The intriguing connections of leptin to hyperparathyroidism

Musculoskeletal effects of obesity and bariatric surgery – a narrative review

Obesity affects several areas of the human body, leading to increased morbidity and mortality and the likelihood of other diseases, such as type 2 diabetes mellitus, cardiovascular diseases and musculoskeletal disorders. These conditions predispose to bone fractures and sarcopenic obesity, defined by the presence of an obesity-associated decrease in muscle mass and strength. Both bone fragility and sarcopenic obesity disease are consequences of several factors, such as a low degree of chronic inflammation, insulin resistance, hormonal changes, nutritional deficiencies, ectopic fat deposits and sedentary lifestyle. The diagnosis of obesity-related musculoskeletal disorders is limited by the lack of sarcopenia criteria and lower accuracy of bone mineral density measurement by dual-energy X-ray absorptiometry in overweight people. Reducing body weight provides undeniable benefits to this population, however treating cases of severe obesity with bariatric surgery can cause even greater damage to bone and muscle health, especially in the long term. The mechanisms involved in this process are not yet fully understood, but factors related to nutrient malabsorption and mechanical discharge as well as changes in gut hormones, adipokines and bone marrow adiposity should be taken into account. Depending on the surgical technique performed, greater musculoskeletal damage may occur, especially in cases of malabsorptive surgeries such as Roux-en-Y gastric bypass, when compared to restrictive techniques such as sleeve gastrectomy. This difference is probably due to greater weight loss, nutrient malabsorption and important hormonal changes that occur as a consequence of the diversion of intestinal transit and loss of greater absorptive surface. Thus, people undergoing bariatric procedures, especially malabsorptive ones, should have their musculoskeletal health supervised to allow early diagnosis and appropriate therapeutic interventions to prevent osteoporotic fractures and preserve the functionality of the skeletal muscles.

Substantial early changes in bone and calcium metabolism among adult pharmacoresistant epilepsy patients on a modified Atkins diet

Objective

The aim of this study was to investigate whether the modified Atkins diet (MAD), a variant of the ketogenic diet, has an impact on bone‐ and calcium (Ca) metabolism.

Methods

Two groups of adult patients with pharmacoresistant epilepsy were investigated. One, the diet group (n = 53), was treated with MAD for 12 weeks, whereas the other, the reference group (n = 28), stayed on their habitual diet in the same period. All measurements were performed before and after the 12 weeks in both groups. We assessed bone health by measuring parathyroid hormone (PTH), Ca, 25‐OH vitamin D (25‐OH vit D), 1,25‐OH vitamin D (1,25‐OH vit D), phosphate, alkaline phosphatase (ALP), and the bone turnover markers procollagen type 1 N‐terminal propeptide (P1NP) and C‐terminal telopeptide collagen type 1 (CTX‐1). In addition, we examined the changes of sex hormones (estradiol, testosterone, luteinizing hormone, follicle‐stimulating hormone), sex hormone‐binding globulin, and leptin.

Results

After 12 weeks of MAD, we found a significant reduction in PTH, Ca, CTX‐1, P1NP, 1,25‐OH vit D, and leptin. There was a significant increase in 25‐OH vit D. These changes were most pronounced among patients <37 years old, and in those patients with the highest body mass index (≥25.8 kg/m²), whereas sex and type of antiseizure medication had no impact on the results. For the reference group, the changes were nonsignificant for all the analyses. In addition, the changes in sex hormones were nonsignificant.

Significance

Twelve weeks of MAD treatment leads to significant changes in bone and Ca metabolism, with a possible negative effect on bone health as a result. A reduced level of leptin may be a triggering mechanism. The changes could be important for patients on MAD, and especially relevant for those patients who receive treatment with MAD at an early age before peak bone mass is reached.

Early Post-Transplant Leptin Concentration Changes in Kidney Transplant Recipients

Background and Objectives: Kidney transplant recipients represent a unique population with metabolic abnormalities, altered nutritional and immune status, as well as an imbalanced regulation of adipocytokine metabolism. Leptin is a hormonally active protein mainly produced by fat tissue that modulates appetite, satiety, and influences growth, energy, and bone metabolism. There has been great interest in the role of this hormone in chronic kidney disease-related protein energy wasting; thus, a positive leptin correlation with body mass index and fat mass was confirmed. This study was designed to determine the association of pre and post-kidney transplant leptin concentration with nutritional status and body composition. Materials and Methods: We studied 65 kidney transplant recipients. Nutritional status was evaluated before kidney transplantation and 6 months later using three different malnutrition screening tools (Subjective Global Assessment Scale (SGA), Malnutrition Inflammation Score (MIS), and Geriatric Nutritional Risk Index (GNRI)), anthropometric measurements, and body composition (bioelectrical impedance analysis (BIA)). Demographic profile, serum leptin levels, and other biochemical nutritional markers were collected. Statistical analysis was performed with R software. Results: Median age of the studied patients was 45 years, 42% were females, and 12% had diabetes. Leptin change was associated with body weight (p < 0.001), waist circumference (p < 0.001), fat mass (p < 0.001) and body fat percentage (p < 0.001), decrease in parathyroid hormone (PTH) (p < 0.001) transferrin (p < 0.001), diabetes mellitus (p = 0.010), and residual renal function (p = 0.039), but not dependent on dialysis vintage, estimated glomerular filtration rate (eGFR), or delayed graft function at any time during the study. After adjustment for age and sex, body mass index (BMI) (p < 0.001), fat mass (p < 0.001), and body fat percentage (p < 0.001) were independent variables significantly associated with post-transplant leptin change. Lower leptin values were found both before and after kidney transplantation in the SGA B group. GNRI as a nutritional status tool was strongly positively related to changes in leptin within the 6-month follow-up period. Conclusions: Kidney transplant recipients experience change in leptin concentration mainly due to an increase in fat mass and loss of muscle mass. GNRI score as compared to SGA or MIS score identifies patients in whom leptin concentration is increasing alongside an accumulation of fat and decreasing muscle mass. Leptin concentration evaluation in combination with BIA, handgrip strength measurement, and GNRI assessment are tools of importance in defining nutrition status in the early post-kidney transplant period.

Association Between Secondary Hyperparathyroidism and Body Composition in Pediatric Patients With Moderate and Advanced Chronic Kidney Disease

Objective: This single center cross-sectional study aims to investigate the association between secondary hyperparathyroidism and body composition in pediatric patients with moderate (stage 3) and advanced (stage 4-5) chronic kidney disease (CKD). Methods: 61 patients (median age: 13.4 years) were included. Body composition indices, including lean tissue index (LTI) and fat tissue index (FTI), were measured using multi-frequency bio-impedance spectroscopy. Muscle wasting was defined as LTI adjusted to height-age (HA) z-score < -1.65 SD and high adiposity as FTI z-score > 1.65 SD. Serum mineral metabolism parameters, including serum intact parathormone (iPTH), calcium, phosphorus and 25-hydroxyvitamin D, as well as serum leptin were measured in each patient. In advanced CKD patients, the mean values of serum mineral laboratory parameters of the 6 months prior to body composition assessment were recorded, and alfacalcidol index, defined as weekly alfacalcidol dose (mcg/week) per pg/ml of iPTH × 1,000, was calculated. Results: In moderate CKD (31 patients), high iPTH (>90 ng/ml) was observed in 10 (32.3%) patients and was associated with higher FTI z-score (p = 0.022). Moreover, serum iPTH was negatively correlated to LTI HA z-score (rs = -0.486, p = 0.006), and positively correlated to serum leptin levels (rs = 0.369, p = 0.041). The positive correlation between FTI z-score and iPTH (rs = 0.393, p = 0.039) lost significance after adjustment for serum leptin. iPTH was positively associated with high adiposity (12 patients, 38.7%) after adjustment for the other mineral metabolism parameters (OR 1.023, 95% CI 1.002-1.045, p = 0.028). In advanced CKD (30 patients), no significant correlation was observed between iPTH and body composition indices and serum leptin levels. Eleven (36.7%) patients with muscle wasting presented lower alfacalcidol index (p = 0.017). Alfacalcidol index ≤ 24 was strongly associated with muscle wasting after adjustment for CKD stage and other mineral metabolism parameters (OR 7.226, 95% CI 1.150-45.384, p = 0.035). Conclusion: Secondary hyperparathyroidism is associated with high adiposity in moderate but not in advanced CKD, with leptin acting as a potential contributive factor. In advanced CKD, targeting higher alfacalcidol weekly dose per each unit of serum PTH seems beneficial for preventing muscle wasting.

Update on the Crosstalk Between Adipose Tissue and Mineral Balance in General Population and Chronic Kidney Disease

Adipose tissue is nowadays considered as a major endocrine organ, which apart from controlling lipid metabolism, displays a significant role in energy expenditure, food intake and in the regulation of various systemic physiological processes. Adipose derived pro-inflammatory cytokines and adipokines, particularly leptin and adiponectin, provide inter-communication of adipose tissue with various metabolic pathways, ultimately resulting in a complex network of interconnected organ systems. Recent clinical and experimental research has been focused on exploring the direct interaction between adipokine profile and elements of mineral metabolism, including parathormone (PTH), fibroblast growth factor-23 (FGF23) and calcitriol. The emerging crosstalk between adipose tissue and calcium and phosphorus homeostasis suggests that metabolic disorders from one system may directly affect the other and vice versa. It is current knowledge that fat metabolism disturbance, commonly encountered in obese individuals, influences the expression of calciotriopic hormones in general population, while various clinical trials attempting to successfully achieve body fat loss by modulating mineral profile have been published. In chronic kidney disease (CKD) state, there is an increasing evidence suggesting that mineral disorders, influence adipose tissue and linked endocrine function. On the contrary, the impact of disturbed fat metabolism on CKD related mineral disorders has been also evocated in clinical studies. Recognizing the pathogenetic mechanisms of communication between adipose tissue and mineral balance is critical for understanding the effects of metabolic perturbations from the one system to the other and for identifying possible therapeutic targets in case of disrupted homeostasis in one of the two connected systems. To that end, this review aims to enlighten the recent advances regarding the interplay between mineral metabolism, fat mass and adipokine profile, based on in vitro, in vivo and clinical studies, in general population and in the course of CKD.

The functional nutritional and regulatory activities of calcium supplementation from eggshell for obesity disorders management

The present study was to investigate the effective role of renewable sources of Ca⁺² from eggshell (ES) with different doses to restrict obesity disorders. Rats were classified as follows, G₁ : normal diet for 26 weeks; G₂ : high-fat diet (HFD) for 26 weeks; G₃ , G₄ , and G₅ were supplemented with HFD for 16 weeks and treated with 7.2 g Ca⁺² ES/Kg rat chow, 18 g Ca⁺² ES/Kg rat chow, and 2% diet containing fat (DCF), respectively, for the remaining 10 weeks. Results revealed a significant effect of the low dose of Ca⁺² supplement in form of ES than high dose and 2% DCF; on basis of anthropometric parameters, lipid, leptin, adiponectin, thyroid hormones, Ca⁺² , 25-hydroxyl vitamin-D, and oxidative and inflammatory parameters were regulated. Results were confirmed with the histopathological study. Therefore, it was concluded that Ca⁺² supplementation can be used as a beneficial source for obesity management with anticholesterol actions. PRACTICAL APPLICATIONS: Obesity represented public health hazards. The eggshell is one of the waste products that contain a high percentage of Ca⁺² . The current data exposed using a low dose of ES as a new source of Ca⁺² supplement for treatment of HFD rats leads to significant enhancement of lipid profiles, liver enzymes, kidney functions, leptin, adiponectin, Ca⁺² , 25(OH)-D, TSH, fT_4, and PTH levels. Also, there was a reduction in weight gain, Bwt, BMI, BG, insulin, and HOMA-IR. Moreover, the oxidant-pro-oxidant system was improved in both hepatic and adipose tissues where NO and TBARS concentrations were diminished, and SOD specific activity was elevated. Additionally, TNF-α and ADAM17 expression were downregulated. Hence, it was concluded that there was good evidence that diets supplemented with ES were associated with the reduction of obesity complications especially regulating fat processing and storage in the body.

Cardiovascular consequences of parathyroid disorders in adults

PTH is a metabolic active hormone primarily regulating calcium and phosphate homeostasis in a very tight and short term-manner. Parathyroid disorders in adult patients reflect a variety of different conditions related either to the parathyroid glands itself or to the effects of the secreted hormone. The clinical spectrum varies from the common disease primary hyperparathyroidism (PHPT) to the orphan conditions pseudohypoparathyroidism (Ps-HypoPT) and chronic hypoparathyroidism (HypoPT). The purpose of this review is to describe the consequences of disturbances in levels or action of PTH for cardiac function and cardiovascular risk in adult patients with these disorders. Most patients with PHPT achieve the diagnose by chance and have minor or no specific symptoms. Still, these patients with mild PHPT do possess cardiovascular (CV) morbidity, however so far not proven ameliorated by surgery in controlled trials. In severe cases, the CV risk is increased and with a potential reversibility by treatment. Patients with Ps-HypoPT have resistance to PTH action, but not necessarily total resistance in all tissues. So far, no clear CV morbidity or risk has been demonstrated, but there are several aspects of interest for further studies. Most patients with HypoPT do get their hormonal deficiency syndrome following neck surgery. These patients do experience multiple symptoms and do have an increased CV-risk before the primary surgery. Based on existing data, their CV mortality do not deviate from the expected when adjusting for the preexisting increased risk. Patients with nonsurgical (NS-) HypoPT do demonstrate increased CV-risk also associated with exposure time. Endocrine disorders with alterations in PTH function have major impact on the cardiovascular system of importance for morbidity and mortality, wherefore management of these specific diseases should be optimized currently, as new data become available, however also avoiding over-treating asymptomatic patients.

Parathyroid hormone in surgery-induced weight loss: no glucometabolic effects but potential adaptive response to skeletal loading

PURPOSE

Increased parathyroid hormone (PTH) is commonly associated with obesity, and its role in the pathogenesis of obesity-related glucometabolic abnormalities is uncertain. We aimed to explore the relationships of PTH with glucose/insulin homeostasis parameters before and after bariatric surgery-induced weight loss, and whether they depend or not on 25-hydroxyvitamin D (25OHD) status.

METHODS

We included 42 subjects (27 women, aged 40 ± 5 years, BMI 48.5 ± 7.3 kg/m²) without diabetes, chronic kidney disease, or hyperparathyroidism undergoing sleeve gastrectomy. The following parameters were evaluated before and 6 months after surgery: circulating levels of PTH, calcium, phosphorus, 25OHD, leptin, insulin growth factor (IGF)-1; 75-g oral glucose tolerance test to derive measures of insulin sensitivity (ISI) and secretion (Stumvoll index); dual-energy X-ray absorptiometry to assess fat distribution and bone mineral density.

RESULTS

Weight loss was accompanied by significant reduction of PTH levels (77.9 ± 19.1 vs. 60.5 ± 13.4 pg/ml; p = 0.005), without concomitant modification of 25OHD status. Both baseline PTH and its postoperative percent change resulted associated, with baseline fat mass (β = 0.615, p = 0.003) and its concurrent postoperative reduction (r = 0.419; p = 0.006), but neither with glucose homeostasis parameters nor their respective variations after weight loss. Interestingly, leptin reduction after weight loss was independently related to PTH change (β = 0.396, p = 0.015) and IGF-1 levels (β = 0.176, p = 0.059).

CONCLUSIONS

Circulating PTH decreases with fat mass reduction independent of 25OHD status, but it  is not associated with improvement of insulin resistance and related metabolic parameters. Leptin and PTH may mediate the cross-talk between adipose tissue and parathyroid glands, which possibly contributes to bone adaptation to excess body weight.