Postmenopausal population is at increased risk of musculoskeletal impairments. Sarcopenia and osteoporosis are associated with significant morbidity and social and health-care costs. These two conditions are uniquely linked with similarities in pathophysiology and diagnostic methods. Uniform diagnostic criteria for sarcopenia are still evolving. Postmenopausal sarcopenia and osteoporosis share many environmental risk- and preventive factors. Moreover, geriatric frailty syndrome may result from interaction of osteoporosis and sarcopenia and may lead to increased mortality. The present paper reviews the factors in evolution of postmenopausal sarcopenia and osteoporosis.
Human aging is characterized by both physical and physiological frailty. A key feature of frailty, sarcopenia is the age-associated decline in skeletal muscle mass, strength, and endurance that characterize even the healthy elderly. Increases in adiposity, particularly in visceral adipose tissue, are almost universal in aging individuals and can contribute to sarcopenia and insulin resistance by increasing levels of inflammatory cytokines known collectively as adipokines. Aging also is associated with declines in adaptive and innate immunity, known as immune senescence, which are risk factors for cancer and all-cause mortality. The cytokine interleukin-15 (IL-15) is highly expressed in skeletal muscle tissue and declines in aging rodent models. IL-15 inhibits fat deposition and insulin resistance, is anabolic for skeletal muscle in certain situations, and is required for the development and survival of natural killer (NK) lymphocytes. We review the effect that adipokines and myokines have on NK cells, with special emphasis on IL-15. We posit that increased adipokine and decreased IL-15 levels during aging constitute a common mechanism for sarcopenia, obesity, and immune senescence.
Skeletal muscle; adipose tissue; Sarcopenia; obesity; immunity; natural killer lymphocytes; aging
Metabolic syndrome comprises a cluster of cardiovascular risk factors (hypertension, altered glucose metabolism, dyslipidemia, and abdominal obesity) that occur in obese children. However, metabolic syndrome can also occur in lean individuals, suggesting that obesity is a marker for the syndrome, not a cause. Metabolic syndrome is difficult to define, due to its nonuniform classification and reliance on hard cutoffs in the evaluation of disorders with non-Gaussian distributions. Defining the syndrome is even more difficult in children, owing to racial and pubertal differences and lack of cardiovascular events. Lipid partitioning among specific fat depots is associated with insulin resistance, which can lead to mitochondrial overload and dysfunctional subcellular energy use and drive the various elements of metabolic syndrome. Multiple environmental factors, in particular a typical Western diet, drive mitochondrial overload, while other changes in Western society, such as stress and sleep deprivation, increase insulin resistance and the propensity for food intake. These culminate in an adverse biochemical phenotype, including development of altered glucose metabolism and early atherogenesis during childhood and early adulthood.
metabolic syndrome; obesity; diet; insulin resistance; reactive oxygen species
Multiple factors of metabolic syndrome have been implicated in the pathogenesis of Alzheimer's disease (AD), including abdominal obesity, insulin resistance, endocrine dysfunction and dyslipidemia. High fat diet, a common experimental model of obesity and metabolic syndrome, has been shown to accelerate cognitive decline and AD-related neuropathology in animal models. However, sex interacts with the metabolic outcomes of high fat diet and, therefore, may alter neuropathological consequences of dietary manipulations. This study examines the effects of sex and high fat diet on metabolic and AD-related neuropathological outcomes in 3xTg-AD mice. Three month-old male and female 3xTg-AD mice were fed either standard or high fat diets for 4 months. Obesity was observed in all high fat fed mice; however, ectopic fat accumulation, hyperglycemia and hyperinsulinemia were observed only in males. Interestingly, despite the different metabolic outcomes of high fat diet, the neuropathological consequences were similar: both male and female mice maintained under high fat diet exhibited significant worsening in behavioral performance and hippocampal accumulation of β-amyloid protein. Because high fat diet resulted in obesity and increased AD-like pathology in both sexes, these data support a role of obesity-related factors in promoting AD pathogenesis.
Metabolic syndrome is a disorder characterized by abdominal obesity, hypertension, increased triglycerides, decreased HDL cholesterol and increased blood glucose. Accumulating evidence strongly indicates that insulin resistance and an increased amount of abdominal fat are the pathogenic factors for the characteristics of metabolic syndrome. The metabolic syndrome is characterized by an increased risk for the development of cardiovascular disease and type 2 diabetes mellitus. Studies indicate that sleep apnea may be a manifestation of the metabolic syndrome. It has also been suggested that the metabolic syndrome or "syndrome X" should also comprise obstructive sleep apnea and should then be called syndrome "Z". It appears that obstructive sleep apnea and the metabolic syndrome are characterized by the same pathophysiologic environment, which increases the risk for the development of cardiovascular disease. The increased amount of visceral fat and the accompanying insulin resistance seem to be the main characteristics responsible for the development of obstructive sleep apnea and the metabolic syndrome.
metabolic syndrome; sleep apnea; obstructive sleep apnea; obesity
Frailty is a geriatric syndrome of impaired resistance to stressors due to a decline in physiologic reserve. Frailty and cardiovascular disease (CVD) share a common biological pathway, and CVD may accelerate the development of frailty. Frailty is identified in 25% to 50% of patients with CVD, depending on the frailty scale used and the population studied. Frail patients with CVD, especially those undergoing invasive procedures or suffering from coronary artery disease and heart failure, are more likely to suffer adverse outcomes as compared to their non-frail counterparts. Five-meter gait speed is a simple and effective way of objectively measuring frailty in patients with CVD and should be incorporated in risk assessment.
Aging; Frailty; Cardiovascular diseases; Cardiac surgery
Atherogenic dyslipidemia comprises a triad of increased blood concentrations of small, dense low-density lipoprotein (LDL) particles, decreased high-density lipoprotein (HDL) particles, and increased triglycerides. A typical feature of obesity, the metabolic syndrome, insulin resistance, and type 2 diabetes mellitus, atherogenic dyslipidemia has emerged as an important risk factor for myocardial infarction and cardiovascular disease. A number of genes have now been linked to this pattern of lipoprotein changes. Low-carbohydrate diets appear to have beneficial lipoprotein effects in individuals with atherogenic dyslipidemia, compared to high-carbohydrate diets, whereas the content of total fat or saturated fat in the diet appears to have little effect. Achieving a better understanding of the genetic and dietary influences underlying atherogenic dyslipidemia may provide clues to improved interventions to reduce the risk of cardiovascular disease in high-risk individuals.
Lipids; Lipoproteins; Cardiovascular diseases; Genetics
The metabolic syndrome is a highly prevalent clinical entity. The recent Adult Treatment Panel (ATP III) guidelines have called specific attention to the importance of targeting the cardiovascular risk factors of the metabolic syndrome as a method of risk reduction therapy. The main factors characteristic of this syndrome are abdominal obesity, atherogenic dyslipidemia, elevated blood pressure, insulin resistance (with or without glucose intolerance), prothrombotic and proinflammatory states. An insulin resistance following nuclear peroxisome proliferator activated receptors (PPAR) deactivation (mainly obesity-related) is the key phase of metabolic syndrome initiation. Afterwards, there are 2 principal pathways of metabolic syndrome development: 1) with preserved pancreatic beta cells function and insulin hypersecretion which can compensate for insulin resistance. This pathway leads mainly to the macrovascular complications of metabolic syndrome; 2) with massive damage of pancreatic beta cells leading to progressively decrease of insulin secretion and to hyperglycemia (e.g. overt type 2 diabetes). This pathway leads to both microvascular and macrovascular complications. We suggest that a PPAR-based appraisal of metabolic syndrome and type 2 diabetes may improve our understanding of these diseases and set a basis for a comprehensive approach in their treatment.
Metabolic syndrome; Diabetes mellitus; Peroxisome proliferator activated receptors (PPAR); Obesity; Insulin resistance
The metabolic syndrome, a constellation of interrelated risk factors for cardiovascular disease and type 2 diabetes mellitus, has become a major public health concern against the backdrop of increasing rates of obesity. Insulin resistance plays a pivotal role as the underlying pathophysiological linchpin of the various components of the syndrome. The metabolic syndrome is well recognized in adults, and there is convincing evidence that it starts in childhood, with progressive clustering of the various components over time and tracking through adulthood. Adult women and adolescents with polycystic ovary syndrome (PCOS) have higher prevalence rates of the metabolic syndrome compared with the general population. Several anthropometric (obesity, particularly abdominal obesity), metabolic (insulin resistance/hyperinsulinemia, dyslipidemia) and hormonal (low IGFBP1, IGFBP2 and low sex hormone binding globulin) features of adolescents with PCOS are also features of the metabolic syndrome. Insulin resistance, believed to be a key pathogenic factor in both PCOS and the metabolic syndrome, may be the thread that links the two conditions. Menstrual health in adolescents could be viewed as yet another component in the evaluation of the metabolic syndrome. Careful assessment of menstrual history and appropriate laboratory work-up could reveal the presence of PCOS in obese at-risk adolescent girls with a family history of the metabolic syndrome.
adolescents; menstrual cycle; metabolic syndrome
Metabolic syndrome is defined by a cluster of different metabolic risk
factors that include overall and central obesity, elevated fasting glucose
levels, dyslipidemia, hypertension, and intimal atherogenesis. Metabolic
syndrome leads to increased risk for the development of type 2 diabetes and
cardiovascular disease (e.g., heart disease and stroke). The exacerbated
progression of metabolic syndrome to cardiovascular disease has lead to intense
study of the physiological ramifications of metabolic syndrome on the blood
vasculature. These studies have particularly focused on the signaling and
architectural alterations that manifest in hypertension and atherosclerosis.
However, despite the overlap of metabolic syndrome pathology with lymphatic
function, tangent effects on the lymphatic system have not been extensively
documented. In this review, we discuss the current status of metabolic syndrome
and provide evidence and remaining challenges in the connection between the
lymphatic system, lipid transport, obesity, insulin resistance, and general
metabolic syndrome; lymphatic pump; lymphatics and lipid transport; inflammation
The metabolic syndrome is a clustering of cardiovascular risk factors, including insulin resistance, abdominal obesity, dyslipidemia, and hypertension, and is associated with other comorbidities such as a proinflammatory state and nonalcoholic fatty liver disease (NAFLD). Its prevalence is high, especially among developed countries, and mainly reflects overnutrition and sedentary lifestyle. Moreover, the developing countries are not spared, as obesity and its related problems such as the metabolic syndrome are increasing quickly. We review the potential primary role of skeletal muscle insulin resistance in the pathophysiology of the metabolic syndrome, showing that in lean, young, insulin-resistant individuals, impaired muscle glucose transport and glycogen synthesis redirect energy derived from carbohydrate into hepatic de novo lipogenesis, promoting the development of atherogenic dyslipidemia and NAFLD. The demonstration of a link between skeletal muscle insulin resistance and the metabolic syndrome offers opportunities in targeting early defects in muscle insulin action in order to counteract the development of the disease and its related complications.
intramyocellular lipids; muscle glycogen synthesis; hepatic de novo lipogenesis; mitochondrial dysfunction; physical activity
Overweight and obesity in youth is a worldwide public health problem. Overweight and obesity in childhood and adolescents have a substantial effect upon many systems, resulting in clinical conditions such as metabolic syndrome, early atherosclerosis, dyslipidemia, hypertension and type 2 diabetes (T2D). Obesity and the type of body fat distribution are still the core aspects of insulin resistance and seem to be the physiopathologic links common to metabolic syndrome, cardiovascular disease and T2D. The earlier the appearance of the clustering of risk factors and the higher the time of exposure, the greater will be the chance of developing coronary disease with a more severe endpoint. The age when the event may occur seems to be related to the presence and aggregation of risk factors throughout life.
The treatment in this age-group is non pharmacological and aims at promoting changes in lifestyle. However, pharmacological treatments are indicated in special situations.
The major goals in dietary treatments are not only limited to weight loss, but also to an improvement in the quality of life. Modification of risk factors associated to comorbidities, personal satisfaction of the child or adolescent and trying to establish healthy life habits from an early age are also important. There is a continuous debate on the best possible exercise to do, for children or adolescents, in order to lose weight. The prescription of physical activity to children and adolescents requires extensive integrated work among multidisciplinary teams, patients and their families, in order to reach therapeutic success.
The most important conclusion drawn from this symposium was that if the growing prevalence of overweight and obesity continues at this pace, the result will be a population of children and adolescents with metabolic syndrome. This would lead to high mortality rates in young adults, changing the current increasing trend of worldwide longevity. Government actions and a better understanding of the causes of this problem must be implemented worldwide, by aiming at the prevention of obesity in children and adolescents.
Obesity has significant implications for healthcare, since it is a major risk factor for both type 2 diabetes and the metabolic syndrome. This syndrome is a common and complex disorder combining obesity, dyslipidemia, hypertension, and insulin resistance. It is associated with high atherosclerotic cardiovascular risk, which can only partially be explained by its components. Therefore, to explain how obesity contributes to the development of metabolic and cardiovascular disorders, more and better insight is required into the effects of personal and environmental stress on disease processes. In this paper, we show that obesity is a chronic inflammatory disease, which has many molecular mechanisms in common with atherosclerosis. Furthermore, we focus on the role of oxidative stress associated with obesity in the development of the metabolic syndrome. We discuss how several stress conditions are related to inflammation and oxidative stress in association with obesity and its complications. We also emphasize the relation between stress conditions and the deregulation of epigenetic control mechanisms by means of microRNAs and show how this impairment further contributes to the development of obesity, closing the vicious circle. Finally, we discuss the limitations of current anti-inflammation and antioxidant therapy to treat obesity.
Obesity is a leading risk factor for metabolic syndrome whose further expression is non-alcoholic fatty liver disease. Metabolic syndrome is associated with a proinflammatory state that contributes to insulin resistance. Finally, a "metabolically benign obesity" that is not accompanied by insulin resistance has recently been postulated to exist.
To find whether any inflammation markers were independently associated with the presence of insulin resistance, evaluating specific anthropometric, ultrasonographic and laboratory parameters in a population of young adult obese subjects.
Of forty two young individuals, divided into two groups (with or without insulin resistance), were studied serum C-reactive protein and fibrinogen as indexes of chronic pro-inflammatory status. Body mass index, waist circumference and metabolic syndrome presence were assessed as part of the metabolic evaluation. Ultrasonography weighted visceral and subcutaneous abdominal fat thickness, spleen size as longitudinal diameter and liver hyperechogenicity.
Results and Discussion
Serum C-reactive protein and fibrinogen as well as spleen longitudinal diameter were significantly increased in the obese young with insulin resistance compared to non-insulin resistance group. Insulin resistance was significantly associated with hepatic steatosis score at sonography (r = 0.33, P = 0.03), spleen longitudinal diameter (r = 0.35, P = 0.02) and C-reactive protein (r = 0.38, P = 0.01), but not with body mass index, visceral or subcutaneous abdominal adipose tissue, waist circumference and fibrinogen (P = 0.18, 0.46, 0.33, 0.37 and 0.4, respectively). Steatosis score at sonography was well associated with spleen volume (rho = 0.40, P = 0.01) and C-reactive protein levels (rho = 0.49, P = 0.002). Metabolic syndrome was much more frequent in obese patients with insulin resistance. These findings show that in young adults the only abdominal adiposity without insulin resistance, plays a scarce role in determining hepatic steatosis as well as metabolic syndrome.
Increases in spleen size and CRP levels represent a reliable tool in diagnosing insulin resistance.
Growth hormone (GH) secretion and muscle mass decline from mid-puberty throughout life culminating in sarcopenia, frailty, decreased function and loss of independence.
Determine if an oral ghrelin mimetic (MK-677) would enhance GH secretion into the young adult range without serious adverse effects, prevent the decline of fat-free mass (FFM), and decrease abdominal visceral fat (AVF) in healthy older adults.
Two-year, double-blind, randomized, placebo-controlled, modified-crossover clinical trial.
General Clinical Research Center study performed at a University Hospital.
Sixty-five healthy men and women (on or off hormone replacement therapy) ages 60-81.
Oral administration of MK-677 (25 mg) or placebo once daily.
Growth hormone and insulin-like growth factor-I (IGF-I); FFM and AVF were the primary endpoints after one year of treatment. Other endpoints: weight, fat mass, insulin sensitivity, lipid and cortisol levels, bone mineral density, limb lean and fat mass, isokinetic strength, function and quality of life; all endpoints were assessed at baseline and every 6 months.
Study design (duration and subject number) not sufficient to evaluate functional endpoints in healthy elderly
Daily MK-677 significantly increased GH and IGF-I levels to those of healthy young adults without serious adverse effects. With placebo, mean (95% Cl) FFM decreased -0.5 (-1.1 to 0.2) kg, however, FFM increased 1.1 (0.7 to 1.5) kg with MK-677 (P<0.001, MK-677 vs. placebo); body cell mass as reflected by intracellular water decreased -1.0 (-2.1 to 0.2) kg with placebo, but increased 0.8 (-0.1 to 1.6) kg with MK-677 (P=0.021). There were no significant differences in AVF or total fat mass. However, the average increase in limb fat in the MK-677 group (1.1 kg) was greater than with placebo (0.24 kg); P=0.001. Body weight increased 0.8 (-0.3 to 1.8) kg with placebo and 2.7 (2.0 to 3.5) kg with MK-677 (P=0.003). Fasting blood glucose increased an average of 0.3 mmol/L (5 mg/dL) with MK-677 (P=0.015) and insulin sensitivity declined. The most frequent side effects were an increase in appetite that subsided within a few months and transient, mild lower extremity edema and muscle pain. Low density lipoprotein cholesterol decreased -0.14 (-0.27 to -0.01) mmol/L [-5.4 (-10.4 to -0.4) mg/dL] with MK-677 (P=0.026); there were no differences in total or high density lipoprotein cholesterol. Cortisol increased 47 (28 to 71) nmol/L [1.7 (1.0 to 2.6 µg/dL)] with MK-677 (P=0.020). Changes in bone mineral density consistent with increased bone remodeling occurred in MK-677-treated subjects. Increased FFM did not result in changes in strength or function. Two-year exploratory analyses confirmed the 1-year results.
The ghrelin mimetic MK-677 enhanced pulsatile GH secretion and significantly increased FFM over 12 months and was generally well tolerated. Long-term functional, and ultimately pharmaco-economic, studies in elderly adults are indicated.
Ghrelin; ghrelin mimetic; body composition; aging; sarcopenia; frailty; healthspan; growth hormone; growth hormone secretagogue
Sarcopenia, the age-related loss of skeletal muscle mass, is characterized by a deterioration of muscle quantity and quality leading to a gradual slowing of movement, a decline in strength and power, increased risk of fall-related injury, and, often, frailty. Since sarcopenia is largely attributed to various molecular mediators affecting fiber size, mitochondrial homeostasis, and apoptosis, the mechanisms responsible for these deleterious changes present numerous therapeutic targets for drug discovery. Resistance training combined with amino acid-containing supplements is often utilized to prevent age-related muscle wasting and weakness. In this review, we summarize more recent therapeutic strategies (myostatin or proteasome inhibition, supplementation with eicosapentaenoic acid (EPA) or ursolic acid, etc.) for counteracting sarcopenia. Myostatin inhibitor is the most advanced research with a Phase I/II trial in muscular dystrophy but does not try the possibility for attenuating sarcopenia. EPA and ursolic acid seem to be effective as therapeutic agents, because they attenuate the degenerative symptoms of muscular dystrophy and cachexic muscle. The activation of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) in skeletal muscle by exercise and/or unknown supplementation would be an intriguing approach to attenuating sarcopenia. In contrast, muscle loss with age may not be influenced positively by treatment with a proteasome inhibitor or antioxidant.
Obesity and dyslipidemia are emerging as major public health challenges in South Asian countries. The prevalence of obesity is more in urban areas than rural, and women are more affected than men. Further, obesity in childhood and adolescents is rising rapidly. Obesity in South Asians has characteristic features: high prevalence of abdominal obesity, with more intra-abdominal and truncal subcutaneous adiposity than white Caucasians. In addition, there is greater accumulation of fat at “ectopic” sites, namely the liver and skeletal muscles. All these features lead to higher magnitude of insulin resistance, and its concomitant metabolic disorders (the metabolic syndrome) including atherogenic dyslipidemia. Because of the occurrence of type 2 diabetes, dyslipidemia and other cardiovascular morbidities at a lower range of body mass index (BMI) and waist circumference (WC), it is proposed that cut-offs for both measures of obesity should be lower (BMI 23–24.9 kg/m2 for overweight and ≥25 kg/m2 for obesity, WC ≥80 cm for women and ≥90 cm for men for abdominal obesity) for South Asians, and a consensus guideline for these revised measures has been developed for Asian Indians. Increasing obesity and dyslipidemia in South Asians is primarily driven by nutrition, lifestyle and demographic transitions, increasingly faulty diets and physical inactivity, in the background of genetic predisposition. Dietary guidelines for prevention of obesity and diabetes, and physical activity guidelines for Asian Indians are now available. Intervention programs with emphasis on improving knowledge, attitude and practices regarding healthy nutrition, physical activity and stress management need to be implemented. Evidence for successful intervention program for prevention of childhood obesity and for prevention of diabetes is available for Asian Indians, and could be applied to all South Asian countries with similar cultural and lifestyle profiles. Finally, more research on pathophysiology, guidelines for cut-offs, and culturally-specific lifestyle management of obesity, dyslipidemia and the metabolic syndrome are needed for South Asians.
obesity; abdominal obesity; dyslipidemia; triglycerides; Asian Indians; high density lipoprotein cholesterol (HDL); South Asians; nutrition; physical activity; type 2 diabetes
Obesity is one of the constellation of factors that make up the definition of the metabolic syndrome. Metabolic syndrome is also associated with insulin resistance, dyslipidemia, hypertriglyceridemia, and type 2 diabetes mellitus. The presence of obesity and metabolic syndrome in men and women is also associated with increased risk of cardiovascular disease and hypertension. In men, obesity and metabolic syndrome are associated with reductions in testosterone levels. In women, obesity and metabolic syndrome is associated with increases in androgen levels. In men reductions in androgen levels is associated with inflammation. Androgen supplements reduce inflammation in men. In women, increases in androgens are associated with increases in inflammatory cytokines, and reducing androgens reduces inflammation. In this review the possibility that androgens may have different effects on metabolic syndrome and its sequelae in males and females will be discussed.
polycystic ovary syndrome; menopause; aging; inflammation; androgens; metabolic syndrome; postmenopausal hypertension
Metabolic syndrome is a cluster of cardiovascular risk factors including obesity, diabetes and dyslipidemia. Insulin resistance (IR) is at the core of metabolic syndrome. In adipose tissue and muscle, IR results in decreased insulin signaling, primarily affecting downstream phosphatidylinositol 3-kinase (PI3K)/Akt signaling. It was recently proposed that neurons can develop hyperinsulinemia-induced IR, which in turn results in injury to the peripheral and central nervous systems and is probably pathogenic in common neurological disorders such as diabetic neuropathy and Alzheimer’s disease (AD). This review presents evidence indicating that, similarly to insulin-dependent metabolically active tissues such as fat and muscle, neurons also develop IR and thus cannot respond to the neurotrophic properties of insulin, resulting in neuronal injury, subsequent dysfunction and disease states.
Sarcopenia often co-exists with obesity, and may have additive effects on insulin resistance. Sarcopenic obese individuals could be at increased risk for type 2 diabetes. We performed a study to determine whether sarcopenia is associated with impairment in insulin sensitivity and glucose homeostasis in obese and non-obese individuals.
We performed a cross-sectional analysis of National Health and Nutrition Examination Survey III data utilizing subjects of 20 years or older, non-pregnant (N = 14,528). Sarcopenia was identified from bioelectrical impedance measurement of muscle mass. Obesity was identified from body mass index. Outcomes were homeostasis model assessment of insulin resistance (HOMA IR), glycosylated hemoglobin level (HbA1C), and prevalence of pre-diabetes (6.0≤ HbA1C<6.5 and not on medication) and type 2 diabetes. Covariates in multiple regression were age, educational level, ethnicity and sex.
Sarcopenia was associated with insulin resistance in non-obese (HOMA IR ratio 1.39, 95% confidence interval (CI) 1.26 to 1.52) and obese individuals (HOMA-IR ratio 1.16, 95% CI 1.12 to 1.18). Sarcopenia was associated with dysglycemia in obese individuals (HbA1C ratio 1.021, 95% CI 1.011 to 1.043) but not in non-obese individuals. Associations were stronger in those under 60 years of age. We acknowledge that the cross-sectional study design limits our ability to draw causal inferences.
Sarcopenia, independent of obesity, is associated with adverse glucose metabolism, and the association is strongest in individuals under 60 years of age, which suggests that low muscle mass may be an early predictor of diabetes susceptibility. Given the increasing prevalence of obesity, further research is urgently needed to develop interventions to prevent sarcopenic obesity and its metabolic consequences.
Sarcopenia is the loss of skeletal muscle mass and function with aging. Although the term sarcopenia was first coined in 1989, its etiology is still poorly understood. Moreover, a consensus for defining sarcopenia continues to elude us. Sarcopenic changes in the muscle include losses in muscle fiber quantity and quality, alpha-motor neurons, protein synthesis rates, and anabolic and sex hormone production. Other factors include basal metabolic rate, increased protein dietary requirements, and chronic inflammation secondary to age-related changes in cytokines and oxidative stress. These changes lead to decreased overall physical functioning, increased frailty, falls risk, and ultimately the loss of independent living. Because the intertwining relationships of these factors are complex, effective treatment options are still under investigation. The published data on sarcopenia are vast, and this review is not intended to be exhaustive. The aim of this review is to provide an update on the current knowledge of the definition, etiology, consequences, and current clinical trials that may help address this pressing public health problem for our aging populations.
aging; muscle loss; nutrition; physical activity
We investigated the prevalence of sarcopenic obesity (SO) and its relationship with metabolic syndrome in a community-based elderly cohort in Korea.
RESEARCH DESIGN AND METHODS
In this study, 287 men and 278 women aged 65 or older were recruited. Sarcopenia was defined as the appendicular skeletal muscle mass (ASM) divided by height squared (Ht2) (kg/m2) or by weight (Wt) (%) of <1 SD below the sex-specific mean for young adults. Obesity was defined as a visceral fat area ≥100 cm2.
The prevalence of SO was 16.7% in men and 5.7% in women with sarcopenia defined by ASM/Ht2; however, it was 35.1% in men and 48.1% in women by ASM/Wt. Using ASM/Wt, the homeostasis model assessment of insulin resistance of subjects with SO was higher and they were at higher risk for metabolic syndrome (odds ratio [OR] 8.28 [95% CI 4.45–15.40]) than the obese (5.51 [2.81–10.80]) or sarcopenic group (2.64 [1.08–6.44]).
SO defined by ASM/Wt was more closely associated with metabolic syndrome than either sarcopenia or obesity alone.
Insulin resistance is the key feature of the “metabolic syndrome,” a cluster of risk factors for cardiovascular disease and diabetes that includes hypertension, dyslipidemia, obesity, and hyperglycemia. Existing treatments target individual metabolic syndrome components, and act non-specifically with respect to disease pathophysiology. Our goal is to understand the link between insulin resistance and the metabolic syndrome, and how to develop treatment approaches.
We present three cases of extreme, syndromic insulin resistance: lipodystrophy, autoantibodies to the insulin receptor, and mutations of the insulin receptor, with discussion of pathophysiology and treatment.
In lipodystrophy, insulin resistance is a direct consequence of leptin deficiency, and thus leptin replacement reverses metabolic syndrome abnormalities, including diabetes and hypertriglyeridemia. The insulin “receptoropathies”, including autoantibodies to the insulin receptor and insulin receptor mutations, are characterized by extreme insulin resistance and ovarian hyperandrogenism, without dyslipidemia or fatty liver disease. Autoantibodies to the insulin receptor can be treated using an immunosuppressive paradigm adapted from treatment of other autoimmune and neoplastic conditions. Leptin treatment has shown some success in treating hyperglycemia in insulin receptor mutations. Treatment for this condition remains inadequate, and novel therapies that bypass insulin receptor signaling, such as enhancers of brown adipose tissue, are needed.
We presented a clinical approach to treatment of syndromic insulin resistance. The study of rare diseases that replicate the metabolic syndrome, with clear-cut pathophysiology, allows the opportunity to understand novel physiology, and develop targeted therapies that may be applicable to the broader population with obesity, insulin resistance, and diabetes.
Insulin resistance; Metabolic syndrome; Lipodystrophy; Leptin; Type B insulin resistance; Insulin receptor mutation
The prevalence of insulin resistance, metabolic syndrome, and cardiovascular disease is greatest in older obese patients, and effective evidence-based treatment strategies are lacking.
A prospective controlled study was conducted on 24 older (65.5 ± 5.0 years) obese (body mass index, 34.3 ± 5.2 kg/m2) adults with clinically diagnosed metabolic syndrome. We examined the effect of exercise alone (EX) or exercise combined with moderate caloric restriction (−500 kcal, EX + CR) on metabolic and cardiovascular risk factors. Measures of insulin sensitivity assessed by euglycemic hyperinsulinemic clamp and by oral glucose tolerance test, lipid profiles, blood pressure, body composition, abdominal fat, and aerobic capacity were all obtained before and after the interventions.
Both groups experienced significant weight loss, but the reduction was greater in the EX + CR group than in the EX group (−6.8 ± 2.7 kg vs −3.7 ± 3.4 kg, respectively, p = .02). Both interventions improved insulin sensitivity (2.4 ± 2.4 mg/kg FFM/min and 1.4 ± 1.7 mg/kgFFM/min, respectively, p < .001) and indices of metabolic syndrome (systolic/diastolic blood pressure, waist circumference, glucose, and triglycerides; p < .05). High-density lipoprotein levels remained unchanged. Total abdominal, subcutaneous, and visceral fat; aerobic capacity; and total and low-density lipoprotein cholesterol were also improved. With the exception of weight loss and subcutaneous fat, there was no difference in the magnitude of improvement between the interventions.
These data suggest that exercise alone is an effective nonpharmacological treatment strategy for insulin resistance, metabolic syndrome, and cardiovascular disease risk factors in older obese adults.
Aging; Obesity; Diabetes; Impaired glucose tolerance
Prevalence of the metabolic syndrome has increased dramatically in recent years. Optimal patient care demands a multifaceted approach, with many individuals requiring several therapies to minimize the significant associated cardiovascular burden. The need for novel agents in the management of the metabolic syndrome is emphasized by the current lack of drugs to treat insulin resistance, one of the major components of the metabolic syndrome that has several deleterious consequences.
The objective of this review is to assess the emerging evidence for the potential use of K-111 in treatment of the metabolic syndrome.
K-111 is a peroxisome proliferator-activated receptor (PPAR)-alfa agonist that, in preclinical studies, has shown efficacy in improving insulin resistance, reducing bodyweight, and ameliorating atherogenic dyslipidemia. Preliminary evidence suggests that toxicity and adverse events are low.
The improvements in obesity and insulin resistance, together with other beneficial effects following activation of PPAR alfa by K-111 in preclinical models, are encouraging and offer several potential advantages over currently available therapies for patients with the metabolic syndrome. However, K-111 is at an early stage of development and establishment of its role will require full analysis of clinical trials carefully designed to determine its overall benefits in this increasingly important disease area.
BM 17.0744; cardiovascular diseases; insulin resistance; K-111; metabolic syndrome X; PPAR alfa