP biosynthesis namely Adenylosuccinate lyase (ADSL).MethodsRat primary hepatocytes were cultured under metabolic overload conditions (500 μM palmitate) to induce insulin resistance. ADSL was overexpressed in these hepatocytes and its effect on hepatic glucose output, and triglyceride accumulation was checked. In addition to this, ADSL was overexpressed in high fat diet induced obese mice by hydrodynamic tail vein injection and its effect on fasting glucose, glucose tolerance and pyruvate tolerance were checked.ResultsRat primary hepatocytes when cultured under metabolic overload conditions developed insulin resistance as measured in terms of failure of insulin to suppress the glucose output. Overexpressing the ADSL in these hepatocytes resulted in increased AMPK phosporylation and improved the insulin sensitivity and also resulted in reduced triglyceride accumulation and inflammatory cytokine levels. In addition to this, when ADSL was overexpressed in high fat diet induced obese mice, it resulted in reduced the fasting hyperglycemia (20% reduction), and increased glucose and pyruvate tolerance.ConclusionsThis study indicates that activating ADSL can be a potential mechanism to achieve the activation of AMPK in the cells. This leads to a novel idea of exploring the purine nucleotide metabolic pathway as a promising therapeutic target for diabetes and metabolic syndrome.

No pain, no gain: somatosensation from skeletal muscle

No pain, no gain: somatosensation from skeletal muscle

Remodeling of Oxidative Energy Metabolism by Galactose Improves Glucose Handling and Metabolic Switching in Human Skeletal Muscle Cells

Cultured human myotubes have a low mitochondrial oxidative potential. This study aims to remodel energy metabolism in myotubes by replacing glucose with galactose during growth and differentiation to ultimately examine the consequences for fatty acid and glucose metabolism. Exposure to galactose showed an increased [14C]oleic acid oxidation, whereas cellular uptake of oleic acid uptake was unchanged. On the other hand, both cellular uptake and oxidation of [14C]glucose increased in myotubes exposed to galactose. In the presence of the mitochondrial uncoupler carbonylcyanide p-trifluormethoxy-phenylhydrazone (FCCP) the reserve capacity for glucose oxidation was increased in cells grown with galactose. Staining and live imaging of the cells showed that myotubes exposed to galactose had a significant increase in mitochondrial and neutral lipid content. Suppressibility of fatty acid oxidation by acute addition of glucose was increased compared to cells grown in presence of glucose. In summary, we show that cells grown in galactose were more oxidative, had increased oxidative capacity and higher mitochondrial content, and showed an increased glucose handling. Interestingly, cells exposed to galactose showed an increased suppressibility of fatty acid metabolism. Thus, galactose improved glucose metabolism and metabolic switching of myotubes, representing a cell model that may be valuable for metabolic studies related to insulin resistance and disorders involving mitochondrial impairments.