Weight cycling enhances adipose tissue inflammatory responses in male mice

The Impact of Weight Cycling on Health and Obesity

Obesity is a systemic and chronic inflammation, which seriously endangers people's health. People tend to diet to control weight, and the short-term effect of dieting in losing weight is significant, but the prognosis is limited. With weight loss and recovery occurring frequently, people focus on weight cycling. The effect of weight cycling on a certain tissue of the body also has different conclusions. Therefore, this article systematically reviews the effects of body weight cycling on the body and finds that multiple weight cycling (1) increased fat deposition in central areas, lean mass decreased in weight loss period, and fat mass increased in weight recovery period, which harms body composition and skeletal muscle mass; (2) enhanced the inflammatory response of adipose tissue, macrophages infiltrated into adipose tissue, and increased the production of pro-inflammatory mediators in adipocytes; (3) blood glucose concentration mutation and hyperinsulinemia caused the increase or decrease in pancreatic β-cell population, which makes β-cell fatigue and leads to β-cell failure; (4) resulted in additional burden on the cardiovascular system because of cardiovascular rick escalation. Physical activity combined with calorie restriction can effectively reduce metabolic disease and chronic inflammation, alleviating the adverse effects of weight cycling on the body.

Weight-centric prevention of cancer

Background

The link between excess adiposity and carcinogenesis has been well established for multiple malignancies, and cancer is one of the main contributors to obesity-related mortality. The potential role of different weight-loss interventions on cancer risk modification has been assessed, however, its clinical implications remain to be determined. In this clinical review, we present the data assessing the effect of weight loss interventions on cancer risk.

Methods

In this clinical review, we conducted a comprehensive search of relevant literature using MEDLINE, Embase, Web of Science, and Google Scholar databases for relevant studies from inception to January 20, 2024. In this clinical review, we present systematic reviews and meta-analysis, randomized clinical trials, and prospective and retrospective observational studies that address the effect of different treatment modalities for obesity in cancer risk. In addition, we incorporate the opinions from experts in the field of obesity medicine and oncology regarding the potential of weight loss as a preventative intervention for cancer.

Results

Intentional weight loss achieved through different modalities has been associated with a reduced cancer incidence. To date, the effect of weight loss on the postmenopausal women population has been more widely studied, with multiple reports indicating a protective effect of weight loss on hormone-dependent malignancies. The effect of bariatric interventions as a protective intervention for cancer has been studied extensively, showing a significant reduction in cancer incidence and mortality, however, data for the effect of bariatric surgery on certain specific types of cancer is conflicting or limited.

Conclusion

Medical nutrition therapy, exercise, antiobesity medication, and bariatric interventions, might lead to a reduction in cancer risk through weight loss-dependent and independent factors. Further evidence is needed to better determine which population might benefit the most, and the amount of weight loss required to provide a clinically significant preventative effect.

High-fat diet-induced elevation of body weight set point in male mice

OBJECTIVE

High-fat diets (HFD) are thought to disrupt energy homeostasis to drive overeating and obesity. However, weight loss resistance in individuals with obesity suggests that homeostasis is intact. This study aimed to reconcile this difference by systematically assessing body weight (BW) regulation under HFD.

METHODS

Male C57BL/6 N mice were fed diets with varying fat and sugar in different durations and patterns. BW and food intake were monitored.

RESULTS

BW gain was transiently accelerated by HFD (≥40%) prior to plateauing. The plateau was consistent regardless of starting age, HFD duration, or fat/sugar content. Reverting to a low-fat diet (LFD) caused transiently accelerated weight loss, which correlated with how heavy mice were before the diet relative to LFD-only controls. Chronic HFD attenuated the efficacy of single or repetitive dieting, revealing a defended BW higher than that of LFD-only controls.

CONCLUSIONS

This study suggests that dietary fat modulates the BW set point immediately upon switching from LFD to HFD. Mice defend a new elevated set point by increasing caloric intake and efficiency. This response is consistent and controlled, suggesting that hedonic mechanisms contribute to rather than disrupt energy homeostasis. An elevated floor of the BW set point after chronic HFD could explain weight loss resistance in individuals with obesity.

Weight cycling based on altered immune microenvironment as a result of metaflammation

As a result of the obesity epidemic, more people are concerned about losing weight; however, weight regain is common, leading to repeated weight loss and weight cycling. The health benefits of early weight loss are nullified by weight regain after weight cycling, which has much more severe metabolic consequences. Weight cycling alters body composition, resulting in faster fat recovery and slower muscle reconstruction. This evident fat accumulation, muscle loss, and ectopic fat deposition destroy the intestinal barrier, increase the permeability of the small intestinal epithelium, and cause the lipotoxicity of lipid metabolites and toxins to leak into extraintestinal tissues and circulation. It causes oxidative stress and hypoxia in local tissues and immune cell infiltration in various tissues, all contributing to the adaptation to this metabolic change. Immune cells transmit inflammatory responses in adipose and skeletal muscle tissue by secreting cytokines and adipokines, which mediate immune cell pathways and cause metaflammation and inefficient metabolic degradation. In this review, we focus on the regulatory function of the immunological microenvironment in the final metabolic outcome, with a particular emphasis on the cellular and molecular processes of local and systemic metaflammation induced by weight cycling-induced changes in body composition. Metaflammation in adipose and muscle tissues that is difficult to relieve may cause weight cycling. As this chronic low-grade inflammation spreads throughout the body, metabolic complications associated with weight cycling are triggered. Inhibiting the onset and progression of metabolic inflammation and enhancing the immune microenvironment of adipose and muscle tissues may be the first step in addressing weight cycling.

Association of Long-Term Body Weight Variability With Dementia: A Prospective Study

BACKGROUND

Body weight variability (BWV) refers to intraindividual weight loss and gain over a period. The association of long-term BWV with dementia remains unclear and whether this association is beyond body weight change is undetermined.

METHODS

In the Health and Retirement Study, a total of 5 547 dementia-free participants (56.7% women; mean [SD] age, 71.1 [3.2] years) at baseline (2008) were followed up to 8 years (mean = 6.8 years) to detect incident dementia. Body weight was self-reported biennially from 1992 to 2008. BWV was measured as the coefficient of variation utilizing the body weight reported 9 times across 16 years before baseline. Cox-proportional hazard model was used to estimate the hazard ratio (HR) and 95% confidence interval (CI).

RESULTS

Among the 5 547 participants, a total of 427 incident dementia cases were identified during follow-up. Greater long-term BWV was significantly associated with a higher risk of dementia (HR comparing extreme quartiles: 2.01, 95% CI: 1.48-2.72; HR of each SD increment: 1.21, 95% CI: 1.10-1.32; p-trend < .001) independent of mean body weight and body weight change. This significant association was even observed for BWV estimated approximately 15 years preceding dementia diagnosis (HR of each SD increment: 1.13, 95% CI: 1.03-1.23) and was more pronounced for that closer to diagnosis.

CONCLUSION

Our prospective study suggested that greater BWV may be a novel risk factor for dementia.

A Comparative Study of the Anti-Obesity Effects of Dietary Sea Cucumber Saponins and Energy Restriction in Response to Weight Loss and Weight Regain in Mice

Dietary supplementation of sea cucumber saponins and calorie restriction have been proved to be effective in alleviating obesity, but the differences of anti-obesity effects between sea cucumber saponins and energy restriction during weight loss and weight regain are still unknown. In the present study, high-fat-induced obesity mice were randomly divided into three groups, including a high-fat diet group (HF), an energy restriction by 40% group (HF-L), and a sea cucumber saponins group (HF-S), to compare the effects of dietary sea cucumber saponins and energy restriction on the weight, glucose, and lipid metabolism of obese mice during weight loss and weight regain. The results showed that dietary 0.06% sea cucumber saponins and limiting energy intake by 40% had the same weight loss effect. Interestingly, sea cucumber saponins could alleviate impaired glucose tolerance and insulin resistance caused by obesity. In addition, the inhibited SREBP-1c mediated lipogenesis might lead to the alleviation of weight regain after resuming the high-fat diet even when sea cucumber saponins were no longer supplemented. In contrast, limiting energy intake tended to promote lipid synthesis in the liver and white adipose tissue after restoring a high-fat diet, and inflammation was also induced. The findings indicated that sea cucumber saponins could replace calorie restriction to prevent obesity and might be used as a functional food or drug to resist obesity and related diseases caused by obesity.

Supplementation of diet with Brazil nut modulates body composition, bone parameters, and lipid peroxidation in Wistar rats

Oxidative stress, adipose tissue, and bone compartments can be disturbed in chronic diseases. Non-pharmacological strategies, such as Brazil nuts (BNs), can improve these parameters. This study evaluated the effects of BN supplementation at different concentrations on body composition, lipid profile, and peroxidation in healthy rats. Male Wistar rats were divided into three groups: control (CT), Brazil nut 5% (BN5), and Brazil nut 10% (BN10) groups. Body composition, brown adipose tissue (BAT), plasma lipid peroxidation, and lipid profile were evaluated in the three groups. The BN5 group showed an improvement in all bone parameters compared with that of the CT group (p  < .0001). The BN5 and BN10 groups showed reduced plasma lipid peroxidation compared with that of the CT group (p = .0009), whereas the BN10 group presented lower BAT lipid peroxidation than that of the other groups (p = .01). High-density lipoprotein-cholesterol (HDL-c) levels were higher in the BN5 group than in the CT group (p = .01). Conclusively, the use of BNs in a controlled manner promoted improvement in bone parameters, HDL-c levels, and lipid peroxidation in healthy rats. PRACTICAL APPLICATIONS: Nuts has been included in the diet because of their versatility, acceptance, and easy access. Among them, Brazil nut (BN) is considered one of the major known food sources of selenium as well as a source of fibers, unsaturated fatty acids, and phenolic compounds. Studies have shown that BN supplementation is effective in reducing oxidative stress, inflammation, lipid peroxidation, and selenium deficiency when used as a non-pharmacological strategy in experimental models of chronic diseases and in clinical trials. The present study showed that controlled administration of BN improved bone parameters, high-density lipoprotein-cholesterol levels, and lipid peroxidation in healthy rats. Therefore, BN is a promising non-pharmacological agent for the prevention of the onset of chronic non-communicable diseases.

Multiomics reveals persistence of obesity-associated immune cell phenotypes in adipose tissue during weight loss and weight regain in mice

Within adipose tissue (AT), immune cells and parenchymal cells closely interact creating a complex microenvironment. In obesity, immune cell derived inflammation contributes to insulin resistance and glucose intolerance. Diet-induced weight loss improves glucose tolerance; however, weight regain further exacerbates the impairment in glucose homeostasis observed with obesity. To interrogate the immunometabolic adaptations that occur in AT during murine weight loss and weight regain, we utilized cellular indexing of transcriptomes and epitopes by sequencing (CITEseq) in male mice. Obesity-induced imprinting of AT immune cells persisted through weight-loss and progressively worsened with weight regain, ultimately leading to impaired recovery of type 2 regulatory cells, activation of antigen presenting cells, T cell exhaustion, and enhanced lipid handling in macrophages in weight cycled mice. This work provides critical groundwork for understanding the immunological causes of weight cycling-accelerated metabolic disease. For further discovery, we provide an open-access web portal of diet-induced AT immune cell imprinting: https://hastylab.shinyapps.io/MAIseq .

The impact of weight cycling on health outcomes in animal models: A systematic review and meta-analysis

The pattern of weight loss and regain, termed "weight cycling," is common in overweight individuals. It is unclear whether the well-established benefits of weight loss persist following weight regain or whether weight cycling is harmful. Human studies of weight cycling have conflicting results reflecting limitations of the observational designs of these studies. By controlling the macronutrient content of diets in animal studies, weight cycling can be studied in a highly controlled manner, thereby overcoming the limitations of human studies. We conducted a systematic review and meta-analysis of animal studies which assessed the health consequences of weight cycling. Studies were classified into those which compared weight cycling to lifelong obesity and those which compared weight cycling to later onset obesity. There were no differences in health outcomes between weight cycled animals and those with lifelong obesity, highlighting that weight regain reverses health benefits achieved by weight loss. In comparison with animals with later onset obesity, weight cycled animals had higher fasting glucose levels and more impaired glucose tolerance following weight regain. Our review of animal studies suggests that health benefits of diet-induced weight loss do not persist after weight regain and weight cycling results in adverse metabolic outcomes.

The Shades of Grey in Adipose Tissue Reprogramming

The adipose tissue (AT) has a major role in contributing to obesity-related pathologies through regulating systemic immunometabolism. The pathogenicity of the AT is underpinned by its remarkable plasticity to be reprogrammed during obesity, in the perspectives of tissue morphology, extracellular matrix (ECM) composition, angiogenesis, immunometabolic homoeostasis and circadian rhythmicity. Dysregulation in these features escalates the pathogenesis conferred by this endometabolic organ. Intriguingly, the potential to be reprogrammed appears to be an Achilles’ heel of the obese AT that can be targeted for the management of obesity and its associated comorbidities. Here, we provide an overview of the reprogramming processes of white AT (WAT), with a focus on their dynamics and pleiotropic actions over local and systemic homoeostases, followed by a discussion of potential strategies favouring therapeutic reprogramming. The potential involvement of AT remodelling in the pathogenesis of COVID-19 is also discussed.

Obese mice weight loss role on nonalcoholic fatty liver disease and endoplasmic reticulum stress treated by a GLP-1 receptor agonist

BACKGROUND/OBJECTIVES

The weight loss following Semaglutide treatment, a GLP-1 receptor agonist, might be responsible for some effects observed on the nonalcoholic fatty liver disease of obese mice.

SUBJECTS/METHODS

Two groups of C57BL/6 male mice (n = 30/group) were fed the diets Control (C) or high-fat (HF) for 16 weeks. Then, separated into six new groups for an additional four weeks (n = 10/group) and treated with Semaglutide (S, 40 µg/kg) or paired feeding (PF) with S groups (C; C-S; C-PF; HF; HF-S; HF-PF).

RESULTS

Semaglutide reduced energy consumption leading to weight loss. Simultaneously it improved glucose intolerance, glycated hemoglobin, insulin resistance/sensitivity, plasma lipids, and gastric inhibitory polypeptide. Semaglutide and paired feeding mitigated liver steatosis and adipose differentiation-related protein (Plin2) expression. Semaglutide also improved hormones and adipokines, reduced lipogenesis and inflammation, and increased beta-oxidation. Semaglutide lessened liver glucose uptake and endoplasmic reticulum (ER) stress. Among the 14 genes analyzed, 13 were modified by Semaglutide (93 %, six genes were changed exclusively by Semaglutide, and seven other genes were affected by the combination of Semaglutide and paired feeding). In seven genes, the paired diet showed no effect (50% of the genes tested). No marker was affected exclusively by paired feeding.

CONCLUSIONS

Semaglutide and the consequent weight loss reduced obese mice liver inflammation, insulin resistance, and ER stress. However, weight loss alone did show few or no action on some significant study findings, like liver steatosis, leptin, insulin, resistin, and amylin. Furthermore, hepatic inflammation mediated by MCP-1 and partially by TNF-alpha and IL6 were also not reduced by weight loss. Furthermore, weight loss alone did not lessen hepatic lipogenesis as determined by the findings of SREBP-1c, CHREBP, PPAR-alpha, and SIRT1. Semaglutide was implicated in improving glucose uptake and lessening ER stress by reducing GADD45, independent of weight loss.

Subacute Toxicity Evaluation of Methanolic Extract of Syzygium polyanthum in Rats

Syzygium polyanthum (Wight) Walp. var. polyanthum (serai kayu) leaves is a popular herb and widely used in traditional medicine. Despite the ethnomedicinal benefits, very limited studies have researched on the toxicity of this plant. The aim of the present study was to investigate the potential effects of methanolic extract of Syzygium polyanthum (MESP) leaves via 28-day repeated oral dosing in Sprague Dawley rats. MESP leaves was administered at doses of 0 (control), 400, 1000 or 2000 mg/kg to an equal number of male and female rats (n = 10/group). Results obtained indicated that MESP did not affect the general conditions (body weight, feed intake and oestrous cycle) and apparent behavioural changes of the rats. Biochemical parameters revealed a slight significant variation in the aspartate aminotransferase (AST) level between the male rats treated with the lowest and highest doses of MESP, but these findings were both statistically insignificant when compared to the control group. The liver of the males (dose 1000 and 2000 mg/kg/day) also exhibited histoarchitectural defects on the hepatocytes and cytoplasm when compared to those of the control group. In contrast, female rats did not encounter any significant findings in all parameters tested. In conclusion, this study suggests that the MESP leaves might exhibit sex-based variation effects and thus, the use of this extract particularly at higher doses should be thoroughly considered.

Body weight variability and cancer incidence in men aged 40 years and older-Korean National Insurance Service Cohort

Repeated weight fluctuation has been proposed as a potential risk factor for increasing morbidity and mortality including cancer. We aimed to investigate the association between body weight variability (BWV) and all cancer and site-specific cancer incidence and the impact of smoking on these associations. A total of 1,759,848 cancer-free male subjects who had their weight measured at least 5 times from the National Health Insurance Service-Health Screening Cohort from 2002 to 2011 were included and followed up until 2015. BWV was defined as the average absolute difference between successive values (ASV). The risk of cancer and site-specific cancer from BWV was identified using Cox proportional hazards regression analysis using hazard ratios (HRs) and 95% confidence intervals (CIs) adjusted for potential confounders including weight, and stratified analysis was also conducted according to smoking status. During the 7,015,413 person-years of follow-up, 11,494 patients (0.65%) developed new-onset cancers. BWV was associated with a higher risk of all cancers after adjustment for confounders. The highest BWV quintile group compared to the lowest had greater risks of all cancers and site-specific cancers including lung, liver, and prostate cancer (HR 1.22, 95% CI 1.15–1.30; HR 1.22, 95% CI 1.07–1.39; HR 1.46, 95% CI 1.19–1.81; HR 1.36, 95% CI 1.15–1.62, in all cancers, lung, liver and prostate cancer, respectively). Due to small number of cancer occurrence, the risk of kidney cancer was increased, but statistically insignificant (HR 1.38, 95% CI 0.91–2.10). Similar results were observed in noncurrent smokers. However, in current smokers, the risks of all cancers and only prostate cancer were significantly increased in the highest BWV quintile group (HR 1.19, 95% CI 1.09–1.31; HR 1.51, 95% CI 1.08–2.11). The risk of kidney cancer also increased in this group, although the finding was not statistically significant (HR 1.77, 95% CI 0.87–3.63) This study suggested BWV is an independent risk factor for cancer in men, especially in lung, liver, and prostate cancer, but evidence was weaker in kidney cancer. This association remained significant only in prostate cancer in current smokers.

Body weight variability is not associated with changes in risk factors for cardiometabolic disease

CONTEXT

Weight loss is known to improve health, however the influence of variability in body weight around the overall trajectory on these outcomes is unknown. Few studies have measured body weight frequently enough to accurately estimate the variability component.

OBJECTIVE

To investigate the association of 12-month weight variability and concurrent weight change with changes in health markers and body composition.

METHODS

This study was a secondary analysis of the NoHoW trial, a 2 × 2 factorial randomised controlled trial promoting evidence-based behaviour change for weight loss maintenance. Outcome measurements related to cardiometabolic health and body composition were taken at 0, 6 and 12 months. Participants were provided with Wi-Fi connected smart scales (Fitbit Aria 2) and asked to self-weigh regularly over this period. Associations of weight variability and weight change with change in outcomes were investigated using multiple linear regression with multiple levels of adjustment in 955 participants.

RESULTS

Twelve models were generated for each health marker. Associations between weight variability and changes in health markers were inconsistent between models and showed no evidence of a consistent relationship, with all effects explaining <1% of the outcome, and most 0%. Weight loss was consistently associated with improvements in health and body composition, with the greatest effects seen in percent body fat (R2 = 10.4-11.1%) followed by changes in diastolic (4.2-4.7%) and systolic (3-4%) blood pressure.

CONCLUSION

Over 12-months, weight variability was not consistently associated with any measure of cardiometabolic health or body composition, however weight loss consistently improved all outcomes.

TRIAL REGISTRATION NUMBER

ISRCTN88405328.

Impact of weight loss and partial weight regain on immune cell and inflammatory markers in adipose tissue in male mice

Weight fluctuations are common among individuals with obesity and are associated with increased morbidity. We examined adipose tissue immune and inflammatory markers in mice following weight loss and partial weight regain. Male C57BL/6 mice were randomized into four groups (n = 8-10/group): low-fat diet for 32 wk (LFD), high-fat diet for 32 wk (HFD), LFD for 28 wk and then changed to a HFD for 4 wk (LFD→H), and HFD for 21 wk and then changed to LFD for 7 wk and then changed to HFD for 4 wk (HFD→L→H). LFD→H and HFD→L→H mice did not differ in body weight, fat mass, or fat percentage; however, these parameters were greater than in LFD (P < 0.05) but lower than in HFD (P < 0.05). HFD→L→H mice had smaller adipocytes than HFD and LFD→H (P < 0.05) but not LFD mice. Expressions of CD11c and CD8a genes were elevated in epididymal fat of HFD→L→H compared with LFD→H and LFD (P < 0.05)mice. However, CD11c was lower in HFD→L→H than in HFD mice (P < 0.05), but there was no difference in CD8a between these groups. TNFα and IFNγ expressions were increased in HFD→L→H compared with LFD and LFD→H mice (P < 0.05), although HFD→L→H had lower expression of these cytokines than HFD (P < 0.05). IL-1β was greater in HFD→L→H compared with LFD (P < 0.05) but was not different from LFD→H or HFD mice. Monocyte chemoattractant protein-1 was lower (P < 0.05) in HFD→L→H than in LFD→H. These data reinforce the importance of maintaining a body weight in the range that is recommended for optimal health to reduce immune and inflammatory perturbations associated with obesity.NEW & NOTEWORTHY We examined the immune and inflammatory status of adipose tissue in mice after they underwent weight loss followed by partial weight regain. We show an increase in selected immune cells and inflammatory mediators, in high-fat diet-fed mice that had prior exposure to a high-fat diet. Although weight fluctuations appear to exacerbate immune cell abundance and inflammation in adipose tissue, severity is less than in mice that were exposed to sustained high-fat diet feedings.

PPAR-α activation counters brown adipose tissue whitening: a comparative study between high-fat- and high-fructose-fed mice

OBJECTIVES

To examine the effects of a selective peroxisome proliferator-activated receptor (PPAR-α) agonist treatment on interscapular brown adipose tissue (iBAT) whitening, focusing on thermogenic, lipolysis, and lipid oxidation markers in mice fed a high-fat or high-fructose diet.

METHODS

Fifty animals were randomly assigned to receive a control diet (C, 10% lipids as energy), high-fat diet (HF, 50% lipids as energy), or high-fructose diet (HFRU, 50% fructose as energy) for 12 wk. Each group was redivided to begin the 5-wk treatment, totaling five experimental groups: C, HF, HF-a, HFRU, and HFRU-a. The drug was mixed with diet at the dose of 3.5 mg/kg body mass.

RESULTS

HF group was the heaviest group, and the HF and HFRU groups had glucose intolerance. PPAR-α activation alleviated these metabolic constraints. HF and HFRU groups had negative vascular endothelial growth factor A (VEGF-A) immunostaining, but only the HF group had a pattern of lipid droplet accumulation that resembled the white adipose tissue, characterizing the whitening phenomenon. Whitening in the HF group was accompanied by decreased expression of genes related to thermogenesis, β-oxidation, and antiinflammatory effects. All of them were augmented by the PPAR-α activation in HF-a and HFRU-a groups, countering the whitening in the HF-a group. Treated groups also had a lower respiratory exchange ratio than untreated groups, suggesting that lipids were used as fuel for the enhanced thermogenesis.

CONCLUSIONS

The PPAR-α agonist countered iBAT whitening by inducing the thermogenic pathway and reducing the lipid droplet size, in addition to enhanced VEGF-A expression, adrenergic stimulus, and lipolysis in HF-fed mice.

Weight Regain in Formerly Obese Mice Hastens Development of Hepatic Steatosis Due to Impaired Adipose Tissue Function

OBJECTIVE

Weight regain after weight loss is common, and there is evidence to suggest negative effects on health because of weight cycling. This study sought to investigate the impact of weight regain in formerly obese mice on adipose tissue architecture and stromal cell function.

METHODS

A diet-switch model was employed for obesity induction, weight loss, and weight regain in mice. Flow cytometry quantified adipose tissue leukocytes in adipose tissue. Liver and adipose tissue depots were compared to determine tissue-specific effects of weight cycling.

RESULTS

Epididymal white adipose tissue of formerly obese mice failed to expand in response to repeat exposure to high-fat diet and retained elevated numbers of macrophages and T cells. Weight regain was associated with disproportionally elevated liver mass, hepatic triglyceride content, serum insulin concentration, and serum transaminase concentration. These effects occurred despite an extended 6-month weight loss cycle and they demonstrate that formerly obese mice maintain durable alterations in their physiological response to weight regain. Conditioned media from epididymal adipose tissue of formerly obese mice inhibited adipogenesis of 3T3-L1 preadipocytes, suggesting a potential mechanism to explain failed epididymal adipose tissue expansion during weight regain.

CONCLUSIONS

Metabolic abnormalities related to defects in adipose tissue expansion and ongoing dysfunction manifest in formerly obese mice during weight regain.

Trained Immunity: Linking Obesity and Cardiovascular Disease across the Life-Course?

Obesity, a chronic inflammatory disease, is the most prevalent modifiable risk factor for cardiovascular disease. The mechanisms underlying inflammation in obesity are incompletely understood. Recent developments have challenged the dogma of immunological memory occurring exclusively in the adaptive immune system and show that the innate immune system has potential to be reprogrammed. This innate immune memory (trained immunity) is characterized by epigenetic and metabolic reprogramming of myeloid cells following endogenous or exogenous stimulation, resulting in enhanced inflammation to subsequent stimuli. Trained immunity phenotypes have now been reported for other immune and non-immune cells. Here, we provide a novel perspective on the putative role of trained immunity in mediating the adverse cardiovascular effects of obesity and highlight potential translational pathways.

Adipose tissue macrophages: Unique polarization and bioenergetics in obesity

Macrophages comprise a majority of the resident immune cells in adipose tissue (AT) and regulate both tissue homeostasis in the lean state and metabolic dysregulation in obesity. Since the AT environment rapidly changes based upon systemic energy status, AT macrophages (ATMs) must adapt phenotypically and metabolically. There is a distinct dichotomy in the polarization and bioenergetics of in vitro models, with M2 macrophages utilizing oxidative phosphorylation (OX PHOS) and M1 macrophages utilizing glycolysis. Early studies suggested differential polarization of ATMs, with M2-like macrophages predominant in lean AT and M1-like macrophages in obese AT. However, recent studies show that the phenotypic plasticity of ATMs is far more complicated, which is also reflected in their bioenergetics. Multiple ATM populations exist along the M2 to M1 continuum and appear to utilize both glycolysis and OX PHOS in obesity. The significance of the dual fuel bioenergetics is unclear and may be related to an intermediate polarization, their buffering capacity, or the result of a mixed population of distinct polarized ATMs. Recent evidence also suggests that ATMs of lean mice serve as a substrate buffer or reservoir to modulate lipid, catecholamine, and iron availability. Furthermore, recent models of weight loss and weight cycling reveal additional roles for ATMs in systemic metabolism. Evaluating ATM phenotype and intracellular metabolism together may more accurately illuminate the consequences of ATM accumulation in obese AT, lending further insight into obesity-related comorbidities in humans.

Links between Immunologic Memory and Metabolic Cycling

Treatments for metabolic diseases, such as diet and therapeutics, often provide short-term therapy for metabolic stressors, but relapse is common. Repeated bouts of exposure to, and relief from, metabolic stimuli results in a phenomenon we call "metabolic cycling." Recent human and rodent data suggest metabolic cycling promotes an exaggerated response and ultimately worsened metabolic health. This is particularly evident with cycling of body weight and hypertension. The innate and adaptive immune systems have a profound impact on development of metabolic disease, and current data suggest that immunologic memory may partially explain this association, especially in the context of metabolic cycling. In this Brief Review, we highlight recent work in this field and discuss potential immunologic mechanisms for worsened disease prognosis in individuals who experience metabolic cycling.

Beneficial effects of intermittent fasting on steatosis and inflammation of the liver in mice fed a high-fat or a high-fructose diet

OBJECTIVE

Intermittent fasting (IF) is a nutritional intervention with significant metabolic effects on the liver that are not yet fully understood. The aim of this study was to investigate the effects of IF on body mass, lipid profile, glucose metabolism, liver lipogenesis, β-oxidation, and inflammation.

METHODS

We used cellular and molecular techniques to investigate the effects of IF on 3-mo-old male C57 BL/6 mice that were fed control (10% kcal fat), high-fat (HF; 50% kcal fat), or high-fructose (HFr; 50% kcal fructose) diets for 8 wk. Half of the animals were submitted to IF (1 d fed, 1 d fast) for an additional 4 wk.

RESULTS

Although food intake on the fed day did not differ between the groups, mice in the HF and HFr groups showed diminished body mass, total cholesterol, and triacylglycerol levels. Also, plasma adiponectin increased in the HFr group and leptin decreased in the HF mice. Oral glucose tolerance test and insulin were ameliorated by IF, regardless of the diet consumed (HF or HFr), and decreased hepatic lipogenesis and increased β-oxidation markers, resulting in a reduction of the hepatic steatosis and inflammation.

CONCLUSIONS

There were beneficial effects of IF even with the continuity of the obesogenic diet and proinflammatory diet in mice. It is recommended that based on the beneficial effects of IF on glucose and liver metabolism and inflammation that IF be a coadjutant factor in the treatment of hepatic metabolic issues and steatosis.

Association of Weight Fluctuation With Mortality in Japanese Adults

IMPORTANCE

Weight cycling is associated with the risk of mortality from heart disease, but many studies have not distinguished between simple nonlinear (monotone) weight changes and more complex changes that reflect fluctuations.

OBJECTIVE

To assess whether extreme body weight variation is associated with mortality after controlling for nonlinear weight changes.

DESIGN, SETTING, AND PARTICIPANTS

In this prospective clinical cohort study, 4796 Japanese atomic bomb survivors were examined in the clinic as part of a biennial health examination and research program. The study consisted of a 20-year longitudinal baseline period (July 1, 1958, to June 30, 1978) and subsequent mortality follow-up of 27 years (July 1, 1978, to June 30, 2005) Participants were initially between the ages of 20 and 49 years during the baseline period and, throughout the baseline period, had no diagnoses of cardiovascular disease (CVD) or cancer and attended at least 7 of 10 scheduled examinations. Data analysis was performed from October 16, 2015, to May 13, 2016.

EXPOSURES

Residual variability in body mass index (BMI) during the baseline period.

MAIN OUTCOMES AND MEASURES

Outcomes were mortality from ischemic heart disease, cerebrovascular disease, other CVDs combined, other causes (except cancer), and cancer. Root mean squared error was calculated to capture individual residual variation in BMI after adjustment for baseline BMI trends, and the association of magnitude of residual variation with mortality was calculated as relative risk.

RESULTS

In total, 4796 persons (mean [SD] age, 35.0 [7.3] years at first baseline examination; 3252 [67.8%] female; mean [SD] BMI, 21.2 [2.8] at first baseline visit [20.6 (2.4) among men and 21.5 (2.9) among women]) participated in the study. During follow-up, 1550 participants died: 82 (5.3% of all deaths) of ischemic heart disease, 181 (11.7%) of cerebrovascular disease, 186 (12.0%) of other CVDs, 615 (39.7%) of cancer, and 486 (31.3%) of other causes. Magnitude of residual variation in weight was associated with all-cause mortality (relative risk, 1.25 for 1 U of additional variation; 95% CI, 1.06-1.47) and ischemic heart disease mortality (relative risk, 2.49; 95% CI, 1.41-4.38).

CONCLUSIONS AND RELEVANCE

The findings suggest that an association exists between weight variation and heart disease mortality and that weight loss interventions, if deemed to be necessary, should be considered carefully.

Endothelial Dysfunction and Inflammation Precedes Elevations in Blood Pressure Induced by a High-Fat Diet

Background

Obesity leads to a chronic inflammatory state, endothelial dysfunction and hypertension.

Objective

To establish the time-course of events regarding inflammatory markers, endothelial dysfunction, systolic blood pressure (SBP) in obesity in only one experimental model.

Methods

We fed male Wistar rats (eight-week age) with a standard diet (Control - CT, n = 35), or palatable high-fat diet (HFD, n = 35) for 24 weeks. Every six weeks, 7 animals from each group were randomly selected for euthanasia. SBP and serum levels of interleukin-6, tumor necrosis factor-α, C-reactive protein, adiponectin and nitric oxide were determined. Endothelial and vascular smooth muscle functions were determined in dissected aorta and lipid peroxidation was measured. Statistical significance was set at p < 0.05.

Results

Levels of pro-inflammatory cytokines began to increase after six weeks of a high-fat diet, while those of the anti-inflammatory cytokine adiponectin decreased. Interestingly, the endothelial function and serum nitric oxide began to decrease after six weeks in HFD group. The SBP and lipid peroxidation began to increase at 12 weeks in HFD group. In addition, we showed that total visceral fat mass was negatively correlated with endothelial function and positively correlated with SBP.

Conclusion

Our results show the time-course of deleterious effects and their correlation with obesity.

Involvement of M1 and M3 receptors in isolated pancreatic islets function during weight cycling in ovariectomized rats

We investigated the structural and functional adaptations of the pancreas during weight cycling in animals submitted to hypoestrogenism. Female Wistar rats were distributed among the following test groups: ShamAL (AL, ad libitum); OVXAL (ovariectomized); and OVXcycle (dietary restriction with weight cycling). The ShamAL and OVXAL groups received commercial feed ad libitum, whereas the OVXcycle group received 21 days of commercial feed ad libitum, and 21 days of caloric restriction, with caloric intake amounting to 40% of the amount of feed consumed by the rats in the OVXAL group. The tolerance tests for glucose and insulin were applied. After euthanasia, the pancreas and adipose tissue were collected. The disappearance of glucose during the insulin assay occurred at a higher rate in tissues from the OVXcycle group, compared with the OVXAL group. Fasting glycemia and perirenal adipose tissue were lower in the OVXcycle group. By comparison with the ShamAL and OVXAL groups, the OVXcycle group showed higher protein expression of the M1 and M3 receptors and SOD1-2, as well as higher carbachol-induced insulin secretion. Under highly stimulatory conditions with 16.7 mmol/L glucose, the OVXAL and OVXcycle groups presented lower insulin secretion compared with the ShamAL group. Morphological analysis revealed higher iron deposition in the OVXAL islets by comparison with the OVXcycle group. These results show that ovariectomy accelerated the loss of pancreatic islet function, and that weight cycling could restore the function of the islets.

Weight Cycling Increases Longevity Compared with Sustained Obesity in Mice

OBJECTIVE

Despite the known health benefits of weight loss among persons with obesity, observational studies have reported that cycles of weight loss and regain, or weight cycling, are associated with increased mortality. To study whether weight loss must be sustained to achieve health and longevity benefits, we performed a randomized controlled feeding study of weight cycling in mice.

METHODS

In early adult life, obese mice were randomized to ad libitum feeding to sustain obesity, calorie restriction to achieve a "normal" or intermediate body weight, or weight cycling (repeated episodes of calorie restriction and ad libitum refeeding). Body weight, body composition, and food intake were followed longitudinally until death. A subsample of mice was collected from each group for determination of adipose cell size, serum analytes, and gene expression.

RESULTS

Weight loss significantly reduced adipose mass and adipocyte size in both sexes, whereas weight cycling animals regained body fat and cell size during refeeding. Sustained weight loss resulted in a dose-dependent decrease in mortality compared with ad libitum feeding.

CONCLUSIONS

Weight cycling significantly increased life-span relative to remaining with obesity and had a similar benefit to sustained modest weight loss.

Attenuation of diet-induced hypothalamic inflammation following bariatric surgery in female mice

Background

Exposure of rodents to chronic high-fat diet (HFD) results in upregulation of inflammatory markers and proliferation of microglia within the mediobasal hypothalamus. Such hypothalamic inflammation is associated with metabolic dysfunction, central leptin resistance, and maintenance of obesity. Bariatric surgeries result in long-term stable weight loss and improved metabolic function. However, the effects of such surgical procedures on HFD-induced hypothalamic inflammation are unknown. We sought to characterize the effects of two bariatric surgical procedures, Roux-en-Y gastric bypass (RYGB) and biliary diversion (BD-IL), in female mice with particular emphasis on HFD-induced hypothalamic inflammation and microgliosis.

Methods

RYGB and BD-IL were performed on diet-induced obese (DIO) mice. Quantitative RT-PCR and fluorescent microscopy were used to evaluate hypothalamic inflammatory gene expression and microgliosis. Results were compared to lean (CD), DIO sham-surgerized mice (DIO-SHAM), and dietary weight loss (DIO-Rev) controls.

Results

In female mice, RYGB and BD-IL result in normalization of hypothalamic inflammatory gene expression and microgliosis within 8 weeks of surgery, despite ongoing exposure to HFD. Paralleling these results, the hypothalamic expression levels of the orexigenic neuropeptide Agrp and the anorexic response of surgical mice to exogenous leptin were comparable to lean controls (CD). In contrast, results from DIO-Rev mice were comparable to DIO-SHAM mice, despite transition back to standard rodent show and normalization of weight.

Conclusion

Bariatric surgery attenuates HFD-induced hypothalamic inflammation and microgliosis and restores leptin sensitivity, despite ongoing exposure to HFD.

Impact of weight cycling on CTRP3 expression, adipose tissue inflammation and insulin sensitivity in C57BL/6J mice

Impacts of weight cycling on C1q/tumor necrosis factor (TNF)-related protein-3 (CTRP3) expression, adipose tissue inflammation and insulin sensitivity in C57BL/6J mice were evaluated in the current study. A total of 30 male C57Bl/6J mice were divided randomly into three groups; normal control (n=10), high-fat diet (OB, n=10) and weight cycling (WC, n=10), which were fed with high-fat diet in the first and last 8 weeks and regular chow in between. Systemic glucose metabolic status and insulin sensitivity were detected by intraperitoneal glucose tolerance test and hyperinsulinemic-euglycemic clamp, respectively. Blood levels of interleukin (IL)-6 and TNF-α were determined using ELISA. Relative CTRP3, IL-6, TNF-α and glucose transporter (GLUT)4 mRNA expression in adipose tissue was detected using reverse transcription-quantitative polymerase chain reaction assays. Relative CTRP3, phosphatidylinositide 3-kinases (PI3K) and protein kinase B (PKB; Ser473) protein expression were detected by western blot analysis. Area under the curve of glucose and glucose infusion rate of the WC group were significantly increased compared with the OB group (P<0.01). CTRP3 mRNA and protein levels of the WC group were significantly decreased by 20.3 and 23.1%, respectively, compared with the OB group (P<0.01). IL-6 and TNF-α protein plasma levels and gene expression in adipose tissue of the WC group were significantly increased compared with the OB group (P<0.01). Expression and phosphorylation of insulin signaling molecules PI3K and PKB (Ser473), respectively and GLUT4 gene expression in adipose tissue of the WC group were significantly decreased compared with the OB group (P<0.01). In conclusion, weight cycling impaired glucose metabolism and insulin sensitivity by decreasing CTRP3, PI3K, phosphorylated-PKB (Ser473) and GLUT4 expression, and increasing IL-6 and TNF-α levels.

Hypothalamic miR-219 regulates individual metabolic differences in response to diet-induced weight cycling

Consumption of a low calorie diet is the most common approach to lose weight. While generally effective at first, it is frequently followed by a relapse where the pre-diet weight is regained, and often exceeded. This pattern of repeated weight loss/regain is referred to as weight cycling and the resulting metabolic response varies greatly between individuals.

Objective

We attempted to address the issue of individual differences in the response to weight cycling in male mice.

Methods

We first exposed adult wild type mice to repeated cycles of high/low fat food. Next, using a lentiviral approach, we knocked-down or over-expressed miR-219 in the ventromedial hypothalamus (VMH) of an additional mouse cohort and performed a full metabolic assessment.

Results

Exposure of wild type males to weight cycling resulted in the division of the cohort into subsets of resistant versus metabolic-syndrome-prone (MS) animals, which differed in their metabolic profile and hypothalamic miR-219 levels. Lentiviral knock-down of miR-219 in the VMH led to exacerbation of metabolic syndrome. In contrast, over-expression of miR-219 resulted in moderation of the metabolic syndrome phenotype.

Conclusions

Our results suggest a role for miR-219 in the mediation of the metabolic phenotype resulting from repeated weight cycling.

•

Repeated cycles of high fat diet induce different responses in adult males.

•

Low miR-219 in ventromedial hypothalamus are linked to metabolic-syndrome proneness.

•

Lentiviral knockdown of miR-219 induces metabolic-syndrome-prone phenotype.

•

Lentiviral overexpression of miR-219 provides moderate protection from metabolic-syndrome.

Global transcriptome analysis identifies weight regain-induced activation of adaptive immune responses in white adipose tissue of mice

Objective:

Studies have indicated that weight regain following weight loss predisposes obese individuals to metabolic disorders; however, the molecular mechanism of this potential adverse effect of weight regain is not fully understood. Here we investigated global transcriptome changes and the immune response in mouse white adipose tissue caused by weight regain.

Design:

We established a diet switch protocol to compare the effects of weight regain with those of weight gain without precedent weight loss, weight loss maintenance and chow diet. We conducted a time course analysis of global transcriptome changes in gonadal white adipose tissue (gWAT) during the weight fluctuation. Co-expression network analysis was used to identify functional modules associated with the weigh regain phenotype. Immune cell populations in gWAT were characterized by flow-cytometric immunophenotyping. Metabolic phenotypes were monitored by histological analysis of adipose tissue and liver, and blood-chemistry and body weight/composition analyses.

Results:

In total, 952 genes were differentially expressed in the gWAT in the weight regain vs the weight gain group. Upregulated genes were associated with immune response and leukocyte activation. Co-expression network analysis showed that genes involved in major histocompatibility complex I and II-mediated antigen presentation and T-cell activation function were upregulated. Consistent with the transcriptome analysis results, flow cytometry demonstrated significant increases in subsets of T cells and proinflammatory M1 macrophages in the gWAT in the weight regain as compared to the weight gain group. In addition, upregulation of adaptive immune responses was associated with high incidence of adipocyte death and upregulation of high mobility group box 1, a well-known component of damage-associated molecular patterns.

Conclusions:

Our global transcriptome analysis identified weight regain-induced activation of adaptive immune responses in mouse white adipose tissue. Results suggest that activation of adipocyte death-associated adaptive immunity in adipose tissue may contribute to unfavorable metabolic effects of weight regain following weight loss.

Adaptive Immunity and Metabolic Health: Harmony Becomes Dissonant in Obesity and Aging

Adipose tissue (AT) is the primary energy reservoir organ, and thereby plays a critical role in energy homeostasis and regulation of metabolism. AT expands in response to chronic overnutrition or aging and becomes a major source of inflammation that has marked influence on systemic metabolism. The chronic, sterile inflammation that occurs in the AT during the development of obesity or in aging contributes to onset of devastating diseases such as insulin resistance, diabetes, and cardiovascular pathologies. Numerous studies have shown that inflammation in the visceral AT of humans and animals is a critical trigger for the development of metabolic syndrome. This work underscores the well-supported conclusion that the inflammatory immune response and metabolic pathways in the AT are tightly interwoven by multiple layers of relatively conserved mechanisms. During the development of diet-induced obesity or age-associated adiposity, cells of the innate and the adaptive immune systems infiltrate and proliferate in the AT. Macrophages, which dominate AT-associated immune cells in mouse models of obesity, but are less dominant in obese people, have been studied extensively. However, cells of the adaptive immune system, including T cells and B cells, contribute significantly to AT inflammation, perhaps more in humans than in mice. Lymphocytes regulate recruitment of innate immune cells into AT, and produce cytokines that influence the helpful-to-harmful inflammatory balance that, in turn, regulates organismal metabolism. This review describes inflammation, or more precisely, metabolic inflammation (metaflammation) with an eye toward the AT and the roles lymphocytes play in regulation of systemic metabolism during obesity and aging. © 2017 American Physiological Society. Compr Physiol 7:1307-1337, 2017.

Sex Steroid Hormones Regulate Leptin Transcript Accumulation and Protein Secretion in 3T3-L1 Cells

Leptin is an adipokine produced by fat cells that regulates food consumption and metabolic activity. Sexual dimorphism in leptin and fat stores have been observed in humans and rodents with females having more leptin and greater levels of subcutaneous fat than males. One potential mechanism leading to this dimorphism is steroid hormone regulated synthesis of transcripts encoding leptin. Identification of direct regulatory mechanisms is difficult in animals or primary adipocytes due to these intertwined dimorphisms. We used well-characterized 3T3-L1 murine adipocytes to demonstrate that dihydrotestosterone (DHT) reduced Leptin (Lep) transcript abundance and cytosolic and secreted leptin protein. The magnitude of this effect was greatest on secreted leptin, which was decreased by DHT to 30% of the control. In contrast, 17β-estradiol significantly increased the abundance of transcripts encoding leptin and increased secreted leptin to 230% of the control. Treatment with estrogen and androgen receptor antagonists had opposite effects on Lep transcript abundance to steroid treatments, indicating that these transcriptional effects are mediated through the canonical steroid hormone signaling pathways. These results indicate that short-term treatments with steroid hormones are sufficient to alter both Lep transcript accumulation and leptin protein secretion, and may play a role in the sexual dimorphism of this adipokine.

A fish oil diet induces mitochondrial uncoupling and mitochondrial unfolded protein response in epididymal white adipose tissue of mice

White adipose tissue (WAT) mitochondrial dysfunction is linked to the pathogenesis of obesity driven insulin resistance. Dietary conditions that alter fat mass are known to affect white adipocyte mitochondrial function, however, the impact of high calorie diets on white adipocyte mitochondria is not fully understood. The aim of this study is to assess the effect of a diet rich in saturated or polyunsaturated fat on mitochondrial unfolded protein response (UPR^mt), a retrograde signaling response that maintains mitochondrial homeostasis, in epididymal WAT (eWAT). Mice were fed a low fat diet (LFD), saturated fat diet (SFD) or fish oil (unsaturated fat diet, UFD) and assessed changes in eWAT mitochondria. Compared to mice fed a LFD, SFD-fed mice have reduced mitochondrial biogenesis markers, mitochondrial fatty acid oxidation enzymes and TCA cycle enzymes, suggesting an impaired mitochondrial function that could contribute to increased fat mass. In contrast, isocaloric UFD-fed mice have increased expression of mitochondrial uncoupling protein 1 (UCP1) and peroxisomal fatty acid oxidation enzymes suggesting that elevated mitochondrial uncoupling and peroxisomal fatty acid oxidation could contribute to the reduction in fat mass. Interestingly, expression of UPR^mt-associated proteins caseinolytic peptidase (ClpP) and heat shock protein 60 (Hsp60) are induced by UFD, whereas SFD reduced the expression of ClpP. Based on our data, we propose that induction of UPR^mt helps to preserve a functional mitochondria and efficient utilization of fat by UFD whereas a dampened UPR^mt response might impair mitochondrial function and promote fat accumulation by SFD. Thus, our findings suggest a potential role of UPR^mt in mediating the beneficial effects of fish oil.

CD4+ T cells memorize obesity and promote weight regain

Body weight regain often causes failure of obesity therapies while the underlying mechanism remains largely unknown. In this study, we report that immune cells, especially CD4+ T cells, mediate the ‘memory’ of previous obese status. In a weight gain-loss-regain model, we found that C57BL/6J mice with an obesity history showed a much faster rate of body weight regain. This obesity memory could last for at least 2 months after previously obese mice were kept at the same body weight as non-obese mice. Surprisingly, such obesity memory was abrogated by dexamethasone treatment, whereas immunodeficient Rag1^−/− and H2A^−/− mice failed to establish such memory. Rag1^−/− mice repossessed the obesity memory when immune cells or CD4+ T cells isolated from previously obese mice were transferred. Furthermore, depletion of CD4+ T cells led to obesity memory ablation. Taken together, we conclude that CD4+ T cells mediate obesity memory and promote weight regain.

Weight Fluctuation and Cancer Risk in Postmenopausal Women: The Women's Health Initiative

Background: Weight cycling, defined by an intentional weight loss and subsequent regain, commonly occurs in overweight and obese women and is associated with some negative health outcomes. We examined the role of various weight-change patterns during early to mid-adulthood and associated risk of highly prevalent, obesity-related cancers (breast, endometrial, and colorectal) in postmenopausal women.Methods: A total of 80,943 postmenopausal women (age, 63.4 ± 7.4 years) in the Women's Health Initiative Observational Study were categorized by self-reported weight change (weight stable; weight gain; lost weight; weight cycled [1-3, 4-6, 7-10, >10 times]) during early to mid-adulthood (18-50 years). Three site-specific associations were investigated using Cox proportional hazard models [age, race/ethnicity, income, education, smoking, alcohol, physical activity, hormone therapy, diet, and body mass index (BMI)].Results: A total of 7,464 (breast = 5,564; endometrial = 788; and colorectal = 1,290) incident cancer cases were identified between September 1994 and August 2014. Compared with weight stability, weight gain was significantly associated with risk of breast cancer [hazard ratio (HR), 1.11; 1.03-1.20] after adjustment for BMI. Similarly, weight cycling was significantly associated with risk of endometrial cancer (HR = 1.23; 1.01-1.49). Weight cycling "4 to 6 times" was most consistently associated with cancer risk, showing a 38% increased risk for endometrial cancer [95% confidence interval (CI), 1.08-1.76] compared with weight stable women.Conclusions: Weight gain and weight cycling were positively associated with risk of breast and endometrial cancer, respectively.Impact: These data suggest weight cycling and weight gain increase risk of prevalent cancers in postmenopausal women. Adopting ideal body-weight maintenance practices before and after weight loss should be encouraged to reduce risk of incident breast and endometrial cancers. Cancer Epidemiol Biomarkers Prev; 26(5); 779-86. ©2017 AACR.

AT1 receptor antagonist induces thermogenic beige adipocytes in the inguinal white adipose tissue of obese mice

PURPOSE

To evaluate whether losartan is able to induce beige adipocytes formation, focusing on the thermogenic gene expression and adipocyte remodeling in the subcutaneous white adipose tissue of diet-induced obese mice.

METHODS

Male C57BL/6 mice received a control diet (10% energy as lipids) or a high-fat diet (50% energy as lipids) for 10 weeks, followed by a 5-week treatment with losartan: control group, control-losartan group (10 mg/Kg/day), high-fat group and high-fat-losartan group (10 mg/Kg/day). Biochemical, morphometrical, stereological and molecular approaches were used to evaluate the outcomes.

RESULTS

The high-fat diet elicited overweight, insulin resistance and adipocyte hypertrophy in the high-fat group, all of which losartan rescued in the high-fat-losartan group. These effects comply with the induction of beige adipocytes within the inguinal fat pads in high-fat-losartan group as they exhibited the greatest energy expenditure among the groups along with the presence uncoupling protein 1 positive multilocular adipocytes with enhanced peroxisome proliferator-activated receptor gamma coactivator 1-alpha and PR domain containing 16 mRNA levels, indicating a significant potential for mitochondrial biogenesis and adaptive thermogenesis.

CONCLUSIONS

Our results show compelling evidence that losartan countered diet-induced obesity in mice by enhancing energy expenditure through beige adipocytes induction. Reduced body mass, increased insulin sensitivity, decreased adipocyte size and marked expression of uncoupling protein 1 by ectopic multilocular adipocytes support these findings. The use of losartan as a coadjutant medicine to tackle obesity and its related disorders merits further investigation.

A rich medium-chain triacylglycerol diet benefits adiposity but has adverse effects on the markers of hepatic lipogenesis and beta-oxidation

We investigated the increasing amounts of medium-chain triacylglycerol (MCT) in the diet on hepatic lipid metabolism.

Fish oil diet modulates epididymal and inguinal adipocyte metabolism in mice

We aimed to investigate the impact of different high-fat diets containing fish oil on adiposity and white adipose tissue (WAT) function in mice, comparing the effects on epididymal (eWAT) and subcutaneous (sWAT) depots. For this, we used C57BL/6 male mice fed four types of diets for eight weeks: standard chow (SC), high-fat lard (HF-L), high-fat lard plus fish oil (HF-L + FO), and high-fat fish oil (HF-FO). The HF-L group had a greater body mass (BM) gain, insulin resistance, increased gene expression related to lipogenesis (CD36, aP2, SREBP1c, and FAS), decreased gene expression of perilipin in both eWAT and sWAT, and reduced expression of genes related to beta-oxidation (CPT-1a) and to mitochondrial biogenesis (PGC1alpha, NRF1, and TFAM) in eWAT and sWAT. On the other hand, the HF-L + FO and HF-FO groups showed a smaller BM gain and adiposity, and normalization of insulin resistance and lipogenic genes in both eWAT and sWAT. These animals also showed decreased perilipin gene expression and elevated expression of beta-oxidation and mitochondrial biogenesis genes in eWAT and sWAT. 'Beige' adipocytes were identified in sWAT of the HF-FO animals. In conclusion, fish oil intake has anti-obesity effects through modulation of both eWAT and sWAT metabolism in mice and is relevant in diminishing the BM gain, adiposity, and insulin resistance even in combination with a high-fat lard diet in mice.

Metabolic dysfunction following weight cycling in male mice

Background

Combatting over-weight or obesity can lead to large fluctuations in an individual’s body weight, often referred to as weight cycling or “yo-yo” dieting. Current evidence regarding the potentially damaging effects of these changes is conflicting.

Methods

Here, we assess the metabolic effects of weight cycling in a murine model, comprising three dietary switches to normal or high fat diets at 6 week intervals; male C57BL/6 mice were fed either a control (C) or high fat (F) diet for 6 weeks (n=140/group). C and F groups were then either maintained on their initial diet (CC and FF respectively) or switched to a high fat (CF) or control (FC) diet (n=35/group). For the final 6 week interval, CC and CF groups were returned to the control diet (CCC and CFC groups) while FC and FF groups were placed on a high fat diet (FCF and FFF) (n=28/group).

Results

For the majority of metabolic outcomes changes aligned with dietary switches; however assessment of neuropeptides and receptors involved in appetite regulation and reward signalling pathways reveal variable patterns of expression. Furthermore, we demonstrate that multiple cycling events leads to a significant increase in internal fat deposition, even when compared to animals maintained on a high fat diet (Internal Fat: FCF: 7.4 ± 0.2g vs. FFF: 5.6 ± 0.2g; p<0.01).

Conclusions

Increased internal adipose tissue is strongly linked to the development of metabolic syndrome associated conditions such as type 2 diabetes, cardiovascular disease and hypertension. While further work will be required to elucidate the mechanisms underlying the neuronal control of energy homeostasis, these studies provide a causative link between weight cycling and adverse health.

Maternal vitamin D-restricted diet has consequences in the formation of pancreatic islet/insulin-signaling in the adult offspring of mice

The maternal deficiency of vitamin D can act on organogenesis in mice offspring, being a risk factor for chronic diseases in adulthood. This study investigates the effects of maternal deficiency of vitamin D on structural islet remodeling and insulin-signaling pathway in the offspring. We studied male C57Bl/6 offspring at 3-month old (n = 10/group) from mother fed one of the two diets: control diet (C) or vitamin D-restricted diet (VitD^-). After weaning, offspring only fed the control diet ad libitum. In the offspring, we studied insulin production, islet remodeling, and islet protein expression of the insulin-signaling pathway (Western blotting, isolated islet, n = 5/group). VitD^- offspring showed greater glycemia (P = 0.012), smaller beta-cell mass (P = 0.014), and hypoinsulinemia (P = 0.024) than C offspring. Comparing VitD^- offspring with C offspring, we observed lower protein levels in islet of insulin (P = 0.003), insulin receptor substrate-1 (P = 0.025), phosphatidylinositol-3-kinases (P = 0.045), 3-phosphoinositide-dependent protein kinase 1 (P = 0.017), protein kinase B (P = 0.028), with reduced expression of pancreas/duodenum homeobox-1 (PDX-1) (P = 0.016), glucose transporter-2 (P = 0.003), and glucokinase (P = 0.045). The maternal vitamin D-restricted diet modifies the development of the pancreas of the offspring, leading to islet remodeling and altered insulin-signaling pathway. The decrease of PDX-1 is probably significant to the changes in the beta-cell mass and insulin secretion in adulthood.

Resistin's, obesity and insulin resistance: the continuing disconnect between rodents and humans

PURPOSE

This review aimed to discuss the conflicting findings from resistin research in rodents and humans as well as recent advances in our understanding of resistin's role in obesity and insulin resistance.

METHODS

A comprehensive review and synthesis of resistin's role in obesity and insulin resistance as well as conflicting findings from resistin research in rodents and humans.

RESULTS

In rodents, resistin is increased in high-fat/high-carbohydrate-fed, obese states characterized by impaired glucose uptake and insulin sensitivity. Resistin plays a causative role in the development of insulin resistance in rodents via 5' AMP-activated protein kinase (AMPK)-dependent and AMPK-independent suppressor of cytokine signaling-3 (SOCS-3) signaling. In contrast to rodents, human resistin is primarily secreted by peripheral-blood mononuclear cells (PBMCs) as opposed to white adipocytes. Circulating resistin levels have been positively associated with central/visceral obesity (but not BMI) as well as insulin resistance, while other studies show no such association. Human resistin has a role in pro-inflammatory processes that have been conclusively associated with obesity and insulin resistance. PBMCs, as well as vascular cells, have been identified as the primary targets of resistin's pro-inflammatory activity via nuclear factor-κB (NF-κB, p50/p65) and other signaling pathways.

CONCLUSION

Mounting evidence reveals a continuing disconnect between resistin's role in rodents and humans due to significant differences between these two species with respect to resistin's gene and protein structure, differential gene regulation, tissue-specific distribution, and insulin resistance induction as well as a paucity of evidence regarding the resistin receptor and downstream signaling mechanisms of action.

The insulin-signaling pathway of the pancreatic islet is impaired in adult mice offspring of mothers fed a high-fat diet

OBJECTIVE

Mothers fed a high-fat (HF) diet can cause different adverse alterations in their offspring. The study aimed to verify the pancreatic islet structure and insulin-signaling pathway in adulthood of offspring of mothers fed a HF diet during the pregnancy.

METHODS

Female mice (mothers) were randomly assigned to receive either standard chow (Mo-SC) or a HF diet (Mo-HF) ad libitum. After 2 mo on the experimental diets, 3-mo-old female mice were mated with male C57 BL/6 mice that were fed a SC diet. The male offspring was evaluated at 6 mo old.

RESULTS

At 6 mo of age, Mo-HF offspring had an increment in body mass and adiposity, hypercholesterolemia, and hypertriacylglycerolemia, higher levels of insulin, and leptin with a concomitant decrease in adiponectin levels. In the islet, we observed an alteration in the structure characterized by the migration of some alpha cells from the edge to the core of the islet in association with an increase in the masses of the islet, beta cell, and alpha cell, featuring a pancreatic islet remodeling. Additionally, the Mo-HF offspring demonstrated a decrease in IRS1, PI3 k p-Akt, Pd-1, and Glut2 protein expressions compared to Mo-SC offspring. However, an increase was observed in FOXO1 and insulin protein expressions in Mo-HF offspring compared to Mo-SC offspring.

CONCLUSION

The present study demonstrated that a maternal HF diet is responsible for remodeling the islet structure coupled with an adverse carbohydrate metabolism and impairment of the insulin-signaling pathway in adult male mice offspring.

Adipose tissue attenuation as a marker of adipose tissue quality: Associations with six-year changes in body weight

OBJECTIVE

Weight gain is associated with fat volume increases, but associations with fat quality are less well characterized The associations of weight change with visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) volume and attenuation were investigated.

METHODS

Computed tomography abdominal scans were acquired on a Framingham Heart Study subset (N = 836; 40.2% women; mean age 45.7 years), a mean of 6.1 years apart. Fat attenuation estimated fat quality.

RESULTS

Mean weight change was +2.0 (SD 6.8; IQR -0.7, 5.0) kg in women and +2.7 (SD 6.0; IQR -0.5, 5.4) kg in men. Per 2.5 kg weight increase in women, VAT volume increased 126 cm(3) (95% CI, 112-140, p < 0.0001), SAT volume increased 258 cm(3) (95% CI, 239-278, p < 0.0001), and fat attenuation decreased (i.e., fat quality worsened) in VAT and SAT (p < 0.0001). Increasing VAT volume was associated with decreasing fat attenuation even after accounting for weight change. Relative to weight-stable women (n = 129), women who lost >2.5 kg (n = 58) had smaller SAT attenuation decreases (p < 0.0001). Similar patterns were seen in men.

CONCLUSIONS

Weight gain was associated with decreases in fat attenuation independent of VAT and SAT volume changes. These findings highlighted the associations of weight gain and worsening fat attenuation, suggesting fat attenuation may be dynamic.

Heat-killed Lactobacillus Reuteri GMNL-263 Prevents Epididymal Fat Accumulation and Cardiac Injury in High-Calorie Diet-Fed Rats

High-calorie diet-induced obesity leads to cardiomyocyte dysfunction and apoptosis. Impaired regulation of epididymal fat content in obese patients has been known to increase the risk of cardiac injury. In our study, a lactic acid bacteria, Lactobacillus reuteri GMNL-263, was evaluated for its potential to reduce body weight and body fat ratio and to prevent heart injury in rats with high-fat diet-induced obesity. Lactic acid bacteria supplementation restored the cardiac function and decreased the physiological changes in the heart of the obese rats. In addition, the Fas/Fas-associated protein pathway-induced caspase 3/e Poly polymerase mediated apoptosis in the cardiomyocytes of the obese rats was reversed in the Lr263-treated rats. These results reveal that fed with Lr-263 reduces body fat ratio, inhibits caspase 3-mediated apoptosis and restores cardiac function in obese rats through recovery of ejection fraction and fractional shortening. Our results indicated that the administration of Lr263 lactic acid bacteria can significantly down-regulate body fat and prevent cardiomyocyte injury in obese rats.

Adipose tissue inflammation and metabolic dysfunction: a clinical perspective

Obesity is characterized by a state of chronic low-grade inflammation due to increased immune cells, specifically infiltrated macrophages into adipose tissue, which in turn secrete a range of proinflammatory mediators. This nonselective low-grade inflammation of adipose tissue is systemic in nature and can impair insulin signaling pathways, thus, increasing the risk of developing insulin resistance and type 2 diabetes. The aim of this review is to provide an update on clinical studies examining the role of adipose tissue in the development of obesity-associated complications in humans. We will discuss adipose tissue inflammation during different scenarios of energy imbalance and metabolic dysfunction including obesity and overfeeding, weight loss by calorie restriction or bariatric surgery, and conditions of insulin resistance (diabetes, polycystic ovarian syndrome).