Weight loss-induced stress in subcutaneous adipose tissue is related to weight regain

Expression of Adipose Tissue Extracellular Matrix-Related Genes Predicts Weight Loss after Bariatric Surgery

BACKGROUND

We evaluated the association between white adipose tissue parameters before bariatric surgery (BS) and post-surgical weight loss, with an especial focus on extracellular matrix (ECM) gene expression.

METHODS

Paired samples from subcutaneous (SAT) and visceral adipose tissue (VAT) were obtained from 144 subjects undergoing BS. The association between total body weight loss (%TBWL) at 12 months after BS and the histological characteristics and gene expression of selected genes in SAT and VAT was analyzed.

RESULTS

Fat cell area, size-frequency distribution, and fibrosis in SAT or VAT prior to surgery were not associated with %TBWL. On the contrary, the SAT expression of COL5A1 and COL6A3 was associated with %TBWL after BS (both p < 0.001), even after adjusting for age, gender, baseline BMI, and type 2 diabetes status (T2D). Furthermore, in logistic regression analyses, the expression of these genes was significantly associated with insufficient WL (IWL = TBWL < 20%) after BS (respectively, p = 0.030 and p = 0.031). Indeed, in ROC analysis, the prediction of IWL based on sex, age, BMI, T2D, and the type of surgery (AUC = 0.71) was significantly improved with the addition of SAT-COL5A1 gene expression (AUC = 0.88, Z = 2.13, p = 0.032).

CONCLUSIONS

Our data suggest that the expression of SAT ECM-related genes may help explain the variability in TBWL following BS.

Dietary Temperature's Influence on Energy Balance in Humans: Protocol for a Randomized Controlled Trial and Crossover Design

BACKGROUND

According to the first law of thermodynamics, energy cannot be created or destroyed in an isolated system. Water has a characteristically high heat capacity, indicating that the temperature of ingested fluids and meals could contribute to energy homeostasis. Citing the underlying molecular mechanisms, we present a novel hypothesis that states that the temperature of one's food and drink contributes to energy balance and plays a role in the development of obesity. We provide strong associations with certain molecular mechanisms that are activated by heat and correlate them with obesity and a hypothetical trial that could test this hypothesis. We conclude that if meal or drink temperature proves to contribute to energy homeostasis, then depending on its contribution and scale, future clinical trials should attempt to adjust this effect when analyzing data. In addition, previous research and established relationships of disease states with dietary patterns, energy intake, and food component intakes should be revisited. We understand the common assumption that thermal energy in food is absorbed by the body during digestion and dissipated as heat into the environment, not contributing to the energy balance. We challenge this assumption herein, including a proposed study design that would test our hypothesis.

OBJECTIVE

This paper hypothesizes that the temperature of ingested foods or fluids influences energy homeostasis through the expression of heat shock proteins (HSPs), especially HSP-70 and HSP-90, which are expressed to a greater extent in obesity and are known to cause deficits in glucose metabolism.

METHODS

We provide preliminary evidence supporting our hypothesis that greater dietary temperatures disproportionally induce activation of both intracellular and extracellular HSPs and that these HSPs influence energy balance and contribute to obesity.

RESULTS

This trial protocol has not been initiated and funding has not been sought at the time of this publication.

CONCLUSIONS

To date, no clinical trials are available regarding the potential effects of meal and fluid temperature on weight status or its confounding effects in data analysis. A potential mechanism is proposed as a basis by which higher temperatures of foods and beverages might influence energy balance via HSP expression. On the basis of the evidence supporting our hypothesis, we propose a clinical trial that will further elucidate these mechanisms.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/42846.

Physiology of the Weight-Reduced State and Its Impact on Weight Regain

Obesity is a chronic disease characterized by long duration, slow progression, and periods of remission and relapses. Despite the development of effective medical and surgical interventions and millions of people conducting tremendous personal efforts to manage their weight every year, recidivism remains a significant barrier to attaining long-term weight maintenance. This review aimed to explain the underlying physiology of the weight-reduced state including changes in energy balance, adipose tissue, genetic, environmental, and behavioral factors that may predispose individuals to weight regain following weight loss.

Plasma Levels of Triglycerides and IL-6 Are Associated With Weight Regain and Fat Mass Expansion

CONTEXT

Long-term weight loss (WL) maintenance is the biggest challenge for overweight and obesity because of the almost unavoidable phenomenon of partial or even total weight regain (WR) after WL.

OBJECTIVE

In the present study we investigated the relations of (the changes of) adipocyte size and other risk biomarkers with WR during the follow-up of the Yoyo dietary intervention.

METHODS

In this randomized controlled study, 48 overweight/obese participants underwent a very-low-calorie diet to lose weight, followed by a weight-stable period of 4 weeks and a follow-up period of 9 months. Anthropometric measurements, adipocyte volume of abdominal subcutaneous adipose tissue, and plasma metabolic parameters (free fatty acids [FFAs], triglycerides [TGs], total cholesterol, glucose, insulin, homeostasis model assessment of insulin resistance [HOMA-IR], interleukin 6 [IL-6], angiotensin-converting enzyme [ACE] activity, retinol binding protein 4 [RBP4]) at the beginning and the end of follow-up were analyzed.

RESULTS

Our results show that changes of TGs, IL-6, HOMA-IR, and ACE are significantly positively correlated with WR. Multiple linear regression analysis shows that only TG and IL-6 changes remained significantly correlated with WR and increased body fat mass. Moreover, the change in HOMA-IR was tightly correlated with the change in TGs. Surprisingly, change in adipocyte volume during follow-up was not correlated with WR nor with other factors, but positive correlations between adipocyte volume and HOMA-IR were found at the beginning and end of the follow-up.

CONCLUSION

These results suggest that TGs and IL-6 are independently linked to WR via separate mechanisms, and that HOMA-IR and adipocyte volume may indirectly link to WR through the change of plasma TGs.

Diet or exercise: The role of diet and/or exercise on changes of pro-inflammatory markers during a weight loss program in adult women with overweight

BACKGROUND AND AIMS

Obesity is associated with increased inflammation leading to a higher risk for non-communicable diseases. There was a controversy about whether exercise has a better influence on reducing inflammation during a lifestyle modification program among individuals with obesity. The objective of this study was to evaluate whether exercise could provide a benefit in reducing inflammatory markers in the context of a weight loss program.

METHODS

This is an experimental study with control. Subjects were pre-menopausal adult women with overweight and assigned for low-calorie diet only (LCD) or low-calorie diet and exercise (LCDex) without randomization. We compared the effect of LCDex (n = 36) and LCD (n = 36) on inflammation markers (leptin and interleukin 6/IL6) for 8 weeks.

RESULTS

We showed that after the weight loss program, there was a significant increase in IL6 (p = 0.009) but no changes in leptin (p = 0.760) concentration in both groups. There were no difference in changes of IL6 between LCDex and LCD (p = 0.483).

CONCLUSIONS

A weight loss program was associated with increased inflammation. Among premenopausal women with overweight, a combination of LCD with exercise does not provide a greater benefit in reducing inflammation than those with LCD alone.

TRIAL REGISTRATION

KE/0700/06/2018.

Physiological Responses of Post-Dietary Effects: Lessons from Pre-Clinical and Clinical Studies

Dieting regimens such as calorie restriction (CR) are among the most commonly practiced interventions for weight management and metabolic abnormalities. Due to its independence from pharmacological agents and considerable flexibility in regimens, many individuals turn to dieting as a form of mitigation and maintenance of metabolic health. While metabolic benefits of CR have been widely studied, weight loss maintenance and metabolic benefits are reported to be lost overtime when the diet regimen has been terminated—referred to as post-dietary effects. Specifically, due to the challenges of long-term adherence and compliance to dieting, post-dietary repercussions such as body weight regain and loss of metabolic benefits pose as major factors in the efficacy of CR. Intermittent fasting (IF) regimens, which are defined by periodic energy restriction, have been deemed as more flexible, compliant, and easily adapted diet interventions that result in many metabolic benefits which resemble conventional CR diets. Many individuals find that IF regimens are easier to adhere to, resulting in fewer post-dietary effects; therefore, IF may be a more effective intervention. Unfortunately, there is a severe gap in current research regarding IF post-dietary effects. We recognize the importance of understanding the sustainability of dieting; as such, we will review the known physiological responses of CR post-dietary effects and its potential mechanisms through synthesizing lessons from both pre-clinical and clinical studies. This review aims to provide insight from a translational medicine perspective to allow for the development of more practical and effective diet interventions. We suggest more flexible and easily practiced dieting regimens such as IF due to its more adaptable and practical nature.

Mechanisms of weight regain after weight loss - the role of adipose tissue

One of the biggest challenges in the management of obesity is the prevention of weight regain after successful weight loss. Weight regain after weight loss has large interindividual variation. Although many factors probably contribute to this variation, we hypothesize that variability in biological responses associated with weight loss-induced shrinking of subcutaneous adipocytes has an important role. In this Review, we show that weight loss-induced variations in cellular stress, extracellular matrix remodelling, inflammatory responses, adipokine secretion and lipolysis seem to be associated with the amount of weight that is regained after successful weight loss. Weight regain could therefore, at least in part, depend on a combination of these factors. Further research on the causality of these associations could aid the development of effective strategies to prevent weight regain after successful weight loss.

Combined Analysis of Stress- and ECM-Related Genes in Their Effect on Weight Regain

OBJECTIVE

During weight loss, the volume of adipocytes decreases, leading to stress because of the misfit between the cell contents and the surrounding extracellular matrix (ECM). This stress can be resolved by remodeling the ECM or the restorage of triglycerides within the adipocytes. The objective of this study was to investigate the existence of a connection between stress-related and ECM-related genes that is associated with weight regain.

METHODS

Thirty-one participants with overweight or obesity followed a 5-week very-low-calorie diet (500 kcal/d) with a subsequent 4-week weight-stable diet (WS), and then an uncontrolled 9-month follow-up. Adipose tissue biopsies were collected for microarray analysis. A correlation and interaction analysis was performed with the weight regain percentage (WR%) ([weight after follow-up - weight after WS] ÷ weight after WS × 100%) by using two gene sets that were previously defined as "stress-related" (n = 107) and "ECM-related" genes (n = 277).

RESULTS

During WS, a coexpression network of 8 stress-related genes and 15 ECM-related genes correlating with WR% could be constructed, with links to multiple biological processes. Interaction analysis between stress- and ECM-related genes revealed that several gene combinations were highly related to weight regain.

CONCLUSIONS

Our findings underscore the importance of the connection between stress- and ECM-related genes in the risk for weight regain.

Dietary Intake after Weight Loss and the Risk of Weight Regain: Macronutrient Composition and Inflammatory Properties of the Diet

Weight regain after successful weight loss is a big problem in obesity management. This study aimed to investigate whether weight regain after a weight loss period is correlated with the macronutrient composition and/or the inflammatory index of the diet during that period. Sixty one overweight and obese adults participated in this experimental study. Subjects lost approximately 10% of their initial weight by means of very low-calorie diet for five weeks, or a low calorie diet for 12 weeks. After that, subjects in both groups followed a strict weight maintenance diet based on individual needs for four weeks, which was followed by a nine-month weight maintenance period without dietary counseling. Anthropometrics and dietary intake data were recorded before weight loss (baseline) and during the weight maintenance period. On average, participants regained approximately half of their lost weight. We found no evidence that macronutrient composition during the weight maintenance period was associated with weight regain. The dietary inflammatory index (r = 0.304, p = 0.032) was positively correlated with weight regain and remained significant after correction for physical activity (r = 0.287, p = 0.045). Our data suggest that the inflammatory properties of diet play a role in weight regain after weight loss in overweight and obese adults.

A role for leukocyte integrins and extracellular matrix remodeling of adipose tissue in the risk of weight regain after weight loss

Background: Weight loss (WL) is often followed by weight regain after an energy-restricted dietary intervention (DI). When people are following a diet, the volume of an adipocyte decreases by loss of triglycerides, which creates stress between the cell contents and the surrounding extracellular matrix (ECM). Previously, we observed that genetic variations in ECM genes are associated with an increased risk of weight regain.Objective: We investigated the relation between the expression of ECM genes during WL and a period of weight stabilization (WS) and the risk of weight regain.Design: In this randomized controlled trial, 61 healthy overweight or obese participants followed either a 5-wk very-low-calorie diet (VLCD; 500 kcal/d) or a 12-wk low-calorie diet (1250 kcal/d) (WL period) with a subsequent 4-wk WS period and a 9-mo follow-up. The WL and WS periods combined were considered the DI. Abdominal subcutaneous adipose tissue biopsy samples were collected for microarray analysis. Gene expression changes for a broad set of ECM-related genes were correlated with the weight-regain percentage (WR%).Results: A total of 26 of the 277 genes were significantly correlated with WR% during WL, WS, or the DI periods. Most correlations were observed in the VLCD group during the WS period. Four genes code for leukocyte-specific receptors. These and other genes belong to a group of 26 genes, among which the expression changes were highly correlated (r ≥ 0.7, P ≤ 0.001). This group could be divided into 3 subclusters linking to 2 biological processes-leukocyte integrin gene activity and ECM remodeling-and a link to insulin sensitivity was also apparent.Conclusions: Our present findings indicate the importance of adipose tissue leukocytes for the risk of weight regain. ECM modification also seems to be involved, and we observed a link to insulin sensitivity. This trial was registered at clinicaltrials.gov as NCT01559415.

Weight loss-induced cellular stress in subcutaneous adipose tissue and the risk for weight regain in overweight and obese adults

BACKGROUND/OBJECTIVE

Weight loss is often followed by weight regain after the dietary intervention (DI). Cellular stress is increased in adipose tissue of obese individuals. However, the relation between cellular stress and weight regain is unclear. Previously, we observed increased adipose tissue cellular stress of participants regaining weight compared with participants maintaining weight loss. In the current study, we further investigated the relation between weight regain and changes in the expression of stress-related genes and stress protein levels to determine possible predictors of weight regain.

PARTICIPANTS/METHODS

In this randomized controlled trial, sixty-one healthy overweight/obese participants followed a DI of either a 5-week very-low-calorie diet (500 kcal per day) or a 12-week low-calorie diet (1250 kcal per day; WL period) with a subsequent 4-week weight stable diet (WS period), and a 9-month follow-up. The WL and WS period taken together was named the DI. Abdominal subcutaneous adipose tissue biopsies were collected in 53 participants for microarray and liquid chromatography-mass spectrometry analysis. RNA and protein levels for a broad set of stress-related genes were correlated to the weight regain percentage.

RESULTS

Different gene sets correlated to weight regain percentage during WS and DI. Bioinformatics clustering suggests that during the WS phase-defined genes for actin filament dynamics, glucose handling and nutrient sensing are related to weight regain. HIF-1 (hypoxia-inducible factor-1) is indicated as an important regulator. With regard to DI, clustering of correlated genes indicate that LGALS1, ENO1 and ATF2 are important nodes for conferring risk for weight regain.

CONCLUSIONS

Our present findings indicate that the risk for weight regain is related to expression changes of distinct sets of stress-related genes during the first 4 weeks after returning to energy balance, and during the DI. Further research is required to investigate the mechanistic significance of these findings and find targets for preventing weight regain.