An OGT-STAT5 Axis in Regulatory T Cells Controls Energy and Iron Metabolism

The immunosuppressive regulatory T (Treg) cells exert emerging effects on adipose tissue homeostasis and systemic metabolism. However, the metabolic regulation and effector mechanisms of Treg cells in coping with obesogenic insults are not fully understood. We have previously established an indispensable role of the O-linked N-Acetylglucosamine (O-GlcNAc) signaling in maintaining Treg cell identity and promoting Treg suppressor function, via STAT5 O-GlcNAcylation and activation. Here, we investigate the O-GlcNAc transferase (OGT)-STAT5 axis in driving the immunomodulatory function of Treg cells for metabolic homeostasis. Treg cell-specific OGT deficiency renders mice more vulnerable to high-fat diet (HFD)-induced adiposity and insulin resistance. Conversely, constitutive STAT5 activation in Treg cells confers protection against adipose tissue expansion and impaired glucose and insulin metabolism upon HFD feeding, in part by suppressing adipose lipid uptake and redistributing systemic iron storage. Treg cell function can be augmented by targeting the OGT-STAT5 axis to combat obesity and related metabolic disorders.

Impact of Protein Sources in a Guideline-Based Omnivorous Diet on Circulating Biogenic Amine Metabolites: A Randomized Controlled-Feeding Trial

Objectives

Age is a risk factor for chronic diseases—the leading causes of death and disability. An omnivorous diet compared to a plant-based diet was shown to increase blood Trimethylamine-N-oxide (TMAO)—a biogenic amine biomarker for atherosclerosis that may also increase the risk for insulin resistance and certain cancers. Worldwide, pork and chicken are the most popular animal proteins, however, poultry is perceived as healthier. It is unknown if pork intake differentially modifies the TMAO-response than poultry which was investigated here using a non-inferiority study design to avoid any potential negative results.

Methods

In a randomized, active-controlled, 2-arm-crossover trial (NCT03539666), healthy adults (n = 38/arm, age ≥ 50 y) consumed 156 g/day of lean pork or white-meat chicken as the main protein source as part of an omnivorous diet based on the 2015 USDA dietary guidelines. The feeding arms were matched for food ingredients, nutrients, and energy. Overnight-fasted samples were collected before and after each diet phase. LC/MS with isotope-labeled internal standards and 16S-rDNA sequencing were used for metabolite and microbiome measurements, respectively. Univariate and multivariate data were analyzed using supervised and unsupervised machine learning algorithms in R.

Results

A non-inferiority of pork to poultry for a circulating TMAO-response (97.5% CI, linear mixed model) was observed for the first time. In addition, global biogenic amine signature (346 metabolites, 95% CI), microbiota-dependent essential TMAO precursor—trimethylamine (97.5% CI), three dietary TMAO substrates (choline, betaine, and L-carnitine) as well as the microbiota composition (95% CI) underlying the observed TMAO-response were not different between the two proteins. TMAO phenotype varied at baseline; a higher baseline circulating TMAO concentration associated with distinct microbiota profiles (all, FDR corrected p < 0.05) and greater TMAO-response (p = 0.0001) independent of the dietary proteins.

Conclusions

Lean pork does not exacerbate TMAO-risk in omnivores 50 years or older. With 95% of Americans being omnivorous and a third of them fast aging, lean pork increases dietary protein options that may help improve adherence to dietary recommendations for greater healthspan.

Funding Sources

National Pork Board, National Institute of Food & Agriculture

Brown adipose tissue involution associated with progressive restriction in progenitor competence

Human brown adipose tissue (BAT) undergoes progressive involution. This involution process is not recapitulated in rodents, and the underlying mechanisms are poorly understood. Here we show that the interscapular BAT (iBAT) of rabbits whitens rapidly during early adulthood. The transcriptomic remodeling and identity switch of mature adipocytes are accompanied by loss of brown adipogenic competence of progenitors. Single-cell RNA sequencing reveals that rabbit and human iBAT progenitors highly express the FSTL1 gene. When iBAT involutes in rabbits, adipocyte progenitors reduce FSTL1 expression and are refractory to brown adipogenic recruitment. Conversely, FSTL1 is constitutively expressed in mouse iBAT to sustain WNT signaling and prevent involution. Progenitor incompetence and iBAT paucity can be induced in mice by genetic deletion of the Fstl1 gene or ablation of Fstl1⁺ progenitors. Our results highlight the hierarchy and dynamics of the BAT progenitor compartment and implicate the functional incompetence of FSTL1-expressing progenitors in BAT involution.

Effects of Lean Pork on Microbiota and Microbial-Metabolite Trimethylamine-N-Oxide: A Randomized Controlled Non-Inferiority Feeding Trial Based on the Dietary Guidelines for Americans

SCOPE

Trimethylamine-N-oxide (TMAO) is a microbiota-dependent and primarily animal-protein-derived proatherogenic metabolite. The ecological impact of pork-the most popular animal protein worldwide-on the human microbiome, and in the physiological context of TMAO and other biogenic amines, remains unclear. Poultry being the recommended heart-healthier animal protein, we inquired-if pork intake results in inferior-to-chicken TMAO-response while consuming a US. Dietary Guidelines (DGA)-diet?

METHODS AND RESULTS

In a randomized, controlled, all-food-provided, crossover, feeding trial, healthy adults consumed 156 g/day of lean-pork or chicken (active-control) as primary proteins. Mixed-effect modeling shows pork as noninferior to chicken for circulating TMAO response and microbiota-generated essential TMAO-precursor-trimethylamine (97.5% CI, n = 36/protein). Markers of lipid metabolism, inflammation and oxidative stress, serum levels of betaine, choline, L-carnitine, composition and functional-capability of the microbiota, and association of baseline TMAO-levels with TMAO-response (both, r>0.6, p = 0.0001) were nondistinguishable between the protein groups. TMAO reduction and similar shifts in microbiota and biogenic-amine signatures postdiet in both groups indicate a background DGA-effect.

CONCLUSIONS

Unlike extrapolating negative results, we present noninferiority-testing based evidence that consuming pork as a predominant protein within an omnivorous DGA-diet does not exacerbate TMAO-response. Results highlight the importance of understanding protein-TMAO interactions within dietary patterns. This article is protected by copyright. All rights reserved.