Leptin: Amenorrhea, Reproduction, Anorexia Hazel Leung, Ahrad Nathan, Seja Saddy, Judy Tang
Introduction: What is leptin? Adipocyte-derived hormone (WAT) Receptor roles Class I cytokine receptor superfamily Metreleptin: analog of leptin Leptin deficiency Figure: Jeffrey Brumbaugh (UCLA)
Leptin: W(h)AT is WAT? White Adipose Tissue: site of leptin synthesis Regulated by hormones and agents Agents differentiated by effects on leptin mrna levels Inhibitors v.s. Secretagogues Regulator of food intake, energy homeostasis via hypothalamus Figure: American Journal of Physiology: Endocrinology and Metabolism
Leptin Receptors Leptin as a product of obese gene (mrna) 5 isoforms, each characterized by Ob(a-f) Receptors characterized by ObR(a-f) FOCUS: ObRb isoform Extended C-terminal region Capable of complete intracellular signal transduction Activator of JAK-STAT pathway Figure: sciencedirect.com
Leptin: Class I Cytokine receptor superfamily Strong homology to IL-6 receptor family s gp-130 Suggests that leptin binding mediates cytokine-receptor like signals Cytokine receptors binds to cytokines, induce signal transduction Figure: Yale University
Metreleptin v.s. Leptin Metreleptin: recombinant methionyl human leptin Analog: Increased stability Improved potency Enhanced blood-brain-barrier transport Figure: Pharmcodia.com
Leptin Deficiency Figure: Indian Journal of Endocrinology and Metabolism
Hypothalamic Amenorrhea: Characteristics, Causes Figure: awaremed.com
Experiment: Goals, Procedures Metreleptin admin was s.c. Observe the effects of metreleptin as treatment for HA Hypothalamic release of GnRH Bone mass, metabolism (BMD), body fat composition Women s fertility Comparison between treatment, placebo group every 4 weeks Expt: Leptin as an effective treatment for hypothalamic amenorrhea
1ST, 2ND TRIALS TRIAL 1 Proof-of concept, open-label pilot study Administered metreleptin subcutaneously for 3 mo Normalized leptin levels PROBLEMS? Open-nature of study Bone metabolism not fully studied Duration of trial was too short DISCOVERED METRELEPTIN TX LEAD TO: Ovulatory menses High levels of LH Estradiol IGF1 Thyroid hormones Bone formation markers
1ST, 2ND TRIALS TRIAL 2 Double-blind, placebo-controlled, randomized Duration: 36 weeks Better assessment of study outcomes OUTCOMES STUDIED Reproductive, neuroendocrine functions Markers of bone metabolism via BMD Resting energy expenditure Established background (not in previous trial)
Question: Is there a causal role of leptin in the pathogenesis of hypothalamic amenorrhea?
Results: Baseline characteristics Insignificant differences in age, weight, BMI, body fat composition, duration of amenorrhea, leptin levels, LH, FSH, estradiol, and BMD between metreleptin and placebo groups.
Table 1. Changes in neuroendocrine axes and markers of bone turnover over time
Results: Subject Completion 20 subjects enrolled 11 subjects randomly assigned to receive metreleptin, 1 of whom withdrew due to injection-site reactions 9 subjects received placebo 7 out of 11 metreleptin-treated subjects and 6 out of 9 placebo treated subjects completed the entire study 1 metreleptin-treated subject became pregnant and was discontinued from the study due to persistent weight loss despite adjustments in study medication dose 1 metreleptin-treated subject and 3 placebo-treated subjects withdrew due to travelling
Results: Weight, Body Composition, and Metabolic Rate All but one subject, including metreleptin and placebo-treated groups, maintained stable weights during the study 4 participants taking metreleptin required decreased doses because of weight loss No significant change in BMI in metreleptin group compared to control group Metreleptin-treated group progressively lost fat mass throughout the study. Respiratory quotient increased in both groups, but more significantly in the metreleptin group
Fig. 1. Body composition
Results: Leptin, Free Leptin, and Antileptin Antibody Levels Metreleptin-treated group Significant serum total leptin level increased after week 4 This continued to rise throughout the study Week 12, dose of 4 participants increased due to lack of menstruation, 2 of whom had the dose reduced again due to weight loss Free Leptin increased ⅞ developed antileptin antibodies at week 12 (first checkpoint) Control group No significant changes in leptin levels
Metreleptin Treated Group Subject Completion: 11 subjects randomly assigned to receive metreleptin, 1 of whom withdrew due to injection-site reactions. 7 of these subjects completed the entire study. 1 Subject became pregnant and was discontinued. 1 subject withdrew due to traveling. Weight, Body Composition, and Metabolic Rate: 4 subjects required decreased dosed because of weight loss. Subjects progressively loss fat mass throughout the study. Leptin, Free Leptin, and Antileptin Antibody Levels: Significant serum total leptin level increased after week 4, which continued to rise throughout the study. At week 12, the dose of 4 of the participants was increased due to lack of menstruation. This had to be reduced again due to weight loss. Free leptin increased. 7 of 8 subjects developed antileptin bodies at week 12 (the first checkpoint) Both Groups Baseline Characteristics: Insignificant differences in age, weight, BMI, body fat composition, duration of amenorrhea, leptin levels, LF, FSH, and BMD Weight, Body Composition, and Metabolic Rate: All but one subject overall maintained stable weights throughout the study. No significant change in BMI. Increase in respiratory quotient (more significant in metreleptin group). Control Group Subject Completion: 9 subjects received placebo, 6 of whom completed the entire study. 3 subjects withdrew due to traveling. Leptin, Free Leptin, and Antileptin Antibody Levels: No significant changes in leptin levels.
Results: Menstruation and Fertility Metreleptin-treated Group 7/10 subjects developed menstruation at various stages of metreleptin therapy, 4 of whom were determined to be ovulating 1 subject became pregnant Placebo-treated group 2/9 subjects developed menstruation
Table 2. Individual data on presence of menstruation, metreleptin dose, and weight: Treatment group
Results: Hormone Levels No significant difference in LH, FSH, inhibin B, testosterone, TSH, ft3, ft4, and prolactin levels between the two groups Metreleptin-treated group Estradiol and progesterone levels increased significantly compared to placebo-treated group Cortisol levels decreased Significantly higher ratio of IGF1:IGF binding protein 3 compared to placebo group Placebo-treated group Cortisol remained constant
Table 1. Changes in neuroendocrine axes and markers of bone turnover over time
Results: Bone Metabolism No significant differences: Metreleptin-Treated Group BMD at the Lumbar spine Bone-specific alkaline phosphatase (BASP) C-telopeptides of type 1 collagen (NTX) Osteocalcin levels increased compared to placebo-treated group Placebo-Treated Group Higher increase in NTX
Table 1. Changes in neuroendocrine axes and markers of bone turnover over time
Results: Safety of Metreleptin Therapy 1 subject developed erythematous rashes within a few weeks after starting metreleptin, resulting in her withdrawing 1 subject had persistent weight loss Symptoms went away 1 week after stopping treatment Withdrew from the study No other effects due to medication or procedure were observed
Discussion: HPG Axis HA leads to infertility due to disruption of hypothalamic - pituitary - gonadal axis GnRH LH & FSH estrogen & progesterone Low levels of leptin inhibits release of GnRH cessation of menses
Discussion: Leptin s Link to Reproduction Metreleptin therapy led to restoration of menses with >50% ovulating Experimental group: 5 participants within 12 weeks Experimental group: 2 subjects after 12 weeks Placebo group: 2 subjects At the 52 week follow up, only 1 still had a menstrual cycle
Discussion: Leptin s Link to Bone Mineral Density Results: Increase in osteocalcin Stabilization of NTX:creatinine ratio Yet: Saw no significant changes in BMD 36 weeks too short of a study to observe potential change(?) Have another study that assess 2 years of metreleptin administration
Discussion: Leptin s Link to Bone Mineral Density Possible pathways for BMD improvements: 1. Via neuroendocrine axes: 2. Via direct effects on bone: Increased estradiol Increased IGF1 Decreased cortisol Increased osteoblast proliferation Decreased osteoclastogensis
Discussion: Body Fat Loss Adjusted metreleptin doses to control for weight and BMI Saw significant weight loss before controlling for it Why? Weight loss due to increased energy expenditure or decreased fat intake? Direct lipolytic effect of metreleptin on adipose tissue? No change in resting energy expenditure Direct calorimetry for 24-h cycles more accurate Total energy expenditure more accurate
Discussion: Significance of Results Exogenous administration of leptin can treat dysfunction in axes Daily s.c. metreleptin injections led to elevated levels of leptin within the first month of treatment Metreleptin treatment in physiologic doses may be a safe, effective therapy for those with HA
Discussion: Experimental Design Low number of participants Who are the participants? Participant withdrawal rate Length of study Physiological symptoms/problems Need to be in a specific place Dramatic weight loss Pregnancy