Paternal Diet-Induced Obesity Retards Early Mouse Embryo Development,Mitochondrial Activity and Pregnancy Health

Worldwide, 48% of adult males are overweight or obese. An association between infertility and excessive body weight is now accepted, although focus remains primarily on females. It has been shown that parental obesity results in compromised embryo development, disproportionate changes in embryo metabolism and reduced blastocyst cell number. The aim of this study was to determine whether paternal obesity has negative effects on the resultant embryo. Specifically, using in vitro fertilisation (IVF), we wanted to isolate the functional effects of obesity on sperm by examining the subsequent embryo both pre- and post-implantation. Epididymal sperm was collected from age matched normal and obese C57BL/6 mice and cryopreserved for subsequent IVF with oocytes collected from Swiss females (normal diet/weight). Obesity was induced in male mice by feeding a high fat diet of 22% fat for 10 weeks. Resultant embryos were cultured individually and development monitored using time-lapse microscopy. Paternal obesity resulted in a significant delay in preimplantation embryo development as early as syngamy (P<0.05). Metabolic parameters were measured across key developmental stages, demonstrating significant reduction in mitochondrial membrane potential (P<0.01). Blastocysts were stained to determine trophectoderm (TE) and inner cell mass (ICM) cell numbers, revealing significant differences in the ratio of cell allocation to TE and ICM lineages (P<0.01). Functional studies examining blastocyst attachment, growth and implantation demonstrated that blastocysts derived from sperm of obese males displayed significantly reduced outgrowth on fibronectin in vitro (P<0.05) and retarded fetal development in vivo following embryo transfer (P<0.05). Taken together, these data clearly demonstrate that paternal obesity has significant negative effects on the embryo at a variety of key early developmental stages, resulting in delayed development, reduced placental size and smaller offspring.     

Antiobesity Activity of Vigna nakashimae Extract in High-Fat Diet-Induced Obesity

The inhibitory effect of hop bract polyphenols (HBP) on cariogenic streptococci was investigated. It was found that the high molecular weight polyphenol (estimated about 36,000–40,000) inhibited the cellular adherence of Streptococcus mutans MT8148 (serotype C) and Streptococcus sobrinus ATCC 33478 (serotype g) at much smaller concentrations than the polyphenols extracted from oolong tea or green tea leaves. Furthermore, HBP also inhibited the action of glucosyltransferase, which was involved in the water-insoluble glucan synthesis, but did not suppress the growth and the acid production of the bacteria. These results suggest that HBP would be a candidate to act against dental caries caused by Mutans Streptococci.     

Maternal Obesity during the Preconception and Early Life Periods Alters Pancreatic Development in Early and Adult Life in Male Mouse Offspring

Maternal obesity induced by a high fat (HF) diet may program susceptibility in offspring, altering pancreatic development and causing later development of chronic degenerative diseases, such as obesity and diabetes. Female mice were fed standard chow (SC) or an HF diet for 8 weeks prior to mating and during the gestational and lactational periods. The male offspring were assessed at birth, at 10 days, and at 3 months of age. The body mass (BM) gain was 50% greater before pregnancy and 80% greater during pregnancy in HF dams than SC dams. Dams fed an HF diet showed higher oral glucose tolerance test (OGTT), blood pressure, serum corticosterone, and insulin levels than dams fed SC. At 10 days of age and at 3 mo old the HF offspring showed greater BM and higher blood glucose levels than the SC offspring. The mean diameter of the islets had increased by 37% in the SC offspring and by 155% in the HF offspring at 10 days of age. The islet mass ratio (IM/PM) was 88% greater in the HF offspring at 10 days of age, and 107% greater at 3 mo of age, compared to the values obtained at birth. The HF offspring had a beta cell mass (BCM)/PM ratio 54% lower than SC offspring at birth. However, HF offspring displayed a 146% increase in the BCM/PM ratio at 10 days of age, and 112% increase at 3 months of age than values at birth. A 3 mo of age, the HF offspring showed a greater OGTT and higher levels of than SC offspring. In conclusion, a maternal HF diet consumed during the preconceptional period and throughout the gestational and lactational periods in mice results in dramatic alterations in the pancreata of the offspring.     

Sympathetic Activity,Age, Sucrose Preference,and Diet-Induced Obesity

Only half the adult male Sprague-Dawley rats which are placed on a diet relatively high in calories, fat, and sucrose (HE diet) develop diet-induced obesity (DIO). The rest are diet-resistant (DR). Some chowfed rats prone to develop DIO on an HE diet have greater initial food intake of this diet and all have greater glucose-induced plasma norepinephrine (NE) increases than DR-prone rats. Here we looked for a relationship of sucrose preference or 24-hour urinary catecholamine excretion as possible phenotypic markers of the DIO- and DR-prone states before HE diet exposure as a function of age. When begun on an HE diet at 3 months of age, DIO-prone rats gained 30% more weight over 3 months than DR-prone rats and had 35% heavier retroperitoneal fat pads. While still on chow, sucrose preferences were similar, but 24 hour urine NE levels were 29% higher in DIO-than in DR-prone rats. The slope of the curve of urine NE versus body weight gain after 3 months on HE diet was 4-fold greater in DIO- thaain DR-prone rats. After 3 months on the HE diet, there was no statistical relationship between 24-hour urine NE and body weight or prior body weight gain in DIO or DR rats. Six-month-old DIO-prone rats had 126% and 128% more urine NE and gained 112% and 232% more weight after 3 months on HE diet than DR-prone and chowfed rats, respectively. Only DIO-prone rats showed a correlation (r=0.879; p=O.OS) between urine NE levels and subsequent weight gain on HE diet. Thus, 3- or 6- month-old DIO- and DR-prone rats can be identified by their 24-hour basal urine NE levels but not sucrose preference prior to HE diet exposure. While this may suggest higher basal sympathetic activity in DIO-prone rats, other explanations are possible. (OBESITY RESEARCH 1993;1:281–287)     

Pharmacological Blockade of Cannabinoid CB1 Receptors in Diet-Induced Obesity Regulates Mitochondrial Dihydrolipoamide Dehydrogenase in Muscle

Cannabinoid CB₁ receptors peripherally modulate energy metabolism. Here, we investigated the role of CB₁ receptors in the expression of glucose/pyruvate/tricarboxylic acid (TCA) metabolism in rat abdominal muscle. Dihydrolipoamide dehydrogenase (DLD), a flavoprotein component (E3) of α-ketoacid dehydrogenase complexes with diaphorase activity in mitochondria, was specifically analyzed. After assessing the effectiveness of the CB₁ receptor antagonist AM251 (3 mg kg^-1, 14 days) on food intake and body weight, we could identified seven key enzymes from either glycolytic pathway or TCA cycle—regulated by both diet and CB₁ receptor activity—through comprehensive proteomic approaches involving two-dimensional electrophoresis and MALDI-TOF/LC-ESI trap mass spectrometry. These enzymes were glucose 6-phosphate isomerase (GPI), triosephosphate isomerase (TPI), enolase (Eno3), lactate dehydrogenase (LDHa), glyoxalase-1 (Glo1) and the mitochondrial DLD, whose expressions were modified by AM251 in hypercaloric diet-induced obesity. Specifically, AM251 blocked high-carbohydrate diet (HCD)-induced expression of GPI, TPI, Eno3 and LDHa, suggesting a down-regulation of glucose/pyruvate/lactate pathways under glucose availability. AM251 reversed the HCD-inhibited expression of Glo1 and DLD in the muscle, and the DLD and CB₁ receptor expression in the mitochondrial fraction. Interestingly, we identified the presence of CB₁ receptors at the membrane of striate muscle mitochondria. DLD over-expression was confirmed in muscle of CB ₁ ^-/- mice. AM251 increased the pyruvate dehydrogenase and glutathione reductase activity in C₂C₁₂ myotubes, and the diaphorase/oxidative activity in the mitochondria fraction. These results indicated an up-regulation of methylglyoxal and TCA cycle activity. Findings suggest that CB₁ receptors in muscle modulate glucose/pyruvate/lactate pathways and mitochondrial oxidative activity by targeting DLD.     

Effects of Murine Norovirus Infection on a Mouse Model of Diet-Induced Obesity and Insulin Resistance

Murine norovirus (MNV) is prevalent in SPF mouse facilities in the United States, and we currently lack sufficient data to determine whether it should be eliminated. It is generally accepted that the virus does not cause clinical symptoms in immunocompetent mice. However, we previously reported that MNV infection alters the phenotype of a mouse model of bacteria-induced inflammatory bowel disease in part through its effects on dendritic cells. The tropism of MNV toward macrophages and dendritic cells makes MNV a potential intercurrent variable in murine models of macrophage-driven inflammatory diseases, such as obesity, insulin resistance, and atherosclerosis. Therefore, we determined whether MNV infection altered obesity and insulin resistance phenotypes in C57BL/6 mice, a widely used model of diet-induced obesity. We found that MNV did not alter weight gain, food intake, and glucose metabolism in this model, but it did induce subtle changes in lymphoid tissue. Further studies using other models of metabolic diseases are needed to provide additional information on the potential role this ‘subclinical’ virus might have on disease progression in mouse models of inflammatory diseases.Abbreviations: HFD, high-fat diet; IPGTT, intraperitoneal glucose tolerance test; IPITT, intraperitoneal insulin tolerance test; MLN, mesenteric lymph node; MNV, murine norovirusMurine norovirus (MNV) is endemic in many SPF mouse colonies across North America,⁵ creating considerable potential for this virus to interfere with mouse models of human diseases. In addition, the presence of MNV in some mouse colonies and not in others may help explain phenotypic variability in mouse models across institutions. This virus is related to the human Norwalk virus that causes gastrointestinal inflammation in humans. Although MNV does not cause any overt illness in immunocompetent mice, significant inflammation and mortality can be induced in mice with abnormal innate immunity.⁷ Previously, we investigated the influence of MNV on the development of bacteria-induced inflammatory bowel disease in FVB.129P2-PAbcb1atm1Bor (Mdr1a^−/−) mice.⁸ We found that infection with MNV accelerated the progression of inflammatory bowel disease in this mouse model when mice were coinfected with Helicobacter bilis. In addition, infection with MNV alone altered the immune response, probably through changes in dendritic cells.⁸ These findings suggest that MNV may induce subtle changes in immune responses even in immunocompetent mice, given that MNV is known to preferentially infect macrophages and dendritic cells.²²Obesity has been defined as a disease of chronic inflammation, and in recent years, the prominent role that macrophages play in this process has been recognized.^9,10,21,24 Obesity is a risk factor for various chronic diseases that share inflammation as a critical component of the disease process, such as metabolic syndrome, diabetes, and atherosclerosis.³ Because MNV has tropism for macrophages, we wished to determine whether MNV infection influences the development of obesity and insulin resistance in a widely used animal model of diet-induced obesity. C57BL/6 mice are the most frequently used ‘wild-type’ strain and are prone to develop insulin resistance as obesity develops during high-fat feeding.¹ We hypothesized that MNV may accelerate inflammation by stimulating macrophage accumulation in adipose tissue, resulting in a more severe obesity or insulin resistance phenotype when mice are fed a high-fat diet.     

Perinatal Protein Malnutrition Affects Mitochondrial Function in Adult and Results in a Resistance to High Fat Diet-Induced Obesity

Epidemiological findings indicate that transient environmental influences during perinatal life, especially nutrition, may have deleterious heritable health effects lasting for the entire life. Indeed, the fetal organism develops specific adaptations that permanently change its physiology/metabolism and that persist even in the absence of the stimulus that initiated them. This process is termed “nutritional programming”. We previously demonstrated that mothers fed a Low-Protein-Diet (LPD) during gestation and lactation give birth to F1-LPD animals presenting metabolic consequences that are different from those observed when the nutritional stress is applied during gestation only. Compared to control mice, adult F1-LPD animals have a lower body weight and exhibit a higher food intake suggesting that maternal protein under-nutrition during gestation and lactation affects the energy metabolism of F1-LPD offspring. In this study, we investigated the origin of this apparent energy wasting process in F1-LPD and demonstrated that minimal energy expenditure is increased, due to both an increased mitochondrial function in skeletal muscle and an increased mitochondrial density in White Adipose Tissue. Importantly, F1-LPD mice are protected against high-fat-diet-induced obesity. Clearly, different paradigms of exposure to malnutrition may be associated with differences in energy expenditure, food intake, weight and different susceptibilities to various symptoms associated with metabolic syndrome. Taken together these results demonstrate that intra-uterine environment is a major contributor to the future of individuals and disturbance at a critical period of development may compromise their health. Consequently, understanding the molecular mechanisms may give access to useful knowledge regarding the onset of metabolic diseases.     

Enhanced Lipid Oxidation and Maintenance of Muscle Insulin Sensitivity Despite Glucose Intolerance in a Diet-Induced Obesity Mouse Model

Background

Diet-induced obesity is a rising health concern which can lead to the development of glucose intolerance and muscle insulin resistance and, ultimately, type II diabetes mellitus. This research investigates the associations between glucose intolerance or muscle insulin resistance and tissue specific changes during the progression of diet-induced obesity.

Methodology

C57BL/6J mice were fed a normal or high-fat diet (HFD; 60% kcal fat) for 3 or 8 weeks. Disease progression was monitored by measurements of body/tissue mass changes, glucose and insulin tolerance tests, and ex vivo glucose uptake in intact muscles. Lipid metabolism was analyzed using metabolic chambers and ex vivo palmitate assays in intact muscles. Skeletal muscle, liver and adipose tissues were analyzed for changes in inflammatory gene expression. Plasma was analyzed for insulin levels and inflammatory proteins. Histological techniques were used on muscle and liver cryosections to assess metabolic and morphological changes.

Principal Findings/Conclusions

A rapid shift in whole body metabolism towards lipids was observed with HFD. Following 3 weeks of HFD, elevated total lipid oxidation and an oxidative fiber type shift had occurred in the skeletal muscle, which we propose was responsible for delaying intramyocellular lipid accumulation and maintaining muscle’s insulin sensitivity. Glucose intolerance was present after three weeks of HFD and was associated with an enlarged adipose tissue depot, adipose tissue inflammation and excess hepatic lipids, but not hepatic inflammation. Furthermore, HFD did not significantly increase systemic or muscle inflammation after 3 or 8 weeks of HFD suggesting that early diet-induced obesity does not cause inflammation throughout the whole body. Overall these findings indicate skeletal muscle did not contribute to the development of HFD-induced impairments in whole-body glucose tolerance following 3 weeks of HFD.     

Transcriptome and DNA Methylome Analysis in a Mouse Model of Diet-Induced Obesity Predicts Increased Risk of Colorectal Cancer

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Asymmetric Reprogramming Capacity of Parental Pronuclei in Mouse Zygotes

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Antiobesity Effects of Bifidobacterium breve Strain B-3 Supplementation in a Mouse Model with High-Fat Diet-Induced Obesity

The aim of the present study was to evaluate the anti-obesity activity of a probiotic bifidobacterial strain in a mouse model with obesity induced by a high-fat diet. The mice were fed a high-fat diet supplemented with Bifidobacterium breve B-3 at 10⁸ or 10⁹ CFU/d for 8 weeks. B. breve B-3 supplementation dose-dependently suppressed the accumulation of body weight and epididymal fat, and improved the serum levels of total cholesterol, fasting glucose and insulin. The bifidobacterial counts in the caecal contents and feces were significantly increased with the B. breve B-3 administration. The expression of genes related to fat metabolism and insulin sensitivity in the gut and epididymal fat tissue was up-regulated by this administration. These results suggest that the use of B. breve B-3 would be effective in reducing the risk of obesity.     

Role of Hypothalamic Reactive Astrocytes in Diet-Induced Obesity

Hypothalamus is a brain region that controls food intake and energy expenditure while sensing signals that convey information about energy status. Within the hypothalamus, molecularly and functionally distinct neurons work in concert under physiological conditions. However, under pathological conditions such as in diet-induced obesity (DIO) model, these neurons show dysfunctional firing patterns and distorted regulation by neurotransmitters and neurohormones. Concurrently, resident glial cells including astrocytes dramatically transform into reactive states. In particular, it has been reported that reactive astrogliosis is observed in the hypothalamus, along with various neuroinflammatory signals. However, how the reactive astrocytes control and modulate DIO by influencing neighboring neurons is not well understood. Recently, new lines of evidence have emerged indicating that these reactive astrocytes directly contribute to the pathology of obesity by synthesizing and tonically releasing the major inhibitory transmitter GABA. The released GABA strongly inhibits the neighboring neurons that control energy expenditure. These surprising findings shed light on the interplay between reactive astrocytes and neighboring neurons in the hypothalamus. This review summarizes recent discoveries related to the functions of hypothalamic reactive astrocytes in obesity and raises new potential therapeutic targets against obesity.     

Early Maternal Alcohol Consumption Alters Hippocampal DNA Methylation,Gene Expression and Volume in a Mouse Model

The adverse effects of alcohol consumption during pregnancy are known, but the molecular events that lead to the phenotypic characteristics are unclear. To unravel the molecular mechanisms, we have used a mouse model of gestational ethanol exposure, which is based on maternal ad libitum ingestion of 10% (v/v) ethanol for the first 8 days of gestation (GD 0.5-8.5). Early neurulation takes place by the end of this period, which is equivalent to the developmental stage early in the fourth week post-fertilization in human. During this exposure period, dynamic epigenetic reprogramming takes place and the embryo is vulnerable to the effects of environmental factors. Thus, we hypothesize that early ethanol exposure disrupts the epigenetic reprogramming of the embryo, which leads to alterations in gene regulation and life-long changes in brain structure and function. Genome-wide analysis of gene expression in the mouse hippocampus revealed altered expression of 23 genes and three miRNAs in ethanol-exposed, adolescent offspring at postnatal day (P) 28. We confirmed this result by using two other tissues, where three candidate genes are known to express actively. Interestingly, we found a similar trend of upregulated gene expression in bone marrow and main olfactory epithelium. In addition, we observed altered DNA methylation in the CpG islands upstream of the candidate genes in the hippocampus. Our MRI study revealed asymmetry of brain structures in ethanol-exposed adult offspring (P60): we detected ethanol-induced enlargement of the left hippocampus and decreased volume of the left olfactory bulb. Our study indicates that ethanol exposure in early gestation can cause changes in DNA methylation, gene expression, and brain structure of offspring. Furthermore, the results support our hypothesis of early epigenetic origin of alcohol-induced disorders: changes in gene regulation may have already taken place in embryonic stem cells and therefore can be seen in different tissue types later in life.