Exercise improves adipose function and inflammation and ameliorates fatty liver disease in obese diabetic mice

The association between visceral adipocyte hypertrophy and NAFLD in subjects with different degrees of adiposity

OBJECTIVE

To investigate the association between visceral adipocyte hypertrophy and the onset and development of non-alcoholic fatty liver disease (NAFLD) in subjects with different degrees of adiposity.

METHODS

Omental adipose tissue and liver biopsies were collected from obese subjects. NAFLD was defined according to the NASH Clinical Research Network scoring system. Adipocyte size was measured using pathological section analysis. Adipose tissue insulin resistance (Adipo-IR) was calculated as fasting insulin (pmol/L) × fasting free fatty acid concentration (mmol/L).

RESULTS

In total, 275 obese patients were enrolled, including 158 females and 58 males with NAFLD. In females, adipocyte size was significantly larger in NAFLD participants as compared to the controls (99.37 ± 14.18 vs. 84.14 ± 12.65 [Formula: see text]m, p < 0.001). Moreover, adipocyte size was larger in females with non-alcoholic steatohepatitis (NASH) as compared to those with non-alcoholic fatty liver (NAFL) (101.45 ± 12.77 vs. 95.79 ± 15.80 [Formula: see text]m, p = 0.015). Mediation analysis showed that adipocyte size impacted the NAFLD activity score through Adipo-IR (b = 0.007 [95% bootstrap CI 0.002, 0.013]). Furthermore, the females were divided into: Q1 (BMI < 32.5 kg/m²), Q2 (BMI 32.5-35.5 kg/m²), Q3 (BMI 35.5-38.8 kg/m²) and Q4 (BMI ≥ 38.8 kg/m²) according to BMI quartiles. Omental adipocyte size was larger in NAFLD subjects in Q1-Q3, but not in Q4. No similar results were observed in males.

CONCLUSION

For the first time, we reported that visceral adipocyte hypertrophy was associated with the onset and progression of NAFLD in mild to moderate adiposity but not in severe obesity, which may be mediated by adipose tissue insulin resistance.

The effect of varied exercise intensity on antioxidant function, aortic endothelial function, and serum lipids in rats with non-alcoholic fatty liver disease

This study aimed to compare the effects of diet and exercise of different intensities on antioxidant function, aortic endothelial cell function and serum lipids in NAFLD (nonalcoholic fatty liver disease) rats. Fifty Sprague-Dawley (SD) rats (180-220g) were randomly divided into two experimental groups and fed either a standard rodent chow diet (CON; n=10) or a high-fat diet (HFD; n=40). After 16 weeks, the animals that received the HFD were randomly separated into a high-fat control group (HFC; n=10) or three ex-ercise training groups: HFD and low-intensity exercise (LE; n=10), HFD and moderate-intensity exercise (ME; n=10), and HFD and incremental intensity exercise (IE; n=10). These experimental rats keep sedentary or trained for the next six weeks. A detection kit was used to detect nitric oxide synthase (NOs), nitric oxide (NO), malondialdehyde (MDA) and other markers of aor-tic oxidative stress. The expression levels of endothelial nitric oxide synthase (e-NOS) and endothelin-1 (ET-1) were detected by immunohistochemistry. TC, TG, and other lipid metabolism parameters were detected by an auto-matic analyzer. Exercise with different intensities could improve lipid me-tabolism, enhance antioxidant function, reduce MDA (P<0.01), increase NO (P<0.01), and improve the expression of e-NOS and ET-1 (P<0.01) protein levels in NAFLD rats. Decreased blood lipids were exhibited in all exercise groups. Notably, the moderate-intensity exercise demonstrated more effecton increasing glutathione (GSH) contents (P<0.01) and decreased the ex-pression of ET-1protein levels (P<0.01). The results showed that exercise at different intensities improved lipid metabolism and enhanced anti-oxidation function. Moderate exercise could improve the function of aortic endothelial cells.

Concurrent betaine administration enhances exercise-induced improvements to glucose handling in obese mice

BACKGROUND AND AIMS

Betaine supplementation has been shown to enhance hepatic lipid metabolism in obese mice and improve exercise performance in healthy populations. We examined effects of betaine supplementation, alone or in combination with treadmill exercise, on the metabolic consequences of high fat diet (HFD)-induced obesity in mice.

METHODS AND RESULTS

Male C57BL/6 J mice were fed chow or HFD. After 15 weeks, HFD mice were split into: HFD, HFD with betaine (1.5% w/v), HFD with treadmill exercise, and HFD with both betaine and exercise (15 m/min for 45min, 6 days/week; n = 12/group) for 10 weeks. Compared to HFD mice, body weight was significantly reduced in exercise and exercise-betaine mice, but not in mice given betaine alone. Similarly, adiposity was reduced by exercise but not by betaine alone. HFD-induced glucose intolerance was slightly improved by exercise, but not with betaine alone. Significantly greater benefits were observed in exercise-betaine mice, compared to exercise alone, such that GTT-outcomes were similar to controls. This was associated with reduced insulin levels during ipGTT, suggesting enhanced insulin sensitivity. Modest benefits were observed in fatty acid metabolism genes in skeletal muscle, whilst limited effects were observed in the liver. HFD-induced increases in hepatic Mpc1 (mitochondrial pyruvate carrier 1) were normalized by all treatments, suggesting potential links to altered glucose metabolism.

CONCLUSIONS

Our data show that drinking 1.5% betaine was sufficient to augment metabolic benefits of exercise in obese mice. These processes appear to be facilitated by altered glucose metabolism, with limited effects on hepatic lipid metabolism.

Sestrin2 ablation attenuates the exercise-induced browning of white adipose tissue in C57BL/6J mice

AIM

With exercise, white adipose tissues (WAT) are readily convertible to a "brown-like" state, altering from lipid-storing to energy-catabolizing function, which counteracts obesity and increases insulin sensitivity. Sestrin2 (SESN2) is a stress-inducible protein that can regulate the cold-induced increase of uncoupling protein 1 (UCP1), which is paramount for the thermogenic capacity of brown-like WAT. This study aimed to elucidate the necessity of SESN2 in mediating exercise-induced browning of WAT.

METHODS

We used 8-week, male wild-type and SESN2 knockout C57BL/6J mice to explore the potential role of SESN2 in the exercise-induced WAT browning process. Over a 3-week intervention (sedentary versus treadmill exercise, normal chow versus 60% high-fat diet), we examined the exercise-induced alterations of the browning phenotype in different depots of white fat. In vitro, 3T3-L1 pre-adipocytes and primary adipocytes were used to determine the potential mechanism.

RESULTS

Our data revealed that SESN2 was required for the exercise-induced subcutaneous WAT (scWAT) browning. This may be mediated by higher fibronectin type III domain containing 5 (FNDC5) contents in scWAT locally, rather than skeletal muscle FNDC5 expression and circulating serum irisin levels. SESN2 ablation significantly impaired the exercise-improved glucose metabolism, where browning of scWAT may serve as an essential pathway. Moreover, SESN2 ablation significantly attenuated the exercise-promoted respiratory exchange ratio and indexes of energy metabolism (oxygen uptake and energy expenditure).

CONCLUSION

Taken together, our results provided evidence that SESN2 is a key integrating factor in driving the diverse metabolic benefits conferred by aerobic exercise.

Physical Exercise Repairs Obstructive Jaundice-Induced Damage to Intestinal Mucosal Barrier Function via H2S-Mediated Regulation of the HMGB1/Toll Like Receptors 4/Nuclear Factor Kappa B Pathway

The present study aimed to determine the effect of aerobic exercise on improving damage to intestinal mucosal barrier function caused by obstructive jaundice (OJ) and explore the mechanism. Fifty male KM mice were divided into five groups: sham operation group (S), model group (M), exercise group (TM), DL-propargylglycine + exercise (PT) group, and sodium hydrosulfide + exercise (NT) group. Additionally, mice in S group underwent common bile duct ligation for 48 h to establish a murine obstructive jaundice model. In PT group, propargylglycine (40 mg/kg) was intraperitoneally injected 7 days after surgery. NaHS (50 μmol/kg) was intraperitoneally injected into mice in the NT group 7 days after surgery. The TM group, NT group and PT group exercised on a slope of 0% at a speed of 10 m/min without weight training (30 min/day). HE staining showed that the intestinal mucosa of group M was atrophied and that the villi were broken. The intestinal mucosal structure of mice in the TM group was improved. Serum assays showed that H2S levels were higher in the TM group than in the M group; compared with the levels in the TM group, the PT group levels were decreased and the NT group levels were increased. In addition, aerobic exercise inhibits the HMGB1/TLR4/NF-κB signaling pathway by promoting endogenous H2S production, thereby exerting a protective effect on the intestinal mucosal barrier.

Exercise-induced benefits on glucose handling in a model of diet-induced obesity are reduced by concurrent nicotinamide mononucleotide

Almost 40% of adults worldwide are classified as overweight or obese. Exercise is a beneficial intervention in obesity, partly due to increases in mitochondrial activity and subsequent increases in nicotinamide adenine dinucleotide (NAD⁺), an important metabolic cofactor. Recent studies have shown that increasing NAD⁺ levels through pharmacological supplementation with precursors such as nicotinamide mononucleotide (NMN) improved metabolic health in high-fat-diet (HFD)-fed mice. However, the effects of combined exercise and NMN supplementation are unknown. Thus, here we examined the combined effects of NMN and treadmill exercise in female mice with established obesity after 10 wk of diet. Five-week-old female C57BL/6J mice were exposed to a control diet (n = 16) or HFD. Mice fed a HFD were either untreated (HFD; n = 16), received NMN in drinking water (400 mg/kg; HNMN; n = 16), were exposed to treadmill exercise 6 days/wk (HEx; n = 16), or were exposed to exercise combined with NMN (HNEx; n = 16). Although some metabolic benefits of NMN have been described, at this dose, NMN administration impaired several aspects of exercise-induced benefits in obese mice, including glucose tolerance, glucose-stimulated insulin secretion from islets, and hepatic triglyceride accumulation. HNEx mice also exhibited increased antioxidant and reduced prooxidant gene expression in both islets and muscle, suggesting that altered redox status is associated with the loss of exercise-induced health benefits with NMN cotreatment. Our data show that NMN treatment impedes the beneficial metabolic effects of exercise in a mouse model of diet-induced obesity in association with disturbances in redox metabolism.NEW & NOTEWORTHY NMN dampened exercise-induced benefits on glucose handling in diet-induced obesity. NMN administration alongside treadmill exercise enhanced the ratio of antioxidants to prooxidants. We suggest that NMN administration may not be beneficial when NAD⁺ levels are replete.

Putting ATM to BED: How Adipose Tissue Macrophages Are Affected by Bariatric Surgery, Exercise, and Dietary Fatty Acids

With increasing adiposity in obesity, adipose tissue macrophages contribute to adipose tissue malfunction and increased circulating proinflammatory cytokines. The chronic low-grade inflammation that occurs in obesity ultimately gives rise to a state of metainflammation that increases the risk of metabolic disease. To date, only lifestyle and surgical interventions have been shown to be somewhat effective at reversing the negative consequences of obesity and restoring adipose tissue homeostasis. Exercise, dietary interventions, and bariatric surgery result in immunomodulation, and for some individuals their effects are significant with or without weight loss. Robust evidence suggests that these interventions reduce chronic inflammation, in part, by affecting macrophage infiltration and promoting a phenotypic switch from the M1- to M2-like macrophages. The purpose of this review is to discuss the impact of dietary fatty acids, exercise, and bariatric surgery on cellular characteristics affecting adipose tissue macrophage presence and phenotypes in obesity.

Dysfunction of perivascular adipose tissue in mesenteric artery is restored by aerobic exercise in high-fat diet induced obesity

This study investigated the function of perivascular adipose tissue (PVAT) on vascular contractility within resistant arteries in high-fat diet induced obese rats after long-term aerobic exercise. Male Sprague-Dawley rats were subjected to normal diet control group (N-CTRL), normal diet exercise group (N-EX), high-fat diet control group (H-CTRL), and high-fat diet exercise group (H-EX) (n = 8 in each group). After intervention, adipose tissues morphology was observed. Vasomotor function of mesenteric arteries with or without PVAT were assessed; mesenteric PVAT isolated from each group were transferred to chambers bath with untreated vessels (without PVAT) to evaluate the independent effect. Isolated PVAT was further pre-treated with inhibitor of cystathionine-γ-lyase (CSE), a key hydrogen sulphide (H2 S) enzyme. Results showed that the size of lipid droplet around mesenteric arteries from H-EX was significantly reduced (P < .05); uncoupling protein1 (UCP1) in PVAT from H-EX was enhanced. In N-CTRL, N-EX, and H-EX, vessels without PVAT showed higher sensitivity to serotonin (5-HT) than that with intact PVAT. Vascular tension by 5-HT was significantly reduced in H-EX than H-CTRL (P < .05) in vessels with PVAT. Transferred PVAT from H-EX compared with H-CTRL significantly reduced vascular sensitivity to 5-HT (P < .05), and this effect was eliminated through inhibiting CSE. In summary, the anti-contractile effect of PVAT on resistance artery was impaired in obesity but restored by long-term aerobic exercise. The function of PVAT modified by obesity or by exercise has an independent influence on vascular reactivity, and PVAT derived H2 S may participate in this process.

Exercise retards hepatocarcinogenesis in obese mice independently of weight control

BACKGROUND & AIMS

Obesity and type 2 diabetes increase hepatocellular carcinoma (HCC) incidence in humans and accelerate diethylnitrosamine (DEN)-induced hepatocarcinogenesis in mice. We investigated whether exercise reduces HCC development in obese/diabetic Alms1 mutant (foz/foz) mice and studied protective mechanisms.

METHODS

We measured HCC development in DEN-injected male foz/foz and wild-type (WT) littermates housed with or without an exercise wheel from week 4 until 12 or 24 weeks, and in foz/foz mice pair-fed to WT littermates. We also studied HCC development in DEN-injected Jnk1^-/-.foz/foz mice generated by cross breeding, as well as their genetic controls. Dysplastic hepatocytes were identified by glutathione-S-transferase pi form (GST-pi) immunohistochemistry, liver nodules were counted, and HCC was analysed by histopathology.

RESULTS

Exercising foz/foz mice maintained similar weight as WT mice up to 10 weeks, but then gained weight and were obese by 24 weeks; a similar body weight profile was obtained by pair-feeding foz/foz mice to WT. At 12 weeks, livers of exercising foz/foz mice exhibited fewer GST-pi positive hepatocytes than sedentary counterparts; by 24 weeks, fewer exercising foz/foz mice developed HCC (15% vs. 64%, p <0.05). Conversely, pair-feeding foz/foz mice failed to reduce HCC incidence. In these insulin-resistant foz/foz mice, exercise failed to activate hepatic AMPK or Akt/mTORC1. Instead, it improved insulin sensitivity, ameliorated steatosis and liver injury, activated p53 to increase p27 expression, and prevented JNK activation. This was associated with suppression of hepatocellular proliferation. DEN-injected Jnk1^-/-.foz/foz mice failed to develop liver tumours or HCC at 24 weeks.

CONCLUSIONS

Direct effects of exercise dampen proliferation of dysplastic hepatocytes to reduce 3-month dysplastic foci and 6-month incidence of DEN-induced HCC in obese, insulin-resistant mice. The effects of exercise that potentially slow hepatocarcinogenesis include p53-mediated induction of p27 and prevention of JNK activation.

LAY SUMMARY

Fatty liver disease commonly occurs alongside obesity and diabetes, contributing to rapidly increasing rates of liver cancer throughout the world. Herein, we show that exercise reduces the incidence and progression of hepatocellular carcinoma in mouse models. The effect of exercise on cancer risk was shown to be independent of changes in weight. Exercise could be a protective mechanism against liver cancer in at-risk individuals.

Maternal exercise via exerkine apelin enhances brown adipogenesis and prevents metabolic dysfunction in offspring mice

The obesity rate is rapidly increasing, which has been attributed to lack of exercise and excessive energy intake. Here, we found a previously unidentified explanation, due to lack of maternal exercise. In this study, healthy maternal mice were assigned either to a sedentary lifestyle or to exercise daily, and fetal brown adipose tissue (BAT) development and offspring metabolic health were analyzed. Compared to the sedentary group, maternal exercise enhanced DNA demethylation of Prdm16 promoter and BAT development and prevented obesity of offspring when challenged with a high-energy diet. Apelin, an exerkine, was elevated in both maternal and fetal circulations due to exercise, and maternal administration of apelin mimicked the beneficial effects of exercise on fetal BAT development and offspring metabolic health. Together, maternal exercise enhances thermogenesis and the metabolic health of offspring mice, suggesting that the sedentary lifestyle during pregnancy contributes to the obesity epidemic in modern societies.

Exercise with food withdrawal at thermoneutrality impacts fuel use, the microbiome, AMPK phosphorylation, muscle fibers, and thyroid hormone levels in rats

Exercise under fasting conditions induces a switch to lipid metabolism, eliciting beneficial metabolic effects. Knowledge of signaling responses underlying metabolic adjustments in such conditions may help to identify therapeutic strategies. Therefore, we studied the effect of mild exercise on rats submitted to food withdrawal at thermoneutrality (28°C) for 3 days. Animals were housed at thermoneutrality rather than the standard housing temperature (22°C) to avoid beta-adrenergic signaling responses that themselves affect metabolism and well-being. Quantitative analysis of multi-organ mRNA levels, myofibers, and serum metabolites shows that this protocol (a) boosts fat oxidation in muscle and liver, (b) reduces lipogenesis and increases gluconeogenesis in liver, (c) increases serum acylcarnitines (especially C4 OH) and ketone bodies and the use of the latter as fuel in muscle, (d) increases Type I myofibers, and (e) is associated with an increased thyroid hormone uptake and metabolism in muscle. In addition, stool microbiome DNA analysis revealed that food withdrawal dramatically alters the presence of bacterial genera associated with ketone metabolism. Taken together, this protocol induces a drastic switch toward increased lipid and ketone metabolism compared to exercise or food withdrawal alone, which may prove beneficial and may involve local thyroid hormones, which may be regarded as exercise mimetics.

The Exercise Training Modulatory Effects on the Obesity-Induced Immunometabolic Dysfunctions

Reduced physical activity rate in people's lifestyle is a global concern associated with the prevalence of health disorders such as obesity and metabolic disturbance. Ample evidence has indicated a critical role of the immune system in the aggravation of obesity. The type, duration, and production of adipose tissue-released mediators may change subsequent inactive lifestyle-induced obesity, leading to the chronic systematic inflammation and monocyte/macrophage (MON/MФ) phenotype polarization. Preliminary adipose tissue expansion can be inhibited by changing the lifestyle. In this context, exercise training is widely recommended due to a definite improvement of energy balance and the potential impacts on the inflammatory signaling cascades. How exercise training affects the immune system has not yet been fully elucidated, because its anti-inflammatory, pro-inflammatory, or even immunosuppressive impacts have been indicated in the literature. A thorough understanding of the mechanisms triggered by exercise can suggest a new approach to combat meta-inflammation-induced metabolic diseases. In this review, we summarized the obesity-induced inflammatory pathways, the roles of MON/MФ polarization in adipose tissue and systemic inflammation, and the underlying inflammatory mechanisms triggered by exercise during obesity.

Automated computerized image analysis for the user-independent evaluation of disease severity in preclinical models of NAFLD/NASH

Pathologists use a semiquantitative scoring system (NAS or SAF score) to facilitate the reporting of disease severity and evolution. Similar scores are applied for the same purposes in rodents. Histological scores have inherent inter- and intra-observer variability and yield discrete and not continuous values. Here we performed an automatic numerical quantification of NASH features on liver sections in common preclinical NAFLD/NASH models. High-fat diet-fed foz/foz mice (Foz HF) or wild-type mice (WT HF) known to develop progressive NASH or an uncomplicated steatosis, respectively, and C57Bl6 mice fed a choline-deficient high-fat diet (CDAA) to induce steatohepatitis were analyzed at various time points. Automated software image analysis of steatosis, inflammation, and fibrosis was performed on digital images from entire liver sections. Data obtained were compared with the NAS score, biochemical quantification, and gene expression. As histologically assessed, WT HF mice had normal liver up to week 34 when they harbor mild steatosis with if any, little inflammation. Foz HF mice exhibited grade 2 steatosis as early as week 4, grade 3 steatosis at week 12 up to week 34; inflammation and ballooning increased gradually with time. Automated measurement of steatosis (macrovesicular steatosis area) revealed a strong correlation with steatosis scores (r = 0.89), micro-CT liver density, liver lipid content (r = 0.89), and gene expression of CD36 (r = 0.87). Automatic assessment of the number of F4/80-immunolabelled crown-like structures strongly correlated with conventional inflammatory scores (r = 0.79). In Foz HF mice, collagen deposition, evident at week 20 and progressing at week 34, was automatically quantified on picrosirius red-stained entire liver sections. The automated procedure also faithfully captured and quantitated macrovesicular steatosis, mixed inflammation, and pericellular fibrosis in CDAA-induced steatohepatitis. In conclusion, the automatic numerical analysis represents a promising quantitative method to rapidly monitor NAFLD activity with high-throughput in large preclinical studies and for accurate monitoring of disease evolution.

Maintaining mitochondria in beige adipose tissue

Individual cell types vary enormously in the amount of different organelles they contain. One such organelle is the mitochondrion. Understanding how mitochondrial levels are controlled is essential since so many disease states seem to involve mitochondrial function. The beige adipocyte is an inducible form of adipocyte that emerges in response to cold exposure and some other external stimuli. To perform its thermogenic function, its level of mitochondria increases dramatically. If the stimuli are removed the mitochondrial levels return to base line. Following the withdrawal of external stimuli, beige adipocytes directly acquire a white fat-like phenotype through mitophagy-mediated mitochondrial degradation. The beige cell is therefore a dynamic model for studying the mechanism of mitochondrial biogenesis and degradation.

In vitro tissue-engineered adipose constructs for modeling disease

BACKGROUND

Adipose tissue is a vital tissue in mammals that functions to insulate our bodies, regulate our internal thermostat, protect our organs, store energy (and burn energy, in the case of beige and brown fat), and provide endocrine signals to other organs in the body. Tissue engineering of adipose and other soft tissues may prove essential for people who have lost this tissue from trauma or disease.

MAIN TEXT

In this review, we discuss the applications of tissue-engineered adipose tissue specifically for disease modeling applications. We provide a basic background to adipose depots and describe three-dimensional (3D) in vitro adipose models for obesity, diabetes, and cancer research applications.

CONCLUSIONS

The approaches to engineering 3D adipose models are diverse in terms of scaffold type (hydrogel-based, silk-based and scaffold-free), species of origin (H. sapiens and M. musculus) and cell types used, which allows researchers to choose a model that best fits their application, whether it is optimization of adipocyte differentiation or studying the interaction of adipocytes and other cell types like endothelial cells. In vitro 3D adipose tissue models support discoveries into the mechanisms of adipose-related diseases and thus support the development of novel anti-cancer or anti-obesity/diabetes therapies.

Exercise regulates lipid droplet dynamics in normal and fatty liver

Lipids droplets (LD) are dynamics organelles that accumulate neutral lipids during nutrient surplus. LD alternates between periods of growth and consumption through regulated processes including as de novo lipogenesis, lipolysis and lipophagy. The liver is a central tissue in the regulation of lipid metabolism. Non-Alcoholic Fatty Liver Diseases (NAFLD) is result of the accumulation of LD in liver. Several works have been demonstrated a positive effect of exercise on reduction of liver fat. However, the study of the exercise on liver LD dynamics is far from being understood. Here we investigated the effect of chronic exercise in the regulation of LD dynamics using a mouse model of high fat diet-induced NAFLD. Mice were fed with a high-fat diet or control diet for 12 weeks; then groups were divided into chronic exercise or sedentary for additional 8 weeks. Our results showed that exercise reduced fasting glycaemia, insulin and triacylglycerides, also liver damage. However, exercise did not affect the intrahepatic triacylglycerides levels and the number of LD but reduced their size. In addition, exercise decreased the SREBP-1c levels, without changes in lipolysis, mitochondrial proteins or autophagy/lipophagy markers. Unexpectedly in the control mice, exercise increased the number of LD, also PLIN2, SREBP-1c, FAS, ATGL, HSL and MTTP levels. Our findings show that exercise rescues the liver damage in a model of NAFLD reducing the size of LD and normalizing protein markers of de novo lipogenesis and lipolysis. Moreover, exercise increases proteins associated to LD dynamics in the control mice.

Voluntary exercise in mice fed an obesogenic diet alters the hepatic immune phenotype and improves metabolic parameters - an animal model of life style intervention in NAFLD

Reproducible animal models to recapitulate the pathophysiology of non-alcoholic fatty liver disease (NAFLD) are urgently required to improve the understanding of the mechanisms of liver injury and to explore novel therapeutic options. Current guidelines recommend life-style interventions as first-line therapy for NAFLD and these types of intervention are considered standard-of-care. The current study establishes a reproducible mouse model of a life-style intervention in NAFLD using voluntary wheel running (VWR). Male C57BL/6J mice were fed a high-fat, high-carbohydrate diet (HFD) to induce NAFLD or a corresponding control diet for 12 weeks. Starting at week 9 of the obesogenic NAFLD diet, mice were randomized to either free access to a running wheel or being single caged resembling a sedentary (SED) life-style. VWR induced a transient weight reduction in HFD-fed mice up until week 10. In contrast to the SED mice, VWR mice exhibited normal ALT at the end of the intervention, while the metabolic alterations including elevated fasting glucose, insulin, triglyceride, and total cholesterol levels remained almost unchanged. Additionally, VWR prevented HFD-induced hepatic steatosis by alterations in key liver metabolic processes including the induction of fatty acid β-oxidation and lipogenesis inhibition following increased AMP-activated protein kinase (AMPK)-α activity. Phosphorylation of the serine kinase Akt in hepatic tissue was enhanced following VWR. Furthermore, VWR mice were protected from HFD-induced expression of pro-inflammatory cytokines, chemokines and liver macrophage infiltration. The SED/HFD group exhibited increasing activity of hepatic nuclear factor (NF)-κB p65, which was absent following exercise in the VWR/HFD group. In summary, in an obesogenic mouse model of NAFLD physical exercise improves fatty acid and glucose homeostasis and protects from macrophage-associated hepatic inflammation.

Mechanisms of obesity-induced metabolic and vascular dysfunctions

Obesity has reached epidemic proportions and its prevalence is climbing. Obesity is characterized by hypertrophied adipocytes with a dysregulated adipokine secretion profile, increased recruitment of inflammatory cells, and impaired metabolic homeostasis that eventually results in the development of systemic insulin resistance, a phenotype of type 2 diabetes. Nitric oxide synthase (NOS) is an enzyme that converts L-arginine to nitric oxide (NO), which functions to maintain vascular and adipocyte homeostasis. Arginase is a ureohydrolase enzyme that competes with NOS for L-arginine. Arginase activity/expression is upregulated in obesity, which results in diminished bioavailability of NO, impairing both adipocyte and vascular endothelial cell function. Given the emerging role of NO in the regulation of adipocyte physiology and metabolic capacity, this review explores the interplay between arginase and NO, and their effect on the development of metabolic disorders, cardiovascular diseases, and mitochondrial dysfunction in obesity. A comprehensive understanding of the mechanisms involved in the development of obesity-induced metabolic and vascular dysfunction is necessary for the identification of more effective and tailored therapeutic avenues for their prevention and treatment.

Therapeutic and preventive effects of exercise on cardiometabolic parameters in aging and obese rats

BACKGROUND AND AIMS

Aging, obesity and sedentarism are among the most important predictors of cardiometabolic diseases. Aiming to reduce the impact of the combination of these three factors, we tested the therapeutic and preventive effects of exercise in aging and obese rats on the following cardiometabolic disease risk parameters: body fat, blood pressure, blood lipids, and glycemic homeostasis.

METHODS

Eighteen male Wistar rats (initial age = 4 months, and final age = 14 months) were randomly distributed into three aging and obese groups: sedentary, therapeutic exercise and preventive exercise. Food and caloric intake, body adiposity, muscle mass, cardiovascular parameters, biochemical markers, glycemic homeostasis, and gene expression of insulin-dependent, insulin-independent and insulin resistance pathways in skeletal muscle were evaluated.

RESULTS

Therapeutic and preventive exercises were associated with higher food and caloric intake, and expression of TBC1D1 in the soleus muscle, as well as lower total cholesterol/HDL and LDL/HDL ratios, glucose levels at the end (90 min) of the glucose tolerance test and IKBKB expression in the gastrocnemius and soleus muscles. Only the preventive exercise improved the cardiovascular and body composition parameters, glucose tolerance, insulin resistance and insulin sensitivity, besides reducing total cholesterol, triglycerides, triglycerides/HDL ratio, plasmatic insulin and MAPK8 expression in soleus. The preventive exercise group also presented greater expression of INRS, IRS1, IRS2, PIK3CA, AKT1, and SLC2A4 in gastrocnemius and soleus, TBC1D1 in gastrocnemius, and AKT2 and PRKAA1 in soleus.

CONCLUSIONS

Therapeutic exercise promoted some improvements on cardiometabolic parameters in aging and obese rats, however, the best benefits were achieved through the preventive exercise.

Mouse models of non-alcoholic steatohepatitis: A reflection on recent literature

Non-alcoholic steatohepatitis (NASH) is strongly associated with overnutrition, insulin resistance, and predisposition to type 2 diabetes. To critically analyze the translational significance of currently used animal models of NASH, we reviewed articles published during the last 3 years that studied NASH pathogenesis using mouse models. Among 146 articles, 34 (23%) used models in which overnutrition was reported, and 36 (25%) demonstrated insulin resistance, with or without glucose intolerance. Half the articles contained no information on whether mice exhibited overnutrition or insulin resistance. While 75 papers (52%) reported > 2-fold increase of serum/plasma alanine aminotransferase (ALT) compared with controls, ALT levels were near normal or not reported in 48%. Liver pathology was assessed by a pathologist with an interest in liver pathology in 53% of articles published in gastroenterology/hepatology journals, versus 43-44% in other journals. While there appears to be a trend to use models that are potentially relevant to the pathogenesis of human NASH, journals currently publish data on mouse models in which overnutrition and insulin resistance do not occur, without ALT increase or appropriate analysis of NASH pathology. We recommend that investigators, reviewers, and journal editors carefully consider the validity of NASH models in current use and that moves are made to reach a consensus on what the minimal criteria should be.

Novel therapeutic drug identification and gene correlation for fatty liver disease using high-content screening: Proof of concept

Non-alcoholic fatty liver disease (NAFLD) is a problem in obese people caused by increasing intake of high-calorie food such as fructose implicated in the elevated prevalence. It is necessary to identify novel drugs to develop effective therapies. In this study, we combined LOPAC® (The Library of Pharmacologically Active Compounds) and High-Content screening to identify compounds that significantly reduced intracellular lipid droplets (LD) after high fat medium (HFM) treatment. Among 1280 compounds, we identified 239 compounds that reduced LD by >50%. Of these, 17 maintained cell viability. Nine of them were selected for validation using normal primary hepatocytes, of which five compounds showed dose-dependent efficacy. Whole genome transcriptomic network analysis was performed to construct the underlying regulatory network. There were 831 (711 up-regulated and 120 down-regulated genes) and 3480 (2009 up-regulated and 1471 down-regulated genes) genes that showed a significant change (>2-fold; p < 0.05) after 12 and 24 h HFM treatment, respectively. Gene enrichment and pathway analysis showed several immune responses mediated by MIF, IL-17, TLR, and IL-6. These compounds modulate lipogenesis via GSK3β and CREB1, which is followed by an alteration in the expression of several downstream genes related to hepatocellular carcinoma and hepatitis. CREB1 is a core transcription factor and may be a potential therapeutic target for liver disease. In conclusion, this proof of concept provides a strategy for identifying novel drugs for treatment of fatty liver disease as well as elucidates their underlying mechanisms. This research provides opportunity for developing future pharmaceutical therapeutics.

Exercise-induced 'browning' of adipose tissues

Global rates of obesity continue to rise and are necessarily the consequence of a long-term imbalance between energy intake and energy expenditure. This is the result of an expansion of adipose tissue due to both the hypertrophy of existing adipocytes and hyperplasia of adipocyte pre-cursors. Exercise elicits numerous physiological benefits on adipose tissue, which are likely to contribute to the associated cardiometabolic benefits. More recently it has been demonstrated that exercise, through a range of mechanisms, induces a phenotypic switch in adipose tissue from energy storing white adipocytes to thermogenic beige adipocytes. This has generated the hypothesis that the process of adipocyte 'browning' may partially underlie the improved cardiometabolic health in physically active populations. Interestingly, 'browning' also occurs in response to various stressors and could represent an adaptive response. In the context of exercise, it is not clear whether the appearance of beige adipocytes is metabolically beneficial or whether they occur as a transient adaptive process to exercise-induced stresses. The present review discusses the various mechanisms (e.g. fatty acid oxidation during exercise, decreased thermal insulation, stressors and angiogenesis) by which the exercise-induced 'browning' process may occur.

Causes and mechanisms of adipocyte enlargement and adipose expansion

Adipose tissue plays a significant role in whole body energy homeostasis. Obesity-associated diabetes, fatty liver and metabolic syndrome are closely linked to adipose stress and dysfunction. Genetic predisposition, overeating and physical inactivity influence the expansion of adipose tissues. Under conditions of constant energy surplus, adipocytes become hypertrophic and adipose tissues undergo hyperplasia so as to increase their lipid storage capacity, thereby keeping circulating blood glucose and fatty acids below toxic levels. Nonetheless, adipocytes have a saturation point where they lose capacity to store more lipids. At this stage, when adipocytes are fully lipid-engorged, they express stress signals. Adipose depots (particularly visceral compartments) from obese individuals with a severe metabolic phenotype are characterized by the high proportion of hypertrophic adipocytes. This review focuses on the mechanisms of adipocyte enlargement in relation to adipose fatty acid and cholesterol metabolism, and considers how this may be related to adipose dysfunction.

Pathogenesis of NASH: How Metabolic Complications of Overnutrition Favour Lipotoxicity and Pro-Inflammatory Fatty Liver Disease

Overnutrition, usually with obesity and genetic predisposition, lead to insulin resistance, which is an invariable accompaniment of nonalcoholic fatty liver disease (NAFLD). The associated metabolic abnormalities, pre- or established diabetes, hypertension and atherogenic dyslipidemia (clustered as metabolic syndrome) tend to be worse for nonalcoholic steatohepatitis (NASH), revealing it as part of a continuum of metabolic pathogenesis. The origins of hepatocellular injury and lobular inflammation which distinguish NASH from simple steatosis have intrigued investigators, but it is now widely accepted that NASH results from liver lipotoxicity. The key issue is not the quantity of liver fat but the type(s) of lipid molecules that accumulate, and how they are "packaged" to avoid subcellular injury. Possible lipotoxic mediators include free (unesterified) cholesterol, saturated free fatty acids, diacylglycerols, lysophosphatidyl-choline, sphingolipids and ceramide. Lipid droplets are intracellular storage organelles for non-structural lipid whose regulation is influenced by genetic polymorphisms, such as PNPLA3. Cells unable to sequester chemically reactive lipid molecules undergo mitochondrial injury, endoplasmic reticulum (ER) stress and autophagy, all processes of interest for NASH pathogenesis. Lipotoxicity kills hepatocytes by apoptosis, a highly regulated, non-inflammatory form of cell death, but also by necrosis, necroptosis and pyroptosis; the latter involve mitochondrial injury, oxidative stress, activation of c-Jun N-terminal kinase (JNK) and release of danger-associated molecular patterns (DAMPs). DAMPs stimulate innate immunity by binding pattern recognition receptors, such as Toll-like receptor 4 (TLR4) and the NOD-like receptor protein 3 (NLRP3) inflammasome, which release a cascade of pro-inflammatory chemokines and cytokines. Thus, lipotoxic hepatocellular injury attracts inflammatory cells, particularly activated macrophages which surround ballooned hepatocytes as crown-like structures. In both experimental and human NASH, livers contain cholesterol crystals which are a second signal for NLRP3 activation; this causes interleukin (IL)-1β and IL18 secretion to attract and activate macrophages and neutrophils. Injured hepatocytes also liberate plasma membrane-derived extracellular vesicles; these have been shown to circulate in NASH and to be pro-inflammatory. The way metabolic dysfunction leads to lipotoxicity, innate immune responses and the resultant pattern of cellular inflammation in the liver are likely also relevant to hepatic fibrogenesis and hepatocarcinogenesis. Pinpointing the key molecules involved pharmacologically should eventually lead to effective pharmacotherapy against NASH.

Physical exercise remodels visceral adipose tissue and mitochondrial lipid metabolism in rats fed a high-fat diet

We aimed to investigate the effects of two physical exercise models, voluntary physical activity (VPA) and endurance training (ET) as preventive and therapeutic strategies, respectively, on lipid accumulation regulators and mitochondrial content in VAT of rats fed a high-fat diet (HFD). Sprague-Dawley rats (6 weeks old, n=60) were assigned into sedentary and VPA groups fed isoenergetic diets: standard (S, 35 kcal% fat) or HFD (71 kcal% fat). The VPA groups had free access to wheel running during the entire protocol. After 9 weeks, half of the sedentary animals were exercised on a treadmill while maintaining the dietary treatments. The HFD induced no changes in plasma non-esterified fatty acids (NEFA) and glycerol levels and decreased oxidative phosphorylation (OXPHOS) subunit IV and increased truncated/full-length sterol regulatory element-binding transcription factor 1c (SREBP1c) ratio in epididymal white adipose tissue (eWAT). VPA decreased plasma glycerol levels, aquaglyceroporin 7 (AQP7) and increased subunit I of cytochrome c oxidase (COX) protein, in standard diet fed animals. Eight weeks of ET decreased body weight, visceral adiposity and adipocyte size and plasma NEFA and glycerol levels, as well as AQP7 protein expression in eWAT. ET increased fatty acid translocase (FAT/CD36), mitochondrial content of complexes IV and V subunits, mitochondrial biogenesis and dynamic (mitofusins and optic atrophy 1)-related proteins. Moreover, lipogenesis-related markers (SREBP1c and acetyl CoA carboxylase) were reduced after 8 weeks of ET. In conclusion, ET-induced alterations reflect a positive effect on mitochondrial function and the overall VAT metabolism of HFD-induced obese rats.

The selective peroxisome proliferator-activated receptor-delta agonist seladelpar reverses nonalcoholic steatohepatitis pathology by abrogating lipotoxicity in diabetic obese mice

Lipotoxicity associated with insulin resistance is central to nonalcoholic steatohepatitis (NASH) pathogenesis. To date, only weight loss fully reverses NASH pathology, but mixed peroxisome proliferator–activated receptor‐alpha/delta (PPAR‐α/δ) agonists show some efficacy. Seladelpar (MBX‐8025), a selective PPAR‐δ agonist, improves atherogenic dyslipidemia. We therefore used this agent to test whether selective PPAR‐δ activation can reverse hepatic lipotoxicity and NASH in an obese, dyslipidemic, and diabetic mouse model. From weaning, female Alms1 mutant (foz/foz) mice and wild‐type littermates were fed an atherogenic diet for 16 weeks; groups (n = 8‐12) were then randomized to receive MBX‐8025 (10 mg/kg) or vehicle (1% methylcellulose) by gavage for 8 weeks. Despite minimally altering body weight, MBX‐8025 normalized hyperglycemia, hyperinsulinemia, and glucose disposal in foz/foz mice. Serum alanine aminotransferase ranged 300‐600 U/L in vehicle‐treated foz/foz mice; MBX‐8025 reduced alanine aminotransferase by 50%. In addition, MBX‐8025 normalized serum lipids and hepatic levels of free cholesterol and other lipotoxic lipids that were increased in vehicle‐treated foz/foz versus wild‐type mice. This abolished hepatocyte ballooning and apoptosis, substantially reduced steatosis and liver inflammation, and improved liver fibrosis. In vehicle‐treated foz/foz mice, the mean nonalcoholic fatty liver disease activity score was 6.9, indicating NASH; MBX‐8025 reversed NASH in all foz/foz mice (nonalcoholic fatty liver disease activity score 3.13). Conclusion: Seladelpar improves insulin sensitivity and reverses dyslipidemia and hepatic storage of lipotoxic lipids to improve NASH pathology in atherogenic diet–fed obese diabetic mice. Selective PPAR‐δ agonists act independently of weight reduction, but counter lipotoxicity related to insulin resistance, thereby providing a novel therapy for NASH. (Hepatology Communications 2017;1:663–674)

Voluntary distance running prevents TNF-mediated liver injury in mice through alterations of the intrahepatic immune milieu

Physical activity confers a broad spectrum of health benefits. Beyond the obvious role in metabolically driven diseases, the role of physical activity in acute liver injury is poorly explored. To study the role of physical activity in acute liver injury, a novel model of voluntary distance running in mice was developed and mice were subjected to acute liver injury induced by N-galactosamine (GalN) and lipopolysaccharide (LPS). Analyses included histological stains, immunoblotting, qRT-PCR and FACS analysis. Voluntary distance running increased to an average of 10.3 km/day after a learning curve. Running lead to a decrease in the absolute numbers of intrahepatic CD4+ T and B lymphocytes and macrophages after 7 weeks. In parallel, hepatic mRNA expression of inflammatory cytokines including IL-6 and IL-1beta, TGF-beta and monocyte chemoattractant protein-1 (MCP-1/CCL2) were suppressed, while TNF-α was not affected by exercise. Likewise, expression of the macrophage-specific antigen F4/80 was downregulated 1.6-fold from exercise. Notably, acute liver injury from GaIN/LPS was significantly blunted following 7 weeks of voluntary exercise as determined by liver histology, a 84.6% reduction of alanine aminotransferase (P<0.01) and a 54.6% reduction of aspartate aminotransferase (P<0.05) compared with sedentary mice. Additionally, proinflammatory cytokines, activation of caspase 3 and JNK were significantly lower, while antiapoptotic protein A20 increased. Voluntary distance running alters the intrahepatic immune phenotype producing an environment that is less susceptible to acute liver injury.

Exercise effects on perivascular adipose tissue: endocrine and paracrine determinants of vascular function

Obesity is a global epidemic, accompanied by increased risk of type 2 diabetes and cardiovascular disease. Adipose tissue hypertrophy is associated with adipose tissue inflammation, which alters the secretion of adipose tissue-derived bioactive products, known as adipokines. Adipokines determine vessel wall properties such as smooth muscle tone and vessel wall inflammation. Exercise is a mainstay of prevention of chronic, non-communicable diseases, type 2 diabetes and cardiovascular disease in particular. Aside from reducing adipose tissue mass, exercise has been shown to reduce inflammatory activity in this tissue. Mechanistically, contracting muscles release bioactive molecules known as myokines, which alter the metabolic phenotype of adipose tissue. In adipose tissue, myokines induce browning, enhance fatty acid oxidation and improve insulin sensitivity. In the past years, the perivascular adipose tissue (PVAT) which surrounds the vasculature, has been shown to control vascular tone and inflammation through local release of adipokines. In obesity, an increase in mass and inflammation of PVAT culminate in dysregulation of adipokine secretion, which contributes to vascular dysfunction. This review describes our current understanding of the mechanisms by which active muscles interact with adipose tissue and improve vascular function. Aside from the exercise-dependent regulation of canonical adipose tissue function, we will focus on the interactions between skeletal muscle and PVAT and the role of novel myokines, such as IL-15, FGF21 and irisin, in these interactions.

LINKED ARTICLES

This article is part of a themed section on Molecular Mechanisms Regulating Perivascular Adipose Tissue - Potential Pharmacological Targets? To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.20/issuetoc.

Habitual physical activity protects against lipopolysaccharide-induced inflammation in mouse adipose tissue

Sepsis is a systemic inflammatory response to infection, with no preventative strategies. In this study, we identify a role for habitual physical activity in the prevention of adipose tissue inflammation induced by a model of sepsis, lipopolysaccharide (LPS). Male C57BL/6J mice (8 weeks old) were housed with access to voluntary wheel running (VWR) or sedentary (SED) for 10 weeks. Mice were then injected with LPS (2 mg/kg) or saline (SAL), and tissues were removed 6 hours post-injection. VWR attenuated body, epididymal adipose tissue (eWAT), and subcutaneous inguinal adipose tissue (iWAT) mass gain, improved glucose tolerance, increased markers of mitochondrial biogenesis in iWAT and eWAT, and increased UCP-1 protein content in iWAT. In iWAT, VWR attenuated the LPS induced increase in mRNA expression of TNF-α, MCP-1, and follistatin, along with phosphorylation of STAT3. In addition, VWR had a main effect for reducing iWAT mRNA expression of IL-1β, IL-6, and SOCS3. In eWAT, VWR had a main effect for reducing mRNA expression of IL-1β, MCP-1, IL-6, and follistatin. Further, VWR increased SOCS3 mRNA expression and phosphorylation of STAT3 in SAL mice, thus the relative change in response to LPS for these markers was attenuated. The protective effect of prior physical activity occurred in conjunction with increases in the protein content of a component of the LPS binding complex, MyD88. Overall, the results from this study demonstrate that habitual physical activity can attenuate the LPS induced inflammatory response in adipose tissue and this occurs to a greater extent in iWAT compare with eWAT.

Obeticholic acid improves adipose morphometry and inflammation and reduces steatosis in dietary but not metabolic obesity in mice

OBJECTIVE

Nonalcoholic steatohepatitis (NASH) is the outcome of interactions between overnutrition, energy metabolism, and adipose function. Obeticholic acid (OCA) improves steatosis in patients but for unknown reasons does not resolve NASH pathology. This study therefore investigated OCA effects in Wt mice, which develop obesity with atherogenic dietary feeding, and appetite-dysregulated, Alms1 mutant foz/foz mice fed the same diet, which develop metabolic obesity and diabetes.

METHODS

OCA (1 mg/kg) was administered orally to female foz/foz mice and Wt littermates from weaning until 28 weeks. Adipose indices, glucose tolerance, and fatty liver pathology were studied. Experiments were repeated with OCA 10 mg/kg.

RESULTS

OCA reduced body weight and hepatic lipids and improved glucose disposal only in Wt mice. OCA limited Wt adipose expansion, altered morphometry in favor of small adipocytes, enhanced expression of genes indicating adipose browning, and reduced crown-like structure number in visceral adipose tissue. foz/foz mice showed more crown-like structures in all compartments; OCA failed to alter adipose morphometry, browning, inflammation, or improve NASH severity, even at 10 mg/kg.

CONCLUSIONS

OCA improved adipose indices, glucose tolerance, and steatosis in a milder metabolic phenotype but failed to improve these factors in morbidly obese diabetic mice. These results help explain OCA's limited efficacy to reverse human NASH.

'Browning' the cardiac and peri-vascular adipose tissues to modulate cardiovascular risk

Excess visceral adiposity, in particular that located adjacent to the heart and coronary arteries is associated with increased cardiovascular risk. In the pathophysiological state, dysfunctional adipose tissue secretes an array of factors modulating vascular function and driving atherogenesis. Conversely, brown and beige adipose tissues utilise glucose and lipids to generate heat and are associated with improved cardiometabolic health. The cardiac and thoracic perivascular adipose tissues are now understood to be composed of brown adipose tissue in the healthy state and undergo a brown-to-white transition i.e. during obesity which may be a driving factor of cardiovascular disease. In this review we discuss the risks of excess cardiac and vascular adiposity and potential mechanisms by which restoring the brown phenotype i.e. “re-browning” could potentially be achieved in clinically relevant populations.

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Epicardial, paracardial and thoracic perivascular adipose tissues resemble BAT at birth.

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Despite ‘whitening’ in early life these depots remain metabolically active and potentially thermogenic into adulthood.

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Obesity induces further ‘whitening’ and inflammation in these depots likely driving the atherogenesis.

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Maintaining or inducing the brown phenotype in these depots could prevent atherosclerotic disease.

Exercise-Induced Release of Pharmacologically Active Substances and Their Relevance for Therapy of Hepatic Injury

Chronic liver disease (CLD) features constant parenchymal injury and repair together with an increasing hepatic impairment, finally leading to fibrosis and cirrhosis and a heightened risk of hepatocellular carcinoma (HCC). Closely related to the rise in obesity, the worldwide prevalence of nonalcoholic fatty liver disease, the most common form of CLD, has reached an epidemic dimension and is estimated to afflict up to 46% of the general population, including more than one out of three U.S. citizens. Up to now there is no effective drug treatment available, which is why recommendations encompass both exercise programs and changes in dietary habits. Exercise is well-known for unleashing potent anti-inflammatory effects, which can principally counteract liver inflammation and chronic low-grade inflammation. This review article summarizes the underlying mechanisms responsible for the exercise-mediated anti-inflammatory effects, illustrates the application in animal models as well as in humans, and highlights the therapeutic value when possible. Based on the available results there is no doubt that exercise can even be beneficial in an advanced stage of liver disease and it is the goal of this review article to provide evidence for the therapeutic impact on fibrosis, cirrhosis, and HCC and to assess whether exercise might be of value as adjuvant therapy in the treatment of CLD. In principle, all exercise programs carried out in these high-risk patients should be guided and observed by qualified healthcare professionals to guarantee the patients’ safety. Nevertheless, it is also necessary to additionally determine the optimal amount and intensity of exercise to maximize its value, which is why further studies are essential.

Interference effect of oral administration of mulberry branch bark powder on the incidence of type II diabetes in mice induced by streptozotocin

Background

Diabetes is a group of metabolic diseases that has become a global health problem worldwide. Many researchers have found that mulberry branches have a hypoglycemic effect, but there have been few studies or investigations regarding the use of mulberry branches to prevent the incidence of diabetes.

Objective

This study aimed to investigate the potential preventive effect of mulberry branch bark powder (MBBP) from Morus multicaulis L against type II diabetes in mice induced by streptozotocin (STZ).

Design

The normal mice were fed a diet containing 2.5, 5.0, and 10.0%, MBBP, respectively, for 2 weeks. After that, STZ (100 mg/kg) was injected into the caudal vein of these mice. These mice continued to be fed the same diet, and the fasting blood glucose (FBG) levels were monitored on the 17th and 21st days.

Results

Oral administration of MBBP could effectively inhibit weight loss and maintain the FBG level. The incidence of diabetes in mice was almost inhibited by treatment with 10% MBBP. MBBP could also maintain the original antioxidant capacity and regulate the lipid metabolism in mice. An immunohistochemical assay showed that MBBP could prevent the injury of the insulin-secreting islet beta cells induced by STZ. RT-PCR also confirmed that the mRNA expression of the genes PI3K, Pdk1, Akt, and FoxO1, which were involved in the PI3K/Akt signaling pathway, hardly suffered from STZ in the 10% MBBP-dose group.

Conclusions

Our results indicate that powdered mulberry branch bark has a powerful anti-diabetic effect. These results clearly illustrated that MBBP has a potential use as a health food additive in the prevention of diabetes.

Exercise Decreases Lipogenic Gene Expression in Adipose Tissue and Alters Adipocyte Cellularity during Weight Regain After Weight Loss

Exercise is a potent strategy to facilitate long-term weight maintenance. In addition to increasing energy expenditure and reducing appetite, exercise also favors the oxidation of dietary fat, which likely helps prevent weight re-gain. It is unclear whether this exercise-induced metabolic shift is due to changes in energy balance, or whether exercise imparts additional adaptations in the periphery that limit the storage and favor the oxidation of dietary fat. To answer this question, adipose tissue lipid metabolism and related gene expression were studied in obese rats following weight loss and during the first day of relapse to obesity. Mature, obese rats were weight-reduced for 2 weeks with or without daily treadmill exercise (EX). Rats were weight maintained for 6 weeks, followed by relapse on: (a) ad libitum low fat diet (LFD), (b) ad libitum LFD plus EX, or (c) a provision of LFD to match the positive energy imbalance of exercised, relapsing animals. 24 h retention of dietary- and de novo-derived fat were assessed directly using ¹⁴C palmitate/oleate and ³H₂0, respectively. Exercise decreased the size, but increased the number of adipocytes in both retroperitoneal (RP) and subcutaneous (SC) adipose depots, and prevented the relapse-induced increase in adipocyte size. Further, exercise decreased the expression of genes involved in lipid uptake (CD36 and LPL), de novo lipogenesis (FAS, ACC1), and triacylglycerol synthesis (MGAT and DGAT) in RP adipose during relapse following weight loss. This was consistent with the metabolic data, whereby exercise reduced retention of de novo-derived fat even when controlling for the positive energy imbalance. The decreased trafficking of dietary fat to adipose tissue with exercise was explained by reduced energy intake which attenuated energy imbalance during refeeding. Despite having decreased expression of lipogenic genes, the net retention of de novo-derived lipid was higher in both the RP and SC adipose of exercising animals compared to their energy gap-matched controls. Our interpretation of this data is that much of this lipid is being made by the liver and subsequently trafficked to adipose tissue storage. Together, these concerted effects may explain the beneficial effects of exercise on preventing weight regain following weight loss.