Biology subjects

Seeley, R.

Publications and source records attributed to Seeley, R..

5 recordsLinked to original sources

bioRxiv2023

Calorie Restriction Outperforms Bariatric Surgery in a Murine Model of Obesity and Triple-Negative Breast Cancer

Obesity promotes triple-negative breast cancer (TNBC), and effective interventions are urgently needed to break the obesity-TNBC link. Epidemiologic studies indicate that bariatric surgery reduces TNBC risk, while evidence is limited or conflicted for weight loss via low-fat diet (LFD) or calorie restriction (CR). Using a murine model of obesity- driven TNBC, we compared the antitumor effects of vertical sleeve gastrectomy (VSG) with LFD, chronic CR, and intermittent CR. Each intervention generated weight and fat loss and suppressed tumor growth relative to obese mice (greatest suppression with CR). VSG and CR regimens exerted both similar and unique effects, as assessed using multi-omic approaches, in reversing obesity-associated transcriptional, epigenetic, secretome, and microbiota changes and restoring antitumor immunity. Thus, in a murine model of TNBC, bariatric surgery and CR each reverse obesity-driven tumor growth via shared and distinct antitumor mechanisms, and CR is superior to VSG in reversing obesitys procancer effects.

cancer biology↗

bioRxiv2023

Osteoblast-intrinsic defect in glucose metabolism impairs bone formation in type II diabetic mice

Skeletal fragility is associated with type 2 diabetes mellitus (T2D), but the underlying mechanism is not well understood. Here, in a mouse model for youth-onset T2D, we show that both trabecular and cortical bone mass are reduced due to diminished osteoblast activity. Stable isotope tracing in vivo with 13C-glucose demonstrates that both glycolysis and glucose fueling of the TCA cycle are impaired in diabetic bones. Similarly, Seahorse assays show suppression of both glycolysis and oxidative phosphorylation by diabetes in bone marrow mesenchymal cells as a whole, whereas single-cell RNA sequencing reveals distinct modes of metabolic dysregulation among the subpopulations. Metformin not only promotes glycolysis and osteoblast differentiation in vitro, but also improves bone mass in diabetic mice. Finally, targeted overexpression of Hif1a or Pfkfb3 in osteoblasts of T2D mice averts bone loss. The study identifies osteoblast-intrinsic defects in glucose metabolism as an underlying cause of diabetic osteopenia, which may be targeted therapeutically.

physiology↗

bioRxiv2022

GDF15 Is Required for Cold-Induced Thermogenesis and Contributes to Improve Systemic Metabolic Health Following Loss of OPA1 in Brown Adipocytes

Previously we showed that mice lacking the protein optic atrophy 1 (OPA1 BKO) in brown adipose tissue (BAT) have induction of the activating transcription factor 4 (ATF4), which promotes fibroblast growth factor 21 (FGF21) secretion as a batokine. FGF21 increases metabolic rates at baseline conditions but is dispensable for the resistance to diet-induced obesity (DIO) reported in OPA1 BKO mice [1]. To determine alternative mediators of this phenotype, we performed transcriptome analysis, which revealed increased levels of growth differentiation factor 15 (GDF15) in BAT. To determine if ATF4 induction was mediated by the protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), and to evaluate the contribution of GDF15 to the resistance to DIO, we selectively deleted PERK or GDF15 in OPA1 BKO mice. Mice lacking both OPA1 and PERK in BAT had preserved induction of ATF4. Importantly, simultaneous deletion of OPA1 and GDF15 partially reversed the resistance to diet-induced obesity and abrogated the improvements in glucose tolerance. Furthermore, GDF15 mediated cold-induced thermogenesis, likely via sympathetic activation of iWAT. Taken together, our data indicate that PERK is dispensable for ATF4 induction, but GDF15 contributes to the resistance to DIO, and is required for glucose homeostasis and thermoregulation in OPA1 BKO mice.

physiology↗

bioRxiv2020

Intestinal-derived FGF15 preserves muscle and bone mass following sleeve gastrectomy

Bariatric surgeries such as the Vertical Sleeve Gastrectomy (VSG) are invasive, but provide the most effective long-term metabolic improvements in obese and Type 2 diabetic patients. These powerful effects of manipulating the gastrointestinal tract point to an important role of gastrointestinal signals in regulating both energy balance and metabolism. To that end, we have used mouse models of VSG to identify key gut signals that mediate these beneficial effects. Preliminary data from our rodent model of VSG led us to hypothesize a potential role for the hormone Fibroblast-Growth Factor15/19 (mouse/human ortholog) which pharmacologically can regulate many aspects of energy homeostasis and glucose handling. FGF15 is expressed in ileal enterocytes of the small intestine and is released postprandially. Like many other gut hormones, postprandial plasma levels in humans and ileal FGF15 expression in mice increase after VSG. We generated intestinal-specific FGF15 knock out (VilCreERT2; Fgf15f/f) mice and controls, which were maintained on 60% high-fat diet. Interestingly, ablation of intestinal FGF15 in adult mice results in little change to body weight or glucose regulation when challenged with a high-fat diet. Unlike what we had predicted, intestinal-specific FGF15 knock out mice lost more weight after VSG and this was a result of increased lean tissue loss compared to control mice. Further, the loss of bone mineral density observed after VSG in control mice was increased in intestinal-specific FGF15 knock out mice. Finally the effect of VSG to reduce hepatic cholesterol was also absent in intestinal-specific FGF15 knock out mice. These data point to an important role for intestinal FGF15 to protect the organism from deleterious effects of rapid weight loss that occurs after VSG.Competing Interest StatementRJS has received research support from Ethicon Endo-Surgery, Zafgen, Novo Nordisk, Kallyope, and MedImmune. RJS has served on scientific advisory boards for Ethicon Endo-Surgery, Novo Nordisk, Sanofi, Janssen, Kallyope, Scohia, and Ironwood Pharma. RJS is a stakeholder of Zafgen. KMH is a paid-employee of Novo Nordisk.View Full Text

physiology↗

bioRxiv2020

The role of elevated branched chain amino acids in the potent effects of vertical sleeve gastrectomy to reduce weight and improve glucose regulation in mice

Obesity and type 2 diabetes mellitus (T2D) are growing epidemics resulting in increased morbidity and mortality. An emerging body of evidence has shown that elevated levels of branched-chain amino acids (BCAA) and their metabolites are strongly positively associated with obesity, insulin-resistance and T2D. Bariatric surgery is among the best treatments for weight loss and the alleviation of T2D. Additionally, clinical studies have reported that bariatric surgery decreases the circulating levels of BCAA. The objective of these studies was to test the hypothesis that reduced BCAA levels contribute to the metabolic improvements after VSG. We find that, as in humans, circulating BCAA levels are significantly lower in VSG rats and mice compared to Sham controls. In order to increase circulating BCAA levels, we tested mice with either increased dietary intake of BCAA or impaired BCAA catabolism by total body deletion of mitochondrial phosphatase 2C, Pp2cm, a key enzyme in the rate-limiting step in BCAA catabolism. Our results show that a decrease in circulating BCAA levels is not necessary for sustained body weight loss and improved glucose tolerance after VSG. While it is clear that circulating levels of BCAAs are excellent biomarkers for metabolic status, the current data do not support a causal role in determining metabolic regulation and the response to VSG.

physiology↗