Basal and cold-induced fatty acid uptake of human brown adipose tissue is impaired in obesity.

Fatty acids (FA) are important substrates for brown adipose tissue (BAT) metabolism, however, it remains unclear whether there exists a difference in FA metabolism of BAT between lean and obese healthy humans. In this study we evaluated supraclavicular BAT fatty acid uptake (FAU) along with blood perfusion in lean and obese subjects during cold exposure and at room temperature using positron emission tomography (PET)/computed tomography (CT). Additionally, tissue samples were taken from supraclavicular region (typical BAT region) from a subset of subjects to evaluate histological presence of BAT. Non-shivering cold stress elevated FAU and perfusion of BAT in lean, but not in obese subjects. Lean subjects had greater FAU in BAT compared to obese subjects during cold exposure and interestingly also at room temperature. The higher BAT FAU was related to younger age and several indicators of superior systemic metabolic health. The subjects who manifested BAT histologically had several folds higher BAT FAU compared to subjects with no such histological manifestation. Together, obese subjects have less active tissue in supraclavicular region both in basal and cold-activated state and the FA metabolism of BAT is blunted in obesity.

Brown adipose tissue triglyceride content is associated with decreased insulin sensitivity, independently of age and obesity.

The aim of the present study was to determine whether single-voxel proton magnetic resonance spectroscopy ((1)H-MRS) can non-invasively assess triglyceride content in both supraclavicular fat depots and subcutaneous white adipose tissue (WAT) to determine whether these measurements correlate to metabolic variables. A total of 25 healthy volunteers were studied using (18)F-fluorodeoxyglucose positron emission tomography (PET) and (15)O-H2O PET perfusion during cold exposure, and (1)H-MRS at ambient temperature. Image-guided biopsies were collected from nine volunteers. The supraclavicular triglyceride content determined by (1)H-MRS varied between 60 and 91% [mean ± standard deviation (s.d.) 77 ± 10%]. It correlated positively with body mass index, waist circumference, subcutaneous and visceral fat masses and 8-year diabetes risk based on the Framingham risk score and inversely with HDL cholesterol and insulin sensitivity (M-value; euglycaemic-hyperinsulinaemic clamp). Subcutaneous WAT had a significantly higher triglyceride content, 76-95% (mean ± s.d. 87 ± 5%; p = 0.0002). In conclusion, the triglyceride content in supraclavicular fat deposits measured by (1)H-MRS may be an independent marker of whole-body insulin sensitivity, independent of brown adipose tissue metabolic activation.

Follow-ups of the Cardiovascular Risk in Young Finns Study in 2001 and 2007: levels and 6-year changes in risk factors.

OBJECTIVES: To examine cardiovascular risk factor levels in 2007 and their 6-year changes between 2001 and 2007 using the data collected in the follow-ups of the Cardiovascular Risk in Young Finns Study. DESIGN: Population-based follow-up study. SUBJECTS: A total of 2204 healthy Finnish adults aged 30-45 years (1210 women; 994 men). MAIN OUTCOME MEASURES: Levels in 2007 and changes between 2001 and 2007 of lipids, insulin, glucose, blood pressure, smoking, body mass index, alcohol consumption, waist and hip circumferences. RESULTS: The mean serum total cholesterol, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol and triglyceride concentrations in 30- to 45-year-old adults were 5.05, 3.09, 1.34 and 1.40 mmol L(-1), respectively. Significant changes (P < 0.05) between 2001 and 2007 in 30- to 39-year-old subjects included a decrease in total cholesterol (-6.6% in men, -5.8% in women), LDL-cholesterol (-10.2% and -11.6%) and an increase in diastolic blood pressure (3.5% and 3.9%). Waist circumference (1.8% and 5.5%) and systolic blood pressure increased in 36-39 year olds (2.3% and 2.3%). HDL-cholesterol increased in 30- to 33-year-old women (5.8%) Glucose levels increased in 30- to 39-year-old women (3.7%) and 36- to 39-year-old men (3.6%). Smoking prevalence decreased in 36- to 39-year-old men from 29.8% to 22.2%. CONCLUSIONS: The 6-year changes in total cholesterol, LDL-cholesterol and HDL-cholesterol in young Finns were favourable between 2001 and 2007. However, waist circumference, glucose and blood pressure levels increased. Therefore, continuous efforts are still needed in fighting against cardiovascular risk factors.