High insulin (hyperinsulinemia) is associated with buffalo hump, one of the body fat changes seen in people taking HAART, according to an Australian study published in the February 1st edition of the Journal of Acquired Immune Deficiency Syndromes. They caution that growth hormone, which has been investigated as a therapy for lipodystrophy, can induce hyperinsulinemia and therefore may not be an ideal treatment for patients with buffalo hump.
Accumulation of fat between the shoulder blades has been observed in between 2% and 13% of HIV-positive individuals and is recognised as part of the lipodystrophy syndrome of body fat changes and metabolic complications seen in HIV-positive individuals. Compared to fat loss, comparatively little is known about the causes of buffalo hump.
Accordingly investigators investigated data from two cohorts of Australian patients to identify the risk factors associated with buffalo hump.
Between 1998 and 1999 a total of 1348 patients were recruited to the Australian Lipodystrophy Prevalence Survey (APS). The prevalence of lipodystrophy in this study was 53%. The HIV Lipodystrophy Case Definition Study (LDCD) recruited 417 patients with body fat or metabolic abnormalities between 2000 and 2001.
Buffalo hump was diagnosed by doctors in the APS, whereas in the LDCD buffalo hump was diagnosed on the basis of either a doctor’s or a patient’s report.
In both studies, demographic data were gathered as were details of HIV treatment, LDL and HDL cholesterol, triglycerides, glucose, and insulin. Total and regional body composition was also assessed using DEXA and CT scans.
Buffalo hump was diagnosed in 2% of patients in the APS cohort and 19% of individuals in the LDCD study population. In both the APS patients (p = 0.007) and the LDCD group (p = 0.002) elevated insulin was independently associated with buffalo hump. Amongst the LDCD study population, diastolic blood pressure (p = 0.003) was significantly associated with buffalo hump, whereas systolic blood pressure (p = 0.001) was independently associated with the side-effect in APS patients. An association was also found between the use of specific anti-HIV drugs and buffalo hump. Amongst the LDCD patients, use of AZT for over six months (p = 0.005) was associated with buffalo hump, whereas amongst APS patients total duration of treatment with full dose ritonavir was independently associated with the side-effect (p = 0.004).
The investigators also noted that fat loss or fat gain was from other sites was almost universally reported by patients in both study cohort.
The investigators conclude that individuals with buffalo hump should be closely monitored for insulin resistance and diabetes. They caution that growth hormone, which has been investigated as a therapy for body fat changes caused by HAART, may not be appropriate for buffalo hump as it can cause hyperinsulinemia.
Reference
Mallon PGW et al. Buffalo hump seen in HIV-associated lipodystrophy is associated with hyperinsulinemia but not dyslipidemia. J Acquir Immune Defic 38: 156 – 162, 2005.