Nipsnap1-A regulatory factor required for long-term maintenance of non-shivering thermogenesis.

OBJECTIVE: The activation of non-shivering thermogenesis (NST) has strong potential to combat obesity and metabolic disease. The activation of NST however is extremely temporal and the mechanisms surrounding how the benefits of NST are sustained once fully activated, remain unexplored. The objective of this study is to investigate the role of 4-Nitrophenylphosphatase Domain and Non-Neuronal SNAP25-Like 1 (Nipsnap1) in NST maintenance, which is a critical regulator identified in this study. METHODS: The expression of Nipsnap1 was profiled by immunoblotting and RT-qPCR. We generated Nipsnap1 knockout mice (N1-KO) and investigated the function of Nipsnap1 in NST maintenance and whole-body metabolism using whole body respirometry analyses. We evaluate the metabolic regulatory role of Nipsnap1 using cellular and mitochondrial respiration assay. RESULTS: Here, we show Nipsnap1 as a critical regulator of long-term thermogenic maintenance in brown adipose tissue (BAT). Nipsnap1 localizes to the mitochondrial matrix and increases its transcript and protein levels in response to both chronic cold and ß3 adrenergic signaling. We demonstrated that these mice are unable to sustain activated energy expenditure and have significantly lower body temperature in the face of an extended cold challenge. Furthermore, when mice are exposed to the pharmacological ß3 agonist CL 316, 243, the N1-KO mice exhibit significant hyperphagia and altered energy balance. Mechanistically, we demonstrate that Nipsnap1 integrates with lipid metabolism and BAT-specific ablation of Nipsnap1 leads to severe defects in beta-oxidation capacity when exposed to a cold environmental challenge. CONCLUSION: Our findings identify Nipsnap1 as a potent regulator of long-term NST maintenance in BAT.

Thermogenic adipose tissue in energy regulation and metabolic health.

The ability to generate thermogenic fat could be a targeted therapy to thwart obesity and improve metabolic health. Brown and beige adipocytes are two types of thermogenic fat cells that regulate energy balance. Both adipocytes share common morphological, biochemical, and thermogenic properties. Yet, recent evidence suggests unique features exist between brown and beige adipocytes, such as their cellular origin and thermogenic regulatory processes. Beige adipocytes also appear highly plastic, responding to environmental stimuli and interconverting between beige and white adipocyte states. Additionally, beige adipocytes appear to be metabolically heterogenic and have substrate specificity. Nevertheless, obese and aged individuals cannot develop beige adipocytes in response to thermogenic fat-inducers, creating a key clinical hurdle to their therapeutic promise. Thus, elucidating the underlying developmental, molecular, and functional mechanisms that govern thermogenic fat cells will improve our understanding of systemic energy regulation and strive for new targeted therapies to generate thermogenic fat. This review will examine the recent advances in thermogenic fat biogenesis, molecular regulation, and the potential mechanisms for their failure.

Age-dependent Pdgfrß signaling drives adipocyte progenitor dysfunction to alter the beige adipogenic niche in male mice.

Perivascular adipocyte progenitor cells (APCs) can generate cold temperature-induced thermogenic beige adipocytes within white adipose tissue (WAT), an effect that could counteract excess fat mass and metabolic pathologies. Yet, the ability to generate beige adipocytes declines with age, creating a key challenge for their therapeutic potential. Here we show that ageing beige APCs overexpress platelet derived growth factor receptor beta (Pdgfrß) to prevent beige adipogenesis. We show that genetically deleting Pdgfrß, in adult male mice, restores beige adipocyte generation whereas activating Pdgfrß in juvenile mice blocks beige fat formation. Mechanistically, we find that Stat1 phosphorylation mediates Pdgfrß beige APC signaling to suppress IL-33 induction, which dampens immunological genes such as IL-13 and IL-5. Moreover, pharmacologically targeting Pdgfrß signaling restores beige adipocyte development by rejuvenating the immunological niche. Thus, targeting Pdgfrß signaling could be a strategy to restore WAT immune cell function to stimulate beige fat in adult mammals.

In Utero Heat Stress Has Minimal Impacts on Processed Pork Products: A Comparative Study.

This study aimed to determine what effects in utero heat stress (IUHS) in pigs may have on quality of processed pork products. In two experiments, patties and emulsion sausages were prepared from lean and fat from pigs subjected to IUHS or in utero thermoneutral (IUTN) conditions. Patties formulated to contain 25% added fat had altered textural properties compared to those without additional fat, as shown by lower hardness, cohesiveness, springiness, and chewiness values (p < 0.05), which was not affected by IUHS treatment. Neither fat content nor IUHS treatment affected fluid losses of patties (p > 0.05). In general, 25% added fat patties had greater L*, a*, b*, hue angle, and chroma values than lean patties (p < 0.05). However, 25% added fat patties from the IUHS treatment maintained superior color stability during aerobic display, despite lean patties from this treatment exhibiting increased lipid oxidation (p < 0.05). For emulsion sausages, minimal differences in quality attributes and oxidative stability were found between treatment groups. Subcutaneous fat from IUHS pigs had greater C20:1 and C20:2 than IUTN (p < 0.05), although the magnitude of these differences was slight. Overall, the findings of this study suggest IUHS would have minimal impacts on the functional properties of raw pork, resulting in similar final quality of processed products to IUTN.

Evaluation of functional and chemical properties of crust from dry-aged beef loins as a novel food ingredient.

Efficacy of utilizing dry-aged beef crusts as a functional food ingredient was investigated. Paired beef M. longissimus lumborum (n = 13) were aged under various conditions (dry-aging, DA; dry-aging in water-permeable bag, DWA; dry-aging under UV light, UDA; wet-aging, WA; unaged-initial, INI) for 28 d. Crusts were collected and lyophilized to characterize functional and technological properties. Crusts from dry-aged samples (DA/DWA/UDA) had lower chroma values, higher lipid and protein oxidation extents than WA and INI (P < 0.05). However, crust from DA had higher antioxidant and emulsifying capacities compared to the others (P < 0.05). Adding 5% (w/w) crusts to beef patties resulted in equivalent textural properties and oxidative stability to the no-crust patties (P > 0.05). Trained sensory-panel found enhanced brown-roasted/grilled (P < 0.05) and umami flavors (P = 0.0512) in DA-patties compared to the others. Volatile analysis found decane in only DA-patties. The results indicate the potential feasibility of beef crust from dry-aged beef as a novel food ingredient.

Effects of ultrasound frequency mode on myofibrillar protein structure and emulsifying properties.

In this study, different ultrasound frequencies, including 20 kHz, 23 kHz, and 20/23 kHz, were applied for the treatment of myofibrillar protein (MP) with different protein concentrations (20, 40, and 60 mg/mL). The structures and emulsifying properties of the treated and untreated MPs were compared. The MP structural changes were confirmed based on the active sulfhydryl content (ASC), surface hydrophobicity (SUH), particle size, and turbidity, and the degree of change decreased in the order of 20/23 kHz > 20 kHz ≈ 23 kHz > control (CON). Moreover, the MP emulsifying properties, determined based on the emulsifying activity index (EAI), emulsion stability index (ESI), and creaming stability, were in accordance with the structural changes. Notably, frequency superposition provided more external force through the resonance of cavitation bubbles to induce stronger stress response of myosin in MP, thereby promoting the change of protein structure and emulsifying properties. Results implied that MPs treated with different ultrasound frequencies, especially the superposition of two frequencies, have the potential for wide applications in emulsified-type meat products.

Application of high-pressure treatment improves the in vitro protein digestibility of gel-based meat product.

Effects of high-pressure treatments (HPT, 100-300 MPa, 9 min, 25 °C) on the in vitro digestibility of gel-type meat products were studied using a simulated digestion-model. In vitro digestibilities of the cooked rabbit meat batters throughout the simulated oral-, gastric-, and intestinal-phases were determined. Peptides in the intestinal digesta were identified via Mass Spectrometer. Results revealed that in vitro digestibilities of HPT-samples were higher than the control (1.98%, 6.13% and 61.31% for oral-, gastric- and intestinal-phase respectively) throughout the digestion (P < 0.05). Alterations of the peptide profiles were induced by HPT, showing HPT-specific patterns of mutual peptides in the digestive products. Coupled with the identifications of salt-soluble proteins from raw batters, it was confirmed that myofibrillar proteins account for the major contribution to the HPT-induced changes. The results indicated that HPT can potentially be an effective technology to improve the digestibility of meat products.

Effects of probiotic supplementation and postmortem storage condition on the oxidative stability of M. Pectoralis major of laying hens.

Dietary probiotic supplementation is a promising alternative to antibiotics in the poultry industry, and some studies have found its positive impacts on meat quality attributes. The objective of this study was to evaluate the effects of dietary treatments on oxidative stability of postmortem chicken fillet (M. Pectoralis major) muscles during 7 d of storage under either high oxygen (HIOX) or vacuum (VAC) conditions. A total of 264 Hy-Line Brown laying hens (11 birds per cage) were assigned to 2 different dietary treatments (regular diet or 300 ppm probiotic, Sporulin enhanced diet) before being sacrificed. At 17 wk, one bird per cage from 6 cages per treatment was randomly selected and slaughtered (n = 12). Chicken fillets from both sides were collected and randomly assigned to HIOX or VAC conditions. Within each fillet side, the muscle was divided into 3 portions, assigned to 1 or 7 d storage period, while the caudal portion was allocated as the 0 d samples for proximate composition and fatty acid profiling. Results revealed that the muscle crude compositions were not altered in laying hens that were fed probiotic supplementary diet compared to controls (P > 0.05). However, the muscle samples from probiotic fed laying hens had higher proportions of unsaturated fatty acid (74.76 vs. 71.65%, P < 0.05) and 2-thiobarbituric acid reactive substances (0.79 vs. 0.67 mg malondialdehyde/kg meat, P < 0.05) than the samples from the control. In addition, the probiotic fed laying hens, but not controls, had higher levels of conjugated dienes (3.32 vs. 2.63 µg/g meat) and peroxides (0.40 vs. 0.30 milliequivalent O2/kg fat) in the muscle samples after 7 d of storage (P < 0.05). The results from the present study indicated that postmortem fillet muscles obtained from the laying hens fed with probiotic supplementation would be more prone to be oxidized, especially under more oxidizing conditions (HIOX and extended storage time).

Applications of high pressure to pre-rigor rabbit muscles affect the water characteristics of myosin gels.

Myosin was extracted immediately after high-pressure treatment (HP, 100-300MPa for 15 or 180s) to pre-rigor rabbit muscles (PRRMs) for evaluating the influences of HP-treatment on gel properties, using untreated muscles as Controls. Assessment of myosin yields, water-holding capacity (WHC), water mobility and distribution demonstrated that HP modified myosin before its extraction. Myosin gels subjected to HP at 100MPa 180s and 200MPa 15s had enhanced WHC compared with Controls. Also, the highest proportion of immobile-water was observed in myosin gels treated at 200MPa for 15s. HP-treatment of PRRMs affected their physicochemical properties as evidenced by alterations in tertiary, secondary conformations and rheological properties during subsequent heating. These modifications appear to induce various degrees of exposure of hydrophobic and sulfhydryl groups, resulting in different gelation rates. These alterations partly explain the various gel qualities obtained and indicate the potential of HP for pre-rigor muscles.

High-pressure effects on the molecular aggregation and physicochemical properties of myosin in relation to heat gelation.

Myosin was extracted from the M. psoas muscle of rabbits, and dissolved in 0.6M KCl buffer (pH6.5). Effects of high-pressure (HP, 100 to 300MPa, 9min, 25°C) treatment on myosin solubility, molecular traits (molecular weight and morphology), flow behavior and strength of heat-induced myosin gels were studied and compared with the untreated controls. Myosin subjected to 200MPa HP treatment had lower solubility than samples treated at other pressures (P<0.05). Molecular dimerization and morphological swelling of myosin was observed using gel-permeation chromatography and atomic-force microscopy. Additionally, the shear-thinning behavior of myosin solutions (10mg/mL) was improved by HP treatment (≥200MPa), and a positive trend in gel-strength enhancement was inferred. It is postulated that significant morphological changes in myosin accounted for changes in its functional properties, by the influence of HP treatment on protein-protein and/or protein-water interactions. There is a relationship between molecular morphology and the coalescing behavior of myosin, since significant changes of both attributes were observed at pressures ≥200MPa.

Contribution of High-Pressure-Induced Protein Modifications to the Microenvironment and Functional Properties of Rabbit Meat Sausages.

Rabbit meat batters were subjected to high pressure (HP, 100 to 300 MPa for 3, 9, or 15 min) to elucidate their effects on proteins structures, the microenvironment, and the resulting functionalities of the subsequently heated products. To determine these effects, we investigated structural and microenvironmental changes using Raman spectroscopy and also expressible moisture content, textural characteristics, and dynamic rheological properties of batters during heating (20 to 80 °C). Untreated samples served as controls. Analysis of specific Raman spectral regions demonstrated that applications of HP to rabbit meat batters tended to induce the transformation of the all-gauche S-S conformation to gauche-gauche-trans in the batter system. HP treatment higher than 100 MPa for 9 min promoted secondary structural rearrangements, and molecular polarity enhancement in the proteins prior to cooking. Also, increases of O-H stretching intensities of rabbit meat sausages were obtained by HP treatment, denoting the strengthening of water-holding capacity. These HP-induced alterations resulted in improved texture and, perhaps, improved juiciness of rabbit meat sausages (P < 0.05), however they had relatively poorer rheological properties than the controls. Nevertheless, HP treatment, especially 200 MPa for 9 or 15 min, was an effective technique for improving the functionalities of gel-type products through modification of meat proteins.

Applications of high pressure to pre-rigor rabbit muscles affect the functional properties associated with heat-induced gelation.

High pressure (HP) was applied to pre-rigor rabbit muscles (PRRMs) for the manufacture of value-added gel-type products. A 2×3 factorial design was adopted for HP-treatment (100, 200 and 300MPa for 15 or 180s) to PRRMs. The HP-treated meat was used for gel preparation and determination of water mobility properties and textural profiles. Salt-soluble meat proteins (SSMP) were then extracted from meat for estimating the tertiary conformational changes (hydrophobic and sulfhydryl groups). The water-holding capacity of treated samples increased significantly (P<0.05) except for those treated at 300-180 (MPa-s). The hardness, cohesiveness and chewiness were significantly improved (P<0.05) by moderate HP-treatments (100-200MPa for 15 or 180s). HP-induced the de-polymerization of some protein components, together with unfolding and refolding of protein tertiary conformations, partly explaining the observed functionality changes. In conclusion, application of moderate HP to PRRM modified the protein conformation in a manner that improved the functional properties of gels.