High fat diet attenuates hyperglycemia, body composition changes, and bone loss in male streptozotocin-induced type 1 diabetic mice

Alkaline Water Mitigates Bone Loss in Streptozotocin-Induced Type II Diabetic Rats

Background A decline in bone mineral density is a defining feature of osteoporosis, which is a prevalent bone complication associated with diabetes. This study aims to shed light on the protective effect of Zamzam water (ZW), a famous alkaline water, on diabetes-induced osteoporosis. Methodology Of a total of 40 male rats, 10 male rats each were divided into the following four groups: group I (normal control rats), group II (ZW group), group III (diabetic rats), and group IV (DM + ZW). Anteroposterior and lateral X-rays were taken of the rats in each group before the end of the experiment. The study assessed serum levels of inflammatory markers including interleukin 6, interleukin-1 beta, and tumor necrosis factor-alpha; bone formation markers including osteocalcin (OC); alkaline phosphatase (ALP); and bone resorption markers including the N-terminal telopeptide of collagen type I (NTX-1), bone deoxypyridinoline (DPD), and tartrate-resistant acid phosphatase 5b (TRAP-5b). Results Rats with diabetes who consumed ZW exhibited a significant (p < 0.001) increase in OC and ALP bone formation markers and a decrease in NTX-1, DPD, and TRAP-5b bone resorption markers, with improvements in the X-ray image of the vertebral column at the L6 vertebra level. Conclusions ZW improved diabetes-induced osteoporosis in rats by enhancing osteoblastic activity and downregulating osteoclastic activity.

MiR-184-5p represses neuropathic pain by regulating CCL1/CCR8 signaling interplay in the spinal cord in diabetic mice

BACKGROUND

Diabetic neuropathic pain (DNP) is a serious complication for diabetic patients involving nervous system. MicroRNAs (miRNAs) are small-noncoding RNAs which are dysregulated in neuropathic pain, and might be critical molecules for pain treatment. Our previous study has shown miR-184-5p was significantly downregulated in DNP. Therefore, the mechanism of miR-184-5p in DNP was investigated in this study.

METHODS

A DNP model was established through streptozotocin (STZ). The pharmacological tools were injected intrathecally, and pain behavior was evaluated by paw withdrawal mechanical thresholds (PWMTs). Bioinformatics analysis, Dual-luciferase reporter assay and fluorescence-in-situ-hybridization (FISH) were used to seek and confirm the potential target genes of miR-184-5p. The expression of relative genes and proteins was analyzed by quantitative reverse transcriptase real-time PCR (qPCR) and western blotting.

RESULTS

MiR-184-5p expression was down-regulated in spinal dorsal on days 7 and 14 after STZ, while intrathecal administration of miR-184-5p agomir attenuates neuropathic pain induced by DNP and intrathecal miR-184-5p antagomir induces pain behaviors in naïve mice. Chemokine CC motif ligand 1 (CCL1) was found to be a potential target of miR-184-5p and the protein expression of CCL1 and the mRNA expression of CCR8 were up-regulated in spinal dorsal on days 7 and 14 after STZ. The luciferase reporter assay and FISH demonstrated that CCL1 is a direct target of miR-184-5p. MiR-184-5p overexpression attenuated the expression of CCL1/CCR8 in DNP; intrathecal miR-184-5p antagomir increased the expression of CCL1/CCR8 in spinal dorsal of naïve mice.

CONCLUSION

This research illustrates that miR-184-5p alleviates DNP through the inhibition of CCL1/CCR8 signaling expression.

High fat diet is protective against kidney injury in hypertensive-diabetic mice, but leads to liver injury

Chronic kidney disease (CKD) is a worldwide health burden with increases risk of end-stage renal function if left untreated. CKD induced in the context of metabolic syndrome (MS) increases risks of hypertension, hyperglycemia, excess body fat and dyslipidemia. To test if combining a high-fat diet (HFD) regimen onto the hypertensive/ diabetic phenotype would mimic features of MS induced-CKD in mice, hyperglycemia was induced in genetically hypertensive mice (Lin), followed by HFD regimen. For that, 8-week-old male were subjected to streptozotocin (STZ) intraperitoneal (i.p.) injections (50 mg/kg, 5 days consecutive). LinSTZ were fed a 60% kCal HFD for 8 weeks. Lin mice treated with STZ developed polydipsia, became hypertensive and hyperglycemic. HFD induced weight gain, protected against glomerular hypertrophy, scarring, and albuminuria at endpoint compared to regular diet fed LinSTZ. On the other hand, HFD induced steatosis, liver fibrosis, inflammation, and increase in AST/ALT ratio, characteristics of non-alcoholic liver disease. Taken together, our results show that LinSTZ mice fed a HFD did not lead to a more robust model of MS-induced CKD, protected against kidney injury, but inducing liver damage. More studies are necessary to understand the kidney protective mechanisms of HFD when superimposed with hypertension and type 1 diabetes.

Empagliflozin ameliorates type 2 diabetes mellitus-related diabetic nephropathy via altering the gut microbiota

BACKGROUND

The dysregulation of gut microbiota can be found in patients with type 2 diabetes mellitus (T2DM)-related diabetic nephropathy (DN). Inhibitors of sodium-glucose co-transporter 2 (SGLT2) were reported to affect gut microbiota. This study aimed to identify whether empagliflozin (EMPA) attenuated DN via regulating gut microbiota.

MATERIALS AND METHODS

The high-fat diet (HFD) combining streptozocin (STZ) injection was performed to induce DN in mice. The therapeutic effects of EMPA were observed by staining of renal tissues and urine albumin/creatinine ratio (UACR). Mouse feces were collected for 16S rRNA sequencing. Fecal short-chain fatty acids (SCFAs) and fecal and serum lipopolysaccharide (LPS) were determined. An antibiotic-ablated model was established to confirm the role of the gut microbiota in the actions of EMPA.

RESULTS

EMPA reduced the elevation of blood glucose and UACR caused by HFD/STZ. It inhibited the thickening of the colonic crypt and restored goblet cells and the expressions of ZO-1 and Occludin. The 16S rRNA sequencing showed that the diversity of gut microbiota was reduced after HFD/STZ treatment, while it was restored after EMPA treatment. The LPS-producing bacteria, Oscillibacter, and the SCFA-producing bacteria, Bateroid and Odoribacter, were changed after EMPA administration. The therapeutic effects of EMPA on ABX-treated mice were reduced. Meanwhile, the level of fecal SCFAs was decreased, while the levels of fecal and serum LPS were elevated, in T2DM mice, and they were negated by the administration of EMPA.

CONCLUSION

EMPA ameliorates T2DM-related DN via altering the gut microbiota, especially reducing LPS-producing bacteria and increasing SCFA-producing bacteria.

Resistance Training Improves Beta Cell Glucose Sensing and Survival in Diabetic Models

Resistance training increases insulin secretion and beta cell function in healthy mice. Here, we explored the effects of resistance training on beta cell glucose sensing and survival by using in vitro and in vivo diabetic models. A pancreatic beta cell line (INS-1E), incubated with serum from trained mice, displayed increased insulin secretion, which could be linked with increased expression of glucose transporter 2 (GLUT2) and glucokinase (GCK). When cells were exposed to pro-inflammatory cytokines (in vitro type 1 diabetes), trained serum preserved both insulin secretion and GCK expression, reduced expression of proteins related to apoptotic pathways, and also protected cells from cytokine-induced apoptosis. Using 8-week-old C57BL/6 mice, turned diabetic by multiple low doses of streptozotocin, we observed that resistance training increased muscle mass and fat deposition, reduced fasting and fed glycemia, and improved glucose tolerance. These findings may be explained by the increased fasting and fed insulinemia, along with increased beta cell mass and beta cell number per islet, observed in diabetic-trained mice compared to diabetic sedentary mice. In conclusion, we believe that resistance training stimulates the release of humoral factors which can turn beta cells more resistant to harmful conditions and improve their response to a glucose stimulus.

Interactions between diabetes mellitus and osteoarthritis; from animal studies to clinical data

Diabetes mellitus (DM) and osteoarthritis (OA) are commonly known metabolic diseases that affect a large segment of the world population. These two conditions share several risk factors such as obesity and aging; however, there is still no consensus regarding the direct role of DM on OA development and progression. Interestingly, both animal and human studies have yielded conflicting results, with some showing a significant role for DM in promoting OA, while others found no significant interactions between these conditions. In this review, we will discuss preclinical and clinical data that assessed the interaction between DM and OA. We will also discuss possible mechanisms associated with the effect of high glucose on the articular cartilage and chondrocytes. An emerging theme dominates the breath of published work in this area: most of the studies discussed in this review do not take into consideration the role of other factors such as the type of diabetes, age, biological sex, type of animal model, body mass index, and the use of pain medications when analyzing and interpreting data. Therefore, future studies should be more rigorous when designing experiments looking at DM and its effects on OA and should carefully account for these confounding factors, so that better approaches can be developed for monitoring and treating patients at risk of OA and DM. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Pregnancy-Associated Plasma Protein (PAPP)-A2 in Physiology and Disease

The growth hormone (GH)/insulin-like growth factor (IGF) axis plays fundamental roles during development, maturation, and aging. Members of this axis, composed of various ligands, receptors, and binding proteins, are regulated in a tissue- and time-specific manner that requires precise control that is not completely understood. Some of the most recent advances in understanding the implications of this axis in human growth are derived from the identifications of new mutations in the gene encoding the pregnancy-associated plasma protein PAPP-A2 protease that liberates IGFs from their carrier proteins in a selective manner to allow binding to the IGF receptor 1. The identification of three nonrelated families with mutations in the PAPP-A2 gene has shed light on how this protease affects human physiology. This review summarizes our understanding of the implications of PAPP-A2 in growth physiology, obtained from studies in genetically modified animal models and the PAPP-A2 deficient patients known to date.

FGF19 protects against obesity-induced bone loss by promoting osteogenic differentiation

Human fibroblast growth factor 19 (FGF19) has become a potential therapeutic target for metabolic-related diseases. However, the effects of FGF19 on obesity-induced bone loss have not been completely elucidated. The aim of this study was to investigate the protective effects of FGF19 in high-fat diet (HFD)-fed obese mice and palmitic acid (PA)-treated osteoblasts and to further explore its underlying mechanisms. In vivo, we found that FGF19 alleviated the decreased bone mineral density (BMD) induced by HFD. Micro-CT analysis of femur samples and histological analysis indicated that FGF19 alleviated HFD-induced loss of bone trabeculae and damage to the bone trabecular structure. In vitro, the results suggested that FGF19 ameliorated the PA-induced decline in osteoblast proliferation, increased cell death and impaired cell morphology. Additionally, FGF19 protected against the decline in activation of alkaline phosphatase (ALP) and protein expression of Collagen-1, Runx-2, and osteopontin (OPN) induced by PA. Furthermore, FGF19 might enhance osteogenic differentiation via the Wnt/β-catenin pathway and inhibit osteoclastogenesis by regulating the osteoprotegerin (OPG)/receptor activator of NF-κB ligand (RANKL) axis, thus attenuating the negative effect of PA in osteoblasts. In conclusion, our results suggested that FGF19 might promote osteogenic differentiation partially through activation of the Wnt/β-catenin pathway and alleviate obesity-induced bone loss.

Islet isograft transplantation improves insulin sensitivity in a murine model of type 2 diabetes

PURPOSE

Type 2 diabetes develops in the presence of chronic overnutrition and genetic susceptibility, and causes insulin resistance and relative insulin deficiency. We hypothesized that islet transplantation can improve insulin sensitivity by modifying the mediators of insulin sensitivity in the pancreas, liver, muscle, and adipose tissues.

METHODS

Eight-week-old male mice were used as both recipients and donors in this study. To induce type 2 diabetes with partial β-cell failure, the mice were fed a high-fat diet for 4 weeks and then injected with low-dose streptozotocin. Approximately 400 islet cells from a donor mouse were injected into the renal capsule of a recipient mouse for islet transplantation. After 6 weeks following transplantation, the mediators of insulin sensitivity in the pancreas, liver, muscle, and adipose tissues were quantitatively compared between islet-transplanted and non-transplanted groups.

RESULTS

Intravenous glucose tolerance test showed that whereas the non-transplanted mice failed to show notable reductions in the glucose level, the islet-transplanted mice showed significant reductions in the serum glucose level to ~200 mg/dL at 6 weeks after islet transplantation. The islet-transplanted mice showed significantly higher Matsuda index and significantly lower HOMA-IR than did the non-transplanted mice, thus signifying improved insulin sensitivity.

CONCLUSIONS

Islet transplantation resulted in improvements in multiple indices of insulin sensitivity in a murine model of type 2 diabetes. Islet transplantation may be utilized to improve insulin sensitivity in patients with type 2 diabetes.

A dual regulatory effect of naringenin on bone homeostasis in two diabetic mice models

Objective: Naringenin (NAR), a flavanone in citrus fruits, has been reported to have both anti-diabetic and anti-osteoporotic effects. This study aimed to explore the effect of NAR on bone homeostasis under diabetic condition.

Methods: High fat diet and streptozotocin (STZ) induced type 1 diabetic (T1DM) and leptin receptor knockout (db/db) type 2 diabetic (T2DM) mice were used to evaluate NAR effects. Melbine (DMBG) was administrated as positive control. Body weight and fasting blood glucose were monitored weekly and monthly. After 8 weeks and 74 days treatment, bone mass was evaluated by microcomputed tomography ([Formula: see text]CT) including BV/TV, Tb.N, and Tb.Th, as well as histological and histomorphometric detection. Bone resorption rate indicated by C-terminal telopeptide of type I collagen (CTIX) and N-terminal propeptide of type I procollagen (PINP) was examined by ELISA assays.

Results: NAR treatment reduced body weight and blood glucose in both diabetic models, and had better hypoglycemic effect than DMBG at early stage. High fat diet and STZ-treated mice lost while db/db mice gained bone mass. NAR improved bone microarchitecture by regulating the related parameters to the similar levels as the control. Osteoblast activity was little affected, but osteoclast function was decreased in NAR-treated STZ mice. Consistently, NAR reduced bone resorption rate which was increased in both diabetic models.

Conclusion: NAR exerts an anti-diabetic effect by lowering elevated level of blood glucose, regulating impaired bone mass, and reducing overactivated bone resorption rate in T1DM and T2DM conditions. Naringenin has a potential to prevent diabetes induced impairment in bone.

Bone regeneration in a mouse model of type 1 diabetes: Influence of sex, vitamin D3, and insulin

AIM

This study set forth a question: are there any differences in bone responses to insulin and/or vitamin D3 treatment in female and male type 1 diabetic (T1D) mice?

MAIN METHODS

To address this issue, a non-critical sized femur defect was created in streptozotocin (STZ)-T1D mice. Control non-diabetic and T1D female and male mice received: saline; vitamin D3; insulin; or vitamin D3 plus insulin, for 21 days.

KEY FINDINGS

Female and male T1D mice showed impaired bone healing, as indicated by histological and micro-computed tomography (micro-CT) analysis. Vitamin D3 or insulin improved the bone regeneration in T1D mice, irrespective of sex. Vitamin D3 plus insulin did not exhibit any additional effects. There were no differences regarding the numbers of TRAP-stained osteoclasts in either evaluated groups. The osteoblast-related gene osterix was upregulated in vitamin D3-treated male T1D mice, as revealed by RT-qPCR. Female T1D mice treated with vitamin D3, insulin, or vitamin D3 plus insulin presented an increased expression of insulin growth factor-1 (IGF-1) mRNA. Conversely, IGF-1 mRNA levels were reduced by the same treatments in male TD1 mice.

SIGNIFICANCE

Altogether, the results suggested that T1D similarly delayed the osseous healing in female and male mice, with beneficial effects for either vitamin D3 or insulin in T1D mice of both sexes. However, data indicated marked sex differences regarding the expression of genes implicated in bone formation, in T1D mice treated with vitamin D3 and/or insulin.

Zinc Supplementation Increased Bone Mineral Density, Improves Bone Histomorphology, and Prevents Bone Loss in Diabetic Rat

Diabetic osteoporosis (DOP) is a complication of diabetes, with the characteristics of bone mineral density (BMD) reduction and bone structure destruction. Zinc was reported has a benefit effect on postmenopausal osteoporosise, it was also has hypoglycemic effect, whether zinc was beneficial on diabetes-induced osteoporosis has not been reported. So in the present study, we established a diabetic rat model by streptozotocin injection (60 mg/kg), and administered zinc sulfate by oral gavage to investigate the protective effects of zinc on DOP and the underline possible mechanism. Thirty six Sprague Dawley rats were divided into T1DM group (diabetic rats), control group (vehicle treatment), and T1DM-Zinc group (diabetic rats administered zinc sulfate 0.25 mg/kg by oral gavage). The bone histomorphological parameters, serum bone metabolism markers (including ALP, OPG, RUNX 2, and RANKL), BMD, and bone marrow adipocyte numbers were detected after eight weeks of zinc sulfate treatment. The results showed zinc sulfate administration (0.25 mg/kg/d) decreased blood glucose, increased the BMD, decreased serum ALP, and RANKL, increased serum OPG and RUNX 2 levels, as well as OPG/RANKL ratio of T1DM rats. Meanwhile, the bone histomorphological parameters, bone marrow adipocytes numbers were returned to be normal. The RUNX 2, and OPG mRNA expression levels in bone tissues of T1DM-Zinc group rats were increased after zinc sulfate treatment compared with the diabetic rats (P < 0.05). Those indicating that zinc sulfate can prevent DOP, the protective mechanism were mainly related to its hypoglycemic effect, bone marrow lipogenesis inhibition effect, OPG/RANKL ratio and RUNX 2 up-regulation effect.

The increase in bone resorption in early-stage type I diabetic mice is induced by RANKL secreted by increased bone marrow adipocytes

Bone marrow adipose tissue (BMAT) has recently been found to induce osteoclastogenesis by secreting RANKL. Although Type 1 diabetes mellitus (T1DM) has been reported to be associated with increased BMAT and bone loss, little is known about the relationship between BMAT and osteoclasts in T1DM. We studied the role of BMAT in the alterations of osteoclast activities in early-stage T1DM, by using a streptozotocin-induced T1DM mouse model. Our results showed that osteoclast activity was enhanced in the long bones of T1DM mice, accompanied by increased protein expression of RANKL. However, RANKL mRNA levels in bone tissues of T1DM mice remained unchanged. Meanwhile, we found that BMAT was significantly increased in the long bones of T1DM mice, and both mRNA and protein levels of RANKL were elevated in the diabetic BMAT. More importantly, RANKL protein was mainly expressed on the cell membranes of the increased adipocytes, most of which were located next to the metaphyseal region. These results suggest that the enhanced bone resorption in early-stage diabetic mice is induced by RANKL derived from BMAT rather than the bone tissue itself.

Effects of Combined Exposure to Cadmium and High-Fat Diet on Bone Quality in Male Mice

This study investigated the effects of combined exposure to low-dose cadmium and high-fat diet on femoral bone quality in male mice. Eight-week-old male SPF C57BL/6J mice were randomly divided into four groups: normal control group (Con), low-cadmium group (Cd), high-fat diet group (HFD), and high-fat diet plus low-dose cadmium group (HFD + Cd); the second and fourth groups were treated intraperitoneally with CdCl₂ (1.0 mg/kg body weight) twice weekly for 20 weeks. Assays related to bone quality were performed. Body weight of HFD plus Cd mice was significantly lower than HFD mice. Femoral length was not different among groups, but femoral weight was decreased in the HFD plus Cd group compared with other three groups. Level of Cd in bone was significantly increased in HFD plus Cd group. There was no difference in cortical BMD among groups; however, cortical bone quality parameters were decreased in HFD plus Cd group. Cd and HFD each reduced trabecular bone quality and together had further detrimental effects on these bone parameters. Based on biomechanical analysis, femoral bone strength was decreased, being more brittle and less resistant to biomechanical forces in the HFD plus Cd mice. HFD plus Cd mice had lower OPG mRNA expression and higher RANKL mRNA expression than others. HFD or Cd can cause adverse effects on bone and together had further detrimental effects associated with RANKL/OPG signaling.

Marrow Adipocytes: Origin, Structure, and Function

The skeleton harbors an array of lineage cells that have an essential role in whole body homeostasis. Adipocytes start the colonization of marrow space early in postnatal life, expanding progressively and influencing other components of the bone marrow through paracrine signaling. In this unique, closed, and hypoxic environment close to the endosteal surface and adjacent to the microvascular space the marrow adipocyte can store or provide energy, secrete adipokines, and target neighboring bone cells. Adipocyte progenitors can also migrate from the bone marrow to populate white adipose tissue, a process that accelerates during weight gain. The marrow adipocyte also has an endocrine role in whole body homeostasis through its varied secretome that targets distant adipose depots, skeletal muscle, and the nervous system. Further insights into the biology of this unique and versatile cell will undoubtedly lead to novel therapeutic approaches to metabolic and age-related disorders such as osteoporosis and diabetes mellitus.

Icariin Prevents Diabetes-Induced Bone Loss in Rats by Reducing Blood Glucose and Suppressing Bone Turnover

Diabetic Osteoporosis (DOP) is a common metabolic bone disease, characterized by decreased bone mineral density (BMD) and destruction of bone microstructure. It has been reported that icariin is beneficial for estrogen deficiency-induced osteoporosis, and alcohol-induced osteoporosis; whether icariin has protective effects on diabetes-induced osteoporosis has not been reported. In this study, a rat model of diabetic osteoporosis was established by streptozotocin injection, the bone protective effects and potential mechanism of icariin on diabetes-induced bone loss was observed. Thirty 8-week-old female Sprague Dawley rats were divided into control group (vehicle treatment), T1DM (diabetic) group and T1DM-icariin (ICA) group (diabetic rats treated with icariin), 10 rats in each group. The bone histomorphometry parameters, bone mineral density (BMD), serum bone turnover markers, and bone marrow adipogenesis were analyzed after 8 weeks of icariin administration. The results showed consumption of icariin at a doses of 100 mg kg⁻¹ decreased blood glucose, and increased the BMD of diabetic rats. Icariin effectively decreased serum bone turnover marker levels, including CTX-1, ALP, TRACP 5b, osteocalcin, and PINP. Meanwhile, the bone histomorphometry parameters, the number of osteoclasts per bone perimeter were turned to be normal level, and the icariin treatment suppressed bone marrow adipogenesis. The runt-related transcription factor 2 (RUNX 2), as well as the osteoprotegerin (OPG)/receptor activator of nuclear factor-κ B ligand (RANKL) ratio in serum and bone tissues were increased significantly after icariin treatment in diabetic rats. All of the above indicate that oral administration of icariin can prevent diabetic osteoporosis; the effect is mainly related to its ability to reduce blood glucose, inhibit bone turnover and bone marrow adipogenesis, as well as up-regulate bone RUNX 2, and OPG expression.

A novel mouse model overexpressing Nocturnin results in decreased fat mass in male mice

Nocturnin (NOCT) belongs to the Mg²⁺ dependent Exonucleases, Endonucleases, Phosphatase (EEP) family of enzymes that exhibit various functions in vitro and in vivo. NOCT is known to function as a deadenylase, cleaving poly-A tails from mRNA (messenger RNA) transcripts. Previously, we reported a role for NOCT in regulating bone marrow stromal cell differentiation through its interactions with PPARγ. In this study, we characterized the skeletal and adipose tissue phenotype when we globally overexpressed Noct in vivo. After 12 weeks of Noct overexpression, transgenic male mice had lower fat mass compared to controls, with no significant differences in the skeleton. Based on the presence of a mitochondrial target sequence in NOCT, we determined that mouse NOCT protein localizes to the mitochondria; subsequently, we found that NOCT overexpression led to a significant increase in the preadipocytes ability to utilize oxidative phosphorylation for ATP (adenosine triphosphate) generation. In summary, the effects of NOCT on adipocytes are likely through its novel role as a mediator of mitochondrial function.

Exercise prevents high fat diet-induced bone loss, marrow adiposity and dysbiosis in male mice

High fat diets can have detrimental effects on the skeleton as well as cause intestinal dysbiosis. Exercise prevents high fat (HF) diet-induced obesity and also improves bone density and prevents the intestinal dysbiosis that promotes energy storage. Previous studies indicate a link between intestinal microbial balance and bone health. Therefore, we examined whether exercise could prevent HF-induced bone pathology in male mice and determined whether benefits correlate to changes in host intestinal microbiota. Male C57Bl/6 mice were fed either a low fat diet (LF; 10 kcal% fat) or a HF diet (60 kcal% fat) and put under sedentary or voluntary exercise conditions for 14 weeks. Our results indicated that HF diet reduced trabecular bone volume, when corrected for differences in body weight, of both the tibia (40% reduction) and vertebrae (25% reduction) as well and increased marrow adiposity (44% increase). More importantly, these effects were prevented by exercise. Exercise also had a significant effect on several cortical bone parameters and enhanced bone mechanical properties in LF but not HF fed mice. Microbiome analyses indicated that exercise altered the HF induced changes in microbial composition by reducing the Firmicutes/Bacteriodetes ratio. This ratio negatively correlated with bone volume as did levels of Clostridia and Lachnospiraceae. In contrast, the abundance of several Actinobacteria phylum members (i.e., Bifidobacteriaceae) were positively correlated with bone volume. Taken together, exercise can prevent many of the negative effects of a high fat diet on male skeletal health. Exercise induced changes in microbiota composition could represent a novel mechanism that contributes to exercise induced benefits to bone health.