Jeremy E. Davis

Tlr-4 Deficiency Selectively Protects Against Obesity Induced by Diets High in Saturated Fat

Toll‐like receptor‐4 (Tlr‐4), a key pattern recognition receptor involved in innate immune response, is activated by saturated fatty acids (SFAs). To investigate the involvement of this receptor in obesity caused by consumption of diets high in fat, we utilized male Tlr‐4‐deficient 10ScN mice and 10J controls. Mice were fed either low fat (low‐fat control (LFC)), high unsaturated fat (high‐fat control (HFC)), or high saturated fat + palmitate (HFP) diets ad libitum for 16 weeks. Relative to the LFC diet, the HFC diet resulted in greater epididymal fat pad weights and adipocyte hypertrophy in both Tlr‐4‐deficient and normal mice. However, the 10ScN mice were completely protected against the obesigenic effects of the HFP diet. Moreover, macrophage infiltration and monocyte chemotactic protein‐1 (MCP‐1) transcript abundance were lower in adipose tissue of 10ScN mice fed the HFP diet, and the hyperinsulinemic response was negated. Tlr‐4‐deficient mice also had markedly lower circulating concentrations of MCP‐1 and much less nuclear factor‐κB (NFκB) protein in nuclear extracts prepared from adipose tissue, irrespective of diet. In contrast, Tlr‐4 deficiency did not attenuate the induction of tumor necrosis factor‐α (TNF‐α) or interleukin‐6 (IL‐6) expression in adipose tissue. These data indicate that Tlr‐4 deficiency selectively protects against the obesigenic effects of SFA and alters obesity‐related inflammatory responses in adipose tissue.

Absence of Tlr2 protects against high-fat diet-induced inflammation and results in greater insulin-stimulated glucose transport in cultured adipocytes

We have previously shown that toll-like receptor-4 (Tlr4) is involved in obesity-induced inflammation in adipose tissue (AT). However, less is known about the role of Tlr2 in this process. To determine the involvement of this receptor in obesity-induced inflammation, we utilized male Tlr2(-/-) mice that were backcrossed onto a mouse model of diet-induced obesity (DIO). Mice were fed either low-fat control (LFD) or high-fat diet (HFD) ad libitum for 16 weeks. Despite negligible differences in body weight or energy intake, Tlr2(-/-) mice were protected from HFD-induced adiposity as was evident by reduced epididymal fat pad weight and carcass lipid content. Corresponding with these effects was a blunted accumulation of F4/80-positive macrophages in AT of Tlr2(-/-) mice. Furthermore, transcript abundance of proinflammatory mediators, including monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-α (TNFα) and nitric oxide synthase-2 (NOS2) in AT of Tlr2(-/-) mice, was lower or less responsive to DIO. There were no significant differences in serum markers of insulin sensitivity (data not shown). However, adipocytes derived from stromal vascular cells (SVCs) isolated from AT of Tlr2(-/-) mice had considerably greater basal and insulin-stimulated glucose uptake as compared with those obtained from Tlr2(+/+) mice. Furthermore, the absence of Tlr2(-/-) precluded the induction of insulin resistance by zymosan A (ZymA) but not by palmitate. These data indicate that Tlr2 may be directly involved in HFD-induced inflammation and may also regulate basal and insulin-stimulated glucose uptake in adipocytes.

The c-Jun N-terminal kinase mediates the induction of oxidative stress and insulin resistance by palmitate and toll-like receptor 2 and 4 ligands in 3T3-L1 adipocytes.

Saturated fatty acids (SFAs) are known to induce inflammation and insulin resistance in adipocytes through toll-like receptor-4 (Tlr4) signaling, but the mechanisms are not well delineated. Furthermore, the potential roles of Tlr2 and the c-Jun N-terminal kinase (JNK) in inflammation in adipocytes have not been investigated. We demonstrated that palmitate, lipopolysaccharide (LPS), and the toll-like receptor-2 (Tlr2) agonist, zymosan A (ZymA), induced insulin resistance in a time- and dose-dependent manner in 3T3-L1 adipocytes. Corresponding with the reduction of insulin sensitivity was an increased expression of IL-6, as well as activation of the proinflammatory transcription factors, nuclear factor kappa B, and activator protein-1. Reactive oxygen species (ROS) accumulation was also observed in palmitate and Tlr agonist treated adipocytes. The JNK inhibitor, SP600125, attenuated insulin resistance mediated by SFA and Tlr agonists, which corresponded with a diminished proinflammatory response and reduced ROS accumulation. Collectively, these results demonstrated Tlr2 involvement in adipocyte inflammation and therefore implicated the receptor as a potential target for SFA. Moreover, activation of JNK also appeared to be essential to Tlr2-, as well as Tlr4-induced insulin resistance and oxidative stress.

Soy Protein and Isoflavones Influence Adiposity and Development of Metabolic Syndrome in the Obese Male ZDF Rat

Background/Aims: Previously, we demonstrated that soy protein ameliorates the diabetic phenotype in several rodent models of obesity and metabolic syndrome (MS). This study was designed to further elucidate factors related to adiposity, glycemic control, and renal function in male Zucker Diabetic Fatty (ZDF/Leprfa) rats. Methods: Animals were randomly assigned to one of four diets: control, casein (C); low isoflavone (LIS) soy protein; high isoflavone (HIS) soy protein, or casein + rosiglitazone (CR) for 11 weeks. At sacrifice, physiological, biochemical, and molecular parameters were determined. Results: Body weight and total adiposity were higher in LIS and CR diet groups despite lower food intake. Additionally, these animals exhibited differential regulation of adipose-specific proteins (PPAR-γ and GLUT4) and enzyme activity (FAS and GPDH). HIS-fed animals had reduced total and liver adiposity. Glycemic control was prolonged in both soy-based and rosiglitazone (RGZ) groups. Renal dysfunction was significantly reduced in soy-fed and RGZ-treated rodents as demonstrated by lower levels of proteinuria and dilated tubules with proteinaceous casts. Conclusion: Collectively, these data provide evidence that soy protein with low or high isoflavone content may have therapeutic significance in reducing severity of diabetes, MS, and renal disease as demonstrated in this preclinical model.

Stearidonic Acid: Is There a Role in the Prevention and Management of Type 2 Diabetes Mellitus?

Obesity and its related comorbidities are major public health concerns in the United States with over two-thirds of adults and one-third of children classified as overweight or obese. The prevalence of type 2 diabetes mellitus (T2DM) has similarly risen to an estimated 25.8 million, which accounts for a staggering

Age-Related Differences in Response to High-Fat Feeding on Adipose Tissue and Metabolic Profile in ZDSD Rats.

174 billion in annual healthcare costs. Identification of dietary interventions that protect against the development of T2DM would markedly reduce the medical and economic consequences of the disease. Hence, we review current evidence supporting a role of (n-3) PUFA in T2DM and explore potential therapeutic implications of stearidonic acid (SDA). The low consumption of fish in the US along with a reduced efficiency to interconvert most plant (n-3) PUFA highlights a need to find alternative sources of (n-3) PUFA. The efficient biological conversion of SDA to EPA underscores the potential implications of SDA as a source of (n-3) PUFA. The full therapeutic efficacy of SDA remains to be further determined. However, recent data have suggested a protective role of SDA consumption on markers of dyslipidemia and inflammation. The AHA recommends that healthy individuals consume oily fish at least twice per week and individuals with a history of cardiovascular disease consume 1 g of EPA+DHA/d. These goals will likely not be met by the typical American diet. Therefore, SDA may represent a sustainable alternative to marine-based (n-3) PUFA and may have novel therapeutic efficacy regarding the development of T2DM.

Fat Accumulation in the Liver of Obese Rats is Alleviated by Soy Protein Isolate through β-catenin signaling

The recruitment of new fat cells through adipogenesis may prevent the development of obesity-related comorbidities. However, adipogenic capacity is markedly reduced in mature adults. This study examined how initiation of high-fat feeding at different phases of adulthood modified adipose tissue (AT) morphology and obesity phenotype in obese and diabetic Zucker Diabetic Sprague Dawley (ZDSD) rats. For this, rodents were provided high-fat diet (HFD) beginning at 63, 84, or 112 d after parturition until termination (n = 6). At termination, ZDSD rats fed HFD beginning at 63 d after parturition (early adulthood) exhibited greater body fat and lower lean mass without significant changes to energy intake or body weight. Moreover, early high fat feeding increased adipocyte size and number, whereas these effects were absent at 84 or 112 d after parturition. At 126 d after parturition, there were no detectable transcript differences in PPARγ or C/EBPα. However, rodents provided HFD in early adolescence exhibited lower expression of canonical Wnt signaling intermediates. Corresponding with these changes was a marked reduction in AT-specific inflammation, as well as overall improvement in systemic glucose, lipid, and inflammatory homeostasis. Taken together, these data indicate that dietary regulation of adipocyte recruitment in adolescence may represent a major determinant of obesity phenotype.

Soy protein isolate modified metabolic phenotype and hepatic Wnt signaling in obese Zucker rats.

To investigate the effects of soy protein isolate (SPI) on Wnt/β‐catenin signaling in the liver of obese rats, as well as the roles of this pathway in regulating the hepatic fat accumulation.

Interleukin-6 and Delayed Onset Muscle Soreness Do Not Vary during the Menstrual Cycle

We have previously shown that soy protein isolate (SPI) with intact phytoestrogen content prevented obesity-related dysfunction. Recent data have suggested that soy ingredients may act as regulators of adipogenic programming in adipose tissue (AT) and liver. Thus, the current study was undertaken to determine whether the beneficial effects of SPI are linked to changes in adipogenic regulators, such as the Wnt signaling cascade. For this, lean (LZR) and obese Zucker (OZR) rats were provided isocaloric and isonitrogenous diets containing SPI, sodium caseinate, or dairy whey protein for 17 weeks. At termination, SPI increased body weight and total adiposity in rodents, which corresponded with an increase in both adipocyte size and number. Furthermore, markers of inflammation, hypercholesterolemia, and hepatic steatosis were all reduced in OZR rats provided SPI. Transcript abundance of several canonical and noncanonical Wnt signaling intermediates in liver, but not AT, was distinctly modified by SPI. Collectively, these data confirm the protective SPI attenuated obesity-related metabolic dysfunction conceivably through regulation of adipogenic programming, as evident by changes in AT morphology and hepatic Wnt signaling. Collectively, this study confirmed the potential utilization of soy protein and its bioactive ingredients for prevention and treatment of obesity-related comorbidities.

Effect of stearidonic acid-enriched soybean oil on fatty acid profile and metabolic parameters in lean and obese Zucker rats.

The purpose of this study was to determine if a difference in interleukin-6 (IL-6) and delayed onset muscles soreness (DOMS) exists in two different phases of the menstrual cycle. Nine runners performed one 75-min high-intensity interval running session during the early follicular (EF) phase and once during the midluteal (ML) phase of the menstrual cycle. Estrogen and progesterone levels were significantly reduced in the EF phase when compared to the ML phase. IL-6 levels increased from pre- to postexercise in the EF and ML phases (p < .001). There was no relationship between the IL-6 level and DOMS. The results suggest that menstruating female runners need not vary training throughout the month to reduce DOMS.