Protein and amino acids in obesity: friends or foes?

PURPOSE OF REVIEW: Nutritional interventions using protein and amino acids in obesity are popular therapeutical strategies to limit obesity development. However, the effects of dietary protein intake and amino acid metabolic alterations involved in obesity pathophysiology have not been completely unravelled. Significant recent studies have brought to light new findings in these areas, which are the primary focus of this review. RECENT FINDINGS: We describe the effects of protein intake on weight regain prevention, the influence on gut microbiota, the response to low-protein highly processed foods, and the contrasting impacts of a high-protein diet on adults and children. We also explore newly discovered correlations between amino acids, liver fat accumulation, and the dysregulation of the liver-pancreas axis due to alterations in amino acid levels in the context of obesity. Lastly, we consider branched-chain amino acids, along with glycine and tryptophan, as significant biomarkers during periods of positive or negative energy balance. SUMMARY: Interventions using dietary protein in obesity may be useful, especially during energy restriction but also in sarcopenic obesity. Furthermore, metabolic profiles that encompass alterations in certain amino acids can provide valuable insights into the metabolic condition of patients with obesity, particularly in relation to insulin resistance and the risk of developing type 2 diabetes.

Targeting the gut to prevent and counteract metabolic disorders and pathologies during aging.

Impairment of gut function is one of the explanatory mechanisms of health status decline in elderly population. These impairments involve a decline in gut digestive physiology, metabolism and immune status, and associated to that, changes in composition and function of the microbiota it harbors. Continuous deteriorations are generally associated with the development of systemic dysregulations and ultimately pathologies that can worsen the initial health status of individuals. All these alterations observed at the gut level can then constitute a wide range of potential targets for development of nutritional strategies that can impact gut tissue or associated microbiota pattern. This can be key, in a preventive manner, to limit gut functionality decline, or in a curative way to help maintaining optimum nutrients bioavailability in a context on increased requirements, as frequently observed in pathological situations. The aim of this review is to give an overview on the alterations that can occur in the gut during aging and lead to the development of altered function in other tissues and organs, ultimately leading to the development of pathologies. Subsequently is discussed how nutritional strategies that target gut tissue and gut microbiota can help to avoid or delay the occurrence of aging-related pathologies.

Transgenerational supplementation with eicosapentaenoic acid reduced the metabolic consequences on the whole body and skeletal muscle in mice receiving an obesogenic diet.

PURPOSE: The effect of manipulating the fatty acid profile of the diet over generations could affect the susceptibility to develop obesity and metabolic disorders. Although some acute effects were described, the impact of transgenerational continuous supplementation with omega 3 fatty acids on metabolic homeostasis and skeletal muscle metabolic flexibility during a nutritional stress is unknown. METHODS: We analyzed the effect of an obesogenic diet in mice after transgenerational supplementation with an omega-3 rich oil (mainly EPA) or a control oil. Young F3 animals received a high fat and high sucrose diet for 4 months. Whole-body biometric data were recorded and lipidomic/transcriptomic adaptations were explored in the skeletal muscle. RESULTS: F3 mice from the lineage supplemented with EPA gained less weight, fat mass, and exhibited better metabolic parameters after the obesogenic diet compared to mice from the control lineage. Transcriptomic exploration of skeletal muscle showed differential regulation of biological processes such as fibrosis, fatty acid catabolism, and inflammation between lineages. These adaptations were associated to subtle lipid remodeling of cellular membranes with an enrichment in phospholipids with omega 3 fatty acid in mice from the EPA lineage. CONCLUSION: Transgenerational and continuous intake of EPA could help to reduce cardiovascular and metabolic risks related to an unbalanced diet by the modulation of insulin sensitivity, fatty acid metabolism, and fibrosis in skeletal muscle.

Modulation of Insulin Resistance and the Adipocyte-Skeletal Muscle Cell Cross-Talk by LCn-3PUFA.

The cross-talk between skeletal muscle and adipose tissue is involved in the development of insulin resistance (IR) in skeletal muscle, leading to the decrease in the anabolic effect of insulin. We investigated if the long chain polyunsaturated n-3 fatty acids (LCn-3PUFA), eicosapentaenoic and docosapentaenoic acids (EPA and DPA, respectively) could (1) regulate the development of IR in 3T3-L1 adipocytes and C2C12 muscle cells and (2) inhibit IR in muscle cells exposed to conditioned media (CM) from insulin-resistant adipocytes. Chronic insulin (CI) treatment of adipocytes and palmitic acid (PAL) exposure of myotubes were used to induce IR in the presence, or not, of LCn-3PUFA. EPA (50 µM) and DPA (10 µM) improved PAL-induced IR in myotubes, but had only a partial effect in adipocytes. CM from adipocytes exposed to CI induced IR in C2C12 myotubes. Although DPA increased the mRNA levels of genes involved in fatty acid (FA) beta-oxidation and insulin signaling in adipocytes, it was not sufficient to reduce the secretion of inflammatory cytokines and prevent the induction of IR in myotubes exposed to adipocyte's CM. Treatment with DPA was able to increase the release of adiponectin by adipocytes into CM. In conclusion, DPA is able to protect myotubes from PAL-induced IR, but not from IR induced by CM from adipocytes.

N-3PUFA differentially modulate palmitate-induced lipotoxicity through alterations of its metabolism in C2C12 muscle cells.

Excessive energy intake leads to fat overload and the formation of lipotoxic compounds mainly derived from the saturated fatty acid palmitate (PAL), thus promoting insulin resistance (IR) in skeletal muscle. N-3 polyunsaturated fatty acids (n-3PUFA) may prevent lipotoxicity and IR. The purpose of this study was to examine the differential effects of n-3PUFA on fatty acid metabolism and insulin sensitivity in muscle cells. C2C12 myotubes were treated with 500 µM of PAL without or with 50 µM of alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) for 16 h. PAL decreased insulin-dependent AKT activation and glucose uptake and increased the synthesis of ceramides and diglycerides (DG) derivatives, leading to protein kinase Cθ activation. EPA and DHA, but not ALA, prevented PAL-decreased AKT activation but glucose uptake was restored to control values by all n-3PUFA vs. PAL. Total DG and ceramide contents were decreased by all n-3PUFA, but only EPA and DHA increased PAL ß-oxidation, decreased PAL incorporation into DG and reduced protein kinase Cθ activation. EPA and DHA emerge as better candidates than ALA to improve fatty acid metabolism in skeletal muscle cells, notably via their ability to increase mitochondrial ß-oxidation.

EPA prevents fat mass expansion and metabolic disturbances in mice fed with a Western diet.

The impact of alpha linolenic acid (ALA), EPA, and DHA on obesity and metabolic complications was studied in mice fed a high-fat, high-sucrose (HF) diet. HF diets were supplemented with ALA, EPA, or DHA (1% w/w) and given to C57BL/6J mice for 16 weeks and to Ob/Ob mice for 6 weeks. In C57BL/6J mice, EPA reduced plasma cholesterol (-20%), limited fat mass accumulation (-23%) and adipose cell hypertrophy (-50%), and reduced plasma leptin concentration (-60%) compared with HF-fed mice. Furthermore, mice supplemented with EPA exhibited a higher insulin sensitivity (+24%) and glucose tolerance (+20%) compared with HF-fed mice. Similar effects were observed in EPA-supplemented Ob/Ob mice, although fat mass accumulation was not prevented. By contrast, in comparison with HF-fed mice, DHA did not prevent fat mass accumulation, increased plasma leptin concentration (+128%) in C57BL/6J mice, and did not improve glucose homeostasis in C57BL/6J and Ob/Ob mice. In 3T3-L1 adipocytes, DHA stimulated leptin expression whereas EPA induced adiponectin expression, suggesting that improved leptin/adiponectin balance may contribute to the protective effect of EPA. In conclusion, supplementation with EPA, but not ALA and DHA, could preserve glucose homeostasis in an obesogenic environment and limit fat mass accumulation in the early stage of weight gain.

Improving the functional detection of sarcopenic obesity: prevalence and handgrip scoring in the OBESAR cohort.

OBJECTIVE: The study objectives were: 1) to detect early signs of low muscle function and assess sarcopenic obesity (SO) prevalence in patients with obesity; and 2) to introduce a new online diagnostic tool for scoring handgrip strength (HGS), adjusted for age and sex. METHODS: Patients from the OBESAR cohort (184 men and 499 women) were tested for body composition and functional testing (chair stand test or HGS based on the cutoffs from the European Society for Clinical Nutrition and Metabolism [ESPEN]/European Association for the Study of Obesity [EASO] or adjusted HGS [adHGS] based on reference values), and SO prevalence was calculated accordingly. RESULTS: Among the 683 patients (mean [SD], age 42.6 [12.8] years; BMI 44.4 [6.3] kg/m2), HGS averaged 25.6 (6.8) kg for women and 43.2 (10.4) kg for men. A total of 25.2% of patients had adHGS lower than the 10th percentile, but this was true for only 5.6% using ESPEN/EASO cutoffs of HGS. SO prevalence rates were different according to functional tests: 5.4%, 24.5%, and 3.2% for HGS, adHGS, and the chair stand test, respectively. CONCLUSIONS: Using adHGS through a scoring process considering age and sex may help to detect early signs of SO in a primary care setting in order to better prevent SO through a personalized approach in adults with obesity. A free online application, "GRip And Sarcopenia Prediction" (GRASP), is proposed to diagnose probable SO.

Chemotherapy effects on mitochondrial function in adipose tissue in oesophageal and gastroesophageal junction adenocarcinomas with or without associated cachexia: protocol for a prospective, comparative observational study (ChiFMeOE).

INTRODUCTION: Cachexia is strongly associated with digestive cancers, particularly oesogastric cancer. Mitochondria in adipose tissue are involved in the regulation of metabolism and physiopathology of cancer cachexia in animal studies. Chemotherapeutic regimens used to control tumour development could also alter mitochondrial function in adipose tissue. We hypothesise that cachexia induces an increase in adipose tissue mitochondrial energy metabolism and that chemotherapy can mitigate this. The purpose of the ChiFMeOE study is to identify adipocyte factors involved in the energy imbalance associated with the cachectic process and their response to chemotherapeutic treatments in patients with oesogastric cancer. METHODS AND ANALYSIS: ChiFMeOE is a single-centre observational study that will prospectively include 60 patients referred to chemotherapy and surgery for oesophageal and gastro-oesophageal junction adenocarcinomas at the University Hospital of Clermont-Ferrand, France. Visceral and subcutaneous adipose tissue biopsies will be collected during surgery scheduled before and after neoadjuvant chemotherapy administration, as well as cachexia and nutritional assessment. The primary outcome is the maximum mitochondrial respiration rate (Vmax) measured by high-resolution respirometry. Secondary outcomes are other mitochondrial parameters (ie, enzymatic activities, proteins content and gene expression), tumour characteristics, nutritional status and body composition. ETHICS AND DISSEMINATION: The study was approved by an independent institutional review board on June 2023 (Comité de protection des personnes Sud-Méditerranée V; 2023-A00582-43) and declared to the French regulatory authority for research. Written informed consent will be obtained prior to patient inclusion. The principal investigator will be notified of any changes in patient's health status requiring a modification of his management and/or treatment during the course of the protocol. Results will be published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov, NCT05954117.

Sarcopenia and Sarcopenic Obesity and Mortality Among Older People.

Importance: Sarcopenia and obesity are 2 global concerns associated with adverse health outcomes in older people. Evidence on the population-based prevalence of the combination of sarcopenia with obesity (sarcopenic obesity [SO]) and its association with mortality are still limited. Objective: To investigate the prevalence of sarcopenia and SO and their association with all-cause mortality. Design, Setting, and Participants: This large-scale, population-based cohort study assessed participants from the Rotterdam Study from March 1, 2009, to June 1, 2014. Associations of sarcopenia and SO with all-cause mortality were studied using Kaplan-Meier curves, Cox proportional hazards regression, and accelerated failure time models fitted for sex, age, and body mass index (BMI). Data analysis was performed from January 1 to April 1, 2023. Exposures: The prevalence of sarcopenia and SO, measured based on handgrip strength and body composition (BC) (dual-energy x-ray absorptiometry) as recommended by current consensus criteria, with probable sarcopenia defined as having low handgrip strength and confirmed sarcopenia and SO defined as altered BC (high fat percentage and/or low appendicular skeletal muscle index) in addition to low handgrip strength. Main Outcome and Measure: The primary outcome was all-cause mortality, collected using linked mortality data from general practitioners and the central municipal records, until October 2022. Results: In the total population of 5888 participants (mean [SD] age, 69.5 [9.1] years; mean [SD] BMI, 27.5 [4.3]; 3343 [56.8%] female), 653 (11.1%; 95% CI, 10.3%-11.9%) had probable sarcopenia and 127 (2.2%; 95% CI, 1.8%-2.6%) had confirmed sarcopenia. Sarcopenic obesity with 1 altered component of BC was present in 295 participants (5.0%; 95% CI, 4.4%-5.6%) and with 2 altered components in 44 participants (0.8%; 95% CI, 0.6%-1.0%). An increased risk of all-cause mortality was observed in participants with probable sarcopenia (hazard ratio [HR], 1.29; 95% CI, 1.14-1.47) and confirmed sarcopenia (HR, 1.93; 95% CI, 1.53-2.43). Participants with SO plus 1 altered component of BC (HR, 1.94; 95% CI, 1.60-2.33]) or 2 altered components of BC (HR, 2.84; 95% CI, 1.97-4.11) had a higher risk of mortality than those without SO. Similar results for SO were obtained for participants with a BMI of 27 or greater. Conclusions and Relevance: In this study, sarcopenia and SO were found to be prevalent phenotypes in older people and were associated with all-cause mortality. Additional alterations of BC amplified this risk independently of age, sex, and BMI. The use of low muscle strength as a first step of both diagnoses may allow for early identification of individuals at risk for premature mortality.

Adipose Tissue Dysfunctions in Response to an Obesogenic Diet Are Reduced in Mice after Transgenerational Supplementation with Omega 3 Fatty Acids.

Obesity is characterized by profound alterations in adipose tissue (AT) biology, leading to whole body metabolic disturbances such as insulin resistance and cardiovascular diseases. These alterations are related to the development of a local inflammation, fibrosis, hypertrophy of adipocytes, and dysregulation in energy homeostasis, notably in visceral adipose tissue (VAT). Omega 3 (n-3) fatty acids (FA) have been described to possess beneficial effects against obesity-related disorders, including in the AT; however, the long-term effect across generations remains unknown. The current study was conducted to identify if supplementation with n-3 polyunsaturated FA (PUFA) for three generations could protect from the consequences of an obesogenic diet in VAT. Young mice from the third generation of a lineage receiving a daily supplementation (1% of the diet) with fish oil rich in eicosapentaenoic acid (EPA) or an isocaloric amount of sunflower oil, were fed a high-fat, high-sugar content diet for 4 months. We explore the transcriptomic adaptations in each lineage using DNA microarray in VAT and bioinformatic exploration of biological regulations using online databases. Transgenerational intake of EPA led to a reduced activation of inflammatory processes, perturbation in metabolic homeostasis, cholesterol metabolism, and mitochondrial functions in response to the obesogenic diet as compared to control mice from a control lineage. This suggests that the continuous intake of long chain n-3 PUFA could be preventive in situations of oversupply of energy-dense, nutrient-poor foods.

Lipid accumulation and mitochondrial abnormalities are associated with fiber atrophy in the skeletal muscle of rats with collagen-induced arthritis.

Rheumatoid arthritis (RA) has a negative impact on muscle mass, and reduces patient's mobility and autonomy. Furthermore, RA is associated with metabolic comorbidities, notably in lipid homeostasis by unknown mechanisms. To understand the links between the loss in muscle mass and the metabolic abnormalities, arthritis was induced in male Sprague Dawley rats (n = 11) using the collagen-induced arthritis model. Rats immunized with bovine type II collagen were compared to a control group of animals (n = 11) injected with acetic acid and complete Freund's adjuvant. The clinical severity of the ensuing arthritis was evaluated weekly by a semi-quantitative score. Skeletal muscles from the hind limb were used for the histological analysis and exploration of mitochondrial activity, lipid accumulation, metabolism and regenerative capacities. A significant atrophy in tibialis anterior muscle fibers was observed in the arthritic rats despite a non-significant decrease in the weight of the muscles. Despite moderate inflammation, accumulation of triglycerides (P < 0.05), reduced mitochondrial DNA copy number (P < 0.05) and non-significant dysfunction in mitochondrial cytochrome c oxidase activity were found in the gastrocnemius muscle. Concomitantly, our results suggested an activation of the muscle specific E3 ubiquitin ligases MuRF-1 and MAFbx. Finally, the adipose tissue from the arthritic rats exhibited decreased PPARγ mRNA suggesting reduced adipogenic capacities. In conclusion, the reduced adipose tissue adipogenic capacity and skeletal muscle mitochondrial capacity are probably involved in the activation of protein catabolism, inhibition of myogenesis, accumulation of lipids and fiber atrophy in the skeletal muscle during RA.

An Integrated Analysis of miRNA and Gene Expression Changes in Response to an Obesogenic Diet to Explore the Impact of Transgenerational Supplementation with Omega 3 Fatty Acids.

Insulin resistance decreases the ability of insulin to inhibit hepatic gluconeogenesis, a key step in the development of metabolic syndrome. Metabolic alterations, fat accumulation, and fibrosis in the liver are closely related and contribute to the progression of comorbidities, such as hypertension, type 2 diabetes, or cancer. Omega 3 (n-3) polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA), were identified as potent positive regulators of insulin sensitivity in vitro and in animal models. In the current study, we explored the effects of a transgenerational supplementation with EPA in mice exposed to an obesogenic diet on the regulation of microRNAs (miRNAs) and gene expression in the liver using high-throughput techniques. We implemented a comprehensive molecular systems biology approach, combining statistical tools, such as MicroRNA Master Regulator Analysis pipeline and Boolean modeling to integrate these biochemical processes. We demonstrated that EPA mediated molecular adaptations, leading to the inhibition of miR-34a-5p, a negative regulator of Irs2 as a master regulatory event leading to the inhibition of gluconeogenesis by insulin during the fasting-feeding transition. Omics data integration provided greater biological insight and a better understanding of the relationships between biological variables. Such an approach may be useful for deriving innovative data-driven hypotheses and for the discovery of molecular-biochemical mechanistic links.

n-3 Polyunsaturated fatty acids modulate metabolism of insulin-sensitive tissues: implication for the prevention of type 2 diabetes.

Obesity is frequently associated with the development of type 2 diabetes which is firstly characterized by a defect in the response of key metabolic tissues to insulin (insulin resistance). The imbalance in fatty composition of the diet, a low-grade inflammatory state have been described to be involved in the initiation or the amplification of the molecular events involved in this process. The concept of a specific nutritional intervention has emerged as a promising tool against metabolic disorders associated with obesity. In this context, many investigations were conducted to evaluate the potential beneficial impacts of n-3 polyunsaturated fatty acids (n-3 PUFA). The aim of the present review was to summarize the current knowledge about the role of docosahexanoic acid (DHA, 22:6n-3) and eicosapentanoic acid (EPA, 20:5n-3) on key metabolic organs. Only studies aiming to understand the mechanism of actions were selected. The analysis of randomized clinical trial about n-3 PUFA was not considered here. The effects of n-3 PUFA were analyzed in the adipose tissue, the liver, skeletal muscle and the pancreas in the context of obesity and lipid oversupply. Furthermore, in line with recent findings about the role of the modulation of gut microbiota in obesity-related disorders, we summarized the recent findings about the possible link between n-3 PUFA and change in microbiota composition.

Effects of enriched environment on COX-2, leptin and eicosanoids in a mouse model of breast cancer.

Cyclooxygenase-2 (COX-2) and adipokines have been implicated in breast cancer. This study investigated a possible link between COX-2 and adipokines in the development of mammary tumors. A model of environmental enrichment (EE), known to reduce tumor growth was used for a syngeneic murine model of mammary carcinoma. 3-week-old, female C57BL/6 mice were housed in standard environment (SE) or EE cages for 9 weeks and transplanted orthotopically with syngeneic EO771 adenocarcinoma cells into the right inguinal mammary fat pad. EE housing influenced mammary gland development with a decrease in COX-2 expressing cells and enhanced side-branching and advanced development of alveolar structures of the mammary gland. Tumor volume and weight were decreased in EE housed mice and were associated with a reduction in COX-2 and Ki67 levels, and an increase in caspase-3 levels. In tumors of SE mice, high COX-2 expression correlated with enhanced leptin detection. Non-tumor-bearing EE mice showed a significant increase in adiponectin levels but no change in those of leptin, F(2)-isoprostanes, PGF(2α), IL-6, TNF-α, PAI-1, and MCP-1 levels. Both tumor-bearing groups (SE and EE housing) had increased resistin, IL-6, TNF-α, PAI-1 and MCP-1 levels irrespective of the different housing environment demonstrating higher inflammatory response due to the presence of the tumor. This study demonstrates that EE housing influenced normal mammary gland development and inhibited mammary tumor growth resulting in a marked decrease in intratumoral COX-2 activity and an increase in the plasma ratio of adiponectin/leptin levels.

N-3 polyunsaturated fatty acids modulate metabolism of insulin-sensitive tissues: implication for the prevenrion of type 2 diabetes

Obesity is frequently associated with the development of type 2 diabetes which is firstly characterized by a defect in the response of key metabolic tissues to insulin (insulin resistance). The imbalance in fatty composition of the diet, a low-grade inflammatory state have been described to be involved in the initiation or the amplification of the molecular events involved in this process. The concept of a specific nutritional intervention has emerged as a promising tool against metabolic disorders associated with obesity. In this context, many investigations were conducted to evaluate the potential beneficial impacts of n−3 polyunsaturated fatty acids (n−3 PUFA). The aim of the present review was to summarize the current knowledge about the role of docosahexanoic acid (DHA, 22:6n−3) and eicosapentanoic acid (EPA, 20:5n−3) on key metabolic organs. Only studies aiming to understand the mechanism of actions were selected. The analysis of randomized clinical trial about n−3 PUFA was not considered here. The effects of n−3 PUFA were analyzed in the adipose tissue, the liver, skeletal muscle and the pancreas in the context of obesity and lipid oversupply. Furthermore, in line with recent findings about the role of the modulation of gut microbiota in obesity-related disorders, we summarized the recent findings about the possible link between n−3 PUFA and change in microbiota composition