Clinical implications of leptin and its potential humoral regulators in long-term low-calorie diet therapy for obese humans

Novel compound heterozygous mutations in LEP responsible for obesity in a Chinese family

Background

Early childhood obesity poses a significant global public health challenge, necessitating the identification of treatable causes, particularly congenital leptin deficiencies. Serum leptin level measurement aids in diagnosing these rare contributors, guiding effective management.

Methods

A Chinese family with early-onset obesity underwent LEP mutational screening via direct sequencing. mRNA expression and protein stability patterns of LEP were separately analyzed using qPCR and bioinformatics.

Results

We present a case of a 12.5-year-old girl born to non-obese, non-consanguineous Chinese parents, exhibiting low leptin levels. Leptin gene sequencing revealed novel compound heterozygous mutations in exon 3. RT-PCR analysis showed the mutation didn't affect leptin production. Bioinformatics analysis indicated the variant rendered the leptin protein unstable.

Conclusion

Loss-of-function mutations in LEP underlies early-onset obesity in the patient.

Cancer and comorbidity: The role of leptin in breast cancer and associated pathologies

Obesity is an important risk factor for postmenopausal breast cancer and also a poor prognostic factor among cancer patients. Moreover, obesity is associated with a number of health disorders such as insulin resistance/type-2 diabetes mellitus, hypertension, and other cardiovascular diseases. Frequently, these health disorders exhibit as components/complications of the metabolic syndrome. Nevertheless, obesity-related diseases may coexist with postmenopausal breast cancer; and these comorbid conditions could be substantial. Therefore, it may be assumed that different diseases including breast cancer could originate from a common pathological background in excessive adipose tissue. Adipocyte-released hormone-like cytokine (or adipokine) leptin behaves differently in a normal healthy state and obesity. A growing body of evidence suggests an important role of leptin in our major obesity-related health issues such as insulin resistance, hypertension, and neoplasia. In this context, this review describes the relationships of the abovementioned pathologies with leptin.

Genetics of Severe Obesity

PURPOSE OF REVIEW

This review aims to present current information on genes underlying severe obesity, with the main emphasis on the three genes LEP, LEPR and MC4R.

RECENT FINDINGS

There is a substantial amount of evidence that variants in at least ten different genes are the cause of severe monogenic obesity. The majority of these are involved in the leptin-melanocortin signalling pathway. Due to the frequency of some of the identified variants, it is clear that monogenic variants also make a significant contribution to common obesity. The artificial distinction between rare monogenic obesity and common polygenic obesity is now obsolete with the identification of MC4R variants of strong effect in the general population.

Safety and feasibility of diet-treated donors with steatotic livers at the initial consultation for living-donor liver transplantation

BACKGROUND

The purpose of this study was to evaluate both safety of diet-treated donors and the feasibility of their use for living-donor liver transplantation (LDLT).

METHODS

A total of 128 living donors were enrolled in this study between April 2003 and March 2010. Of them, 41 were diagnosed with hepatic steatosis at the initial consultation. Donor selection was based on the findings of liver biopsy accompanied with normalization of liver function tests after diet treatment consisting of an 800 to 1400 kcal/day diet and a 100 to 400 kcal/day exercise without drug treatment, targeting body mass index of 22 kg/m².

RESULTS

Body mass index of diet-treated donors was significantly reduced with diet from 23.3 ± 0.6 to 21.9 ± 0.4 kg/m² (P<0.0001). Liver function tests associated with fatty liver, including alanine aminotransferase, gamma-glutamyl transpeptidase, and total cholesterol levels, also improved with diet (P=0.0128, 0.0016, and 0.0004, respectively). The liver biopsy results of most of these donors showed stage 0/1 fibrosis and minimal/mild steatosis after the diet therapy. Surgical outcomes, including postoperative liver function tests, perioperative complications, and liver regeneration rates, did not significantly differ between nondiet-treated and diet-treated donors. Surgical outcomes and the overall survival did not significantly differ between recipients of grafts from nondiet-treated and diet-treated donors.

CONCLUSION

The use of diet-treated donors for living-donor liver transplantation is feasible with respect to donor safety and the outcome of the recipient when strict selection criteria are used.

Effect of chronic and intermittent calorie restriction on serum adiponectin and leptin and mammary tumorigenesis

The effect of chronic (CCR) and intermittent (ICR) caloric restriction on serum adiponectin and leptin levels was investigated in relation to mammary tumorigenesis. 10-wks old MMTV-TGF-α female mice were assigned to ad libitum fed (AL; AIN-93M diet), ICR (3-week 50% caloric restriction, AIN-93M-mod diet, 2× protein, fat, vitamins, and minerals followed by 3-wks 100% AL consumption of AIN-93M), and CCR (calorie and nutrient intake matched for each 6-wks ICR cycle, ∼ 75% of AL) groups. Mice were sacrificed at 79 (end of restriction) or 82 (end of refeeding) wks of age. Serum was obtained in cycles 1, 3, 5, 8, 11, and terminal. Mammary tumor incidence was 71.0%, 35.4%, and 9.1% for AL, CCR, and ICR mice, respectively. Serum adiponectin levels were similar among groups with no impact of either CCR or ICR. Serum leptin level rose in AL mice with increasing age but was significantly reduced by long-term CCR and ICR. The ICR protocol was also associated with an elevated adiponectin/leptin ratio. In addition, ICR-restricted mice had increased mammary tissue AdipoR1 expression and decreased leptin and ObRb expression compared with AL mice. Mammary fat pads from tumor-free ICR-mice had higher adiponectin expression than AL and CCR mice whereas all tumor-bearing mice had weak adiponectin signal in mammary fat pad. Although we did not show an association of either adiponectin or leptin with individual mice in relation to mammary tumorigenesis, we did find that reduced serum leptin and elevated adiponectin/leptin ratio were associated with the protective effect of intermittent calorie restriction.

Adipokines and dietary interventions in human obesity

Obesity is a multisystem disorder associated with cardiovascular and metabolic complications. According to recent studies, it is characterized as a condition of low-grade inflammation with altered adipose tissue function and secretion of various adipokines. One of the strategies in obesity treatment is dietary intervention (DI) that could modulate cytokine levels in a favourable way. The aim of this review was to summarize the results of studies performed in the last 13 years investigating DI programmes accompanied with weight loss in relation to profile of adipokines at different level (adipose tissue mRNA, adipose tissue secretion and circulating level) and identify whether modulations of adipokines are implicated in the positive effects of DIs. The overall finding is that DIs leading to 5-10% weight loss modulate production of certain adipokines and generally induce improvement of clinical parameters, e.g. insulin sensitivity, but the amelioration of obesity complications is not coherent with the pattern of adipokine regulation, except maybe for leptin. Global analysis of the adipose tissue secretome and measurement of panels of adipokines may prove more informative than studies on individual molecules.

Do calorie restriction or alternate-day fasting regimens modulate adipose tissue physiology in a way that reduces chronic disease risk?

Adipose tissue physiology plays an important role in the development of several obesity-related disorders. Dietary restriction regimens, i.e., daily calorie restriction (CR) or alternate-day fasting (ADF), have been shown to decrease the risk of these disorders. Whether changes in adipose mass or physiology are required for the beneficial effects of CR or ADF is an important question. Accordingly, this review summarizes the effects of CR and ADF regimens on parameters of adipose physiology, i.e., adipose tissue morphology, triglyceride metabolism, and adipokine release, and attempts to link these changes to indicators of chronic disease risk.

Gene expression profiling of human skeletal muscle in response to stabilized weight loss

BACKGROUND

Diet-induced weight reduction promotes a decrease in resting energy expenditure that could partly explain the difficulty in maintaining reduced body mass. Whether this reduction remains after stabilized weight loss is still controversial, and the molecular mechanisms are unknown.

OBJECTIVE

The objective was to investigate the effect of a stabilized 10% weight loss on body composition, metabolic profile, and skeletal muscle gene expression profiling.

DESIGN

Obese women were assigned to a 4-wk very-low-calorie diet, a 3-6-wk low-calorie diet, and a 4-wk weight-maintenance program to achieve a 10% weight loss. Resting energy expenditure, body composition, plasma variables, and skeletal muscle transcriptome were compared before weight loss and during stabilized weight reduction.

RESULTS

Energy restriction caused an 11% weight loss. Stabilization to the new weight was accompanied by an 11% decrease in the resting metabolic rate normalized to the body cellular mass. A large number of genes were regulated with a narrow range of regulation. The main regulated genes were slow/oxidative fiber markers, which were overexpressed, and the gene encoding the glucose metabolism inhibitor PDK4, which tended to be down-regulated. The knowledge-based approach gene set enrichment analysis showed that a set of genes related to long-term calorie restriction was up-regulated, whereas sets of genes related to insulin, interleukin 6, and ubiquitin-mediated proteolysis were down regulated.

CONCLUSIONS

Weight loss-induced decreases in resting metabolic rate persist after weight stabilization. Changes in skeletal muscle gene expression indicate a shift toward oxidative metabolism.

Energy balance adiposity and breast cancer - energy restriction strategies for breast cancer prevention

Excess adiposity over the pre- and postmenopausal years is linked to risk of postmenopausal breast cancer. Weight loss could potentially reduce risk amongst those with excess weight via beneficial effects on the hormonal (decreased circulating levels of oestradiol, testosterone, insulin) and secretory profiles of adipocytes (decreased production of leptin, tumour necrosis factor-alpha, interleukin 6 and increased production of adiponectin). Only modest reductions in adipose tissue are achieved and sustained with current weight loss programmes, which makes strategies to mitigate the adverse metabolic effect of adiposity a priority for cancer prevention. The adverse hormonal and secretory effects of adipose tissue are influenced substantially by acute changes in energy balance prior to changes in adiposity. Human and animal studies have shown dietary energy restriction to bring about favourable changes in circulating levels of insulin, leptin, sex hormone binding globulin, insulin-like growth factor-1, oestradiol, testosterone, reactive oxygen species, and the production and secretion of locally acting adipokines and inflammatory cytokines, that is, increased adiponectin and decreased interleukin-6. Achieving and sustaining energy restriction remains a difficult challenge. Intermittent energy restriction is a potential strategy for promoting periods of energy restriction on a long-term basis. Animal and human data suggest that intermittent energy restriction may have cancer preventative effects beyond that of chronic energy restriction and weight loss. Intermittent energy restriction may be a potential strategy for the primary prevention of breast cancer.