Review article: effects of type 2 diabetes therapies on bone metabolism

Association Analysis of Triglyceride Glucose-Body Mass Index and Bone Turnover Markers in Patients with Type 2 Diabetes Mellitus

Objective

In view of the high prevalence of osteoporosis in diabetic patients, this study aimed to investigate the correlation between TyG-BMI, which represents insulin resistance, and bone loss markers, which represent bone metabolism, in an attempt to provide new ideas for the early prevention and diagnosis of osteoporosis in patients with T2DM.

Patients and Methods

A total of 1148 T2DM were enrolled. The clinical data and laboratory indicators of the patients were collected. TyG-BMI was calculated based on fasting blood glucose (FBG), triglycerides (TG), and body mass index (BMI) levels. Patients were divided into Q1-Q4 groups according to TyG-BMI quartiles. According to gender, two groups were divided into men and postmenopausal women. Subgroup analysis was performed according to age, course of disease, BMI, TG level and 25(OH)D3 level. The correlation between TyG-BMI and BTMs was investigated by correlation analysis and multiple linear regression analysis using SPSS25.0 statistical software.

Results

1. Compared with Q1 group, the proportion of OC, PINP and β-CTX in Q2, Q3 and Q4 groups decreased significantly. 2. Correlation analysis and multiple linear regression analysis showed that TYG-BMI was negatively correlated with OC, PINP and β-CTX in all patients and male patients. In postmenopausal women, TyG-BMI was negatively correlated with OC and β-CTX, but not with PINP. 3. Subgroup analysis of male patients and postmenopausal female patients according to age, course of disease, BMI, TG and 25(OH)D3 showed that TyG-BMI had a stronger negative correlation with BTMs in male patients with age < 65, disease duration < 10, BMI≥24, TG < 1.7, and 25(OH)D3≥20.

Conclusion

This study was the first to show an inverse association between TyG-BMI and BTMs in T2DM patients, suggesting that high TyG-BMI may be associated with impaired bone turnover.

Unlocking the Full Potential of SGLT2 Inhibitors: Expanding Applications beyond Glycemic Control

The number of diabetic patients has risen dramatically in recent decades, owing mostly to the rising incidence of type 2 diabetes mellitus (T2DM). Several oral antidiabetic medications are used for the treatment of T2DM including, α-glucosidases inhibitors, biguanides, sulfonylureas, meglitinides, GLP-1 receptor agonists, PPAR-γ agonists, DDP4 inhibitors, and SGLT2 inhibitors. In this review we focus on the possible effects of SGLT2 inhibitors on different body systems. Beyond the diabetic state, SGLT2 inhibitors have revealed a demonstrable ability to ameliorate cardiac remodeling, enhance myocardial function, and lower heart failure mortality. Additionally, SGLT2 inhibitors can modify adipocytes and their production of cytokines, such as adipokines and adiponectin, which enhances insulin sensitivity and delays diabetes onset. On the other hand, SGLT2 inhibitors have been linked to decreased total hip bone mineral deposition and increased hip bone resorption in T2DM patients. More data are needed to evaluate the role of SGLT2 inhibitors on cancer. Finally, the effects of SGLT2 inhibitors on neuroprotection appear to be both direct and indirect, according to scientific investigations utilizing various experimental models. SGLT2 inhibitors improve vascular tone, elasticity, and contractility by reducing oxidative stress, inflammation, insulin signaling pathways, and endothelial cell proliferation. They also improve brain function, synaptic plasticity, acetylcholinesterase activity, and reduce amyloid plaque formation, as well as regulation of the mTOR pathway in the brain, which reduces brain damage and cognitive decline.

Investigation of the effects of eugenol and quercetin on bone loss in STZ-NA induced diabetic rats utilizing micro CT

Purpose

Diabetes Mellitus (DM) is a systemic disease that can effect tissues and their physiological functions at molecular and biochemical levels. Diabetic osteoporosis is one of the chronic diseases of bone metabolism effected by and characterized by augmented risk of osteoporotic fractures and destroying of bone microarchitecture. It was aimed to investigate the alterations in femoral bone structure that may take place as a complication of DM by using the antioxidant properties of eugenol and quercetin, which are phenolic compounds, in streptozotocin nicotinamide (STZ-NA) induced rats as an experimental type 2 DM (T2 DM) model.

Methods

The antioxidant effect of eugenol and quercetin in case of DM development was determined by GSH ELISA kit. The effect of DM on alterations in bone structure was analyzed by micro CT. BMD, Tb.Bv/Tb.Tv, Tb.N, Tb.Th, Ct.Th, Tb.Sp and SMI data were calculated with the software CTAn.

Results

Serum GSH levels, Tb.Th and Tb.Bv/Tb.Tv values statistically decreased, and SMI values statistically increased in diabetic group compared with controls. Serum GSH levels in eugenol group were higher than diabetic group, and Tb.Bv/Tb.Tv values in eugenol group were lower than controls. Quercetin group had higher serum GSH levels and Tb.Th values compared with diabetic group, while SMI values were lower in quercetin group compared with diabetic group.

Conclusion

Eugenol and quercetin were revealed to have antioxidant, antidiabetic and osteoprotective effects on the repair of bone structure in experimental STZ-NA T2 DM model.

Novel Insight into the Relationship Between Muscle-Fat and Bone in Type 2 Diabetes Ranging from Normal Weight to Obesity

OBJECTIVE

Decreased bone mineral density (BMD) is a common complication in individuals with type 2 diabetes mellitus (T2DM). Body weight, mainly consisting of muscle and fat, is the main determinant of BMD and fracture risks but does not accurately describe nutritional status. Most studies suggest that skeletal muscle mass (SMM) promotes BMD, while body fat mass (BFM) decreases BMD. However, the combined effect of SMM and BFM on BMD is elusive. Thus, the study aims to explore the combined effect of fat and muscle by the ratio index SMM/BFM on BMD in T2DM.

METHODS

BFM and SMM were measured by the bioelectrical impedance analysis (BIA) method among 593 T2DM individuals ranging from normal weight and obesity. BMD was analyzed by DXA. Novel non-linear generalized additive models (GAMs) were used as the statistical analysis method.

RESULTS

The results demonstrated that BMD T score/Z score of both femur and lumbar vertebrae were significantly higher and waist-hip ratio (WHR) was significantly lower in the high SMM/BFM group of both normal weight and overweight groups in T2DM individuals. Hence, SMM/BFM might be a good factor indicating BMD in different weight ranges. Additionally, the relationship between muscle fat and BMD was not linear. Notably, this correlation was not influenced by hyperglycemia in T2DM since different analytic models adjusted with the age, gender, BMI and HbA1c were adopted in this study. Furthermore, the impact of trunk fat (central, visceral fat most) and non-trunk fat (peripheral, the sum of subcutaneous limb fat most) on BMD was inconsistent. BMD presented unlimited reduction with trunk BFM increasing, while sustaining minimal diminishment with non-trunk BFM accumulation.

CONCLUSION

Our study provided a novel viewpoint relationship between muscle-fat and bone, and SMM/BFM might be a potential biomarker for bone health and clinical treatments of diabetes and related metabolic syndromes.

Characteristics of bone metabolism in postmenopausal women with newly diagnosed type 2 diabetes mellitus

OBJECTIVE

The characteristics of bone metabolism in T2DM are still controversial. This study aims to recognize bone turnover features in patients with newly diagnosed T2DM who have never been treated with anti-diabetic drugs and further explore the possible factors contributing to their impaired bone turnover.

MATERIALS AND METHODS

An analytic sample of 88 patients with newly diagnosed T2DM and 152 non-diabetic control individuals were studied. All the participants were postmenopausal women. Demographics variables and clinical history were recorded. We measured lipid profile, glucose metabolism, bone turnover markers indices as well as their related hormones, serum calcium and phosphorus. Bone mineral density was detected by dual-energy X-ray absorptiometry. We compared the differences in bone turnover markers and their regulating hormones between two groups and further analysed the factors related to bone turnover in T2DM.

RESULTS

Compared with the control group, patients with T2DM had a higher level of bone alkaline phosphatase (BALP), lower levels of procollagen type I intact N-terminal (P1NP), osteocalcin (OC) and parathyroid hormone (PTH). Multiple linear regression analysis showed that in patients with T2DM, HbA1c was negatively correlated with P1NP and OC. For patients without diabetes, HbA1c was negatively related to BALP and OC.

CONCLUSIONS

Patients with newly diagnosed T2DM may have impaired osteoblastic maturation and bone formation, which may be mainly attributed to hyperglycaemia.

Comparison of the Effects of Various Antidiabetic Medication on Bone Mineral Density in Patients with Type 2 Diabetes Mellitus

BACKGROUND

Prospective comparative studies on the effects of various antidiabetic agents on bone metabolism are limited. This study aimed to assess changes in bone mass and biochemical bone markers in postmenopausal patients with type 2 diabetes mellitus (T2DM).

METHODS

This prospective, multicenter, open-label, comparative trial included 264 patients with T2DM. Patients who had received a metformin, or sulfonylurea/metformin combination (Group 1); a thiazolidinedione combination (Group 2); a dipeptidyl peptidase-4 inhibitor (gemigliptin) combination (Group 3); or an sodium-glucose cotransporter 2 inhibitor (empagliflozin) combination (Group 4) were prospectively treated for 12 months; bone mineral density (BMD) and bone turnover marker (BTM) changes were evaluated.

RESULTS

The femoral neck BMD percentage changes were -0.79%±2.86% (Group 1), -2.50%±3.08% (Group 2), -1.05%±2.74% (Group 3), and -1.24%±2.91% (Group 4) (P<0.05). The total hip BMD percentage changes were -0.57%±1.79% (Group 1), -1.74%±1.48% (Group 2), -0.75%±1.87% (Group 3), and -1.27%±1.72% (Group 4) (P<0.05). Mean serum BTM (C-terminal type 1 collagen telopeptide and procollagen type 1 amino-terminal propeptide) levels measured during the study period did not change over time or differ between groups.

CONCLUSION

Significant bone loss in the femoral neck and total hip was associated with thiazolidinedione combination regimens. However, bone loss was not significantly associated with combination regimens including gemigliptin or empagliflozin. Caution should be exercised during treatment with antidiabetic medications that adversely affect the bone in patients with diabetes at a high risk of bone loss.

Spirulina supplementation improves bone structural strength and stiffness in streptozocin-induced diabetic rats

Spirulina (blue-green algae) contains a wide range of nutrients with medicinal properties which include β-carotene, chromium, and moderate amounts of vitamins B₁₂. This study aims to determine the preventive effect of spirulina against bone fragility linked to type 2 diabetes mellitus. Thirty Sprague-Dawley rats were divided into five groups (n = 6) and diabetes was induced using streptozocin. Rats with a plasma glucose level of 10 mmol/L and above were orally treated for twelve weeks with either a single dose of spirulina, metformin, or a combined dose of spirulina + metformin per day. After the treatment, blood and bones were taken for biochemical analysis, three-dimensional imaging, 3-point biomechanical analysis, histology imaging and gene expression using qPCR. Results showed that diabetes induction and treatment with metformin caused destruction in the trabecular microarchitecture of the femur bone, reduction in serum bone marker and expression of bone formation marker genes in the experimental rats. Spirulina supplementation showed improved trabecular microarchitecture with a denser trabecular network, increased 25-OH vitamin D levels, and lowered the level of phosphate and calcium in the serum. Biomechanical tests revealed increased maximum force, stress strain, young modulus and histology images showed improvement in regular mesh and an increase in osteoblasts and osteocytes. There was an increase in the expression of bone formation marker osteocalcin. The results suggest that spirulina supplementation was more effective at improving bone structural strength and stiffness in diabetic rats compared to metformin. Spirulina may be able to prevent T2DM-related brittle bone, lowering the risk of fracture.

Direct and Indirect Effect of Honey as a Functional Food Against Metabolic Syndrome and Its Skeletal Complications

Metabolic syndrome (MetS) refers to the simultaneous presence of hypertension, hyperglycemia, dyslipidemia and/or visceral obesity, which predisposes a person to cardiovascular diseases and diabetes. Evidence suggesting the presence of direct and indirect associations between MetS and osteoporosis is growing. Many studies have reported the beneficial effects of polyphenols in alleviating MetS in in vivo and in vitro models through their antioxidant and anti-inflammation actions. This review aims to summarize the effects of honey (based on unifloral and multi-floral nectar sources) on bone metabolism and each component of MetS. A literature search was performed using the PubMed and Scopus databases using specific search strings. Original studies related to components of MetS and bone, and the effects of honey on components of MetS and bone were included. Honey polyphenols could act synergistically in alleviating MetS by preventing oxidative damage and inflammation. Honey intake is shown to reduce blood glucose levels and prevent excessive weight gain. It also improves lipid metabolism by reducing total cholesterol, triglycerides and low-density lipoprotein, as well as increasing high-density lipoprotein. Honey can prevent bone loss by reducing the adverse effects of MetS on bone homeostasis, apart from its direct action on the skeletal system. In conclusion, honey supplementation could be integrated into the management of MetS and MetS-induced bone loss as a preventive and adjunct therapeutic agent.

Helicobacter pylori Related Diseases and Osteoporotic Fractures (Narrative Review)

Osteoporosis (OP) and osteoporotic fractures (OFs) are common multifactorial and heterogenic disorders of increasing incidence. Helicobacter pylori (H.p.) colonizes the stomach approximately in half of the world's population, causes gastroduodenal diseases and is prevalent in numerous extra-digestive diseases known to be associated with OP/OF. The studies regarding relationship between H.p. infection (HPI) and OP/OFs are inconsistent. The current review summarizes the relevant literature on the potential role of HPI in OP, falls and OFs and highlights the reasons for controversies in the publications. In the first section, after a brief overview of HPI biological features, we analyze the studies evaluating the association of HPI and bone status. The second part includes data on the prevalence of OP/OFs in HPI-induced gastroduodenal diseases (peptic ulcer, chronic/atrophic gastritis and cancer) and the effects of acid-suppressive drugs. In the next section, we discuss the possible contribution of HPI-associated extra-digestive diseases and medications to OP/OF, focusing on conditions affecting both bone homeostasis and predisposing to falls. In the last section, we describe clinical implications of accumulated data on HPI as a co-factor of OP/OF and present a feasible five-step algorithm for OP/OF risk assessment and management in regard to HPI, emphasizing the importance of an integrative (but differentiated) holistic approach. Increased awareness about the consequences of HPI linked to OP/OF can aid early detection and management. Further research on the HPI-OP/OF relationship is needed to close current knowledge gaps and improve clinical management of both OP/OF and HPI-related disorders.

Probiotics ameliorate pioglitazone-associated bone loss in diabetic rats

Background

Pioglitazone, as a PPAR gamma agonist, is used for the management of type 2 diabetes mellitus. Nevertheless, evidence showed that the therapeutic modulation of PPAR gamma activity using pioglitazone might be linked with bone mass reduction and fracture risk in type 2 diabetes mellitus patients. The objective of the current research was to inspect the preventive role of some types of probiotic strains, including (Lactobacillus acidophilus, Lactobacillus reuteri, Lactobacillus casei, Bifidobacterium longum, and Bacillus coagulans) against pioglitazone-induced bone loss.

Methods

Streptozotocin (60 mg/kg) was administered for diabetes induction. Diabetic rats were fed orally with pioglitazone (300 mg/kg) and probiotics (1 × 109 CFU/ml/day) alone and in combination for four weeks. Dual-energy X-ray absorptiometry (DXA) was used to assess BMD, BMC, and area of the femur, spine, and tibia at the end of the experiment. Serum glucose, serum calcium (Ca), alkaline phosphatase (ALP), phosphorus (P), Blood urea nitrogen (BUN), creatinine, and urine calcium were also analyzed.

Results

Administration of pioglitazone and probiotics alone and, in combination, significantly reduced elevated blood glucose. Pioglitazone treatment significantly increased urinary calcium and BUN and decreased ALP and creatinine. Co-treatment of probiotics with pioglitazone significantly decreased urinary calcium, creatinine, and ALP. Pioglitazone showed detrimental effects on femur-BMD, whereas treatment with probiotics remarkably ameliorated these effects. Among the tested probiotics, Bifidobacterium longum displayed the best protective effects on pioglitazone-induced bone loss in diabetic rats.

Conclusion

This study suggests probiotic supplementation in diabetic patients on pioglitazone regime could be considering as an excellent strategy to ameliorate bone loss induced by pioglitazone.

Effect of Metformin vs. Placebo in Combination with Insulin Analogues on Bone Markers P1NP and CTX in Patients with Type 2 Diabetes Mellitus

Preclinical studies have shown a potential osteoanabolic effect of metformin but human studies of how metformin affects bone turnover are few. A post hoc sub-study analysis of an 18-month multicenter, placebo-controlled, double-blinded trial in type 2 diabetes mellitus (T2DM), randomizing participants to metformin versus placebo both in combination with different insulin analogue regimens (Metformin + Insulin vs. Placebo + Insulin). Patients were not treatment naive at baseline, 83% had received metformin, 69% had received insulin, 57.5% had received the combination of metformin and insulin before entering the study. Bone formation and resorption were assessed by measuring, N-terminal propeptide of type I procollagen (P1NP) and C-terminal telopeptide of type I collagen (CTX) at baseline and end of study. The influence of gender, age, smoking, body mass index (BMI), T2DM duration, glycosylated hemoglobin A1c (HbA1c), c-reactive protein (CRP) and insulin dosage was also included in the analyses. The levels of bone formation marker P1NP and bone resorption marker CTX increased significantly in both groups during the trial. P1NP increased less in the Metformin + Insulin compared to the placebo + insulin group (p = 0.001) (between group difference change), while the increases in CTX levels (p = 0.11) were not different. CRP was inversely associated (p = 0.012) and insulin dosage (p = 0.011) was positively related with change in P1NP levels. BMI (p = 0.002) and HbA1C (p = 0.037) were inversely associated with change in CTX levels. During 18 months of treatment with metformin or placebo, both in combination with insulin, bone turnover increased in both groups. But the pattern was different as the bone formation marker (P1NP) increased less during Metformin + Insulin treatment, while change in bone resorption (CTX) was not significantly different between the two groups.

The Effects of Diabetes and Diabetic Medications on Bone Health

The incidence and prevalence of diabetes continues to increase, and proper understanding of the adverse effects on bone metabolism is important. This review attempts to discuss the pathophysiology of the effects of diabetes and diabetic medications on bone metabolism and bone health. In addition, this review will address the mechanisms resulting in increased fracture risk and delayed bone healing to better treat and manage diabetic patients in the orthopedic clinical setting.

[Diagnosis and management of patients with diabetes and co-existing osteoporosis (Update 2019) : Common guideline of the Autrian Society for Bone and Mineral Research and the Austrian Diabetes Society]

Fragility fractures are increasingly recognized as a complication of both type 1 and type 2 diabetes, with fracture risk that increases with disease duration and poor glycemic control. The identification and management of fracture risk in these patients remains challenging. This manuscript explores the clinical characteristics of bone fragility in adults with diabetes and highlights recent studies that have evaluated areal bone mineral density (BMD), bone microstructure and material properties, biochemical markers, and fracture prediction algorithms (FRAX) in these patients. It further reviews the impact of diabetes drugs on bone tissue as well as the efficacy of osteoporosis treatments in this population. An algorithm for the identification and management of diabetic patients at increased fracture risk is proposed.

Effects of glucagon-like peptide 1 receptor agonists on comorbidities in older patients with diabetes mellitus

Elderly patients with diabetes are at high risk of polypharmacy because of multiple coexisting diseases and syndromes. Polypharmacy increases the risk of drug–drug and drug–disease interactions in these patients, who may already have age-related sensory and cognitive deficits; such deficits may delay timely communication of early symptoms of adverse drug events. Several glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have been approved for diabetes: liraglutide, exenatide, lixisenatide, dulagluatide, semaglutide, and albiglutide. Some are also approved for treatment of obesity. The current review of literature along with clinical case discussion provides evidence supporting GLP-1 RAs as diabetes medications for polypharmacy reduction in older diabetes patients because of their multiple pleiotropic effects on comorbidities (e.g. hyperlipidemia, hypertension, and fatty liver) and syndromes (e.g. osteoporosis and sleep apnea) that commonly co-occur with diabetes. Using one medication (in this case, GLP-1 RAs) to address multiple conditions may help reduce costs, medication burden, adverse drug events, and medication nonadherence.

Metabolic and bone profile in postmenopausal women with and without type 2 diabetes: a cross-sectional study

INTRODUCTION

Current studies support the implication of metabolic changes associated with type 2 diabetes in altering bone metabolism, structure and resistance.

OBJECTIVE

We conducted a cross-sectional study on postmenopausal women aimed to analyze the differences in metabolic and bone profile in patients with and without type 2 diabetes Methods. We analyzed the metabolic and bone profile in postmenopausal women with and without type 2 diabetes (T2DM). Clinical, metabolic, hormonal parameters, along with lumbar, hip and femoral bone mineral density (BMD) and trabecular bone score (TBS) were evaluated.

RESULTS

56 women with T2DM(63.57±8.97 years) and 83 non-T2DM (60.21±8.77 years) were included. T2DM patients presented a higher value of body mass index (BMI) and BMD vs. control group (p = 0.001; p = 0.03-lumbar level, p = 0.07-femoral neck and p = 0.001-total hip). Also, BMI correlated positively with lumbar-BMD and glycated hemoglobin (HbA1c) (r = 0.348, p = 0.01; r = 0.269, p = 0.04), correlation maintained even after age and estimated glomerular filtration rate (eGFR) adjustment (r = 0.383, p = 0.005; r = 0.237, p = 0.08). Diabetic patients recorded lower levels of 25(OH)D(p = 0.05), bone markers (p ≤ 0.05) and TBS(p = 0.07). For the entire patient group we found a negative correlation between HbA1c level and bone markers: r = -0.358, p = 0.0005-osteocalcin, r = -0.40, p = 0.0005-P1NP, r = -0.258, p = 0.005-crosslaps.

CONCLUSIONS

Our results indicate the presence of altered bone microarchitecture in T2DZ patients according to the TBS score, combined with lower levels of bone markers, with a statistically significant negative correlation between HbA1c level and bone markers.

Exploring the potential of tocotrienol from Bixa orellana as a single agent targeting metabolic syndrome and bone loss

Metabolic syndrome (MetS) is associated with osteoporosis due to the underlying inflammatory and hormonal changes. Annatto tocotrienol has been shown to improve medical complications associated with MetS or bone loss in animal studies. This study aimed to investigate the effects of annatto tocotrienol as a single treatment for MetS and osteoporosis in high-carbohydrate high-fat (HCHF) diet-induced MetS animals. Three-month-old male Wistar rats were randomly divided into five groups. The baseline group was euthanized at the onset of the study. The normal group received standard rat chow and tap water. The remaining groups received HCHF diet and treated with three different regimens orally daily: (a) tocopherol-stripped corn oil (the vehicle of tocotrienol), (b) 60 mg/kg annatto tocotrienol, and (c) 100 mg/kg annatto tocotrienol. At the end of the study, measurements of MetS parameters, body compositions, and bone mineral density were performed in animals before sacrifice. Upon euthanasia, blood and femur of the rats were harvested for the evaluations of bone microstructure, biomechanical strength, remodelling activities, hormonal changes, and inflammatory response. Treatment with annatto tocotrienol improved all MetS parameters (except abdominal obesity), trabecular bone microstructure, bone strength, increased osteoclast number, normalized hormonal changes and inflammatory response in the HCHF animals. In conclusion, annatto tocotrienol is a potential agent for managing MetS and osteoporosis concurrently. The beneficial effects of annatto tocotrienol may be attributed to its ability to prevent the hormonal changes and pro-inflammatory state in animals with MetS.

Diabetes Mellitus-induced Bone Fragility

Accumulating evidence has shown that the risk of osteoporotic fractures is increased in patients with diabetes mellitus (DM). Thus, DM-induced bone fragility has been recently recognized as a diabetic complication. Because the fracture risk is independent of the reduction in bone mineral density, deterioration of the bone quality may be the main cause of bone fragility. Although its mechanism remains poorly understood, accumulated collagen cross-links of advanced glycation end-products (AGEs) and dysfunctions of osteoblast and osteocyte may be involved. Previous studies have suggested that various diabetes-related factors, such as chronic hyperglycemia, insulin, insulin-like growth factor-I, AGEs, and homocysteine, are associated with the risk of bone fragility caused by impaired bone formation and bone remodeling. Furthermore, several anti-diabetic drugs are known to affect bone metabolism and fracture risk. We herein review the association between DM and fracture risk as well as the mechanism of DM-induced bone fragility based on recent evidence.

The Effects of Vitamin E from Elaeis guineensis (Oil Palm) in a Rat Model of Bone Loss Due to Metabolic Syndrome

The beneficial effects of vitamin E in improving components of MetS or bone loss have been established. This study aimed to investigate the potential of palm vitamin E (PVE) as a single agent, targeting MetS and bone loss concurrently, using a MetS animal model. Twelve-week-old male Wistar rats were divided into five groups. The baseline group was sacrificed upon arrival. The normal group was given standard rat chow. The remaining three groups were fed with high-carbohydrate high-fat (HCHF) diet and treated with tocopherol-stripped corn oil (vehicle), 60 mg/kg or 100 mg/kg PVE. At the end of the study, the rats were evaluated for MetS parameters and bone density. After euthanasia, blood and femurs were harvested for the evaluation of lipid profile, bone histomorphometric analysis, and remodeling markers. PVE improved blood pressure, glycemic status, and lipid profile; increased osteoblast surface, osteoid surface, bone volume, and trabecular thickness, as well as decreased eroded surface and single-labeled surface. Administration of PVE also significantly reduced leptin level in the HCHF rats. PVE is a potential agent in concurrently preventing MetS and protecting bone loss. This may be, in part, achieved by reducing the leptin level and modulating the bone remodeling activity in male rats.

A collagen domain-derived short adiponectin peptide activates APPL1 and AMPK signaling pathways and improves glucose and fatty acid metabolisms

Adiponectin is a fat tissue-derived adipokine with beneficial effects against diabetes, cardiovascular diseases, and cancer. Accordingly, adiponectin-mimetic molecules possess significant pharmacological potential. Oligomeric states of adiponectin appear to determine its biological activity. We identified a highly conserved, 13-residue segment (ADP-1) from adiponectin's collagen domain, which comprises GXXG motifs and has one asparagine and two histidine residues that assist in oligomeric protein assembly. We therefore hypothesized that ADP-1 promotes oligomeric assembly and thereby mediates potential metabolic effects. We observed here that ADP-1 is stable in human serum and oligomerizes in aqueous environments. We also found that ADP-1 activates AMP-activated protein kinase (AMPK) in an adaptor protein, phosphotyrosine interacting with PH domain and leucine zipper 1 (APPL1)-dependent pathway and stimulates glucose uptake in rat skeletal muscle cells (L6 myotubes). ADP-1-induced glucose transport coincided with ADP-1-induced biosynthesis of glucose transporter 4 and its translocation to the plasma membrane. ADP-1 induced an interaction between APPL1 and the small GTPase Rab5, resulting in AMPK phosphorylation, in turn leading to phosphorylation of p38 mitogen-activated protein kinase (MAPK), acetyl-CoA carboxylase, and peroxisome proliferator-activated receptor α. Similar to adiponectin, ADP-1 increased the expression of the adiponectin receptor 1 (AdipoR1) gene. Of note, ADP-1 decreased blood glucose levels and enhanced insulin production in pancreatic β cells in db/db mice. Further, ADP-1 beneficially affected lipid metabolism by enhancing lipid globule formation in mouse 3T3-L1 adipocytes. To our knowledge, this is the first report on identification of a short peptide from adiponectin with positive effects on glucose or fatty acid metabolism.