Adoptive transfer of regulatory NKT lymphocytes ameliorates non-alcoholic steatohepatitis and glucose intolerance in ob/ob mice and is associated with intrahepatic CD8 trapping

The aim of this study was to determine the effect of adoptive transfer of regulatory natural killer T (NKT) lymphocytes on the metabolic disorder in leptin-deficient ob/ob mice, which feature depletion and defective function of NKT and CD4 lymphocytes. Leptin-deficient ob/ob mice were subjected to transplantation of 1 x 10(6) of either ob/ob or wild-type-derived NKT lymphocytes, or to transplantation of either ob/ob or wild-type-derived splenocytes. The effect on hepatic fat content was measured by magnetic resonance imaging (signal intensity index) and histology, using the steatohepatitis grading scale. The degree of glucose intolerance was measured by an oral glucose tolerance test (GTT). Adoptive transfer of wild-type or ob/ob-derived regulatory NKT cells led to a 12% decrease in hepatic fat content. A significant histological shift from macrosteatosis to microsteatosis was observed. Marked improvement in the GTT was noted in wild-type or ob/ob-derived NKT recipients. Metabolic effects were associated with a significant decrease in peripheral and intrahepatic CD4/CD8 lymphocyte ratios. Intrahepatic CD8 trapping was observed in all responders. Serum interleukin 10 levels decreased significantly. In conclusion, adoptive transfer of a relatively small number of regulatory NKT lymphocytes into ob/ob mice results in a significant reduction in hepatic fat content, a shift from macro to microsteatosis, and significant improvement in glucose intolerance. These effects were associated with decreased peripheral and intrahepatic CD4/CD8 ratios and decreased interleukin 10 levels. The results further support a role for regulatory NKT lymphocytes in the pathogenesis of non-alcoholic steatohepatitis in the leptin-deficient murine model.     

Genetic factors in sleep-disordered breathing

Sleep-disordered breathing (SDB) is characterized by repetitive episodes of decreased or arrested respiratory airflow during sleep. SDB is common and affects approximately 20% of the Japanese general population. Most traits of normal sleep and SDB show familial aggregation, suggesting significant effects of genetic factors. Obstructive sleep apnea (OSA) is the most common type of SDB and has a high heritability. Regardless of high heritability, no risk locus for OSA has reached a genome-wide level of significance (P < 5×10^?8) in linkage or candidate gene analysis. However, a recent genome-wide association study identified some genetic risks for OSA with P < 5×10^?8 for the first time. The identified genes are associated with inflammation, hypoxia signaling, and sleep pathways. The effects of genetic factors on the consequences of OSA has not been determined, although a correlation between OSA and cardiovascular disease may differ across races. Congenital central hypoventilation syndrome (CCHS) is a genetically inherited disorder caused by mutations in the paired-like homeobox 2B (PHOX2B) gene of polyalanine repeat mutations in the 20-alanine repeat or non-polyalanine repeat mutations. PHOX2B genotypes are also associated with clinical phenotypes of CCHS, including severity of hypoventilation. SDB, including obesity hypoventilation syndrome, is often seen in genetic obesity-associated disorders such as Prader-Willi syndrome. Although advances in genetics have resulted in identification of some genetic causes of SDB, further studies are required to elucidate the cellular and molecular mechanisms between genetic risks and clinical manifestations.     

Effects of leptin on femoral fracture in rats

In this study, our objective was to evaluate effects of leptin on fracture healing in rats. Seventy two male SpragueDawley (SD) rats were randomized into 3 groups. Standardized femoral fractures were created in all the rats. Group A was treated with 1 mL normal saline (NS), group B with 0.3 μg/kg leptin in 1 mL NS, and group C with 0.5 μg/kg leptin in 1 mL NS for 2 weeks intraperitoneally. Each group was divided into three subgroups including 8 rats for evaluation at 2, 4 and 8 weeks. Radiological evaluation showed that callus formation of group B and C was all significantly higher than group A at 8 weeks (P = 0.04 and P = 0.013, respectively). There was no statistically significant difference in fracture healing between group B and group C at 8 weeks (P = 0.197). Histological evaluation revealed fracture healing of group B and C was better than group A at 4 weeks (P = 0.01 and P = 0.002, respectively) and 8 weeks (P = 0.008 and P = 0.003, respectively). Micro-computed tomography (Micro-CT) analysis demonstrated that greater amounts of bony callus and evidence of bone fusion were observed in group B and C at 4 weeks (P = 0.02 and P = 0.04, respectively) and 8 weeks (P = 0.005 and P = 0.001, respectively) compared to group A. Group C also had better fracture healing than group B at 8 weeks (P = 0.01). In conclusion, leptin has a positive effect on rat femoral fracture healing.     

A critical period for the trophic actions of leptin on AgRP neurons in the arcuate nucleus of the hypothalamus

In the developing hypothalamus, the fat‐derived hormone leptin stimulates the growth of axons from the arcuate nucleus of the hypothalamus (ARH) to other regions that control energy balance. These projections are significantly reduced in leptin deficient (Lep^ob/ob) mice and this phenotype is largely rescued by neonatal leptin treatments. However, treatment of mature Lep^ob/ob mice is ineffective, suggesting that the trophic action of leptin is limited to a developmental critical period. To temporally delineate closure of this critical period for leptin‐stimulated growth, we treated Lep^ob/ob mice with exogenous leptin during a variety of discrete time periods, and measured the density of Agouti‐Related Peptide (AgRP) containing projections from the ARH to the ventral part of the dorsomedial nucleus of the hypothalamus (DMHv), and to the medial parvocellular part of the paraventricular nucleus (PVHmp). The results indicate that leptin loses its neurotrophic potential at or near postnatal day 28. The duration of leptin exposure appears to be important, with 9‐ or 11‐day treatments found to be more effective than shorter (5‐day) treatments. Furthermore, leptin treatment for 9 days or more was sufficient to restore AgRP innervation to both the PVHmp and DMHv in Lep^ob/ob females, but only to the DMHv in Lep^ob/ob males. Together, these findings reveal that the trophic actions of leptin are contingent upon timing and duration of leptin exposure, display both target and sex specificity, and that modulation of leptin‐dependent circuit formation by each of these factors may carry enduring consequences for feeding behavior, metabolism, and obesity risk.     

Hypogonadism and male obesity: Focus on unresolved questions

Obesity, increasing in prevalence globally, is the clinical condition most strongly associated with lowered testosterone concentrations in men and presents as one of the strongest predictors of receiving testosterone treatment. While low circulating total testosterone concentrations in modest obesity primarily reflect reduced concentrations of sex hormone binding globulin, more marked obesity can lead to genuine hypothalamic‐pituitary‐testicular axis (HPT) suppression. HPT axis suppression is likely mediated via pro‐inflammatory cytokine and dysregulated leptin signalling and aggravated by associated comorbidities. Whether oestradiol‐mediated negative hypothalamic‐pituitary feedback plays a pathogenic role requires further study. Although the obesity‐hypogonadism relationship is bidirectional, the effects of obesity on testosterone concentrations are more substantial than the effects of testosterone on adiposity. In markedly obese men submitted to bariatric surgery, substantial weight loss is very effective in reactivating the HPT axis. In contrast, lifestyle measures are less effective in reducing weight and generally only associated with modest increases in circulating testosterone. In randomized controlled clinical trials (RCTs), testosterone treatment does not reduce body weight, but modestly reduces fat mass and increases muscle mass. Short‐term studies have shown that testosterone treatment in carefully selected obese men may have modest benefits on symptoms of androgen deficiency and body composition even additive to diet alone. However, longer term, larger RCTs designed for patient‐important outcomes and potential risks are required. Until such trials are available, testosterone treatment cannot be routinely recommended for men with obesity‐associated nonclassical hypogonadism. Lifestyle measures or where indicated bariatric surgery to achieve weight loss, and optimization of comorbidities remain first line.     

Microsomal prostaglandin E synthase‐1 inhibition blocks proliferation and enhances apoptosis in oesophageal adenocarcinoma cells without affecting endothelial prostacyclin production

Prostaglandins are important in the progression of various gastrointestinal cancers including oesophageal adenocarcinoma (OAC). Cyclo‐oxygenase (COX)‐2 inhibitors reduce OAC prostaglandin production but also have potentially detrimental effects on vascular endothelial function by reducing prostacyclin production and increasing the risk of cardiovascular events. We have examined the effects of inhibiting microsomal prostaglandin synthase‐1 (mPGES‐1), the enzyme downstream of COX‐2 in the prostaglandin synthetic cascade. In OAC cells, reduction of mPGES‐1 with RNA interference blocked PGE2 production, inhibited serum‐induced proliferation and enhanced apoptosis in the COX‐2 expressing cell lines (OE33 and FLO) but had no effect in COX‐2 deficient BIC‐1 cells. Three different methods of inhibiting mPGES‐1 (RNA interference, a novel small molecule inhibitor and the endogenous inhibitor 15‐deoxy‐Δ^12,14‐PGJ₂) also blocked leptin induced mPGES‐1 expression and PGE2 production and abolished the leptin‐induced proliferative and anti‐apoptotic effects in OE33 cells, without affecting COX‐2 expression. The anti‐proliferative effects were equivalent to those produced by COX‐2 inhibitory concentrations of celecoxib and NS‐398. However, unlike the two COX‐2 inhibitors, mPGES‐1 inhibition did not reduce endothelial prostacyclin production. In contrast to the effects of the COX‐2 inhibitor celecoxib, mPGES‐1 inhibition had no effects on Akt kinase activity in OAC cells. We conclude that inhibition of mPGES‐1 has potentially beneficial effects in OAC without the potentially detrimental effects on vascular endothelial prostacyclin synthesis. We have also confirmed that celecoxib has anticancer actions separate from the inhibition of COX‐2. Inhibition of mPGES‐1 may be therapeutically useful in the treatment and prevention of OAC.