Twenty-four-hour variation in serum leptin in the elderly

Obesity paradox in uveal melanoma: high body mass index is associated with low metastatic risk

BACKGROUND

Metabolic factors and obesity may influence the development and progression of cancer. In this study, we examine their association with the risk of developing metastases of uveal melanoma.

METHODS

Data on metabolic factors, medications, serum leptin levels, tumour leptin receptor RNA expression and clinical outcomes were examined in three cohorts. HRs for metastasis and cumulative incidences of melanoma-related mortality were calculated, and the levels of tumour leptin receptor expression were compared with prognostic factors including BAP1 mutation, and tumour cell morphology.

RESULTS

Of 581 patients in the main cohort, 116 (20%) were obese and 7 (1 %) had metastatic disease at presentation. In univariate Cox regressions, tumour diameter, diabetes type II and use of insulin were associated with metastases, but patients with obesity had a lower risk. The beneficial prognostic implication of obesity was retained in multivariate regressions. In competing risk analyses, the incidence of melanoma-related mortality was significantly lower for patients with obesity. Serum leptin levels≥median were associated with a reduced risk for metastasis, independent of patient sex and cancer stage in a separate cohort (n=80). Similarly, in a third cohort (n=80), tumours with BAP1 mutation and epithelioid cells had higher leptin receptor RNA expression levels, which have a negative correlation with serum leptin levels.

CONCLUSION

Obesity and elevated serum leptin levels are associated with a lower risk for developing metastases and dying from uveal melanoma.

Circadian variations in the elderly: A scoping review

The circadian clock plays important roles in several physiological processes. With aging, some of these circadian rhythms have been shown to be disrupted and suggested contributing to age-related diseases. The aim of this scoping review was to examine and map the existing evidence of circadian differences between young and older people in body fluid composition. Literature search was carried out on PubMed, Embase, Scopus and OpenGrey. The studies were screened based on inclusion and exclusion criteria by two independent reviewers and the results were summarized tabularly and narratively. The review process resulted in the identification of 1889 publications, of which 42 were eligible for inclusion. Forty-eight parameters or families of parameters were identified, including cortisol and melatonin, sex hormones, thyroid-related hormones, steroids and aldosterone. However, many were reported by only a single study. The results from the studies were heterogeneous. Even though the majority suggested the flattening of several circadian oscillations in the elderly population, this was not always observed for all the parameters analyzed, and some contradictory results were found. This review revealed a substantial number of publications that explored this research question, but further studies would be important to elucidate the clinical significance of these alterations.

Circadian Dysfunction in Adipose Tissue: Chronotherapy in Metabolic Diseases

Essential for survival and reproduction, the circadian timing system (CTS) regulates adaptation to cyclical changes such as the light/dark cycle, temperature change, and food availability. The regulation of energy homeostasis possesses rhythmic properties that correspond to constantly fluctuating needs for energy production and consumption. Adipose tissue is mainly responsible for energy storage and, thus, operates as one of the principal components of energy homeostasis regulation. In accordance with its roles in energy homeostasis, alterations in adipose tissue's physiological processes are associated with numerous pathologies, such as obesity and type 2 diabetes. These alterations also include changes in circadian rhythm. In the current review, we aim to summarize the current knowledge regarding the circadian rhythmicity of adipogenesis, lipolysis, adipokine secretion, browning, and non-shivering thermogenesis in adipose tissue and to evaluate possible links between those alterations and metabolic diseases. Based on this evaluation, potential therapeutic approaches, as well as clock genes as potential therapeutic targets, are also discussed in the context of chronotherapy.

A serum protein signature at the time of Uveal Melanoma diagnosis predicts long-term patient survival

PURPOSE

To develop a prognostic test based on a single blood sample obtained at the time of uveal melanoma diagnosis.

METHODS

83 patients diagnosed with posterior uveal melanoma between 1996 and 2000 were included. Peripheral serum samples were obtained at diagnosis and kept at -80 °C until this analysis. Protein profiling of 84 cancer-related proteins was used to screen for potential biomarkers and a prognostic test that stratifies patients into metastatic risk categories was developed (serUM-Px) in a training cohort and then tested in a validation cohort.

RESULTS

Low serum leptin levels and high osteopontin levels were found to identify patients with poor prognosis and were therefore selected for inclusion in the final test. In the validation cohort, patient sex and American Joint Committee on Cancer stages were similarly distributed between the low, intermediate, and high metastatic risk categories. With increasing metastatic risk category, patients had shorter metastasis-free- and overall survival, as well as greater cumulative incidence of uveal melanoma-related mortality in competing risk analysis (P = 0.007, 0.018 and 0.029, respectively). In multivariate Cox regression, serUM-Px was an independent predictor of metastasis with tumor size and patient sex as covariates (hazard ratio 3.2, 95% CI 1.5-6.9).

CONCLUSIONS

A prognostic test based on a single peripheral venous blood sample at the time of uveal melanoma diagnosis stratifies patients into low, intermediate, and high metastatic risk categories. Prospective validation will facilitate its clinical utility.

Sleep and metabolic control: waking to a problem?

1. The aim of the present review is to outline: (i) the association between sleep and metabolism; (ii) how sleep duration influences the development of disease; and (iii) how sex differences, ageing and obesity may potentially influence the relationship between sleep, metabolic control and subsequent disease. 2. Sleep is associated with a number of endocrine changes, including a change in insulin action in healthy young individuals. Sleep duration shows a prospective U-shaped relationship with all-cause mortality, cardiovascular disease and Type 2 diabetes. 3. Chronic sleep restriction is becoming more common. Experimental sleep restriction impedes daytime glucose control and increases appetite. 4. The sex hormones oestrogen and testosterone influence sleep duration and quality and may account for sex differences in the prevalence of sleep-related disorders. 5. Ageing is associated with a decreased sleep duration, decreased muscle mass and impaired insulin action. 6. Obesity impairs insulin action and is associated with the incidence and severity of obstructive sleep apnoea. 7. Sleep plays an integral role in metabolic control. Consequently, insufficient sleep may represent a modifiable risk factor for the development of Type 2 diabetes. The challenge ahead is to identify how sex differences, ageing and obesity could potentially influence the relationship between sleep and metabolism.

Linkage of serum leptin levels in families with sleep apnea

OBJECTIVE

To identify regions on the genome linked to plasma leptin levels.

DESIGN

Full genome scan with 402 microsatellite markers, spaced approximately 10 cM apart. Data were analyzed using the Haseman-Elston regression linkage analysis.

SUBJECTS

A total of 160 sibling pairs from 59 predominantly African American, obese families recruited to participate in a genetic-epidemiological study of obstructive sleep apnea.

MEASUREMENTS

Serum leptin levels adjusted for age, sex, race and body mass index (BMI).

RESULTS

Suggestive linkage peaks were observed on chromosomes 2 (P=0.00170; marker D2S1384), 3 (P=0.00007; marker D3S3034), 4 (P=0.00020; marker D4S1652) and 21 (P=0.00053; marker D21s1411).

CONCLUSION

The peak on chromosome 3 is near the gene for glycogensynthase kinase 2 beta, an important factor in glucose homeostasis. Linkage was generally stronger after BMI adjustment, suggesting the potential influence of a number of metabolic pathways on leptin levels other than those that directly determine obesity levels. The evidence of linkage for leptin levels is consistent with prior linkage analyses for cholesterol, hypertension and other metabolic phenotypes.

Leptin levels are appropriate for body mass index in older men who experience involuntary weight loss

OBJECTIVES

To determine the relationship between leptin and unintentional weight loss in older adults.

DESIGN

Prospective cohort study over 2 years.

SETTING

University-affiliated Veterans Affairs Medical Center.

PARTICIPANTS

The subjects were 105 community-dwelling male veterans aged 65 and older who had participated in a prospective cohort study on nutrition and health conducted at the Veterans Affairs Puget Sound Health Care System from 1986 to 1989.

MEASUREMENTS

Anthropometric data and fasting blood specimens were collected at baseline and annually for the subsequent 2 years. Stored blood specimens were analyzed for leptin, insulin, glucose, C-reactive protein, sex hormone binding globulin, and testosterone levels.

RESULTS

Over 2 years, 75 men were weight stable (weight loss <4% of baseline) and 30 men had unintentional weight loss (weight loss>4% of baseline). The baseline body mass index (BMI) and leptin levels for the two groups were not statistically different. Positive correlations existed between leptin level and BMI at each time point for weight-stable and weight-loss subjects. Furthermore, a significant relationship existed between changes in leptin and changes in BMI over 1 year in multiple regression analysis (r =.436, P <.001 after the first year; and r =.630, P =.027 after the second year).

CONCLUSIONS

Like in younger adults, plasma leptin levels remained proportional to BMI, and changes in BMI were accurately reflected by changes in leptin levels in older individuals. Fasting leptin levels did not predict involuntary weight loss over 2 years of follow-up.

Overweight, waist circumference, age, gender, and insulin resistance as risk factors for hyperleptinemia

OBJECTIVE

To evaluate the influence of overweight, waist circumference, age, gender, and insulin resistance as risk factors for hyperleptinemia.

RESEARCH METHODS AND PROCEDURES

A cross-sectional study was carried out in a population of 197 subjects: 59 men (21 aged < 60 years and 38 aged > or =60 years) and 138 women (37 aged < 60 years and 101 aged > or =60 years). The groups were stratified by overweight and normal weight. After a 12-hour fasting period, we measured serum leptin and insulin levels with radioimmunoassay methods. We also measured serum glucose and lipid profile. The data were analyzed by means of comparative tests. A variance-stabilizing transformation (natural logarithmic) was used to meet multiple linear regression, analysis of covariance, and logistic regression models.

RESULTS

The leptin serum levels were higher and statistically significant in young and older women than they were in men. We observed an interaction between gender and body mass index to explain the difference in leptin levels (p < 0.0001). Our study demonstrated an inverse relationship between leptin with age and high-density lipoprotein cholesterol. In logistic regression analysis, the overweight x gender interaction and waist circumference have a statistically significant influence as independent variables on hyperleptinemia (overweight x gender odds ratio = 6.81; 95% confidence interval, 1.10 to 46.86; p < 0.05 and waist circumference odds ratio = 4.34; 95% confidence interval, 1.47 to 12.83; p = 0.001).

DISCUSSION

Women who were overweight or had a higher waist circumference (women > or = 88 cm and men > or = 102 cm) have a significantly higher risk of having hyperleptinemia. The increase in age as an isolated variable is not a risk factor for hyperleptinemia.

Leptin and reproduction: a review

OBJECTIVE

To review recent advances in understanding the role of leptin in the physiology and pathophysiology of reproduction, with a focus on relevant clinical situations.

DESIGN

A MEDLINE computer search was performed to identify relevant articles.

RESULT(S)

Leptin, an adipocyte hormone important in regulating energy homeostasis, interacts with the reproductive axis at multiple sites, with stimulatory effects at the hypothalamus and pituitary and inhibitory actions at the gonads. More recently, leptin has been shown to play a role in other target reproductive organs, such as the endometrium, placenta, and mammary gland, with corresponding influences on important physiologic processes such as menstruation, pregnancy, and lactation. As a marker of whether nutritional stores are adequate, leptin may act in concert with gonadotropins and the growth hormone axis to initiate the complex process of puberty. Conditions in which nutritional status is suboptimal, such as eating disorders, exercise-induced amenorrhea, and functional hypothalamic amenorrhea, are associated with low serum leptin levels; and conditions with excess energy stores or metabolic disturbances, such as obesity and polycystic ovarian syndrome, often have elevated serum or follicular fluid leptin levels, raising the possibility that relative leptin deficiency or resistance may be at least partly responsible for the reproductive abnormalities that occur with these conditions.

CONCLUSION(S)

Leptin may act as the critical link between adipose tissue and the reproductive system, indicating whether adequate energy reserves are present for normal reproductive function. Future interventional studies involving leptin administration are expected to further clarify this role of leptin and may provide new therapeutic options for the reproductive dysfunction associated with states of relative leptin deficiency or resistance.

Sexual dimorphism in relationship of serum leptin and relative weight for the standard in normal-weight, but not in overweight, children as well as adolescents

OBJECTIVE

To demonstrate sexual dimorphism in serum leptin levels not only during puberty, but also in childhood in Japan.

DESIGN

Cross-sectional study.

SETTING

Hamamatsu-Hokuen study in Japan.

SUBJECTS

Body weight and height were measured in normal-weight Japanese children and adolescents (143 boys, 178 girls), and 161 boys and 129 girls whose percentage of overweight for the standard (%Wt) was more than+25%. Serum leptin levels were compared with %Wt. Subjects were divided into group 1 (6-10 y of age) and group 2 (11-15 y of age) according to their age.

RESULTS

In overweight subjects, leptin was more highly correlated with %Wt in boys of group 2 (r=0.67, P<0.0001) than group 1 (r=0.32, P=0.004). In girls as well, a correlation coefficient was greater in group 2 (r=0.67, P<0.0001) than group 1 (r=0.44, P=0.0011). In normal-weight boys, there was no significant correlation between serum leptin and %Wt both in groups 1 and 2. On the contrary, statistical significance was demonstrated in the correlation between serum leptin and %Wt in group 1 (r=0.31, P=0.0019) and group 2 (r=0.35, P=0.0014) as well as in the total normal-weight girls (r=0.28, P=0.0011).

CONCLUSIONS

It is suggested that sexual dimorphism is present in serum leptin levels, especially when compared to weight, as early as during childhood.

Twenty-four-hour profiles of serum leptin in siberian and golden hamsters: photoperiodic and diurnal variations

Serum leptin concentrations were obtained from male Siberian hamsters (Phodopus sungorus) and golden hamsters (a.k.a. Syrian, Mesocricetus auratus) housed on long [light:dark (LD) 16:8] and short (LD 6:18) photoperiods for 10-11 weeks. Blood samples were collected at 45-min intervals for 24 h from individual animals using an in-dwelling atrial catheter. In Siberian hamsters, exposure to short photoperiods as compared to long photoperiods reduced body weight (32.5 +/- 1.5 vs 47.7 +/- 1.1 g) and leptin (24-h mean: 5.3 +/- 0.4 ng/ml vs 18.6 +/- 2.1 ng/ml). Although photoperiod influenced the temporal distribution of leptin in golden hamsters, the main effect of photoperiod on leptin levels in golden hamsters did not reach significance (24-h mean: 7.1 +/- 1.0 ng/ml vs 5.1 +/- 0.8 ng/ml.). Body weights of golden hamsters did not vary significantly following exposure to short photoperiod for 11 weeks (178.3 +/- 3.6 g in LD 6:18 vs 177.8 +/- 7.3 g in LD 16:8). There was no nocturnal increase in serum leptin in either species. Marked interindividual differences were apparent in individual leptin profiles. Periodogram analysis revealed that only a few animals exhibited 24-h periodicities; the presence of a significant 24-h periodicity was more common in hamsters exposed to short days. Photoperiod-associated differences in the 24-hour profile of leptin secretion may be the result of photoperiod-associated changes in feeding behavior or metabolism. A full understanding of the regulation of leptin secretion in multiple time domains may enhance our understanding of the function of leptin.

Leptin and aging: correlation with endocrine changes in male and female healthy adult populations of different body weights

Aging is associated with changes in plasma levels of several hormones. There are conflicting reports on whether circulating leptin levels change during aging, the possible explanation for which is that alterations in adiposity and body mass index (BMI) also occur. In this study we measured plasma leptin and other hormonal parameters known to influence leptin in 150 men and 320 women of a wide age (18-77 yr) and BMI (18.5-61.1 kg/m2) range. Subjects of each gender were separated into 2 groups of similar BMI, i.e. nonobese (BMI, <30) and obese (BMI, >30), and treated separately. Statistical analysis was performed, treating each group of subjects as a whole population or divided into age groups (<30, 30-50, and >50 yr). BMI-adjusted leptin levels were progressively lower with increasing age in women, with a consistent fall after menopause (-21%; P < 0.001); in men, leptin levels also tended to be lower in subjects more than 50 yr of age, but the reduction was not significant. Multiple linear regression analysis, performed on subjects treated either as a whole population or divided into obese and nonobese, showed that in both genders BMI and age were independent contributors of leptin levels, and there was an inverse relationship between leptin and age in both obese (standardized coefficient beta = -0.25 in women and -0.23 in men; P < 0.01) and nonobese (-0.22 in women and -0.20 in men; P < 0.05) subjects. The correlation of leptin and age with plasma levels of sex and thyroid hormones, GH, insulin-like growth factor I, PRL, and insulin was also evaluated. The variables that correlated with leptin were included in a multiple regression model that included BMI and age. Testosterone in men (-0.43 in nonobese and -0.19 in obese; P < 0.05) and estradiol in women (0.22 in nonobese and 0.24 in obese; P < 0.05) were important contributors to leptin levels; also, dehydroepiandrosterone sulfate in obese women (-0.16) and sex hormone-binding globulin in obese subjects of both genders (0.15 in women and 0.19 in men) were significant determinants in the model. However, none of the hormonal parameters abolished the negative correlation between leptin and age or the gender difference in leptin levels. In conclusion, our data show that in adult humans of different body weight, serum leptin gradually declines during aging; leptin reduction is higher in women than in men, but it is independent from BMI and other age-related endocrine changes.