ACTION OF LEPTIN ON BONE AND ITS RELATIONSHIP TO MENOPAUSE

Linking metabolic syndrome with low bone mass through insights from BMI and health behaviors

The objective of this study is to investigate the relationship between metabolic syndrome (MetS), and bone density in a 30- to 50-year-old Taiwanese population, and to explore the combined effects of BMI and health behaviors on this association. A total of 52,912 individuals aged 30-50 years from the Taiwan Biobank were included in this cross-sectional study. Bone density status was assessed using quantitative ultrasound (QUS). The joint effect was assessed by including an interaction term in the multi-logistic regression models to test the association between MetS, BMI, and bone density while controlling for potential confounders. MetS was associated with reduced bone density, with the risk of severe low bone density (SLBD) higher among BMI < 24 kg/m2 individuals with MetS (adjusted odds ratio [aOR] 1.5, 95% confidence interval [CI] 1.09-2.16), while the risk was not significant among BMI ≥ 24 kg/m2 individuals with MetS. Smoking, alcohol consumption, and lack of regular exercise among individuals with a BMI < 24 kg/m2 and MetS were associated with higher risk of severe low bone density (SLBD), the aORs (95%CI) were 2.9 (1.59-5.20), 2.1 (1.06-4.22), and 1.8 (1.24-2.54) respectively. Our study suggests that metabolic syndrome could increase the risk of severe low bone density, but this risk can be minimized through higher BMI, non-smoking, no alcohol consumption, and regular exercise. Conversely, smoking, alcohol consumption or lack of regular exercise may exacerbate the risk of severe low bone density. These findings highlight the importance of a multifactorial approach in managing bone healthcare.

The Head-to-Toe Hormone: Leptin as an Extensive Modulator of Physiologic Systems

Leptin is a well-known hunger-sensing peptide hormone. The role of leptin in weight gain and metabolic homeostasis has been explored for the past two decades. In this review, we have tried to shed light upon the impact of leptin signaling on health and diseases. At low or moderate levels, this peptide hormone supports physiological roles, but at chronically higher doses exhibits detrimental effects on various systems. The untoward effects we observe with chronically higher levels of leptin are due to their receptor-mediated effect or due to leptin resistance and are not well studied. This review will help us in understanding the non-anorexic roles of leptin, including their contribution to the metabolism of various systems and inflammation. We will be able to get an alternative perspective regarding the physiological and pathological roles of this mysterious peptide hormone.

Leptin and its cardiovascular effects: Focus on angiogenesis

Leptin is an endocrine hormone synthesized by adipocytes. It plays a key role in the energy homeostasis in central and peripheral tissues and has additional roles are attributed to it, such as the regulation of reproduction, immune function, bone homeostasis, and angiogenesis. The plasma concentration of leptin significantly increases in obese individuals. In the present review, we give an introduction concerning leptin, its receptors, signaling pathways, and its effect on cardiovascular system, especially on angiogenesis.

Similar and additive effects of ovariectomy and diabetes on insulin resistance and lipid metabolism

Type 2 diabetes mellitus (T2DM) is among the leading causes of death in postmenopausal women. The disruption of ovarian function may contribute to the incidence of T2DM. The purpose of this study was to investigate the effects of ovariectomy and T2DM on glucose and lipid homeostasis, perilipin levels in adipose tissues, as a lipolytic regulator, and levels of certain adipokines. Ovariectomized (OVX) rats were used as a model for postmenopausal women. The study was performed on sham, OVX, sham diabetic, and OVX diabetic female rats. The results indicated that ovariectomy alters adipose tissue metabolism through reducing perilipin content in white adipose tissue (WAT); however it has no effect on perilipin level in brown adipose tissue (BAT). OVX diabetic females suffer from serious metabolic disturbances, suggested by exacerbation of insulin resistance in terms of disrupted lipid profile, higher HOMA-IR, hyperinsulinemia, higher leptin, and lower adiponectin concentrations. These metabolic derangements may underlie the predisposition for cardiovascular disease in women after menopause. Therefore, for efficient treatment, the menopausal status of diabetic female should be addressed, and the order of events is of great importance because ovariectomy following development of diabetes has more serious complications compared to development of diabetes as result of menopause.

Obesity: Friend or foe for osteoporosis

Osteoporosis and obesity are worldwide health problems. Interestingly, both are associated with significant morbidity and mortality. Both the diseases have common linkage as bone marrow mesenchymal stromal cells are the common precursors for both osteoblasts and adipocytes. Aging may shift composition of bone marrow by increasing adipocytes, osteoclast activity, and decreasing osteoblast activity, resulting into osteoporosis. Adipocytes secret leptin, adiponectin, adipsin, as well as proinflammatory cytokines, that contributes in pathogenesis of osteoporosis. This new concept supports the hypothesis, that the positive correlation of weight and body mass index (BMI) with bone mineral density (BMD) is not confirmed by large population-based studies. Thus, the previous concept, that obesity is protective for osteoporosis may not stand same as bone marrow fat deposition (adipogenesis) seen in obesity, is detrimental for bone health.

Association between serum osteocalcin and insulin resistance in postmenopausal, but not premenopausal, women in Korea

OBJECTIVE

Menopause is known to compound cardiometabolic disease risk factors, and a deeper understanding of the mechanism of this effect is needed. Recently, the osteoblast-derived protein osteocalcin was found to function as a regulator of glucose and fat metabolism. However, there is a lack of studies comparing the extent of association between osteocalcin and glucose metabolism in postmenopausal versus premenopausal women.

METHODS

To examine the relationship between serum osteocalcin and glucose metabolism in premenopausal versus postmenopausal women, we identified well-balanced pairs of premenopausal and postmenopausal women matched on propensity score. The interactions between serum osteocalcin levels and menopause status on fasting glucose, fasting insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) and the associations of these parameters with serum osteocalcin levels in premenopausal and postmenopausal women were statistically analyzed.

RESULTS

Among the 61 matched pairs of premenopausal and postmenopausal women, significant interactions of menopause status and serum osteocalcin levels were observed for fasting insulin (P = 0.031) and HOMA-IR (P = 0.019). Furthermore, after logarithmical transformation for each variable, significant relationships between serum osteocalcin levels and fasting insulin (r = -0.307, P = 0.016) and HOMA-IR (r = -0.298, P = 0.019) were found in postmenopausal women, but no significant correlation was seen in premenopausal women (r = 0.002, P = 0.989 and r = 0.062, P = 0.633, respectively).

CONCLUSIONS

Our study shows that the association between serum osteocalcin and insulin resistance varies according to menopause status, and that serum osteocalcin is associated with insulin resistance in postmenopausal women but not in premenopausal women. As postmenopausal women have a higher prevalence of obesity and other cardiac risk factors, the potential endocrine actions of osteocalcin may serve as a marker of metabolism in menopause status. Further studies are needed to define the precise nature of the relationship between osteocalcin and insulin resistance in postmenopausal women.

The complex interaction between obesity, metabolic syndrome and reproductive axis: a narrative review

The aim of this narrative review is to provide current evidence for the interaction between obesity, metabolic syndrome (MS) and reproductive axis. Gonadotropin-releasing hormone (GnRH) pulses and, consequently, normal function of reproductive (hypothalamus-pituitary-gonadal) axis depend on normal energy balance, which presupposes sufficient food intake, reasonable energy consumption and average thermoregulatory costs. In case of an energy imbalance, reproductive dysfunction may occur. In young women, excessive leanness is accompanied by puberty delay, whereas premature puberty might be a manifestation of obesity. In a similar way, obesity in men affects fertility. Excess adipose tissue results in increased conversion of testosterone to estradiol, which may lead to secondary hypogonadism through reproductive axis suppression. Moreover, oxidative stress at the level of the testicular micro-environment may result in decreased spermatogenesis and sperm damage. Products of the adipocyte, such as leptin, adiponectin and resistin, and gut peptides, such as ghrelin, are considered to be crucial in the interaction between energy balance and reproduction. Finally, an indirect evidence for the interplay between MS and reproductive axis is the fact that when treating components of one, parameters of the other can be improved as well. These therapeutic interventions include lifestyle modifications, pharmacological agents, such as sex hormone replacement therapy, and surgical procedures. Although many issues remain unclear, the elucidation of the complex interaction between MS and reproductive axis will have obvious clinical implications in the therapeutic approach of both entities.

Association between obesity, metabolic risks and serum osteocalcin level in postmenopausal women

BACKGROUND

Osteocalcin, a marker of bone formation, is also known as a regulator of glucose and fat mass. The purpose of this study was to determine the association between obesity, metabolic risks and serum osteocalcin in postmenopausal women.

METHODS

We selected 214 postmenopausal women and determined serum osteocalcin, fasting plasma glucose (FPG), fasting insulin, high-sensitivity C-reactive protein (hs-CRP), the homeostasis model assessment of insulin resistance (HOMA-IR), lipid profile, and anthropometric values (body mass index [BMI], waist-to-hip ratio [WHR], body fat, and visceral fat area [VFA]).

RESULTS

After adjustment for age and years since menopause, WHR and VFA were negatively correlated with serum osteocalcin, but BMI did not show a significant correlation. Serum osteocalcin was negatively correlated with fasting insulin and HOMA-IR, but FPG, lipid profile, and blood pressure did not show a significant correlation. Based on multiple regression analysis, age and HOMA-IR were the most important predictors of osteocalcin.

CONCLUSION

Our study showed that serum osteocalcin has some significance as an indicator of metabolic risk, including abdominal obesity and insulin resistance. Bone as well as adipose tissue may be an active organ that regulates energy metabolism. A larger study will be needed to clarify the potential of osteocalcin as an indicator of cardiovascular disease.