Fish oil consumption prevents hepatic lipid accumulation induced by high-cholesterol feeding in obese KK mice.

Fish oil (FO) is rich in the n-3 polyunsaturated fatty acids. It has been demonstrated that FO intake possesses lipid-lowering properties. Conversely, a high-cholesterol (CH) diet promotes lipid accumulation in the liver and induces fatty liver. This study investigated the effects of FO feeding on hepatic lipid accumulation induced by high-cholesterol feeding in KK mice. All experimental diets had a fat energy ratio of 25%, the SO group had all fat sources as safflower oil (SO), the 12.5 FO group had half of the SO replaced with FO, and the 25 FO group had all of the SO replaced with FO, each with or without 2 weight % (wt%) cholesterol (SO/CH, 12.5 FO/CH, and 25 FO/CH groups, respectively), for 8 weeks. The hepatic triglyceride and total cholesterol levels were significantly lower in the 25 FO/CH group than in the SO/CH group. The hepatic mRNAs of fatty acid synthesis-related genes were downregulated by the FO feeding groups. In view of importance to establish the benefit of FO for preventing severe NAFLD, our results suggest that FO intake prevents excessive hepatic fat accumulation induced by a high-cholesterol diet in obese KK mice through the inhibition of fatty acid synthesis.

Effect of Intracerebroventricular Administration of Galanin-Like Peptide on Hepatokines in C57BL/6 J Mice.

Galanin-like peptide (GALP) is a neuropeptide that was first isolated and identified from the porcine hypothalamus. Studies have described an anti-obesity effect of GALP. We previously found that intracerebroventricular administration of GALP in mice resulted in an increase in respiratory exchange rate 12 to 16 h later. GALP may also affect glucose metabolism, but the detailed mechanism has not been elucidated. In this study, we investigated the effects of GALP on glucose and lipid metabolism in the liver. Nine-week-old male C57BL / 6 J mice were administered a single intracerebroventricular dose of saline or GALP and dissected 16 h later. There were no significant between-group differences in body weight and blood glucose levels. With regard to gene and protein expression, G6Pase associated with hepatic gluconeogenesis was significantly reduced in the GALP group. In addition, the hepatokines selenoprotein P and fetuin-A, which induce insulin resistance in the liver, were significantly decreased in the GALP group. These results suggest that intracerebroventricular administration of GALP decreases the expression of key hepatokines, thereby enhancing glucose metabolism.

Fish oil-derived n-3 polyunsaturated fatty acids downregulate aquaporin 9 protein expression of liver and white adipose tissues in diabetic KK mice and 3T3-L1 adipocytes.

Aquaporin 9 (AQP9) is an integral membrane protein that facilitates glycerol transport in hepatocytes and adipocytes. Glycerol is necessary as a substrate for gluconeogenesis in the physiological fasted state, suggesting that inhibiting AQP9 function may be beneficial for treating type 2 diabetes associated with fasting hyperglycemia. The n-3 polyunsaturated fatty acids (PUFAs), including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are rich in fish oil and lower the risk of metabolic syndrome; however, the effects of EPA and DHA on AQP9 expression in obese and type 2 diabetes are unclear. The KK mouse is an animal model of obesity and type 2 diabetes because of the polymorphisms on leptin receptor gene, which results in a part of cause for obese and diabetic conditions. In this study, we determined the effect of fish oil-derived n-3 PUFA on AQP9 protein expression in the liver and white adipose tissue (WAT) of KK mice and mouse 3T3-L1 adipocytes. The expression of AQP9 protein in the liver, epididymal WAT, and inguinal WAT were markedly decreased following fish oil administration. We also demonstrated that n-3 PUFAs, such as DHA, and to a lesser extent EPA, downregulated AQP9 protein expression in 3T3-L1 adipocytes. Our results suggest that fish oil-derived n-3 PUFAs may regulate the protein expressions of AQP9 in glycerol metabolism-related organs in KK mice and 3T3-L1 adipocytes.

Association of Aquaporin 7 and 9 with Obesity and Fatty Liver in db/db Mice.

Aquaporin (AQP) 7 and AQP9 are membrane channel proteins called aquaglyceroporins and are related to glucose and lipid metabolism. AQP7 is mainly expressed in white adipose tissue (WAT) and is involved in releasing glycerol into the bloodstream. AQP9 is the glycerol channel in the liver that supplies glycerol to the hepatic cells. In this study, we investigated the relationship between the expression of aquaglyceroporins and lifestyle-related diseases, such as obesity and fatty liver, using 22-week-old db/db mice. Body weight, WAT, and liver weight showed increases in db/db mice. The levels of liver lipids, plasma lipids, insulin, and leptin were also increased in db/db mice. Gene expression related to fatty acid and triglyceride synthesis in the liver was enhanced in db/db mice. In addition, gene and protein expression of gluconeogenesis-related enzymes was increased. Conversely, lipolysis-related gene expression in WAT was reduced. In the db/db mice, AQP9 expression in the liver was raised; however, AQP7 expression in WAT was reduced. These results suggest that in db/db mice, enhanced hepatic AQP9 expression increased the supply of glycerol to the liver and induced fatty liver and hyperglycemia. Additionally, reduced AQP7 expression in WAT is associated with excessive lipid accumulation in adipocytes. Aquaglyceroporins are essential molecules for glucose and lipid metabolism, and may be potential target molecules for the treatment of obesity and lifestyle-related diseases.

Docosapentaenoic acid-rich oil lowers plasma glucose and lipids in a mouse model of diabetes and mild obesity.

Many studies have investigated the beneficial effects of n-3 polyunsaturated fatty acids, such as their potential for lowering lipid levels and reducing diabetes risk. However, few studies have specifically examined docosapentaenoic acid (DPA), an n-3 polyunsaturated fatty acid with limited availability in its pure form. We hypothesized that DPA would have lipid-lowering effects and improve insulin resistance in KK/Ta mice. To test our hypothesis, 7-week-old KK/Ta mice were fed a high-fat diet for 12 weeks to induce obesity before being divided into 3 groups and fed an experimental diet for 10 weeks. The experimental diets were: LSO, using lard and safflower oil as fat sources; SO, in which lard in the LSO diet was replaced with safflower oil; and DPA, in which lard in the LSO diet was replaced with DPA oil. After 10 weeks, plasma triglyceride and total cholesterol concentrations were significantly decreased in the DPA group, but not in the SO group. Sterol regulatory element-binding protein-1 and stearoyl-CoA desaturase-1 gene expressions involved in fatty acid synthesis in the liver were significantly lower in the DPA group compared with the LSO group. Plasma glucose concentrations were significantly decreased in both the SO group and the DPA group compared with the LSO group, whereas plasma insulin concentrations were significantly decreased in the DPA group alone. These results indicate that DPA has plasma lipid-lowering and hypoglycemic effects, possibly from suppression of fatty acid synthesis in the liver.

Phenotypic and genotypic changes in obesity and type 2 diabetes of male KK mice with aging.

Research into the prevention and treatment of age-related metabolic diseases are important in the present-day situation of the aging population. We propose that an elderly diabetic mouse model may be useful to such research as it exhibits deterioration of glucose and lipid metabolism. Although the KK mouse strain is commonly used as a model of moderate obesity and type 2 diabetes, the utility of this strain as an elderly obese and diabetic model mouse for research into aging remains unclear. The present study aimed to investigate age-related changes of glucose and lipid metabolism in male KK mice fed a standard chow diet. We demonstrate that 40 weeks KK mice exhibit age-related dysfunctions, such as development of insulin resistance associated with pancreatic islet hypertrophy and decreased lipolysis in white adipose tissue (WAT) compared with 15 weeks KK mice. However, aging does not appear to cause mitochondrial dysfunction of brown adipose tissue. Unexpectedly, hyperglycemia, potential glucose uptake in insulin-sensitive organs, hepatic lipid accumulation, hypertrophy of adipocytes, and inflammation in epididymal WAT did not worsen but rather compensated in 40 weeks KK mice. Our data indicate that the use of male KK mice as an elderly obese and diabetic mouse model has some limitations and in order to represent a useful elderly obese and diabetic animal model, it may be necessary to induce deterioration of glucose and lipid metabolism in KK mice through breeding with high-sucrose or high-fat diets.

Distance from the nearest grocery stores and frequency of store-specific shopping are associated with dietary intake frequency among the community-dwelling independent elderly population.

BACKGROUND: Low accessibility to grocery stores may change dietary habits and increase health problems for elderly people living in communities. AIM: This study investigated whether the distance from the nearest grocery stores, including supermarkets, convenience stores, and drugstores, and the frequency of store-specific shopping were associated with dietary intake frequency among elderly people. METHODS: A cross-sectional study was conducted in two towns of suburban cities. A total of 177 people aged ≥65 years were recruited (M age=76.7 years). The frequency of intake of 10 food groups and dietary variety scores (DVS) were evaluated. Distances from the districts to the nearest grocery stores and the frequency of shopping during a week at each store were evaluated using a geographic information system. RESULTS: For supermarkets, people living <300 metres from the nearest supermarket showed a higher intake frequency of fruit (p=0.024) and oil/fat (p=0.045), and those shopping three or more times a week showed a higher intake frequency of meat (p=0.025). In the case of drugstores, people shopping one or more times a week showed a higher intake frequency of eggs (p=0.006) and oil/fat (p=0.048). People living <300 m from the nearest supermarkets (p=0.048) and drugstores (p=0.047) showed higher DVS than those living ≥500 m from the nearest supermarkets and drugstores. CONCLUSIONS: Our findings suggest that shopping at supermarkets and drugstores is associated with dietary intake frequency and dietary quality for elderly people living in suburban cities.

Impact of discontinuation of fish oil after pioglitazone-fish oil combination therapy in diabetic KK mice.

Pioglitazone is one of the thiazolidinediones (TZDs) and an insulin-sensitive drug for type 2 diabetes. In our previous study, a combination of pioglitazone and fish oil rich in n-3 polyunsaturated fatty acids (PUFAs) was shown to inhibit pioglitazone-induced side effects, such as accumulation of subcutaneous fat and body weight gain. However, the effects of the discontinuation of fish oil after combination treatment with TZD and fish oil are not clear. In this study, discontinuation of fish oil for 4 weeks showed several unfavorable effects: (1) return of plasma adiponectin level, (2) reversal of the inhibition of lipogenesis and activation of fatty acid ß-oxidation in liver, (3) increase in hypertrophic adipocytes in epidydimal white adipose tissue (WAT) and (4) accumulation of lipids in brown adipose tissue (BAT). However, insulin resistance was ameliorated by pioglitazone with or without fish oil treatment and the discontinuation of fish oil. These findings indicate that discontinuation of n-3 PUFA after combination therapy with TZDs adversely affects lipid metabolism and energy homeostasis in liver, epididymal WAT and BAT.

Blackcurrant Extract Ameliorates Hyperglycemia in Type 2 Diabetic Mice in Association with Increased Basal Secretion of Glucagon-Like Peptide-1 and Activation of AMP-Activated Protein Kinase.

Blackcurrants are berries that contain high levels of anthocyanins, particularly delphinidin 3-rutinoside (D3R). Several studies have reported that the consumption of blackcurrant extract (BCE) lowers blood glucose levels and ameliorates glucose tolerance, but the mechanism underlying this effect remains unclear. Glucagon-like peptide-1 (GLP-1) and AMP-activated protein kinase (AMPK) are considered one of the most significant molecular targets for the prevention and treatment of type 2 diabetes. In this study, we showed that dietary BCE significantly reduced blood glucose concentration and improved glucose tolerance in type 2 diabetic mice (KK-Ay). The basal GLP-1 concentration in plasma was significantly increased in the BCE group accompanied by upregulation of prohormone convertase 1/3 (PC1/3), the enzyme that processes intestinal proglucagon. Moreover, the level of phospho-AMPKα protein in skeletal muscle was significantly increased in the BCE group, and this was increase accompanied by significant upregulation of glucose transporter 4 (Glut4) proteins in the plasma membrane of BCE group. In conclusion, dietary BCE significantly reduced blood glucose concentration and improved glucose tolerance in association with increased basal GLP-1 concentration in plasma, upregulation of PC1/3 expression, and translocation of Glut4 to the plasma membrane of skeletal muscle in type 2 diabetic mice; furthermore, these effects were accompanied by activation of AMPK. Our findings demonstrated that D3R-rich BCE may help prevent diabetes and allow the dosages of diabetes drugs to be reduced.

Benefits of combination low-dose pioglitazone plus fish oil on aged type 2 diabetes mice.

The elderly patients with type 2 diabetes suffer more adverse drug events than young adults due to pharmacokinetic and pharmacodynamic changes associated with aging. Reducing the risks of these medication-related problems are equally important for the clinical care of older type 2 diabetes patients. Pioglitazone is used for treating type 2 diabetes as an oral antidiabetic drug. Despite pioglitazone is used helpful insulin sensitizers, the accumulation of subcutaneous fat is considered a major adverse effect of pioglitazone therapy. We investigated to reduce the adverse effect of pioglitazone by combination with fish oil rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in aged diabetic KK mice. The accumulation of subcutaneous fat associated with high-dose pioglitazone is reduced by fish oil, suppressing lipogenesis and stimulating fatty acid ß-oxidation in the liver. Our data suggest that adding fish oil to low-dose pioglitazone results in antidiabetic efficacy similar to that of the high-dose without concomitant body weight gain.

Fish oil and fenofibrate inhibit pancreatic islet hypertrophy, and improve glucose and lipid metabolic dysfuntions with different ways in diabetic KK mice.

We examined the effects of fish oil and fenofibrate (FF) on the pancreatic islet hypertrophy, and on the modification of glucose and lipid metabolic dysfunctions in KK mice with insulin resistance. The mice were fed one of four diets [25en% lard/safflower oil (LSO), 25en% fish oil (FO), or each of these diets plus 0.1wt% FF (LSO/FF, FO/FF)] for 9 weeks. FO group and both FF groups had significantly lower final body and adipose tissue weights than LSO group. Pancreatic islet hypertrophy was observed only in LSO group but not in the other groups with fish oil or FF. And, it is likely that fish oil has a stronger therapeutic effect on islet hypertrophy. Plasma adiponectin level was significantly higher in FO group but not in both FF groups. Expression of hepatic lipogenic enzyme genes such as fatty acid synthase (FAS) and stearoyl-CoA desaturase-1 (SCD-1) was lower in FO groups with or without FF, whereas fatty acid oxidation-related mRNAs such as acyl-CoA oxidase (AOX) and uncoupling protein-2 (UCP-2) were more abundant in FF groups with or without fish oil. Our results suggest that both fish oil and FF improve pancreatic islet hypertrophy with the amelioration of insulin resistance. Fish oil enhances insulin sensitivity by increasing plasma adiponectin; however, the beneficial effect of FF on insulin resistance seems to be independent of the plasma adiponectin level. These results mean that improvement of glucose and lipid metabolic dysfuctions in diabetic KK mice are independently approached by fish oil and FF.

Effect of Intranasal Administration of Galanin-like Peptide (GALP) on Body Weight and Hepatic Lipids Accumulation in Mice with Diet-induced Obesity.

Galanin-like peptide (GALP) is a neuropeptide involved in the regulation of food intake behavior, body weight and energy metabolism. In previous studies, we demonstrated that the intranasal administration of GALP has weight loss effects, although the mechanism of this action was not clarified. The aim of this study was to demonstrate the functional significance of GALP on lipid metabolism in the liver. Mice were fed a high fat diet to cause diet-induced obesity (DIO) and then administered GALP intranasally for 2 weeks (experimental), or vehicle (control). Body weights, along with lipid levels in the plasma and liver, and lipid metabolism-related gene expression in the liver were subsequently measured. Body weight gain was decreased by the GALP treatment compared to the control group. Lipid droplet levels in hepatocytes and hepatic triglyceride levels were decreased in the GALP group compared with the vehicle group, whereas hepatic fatty acid ß-oxidation-related gene mRNA levels were increased in the GALP group. These results suggest that the intranasal administration of GALP has an inhibitory effect on lipid accumulation in the liver.

Protective effects of fish oil and pioglitazone on pancreatic tissue in obese KK mice with type 2 diabetes.

n-3 Polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have protective effects against the pancreatic ß-cell dysfunction through several mechanisms. Thiazolidines are insulin sensitizers and are used in treating patients with type 2 diabetes. Our previous study demonstrated that a combination of fish oil, which is rich with EPA and DHA, and pioglitazone exerts beneficial effects on obesity and diabetes through their actions on the liver and adipose tissue. However, it remains largely unknown whether such combination therapy affects the pancreas. To answer this question, KK mice, which serve as a model for obesity and type 2 diabetes, were treated for 8 weeks with fish oil and pioglitazone. The combined regimen suppressed pancreatic islet hypertrophy (mean islet area decreased by an average of 49% vs. control) compared with mice treated with fish oil or pioglitazone alone (decreased by an average of 21% and 32% vs. control, respectively). Compared with the controls, individual or combined treatment significantly increased the percentage of ß-cell area in the pancreatic islets, significantly decreased endoplasmic reticulum stress, and reduced the percentage of apoptotic cell death in the pancreatic islets. These findings suggest that fish oil and/or pioglitazone prevents ß-cell dysfunction by improving the insulin resistance and decreasing the ER stress.

Behavioral and omics analyses study on potential involvement of dipeptide balenine through supplementation in diet of senescence-accelerated mouse prone 8.

This study investigates effects of dipeptide balenine, as a major component of whale meat extract (hereafter, WME), supplementation on senescence-accelerated mouse prone 8 (SAMP8), an Alzheimer's disease (AD) model at level of learning and memory formation and brain expression profiles genome-wide in brain. Mice fed experimental balenine (+ WME) supplemented diet for 26 weeks were subjected to four behavioral tests - open field, Y-maze, new object recognition, and water-filled multiple T-maze - to examine effects on learning and memory. Brain transcriptome of SAMP8 mice-fed the WME diet over control low-safflower oil (LSO) diet-fed mice was delineated on a 4 × 44 K mouse whole genome DNA microarray chip. Results revealed the WME diet not only induced improvements in the learning and memory formation but also positively modulated changes in the brain of the SAMP8 mouse; the gene inventories are publically available for analysis by the scientific community. Interestingly, the SAMP8 mouse model presented many genetic characteristics of AD, and numerous novel molecules (Slc2a5, Treh, Fbp1, Aldob, Ppp1r1a, DNase1, Agxt2l1, Cyp2e1, Acsm1, Acsm2, and Pah) were revealed over the SAMR1 (senescence-accelerated mouse resistant 1) mouse, to be oppositely regulated/recovered under the balenine (+ WME) supplemented diet regime by DNA microarray and bioinformatics analyses. Our present study demonstrates an experimental strategy to understand the effects of dipeptide balenine, prominetly contained in meat diet, on SAMP8, providing new insight into whole brain transcriptome changes genome-wide. The gene expression data has been deposited into the Gene Expression Omnibus (GEO): GSE76459. The data will be a valuable resource in examining the effects of natural products, and which could also serve as a human model for further functional analysis and investigation.

Autonomic nervous system-mediated effects of galanin-like peptide on lipid metabolism in liver and adipose tissue.

Galanin-like peptide (GALP) is a neuropeptide involved in the regulation of feeding behavior and energy metabolism in mammals. While a weight loss effect of GALP has been reported, its effects on lipid metabolism have not been investigated. The aim of this study was to determine if GALP regulates lipid metabolism in liver and adipose tissue via an action on the sympathetic nervous system. The respiratory exchange ratio of mice administered GALP intracerebroventricularly was lower than that of saline-treated animals, and fatty acid oxidation-related gene mRNA levels were increased in the liver. Even though the respiratory exchange ratio was reduced by GALP, this change was not significant when mice were treated with the sympatholytic drug, guanethidine. Lipolysis-related gene mRNA levels were increased in the adipose tissue of GALP-treated mice compared with saline-treated animals. These results show that GALP stimulates fatty acid ß-oxidation in liver and lipolysis in adipose tissue, and suggest that the anti-obesity effect of GALP may be due to anorexigenic actions and improvement of lipid metabolism in peripheral tissues via the sympathetic nervous system.

The relationship between aquaglyceroporin expression and development of fatty liver in diet-induced obesity and ob/ob mice.

Aquaporin (AQP) 7 and AQP9 are subcategorised as aquaglyceroporins which transport glycerin in addition to water. These AQPs may play a role in the homeostasis of energy metabolism. We examined the effect of AQP7, AQP9, and lipid metabolism-related gene expression in obese mice. In diet-induced obese (DIO) mice, excess lipid accumulated in the liver, which was hyperleptinemic and hyperinsulinemic. Hepatic AQP9 gene expression was significantly increased in both DIO and ob/ob mice compared to controls. The mRNA expression levels of fatty acid and triglyceride synthesis-related genes and fatty acid ß oxidation-related genes in the liver were also higher in both mouse models, suggesting that triglyceride synthesis in this organ is promoted as a result of glycerol release from adipocytes. Adipose AQP7 and AQP9 gene expressions were increased in DIO mice, but there was no difference in ob/ob mice compared to wild-type mice. In summary, adipose AQP7 and AQP9 gene expressions are increased by diet-induced obesity, indicating that this is one of the mechanisms by which lipid accumulates in response to a high fat diet, not the genetic mutation of ob/ob mice. Hepatic AQP9 gene expression was increased in both obesity model mice. AQP7 and AQP9 therefore have the potential of defining molecules for the characterisation of obesity or fatty liver and may be a target molecules for the treatment of those disease.

Fish oil prevents excessive accumulation of subcutaneous fat caused by an adverse effect of pioglitazone treatment and positively changes adipocytes in KK mice.

Pioglitazone, a thiazolidinedione (TZD), is widely used as an insulin sensitizer in the treatment of type 2 diabetes. However, body weight gain is frequently observed in TZD-treated patients. Fish oil improves lipid metabolism dysfunction and obesity. In this study, we demonstrated suppression of body weight gain in response to pioglitazone administration by combination therapy of pioglitazone and fish oil in type 2 diabetic KK mice. Male KK mice were fed experimental diets for 8 weeks. In safflower oil (SO), safflower oil/low-dose pioglitazone (S/PL), and safflower oil/high-dose pioglitazone (S/PH) diets, 20% of calories were provided by safflower oil containing 0%, 0.006%, or 0.012% (wt/wt) pioglitazone, respectively. In fish oil (FO), fish oil/low-dose pioglitazone (F/PL), and fish oil/high-dose pioglitazone (F/PH) diets, 20% of calories were provided by a mixture of fish oil and safflower oil. Increased body weight and subcutaneous fat mass were observed in the S/PL and S/PH groups; however, diets containing fish oil were found to ameliorate these changes. Hepatic mRNA levels of lipogenic enzymes were significantly decreased in fish oil-fed groups. These findings demonstrate that the combination of pioglitazone and fish oil decreases subcutaneous fat accumulation, ameliorating pioglitazone-induced body weight gain, through fish oil-mediated inhibition of hepatic de novo lipogenesis.

Fish oil prevents excessive hepatic lipid accumulation without inducing oxidative stress.

We examined the effects of fish oil (FO) on high-cholesterol diet-induced hepatic lipid accumulation and oxidative stress. Female C57BL/6J mice were fed diets consisting of safflower oil (SO), 1 en% FO (1FO), 2 en% FO (2FO), or 20 en% FO (20FO) with or without 2 weight% (wt%) cholesterol (SO/CH, 1FO/CH, 2FO/CH, and 20FO/CH groups, respectively) for 8 weeks. The hepatic triacylglyceride levels were significantly lower in the 2FO/CH and 20FO/CH groups than in the SO/CH group. The hepatic mRNAs of fatty acid oxidation-related genes were upregulated and the fatty acid synthesis-related genes were downregulated by the FO feeding. Adverse effects were not observed in the plasma levels of indicators of oxidative stress in response to the consumption of FO up to 20 en%. These results suggest that FO consumption in the range of 2-20 en% prevents hepatic lipid accumulation, thus improving lipid metabolism without causing oxidative stress.