[Leptin as a neuroprotector and functional stability factor in the central neural system]

Adipokines secreted by adipose tissue are recognized to be crucial for the regulation and maintenance of energy homeostasis. Leptin is the best characterized adipokine involved in energy metabolism and inflammatory status, being associated with the development of a number of diseases, including atherosclerosis, diabetes, certain cancers and immune-mediated processes. Recently leptin was found to exert neurotrophic effects and neuroprotective activity slowing down neuronal damage after acute brain injuries as well as during long-term neurodegenerative processes. Moreover there are the evidences that leptin influences receptor signalling as well as the synthesis and releasing of several neurotransmitters. The aim of this review is to discuss the role of leptin in the neuroprotection and the regulation of diverse neuronal functions in the health and disease.

Leptin action in the ventromedial hypothalamic nucleus is sufficient, but not necessary, to normalize diabetic hyperglycemia

In rodent models of type 1 diabetes, leptin administration into brain ventricles normalizes blood glucose at doses that have no effect when given peripherally. The ventromedial nucleus of the hypothalamus (VMN) is a potential target for leptin's antidiabetic effects because leptin-sensitive neurons in this brain area are implicated in glucose homeostasis. To test this hypothesis, we injected leptin directly into the bilateral VMN of rats with streptozotocin-induced uncontrolled diabetes mellitus. This intervention completely normalized both hyperglycemia and the elevated rates of hepatic glucose production and plasma glucagon levels but had no effect on tissue glucose uptake in the skeletal muscle or brown adipose tissue as measured using tracer dilution techniques during a basal clamp. To determine whether VMN leptin signaling is required for leptin-mediated normalization of diabetic hyperglycemia, we studied mice in which the leptin receptor gene was deleted in VMN steroidogenic factor 1 neurons using cre-loxP technology. Our findings indicate leptin action within these neurons is not required for the correction of diabetic hyperglycemia by central leptin infusion. We conclude that leptin signaling in the VMN is sufficient to mediate leptin's antidiabetic action but may not be necessary for this effect. Leptin action within a distributed neuronal network may mediate its effects on glucose homeostasis.

Adipokines in the HIV/HAART-associated lipodystrophy syndrome

The use of highly active antiretroviral therapy (HAART) in the treatment of human immunodeficiency virus has dramatically altered both the landscape of this disease and the prognosis for those affected. With more patients now receiving HAART, adverse effects such as lipodystrophy and metabolic syndrome have emerged. In HIV/HAART-associated lipodystrophy syndrome (HALS), patients demonstrate fat maldistribution with dyslipidemia, insulin resistance, and other metabolic complications. Recent studies have contributed to the elucidation of the pathophysiological abnormalities seen in this syndrome and have provided guidance for the study and use of potential treatments for these patients, but widely accepted guidelines have not yet been established. Two adipokines, leptin and adiponectin, are decreased in patients with HALS and lipoatrophy or lipodystrophy. Further, recent proof-of-concept clinical trials have proven the efficacy of leptin replacement and medications that increase circulating adiponectin levels in improving the metabolic profile of HALS patients. This review article highlights recent evidence on leptin replacement and compares leptin's efficacy to that of other treatments, including metformin and thiazolidinediones, on metabolic abnormalities such as impaired insulin-glucose homeostasis associated with lipodystrophy in patients receiving HAART. It is hoped that forthcoming large phase III clinical trials will allow the addition of leptin to our therapeutic armamentarium for use in patients suffering from this disease state.

The role of leptin in obesity and the potential for leptin replacement therapy

Leptin (from the Greek word "lepto'' meaning "thin") is a 167-amino acid peptide hormone encoded by the obesity (ob) gene and secreted by white adipocytes. Blood leptin concentrations are increased in obese individuals. Leptin is a satiety hormone that provides negative feedback to the hypothalamus, controlling appetite and energy expenditure. Leptin binds to presynaptic GABAergic neurons to produce its effect, raising the distinct possibility that GABAergic axon terminals are the ultimate subcellular site of action for its effects. Released into the circulation, leptin crosses the blood-brain barrier and binds to leptin receptors, influencing the activity of various hypothalamic neurons, as well as encoding orexigenic and anorexigenic neuropeptides. Moreover, leptin affects a wide range of metabolic functions in the peripheral tissue. In this review, we discuss some physiologic functions of leptin, including effects on obesity and some effects of leptin replacement therapy.

Leptin administration enhances islet transplant performance in diabetic mice

Islet transplantation is an effective method to obtain long-term glycemic control for patients with type 1 diabetes, yet its widespread use is limited by an inadequate supply of donor islets. The hormone leptin has profound glucose-lowering and insulin-sensitizing action in type 1 diabetic rodent models. We hypothesized that leptin administration could reduce the dose of transplanted islets required to achieve metabolic control in a mouse model of type 1 diabetes. We first performed a leptin dose-response study in C57Bl/6 mice with streptozotocin (STZ)-induced diabetes to determine a leptin dose insufficient to reverse hyperglycemia. Subsequently, we compared the ability of suboptimal islet transplants of 50 or 125 syngeneic islets to achieve glycemic control in STZ-induced diabetic C57Bl/6 mice treated with or without this dose of leptin. The dose-response study revealed that leptin reverses STZ-induced diabetes in a dose-dependent manner. Supraphysiological leptin levels were necessary to restore euglycemia but simultaneously increased risk of hypoglycemia, and also lost efficacy after 12 days of administration. In contrast, 1 µg/day leptin only modestly reduced blood glucose but maintained efficacy throughout the study duration. We then administered 1 µg/day leptin to diabetic mice that underwent transplantation of 50 or 125 islets. Although these islet doses were insufficient to ameliorate hyperglycemia alone, coadministration of leptin with islet transplantation robustly improved control of glucose and lipid metabolism, without increasing circulating insulin levels. This study reveals that low-dose leptin administration can reduce the number of transplanted islets required to achieve metabolic control in STZ-induced diabetic mice.

The liver diseases of lipodystrophy: the long-term effect of leptin treatment

BACKGROUND & AIMS

Lipodystrophies are hypoleptinemic conditions characterized by fat loss, severe insulin resistance, hypertriglyceridemia, and ectopic fat accumulation. Non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) are also features of this condition. We studied the spectrum of liver disease in lipodystrophy and the effects of leptin replacement.

METHODS

This was an open-label, prospective study of leptin therapy in patients with inherited and acquired lipodystrophy at the National Institutes of Health. Liver biopsies were performed at baseline (N=50) and after leptin replacement (N=27). NASH activity was assessed using the NASH Clinical Research Network (CRN) scoring system. Fasting blood glucose, triglyceride, hemoglobin A1c and liver enzymes were measured at baseline and at the time of the final liver biopsy.

RESULTS

In leptin-treated patients, 86% met criteria for NASH at baseline, while only 33% had NASH after leptin replacement for 25.8 ± 3.7 months (mean ± SE, p=0.0003). There were significant improvements in steatosis grade (reduction of mean score from 1.8 to 0.9) and ballooning injury scores (from 1.2 to 0.4), with a 44.2% reduction in mean NAFLD activity score (p<0.0001). Patients who already had fibrosis remained stable on leptin replacement. We observed significant improvement in metabolic profile, ALT and AST. In addition to NASH, four patients with acquired generalized lipodystrophy (AGL) had autoimmune hepatitis.

CONCLUSIONS

The fundamental liver disease of lipodystrophy is NASH, although autoimmune hepatitis was observed in some patients with AGL. Leptin appears to be a highly effective therapy for NASH in hypoleptinemic lipodystrophic patients.

Leptin therapy in type 2 diabetes

There is a pressing need for new effective therapeutic strategies for addressing the epidemic of type 2 diabetes. Leptin has been shown to reduce hyperglycaemia in rodent models of type 1 diabetes and has recently been shown to normalize fasting plasma glucose concentrations in a rodent model of polygenic obesity and type 2 diabetes. Overall, these findings suggest that leptin may be an effective therapeutic option for both type 1 and type 2 diabetes. However, short-term human clinical studies in overweight and obese patients with recently diagnosed type 2 diabetes have reported minimal efficacy of leptin administration to lower blood glucose levels. Herein, the role of leptin in the maintenance of glucose homeostasis and the potential use of leptin in the treatment of type 2 diabetes are discussed.

Emerging combinatorial hormone therapies for the treatment of obesity and T2DM

Peptide hormones and proteins control body weight and glucose homeostasis by engaging peripheral and central metabolic signalling pathways responsible for the maintenance of body weight and euglycaemia. The development of obesity, often in association with type 2 diabetes mellitus (T2DM), reflects a dysregulation of metabolic, anorectic and orexigenic pathways in multiple organs. Notably, therapeutic attempts to normalize body weight and glycaemia with single agents alone have generally been disappointing. The success of bariatric surgery, together with emerging data from preclinical studies, illustrates the rationale and feasibility of using two or more agonists, or single co-agonists, for the treatment of obesity and T2DM. Here, we review advances in the science of co-agonist therapy, and highlight promising areas and challenges in co-agonist development. We describe mechanisms of action for combinations of glucagon-like peptide 1, glucagon, gastric inhibitory polypeptide, gastrin, islet amyloid polypeptide and leptin, which enhance weight loss whilst preserving glucoregulatory efficacy in experimental models of obesity and T2DM. Although substantial progress has been achieved in preclinical studies, the putative success and safety of co-agonist therapy for the treatment of patients with obesity and T2DM remains uncertain and requires extensive additional clinical validation.

Randomized double-blind placebo-controlled study of leptin administration after gastric bypass

OBJECTIVE

Obese individuals have high levels of circulating leptin and are resistant to the weight-reducing effect of leptin administration at physiological doses. Although Roux-en-Y gastric bypass (RYGB) is an effective weight loss procedure, there is a plateau in weight loss and most individuals remain obese. This plateau may be partly due to the decline in leptin resulting in a state of relative leptin insufficiency. The main objective of this study was to determine whether leptin administration to post-RYGB patients would promote further weight reduction.

DESIGN AND METHODS

This was a randomized, double-blind, placebo-controlled cross-over study of 27 women who were at least 18 months post-RYGB and lost on average 30.8% of their presurgical body weight. Subjects received either leptin or placebo via subcutaneous injection twice daily for 16 weeks, then crossed over to receive the alternate treatment for 16 weeks.

RESULTS

Weight change after 16 weeks of placebo was not significantly different from that after 16 weeks of leptin. No changes were observed in percent fat mass, resting energy expenditure, thyroid hormones, or cortisol levels.

CONCLUSION

Contrary to our hypothesis, we did not observe a significant effect of leptin treatment on body weight in women with relative hypoleptinemia after RYGB.

[Therapy resistant diabetes mellitus and lipodystrophy: leptin therapy leads to improvement]

Lipodystrophy is a congenital or acquired disorder characterized by complete or partial absence of subcutaneous fat tissue, often accompanied by insulin resistance, diabetes mellitus (DM), hypertriglyceridemia and hepatic steatosis. A decrease in both number and function of adipocytes leads to ectopic fat depositions and decreased production of adipokines such as leptin. We present 2 patients with inadequately regulated DM, hypertriglyceridemia and hepatic steatosis who were eventually diagnosed with lipodystrophy: 1 with congenital generalized lipodystrophy (Berardinelli-Seip syndrome) and 1 with congenital partial lipodystrophy (Dunnigan syndrome). Both received recombinant human leptin therapy (methionylleptin, available on a compassionate-use basis). This resulted in improved plasma levels of triglyceride, glucose and HbA1c and a decrease in liver size. In addition, hepatic triglyceride content decreased from 19.3% to 1.3% in the first patient and from 20.6% to 12.4% in the second. Leptin therapy is an effective and safe treatment for therapy-resistant diabetes and hypertriglyceridemia in patients with congenital lipodystrophy.

Potential role of leptin against glucocorticoid-induced secondary osteoporosis in adult female rats

OBJECTIVES

The present study assessed the potential role of leptin administration in the protection and intervention against glucocorticoid-induced secondary osteoporosis in female rats.

MATERIALS AND METHODS

For this purpose five groups of female Sprague Dawley rats were classified into: (1) negative control group in which the healthy rats received saline as vehicle, (2) a group orally administered with prednisolone (5 mg kg b.wt.-1) daily for six months (osteoporotic group), (3) a group subcutaneously administered with leptin (400 microg kg b.wt.-1) three times weekly for six months (positive control), (4) a group orally administered with prednisolone daily with simultaneous subcutaneous administration of leptin three times weekly for six months (protective group), and (5) a group orally administered with prednisolone daily for six months then subcutaneously administered with leptin three times weekly for other six months (therapeutic group).

RESULTS

The obtained data revealed that prednisolone administration resulted in significant decrease in serum osteoprotegerin (OPG) level accompanied with significant increase in serum receptor activator of nuclear factor-κB ligand (RANKL) and beta2-microglobulin levels in comparison with the negative control group. Moreover, prednisolone significantly decreased bone mineral density and content of different areas of the right femur bones as compared to the negative control group. Furthermore, administration of leptin with/after stopping prednisolone administration resulted in a marked modulation in the majority of bone biomarkers as well as improvement in bone mineral density and content.

CONCLUSIONS

Leptin provided promising effect on bone through its direct action on bone and matrix mineralization.

Leptin replacement therapy does not improve the abnormal lipid kinetics of hypoleptinemic patients with HIV-associated lipodystrophy syndrome

Patients with HIV-associated dyslipidemic lipodystrophy (HADL) have characteristic lipid kinetic defects: accelerated lipolysis, blunted fat oxidation and increased hepatic fatty acid reesterification. HADL patients with lipoatrophy also have leptin deficiency. Small or non-randomized studies have suggested that leptin replacement improves glucose metabolism in HADL, with very limited data regarding its effects on the lipid kinetic abnormalities. We performed a randomized, double-blind, placebo-controlled, dose-escalating (0.02 mg/kg/d for two months; 0.04 mg/kg/d for a further two months) study of the effects of metreleptin on lipid kinetics in 17 adults with HADL, hypertriglyceridemia and hypoleptinemia. Rates of lipolysis, intra-adipocyte and intrahepatic reesterification and fatty acid oxidation were measured using infusions of (13)C(1)-palmitate and (2)H(5)-glycerol, and indirect calorimetry. Fasting lipid profiles and glucose and insulin responses to oral glucose challenge were also measured. Metreleptin treatment induced significant, dose-dependent increases in fasting plasma leptin levels. There was no significant change in total lipolysis, net lipolysis, adipocyte or hepatic re-esterification or fatty acid oxidation, or in fasting triglyceride or HDL-C concentrations, with metreleptin treatment. Metreleptin decreased fasting non-HDL-C levels (P<.01) and area-under-the-curve for glucose (P<.05). In hypoleptinemic HADL patients, treatment with metreleptin at 0.02 or 0.04 mg/kg/d does not improve abnormal fasting lipid kinetics, or triglyceride or HDL-C levels. Metreleptin does, however, improve glycemia and non-HDL-C in these patients. These results suggest a dissociation between leptin's effects on glucose metabolism compared to those on lipid kinetics in HADL.

Leptin as mediator of the effects of developmental programming

Considerable epidemiological, experimental and clinical data have amassed showing that the risk of developing disease in later life is dependent upon early life conditions. In particular, altered maternal nutrition, including undernutrition and overnutrition, can lead to metabolic disorders in offspring characterised by obesity and leptin resistance. The adipokine leptin has received significant interest as a potential programming factor; alterations in the profile of leptin in early life are associated with altered susceptibility to obesity and metabolic disorders in adulthood. Maintenance of a critical leptin level during early development facilitates the normal maturation of tissues and signalling pathways involved in metabolic homeostasis. A period of relative hypo- or hyperleptinemia during this window of development will induce some of the metabolic adaptations which underlie developmental programming. However, it remains unclear whether leptin alone is a critical factor for the programming of obesity. At least in animal experimental studies, developmental programming is potentially reversible by manipulating the concentration of circulating leptin during a critical window of developmental plasticity and offers an exciting new approach for therapeutic intervention.

Leptin revisited: its mechanism of action and potential for treating diabetes

Since the discovery of leptin in 1994, we now have a better understanding of the cellular and molecular mechanisms underlying its biological effects. In addition to its established anti-obesity effects, leptin exerts antidiabetic actions that are independent of its regulation of body weight and food intake. In particular, leptin can correct diabetes in animal models of type 1 and type 2 diabetes. In addition, long-term leptin replacement therapy improves glycaemic control, insulin sensitivity and plasma triglycerides in patients with severe insulin resistance due to lipodystrophy. These results have spurred enthusiasm for the use of leptin therapy to treat diabetes. Here, we review the current understanding of the glucoregulatory functions of leptin, emphasizing its central mechanisms of action and lessons learned from clinical studies, and discuss possible therapeutic applications of leptin in the treatment of type 1 and type 2 diabetes.

[Topical application of leptin promotes burn wound healing in rats]

OBJECTIVE

To investigate the effect of topical application of leptin in promoting burn wound healing in rats.

METHODS

Four parallel second-degree burn wounds induced on the back of 18 Wistar rats were divided into leptin treatment group (treated with topical application of 400 ng/ml leptin dissolved in PBS) and control group (treated with PBS). The time of wound healing was recorded, and the wound area that was not healed was measured at 3, 7, 11, 15, and 19 days after burns. The tissue at the peripheries of the wound was sampled at 7, 14 and 21 days after burns for pathological examination with HE staining and immunohistochemistry for proliferating cell nuclear antigen (PCNA) to evaluate the proliferation of keratinocytes.

RESULTS

Compared with the control group, leptin-treated wounds showed a shorter time (by 2-3 days) of wound healing, and significant differences were found between the two groups in healing at 7, 11, 15, and 19 days after burns. HE staining and immunohistochemistry revealed a faster rate of epidermis growth and a greater thickness of the cuticular layer in leptin-treated wounds at 7, 14 and 21 days after burns. PCNA positivity in the keratinocytes was stronger in leptin-treated wounds than in the control wounds at 7 and 14 days, but no such distinct difference was noted at 21 days between the two groups.

CONCLUSION

Topical application of leptin can promote re-epithelization in burn wounds to shorten the wound healing time of burns.

Acute leptin treatment enhances functional recovery after spinal cord injury

BACKGROUND

Spinal cord injury is a major cause of long-term disability and has no current clinically accepted treatment. Leptin, an adipocyte-derived hormone, is best known as a regulator of food intake and energy expenditure. Interestingly, several studies have demonstrated that leptin has significant effects on proliferation and cell survival in different neuropathologies. Here, we sought to evaluate the role of leptin after spinal cord injury.

FINDINGS

Based on its proposed neuroprotective role, we have evaluated the effects of a single, acute intraparenchymal injection of leptin in a clinically relevant animal model of spinal cord injury. As determined by quantitative Real Time-PCR, endogenous leptin and the long isoform of the leptin receptor genes show time-dependent variations in their expression in the healthy and injured adult spinal cord. Immunohistochemical analysis of post-injury tissue showed the long isoform of the leptin receptor expression in oligodendrocytes and, to a lesser extent, in astrocytes, microglia/macrophages and neurons. Moreover, leptin administered after spinal cord injury increased the expression of neuroprotective genes, reduced caspase-3 activity and decreased the expression of pro-inflammatory molecules. In addition, histological analysis performed at the completion of the study showed that leptin treatment reduced microglial reactivity and increased caudal myelin preservation, but it did not modulate astroglial reactivity. Consequently, leptin improved the recovery of sensory and locomotor functioning.

CONCLUSIONS

Our data suggest that leptin has a prominent neuroprotective and anti-inflammatory role in spinal cord damage and highlights leptin as a promising therapeutic agent.

Amylin improves the effect of leptin on insulin sensitivity in leptin-resistant diet-induced obese mice

Leptin enhances insulin sensitivity in addition to reducing food intake and body weight. Recently, amylin, a pancreatic β-cell-derived hormone, was shown to restore a weight-reducing effect of leptin in leptin-resistant diet-induced obesity. However, whether amylin improves the effect of leptin on insulin sensitivity in diet-induced obesity is unclear. Diet-induced obese (DIO) mice were infused with either saline (S), leptin (L; 500 μg·kg⁻¹·day⁻¹), amylin (A; 100 μg·kg⁻¹·day⁻¹), or leptin plus amylin (L/A) for 14 days using osmotic minipumps. Food intake, body weight, metabolic parameters, tissue triglyceride content, and AMP-activated protein kinase (AMPK) activity were examined. Pair-feeding and weight-matched calorie restriction experiments were performed to assess the influence of food intake and body weight reduction. Continuous L/A coadministration significantly reduced food intake, increased energy expenditure, and reduced body weight, whereas administration of L or A alone had no effects. L/A coadministration did not affect blood glucose levels during ad libitum feeding but decreased plasma insulin levels significantly (by 48%), suggesting the enhancement of insulin sensitivity. Insulin tolerance test actually showed the increased effect of insulin in L/A-treated mice. In addition, L/A coadministration significantly decreased tissue triglyceride content and increased AMPKα2 activity in skeletal muscle (by 67%). L/A coadministration enhanced insulin sensitivity more than pair-feeding and weight-matched calorie restriction. In conclusion, this study demonstrates the beneficial effect of L/A coadministration on glucose and lipid metabolism in DIO mice, indicating the possible clinical usefulness of L/A coadministration as a new antidiabetic treatment in obesity-associated diabetes.

Comparison of efficacy and safety of leptin replacement therapy in moderately and severely hypoleptinemic patients with familial partial lipodystrophy of the Dunnigan variety

CONTEXT

Leptin replacement therapy improves metabolic complications in patients with lipodystrophy and severe hypoleptinemia (SH), but whether the response is related to the degree of hypoleptinemia remains unclear.

OBJECTIVE

The aim of the study was to compare efficacy of leptin therapy in familial partial lipodystrophy, Dunnigan variety (FPLD) patients with SH (serum leptin<7th percentile of normal) vs. those with moderate hypoleptinemia (MH; serum leptin in 7th to 20th percentiles).

DESIGN, SETTING, AND PATIENTS

We conducted an open-label, parallel group, observational study in 14 SH (mean±sd, serum leptin, 1.9±1.1 ng/ml) and 10 MH (serum leptin, 5.3±1.0 ng/ml) women with FPLD.

INTERVENTION

Patients received 0.08 mg/kg·d of metreleptin by twice daily sc injections for 6 months.

MAIN OUTCOME MEASURES

The primary outcome variable was change in fasting serum triglycerides. Other secondary variables were fasting plasma glucose and insulin, insulin sensitivity, hemoglobin A1c, and hepatic triglyceride content.

RESULTS

Median fasting serum triglycerides decreased from 228 to 183 mg/dl in the SH group (P=0.04) and from 423 to 339 mg/dl in the MH group (P=0.02), but with no difference between the groups (P value for interaction=0.96). Hepatic triglyceride levels similarly declined significantly from 8.8 to 4.9% in the SH group and from 23.7 to 9.2% in the MH group (P value for interaction=0.9). Loss of body weight and body fat occurred in both groups. Fasting glucose, insulin, glucose tolerance, and hemoglobin A1c levels did not change. K value on insulin tolerance test improved slightly in the SH group (0.98 to 1.24%; P=0.01), but not in the MH group (1.1 to 1.27%; P=0.4).

CONCLUSION

Metreleptin replacement therapy is equally effective in FPLD patients with both SH and MH in reducing serum and hepatic triglyceride levels, but did not improve hyperglycemia.

Leptin substitution results in the induction of menstrual cycles in an adolescent with leptin deficiency and hypogonadotropic hypogonadism

BACKGROUND

Leptin deficiency leads to midluteal-phase defect or reduced testicular volume in adults, despite normal gonadotropin levels. All children documented to date with leptin deficiency were prepubertal with physiologically low gonadotropins prior to therapy. A direct effect of leptin on pubertal development in a leptin-naive adolescent has not yet been shown.

METHODS

In 2010, we reported the first connatal leptin-deficient adolescent girl with clinically and chemically proven hypogonadotropic hypogonadism. In this study, we evaluated the effect of recombinant methionyl human leptin substitution.

RESULTS

Initially, the patient had prepubertal basal and stimulated luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels, low growth hormone and insulin-like growth factor 1 (IGF1) levels and no pulsatile secretion of LH and FSH. After 11 weeks of therapy, basal and stimulated LH and FSH levels rose to pubertal values and nocturnal pulsatility was initiated. After 76 weeks of therapy, menstruation occurred at the age of 16.3 years. Pulsatile nocturnal growth hormone secretion, stimulated growth hormone secretion and IGF1 values also normalized.

CONCLUSION

We describe here the first adolescent with hypogonadotropic hypogonadism due to connatal leptin deficiency. Leptin substitution led to a rapid induction of gonadotropin secretion and menarche. These data are further proof of the concept that leptin is needed for a timely maturation of the hypothalamic/pituitary/gonadal axis.

Pregnancy in a woman with congenital generalized lipodystrophy: leptin's vital role in reproduction

BACKGROUND

Congenital generalized lipodystrophy is a rare disorder characterized by scant adipose tissue, profound leptin deficiency, and severe insulin resistance, resulting in multiple metabolic derangements, including hyperandrogenism, anovulation, and impaired fecundity.

CASE

A young woman with congenital generalized lipodystrophy receiving leptin therapy experienced menarche, conceived spontaneously, and delivered a liveborn male neonate.

CONCLUSION

Adipose tissue is important to normal female reproductive function. Leptin in particular appears to play a key role in adipose-mediated regulation of fertility.

Effects of exogenous human leptin on heat shock protein 70 expression in MCF-7 breast cancer cells and breast carcinoma of nude mice xenograft model

BACKGROUND

It is important to identify the multiple sites of leptin activity in obese women with breast cancer. In this study, we examined the effect of exogenous human leptin on heat shock protein 70 (HSP70) expression in MCF-7 human breast cancer cells and in a breast carcinoma xenograft model of nude mice.

METHODS

We cultured MCF-7 human breast cancer cells and established nude mice bearing xenografts of these cells, and randomly divided them into experimental and control groups. The experimental group was treated with human leptin, while the control group was treated with the same volume of normal saline. A real-time reverse transcriptase-polymerase chain reaction (RT-PCR) assay was developed to quantify the mRNA expression of HSP70 in the MCF-7 human breast cancer cells and in tumor tissues. Western blotting analysis was applied to quantify the protein expression of HSP70 in the MCF-7 cells. Immunohistochemical staining was done to assess the positive rate of HSP70 expression in the tumor tissues.

RESULTS

Leptin activated HSP70 in a dose-dependent manner in vitro: leptin upregulated significantly the expression of HSP70 at mRNA and protein levels in MCF-7 human breast cancer cells (P < 0.001). There was no significant difference in expression of HSP70 mRNA in the implanted tumors between the leptin-treated group and the control group (P > 0.05). Immunohistochemical staining revealed no significant difference in tumor HSP70 expression between the leptin-treated group and the control group (P > 0.05).

CONCLUSIONS

A nude mouse xenograft model can be safely and efficiently treated with human leptin by subcutaneous injections around the tumor. HSP70 may be target of leptin in breast cancer. Leptin can significantly upregulate the expression of HSP70 in a dose-dependent manner in vitro.

Insulin resistance is a sufficient basis for hyperandrogenism in lipodystrophic women with polycystic ovarian syndrome

CONTEXT

The lipodystrophies (LD) are characterized by metabolic abnormalities (insulin resistance, hypertriglyceridemia, and diabetes) and a polycystic ovarian syndrome (PCOS) phenotype. Therapeutic administration of leptin improves insulin sensitivity and the metabolic features.

OBJECTIVE

The objective of the study was to investigate whether the PCOS features are corrected by increasing insulin sensitivity as a function of leptin treatment.

DESIGN

This was a prospective, open-label trial using leptin replacement in various forms of lipodystrophy.

SETTING

The study was performed at the Clinical Center at the National Institutes of Health.

PATIENTS OR OTHER PARTICIPANTS

Twenty-three female patients with LD were enrolled in a leptin replacement trial from 2000 to the present. Different parameters were assessed at baseline and after 1 yr of therapy.

INTERVENTION(S)

Patients were treated with leptin for at least 1 yr.

MAIN OUTCOME MEASURE(S)

We evaluated free testosterone, SHBG, and IGF-I at baseline and after 1 yr of leptin.

RESULTS

Testosterone levels decreased from 3.05 ±0.6 ng/ml at baseline to 1.7 ±0.3 ng/ml (P = 0.02). SHBG increased from 14.5 ±2 to 25 ±3.5 nmol/liter after 1 yr of leptin therapy. There were no significant changes in the levels of gonadotropins and ovarian size as a result of leptin replacement therapy. IGF-I increased significantly after leptin therapy from 150 ±14 to 195 ±17. There was a significant decrease in triglycerides and glycosylated hemoglobin in the context of reduced insulin requirements.

CONCLUSIONS

In the present study, we show that LD may be a model for the common forms of PCOS and that the endocrine features are corrected by leptin therapy, which reduces insulin resistance.