1. Substrate movements in forearm muscle and subcutaneous adipose tissue were studied, by measurement of arteriovenous differences and blood flow, in seven normal subjects after an overnight fast and then for 6 h after ingestion of a mixed meal. Overall substrate balances were examined in terms of the flux of gram-atoms of carbon. 2. As found previously, the forearm was approximately in carbon balance (import equal to export) after the overnight fast, whereas adipose tissue was a net exporter of carbon, mainly in the form of non-esterified fatty acids. 3. After the meal, arterialized plasma concentrations of glucose and lactate rose sharply (peak at 60 min), whereas those of non-esterified fatty acids and glycerol fell (nadir at 60-120 min). Plasma triacylglycerol concentrations rose slowly to peak at 240 min;much of this rise was accounted for by a rise in the chylomicron fraction. 4. Both tissues took up glucose at an increased rate after the meal. Release of non-esterified fatty acids and glycerol from adipose tissue was suppressed. Clearance of triacylglycerol by both tissues increased after the meal, but was more marked in adipose tissue, where the fractional extraction of chylomicron-triacylglycerol reached 44% at 240 min. 5. The forearm rapidly became a considerable net importer of carbon, and remained so until 6 h after the meal when it was again in approximate carbon balance. Glucose uptake dominated the forearm carbon balance. Adipose tissue was a net importer of carbon from 30 min until 5 h after the meal and then reverted to net export. Clearance of triacylglycerol carbon made the largest contribution to this positive balance, but towards the end of the study this was increasingly counterbalanced by simultaneous non-esterified fatty acid release.

No abstract

Background There has been an increase in the use of cigarillos in the US. People who smoke cigarillos typically also regularly smoke cigarettes (dual users). Methods We compared puffing topography, biomarkers of acute exposure [exhaled carbon monoxide (COex) and plasma nicotine] and physiologic effects from usual brand cigarette and Black & Mild cigarillo smoking in dual users (N=23) in two laboratory sessions. Results Participants (21 men) smoked an average of 17.5 cigarettes/day. Cigarillo consumption varied widely from as few as 1/week to daily. Participants were highly nicotine dependent (average FTND score: 6.3). There were statistically significant differences in smoking behavior between cigarette and cigarillo smoking in time to smoke, number of puffs, and total puff volume (all P<0.001). Average puff duration, interpuff interval average puff volume, and puff velocity did not differ between cigarettes and cigarillos. Nicotine boost was similar after both cigarettes and cigarillos. COex boost was significantly greater after cigarillo smoking compared to cigarette smoking (P<0.001). Conclusions The smoking pattern and exposure profile indicate that dual users inhale cigarillo smoke just as they inhale cigarette smoke thereby exposing themselves to considerable amounts of nicotine and other components of tobacco smoke. COex exposure results imply that cigarillo smoking may be associated with higher exposure to smoke-delivered volatile components of mainstream cigarillo smoke including carcinogens when compared to cigarettes. Impact The findings that cigarillos and cigarettes are smoked similarly in dual users are relevant to health and regulatory considerations on cigar products.

Adipose tissue is an important site of clearance of circulating triacylglycerol (TAG), especially in the postprandial period. Postprandial lipemia is usually increased in obesity. We studied the extraction of TAG from plasma and TAG-rich lipoproteins (TRLs) in subcutaneous adipose tissue in 11 control and 8 obese subjects before and after a mixed meal. Clearance of plasma TAG and very low-density lipoprotein (VLDL)-TAG was decreased in the obese subjects after an overnight fast. After the meal, chylomicron-TAG extraction increased in the control group whereas VLDL-TAG clearance decreased; these changes were not seen in the obese group, in whom the VLDL particles appeared to be better able to compete with the chylomicrons for clearance by lipoprotein lipase. In the control subjects, removal of TAG from the TRL in the postprandial period was accompanied by a shift toward addition of cholesterol to the high-density lipoprotein (HDL) fraction; this was not observed in the obese subjects. We conclude that disturbed TRL-TAG clearance in adipose tissue is related both to the elevated plasma TAG concentrations and the depressed HDL-cholesterol concentrations typical of obesity.

1. Triacylglycerol extraction by subcutaneous adipose tissue and forearm muscle was studied in nine normal subjects after an overnight fast and after the consumption of a mixed meal. 2. There was an inverse correlation between the total plasma fractional triacylglycerol extraction across the adipose tissue and the fasting arterial plasma triacylglycerol concentration. In contrast, there was no correlation between the lower fractional triacylglycerol extraction across the forearm muscle and the fasting plasma triacylglycerol concentration. 3. Chylomicron-triacylglycerol concentrations in arterial(ized) plasma increased post-prandially and peaked at 240-300 min. There was a comparable increase in the very-low-density lipoprotein-triacylglycerol concentration, peaking at 300 min. 4. Clearance of chylomicron-triacylglycerol by adipose tissue increased after the meal (P less than 0.05). In contrast, the clearance of very-low-density lipoprotein-triacylglycerol by adipose tissue decreased post-prandially (P less than 0.05). 5. Although there was significant uptake of chylomicron-triacylglycerol by the forearm muscle post-prandially, this was less than by the adipose tissue. Very-low-density lipoprotein-triacylglycerol was unaffected by passage through the forearm muscle at any time. 6. We conclude that the extraction of lipoprotein-triacylglycerol by human adipose tissue is important in determining the fasting plasma triacylglycerol concentration. Chylomicron-triacylglycerol, appearing in the plasma post-prandially, may compete with very-low-density lipoprotein-triacylglycerol for clearance by adipose tissue lipoprotein lipase, and this mechanism may explain, at least in part, the post-prandial rise in very-low-density lipoprotein-triacylglycerol. Forearm muscle, in contrast, appears to play a much smaller role in the extraction of plasma triacylglycerol, especially that in the very-low-density lipoprotein fraction.