Disparity in Adiposity among Adults with Normal Body Mass Index and Waist-to-Height Ratio

Tanycytic transcytosis inhibition disrupts energy balance, glucose homeostasis and cognitive function in male mice

OBJECTIVES

In Western society, high-caloric diets rich in fats and sugars have fueled the obesity epidemic and its related disorders. Disruption of the body-brain communication, crucial for maintaining glucose and energy homeostasis, arises from both obesogenic and genetic factors, leading to metabolic disorders. Here, we investigate the role of hypothalamic tanycyte shuttles between the pituitary portal blood and the third ventricle cerebrospinal fluid in regulating energy balance.

METHODS

We inhibited vesicle-associated membrane proteins (VAMP1-3)-mediated release in tanycytes by expressing the botulinum neurotoxin type B light chain (BoNT/B) in a Cre-dependent manner in tanycytes. This was achieved by injecting either TAT-Cre in the third ventricle or an AAV1/2 expressing Cre under the control of the tanycyte-specific promoter iodothyronine deiodinase 2 into the lateral ventricle of adult male mice.

RESULTS

In male mice fed a standard diet, targeted expression of BoNT/B in adult tanycytes blocks leptin transport into the mediobasal hypothalamus and results in normal-weight central obesity, including increased food intake, abdominal fat deposition, and elevated leptin levels but no marked change in body weight. Furthermore, BoNT/B expression in adult tanycytes promotes fatty acid storage, leading to glucose intolerance and insulin resistance. Notably, these metabolic disturbances occur despite a compensatory increase in insulin secretion, observed both in response to exogenous glucose boluses in vivo and in isolated pancreatic islets. Intriguingly, these metabolic alterations are associated with impaired spatial memory in BoNT/B-expressing mice.

CONCLUSIONS

These findings underscore the central role of tanycytes in brain-periphery communication and highlight their potential implication in the age-related development of type 2 diabetes and cognitive decline. Our tanycytic BoNT/B mouse model provides a robust platform for studying how these conditions progress over time, from prediabetic states to full-blown metabolic and cognitive disorders, and the mechanistic contribution of tanycytes to their development. The recognition of the impact of tanycytic transcytosis on hormone transport opens new avenues for developing targeted therapies that could address both metabolic disorders and their associated cognitive comorbidities, which often emerge or worsen with advancing age.

Association between triglyceride-glucose related indices with the all-cause and cause-specific mortality among the population with metabolic syndrome

BACKGROUND

Triglyceride-glucose (TyG) index has been determined to play a role in the onset of metabolic syndrome (MetS). Whether the TyG index and TyG with the combination of obesity indicators are associated with the clinical outcomes of the MetS population remains unknown.

METHOD

Participants were extracted from multiple cycles of the National Health and Nutrition Examination Survey (NHANES) between 1999 and 2018 years. Three indicators were constructed including TyG index, TyG combining with waist circumference (TyG-WC), and TyG combining with waist-to-height ratio (TyG-WHtR). The MetS was defined according to the National Cholesterol Education Program (NCPE) Adult Treatment Panel III. Kaplan-Meier (KM) curves, restricted cubic splines (RCS), and the Cox proportional hazard model were used to evaluate the associations between TyG-related indices and mortality of the MetS population. The sensitive analyses were performed to check the robustness of the main findings.

RESULTS

There were 10,734 participants with MetS included in this study, with 5,570 females and 5,164 males. The median age of the study population was 59 years old. The multivariate Cox regression analyses showed high levels of TyG-related indices were significantly associated with the all-cause mortality of MetS population [TyG index: adjustedhazard ratio (aHR): 1.36, 95%confidence interval (CI): 1.18-1.56, p < 0.001; TyG-WHtR index: aHR = 1.29, 95%CI: 1.13-1.47, p < 0.001]. Meanwhile, the TyG-WC and TyG-WHtR index were associated with cardiovascular mortality of the MetS population (TyG-WC: aHR = 1.45, 95%CI: 1.13-1.85, p = 0.004; TyG-WHtR: aHR = 1.50 95%CI: 1.17-1.92, p = 0.002). Three TyG-related indices showed consistent significant correlations with diabetes mortality (TyG: aHR = 4.06, 95%CI: 2.81-5.87, p < 0.001; TyG-WC: aHR = 2.55, 95%CI: 1.82-3.58, p < 0.001; TyG-WHtR: aHR = 2.53 95%CI: 1.81-3.54, p < 0.001). The RCS curves showed a non-linear trend between TyG and TyG-WC indices with all-cause mortality (p for nonlinearity = 0.004 and 0.001, respectively). The sensitive analyses supported the positive correlations between TyG-related indices with mortality of the MetS population.

CONCLUSION

Our study highlights the clinical value of TyG-related indices in predicting the survival of the MetS population. TyG-related indices would be the surrogate biomarkers for the follow-up of the MetS population.

Waist to height ratio as a simple tool for predicting mortality: a systematic review and meta-analysis

BACKGROUND

The association of central obesity with higher rates of mortality is not well studied. This study evaluates the association between waist-to-height ratio (WHtR), as a measure of central obesity, with mortality.

METHODS

Documents were retrieved from PubMed, Web of Science, Scopus, and Google Scholar databases until May 2022. Data were extracted from cohort studies reporting effect size (hazard ratio (HR)) regarding the association between WHtR as a continuous (per 1 SD increment) or categorical (highest/lowest) measure and all-cause and cause-specific mortality. Screening of included studies was performed independently by two authors. Moreover, the quality assessment of included studies was performed based on the Newcastle-Ottawa assessment scale. Finally, random effect meta-analysis was performed to pool the data, and the outcomes' certainty level was assess based on the GRADE criteria.

RESULTS

Of the 815 initial studies, 20 were included in the meta-analysis. Random effect meta-analysis showed that in the general population, the all-cause mortality HRs for categorical and continuous measurements of WHtR increased significantly by 23% (HR:1.23; 95% CI: 1.04-1.41) and 16% (HR:1.16; 95% CI: 1.07-1.25), respectively. Moreover, the hazard of cardiovascular (CVD) mortality increased significantly for categorical and continuous measurements of WHtR by 39% (HR:1.39; 95% CI: 1.18-1.59) and 19% (HR:1.19; 95% CI: 1.07-1.31). The quality assessment score of all included studies was high.

CONCLUSIONS

Higher levels of WHtR, indicating central obesity, were associated with an increased hazard of CVD and all-cause mortality. This measure can be used in the clinical setting as a simple tool for predicting mortality.

Estimation of Absolute and Relative Body Fat Content Using Noninvasive Surrogates: Can DXA Be Bypassed?

Dual-energy x-ray absorptiometry (DXA) scanning is used for objective determination of body composition, but instrumentation is expensive and not generally available in customary clinical practice. Anthropometric surrogates are often substituted as anticipated correlates of absolute and relative body fat content in the clinical management of obesity and its associated medical risks. DXA and anthropometric data from a cohort of 9230 randomly selected American subjects, available through the ongoing National Health and Nutrition Examination Survey, was used to evaluate combinations of surrogates (age, height, total weight, waist circumference) as predictors of DXA-determined absolute and relative body fat content. Multiple regression analysis yielded linear combinations of the 4 surrogates that were closely predictive of DXA-determined absolute fat content (R2  = 0.93 and 0.96 for male and female subjects). Accuracy of the new algorithm was improved over customary surrogate-based predictors such as body mass index. However prediction of relative body fat was less robust (R2  less than 0.75), probably due to the nonlinear relation between degree of obesity (based on body mass index) and relative body fat. The paradigm was validated using an independent cohort from the National Health and Nutrition Examination Survey, as well as two independent external subject groups. The described regression-based algorithm is likely to be a sufficiently accurate predictor of absolute body fat (but not relative body fat) to substitute for DXA scanning in many clinical situations. Further work is needed to assess algorithm validity for subgroups of individuals with "atypical" body construction.

[Vulnerability of obesity as defined by body mass index, waist circumference, and body fat percentage]

AIM

To ascertain to what extent it is possible to stop being obese (to normalize body mass index [BMI], waist circumference [WC] and/or body fat percentage [BFP]).

DESIGN

Longitudinal observational and retrospective study. SITE: Eleven Spanish health centers.

PARTICIPANTS

Men and women with BMI≥30kg/m² (n=1246) or general obesity (GO), with WC>102cm and >88cm, respectively (n=2122) or abdominal obesity (AO) and with BFP>25% and >35%, respectively (n=2436) or excess body fat (EBF), from the PEPAF Study cohort of 4927 participants aged 20-80years.

MAIN MEASUREMENTS

Data from the PEPAF study at baseline and at 6, 12 and 24months: gender, age, diagnoses of diabetes, hypertension and dyslipidemia, smoking, levels of and compliance with physical activity recommendations, maximum oxygen consumption, weigh, height, WC and three skin-folds (thoracic, umbilical and anterior thigh for men and triceps, suprailiac and anterior thigh for women).

RESULTS

Of 2054 participants with any type of obesity at baseline and valid data at 2years, 240 (11.6%) had normalized all of their obesity diagnostic indexes. 19.5% (95% confidence interval (95%CI: 17.6-21.4) ceased to have EBF, 12.0% (95%CI: 10.4-13.7) ceased to have AO and 10.5% (95%CI: 8.5-12.7) ceased to have GO.

CONCLUSIONS

Obesity differs from other chronic diseases in that it can be «cured» by normalizing the amount of body fat.

Pancreatic Islets and Gestalt Principles

The human brain has inherent methodology to efficiently interpret complex environmental stimuli into understanding. This visual perception is governed by the law of simplicity, which is fundamental to Gestalt theory. First introduced in a seminal article by Wertheimer in 1923, the theory explains how the mind groups similar images and fills in gaps in order to perceive an amenable version of reality. The world we see consists of complex visual scenes, but rarely is the entire picture visible to us. Since it is inefficient for all visual data to be analyzed at once, certain patterns are given higher importance and made to stand out from the rest of the field in our brain. Here we propose that Gestalt theory may explain why rodent islet architecture has historically been seen as having a core-mantle arrangement. By filling in apparent gaps in the non-β-cell lining, the mind interprets it as a "whole" mantle, which may have further led to widely accepted notions regarding islet microcirculation, intra-islet signaling, and islet development. They are largely based on the prevailing stereotypic islet architecture in which an enclosed structure is presumed. Three-dimensional analysis provides more integrated views of islet and pancreatic microcirculation.

Body Mass Dynamics Is Determined by the Metabolic Ohm's Law and Adipocyte-Autonomous Fat Mass Homeostasis

An ODE model integrating metabolic mechanisms with clinical data reveals an Ohm's law governing lifetime body mass dynamics, where fat and lean tissues are analogous to a parallel nonlinear capacitor and resistor, respectively. The law unexpectedly decouples weight stability (a cell-autonomous property of adipocytes) and weight change (a parabolic trajectory governed by Ohm's law). In middle age, insulin resistance causes fat accumulation to avoid excessive body shrinkage in old age. Moderate middle-age spread is thus natural, not an anomaly caused by hypothalamic defects, as proposed by lipostatic theory. These discoveries provide valuable insights into health care practices such as weight control and health assessment, explain certain observed phenomena, make testable predictions, and may help to resolve major conundrums in the field. The ODE model, which is more comprehensive than Ohm's law, is useful to study metabolism at the detailed microscopic levels.