Commonality versus specificity among adiposity traits in normal-weight and moderately overweight adults

Fat Cell Size: Measurement Methods, Pathophysiological Origins, and Relationships With Metabolic Dysregulations

The obesity pandemic increasingly causes morbidity and mortality from type 2 diabetes, cardiovascular diseases and many other chronic diseases. Fat cell size (FCS) predicts numerous obesity-related complications such as lipid dysmetabolism, ectopic fat accumulation, insulin resistance, and cardiovascular disorders. Nevertheless, the scarcity of systematic literature reviews on this subject is compounded by the use of different methods by which FCS measurements are determined and reported. In this paper, we provide a systematic review of the current literature on the relationship between adipocyte hypertrophy and obesity-related glucose and lipid dysmetabolism, ectopic fat accumulation, and cardiovascular disorders. We also review the numerous mechanistic origins of adipocyte hypertrophy and its relationship with metabolic dysregulation, including changes in adipogenesis, cell senescence, collagen deposition, systemic inflammation, adipokine secretion, and energy balance. To quantify the effect of different FCS measurement methods, we performed statistical analyses across published data while controlling for body mass index, age, and sex.

Contribution of Intramyocellular Lipids to Decreased Computed Tomography Muscle Density With Age

Skeletal muscle density, as determined by computed tomography (CT), has been shown to decline with age, resulting in increased frailty and morbidity. However, the mechanism underlying this decrease in muscle density remains elusive. We sought to investigate the role of intramyocellular lipid (IMCL) accumulation in the age-related decline in muscle density. Muscle density was measured using computerized tomography (CT), and IMCL content was quantified using in vivo proton magnetic resonance spectroscopy (¹H-MRS). The study population consisted of 314 healthy participants (142 men, 32–98 years) of the Baltimore Longitudinal Study of Aging (BLSA). In addition to IMCL quantification, obesity-related covariates were measured, including body mass index (BMI), waist circumference, and circulating triglyceride concentration. Higher IMCL concentrations were significantly correlated with lower muscle density in older individuals, independent of age, sex, race, and the obesity-associated covariates (p < 0.01). Lower muscle density was also significantly associated with greater age-adjusted IMCL, a variable we constructed using LOESS regression (p < 0.05). Our results suggest that the accumulation of IMCL may be associated with a decrease in muscle density. This may serve to define a potential therapeutic target for treatment of age-associated decreased muscle function.

The Effect of a Novel Low-Volume Aerobic Exercise Intervention on Liver Fat in Type 2 Diabetes: A Randomized Controlled Trial

OBJECTIVE

The aim of this study was to examine the effect of a novel low-volume high-intensity interval training (HIIT), moderate-intensity continuous training (MICT), or placebo (PLA) intervention on liver fat, glycemia, and cardiorespiratory fitness using a randomized placebo-controlled design.

RESEARCH DESIGN AND METHODS

Thirty-five inactive adults (age 54.6 ± 1.4 years, 54% male; BMI 35.9 ± 0.9 kg/m²) with obesity and type 2 diabetes were randomized to 12 weeks of supervised MICT (n = 12) at 60% VO_2peak for 45 min, 3 days/week; HIIT (n = 12) at 90% VO_2peak for 4 min, 3 days/week; or PLA (n = 11). Liver fat percentage was quantified through proton MRS.

RESULTS

Liver fat reduced in MICT (-0.9 ± 0.7%) and HIIT (-1.7 ± 1.1%) but increased in PLA (1.2 ± 0.5%) (P = 0.046). HbA_1c improved in MICT (-0.3 ± 0.3%) and HIIT (-0.3 ± 0.3%) but not in PLA (0.5 ± 0.2%) (P = 0.014). Cardiorespiratory fitness improved in MICT (2.3 ± 1.2 mL/kg/min) and HIIT (1.1 ± 0.5 mL/kg/min) but not in PLA (-1.5 ± 0.9 mL/kg/min) (P = 0.006).

CONCLUSIONS

MICT or a low-volume HIIT approach involving 12 min of weekly high-intensity aerobic exercise may improve liver fat, glycemia, and cardiorespiratory fitness in people with type 2 diabetes in the absence of weight loss. Further studies are required to elucidate the relationship between exercise-induced reductions in liver fat and improvements in glycemia.

Body Mass Index versus Other Adiposity Traits: Best Predictor of Cardiometabolic Risk

BACKGROUND

A number of anthropometric indices have been used in different world populations as markers to estimate obesity and its related health risks. The present study is large population based study dealing with five anthropometric obesity scales; Body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR), basal adiposity index (BAI), and Visceral adiposity index (VAI) to identify common adiposity trait(s) that best predict obesity and associated health complication(s).

METHODS

A total of 4000 subjects including 1000 in each category of BMI from four provinces (Punjab, Sindh, Kahyber pakhtoonkha and Balochistan) of Pakistan from 2012-2017 were collected. Complete anthropometric measurementswere obtained and blood samples were collected and Biochemical profiling was performed. Descriptive statistics, linear regression, binary and multiple regression analysis was done.

RESULTS

Our data analysis explored the relationships of obesity five indices; BMI, WC, WHR, BAI, and VAI with common metabolic health complications. Effect size analysis clearly indicates that a unit increase in BMI significant raised all anthropometric and clinical parameters. General and sex specific association analysis of adiposity traits with risk phenotypes (hypertension, hyperglycemia and dyslipidemia) indicated significant associations of WC with all three metabolic risks. Varying degrees of correlations of other adiposity traits with metabolic risks were observed. Frequency of different obesity classes among obese population group were as follows; 55.7% class I, 28.50% Class II and 15.80% Class III.

CONCLUSION

WC is the strong predictor of obesity associated metabolic health issues in Pakistani populations. While BMI has significant increasing effect on other obesity indices like WHR, VAI and BAI.

Effect of vitamin D supplementation alone or with calcium on adiposity measures: a systematic review and meta-analysis of randomized controlled trials

CONTEXT

The independent or interactive effects of vitamin D and calcium on adiposity remain inconclusive.

OBJECTIVE

The objective of this systematic review and meta-analysis was to assess whether vitamin D and calcium supplements cause changes in adiposity.

DATA SOURCES

MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials databases were searched for literature published from 1966 to March 2014.

STUDY SELECTION

A systematic search was conducted for randomized clinical trials with ≥ 50 participants aged ≥ 18 years at baseline who had received at least 12 weeks of treatment. Among the inclusion criteria were supplementation with vitamin D with or without calcium and measurement of adiposity (weight, body mass index [BMI], and/or fat mass).

DATA EXTRACTION

The primary endpoints assessed were changes in weight, BMI, or fat mass.

DATA SYNTHESIS

Of 953 trials identified, 26 randomized clinical trials (n = 12, vitamin D alone; n = 10, vitamin D plus calcium versus calcium control; n = 4, vitamin D plus calcium versus placebo) with a total of 42,430 participants (median duration, 12 months) met the inclusion criteria. When compared with placebo, vitamin D supplementation had no significant effect on BMI (weighted mean difference [WMD], -0.06 kg/m(2); 95% confidence interval [95%CI], -0.14 to 0.03), weight (WMD, -0.05 kg; 95%CI, -0.32 to 0.23), or fat mass (WMD, -0.43 kg; 95%CI, -1.69 to 0.84). Likewise, no significant reduction in BMI (WMD, 0.02 kg/m(2); 95%CI, -0.11 to 0.14), weight (WMD, 0.12 kg; 95%CI, -0.24 to 0.49), or fat mass (WMD, 0.12 kg; 95%CI, -0.22 to 0.45) was observed in participants who received vitamin D plus calcium compared with those who received calcium control.

CONCLUSIONS

Supplementation with vitamin D showed no effect on adiposity measures in adults.