Diet Switch Research Articles

PSV-9 Characterization of the Rumen Bacterial Communities of Lambs That Transitioned from Forage to a Concentrate-Based Diet

Abstract Forage and concentrate-based diets are distinct strategies used in ruminant production. The transition from a forage-based diet to a concentrate-based diet has been shown to have a great impact on the rumen microbiome composition due to vast differences in substrates provided by each diet type. To gain further insight on the nature of the changes that occur in the rumen microbiome as a result of a switch in diet, ruminal bacterial composition was compared between lambs initially fed a forage-based diet and lambs that were switched to a concentrate-based diet for approximately 60 days. From rumen fluid that was collected after slaughter, data were generated by Illumina MiSeq 2X300 sequencing of PCR amplicons targeting the V1-V3 regions of the 16S rRNA gene. Next-Generation Sequence data were analyzed using a combination of custom Perl scripts, and publicly available software (Mothur (v.1.35.1), RDP classifier and NCBI Blast). A total of 10,693 species-level operational taxonomic units (OTUs) were identified across all samples, with 86 OTUs shared between diets. A comparative analysis using the non-parametric Kruskal-Wallis test identified 16 highly represented species-level OTUs that differed in abundance across dietary treatments (P < 0.05). Of these, three OTUs, RA-01223, RA1-35340, and RA1-55937, were found to be of particular interest. OTU RA-01223 was at its highest representation in samples from individuals given a concentrate-based diet, with an average abundance of 8.76% compared with 0.80% in samples from animals fed a forage-based diet. RA-01223 was predicted to be a novel species of the family Oscillospiraceae based on its low 16S rRNA gene sequence identity (94.8%) to its closest valid relative, Ruminococcoides bili. OTU RA1-35340, predicted to be a strain of Sharpea azabuensis, was also in much greater abundance in the concentrate-based diet as compared with the forage-based diet (2.83% and 0.05%, respectively). In contrast, RA1-55937, which was predicted to be a strain of Pectinatus haikarae, was at its greatest abundance in samples from individuals given a forage-based diet, with an average representation of 4.91% compared with 0.52% in samples from animals fed a concentrate-based diet. These and other specific ruminal OTUs whose abundance are affected by changes in diet can then be studied further to gain more insight on the effects of the transition from forage to concentrate on rumen physiology.

Short-term dietary changes can result in mucosal and systemic immune depression

Omnivorous animals, including mice and humans, tend to prefer energy-dense nutrients rich in fat over plant-based diets, especially for short periods of time, but the health consequences of this short-term consumption of energy-dense nutrients are unclear. Here, we show that short-term reiterative switching to ‘feast diets’, mimicking our social eating behavior, breaches the potential buffering effect of the intestinal microbiota and reorganizes the immunological architecture of mucosa-associated lymphoid tissues. The first dietary switch was sufficient to induce transient mucosal immune depression and suppress systemic immunity, leading to higher susceptibility to Salmonella enterica serovar Typhimurium and Listeria monocytogenes infections. The ability to respond to antigenic challenges with a model antigen was also impaired. These observations could be explained by a reduction of CD4+ T cell metabolic fitness and cytokine production due to impaired mTOR activity in response to reduced microbial provision of fiber metabolites. Reintroducing dietary fiber rewired T cell metabolism and restored mucosal and systemic CD4+ T cell functions and immunity. Finally, dietary intervention with human volunteers confirmed the effect of short-term dietary switches on human CD4+ T cell functionality. Therefore, short-term nutritional changes cause a transient depression of mucosal and systemic immunity, creating a window of opportunity for pathogenic infection.

The unique gut microbiome of giant pandas involved in protein metabolism contributes to the host’s dietary adaption to bamboo

BackgroundThe gut microbiota of the giant panda (Ailuropoda melanoleuca), a global symbol of conservation, are believed to be involved in the host’s dietary switch to a fibrous bamboo diet. However, their exact roles are still largely unknown.ResultsIn this study, we first comprehensively analyzed a large number of gut metagenomes giant pandas (n = 322), including 98 pandas sequenced in this study with deep sequencing (Illumina) and third-generation sequencing (nanopore). We reconstructed 408 metagenome-assembled genomes (MAGs), and 148 of which (36.27%) were near complete. The most abundant MAG was classified as Streptococcus alactolyticus. A pairwise comparison of the metagenomes and meta-transcriptomes in 14 feces revealed genes involved in carbohydrate metabolism were lower, but those involved in protein metabolism were greater in abundance and expression in giant pandas compared to those in herbivores and omnivores. Of note, S. alactolyticus was positively correlated to the KEGG modules of essential amino-acid biosynthesis. After being isolated from pandas and gavaged to mice, S. alactolyticus significantly increased the relative abundance of essential amino acids in mice jejunum.ConclusionsThe study highlights the unique protein metabolic profiles in the giant panda’s gut microbiome. The findings suggest that S. alactolyticus is an important player in the gut microbiota that contributes to the giant panda’s dietary adaptation by more involvement in protein rather than carbohydrate metabolism.4zh5Ny6QmwZifdgaSCFmHgVideo

Exploring the Plasticity of Diet on Gut Microbiota and Its Correlation with Gut Health.

Dietary habits have been proven to help alter the composition of gut microbiota, and exploring the impact of nutritional patterns on gut microbiota changes can help protect gut health. However, few studies have focused on the dietary impact on the gut microbiota over an experimental timeframe. In this study, 16S rRNA gene sequencing was employed to investigate the gut microbiota of mice under different dietary patterns, including AIN-93G diet (Control), high protein diet (HPD), high fiber diet (HFD), and switch diet (Switch). The alpha diversity of the HPD group significantly decreased, but HFD can restore this decline. During HPD, some genera were significantly upregulated (e.g., Feacalibaculum) and downregulated (e.g., Parabacteroides). However, after receiving HFD, other genera were upregulated (e.g., Akkermansia) and downregulated (e.g., Lactobacillus). In addition, the interaction between pathogenic bacteria was more pronounced during HPD, while the main effect was probiotics during HFD. In conclusion, the plasticity exhibited by the gut microbiota was subject to dietary influences, wherein disparate dietary regimens hold pivotal significance in upholding the well-being of the host. Therefore, our findings provide new ideas and references for the relationship between diets and gut microbiota.

Orlistat exerts anti-obesity and anti-tumorigenic effects in a transgenic mouse model of endometrial cancer.

Among all cancers, endometrial cancer is most strongly associated with obesity, with more than 65% of endometrial cancers attributable to obesity and being overweight. Fatty acid synthase (FAS), a key lipogenic enzyme, is expressed in endometrial cancer tumors and is associated with a worse prognosis for this disease. Orlistat, an FAS inhibitor, is an FDA-approved weight loss medication that has demonstrated anti-tumor activity in a variety of preclinical cancer models. In this study, the Lkb1fl/flp53fl/fl mouse model of endometroid endometrial cancer was exposed to three diet interventions, including a high fat diet (obese), a low fat diet (lean) and switch from a high fat to a low fat diet, and then exposed to orlistat or placebo. The mice fed a high-fat diet had significantly increased body weight and tumor weight compared to mice fed a low-fat diet. Switching from a high-fat diet to a low fat diet led to a reduction in mouse weight and suppressed tumor growth, as compared to both the high fat diet and low fat diet groups. Orlistat effectively decreased body weight in obese mice and inhibited tumor growth in obese, lean, and the high fat diet switch to low fat diet mouse groups through induction of apoptosis. Orlistat also showed anti-proliferative activity in nine of 11 primary cultures of human endometrial cancer. Our findings provide strong evidence that dietary intervention and orlistat have anti-tumor activity in vivo and supports further investigation of orlistat in combination with dietary interventions for the prevention and treatment of endometrial cancer.

Formation and Replacement of Bone and Tooth Mineralized Tissues in Green Iguanas (Iguana iguana) Revealed by In-Vivo Fluorescence Marking.

Hard tissue formation patterns and rates reveal details of animal physiology, life history, and environment, but are understudied in reptiles. Here, we use fluorescence labels delivered in vivo and laser confocal scanning microscopy to study tooth and bone formation in a managed group of green iguanas (Iguana iguana, Linné 1758) kept for 1.5 years under experimentally controlled conditions and undergoing several dietary switches. We constrain rates of tooth elongation, which we observe to be slow when enamel is initially deposited (c. 9 µm/day), but then increases exponentially in the dentin root, reaching c. 55 µm/day or more after crown completion. We further constrain the total timing of tooth formation to ∼40-60 days, and observe highly variable timings of tooth resorption onset and replacement. Fluorescent labels clearly indicate cohorts of teeth recruited within Zahnreihen replacement waves, with faster sequential tooth recruitment and greater wave sizes posteriorly, where each wave initiates. Fluorescence further reveals enamel maturation after initial deposition. Rates of hard tissue formation in long bones range from 0.4 to 3.4 µm/day, correlating with animal weight gain and cortical bone recording the entire history of the experiment. We suggest additional labeling experiments to study hard tissue formation patterns in other reptiles, and propose strategies for chemical analyses of hard tissues in order to extract temporal information about past environments, behaviors, and diets from reptilian fossils throughout the Phanerozoic.

Impact of transgenerational host switch on gut bacterial assemblage in generalist pest, Spodoptera littoralis (Lepidoptera: Noctuidae).

Diet composition is vital in shaping gut microbial assemblage in many insects. Minimal knowledge is available about the influence of transgenerational diet transition on gut microbial community structure and function in polyphagous pests. This study investigated transgenerational diet-induced changes in Spodoptera littoralis larval gut bacteriome using 16S ribosomal sequencing. Our data revealed that 88% of bacterial populations in the S. littoralis larval gut comprise Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes. The first diet transition experiment from an artificial diet (F0) to a plant diet (F1), cabbage and cotton, caused an alteration of bacterial communities in the S. littoralis larval gut. The second transgenerational diet switch, where F1 larvae feed on the same plant in the F2 generation, displayed a significant variation suggesting further restructuring of the microbial communities in the Spodoptera larval gut. F1 larvae were also challenged with the plant diet transition at the F2 generation (cabbage to cotton or cotton to cabbage). After feeding on different plant diets, the microbial assemblage of F2 larvae pointed to considerable differences from other F2 larvae that continued on the same diet. Our results showed that S. littoralis larval gut bacteriome responds rapidly and inexplicably to different diet changes. Further experiments must be conducted to determine the developmental and ecological consequences of such changes. Nevertheless, this study improves our perception of the impact of transgenerational diet switches on the resident gut bacteriome in S. littoralis larvae and could facilitate future research to understand the importance of symbiosis in lepidopteran generalists better.

1663-P: Estrogenic Regulation of Energy Balance in the Medial Amygdala

Compelling evidence has demonstrated that estradiol (E2) and estrogen receptors α/β (ERα/β) play critical roles in the central regulation of energy balance and glucose homeostasis. Our previous research proved that ERα in the medial amygdala (ERαMeA) mediates estrogenic actions to stimulate physical activity, promote energy expenditure, and prevent diet-induced obesity (DIO). Interestingly, ERβ is also highly expressed in the MeA neurons. To explore the metabolic functions of ERβMeA, we generated a mouse model with ERβ selectively deleted in the MeA (ERβKOMeA) during adulthood by using AAV virus-mediated Cre-Lox site-specific recombination. When fed on a high-fat diet (HFD) but not a standard chow diet, both male and female ERβKOMeA mice showed decreased body weight gain and fat deposition, associated with a decrease in ambulatory activity. Consistently, we also observed an increase in energy expenditure of female ERβKOMeA mice during diet switching from chow to HFD, suggesting a diet-dependent regulatory role of ERβMeA in body weight control. In addition, both electrophysiology and immunohistochemistry staining results indicated that half of the ERαMeA neurons co-express ERβ. In these ERα&β co-expressing MeA neurons, ERα agonist propyl pyrazole trio (PPT) induced ERα-dependent depolarization, while ERβ agonist diarypropionitrile (DPN) induced ERβ-dependent hyperpolarization. Further, we found that the chemogenetic activation of ERαMeA neurons promotes physical activity and stimulates body thermogenesis, while the inhibition of ERβMeA neurons downregulates physical activity and body thermogenesis. In line with this, inhibition of ERβMeA neurons impaired cold-induced brown adipose tissue thermogenesis, resulting in lower rectal temperature during acute cold exposure. Collectively, our results support a model that E2 acts on ERα/βMeA neurons to provide bidirectional regulation of body weight and resistance to DIO. Disclosure H.Ye: None. M.Mun: None. Y.He: None. P.Xu: None. B.Feng: None. P.Luo: None. L.Carrillo-sáenz: None. V.C.Torres irizarry: None. L.Ibrahimi: None. N.Antony: None. M.Kota: None. D.Dixit: None. Funding National Institutes of Health (R01DK123098, P30DK020595, P20GM135002, R01DK129548, T32AA026577, K01DK119471); U.S. Department of Agriculture (3092-51000-062-04(B)S); American Heart Association (915789, 19CDA34660335, 20POST35120600); U.S. Department of Defense (W81XWH-20-1-0075)

Quantifying spatio-temporal consistency in the trophic ecology of two sympatric flatfishes.

Sympatric flatfish predators may partition their resources in coastal environments to reduce competition and maximise foraging efficiency. However, the degree of spatial and temporal consistency in their trophic ecology is not well understood because dietary studies tend to overlook the heterogeneity of consumed prey. Increasing the spatial and temporal scale of dietary analyses can thus help to resolve predator resource use. We applied a stomach content and multi-tissue (liver and muscle) stable isotope (δ13 C, δ15 N and δ34 S) approach to investigate the feeding habits of two co-occurring flatfish predators, common dab (Limanda limanda) and European plaice (Pleuronectes platessa), across four bays on the Northumberland coast (UK) over short (hours), medium (days) and long (months) temporal scales. Stomach content analyses showed spatial consistencies in predator resource use, whereas stable isotope mixing models revealed considerable inter-bay diet variability. Stomach contents also indicated high dietary overlap between L. limanda and P. platessa, whilethe stable isotope data yielded low to moderate levels of overlap, with cases of complete niche separation. Furthermore, individual specialisation metrics indicated consistently low levels of specialisation among conspecifics over time. We document changes in resource partitioning in space and time, reflecting diet switching in response to local and temporal fluctuations of patchily distributed prey. This study highlights how trophic tracers integrated at multiple temporal and spatial scales (within tens of kilometres) provide a more integrative approach for assessing the trophic ecology of sympatric predators in dynamic environments.

Abstract 3040: A modified microbiota-accessible carbohydrates diet could change gut microbiota in patients with colorectal cancer after surgery

Abstract Dietary factors have important role in modulating the gut microbiome, which in-turn regulates the molecular events in colonic mucosa. The composition and resulting metabolism of the gut microbiome are decisive factors in colorectal cancer (CRC) tumorigenesis. Microbiota-Accessible Carbohydrates (MAC) refer to carbohydrates that the human intestine cannot digest, but that can be digested by intestinal microbes. During that process, short chain fatty acid (SCFA) is produced, which is known to increase beneficial intestinal bacteria and decrease inflammation around intestinal cells. This prospective, longitudinal study aims to explore the changes in the composition and diversity of intestinal microbiota according to the diet pattern in patients with stage I to lll CRC. Participants were assigned to 3-week modified MAC diet group or free diet group followed by diet switching for 3 weeks. Modified MAC diet was designed to adapt to a high fiber diet including 30g of dietary fiber daily and delivered to the patient’s home for 3 weeks as a meal kit supported by Dr. Kitchen Corp. We collected 113 fecal samples from 40 CRC patients before and after diet switching. To explore the effect of diet on the composition of the microbiota and pattern of defecation, 16S rRNA sequencing were performed using fecal samples. Biological information was processed by Qiime2 plugins, DESeq2 and Lefse. Among total 40 participants, 26 (65%) were male. There were 11 (27.5%) with right colon cancer and 29 patients with left colon and rectal cancer. 18 patients without adjuvant chemotherapy were lower stage and higher compliance to modified MAC diet (median 89%) than 22 patients with adjuvant chemotherapy (median 60%). In all participants, protein and dietary fiber intake increased by more than 90% and sodium intake decreased by more than half during modified MAC diet compared to the free diet. There was no difference in alpha diversity change between chemotherapy group and non-chemotherapy group but a significant difference was observed in beta diversity change. Especially, Lachnospiraceae Eubacterium hallii were enriched in non-chemotherapy group. During the modified MAC diet in the group not receiving chemotherapy, Lactobacillaceae Pediococcus, Prevotellaceae Prevotella, Streptococcaceae Lactococcus were increased and Ruminococcaceae Eubacterium siraeum group, Ruminococcaceae UBA1819 were decreased. This study results showed that 3 weeks dietary intake influences the structure and activity of gut microbiome even though the dietary responsiveness of the individual’s microbiota varied substantially. The joint study of microbiome and metabolome has been ongoing now as the most promising approach to evaluate host-microbiome interaction. In order to prove the importance of a balanced diet after colorectal cancer surgery, it will be necessary to analyze the relationship with clinical outcomes. Citation Format: Boyeon Kim, Jiwon Lee, Jin Kim, Jung-Myun Kwak, Hye-Jin Cho, Eun Sung Jung, Sunyoung Lee, Dong Ho Suh, Yu Jin Park, Soohyeon Lee. A modified microbiota-accessible carbohydrates diet could change gut microbiota in patients with colorectal cancer after surgery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3040.

Dynamics of chewing and eating behavior, lying behavior, and salivary characteristics associated with duration of high grain feeding in cows with or with no phytogenic supplement

This study evaluated the adaptive changes in chewing and eating behavior, lying behavior, and salivary properties due to the switch from forage to high grain and the duration of high grain feeding in cows, with or without a phytogenic feed additive. Nine non-lactating cannulated Holstein cows were used in a cross-over design with two experimental periods. Each period included one week of forage feeding, one week of diet transition, and four weeks of high grain feeding (35:65 forage to concentrate ratio; DM basis). Cows were either not supplemented (CON) or supplemented with a phytogenic additive (PHY) characterised by menthol, thymol and eugenol. Switching to high grain decreased (P < 0.01) rumination time compared to forage feeding; however, compared to week 2, rumination time increased (P < 0.01) by 73.8 and 53.21 min/d in weeks 3 and 4 on high grain, respectively. In week 4 on high grain, the PHY-supplemented cows tended (P = 0.08) to ruminate (263 vs. 204 min/d) and chew (406 vs. 347 min/d) longer compared to CON counterparts. The change to high grain increased (P < 0.05) sorting for long and medium size feed particles compared to forage diet, and there was a further increase (P < 0.05) in sorting for long and medium size feed particles in week 3 and 4 on high grain compared to the initial stage of the high grain challenge. Interestingly, PHY supplementation contributed to a more uniform intake of the diet by reducing (P < 0.05) the sorting of both medium and fine particles. Compared to week 1, lying time increased (P < 0.05) by 50 min/d in week 3 on high grain. High grain diet decreased (P < 0.05) salivary pH in week 1, while PHY supplementation helped maintaining this variable at physiological level during this initial grain challenge. Salivary bicarbonate was lower (P < 0.05) in weeks 3 and 4 compared to week 2 on high grain. Overall, the switch to high grain and the duration of feeding influenced chewing and eating behavior, lying behavior and salivary characteristics. Effects were still found 3 or 4 weeks after the diet switch; whereas PHY supplementation contributed to a more uniform nutrient intake by decreasing sorting behavior, which was reflected in stabilized salivary pH at the beginning of the grain challenge, and a tendency for increased chewing activity. However, more research is warranted to evaluate the positive role of PHY supplementation in decreasing feed sorting on metabolic health status and welfare of high-producing dairy cows, which are commonly affected due to high grain feeding.

Better or worse food: Nutrition value of the prey fishes and the potential health implications for Indo-Pacific humpback dolphins

IntroductionOverfishing and climate change have combined to cause fishery stocks to decline and fish community composition to change, further threatening the predation and nutritional health of marine mammals.MethodsIn this study, we collected potential prey fishes catched by fishermen in six habitats of Indo-Pacific humpback dolphins and analyzed their proximate composition (moisture, water, fat and protein), the fatty acid composition and the amino acid composition to evaluate the possible health effect on humpback dolphins.ResultsThe results showed that the nutritional composition varied significantly with species and locations. Fishes in the families Sciaenidae and Engraulidae displayed richer fatty acid composition, while those in the family Clupeidae had the highest value of amino acid quality index. In Zhuhai, home to the largest Indo-Pacific humpback dolphin population, pelagic/neritic prey fishes possessed lower energy density, PUFA content, PUFA/SFA ratio, DHA content, and EAA content compared to demersal fish, suggesting nutritional stress when there is a dietary switch from demersal to pelagic/neritic fishes in Zhuhai population.DiscussionOur study provided a framework, with energy density and fatty acid composition as its most important indicator, for assessment of the marine top predators based on the nutritional composition of their prey fishes and revealed the potential threats. Data here is expected to facilitate the development of scientific programs for successful conservation of not only the Indo-Pacific humpback dolphins, but also other marine top predators, possibly through reconstructing their prey fish’s quantity and quality.

Sex-Specific Effects on Total Body Fat Gain with 4-Week Daily Dosing of Raspberry Ketone [4-(4-Hydroxyphenyl)-2-butanone] and Ketogenic Diet in Mice

Background: Raspberry ketone (RK: [4-(4-Hydroxyphenyl)-2-butanone]) is a dietary supplement marketed for weight control. RK is structurally unrelated to the ketone bodies elevated with a ketogenic diet (KD). This study aims to determine whether RK oral supplementation with KD improves the weight loss outcomes in high-fat diet (HFD; 45% fat)-fed mice. Methods: Male and female C57BL/6J mice were HFD-fed for 9 weeks and switched to KD (80% fat) or a control diet (CD; 10% fat) or continued with the HFD for 4 weeks. Coincident with the diet switch, each diet group received oral RK (200 mg/kg/day) or a vehicle. Results: In male KD-fed mice, oral RK reduced body weight by ~6% (KD_Veh: -9.2 ± 1% vs. KD_RK: -15.1 ± 1%) and fat composition by ~18% (KD_Veh: -16.0 ± 4% vs. KD_RK: -34.2 ± 5%). HFD and KD feeding induced glucose intolerance in both male and female mice. Oral RK decreased the glucose area under the curve in female mice by ~6% (KD_Veh: 44,877 ± 957 vs. KD_RK: 42,040 ± 675 mg*min/dl). KD also had gut microbiota alterations with higher alpha diversity in males and more beta diversity with RK. These findings suggest sex-specific weight loss effects with RK and KD in mice.

Novel 13C enrichment technique reveals early turnover of DHA in peripheral tissues

The brain is rich in DHA, which plays important roles in regulating neuronal function. Recently, using compound-specific isotope analysis that takes advantage of natural differences in carbon-13 content (13C/12C ratio or δ13C) of the food supply, we determined the brain DHA half-life. However, because of methodological limitations, we were unable to capture DHA turnover rates in peripheral tissues. In the current study, we applied compound-specific isotope analysis via high-precision GC combustion isotope ratio mass spectrometry to determine half-lives of brain, liver, and plasma DHA in mice following a dietary switch experiment. To model DHA tissue turnover rates in peripheral tissues, we added earlier time points within the diet switch study and took advantage of natural variations in the δ13C-DHA of algal and fish DHA sources to maintain DHA pool sizes and used an enriched (uniformly labeled 13C) DHA treatment. Mice were fed a fish-DHA diet (control) for 3 months, then switched to an algal-DHA treatment diet, the 13C enriched-DHA treatment diet, or they stayed on the control diet for the remainder of the study time course. In mice fed the algal and 13C enriched-DHA diets, the brain DHA half-life was 47 and 46 days, the liver half-life was 5.6 and 7.2 days, and the plasma half-life was 4.7 and 6.4 days, respectively. By using improved methodologies, we calculated DHA turnover rates in the liver and plasma, and our study for the first time, by using an enriched DHA source (very high δ13C), validated its utility in diet switch studies.

You are what you eat? Rodent study suggests defended body weight mainly dictated by fatcontent of diet.

Preclinical and clinical data suggest that body weight (i.e., body fat) is physiologically regulated, and the high heritability seen from monozygotic twin studies suggests a genetic basis to one's defended body weight. Genome-wide association studies have found that a high proportion of variants that correlate with elevated body mass index are expressed in the central nervous system, signifying that the molecular predicates that likely encode for defended body weight will be found in the brain [(1)]. In this context, an individual integrates peripheral signals (e.g., adipokines, myokines, hepatokines) relaying the metabolic state of various tissues to the brain and reacts to maintain relatively stable weight. However, the recent increased prevalence of obesity/overweight reveals that environmental factors must be influencing this system, and why some people are more susceptible to weight gain in a given environment is not fully understood [(2)]. In this issue, Fang et al. [(3)] present an interesting and thorough set of experiments that demonstrate how fat content in diet affects defended body weight in C57BL/6N mice. By changing the macronutrient composition (fat and carbohydrate) of diets and undertaking switches in diet at different ages (young and adult) and for different durations (4, 8, or 24 weeks), as well as putting mice through rounds of weight gain and weight loss (yo-yo dieting), they provide strong evidence that the major driver of defended body weight in these animals is the amount of fat within the diet. The key takeaway message is that higher-fat diets (HFDs, i.e., diets with 45% fat or more) cause defense of an elevated body weight plateau, whereas lower-fat diets (LFDs, i.e., diets with 10% or 25% fat) cause defense of a lower body weight plateau irrespective of the age at which the diets start or their duration. Furthermore, HFD- and LFD-fed animals showed similar physiology to a 16-hour fast, and switching mice back to LFDs after HFD feeding caused rapid and sustained weight loss, with most groups returning to the LFD-fed weight. They suggest that HFDs do not impede normal physiological defense of body weight but rather cause an increase to a new defended body weight. This paradigm shift is subtle but important. Although understanding the mechanisms behind these findings is beyond the scope of the paper, increases in circulating lipids from diets have been causally linked to inflammation of the hypothalamus and may, in part, explain the present findings [(4)]. Of course, humans are exposed to many different variables that are hard to replicate in rodent models. For example, workers are much more sedentary than in the past, numerous excess calories are consumed through simple sugars found in soft drinks, and we undertake numerous activities and hobbies that directly affect our daily metabolic rate. All of these parameters likely contribute to our defended body weight; however, the diet likely remains one of the major modifiable inputs. The search for the molecular underpinnings of defense of body weight will continue to evolve with each new study adding to our overall understanding of this important physiological regulation; however, this study [(3)] clearly demonstrates that fat content seems directly implicated in body weight regulation. The type of food we eat likely influences the system of how our body weight is regulated, and understanding these interactions is crucial. This study suggests that eating diets high in fat may result in the overconsumption of calories leading to elevated body weight. Would you like meringue and gruyère double cream just after having eaten a large fondue? Of course you would. Open access funding provided by Universite de Fribourg. The author declared no conflict of interest.

Consumption of a Glucose Diet Enhances the Sensitivity of Pancreatic Islets from Adrenalectomized Genetically Obese (ob/ob) Mice to Glucose-Induced Insulin Secretion

Consumption of a glucose diet for 4 d markedly elevates plasma insulin concentrations in adrenalectomized ob/ob mice. The present study examined regulation of insulin secretion from perifused pancreatic islets of female adrenalectomized genetically obese (ob/ob) and lean mice fed a glucose diet for 4 d. These mice were fed a high carbohydrate commercial diet for 21 d, or the high carbohydrate commercial diet for 17 d and a purified high glucose diet for the last 4 d of the 21-d feeding period. Adrenalectomy equalized plasma insulin concentrations, pancreatic islet size, rates of insulin secretion in response to 20 mmol/L glucose and insulin mRNA relative abundance in ob/ob and lean mice fed the commercial diet, but the threshold for glucose-induced insulin secretion determined by a linear glucose gradient remained lower in islets from adrenalectomized ob/ob mice than in those from lean mice (3.8 ± 0.1 vs. 4.9 ± 0.2 mmol/L glucose), and addition of acetylcholine to the perifusate lowered the threshold to only 2.0 ± 0.1 mmol/L glucose in islets from ob/ob mice vs. 3.3 ± 0.1 mmol/L glucose in lean mice. Switching from the commercial diet to the glucose diet for 4 d increased plasma insulin concentrations ∼10-fold in islets from adrenalectomized ob/ob mice without affecting islet size, 20 mmol/L glucose-induced insulin secretion or insulin mRNA abundance. Consumption of the glucose diet did, however, markedly lower the threshold for glucose-induced insulin secretion in islets from adrenalectomized ob/ob mice to approximate the abnormally low glucose thresholds in intact ob/ob mice. Islets from lean mice were unaffected by the diet switch. The signaling pathway that sensitizes islets to glucose-induced insulin secretion seems to be persistently altered in ob/ob mice.

Chronic refined carbohydrate consumption measured by glycemic load and variation in cognitive performance in healthy people

A massive diet switch has occurred in the occidental world since the second half of the 20th century, with a dramatic increase in refined carbohydrate consumption generating numerous deleterious health effects. Physiological mechanisms associated with refined carbohydrate consumption, such as hyperinsulinemia and insulin resistance, may impact cognition in healthy people before overt obesity, metabolic disease onset or dementia. To explore this possibility, the relationship between cognitive performance and chronic refined carbohydrate consumption was studied in healthy young adults (N = 95). Evaluation of chronic refined consumption was based on the glycemic load (a proxy of glycemic and insulinemic responses) of three mealtimes at higher glycemic risk: breakfast, afternoon snacking and between-meal snacking. Immediate consumption of refined carbohydrates was experimentally controlled. High chronic between-meal glycemic load is associated to a decrease of cognitive performance for men and women in the presence of several control variables, including energy intake. The different physiological ecologies of the three meals and the interpretation of the results in terms of adaptation or maladaptation to the modern dietary environment are discussed.

Recovery of a marine keystone predator transforms terrestrial predator–prey dynamics

Sea otters (Enhydra lutris) and wolves (Canis lupus) are two apex predators with strong and cascading effects on ecosystem structure and function. After decades of recovery from near extirpation, their ranges now overlap, allowing sea otters and wolves to interact for the first time in the scientific record. We intensively studied wolves during 2015 to 2021 in an island system colonized by sea otters in the 2000s and by wolves in 2013. After wolf colonization, we quantified shifts in foraging behavior with DNA metabarcoding of 689 wolf scats and stable isotope analyses, both revealing a dietary switch from Sitka black-tailed deer (Odocoileus hemionus), the terrestrial insitu primary prey, to sea otters. Here we show an unexpected result of the reintroduction and restoration of sea otters, which became an abundant marine subsidy for wolves following population recovery. The availability of sea otters allowed wolves to persist and continue to reproduce, subsequently nearly eliminating deer. Genotypes from 390 wolf scats and telemetry data from 13 wolves confirmed island fidelity constituting one of the highest known wolf population densities and upending standardly accepted wolf density predictions based on ungulate abundance. Whereas marine subsidies in other systems are generally derived from lower trophic levels, here an apex nearshore predator became a key prey species and linked nearshore and terrestrial food webs in a recently deglaciated and rapidly changing ecosystem. These results underscore that species restoration may serve as an unanticipated nutrient pathway for recipient ecosystems even resulting in cross-boundary subsidy cascades.

Gene expressions between obligate bamboo-eating pandas and non-herbivorous mammals reveal converged specialized bamboo diet adaptation

BackgroundIt is inevitable to change the function or expression of genes during the environmental adaption of species. Both the giant panda (Ailuropoda melanoleuca) and red panda (Ailurus fulgens) belong to Carnivora and have developed similar adaptations to the same dietary switch to bamboos at the morphological and genomic levels. However, the genetic adaptation at the gene expression level is unclear. Therefore, we aimed to examine the gene expression patterns of giant and red panda convergent specialized bamboo-diets. We examined differences in liver and pancreas transcriptomes between the two panda species and other non-herbivorous species.ResultsThe clustering and PCA plots suggested that the specialized bamboo diet may drive similar expression shifts in these two species of pandas. Therefore, we focused on shared liver and pancreas DEGs (differentially expressed genes) in the giant and red panda relative to other non-herbivorous species. Genetic convergence occurred at multiple levels spanning carbohydrate metabolism, lipid metabolism, and lysine degradation. The shared adaptive convergence DEGs in both organs probably be an evolutionary response to the high carbohydrate, low lipid and lysine bamboo diet. Convergent expression of those nutrient metabolism-related genes in both pandas was an intricate process and subjected to multi-level regulation, including DNA methylation and transcription factor. A large number of lysine degradation and lipid metabolism related genes were hypermethylated in promoter regions in the red panda. Most genes related to carbohydrate metabolism had reduced DNA methylation with increased mRNA expression in giant pandas. Unlike the red panda, the core gene of the lysine degradation pathway (AASS) doesn’t exhibit hypermethylation modification in the giant panda, and dual-luciferase reporter assay showed that transcription factor, NR3C1, functions as a transcriptional activator in AASS transcription through the binding to AASS promoter region.ConclusionsOur results revealed the adaptive expressions and regulations of the metabolism-related genes responding to the unique nutrients in bamboo food and provided data accumulation and research hints for the future revelation of complex mechanism of two pandas underlying convergent adaptation to a specialized bamboo diet.

Multi‐locus DNA metabarcoding reveals seasonality of foraging ecology of western spotted skunks in the Pacific Northwest

AbstractThere are increasing concerns about the declining population trends of small mammalian carnivores around the world. Their conservation and management are often challenging due to limited knowledge about their ecology and natural history. To address one of these deficiencies for western spotted skunks (Spilogale gracilis), we investigated their diet in the Oregon Cascades of the Pacific Northwest during 2017–2019. We collected 130 spotted skunk scats opportunistically and with detection dog teams and identified prey items using DNA metabarcoding and mechanical sorting. Western spotted skunk diet consisted of invertebrates, such as wasps, millipedes, and gastropods; vertebrates, such as small mammals, amphibians, and birds; and plants, such as Gaultheria, Rubus, and Vaccinium. Diet also consisted of items, such as black‐tailed deer, that were likely scavenged. Comparison in diet by season revealed that spotted skunks consumed more insects during the dry season (June–August), particularly wasps (75% of scats in the dry season), and marginally more mammals during the wet season (September–May). We observed a similar diet in areas with no record of human disturbance and areas with a history of logging at most spatial scales, but scats collected in areas with older forest within a skunk's home range (1‐km buffer) were more likely to contain insects. Western spotted skunks provide food web linkages between aquatic, terrestrial, and arboreal systems and serve functional roles of seed dispersal and scavenging. Due to their diverse diet and prey switching, western spotted skunks may dampen the effects of irruptions of prey, such as wasps, during dry springs and summers. By studying the natural history of western spotted skunks in the Pacific Northwest forests, while they are still abundant, we provide key information necessary to achieve the conservation goal of keeping this common species common.