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IntroductionChronic low-grade inflammation is associated with obesity and diabetes. However, what causes and mediates chronic inflammation in metabolic disorders is not well understood. Toll-like receptor 4 (TLR4) mediates both infection-induced and sterile inflammation by recognizing pathogen-associated molecular patterns and endogenous molecules, respectively. Saturated fatty acids can activate TLR4, and TLR4-deficient mice were protected from high fat diet (HFD)-induced obesity and insulin resistance, suggesting that TLR4-mediated inflammation may cause metabolic dysfunction, such as obesity and insulin resistance.MethodsWe generated two transgenic (TG) mouse lines expressing a constitutively active TLR4 in adipose tissue and determined whether these TG mice would show increased insulin resistance.ResultsTG mice fed a high fat or a normal chow diet did not exhibit increased insulin resistance compared to their wild-type controls despite increased localized inflammation in white adipose tissue. Furthermore, females of one TG line fed a normal chow diet had improved insulin sensitivity with reduction in both adiposity and body weight when compared with wild-type littermates. There were significant differences between female and male mice in metabolic biomarkers and mRNA expression in proinflammatory genes and negative regulators of TLR4 signaling, regardless of genotype and diet.ConclusionsTogether, these results suggest that constitutively active TLR4-induced inflammation in white adipose tissue is not sufficient to induce systemic insulin resistance, and that high fat diet-induced insulin resistance may require other signals in addition to TLR4-mediated inflammation.

Aims Angiotensin II (AngII) is a potent vasoconstrictor implicated in both hypertension and insulin resistance. Insulin dilates the vasculature in skeletal muscle to increase microvascular blood flow and enhance glucose disposal. In the present study, we investigated whether acute AngII infusion interferes with insulin's microvascular and metabolic actions in skeletal muscle. Methods and results Adult, male Sprague-Dawley rats received a systemic infusion of either saline, AngII, insulin (hyperinsulinaemic euglycaemic clamp), or insulin (hyperinsulinaemic euglycaemic clamp) plus AngII. A final, separate group of rats received an acute local infusion of AngII into a single hindleg during systemic insulin (hyperinsulinaemic euglycaemic clamp) infusion. In all animals' systemic metabolic effects, central haemodynamics, femoral artery blood flow, microvascular blood flow, and skeletal muscle glucose uptake (isotopic glucose) were monitored. Systemic AngII infusion increased blood pressure, decreased heart rate, and markedly increased circulating glucose and insulin concentrations. Systemic infusion of AngII during hyperinsulinaemic euglycaemic clamp inhibited insulin-mediated suppression of hepatic glucose output and insulin-stimulated microvascular blood flow in skeletal muscle but did not alter insulin's effects on the femoral artery or muscle glucose uptake. Local AngII infusion did not alter blood pressure, heart rate, or circulating glucose and insulin. However, local AngII inhibited insulin-stimulated microvascular blood flow, and this was accompanied by reduced skeletal muscle glucose uptake. Conclusions Acute infusion of AngII significantly alters basal haemodynamic and metabolic homeostasis in rats. Both local and systemic AngII infusion attenuated insulin's microvascular actions in skeletal muscle, but only local AngII infusion led to reduced insulin-stimulated muscle glucose uptake. While increased local, tissue production of AngII may be a factor that couples microvascular insulin resistance and hypertension, additional studies are needed to determine the molecular mechanisms responsible for these vascular defects. [ABSTRACT FROM AUTHOR]

Long chain acyl-CoA synthetases (ACSLs) convert fatty acids (FA) to fatty acyl-CoAs that are utilized for various cellular processes, including triglyceride synthesis, activation of transcription factors, signal transduction, and providing energy sources via oxidation. Among 5 isotypes (ACSL1, 3, 4, 5, and 6), ACSL1 is the predominant isotype in adipocytes, and it is known to play important roles in adipocyte physiology, including FA uptake, triglyceride (TG) synthesis, thermogenesis, and FA oxidation. However, the roles of ACSL1 in brown adipocyte differentiation is incompletely understood. During the in vitro differentiation of brown adipocytes from stromal vascular cells (SVC), mRNA expression of ACSL1 was drastically increased. Pharmacological inhibition of ACSLs by triacsin C suppressed the differentiation of brown adipocytes. Interestingly, triacsin C inhibited the expression of uncoupled protein 1 (UCP1), which plays the major role in thermogenesis in mitochondria. Thus, we hypothesize that ACSL1 regulates thermogenesis and energy utilization by regulation of brown adipocyte differentiation. To examine the role of ACSL1 in brown adipose tissue (BAT), we generated BAT specific ACSL1 knockout mice by breeding UCP1-Cre with ACSL1 flox/flox mice (ACSL1BATKO). ACSL1 deficiency in BAT reduced the weight gain and glucose intolerance in high fat diet (HFD)-fed mice. ACSL1BATKO mice were severely cold intolerant. Furthermore, ACSL1BATKO mice were resistant to beta 3-agonist (CL-316243)-stimulated weight loss. Fat mass in HFD-fed ACSL1BATKO was lower than HFD-fed wild type mice. These data suggest that ACSL1 in BAT contributes to BAT differentiation, which causes the impairment of FA utilization. However, the mechanisms by which deficiency of ACSL1 in BAT reduces HFD-induced weight gain need to be further investigated. Disclosure: G. Ren: None. J. Kim: None. Funding: National Institutes of Health (R01HL128695R03AG058078) [ABSTRACT FROM AUTHOR]

Consumption of green tea is associated with decreased cardiovascular morbidity and mortality. Tissue and circulating levels of the potent vasoconstrictor ET-1 are elevated in patients with diabetes. We hypothesized that EGCG, a bioactive polyphenol in green tea, may reduce expression of ET-1 in vascular endothelial cells. In bovine aortic endothelial cells (BAEC) in primary culture, acute treatment of cells with EGCG increased phosphorylation of Akt (Ser[sup 473]) and FOXO-1 (Akt phosphorylation site Thr[sup 24]) in a time- and dose-dependent manner (maximal increases at 30 min and 50 µM as determined by immunoblotting with phospho-specific antibodies). Chronic EGCG treatment (8 h, l0 µM) also caused phosphorylation of Akt and FOXO-1 (immunoblotting) with an increase in the amount of FOXO-1 localized to the cytoplasm (immunohistochemistry). Treatment of BAEC with EGCG (8 h, l0 µM) reduced ET-1 mRNA by 60% (quantitative real time PCR, p < 0.001). Moreover, ET-l protein secreted into conditioned media was also reduced 70% (ELISA, p < 0.0001) and intracellular ET-1 protein levels were reduced 65% (ELISA, p <0.005). Treatment of human aortic endothelial cells (HAEC) with EGCG (50 µM, 1 h) reduced ET- 1 promoter activity (assessed by chromatin immunoprecipitation with FOXO-1 antibodies; p < 0.05). We examined ET-l promoter activity by transfecting BAEC with a luciferase reporter containing the human ET-1 promoter. Co-transfection of BAEC with the reporter and human FOXO-1 increased ET-1 promoter activity 2.5-fold when compared with cells co-transfected with reporter and empty vector (p < 0.05). When we truncated or mutated a putative FOXO-1 binding sequence in our reporter (TGTTTAC to TGTcTAC), co-transfection of BAEC with these mutants and either wild-type or constitutively active FOXO-1 did not increase luciferase activity. Finally, results from EMSA assays demonstrate that recombinant FOXO-1 binds to the human ET-1 promoter. Thus, our data suggest that EGCG reduces ET-1 expression and secretion in endothelial cells using a mechanism involving phosphorylation of FOXO-1 and dissociation of FOXO-1 from the ET-1 promoter. We conclude that the ET-1 promoter is a novel target for FOXO-1 and that beneficial effects of green tea consumption on cardiovascular health may be mediated, in part, by actions of EGCG to reduce ET-1 expression and secretion. [ABSTRACT FROM AUTHOR]

Innovative biomaterial strategies are required to improve islet cell retention, viability, and functionality, and thereby obtain clinically successful outcomes from pancreatic islet cell transplantation. To address this need, we have developed a peptide amphiphile-based nanomatrix that incorporates multifunctional bioactive cues and sustained release of nitric oxide. The goal of this study was to evaluate the effect of this peptide amphiphile nanomatrix on the viability and functionality of MIN-6 islet cells. Additionally, this study provides insight into the role of nitric oxide in islet cell biology, given that conventional nitric oxide donors are unable to release nitric oxide in a controlled, sustained manner, leading to ambiguous results. It was hypothesized that controlled nitric oxide release in synergy with multifunctional bioactive cues would promote islet cell viability and functionality. Nitric oxide-releasing peptide amphiphile nanomatrices within the range of 16.25 μmol to 130 μmol were used to analyze MIN-6 cell behavior. Both 32.5 μmol and 65 μmol peptide amphiphiles showed improved MIN-6 functionality in response to glucose over a 7-day time period, and the elevated functionality was correlated with both PDX-1 and insulin gene expression. Our results demonstrate that nitric oxide has a beneficial effect on MIN-6 cells in a concentration-dependent manner.