Effect of thiazolidinediones on skeletal health in women with Type 2 diabetes

Orchestra of ligand-activated transcription factors in the molecular symphony of SERPINE 1 / PAI-1 gene regulation

Plasminogen activator inhibitor 1 (PAI-1) is a crucial serine protease inhibitor that prevents plasminogen activation by inhibiting tissue- and urokinase-type plasminogen activators (tPA, uPA). PAI-1 is well-known for its role in modulating hemocoagulation or extracellular matrix formation by inhibiting plasmin or matrix metalloproteinases, respectively. PAI-1 is induced by pro-inflammatory cytokines across various tissues, yet its regulation by ligand-activated transcription factors is partly disregarded. Therefore, we have attempted to summarize the current knowledge on the transcriptional regulation of PAI-1 expression by the most relevant xenobiotic and endocrine receptors implicated in modulating PAI-1 levels. This review aims to contribute to the understanding of the specific, often tissue-dependent regulation of PAI-1 and provide insights into the modulation of PAI-1 levels beyond its direct inhibition.

Extract of Artemisia dracunculus L. Modulates Osteoblast Proliferation and Mineralization

Thiazolidinediones (TZD) significantly improve insulin sensitivity via action on adipocytes. Unfortunately, TZDs also degrade bone by inhibiting osteoblasts. An extract of Artemisia dracunculus L., termed PMI5011, improves blood glucose and insulin sensitivity via skeletal muscle, rather than fat, and may therefore spare bone. Here, we examine the effects of PMI5011 and an identified active compound within PMI5011 (2',4'-dihydroxy-4-methoxydihydrochalcone, DMC-2) on pre-osteoblasts. We hypothesized that PMI5011 and DMC-2 will not inhibit osteogenesis. To test our hypothesis, MC3T3-E1 cells were induced in osteogenic media with and without PMI5011 or DMC-2. Cell lysates were probed for osteogenic gene expression and protein content and were stained for osteogenic endpoints. Neither compound had an effect on early stain outcomes for alkaline phosphatase or collagen. Contrary to our hypothesis, PMI5011 at 30 µg/mL significantly increases osteogenic gene expression as early as day 1. Further, osteogenic proteins and cell culture mineralization trend higher for PMI5011-treated wells. Treatment with DMC-2 at 1 µg/mL similarly increased osteogenic gene expression and significantly increased mineralization, although protein content did not trend higher. Our data suggest that PMI5011 and DMC-2 have the potential to promote bone health via improved osteoblast maturation and activity.

Sex hormones influence expression and function of peroxisome proliferator-activated receptor γ in adipocytes: pathophysiological aspects

Abstract Adipose tissue plays important roles not only in storing fat but also in maintaining metabolic homeostasis by regulating hundreds of biological signaling events and the secretion of various cytokines. One of the central regulators of adipocyte differentiation is peroxisome proliferator-activated receptor γ (PPARγ), which promotes downstream transcriptional activities, such as adiponectin. Disruption of homeostasis leads to the onset of metabolic diseases such as type 2 diabetes and other triggers for metabolic syndrome. Males and post-menopausal females are more likely to be affected with metabolic diseases than pre-menopausal females, suggesting that sex hormones might be involved in the pathogenesis and development of metabolic diseases. Indeed, 17β-estradiol, testosterone, dihydrotestosterone, and their receptors clearly play a role in adipose regulation: they can alter fat distribution and can modify the expression and activities of PPARγ and its downstream adipocytokines. Furthermore, sex hormones affect inflammatory factors such as nitric oxygen, nitric oxygen synthase, and their surrounding components. Sex hormones are also suggested to be involved with sex differences in the efficacy of the PPARγ agonist thiazolidinediones. Therefore, thorough investigation of how sex hormone-dependent regulation of metabolic homeostasis occurs is necessary in order to develop individualized clinical therapies optimized with regard to each patient's biological condition and drug sensitivities.

Sex-specific differences in progressive glucose intolerance and hip geometry: the Baltimore Longitudinal Study of Aging

Fracture risk is increased in type 2 diabetes mellitus (T2DM). The effect of pre-diabetes and T2DM on bone macroarchitecture and strength has not been well investigated. In this study, we show that in women only, both pre-diabetes and T2DM are associated with decreased hip bending strength and mineralization which might lead to skeletal weakness.

INTRODUCTION

Older men and women with T2DM are at increased risk for fracture despite normal bone mineral density (BMD). The discordance between bone quantity and skeletal fragility has driven investigation into additional determinants of fracture resistance in T2DM. Additionally, the effect of pre-diabetes on bone strength has not been well described. The aim of this study was to determine differences in bone macroarchitecture and strength, measured by hip geometry, in persons with normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and T2DM.

METHODS

We performed cross-sectional analyses of older (age >55 years) men (n = 472) and women (n = 473) participating in the Baltimore Longitudinal Study of Aging (BLSA) classified as NGT, IGT, or T2DM based on oral glucose tolerance testing. Bone strength measures included the hip geometry parameters of section modulus (Z), cross-sectional area (CSA), and buckling ratio (BR). Sex-stratified analyses were conducted using adjusted stepwise regression models.

RESULTS

In women, IGT and T2DM were negatively associated with hip geometry parameters including mineralization in cross section (CSA, ß -0.076 and -0.073, respectively; both p < 0.05) and hip bending strength (Z, ß -0.097 and -0.09, respectively; both p < 0.05); conversely, IGT and T2DM were associated with improved compressive strength (BR, ß -0.31 and -0.29, respectively; both p < 0.05). There was no significant association between glycemic status and hip geometry in men.

CONCLUSIONS

In women only, both IGT and T2DM were inversely associated with bone macroarchitecture and measures of bone mineralization and bending strength. The same association between worsening glycemic status and bone strength was not observed in men. These data suggest a differential effect of sex on hip geometry with evolving glucose intolerance.

Minireview: nuclear receptor regulation of osteoclast and bone remodeling

Osteoclasts are bone-resorbing cells essential for skeletal remodeling and regeneration. However, excessive osteoclasts often contribute to prevalent bone degenerative diseases such as osteoporosis, arthritis, and cancer bone metastasis. Osteoclast dysregulation is also associated with rare disorders such as osteopetrosis, pycnodysostosis, Paget's disease, and Gorham-Stout syndrome. The nuclear receptor (NR) family of transcription factors functions as metabolic sensors that control a variety of physiological processes including skeletal homeostasis and serves as attractive therapeutic targets for many diseases. In this review, we highlight recent findings on the new players and the new mechanisms for how NRs regulate osteoclast differentiation and bone resorption. An enhanced understanding of NR functions in osteoclastogenesis will facilitate the development of not only novel osteoprotective medicine but also prudent strategies to minimize the adverse skeletal effects of certain NR-targeting drugs for a better treatment of cancer and metabolic diseases.

The alliance of mesenchymal stem cells, bone, and diabetes

Bone fragility has emerged as a new complication of diabetes. Several mechanisms in diabetes may influence bone homeostasis by impairing the action between osteoblasts, osteoclasts, and osteocytes and/or changing the structural properties of the bone tissue. Some of these mechanisms can potentially alter the fate of mesenchymal stem cells, the initial precursor of the osteoblast. In this review, we describe the main factors that impair bone health in diabetic patients and their clinical impact.

Relationship between MRI-measured bone marrow adipose tissue and hip and spine bone mineral density in African-American and Caucasian participants: the CARDIA study

CONTEXT

An increasing number of studies suggest that bone marrow adipose tissue (BMAT) might play a role in the pathogenesis of osteoporosis. Our previous study of Caucasian women demonstrated that there is an inverse relationship between BMAT and whole-body bone mineral density (BMD). It is unknown whether visceral adipose tissue (VAT), sc adipose tissue (SAT), and skeletal muscle had an effect on the relationship between BMAT and BMD.

OBJECTIVE

In the present study we investigated the relationship between pelvic, hip, and lumbar spine BMAT with hip and lumbar spine BMD in the population-based Coronary Artery Risk Development in Young Adults (CARDIA) sample with adjustment for whole-body magnetic resonance imaging (MRI)-measured VAT, SAT, and skeletal muscle.

DESIGN

T1-weighted MRI was acquired for 210 healthy African-American and Caucasian men and women (age 38-52 yr). Hip and lumbar spine BMD were measured by dual-energy x-ray absorptiometry.

RESULTS

Pelvic, hip, and lumbar spine BMAT had negative correlations with hip and lumbar spine BMD (r = -0.399 to -0.550, P < 0.001). The inverse associations between BMAT and BMD remained strong after adjusting for demographics, weight, skeletal muscle, SAT, VAT, total adipose tissue (TAT), menopausal status, lifestyle factors, and inflammatory markers (standardized regression coefficients = -0. 296 to -0.549, P < 0.001). Among body composition measures, skeletal muscle was the strongest correlate of BMD after adjusting for BMAT (standardized regression coefficients = 0.268-0.614, P < 0.05), with little additional contribution from weight, SAT, VAT, or total adipose tissue.

CONCLUSION

In this middle-aged population, a negative relationship existed between MRI-measured BMAT and hip and lumbar spine BMD independent of demographics and body composition. These observations support the growing evidence linking BMAT with low bone density.

Neurosurgical management of symptomatic thoracic spinal ossification in a patient with fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder characterized by heterotopic ossification of soft connective and muscle tissues, often as the result of minor trauma. The sequelae include joint fusion, accumulation of calcified foci within soft tissues, thoracic insufficiency syndrome, and progressive immobility. The authors report on a patient with FOP who developed severe spinal canal stenosis in the thoracic spine causing substantial myelopathy. He underwent a thoracic laminectomy and resection of a large posterior osteophyte. Unique considerations are required in treating patients with FOP, including steroid administration to prevent ossification and anesthetic technique. The nuances of neurosurgical and medical management as they pertain to this disease are discussed.

TZDs and Bone: A Review of the Recent Clinical Evidence

Over the past two years, evidence has emerged that the currently available thiazolidinediones (TZDs), rosiglitazone, and pioglitazone have negative skeletal consequences, at least in women, which are clinically important. Increased fracture risk in women, but not men, was reported for both TZDs, based on analyses of adverse event reports from clinical trials. In short-term clinical trials in women, both TZDs caused more rapid bone loss. In these trials, changes in bone turnover markers suggest a pattern of reduced bone formation without a change in resorption. Although limited, these results support the hypothesis based on rodent and in vitro models that reduced bone formation resulting from activation of peroxisome proliferator-activated receptor-γ (PPARγ) is a central mechanism for TZDs' effect on bone. Research is needed to better understand the mechanisms of bone loss with TZDs, to identify factors that influence susceptibility to TZD-induced osteoporosis, and to test treatments for its prevention.

Pharmacologic management of the older patient with type 2 diabetes mellitus

BACKGROUND

Pharmacologic options for the treatment of elderly patients with type 2 diabetes mellitus (T2DM) are the same as in younger adults; however, treatment considerations differ in the elderly due to changes in renal and hepatic function, life expectancy, and various other clinical and practical considerations.

OBJECTIVE

This article discusses geriatric considerations in the pharmacologic management of T2DM and reviews the potential clinical advantages and disadvantages of pharmacologic agents currently available for the treatment of T2DM, including oral and injectable medications.

METHODS

A search of MEDLINE was conducted for articles published in English between January 1966 and September 2009 using the terms type 2 diabetes mellitus, elderly, geriatric, treatment, insulin, metformin, sulfonylurea, thiazolidinedione, alpha-glucosidase inhibitor, meglitinide, DPP-4 inhibitor, colesevelam, exenatide, and pramlintide. Meta-analyses, randomized controlled trials of pharmacologic treatment, and evidence-based reviews and/or expert opinions regarding the treatment of T2DM in the elderly were selected for review.

RESULTS

In overweight patients, metformin has been associated with reductions in risk for all-cause mortality and stroke compared with insulin and sulfonylureas. Older patients who are frail, anorexic, or underweight and those with congestive heart failure (CHF), renal or hepatic insufficiency, or dehydration may not be appropriate candidates for metformin therapy. The substantial risk of hypoglycemia with insulin secretagogues is increased by 36% in the elderly compared with younger adults; however, this risk is counterbalanced by the extensive clinical experience with these agents in the geriatric population. Thiazolidinediones should generally be avoided in patients with CHF and are absolutely contraindicated in patients with class II-IV heart failure. They have been associated with peripheral edema, as well as with decreases in bone mineral density in women. There is limited information on the use of dipeptidyl peptidase-4 inhibitors in the elderly, although dose adjustment is required in patients with renal compromise. In practice, substantial gastrointestinal adverse effects limit the use of alpha-glucosidase inhibitors in older patients. Colesevelam is associated with numerous drug interactions and can cause new or worsening constipation. There are limited data on the use of exenatide in the elderly. It may be beneficial in older patients with limited mobility who could benefit from weight loss, whereas it may not be a good option for frail, underweight adults. Use of exenatide is not recommended in patients with a creatinine clearance <30 mL/min. Given the increased monitoring required to avoid hypoglycemic events with pramlintide, this agent should be used with caution in older adults, particularly the frail elderly. Most patients with T2DM eventually require insulin; however, due to the risk of hypoglycemia and related morbidity, careful use of insulin is warranted in the geriatric population.

CONCLUSIONS

Overall, there is a scarcity of data regarding the use of pharmacologic agents in older adults with T2DM, and clinical guidance is largely based on data obtained from younger populations. The selection of appropriate drug regimens for these patients remains challenging.

Metformin regulates osteoblast and adipocyte differentiation of rat mesenchymal stem cells

Metformin is widely used for the treatment of type 2 diabetes mellitus. In this study, we evaluated the effects of metformin on the osteoblast and adipocyte differentiation of rat marrow mesenchymal stem cells (MSCs) in culture. Treatment of MSCs in osteoblastic or adipogenic medium with 100 μM metformin for 21 days led to an increased mRNA expression of the osteoblast markers but a decreased mRNA expression of the adipocyte markers in the MSCs. Metformin markedly stimulated deposition of mineralized nodules and blocked the formation of cytoplasmic lipid droplets. In addition, alkaline phosphate activity and Western blot analysis for core binding factor a1 (Cbfa 1) and peroxisome proliferator-activated receptor gamma 2 (PPARγ2) proteins also confirmed that metformin inhibited adipocyte differentiation and promoted osteoblast differentiation. The reciprocal relationship between osteoblastic and adipogenic differentiation suggests that metformin may regulate osteoblastic and adipogenic differentiation through inhibition of PPARγ.

The effect of thiazolidinediones on bone mineral density in Chinese older patients with type 2 diabetes

The effect of thiazolidinediones (TZDs) on bone mineral density (BMD) and bone metabolism in patients with type 2 diabetes is still in debate. Accumulating evidence has emerged that long-term administration of TZDs may increase the occurrence of osteoporosis, at least in postmenopausal women. Because little clinical data has been reported on Chinese people, a retrospective study was performed. One-hundred ninety-eight Chinese people, all from our inpatients, were selected for a 24-28 month review (26 +/- 0.5 m). Four groups divided according to gender and TZD use were designated fTZD, mTZD, f and m. Changes of subjects' BMD and bone metabolism markers were noted and analyzed. Compared with group f, bone loss from fTZD in this over 24-month review was more significant in lumbar spine (L1-L4) (0.1 +/- 0.15 vs. 0.06 +/- 0.11) and right hip (0.09 +/- 0.15 vs. 0.05 +/- 0.14) (g/cm(3)) (P < 0.05). However, the opposite result was found in male patients with less bone loss in group mTZD. Two bone metabolism markers, including beta C-terminal telopeptide of type I collagen (beta-CTX) and osteocalcin (OC), in this study did not prove valuable in revealing changes among groups. We concluded that long-term TZD use may increase the risk of bone loss in Chinese postmenopausal patients with type 2 diabetes, which may provide caution on drug treatment in clinical practice. Whether TZD can protect male patients against BMD loss or not awaits further research.

Improving cardiovascular risk--applying evidence-based medicine to glucose-lowering therapy with thiazolidinediones in patients with type 2 diabetes

BACKGROUND

The management of patients with type 2 diabetes aims to reduce the elevated risk of cardiovascular disease (CVD) by addressing established risk factors including hyperglycaemia, dyslipidaemia and hypertension. The thiazolidinediones are equally effective in improving glycaemic control when used in combination regimens in patients with type 2 diabetes, but have differing effects on the diabetic dyslipidaemia.

AIMS

To compare the effects of rosiglitazone and pioglitazone on inflammatory mediators associated with atherosclerosis and CVD, surrogate cardiovascular endpoints, and hard cardiovascular outcomes in patients with type 2 diabetes.

MATERIALS AND METHODS

A search of the PubMed database plus manual search of referenced papers for other relevant citations.

RESULTS

Both glitazones reduce inflammatory markers and other circulating markers of CV disease. Available data suggest that pioglitazone can delay progression of atherosclerosis in patients with type 2 diabetes, as shown by the PERISCOPE and CHICAGO studies, and that it can reduce the rate of clinical CV events as shown by PROactive. Clinical end-point data for rosiglitazone are inconclusive, providing no evidence of benefit and a possible increase in myocardial infarction.

DISCUSSION

There is a consistency of benefit with pioglitazone on markers, surrogate cardiovascular outcomes and clinical end-point trials.

CONCLUSION

Pioglitazone is the preferred thiazolidinedione to reduce cardiovascular risk in people with type 2 diabetes.

Metabolic diseases and associated complications: sex and gender matter!

BACKGROUND

Clinicians and health professionals are increasingly challenged to understand and consider the different health needs of women and men. The increase of gender awareness and the expanding science of gender medicine will affect more and more clinical practice. This review addresses gender-specific aspects in metabolic disorders and related complications, which represent an increasing burden of this century and a great challenge to public health.

DESIGN

There is increasing evidence of gender-related differences in risk factors, clinical manifestation and sequelae of obesity and diabetes and increasing knowledge that prevention, detection and therapy of illness affect men and women differently.

RESULTS

Some gender-specific aspects, especially regarding cardiovascular disease, have been studied in more detail, but for many complications sex-related analyses of the results of both clinical trials and basic science are still missing or disregarded. Impaired glucose and lipid metabolism as well as dysregulation of energy balance and body fat distribution have a great impact on overall health via neuroendocrine changes and inflammatory pathways and deteriorate the course of many diseases with particular harm for women. Metabolic diseases dramatically affect life of men and women from infancy up to old age and are a major challenge for women during pregnancy. Great impact is attached to the intrauterine period and the lifelong implications of fetal programming.

CONCLUSIONS

Initiation of prospective studies on the impact of gender as primary outcome and investigation of gender-related pathophysiological mechanisms of chronic diseases will help to improve patient care and to implement evidence-based gender-specific prevention programs and clinical recommendations in future.

Treating type 2 diabetes: how safe are current therapeutic agents?

Sulphonylureas (SUs) and biguanides (metformin) are the current mainstays in the treatment of type 2 diabetes (T2DM) and represent the most commonly used oral hypoglycaemic agents (OHAs). In recent years, a variety of new OHAs have become available, including thiazolidinediones, glinides, alpha-glucosidase inhibitors, glucagon-like peptide-1 agonists, amylin analogues and dipeptidyl peptidase-IV inhibitors, providing physicians with a larger therapeutic catalogue than ever before. The traditional drugs metformin and SUs have an established safety profile through long-term use. However, long-term clinical trials and routine use are lacking for many of the new agents, and some potentially serious side effects have been reported with several of these compounds. Until adequate data is obtained, it is difficult to assess the risk-benefit ratio of these agents in relation to the traditional drugs. Until that becomes fully documented, it may be wise to start pharmacologic treatment of patients on an individual basis, weighing the benefits and costs of each medication. Thus, there remains a place for well-established drugs that have a proven safety record and are supported by years of clinical use for the treatment of T2DM.

Effectiveness of bisphosphonate therapy in a community setting

BACKGROUND

Osteoporosis is a major cause of morbidity and mortality. Clinical trials have shown the effectiveness of bisphosphonates, the most commonly prescribed treatments, in reducing fracture risk. The population-based effectiveness of bisphosphonates in clinical practice is uncertain.

METHODS

This retrospective cohort study used a matched design that compared time to clinical fracture in at-risk community women who initiated a bisphosphonate medication between 7/1/1996 and 6/30/2006 to those who did not. The study was conducted in an HMO in Oregon and Washington. Clinical electronic databases provided data. Eligible members were newly treated women aged > or = 55 years with either a BMD T-score of < or = -2.0 or a prior qualifying clinical fracture. They did not have contraindications for bisphosphonate therapy or a diagnosis associated with secondary osteoporosis (n=1829). They were matched to a similar comparison group (n=1829; total N=3658). The primary outcome was the first new incident fracture validated through chart review (closed clinical fracture of any bone except face, skull, finger, or toe or pathological fracture secondary to malignancy) during follow-up. An intention-to-treat analysis used Cox proportional hazards models to estimate the hazard ratio of fracture for treated relative to comparison patients, adjusting for differences in potential confounders.

RESULTS

Treated and comparison patients were similar in mean age (72.0 years) and history of fracture (about 45%). The treated group had more women with T-scores of < or = -2.5 (67.3% vs. 54.7%) and a lower mean weight (146.6 lb vs. 151.8 lb). Only about 45% of treated patients had a bisphosphonate medication possession ratio (MPR) of > or = 0.80. During follow-up, 198 (10.8%) of patients in the treated group had incident fractures, vs. 179 (9.8%) of patients in the comparison group. After adjustments, patients in the treated group were 0.91 (95% CI 0.74-1.13) as likely to have an incident fracture as the comparison patients (p=0.388). The treatment effect remained non-significant after accounting for MPR.

CONCLUSIONS

In this analysis of a community cohort of post-menopausal women at risk, the fracture risk of patients who received bisphosphonates did not differ significantly from those who did not. An enhanced understanding of this lack of treatment effect is urgently needed.

Identification of novel PPARgamma target genes by integrated analysis of ChIP-on-chip and microarray expression data during adipocyte differentiation

PPARgamma (peroxisome proliferator-activated receptor gamma) acts as a key molecule of adipocyte differentiation, and transactivates multiple target genes involved in lipid metabolic pathways. Identification of PPARgamma target genes will facilitate to predict the extent to which the drugs can affect and also to understand the molecular basis of lipid metabolism. Here, we have identified five target genes regulated directly by PPARgamma during adipocyte differentiation in 3T3-L1 cells using integrated analyses of ChIP-on-chip and expression microarray. We have confirmed the direct PPARgamma regulation of five genes by luciferase reporter assay in NIH-3T3 cells. Of these five genes Hp, Tmem143 and 1100001G20Rik are novel PPARgamma targets. We have also detected PPREs (PPAR response elements) sequences in the promoter region of the five genes computationally. Unexpectedly, most of the PPREs detected proved to be atypical, suggesting the existence of more atypical PPREs than previously thought in the promoter region of PPARgamma regulated genes.