Recombinant Leptin Treatment Research Articles

Lipocalin-2 activates hepatic stellate cells and promotes nonalcoholic steatohepatitis in high-fat diet-fed Ob/Ob mice.

In obesity and type 2 diabetes mellitus, leptin promotes insulin resistance and contributes to the progression of NASH via activation of hepatic stellate cells (HSCs). However, the pathogenic mechanisms that trigger HSC activation in leptin-deficient obesity are still unknown. This study aimed to determine how HSC-targeting lipocalin-2 (LCN2) mediates the transition from simple steatosis to NASH. Male wild-type (WT) and ob/ob mice were fed a high-fat diet (HFD) for 20 weeks to establish an animal model of NASH with fibrosis. Ob/ob mice were subject to caloric restriction or recombinant leptin treatment. Double knockout (DKO) mice lacking both leptin and lcn2 were also fed an HFD for 20 weeks. In addition, HFD-fed ob/ob mice were treated with gadolinium trichloride to deplete Kupffer cells. The LX-2 human HSCs and primary HSCs from ob/ob mice were used to investigate the effects of LCN2 on HSC activation. Serum and hepatic LCN2 expression levels were prominently increased in HFD-fed ob/ob mice compared with normal diet-fed ob/ob mice or HFD-fed WT mice, and these changes were closely linked to liver fibrosis and increased hepatic α-SMA/matrix metalloproteinase 9 (MMP9)/signal transducer and activator of transcription 3 (STAT3) protein levels. HFD-fed DKO mice showed a marked reduction of α-SMA protein compared with HFD-fed ob/ob mice. In particular, the colocalization of LCN2 and α-SMA was increased in HSCs from HFD-fed ob/ob mice. In primary HSCs from ob/ob mice, exogenous LCN2 treatment induced HSC activation and MMP9 secretion. By contrast, LCN2 receptor 24p3R deficiency or a STAT3 inhibitor reduced the activation and migration of primary HSCs. LCN2 acts as a key mediator of HSC activation in leptin-deficient obesity via α-SMA/MMP9/STAT3 signaling, thereby exacerbating NASH.

Differential Role of Leptin as an Immunomodulator in Controlling Visceral Leishmaniasis in Normal and Leptin-Deficient Mice.

Visceral leishmaniasis (VL) is caused by the protozoan parasite Leishmania donovani. There are no vaccines and available drugs against leishmaniasis are toxic. Immunomodulators that specifically boost the anti-microbial activities of the immune cells could alleviate several of these limitations. Therefore, finding novel immunomodulators for VL therapy is a pressing need. This study is aimed to evaluate the immunomodulatory role of leptin, an adipocyte-derived hormone capable of regulating the immune response, in L. donovani-infected mice. We observed that recombinant leptin treatment reduced splenic parasite burden compared with non-treated infected normal mice. Decrease in parasite burden correlated with an induction of innate immune response in antigen-presenting cells that showed an increase in nitric oxide, enhanced pro-inflammatory cytokine (interferon gamma [IFNγ], interleukin12 [IL]12, and IL1β) response in the splenocytes, indicating host-protecting Th1 response mediated by leptin. Moreover, in infected normal mice, leptin treatment induced IFNγ production from both CD4+ and CD8+ T cells, compared with non-treated infected mice. Alternatively, leptin-deficient (Ob/Ob) mice had higher splenic and liver parasite burden compared with the infected normal mice. However, leptin treatment failed to reduce the splenic parasite burden and improve a host-protective cytokine response in these mice. In addition, in contrast to dendritic cells (DCs) from a normal mouse, Ob/Ob mouse–derived DCs showed a defect in the induction of innate immune response on Leishmania infection that could not be reversed by leptin treatment. Therefore, our findings reveal that leptin has a differential immunomodulatory effect in controlling VL in normal and Ob/Ob mice.

Adipokine Regulation Of Myostatin Signaling In Aged Skeletal Muscle

Skeletal muscle atrophies with age, a phenomenon referred to as the sarcopenia of aging. The secreted factor myostatin (GDF-8) is known to suppress myofiber hypertrophy and induce muscle atrophy, and elevated myostatin expression has been implicated in muscle loss with aging. Myostatin expression may be regulated in part by the fat-derived hormone leptin. Mice lacking leptin have reduced muscle mass and elevated myostatin expression, which can be reversed with recombinant leptin therapy. PURPOSE: To determine the effects of leptin treatment on muscle mass and myostatin signaling in aged skeletal muscle. METHODS: C57BL/6 mice 12 and 24 months of age received daily subcutaneous injections of either vehicle (saline) or recombinant leptin (10 μg/day) for 10 days. Mice were euthanized after the 10 day treatment period and body weight and quadriceps mass recorded. The extensor digitorum longus (EDL) was dissected free, embedded in OCT medium, and snap frozen. Muscle fiber cross-sectional areas were measured from cryostat sections of the EDL, and real-time PCR used to quantify expression of myostatin and its receptor (ActRIIB) from the tibialis anterior. RESULTS: Leptin treatment did not significantly alter body weight in mice of either age group, but quadriceps muscle weights were significantly lower (P<.001) in the aged mice. Leptin treatment significantly increased quadriceps muscle mass both absolutely (P<.05) and relative to body mass (P<.01) in the aged mice but not in the younger mice. Muscle fiber cross-sectional areas of the extensor digitorum longus muscle (EDL) were slightly lower in aged mice, and leptin treatment significantly (P<.05) increased EDL fiber area in the aged mice but not the young mice. Leptin treatment was found to decrease myostatin expression by ∼40% and ActRIIB expression by ∼50% in the tibialis anterior of aged mice compared to that of saline-treated aged mice. CONCLUSIONS: Results from our study support the hypothesis that the adipokine leptin is a key factor linking nutrient intake with normal muscle function, and reveal that leptin can alter myostatin signaling in aged muscle. Recombinant leptin treatment may therefore have potential as a novel therapeutic approach for the prevention of sarcopenia. Supported by US Army Medical Research Acquisition Activity Award PR093619

Effects of very low calorie diet induced body weight loss with or without human pegylated recombinant leptin treatment on changes in ghrelin and adiponectin concentrations

The aim of the study was to investigate the effects of energy restriction with or without pegylated recombinant leptin (PEG-leptin) treatment on ghrelin, adiponectin, insulin and glucose concentrations. A randomized double-blind placebo-controlled trial was performed in 24 moderately overweight/obese men. PEG-leptin or placebo was administered weekly for 6 weeks, combined with a restricted energy intake of 2.1 MJ/d. At days 1, 25, and 46 a blood sample was taken and body-weight (BW) was measured. Days 1–25 was named phase 1, and days 25–46 phase 2. During phase 1 the rate of BW loss was significantly higher in the PEG-leptin compared to the placebo group (0.38 ± 0.07 vs 0.32 ± 0.06 kg/d, p < 0.05). The rate of BW loss during phase 2 was 0.24 ± 0.08 and 0.18 ± 0.09 kg/d, respectively ( p = 0.07). In both groups the rate of BW loss during phase 1 was significantly higher than during phase 2 ( p < 0.001). Energy balance (EB) was significantly more negative during phase 1 than during phase 2 in both groups ( p < 0.0005). During phase 1 insulin, glucose and adiponectin decreased significantly in both groups. Adiponectin and ghrelin concentrations changed in the opposite direction between phase 1 and phase 2 ( p < 0.05). Initial BW loss due to a considerable negative EB induced decreased ghrelin, adiponectin, insulin and glucose levels. However, when EB became less negative and the rate of BW loss decreased, these changes were reversed for adiponectin and ghrelin. The PEG-leptin injections did not have an effect on the changes in insulin, glucose and adiponectin, but had an effect on the changes in ghrelin concentrations.

Effect of three treatment schedules of recombinant methionyl human leptin on body weight in obese adults: a randomized, placebo‐controlled trial

The aim of this study was to evaluate the effect on body weight and safety of subcutaneously administered recombinant leptin in obese adults and to evaluate whether the timing of recombinant leptin administration influences efficacy. A randomized, double-blind, placebo-controlled, multicentre study was designed, comprising of a 3-week dietary lead-in followed by a 12-week leptin or placebo treatment period. A total of 284 overweight and obese (body mass index 27-37.0 kg/m(2)) predominantly white (98%) women (66%) and men (34%) with a mean (+/-s.d.) 46.8+/-10.4 years of age were randomized into three treatment groups with three matching placebo groups. Recombinant leptin was administered by subcutaneous injection [10 mg/morning, 10 mg/evening or 20 mg/day (10 mg twice daily)]. Patients were counselled at baseline to reduce dietary intake by 2,100 kJ/day (500 kcal/day), and dietary advice was reinforced every 2-4 weeks. No statistically significant change in body weight occurred with recombinant leptin treatment compared with placebo treatment in any treatment group. No clinically significant adverse effects were observed with the exception of an increase in injection-site reactions in patients treated with recombinant leptin (83%) vs. placebo (36%). Administration of recombinant leptin to an overweight and obese population, in addition to a mildly energy-restricted diet, was not efficacious in terms of weight loss at the doses and schedules studied. The hypothesis that nocturnal administration of recombinant leptin might have a specific effect on weight loss was not supported.

Leptin receptor isoform expression in rat osteoblasts and their functional analysis

The genetic defect in producing the adipose hormone leptin results among others in a drastic increase of bone mass. The current understanding is that under normal circumstances, osteoblast activity is indirectly suppressed by a hypothalamic relay induced by leptin-signalling in the brain. To investigate whether leptin might also regulate osteoblast activity in a direct manner, expression of leptin receptors in rat osteoblasts was determined and their functionality was analyzed upon recombinant leptin treatment. Reverse transcription-PCR confirmed the expression of four among the six currently described receptor isoforms, which were also able to transduce cell signalling as shown by STAT3 phosphorylation after activation.

Restoration of fertility in young obese (Lep(ob) Lep(ob)) male mice with low dose recombinant mouse leptin treatment.

We investigated the effects of low-dose leptin treatment on restoration of fertility in young adult male leptin deficient obese mice. MMTV-TGF-alpha Lep(ob) Lep(ob) mice (8--10 weeks old) were treated with recombinant mouse leptin. In experiment 1, four mice (5 microg/g body weight leptin followed by 2.5 microg/g) lost weight and impregnated females (number of pregnancies/number of females, 3/6, 5/6, 5/10, 4/10). In experiment 2, Leptin-Obese (2.5 microg/g) and Control-Lean mice weighed significantly less than Control-Obese mice. Epididymal pad weights of Control-Obese mice were the heaviest, followed by those of Leptin-Obese mice, and Control-Lean mice were the lightest. Testes weight was greater in Control-Lean vs Control-Obese mice. Leptin-Obese mice had testes weight not significantly different from either control group. Four of five Leptin-Obese mice impregnated females (4/10, 5/10, 2/10, 5/12, 0/10). These results indicate that low-dosage mouse recombinant leptin treatment restored fertility to young Lep(ob) Lep(ob) male mice. Although body weights of Leptin-Obese mice were similar to those of lean age-matched mice, epididymal fat pad weights were heavier. International Journal of Obesity (2001) 25, 95-97