Characteristics of Abdominal Visceral Adipose Tissue, Metabolic Health and the Gut Microbiome in Adults.

CONTEXT: Compared with the relatively benign effects of increased subcutaneous adipose tissue (SAT), increased visceral adipose tissue (VAT) volume is a causal risk factor for hypertension, hyperlipidemia, type 2 diabetes, and cardiovascular disease. In rodents, increased VAT volume and triglyceride density and ectopic lipid accumulation in kidneys and liver have been induced by alterations in the gut microbiome. However, few studies have characterized these relationships in humans. OBJECTIVE: To evaluate the tissue triglyceride content of VAT and SAT, liver, kidneys, and pancreas in male and female adults and assess associations with markers of glucose tolerance, serum insulin, and lipids and characteristics of the gut microbiome. METHODS: Cross-sectional observational study of healthy human adults (n = 60) at a clinical research center. Body mass index (BMI), body composition, and oral glucose tolerance were assessed. Microbiome analysis was conducted on stool samples using 16S rRNA v3 amplicon sequencing. The triglyceride content of VAT, SAT, liver, kidney and pancreas were determined by assessing proton density fat fraction (PDFF) with magnetic resonance imaging (MRI). RESULTS: Higher VAT PDFF and the ratio of VAT to SAT PDFF were related to higher BMI, HbA1c, HOMA-IR, non-high-density lipoprotein cholesterol, plasma triglycerides, low-density lipoprotein (LDL) cholesterol, and lower high-density lipoprotein (HDL) cholesterol. A higher VAT PDFF and VAT to SAT PDFF ratio were associated with lower alpha diversity and altered beta diversity of the gut microbiome. Differences in VAT were associated with higher relative abundance of the phylum Firmicutes, lower relative abundance of the phylum Bacteroidetes, and enrichment of the bacterial genera Dorea, Streptococcus, and Solobacterium. CONCLUSION: VAT PDFF measured with MRI is related to impaired glucose homeostasis, dyslipidemia, and differences in the gut microbiome, independently of the total body fat percentage.

Managing Obesity in Young Children: A Multiple Methods Study Assessing Feasibility, Acceptability, and Implementation of a Multicomponent, Family-Based Intervention.

Background: We developed a multicomponent, family-based intervention for young children with obesity consisting of parent group sessions, home nursing visits, and multidisciplinary clinical encounters. Our objective was to assess intervention feasibility, acceptability, and implementation. Methods: From 2017 to 2020, we conducted a multiple methods study in the obesity management clinic at a tertiary children's hospital (Toronto, Canada). We included 1-6 year olds with a body mass index ≥97th percentile and their parents; we also included health care providers (HCPs) who delivered the intervention. To assess feasibility, we performed a pilot randomized controlled trial (RCT) comparing the intervention to usual care. To explore acceptability, we conducted parent focus groups. To explore implementation, we examined contextual factors with HCPs using the Consolidated Framework for Implementation Research. Results: There was a high level of ineligibility (n = 34/61) for the pilot RCT. Over 21 months, 11 parent-child dyads were recruited; of 6 randomized to the intervention, 3 did not participate in group sessions or home visits. In focus groups, themes identified by parents (n = 8) related to information provided at referral; fit between the intervention and patient needs; parental gains from participating in the intervention; and feasibility of group sessions. HCPs (n = 10) identified contextual factors that were positively and negatively associated with intervention implementation. Conclusions: We encountered challenges related to intervention feasibility, acceptability, and implementation. Lessons learned from this study will inform the next iteration of our intervention and are relevant to intervention development and implementation for young children with obesity. Clinical Trial Registration number: NCT03219658.

Lower brown adipose tissue activity is associated with non-alcoholic fatty liver disease but not changes in the gut microbiota.

In rodents, lower brown adipose tissue (BAT) activity is associated with greater liver steatosis and changes in the gut microbiome. However, little is known about these relationships in humans. In adults (n = 60), we assessed hepatic fat and cold-stimulated BAT activity using magnetic resonance imaging and the gut microbiota with 16S sequencing. We transplanted gnotobiotic mice with feces from humans to assess the transferability of BAT activity through the microbiota. Individuals with NAFLD (n = 29) have lower BAT activity than those without, and BAT activity is inversely related to hepatic fat content. BAT activity is not related to the characteristics of the fecal microbiota and is not transmissible through fecal transplantation to mice. Thus, low BAT activity is associated with higher hepatic fat accumulation in human adults, but this does not appear to have been mediated through the gut microbiota.

Careful conversations: an educational video to support parents in communicating about weight with their children.

BACKGROUND: Parents may struggle to initiate healthy weight-related conversations with their children. Educational videos may be an effective tool for improving parents' knowledge and self-efficacy on this topic. The aim of this pilot study was to develop an educational video to assist parents in weight-related conversations with their child, and to assess changes in parents' self-efficacy on this topic. METHODS: Video development was based on a scoping review and semi-structured interviews with parents. Respondent demographics and user satisfaction were assessed at pre- and post- video, and 4-6 months later. Self-efficacy scores were compared between parent groups based on weight concerns over time. RESULTS: Fifty-seven parents participated in the video questionnaires, and 40 repeated measures 4-6 months later. Significant improvements in self-efficacy in "raising the issue of weight" and "answering questions or concerns" were found after watching the video (p ≤ 0.002) compared to baseline, and scores 4-6 months post baseline remained slightly elevated, but non-significant. Parents with concerns about their child being overweight had significantly lower perceived self-efficacy scores compared to parents with no concerns about their child's weight (p = 0.031). The video was found to be positively received and of relevance to parents across a number of different domains. CONCLUSION(S): Preliminary findings suggest an educational video about initiating weight-related conversations may be an effective tool for increasing parents' perceived self-efficacy in the short term. Further work is needed to validate findings in a randomized controlled trial, and with diverse parent populations. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03664492 . Registered 10 September 2018 - Retrospectively registered.

MRI Reveals Human Brown Adipose Tissue Is Rapidly Activated in Response to Cold.

CONTEXT: In rodents, cold exposure induces the activation of brown adipose tissue (BAT) and the induction of intracellular triacylglycerol (TAG) lipolysis. However, in humans, the kinetics of supraclavicular (SCV) BAT activation and the potential importance of TAG stores remain poorly defined. OBJECTIVE: To determine the time course of BAT activation and changes in intracellular TAG using MRI assessment of the SCV (i.e., BAT depot) and fat in the posterior neck region (i.e., non-BAT). DESIGN: Cross-sectional. SETTING: Clinical research center. PATIENTS OR OTHER PARTICIPANTS: Twelve healthy male volunteers aged 18 to 29 years [body mass index = 24.7 ± 2.8 kg/m2 and body fat percentage = 25.0% ± 7.4% (both, mean ± SD)]. INTERVENTIONS: Standardized whole-body cold exposure (180 minutes at 18°C) and immediate rewarming (30 minutes at 32°C). MAIN OUTCOME MEASURES: Proton density fat fraction (PDFF) and T2* of the SCV and posterior neck fat pads. Acquisitions occurred at 5- to 15-minute intervals during cooling and subsequent warming. RESULTS: SCV PDFF declined significantly after only 10 minutes of cold exposure [-1.6% (SE: 0.44%; P = 0.007)] and continued to decline until 35 minutes, after which time it remained stable until 180 minutes. A similar time course was also observed for SCV T2*. In the posterior neck fat (non-BAT), there were no cold-induced changes in PDFF or T2*. Rewarming did not result in a change in SCV PDFF or T2*. CONCLUSIONS: The rapid cold-induced decline in SCV PDFF suggests that in humans BAT is activated quickly in response to cold and that TAG is a primary substrate.

Recent advances in the detection of brown adipose tissue in adult humans: a review.

The activation of brown adipose tissue (BAT) is associated with reductions in circulating lipids and glucose in rodents and contributes to energy expenditure in humans indicating the potential therapeutic importance of targetting this tissue for the treatment of a variety of metabolic disorders. In order to evaluate the therapeutic potential of human BAT, a variety of methodologies for assessing the volume and metabolic activity of BAT are utilized. Cold exposure is often utilized to increase BAT activity but inconsistencies in the characteristics of the exposure protocols make it challenging to compare findings. The metabolic activity of BAT in response to cold exposure has most commonly been measured by static positron emission tomography of 18F-fluorodeoxyglucose in combination with computed tomography (18F-FDG PET-CT) imaging, but recent studies suggest that under some conditions this may not always reflect BAT thermogenic activity. Therefore, recent studies have used alternative positron emission tomography and computed tomography (PET-CT) imaging strategies and radiotracers that may offer important insights. In addition to PET-CT, there are numerous emerging techniques that may have utility for assessing BAT metabolic activity including magnetic resonance imaging (MRI), skin temperature measurements, near-infrared spectroscopy (NIRS) and contrast ultrasound (CU). In this review, we discuss and critically evaluate the various methodologies used to measure BAT metabolic activity in humans and provide a contemporary assessment of protocols which may be useful in interpreting research findings and guiding the development of future studies.