Leptin reverses insulin resistance and hepatic steatosis in patients with severe lipodystrophy

In the paper

“At the time of the postleptin treatment study, all patients had their antidiabetic medication discontinued (5).”

What the sources say

• Disputed

  Table 1 (Patient No.; page unavailable in our copy) shows that patients 3, 7, and 8 were still receiving antidiabetic medication at four months; patient 9 had none to discontinue. The Study Design and Changes in Metabolic Control sections say treatments were tapered or discontinued as needed, not discontinued for all patients. (LLM, conf=0.95)

  Checked by a reasoning model — may be wrong.

  cites [5] sourceExperimental — accuracy not yet measured

In the paper

“Energy expenditure was assessed by indirect calorimetry in all patients before and after leptin treatment and was found to be slightly, but not significantly, lower in all patients after leptin treatment (1,660 ± 108 kcal/day before treatment versus 1,403 ± 62 kcal/day after treatment, P = 0.08).”

• Also stated in: another passage · hedged

  “In contrast, we found that leptin treatment tended to cause a decrease in energy expenditure, which is consistent with the observations in the entire set of lipodystrophic patients (5).”

What the sources say

• Disputed

  In “Changes in Energy Balance” (page not provided), the paper reports a decrease in resting metabolic rate in all nine patients, but gives different values and finds it statistically significant: 1,920 ± 150 to 1,580 ± 80 kcal/day (P = 0.003). The cited claim instead gives 1,660 ± 108 to 1,403 ± 62 kcal/day and calls the decrease nonsignificant (P = 0.08). (LLM, conf=0.90)

  Checked by a reasoning model — may be wrong.

  cites [5] sourceExperimental — accuracy not yet measured

In the paper

“it is likely that a fatty acid-derived intermediate, rather than intramyocellular triglyceride, is responsible for mediating the insulin resistance (23).”

What the sources say

• Supported

  In “A unifying hypothesis for common forms of human insulin resistance” (page not provided), the paper says that triglycerides accumulate but intracellular fatty acid metabolites are “probably more importantly” involved in insulin-signaling defects and insulin resistance. This supports the citing sentence’s qualified comparison. (LLM, conf=0.93)

  cites [23] source

In the paper

“The improved glycemic control could be attributed to a marked increase in their insulin responsiveness, as reflected by an almost fourfold increase in the rate of glucose infusion required to maintain euglycemia during the clamp”

What the sources say

• Partly supported

  The Changes in Metabolic Control section reports improved glycemic control and insulin sensitivity after leptin therapy. But the Procedures section describes an insulin-tolerance test, not a euglycemic clamp; the reported glucose-disappearance constant rose from 0.007 to 0.017, not an almost fourfold increase in a glucose-infusion rate. No page numbers are available in our copy. (LLM, conf=0.88)

  cites [5] sourceExperimental — accuracy not yet measured

In the paper

“These data support the hypothesis that a similar mechanism for insulin resistance might occur in patients with severe lipodystrophy and more common forms of insulin resistance associated with obesity and type 2 diabetes (23).”

What the sources say

• Supported

  The section “A unifying hypothesis for common forms of human insulin resistance” explicitly proposes a shared mechanism for insulin resistance in lipodystrophy, obesity, and type 2 diabetes. It presents this as a hypothesis, matching the citing sentence’s uncertainty. (LLM, conf=0.94)

  cites [23] source

In the paper

“Previous studies by our group (9, 17-20) and others (7, 21, 22) have demonstrated a strong relationship between triglyceride content in liver and muscle and insulin resistance in these tissues.”

What the sources say

• Supported

  The Discussion (page not available) reports that improved insulin responsiveness was associated with reduced hepatic triglyceride content, and the References list prior studies linking muscle triglyceride or lipid content with insulin resistance. The paper also notes that muscle triglyceride did not fall despite improved muscle insulin sensitivity in its own trial; this does not negate the cited claim about relationships demonstrated in previous studies. (LLM, conf=0.83)

  cites [9] source
• ?Could not verify

  The Introduction and Discussion report that elevated plasma free fatty acids induce insulin resistance in human skeletal muscle. They do not report a relationship between triglyceride content in liver or muscle and insulin resistance in those tissues (searched: triglyceride content, intramuscular triglyceride, liver triglyceride). (LLM, conf=0.72)

  cites [17] sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [18] source
• ?Not checked — no full text of the sourcecites [19] source
• ?Not checked — no full text of the sourcecites [20] source
• ?Not checked — no full text of the sourcecites [7] Szczepaniak, 1999, Am J Physiol source
• ?Not checked — no full text of the sourcecites [21] source
• Partly supported

  The Discussion reports a strong correlation between liver fat percentage and hepatic insulin sensitivity, supporting the liver portion of the claim. Our copy does not report a relationship between muscle triglyceride content and muscle insulin resistance; its mention of skeletal-muscle insulin resistance does not establish that relationship. The indexed passages provide section labels but no page numbers. (LLM, conf=0.88)

  cites [22] sourceExperimental — accuracy not yet measured

In the paper

“Energy intake was monitored in patient NIH-6, and leptin treatment caused an approximately 50% reduction in energy intake, from 2,017 kcal/day before treatment to 962 kcal/day after 3 months of treatment.”

• Also stated in: another passage · hedged

  “Furthermore, when energy intake was carefully monitored in an inpatient setting, we found an approximately 50% reduction in the caloric intake in one patient following leptin therapy, which is similar to the self-reported observations by Arioglu Oral et al. (5) in the entire set of nine lipodystrophic patients and by Farooqi et al. (27) in a child with congenital leptin deficiency who was treated”

What the sources say

• Partly supported

  The Changes in Energy Balance section reports that mean self-reported intake fell during leptin therapy, from 2,680 to 1,600 kcal/day after four months. It does not report the claimed 2,017-to-962 kcal/day change for patient NIH-6 after three months; the Procedures section says food intake was reported at baseline and four months. (LLM, conf=0.88)

  cites [5] sourceExperimental — accuracy not yet measured
• ?Not checked — no full text of the sourcecites [27] source

In the paper

“While there were no appreciable differences in intramyocellular triglyceride content between the control and lipodystrophic patients”

In the paper

“Consistent with the former possibility, all patients reported a marked reduction in appetite following leptin treatment.”

In the paper

“The lipodystrophic patients were severely insulin resistant, as reflected by the very low rates of glucose infusion required to maintain euglycemia during the hyperinsulinemic-euglycemic clamp (lipodystrophic, 1.2 ± 0.2 mg/kg/min versus control, 12.7 ± 0.9 mg/kg/min; P < 0.0001)”

In the paper

“and a 33% ± 3% decrease in muscle triglyceride content ( P = 0.006 compared with before leptin treatment) (Figure 5).”

In the paper

“Hepatic insulin responsiveness also improved, as reflected by an increase of insulin suppression of glucose production during the clamp to 82% ± 5% compared with 40% ± 6% prior to leptin treatment ( P < 0.05) (Figure 4).”

In the paper

“and an almost twofold increase in the rate of insulin-stimulated whole-body glucose metabolism (6.1 ± 1.0 mg/kg/min after leptin versus 3.5 ± 0.3 before leptin; P = 0.08).”

In the paper

“we also assessed rates of hepatic and peripheral glucose metabolism and found that leptin therapy caused an approximately twofold increase in insulin suppression of hepatic glucose production”

In the paper

“as well as a marked reduction in insulin-stimulated whole-body glucose metabolism (Figure 2).”

In the paper

“This improvement in glycemic control could be attributed to a large increase in whole-body insulin sensitivity, as reflected by an approximately fourfold increase in the rate of glucose infusion required to maintain euglycemia (5.4 ± 0.9 mg/kg/min after treatment versus 1.2 ± 0.2 mg/kg/min before treatment; P = 0.04) (Figure 4)”

In the paper

“Furthermore, the lipodystrophic patients had severe hepatic insulin resistance, as reflected by decreased insulin suppression of glucose production during the hyperinsulinemic clamp (40% ± 6%) compared with the control subjects (92% ± 7% suppression, P = 0.0004) (Figure 1).”

In the paper

“Basal rates of glycerol turnover were markedly increased in the lipodystrophic patients, reflecting very high rates of lipolysis per kg fat tissue (Figure 3)”

In the paper

“The leptin treatmentinduced reduction in muscle triglyceride content was matched by an approximately 30% decrease in muscle total fatty acyl CoA concentrations (Figure 5, inset).”

In the paper

“These changes in hepatic and peripheral insulin sensitivity were associated with an 86% ± 8% reduction in hepatic triglyceride content ( P =0.008 compared with before leptin treatment)”

In the paper

“and an almost twofold increase in insulin-stimulated peripheral glucose disposal.”

In the paper

“Rates of fasting glucose production were higher in the lipodystrophic subjects than in the control subjects (lipodystrophic, 3.6 ± 0.8 mg/kg/min versus control, 1.9 ± 0.1 mg/kg/min; P = 0.019) (Figure 1).”

In the paper

“Given their almost complete lack of subcutaneous and visceral fat, these data suggest that there is a significant amount of intrahepatic or intravascular triglyceride lipolysis occurring in these individuals.”

In the paper

“Hepatic accumulation of triglyceride and fatty acid-derived metabolites is likely to cause insulin resistance in the liver by a similar mechanism.”

In the paper

“Basal rates of glycerol turnover were markedly increased in the lipodystrophic patients, reflecting very high rates of lipolysis per kg fat tissue (Figure 3)”