Fatty acid-induced inflammation and insulin resistance in skeletal muscle and liver

NLRP3 inflammasome mediate palmitate-induced endothelial dysfunction

AIMS

Free fatty acids (FFA) is a key contributor to insulin resistance and endothelial dysfunction. However, the precise mechanism underlying the role of FFA remains elusive. This study aimed to investigate the role of NLRP3 (NOD-like receptor pyrin domain containing-3) inflammasome in FFA induced endothelial dysfunction.

MAIN METHODS

HUVECs were transfected with NLRP3 siRNA and then stimulated with LPS and palmitate. C57 BL/6 J mice transfected with NLRP3 Lenti-Virus were fed with a high-fat diet (HFD). The levels of NLRP3 inflammasome, AMPKα (AMP-activated protein kinase), endothelial nitric oxide synthase (eNOS) and the activity of the insulin signal pathway, in endothelial cells were determined via Western blotting. Endothelial function was determined by measuring the level of endothelium-dependent vasodilatation.

KEY FINDINGS

FFA could activate NLRP3 inflammasome and induce IL-1β release both in vitro. and in vivo. Using siRNA and Lenti-Virus to inhibit NLRP3 abolished palmitate-induced IL-1β release and restored impaired phosphorylation of IRS-1 (Tyr), Akt (Ser473) and eNOS (Ser1177) and ACh-mediated endothelium-dependent vasorelaxation induced by palmitate. AMPKα activator AICAR(5-aminoimidazole-4-carbox-amide-1-β-d-ribofuranoside) inhibited NLRP3 inflammasome activation and decreased IL-1β release and restored impaired insulin signal pathway induced by palmitate.

SIGNIFICANCE

NLRP3 inflammasome activation via AMPKα inactivation mediated palmitate-induced endothelial dysfunction through involves IL-1β-induced insulin signal pathway.

Retrospective Evaluation of an Online Diabetes Health Coaching Program: A Pilot Study

An estimated one third of American adults have prediabetes; over 30 million have type 2 diabetes mellitus. Health and wellness coaching is an emerging tool for preventing and treating chronic disease. Mastering Diabetes (MD) promotes a low-fat, plant-based, whole-food diet, utilizing online education, day-to-day accountability and support, and video conferencing. This pilot study provides a retrospective view of the effectiveness of MD to treat diabetes. Current and former clients of MD were invited to participate in a survey. On completion of the online consent, subjects were asked a series of questions in a REDCap-based survey: age, gender, enrollment date in MD, changes in weight, HbA1c, medication use, overall health, and current level of adherence to achieved changes. Overall, 253 (8.9%) participants responded to the survey; 80.6% were females, mean age was 56 years. Most of those responding (78.4%, P < .001) reported weight loss; 68.8% (P < .001) reported decreased HbA1c; 52.4% reported decreased medication use; 86.8% reported continued health improvement since having participated in MD; and 83.5% found the online program very helpful. This study demonstrated improvement in HbA1c and weight in participants in an online health and wellness coaching. Study limitations prevent drawing generalizable conclusions; further prospective evaluation is needed.

Ghrelin Signaling in Immunometabolism and Inflamm-Aging

Intracellular changes in immune cells lead to metabolic dysfunction, which is termed immunometabolism. Chronic inflammation is a hallmark of aging; this phenomenon is described as inflamm-aging. Immunometabolism and inflamm-aging are closely linked to obesity, insulin resistance, type 2 diabetes (T2D), cardiovascular diseases, and cancers, which consequently reduce life span and health span of the elderly. Ghrelin is an orexigenic hormone that regulates appetite and food intake. Ghrelin's functions are mediated through its receptor, growth hormone secretagogue receptor (GHS-R). Ghrelin and GHS-R have important roles in age-associated obesity, insulin resistance, and T2D. In this chapter, we have discussed the roles of ghrelin signaling in diet-induced obesity and normal aging as it relates to energy metabolism and inflammation in key metabolic tissues and organs. The new findings reveal that ghrelin signaling is an important regulatory mechanism for immunometabolism and inflamm-aging. Ghrelin signaling offers an exciting novel therapeutic strategy for treatment of obesity and insulin resistance of the elderly.

Transplantation of neuregulin 4-overexpressing adipose-derived mesenchymal stem cells ameliorates insulin resistance by attenuating hepatic steatosis

IMPACT STATEMENT

Due to high-fat and high-sugar diets accompanied by sedentary lifestyles, diabetes has become a global epidemic. Literature findings suggest a potential therapeutic effect of Nrg4 on treating obesity-related metabolic disorders including type 2 diabetes (T2D). Adipose tissue-derived MSCs (ADSCs) were used in our study as they are abundant and can be harvested with minimally invasive procedures. In the end, our study reveals that ADSC transplantation improves glucose tolerance and metabolic balance in HFD-fed mice by multiple mechanisms, including upregulating GLUT4 expression and suppressing inflammation. More importantly, our study shows that Nrg4 overexpression could improve the efficacy of ADSCs in ameliorating insulin resistance (IR) and other obesity-related metabolic disorders, given the function of Nrg4 in attenuating hepatic lipogenesis. It would provide a new therapeutic strategy for the treatment of obesity, IR, and T2D.

High level of dietary soybean oil affects the glucose and lipid metabolism in large yellow croaker Larimichthys crocea through the insulin-mediated PI3K/AKT signaling pathway

The present study was conducted to investigate the metabolic responses of glucose and lipid in large yellow croaker Larimichthys crocea (initial weight, 36.80 ± 0.39 g) to high level of dietary soybean oil. Three isonitrogenous (46% crude protein) and isolipidic (13% crude lipid) experimental diets were designed, with 100% fish oil (FO), 50% fish oil and 50% soybean oil (FS) and 100% soybean oil (SO), respectively. After a 12-week growth trial, the results showed that compared with FO group, contents n-6 PUFAs increased while the n-3 PUFAs decreased significantly both in liver and muscle in FS and SO groups. Concentrations of blood glucose, leptin, free fatty acid and total triglyceride reached the highest values in SO group, while blood insulin showed no significant difference among all groups. The gene expressions of insulin receptor substrate-2, glucose-6-phosphatase, phosphoenolpyruvate carboxykinase, fatty acid synthetase, and lipoprotein lipase increased, and the insulin receptor substrate-1, phosphotidylinsositol-3-kinase (PI3K), hexokinase, glycogen synthetase and glucose transporter 2 in liver decreased significantly in SO group. Meanwhile, the phosphorylation of protein kinase B (AKT) also decreased significantly in this group. These results suggested that high level of dietary soybean oil depressed PI3K/AKT signaling pathway, and then affected glucose and lipid metabolism by glycolysis, gluconeogenesis, glucose transportation, glycogenesis and lipogenesis.

Physical activity for children with chronic disease; a narrative review and practical applications

BACKGROUND

Physical activity (PA) is associated with a diverse range of health benefits. International guidelines suggest that children should be participating in a minimum of 60 min of moderate to vigorous intensity PA per day to achieve these benefits. However, current guidelines are intended for healthy children, and thus may not be applicable to children with a chronic disease. Specifically, the dose of PA and disease specific exercise considerations are not included in these guidelines, leaving such children with few, if any, evidence-based informed suggestions pertaining to PA. Thus, the purpose of this narrative review was to consider current literature in the area of exercise as medicine and provide practical applications for exercise in five prevalent pediatric chronic diseases: respiratory, congenital heart, metabolic, systemic inflammatory/autoimmune, and cancer.

METHODS

For each disease, we present the pathophysiology of exercise intolerance, summarize the pediatric exercise intervention research, and provide PA suggestions.

RESULTS

Overall, exercise intolerance is prevalent in pediatric chronic disease. PA is important and safe for most children with a chronic disease, however exercise prescription should involve the entire health care team to create an individualized program.

CONCLUSIONS

Future research, including a systematic review to create evidence-based guidelines, is needed to better understand the safety and efficacy of exercise among children with chronic disease.

Probiotic Lactobacillus gasseri SBT2055 improves insulin secretion in a diabetic rat model

The probiotic Lactobacillus gasseri SBT2055 (LG2055) has a protective effect against metabolic syndrome in rats and humans. Metabolic syndrome increases the risk of type 2 diabetes mellitus. In this study, Goto-Kakizaki rats were used as a diabetic model and fed diets containing LG2055-fermented or nonfermented skim milk for 4 wk. Indices of diabetes such as blood glucose levels, serum glucagon levels, plasma levels of insulin, C-peptide, and glucagon-like peptide-1, tissue glycogen contents, and pancreatic mRNA levels were measured. The plasma C-peptide levels and pancreatic mRNA levels of insulin genes (Ins1 and Ins2) and Pdx1 (a transcriptional factor of insulin genes) were increased in LG2055 diet-fed rats. The increase in insulin secretion corresponded to an improvement in serum and pancreatic inflammatory status, associated with decreases in serum levels of serum amyloid P and pancreatic levels of granulocyte colony-stimulating factor. Insulin resistance in Goto-Kakizaki rats was ameliorated by increased glycogen storage in the liver and quadriceps femoris muscles and decreased serum free fatty acid levels. This improvement may be related to the increased cecal production of short-chain fatty acids. In conclusion, dietary LG2055 improved insulin secretion in diabetic rats by improving the inflammatory status in the pancreas and serum.

Changes in body composition and metabolic disease risk

As individuals gain weight, they increase the amount of fat that they accrue on their body. This causes adipocytes to enlarge and increases not only subcutaneous fat but also deposits fat in other vulnerable areas of the body. This ectopic fat is deposited in the intra-abdominal visceral fat depot, in muscle, in the liver and in the beta cells. Fat in these locations initiates a dysfunctional state in these insulin-sensitive tissues leading to insulin resistance, the appearance of the Metabolic Syndrome, and an increased risk of developing both type 2 diabetes and cardiovascular disease. A loss of weight and with it a loss of fat decreases this risk.

Blood-based novel biomarkers for nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease has become a social health challenge of global concern. The term nonalcoholic steatohepatitis (NASH) is a more severe condition than simple steatosis and distinguishing NASH from nonalcoholic fatty liver disease is particularly important. Liver biopsy remains a gold standard in diagnosing NASH. Meanwhile, radiological techniques such as ultrasonography and MRI are also applied widely. However, the invasive and expensive examination is not suitable for screening, and there is a great need for reliable and appropriate biomarkers to screen patients for NASH. Based on the current studies of blood-based novel biomarkers, we attempt to summarize the latest findings on biomarkers for NASH, including blood biomarkers encompassing proteins, lipids and miRNAs; the correlation between extracellular vesicles and NASH; and treatment strategies for NASH.

Liraglutide suppresses non-esterified free fatty acids and soluble vascular cell adhesion molecule-1 compared with metformin in patients with recent-onset type 2 diabetes

Background

It has been suggested that liraglutide could have an impact on glucose and lipid metabolism disorder and adhesion molecule activation, which may play important roles in the vascular damage of diabetes. In this study, we examined the effects of liraglutide versus metformin on non-esterified free fatty acids, beta-cell insulin secretion, and adhesion molecule levels in patients with recent-onset type 2 diabetes mellitus.

Methods

In this study, 60 patients newly diagnosed with type 2 diabetes mellitus (mean age 33.97 ± 5.67 years) were randomly assigned to receive once-daily subcutaneous liraglutide or oral metformin. Before the study and after the 8-week treatment period, a 75 g oral glucose tolerance test was performed. Plasma glucose, lipids and lipoprotein, plasma insulin, glycaemic and insulin responses, non-esterified free fatty acids (NEFA), and soluble vascular cell adhesion molecule-1 (sVCAM-1) levels were evaluated.

Results

After 8 weeks, 120 min of NEFA (155 ± 125 vs 99 ± 73 µmol/L, P = 0.026) and the levels of sVCAM-1 (465 ± 136 vs 382 ± 131 ng/ml, P = 0.013) significantly decreased, while the early phase insulin secretion index (24.94 [7.78, 38.89] vs. 31.13 [17.67, 59.09], P = 0.031), fasting plasma insulin (104 [51, 123] vs 113 [54, 171] mIU/L, P = 0.015), 60 min plasma insulin (326 [165, 441] vs 471 [334, 717] mIU/L, P = 0.005), 120 min plasma insulin (401 [193, 560] vs 500 [367, 960] mIU/L, P = 0.047), and insulin area under the curve (AUCins) (648 [321, 742] vs 738 [451, 1118] mIU/L, P = 0.005) remarkably increased for patients in the liraglutide treatment group. The levels of sVCAM-1 dramatically decreased after 8 weeks of liraglutide treatment (503 ± 182 vs 382 ± 131 ng/ml, P = 0.046) compared to that of the metformin treatment group. At the same time, the differences before and after liraglutide treatment in 120 min of NEFA (− 32 [− 96, − 5] vs 5 [− 35, 38] µmol/L, P = 0.033) and AUCins (738 [451, 1118] vs 594 [357, 1216] mIU/L, P = 0.014) were remarkably enhanced compared to that of the metformin therapy. Nevertheless, there were no significant differences in fasting NEFA after liraglutide or metformin treatment. The reduction of 120 min NEFA (ΔNEFA) was positively correlated with the decrease of sVCAM-1 (ΔsVCAM-1) after 8 weeks of liraglutide treatment (r = 0.523, P = 0.003).

Conclusions

Our results demonstrate that liraglutide administration is more effective than metformin in reducing 120 min NEFA and suppressing sVCAM-1 levels for recent-onset type 2 diabetes mellitus. We suggest that this outcome may be because liraglutide is associated with potentiating insulin secretion capacity, inhibiting vascular inflammatory cytokines, and antagonizing atherosclerosis.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0701-4) contains supplementary material, which is available to authorized users.

Palmitic Acid Induces Müller Cell Inflammation that is Potentiated by Co-treatment with Glucose

Chronic hyperglycemia is thought to be the major stimulator of retinal dysfunction in diabetic retinopathy (DR). Thus, many diabetes-related systemic factors have been overlooked as inducers of DR pathology. Cell culture models of retinal cell types are frequently used to mechanistically study DR, but appropriate stimulators of DR-like factors are difficult to identify. Furthermore, elevated glucose, a gold standard for cell culture treatments, yields little to no response from many primary human retinal cells. Thus, the goal of this project was to demonstrate the effectiveness of the free fatty acid, palmitic acid and compare its use alone and in combination with elevated glucose as a stimulus for human Müller cells, a retinal glial cell type that is activated early in DR pathogenesis and uniquely responsive to fatty acids. Using RNA sequencing, we identified a variety of DR-relevant pathways, including NFκB signaling and inflammation, intracellular lipid signaling, angiogenesis, and MAPK signaling, that were stimulated by palmitic acid, while elevated glucose alone did not significantly alter any diabetes-relevant pathways. Co-treatment of high glucose with palmitic acid potentiated the expression of several DR-relevant angiogenic and inflammatory targets, including PTGS2 (COX-2) and CXCL8 (IL-8).

A novel PPARα/γ agonist, propane-2-sulfonic acid octadec-9-enyl-amide, ameliorates insulin resistance and gluconeogenesis in vivo and vitro

Peroxisome proliferator-activated receptor alpha/gamma (PPARα/γ) agonists have emerged as important pharmacological agents for improving insulin action. Propane-2-sulfonic acid octadec-9-enyl-amide (N15) is a novel PPARα/γ dual agonist synthesized in our laboratory. The present study investigates the efficacy and safety of N15 on insulin resistance regulation in high fat diet (HFD)-and streptozotocin (STZ)-induced diabetic mice and in palmitic acid (PA)-induced HepG2 cells. Our results showed that N15 remarkably ameliorated insulin resistance and dyslipidemia in vivo, as well as rectified the glucose consumption and gluconeogenesis in vitro. Moreover, the glucose-lowering effect of N15 was associated with PPARγ mediated up-regulation of hepatic glucose consumption and down-regulation of gluconeogenesis. Meanwhile, N15 exerted advantageous effects on glucose and lipid metabolism without triggering weight gain and hepatotoxicity in mice. In conclusion, our data demonstrated that by alleviating glucose and lipid abnormalities, N15 could be used as a potential prophylactic and therapeutic agent against type 2 diabetes and related metabolic disorders.

Metabolic and molecular changes associated with the increased skeletal muscle insulin action 24-48 h after exercise in young and old humans

The molecular and metabolic mechanisms underlying the increase in insulin sensitivity (i.e. increased insulin-stimulated skeletal muscle glucose uptake, phosphorylation and storage as glycogen) observed from 12 to 48 h following a single bout of exercise in humans remain unresolved. Moreover, whether these mechanisms differ with age is unclear. It is well established that a single bout of exercise increases the translocation of the glucose transporter, GLUT4, to the plasma membrane. Previous research using unilateral limb muscle contraction models in combination with hyperinsulinaemia has demonstrated that the increase in insulin sensitivity and glycogen synthesis 24 h after exercise is also associated with an increase in hexokinase II (HKII) mRNA and protein content, suggesting an increase in the capacity of the muscle to phosphorylate glucose and divert it towards glycogen synthesis. Interestingly, this response is altered in older individuals for up to 48 h post exercise and is associated with molecular changes in skeletal muscle tissue that are indicative of reduced lipid oxidation, increased lipogenesis, increased inflammation and a relative inflexibility of changes in intramyocellular lipid (IMCL) content. Reduced insulin sensitivity (insulin resistance) is generally related to IMCL content, particularly in the subsarcolemmal (SSL) region, and both are associated with increasing age. Recent research has demonstrated that ageing per se appears to cause an exacerbated lipolytic response to exercise that may result in SSL IMCL accumulation. Further research is required to determine if increased IMCL content affects HKII expression in the days after exercise in older individuals, and the effect of this on skeletal muscle insulin action.

Links Between Obesity-Induced Brain Insulin Resistance, Brain Mitochondrial Dysfunction, and Dementia

It is widely recognized that obesity and associated metabolic changes are considered a risk factor to age-associated cognitive decline. Inflammation and increased oxidative stress in peripheral areas, following obesity, are patently the major contributory factors to the degree of the severity of brain insulin resistance as well as the progression of cognitive impairment in the obese condition. Numerous studies have demonstrated that the alterations in brain mitochondria, including both functional and morphological changes, occurred following obesity. Several studies also suggested that brain mitochondrial dysfunction may be one of underlying mechanism contributing to brain insulin resistance and cognitive impairment in the obese condition. Thus, this review aimed to comprehensively summarize and discuss the current evidence from various in vitro, in vivo, and clinical studies that are associated with obesity, brain insulin resistance, brain mitochondrial dysfunction, and cognition. Contradictory findings and the mechanistic insights about the roles of obesity, brain insulin resistance, and brain mitochondrial dysfunction on cognition are also presented and discussed. In addition, the potential therapies for obese-insulin resistance are reported as the therapeutic strategies which exert the neuroprotective effects in the obese-insulin resistant condition.

Dynamic Change in Insulin Resistance Induced by Free Fatty Acids Is Unchanged Though Insulin Sensitivity Improves Following Endurance Exercise in PCOS

Background: Insulin resistance (IR) is the hallmark of PCOS and it is known that exercise may decrease it. What is unknown is whether exercise may mechanistically alter the underlying IR, attenuating the dynamic lipid induced IR in insulin resistant subjects. Methods: 12 women with polycystic ovary syndrome (PCOS) and 10 age and body mass index matched controls completed an 8 week supervised exercise program at 60% maximal oxygen consumption. Before and after the exercise program, all participants underwent hyperinsulinaemic euglycaemic clamps with either saline or intralipid infusions. Skewed data were log transformed and expressed as mean ± SEM. Results: Before exercise, women with PCOS had a higher HOMA-IR and lower VO₂ max than controls. Compared to saline, lipid infusion lowered the rate of insulin stimulated glucose disposal (M value; mg/kg/min) by 67 ± 5% (from 0.5 ± 0.03 to -0.25 ± 0.2, p = 0.01) in PCOS, and by 49 ± 7% (from 0.65 ± 0.06 to 0.3 ± 0.1, p = 0.01) in controls. The M value was significantly less in PCOS compared to controls for both saline (p < 0.01) and lipid (p < 0.05). Endurance exercise in PCOS improved VO₂ max and HOMA-IR, but not weight, to those of pre-exercise control subjects. The glucose disposal rate during the lipid infusion was reduced following exercise in PCOS, indicating decreased IR (67 ± 5 vs. 50 ± 7%, p = 0.02), but IR was not altered in controls (49 ± 7 vs. 45 ± 6%, p = 0.58). The incrementally increased IR induced by the lipid infusion did not differ between controls and PCOS. Conclusion: Insulin sensitivity improved with exercise in the PCOS group alone showing that IR can be modified, though likely transiently. However, the maximal IR response to the lipid infusion did not differ within and between control and PCOS subjects, indicating that the fundamental mechanism underlying insulin resistance was unchanged with exercise. Precis: Maximal insulin resistance induced by lipid infusion determined at baseline and 8 weeks after exercise in control and PCOS women did not differ, though insulin sensitivity increased in PCOS after exercise.

Cold-Induced Brown Adipose Tissue Activity Alters Plasma Fatty Acids and Improves Glucose Metabolism in Men

CONTEXT

Mounting evidence suggests beneficial effects of brown adipose tissue (BAT) activation on glucose and lipid metabolism in humans. It is unclear whether cold-induced BAT activation affects not only insulin sensitivity but also insulin secretion. Likewise, the role in clearing circulating fatty acids (FAs) has not been fully explored.

OBJECTIVE

Exploring the effects of cold-induced BAT activation on insulin sensitivity and secretion, as well as on plasma FA profiles.

DESIGN

Fifteen healthy men participated in a cross-balanced repeated within-subject study with two experimental conditions. Subjects were exposed to thermoneutrality (22°C) and to moderate cold (18.06°C, shivering excluded) by use of a water-perfused whole body suit. Cold-induced BAT activation was quantified by [18F]-fluorodeoxyglucose positron emission tomography-computed tomography in a subset of volunteers. A Botnia clamp procedure was applied to determine pancreatic first phase insulin response (FPIR) and insulin sensitivity. Hormones and metabolites, including 26 specific plasma FAs, were sampled throughout the experiment.

RESULTS

Cold exposure induced BAT activity. Plasma noradrenaline and dopamine concentrations increased in response to cold. Peripheral glucose uptake and insulin sensitivity significantly improved by ∼20%, whereas FPIR remained stable. Lignoceric acid (C24:0) concentrations increased, whereas levels of eicosanoic acid (C20:1n9), nervonic acid (C24:1n9), and behenic acid (C22:0) decreased.

CONCLUSIONS

Cold-exposure induces sympathetic nervous system activity and BAT metabolism in humans, resulting in improved glucose metabolism without affecting pancreatic insulin secretion. In addition, BAT activation is associated with altered circulating concentrations of distinct FAs. These data support the concept that human BAT metabolism significantly contributes to whole body glucose and lipid utilization in a coordinated manner.

Serum oxLDL-β2GPI complex reflects metabolic syndrome and inflammation in adipose tissue in obese

BACKGROUND/OBJECTIVES

OxLDL-β2GPI complex has been suggested to have a role in the development of atherosclerosis and other inflammatory diseases. The aim of this study was to investigate the possible association of circulating oxLDL-β2GPI with obesity-induced inflammatory state of adipose tissue and related comorbidities as metabolic syndrome development.

SUBJECTS/METHODS

Two cohorts of subjects were examined in the study. Cohort I: 36 women with wide range of body mass index (17-48 kg m^-2) and metabolic status (with or without metabolic syndrome (MS); cohort II: 20 obese women undergoing a dietary intervention (DI) consisting of 1-month very-low-calorie diet, and 5 months of weight-stabilization period. Serum levels of oxLDL-β2GPI were measured by enzyme-linked immunosorbent assay. Insulin sensitivity was evaluated by hyperinsulinemic-euglycemic clamp and homeostasis model assessment of insulin resistance. mRNA expression of macrophage markers was determined in both subcutaneous (SAT) and visceral (VAT) adipose tissue in cohort I and in SAT in cohort II.

RESULTS

Serum oxLDL-β2GPI levels were increased in obese subjects with MS compared to lean or obese without MS (obese with MS: 26.6±5.0 vs lean: 15.17±1.97, P<0.001; vs obese without MS: 16.36±2.89, P<0.05). Serum oxLDL-β2GPI correlated with MS indices (glucose, high-density lipoprotein, triglyceride and ureic acid) and with mRNA expression of macrophage markers in VAT. Weight-reducing DI decreased serum oxLDL-β2GPI levels together with lipid parameters and the mRNA expression of inflammatory markers in SAT.

CONCLUSIONS

OxLDL-β2GPI seems to be an important marker of visceral adipose tissue inflammation and possibly a factor contributing to insulin resistance and metabolic syndrome development in obese patients.

Aberrant hepatic lipid storage and metabolism in canine portosystemic shunts

Non-alcoholic fatty liver disease (NAFLD) is a poorly understood multifactorial pandemic disorder. One of the hallmarks of NAFLD, hepatic steatosis, is a common feature in canine congenital portosystemic shunts. The aim of this study was to gain detailed insight into the pathogenesis of steatosis in this large animal model. Hepatic lipid accumulation, gene-expression analysis and HPLC-MS of neutral lipids and phospholipids in extrahepatic (EHPSS) and intrahepatic portosystemic shunts (IHPSS) was compared to healthy control dogs. Liver organoids of diseased dogs and healthy control dogs were incubated with palmitic- and oleic-acid, and lipid accumulation was quantified using LD540. In histological slides of shunt livers, a 12-fold increase of lipid content was detected compared to the control dogs (EHPSS P<0.01; IHPSS P = 0.042). Involvement of lipid-related genes to steatosis in portosystemic shunting was corroborated using gene-expression profiling. Lipid analysis demonstrated different triglyceride composition and a shift towards short chain and omega-3 fatty acids in shunt versus healthy dogs, with no difference in lipid species composition between shunt types. All organoids showed a similar increase in triacylglycerols after free fatty acids enrichment. This study demonstrates that steatosis is probably secondary to canine portosystemic shunts. Unravelling the pathogenesis of this hepatic steatosis might contribute to a better understanding of steatosis in NAFLD.

Association of calf circumference with insulin resistance and non-alcohol fatty liver disease: the REACTION study

BACKGROUND

The feature of nonalcoholic fatty liver disease (NAFLD) is pathological excessive liver lipid accumulation of subjects who without history of alcohol abuse. Calf circumference is a proxy for lower-body fat and screening method for the identification of subjects with acatastatic lipid accumulation. The objective of this study was to examine the association between calf circumference and NAFLD.

METHODS

The study was a cross-sectional analysis including 8850 middle-aged and elderly individuals. NAFLD was examined by hepatic ultrasound and without alcohol abuse and other liver diseases. Calf circumference was measured on the lower right leg at the point of maximal circumference.

RESULTS

The mean of calf circumference were 35.7 cm for male and 34.6 cm for female (P < 0.001), respectively. Compared with the lowest calf circumference quartile, the odds ratio for NAFLD in the highest quartile was 2.73 (95% CI 2.34-3.19, P _trend <0.001) after adjusted for potential cofounders. There were also significant positive correlation between calf circumference and HOMA-IR, liver enzyme levels and triglycerides. In addition, we found significant positive correlation of calf circumference with the HOMA-IR and fasting insulin level in overweight and obese subjects (BMI ≥ 24 kg/m2) but not in lean subjects (test for interaction: P both less than 0.001 for insulin and HOMA-IR).

CONCLUSION

High calf circumference is significantly associated with elevated prevalence of NAFLD and increasing insulin resistance.

Adipocytes properties and crosstalk with immune system in obesity-related inflammation

Obesity is a condition likely associated with several dysmetabolic conditions or worsening of cardiovascular and other chronic disturbances. A key role in this mechanism seem to be played by the onset of low-grade systemic inflammation, highlighting the importance of the interplay between adipocytes and immune system cells. Adipocytes express a complex and highly adaptive biological profile being capable to selectively activate different metabolic pathways in order to respond to environmental stimuli. It has been demonstrated how adipocytes, under appropriate stimulation, can easily differentiate and de-differentiate thereby converting themselves into different phenotypes according to metabolic necessities. Although underlying mechanisms are not fully understood, growing in adipocyte size and the inability of storing triglycerides under overfeeding conditions seem to be crucial for the switching to a dysfunctional metabolic profile, which is characterized by inflammatory and apoptotic pathways activation, and by the shifting to pro-inflammatory adipokines secretion. In obesity, changes in adipokines secretion along with adipocyte deregulation and fatty acids release into circulation contribute to maintain immune cells activation as well as their infiltration into regulatory organs. Over the well-established role of macrophages, recent findings suggest the involvement of new classes of immune cells such as T regulatory lymphocytes and neutrophils in the development inflammation and multi systemic worsening. Deeply understanding the pathways of adipocyte regulation and the de-differentiation process could be extremely useful for developing novel strategies aimed at curbing obesity-related inflammation and related metabolic disorders.

Intramyocellular lipid content and lipogenic gene expression responses following a single bout of resistance type exercise differ between young and older men

The aim of this study was to examine the temporal relationship between intramyocellular lipid (IMCL) content and the expression of genes associated with IMCL turnover, fat metabolism, and inflammation during recovery from an acute bout of resistance type exercise in old versus young men. Seven healthy young (23±2years, 77.2±2.9kg) and seven healthy older (72±1years, 79.3±4.9kg) males performed a single bout of resistance exercise involving 6 sets of 10 repetitions of leg press and 6 sets of 10 repetitions of leg extension at 75% one-repetition maximum (1-RM). Muscle biopsy samples were obtained before and 12, 24 and 48h after the completion of exercise and analysed for IMCL content and the expression of 48 genes. The subjects refrained from further heavy physical exercise and consumed a standardized diet for the entire experimental period. The IMCL content was ~2-fold higher at baseline and 12h post-exercise in old compared with young individuals. However, no differences between groups were apparent after 48h of recovery. There was higher expression of genes involved in fatty acid synthesis (FASN and PPARγ) during the first 24h of recovery. Differential responses to exercise were observed between groups for a number of genes indicating increased inflammatory response (IL6, IkBalpha, CREB1) and impaired fat metabolism and TCA cycle (LPL, ACAT1, SUCLG1) in older compared with younger individuals. A singe bout of resistance type exercise leads to molecular changes in skeletal muscle favouring reduced lipid oxidation, increased lipogenesis, and exaggerated inflammation during post-exercise recovery in the older compared with younger individuals, which may be indicative of a blunted response of IMCL turnover with ageing.

Pathophysiology of Non Alcoholic Fatty Liver Disease

The physiopathology of fatty liver and metabolic syndrome are influenced by diet, life style and inflammation, which have a major impact on the severity of the clinicopathologic outcome of non-alcoholic fatty liver disease. A short comprehensive review is provided on current knowledge of the pathophysiological interplay among major circulating effectors/mediators of fatty liver, such as circulating lipids, mediators released by adipose, muscle and liver tissues and pancreatic and gut hormones in relation to diet, exercise and inflammation.

Calorie Restricted High Protein Diets Downregulate Lipogenesis and Lower Intrahepatic Triglyceride Concentrations in Male Rats

The purpose of this investigation was to assess the influence of calorie restriction (CR) alone, higher-protein/lower-carbohydrate intake alone, and combined CR higher-protein/lower-carbohydrate intake on glucose homeostasis, hepatic de novo lipogenesis (DNL), and intrahepatic triglycerides. Twelve-week old male Sprague Dawley rats consumed ad libitum (AL) or CR (40% restriction), adequate (10%), or high (32%) protein (PRO) milk-based diets for 16 weeks. Metabolic profiles were assessed in serum, and intrahepatic triglyceride concentrations and molecular markers of de novo lipogenesis were determined in liver. Independent of calorie intake, 32% PRO tended to result in lower homeostatic model assessment of insulin resistance (HOMA-IR) values compared to 10% PRO, while insulin and homeostatic model assessment of β-cell function (HOMA-β) values were lower in CR than AL, regardless of protein intake. Intrahepatic triglyceride concentrations were 27.4 ± 4.5 and 11.7 ± 4.5 µmol·g⁻¹ lower (p < 0.05) in CR and 32% PRO compared to AL and 10% PRO, respectively. Gene expression of fatty acid synthase (FASN), stearoyl-CoA destaurase-1 (SCD1) and pyruvate dehydrogenase kinase, isozyme 4 (PDK4) were 45% ± 1%, 23% ± 1%, and 57% ± 1% lower (p < 0.05), respectively, in CR than AL, regardless of protein intake. Total protein of FASN and SCD were 50% ± 1% and 26% ± 1% lower (p < 0.05) in 32% PRO compared to 10% PRO, independent of calorie intake. Results from this investigation provide evidence that the metabolic health benefits associated with CR—specifically reduction in intrahepatic triglyceride content—may be enhanced by consuming a higher-protein/lower-carbohydrate diet.

Evaluation of treadmill exercise effect on muscular lipid profiles of diabetic fatty rats by nanoflow liquid chromatography-tandem mass spectrometry

We compare comprehensive quantitative profiling of lipids at the molecular level from skeletal muscle tissues (gastrocnemius and soleus) of Zucker diabetic fatty rats and Zucker lean control rats during treadmill exercise by nanoflow liquid chromatography-tandem mass spectrometry. Because type II diabetes is caused by decreased insulin sensitivity due to excess lipids accumulated in skeletal muscle tissue, lipidomic analysis of muscle tissues under treadmill exercise can help unveil the mechanism of lipid-associated insulin resistance. In total, 314 lipid species, including phospholipids, sphingolipids, ceramides, diacylglycerols (DAGs), and triacylglycerols (TAGs), were analyzed to examine diabetes-related lipid species and responses to treadmill exercise. Most lysophospholipid levels increased with diabetes. While DAG levels (10 from the gastrocnemius and 13 from the soleus) were >3-fold higher in diabetic rats, levels of most of these decreased after exercise in soleus but not in gastrocnemius. Levels of 5 highly abundant TAGs (52:1 and 54:3 in the gastrocnemius and 48:2, 50:2, and 52:4 in the soleus) displaying 2-fold increases in diabetic rats decreased after exercise in the soleus but not in the gastrocnemius in most cases. Thus, aerobic exercise has a stronger influence on lipid levels in the soleus than in the gastrocnemius in type 2 diabetic rats.

Withaferin A protects against palmitic acid-induced endothelial insulin resistance and dysfunction through suppression of oxidative stress and inflammation

Activation of inflammatory pathways via reactive oxygen species (ROS) by free fatty acids (FFA) in obesity gives rise to insulin resistance and endothelial dysfunction. Withaferin A (WA), possesses both antioxidant and anti-inflammatory properties and therefore would be a good strategy to suppress palmitic acid (PA)-induced oxidative stress and inflammation and hence, insulin resistance and dysfunction in the endothelium. Effect of WA on PA-induced insulin resistance in human umbilical vein endothelial cells (HUVECs) was determined by evaluating insulin signaling mechanisms whilst effect of this drug on PA-induced endothelial dysfunction was determined in acetylcholine-mediated relaxation in isolated rat aortic preparations. WA significantly inhibited ROS production and inflammation induced by PA. Furthermore, WA significantly decreased TNF-α and IL-6 production in endothelial cells by specifically suppressing IKKβ/NF-κβ phosphorylation. WA inhibited inflammation-stimulated IRS-1 serine phosphorylation and improved the impaired insulin PI3-K signaling, and restored the decreased nitric oxide (NO) production triggered by PA. WA also decreased endothelin-1 and plasminogen activator inhibitor type-1 levels, and restored the impaired endothelium-mediated vasodilation in isolated aortic preparations. These findings suggest that WA inhibited both ROS production and inflammation to restore impaired insulin resistance in cultured endothelial cells and improve endothelial dysfunction in rat aortic rings.

Muscle Mass Index and Animal Source of Dietary Protein Are Positively Associated with Insulin Resistance in Participants of the NuAge Study

OBJECTIVES

Contribute evidence towards the complex interrelationships of body composition, insulin sensitivity and protein intake independently from adiposity in an older population.

DESIGN

This is a cross-sectional analysis of an existing dataset in which a literature-supported model linking together the variables of interest is tested using path analysis.

SETTING

The loss of muscle mass has been implicated in the development of insulin resistance. We propose to test associations of muscle mass with insulin sensitivity and their respective associations with animal and vegetable sources of protein intake, independently from adiposity.

PARTICIPANTS

Non-diabetic participants aged 68-82 years from the NuAge study with all available measures (n=441) were included.

MEASUREMENTS

A model considering age, sex, chronic diseases, physical activity; smoking and sources of protein intake influencing body composition components and insulin sensitivity was created and tested with Path Analysis for their independent associations. Muscle mass index (MMI; kg/height in m2) and % body fat were derived from DXA and BIA. Insulin resistance was estimated by the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) score and physical activity by the Physical Activity Scale for the Elderly (PASE) questionnaire. Protein intakes were obtained from three non-consecutive 24h-diet recalls.

RESULTS

In the final model, direct positive associations were observed between HOMA-IR score and MMI (ß=0.42; 95%CI: 0.24; 0.6) and % body fat (ß=0.094; 95%CI: 0.07; 0.11). There were no direct associations between animal protein intake and MMI or with HOMA-IR. There was a significant direct negative association between plant protein intake and MMI (ß= -0.068; 95%CI: -0.13; -0.003) and significant indirect associations mediated through MMI and % body fat between HOMA-IR and animal protein intake (ß=0.0321; 95%CI: 0.01; 0.05), as well as plant protein intake (ß= -0.07; 95%CI: -0.1; 0.0).

CONCLUSIONS

Our final model indicated that MMI and HOMA score were significantly positively associated. Protein intake sources were related to HOMA-IR score differently through MMI and % body fat, respectively.

Effect of Bariatric Surgery on Adipose Tissue Glucose Metabolism in Different Depots in Patients With or Without Type 2 Diabetes

OBJECTIVE

We investigated fat distribution and tissue-specific insulin-stimulated glucose uptake (GU) in seven fat compartments (visceral and subcutaneous) and skeletal muscle in morbidly obese patients with (T2D) and without (ND) type 2 diabetes before and 6 months after bariatric surgery.

RESEARCH DESIGN AND METHODS

A total of 23 obese patients (BMI 43.0 ± 3.6 kg/m(2); 9 T2D and 14 ND) were recruited from a larger, randomized multicenter SLEEVEPASS study. MRI (for fat distribution) and [(18)F]-fluorodeoxyglucose PET (for GU) studies were performed for the obese patients before and 6 months postsurgery; 10 lean subjects served as control subjects and were studied once.

RESULTS

At baseline, visceral fat GU was 30 ± 7% of muscle GU in control subjects and 57 ± 5% in obese patients. Visceral and deep subcutaneous fat were more abundant (despite same total fat mass) and less insulin sensitive in T2D than ND; in both, GU was impaired compared with control subjects. Postsurgery, visceral fat mass decreased (∼40%) more than subcutaneous fat (7%). Tissue-specific GU was improved, but not normalized, at all sites in T2D and ND alike. The contribution of visceral fat to whole-body GU was greater in T2D than ND but decreased similarly with surgery. Subcutaneous fat made a fourfold greater contribution to whole-body GU in obese versus lean subjects (15% vs. 4%) both before and after surgery.

CONCLUSIONS

Bariatric surgery leads to sustained weight loss and improves tissue-specific glucose metabolism in morbidly obese patients. We conclude that 1) enhanced visceral fat accumulation is a feature of T2D, 2) severe obesity compromises muscle insulin sensitivity more than fat insulin sensitivity, and 3) fat mass expansion is a sink for plasma glucose.

Glucagon-like peptide 1 decreases lipotoxicity in non-alcoholic steatohepatitis

BACKGROUND & AIMS

Insulin resistance and lipotoxicity are pathognomonic in non-alcoholic steatohepatitis (NASH). Glucagon-like peptide-1 (GLP-1) analogues are licensed for type 2 diabetes, but no prospective experimental data exists in NASH. This study determined the effect of a long-acting GLP-1 analogue, liraglutide, on organ-specific insulin sensitivity, hepatic lipid handling and adipose dysfunction in biopsy-proven NASH.

METHODS

Fourteen patients were randomised to 1.8mg liraglutide or placebo for 12-weeks of the mechanistic component of a double-blind, randomised, placebo-controlled trial (ClinicalTrials.gov-NCT01237119). Patients underwent paired hyperinsulinaemic euglycaemic clamps, stable isotope tracers, adipose microdialysis and serum adipocytokine/metabolic profiling. In vitro isotope experiments on lipid flux were performed on primary human hepatocytes.

RESULTS

Liraglutide reduced BMI (-1.9 vs. +0.04kg/m(2); p<0.001), HbA1c (-0.3 vs. +0.3%; p<0.01), cholesterol-LDL (-0.7 vs. +0.05mmol/L; p<0.01), ALT (-54 vs. -4.0IU/L; p<0.01) and serum leptin, adiponectin, and CCL-2 (all p<0.05). Liraglutide increased hepatic insulin sensitivity (-9.36 vs. -2.54% suppression of hepatic endogenous glucose production with low-dose insulin; p<0.05). Liraglutide increased adipose tissue insulin sensitivity enhancing the ability of insulin to suppress lipolysis both globally (-24.9 vs. +54.8pmol/L insulin required to ½ maximally suppress serum non-esterified fatty acids; p<0.05), and specifically within subcutaneous adipose tissue (p<0.05). In addition, liraglutide decreased hepatic de novo lipogenesis in vivo (-1.26 vs. +1.30%; p<0.05); a finding endorsed by the effect of GLP-1 receptor agonist on primary human hepatocytes (24.6% decrease in lipogenesis vs. untreated controls; p<0.01).

CONCLUSIONS

Liraglutide reduces metabolic dysfunction, insulin resistance and lipotoxicity in the key metabolic organs in the pathogenesis of NASH. Liraglutide may offer the potential for a disease-modifying intervention in NASH.

An Evolutionary Perspective of Nutrition and Inflammation as Mechanisms of Cardiovascular Disease

When cardiovascular diseases are viewed from an evolutionary biology perspective, a heightened thrifty and an inflammatory design could be their mechanisms. Human ancestors confronted a greater infectious load and were subjected to the selection for proinflammatory genes and a strong inflammatory function. Ancestors also faced starvation periods that pressed for a thrifty genotype which caused fat accumulation. The pressure of sustaining gluconeogenesis during periods of poor nourishment selected individuals with insulin resistance. Obesity induces a proinflammatory state due to the secretion of adipokines which underlie cardiometabolic diseases. Our actual lifestyle needs no more of such proinflammatory and thrifty genotypes and these ancestral genes might increase predisposition to diseases. Risk factors for atherosclerosis and diabetes are based on inflammatory and genetic foundations that can be accounted for by excess fat. Longevity has also increased in recent times and is related to a proinflammatory response with cardiovascular consequences. If human ancestral lifestyle could be recovered by increasing exercise and adapting a calorie restriction diet, obesity would decrease and the effects on chronic low-grade inflammation would be limited. Thereby, the rates of both atherosclerosis and diabetes could be reduced.

Palmitate-induced endothelial dysfunction is attenuated by cyanidin-3-O-glucoside through modulation of Nrf2/Bach1 and NF-κB pathways

Free fatty acids (FFA), commonly elevated in diabetes and obesity, have been shown to impair endothelial functions and cause oxidative stress, inflammation, and insulin resistance. Anthocyanins represent one of the most important and interesting classes of flavonoids and seem to play a role in preventing cardiovascular diseases. Herein, we investigated the in vitro protective effects of cyanidin-3-O-glucoside (C3G) on cell signaling pathways in human umbilical vein endothelial cells (HUVECs) exposed to palmitic acid (PA), the most prevalent saturated FFA in circulation. Our data reported a significant augmentation of free radicals and oxidative stress in HUVECs exposed to PA for 3h, while C3G pretreatment improved intracellular redox status altered by FFA. Moreover, C3G significantly inhibited NF-κB proinflammatory pathway and adhesion molecules induced by PA, and these effects were attributed to the activation of Nrf2/EpRE pathway. In fact, C3G induced Nrf2 nuclear localization and activation of cellular antioxidant and cytoprotective genes at baseline and after PA exposure in endothelial cells. Our data confirm the hypothesis that natural Nrf2 inducers, such as C3G, might be a potential therapeutic strategy to protect vascular system against various stressors preventing several pathological conditions.

Palmitate activates mTOR/p70S6K through AMPK inhibition and hypophosphorylation of raptor in skeletal muscle cells: Reversal by oleate is similar to metformin

Excessive saturated free fatty acids (SFFAs; e.g. palmitate) in blood are a pathogenic factor in diabetes, obesity, cardiovascular disease and liver failure. In contrast, monounsaturated free fatty acids (e.g. oleate) prevent the toxic effect of SFFAs in various types of cells. The mechanism is poorly understood and involvement of the mTOR complex is untested. In the present study, we demonstrate that oleate preconditioning, as well as coincubation, completely prevented palmitate-induced markers of inflammatory signaling, insulin resistance and cytotoxicity in C2C12 myotubes. We then examined the effect of palmitate and/or oleate on the mammalian target of rapamycin (mTOR) signal path and whether their link is mediated by AMP-activated protein kinase (AMPK). Palmitate decreased the phosphorylation of raptor and 4E-BP1 while increasing the phosphorylation of p70S6K. Palmitate also inhibited phosphorylation of AMPK, but did not change the phosphorylated levels of mTOR or rictor. Oleate completely prevented the palmitate-induced dysregulation of mTOR components and restored pAMPK whereas alone it produced no signaling changes. To understand this more, we show activation of AMPK by metformin also prevented palmitate-induced changes in the phosphorylations of raptor and p70S6K, confirming that the mTORC1/p70S6K signaling pathway is responsive to AMPK activity. By contrast, inhibition of AMPK phosphorylation by Compound C worsened palmitate-induced changes and correspondingly blocked the protective effect of oleate. Finally, metformin modestly attenuated palmitate-induced insulin resistance and cytotoxicity, as did oleate. Our findings indicate that palmitate activates mTORC1/p70S6K signaling by AMPK inhibition and phosphorylation of raptor. Oleate reverses these effects through a metformin-like facilitation of AMPK.

Forced Hepatic Overexpression of CEACAM1 Curtails Diet-Induced Insulin Resistance

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) regulates insulin sensitivity by promoting hepatic insulin clearance. Liver-specific inactivation or global null-mutation of Ceacam1 impairs hepatic insulin extraction to cause chronic hyperinsulinemia, resulting in insulin resistance and visceral obesity. In this study we investigated whether diet-induced insulin resistance implicates changes in hepatic CEACAM1. We report that feeding C57/BL6J mice a high-fat diet reduced hepatic CEACAM1 levels by >50% beginning at 21 days, causing hyperinsulinemia, insulin resistance, and elevation in hepatic triacylglycerol content. Conversely, liver-specific inducible CEACAM1 expression prevented hyperinsulinemia and markedly limited insulin resistance and hepatic lipid accumulation that were induced by prolonged high-fat intake. This was partly mediated by increased hepatic β-fatty acid oxidation and energy expenditure. The data demonstrate that the high-fat diet reduced hepatic CEACAM1 expression and that overexpressing CEACAM1 in liver curtailed diet-induced metabolic abnormalities by protecting hepatic insulin clearance.

Long-term High-fat High-sucrose Diet Promotes Enlarged Islets and β-Cell Damage by Oxidative Stress in Bama Minipigs

OBJECTIVES

The effect of a long-term high-fat, high-caloric diet on the dysfunction of pancreas has not been clarified. We investigated the pancreatic histopathology and β-cell apoptosis in Bama minipigs after 23 months on a high-fat high-sucrose diet (HFHSD).

METHODS

Bama minipigs were randomly assigned to control (n = 6) and HFHSD groups (n = 6) for 23 months, and biochemical parameters were measured. Pancreata were subjected to histological analysis, followed by assessment with transmission electron microscopy. Lipid peroxidation was determined by the malondialdehyde concentration and antioxidant enzyme activity. Β-cell apoptosis was measured by an immunohistochemical method.

RESULTS

In the HFHSD group, the islets were enlarged, and the pancreatic tissue had observed significant fatty infiltration. Moreover, the feeding program damaged the normal pancreatic tissue structure. The level of lipid peroxidation was increased, and the activities of pancreatic antioxidant enzymes were significantly decreased. The expression levels of caspase-3, Bax, and insulin were significantly increased (P < 0.05), and the expression levels of proliferating cell nuclear antigen and Bcl-2 were decreased (P < 0.05).

CONCLUSIONS

The long-term HFHSD promotes pancreatic steatosis and oxidative stress, which increases β-cell apoptosis as indicated by the activation of caspase-3 through the mitochondrial pathway (Bcl-2/Bax).

Advances in the Science, Treatment, and Prevention of the Disease of Obesity: Reflections From a Diabetes Care Editors' Expert Forum

As obesity rates increase, so too do the risks of type 2 diabetes, cardiovascular disease, and numerous other detrimental conditions. The prevalence of obesity in U.S. adults more than doubled between 1980 and 2010, from 15.0 to 36.1%. Although this trend may be leveling off, obesity and its individual, societal, and economic costs remain of grave concern. In June 2014, a Diabetes Care Editors' Expert Forum convened to review the state of obesity research and discuss the latest prevention initiatives and behavioral, medical, and surgical therapies. This article, an outgrowth of the forum, offers an expansive view of the obesity epidemic, beginning with a discussion of its root causes. Recent insights into the genetic and physiological factors that influence body weight are reviewed, as are the pathophysiology of obesity-related metabolic dysfunction and the concept of metabolically healthy obesity. The authors address the crucial question of how much weight loss is necessary to yield meaningful benefits. They describe the challenges of behavioral modification and predictors of its success. The effects of diabetes pharmacotherapies on body weight are reviewed, including potential weight-neutral combination therapies. The authors also summarize the evidence for safety and efficacy of pharmacotherapeutic and surgical obesity treatments. The article concludes with an impassioned call for researchers, clinicians, governmental agencies, health policymakers, and health-related industries to collectively embrace the urgent mandate to improve prevention and treatment and for society at large to acknowledge and manage obesity as a serious disease.

[Role of metabolic lipases and lipotoxicity in the development of non-alcoholic steatosis and non-alcoholic steatohepatitis]

Non-alcoholic fatty liver disease (NAFLD) has become the most common liver disease in developed countries, covering a spectrum of pathological conditions ranging from single steatosis to non-alcoholic steatohepatitis, cirrhosis and hepatocellular carcinoma. Its pathogenesis has been often interpreted by the "double-hit" hypothesis, where the lipid accumulation in the liver is followed by proinflammatory mediators inducing inflammation, hepatocellular injury and fibrosis. Nowadays, a more complex model suggests that free fatty acids and their metabolites could be the true lipotoxic agents that contribute to the development of NAFLD and hepatic insulin resistance, suggesting a central role for metabolic lipases in that process.

Intravenous Mycobacterium Bovis Bacillus Calmette-Guérin Ameliorates Nonalcoholic Fatty Liver Disease in Obese, Diabetic ob/ob Mice

Inflammation and immune response profoundly influence metabolic syndrome and fatty acid metabolism. To analyze influence of systemic inflammatory response to metabolic syndrome, we inoculated an attenuated vaccine strain of Mycobacterium bovis Bacillus Calmette–Guérin (BCG) into leptin-deficient ob/ob mice. BCG administration significantly decreased epididymal white adipose tissue weight, serum insulin levels, and a homeostasis model assessment of insulin resistance. Serum high molecular weight (HMW) adiponectin level and HMW/total adiponectin ratio of the BCG treated mice were significantly higher than those of control mice. Hepatic triglyceride accumulation and macrovesicular steatosis were markedly alleviated, and the enzymatic activities and mRNA levels of lipogenic-related genes in liver were significantly decreased in the BCG injected mice. We also exposed human hepatocellular carcinoma HepG2 cells to high levels of palmitate, which enhanced endoplasmic reticulum stress-related gene expression and impaired insulin-stimulated Akt phosphorylation (Ser473). BCG treatment ameliorated both of these detrimental events. The present study therefore suggested that BCG administration suppressed development of nonalcoholic fatty liver disease, at least partly, by alleviating fatty acid-induced insulin resistance in the liver.

Non-alcoholic fatty liver disease: The diagnosis and management

Non-alcoholic fatty liver disease (NAFLD) is now the most frequent chronic liver disease that occurs across all age groups and is recognized to occur in 14%-30% of the general population, representing a serious and growing clinical problem due to the growing prevalence of obesity and overweight. Histologically, it resembles alcoholic liver injury but occurs in patients who deny significant alcohol consumption. NAFLD encompasses a spectrum of conditions, ranging from benign hepatocellular steatosis to inflammatory nonalcoholic steatohepatitis, fibrosis, and cirrhosis. The majority of hepatocellular lipids are stored as triglycerides, but other lipid metabolites, such as free fatty acids, cholesterol, and phospholipids, may also be present and play a role in disease progression. NAFLD is associated with obesity and insulin resistance and is considered the hepatic manifestation of the metabolic syndrome, a combination of medical conditions including type 2 diabetes mellitus, hypertension, hyperlipidemia, and visceral adiposity. Confirmation of the diagnosis of NAFLD can usually be achieved by imaging studies; however, staging the disease requires a liver biopsy. Current treatment relies on weight loss and exercise, although various insulin-sensitizing agents, antioxidants and medications appear promising. The aim of this review is to highlight the current information regarding epidemiology, diagnosis, and management of NAFLD as well as new information about pathogenesis, diagnosis and management of this disease.

Usual breakfast eating habits affect response to breakfast skipping in overweight women

OBJECTIVE

This randomized, cross-over trial was designed to investigate the metabolic and appetitive responses to skipping breakfast in overweight women who were habitual breakfast Eaters or Skippers.

METHODS

Nine Eaters and nine Skippers were studied on two separate days during which subjects ate breakfast (B) or had no breakfast (NB), followed by a standard lunch meal 4 h later. Blood sampling for hormones and metabolites was performed after lunch, and appetite was rated throughout the day.

RESULTS

Interactions between day and habitual breakfast pattern were seen for area under the curve (AUC) for insulin and free fatty acids (FFA). Both insulin (P = 0.020) and FFA (P = 0.023) AUC were higher on the NB day for Eaters but similar on both days for Skippers. Eaters had higher pre lunch hunger AUC on the NB day (P = 0.015) as well as lower pre lunch satiety AUC under both conditions (P = 0.019).

CONCLUSIONS

Overall, this study showed that the adverse effects of skipping breakfast (higher insulin and FFA responses to lunch, increased hunger, and decreased satiety) were found primarily in habitual breakfast eaters. This suggests that meal skipping may have enhanced effects in habitual Eaters due to entrainment of metabolic and appetitive regulatory systems.

Fermented green tea extract alleviates obesity and related complications and alters gut microbiota composition in diet-induced obese mice

Obesity is caused by an imbalance between caloric intake and energy expenditure and accumulation of excess lipids in adipose tissues. Recent studies have demonstrated that green tea and its processed products (e.g., oolong and black tea) are introduced to exert beneficial effects on lipid metabolism. Here, we propose that fermented green tea (FGT) extract, as a novel processed green tea, exhibits antiobesity effects. FGT reduced body weight gain and fat mass without modifying food intake. mRNA expression levels of lipogenic and inflammatory genes were downregulated in white adipose tissue of FGT-administered mice. FGT treatment alleviated glucose intolerance and fatty liver symptoms, common complications of obesity. Notably, FGT restored the changes in gut microbiota composition (e.g., the Firmicutes/Bacteroidetes and Bacteroides/Prevotella ratios), which is reported to be closely related with the development of obesity and insulin resistance, induced by high-fat diets. Collectively, FGT improves obesity and its associated symptoms and modulates composition of gut microbiota; thus, it could be used as a novel dietary component to control obesity and related symptoms.

Niche-dependent regulations of metabolic balance in high-fat diet-induced diabetic mice by mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have great potential to maintain glucose homeostasis and metabolic balance. Here, we demonstrate that in mice continuously fed with high-fat diet (HFD) that developed non-insulin-dependent diabetes, two episodes of systemic MSC transplantations effectively improve glucose tolerance and blood glucose homeostasis and reduce body weight through targeting pancreas and insulin-sensitive tissues and organs via site-specific mechanisms. MSCs support pancreatic islet growth by direct differentiation into insulin-producing cells and by mitigating the cytotoxicity of interleukin 1 (IL-1) and tumor necrosis factor-α (TNF-α) in the pancreas. Localization of MSCs in the liver and skeletal muscles in diabetic animals is also enhanced and therefore improves glucose tolerance, although long-term engraftment is not observed. MSCs prevent HFD-induced fatty liver development and restore glycogen storage in hepatocytes. Increased expression of IL-1 receptor antagonist and Glut4 in skeletal muscles after MSC transplantation results in better blood glucose homeostasis. Intriguingly, systemic MSC transplantation does not alter adipocyte number, but it decreases HFD-induced cell infiltration in adipose tissues and reduces serum levels of adipokines, including leptin and TNF-α. Taken together, systemic MSC transplantation ameliorates HFD-induced obesity and restores metabolic balance through multisystemic regulations that are niche dependent. Such findings have supported systemic transplantation of MSCs to correct metabolic imbalance.

Intermittent hypoxia-induced glucose intolerance is abolished by α-adrenergic blockade or adrenal medullectomy

Obstructive sleep apnea causes intermittent hypoxia (IH) during sleep and is associated with dysregulation of glucose metabolism. We developed a novel model of clinically realistic IH in mice to test the hypothesis that IH causes hyperglycemia, glucose intolerance, and insulin resistance via activation of the sympathetic nervous system. Mice were exposed to acute hypoxia of graded severity (21, 14, 10, and 7% O2) or to IH of graded frequency [oxygen desaturation index (ODI) of 0, 15, 30, or 60, SpO2 nadir 80%] for 30 min to measure levels of glucose fatty acids, glycerol, insulin, and lactate. Glucose tolerance tests and insulin tolerance tests were then performed under each hypoxia condition. Next, we examined these outcomes in mice that were administered phentolamine (α-adrenergic blockade) or propranolol (β-adrenergic blockade) or that underwent adrenal medullectomy before IH exposure. In all experiments, mice were maintained in a thermoneutral environment. Sustained and IH induced hyperglycemia, glucose intolerance, and insulin resistance in a dose-dependent fashion. Only severe hypoxia (7% O2) increased lactate, and only frequent IH (ODI 60) increased plasma fatty acids. Phentolamine or adrenal medullectomy both prevented IH-induced hyperglycemia and glucose intolerance. IH inhibited glucose-stimulated insulin secretion, and phentolamine prevented the inhibition. Propranolol had no effect on glucose metabolism but abolished IH-induced lipolysis. IH-induced insulin resistance was not affected by any intervention. Acutely hypoxia causes hyperglycemia, glucose intolerance, and insulin resistance in a dose-dependent manner. During IH, circulating catecholamines act upon α-adrenoreceptors to cause hyperglycemia and glucose intolerance.