Different protein composition of low-calorie diet differently impacts adipokine profile irrespective of weight loss in overweight and obese women

Similar effects of milk protein and blends of milk and plant-based protein on appetite-related hormones in 7- to 8-year-old healthy Danish children: secondary analyses from the PROGRO randomised trial

AIM

The effect of different protein sources on the appetite-related hormones in children is largely unknown. We investigated the effect of milk protein versus blends of milk and rapeseed protein on plasma leptin and adiponectin in children.

METHODS

We included 88 Danish 7- to 8-year-old children randomised to receive 35 g protein/day for 4 weeks in 2018 as either milk protein or blends of milk and rapeseed protein (ratio 54:46 or 30:70). Outcomes included absolute and fat mass-adjusted adiponectin and leptin measured at baseline, Weeks 1 and 4.

RESULTS

There was no difference in changes in absolute and fat mass-adjusted adiponectin and leptin after 1 or 4 weeks between the three groups (p ≥ 0.100). Leptin increased within all groups (p ≤ 0.046). Combining the three groups, leptin and fat mass-adjusted leptin increased by 23% (95% CI 11;35) and 17% (6.4;29) during the intervention respectively (both p ≤ 0.001). Adiponectin variables did not change during the intervention period.

CONCLUSION

There were no differences between milk protein and blends of milk and rapeseed protein on absolute and fat mass-adjusted leptin and adiponectin in healthy children with a habitual intake of milk. However, leptin increased within all three groups. Future studies should further investigate effect on appetite-related hormones of rapeseed protein alone.

Interplay of retinol binding protein 4 with obesity and associated chronic alterations (Review)

Obesity is a multifactorial disease, defined as excessive fat deposition in adipose tissue. Adipose tissue is responsible for the production and secretion of numerous adipokines that induce metabolic disorders. Retinol‑binding protein 4 (RBP4) is an adipokine that transports vitamin A or retinol in the blood. High levels of RBP4 are associated with development of metabolic disease, including obesity, insulin resistance (IR), metabolic syndrome, and type 2 diabetes (T2D). The present review summarizes the role of RBP4 in obesity and associated chronic alterations. Excessive synthesis of RBP4 contributes to inflammatory characteristic of obesity by activation of immune cells and release of proinflammatory cytokines, such as TNFα and ILs, via the Toll‑like receptor/JNK pathway. The retinol‑RBP4 complex inhibits insulin signaling directly in adipocytes by activating Janus kinase 2 (JAK2)/STAT5/suppressor of cytokine signaling 3 signaling. This mechanism is retinol‑dependent and requires vitamin A receptor stimulation by retinoic acid 6 (STRA6). In muscle, RBP4 is associated with increased serine 307 phosphorylation of insulin receptor substrate‑1, which decreases its affinity to PI3K and promotes IR. In the liver, RBP4 increases hepatic expression of phosphoenolpyruvate carboxykinase, which increases production of glucose. Elevated serum RBP4 levels are associated with β‑cell dysfunction in T2D via the STRA6/JAK2/STAT1/insulin gene enhancer protein 1 pathway. By contrast, RBP4 induces endothelial inflammation via the NF‑κB/nicotinamide adenine dinucleotide phosphate oxidase pathway independently of retinol and STRA6, which stimulates expression of proinflammatory molecules, such as vascular cell adhesion molecule 1, E‑selectin, intercellular adhesion molecule 1, monocyte chemoattractant protein 1 and TNFα. RBP4 promotes oxidative stress by decreasing endothelial mitochondrial function; overall, it may serve as a useful biomarker in the diagnosis of obesity and prognosis of associated disease, as well as a potential therapeutic target for treatment of these diseases.

Low-carbohydrate versus balanced-carbohydrate diets for reducing weight and cardiovascular risk

BACKGROUND

Debates on effective and safe diets for managing obesity in adults are ongoing. Low-carbohydrate weight-reducing diets (also known as 'low-carb diets') continue to be widely promoted, marketed and commercialised as being more effective for weight loss, and healthier, than 'balanced'-carbohydrate weight-reducing diets.

OBJECTIVES

To compare the effects of low-carbohydrate weight-reducing diets to weight-reducing diets with balanced ranges of carbohydrates, in relation to changes in weight and cardiovascular risk, in overweight and obese adults without and with type 2 diabetes mellitus (T2DM).

SEARCH METHODS

We searched MEDLINE (PubMed), Embase (Ovid), the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science Core Collection (Clarivate Analytics), ClinicalTrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) up to 25 June 2021, and screened reference lists of included trials and relevant systematic reviews. Language or publication restrictions were not applied.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in adults (18 years+) who were overweight or living with obesity, without or with T2DM, and without or with cardiovascular conditions or risk factors. Trials had to compare low-carbohydrate weight-reducing diets to balanced-carbohydrate (45% to 65% of total energy (TE)) weight-reducing diets, have a weight-reducing phase of 2 weeks or longer and be explicitly implemented for the primary purpose of reducing weight, with or without advice to restrict energy intake.  DATA COLLECTION AND ANALYSIS: Two review authors independently screened titles and abstracts and full-text articles to determine eligibility; and independently extracted data, assessed risk of bias using RoB 2 and assessed the certainty of the evidence using GRADE. We stratified analyses by participants without and with T2DM, and by diets with weight-reducing phases only and those with weight-reducing phases followed by weight-maintenance phases. Primary outcomes were change in body weight (kg) and the number of participants per group with weight loss of at least 5%, assessed at short- (three months to < 12 months) and long-term (≥ 12 months) follow-up.

MAIN RESULTS

We included 61 parallel-arm RCTs that randomised 6925 participants to either low-carbohydrate or balanced-carbohydrate weight-reducing diets. All trials were conducted in high-income countries except for one in China. Most participants (n = 5118 randomised) did not have T2DM. Mean baseline weight across trials was 95 kg (range 66 to 132 kg). Participants with T2DM were older (mean 57 years, range 50 to 65) than those without T2DM (mean 45 years, range 22 to 62). Most trials included men and women (42/61; 3/19 men only; 16/19 women only), and people without baseline cardiovascular conditions, risk factors or events (36/61). Mean baseline diastolic blood pressure (DBP) and low-density lipoprotein (LDL) cholesterol across trials were within normal ranges. The longest weight-reducing phase of diets was two years in participants without and with T2DM. Evidence from studies with weight-reducing phases followed by weight-maintenance phases was limited. Most trials investigated low-carbohydrate diets (> 50 g to 150 g per day or < 45% of TE; n = 42), followed by very low (≤ 50 g per day or < 10% of TE; n = 14), and then incremental increases from very low to low (n = 5). The most common diets compared were low-carbohydrate, balanced-fat (20 to 35% of TE) and high-protein (> 20% of TE) treatment diets versus control diets balanced for the three macronutrients (24/61). In most trials (45/61) the energy prescription or approach used to restrict energy intake was similar in both groups. We assessed the overall risk of bias of outcomes across trials as predominantly high, mostly from bias due to missing outcome data. Using GRADE, we assessed the certainty of evidence as moderate to very low across outcomes.  Participants without and with T2DM lost weight when following weight-reducing phases of both diets at the short (range: 12.2 to 0.33 kg) and long term (range: 13.1 to 1.7 kg).  In overweight and obese participants without T2DM: low-carbohydrate weight-reducing diets compared to balanced-carbohydrate weight-reducing diets (weight-reducing phases only) probably result in little to no difference in change in body weight over three to 8.5 months (mean difference (MD) -1.07 kg, (95% confidence interval (CI) -1.55 to -0.59, I2 = 51%, 3286 participants, 37 RCTs, moderate-certainty evidence) and over one to two years (MD -0.93 kg, 95% CI -1.81 to -0.04, I2 = 40%, 1805 participants, 14 RCTs, moderate-certainty evidence); as well as change in DBP and LDL cholesterol over one to two years. The evidence is very uncertain about whether there is a difference in the number of participants per group with weight loss of at least 5% at one year (risk ratio (RR) 1.11, 95% CI 0.94 to 1.31, I2 = 17%, 137 participants, 2 RCTs, very low-certainty evidence).  In overweight and obese participants with T2DM: low-carbohydrate weight-reducing diets compared to balanced-carbohydrate weight-reducing diets (weight-reducing phases only) probably result in little to no difference in change in body weight over three to six months (MD -1.26 kg, 95% CI -2.44 to -0.09, I2 = 47%, 1114 participants, 14 RCTs, moderate-certainty evidence) and over one to two years (MD -0.33 kg, 95% CI -2.13 to 1.46, I2 = 10%, 813 participants, 7 RCTs, moderate-certainty evidence); as well in change in DBP, HbA1c and LDL cholesterol over 1 to 2 years. The evidence is very uncertain about whether there is a difference in the number of participants per group with weight loss of at least 5% at one to two years (RR 0.90, 95% CI 0.68 to 1.20, I2 = 0%, 106 participants, 2 RCTs, very low-certainty evidence).  Evidence on participant-reported adverse effects was limited, and we could not draw any conclusions about these.  AUTHORS' CONCLUSIONS: There is probably little to no difference in weight reduction and changes in cardiovascular risk factors up to two years' follow-up, when overweight and obese participants without and with T2DM are randomised to either low-carbohydrate or balanced-carbohydrate weight-reducing diets.

Effect of different protein diets on weight loss, inflammatory markers, and cardiometabolic risk factors in obese women

BACKGROUND

Reducing and maintaining body weight has become more important than ever as obesity is becoming increasingly common worldwide. This study was aimed to investigate the effects of diets with different protein contents administered to obese women on anthropometric measurements, inflammatory markers, and cardiometabolic risk factors.

MATERIALS AND METHODS

This randomized controlled trial was conducted with sixty volunteering obese women aged between 20 and 45 years. The subjects were divided into two groups in equal numbers. The high-protein (HP) group (n = 30) was administered an iso-caloric HP diet (25% protein, 30% fat, and 45% carbohydrate), and the control group (n = 30) an isocaloric low-protein diet (15% protein, 30% fat, and 55% carbohydrate), and both groups were followed up for 8 weeks. The subjects' descriptive data, anthropometric measurements, homeostatic model assessment-insulin resistance (HOMA-IR), lipid profiles, and high-sensitive C-reactive protein (hs-CRP), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) levels were analyzed.

RESULTS

There was no significant difference at baseline (except for low-density lipoprotein cholesterol [LDL-C]), and end-of-study (except for IL-6, systolic blood pressure [SBP], and diastolic blood pressure) values of parameters between the two groups; after adjusted for baseline measurements, a significant difference was observed between the groups for body weight, body mass index, waist circumference, HOMA-IR, LDL-C, hs-CRP, TNF-α, IL-6, and SBP (P = 0.004, P = 0.001, P = 0.003, P = 0.029, P = 0.004, P = 0.016, P = 0.004, P = 0.010, and P = 0.000, respectively) and were greater in the HP group than in the control group (P < 0.05).

CONCLUSION

The HP diet was effective on improvement in HOMA-IR, SBP, LDL-C, hs-CRP, TNF-α, IL-6, and resulted in body weight loss.

Adiponectin and Sarcopenia: A Systematic Review With Meta-Analysis

BACKGROUND

Sarcopenia is a progressive loss of skeletal muscle mass whose pathophysiology has been proposed to possibly involve mechanisms of altered inflammatory status and endocrine function. Adiponectin has been shown to modulate inflammatory status and muscle metabolism. However, the possible association between adiponectin levels and sarcopenia is poorly understood. In order to fill this gap, in the present manuscript we aimed to summarize the current evidence with a systematic review and a meta-analysis of studies reporting serum adiponectin levels in patients with sarcopenia compared to non-sarcopenic controls.

METHODS

An electronic search through Medline/PubMed, Cochrane Library, and Science Direct was performed till March 1, 2020. From the included papers, meta-analysis of cross-sectional studies comparing serum levels of adiponectin between patients with sarcopenia and controls was performed.

RESULTS

Out of 1,370 initial studies, seven studies were meta-analyzed. Sarcopenic participants had significantly higher levels of adiponectin Hedges' g with 95% confidence interval (CI): 1.20 (0.19-2.22), p = 0.02 than controls. Subgroup analysis, performed in Asian population and focused on identification of the condition based on AWGS criteria, reported higher adiponectin levels in sarcopenic population (2.1 (0.17-4.03), p = 0.03 and I2 = 98.98%. Meta-regression analysis revealed female gender to significantly influence the results as demonstrated by beta = 0.14 (95% CI (0.010-0.280), p = 0.040).

CONCLUSIONS

Our meta-analysis found evidence that sarcopenia is associated with higher adiponectin levels. However, caution is warranted on the interpretation of these findings, and future longitudinal research is required to disentangle and better understand the topic.

Is the Retinol-Binding Protein 4 a Possible Risk Factor for Cardiovascular Diseases in Obesity?

Although many preventive and treatment approaches have been proposed, cardiovascular disease (CVD) remains one of the leading causes of deaths worldwide. Current epidemiological data require the specification of new causative factors, as well as the development of improved diagnostic tools to provide better cardiovascular management. Excessive accumulation of adipose tissue among patients suffering from obesity not only constitutes one of the main risk factors of CVD development but also alters adipokines. Increased attention is devoted to bioactive adipokines, which are also produced by the adipose tissue. The retinol-binding protein 4 (RBP4) has been associated with numerous CVDs and is presumably associated with an increased cardiovascular risk. With this in mind, exploring the role of RBP4, particularly among patients with obesity, could be a promising direction and could lead to better CVD prevention and management in this patient group. In our review, we summarized the current knowledge about RBP4 and its association with essential aspects of cardiovascular disease-lipid profile, intima-media thickness, atherosclerotic process, and diet. We also discussed the RBP4 gene polymorphisms essential from a cardiovascular perspective.

Effect of Lifestyle Intervention in the Concentration of Adipoquines and Branched Chain Amino Acids in Subjects with High Risk of Developing Type 2 Diabetes: Feel4Diabetes Study

Introduction: The global prevalence of type 2 diabetes (T2D) is increasing rapidly, especially in low- and middle-income countries and has a high number of associated comorbidities. Plasmatic concentrations of branched chain amino acids (BCAA) and retinol-binding protein 4 (RBP4) have been shown to be elevated in T2D subjects in cross-sectional studies. However, the effect of lifestyle community-based interventions on BCAA and RBP4 concentrations has not yet been analyzed. Material and methods: The Feel4Diabetes study is a school and community-based intervention that identified 360 European families with a high risk of developing T2D according to the FINDRISC questionnaire. Families were randomized in control and intervention groups were followed-up from 2016 to 2018. In the Spanish families, the concentration of BCAA and RBP4 was determined in 266 subjects (115 control and 151 intervention group) that attended the three time-point assessments by colorimetric and ELISA reaction, respectively. Results: Baseline BCAA levels showed positive correlations with the FINDRISC score and glucose impairment (baseline glucose, insulin, and glycated hemoglobin), body mass index, and body weight. The participants receiving the community-based intervention showed a significant decrease in glycated hemoglobin and BCAA levels compared to the control group (p = 0.011 and p < 0.001, respectively). However, baseline RBP4 did not show significant correlations with anthropometric and glycemic parameters, and no significant change was observed in anthropometric parameters and RBP4 concentrations throughout the follow-up. Conclusion: A community-based intervention on lifestyle led to a significant reduction in BCAA levels regardless of weight loss. These findings suggest that this interventional approach could be promising in T2D prevention.

Dietary modifications for weight loss and weight loss maintenance

Worldwide obesity rates remain at a rise, and to treat obesity is at the top of the global public health agenda. In 2013, the AHA/ACC/TOS obesity management guidelines were published, in essence suggesting that any dietary scheme seems to be effective for weight loss, as long as it can induce a sustainable energy deficit. In the present review, we update and critically discuss available information regarding dietary modifications for weight loss and weight loss maintenance, published after the 2013 guidelines. Regarding weight loss, we found no proof to support that a single dietary scheme, be it nutrient-, food group- or dietary pattern- based, is more efficacious of the other for achieving weight loss. For weight loss maintenance, published interventions point towards the same direction, although inconclusively. Most research explores the effect of weight loss regimes on weight loss maintenance and not the effect of the diet during weight loss maintenance, and this literature gap should be more thoroughly investigated.