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ZengKui Guo

Publications and source records attributed to ZengKui Guo.

7 recordsLinked to original sources
PubMed2004

Evidence for increased and insulin-resistant lipolysis in skeletal muscle of high-fat-fed rats.

The metabolic and isotopic profiles of glycerol in skeletal muscle were examined using awake, fasted lean and high-fat-induced obese rats, and hyperinsulinemic-euglycemic clamp was performed to assess the effect of insulin. During the clamp, Intralipid (no heparin; Fresnius Kabi Clayton, Clayton, NC), free fatty acids, glycerol, and glucose were coinfused to maintain their respective basal plasma levels in both groups. At steady-state, [U-(14)C]glycerol was infused intravenously for 120 minutes followed by muscle biopsy. The classical phenotypic characteristics of obesity, namely, reduced insulin-stimulated glucose uptake, a failure to suppress systemic lipolysis by insulin, and elevated plasma fatty acid concentration, were observed in the obese rats. Novel observations showed that in the basal state, the isotopic specific activity (S.A.) of glycerol (dpm/nmol) in gastrocnemius (0.03 v 0.12), soleus (0.05 v 0.12), and tibialis anterior (0.03 v 0.12) was significantly lower (all P <.003) in obese than in lean rats despite similar concentrations, indicating an active basal intramyocellular lipolysis. In addition, the lipolysis appeared resistant to insulin because the suppression of muscle glycerol during the clamp was 8%, 12%, and 8% in obese compared to 67%, 71%, and 63% in the lean control for gastrocnemius (P =.001), soleus (P =.007), and tibialis anterior (P =.004), respectively. The active intracellular lipolysis likely disturbs metabolic functions that may contribute to insulin resistance.

Animal Feed↗
PubMed2004

Splanchnic lipolysis in human obesity.

Elevated FFA concentrations have been shown to reproduce some of the metabolic abnormalities of obesity. It has been hypothesized that visceral adipose tissue lipolysis releases excess FFAs into the portal vein, exposing the liver to higher FFA concentrations. We used isotope dilution/hepatic vein catheterization techniques to examine whether intra-abdominal fat contributes a greater portion of hepatic FFA delivery in visceral obesity. Obese women (n = 24) and men (n = 20) with a range of obesity phenotypes, taken together with healthy, lean women (n = 12) and men (n = 12), were studied. Systemic, splanchnic, and leg FFA kinetics were measured. The results showed that plasma FFA concentrations were approximately 20% greater in obese men and obese women. The contribution of splanchnic lipolysis to hepatic FFA delivery ranged from less than 10% to almost 50% and increased as a function of visceral fat in women (r = 0.49, P = 0.002) and in men (r = 0.52, P = 0.002); the slope of the relationship was greater in women than in men (P < 0.05). Leg and splanchnic tissues contributed a greater portion of systemic FFA release in obese men and women than in lean men and women. We conclude that the contribution of visceral adipose tissue lipolysis to hepatic FFA delivery increases with increasing visceral fat in humans and that this effect is greater in women than in men.

Abdomen↗
PubMed2003

Substrate concentration and metabolism in left and right muscles of rats.

Skeletal muscle fiber heterogeneity among muscle groups is well known; however, laterality of muscle metabolism has not been addressed. In the present studies, metabolite concentrations in left and right gastrocnemius, tibialis anterior, quadriceps, and soleus muscles and their response to exogenous insulin have been compared in fasted awake rats. The results indicated that the concentrations of muscle free glycerol (P >.4), glycerol 3-phosphate (P >.1) nonesterified fatty acids (NEFA) (P >.6) and intramyocellular triglycerides (imcTG) (P >.08) are comparable between left and right of the same muscle, and are similar among mixed glycolytic-oxidative muscles. The concentration of free glycerol in soleus responded to exogenous insulin in a pattern distinct to that seen for the mixed muscles. The results support interchangeable use of left and right side of same muscles, and probably among different muscles of similar fiber type, but not muscles of different fiber types.

Animals↗
PubMed2003

Energy expenditure, sex, and endogenous fuel availability in humans.

Adipose tissue lipolysis supplies circulating FFAs, which largely meet lipid fuel needs; however, excess FFAs, can contribute to the adverse health consequences of obesity. Because "normal" FFA release has not been well defined, average (mean of 4 days) basal FFA release and its potential regulation factors were measured in 50 lean and obese adults (25 women). Resting energy expenditure (REE), but not body composition, predicted most of the interindividual variation in FFA release. There was a significant, positive linear relationship between palmitate release and REE; however, women released approximately 40% more FFA than men relative to REE. Neither plasma palmitate concentrations nor respiratory quotient by indirect calorimetry differed between men and women. Glucose release rates were not different in men and women whether related to REE or fat free mass. These findings indicate that nonoxidative FFA clearance is greater in women than in men. This could be an advantage at times of increased fuel needs. We conclude that "normal" adipose tissue lipolysis is different in men and women and that the fuel export role of adipose tissue in obesity will need to be reassessed.

Adipose Tissue↗
PubMed2002

Determination of skeletal muscle triglyceride synthesis using a single muscle biopsy.

A novel stable isotopic technique for the determination of triglyceride synthesis in skeletal muscle by using a single muscle biopsy has been developed and evaluated in rats. In previous studies using (13)C-tracers, muscle triglyceride synthesis is usually determined using at least 2 biopsies, the first of which serves as the baseline sample for the measurement of natural (13)C abundance. In the present studies, the baseline biopsy has been eliminated by making the use of the isotopic information of a nontraced fatty acid in the muscle triglyceride pool. This is based on the fact that the source and, hence, the natural (13)C abundance of fatty acids in the same triglyceride pool is similar. To demonstrate and validate the method, a series of rat studies have been conducted to have established that (1) the natural (13)C abundance of 4 major fatty acids in the muscle triglyceride pool is similar; (2) there are no (13)C-label exchanges between fatty acids in the lipid pool; and (3) the incorporation of (13)C-palmitate into muscle triglycerides determined using this technique favorably compared with that determined by the traditional method. This approach makes stable isotope studies possible in which more than 1 muscle biopsy is difficult or impossible. Therefore, it has the potential to facilitate investigation of triglyceride metabolism in the skeletal muscle.

Animals↗