Parkin Insufficiency Accentuates High-Fat Diet-Induced Cardiac Remodeling and Contractile Dysfunction Through VDAC1-Mediated Mitochondrial Ca2+ Overload.

Mitochondrial Ca2+ overload contributes to obesity cardiomyopathy, yet mechanisms that directly regulate it remain elusive. The authors investigated the role of Parkin on obesity-induced cardiac remodeling and dysfunction in human hearts and a mouse model of 24-week high-fat diet (HFD) feeding. Parkin knockout aggravated HFD-induced cardiac remodeling and dysfunction, mitochondrial Ca2+ overload, and apoptosis without affecting global metabolism, blood pressure, and aortic stiffness. Parkin deficiency unmasked HFD-induced decline in voltage-dependent anion channel (VDAC) type 1 degradation through the ubiquitin-proteasome system but not other VDAC isoforms or mitochondrial Ca2+ uniporter complex. These data suggest that Parkin-mediated proteolysis of VDAC type 1 is a promising therapeutic target for obesity cardiomyopathy.

New evidence for dietary fatty acids in the neutrophil traffic between the bone marrow and the peripheral blood.

Chronic administration of a high-fat diet in mice has been established to influence the generation and trafficking of immune cells such as neutrophils in the bone marrow, the dysregulation of which may contribute to a wide range of diseases. However, no studies have tested the hypothesis that a short-term, high-fat diet could early modulate the neutrophil release from bone marrow at fasting and at postprandial in response to a high-fat meal challenge, and that the predominant type of fatty acids in dietary fats could play a role in both context conditions. Based on these premises, we aimed to establish the effects of different fats [butter, enriched in saturated fatty acids (SFAs), olive oil, enriched in monounsaturated fatty acids (MUFAs), and olive oil supplemented with eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids] on neutrophil navigation from bone marrow to blood in mice. The analysis of cellular models for mechanistic understanding and of postprandial blood samples from healthy volunteers for translational purposes was assessed. The results revealed a powerful effect of dietary SFAs in promotion the neutrophil traffic from bone marrow to blood via the CXCL2-CXCR2 axis. Dietary SFAs, but not MUFAs or EPA and DHA, were also associated with increased neutrophil apoptosis and bone marrow inflammation. Similar dietary fatty-acid-induced postprandial neutrophilia was observed in otherwise healthy humans. Therefore, dietary MUFAs might preserve bone marrow health and proper migration of bone marrow neutrophils early in the course of high-fat diets even after the intake of high-fat meals.

Macrophage-derived thrombospondin 1 promotes obesity-associated non-alcoholic fatty liver disease.

BACKGROUND & AIMS: Thrombospondin 1 (TSP1) is a multifunctional matricellular protein. We previously showed that TSP1 has an important role in obesity-associated metabolic complications, including inflammation, insulin resistance, cardiovascular, and renal disease. However, its contribution to obesity-associated non-alcoholic fatty liver disease/non-alcoholic steatohepatitis (NAFLD or NASH) remains largely unknown; thus, we aimed to determine its role. METHODS: High-fat diet or AMLN (amylin liver NASH) diet-induced obese and insulin-resistant NAFLD/NASH mouse models were utilised, in addition to tissue-specific Tsp1-knockout mice, to determine the contribution of different cellular sources of obesity-induced TSP1 to NAFLD/NASH development. RESULTS: Liver TSP1 levels were increased in experimental obese and insulin-resistant NAFLD/NASH mouse models as well as in obese patients with NASH. Moreover, TSP1 deletion in adipocytes did not protect mice from diet-induced NAFLD/NASH. However, myeloid/macrophage-specific TSP1 deletion protected mice against obesity-associated liver injury, accompanied by reduced liver inflammation and fibrosis. Importantly, this protection was independent of the levels of obesity and hepatic steatosis. Mechanistically, through an autocrine effect, macrophage-derived TSP1 suppressed Smpdl3b expression in liver, which amplified liver proinflammatory signalling (Toll-like receptor 4 signal pathway) and promoted NAFLD progression. CONCLUSIONS: Macrophage-derived TSP1 is a significant contributor to obesity-associated NAFLD/NASH development and progression and could serve as a therapeutic target for this disease. LAY SUMMARY: Obesity-associated non-alcoholic fatty liver disease is a most common chronic liver disease in the Western world and can progress to liver cirrhosis and cancer. No treatment is currently available for this disease. The present study reveals an important factor (macrophage-derived TSP1) that drives macrophage activation and non-alcoholic fatty liver disease development and progression and that could serve as a therapeutic target for non-alcoholic fatty liver disease/steatohepatitis.

Monoacylglycerol lipase inhibitors: modulators for lipid metabolism in cancer malignancy, neurological and metabolic disorders.

Monoacylglycerol lipase (MAGL) is a serine hydrolase that plays a crucial role catalysing the hydrolysis of monoglycerides into glycerol and fatty acids. It links the endocannabinoid and eicosanoid systems together by degradation of the abundant endocannabinoid 2-arachidaoylglycerol into arachidonic acid, the precursor of prostaglandins and other inflammatory mediators. MAGL inhibitors have been considered as important agents in many therapeutic fields, including anti-nociceptive, anxiolytic, anti-inflammatory, and even anti-cancer. Currently, ABX-1431, a first-in-class inhibitor of MAGL, is entering clinical phase 2 studies for neurological disorders and other diseases. This review summarizes the diverse (patho)physiological roles of MAGL and will provide an overview on the development of MAGL inhibitors. Although a large number of MAGL inhibitors have been reported, novel inhibitors are still required, particularly reversible ones.

Impact of obese levels on the hepatic expression of nuclear receptors and drug-metabolizing enzymes in adult and offspring mice.

The prevalence of obesity-associated conditions raises new challenges in clinical medication. Although altered expression of drug-metabolizing enzymes (DMEs) has been shown in obesity, the impacts of obese levels (overweight, obesity, and severe obesity) on the expression of DMEs have not been elucidated. Especially, limited information is available on whether parental obese levels affect ontogenic expression of DMEs in children. Here, a high-fat diet (HFD) and three feeding durations were used to mimic different obese levels in C57BL/6 mice. The hepatic expression of five nuclear receptors (NRs) and nine DMEs was examined. In general, a trend of induced expression of NRs and DMEs (except for Cyp2c29 and 3a11) was observed in HFD groups compared to low-fat diet (LFD) groups. Differential effects of HFD on the hepatic expression of DMEs were found in adult mice at different obese levels. Family-based dietary style of an HFD altered the ontogenic expression of DMEs in the offspring older than 15 days. Furthermore, obese levels of parental mice affected the hepatic expression of DMEs in offspring. Overall, the results indicate that obese levels affected expression of the DMEs in adult individuals and that of their children. Drug dosage might need to be optimized based on the obese levels.

Dietary α-lactalbumin alters energy balance, gut microbiota composition and intestinal nutrient transporter expression in high-fat diet-fed mice.

Recently there has been a considerable rise in the frequency of metabolic diseases, such as obesity, due to changes in lifestyle and resultant imbalances between energy intake and expenditure. Whey proteins are considered as potentially important components of a dietary solution to the obesity problem. However, the roles of individual whey proteins in energy balance remain poorly understood. This study investigated the effects of a high-fat diet (HFD) containing α-lactalbumin (LAB), a specific whey protein, or the non-whey protein casein (CAS), on energy balance, nutrient transporters expression and enteric microbial populations. C57BL/6J mice (n 8) were given an HFD containing either 20 % CAS or LAB as protein sources or a low-fat diet containing CAS for 10 weeks. HFD-LAB-fed mice showed a significant increase in cumulative energy intake (P=0·043), without differences in body weight, energy expenditure, locomotor activity, RER or subcutaneous and epididymal white adipose tissue weight. HFD-LAB intake led to a decrease in the expression of glut2 in the ileum (P=0·05) and in the fatty acid transporter cd36 (P<0·001) in both ileum and jejunum. This suggests a reduction in absorption efficiency within the small intestine in the HFD-LAB group. DNA from faecal samples was used for 16S rRNA-based assessment of intestinal microbiota populations; the genera Lactobacillus, Parabacteroides and Bifidobacterium were present in significantly higher proportions in the HFD-LAB group. These data indicate a possible functional relationship between gut microbiota, intestinal nutrient transporters and energy balance, with no impact on weight gain.

7-Hydroxymatairesinol improves body weight, fat and sugar metabolism in C57BJ/6 mice on a high-fat diet.

7-Hydroxymatairesinol (7-HMR) is a plant lignan abundant in various concentrations in plant foods. The objective of this study was to test HMRLignan™, a purified form of 7-HMR, and the corresponding Picea abies extract (total extract P. abies; TEP) as dietary supplements on a background of a high-fat diet (HFD)-induced metabolic syndrome in mice and in the 3T3-L1 adipogenesis model. Mice, 3 weeks old, were fed a HFD for 60 d. Subgroups were treated with 3 mg/kg body weight 7-HMR (HMRLignan™) or 10 mg/kg body weight TEP by oral administration. 7-HMR and TEP limited the increase in body weight (-11 and -13 %) and fat mass (-11 and -18 %) in the HFD-fed mice. Epididymal adipocytes were 19 and -12 % smaller and the liver was less steatotic (-62 and -65 %). Serum lipids decreased in TEP-treated mice (-11 % cholesterol, -23 % LDL and -15 % TAG) and sugar metabolism was ameliorated by both lignan preparations, as shown by a more than 70 % decrease in insulin secretion and insulin resistance. The expression of several metabolic genes was modulated by the HFD with an effect that was reversed by lignan. In 3T3-L1 cells, the 7-HMR metabolites enterolactone (ENL) and enterodiol (END) showed a 40 % inhibition of cell differentiation accompanied by the inhibited expression of the adipogenic genes PPARγ, C/EBPα and aP2. Furthermore, END and ENL caused a 10 % reduction in TAG uptake in HEPA 1-6 hepatoma cells. In conclusion, 7-HMR and TEP reduce metabolic imbalances typical of the metabolic syndrome and obesity in male mice, whereas their metabolites inhibit adipogenesis and lipid uptake in vitro.

Dietary supplementation with blueberry partially restores T-cell-mediated function in high-fat-diet-induced obese mice.

Blueberry, rich in antioxidant and anti-inflammatory phytochemicals, has been demonstrated to lower inflammatory status in adipose induced by high-fat diet (HFD) and obesity. The effect of blueberry on systemic immune functions has not been examined. C57BL/6 mice were randomised to one of three diets - low-fat diet (LFD), HFD and HFD plus 4 % (w/w) blueberry (HFD+B) - for 8 or 12 weeks. Ex vivo T-cell mitogens (concanavalin A (Con A); phytohaemagglutinin), T-cell antibody (anti-CD3; anti-CD3/CD28)-stimulated T-cell proliferation and cytokine production were assessed. After 8 weeks, both HFD groups weighed more (>4 g) than the LFD group; after 12 weeks, HFD+B-fed mice weighed more (>6 g) and had 41 % more adipose tissue than HFD-fed mice (P<0·05). After 12 weeks, T-cell proliferation was less in both HFD groups, compared with the LFD group. HFD-associated decrements in T-cell proliferation were partially (10-50 %) prevented by blueberry supplementation. At 12 weeks, splenocytes from HFD mice, but not from HFD+B mice, produced 51 % less IL-4 (CD3/CD28) and 57 % less interferon-γ (Con A) compared with splenocytes from LFD mice (P<0·05). In response to lipopolysaccharide challenge, splenocytes from both HFD groups produced 24-30 % less IL-6 and 27-33 % less TNF-α compared with splenocytes from LFD mice (P<0·05), indicating impaired acute innate immune response. By demonstrating deleterious impacts of HFD feeding on T-cell proliferation and splenocyte immune responses, our results provide insights into how HFD/obesity can disrupt systemic immune function. The protective effects of blueberry suggest that dietary blueberry can buttress T-cell and systemic immune function against HFD-obesity-associated insults.

Amelioration of Metabolic Syndrome-Associated Cognitive Impairments in Mice via a Reduction in Dietary Fat Content or Infusion of Non-Diabetic Plasma.

Obesity, metabolic syndrome (MetS) and type 2 diabetes (T2D) are associated with decreased cognitive function. While weight loss and T2D remission result in improvements in metabolism and vascular function, it is less clear if these benefits extend to cognitive performance. Here, we highlight the malleable nature of MetS-associated cognitive dysfunction using a mouse model of high fat diet (HFD)-induced MetS. While learning and memory was generally unaffected in mice with type 1 diabetes (T1D), multiple cognitive impairments were associated with MetS, including deficits in novel object recognition, cued fear memory, and spatial learning and memory. However, a brief reduction in dietary fat content in chronic HFD-fed mice led to a complete rescue of cognitive function. Cerebral blood volume (CBV), a measure of vascular perfusion, was decreased during MetS, was associated with long term memory, and recovered following the intervention. Finally, repeated infusion of plasma collected from age-matched, low fat diet-fed mice improved memory in HFD mice, and was associated with a distinct metabolic profile. Thus, the cognitive dysfunction accompanying MetS appears to be amenable to treatment, related to cerebrovascular function, and mitigated by systemic factors.

Black elderberry extract attenuates inflammation and metabolic dysfunction in diet-induced obese mice.

Dietary anthocyanins have been shown to reduce inflammation in animal models and may ameliorate obesity-related complications. Black elderberry is one of the richest sources of anthocyanins. We investigated the metabolic effects of anthocyanin-rich black elderberry extract (BEE) in a diet-induced obese C57BL/6J mouse model. Mice were fed either a low-fat diet (n 8), high-fat lard-based diet (HFD; n 16), HFD+0·25 % (w/w) BEE (0·25 %-BEE; n 16) or HFD+1·25 % BEE (1·25 %-BEE; n 16) for 16 weeks. The 0·25 % BEE (0·034 % anthocyanin, w/w) and 1·25 % BEE (0·17 % anthocyanin, w/w) diets corresponded to estimated anthocyanin doses of 20-40 mg and 100-200 mg per kg of body weight, respectively. After 16 weeks, both BEE groups had significantly lower liver weights, serum TAG, homoeostasis model assessment and serum monocyte chemoattractant protein-1 compared with HFD. The 0·25 %-BEE also had lower serum insulin and TNFα compared with HFD. Hepatic fatty acid synthase mRNA was lower in both BEE groups, whereas PPARγ2 mRNA and liver cholesterol were lower in 1·25 %-BEE, suggesting decreased hepatic lipid synthesis. Higher adipose PPARγ mRNA, transforming growth factor ß mRNA and adipose tissue histology suggested a pro-fibrogenic phenotype that was less inflammatory in 1·25 %-BEE. Skeletal muscle mRNA expression of the myokine IL-6 was higher in 0·25 %-BEE relative to HFD. These results suggest that BEE may have improved some metabolic disturbances present in this mouse model of obesity by lowering serum TAG, inflammatory markers and insulin resistance.

Regulatory role of CD40 in obesity-induced insulin resistance.

Excessive nutrient intake in obesity triggers the accumulation of various types of immune cells in adipose tissue, particularly visceral adipose tissue (VAT). This can result in chronic inflammation which disrupts insulin effects on adipocytes and muscle cells and culminates in development of insulin resistance. The interplay between immune cells and adipose tissue is a key event for the development of insulin resistance that precedes type 2 diabetes. CD40, a well-documented costimulatory receptor, is required for efficient systemic adaptive immune responses. However, we and other groups recently showed that CD40 unexpectedly ameliorates inflammation in VAT and accordingly attenuates obesity-induced insulin resistance. Specifically, although CD40 is typically considered to play its principal immune roles on B lymphocytes and myeloid cells, we found that CD40(+)CD8(+) T lymphocytes were major contributors to the protective effect. This unexpected inhibitory role of CD40 on CD8(+) T cell activation in VAT may reflect unique features of this microenvironment. Additional knowledge gaps include whether CD40 also plays roles in mucosal immunity that control the homeostasis of gut microbiota, and human metabolic diseases. Potential therapeutic approaches, including stimulating CD40 signaling and/or manipulating specific CD40 signaling pathways in the VAT microenvironment, may open new avenues for treatment of obesity-induced insulin resistance, and prevention of type 2 diabetes.

Enhanced insulin signaling in density-enhanced phosphatase-1 (DEP-1) knockout mice.

OBJECTIVE: Insulin resistance can be triggered by enhanced dephosphorylation of the insulin receptor or downstream components in the insulin signaling cascade through protein tyrosine phosphatases (PTPs). Downregulating density-enhanced phosphatase-1 (DEP-1) resulted in an improved metabolic status in previous analyses. This phenotype was primarily caused by hepatic DEP-1 reduction. METHODS: Here we further elucidated the role of DEP-1 in glucose homeostasis by employing a conventional knockout model to explore the specific contribution of DEP-1 in metabolic tissues. Ptprj (-/-) (DEP-1 deficient) and wild-type C57BL/6 mice were fed a low-fat or high-fat diet. Metabolic phenotyping was combined with analyses of phosphorylation patterns of insulin signaling components. Additionally, experiments with skeletal muscle cells and muscle tissue were performed to assess the role of DEP-1 for glucose uptake. RESULTS: High-fat diet fed-Ptprj (-/-) mice displayed enhanced insulin sensitivity and improved glucose tolerance. Furthermore, leptin levels and blood pressure were reduced in Ptprj (-/-) mice. DEP-1 deficiency resulted in increased phosphorylation of components of the insulin signaling cascade in liver, skeletal muscle and adipose tissue after insulin challenge. The beneficial effect on glucose homeostasis in vivo was corroborated by increased glucose uptake in skeletal muscle cells in which DEP-1 was downregulated, and in skeletal muscle of Ptprj (-/-) mice. CONCLUSION: Together, these data establish DEP-1 as novel negative regulator of insulin signaling.

Opening of the mitochondrial permeability transition pore links mitochondrial dysfunction to insulin resistance in skeletal muscle.

Insulin resistance is associated with mitochondrial dysfunction, but the mechanism by which mitochondria inhibit insulin-stimulated glucose uptake into the cytoplasm is unclear. The mitochondrial permeability transition pore (mPTP) is a protein complex that facilitates the exchange of molecules between the mitochondrial matrix and cytoplasm, and opening of the mPTP occurs in response to physiological stressors that are associated with insulin resistance. In this study, we investigated whether mPTP opening provides a link between mitochondrial dysfunction and insulin resistance by inhibiting the mPTP gatekeeper protein cyclophilin D (CypD) in vivo and in vitro. Mice lacking CypD were protected from high fat diet-induced glucose intolerance due to increased glucose uptake in skeletal muscle. The mitochondria in CypD knockout muscle were resistant to diet-induced swelling and had improved calcium retention capacity compared to controls; however, no changes were observed in muscle oxidative damage, insulin signaling, lipotoxic lipid accumulation or mitochondrial bioenergetics. In vitro, we tested 4 models of insulin resistance that are linked to mitochondrial dysfunction in cultured skeletal muscle cells including antimycin A, C2-ceramide, ferutinin, and palmitate. In all models, we observed that pharmacological inhibition of mPTP opening with the CypD inhibitor cyclosporin A was sufficient to prevent insulin resistance at the level of insulin-stimulated GLUT4 translocation to the plasma membrane. The protective effects of mPTP inhibition on insulin sensitivity were associated with improved mitochondrial calcium retention capacity but did not involve changes in insulin signaling both in vitro and in vivo. In sum, these data place the mPTP at a critical intersection between alterations in mitochondrial function and insulin resistance in skeletal muscle.

Maternal high-fat diet consumption impairs exercise performance in offspring.

The aim of the present study was to scrutinise the influence of maternal high-fat diet (mHFD) consumption during gestation and lactation on exercise performance and energy metabolism in male mouse offspring. Female C3H/HeJ mice were fed either a semi-synthetic high-fat diet (HFD; 40 % energy from fat) or a low-fat diet (LFD; 10 % energy from fat) throughout gestation and lactation. After weaning, male offspring of both groups received the LFD. At the age of 7·5 weeks half of the maternal LFD (n 20) and the mHFD (n 21) groups were given access to a running wheel for 28 d as a voluntary exercise training opportunity. We show that mHFD consumption led to a significantly reduced exercise performance (P < 0·05) and training efficiency (P < 0·05) in male offspring. There were no effects of maternal diet on offspring body weight. Lipid and glucose metabolism was disturbed in mHFD offspring, with altered regulation of cluster of differentiation 36 (CD36) (P < 0·001), fatty acid synthase (P < 0·05) and GLUT1 (P < 0·05) gene expression in skeletal muscle. In conclusion, maternal consumption of a HFD is linked to decreased exercise performance and training efficiency in the offspring. We speculate that this may be due to insufficient muscle energy supply during prolonged exercise training. Further, this compromised exercise performance might increase the risk of obesity development in adult life.